Title of Invention

METHOD FOR LOW SPEED TRANSMISSION OF DATA IN THE CONNECTION ORIENTED MODALITY IN A DECT SYSTEM

Abstract

Method for the low speed transmission of data in the connection oriented modality in a DECT system including at least one radio fixed part (RFP) and at least one peripheral unit (PP), where the transmission of data between said units is organised in frames having pre-set duration in which a given number of time slots are allocated. The method foresees the low speed data transmission enabling only the field (S) and the field (A) of each time slot, disabling at the same time the field (B) provided for the transmission of data according to the conventional DECT standard. Disabling the above mentioned field (B), it is possible to reduce by approximately 70% (seventy percent) of the power required to implement data transmission operations. Therefore, said method is partcularly advantageous in whichever "data exchange/data/collectio application foreseeing the use of the DECT standard and requiring fixed or mobile low power consumption peripheral stations with local battery supply.

Full Text

The present invention relates in general to a system for low speed transmission of data in the connection oriented modality on the DECT system, and more particularly relates to a system to offer data services to the users of the DECT system. As it is already known, the cordless system, called DECT (Digital Enhanced Cordless Telephone) includes a plurality of radio fixed transreceiver stations, distributed in order to cover the concerned areas and connected to a communication network of the private type (PABX), and portable user sets which connect via radio to the fixed parts and are therefore able to communicate between them and with other fixed users connected to the public network. Connections can be of the voice type or enable data exchange occupying the equivalent of one or more voice channels. A first structure of the DECT network is outlined as an example in Figure 1. It includes groupings of k (in the example shown in the figure k = 4) radio fixed parts RFP preferably connected, to branches (in the example 3 branches) formed of connection or dorsal lines L through drop/insert devices DI. Without departing from the scope of the present invention, it results possible to star connect each RFP station to the CCFP unit, thus eliminating the above mentioned dorsals lines and of course, also drop/insert DI devices. Each fixed part RFP can manage via radio a given number of PP (Portable Part) users, which are generally mobile ones. 2 The branches revert to a transcoder battery TRAS, and this last is connected to the public network PSTN (Public Switching Telephone Network) through a central control fixed part CCFP (Common Control Fixed Part), associated to a switching network or peripheral advanced module MEP. The interface between the CCFP and the DECT network, as far as the voice signal is concerned, typically consists of 64 Kbit/s The CCFP unit is associated to a battery of transcoders TRAS performing the conversion of the PCM coding on eight bits when used on the PSTH side, in ADPCM coding (Adaptive Differential Pulse Code Modulation), on four bits when used on DECT side. In this way, two 32 Kbit/s channels are grouped on each 6*f Kbit/s channel. The 2.048 Mbit/s (bi-directional) dorsal connecting the CCFP to the different radio fixed parts RFP supports therefore 48 voice channels plus a pre-set number of synchronization and signalling channels. The area covered by a fixed part or cell is generally rather reduced, reaching coverings even in the range of tenths or hundreds of metres of radius. Typical applications of cordless systems are encountered in industrial installations where they can substitute the laying of a cabled network, in commercial complexes or urban centres, where they can advantageously replace public telephone call boxes and others. The telecommunication network for personal calls is of the digital type. The radio access falls under the FDMA - TDMA -TDD class. 3 The system is of the TDD (Time Division Duplex) type since transmission and receipt do not take place at the same time. More in detail, as shown referring to figure 2, the 10 millisecond basic frame is divided into two halves; in general, during the first 5 ms, the fixed part transmits and portable sets receive (TX DECT half frame for the fixed part, and RX DECT for the portable set), and during the subsequent 5 ms, the reverse operation takes place. Each half-frame consists of 12 time slots of the full type (the system is a TDKA one, due to this reason), each of them consisting of 420 (or 424, according to the case) bits. Time slots are transmitted or received using 10 (or more) different frequencies (the system is a FDMA one, due to this reason) totalling 120 (or more) slots available to the system, which are allocated time by time in order not to create interference problems. In the present description, the terms "data and data services" are referred to the transport of digital signals nor originated by voice, such as files, digital images, alphanumeric messages, video (moving digital images) or in general data suitable to supply multimedia services. Though the DECT system has been conceived also for data exchange between users, its present practical implementations are oriented to the transmission of voice services between the users. For the supply of services offered to the users of the DECT system, solutions have been proposed not resulting satisfact - 4 - when the quantity of data to be transmitted is lover than a given extent, for instance in the range of 1-2 Kbit/sec. Works are currently in progress for analogue modems to be used on the DECT system, likewise what happens for the users of the traditional telephone network. This method enables very poor performances in terms of bit rate available to the user, and also the use of analogue modems involves useless analogue/ digital conversions to carry a digital signal on a transmission system being already digital in itself. In practice, through said analogue modems, the signal to be transmitted by the user is converted into an analogue signal and sent as voice on the DECT system. This one, in its turn, converts the signal in the digital format to transfer the same, as it were a voice signal and sends it to the network. These useless conversions significantly deteriorate the Performances which can be obtained from the system. Solutions have also been proposed, involving the modification of DECT access equipment, or of the Radio Fixed Parts (RFP). In practice, in the solution presently under evaluation, a protected air channel is used, identified as Ip channel, where for the voice application a non protected air channel is ised, identified with In channel. The channel protection is referred herein to the errors due to air transmission. The use of the protected channel Ip appears impossible to be proposed, both in terms of efficiency and as for costs, for applications requiring a very low