Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Patent
1997-12-02
1999-09-07
Nguyen, Chau
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
370529, 714755, H04J 322
Patent
active
059497904
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to a data transmission method in a wireless data transmission system where signals with one or more data rates and quality levels are transmitted simultaneously.
The invention further relates to a transmitter intended to be used in the wireless data transmission system where signals with one or more data rates and quality levels are transmitted simultaneously.
PRIOR ART TECHNOLOGY
Requirements set for data transmission methods are continuously increasing. This particularly concerns wireless data transmission systems, such as cellular communication systems of which ever more versatile services are required, such as various kinds of data and video services.
Conventionally, wireless data transmission systems have only been used for speech transmission. An increase in the number of various kinds of services to be transferred means, as far as particularly wireless services are concerned, that the system must be able to transmit signals with differing capacity over the radio path, for example, speech at the data rate 8 kbit/s and data at the rate 64 kbit/s. In addition, there is need for transmitting signals with different quality levels, which typically also require different data rates simultaneously. As a typical example, a video connection could be mentioned in which the picture requires a high data rate but the sound may be transmitted at a slower data rate and at a lower quality level. Consequently, an efficient operation is required of the data transmission system in an environment where transmissions at a multitude of data rates, quality levels and service types are transmitted.
A prior art method of transmitting signals at a multitude of data rates, particularly in applying a CDMA multiple access method, is described in the publication "CDMA radio interface proposal for FPLMTS", International Telecommunications Union, Radiocommunications Study Groups, document 8/1/TEMP/142 (rev1), which is herein incorporated as reference. In the solution according to the above publication, signals between the data rates 1.2-38.4 kbit/s can be transmitted, if the system bandwidth is 1.23 MHz. Higher data rates (76.8 kbit/s) are possible if the system bandwidth is increased to 2.46 MHz. Depending on the data rate of the signal to be transmitted, the signal is channel coded by a convolution code whose coding depth is 1/3, 1/2 or 3/4. In addition, transmitting power is adjusted according to the data rate.
In the method set forth, transmissions are possible at a few specific data rates only. In addition, if several services having different quality requirements are transmitted in parallel, the transmission channel cannot efficiently be utilized because the signal with the lowest quality level sets the transmission requirements.
Another prior art method is described in the publication Baier, A., Fiebig, U.-C., Granzow, W., Koch, W., Teder, P., Thielecke, J.: Design Study for a CDMA-based third generation mobile radio system, IEEE Journal on Selected Areas in Communications, 1994, Vol. 12, no. 4, pp. 733-743, which is herein incorporated as reference. In the method set forth, a fixed length 10 ms frame is used. The transmission rate can change on a frame by frame basis. Convolution coding with puncturing for speech, and concatenated convolution coding as well as Reed-Solomon coding for data are used. A separate control channel is used to inform the receiver of the frame structure and the transmission rate. The control channel and the traffic channel are transmitted in parallel using same spreading code, but in different phase. The signals of both the channels are linearly combined prior to the transmission.
This method needs a large buffer in the receiver because the signal received on the control channel must be decoded before the decoding of the traffic channel can begin. This also introduces additional delay. The linear combining of the traffic channel and the control channel results in a multilevel PAM signal. Ordinary receivers of a mobile station use non-linear power
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Pehkonen Kari
Rikkinen Kari
Nguyen Chau
Nokia Mobile Phones Limited
Vanderpuye Ken
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