Title of Invention	A COMMUNICATION UNIT AND A METHOD OF FREQUENCY RE-PLANNING IN A WIRELESS COMMUNICATION SYSTEM A WIRELESS COMMUNICATION SYSTEM
Abstract	A wireless communication system (100) comprises a wireless infrastructure supporting communication for a plurality of mobile communication units (112-115). The wireless infrastructure comprises a processor (175) configured to generate a frequency re-use plan. The processor (175) generates a frequency re-use plan based on a relationship between one or more interference metrics, such as carrier to interference, and one or more quality of services for a plurality of communication types, to support frequency planning for a radio system with multiple traffic types using non-uniform allocation of penalties on different radio carriers in the same radio cell can be used.

Title of Invention

A COMMUNICATION UNIT AND A METHOD OF FREQUENCY RE-PLANNING IN A WIRELESS COMMUNICATION SYSTEM A WIRELESS COMMUNICATION SYSTEM

Abstract

A wireless communication system (100) comprises a wireless infrastructure supporting communication for a plurality of mobile communication units (112-115). The wireless infrastructure comprises a processor (175) configured to generate a frequency re-use plan. The processor (175) generates a frequency re-use plan based on a relationship between one or more interference metrics, such as carrier to interference, and one or more quality of services for a plurality of communication types, to support frequency planning for a radio system with multiple traffic types using non-uniform allocation of penalties on different radio carriers in the same radio cell can be used.

