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Proceedings of 1994 28th Asilomar Conference on Signals, Systems and Computers (1994)
Pacific Grove, CA, USA
Oct. 31, 1994 to Nov. 2, 1994
ISSN: 1058-6393
ISBN: 0-8186-6405-3
pp: 83-88
A. Goldsmith , California Inst. of Technol., Pasadena, CA, USA
The next generation of wireless networks will require efficient use of the underlying time-varying channel. Cellular architectures efficiently utilize the limited spectrum by reusing the same channel in spatially separated cells. However, frequency reuse introduces cochannel interference, which determines the data rate that can be supported by each channel for a given BER. The efficiency within a cell is quantified by its spectral efficiency: the data rate per user per unit of bandwidth. In this paper the maximum spectral efficiency for cellular systems with channel estimation and transmitter feedback is derived from Shannon theory. We first review capacity results for single-user time-varying channels, which show that efficiency is maximized through a combination of power control, adaptive coding, and variable data rates. We then extend this result to the multiuser capacity region for both broadcast and multiaccess channels. This yields an analytical framework to compare the efficiency of channel sharing within a single cell using TDMA, FDMA, and CDMA. We conclude that CDMA with interference cancellation is optimal, but TDMA and FDMA have superior performance if interference cancellation is not exploited. Moreover, if the received power of all users is kept constant, then CDMA with interference cancellation does no better than FDMA and TDMA.<>
cellular radio, time-varying channels, channel capacity, cochannel interference, land mobile radio, radiofrequency interference, adaptive codes, power control, telecommunication control, time division multiple access, frequency division multiple access, code division multiple access, interference suppression, Gaussian channels

A. Goldsmith, "Multiuser capacity of cellular time-varying channels," Proceedings of 1994 28th Asilomar Conference on Signals, Systems and Computers(ACSSC), Pacific Grove, CA, USA, 1995, pp. 83-88.
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