data flow, often mono-directional, and generally associated to a very reduced power consumption of the device generating the same. As said above, in fact, the DECT system has been structure for the exchange of voice signals on the In channel and for dats exchange on the Ip channel. However, for applications of the type specified above, where a low speed data transmission is required, the use of the above mentioned Ip channel cannot be proposed in relation to the power budget related to the use of said channel, as it shall appear more clear hereafter, and in relation to efficiency problems considered above. In the Italian patent application no. MI96A 000784 in the name of the same applicant, it was also proposed the modificatio of the access profile (GAP) of the user terminal PP into a GAP++ profile capable to implement a data transmission on said unprotected In channel, usually provided for the transmission of voice signals. Even this solution, though requiring no modification of RFPs generally foreseen for the voice service to implement said data transmission, requires the installation of an additional server to establish calls to other users, therefore involving costs which do not appear to be justified when the flow of data to be transmitted has a rather poor speed and mainly for applications requiring a drastic limitation of power consumption. There are in fact, number of systems where a low speed data exchange is requested for which the potter saving problem is rather stringent. Among these systems we mention for instance data exchange/data collection systems requiring fixed 6 or mobile low power consumption peripheral stations, with local battery supply. The general structure of these systems foresees a given number of fixed or mobile peripheral stations, adapted to collect data through appropriate sensors, connected to a data collection station implementing the "data collection" operation, processing the same and taking possible adequate measures, such as for instance the operation of an alarm or the enabling of an actuator. Said known systems have different limits, among which the need of wire or "conventional" radio connection to the data collection station with high plant costs, mainly due to the laying of cabling or conventional radio infrastructures. Other limits of the known systems lie in the fact that they can be installed only in areas close to an electric power distribution network. This is due to the fact that data transmission equipment involve a power absorption such that their supply through local battery systems cannot be proposed. One object of this invention is to implement a method enabling the low speed data transmission on a DECT system. Another object is to implement a method enabling to considerably reduce the power consumption required to implement the above mentioned data transmission. Also, a particular object of the invention is to implement an effective "data exchange/data collection" system to be used - 7 - where it is not recommended the laying of cables and power availability is very reduced. The above mentioned objects are achieved through the method of the present invention consisting in a method for low speed data transmission in a DECT system including at least one radio fixed part and at least one peripheral unit in which data transmission is organized in frames having pre-set duration in which a pre-set number of time slots are allocated, each of saic time slots including: a first field containing useful data for the clock and phase recovery; a second field for the signal transmission, a third field for payload transmission, Said method is characterized in that it transmits in a connection oriented modality (c.f.r. ETS 300 175) data in said second field, disabling the third field at the same time. The invention consists also in a system for low speed data transmission on the DECT system of the type including at least one central unit and at least a peripheral unit in which data transmission is organized in frames having pre-set duration in which a pre-set number of time slots is allocated, each of said time slots including: a first field containing useful data for the clock and phase recovery; a second field for the signal transmission, a third field for payload transmission said second field including in its turn the following sub-fields: a first sub-field, consisting of an identification coding of the content of a second subsequent sub-field; a second sub-field where one out of a pre-set number of logic channels is allocated; a third sub-field containing bits for the cyclic redundane code. Said system is characterized, in that it transmits data in said second field, disabling at the same time said third field, after creation of a specific data profile relevant to a data transmission in the connection oriented modality, to which a specific coding allocated in said first sub-field is assigned. The invention finally consists in a "data exchange/data collection" system emitted by fixed or mobile peripheral units and for the enabling of pre-set functions in relation to the value of data emitted by peripheral units, characterized in that said data collection system includes at least a portable part and at least one radio fixed part of a DECT system. The features of the present invention which are believed to be novel are set forth with particularity in the appended claims: The invention, together with further objects and advantage; thereof, may be understood with reference to the following description, taken in conjunction with the accompanying drawings and in which: Fig.1, already described, shows the general architecture of a DECT system; Fig.2, already described, shows the frame architecture of - 9 - the DECT system in fig. 1 as well as the detail of one of the 24 time slots of the full type; Fig. 3 outlines a geographical connection system on local scale, aimed at the bi-directional transport of data and voice calls between fixed of mobile peripheral units and at least one management and control central unit; Making reference to Fig. 2, the structure of a DECT time slot shall be now recalled in brief. The time slot includes a field provided for the synchronization data transmission and a field D provided for general data transmission. The first field S is used in particular for the phase recovery and includes two words, in particular a first word formed of a sequence of bits having alternatively logic value one and logic value zero for the clock recovery, and a word characterized in that it has a maximum correlation capability. The data field includes in its turn a field A and a field B. The field A is used for signalling purposes, that is for the transmission of the signal aiming at constructing, maintaining and abating connections. The field B on the contrary is provided for the transmission of actual data, that is the so-called payload. As shown in Fig. 2 as well, the field A consists in its turn of three sub-fields, the first of which is identified T or "Tail" is provided for the