협력 릴레이 통신에서 피드백을 사용한 향상된 균등 송신 다이버시티 기법

Abstract

Cooperative relay communication is considered as one of the best schemes providing solution to overcome the effect of the fading. The basic idea of cooperative communication is to take advantages of multiple-input multiple-output (MIMO) systems. The advantages of MIMO system have been widely acknowledged. A certain of transmit diversity methods such as Alamouti coding have been adopted as the wireless communication standards. Tarokh et al. extended the orthogonal design to systems with an arbitrary number of transmit antennas and provided a class of rate-one real orthogonal codes. It has also been proved that full diversity and full code rate block codes do not exist for complex valued symbols and for more than two transmit antennas. Various Quasi-Orthogonal Space-Time Block codes (QO-STBCs) have been proposed to achieve full code rate for more than two transmit antennas at the expense of losing some degree of diversity and increased decoding complexity. The loss of diversity in QO-STBCs occurs due to a relative state between the channels. So, STBCs schemes with four or more transmit antennas using phase feedback have been proposed to remove the relative state between the channels. Full rate Balanced Space-Time Block Codes (BSTBCs) have been proposed, which achieve full diversity for arbitrary number of transmit antennas when one or more feedback bits are transmitted by using relative state between the channels. BSTBCs scheme can be applied to cooperative communication, which is called as Cooperative Balanced Space-Time Block Codes (CBSTBCs) scheme. The CBSTBCs select the maximum relative state between the channels. In this thesis, we propose improved balanced transmit scheme in cooperative communication. The proposed scheme selects the maximum sum of relative state between the channels to obtain maximum transmit diversity. The symbols are rotated in the each relay using few feedback bits. The performance of the proposed scheme is compared to those of CBSTBCs with two and three relays. We evaluate the bit error performance of each scheme through computer simulation.