Title of Invention	COMMUNICATION SYSTEM
Abstract	A communication system is provided which is arranged for accessing a network by a group of first access paths and a group of second access paths. The first and second access paths have a different access technology. An access path monitor is provided for obtaining status information related to the access paths in accordance with the monitoring procedure. An access controller is provided for selecting an access path for a communication session in accordance with a selection procedure and in dependence on the status information. A modifier is provided for modifying one or both of the monitoring procedure and the selection procedure in accordance with a modification procedure and in dependence on decision information.

Title of Invention

COMMUNICATION SYSTEM

Abstract

A communication system is provided which is arranged for accessing a network by a group of first access paths and a group of second access paths. The first and second access paths have a different access technology. An access path monitor is provided for obtaining status information related to the access paths in accordance with the monitoring procedure. An access controller is provided for selecting an access path for a communication session in accordance with a selection procedure and in dependence on the status information. A modifier is provided for modifying one or both of the monitoring procedure and the selection procedure in accordance with a modification procedure and in dependence on decision information.

Full Text	Field of the invention The present invention relates to a communication system for accessing a network via a group of first access paths of a first access technology and a group of second access paths of a second access technology, said second access technology being different from the first access technology. The application also relates to a method of network access via access paths of different access technology. Background of the invention In the field of communications it is known to provide systems in which a given device can obtain access to a network via access paths of differing access technology. This is shown schematically in Figure 2. A communication system 10, e.g. a wireless communication device such as a mobile telephone is able to communicate with stations 11 and 12 that provide communication paths 101, 102 of a first access technology, e.g. a GSM (Global System for Mobile Communication) connection, a WCDMA (Wideband CDMA) connection, a WiMAX (Worldwide Interoperability for Microwave Access) connection, a WINNER (Wireless World Initiative New Radio) connection, a WLAN (Wireless Local Area Network) connection, etc. The communication system 10 can furthermore communicate with stations 13, 14 over communication paths 103, 104 that are of a different access technology than paths 101, 102. If the paths 101, 102 operate in accordance with one of the above-mentioned technologies, then the paths 103, 104 can be provided by any one of the other technologies. The communication system 10 accesses the network 15, e.g. a telephone network or a computer network, such as an intranet or the Internet via the paths 101-104. If the stations 11-14 and the communication system 10 are arranged in such a way that the communication system 10 can from one location access the network 15 via both an access path 101, 102 or 103, 104, then this leads to the problem of managing the selection of one or 2 more paths for conducting a communication session with the network 15. The basic situation of having heterogeneous wireless technologies for communication in a given location has already been studied, e.g. in the context of so-called Ambient Networks (AN), see document ISD- 2002-507134-AN/WB2/D02, MRA Architecture by Rolf Sigle et al, version 1.0, released February 2, 2005. The inventors of the present application are also authors/editors of this document, the contents of which is herewith incorporated by reference. In the context of Ambient Networks it has been proposed to use so- called Multi-Radio Resource Management (MRRM) for managing the different access technologies. An MRRM functionality coordinates the different radio access technologies by mapping service requests on available radio resources for both single-and multi-hop links. Different MRRM objectives can be used e.g. maximizing radio resource efficiency, service coverage or service quality, or enabling services otherwise impossible to deliver over a single radio access. Intelligent load distribution algorithms inside MRRM increase the overall effective network capacity. MRRM functions include advertising, discovery, selection, resource monitoring, and spectrum and congestion control. By monitoring the access paths and obtaining status information related to access paths of different access technology, an access controller can select an access path for a communication session in accordance with a selection procedure and in dependence of the status information. Document EP 0 812 119 A2 discusses an improvement of the idle or standby mode in mobile stations of a cellular communication system. It is mentioned that the IS-136 and the GSM standard require an idle mobile station, i.e. a mobile station that is not in the process of conducting a communication session, to monitor control channels of neighbouring cells. EP 0 812 119 A2 proposes a different standby mode according to which when making measurements of a currently assigned control channel and other control channels, measurements of at least some of the other control channels can be terminated if it 3 is detected that the mobile station has become stationary. The latter can be done by measuring the received signal strength of a monitored neighbouring channel and comparing the temporal change in signal strength with a predetermined threshold. If the change in received signal strength falls below this threshold it is determined that the mobile station is stationary. Object of the invention The object of the invention is to provide an improved communication system and method of accessing a network via groups of access paths of different access technology. It is noted that this object is not restricted to systems having wireless access technology, as the problem of making a selection between access paths of different technology will also occur if one or more of the groups of access paths are wire-bound. Summary of the invention The object of the invention is fulfilled by a communication system having the features of claim 1, a modifier having the features of claim 23, a method of controlling access to a network according to claim 24, and a computer program product of claim 25. Advantageous embodiments are described in the dependent claims. In accordance with the present invention a communication system arranged for accessing a network via a group of first access paths of a first access technology and a group of second access paths of a second access technology different from the first access technology is provided. The communication system can be a terminal, such as a mobile telephone capable of communication in accordance with a variety of wireless technologies, or the communication system can itself be a network, such as a Personal Area Network. The group of first access paths can have one or more members, and the group of second access paths can have one or more members. Naturally, the communication system can be arranged for accessing a network via more than two different types of access technologies. 4 An access path monitor is provided for obtaining status information related to a status of one or more of the first access paths and one or more of the second access paths in accordance with a monitoring procedure. The obtaining of information can e.g. be done by performing measurements on the access paths of interest, or can be obtained in other ways, e.g. received from the network. It is noted that the term "access path" describes any suitable access connection, e.g. a single link, a number of consecutive links, or an entire subnetwork. Furthermore, an access controller is provided for selecting an access path for a communication session from among the first and second access paths in accordance with a selection procedure and in dependence on the status information obtained by the access path monitor. The selecting preferably not only comprises the initial selection of one or more paths for a given session that is to be established, but also the subsequent switching of an established session from an access path of the first access technology to an access path of the second technology or vice versa, while the communication session is active. Furthermore, in accordance with the invention a modifier for modifying one or both of the monitoring procedure and the selection procedure in accordance with a modification procedure and in dependence on decision information is provided. The modifying can be done in any suitable or desirable way e.g. by changing parameters used by a procedure, e.g. the frequency at which status information is obtained. Modifying may also comprise changing a procedure or routine itself, e.g. by switching from one subroutine or mode to another. In accordance with the present invention, the monitoring procedure and/or the selection procedure can be flexibly and dynamically adapted by the modification procedure. This provides an optimised management of the access paths of differing technology. More specifically, it is possible to control the modification in such a 5 way so as to optimise the trade-off between the costs (e.g. in terms of signalling overhead, energy consumption etc.) caused by the monitoring procedure and the benefit (e.g. in terms of improved quality of service) provided by the selection procedure. The balancing of cost and benefit can be done without actually calculating a cost value or a benefit value, e.g. by simply analysing a predetermined criterion for which the cost and benefit balance was previously established. An example of this is to stop the measurement of status information on access paths under observation if the power supply of the communication system is below a predetermined threshold and the signal quality on the active access path is above a predetermined threshold, as in such a case the cost in terms of energy is considered to outweigh any benefit in improved communication quality. On the other hand, it is also possible to explicitly calculate a cost value and/or a benefit value, e.g. based on mathematical functions or on appropriate look- up tables, and to then modify the monitoring and/or selection procedure in accordance with the cost value, benefit value or the relationship between the cost and benefit values. Brief description of figures These and further advantages of the present invention will become more apparent from the following description of preferred embodiments, which makes reference to the enclosed figures in which Fig. 1 shows a schematic representation of an embodiment of the present invention; Fig. 2 shows an arrangement of a communication system that can communicate with a network via a plurality of access paths; and Fig. 3 shows a flowchart of a method embodiment of the present invention. 6 Detailed description of embodiments Fig. 1 shows an embodiment of the present invention, where the inventive concept is applied to an ambient network scenario. Reference numeral 10 describes a communication system, which can be a single unit, like a mobile telephone device, or can be a system of distributed entities, like a personal area network. The communication system 10 is depicted schematically as comprising a plurality of connection entities 25-28, where each connection entity serves to establish one or more communication links in accordance with a different radio access technology. For example, connection entity 25 can be arranged for establishing a WLAN link, connection entity 26 can be arranged for establishing a WCDMA link, connection entity 27 can be arranged for establishing a WiMAX link and connection entity 28 can be arranged for establishing a WINNER link. Naturally, these are only examples, and more or less different wireless access technologies could be provided, and other wireless access technologies could be used instead of those indicated as examples. The communication system 10 has a Generic Link Layer (GLL) entity 24 and a Multi-Radio Resource Management (MRRM) entity 200. The GLL entity 24 comprises generic functions which enable and facilitate efficient link-layer interworking among the diverse radio accesses 25-28. The concept of GLL is well known in the art, such that a further description is not necessary. The MRRM entity provides a generic functionality for the management of the plurality of radio accesses 25-28. For this purpose, the MRRM entity 200 comprises an access controller 22. In accordance with the embodiment of the invention, an access path monitor 21 is also provided, which is arranged for obtaining status information related to a status of one or more access links 201-206 provided by the communication entities 25-28. The controller 22 in accordance with the embodiment of the invention is arranged in such a way that it can select an access link for a communication session from among the different access links in accordance with a selection procedure and in dependence on the status information provided by the access path monitor 21. The 7 MRRM entity 200 furthermore comprises a modifier 23 arranged for modifying one or both of the monitoring procedure of the access path monitor 21 and the selection procedure of the controller 22 in accordance with a modification procedure and in dependence on decision information. Fig. 1 furthermore shows an entity 29, which schematically summarizes all further entities of the communication system 10 for sending or receiving data. For example, if the communication system 10 is a mobile terminal, such as a mobile telephone device, the entity 29 will comprise well known functions provided above the link layer, such as telephone applications, multi-media applications, etc. As has already been mentioned above, the communication system 10 can be a unit or a system of distributed entities. Equally, the access path monitor 21, the access controller 22 and the modifier 23 can be provided in a single unit, e.g. in a single programmable processor, or can be individual entities that are distributed over different locations. According to a preferred embodiment, the communication system 10 is a unit, such as a mobile terminal capable of multiple radio access using at least two different radio access technologies, and the monitor 21, controller 22 and modifier 23 are all provided as functions within a programmable processor. Expressed as a method, the present invention can be embodied as shown in Fig. 3, where the flowchart shows a monitoring procedure S31 as executed by access path monitor 21, followed by a selection