Full Text	A WIRELESS COMMUNICATION SYSTEM, A COMMUNICATION UNIT AND A METHOD OF FREQUENCY RE-PLANNING IN A WIRELESS COMMUNICATION SYSTEM Field of the Invention This invention relates to a wireless communication system, a communication unit and a method of frequency re-planning in a wireless communication system. The invention is applicable to, but not limited to, use of multiple 'S' curves for frequency planning in a multiple technology wireless cell-based communication environment. Background of the Invention Wireless communication systems, for example cellular telephony or private mobile radio communication systems, typically provide for radio telecommunication links to be arranged between a plurality of base transceiver stations (BTSs) and a plurality of subscriber units, often termed mobile stations (MSs). In a wireless communication system, each BTS has associated with it a particular geographical coverage area (or cell). Primarily, a transmitter power level of a BTS defines a coverage area where a BTS can maintain acceptable communications with MSs operating within its serving cell. In addition, receiver sensitivity performance of receiving wireless communication units also affect3 the extent of a given coverage area. In large cellular communication systems, these cells are combined and often overlapped to produce an extensive, wide coverage area. Wireless communication systems are distinguished over fixed communication systems, such as the public switched telephone network (PSTN), principally in that subscriber units/mobile stations move between coverage areas, where communications in the different coverage areas are served by different BTS (and/or different service providers). In doing so, the MSs encounter varying radio propagation environments. In a cellular system, adjacent cells are typically configured to overlap, to ensure a contiguous signal coverage area, whilst the MSs move between cells. The cell overlap region is deliberately designed into the system plan to ensure that MSs can successfully handover between communication cells. The frequencies used in particular cells are generally selected to minimise a level of radio interference generated on adjacent cells. A system design based on cells is typically based on an ideal cell pattern. However, an idealised cell pattern never occurs in practice, due to the nature of the terrain and the fact that cell sites and antennae are not ideally located on a regular grid pattern. The wireless system designer therefore uses frequency-planning tools to estimate the radio propagation for each cell and predict a corresponding coverage area. Based on these propagation models, the system designer is able to develop a frequency plan for the system intended to minimise the expected interference. Frequency planning is arguably the most challenging and time consuming task in designing a mobile communication system. Effective usage of the frequency spectrum, one of the scarcest resources for any operator, leads to both better system quality and increased capacity. In this regard, the frequency plan considers such factors as antenna heights and location, terrain topology, transmitted power levels and the anticipated number of subscriber units. In the context of frequency planning, recent developments in simulation tools have provided the opportunity to 'automatically' perform a frequency re-planning (AFP) operation, based on analysis of measured data and system parameters such as transmit power, subscriber receiver sensitivity, etc. Automating a frequency planning process typically produces better quality frequency plans and yields a multitude of benefits, such as: (i) A better quality of service may be achieved in systems with minimal opportunity for frequency reuse, particularly in systems with tight frequency reuse; (ii) A major capital expenditure in infrastructure may be deferred, as the current system is able to handle more traffic at a given quality of service; and (iii) The time for frequency planning is reduced - enabling system designers enough time to concentrate on other, more complex enhancements to system quality. For systems supporting AFP applications, there is a requirement on active subscriber units to scan as many frequencies as possible to aid frequency planning. This information, in the form of measurement reports, is fed into an AFP application that is able to determine an optimal frequency plan for the communication system. A number of techniques exist for allocating frequencies to cells in a radio system within a frequency planning operation. Typically, these techniques are based on maximising the Carrier to Interference ratio (C/I) for those 'pixels' included in the 'analysis space' of a frequency planning tool. The major weakness of these techniques is that they assume a uniform distribution of subscriber units in a cell. As such the known techniques do not accurately reflect the actual distribution of C/I that can be encountered in a cell. A further weakness of these techniques is that the non-uniform distribution of communication traffic, where the traffic may include speech, data, signalling, video, etc., each of which has different minimum interference requirements, is not captured in the frequency planning algorithm. Furthermore, with the advent of packet switched and adaptive multi-rate technologies, frequency planning based on a single criterion is no longer an optimal solution. Typically, frequency planning tools seek to exceed a minimum C/I in all radio cells. However, radio carriers will now need to support traffic with heterogeneous minimum C/I requirements. Thus, there exists a need in the field of the present invention to provide a wireless communication system, a communication unit and method for frequency re-planning; wherein the aforementioned disadvantages may be alleviated. Statement of Invention In accordance with a first aspect of the present invention there is provided a wireless communication system, as claimed in Claim 1. In accordance with a second aspect of the present invention, there is provided a method of frequency re- planning in a wireless communication system, as claimed in Claim 14. In accordance with a third aspect of the present invention, there is provided a storage medium, as claimed in Claim 19. In accordance with a fourth aspect of the present invention, there is provided a communication unit, as claimed in Claim 20. In summary, the inventive concepts of the present invention propose a wireless communication system (100), a method of frequency planning and a communication unit to generate a frequency plan based on a relationship between one or more interference metrics and one or more quality of services for a plurality of communication types. Preferably, the one or more interference metrics may comprise a carrier to interference metric and the one or more quality of services may comprise frame erasure rate (FER). The preferred embodiment generates and uses multiple 'S' curves, where each curve describes a relationship between, say, C/I and frame erasure rate (FER) for a given technology, traffic class and/or context under specific radio conditions. Thus, each 'S' curve is defined for specific technologies and/or traffic types and/or contexts. Once multiple 'S' curves have been generated, they are applied to a frequency-planning tool. Multiple 'S' curves can then be assessed against each other, for example in the context of a penalty matrix, to identify a specific interference relationship, for example, between a frequency carrier supporting a first communication technology and/or traffic type and/or context on a first cell and a frequency carrier supporting a second communication technology and/or traffic type and/or context on a second cell. Preferably, an overall 'penalty' value is calculated for one or more radio interference scenarios, i.e. a value representing the effect of applying a specific frequency assignment to a cell with specific interference relationships to a set of neighbouring cells. In this manner, the inventive concepts facilitate frequency planning for a non-uniform allocation of penalty values on different radio carriers, for example within the same radio cell. This allows different re-use distances to be achieved for different radio carriers. In so doing, it is now possible to plan for a different quality of service on respective, individual radio carriers. By systematically applying a number of 'S' curves to identify an interference relationship, a carrier-to- carrier penalty matrix can also be derived. In this regard, the frequency planning tool is then able to use the derived penalty matrix to analyse the impact of, and interference interrelationship between, different communication technologies being applied to different cells or BTSs within the cells. This, in turn, enables the frequency planning tool to generate an improved frequency plan for a cellular radio system, particularly one supporting multiple technologies and/or traffic types and/or contexts. Accompanying Brief Description of the Accompaying Drawings Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which: FIG. 1 illustrates a block diagram of a cellular radio communications system adapted to support the various inventive concepts of a preferred embodiment of the present invention; FIG. 2 illustrates a graph of a typical 'S'-curve; FIG. 3 illustrates a penalty table in accordance with the preferred embodiment of the present invention; and FIG. 4 illustrates a flowchart of a frequency re-planning process using multiple 'S'-curves, in accordance with a preferred embodiment of the present invention. Description of Preferred Embodiments Referring first to FIG. 1, a multi-layer cellular telephone communication system 100 is shown, in outline, supporting a Global System for Mobile communication (GSM) air-interface, in accordance with a preferred embodiment of the invention. The European Telecommunications Standards Institute (ETSI) has defined the GSM air- interface. The multi-layer cellular system is shown in a simplified form, with a limited number of system elements shown for clarity purposes only. Generally, the air-interface protocol is administered from base transceiver sites, within the system architecture 110, that are geographically spaced apart - one base site supporting a cell (or, for example, sectors of a cell). A plurality of subscriber units 112-115 is shown as communicating over the selected air-interface 117-120 with a plurality of base transceiver stations (BTS) 122- 132. A limited number of MSs 112-115 andBTSs 122-132 are shown for clarity purposes only. The BTSs 122-132 may be connected to a conventional public-switched telephone network (PSTN) 134 through base site controllers (BSCs) 136-140 and mobile switching centres (MSCs) 142-144. Each BTS 122-132 is principally designed to serve its primary cell, with each BTS 122-132 containing one or more transceiver units to communicate 156-166 with the rest of the cellular system infrastructure Each BSC 136-140 may control one or more BTSs 122-132, with BSCs 136-140 generally interconnected through MSCs 142-144. Processes within the MSCs are provided to account for the situation where a MS (112-115) passes between two BTS serving areas, for example MS 112 moving from an area covered by BTS 122 to an area covered by BTS 124, where the two BTSs are controlled by different BSCs (BSC 136 and BSC 138 in this example). Each MSC 142-144 provides a gateway to the PSTN 134, with MSCs 142-144 interconnected through an operations and management centre (OMC) 146 that administers general control of the cellular telephone communication system 100, as will be understood by those skilled in the art. The various system elements, such as BSCs 136-138 and OMC 146, include control logic 148, 150, 152, with the various system elements usually having an associated memory function 154 (shown only in relation to BSC 138 for the sake of clarity). A memory function 153 of the OMC 146 typically stores historically compiled operational data, as well as in-call data, control algorithms and system information such as neighbouring cell-site lists, for example a list of frequencies to be scanned by the respective MSs. In operation, an initial frequency re-use plan is set by an intelligent optimisation system (IOS) 172 and notified to the OMC 146. The OMC 146 commands the BTSs 122-132 via their BSCs 136-140 to set their operating frequencies accordingly. In accordance with the preferred embodiment of the present invention, an intelligent optimisation system (IOS) 172 is operably coupled to the OMC 146 and the base station controllers 136-140. Notably, the IOS 172 comprises an 'S' curve processing/analysing function 175, which is configured to process/analyse a number of 'S' curves relating to particular technologies and/or traffic types and/or contexts and identify an interference relationship between the technologies and/or traffic types and/or contexts employed in neighbouring cells. The processing of multiple yS' curves enables the OS 172 to generate an improved frequency re-use plan in accordance with the preferred embodiment of the present invention. In alternative embodiments, it is envisaged that the 'S' curve processing/analysing function 175 may be located within the