Design and Implementation of a 6.5-Gb/s Multiradix Simplified Viterbi-Sphere Decoder for Trellis-Coded Generalized Spatial Modulation With Spatial Multiplexing

A simplified Viterbi-sphere decoder (VSD) for trellis-coded generalized spatial modulation (GSM) with spatial multiplexing (TCGSMX) is designed and implemented to exploit the soft information for achieving better performance. Multiple code rates are supported to combat different levels of spatial correlations in fading channels and to offer options for various transmission efficiencies. Hence, the proposed multiradix simplified VSD is configurable to process four radix-2 stages for 1/2 code rate, two radix-4 stages for 2/3 code rate, and one radix-8 stage for 3/4 code rate in one clock cycle to upgrade the throughput by fully pipelined architecture. To reduce the complexity, several techniques are employed, including the efficient settings of survival nodes of sphere decoding and sequence length for backtracing by Viterbi decoding. The chip has been fabricated in TSMC 40-nm CMOS technology. Compared to related works, the implementation provides higher throughput up to 6.5 Gb/s at 1.1-V supply voltage as well as 180.8-MHz operating frequency and consumes 374.3 mW for TCGSMX systems using 16-QAM and code rate of 1/2.