System capacity analysis on cooperative transmission for wireless systems.

摘要

The system capacity of a wireless communication system utilizing cooperative transmissions is studied. Two important applications of cooperative transmission are discussed: relay transmission using cooperative MIMO and cooperative multi-cell transmission.;For relay transmission with cooperative MIMO, an infrastructure relay system which transfers information from a base station (BS) to a randomly located mobile station (MS) using fixed location relay stations (RSs) is studied. Transmission rates are derived for serial, parallel, and hybrid relay transmissions considering the utilization of RSs as a mean to extend the dimensionality of a MIMO transmission. The derived transmission rate for the serial relay transmission is optimized by determining the optimal locations of RSs and the number of hops. In addition, selection schemes for determining which RSs to activate in order to maximize the transmission rate are provided for parallel and hybrid relay topologies. Based on the analytic findings, numerical results are obtained for various deployment scenarios to compare and evaluate different relay topologies and design characteristics.;For cooperative multi-cell transmission, a wireless communication system consisting of a large number of fixed location BSs and random location MSs is studied. Assuming BSs in a multi-cell system are connected to a centralized controller with access to channel state information, it is possible to optimize transmissions such that the system capacity is maximized. This work discusses the performance aspects of such cooperative multi-cell systems based on an accurate modeling of the multi-cell deployment, different levels of cooperation among BSs, and practical per-antenna transmit power constraint of a BS transmit antenna. Performance results are obtained using numerical optimization theory and compared to the lower and upper bounds derived for different scenarios.;In addition, the effect of inaccurate channel knowledge on the system performance of a cooperative multi-cell system is studied. The performance degradation due to optimizing the collaborative downlink transmit signals of multiple BSs based on inaccurate channel knowledge is obtained using a two step optimization process. Two important sources of channel knowledge inaccuracy are considered: quantization and feedback delay.