An Efficient Circulant MIMO Equalizer for CDMA Downlink: Algorithm and VLSI Architecture
Cavallaro, Joseph R.
We present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink. This reduces the direct matrix inverse (DMI) of size (NF×NF) with O((NF)3) complexity to some FFT operations with O(NF log2(F)) complexity and the inverse of some (N×N) submatrices.We then propose parallel and pipelined VLSI architectures with Hermitian optimization and reduced-state FFT for further complexity optimization. Generic VLSI architectures are derived for the (4×4) high-order receiver from partitioned (2 × 2) submatrices. This leads to more parallel VLSI design with 3× further complexity reduction. Comparative study with both the conjugate-gradient and DMI algorithms shows very promising performance/complexity tradeoff. VLSI design space in terms of area/time efficiency is explored extensively for layered parallelism and pipelining with a Catapult C high-level-synthesis methodology.