Efficient QRD for SRI-RLS Based Equalization on Programmable Architecture

Advanced adaptive filters have been shown to be very powerful for tracking time varying channels in various wireless communications system. However, the performance comes at the expense of highly resource-demanding implementations, especially in the context of programmable architecture based SDR. We present the optimizations for programmable implementation of QRD based SRI-RLS, which represents a large family of advanced adaptive filters. The key contribution of our work is to comprehensively and systematically remove the redundant operations in the QRD for SRI-RLS. Although most signal processing and scientific libraries implement householder reflection based QRD, we explore different alternatives and then choose given rotations based QRD to enable the aforementioned systematic redundancy removals. Our work significantly reduces the resource requirements (cycle count, energy consumption, etc.) of SRI-RLS implementation. Comparing to the widely accepted QRD implementation in numerical recipes, our work reduces 96.4% cycle-count on a typical baseband DSP (TI TMS320C6713), enabling efficient implementations. The paper shows that removing redundancy is very effective for modern statistical signal processing algorithms that largely rely on cascaded matrix operations.