Capacity Analysis of Multiple-Access Rician Fading Channel

• Main Authors: Lin, Gu-Rong, 林谷嶸
• Other Authors: Stefan M. Moser
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/95493875007894211721

碩士 === 國立交通大學 === 電信工程系所 === 97 === In this thesis the channel capacity of the noncoherent multiple-access Rician fading channel is investigated. In this channel, the transmitted signal is subject to additive Gaussian noise and Rician fading, i.e., the fading process is Gaussian in addition to a line-of-sight component. On the transmitter side the cooperation between users is not allowed, i.e., the users are assumed to be statistically independent. Based on the known result of the asymptotic capacity of a single-user fading channel, our work is to generalize it to the multiple-user sum-rate capacity. We study the single-antenna case only: all transmitters and the receiver use one antenna. We get a natural upper bound on the capacity if the constraint of independence between the users is relaxed, in which case the channel becomes a multiple-input single-output (MISO) channel. Also, a lower bound can be obtained if all users apart from one are switched off, which corresponds to a single-input single-output (SISO) channel. We improve these bounds and get an exact formula of the asymptotic capacity. The main concept we use in this thesis is escaping to infinity of input distributions, which means that when the available power tends to infinity, the input must use symbols that also tend to infinity. We propose that in the multiple-access fading channel, at least one user's distribution must escape to infinity. Based on this we obtain the result that the asymptotic sum-rate capacity is identical to the previously mentioned lower bound: the single-user SISO capacity. We conclude that in order to achieve the best sum-rate capacity in the multiple-access system, we have to switch off the users with bad channels and only allow those with the best channel to transmit.