Performance and throughput analysis of turbo decoder for the physical layer of digitalvideo-broadcasting-satellite-services-tohandhelds standard

In this study, coding performance of turbo decoder compliant to the physical layer of digital-video-broadcasting-satellite-services-to-handhelds (DVB-SH) standard for additive-white-Gaussian-noise (AWGN) and frequency selective fading channels are presented. The modulation of transmitted bits is carried out with orthogonal-frequency-division-multiplexing (OFDM) technique, incorporating 1 K-fast-Fourier-transform (1K-FFI) where each subcarrier is modulated using quadrature-phase-shift-keying (QPSG) or quadrature-amplitude-modulation (QAM) schemes. Performance analysis of turbo decoder for the decoding iterations of 3, 8, 14 and 18 as well as the sliding window sizes of 10, 20, 30 and 40 are investigated for both the channels. Discussion on the values of these design metrics to achieve optimum coding performance is also presented. The optimisation of system throughput for turbo decoder based on the decoding iteration and sliding window size for various processor speed ranging from 200 MHz to 1 GHz is carried out. Such an analysis is presented for non-parallel radix-2 as well as parallel radix-4 configuration of turbo decoder to meet the system throughput specification of third-generation wireless communication standard ranging from 100 to 300 Mbps. The coding performance of turbo decoder based on max-log-MAP, log-MAP and Maclaurin series-based algorithms are studied for both the channel conditions. Simultaneously, the running time for each of these algorithm in a 64 bit processor is also presented for comparison. Finally, the coding performance of turbo decoder for various code rates of 1/5, 2/9, 1/4, 2/7, 1/3, 2/5 and 1/2 are carried out.