A new MIMO detector architecture based on a Forward-Backward trellis algorithm

In this paper, a recursive forward-backward (F-B) trellis algorithm is proposed for soft-output MIMO detection. Instead of using the traditional tree topology, we represent the search space of the MIMO signals with a fully connected trellis and a forward-backward recursion is applied to compute the a posteriori probability (APP) for each coded data bit. The proposed detector has the following advantages: (a) it keeps a fixed throughput and has a regular datapath structure which makes it amenable to VLSI implementation, and (b) it attempts to maximize the a posteriori probability by tracing both forward and backward on the trellis and it always ensures that at least one candidate exists for every possible transmitted bit x_k isin {-1, +1}. Compared with the soft K-best detector, the proposed detector significantly reduces the complexity because sorting is not required, while still maintaining good performance. A maximum throughput of 533 Mbps is achievable at a cost of 576 K gates for 4 times 4 16-QAM system.