procedure S32 as executed by access controller 22, followed by a modification procedure S33 as executed by modifier 23. Naturally, Fig. 3 is only an example, and the three procedures can also be provided in parallel. As can be seen from the above, the present invention can be embodied as hardware, software or any suitable combination of hardware and software. In Fig. 1, communication system 10 can be regarded as an Ambient Network. Fig. 1 shows a second Ambient Network 80, which comprises 8 communication entities 31-34 and 41-43 for establishing links with communication system 10. For example, entity 31 can be associated with the WINNER access technology, entity 32 with WLAN access technology, entity 33 with WCDMA access technology and entity 34 with WiMAX technology. Equally, communication entity 41 can be associated with WCDMA access technology, entity 42 with WiMAX access technology and entity 43 with WINNER access technology. The communication entities 31-34 are associated with a GLL entity 35 and the communication entities 41-43 are associated with a GLL entity 44. In the example of Fig. 1, the two GLL entities 35 and 44 are associated with a common MRRM entity 50. The ambient network 80 furthermore comprises a connection or gateway entity 60 to a communication network (not shown), such as telephone network, an intranet or the Internet. As an example, the communication entities 31-34 can be associated with one wireless base station and the communication entities 41-43 with another wireless base station. Similar to the description of communication system 10, the ambient network 80 may also be a unit or may be spread out over several locations. Therefore, the just described entities 31-35, 41-44, 50 and 60 may be located together or spread out over several locations and individual networks. It is therefore noted that the representation in Fig. 1 is schematic and oriented along the logical arrangement of entities within a hierarchy of communication layers. In the example of Fig. 1 link 201 is a WLAN link, links 202 and 204 are WCDMA links, links 203 and 205 are WiMAX links and link 205 is a WINNER link. As an example, the access path monitor 21 can obtain status information related to the status of WLAN link 201 and the status of WCDMA links 202 and 204. In this case WLAN link 201 can be seen as an example of a group of first access paths and WCDMA links 202, 204 as a group of second access paths of a different access technology than the first group. In the example of Fig. 1, the monitor 21, the access controller 22 and the modifier 23 are shown as parts of system 10. However, it 9 should be noted that one, two or all of entities 21, 22 and 23 can also be provided in the ambient network 80. In this case the entities 10 and 80 together form a communication system that embodies the present invention. For example, the monitor 21 and modifier 23 can be provided in MRRM entity 50 or in one of GLL entities 35 and 44. Equally, the entities 21, 22, and 23 can be spread out over the entities 10 and 80. For example, the monitor 21 could have a part in MRRM entity 200 and a part in MRRM entity 50, and/or parts in the GLL entities 24, 35 and 44. The same applies to the access controller 22 and the modifier 23, i.e. these entities could be spread out in the same way. The obtaining of information can be done in any suitable or desirable way, e.g. by performing measurements at communication system 10 with respect to desired parameters, such as the signal quality on a link (measured in any suitable or desirable way, e.g. as a bit error rate, a signal strength value, an interference level etc.), a load value (measured in any suitable or desirable way, e.g. as a number of different terminal devices sharing a given link, as a utilization ratio, etc.) etc. On the other hand, the information may also be obtained in other ways e.g. received from the ambient network 80, which may perform measurements and convey the measured information or which may receive such information from the overlying communication network. The status information can be expressed in any suitable or desirable way, e.g. it can be qualitative information such as a message indicating "link not available" or it can be quantitative information such as the numerical value of a given parameter. The selection procedure for selecting an access path for a communication session from among first and second access paths can be chosen in any suitable or desirable way. The present invention is not limited to any particular selection procedure, as the selection procedure can be chosen in dependence on a large number of preferences and strategies. For example, the selection procedure can consist in selecting the link with the highest quality, or it can 10 consist in choosing the link with the lowest load, or it can consist in choosing the link consuming the least amount of energy, etc. It is noted that in the present invention, the selecting of an access path can consist in selecting one access path for carrying a communication session, or can consist in selecting a plurality of access paths for carrying one communication session. As an example, in Fig. 1 a session may be carried over any one of links 201-206, or over more than one of said links simultaneously, e.g. a part of a session may be carried over WLAN link 201 and another part over WCDMA link 204. The selection procedure can comprise the initial selection of an access path for a new session, and preferably also comprises the possibility of switching an established communication session between access paths of different access technologies while the communication session is active. For example, in Fig. 1 the access controller 22 can be arranged to perform a selection procedure such that an active session can be switched from e.g. WCDMA link 204 to WLAN link 201 based on obtained status information, e.g. when the signal quality on link 204 falls below a threshold, when the load on link 201 falls below a predetermined threshold or when the link quality on link 201 exceeds that on link 204 and link 201 is available. The modification procedure can be chosen in any suitable or desirable way in view of a desired strategy and a desired objective. The decision information used by the modifier 23 in the modification procedure will equally depend on the desired strategy or objective. This will become readily understandable from the examples in the following description. In a general sense, the modifying of a procedure (one or both of the selection procedure and the monitoring procedure) can comprise changing parameters used by the procedure (such as e.g. changing the frequency with which the monitoring procedure obtains status information, changing the frequency with which the access path 11 monitor forwards obtain status information to the access controller, or changing the frequency with which the selection procedure takes a selection decision) or the modifying can also consist in adapting the process of the procedure itself. The latter can e.g. be done by having a procedure which comprises a plurality of subroutines or modes, and letting the modification procedure choose a subroutine or mode. As an example of the latter, a monitoring procedure can be envisioned in which in a first mode a large number of access paths is measured at a high frequency, such that this mode is energy intensive, and in a second mode less access paths are measured at a lower frequency, i.e. the second mode is less energy intensive. Then, depending on associated decision information, such as the energy status of the communication system (e.g. the battery status), an appropriate monitoring mode can be chosen. In other words, if the energy status of the communication system is low (i.e. below a predetermined threshold), then the mode that consumes less energy is chosen, whereas if the energy status of the communication system is high (i.e. above a predetermined threshold), the mode with greater energy consumption is chosen. As already mentioned, the modifying of the monitoring procedure and/or selection procedure may comprise modifying the frequency with which status information is obtained and/or modifying the frequency with which the status information is forwarded from the access path monitor to the access controller and/or modifying the frequency at which the selection procedure takes a selection decision. The frequency of obtaining status information, e.g. the frequency of performing measurements on the access paths under observation, and the frequency with which status information is forwarded, is a measure of the amount of energy, processing power and signalling overhead invested in the monitoring and selecting operation. As a consequence, if it is desired to reduce this invested effort under certain situations, then the decision information is chosen to be able to judge the presence or absence of the certain situation (e.g. the certain situation can be a low power status of the communication system or a high processor load, and the decision information is then appropriately chosen, e.g. the power status of the 12 communication system or the processor status), and if the certain situation is present, then one or both of the above-mentioned frequencies can be reduced. On the other hand, if the monitoring or selection procedure are adjusted to expend little effort, the determination that the above-mentioned certain situation is no longer present can be used as a basis for modifying one or both of the monitoring procedure and selection procedure by increasing one or both of the above-mentioned frequencies. Alternatively or additionally, modifying the monitoring procedure may also comprise modifying the status information being obtained for one or more of the access paths. For example, this can mean changing the type of information, such as going from one type of information to another, or adding a new type of information in addition to the old type. For example, if the access path monitor 21 in Fig. 1 is obtaining signal quality information for link 201, a modification of the monitoring procedure can consist in switching to monitoring load information, or can consist in additionally monitoring load information. Additionally or alternatively, modifying the monitoring procedure may comprise modifying the number of access paths for which status information is obtained. As an example, if it is desirable to reduce the effort expended on monitoring access paths, then the number of access paths being observed can be reduced. The modification procedure may furthermore be arranged such that the selecting procedure is modified by modifying the number of access paths from among which an access path for a communication session is selected. In other words, the selecting procedure may be such that a selection is not performed for all available access paths but only from a limited set. For example, in Fig. 1 the selection procedure performed by access controller 22 could be such that only links 201, 202 and 204 are considered for selection, although further links are available. In accordance with the present embodiment, the modification procedure can comprise increasing or reducing the access paths considered for selection. In keeping with the just mentioned example, the selection procedure could be modified by 13 removing link 202 from the set of links considered for selection, such that a selection is only performed between link 201 and link 204, if it is desired to reduce the amount of effort expended on the selection operation. It is noted that the modification of the selection operation can go so far as to reduce the set of access paths under consideration to one, thereby effectively disabling the selection operation. Equally, modifying the number of access paths being monitored by the monitoring procedure can also reduce this number to one or zero, thereby effectively disabling the monitoring procedure. The modifying of the monitoring procedure or selection procedure by modifying the corresponding number of access paths under consideration will now also be explained with respect to an example known from the above-mentioned document IST-2002-507134-AN/WP2/D02 on Ambient Networks. In connection with Ambient Networks and a plurality of radio access links it is known to define a plurality of sets: a Detected Set (DS), which is the set of all access links that are available and to which an ambient network could potentially connect. Some of the access links may actually not have been detected by measurements but can be known due to context information, i.e. it can be known from a MRRM entity that at a certain position a certain radio access is available (such as a WLAN hotspot at e.g. an airport). Such radio accesses can be announced by means of radio access advertisement messages. a Candidate Set (CS) , which is a subset of the detected set, and can be used by an ambient network to connect to one or more other networks. The detected set can contain radio accesses, which are not part of the candidate set. These radio accesses can e.g. be rejected for a given Ambient Network due to policy reasons or due to technical limitations of the access network to use a certain radio access. 14 MRRM Active Set (AS), which is a subset of the candidate set. The MRRM active set contains all radio accesses which are actively managed for a certain communication session. There can be different MRRM active sets for different sessions. The MRRM active set contains only elements out of the candidate set which also fulfil predetermined minimum requirements, e.g. in radio link quality or with respect to system load, and also fulfil service specific requirements for the communication session. The latter can be a quality of service requirement (such as data rate, delay, jitter, etc) , but can also be security requirements (such as encrypted transmission, authenticated transmission, etc). GLL active set, which is a subset of MRRM active set. The GLL active set contains a number of radio accesses that may be dynamically assigned to a communication session by one or more GLL entities. In the example of Fig. 1, the detected set could e.g. be all of links 201-207, where link 207 is indicated as a link not being used by communication system 10 but available. The candidate set could e.g. be links 202-206 while the MRRM active set could e.g. be links 203-206. Finally, the GLL active set could e.g. be links 204-206, which are all associated with the GLL entity 44. In a communication system using the above-mentioned sets of access links or access paths, the modification procedure can comprise changing the links or paths in one or more of any of the above- mentioned sets. For example, the modification of the monitoring procedure may comprise changing the number of links or paths in the MRRM candidate set, and the modifying of the selecting procedure may comprise changing the number of links or paths in the GLL active set. As already mentioned previously, the decision information used by the modifier for modifying one or both of the monitoring procedure and the selection procedure can be chosen in any suitable or desirable way, depending on the desired objective and strategy. 