OMC 146. Indeed, it is envisaged that in alternative embodiments, the 'S' curve processing/analysing function 175 may be operably coupled to other functions within the wireless communication system, or even distributed across a number of elements, if appropriate. The 'S' curve processing/analysing function 175 is configured to receive C/I information and related quality of service metrics, such as frame error rate (FER) information for each communication cell supported by the OMC 146. In the preferred embodiment of the present invention, this 'S' curve information is pre-generated by, say, an Operator, and. loaded into the 'S' curve processing/analysing function 175. In order to derive multiple S-curves, it is envisaged that a physical layer simulation model may be used by, say, the Operator. Advantageously, in the context of frequency planning a cellular system that incorporates a multitude of radio technologies/ the use of multiple 'S'- curves can also be used to capture the effect of discontinuous transmission and frequency hopping. For example in the case of a frequency hopping wireless communication technology, the effect of different Mobile Allocation List lengths on the FER of different technologies, for a given level of radio interference (C/I), could be modelled by the simulator. The results of the simulation may be used to derive corresponding frequency-hopping S-curves for the different technologies. Correspondingly, the effect of combining discontinuous transmission and frequency hopping can be modelled such that the 'S' curve relates their effect on the relationship between C/I and FER. In an alternative embodiment of the present invention/ it is envisaged that the 'S' curve data can be automatically generated in a real-time manner based on received measurement reports (MRs), generated by BTSs or MSs operational within particular cells. Notably, the information received in this scenario, in order to classify the 'S' curve data, also preferably indicates real-time traffic types, technologies used within the cell, system parameters, etc. In this regard, the 'S' curve processing/analysing function 175 within the IOS 172 is operably coupled to a collection function 176, which is operably coupled to the BSCs 136-140 for collating cell information. The 'S' curve processing/analysing function 175 then analyses the interference relationship between multiple 'S' curves, when considered in the context of configuring corresponding cells as neighbouring cells in a wireless communication system. Each 'S' curve describes a relationship between one or more interference metrics, such as C/I, and one or more quality of service (QoS) metrics such as frame erasure rate (FER) for, say, a traffic class under specific radio conditions. Thus, each 'S' curve is defined for specific traffic types and contexts. In this regard, the 'S' curve processing/analysing function 175 generates an interference penalty matrix for each technology and/or traffic type and/or context. The 'S' curve processing/analysing function 175 then analyses a number of these matrices, in the context of neighbouring cells, to identify an overall interference penalty value. These aggregated values are preferably generated by combining matrices, for example in the manner as illustrated in FIG. 3. Once an overall penalty value has been generated, it is applied to a frequency-planning tool 174, within the IOS 172. Thus, multiple 'S' curves can then be assessed against each other, for example in the context of a penalty matrix, to determine an anticipated interference relationship. Preferably, one example could be a relationship between a frequency carrier supporting a first communication technology and/or traffic type and/or context on a first cell and a frequency carrier supporting a second communication technology and/or traffic type and/or context on a second cell. More generally, the 'S' curve processing/analysing function 175 may be programmed into, say, the IOS 172 in any suitable manner. For example, new apparatus may be added to a conventional IOS 172 (or OMC 146) communication unit. Alternatively existing parts of a conventional IOS 172 (or OMC 146) communication unit may be adapted, for example, by reprogramming one or more processors therein. As such the required adaptation may be implemented in the form of processor-implementable instructions stored on a storage medium, such as a floppy disk, hard disk, programmable read only memory (PROM), random access memory (RAM) or any combination of these or other storage media. Thus, a skilled artisan will appreciate that the configuration 100 shown in FIG. 1 is merely a representative preferred example of an architecture that is able to benefit from the inventive concepts described herein. Referring now to FIG. 2, a typical 'S' curve 200 is illustrated. The S-Curve 200 illustrated in FIG. 2 indicates the C/I ratio versus FER for a GSM full rate speech signal relating to a radio environment characterised by a TU3 fading profile with no frequency hopping. The 'S' curve processing/analysing function 175 of FIG. 1 preferably contains (receives and/or generates) a number of 'S' curves in the manner shown in FIG. 2, for the various technologies and/or traffic types and/or contexts. When applying the inventive concepts to frequency planning for a radio system, it is envisaged that • different S-curves may be generated for different radio cells and radio carriers within those cells, depending on contextual parameters. For example in a GSM radio system, contextual parameters might include the level of discontinuous transmission in a neighbouring cell. In the case of frequency planning for a radio network employing frequency-hopping algorithms, contextual parameters might include the number of frequencies being hopped over and the probability of frequency clashes. Other contextual parameters may include, for example, a Rayleigh fading profile in the radio cell. A skilled artisan would appreciate that many other contextual parameters could be used within the 'S' curve concept. In order to consider the interference relationship of the two (or more) neighbouring wireless communication cells, where each cell may support different technologies and/or traffic types and/or contexts, a number of penalty matrices are generated by the 'S' curve processing/analysing function 175. The matrices are based on the corresponding 'S' curve, such as the 'S' curve illustrated in FIG. 2. Referring now to FIG. 3, two penalty matrices 310, 330 and an aggregate penalty matrix 350 are shown. The concept of a penalty matrix having a number of penalty values is described in the published co-pending patent application - GB 2382503 A - having the same Applicant as the present invention, and is incorporated herein by reference. As illustrated in FIG. 3, each penalty matrix 310, 330 indicates the relative impact, defined as a penalty value (or performance metric) relating to the radio interference between respective pairs of cells 'A' to 'C' when they employ the same frequencies. Each of the penalty values relates to a particular 'S' curve for a given technology and/or traffic type and/or context. In each penalty matrix, cells 'A', 'B' and 'C' are illustrated as columns 312, 314, 316 and rows 318, 320, 322 for a first technology and/or traffic type and/or context. Notably, in accordance with the preferred embodiment of the present invention, the penalty matrix is generated for each technology and/or traffic type and/or context based on 'S' curve data. For example, let us assume a technology-based scenario where a first penalty matrix 310 is generated for GSM voice communication and a second penalty matrix 330 is generated for packet data communication in a general packet radio system (GPRS). Let us first consider the first penalty matrix 310. The 'S' curve processing/analysing function 175 (of FIG. 1) is able to determine, for a given technology and/or traffic type and/or context, the relative impact on cell 'A', assuming that cell 'C' is allocated the same channel frequency as cell 'A'. In FIG.3, this interference impact (penalty) value is '12'. In this case, the penalty value may indicate that 12% of measurement reports received from cell 'A' would have a received signal strength lower than the neighbouring cell 'C' by some value, say 'x' dBs. In accordance with the preferred embodiment of the present invention, the 'S' curve processing/analysing function 175 generates a penalty matrix for each technology and/or traffic type and/or context. Let us then consider the second penalty matrix 330, as illustrated in FIG. 3. Cells 'A', 'B' and 'C' are illustrated as columns 332, 334, 336 and rows 338, 340, 342 for the second technology, which is GPRS. Notably, in accordance with the preferred embodiment of the present invention, the penalty matrix is generated for GPRS technology based on corresponding GPRS 'S' curve data. In accordance with the preferred embodiment of the present invention, the two penalty matrices are combined, for example using a summation approach (although it is envisaged that other aggregate techniques could be used) to produce an aggregate penalty matrix 350 for the scenario where the two technologies are used in neighbouring cells. Thus, the aggregate penalty matrix 350 is the matrix that is used to optimise the frequency plan within the frequency planning tool 174. In summary, the 'S' curve processing/analysing function 175 is able to utilise a number of 'S' curves for a particular technology and/or traffic type and/or context to identify and generate a penalty matrix for that technology and/or traffic type and/or context, where each 'S' curve produces a penalty value. A number,, preferably two, of penalty matrices can then be combined to produce an aggregate penalty matrix 350. Advantageously, the aggregate penalty matrix 350 can be generated from dissimilar technologies and/or traffic types and/or contexts. The 'S' curve processing/analysing function 175 is then able to calculate an overall 'penalty' value, i.e. a value representing the interference effect of applying a specific frequency assignment to a cell having specific interference relationships, to a set of neighbouring cells. Thus, by systematically applying the multiple 'S' curve concept to an interference relationship, irrespective of the interfering technologies/ a carrier-to-carrier, aggregate penalty matrix 350 can be derived by the 'S' curve processing/analysing function 175. In this regard, the frequency planning tool 174 is then able to use the multiple derived penalty matrices for each technology or traffic type or context to minimise the impact of, and interference interrelationship between, different communication technologies being applied to different cells or BTS 122-132 within the cells. This, in turn, enables the frequency planning tool 174 to generate an improved frequency plan for a cellular radio system. By using multiple 'S' curves in this manner, it is therefore possible to capture the effect of interference on a specific traffic type, such as voice, data short message services (SMS), video, etc., across multiple technologies, for example, cells supporting general packet radio system (GPRS) communications, adaptive multi-rate codec (AMR) communications, EDGE communications, GSM full rate speech communications, etc. In order to illustrate the benefits provided by the aforementioned inventive concepts, let us consider a few practical examples. Example 1; At a specific C/I, the probability of an erased frame is different for the different technologies and/or traffic types and/or contexts. Let us therefore consider a radio carrier cell with 100% traffic occupancy of which 50% is contributed by Adaptive Multi-rate (AMR) Enhanced Full Rate (EFR) speech and 50% by standard GSM full rate speech. In the case of the GSM full rate speech communication, a FER of close to 100% might be expected for C/I of higher C/I might be required to achieve this FER performance. Thus, in order to capture these requirements, different 'S' curves pertaining to the different technologies and/or traffic types and/or contexts are employed in the calculation of respective 'penalty' values and the subsequent generation of the penalty matrices. Thus, penalties are defined for interference relationships between radio carriers. Therefore, when a specific carrier frequency supports traffic from more than one traffic type, a number of 'S' curves are generated for each context. In this example, if there are eight timeslots available for both types of traffic, then a penalty value can be calculated as follows: Where: x_Occupany_on_Server is a value associated with the occupancy of a particular traffic type on a specific carrier, e.g. AMR (EFR) or full rate speech; Occupancy_on_interferer is a value associated with the traffic occupancy on the interferer carrier; and Intf(x) is the mean FER value for a particular speech codec such as the AMR (EFR) or full rate GSM speech. The penalty calculation is based on the potential interference resulting from a particular frequency assignment and a context or type of traffic or communication technology such as GPRS, AMR, EDGE, GSM full rate speech, etc. Example 2: Again, let us consider a radio carrier with 100% occupancy, of which 50% is contributed by AMR EFR communication and 50% by GSM full rate speech. If there are eight timeslots available for both types of traffic, then a penalty value may be calculated as follows: Penalty - 8 * (Intf_(AMR) * AMR_Occupancy_on_Server Occupancy_on_Interferer + Intf_full rate speech full_rate_Occupancy_on_Server * Occupancy_on_Interferer) Where the following definitions apply: Intf_AMR: a mean FER for AMR speech frames, which is based on the potential interference resulting from a particular frequency assignment. {N.b. it is envisaged that this could be calculated by applying the specific AMR 'S' curve to the distribution of server-interferer signal level differences for a given server-interferer relationship.