Frequency Allocation Scheme In OFDMA Cooperation Relay Cellular System

The fourth generation (4G) wireless communication system is envisioned to provide very high data rates and ubiquitous coverage of radio channels. Multimedia service requires more efficient transmission technology, improved system architecture, and efficient resource operating technique. The basic thinking of cellular relaying network is dividing one-hop link into multi-hop link and shortening the distance between the nodes in communication in order to significantly improve the link quality and channel capacity. The cellular relaying network can expand the cell coverage, increase cell capacity, and meet the coverage requirement of high-speed data service in a large range. In two-hop OFDMA cellular system, two fixed relays with single antenna could form a virtual antenna array and transmitting diversity is achieved. Various results show that cooperative diversity can increase the capacity of system, higher the data rate.Different from one-hop system, the resource management of two-hop cellular system is more complicated. The technologies of resource management which is used for fixed-relay OFDMA cellular system, including frequency planning, relay choice and power control algorithms are addressing in chapter 2.A new cooperation-relay transmission strategy and corresponding sub-channel allocation algorithm for the downlink of cooperation-relay OFDMA cellular network with uniform user distribution are proposed in chapter 3. The cluster of fixed-relay which is composed by two adjacent relays, could reduce path loss between BS and MS, broaden range of signal receiving and achieve Spatial Diversity. In addition, a further adaptive channel assignment algorithm is proposed for the multi-user cooperation-relay OFDMA cellular system with unbalanced traffic distribution. In the proposed algorithm, adjacent clusters share sub-channels for frequency efficient, also sub-channel set for directly transmission and sub-channel set for relay transmission could borrow free sub-channel from each other. The co-channel interference and system capacity is mathematically analyzed. According to the simulation result, the proposed algorithms effectively increase the average frequency efficiency of the system and decrease the system outage probability.