transport of the data content and the third one is a sub-field useful for error determination, known as CRC - 10 - or cyclic redundancy code. The header H contains a coding, expressed through three bits, identifying a respective logic channel which, in fact, is carried in the second sub-field T, that is to the sub-field relevant to the content. Finally, the CRC field has the function to highlight if the logic channel transmitted time by time is correct. Among the logic channel carried in the content sub-field T, we can mention for instance the Qt field relevant to system data the Pt field relevant to paging data, etc. One of said logic channels is in particular the channel Cs which has 2 Kbit/s transmission capacity. According to the DECT standard, said Cs channel is provided for the transmission of high level signals, that is third level signals or data- In conclusion, for the transmission of data, the conventional DECT standard foresees the presence of the following data profiles. I) For the transmission of data in connection oriented mode (c.f.r. ETS 300 175), the use of the field B is required, that is for instance the Ip channel, with a potential transmission capacity of 24.6 Kbit/s. II) For the transmission of data in connectionless mode (c.f.r. ETS 300 175), a field only is allowed, for instance for Cs channel transfer, with a potential transmission capacity of 2 Kbit/s. III) Furthermore, in the case of connection oriented data -11- transmission the use of fields A+B is always required even when, following a basic set-up operation, transmission of data is made in field A and B field does not transport valid data. Referring to data profiles under points I) and III), the DECT foresees a "basic set-up", characterised by the transmissio of data on the field A and by the enabling of whole slot, while another possible set-up form is the so-called "advanced set-up", characterised by data transmission on the field B and by the enabling of the whole slot. In particular the profile III) considered above for data transmission, though foreseeing an "idle" condition for the field B, results expensive as for power consumed. In fact, the radio power is essentially coinciding with power consumed when the field B is actually employed (and therefore contains data). Considering that monitoring systems of the type mentioned above making reference to figure 3 operate at best when the transmission is of the connection oriented mode, it is clear that the use of the connectionless mode cannot be proposed. Also data profiles I) and III) cannot be proposed for power-budget reasons. According to the method of the invention, data are transmitted in the above mentioned field A (that is enabling only the field S and the field A), reaching the target to reduce the power consumption required for the transmission of radiofrequency signals, disabling the field B which has no data content. - 12 - In other words, the method according to the invention foresees the creation of a nev data profile with a specific set-up definitely excluding the field B (that is without determining the enabling of radio equipment during the transmission of this field), but continuing to enjoy the benefits deriving from the protected transmission, thanks to the presence of the CRC sub-field of field A. The new set-up - called for instance "low speed set-up" is characterized by data transmission on field A, where only fields S+A are enabled (including the CRC field). In other words, the method according to the invention consists in assigning a specific coding to said "low speed set-up" which is allocated in the sub-field H of field A. The emission of a low speed set-up by the PP, may be considered as a request to the RFP station to which said PP is connected of a new type of set-up (that is presently not provided for by the DECT standard) showing given characteristics, that is request for a physical channel, characterized by the enabling of fields S and A only. The KFP, in response to the detection of said specific coding in said sub-field H of field A, establishes a communication with the portable part PP which transmits only in fields S and A (i.e. the transmitters are not activated during B field transmission). The method according to the invention enables to reduce the power required for the transmission by more than 70%. - 13 - In fact, as shown always in fig.2, a DECT time slot includes 32 bits in tbe field S, 64 bits in the field A and 324 bits in the field B, in addition to the above mentioned 4 additional bits in the CRC field. Not transmitting the 320 bits of the field B, that is not enabling the radio equipment during the transmission of the field B, a power save equal to 324/420, that is 77% approx. is obtained in power budget terms. The invention results therefore being highly advantageous in all tbe applications where the main constraint is represents by the reduced availability of power. In addition to the above mentioned power saving, saving of the power related to the processing (at the PP and RFP) of data "potentially" present on the field B has to be considered, which as referred to above is enabled even in idle condition according to the known solutions of the DECT standard. In fact, since the field B foreseen by the standard to establish a data transmission in the connection oriented modality foresees the presence of no. 4 sub-fields and of a same quantity of CRC fields, also the use of a sole sub-field involves the processing of the four CRC fields. According to an additional embodiment (not shown in detail) power consumption can be more minimized, periodically enabling (for instance every 2 hours) the portable parts PP and perform a data transmission ending with the transmission, for instance, of a message indicating the fact that the - 14 - transmission will be restarted after a pre-set time. In this way only a clock is supplied, while the remaining part of the circuitry is kept unsupplied. The output of the supply should be restarted only after the above mentioned pre-set time is elapsed. It is evident from the above how the invention enable to transform equipment complying with the DECT standard (not fallin under the"low power" class) into low power like equipment maintaining the advantages related to a connection oriented data transmission. To give a range of magnitude we point out that low power consumption equipment are considered those characterized by a mono-directional transmission, such as for instance remote controls, etc. The invention is fully compatible with the common functions of the DECT system, that is with the transmission of voice signals as specified below, referring also to figure 3. In fact, when one wants to establish a telephone call through the DECT system, the concerned person will use a portable part PP suitable to emit a set-up request of the type generally foreseen to establish a voice communication. In other words in this case, in said sub-field H a specific coding shall be allocated, which translates into the request to the RFP