} Intf_full_rate: a mean FER for full rate speech frames, which is based on the full rate speech 'S' curve; AMR_Occupancy_on_Server: the occupancy of AMR traffic on a specific carrier; full_rate_Occupancy_on_Server: speech traffic occupancy on a server carrier; and Occupancy_on_Interferer: the traffic occupancy on the interferer carrier. Referring now to FIG. 4, a flowchart 400 illustrates an overview of the preferred frequency planning process. The flowchart commences in step 405 with the IOS collecting a number of measurement reports (MRs). These MRs are preferably entered into a database located within, or operably coupled to, the IOS in step 410. For each radio carrier in each cell, the IOS derives a distribution of measured server cell-to-neighbour cell received signal strength indication (RSSI) differences, as shown in step 415. In accordance with an enhanced embodiment of the present invention, for each measured sample of server-neighbour RSSI difference, the IOS 172 computes a (quality index) penalty value using the appropriate 'S' curves, and, having calculated a number of penalty values, generates one or more penalty matrix from the 'S' curves, as shown in step 420. For each server-neighbour pairing, particularly when the pairings contain dissimilar technologies, traffic types and/or contexts, the IOS 172 then preferably performs a weighted summation of the penalty values (effectively from the multiple 'S' curves), as shown in step 435. Based on the weighted summation of (quality index) penalty values for each server-neighbour pairing, the IOS derives an overall aggregate penalty matrix as shown in step 440. Following the generation of the overall aggregate penalty matrix in step 440, the frequency planning tool is able to run a frequency planning algorithm based on such an improved derived penalty matrix that, for example, relates to two or more technologies and/or traffic types and/or contexts, as shown in step 445. Thus, in this manner, an IOS 172 is able to determine rapidly an optimal set of frequencies to be allocated to cells in a multiple technology environment. Although the preferred embodiment of the present invention has been described with reference to a relationship between carrier-to-interference and FER on a given cell for a particular technology, traffic type and/or context, it is within the contemplation of the invention that one or more interference metrics (such as C/I) could be used, in conjunction with one or more quality of services (such as bit error rate (BER), frame error rate, received signal strength indication (RSSI), etc., as would be appreciated by a skilled artisan. It is also within the contemplation of the present invention that the inventive concepts are not limited to minimising interference between voice and data technologies. Indeed, it is envisaged that the inventive concepts can be applied to any wireless cellular communication system. Notably, the inventive concepts can be applied to any wireless communication system that employs multiple radio frequencies, and is therefore particularly suited to frequency planning in a GSM cellular system. The preferred embodiment of the present invention has been described with regard to a cellular telephony communication system, such as the global system for mobile communications (GSM), supporting a number of traffic types. It is envisaged that the invention is equally applicable to other wireless communication systems, such as a universal mobile telecommunication system (UMTS), any code division multiple access (CDMA) or time division multiple access (TDMA) system,, or an integrated digitally enhanced network (iDEN)TM as supplied by MotorolaTM. It is also within the contemplation of the invention that alternative radio communication architectures, such as private or public mobile radio communication systems could benefit from the inventive concepts described herein. It is also envisaged that: the inventive concepts herein described can be equally applied in commercial frequency planning tools such as NetplanTM, PlanetTM, CellOptTM and OdysseyTM. It will be understood that the communication system, communication unit (such as an IOS or adapted OMC), and improved method for frequency re-planning, as described above, provides at least one or more of the following advantages that could not be reliably obtained using existing frequency planning methods: (i) Supports frequency planning for a radio system with multiple traffic types; (ii) Facilitates frequency planning where there is a non-uniform allocation of penalty values on different radio carriers, for example within the same radio cell. This allows different re-use distances to be achieved for different radio carriers. In so doing, it is now possible to plan for a different quality of service on respective, individual radio carriers; (iii) A multiple 'S' curve processing algorithm can be readily incorporated into a penalty generation system employing measurement reports (MRs). This means that the penalty values generated for individual radio carriers are representative of an actual subscriber's perceived interference; and (iv) The inventive concepts allow for the automatic frequency planning of a radio system supporting multiple technologies such as AMR, GSM, GPRS, EDGE and traffic types, such as voice, data, video or contexts, such as a level of discontinuous transmission in a neighbouring cell, a Rayleigh fading profile for a cell, etc. Whilst the specific and preferred implementations of the embodiments of the present invention are described above, it is clear that a skilled artisan could readily apply variations and modifications of such inventive concepts. Thus, a wireless communication system, a communication unit, and a method for frequency re-planning have been provided wherein the aforementioned disadvantages associated with prior art arrangements have been substantially alleviated. WE CLAIM : 1. A wireless communication system (100) comprising a wireless infrastructure supporting communication for a plurality of mobile communication units (112 - 115), wherein the wireless infrastructure comprises a processor (175) configured to generate a frequency re-use plan, the wireless communication system (100) characterised in that: the processor (175) generates a number of carrier-to-carrier penalty tables based on a plurality of relationships between one or more interference metrics and one or more quality of services for a plurality of communication types, wherein the relationships are generated as a plurality of'S' shaped curves characterizing an interference relationship. 2. A wireless communication system (100) as claimed in Claim 1, wherein the one or more interference metrics comprises a carrier to interference level. 3. A wireless communication system (100) as claimed in Claim 1, wherein the plurality of 'S' curves is substantially pre-generated for passing to the processor (175). 4. A wireless communication system (100) as claimed in Claim 1, wherein the plurality of 'S' curves are substantially automatically generated in a real-time manner based on a received measurement report generated by one or more BTSs or one or more MSs operational within a cell of the wireless communication system (100). 5. A wireless communication system (100) as claimed in any preceding Claim, wherein the relationship between one or more interference metrics and one or more quality of service metrics for a plurality of communication types comprises one or more of the following communication types : real-time traffic class, technologies used within one or more communication cells, system parameters. 6. A wireless communication system (100) as claimed in any preceding Claim, wherein the processor (175) is configured to generate multiple interacting carrier-to-carrier penalty tables based on a plurality of relationship information. 7. A wireless communication system (100) as claimed in Claim 6, wherein the processor (175) calculates a penalty value based on values contained in the multiple interacting penalty tables. 8. A wireless communication system (100) as claimed in any preceding Claim, wherein the processor (175) is configured to contain, or be operably coupled to, a frequency-planning tool for effecting a frequency re-use plan. 9. A wireless communication system (100) as claimed in any preceding Claim, wherein the one or more quality of service metrics of a communication type comprises a frame erasure rate (FER). 10. A wireless communication system (100) as claimed in any preceding Claim, wherein the wireless communication system (100) comprises a plurality of base transceiver stations, with a number of base transceiver stations transmitting on at least one radio frequency. 11. A wireless communication system (100) as claimed in any preceding Claim, wherein the wireless communication system (100) supports communication as claimed in two or more communication types, for example two or more of the following: the GSM standard, AMR, GPRS, EDGE. 12. A wireless communication system (100) as claimed in any preceding Claim, wherein the wireless communication system (100) supports a number of different traffic types having different minimum c/I requirements. 13. A method (400) of frequency re-planning in a wireless communication system, wherein the wireless communication system (100) comprises a wireless infrastructure supporting communication for a plurality of mobile communication units (112-115), the method characterised by the steps of: generating (420) a number of carrier-to-carrier penalty tables based on a plurality of relationships, wherein the relationships are generated as a plurality of 'S' shaped curves characterizing an interference relationship ; and generating a frequency re-use plan based on the number of relationships between one or more interference metrics and one or more quality of service metrics for a number of communication cells. 14. A method (400) of frequency re-planning in a wireless communication system as claimed in Claim 13, wherein the relationships are generated dependent upon one or more of the following: real-time traffic class, technologies used within one or more communication cells, system parameters or contexts. 15. A method (400) of frequency re-planning in a wireless communication system as claimed in Claim 13, wherein the method (400) comprises the step of combining (450) two or more carrier-to-carrier penalty tables to generate an aggregate penalty table 16. A method (400) of frequency re-planning in a wireless communication system as claimed in Claim 13 or Claim 15, wherein the method (400) comprises the step of calculating a penalty value based on values contained in the number of carrier-to-carrier penalty tables. 17. A communication unit (146, 172) operating in a cellular communication system that comprises multiple cells, the communication unit comprising : a processor (175) to generate a number of carrier-to-carrier penalty tables based on a plurality of relationships, wherein the relationships are generated as a plurality of 'S' shaped curves characterizing an interference relationship, and to facilitate a frequency planning operation of the cellular communication system based on the relationship between one or more interference metrics and one or more quality of services for a plurality of communication types. 18. A communication unit (146, 172) as claimed in Claim 17, wherein the communication unit (146,172) comprises a receiving function (176) for receiving information relating to one or more interference metrics and / or one or more quality of service metrics for a plurality of communication types. 19. A communication unit (146, 172) as claimed in Claim 17 or Claim 18, wherein the plurality of communication types comprises one or more of the following: real-time traffic class, technologies used within one or more communication cells, system parameters or contexts. A wireless communication system (100) comprises a wireless infrastructure supporting communication for a plurality of mobile communication units (112-115). The wireless infrastructure comprises a processor (175) configured to generate a frequency re-use plan. The processor (175) generates a frequency re-use plan based on a relationship between one or more interference metrics, such as carrier to interference, and one or more quality of services for a plurality of communication types, to support frequency planning for a radio system with multiple traffic types using non-uniform allocation of penalties on different radio carriers in the same radio cell can be used.

