Pulse or digital communications – Apparatus convertible to analog
Reexamination Certificate
1998-10-06
2001-10-16
Bocure, Tesfaldet (Department: 2613)
Pulse or digital communications
Apparatus convertible to analog
C375S279000
Reexamination Certificate
active
06304593
ABSTRACT:
FIELD OF THE INVENTION
The present disclosure describes an adaptive modulation technique optimized for simultaneous voice and data transmission over fading channels. More specifically, the present scheme describes systems which are optimized to maximize spectral efficiency between the voice and the data.
BACKGROUND
Modern communication channels need to carry various information including both voice and data. The data services typically include facsimile, e-mail, Internet access as well as other forms of data communication services. However, the bandwidth of the wireless spectrum is a limiting factor on the amount of information that can be transmitted. This makes it extremely important to maintain spectral efficiency.
Noise problems in wireless communication channels also cause various problems which limit the amount of information through these channels. Multipath causes the amplitude of the received channel to change. For a fixed noise at the receiver, multipath effects will actually change the signal to noise ratio/carrier to noise ratio.
Various techniques have been used to maximize the spectral efficiency of communications. Certain transmission techniques take advantage of the time-varying nature of wireless channels to vary the transmitted power level, symbol rate, coding rate and scheme and constellation size. These techniques are described in T. Ue, S. Sampei, and N. Morinaga, “Symbol rate and modulation level controlled adaptive modulation/TDMA/TDD for personal communication systems,” in
Proc. IEEE Veh. Technol. Conf. VTC'
95,
Chicago, Ill.
, pp. 306-310, July 1995. Full paper published in the
IEICE Trans. Commun.,
vol. E78-B, pp. 1117-1124, August 1995; W. T. Webb and R. Steele, “Variable rate QAM for mobile radio,”
IEEE Trans. on Commun.,
vol. COM-43, pp. 2223-2230, July 1995; S. G. Chua and A. Goldsmith, “Variable-rate variable-power M-QAM for fading channels,” in
Proc. IEEE Veh. Technol. Conf. VTC'
96,
Atlanta, Ga.,
pp. 815-819, April 1996. Full paper to appear in the
IEEE Trans. on Commun.,
October 1997; H. Matsuoka, S. Sampei, N. Morinaga, and Y. Kamio, “Adaptive modulation system with variable coding rate concatenated code for high quality multi-media communication systems,” in
Proc. IEEE Veh. Technol. Conf. VTC'
96,
Atlanta, GA,
pp. 487-491, April 1996. Full paper published in the
IEICE Trans. Commun.,
vol. E79-B, pp. 328-334, March 1996; M. S. Alouini and A. Goldsmith, “Adaptive M-QAM modulation over Nakagami fading channels,” in To appear in
Proc. IEEE Global Commun. Conf. GLOBECOM'
97,
Phoenix, Ariz.
, November 1997. None of these techniques use adaptive techniques of the type described in this application.
The goal of many of these techniques is to improve the average spectral efficiency. The spectral efficiency is often defined as the average transmitted data rate per unit bandwidth for an average specified carrier to noise ratio and bit error rate. Hence, there is often a trade-off between the noise on the channel and the amount of information which can be transmitted over the channel.
Moreover, accurate performance can be enhanced by accurate channel estimation at the receiver, and a reliable feedback path between that estimator and the transmitter. Such systems may also require buffering of the input data since assumption of a low carrier to noise ratio can cause a very high outage probability.
SUMMARY
The present inventors have recognized that certain characteristics of the channels and the information passing through the channels can be used to improve performance and hence the data rate of the output. In general, voice transmission has a low rate requirement. However, voice transmission is very sensitive to real-time delays. A real-time delay will be heard by the user at the other end. However, voice is more tolerable to bit errors. In contrast, data transmission demands higher rates with fewer errors (smaller bit error rate), but has less stringent delay requirements. More information is necessary and fewer errors can be tolerated. However, the actual time when the information arrives can be much more flexible.
The present system, in recognition of the above, uses fixed rate transmission for the voice, combined with power adaption for the data. The transmitter adjusts its power to maintain a relatively constant carrier-to-noise ratio at the receiver. This makes the system well suited to voice. A bursty variable-rate transmission which maximizes average spectral efficiency is used for data communication.
The present scheme preferably uses two independent information streams which are inherently different not only in their nature but also in their delay sensitivity and bit error rate sensitivity.
Another aspect of this system allows changing the rate of the data based on the capacity of the channel. This is done by changing the size of the signal constellation. The binary signal is Gray coded into an analog signal whose amplitude represents the bits. The number of bits represented by each sample of the signal is adaptively varied, according to the signal to noise ratio.
REFERENCES:
patent: 4833706 (1989-05-01), Hughes-Hartogs
patent: 5054034 (1991-10-01), Hughes-Hartogs
patent: 5535238 (1996-07-01), Schilling et al.
patent: 5745480 (1998-04-01), Behtash et al.
patent: 5878329 (1999-03-01), Mallinckrodt
patent: 6061392 (2000-05-01), Bremer et al.
patent: 6128348 (2000-10-01), Kao et al.
Qiang Shen et al., “Power Assignment in CDMA Personal Communication Systems with Integrated Voice/Data Traffic,” IEEE Tran. on Com., pp 168-172, 1996.*
Joom Bae Kim et al., “Resource Allocation for Multiple Classes of DS-CDMA Traffic,” IEEE, Tran. on Vehicular Tech. vol. 49, No. 2, pp 506-519, Mar. 2000.*
Insoo Koo et al., “Capacity-Optimized Power Allocation Scheme in an Integrated Voice and data DS-CDMA System,”IEEE Tencon, pp 1178-1181, 1999.*
Mohamed-Slim et al., “An Adaptive Modualtion Scheme for Simultaneous Voice and Data Transmission over Fading Channels,” IEEE, pp 939-943, 1998.
Alouini Mohamed-Slim
Goldsmith Andrea
Tang Xiaoyi
Bocure Tesfaldet
California Institute of Technology
Fish & Richardson P.C.
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