Highly Improved Low Complexity Hybrid Turbo Codes For 4g Applications

Abstract

ABSTRACT newline newline newline newline newlineError correcting code is essential for wireless communication channels since they are subjected to single and multiple channel reflections, causing signal fading. This leads to errors during the time of transmission of data from sender to receiver. newlineThe Turbo Convolution Codes (TCC) are suitable for any kind of wireless channel and are the best error correcting codes. TCC decoders require high decoding complexity. Even if puncturing is used to improve the coding rate, the complexity of TCC decoder does not reduce. Modified turbo codes require low decoding complexity compared to TCC as they use multiple concatenations of simple block codes and convolution codes. The TCC also known as Parallel Concatenated Convolution Codes (PCCC), it shown the performance newlinenear S hannon0 s channel capacity . At Bit Error Rate (BER) of 10and#8722;5, in a 16-state rate-1/2 newlineTCC with interleaver length of 65536, Signal to Noise Ratio (SNR) Eb/No is 0.5 dB away from S hannon0 s limit in an Additive White Gaussian Noise (AWGN) channel. Even though TCC decoder does the decoding process based on A Posteriori Probability (APP) algorithm and hence the computational complexity is high. By using Maximum A Posteriori (MAP) algorithm in logarithmic domain the decoder complexity is about 480 Additions. newline newlineAverage Equivalent Operations per Information Bit per Iteration(AEO/IB/I) complexity remains unchanged even after puncturing is used to adjust the code rate. Concatenated coding schemes, using relatively simple constituent convolution and block codes, can achieve performance close to the theoretical limits. newlineAlternatively, concatenated Zigzag codes are low complexity parallel concatenated block codes. Rate-1/2 concatenated Zigzag decoder requires 20 AEO/IB/I if Soft-In Soft-Out (SISO) decoding is implemented. For long length of interleaver these codes perform better. However, a long interleaver length leads to more time delay as each decoder requires longer latency in interleaving and deinterleaving the received bits. newlinePreviously, a class