A new forwarding strategy for wireless relay channels: Analog-encode-and-forward (AEF)

Amplify-forward (AF) and decode-forward (DF) continue to dominate the practical strategies for signal relaying. Amplify-forward is a way of forwarding soft reliability information that is extracted directly from the channel reception - without making use of the channel code that may well exist in the packet, whereas decode-forward exploits the coding gain, but forwards only the hard-decisions (provided that decoder succeeds). This paper joins the merits of AF and DF by exploiting “analog codes” - a special class of error correction codes that can directly encode and protect real-valued data. Exploiting useful ideas from the chaos theory and the parallel concatenation structure, we show that how chaos-based analog turbo-like codes can be designed and used in user cooperation. In the proposed “analog-encode-forward (AEF)” scheme, the relay node first soft-decodes the packet from the source, then re-encodes this soft decoder output using an appropriate analog code, and forwards it to the destination. A hybrid scheme that combines AEF and DF is further exploited to improve performance.