Multiplex communications – Communication over free space – Using atm as a wireles protocol
Patent
1998-01-12
2000-05-23
Pham, Chi H.
Multiplex communications
Communication over free space
Using atm as a wireles protocol
375220, H04B 700, H04B 138
Patent
active
060672897
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for transmitting GSM data between at least two stations over a communication network.
BACKGROUND INFORMATION
In previous GSM data connections, in particular for digitized voice data between mobile stations over a communication network such as the public telephone. network (PSTN--Public Switched Telephone Network), the GSM data in GSM format are converted into the frame format of the communication network--64 kbit/s PCM for PSTN--using a transcoder. For DMCS 900 mobile radio systems, such transcoding is performed at the base stations, or the A interface with the PSTN communication network. Pursuant to GSM recommendation 0860/0861, digital voice transmission takes place in "TRAU (Transcode and Rate Adaptor Unit) frames," i.e., in 16 kbit/s format transmission frames at FR (Full Rate) transmission and 8 kbit/s or 16 kbit/s at HR (Half Rate) transmission.
SUMMARY OF THE INVENTION
European Patent No. 0 332 345 describes a recoding device between two stations of a telephone network, wherein it is verified whether the data transmitted by a transmitting station is present in a predefined frame format. If the predefined frame format is recognized, the data to be transmitted is switched through transparently in accordance with the coding rates. If the code rates are different, the data is recoded to the other code rate.
European Patent No. 0 605 311 describes transcoding devices arranged between stations and a communication network and serve for matching the format used by the station to that of the communication network. This transcoding device is always in the proximity of each station using a first transmission format. The transcoding devices are activated only if the format used by the station does not correspond to that used by the network.
An object of the present invention is to provide a method for transmitting data wherein the degradation of the voice quality due to transcoding is avoided, and which can be implemented without increasing the complexity of existing transcoding devices. The voice quality in the GSM network, particularly D1 networks, is improved when voice is transmitted from a mobile station to another mobile station. In addition, a uniform format (predefined TRAU frame format) is used for transmission in the communication network--PSTN network--regardless of whether the data/voice was transmitted at different coding rates--full rate and/or half rate. The uniform format offers the advantage that the "uplink" (transmitter direction) is completely separated from the "downlink" (receiver direction). Even discontinuous transmission operation (DTX) is possible without difficulty. No problems occur in the case of handover between mobile stations during communication.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates transcoder-free transmission with the same compression scheme for uplink and downlink.
FIG. 2 illustrates the frame format for transmission in the communication network.
FIG. 3 illustrates a transcoder-free transmission with different compression schemes for uplink and downlink.
FIG. 4 illustrates a transcoder-free transmission with DTX operation.
FIG. 5 illustrates a flow chart of the method according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the existing GSM network (fixed network side), for example, the DMCS 900 network, transcoding continuously takes place, i.e., voice data is recoded from the given TRAU (Transcode and Rate Adaptor Unit) format into the transmission format of the communication network, for example, the public telephone network PSTN. While the given TRAU frame format uses a 16 kbit/s transmission rate when voice data is transmitted in the FR (Full Rate) mode, the transmission rate in the PSTN network is 64 kbit/s. At HR (Half-Rate mode), the transmission rate is 8 kbit/s or 16 kbit/s. Other transmission rates of the form 1
are also possible, where n is a natural number. FIG. 1 shows the transmission scheme between mobile stations Tl1 and Tl2 for transmission and
REFERENCES:
patent: 4924480 (1990-05-01), Gay et al.
patent: 5497396 (1996-03-01), Delprat
patent: 5953666 (1999-09-01), Lehtimaki
patent: 5991716 (1999-11-01), Lehtimaki
Masami Yabusaki et al., Voice Communication Connection Control in Digital Public Land Mobile Networks, IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, p. 1702-1709, Dec. 1992.
Satoh et al., TDMA Half-Rate Digital Cellular System Based on PDC Standard in Japan; Proceedings of The Vehicular Technology Conference; p. 301-305, Jul. 1995.
Mueller Joerg-Martin
Waechter Bertram
Pham Chi H.
Robert & Bosch GmbH
Tran Maikhanh
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