System Design And Research On Key Technologies For Cyclic Delay Diversity Based Cooperative Communication

By sharing antennas of neighboring nodes in a cooperative manner to construct a virtual environment, cooperative communication systems can combat the signal fading caused by wireless channels effectively. The single-antenna based cooperative system acquires spatial diversity gain and multiplexing gain, as well as the transmission efficiency and reliability. The traditional Space-Time Coding based cooperative communication systems can not be widely applied in the existing point-to-point scenarios since its complex protocol for that the concrete sending matrix has to be assigned in every relay, but also the allocation of the relays for a better environment for communication. Cyclic Delay Diversity (CDD) has been adopted as a basic method for physical layer in LTE-Advanced owing to its simplicity in application, efficient coding ratio and conformable for the existing communication systems. In CDD based cooperative communication, the complex protocol can be avoided and the relays can join in the cooperative process in the manner of silence under any channel environment.The object of this thesis is to have a research on the key technologies for the CDD based cooperative communications. The main subjects investigated are as follows:1. On the basis of introducing the principle of CDD, the system model of CDD and its affect on the channel and the signal is analyzed briefly. After summarizing the existing choosing method for the cyclic shift, a measure that independent of the sending antenna index is proposed. Then we apply the CDD to MIMO-OFDM systems and compare it with the traditional STBC-OFDM system.2. CDD based cooperative communication system model is discussed subsequently. The influence of multi-path channel on the CDD signal is introduced, and then the Winner Filter based channel estimation mechanism is proposed after the simulation and betterment of the estimation method suitable for CDD based transmission. After that we simulate the proposed algorithm under the circumstances of traditional scenario and the cooperative one, which prove the superiority of the algorithm in its robustness to CFOs.3. The influence of multiple Carrier Frequency Offsets (CFOs) on the system performance is investigated. Subsequently based on the model of none-feedback, we propose the signal detection algorithms, Ordered Successive Paralleled Interference Cancellation (OSPIC) and Iterative Interference Cancellation (IIC) under the scenario of cooperative communication; afterwards we simulate the detection algorithm in practical environment and have a research on the complexity.4. Time Varying Cyclic Delay Diversity (TV-CDD) is discussed, and then we apply the Time Varying Cyclic Delay Diversity (TV-CDD) to cooperative communication under the circumstance of frequency selective channels, we design the practical simulation platform and simulate different parameters for practical scenarios.