15 According to one example, the decision information can at least partially be derived from the status information that is being obtained by the monitoring procedure. As an example, the status information can comprise measurements of the signal quality on the access path currently being used for carrying the communication session, and measurements of signal quality on further accessible links. This signal quality information can be used as decision information by the modification procedure in the following way. If the signal quality on the currently used access path exceeds a predetermined threshold, then the monitoring procedure and selection can be disabled, whereas if the signal quality is below the threshold, then the monitoring procedure and selection procedure are activated. The decision information can be identical to the status information, or the status information can be processed for deriving the decision information. For example, if the status information is a parameter, then the temporal change rate (time differential) of said parameter can also be used as decision information. As with the status information, the decision information can also be of any desirable type i.e. it can be qualitative, such as a message indicating "link not available", or it can be qualitative, like a numerical value. According to a preferred embodiment, the decision information comprises numerical values. More preferably, the numerical values comprise values of one or more decision parameters. Examples of such decision parameters can be the previously mentioned status parameters, such as signal quality or load on an access path. The modification procedure can then comprise comparing parameter values associated with one of the decision parameters with a respective threshold. For example, if the signal quality value on the currently used access path is above a predetermined quality threshold and/or the load on the currently used access path is below a predetermined load threshold, then the modification procedure can appropriately modify the monitoring procedure and/or selection procedure, e.g. by reducing the frequency of obtaining information 16 on monitored access paths (up to disabling the monitoring procedure) and by reducing the number of access paths considered for selection (up to disabling the selection procedure). Another example of numerical values comprised in the decision information are change rate values of one or more of the mentioned decision parameters. These change rate values derived from a given decision parameter can be compared with a respective threshold as a part of the modification procedure. For example, if the time differential of the signal quality on the currently used access path is below a quality change rate threshold, and/or the time differential of the load on the currently used access path is below a predetermined load change rate threshold, then the modification may comprise reducing the effort expended on performing the monitoring procedure and/or selection procedure, e.g. by reducing the rate of obtaining status information for the access paths of the different access technologies. As can be seen from the above examples, the decision information may comprise a traffic load indication. This indication can be a quantitative or qualitative information, and it can be indicative of the traffic load on an individual path or the traffic load in a larger context, e.g. the traffic load in an entire Ambient Network under consideration. The decision information can also comprise information derived from the traffic load indication, such as the time differential of traffic load values. The decision information can also comprise a signal quality indication, which can be a qualitative or quantitative information. The signal quality indication can be indicative of the signal quality on the one or more currently used access paths for a communication session, or of the signal quality on access paths being monitored. The decision information can also comprise information derived from the signal quality indication, such as the time derivative of signal quality values. As an example, if it is determined that the change rate of signal quality on access paths being monitored falls below a predetermined threshold, then the 17 modification procedure can reduce the frequency with which status information is obtained, as a high frequency is not necessary. Additionally, or alternatively, in the event that the communication system is mobile, the decision information may comprise an indication of the velocity of the communication system. If the communication systems velocity falls below a predetermined threshold, then the modification procedure can adjust the monitoring procedure and/or selection procedure in such a way as to reduce the effort expended on monitoring and selecting access paths. Namely, if the communication system is only moving very slowly or not moving at all, then there is less expected benefit in the monitoring and selection procedures, such that it can be desirable to reduce the expended effort. Alternatively or additionally the modification procedure can be such that the decision information comprises an indication of resources available to the communication device. Such resources can e.g. be power resources (such as the battery power level) or processing resources (such as the degree to which a processor is being utilized). As indicated previously, in the event that the available resources are low (e.g. low power or little free processing capacity), the modification procedure may modify the monitoring procedure and/or selection procedure in such a way as to reduce the expended effort, e.g. by reducing the frequency with which status information is obtained. As already mentioned in the summary of invention, the choice of the modification procedure and the associated decision information can be done in view of an implicit analysis of costs and/or benefits or a balancing of implicit costs and benefits. However, the decision information may also comprise the use of explicit cost and/or benefit values. Namely, the decision information may comprise one or both of estimated benefit values and estimated cost values for a plurality of different settings of the monitoring procedure. Equally, the decision information may comprise one or both of estimated benefit values and estimated cost values for a plurality 18 of different settings of the selection procedure. An example of a cost function for monitoring a plurality of access paths is: where CMon^tor is the monitoring cost, fMonitor i is tne frequency of monitoring access path i and cMonitor i 1S the cost for monitoring access path i. The sum runs over all access paths i being monitored. The cost cMonitor j_ can be expressed in any suitable or desirable way, i.e. can be a dimensionless variable or can be expressed in terms of a parameter, such as in terms of consume energy. Similarly to equation (1) , the costs for signalling the status information for the access path monitor to the access controller can be expressed as: where fForward i ^s the frequency of forwarding status information for access path i and Cporwarcj i is the cost of forwarding status information for access path i. Similar functions can be formulated for the costs of performing the selection operation, or for the benefits of performing the monitoring procedure and/or the selection procedure. As an example, the modification procedure can be such that the monitoring cost is calculated in accordance with equation (1), and if the total cost CM0n-L^-or exceeds a predetermined threshold, then the monitoring frequencies fMonitor i are changed to make Cf/jQ^tor again fall below the threshold. It is noted that costs and/or benefits can be determined in accordance with mathematical functions as given in above examples 19 (1) and (2), but can also e.g. be determined on the basis of multi- dimensional tables or mappings where a cost value and/or a benefit value is assigned to a vector of input parameter values, such as a vector of the frequency value of monitoring, the number of access paths being monitored, etc. As a further alternative or addition, the decision information used by the modifier may comprise preference information set by one or both of a user of the communication system and an operator of the network. For example, the user of the communication system may have a preference for a certain access technology, and the modifier can be arranged to modify the monitoring procedure in such a way that access paths of said preferred access technology are always monitored if available. As a further alternative or addition, the modifier can be arranged such that the decision information comprises an indication of the momentary sensitivity of the selecting procedure to a timeliness of the status information. When monitoring access paths and performing a selection procedure there is the problem that a delay occurs between the gathering of the status information and the use of said status information in the selection procedure. This delay is caused by the time required for obtaining the status information, and the time necessary for forwarding the status information from the access path monitor to the access controller. Furthermore, the delay depends on the frequency with which status information is obtained and the frequency at which the status information is forwarded from the access monitor to the access controller. Namely, if status information for a given access path being monitored only arrives every At at the access controller, then at the end of the period At the momentary status may have already changed considerably. The momentary sensitivity of the selecting procedure can therefore be an important parameter in modifying one or both of the monitoring procedure and the selection procedure. For example, if it is determined that the momentary sensitivity is above a predetermined threshold, then the modification procedure can modify the monitoring procedure by increasing the frequency of obtaining status 20 information, and vice versa if the momentary sensitivity is below a predetermined threshold, then the modification procedure can reduce the frequency at which status information is obtained. The sensitivity can be e.g. be indicated in terms of the differential of a mathematical selection function with respect to the input status parameter values. As a further alternative or addition, the modifier can be arranged such that said modification procedure comprises a determination of whether one or more service requirements are fulfilled for the communication session. The service requirement can be chosen in any suitable or desirable way, e.g. it can be a data rate value or some other quality of service measure. The criterion for fulfilment is set by defining an associated threshold accordingly. As an example, if the communication session of a user of the communication system is a voice communication, a data rate threshold of e.g. 50 kbit/s can be considered sufficient, such that if the momentary access path or paths provide this data rate, even if a new access path is available that has a higher data rate, there is no benefit in switching to it. As a consequence, the modifier can modify the monitoring procedure and/or the selecting procedure in such a way that the effort expended is reduced if the service requirement is fulfilled, e.g. by disabling the monitoring procedure and the selecting procedure if the threshold data rate is exceeded by the momentary access path(s). The present invention is generally concerned with making the monitoring procedure and/or the selection procedure of a communication system that can access a network via access path of different access technology dynamically adaptable or modifiable, in order to be able to dynamically adjust the trade-off between an effort expended for performing the monitoring and selecting with respect to the benefit derived therefrom. Generally, the balance between cost and benefit is such that when the expected benefit decreases, the expended effort for monitoring and selecting can be decreased and vice versa. For example, if the monitoring procedure is operated to less frequently obtain status information (e.g. by 21 less frequently performing measurements), this reduces the amount of signalling overhead and reduces energy consumption. At the same time, the selection procedure must make decisions based on less timely status information, which can reduce the benefit of performing the selection procedure. As already indicated in some of the examples above, the access path monitoring (monitoring procedure) and access controller (selection procedure) can be modified in view of one or more of the following input parameters: traffic load and experienced rate of change in traffic load. If the traffic load is below a predetermined threshold and/or the rate of change of traffic load is below a threshold, then the monitoring frequency can be reduced. access path quality and experienced rate of change in access path quality. If the access path quality is above a predetermined threshold and/or the rate of change of access path quality is below a predetermined threshold, then the monitoring frequency can be reduced. a number of users in the environment. If few users are in the environment, the benefit of multi-user diversity is low. In this case a diversity gain can be achieved by selecting the access path based on instantaneous access path quality. If many users are present, little diversity gain can be achieved. The diversity gain is a type of benefit. As a consequence, depending on the number of users in the environment of the communication system, the selection procedure can be modified, e.g. the number of access paths considered in the selection procedure is reduced if the number of users in the environment increases beyond a predetermined threshold, and the monitoring procedure is accordingly also modified to provide the appropriate status information. if multiple access paths are available, they can be classified into different sets, as explained previously with respect to the 22 Detected Set, Candidate Set, MRRM Active Set and GLL Active Set. Depending on the set to which an access path belongs, the frequency with which status information is obtained can be adapted. performance desired by user. An example of a user preference is an indication of the desired performance, e.g. a desired quality of service (QoS) or a desired data rate. If the user achieves the desired performance, then the effort expended on the monitoring procedure and selection procedure can be reduced. performance allowed by network. If a user achieves the performance he is allowed by the network, e.g. in terms of