How Many Users should be Turned On in a Multi-Antenna Broadcast Channel

This paper considers broadcast channels with L antennas at the base station and m single-antenna users, where each user has perfect channel knowledge and the base station obtains channel information through a finite rate feedback. The key observation of this paper is that the optimal number of onusers (users turned on), say s, is a function of signal-to-noise ratio (SNR) and other system parameters. Towards this observation, we use asymptotic analysis to guide the design of feedback and transmission strategies. As L, m and the feedback rates approach infinity linearly, we derive the asymptotic optimal feedback strategy and a realistic criterion to decide which users should be turned on. Define the corresponding asymptotic throughput per antenna as the spatial efficiency. It is a function of the number of on-users s, and therefore, s should be appropriately chosen. Based on the above asymptotic results, we also develop a scheme for a system with finite many antennas and users. Compared ...

• Type: Conference
• Year: 2007
• Where: CISS
• Authors: Wei Dai, Youjian Liu, Brian Rider
• Keywords: Asymptotic Optimal Feedback, CISS 2007, Feedback Rates, Finite Rate Feedback, Information Management