Full Text

A WIRELESS COMMUNICATION SYSTEM, A COMMUNICATION UNIT AND A METHOD OF
FREQUENCY RE-PLANNING IN A WIRELESS COMMUNICATION SYSTEM
Field of the Invention
This invention relates to a wireless communication system, a
communication unit and a method of frequency re-planning in a
wireless communication system. The invention is applicable to, but
not limited to, use of multiple 'S' curves for frequency planning in
a multiple technology wireless cell-based communication environment.
Background of the Invention
Wireless communication systems, for example cellular
telephony or private mobile radio communication systems,
typically provide for radio telecommunication links to be
arranged between a plurality of base transceiver stations
(BTSs) and a plurality of subscriber units, often termed
mobile stations (MSs).
In a wireless communication system, each BTS has
associated with it a particular geographical coverage
area (or cell). Primarily, a transmitter power level of
a BTS defines a coverage area where a BTS can maintain
acceptable communications with MSs operating within its
serving cell. In addition, receiver sensitivity
performance of receiving wireless communication units
also affect3 the extent of a given coverage area. In
large cellular communication systems, these cells are
combined and often overlapped to produce an extensive,
wide coverage area.
Wireless communication systems are distinguished over
fixed communication systems, such as the public switched
telephone network (PSTN), principally in that subscriber
units/mobile stations move between coverage areas, where
communications in the different coverage areas are served
by different BTS (and/or different service providers).
In doing so, the MSs encounter varying radio propagation
environments.
In a cellular system, adjacent cells are typically
configured to overlap, to ensure a contiguous signal
coverage area, whilst the MSs move between cells. The
cell overlap region is deliberately designed into the
system plan to ensure that MSs can successfully handover
between communication cells. The frequencies used in
particular cells are generally selected to minimise a
level of radio interference generated on adjacent cells.
A system design based on cells is typically based on an
ideal cell pattern. However, an idealised cell pattern
never occurs in practice, due to the nature of the
terrain and the fact that cell sites and antennae are not
ideally located on a regular grid pattern. The wireless
system designer therefore uses frequency-planning tools
to estimate the radio propagation for each cell and
predict a corresponding coverage area. Based on these
propagation models, the system designer is able to
develop a frequency plan for the system intended to
minimise the expected interference.
Frequency planning is arguably the most challenging and
time consuming task in designing a mobile communication
system. Effective usage of the frequency spectrum, one
of the scarcest resources for any operator, leads to both
better system quality and increased capacity. In this
regard, the frequency plan considers such factors as
antenna heights and location, terrain topology,
transmitted power levels and the anticipated number of
subscriber units.
In the context of frequency planning, recent developments
in simulation tools have provided the opportunity to
'automatically' perform a frequency re-planning (AFP)
operation, based on analysis of measured data and system
parameters such as transmit power, subscriber receiver
sensitivity, etc. Automating a frequency planning
process typically produces better quality frequency plans
and yields a multitude of benefits, such as:
(i) A better quality of service may be achieved in
systems with minimal opportunity for frequency reuse,
particularly in systems with tight frequency reuse;
(ii) A major capital expenditure in infrastructure may
be deferred, as the current system is able to handle more
traffic at a given quality of service; and
(iii) The time for frequency planning is reduced -
enabling system designers enough time to concentrate on
other, more complex enhancements to system quality.
For systems supporting AFP applications, there is a
requirement on active subscriber units to scan as many
frequencies as possible to aid frequency planning. This
information, in the form of measurement reports, is fed
into an AFP application that is able to determine an
optimal frequency plan for the communication system.
A number of techniques exist for allocating frequencies
to cells in a radio system within a frequency planning
operation. Typically, these techniques are based on
maximising the Carrier to Interference ratio (C/I) for
those 'pixels' included in the 'analysis space' of a
frequency planning tool. The major weakness of these
techniques is that they assume a uniform distribution of
subscriber units in a cell. As such the known techniques
do not accurately reflect the actual distribution of C/I
that can be encountered in a cell. A further weakness of
these techniques is that the non-uniform distribution of
communication traffic, where the traffic may include
speech, data, signalling, video, etc., each of which has
different minimum interference requirements, is not
captured in the frequency planning algorithm.
Furthermore, with the advent of packet switched and
adaptive multi-rate technologies, frequency planning
based on a single criterion is no longer an optimal
solution. Typically, frequency planning tools seek to
exceed a minimum C/I in all radio cells. However, radio
carriers will now need to support traffic with
heterogeneous minimum C/I requirements.
Thus, there exists a need in the field of the present
invention to provide a wireless communication system, a
communication unit and method for frequency re-planning;
wherein the aforementioned disadvantages may be
alleviated.
Statement of Invention
In accordance with a first aspect of the present
invention there is provided a wireless communication
system, as claimed in Claim 1.
In accordance with a second aspect of the present
invention, there is provided a method of frequency re-
planning in a wireless communication system, as claimed
in Claim 14.
In accordance with a third aspect of the present
invention, there is provided a storage medium, as claimed
in Claim 19.
In accordance with a fourth aspect of the present
invention, there is provided a communication unit, as
claimed in Claim 20.
In summary, the inventive concepts of the present
invention propose a wireless communication system (100),
a method of frequency planning and a communication unit
to generate a frequency plan based on a relationship
between one or more interference metrics and one or more
quality of services for a plurality of communication
types.
Preferably, the one or more interference metrics may
comprise a carrier to interference metric and the one or
more quality of services may comprise frame erasure rate
(FER). The preferred embodiment generates and uses
multiple 'S' curves, where each curve describes a
relationship between, say, C/I and frame erasure rate
(FER) for a given technology, traffic class and/or
context under specific radio conditions. Thus, each 'S'
curve is defined for specific technologies and/or traffic
types and/or contexts.
Once multiple 'S' curves have been generated, they are
applied to a frequency-planning tool. Multiple 'S'
curves can then be assessed against each other, for
example in the context of a penalty matrix, to identify a
specific interference relationship, for example, between
a frequency carrier supporting a first communication
technology and/or traffic type and/or context on a first
cell and a frequency carrier supporting a second
communication technology and/or traffic type and/or
context on a second cell.
Preferably, an overall 'penalty' value is calculated for
one or more radio interference scenarios, i.e. a value
representing the effect of applying a specific frequency
assignment to a cell with specific interference
relationships to a set of neighbouring cells. In this
manner, the inventive concepts facilitate frequency
planning for a non-uniform allocation of penalty values
on different radio carriers, for example within the same
radio cell. This allows different re-use distances to be
achieved for different radio carriers. In so doing, it
is now possible to plan for a different quality of
service on respective, individual radio carriers.
By systematically applying a number of 'S' curves to
identify an interference relationship, a carrier-to-
carrier penalty matrix can also be derived. In this
regard, the frequency planning tool is then able to use
the derived penalty matrix to analyse the impact of, and
interference interrelationship between, different
communication technologies being applied to different
cells or BTSs within the cells. This, in turn, enables
the frequency planning tool to generate an improved
frequency plan for a cellular radio system, particularly
one supporting multiple technologies and/or traffic types
and/or contexts.
Accompanying
Brief Description of the Accompaying Drawings
Exemplary embodiments of the present invention will now
be described, with reference to the accompanying
drawings, in which:
FIG. 1 illustrates a block diagram of a cellular radio
communications system adapted to support the various
inventive concepts of a preferred embodiment of the
present invention;
FIG. 2 illustrates a graph of a typical 'S'-curve;
FIG. 3 illustrates a penalty table in accordance with the
preferred embodiment of the present invention; and
FIG. 4 illustrates a flowchart of a frequency re-planning
process using multiple 'S'-curves, in accordance with a
preferred embodiment of the present invention.
Description of Preferred Embodiments
Referring first to FIG. 1, a multi-layer cellular
telephone communication system 100 is shown, in outline,
supporting a Global System for Mobile communication (GSM)
air-interface, in accordance with a preferred embodiment
of the invention. The European Telecommunications
Standards Institute (ETSI) has defined the GSM air-
interface. The multi-layer cellular system is shown in a
simplified form, with a limited number of system elements
shown for clarity purposes only.
Generally, the air-interface protocol is administered
from base transceiver sites, within the system
architecture 110, that are geographically spaced apart -
one base site supporting a cell (or, for example, sectors
of a cell).
A plurality of subscriber units 112-115 is shown as
communicating over the selected air-interface 117-120
with a plurality of base transceiver stations (BTS) 122-
132. A limited number of MSs 112-115 andBTSs 122-132
are shown for clarity purposes only. The BTSs 122-132
may be connected to a conventional public-switched
telephone network (PSTN) 134 through base site
controllers (BSCs) 136-140 and mobile switching centres
(MSCs) 142-144. Each BTS 122-132 is principally designed
to serve its primary cell, with each BTS 122-132
containing one or more transceiver units to communicate
156-166 with the rest of the cellular system
infrastructure
Each BSC 136-140 may control one or more BTSs 122-132,
with BSCs 136-140 generally interconnected through MSCs
142-144. Processes within the MSCs are provided to
account for the situation where a MS (112-115) passes
between two BTS serving areas, for example MS 112 moving
from an area covered by BTS 122 to an area covered by BTS
124, where the two BTSs are controlled by different BSCs
(BSC 136 and BSC 138 in this example).
Each MSC 142-144 provides a gateway to the PSTN 134, with
MSCs 142-144 interconnected through an operations and
management centre (OMC) 146 that administers general
control of the cellular telephone communication system
100, as will be understood by those skilled in the art.
The various system elements, such as BSCs 136-138 and OMC
146, include control logic 148, 150, 152, with the
various system elements usually having an associated
memory function 154 (shown only in relation to BSC 138
for the sake of clarity). A memory function 153 of the
OMC 146 typically stores historically compiled
operational data, as well as in-call data, control
algorithms and system information such as neighbouring
cell-site lists, for example a list of frequencies to be
scanned by the respective MSs. In operation, an initial
frequency re-use plan is set by an intelligent
optimisation system (IOS) 172 and notified to the OMC
146. The OMC 146 commands the BTSs 122-132 via their
BSCs 136-140 to set their operating frequencies
accordingly.
In accordance with the preferred embodiment of the
present invention, an intelligent optimisation system
(IOS) 172 is operably coupled to the OMC 146 and the base
station controllers 136-140. Notably, the IOS 172
comprises an 'S' curve processing/analysing function 175,
which is configured to process/analyse a number of 'S'
curves relating to particular technologies and/or traffic
types and/or contexts and identify an interference
relationship between the technologies and/or traffic