quality of service or data rate, then the effort expended on the monitoring procedure or selection procedure can be reduced. battery power of communication system. If the battery of the communication system is low, then the frequency for obtaining status information in the access path monitor can be reduced, the frequency for forwarding status information to the access controller can be reduced, and the processing expended for the selection procedure can be reduced. As an example, both the monitoring procedure and the selection procedure can be effectively disabled if the battery power falls below a predetermined threshold value. system resources. The conducting of a selection procedure generally improves the efficient use of system resources, both in the communication system and in the network. However, if enough system resources are already available (i.e. the value of an appropriate system resource measure is above a predetermined threshold), then the effort expended on the monitoring procedure and the selection procedure can be reduced, e.g. by reducing the frequency which status information is obtained. user behaviour. If the communication system is mobile and a user of the communication system is moving faster than a predetermined velocity threshold, the status parameters may vary rapidly. As a consequence, it can be desirable in this case to 23 increase the frequency at which status information is obtained, in order to have timely status information. The strategies and desired objectives when modifying the frequency at which status information is obtained and the frequency at which status information is forwarded can be manifold. In this connection, one can for example consider a service criterion, a resource criterion or an MRRM performance criterion. The service criterion defines to what extent the requirements of the service and/or the user are met. An example of a service criterion is: is the minimum quality of service threshold achieved? Another example is: is a higher quality of service level required or desired? For example, is an access path having higher resolution or higher rate available for streaming? Or as another example, is the additional cost (e.g. in monetary terms) worth the increase in service performance? A resource criterion defines to what extent transmission resources are critical. Examples are: are system resources highly utilized (e.g. high load) and how many resources remain available? Is the battery power low? The MRRM performance criterion relates to what the estimated benefit or gain of Multi-Radio Resource Management is. In several studies a number of MRRM algorithms have been studied to select a radio link for a user connection. Input parameters can be link quality, service requirements, system load, etc. It has been shown that these algorithms can provide everything from substantial gains in performance to only very small gains. The gain or benefit depends on many aspects: what radio access technologies are used, what deployment patterns are used, how the traffic demand is distributed with respect to the areas of service (e.g. radio cells), what are the service requirements, what input parameters are used for the selection procedure and which selection algorithms are used, how many users are in the system (e.g. due to variations of link quality, a selection procedure can provide a multi-access diversity gain. For a large number of users there is a multi-user diversity gain, which exploits channel variations. If a large multi-user 24 diversity gain is achieved, little additional gain remains for access selection diversity), what costs (in terms of any desired measure) are involved for performing the monitoring procedure and to what extent does this use up the achieved or achievable benefit/gain, what is the position of the MRRM input parameter(s). In this respect, the precision of estimation, the delay of distributing measurements and the degree of variability in the system (variation of load and link quality, e.g. caused by the users mobility) play a role. As explained in connection with Ambient Networks, a number of sets can be defined on which different MRRM functions are performed. Most of these functions require a monitoring procedure for obtaining status information. Within the detected set and candidate set, monitoring provides occasional information about information elements like link quality, load etc. Based on this monitoring input, an access path can be moved to the MRRM/GLL active set. Within the active set, MRRM performs selection and allocation of access paths to user sessions. In order to achieve this, it is desirable to have a more precise monitoring procedure, e.g. status information is obtained more frequently and/or more different types of status information are obtained. The following examples are further embodiments of the invention in this context: Based on the service criterion, resource criterion and/or MRRM performance criterion, it can be decided to what extent a selection procedure in MRRM is feasible. If there is no problem, or little benefit expected, then the expended effort can be kept low. For example, the size of the active set and candidate set can be held to a predetermined small number. If the active set size is limited to one, no selection procedure is effectively performed. Also, the number of alternative access paths in the candidate set can be limited in a similar way. If a selection procedure is performed across a number of access paths (e.g. the active set contains several elements), the appropriate access selection algorithm can be chosen depending on 25 system parameters like access path quality, service, load, or combinations thereof. The access selection frequency can be adapted according to the sensitivity of input parameters of the access selection function and the dynamic variations of system parameters. For example, the gain or benefit of MRRM decreases if outdated input parameters (e.g. measured load or link quality values) are used. At the same time, the consumed resources for the monitoring procedure decrease. If the variability of the system increases, then it is desirable to also increase the frequency at which status information is obtained and/or at which access paths are selected. It may be noted that many of the above examples referred to the embodiment shown in Fig. 1. Although Fig. 1 constitutes a preferred embodiment of the invention, the present invention is by no means restricted thereto. For example, the present invention is not restricted to being applied in a communication system that accesses a network via a group of first radio access links of a first technology and a group of second radio access links of a second access technology different from the first access technology. Namely, the invention also applies to the more general case of access paths that may be multi-hop relay links. Furthermore, the access paths do not have to be radio access paths, as the invention equally applies to the case of wire-bound access paths of differing access technology. As the present invention is not restricted to the field of wireless communication, it can also be applied in the area of media routing. Overlay networks can be used to transmit data to a receiver via different networks. A Media Port makes a routing decision of selecting the right network. For this, the Media Port obtains monitoring information about the status (e.g. load) and capabilities of the different networks. This can also be considered as a monitoring procedure within the meaning of the present invention. The monitoring procedure in this case evaluates a complete sub- network. It can consist of measurement procedures (link ping packet trains), end-user quality of service reports or feedback information of sub-network-specific management functions. 26 Although the present invention has been described with reference to preferred embodiments, these only serve to illustrate the invention, but are by no means restrictive. The invention is defined by the appended claims. Reference signs serve to make the claims easier to read but do not have any limiting effect. 27 WE CLAIM: 1. k communication system arranged for accessing a network via a group of first access paths of s. first access technology and a group of second access paths of a second access technology different from said first access technology, comprising an accesa path monitor for obtaining status information related to a status of one or more of said first access paths and one or more of said second access paths in accordance with a monitoring procedure, an access controller for selecting an access path for a communication session from, ^mong said first and second access paths in accordance with a selection procedure and in dependence on said status information, and a modifier for modifying one or both of said monitoring procedure and said selection procedure in accordance with a modification procedure and in dependence on decision information, wherein said decision information comprises an indication of resources available to said oommunication system. 2. h coiranunication system according to claim 1, wherein said access controller is arranged for switching said communication session between said first and second access paths while said communication session is active. 3. A communication system according to one of claims 1 or 2, wherein modifying said monitoring procedure comprises modifying a frequency with which said status information is obtained. 28 4. A coiraciunication. system according to one of claims 1 to 3, wherein modifying said monitoring procedure coirgprises modifying a frequency with which said status information is forwarded from said access path monitor to said access controller. 5. A communication system according to one of claims 1 to 4, wherein modifying said monitoring procedure comprises modifying the status information being obtained for one or more of said access paths. 6. A communication system according to one ofi claims 1 to 5, wherein modifying said monitoring procedure comprises modifying the number of access paths for which status information, is obtained. 7. A communication system according to one of claims 1 to 6, wherein modifying said selecting procedure comprises modifying the number of access paths from among which an access path for a communication session is selected, 8. A communication system according to one of claims 1 to 7, wherein said decision information is at least partially derived from said status information. 9. A communication system according to one of claims 1 to 8r wherein said decision infc-.rma.tian comprises numerical values.. 10. A communication system according to claim 9J wherein said numerical values comprise values of one or more decision parameters. 29 11. A communication system according to claim 10, wherein said modification procedure comprises comparing parameter values associated with one of said decision parameters with, a respective threshold. 12. A communication system according to claim 9, wherein said numerical values comprise change rate values of one or more decision parameters. 13. A communication system according to claim 12, wherein said modification procedure comprises comparing change rate values associated with one of said decision parameters with a respective threshold. 14. A communication system according to one of claims 1 to 13, wherein said decision information comprises a traffic load indication. 15. A communication system according to one of claims 1 to 14, wherein said decision information comprises a signal quality indication. 15. A communication system according to one. of claims 1 to 15j wherein said communication system is mobile and said decision information comprises an indication of a velocity of said communication system. 17. A communication system according to one of claims 1 to 15, wherein said decision information comprises one or both of estimated benefit values and estimated cost values for a plurality of different settings of said monitoring procedure. 30 18. A communication system according to one of claims 1 to 17, wherein said decision information comprises one or both of estimated benefit values and estimated cost values for a. plurality of different settings of said eeleation procedure. 19. A communication system according to one of claims 1 to 18, wherein said decision information comprises preference information set by One or both of a user of said communication system and an operator of said network. 20. A communication system according to one of claims 1 to 19, wherein said decision information comprises an indication of the momentary sensitivity of said selecting procedure to a timeliness of said status information. 21. A communication system according to one of claims 1 to 20, wherein said modifier is arranged such that said modification procedure comprises a determination of whether one or more service requirements are fulfilled for said communication session. 22. A modifier for modifying one or both of a monitoring procedure of an access path monitor and a selection procedure of an access controller, arranged for operating in a communication system according to one of claims 1 to 21. 23. A method of controlling access to a network via a group of first access paths of a first access technology and a group of second access paths of a second access technology different from said first access technology, comprising 31 obtaining status information related to a status of one or more of said first access paths and one or more o£ Said second access paths in accordance with a monitoring procedure, selecting an access path for a eortminication session from among said first and second access paths in accordance with a selection procedure and in dependence on said status information, end modifyins one or both of said monitoring procedure and said selection procedure in accordance with a modification procedure and in dependence on decision information, wherein said decision information comprises an indication of resources available to said communication system. 24. A computer program product comprising a computer program that is arranged to execute the method of claim 23 when executed by a communication system. Dated this 3rd day of March 2008 A communication system is provided which is arranged for accessing a network by a group of first access paths and a group of second access paths. The first and second access paths have a different access technology. An access path monitor is provided for obtaining status information related to the access paths in accordance with the monitoring procedure. An access controller is provided for selecting an access path for a communication session in accordance with a selection procedure and in dependence on the status information. A modifier is provided for modifying one or both of the monitoring procedure and the selection procedure in accordance with a modification procedure and in dependence on decision information.

