A low complexity complex QR factorization design for signal detection in MIMO OFDM systems

Complex QR factorization is a fundamental operation used in various MIMO signal detection algorithms. In this paper, we revise the Givens Rotation based factorization algorithm and develop an efficient scheme working in the real number domain. The complex matrix is first extended into a block-wise symmetric real number counterpart. The proposed scheme can reduce the computing complexity to almost one half by exploiting the symmetric property. Computing complexity analysis also shows the superiority of our scheme over various factorization schemes. Finally, subject to the EWC 802.11n recommendation, a novel systolic array design featuring fully parallel and deeply pipelined processing was presented. CORDIC algorithm is employed to implement the required rotation operations with low circuit complexity. Synthesis results in TSMC 0.18mum process indicate the proposed design, with a gate count of merely 17.06 K and a maximum clock rate of 202 MHz, can admit a new 2 x 2 complex matrix for factorization in every 8 clock cycles.