A Survey Of The Relay In LTE-Advanced Based On Distributed Turbo

Relay as a key technology of the LTE-Advanced system increases the cell coverage and improves the system capacity. So far, the LTE-Advanced relay technology has focused on its transmission scheme. The distributed Turbo coding(DTC) is a compress-forwarding(CF) relay which can bring a larger coding gain and diversity gain. DTC has received extensive attention in the field of relay cooperative communication applications.Firstly, the characteristics of the LTE-Advanced system and the research background of this paper are summarized. The resource reuse mode, signal transmission and the classification of relay station of LTE-Advanced relay is simple described. The coding and decoding principles of Turbo which meet for 3GPP requirement in B3G system, and the basic structures of DTC are introduced.Secondly, the rate of collaborative approach is fast than non-collaborative that is demonstrated through the mathematical analysis of the rate of several collaborative and non-collaborative approaches of LTE-Advanced relay system. Theoretical analysis and simulations compare the performance of several typical relay methods to determine the way forward by CF method in cooperative relay system. On this basis, the relay transmission technology based on DTC is proposed. For different channel conditions, several distributed Turbo constructions are designed, and its complexity and bandwidth efficiency is analyzed. Theoretical analysis and simulation show that the use of these distributed Turbo models under certain SNR can improve system performance and bandwidth efficiency, and reduce the complexity.To further enhance the performance of the LTE-Advanced relay system which is based on distributed Turbo, the two improved decoding schemes at the terminal based on SNR and pre-hard decision are proposed when the signal to noise ratio of the direct link and the link which is from base station to the terminal through the relay are different. The two improved decoding schemes adjust the credibility of extrinsic information when first iterative decoding to get the performance improvement. Simulation results show that both algorithms given can gain good performance improvement, and the gain is particularly evident when the link is poor. The comparison of the two improved decoding schemes through simulation and complexity analysis shows that the decoding scheme based on SNR is relatively simple and sub-optimal, while the decoding scheme based on pre-hard decision can get greater performance gain for the relay system based on the distributed Turbo. Finally, the two improved decoding algorithms are made fixed-point analysis and a preliminary costs assessment of implementation time and space resources. It have a certain reference value for that the two improved decoding algorithms based on the distributed Turbo apply in LTE-Advanced relay system.