Full Text

Field of the invention
The present invention relates to a communication system for
accessing a network via a group of first access paths of a first
access technology and a group of second access paths of a second
access technology, said second access technology being different
from the first access technology. The application also relates to a
method of network access via access paths of different access
technology.
Background of the invention
In the field of communications it is known to provide systems in
which a given device can obtain access to a network via access paths
of differing access technology. This is shown schematically in
Figure 2. A communication system 10, e.g. a wireless communication
device such as a mobile telephone is able to communicate with
stations 11 and 12 that provide communication paths 101, 102 of a
first access technology, e.g. a GSM (Global System for Mobile
Communication) connection, a WCDMA (Wideband CDMA) connection, a
WiMAX (Worldwide Interoperability for Microwave Access) connection,
a WINNER (Wireless World Initiative New Radio) connection, a WLAN
(Wireless Local Area Network) connection, etc. The communication
system 10 can furthermore communicate with stations 13, 14 over
communication paths 103, 104 that are of a different access
technology than paths 101, 102. If the paths 101, 102 operate in
accordance with one of the above-mentioned technologies, then the
paths 103, 104 can be provided by any one of the other technologies.
The communication system 10 accesses the network 15, e.g. a
telephone network or a computer network, such as an intranet or the
Internet via the paths 101-104.
If the stations 11-14 and the communication system 10 are arranged
in such a way that the communication system 10 can from one location
access the network 15 via both an access path 101, 102 or 103, 104,
then this leads to the problem of managing the selection of one or
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more paths for conducting a communication session with the network
15.
The basic situation of having heterogeneous wireless technologies
for communication in a given location has already been studied, e.g.
in the context of so-called Ambient Networks (AN), see document ISD-
2002-507134-AN/WB2/D02, MRA Architecture by Rolf Sigle et al,
version 1.0, released February 2, 2005. The inventors of the present
application are also authors/editors of this document, the contents
of which is herewith incorporated by reference.
In the context of Ambient Networks it has been proposed to use so-
called Multi-Radio Resource Management (MRRM) for managing the
different access technologies. An MRRM functionality coordinates the
different radio access technologies by mapping service requests on
available radio resources for both single-and multi-hop links.
Different MRRM objectives can be used e.g. maximizing radio resource
efficiency, service coverage or service quality, or enabling
services otherwise impossible to deliver over a single radio access.
Intelligent load distribution algorithms inside MRRM increase the
overall effective network capacity. MRRM functions include
advertising, discovery, selection, resource monitoring, and spectrum
and congestion control. By monitoring the access paths and obtaining
status information related to access paths of different access
technology, an access controller can select an access path for a
communication session in accordance with a selection procedure and
in dependence of the status information.
Document EP 0 812 119 A2 discusses an improvement of the idle or
standby mode in mobile stations of a cellular communication system.
It is mentioned that the IS-136 and the GSM standard require an idle
mobile station, i.e. a mobile station that is not in the process of
conducting a communication session, to monitor control channels of
neighbouring cells. EP 0 812 119 A2 proposes a different standby
mode according to which when making measurements of a currently
assigned control channel and other control channels, measurements of
at least some of the other control channels can be terminated if it
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is detected that the mobile station has become stationary. The
latter can be done by measuring the received signal strength of a
monitored neighbouring channel and comparing the temporal change in
signal strength with a predetermined threshold. If the change in
received signal strength falls below this threshold it is determined
that the mobile station is stationary.
Object of the invention
The object of the invention is to provide an improved communication
system and method of accessing a network via groups of access paths
of different access technology. It is noted that this object is not
restricted to systems having wireless access technology, as the
problem of making a selection between access paths of different
technology will also occur if one or more of the groups of access
paths are wire-bound.
Summary of the invention
The object of the invention is fulfilled by a communication system
having the features of claim 1, a modifier having the features of
claim 23, a method of controlling access to a network according to
claim 24, and a computer program product of claim 25. Advantageous
embodiments are described in the dependent claims.
In accordance with the present invention a communication system
arranged for accessing a network via a group of first access paths
of a first access technology and a group of second access paths of a
second access technology different from the first access technology
is provided. The communication system can be a terminal, such as a
mobile telephone capable of communication in accordance with a
variety of wireless technologies, or the communication system can
itself be a network, such as a Personal Area Network. The group of
first access paths can have one or more members, and the group of
second access paths can have one or more members. Naturally, the
communication system can be arranged for accessing a network via
more than two different types of access technologies.
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An access path monitor is provided for obtaining status information
related to a status of one or more of the first access paths and one
or more of the second access paths in accordance with a monitoring
procedure. The obtaining of information can e.g. be done by
performing measurements on the access paths of interest, or can be
obtained in other ways, e.g. received from the network. It is noted
that the term "access path" describes any suitable access
connection, e.g. a single link, a number of consecutive links, or an
entire subnetwork.
Furthermore, an access controller is provided for selecting an
access path for a communication session from among the first and
second access paths in accordance with a selection procedure and in
dependence on the status information obtained by the access path
monitor. The selecting preferably not only comprises the initial
selection of one or more paths for a given session that is to be
established, but also the subsequent switching of an established
session from an access path of the first access technology to an
access path of the second technology or vice versa, while the
communication session is active.
Furthermore, in accordance with the invention a modifier for
modifying one or both of the monitoring procedure and the selection
procedure in accordance with a modification procedure and in
dependence on decision information is provided. The modifying can be
done in any suitable or desirable way e.g. by changing parameters
used by a procedure, e.g. the frequency at which status information
is obtained. Modifying may also comprise changing a procedure or
routine itself, e.g. by switching from one subroutine or mode to
another.
In accordance with the present invention, the monitoring procedure
and/or the selection procedure can be flexibly and dynamically
adapted by the modification procedure. This provides an optimised
management of the access paths of differing technology. More
specifically, it is possible to control the modification in such a
5

way so as to optimise the trade-off between the costs (e.g. in terms
of signalling overhead, energy consumption etc.) caused by the
monitoring procedure and the benefit (e.g. in terms of improved
quality of service) provided by the selection procedure. The
balancing of cost and benefit can be done without actually
calculating a cost value or a benefit value, e.g. by simply
analysing a predetermined criterion for which the cost and benefit
balance was previously established. An example of this is to stop
the measurement of status information on access paths under
observation if the power supply of the communication system is below
a predetermined threshold and the signal quality on the active
access path is above a predetermined threshold, as in such a case
the cost in terms of energy is considered to outweigh any benefit in
improved communication quality. On the other hand, it is also
possible to explicitly calculate a cost value and/or a benefit
value, e.g. based on mathematical functions or on appropriate look-
up tables, and to then modify the monitoring and/or selection
procedure in accordance with the cost value, benefit value or the
relationship between the cost and benefit values.
Brief description of figures
These and further advantages of the present invention will become
more apparent from the following description of preferred
embodiments, which makes reference to the enclosed figures in which
Fig. 1 shows a schematic representation of an embodiment of the
present invention;
Fig. 2 shows an arrangement of a communication system that can
communicate with a network via a plurality of access
paths; and
Fig. 3 shows a flowchart of a method embodiment of the present
invention.
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Detailed description of embodiments
Fig. 1 shows an embodiment of the present invention, where the
inventive concept is applied to an ambient network scenario.
Reference numeral 10 describes a communication system, which can be
a single unit, like a mobile telephone device, or can be a system of
distributed entities, like a personal area network. The
communication system 10 is depicted schematically as comprising a
plurality of connection entities 25-28, where each connection entity
serves to establish one or more communication links in accordance
with a different radio access technology. For example, connection
entity 25 can be arranged for establishing a WLAN link, connection
entity 26 can be arranged for establishing a WCDMA link, connection
entity 27 can be arranged for establishing a WiMAX link and
connection entity 28 can be arranged for establishing a WINNER link.
Naturally, these are only examples, and more or less different
wireless access technologies could be provided, and other wireless
access technologies could be used instead of those indicated as
examples.
The communication system 10 has a Generic Link Layer (GLL) entity 24
and a Multi-Radio Resource Management (MRRM) entity 200. The GLL
entity 24 comprises generic functions which enable and facilitate
efficient link-layer interworking among the diverse radio accesses
25-28. The concept of GLL is well known in the art, such that a
further description is not necessary. The MRRM entity provides a
generic functionality for the management of the plurality of radio
accesses 25-28. For this purpose, the MRRM entity 200 comprises an
access controller 22. In accordance with the embodiment of the
invention, an access path monitor 21 is also provided, which is
arranged for obtaining status information related to a status of one
or more access links 201-206 provided by the communication entities
25-28. The controller 22 in accordance with the embodiment of the
invention is arranged in such a way that it can select an access
link for a communication session from among the different access
links in accordance with a selection procedure and in dependence on
the status information provided by the access path monitor 21. The
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MRRM entity 200 furthermore comprises a modifier 23 arranged for
modifying one or both of the monitoring procedure of the access path
monitor 21 and the selection procedure of the controller 22 in
accordance with a modification procedure and in dependence on
decision information. Fig. 1 furthermore shows an entity 29, which
schematically summarizes all further entities of the communication
system 10 for sending or receiving data. For example, if the
communication system 10 is a mobile terminal, such as a mobile
telephone device, the entity 29 will comprise well known functions
provided above the link layer, such as telephone applications,
multi-media applications, etc.
As has already been mentioned above, the communication system 10 can
be a unit or a system of distributed entities. Equally, the access
path monitor 21, the access controller 22 and the modifier 23 can be
provided in a single unit, e.g. in a single programmable processor,
or can be individual entities that are distributed over different
locations. According to a preferred embodiment, the communication
system 10 is a unit, such as a mobile terminal capable of multiple
radio access using at least two different radio access technologies,
and the monitor 21, controller 22 and modifier 23 are all provided
as functions within a programmable processor.
Expressed as a method, the present invention can be embodied as
shown in Fig. 3, where the flowchart shows a monitoring procedure
S31 as executed by access path monitor 21, followed by a selection
procedure S32 as executed by access controller 22, followed by a
modification procedure S33 as executed by modifier 23. Naturally,
Fig. 3 is only an example, and the three procedures can also be
provided in parallel.
As can be seen from the above, the present invention can be embodied
as hardware, software or any suitable combination of hardware and
software.
In Fig. 1, communication system 10 can be regarded as an Ambient
Network. Fig. 1 shows a second Ambient Network 80, which comprises
8

