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Cooperation provides transmit diversity in cases where wireless transmitters, due to size, power, or other constraints, cannot support multiple antennas. Cooperation involves two single-antenna sources (which we call users) forming a partnership, in which each achieves space-time diversity by using their partner's antenna as a relay. We propose a new methodology, called coded cooperation, where cooperation is achieved through channel coding methods, instead of a direct relay or repetition. Each codeword is partitioned into two subsets that are transmitted from the user's and partner's antennas, respectively. Coded cooperation achieves impressive gains compared to a non-cooperative system while maintaining the same information rate, transmit power, and bandwidth. We develop tight upper bounds for bit and block error rates, which we validate through simulations. Bit and block error rate results illustrate the improvement of coded cooperation for various combinations of channel conditions between the partners and to the destination.

Abstract-When mobiles cannot support multiple antennas due to size or other constraints, conventional space-time coding cannot be used to provide uplink transmit diversity. To address this limitation, the concept of cooperation diversity has been introduced, where mobiles achieve uplink transmit diversity by relaying each other's messages. A particularly powerful variation of this principle is coded cooperation. Instead of a simple repetition relay, coded cooperation partitions the codewords of each mobile and transmits portions of each codeword through independent fading channels. This paper presents two extensions to the coded cooperation framework. First, we increase the diversity of coded cooperation in the fast-fading scenario via ideas borrowed from space-time codes. We calculate bounds for the bit-and block-error rates to demonstrate the resulting gains. Second, since cooperative coding contains two code components, it is natural to apply turbo codes to this framework. We investigate the application of turbo codes in coded cooperation and demonstrate the resulting gains via error bounds and simulations.

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