User Cooperation with Punctured Turbo Codes

In wireless network transmission, a recently introduced form of spatial diversity, known as user cooperation diversity is an effective way to overcome deep fading. Cooperative users share their antennas and other resources to create a virtual array through distributed transmission and signal processing. In particular, the user cooperation technique is capable of providing sufficient diversity gain in many wireless systems where other conventional transmit diversity methods might not be practical. Recently proposed cooperative schemes rely on powerful channel codes suitable for cooperation. Here we study cooperative coding performance of punctured turbo codes for a quasi-static fading channel and a strict decoding delay constraint. Based on the threshold behavior analysis of the mother and punctured turbo codes, we derive a frame error rate (FER) upper bound for the cooperative coding scheme as a function of user-todestination SNRs, inter-user SNRs, the noise threshold of the mother turbo code, and the puncturing rate which relates the lengths of the originating and partnering users’ codeword transmissions. We show that the FER of cooperative turbo codes demonstrates the expected diversity gain for a sufficiently good inter-user channel quality.