Analog MIMO detection on the basis of Belief Propagation

In this article we present the design of an analog detector for multiple-input multiple-output (MIMO) wireless systems, based on the well known belief propagation (BP) algorithm. BP has been shown to obtain excellent results when solving inference problems in sparsely connected factor graphs. Unfortunately, MIMO detection is an example of inference in a densely connected graph, so other techniques need to be applied. We show that BP in conjunction with simulated annealing can offer near optimal performance when there is enough diversity in the receiver. Interestingly, this algorithm can be easily mapped into analog circuitry, thus leading to potentially low-power area-efficient MIMO detectors. A small analog detector based on this work has been designed and laid out in a 0.25 mum BiCMOS process.