Research On Antenna Selection Algorithm Of MIMO System In Correlated Fading Channel

Multiple input multiple output (MIMO) is a technique, which uses multiple antennas both at transmitting end and receiving end of a wireless communication system and improves the throughput and reliability of a radio system. However, the cost of RF hardware becomes higher because of more antennas and it limits the widespread application of MIMO technology. Hence, it's necessary to overcome these shortcomings by low cost and complexity techniques. Antenna selection, which is able to reduce the cost and complexity of MIMO system by selecting a good subset of all antennas at the transmitter and/or receiver, is an attractive solution. Most existing researches are under the assumption that the fading channels are independent, but in real environment the channel is always correlated due to poor scatterings and small interval between antenna elements. Therefore, antenna selection algorithm based on correlated channel is researched in this paper.Firstly, the basic theories of MIMO system are studied in this paper. The channel model is set up and a detailed analysis and derivation of MIMO channel capacities are given when the channel state information (CSI) is known or unknown at the transmitter. To compare the channel capacities in the two cases, simulations are completed. Furthermore, correlated channel model is introduced and the channel capacity and performance under this model are analyzed. The theoretical analysis results are verified by simulation results at the same time.Secondly, the classical antenna selection algorithms based on maximizing the channel capacity are summarized and the performances of these algorithms are compared by simulation. After that, an improved antenna selection algorithm with low complexity is proposed (only considers antenna selection at the receiver). This algorithm, which combines the increasing and decreasing selection process, makes up the disadvantages that the existing algorithms can only be applied to the situation in which the number of RF chains could be small or large. Simulation results show that the improved algorithm can be applied to any number of RF chains. Moreover, the performance of this algorithm is better than some suboptimal algorithms, such as the uncorrelation based antenna selection algorithm, and is close to optimal antenna selection algorithm.At last, according to the real wireless communication environment, a new transmit antenna selection algorithm under correlated channel is presented. This algorithm reduces the computational complexity efficiently, because it avoids some complicated calculations such as matrix multiplication and singular value decomposition by adopting singular value estimation method. Simulation results show that, whatever the strength of channel correlation is, the channel capacity and BER performance achieved by the proposed algorithm are close to the optimal antenna selection algorithm. Hence, it has strong practicability.