Programmable processor implementations of -best list sphere detector for MIMO receiver

An increasing number of standards in wireless communications have encouraged to study programmable processors as platforms for flexible receivers. A multiple-input multiple-output (MIMO) antenna system combined with orthogonal frequency division multiplexing (OFDM) technique has been introduced in many wireless communications standards, such as in the third generation long term evolution (3G LTE). The MIMO-OFDM system requires an efficient detector and a platform support for parallel processing of multiple subcarriers. A K-best list sphere detector (LSD) provides for near optimal decoding performance and a fixed throughput making it an interesting algorithm from the point of view of practical implementations.In this paper, we compare the implementations of the K-best LSD on four processor platforms: a digital signal processor (DSP), software defined radio (SDR), application-specific processor (ASP) and application-specific instruction-set processor (ASIP). The DSP is a popular very long instruction word (VLIW) device (TMS320C6455), the SDR processor employs multithreading and multiple cores (SB3500 core processor), the ASP is based on transport triggered architecture (TTA), while the ASIP is the SDR processor enhanced with a special instruction-set extension for sorting.A 2×2 MIMO antenna system with 64-quadrature amplitude modulation (64-QAM) is assumed. The chosen list sizes K=8 and 16 are based on simulation results carried out in MATLAB environment with the third generation long term evolution (3G LTE) parameters. The proposed ASIP achieved a promising throughput of 32.0 Mbps, where the software defined radio (SDR) implementation on the SB3500 core processor suffers from an inefficient software sorter. The ASP, in which the minimized hardware complexity has been the goal, achieves a throughput of 7.6 Mbps. However, more essential examination is related to the symbol time, which sets strict parallel processing requirements to the programmable processors.