communication entities 31-34 and 41-43 for establishing links with
communication system 10. For example, entity 31 can be associated
with the WINNER access technology, entity 32 with WLAN access
technology, entity 33 with WCDMA access technology and entity 34
with WiMAX technology. Equally, communication entity 41 can be
associated with WCDMA access technology, entity 42 with WiMAX access
technology and entity 43 with WINNER access technology. The
communication entities 31-34 are associated with a GLL entity 35 and
the communication entities 41-43 are associated with a GLL entity
44. In the example of Fig. 1, the two GLL entities 35 and 44 are
associated with a common MRRM entity 50. The ambient network 80
furthermore comprises a connection or gateway entity 60 to a
communication network (not shown), such as telephone network, an
intranet or the Internet.
As an example, the communication entities 31-34 can be associated
with one wireless base station and the communication entities 41-43
with another wireless base station. Similar to the description of
communication system 10, the ambient network 80 may also be a unit
or may be spread out over several locations. Therefore, the just
described entities 31-35, 41-44, 50 and 60 may be located together
or spread out over several locations and individual networks. It is
therefore noted that the representation in Fig. 1 is schematic and
oriented along the logical arrangement of entities within a
hierarchy of communication layers.
In the example of Fig. 1 link 201 is a WLAN link, links 202 and 204
are WCDMA links, links 203 and 205 are WiMAX links and link 205 is a
WINNER link. As an example, the access path monitor 21 can obtain
status information related to the status of WLAN link 201 and the
status of WCDMA links 202 and 204. In this case WLAN link 201 can be
seen as an example of a group of first access paths and WCDMA links
202, 204 as a group of second access paths of a different access
technology than the first group.
In the example of Fig. 1, the monitor 21, the access controller 22
and the modifier 23 are shown as parts of system 10. However, it
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should be noted that one, two or all of entities 21, 22 and 23 can
also be provided in the ambient network 80. In this case the
entities 10 and 80 together form a communication system that
embodies the present invention. For example, the monitor 21 and
modifier 23 can be provided in MRRM entity 50 or in one of GLL
entities 35 and 44. Equally, the entities 21, 22, and 23 can be
spread out over the entities 10 and 80. For example, the monitor 21
could have a part in MRRM entity 200 and a part in MRRM entity 50,
and/or parts in the GLL entities 24, 35 and 44. The same applies to
the access controller 22 and the modifier 23, i.e. these entities
could be spread out in the same way.
The obtaining of information can be done in any suitable or
desirable way, e.g. by performing measurements at communication
system 10 with respect to desired parameters, such as the signal
quality on a link (measured in any suitable or desirable way, e.g.
as a bit error rate, a signal strength value, an interference level
etc.), a load value (measured in any suitable or desirable way, e.g.
as a number of different terminal devices sharing a given link, as a
utilization ratio, etc.) etc. On the other hand, the information may
also be obtained in other ways e.g. received from the ambient
network 80, which may perform measurements and convey the measured
information or which may receive such information from the overlying
communication network.
The status information can be expressed in any suitable or desirable
way, e.g. it can be qualitative information such as a message
indicating "link not available" or it can be quantitative
information such as the numerical value of a given parameter.
The selection procedure for selecting an access path for a
communication session from among first and second access paths can
be chosen in any suitable or desirable way. The present invention is
not limited to any particular selection procedure, as the selection
procedure can be chosen in dependence on a large number of
preferences and strategies. For example, the selection procedure can
consist in selecting the link with the highest quality, or it can
10

consist in choosing the link with the lowest load, or it can consist
in choosing the link consuming the least amount of energy, etc. It
is noted that in the present invention, the selecting of an access
path can consist in selecting one access path for carrying a
communication session, or can consist in selecting a plurality of
access paths for carrying one communication session. As an example,
in Fig. 1 a session may be carried over any one of links 201-206, or
over more than one of said links simultaneously, e.g. a part of a
session may be carried over WLAN link 201 and another part over
WCDMA link 204.
The selection procedure can comprise the initial selection of an
access path for a new session, and preferably also comprises the
possibility of switching an established communication session
between access paths of different access technologies while the
communication session is active.
For example, in Fig. 1 the access controller 22 can be arranged to
perform a selection procedure such that an active session can be
switched from e.g. WCDMA link 204 to WLAN link 201 based on obtained
status information, e.g. when the signal quality on link 204 falls
below a threshold, when the load on link 201 falls below a
predetermined threshold or when the link quality on link 201 exceeds
that on link 204 and link 201 is available.
The modification procedure can be chosen in any suitable or
desirable way in view of a desired strategy and a desired objective.
The decision information used by the modifier 23 in the modification
procedure will equally depend on the desired strategy or objective.
This will become readily understandable from the examples in the
following description.
In a general sense, the modifying of a procedure (one or both of the
selection procedure and the monitoring procedure) can comprise
changing parameters used by the procedure (such as e.g. changing the
frequency with which the monitoring procedure obtains status
information, changing the frequency with which the access path
11

monitor forwards obtain status information to the access controller,
or changing the frequency with which the selection procedure takes a
selection decision) or the modifying can also consist in adapting
the process of the procedure itself. The latter can e.g. be done by
having a procedure which comprises a plurality of subroutines or
modes, and letting the modification procedure choose a subroutine or
mode. As an example of the latter, a monitoring procedure can be
envisioned in which in a first mode a large number of access paths
is measured at a high frequency, such that this mode is energy
intensive, and in a second mode less access paths are measured at a
lower frequency, i.e. the second mode is less energy intensive.
Then, depending on associated decision information, such as the
energy status of the communication system (e.g. the battery status),
an appropriate monitoring mode can be chosen. In other words, if the
energy status of the communication system is low (i.e. below a
predetermined threshold), then the mode that consumes less energy is
chosen, whereas if the energy status of the communication system is
high (i.e. above a predetermined threshold), the mode with greater
energy consumption is chosen.
As already mentioned, the modifying of the monitoring procedure
and/or selection procedure may comprise modifying the frequency with
which status information is obtained and/or modifying the frequency
with which the status information is forwarded from the access path
monitor to the access controller and/or modifying the frequency at
which the selection procedure takes a selection decision. The
frequency of obtaining status information, e.g. the frequency of
performing measurements on the access paths under observation, and
the frequency with which status information is forwarded, is a
measure of the amount of energy, processing power and signalling
overhead invested in the monitoring and selecting operation. As a
consequence, if it is desired to reduce this invested effort under
certain situations, then the decision information is chosen to be
able to judge the presence or absence of the certain situation (e.g.
the certain situation can be a low power status of the communication
system or a high processor load, and the decision information is
then appropriately chosen, e.g. the power status of the
12

communication system or the processor status), and if the certain
situation is present, then one or both of the above-mentioned
frequencies can be reduced. On the other hand, if the monitoring or
selection procedure are adjusted to expend little effort, the
determination that the above-mentioned certain situation is no
longer present can be used as a basis for modifying one or both of
the monitoring procedure and selection procedure by increasing one
or both of the above-mentioned frequencies.
Alternatively or additionally, modifying the monitoring procedure
may also comprise modifying the status information being obtained
for one or more of the access paths. For example, this can mean
changing the type of information, such as going from one type of
information to another, or adding a new type of information in
addition to the old type. For example, if the access path monitor 21
in Fig. 1 is obtaining signal quality information for link 201, a
modification of the monitoring procedure can consist in switching to
monitoring load information, or can consist in additionally
monitoring load information.
Additionally or alternatively, modifying the monitoring procedure
may comprise modifying the number of access paths for which status
information is obtained. As an example, if it is desirable to reduce
the effort expended on monitoring access paths, then the number of
access paths being observed can be reduced. The modification
procedure may furthermore be arranged such that the selecting
procedure is modified by modifying the number of access paths from
among which an access path for a communication session is selected.
In other words, the selecting procedure may be such that a selection
is not performed for all available access paths but only from a
limited set. For example, in Fig. 1 the selection procedure
performed by access controller 22 could be such that only links 201,
202 and 204 are considered for selection, although further links are
available. In accordance with the present embodiment, the
modification procedure can comprise increasing or reducing the
access paths considered for selection. In keeping with the just
mentioned example, the selection procedure could be modified by
13

removing link 202 from the set of links considered for selection,
such that a selection is only performed between link 201 and link
204, if it is desired to reduce the amount of effort expended on the
selection operation. It is noted that the modification of the
selection operation can go so far as to reduce the set of access
paths under consideration to one, thereby effectively disabling the
selection operation. Equally, modifying the number of access paths
being monitored by the monitoring procedure can also reduce this
number to one or zero, thereby effectively disabling the monitoring
procedure.
The modifying of the monitoring procedure or selection procedure by
modifying the corresponding number of access paths under
consideration will now also be explained with respect to an example
known from the above-mentioned document IST-2002-507134-AN/WP2/D02
on Ambient Networks. In connection with Ambient Networks and a
plurality of radio access links it is known to define a plurality of
sets:
a Detected Set (DS), which is the set of all access links that
are available and to which an ambient network could potentially
connect. Some of the access links may actually not have been
detected by measurements but can be known due to context
information, i.e. it can be known from a MRRM entity that at a
certain position a certain radio access is available (such as a WLAN
hotspot at e.g. an airport). Such radio accesses can be announced by
means of radio access advertisement messages.
a Candidate Set (CS) , which is a subset of the detected set,
and can be used by an ambient network to connect to one or more
other networks. The detected set can contain radio accesses, which
are not part of the candidate set. These radio accesses can e.g. be
rejected for a given Ambient Network due to policy reasons or due to
technical limitations of the access network to use a certain radio
access.
14

MRRM Active Set (AS), which is a subset of the candidate set.
The MRRM active set contains all radio accesses which are actively
managed for a certain communication session. There can be different
MRRM active sets for different sessions. The MRRM active set
contains only elements out of the candidate set which also fulfil
predetermined minimum requirements, e.g. in radio link quality or
with respect to system load, and also fulfil service specific
requirements for the communication session. The latter can be a
quality of service requirement (such as data rate, delay, jitter,
etc) , but can also be security requirements (such as encrypted
transmission, authenticated transmission, etc).
GLL active set, which is a subset of MRRM active set. The GLL
active set contains a number of radio accesses that may be
dynamically assigned to a communication session by one or more GLL
entities.
In the example of Fig. 1, the detected set could e.g. be all of
links 201-207, where link 207 is indicated as a link not being used
by communication system 10 but available. The candidate set could
e.g. be links 202-206 while the MRRM active set could e.g. be links
203-206. Finally, the GLL active set could e.g. be links 204-206,
which are all associated with the GLL entity 44.
In a communication system using the above-mentioned sets of access
links or access paths, the modification procedure can comprise
changing the links or paths in one or more of any of the above-
mentioned sets. For example, the modification of the monitoring
procedure may comprise changing the number of links or paths in the
MRRM candidate set, and the modifying of the selecting procedure may
comprise changing the number of links or paths in the GLL active
set.
As already mentioned previously, the decision information used by
the modifier for modifying one or both of the monitoring procedure
and the selection procedure can be chosen in any suitable or
desirable way, depending on the desired objective and strategy.
15

