Adaptive Decoding Algorithm Based on Multiplicity of Candidate Sequences for Block Turbo Codes

It is known that Block Turbo Codes （BTC） can be nearly optimally decoded by Chase-II algorithm, in which the Least Reliable Bits （LRBs） are chosen empirically to keep the size of the test patterns （sequences） relatively small and to reduce the decoding complexity. While there are also other adaptive techniques, where the decoder＇s LRBs adapt to the external parameter of the decoder like SNR （Signal Noise Ratio） level, a novel adaptive algorithm for BTC based on the statistics of an internal variable of the decoder itself is proposed in this paper. Different from the previous reported results, it collects the statistics of the multiplicity of the candidate sequences, i.e., the number of the same candidate sequences with the same minimum squared Euclidean distance resulted from the decoding of test sequences. It is shown by Monte Carlo simulations that the proposed adaptive algorithm has only about 0.02dB coding loss but the average complexity of the proposed algorithm is about 42% less compared with Pyndiah＇s iterative decoding algorithm using the fixed LRBs parameter.

Block Turbo code modulation for MB-OFDM-based cognitive radio to suppress its side-band interferences

To suppress the side-band interferences caused by multiband orthogonal frequency division multiplexing （MB-OFDM）-based cognitive radio systems, a mathematical expression of the side-band signal is derived. Based on this expression, the constraints among the transmitted symbols, which help to suppress the interferences, are obtained. Combined with the constraints, a type of block Turbo code modulation scheme is proposed. In the modulation scheme, the side-band interferences are attenuated quickly. Compared with other techniques, in this scheme, the interference suppression is implemented more easily and sufficiently. Simultaneously, the bit error rate （BER） performance can be improved. Theoretical analyses and simulation results show that it is highly applicable for MB-OFDM-based cognitive radio systems to suffer from Rayleigh fading.

Unequal error protection system for robust video transmission

With the development of multimedia communication services, robust video transmission over wireless environment poses many challenges. A new UEP_BTC_STBC_OFDM system is proposed to provide unequal error protection for the source coded video stream in dispersive fading channel. The scheme concatenates the Block Turbo Code （BTC） with the Space-Time Block Code （STBC） for an OFDM system. With the proposed system, both the good error correcting capability of BTC and the concurrent large diversity gain characteristic of STBC can be achieved simultaneously with low encoding and decoding complexity. Furthermore, by combining with the data partition of H. 264 and different BTC codes, this system can guarantee high QoS control of video transmission. Simulation result shows that the proposed system outoerforms other reported schemes and has good performance of video transmission.