On the capacity of MIMO Rician broadcast channels
2008 IEEE International Symposium on Information Theory
In this paper, a downlink communication system, in which a Base Station (BS) equipped with M antennas communicates with N (N ≫ 1) single-antenna users, in a Rician fading environment is considered. The asymptotic (in terms of the number of users) sum-rate capacity of the system, as well as the capacity-achieving strategies, are derived. The main results of the paper are as follows: i) in the region of K = o(log N ), where K denotes the Rician factor, the sum-rate capacity scales as M log(1 + P
... les as M log(1 + P M η), where P denotes the SNR and η log N 1+K , which is achieved by Zero-Forcing Beam-Forming (ZFBF) along with a low-complexity user selection algorithm that considers only the scattered component of the users' channels, ii) in the region K = ω(log N ), in the case of co-located transmit antennas, the capacity scales as log(1 + M P ), which is achieved by Time Division Multiple Access (TDMA), iii) in the region K = ω(log N ), in the case of isotropically-distributed specular components, the sum-rate capacity behaves as M log(1 + P ), which is achieved by ZFBF, along with a user selection algorithm that considers only the specular component of the users' channels.