station to which said PP is connected for a set-up showing the usual characteristics, that is a request for a physical channel characterized by the enabling of all the fields, that is of - 15 - fields S,A and B. In this way some portable parts PP can perform a low speed data transmission with the above mentioned advantages referring to the low power consumption, while other portable parts PP (connected or not to the same RFP) can be used to transmit voice signal in a completely conventional way. Fig.3 outlines a "data exchange/data collection" system availing of the invention in order to establish a local geographical connection system, according to the DECT standard, aimed at bi-directional transport of data and voice communicatic between fixed peripheral units or mobile peripheral units and one (or more) Control/Supervision Centers. Field sizes (analogue and/or digital) are detected through appropriate sensors; measurements made and conditions detected are acquired by a local Data Logger. A multiplexer takes care of the multiplexing of all data logged in a unique data flow launched through the PP unit in the DECT system scope of the invention. Through RFP and CCFP, and subsequently, possibly via switched telephone network, total data consisting of data and voice reach the ControVSupervision Center to enable the total management of the data exchange/data collection system. The bi-directionality of the connection enables also to re-launch data from the centre to the periphery in order to perform control operations of the same, enabling for instance regulation elements through actuators. 16 This system can find several applications, in particular where the control of fixed or mobile peripheral units is foreseer by a central unit on local geographical areas (for instance in the urban context, inside buildings, etc.) and in particular in the cases where the peripheral unit is local battery supplied, and therefore with very low power available. It is pointed out that the subject territorial telematic systems involve in general low speed type data transmissions, consistently with the basic method of the invention. The attention is drawn also on the fact that the data exchange/data collection system can integrate, besides connectior for data transmission,also connections of PP units for telephone communications making reference to the compatibility of the low speed data transmission with the usual operation methods of the DECT. Therefore, while a particular embodiment of the present invention has been shown and described, it should be understood that the present invention is not limited thereto since other embodiments may be made by those skilled in the art without departing from the scope thereof. It is thus contemplated that the present invention encompasses any and all such embodiments covered by the following claims. In particular the present invention extends to cover any data exchange/data collection application foreseeing the use of the DECT standard and requiring fixed or mobile low power consumption peripheral stations and therefore with local battery supply. 17 We claim :- 1. Method for the low speed transmission of data in the connection oriented modality in a DECT system comprising at least one radio fixed part (RFP) and at least one portable part (PP) in which data transmission is organized in frames having pre-set duration in which a pre-set number of time slots are allocated, each one of said time slots comprises : a first field(S) comprising useful data for the clock and phase recovery; a second field (A) for the signalling transmission; a third field (B) for payload transmission, said second field (A) comprising in its turn the following subfields a first sub-field (H) consisting of an identification coding of the content of a second subsequent sub-field (T); a second sub-field (T) where one of a pre-set number of logic channels is allocated; a third sub-field (CRC) containing bits for the cyclic redundancy code, said method being characterized in that it transmits data in said second field(A), disabling at the same time said third field(B)i 2. Method for the low speed transmission of data in the connection oriented modality in a DECT system as claimed in claim 1 such that it foresees the following steps : creating a new data profile relevant to a connection oriented data transmission adapted to enable said first field (S) and said second field(A) only; creating a specific set-up of said new profile and assigning - 18 - it a specific coding to be allocated in said first sub-field(H) of the second field (A); supplying at said at least one portable part (PP) said specific coding assigned to said specific set-up; detection by said at least one radip fixed part (RFP) said specific coding assigned to said specific set-up; establishing a data transmission between said at least one portable part and said at least one radio fixed part (RFP) enabling only said first (S) and second (A) field of each time slot, 3. Method for the low speed transmission of data in the connection oriented modality in a DECT system as claimed in claims 1 and 2 such that said data transmission terminates with the transmission of a message giving a command for the restart of transmission operations after a time interval of pre-set duration and in that a clock is associated to said at least one peripheral unit. 4. A data exchange/data collection system by the method as claimed in claim 1 comprises : a transcoder battery (TRAS) to which said at least one radio fixed part (RFP) is connected; a central control fixed part (CCFP) connected to a switching network, wherein said portable part (PP) comprises at least a sensor suitable to supply data on one or more parameters and/or an actuator for the enabling of pre-set functions; a data collection unit (CONTROL/SUPERVISORY CENTER) is connecte to said switching network. - 19 - 5. A data exchange/data collection system as claimed in claim 4 wherein said data collection unit is a personal computer. Dated this 23rd day of July 1997. - 20 - Method for the low speed transmission of data in the connection oriented modality in a DECT system including at least one radio fixed part (RFP) and at least one peripheral unit (PP), where the transmission of data between said units is organised in frames having pre-set duration in which a given number of time slots are allocated. The method foresees the low speed data transmission enabling only the field (S) and the field (A) of each time slot, disabling at the same time the field (B) provided for the transmission of data according to the conventional DECT standard. Disabling the above mentioned field (B), it is possible to reduce by approximately 70% (seventy percent) of the power required to implement data transmission operations. Therefore, said method is partcularly advantageous in whichever "data exchange/data/collectio application foreseeing the use of the DECT standard and requiring fixed or mobile low power consumption peripheral stations with local battery supply.

