No abstract

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.

No abstract

No abstract

Abstract-Various results to date have demonstrated the advantages of one or several relay nodes assisting transmissions in a wireless network. In many practical scenarios, not all nodes in the network are simultaneously involved in every transmission; therefore, protocols are needed to form groups or subsets of nodes for the purposes of cooperation. We consider this problem in the context of regenerative nodes and non-altruistic cooperation (all nodes have data of their own to transmit). For a network-wide diversity advantage, the protocol must provide each transmitting node with enough "partners" that can decode its message with high-enough probability. Assuming that the nodes cannot communicate their control decisions (distributed scenario), and that each node chooses to help n other nodes, we point out a simple, static selection strategy that guarantees diversity n+1 for all transmissions. We then consider centralized control strategies and study the additional gains that arise from a central control, under various amounts of information being available to the central controller.

No abstract

Cooperative communication has recently emerged as an effective form of signaling in wireless fading channels. This work examines cooperative communication in multi-user networks, where the geometry of information flow becomes an issue, i.e., who should cooperate with whom? In particular, one is interested in algorithms that do not require global network information, which is often unavailable due to latency, limited memory, or other constraints. In this work we propose and study distributed protocols for partner selection in cooperative networks. In this class of protocols, wireless users act individually and independently in establishing cooperative communication, without the aid of a central authority. Such a setup is especially of interest in ad-hoc networks, or networks of wireless sensors. We perform outage analysis for the proposed protocols, showing that full diversity in the number of cooperating users is achieved. The cooperative network with the proposed protocols performs significantly better than the non-cooperative counterpart.