Efficient iterative decoding algorithms for turbo and low-density parity-check (LDPC) codes

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A New Method of Improving SOVA Turbo Decoding for AWGN, Rayleigh and Rician Fading Channels

e iterative soft output Viterbi algorithm (SOVA) is a sub-optimum algorithm when it is used to decode turbo codes. By normalizing its extrinsic information we get a performance improvement compared to the standard SOVA. In particular, if the extrinsic information is increased in the last decoding iteration, an additional coding gain improvement is noticed. For example, this is 0.25 dB for a frame length of 1000 bits in the additive white Gaussian noise (AWGN) channel as well as in an uncorrelated Rician fading channel at bit error rate (BER) of IO". Also, this normalized SOVA is only about 0.25 dB worse than a turbo decoder using the Log-MAP algorithm, both in the AWGN channel and in an uncorrelated Rayleigh fading channel at BER of around Furthermore with an 8-state component code, a frame length of 500 hits performs 0.125 dB better than a 16-state Bidirectional (Si)-SOVA turbo decoder at BER of IO-' in the AWGN channel

A New Method of Improving SOVA Turbo Decoding for AWGN, Rayleigh and Rician Fading Channels

e iterative soft output Viterbi algorithm (SOVA) is a sub-optimum algorithm when it is used to decode turbo codes. By normalizing its extrinsic information we get a performance improvement compared to the standard SOVA. In particular, if the extrinsic information is increased in the last decoding iteration, an additional coding gain improvement is noticed. For example, this is 0.25 dB for a frame length of 1000 bits in the additive white Gaussian noise (AWGN) channel as well as in an uncorrelated Rician fading channel at bit error rate (BER) of IO". Also, this normalized SOVA is only about 0.25 dB worse than a turbo decoder using the Log-MAP algorithm, both in the AWGN channel and in an uncorrelated Rayleigh fading channel at BER of around Furthermore with an 8-state component code, a frame length of 500 hits performs 0.125 dB better than a 16-state Bidirectional (Si)-SOVA turbo decoder at BER of IO-' in the AWGN channel

A terabit/second satellite system for European broadband access: a feasibility study

This paper presents a feasibility study for a fixed broadband access High Throughput Satellite terabit/second system by considering appropriate state‐of‐the‐art communication technologies. For the investigated system model, DVB‐S2 and DVB‐RCS2 are assumed as the air interfaces for the forward and return link, respectively. The performance of DVB‐S2 and DVB‐RCS2 Adaptive Coding and Modulation is examined along with potential extensions of these standards. For example, the performance of very low rate DVB‐RCS turbo codes are investigated and their performance is evaluated. In addition, a performance comparison for M‐ary (M=16, 32, 64) constellations in the presence of a linear and a high power amplifier non‐linear channel is carried out. Various frequency reuse schemes and different antenna models are also considered, and their performance is analyzed and evaluated. It is demonstrated that, by using the Q/V (40/50 GHz) bands for the gateways and the Ka (20–30 GHz) band for the user terminals, around 20 gateways and 200 beams are required to provide with the proposed satellite system terabit/second capacity. The obtained performance evaluation results have shown that the forward link is limited by noise rather than interference, whereas the return link is interference limited. Additionally, some further aspects of the system design in relation with the total number of gateways and the payload are discussed

BICMC and TD Comparative Performance Study of 16-APSK Signal Variants for DVB-S2 Systems

A comparative performance study, in terms of Bit Interleaved Coded Modulation Capacity (BICMC) and Total Degradation (TD), between Amplitude Phase Shift Keying (APSK) signal variants for the 2nd generation Digital Video Broadcasting via Satellite (DVB-S2) system is presented. Motivated by the observation that the presence of more signal points in the outer ring of 16-APSK signals appears to improve the performance in a non-linear (NL) channel, we investigate the performance of 2-14 and 3-13 APSK signals with two novel bit-to-symbol mappings as alternatives to the 4-12 APSK, which is currently proposed as the modulation scheme for the DVB-S2 standard. Performance evaluation results are obtained for an air-interface based on this standard, which includes a Non-Linear (NL) High Power Amplifier (HPA), predistortion, raised cosine Nyquist filters and Low-Density Parity-Check (LDPC) codes. Performance results have shown that the proposed 3-13 APSK signal not only achieves the best BICMC performance with higher gains occurring at high signal-to-noise ratios, but also outperforms, in terms of TD performance, all the other considered 16-ary APSK signal variants

Satellite Communications: Research Trends and Open Issues

A panoramic view on the study and design of digital satellite communication links is the focus of this paper. Starting from the characterization of satellite propagation channel in different application environments (from broadcast to fixed terminals, to broadband mobile satellite access), we address physical layer aspects related to satellite communications in the attempt of providing the Reader with an overview of the new trends and open issues in this field