A Reduced Complexity MIMO Decoder

Multiple input and multiple output (MIMO) technique uses multiple antennas at the transmitter and the receiver to increase the data rate or the supported range. Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technique used in MIMO systems. QR decomposition (QRD) is the first step in the decoding of the MIMO receiver. QR decomposition methods described by Gram Schmidt, Householder and Givens are computationally intensive as these involve division operations for normalization. The computation complexity of these methods for MIMO-OFDM systems makes it difficult to handle as the QR decomposition is performed for each subcarrier. In this paper, we propose modifications to QR decomposition for Householder's method, for reducing the computation complexity without affecting the system packet error rate (PER) performance. We show a comparison of basic and modified QRD methods in terms of computational complexity. Similar modifications can easily be performed with other QR decomposition methods to reduce their computational complexity. We will give packet error rate simulation results to show the usefulness of the method in real time for Wireless LAN systems based on IEEE 802.11ac standard. From the simulation results, it is apparent that the proposed methods works well for all frame formats and BW options of the IEEE 802.11ac standard.