Cooperative Signaling with Soft Information Combining

Abstract

We propose a Decode-and-Forward (DF) scheme using distributed Turbo code (DTC) for a three-node (source, relay, and destination) wireless cooperative communication system. The relay decodes, then interleaves, and reencodes the decoded data. It then forwards the reencoded packet and its instantaneous receive SNR to the destination. The performances using both ideal and quantized SNR are studied. The destination uses a modified metric within a Turbo decoding algorithm to scale the soft information calculated for the relay code. The proposed scheme is simple to implement and performs well.

Two-User Cooperative Transmission Using Superposition Modulation and Soft Information Combining

“…In order to recover some of the throughput loss, numerous schemes have been proposed 1 [3]- [11]. For example, using a common relay to forward the messages received from all users simultaneously is widely proposed.…”

“…It drops incorrectly decoded user packets and combines the remaining packets if more than one user's packet is successfully decoded. Therefore, from each user's point of view, selective DF [2] is 1 We consider only communication in which all users are communicating with a common destination.…”

“…Recently, we proposed [1] a DF scheme that forwards hard decisions and reliability information in the form of a quantized SNR value from the relay. A single user network was considered in [1].…”

“…A single user network was considered in [1]. It showed that, even though the relay may decode with some errors, the destination can still extract useful information.…”

“…The re-mapped packet and receive SNRs are forwarded to the destination. The cooperative Turbo decoder of [1] is used at the destination. Both symmetric and asymmetric network topologies are considered.…”