types and/or contexts employed in neighbouring cells.
The processing of multiple yS' curves enables the OS 172
to generate an improved frequency re-use plan in
accordance with the preferred embodiment of the present
invention.
In alternative embodiments, it is envisaged that the 'S'
curve processing/analysing function 175 may be located
within the OMC 146. Indeed, it is envisaged that in
alternative embodiments, the 'S' curve
processing/analysing function 175 may be operably coupled
to other functions within the wireless communication
system, or even distributed across a number of elements,
if appropriate.
The 'S' curve processing/analysing function 175 is
configured to receive C/I information and related quality
of service metrics, such as frame error rate (FER)
information for each communication cell supported by the
OMC 146. In the preferred embodiment of the present
invention, this 'S' curve information is pre-generated
by, say, an Operator, and. loaded into the 'S' curve
processing/analysing function 175.
In order to derive multiple S-curves, it is envisaged
that a physical layer simulation model may be used by,
say, the Operator. Advantageously, in the context of
frequency planning a cellular system that incorporates a
multitude of radio technologies/ the use of multiple 'S'-
curves can also be used to capture the effect of
discontinuous transmission and frequency hopping. For
example in the case of a frequency hopping wireless
communication technology, the effect of different Mobile
Allocation List lengths on the FER of different
technologies, for a given level of radio interference
(C/I), could be modelled by the simulator. The results
of the simulation may be used to derive corresponding
frequency-hopping S-curves for the different
technologies. Correspondingly, the effect of combining
discontinuous transmission and frequency hopping can be
modelled such that the 'S' curve relates their effect on
the relationship between C/I and FER.
In an alternative embodiment of the present invention/ it
is envisaged that the 'S' curve data can be automatically
generated in a real-time manner based on received
measurement reports (MRs), generated by BTSs or MSs
operational within particular cells. Notably, the
information received in this scenario, in order to
classify the 'S' curve data, also preferably indicates
real-time traffic types, technologies used within the
cell, system parameters, etc.
In this regard, the 'S' curve processing/analysing
function 175 within the IOS 172 is operably coupled to a
collection function 176, which is operably coupled to the
BSCs 136-140 for collating cell information. The 'S'
curve processing/analysing function 175 then analyses the
interference relationship between multiple 'S' curves,
when considered in the context of configuring
corresponding cells as neighbouring cells in a wireless
communication system.
Each 'S' curve describes a relationship between one or
more interference metrics, such as C/I, and one or more
quality of service (QoS) metrics such as frame erasure
rate (FER) for, say, a traffic class under specific radio
conditions. Thus, each 'S' curve is defined for specific
traffic types and contexts. In this regard, the 'S'
curve processing/analysing function 175 generates an
interference penalty matrix for each technology and/or
traffic type and/or context. The 'S' curve
processing/analysing function 175 then analyses a number
of these matrices, in the context of neighbouring cells,
to identify an overall interference penalty value. These
aggregated values are preferably generated by combining
matrices, for example in the manner as illustrated in
FIG. 3. Once an overall penalty value has been
generated, it is applied to a frequency-planning tool
174, within the IOS 172.
Thus, multiple 'S' curves can then be assessed against
each other, for example in the context of a penalty
matrix, to determine an anticipated interference
relationship. Preferably, one example could be a
relationship between a frequency carrier supporting a
first communication technology and/or traffic type and/or
context on a first cell and a frequency carrier
supporting a second communication technology and/or
traffic type and/or context on a second cell.
More generally, the 'S' curve processing/analysing
function 175 may be programmed into, say, the IOS 172 in
any suitable manner. For example, new apparatus may be
added to a conventional IOS 172 (or OMC 146)
communication unit. Alternatively existing parts of a
conventional IOS 172 (or OMC 146) communication unit may
be adapted, for example, by reprogramming one or more
processors therein. As such the required adaptation may
be implemented in the form of processor-implementable
instructions stored on a storage medium, such as a floppy
disk, hard disk, programmable read only memory (PROM),
random access memory (RAM) or any combination of these or
other storage media.
Thus, a skilled artisan will appreciate that the
configuration 100 shown in FIG. 1 is merely a
representative preferred example of an architecture that
is able to benefit from the inventive concepts described
herein.
Referring now to FIG. 2, a typical 'S' curve 200 is
illustrated. The S-Curve 200 illustrated in FIG. 2
indicates the C/I ratio versus FER for a GSM full rate
speech signal relating to a radio environment
characterised by a TU3 fading profile with no frequency
hopping. The 'S' curve processing/analysing function 175
of FIG. 1 preferably contains (receives and/or generates)
a number of 'S' curves in the manner shown in FIG. 2, for
the various technologies and/or traffic types and/or
contexts.
When applying the inventive concepts to frequency
planning for a radio system, it is envisaged that •
different S-curves may be generated for different radio
cells and radio carriers within those cells, depending on
contextual parameters. For example in a GSM radio
system, contextual parameters might include the level of
discontinuous transmission in a neighbouring cell. In
the case of frequency planning for a radio network
employing frequency-hopping algorithms, contextual
parameters might include the number of frequencies being
hopped over and the probability of frequency clashes.
Other contextual parameters may include, for example, a
Rayleigh fading profile in the radio cell. A skilled
artisan would appreciate that many other contextual
parameters could be used within the 'S' curve concept.
In order to consider the interference relationship of the
two (or more) neighbouring wireless communication cells,
where each cell may support different technologies and/or
traffic types and/or contexts, a number of penalty
matrices are generated by the 'S' curve
processing/analysing function 175. The matrices are
based on the corresponding 'S' curve, such as the 'S'
curve illustrated in FIG. 2.
Referring now to FIG. 3, two penalty matrices 310, 330
and an aggregate penalty matrix 350 are shown. The
concept of a penalty matrix having a number of penalty
values is described in the published co-pending patent
application - GB 2382503 A - having the same Applicant as
the present invention, and is incorporated herein by
reference. As illustrated in FIG. 3, each penalty matrix
310, 330 indicates the relative impact, defined as a
penalty value (or performance metric) relating to the
radio interference between respective pairs of cells 'A'
to 'C' when they employ the same frequencies. Each of
the penalty values relates to a particular 'S' curve for
a given technology and/or traffic type and/or context.
In each penalty matrix, cells 'A', 'B' and 'C' are
illustrated as columns 312, 314, 316 and rows 318, 320,
322 for a first technology and/or traffic type and/or
context. Notably, in accordance with the preferred
embodiment of the present invention, the penalty matrix
is generated for each technology and/or traffic type
and/or context based on 'S' curve data. For example, let
us assume a technology-based scenario where a first
penalty matrix 310 is generated for GSM voice
communication and a second penalty matrix 330 is
generated for packet data communication in a general
packet radio system (GPRS).
Let us first consider the first penalty matrix 310. The
'S' curve processing/analysing function 175 (of FIG. 1)
is able to determine, for a given technology and/or
traffic type and/or context, the relative impact on cell
'A', assuming that cell 'C' is allocated the same channel
frequency as cell 'A'. In FIG.3, this interference
impact (penalty) value is '12'. In this case, the
penalty value may indicate that 12% of measurement
reports received from cell 'A' would have a received
signal strength lower than the neighbouring cell 'C' by
some value, say 'x' dBs.
In accordance with the preferred embodiment of the
present invention, the 'S' curve processing/analysing
function 175 generates a penalty matrix for each
technology and/or traffic type and/or context. Let us
then consider the second penalty matrix 330, as
illustrated in FIG. 3. Cells 'A', 'B' and 'C' are
illustrated as columns 332, 334, 336 and rows 338, 340,
342 for the second technology, which is GPRS. Notably,
in accordance with the preferred embodiment of the
present invention, the penalty matrix is generated for
GPRS technology based on corresponding GPRS 'S' curve
data.
In accordance with the preferred embodiment of the
present invention, the two penalty matrices are combined,
for example using a summation approach (although it is
envisaged that other aggregate techniques could be used)
to produce an aggregate penalty matrix 350 for the
scenario where the two technologies are used in
neighbouring cells. Thus, the aggregate penalty matrix
350 is the matrix that is used to optimise the frequency
plan within the frequency planning tool 174.
In summary, the 'S' curve processing/analysing function
175 is able to utilise a number of 'S' curves for a
particular technology and/or traffic type and/or context
to identify and generate a penalty matrix for that
technology and/or traffic type and/or context, where each
'S' curve produces a penalty value. A number,, preferably
two, of penalty matrices can then be combined to produce
an aggregate penalty matrix 350. Advantageously, the
aggregate penalty matrix 350 can be generated from
dissimilar technologies and/or traffic types and/or
contexts. The 'S' curve processing/analysing function
175 is then able to calculate an overall 'penalty' value,
i.e. a value representing the interference effect of
applying a specific frequency assignment to a cell having
specific interference relationships, to a set of
neighbouring cells.
Thus, by systematically applying the multiple 'S' curve
concept to an interference relationship, irrespective of
the interfering technologies/ a carrier-to-carrier,
aggregate penalty matrix 350 can be derived by the 'S'
curve processing/analysing function 175. In this regard,
the frequency planning tool 174 is then able to use the
multiple derived penalty matrices for each technology or
traffic type or context to minimise the impact of, and
interference interrelationship between, different
communication technologies being applied to different
cells or BTS 122-132 within the cells. This, in turn,
enables the frequency planning tool 174 to generate an
improved frequency plan for a cellular radio system.
By using multiple 'S' curves in this manner, it is
therefore possible to capture the effect of interference
on a specific traffic type, such as voice, data short
message services (SMS), video, etc., across multiple
technologies, for example, cells supporting general
packet radio system (GPRS) communications, adaptive
multi-rate codec (AMR) communications, EDGE
communications, GSM full rate speech communications, etc.
In order to illustrate the benefits provided by the
aforementioned inventive concepts, let us consider a few
practical examples.
Example 1;
At a specific C/I, the probability of an erased frame is
different for the different technologies and/or traffic
types and/or contexts. Let us therefore consider a radio
carrier cell with 100% traffic occupancy of which 50% is
contributed by Adaptive Multi-rate (AMR) Enhanced Full
Rate (EFR) speech and 50% by standard GSM full rate
speech. In the case of the GSM full rate speech
communication, a FER of close to 100% might be expected
for C/I of higher C/I might be required to achieve this FER
performance.
Thus, in order to capture these requirements, different
'S' curves pertaining to the different technologies
and/or traffic types and/or contexts are employed in the
calculation of respective 'penalty' values and the
subsequent generation of the penalty matrices. Thus,
penalties are defined for interference relationships
between radio carriers. Therefore, when a specific
carrier frequency supports traffic from more than one
traffic type, a number of 'S' curves are generated for
each context.
In this example, if there are eight timeslots available
for both types of traffic, then a penalty value can be
calculated as follows:

Where:
x_Occupany_on_Server is a value associated with
the occupancy of a particular traffic type on a specific
carrier, e.g. AMR (EFR) or full rate speech;
Occupancy_on_interferer is a value associated
with the traffic occupancy on the interferer carrier; and
Intf(x) is the mean FER value for a particular
speech codec such as the AMR (EFR) or full rate GSM
speech.
The penalty calculation is based on the potential
interference resulting from a particular frequency
assignment and a context or type of traffic or
communication technology such as GPRS, AMR, EDGE, GSM
full rate speech, etc.
Example 2:
Again, let us consider a radio carrier with 100%
occupancy, of which 50% is contributed by AMR EFR
communication and 50% by GSM full rate speech. If there
are eight timeslots available for both types of traffic,
then a penalty value may be calculated as follows:
Penalty - 8 * (Intf_(AMR) * AMR_Occupancy_on_Server
*Occupancy_on_Interferer + Intf_full rate speech *
full_rate_Occupancy_on_Server *
Occupancy_on_Interferer)
Where the following definitions apply:
Intf_AMR: a mean FER for AMR speech frames, which
is based on the potential interference resulting from a
particular frequency assignment. {N.b. it is envisaged
that this could be calculated by applying the specific
AMR 'S' curve to the distribution of server-interferer
signal level differences for a given server-interferer
relationship.}
Intf_full_rate: a mean FER for full rate speech
frames, which is based on the full rate speech 'S' curve;
AMR_Occupancy_on_Server: the occupancy of AMR
traffic on a specific carrier;
full_rate_Occupancy_on_Server: speech traffic
occupancy on a server carrier; and
Occupancy_on_Interferer: the traffic occupancy on
the interferer carrier.
Referring now to FIG. 4, a flowchart 400 illustrates an
overview of the preferred frequency planning process.
The flowchart commences in step 405 with the IOS
collecting a number of measurement reports (MRs). These
MRs are preferably entered into a database located
within, or operably coupled to, the IOS in step 410. For
each radio carrier in each cell, the IOS derives a
distribution of measured server cell-to-neighbour cell
received signal strength indication (RSSI) differences,
as shown in step 415.
In accordance with an enhanced embodiment of the present
invention, for each measured sample of server-neighbour
RSSI difference, the IOS 172 computes a (quality index)
penalty value using the appropriate 'S' curves, and,
having calculated a number of penalty values, generates
one or more penalty matrix from the 'S' curves, as shown
in step 420. For each server-neighbour pairing,
particularly when the pairings contain dissimilar
technologies, traffic types and/or contexts, the IOS 172
then preferably performs a weighted summation of the
penalty values (effectively from the multiple 'S'
curves), as shown in step 435.
Based on the weighted summation of (quality index)
penalty values for each server-neighbour pairing, the IOS
derives an overall aggregate penalty matrix as shown in
step 440. Following the generation of the overall
aggregate penalty matrix in step 440, the frequency
planning tool is able to run a frequency planning
algorithm based on such an improved derived penalty
matrix that, for example, relates to two or more
technologies and/or traffic types and/or contexts, as
shown in step 445.
Thus, in this manner, an IOS 172 is able to determine
rapidly an optimal set of frequencies to be allocated to
cells in a multiple technology environment.
Although the preferred embodiment of the present
invention has been described with reference to a
relationship between carrier-to-interference and FER on a
given cell for a particular technology, traffic type
and/or context, it is within the contemplation of the
invention that one or more interference metrics (such as
C/I) could be used, in conjunction with one or more
quality of services (such as bit error rate (BER), frame
error rate, received signal strength indication (RSSI),
etc., as would be appreciated by a skilled artisan.
It is also within the contemplation of the present
invention that the inventive concepts are not limited to
minimising interference between voice and data
technologies. Indeed, it is envisaged that the inventive
concepts can be applied to any wireless cellular
communication system. Notably, the inventive concepts
can be applied to any wireless communication system that
employs multiple radio frequencies, and is therefore
particularly suited to frequency planning in a GSM
cellular system.
The preferred embodiment of the present invention has
been described with regard to a cellular telephony
communication system, such as the global system for
mobile communications (GSM), supporting a number of
traffic types. It is envisaged that the invention is
equally applicable to other wireless communication
systems, such as a universal mobile telecommunication
system (UMTS), any code division multiple access (CDMA)
or time division multiple access (TDMA) system,, or an
integrated digitally enhanced network (iDEN)TM as supplied
by MotorolaTM. It is also within the contemplation of the
invention that alternative radio communication
architectures, such as private or public mobile radio
communication systems could benefit from the inventive
concepts described herein.
It is also envisaged that: the inventive concepts herein
described can be equally applied in commercial frequency
planning tools such as NetplanTM, PlanetTM, CellOptTM and
OdysseyTM.
It will be understood that the communication system,
communication unit (such as an IOS or adapted OMC), and
improved method for frequency re-planning, as described
above, provides at least one or more of the following
advantages that could not be reliably obtained using
existing frequency planning methods:
(i) Supports frequency planning for a radio
system with multiple traffic types;
(ii) Facilitates frequency planning where there
is a non-uniform allocation of penalty values on
different radio carriers, for example within the same
radio cell. This allows different re-use distances to be
achieved for different radio carriers. In so doing, it
is now possible to plan for a different quality of
service on respective, individual radio carriers;
(iii) A multiple 'S' curve processing algorithm
can be readily incorporated into a penalty generation
system employing measurement reports (MRs). This means
that the penalty values generated for individual radio
carriers are representative of an actual subscriber's
perceived interference; and
(iv) The inventive concepts allow for the
automatic frequency planning of a radio system supporting
multiple technologies such as AMR, GSM, GPRS, EDGE and
traffic types, such as voice, data, video or contexts,
such as a level of discontinuous transmission in a
neighbouring cell, a Rayleigh fading profile for a cell,
etc.
Whilst the specific and preferred implementations of the
embodiments of the present invention are described above,
it is clear that a skilled artisan could readily apply
variations and modifications of such inventive concepts.
Thus, a wireless communication system, a communication
unit, and a method for frequency re-planning have been
provided wherein the aforementioned disadvantages
associated with prior art arrangements have been
substantially alleviated.
WE CLAIM :
1. A wireless communication system (100) comprising a wireless infrastructure supporting
communication for a plurality of mobile communication units (112 - 115), wherein the wireless
infrastructure comprises a processor (175) configured to generate a frequency re-use plan, the
wireless communication system (100) characterised in that:
the processor (175) generates a number of carrier-to-carrier penalty tables based on a
plurality of relationships between one or more interference metrics and one or more quality of
services for a plurality of communication types, wherein the relationships are generated as a
plurality of'S' shaped curves characterizing an interference relationship.
2. A wireless communication system (100) as claimed in Claim 1, wherein the one or more
interference metrics comprises a carrier to interference level.
3. A wireless communication system (100) as claimed in Claim 1, wherein the plurality of 'S'
curves is substantially pre-generated for passing to the processor (175).
4. A wireless communication system (100) as claimed in Claim 1, wherein the plurality of 'S'
curves are substantially automatically generated in a real-time manner based on a received
measurement report generated by one or more BTSs or one or more MSs operational within a
cell of the wireless communication system (100).
5. A wireless communication system (100) as claimed in any preceding Claim, wherein the
relationship between one or more interference metrics and one or more quality of service
metrics for a plurality of communication types comprises one or more of the following
communication types : real-time traffic class, technologies used within one or more
communication cells, system parameters.
6. A wireless communication system (100) as claimed in any preceding Claim, wherein the
processor (175) is configured to generate multiple interacting carrier-to-carrier penalty tables
based on a plurality of relationship information.
7. A wireless communication system (100) as claimed in Claim 6, wherein the processor (175)
calculates a penalty value based on values contained in the multiple interacting penalty tables.
8. A wireless communication system (100) as claimed in any preceding Claim, wherein the
processor (175) is configured to contain, or be operably coupled to, a frequency-planning tool
for effecting a frequency re-use plan.
9. A wireless communication system (100) as claimed in any preceding Claim, wherein the one
or more quality of service metrics of a communication type comprises a frame erasure rate
(FER).
10. A wireless communication system (100) as claimed in any preceding Claim, wherein the
wireless communication system (100) comprises a plurality of base transceiver stations, with a
number of base transceiver stations transmitting on at least one radio frequency.
11. A wireless communication system (100) as claimed in any preceding Claim, wherein the
wireless communication system (100) supports communication as claimed in two or more
communication types, for example two or more of the following: the GSM standard, AMR,
GPRS, EDGE.
12. A wireless communication system (100) as claimed in any preceding Claim, wherein the
wireless communication system (100) supports a number of different traffic types having
different minimum c/I requirements.
13. A method (400) of frequency re-planning in a wireless communication system, wherein the
wireless communication system (100) comprises a wireless infrastructure supporting
communication for a plurality of mobile communication units (112-115), the method
characterised by the steps of:
generating (420) a number of carrier-to-carrier penalty tables based on a plurality of
relationships, wherein the relationships are generated as a plurality of 'S' shaped curves
characterizing an interference relationship ; and
generating a frequency re-use plan based on the number of relationships between one or
more interference metrics and one or more quality of service metrics for a number of
communication cells.
14. A method (400) of frequency re-planning in a wireless communication system as claimed in
Claim 13, wherein the relationships are generated dependent upon one or more of the
following: real-time traffic class, technologies used within one or more communication cells,
system parameters or contexts.
15. A method (400) of frequency re-planning in a wireless communication system as claimed
in Claim 13, wherein the method (400) comprises the step of
combining (450) two or more carrier-to-carrier penalty tables to generate an aggregate
penalty table
16. A method (400) of frequency re-planning in a wireless communication system as claimed
in Claim 13 or Claim 15, wherein the method (400) comprises the step of
calculating a penalty value based on values contained in the number of carrier-to-carrier
penalty tables.
17. A communication unit (146, 172) operating in a cellular communication system that
comprises multiple cells, the communication unit comprising :
a processor (175) to generate a number of carrier-to-carrier penalty tables based on a
plurality of relationships, wherein the relationships are generated as a plurality of 'S' shaped
curves characterizing an interference relationship, and to facilitate a frequency planning
operation of the cellular communication system based on the relationship between one or more
interference metrics and one or more quality of services for a plurality of communication types.
18. A communication unit (146, 172) as claimed in Claim 17, wherein the communication unit
(146,172) comprises a receiving function (176) for receiving information relating to one or
more interference metrics and / or one or more quality of service metrics for a plurality of
communication types.
19. A communication unit (146, 172) as claimed in Claim 17 or Claim 18, wherein the plurality
of communication types comprises one or more of the following: real-time traffic class,
technologies used within one or more communication cells, system parameters or contexts.
A wireless communication system (100) comprises a wireless infrastructure
supporting communication for a plurality of mobile communication units (112-115). The
wireless infrastructure comprises a processor (175) configured to generate a frequency re-use
plan. The processor (175) generates a frequency re-use plan based on a relationship between
one or more interference metrics, such as carrier to interference, and one or more quality of
services for a plurality of communication types, to support frequency planning for a radio
system with multiple traffic types using non-uniform allocation of penalties on different radio
carriers in the same radio cell can be used.