According to one example, the decision information can at least
partially be derived from the status information that is being
obtained by the monitoring procedure. As an example, the status
information can comprise measurements of the signal quality on the
access path currently being used for carrying the communication
session, and measurements of signal quality on further accessible
links. This signal quality information can be used as decision
information by the modification procedure in the following way. If
the signal quality on the currently used access path exceeds a
predetermined threshold, then the monitoring procedure and selection
can be disabled, whereas if the signal quality is below the
threshold, then the monitoring procedure and selection procedure are
activated.
The decision information can be identical to the status information,
or the status information can be processed for deriving the decision
information. For example, if the status information is a parameter,
then the temporal change rate (time differential) of said parameter
can also be used as decision information.
As with the status information, the decision information can also be
of any desirable type i.e. it can be qualitative, such as a message
indicating "link not available", or it can be qualitative, like a
numerical value. According to a preferred embodiment, the decision
information comprises numerical values. More preferably, the
numerical values comprise values of one or more decision parameters.
Examples of such decision parameters can be the previously mentioned
status parameters, such as signal quality or load on an access path.
The modification procedure can then comprise comparing parameter
values associated with one of the decision parameters with a
respective threshold. For example, if the signal quality value on
the currently used access path is above a predetermined quality
threshold and/or the load on the currently used access path is below
a predetermined load threshold, then the modification procedure can
appropriately modify the monitoring procedure and/or selection
procedure, e.g. by reducing the frequency of obtaining information
16

on monitored access paths (up to disabling the monitoring procedure)
and by reducing the number of access paths considered for selection
(up to disabling the selection procedure).
Another example of numerical values comprised in the decision
information are change rate values of one or more of the mentioned
decision parameters. These change rate values derived from a given
decision parameter can be compared with a respective threshold as a
part of the modification procedure. For example, if the time
differential of the signal quality on the currently used access path
is below a quality change rate threshold, and/or the time
differential of the load on the currently used access path is below
a predetermined load change rate threshold, then the modification
may comprise reducing the effort expended on performing the
monitoring procedure and/or selection procedure, e.g. by reducing
the rate of obtaining status information for the access paths of the
different access technologies.
As can be seen from the above examples, the decision information may
comprise a traffic load indication. This indication can be a
quantitative or qualitative information, and it can be indicative of
the traffic load on an individual path or the traffic load in a
larger context, e.g. the traffic load in an entire Ambient Network
under consideration. The decision information can also comprise
information derived from the traffic load indication, such as the
time differential of traffic load values.
The decision information can also comprise a signal quality
indication, which can be a qualitative or quantitative information.
The signal quality indication can be indicative of the signal
quality on the one or more currently used access paths for a
communication session, or of the signal quality on access paths
being monitored. The decision information can also comprise
information derived from the signal quality indication, such as the
time derivative of signal quality values. As an example, if it is
determined that the change rate of signal quality on access paths
being monitored falls below a predetermined threshold, then the
17

modification procedure can reduce the frequency with which status
information is obtained, as a high frequency is not necessary.
Additionally, or alternatively, in the event that the communication
system is mobile, the decision information may comprise an
indication of the velocity of the communication system. If the
communication systems velocity falls below a predetermined
threshold, then the modification procedure can adjust the monitoring
procedure and/or selection procedure in such a way as to reduce the
effort expended on monitoring and selecting access paths. Namely, if
the communication system is only moving very slowly or not moving at
all, then there is less expected benefit in the monitoring and
selection procedures, such that it can be desirable to reduce the
expended effort.
Alternatively or additionally the modification procedure can be such
that the decision information comprises an indication of resources
available to the communication device. Such resources can e.g. be
power resources (such as the battery power level) or processing
resources (such as the degree to which a processor is being
utilized). As indicated previously, in the event that the available
resources are low (e.g. low power or little free processing
capacity), the modification procedure may modify the monitoring
procedure and/or selection procedure in such a way as to reduce the
expended effort, e.g. by reducing the frequency with which status
information is obtained.
As already mentioned in the summary of invention, the choice of the
modification procedure and the associated decision information can
be done in view of an implicit analysis of costs and/or benefits or
a balancing of implicit costs and benefits. However, the decision
information may also comprise the use of explicit cost and/or
benefit values. Namely, the decision information may comprise one or
both of estimated benefit values and estimated cost values for a
plurality of different settings of the monitoring procedure.
Equally, the decision information may comprise one or both of
estimated benefit values and estimated cost values for a plurality
18

of different settings of the selection procedure. An example of a
cost function for monitoring a plurality of access paths is:

where CMon^tor is the monitoring cost, fMonitor i is tne frequency
of monitoring access path i and cMonitor i 1S the cost for
monitoring access path i. The sum runs over all access paths i being
monitored. The cost cMonitor j_ can be expressed in any suitable or
desirable way, i.e. can be a dimensionless variable or can be
expressed in terms of a parameter, such as in terms of consume
energy. Similarly to equation (1) , the costs for signalling the
status information for the access path monitor to the access
controller can be expressed as:

where fForward i ^s the frequency of forwarding status information
for access path i and Cporwarcj i is the cost of forwarding status
information for access path i.
Similar functions can be formulated for the costs of performing the
selection operation, or for the benefits of performing the
monitoring procedure and/or the selection procedure.
As an example, the modification procedure can be such that the
monitoring cost is calculated in accordance with equation (1), and
if the total cost CM0n-L^-or exceeds a predetermined threshold, then
the monitoring frequencies fMonitor i are changed to make Cf/jQ^tor
again fall below the threshold.
It is noted that costs and/or benefits can be determined in
accordance with mathematical functions as given in above examples
19

(1) and (2), but can also e.g. be determined on the basis of multi-
dimensional tables or mappings where a cost value and/or a benefit
value is assigned to a vector of input parameter values, such as a
vector of the frequency value of monitoring, the number of access
paths being monitored, etc.
As a further alternative or addition, the decision information used
by the modifier may comprise preference information set by one or
both of a user of the communication system and an operator of the
network. For example, the user of the communication system may have
a preference for a certain access technology, and the modifier can
be arranged to modify the monitoring procedure in such a way that
access paths of said preferred access technology are always
monitored if available.
As a further alternative or addition, the modifier can be arranged
such that the decision information comprises an indication of the
momentary sensitivity of the selecting procedure to a timeliness of
the status information. When monitoring access paths and performing
a selection procedure there is the problem that a delay occurs
between the gathering of the status information and the use of said
status information in the selection procedure. This delay is caused
by the time required for obtaining the status information, and the
time necessary for forwarding the status information from the access
path monitor to the access controller. Furthermore, the delay
depends on the frequency with which status information is obtained
and the frequency at which the status information is forwarded from
the access monitor to the access controller. Namely, if status
information for a given access path being monitored only arrives
every At at the access controller, then at the end of the period At
the momentary status may have already changed considerably. The
momentary sensitivity of the selecting procedure can therefore be an
important parameter in modifying one or both of the monitoring
procedure and the selection procedure. For example, if it is
determined that the momentary sensitivity is above a predetermined
threshold, then the modification procedure can modify the monitoring
procedure by increasing the frequency of obtaining status
20

information, and vice versa if the momentary sensitivity is below a
predetermined threshold, then the modification procedure can reduce
the frequency at which status information is obtained. The
sensitivity can be e.g. be indicated in terms of the differential of
a mathematical selection function with respect to the input status
parameter values.
As a further alternative or addition, the modifier can be arranged
such that said modification procedure comprises a determination of
whether one or more service requirements are fulfilled for the
communication session. The service requirement can be chosen in any
suitable or desirable way, e.g. it can be a data rate value or some
other quality of service measure. The criterion for fulfilment is
set by defining an associated threshold accordingly. As an example,
if the communication session of a user of the communication system
is a voice communication, a data rate threshold of e.g. 50 kbit/s
can be considered sufficient, such that if the momentary access path
or paths provide this data rate, even if a new access path is
available that has a higher data rate, there is no benefit in
switching to it. As a consequence, the modifier can modify the
monitoring procedure and/or the selecting procedure in such a way
that the effort expended is reduced if the service requirement is
fulfilled, e.g. by disabling the monitoring procedure and the
selecting procedure if the threshold data rate is exceeded by the
momentary access path(s).
The present invention is generally concerned with making the
monitoring procedure and/or the selection procedure of a
communication system that can access a network via access path of
different access technology dynamically adaptable or modifiable, in
order to be able to dynamically adjust the trade-off between an
effort expended for performing the monitoring and selecting with
respect to the benefit derived therefrom. Generally, the balance
between cost and benefit is such that when the expected benefit
decreases, the expended effort for monitoring and selecting can be
decreased and vice versa. For example, if the monitoring procedure
is operated to less frequently obtain status information (e.g. by
21

less frequently performing measurements), this reduces the amount of
signalling overhead and reduces energy consumption. At the same
time, the selection procedure must make decisions based on less
timely status information, which can reduce the benefit of
performing the selection procedure.
As already indicated in some of the examples above, the access path
monitoring (monitoring procedure) and access controller (selection
procedure) can be modified in view of one or more of the following
input parameters:
traffic load and experienced rate of change in traffic load.
If the traffic load is below a predetermined threshold and/or the
rate of change of traffic load is below a threshold, then the
monitoring frequency can be reduced.
access path quality and experienced rate of change in access
path quality. If the access path quality is above a predetermined
threshold and/or the rate of change of access path quality is below
a predetermined threshold, then the monitoring frequency can be
reduced.
a number of users in the environment. If few users are in the
environment, the benefit of multi-user diversity is low. In this
case a diversity gain can be achieved by selecting the access path
based on instantaneous access path quality. If many users are
present, little diversity gain can be achieved. The diversity gain
is a type of benefit. As a consequence, depending on the number of
users in the environment of the communication system, the selection
procedure can be modified, e.g. the number of access paths
considered in the selection procedure is reduced if the number of
users in the environment increases beyond a predetermined threshold,
and the monitoring procedure is accordingly also modified to provide
the appropriate status information.
if multiple access paths are available, they can be classified
into different sets, as explained previously with respect to the
22

