  Convergence and density evolution of a low complexity, iterative MIMO
detection based on belief propagation (BP) over a ring-type pair-wise graph are
presented in this paper. The detection algorithm to be considered is
effectively a forward-backward recursion and was originally proposed in [13],
where the link level performance and the convergence for Gaussian input were
analyzed. Presented here are the convergence proof for discrete alphabet and
the density evolution framework for binary input to give an asymptotic
performance in terms of average SINR and bit error rate (BER) without channel
coding. The BER curve obtained via density evolution shows a good match with
simulation results, verifying the effectiveness of the density evolution
analysis and the performance of the detection algorithm.