Documents:

2483-KOLNP-2005-(26-03-2012)-ASSIGNMENT.pdf

2483-KOLNP-2005-(26-03-2012)-CORRESPONDENCE.pdf

2483-KOLNP-2005-(26-03-2012)-FORM-16.pdf

2483-KOLNP-2005-(26-03-2012)-PA-CERTIFIED COPIES.pdf

2483-KOLNP-2005-FORM-27.pdf

2483-kolnp-2005-granted-abstract.pdf

2483-kolnp-2005-granted-claims.pdf

2483-kolnp-2005-granted-correspondence.pdf

2483-kolnp-2005-granted-description (complete).pdf

2483-kolnp-2005-granted-drawings.pdf

2483-kolnp-2005-granted-examination report.pdf

2483-kolnp-2005-granted-form 1.pdf

2483-kolnp-2005-granted-form 18.pdf

2483-kolnp-2005-granted-form 3.pdf

2483-kolnp-2005-granted-form 5.pdf

2483-kolnp-2005-granted-pa.pdf

2483-kolnp-2005-granted-reply to examination report.pdf

2483-kolnp-2005-granted-specification.pdf

« Previous Patent

Next Patent »

Patent Number

224762

Indian Patent Application Number

2483/KOLNP/2005

PG Journal Number

43/2008

Publication Date

24-Oct-2008

Grant Date

22-Oct-2008

Date of Filing

05-Dec-2005

Name of Patentee

MOTOROLA, INC

Applicant Address

1303, EAST ALGONQUIN ROAD, SCHAUMBURG, ILLINOIS

Inventors:

#	Inventor's Name	Inventor's Address
1	WILLIAMS, OLATUNDE	FLAT B, AVON HOUSE, TITHE BARN CRESCENT, SWINDON, WILTSHIRE SN1 4NP
2	BRUSCH, SIMON	1 SANDVIEW, FARINGDON, OXFORDSHIRE SN7 7UT
3	RATFORD, MICHAEL	GROUND FLOOR FLAT, 10 GREAT POLTENEY STREET, BATH, SOMERSET BA2 4BR

PCT International Classification Number

H04Q 7/36, 7/38

PCT International Application Number

PCT/EP2004/050999

PCT International Filing date

2004-06-02

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0317150.1	2003-07-23	U.K.