Improvement of Symbol Error Rate Performance in Spatial Multiplexing Systems Using Transmit Antenna Selection

Dharmendra Chauhan, Jaymin Bhalani, Y. N. Trivedi

In this paper, we consider Mt×M system (Mt > M), where Mt and M are the numbers of antennas at the transmitter and receiver, respectively. We select M out of Mt transmit antennas using two different antenna selection schemes. In scheme 1, we select the subset of M antennas out of total $$(\begin{array}{l}{M_{t}} \\{M}\end{array})$$ subsets. In the selected subset, the minimum SNR is maximum compared to minimum SNR of all the remaining subsets. In scheme 2, Mt available transmit antennas are divided into Mtg disjoint groups of successive antennas, where Mtg = Mt/N. It means that there are N antennas in each group, where N ≤ M. Further both Mt and M are divisible by N and the total possible combinations of available groups are given $$(\begin{array}{l}{M_{tg}} \\{C}\end{array})$$ Then we select the subset of M antennas out of total $$(\begin{array}{l}{M_{tg}} \\{C}\end{array})$$ subsets. In the selected subset, the minimum SNR is maximum compared to minimum SNR of all the remaining subsets. In this scheme, N and C are chosen to meet the requirements of M selected antennas for transmission. After antenna selection, the resulting system will be M×M. We use Minimum Mean Square Error (MMSE) Vertical Bell Laboratories Layered Space Time (VBLAST) detection at the receiver for both the antenna selection schemes. We present MIMO Symbol Error Rate (SER) versus MIMO Symbol SNR using simulations for M-QAM constellations with Rayleigh fading channels. We have compared the performance of the considered systems with prevailing high complexity schemes ML and MMSE Improved VBLAST. The considered scheme 1 with MMSE VBLAST outperforms the prevailing schemes while scheme 2 with MMSE VBLAST provides similar performance in a wide range of SNR compared to prevailing schemes. However, the number of feedback bits used in scheme 2 is less as compared to scheme 1. There is a tradeoff between the SER performance and the number of required feedback bits. As N decreases, scheme 2 performance starts moving towards the performance of scheme 1. Both the systems provide the diversity gain in the fading channel.