Research For Block Turbo Code

Turbo code was first introduced by C.Berrou et al in 1993, which is a kind of parallel concatenation of convolutional codes (PCCC). The encoder of Turbo code consists of two (or more than two) parallel-concatenated convolutional codes, and its decoder uses an iterative soft-input/soft-output decoding rule. This kind of codes have given rise to large interests in the coding area because they can still achieve small bit error rate at low SNR close to the Shannon capacity limit. In 1994, P.Ryndiah used linear block codes as subcodes of Turbo code, and then proposed Block Turbo Code (BTC). The basic concept of product codes, the qualification of random encoding and decoding and the idea of iterative decoding are introduced to the BTC, which makes it have perfect performances at low SNR and be able to counteract all kinds of interference and fading, so BTC is quite possibly used in wireless communication system with worse channel conditions.Firstly, The backgrounds of this problem and development tendency of Turbo codes are introduced in this thesis, and some problems in this area are pointed out. Secondly, a few of fundamental theories of channel code and several kinds of common channel codes are introduced. Thirdly, encoding and decoding principles of Turbo code and main decoding algorithms are described, as well as the simulation results of MAP and SOVA algorithm. Then, we introduce coding and decoding principles of BTC (or TPC) and two sorts of decoding algorithms (Chase iterative decoding algorithm and gradient algorithm) in detail. We program to implement theBTC encoding and decoding system by using the two algorithms and get some simulation results. Lastly, the performances of PCCC, TPC and convolutional code are compared and analyzed.Currently, most of the works on turbo codes have essentially focused on CTCs (Convolutional Turbo Codes), and BTCs have been partially neglected. Many problems on theories and applications of BTC need solving. Yet, the BTC is more attractive for a wide range of applications because of its excellent performances in the wireless channel.