Documents:

01377-cal-1997-abstract.pdf

01377-cal-1997-claims.pdf

01377-cal-1997-correspondence.pdf

01377-cal-1997-description(complete).pdf

01377-cal-1997-drawings.pdf

01377-cal-1997-form-1.pdf

01377-cal-1997-form-2.pdf

01377-cal-1997-form-3.pdf

01377-cal-1997-form-5.pdf

01377-cal-1997-priority document others.pdf

1377-cal-1997-granted-abstract.pdf

1377-cal-1997-granted-acceptance publication.pdf

1377-cal-1997-granted-claims.pdf

1377-cal-1997-granted-correspondence.pdf

1377-cal-1997-granted-description (complete).pdf

1377-cal-1997-granted-drawings.pdf

1377-cal-1997-granted-examination report.pdf

1377-cal-1997-granted-form 1.pdf

1377-cal-1997-granted-form 2.pdf

1377-cal-1997-granted-form 3.pdf

1377-cal-1997-granted-form 5.pdf

1377-cal-1997-granted-form 62.pdf

1377-cal-1997-granted-letter patent.pdf

1377-cal-1997-granted-priority document.pdf

1377-cal-1997-granted-reply to examination report.pdf

1377-cal-1997-granted-specification.pdf

1377-cal-1997-granted-translated copy of priority document.pdf