Convolutional Codes And Differential Modulation Cascade Coding Turbo Detection

Owing to many advantages, digital communication system becomes more and morepopular. In the course of communication, people care for the quality and efficiency most.Encoding and decoding affect the quality of communication directly, so they take hold ofvery importance position in the communication.In order to ensure the digital communication, we need to control the BER in anenough small range. We can adopt the error controlled encoding and decoding technique tolower the BER.In an uncoded digital transmission system with M-PSK or M-DPSK, there is aperformance difference in the required signal-to-noise ratio (SNR) of up to 3 dB ifM-DPSK is detected noncoherently. The difference still remains in coded systems based onconvolutional codes with classical soft decision Viterbi decoding. In this contribution, wejust regard the combination of differential modulatial and convolutional channel coding asa concatenated coding scheme. In this case, the differential modulation is considered as theinner code and the convolutional code as the outer code. Then, before this background,turbo decoding is applied at the receiver resulting in an SNR gain of more than 3.5 dBcompared with classical soft decision Viterbi decoding. Thus, the transmission system withdifferential modulation performs even better than the corresponding system withnon-differential modulation.