| With the development of computer technology, people put forward much higher demands on mobile communications, e.g. speed, bandwidth, QoS. Cooperative diversity, as a new spatial diversity technique, can fight against the harmful effects of radio channel fading, improve system performance and communication quality, which has a broad application prospect. Application of the key technologies of next generation mobile communication system into cooperative network, such as relay and spectrum aggregation, can futher raise network throughput and spectrum utilization.Through the coordination of relay, relay technology changes single direct transfer mode, and improves link quality of mobile terminals, meanwhile increases spectrum efficiency. Therefore, which method is employed for relay selection, and which relay is selected for custom service, become problems needs to be solved, and attract growing attention.In addition, taking the existing spectrum distribution manner and spectrum-use planning into account, limited to continuous allocation strategy and lack of low-frequency spectrum resources, it is difficult to find continuous bandwidth that is greater than the requirement-40MHz in LTE-Advanced system. Thus 3GPP has proposed spectrum aggregation technology, by aggregating two or more discrete bands, to expand the transmission bandwidth, which can fully use current spectrum resources, and meet users’arising demands for bandwidth.For relay technology in cooperative communication, this article studied relay selection strategies from four aspects, i.e. distance, system throughput, outage probability and system power. It designed and implemented four relay selection algorithms, whose separate targets are to minimize distance, maximize system throughput, minimize outage probability and minimize system power. The algorithm based on localtion information has low complexity and is easy to realize. The algorithm based on system throughput has the highest system rate. The algorithm based on outage probability can get the smallest outage probability and increase system reliability.While the algorithm based on system power can reduce the system power and save energy.For spectrum aggregation technology in cooperative communication, this article proposed a spectrum aggregation algorithm based on discrete bands in relay cooperative network. Compared with the non-aggregation algorithm, this method, with the help of relay coordination, can aggregate discrete spectral fragments to form a larger transmission bandwidth, dynamically improve spectrum efficiency, increase system throughput and raise spectrum utility. |
