Improved relay selection with channel prediction in cooperative relays

Abstract

The high data rate required for fourth generation (4G) Wireless systems in large areas do not appear feasible with conventional cellular architecture due to two basic reasons. First, the transmission rates for 4G systems are two orders of magnitude higher than those of 3G systems. This demand creates serious power concerns. Secondly, the spectrum released for 4G systems is almost certainly located well above the 2 GHz band used by the 3G systems. The solution to these problems is to significantly increase the density of base stations, resulting in considerably higher deployment costs. A drastic increase in the number of base stations does not seem economically justifiable. It is obvious that more fundamental enhancements are necessary for the very ambitious throughput and coverage requirements of future systems. Towards this end, in addition to advanced transmission techniques and collocated antenna technologies some major modifications in the wireless network architecture itself that will enable effective distribution and collection of signals to and from wireless users are required. Hence relay transmission is proposed. Multipath fading is a major problem in mobile wireless networks which require high bandwidth efficiency schemes. To combat this problem, time frequency and spatial diversity techniques are used. Cooperative communication is a key technique to mitigate fading in wireless networks through achieving spatial diversity, while resolving the difficulties of installing multiple antennas on small communication terminals. The cooperative relays give diversity gain but at the expense of spectral efficiency because the source and all the relays must transmit in orthogonal channels. The inefficient utilization of the channel resources can be minimized by relay selection algorithms. The available CSI at the transmitter and relays are used for relay selection newline