Detected Set, Candidate Set, MRRM Active Set and GLL Active Set.
Depending on the set to which an access path belongs, the frequency
with which status information is obtained can be adapted.
performance desired by user. An example of a user preference
is an indication of the desired performance, e.g. a desired quality
of service (QoS) or a desired data rate. If the user achieves the
desired performance, then the effort expended on the monitoring
procedure and selection procedure can be reduced.
performance allowed by network. If a user achieves the
performance he is allowed by the network, e.g. in terms of quality
of service or data rate, then the effort expended on the monitoring
procedure or selection procedure can be reduced.
battery power of communication system. If the battery of the
communication system is low, then the frequency for obtaining status
information in the access path monitor can be reduced, the frequency
for forwarding status information to the access controller can be
reduced, and the processing expended for the selection procedure can
be reduced. As an example, both the monitoring procedure and the
selection procedure can be effectively disabled if the battery power
falls below a predetermined threshold value.
system resources. The conducting of a selection procedure
generally improves the efficient use of system resources, both in
the communication system and in the network. However, if enough
system resources are already available (i.e. the value of an
appropriate system resource measure is above a predetermined
threshold), then the effort expended on the monitoring procedure and
the selection procedure can be reduced, e.g. by reducing the
frequency which status information is obtained.
user behaviour. If the communication system is mobile and a
user of the communication system is moving faster than a
predetermined velocity threshold, the status parameters may vary
rapidly. As a consequence, it can be desirable in this case to
23

increase the frequency at which status information is obtained, in
order to have timely status information.
The strategies and desired objectives when modifying the frequency
at which status information is obtained and the frequency at which
status information is forwarded can be manifold. In this connection,
one can for example consider a service criterion, a resource
criterion or an MRRM performance criterion. The service criterion
defines to what extent the requirements of the service and/or the
user are met. An example of a service criterion is: is the minimum
quality of service threshold achieved? Another example is: is a
higher quality of service level required or desired? For example, is
an access path having higher resolution or higher rate available for
streaming? Or as another example, is the additional cost (e.g. in
monetary terms) worth the increase in service performance?
A resource criterion defines to what extent transmission resources
are critical. Examples are: are system resources highly utilized
(e.g. high load) and how many resources remain available? Is the
battery power low?
The MRRM performance criterion relates to what the estimated benefit
or gain of Multi-Radio Resource Management is. In several studies a
number of MRRM algorithms have been studied to select a radio link
for a user connection. Input parameters can be link quality, service
requirements, system load, etc. It has been shown that these
algorithms can provide everything from substantial gains in
performance to only very small gains. The gain or benefit depends on
many aspects: what radio access technologies are used, what
deployment patterns are used, how the traffic demand is distributed
with respect to the areas of service (e.g. radio cells), what are
the service requirements, what input parameters are used for the
selection procedure and which selection algorithms are used, how
many users are in the system (e.g. due to variations of link
quality, a selection procedure can provide a multi-access diversity
gain. For a large number of users there is a multi-user diversity
gain, which exploits channel variations. If a large multi-user
24

diversity gain is achieved, little additional gain remains for
access selection diversity), what costs (in terms of any desired
measure) are involved for performing the monitoring procedure and to
what extent does this use up the achieved or achievable
benefit/gain, what is the position of the MRRM input parameter(s).
In this respect, the precision of estimation, the delay of
distributing measurements and the degree of variability in the
system (variation of load and link quality, e.g. caused by the users
mobility) play a role.
As explained in connection with Ambient Networks, a number of sets
can be defined on which different MRRM functions are performed. Most
of these functions require a monitoring procedure for obtaining
status information. Within the detected set and candidate set,
monitoring provides occasional information about information
elements like link quality, load etc. Based on this monitoring
input, an access path can be moved to the MRRM/GLL active set.
Within the active set, MRRM performs selection and allocation of
access paths to user sessions. In order to achieve this, it is
desirable to have a more precise monitoring procedure, e.g. status
information is obtained more frequently and/or more different types
of status information are obtained. The following examples are
further embodiments of the invention in this context:
Based on the service criterion, resource criterion and/or MRRM
performance criterion, it can be decided to what extent a selection
procedure in MRRM is feasible. If there is no problem, or little
benefit expected, then the expended effort can be kept low. For
example, the size of the active set and candidate set can be held to
a predetermined small number. If the active set size is limited to
one, no selection procedure is effectively performed. Also, the
number of alternative access paths in the candidate set can be
limited in a similar way.
If a selection procedure is performed across a number of
access paths (e.g. the active set contains several elements), the
appropriate access selection algorithm can be chosen depending on
25

system parameters like access path quality, service, load, or
combinations thereof. The access selection frequency can be adapted
according to the sensitivity of input parameters of the access
selection function and the dynamic variations of system parameters.
For example, the gain or benefit of MRRM decreases if outdated input
parameters (e.g. measured load or link quality values) are used. At
the same time, the consumed resources for the monitoring procedure
decrease. If the variability of the system increases, then it is
desirable to also increase the frequency at which status information
is obtained and/or at which access paths are selected.
It may be noted that many of the above examples referred to the
embodiment shown in Fig. 1. Although Fig. 1 constitutes a preferred
embodiment of the invention, the present invention is by no means
restricted thereto. For example, the present invention is not
restricted to being applied in a communication system that accesses
a network via a group of first radio access links of a first
technology and a group of second radio access links of a second
access technology different from the first access technology.
Namely, the invention also applies to the more general case of
access paths that may be multi-hop relay links. Furthermore, the
access paths do not have to be radio access paths, as the invention
equally applies to the case of wire-bound access paths of differing
access technology.
As the present invention is not restricted to the field of wireless
communication, it can also be applied in the area of media routing.
Overlay networks can be used to transmit data to a receiver via
different networks. A Media Port makes a routing decision of
selecting the right network. For this, the Media Port obtains
monitoring information about the status (e.g. load) and capabilities
of the different networks. This can also be considered as a
monitoring procedure within the meaning of the present invention.
The monitoring procedure in this case evaluates a complete sub-
network. It can consist of measurement procedures (link ping packet
trains), end-user quality of service reports or feedback information
of sub-network-specific management functions.
26

Although the present invention has been described with reference to
preferred embodiments, these only serve to illustrate the invention,
but are by no means restrictive. The invention is defined by the
appended claims. Reference signs serve to make the claims easier to
read but do not have any limiting effect.
27

WE CLAIM:
1. k communication system arranged for accessing a network
via a group of first access paths of s. first access
technology and a group of second access paths of a
second access technology different from said first
access technology, comprising
an accesa path monitor for obtaining status information
related to a status of one or more of said first access
paths and one or more of said second access paths in
accordance with a monitoring procedure,
an access controller for selecting an access path for a
communication session from, ^mong said first and second
access paths in accordance with a selection procedure
and in dependence on said status information, and
a modifier for modifying one or both of said monitoring
procedure and said selection procedure in accordance
with a modification procedure and in dependence on
decision information, wherein said decision information
comprises an indication of resources available to said
oommunication system.
2. h coiranunication system according to claim 1, wherein
said access controller is arranged for switching said
communication session between said first and second
access paths while said communication session is active.
3. A communication system according to one of claims 1 or
2, wherein modifying said monitoring procedure comprises
modifying a frequency with which said status information
is obtained.
28

4. A coiraciunication. system according to one of claims 1 to
3, wherein modifying said monitoring procedure coirgprises
modifying a frequency with which said status information
is forwarded from said access path monitor to said
access controller.
5. A communication system according to one of claims 1 to
4, wherein modifying said monitoring procedure comprises
modifying the status information being obtained for one
or more of said access paths.
6. A communication system according to one ofi claims 1 to
5, wherein modifying said monitoring procedure comprises
modifying the number of access paths for which status
information, is obtained.
7. A communication system according to one of claims 1 to
6, wherein modifying said selecting procedure comprises
modifying the number of access paths from among which an
access path for a communication session is selected,
8. A communication system according to one of claims 1 to
7, wherein said decision information is at least
partially derived from said status information.
9. A communication system according to one of claims 1 to
8r wherein said decision infc-.rma.tian comprises numerical
values..
10. A communication system according to claim 9J wherein
said numerical values comprise values of one or more
decision parameters.
29

11. A communication system according to claim 10, wherein
said modification procedure comprises comparing
parameter values associated with one of said decision
parameters with, a respective threshold.
12. A communication system according to claim 9, wherein
said numerical values comprise change rate values of one
or more decision parameters.
13. A communication system according to claim 12, wherein
said modification procedure comprises comparing change
rate values associated with one of said decision
parameters with a respective threshold.
14. A communication system according to one of claims 1 to
13, wherein said decision information comprises a
traffic load indication.
15. A communication system according to one of claims 1 to
14, wherein said decision information comprises a signal
quality indication.
15. A communication system according to one. of claims 1 to
15j wherein said communication system is mobile and said
decision information comprises an indication of a
velocity of said communication system.
17. A communication system according to one of claims 1 to
15, wherein said decision information comprises one or
both of estimated benefit values and estimated cost
values for a plurality of different settings of said
monitoring procedure.
30

18. A communication system according to one of claims 1 to
17, wherein said decision information comprises one or
both of estimated benefit values and estimated cost
values for a. plurality of different settings of said
eeleation procedure.
19. A communication system according to one of claims 1 to
18, wherein said decision information comprises
preference information set by One or both of a user of
said communication system and an operator of said
network.
20. A communication system according to one of claims 1 to
19, wherein said decision information comprises an
indication of the momentary sensitivity of said
selecting procedure to a timeliness of said status
information.
21. A communication system according to one of claims 1 to
20, wherein said modifier is arranged such that said
modification procedure comprises a determination of
whether one or more service requirements are fulfilled
for said communication session.
22. A modifier for modifying one or both of a monitoring
procedure of an access path monitor and a selection
procedure of an access controller, arranged for
operating in a communication system according to one of
claims 1 to 21.
23. A method of controlling access to a network
via a group of first access paths of a first access
technology and a group of second access paths of a
second access technology different from said first
access technology, comprising
31

obtaining status information related to a status of one
or more of said first access paths and one or more o£
Said second access paths in accordance with a monitoring
procedure,
selecting an access path for a eortminication session
from among said first and second access paths in
accordance with a selection procedure and in dependence
on said status information, end
modifyins one or both of said monitoring procedure and
said selection procedure in accordance with a
modification procedure and in dependence on decision
information, wherein said decision information comprises
an indication of resources available to said
communication system.
24. A computer program product comprising a computer program
that is arranged to execute the method of claim 23 when
executed by a communication system.

Dated this 3rd day of March 2008

A communication system is provided which is arranged for accessing a
network by a group of first access paths and a group of second
access paths. The first and second access paths have a different
access technology. An access path monitor is provided for obtaining
status information related to the access paths in accordance with
the monitoring procedure. An access controller is provided for
selecting an access path for a communication session in accordance
with a selection procedure and in dependence on the status
information. A modifier is provided for modifying one or both of the
monitoring procedure and the selection procedure in accordance with
a modification procedure and in dependence on decision information.

Documents:

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Patent Number

268921

Indian Patent Application Number

922/KOLNP/2008

PG Journal Number

39/2015

Publication Date

25-Sep-2015

Grant Date

23-Sep-2015

Date of Filing

03-Mar-2008

Name of Patentee

TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

Applicant Address

SE-164 83 STOCKHOLM

Inventors:

#	Inventor's Name	Inventor's Address
1	SACHS, JOACHIM	AN DEN FINKENWEIDEN 43, 52074 AACHEN
2	PRYTZ, MIKAEL	GUSTAVSLUNDSVÄGEN 38, S-144 63 RÖNNINGE
3	LUNDSJÖ, JOHAN	LUNDAGARDSVÄGEN 41, S-163 51 SPANGA
4	MAGNUSSON, PER, OLOF, MAGNUS	SKOGSGATAN 51, S-587 23 LINKÖPING

PCT International Classification Number

H04Q 7/32

PCT International Application Number

PCT/EP2005/008515

PCT International Filing date

2005-08-05

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA