FPGA implementation of jointly operating channel estimator and parallelized decoder

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2009




In this thesis, implementation details of a joint channel estimator and parallelized decoder structure on an FPGA-based platform is considered. Turbo decoders are used for the decoding process in this structure. However, turbo decoders introduce large decoding latencies since they operate in an iterative manner. To overcome that problem, parallelization is applied to the turbo codes and the resulting parallel decodable turbo code (PDTC) structure is employed for coding. The performance of a PDTC decoder and parameters affecting its performance is given on an additive white Gaussian noise (AWGN) channel. These results are compared with the results of a parallel study which employs a different architecture in implementing the PDTC decoder. In the fading channel case, a pilot symbol assisted estimation method is employed for the channel estimation process. In this method, the channel coefficients are estimated by a 2-way LMS (least mean-squares) algorithm. The difficulties in the implementation of this joint structure in a fixed-point arithmetic and the solutions to overcome these difficulties are described in details. The proposed joint structure is tested with varying design parameters over a Rayleigh fading channel. The overall decoding latencies and allowed data rates are calculated after obtaining a reasonable performance from the design.