High-performance Joint Iterative Detection and Decoding Design in Coded-MIMO Systems

Abstract

Multiple-input multiple-output (MIMO) techniques have been widely used to increase the transmission rate and improve the signal quality in modern wireless communication systems To further ensure transmission reliability error-correcting codes like turbo codes with performance close to the theoretical Shannon limit are adopted for wireless communication systems Up to now many MIMO detection algorithms have been proposed in the literature to recover the transmitted signals from the received noisy signals In particular soft-output MIMO detection algorithms can be used to provide a priori information of the codeword to the following soft-input soft-output (SISO) decoders such as the turbo decoder in coded-MIMO systems In some application scenarios with Rayleigh fading channels the induced unreliable a priori information might result in system performance degradation Exploring high-performance coded-MIMO systems thus becomes a challenging and crucial research area In this dissertation we have developed a high-performance joint iterative detection and turbo decoding design in coded-MIMO systems First a low-complexity high-throughput complex-valued QR factorization (CQRF) design is presented Based on coordinate rotation digital computer (CORDIC) arithmetic a massively parallel array architecture consisting of pipelined and folded CORDIC modules was developed to enhance the throughput The chip implementation result indicates the design with an equivalent gate count of 192 1K can operate at 200 MHz and accomplish the highest 3-Gb/s data rate in 4×4 MIMO systems The proposed design also outperforms related designs in two compound performance indices: data rate normalized with respect to gate count and power consumption Second we developed a mean-aided early-pruned scheme in MIMO detector based on sort-free fixed-complexity sphere decoding algorithm The modified MIMO detector can reduce the number of node computations while maintaining the BER performance of the original sort-free algorithm Experimental results show that the proposed reconfigurable detector design with 4×4 antenna array has a higher normalized throughput than those of existing detectors using the same system configuration Third an efficient joint iterative MIMO detection and turbo decoding design was developed For the turbo decoding a modified parallel-window MAP algorithm was proposed to reduce the warm-up computation In the initial iteration the reliability of the soft information of a MIMO detector can be greatly improved by applying the proposed extended tree search scheme A modified updating strategy is presented to acquire the highly reliable extrinsic information from the soft-output MIMO detector in iterative system development Compared to the list sphere decoding (LSD) algorithm about 94% reduction in the memory requirement of log-likelihood ratio (LLR) computation can be achieved by using the proposed candidate node selection strategy Finally based on the analysis of iteration profile the overall system performance can be maintained with a fewer number of searched nodes than existing works

Date of Award	2015 Aug 28
Original language	English
Supervisor	Ming-Der Shieh (Supervisor)