Asynchronous Denoise and Forward Two-Way Relay Using ECPM

Abstract

In a denoise-and-forward (DNNF) two-way relay system, since the relay is at different distances with the end users, the signals are combined with asynchronous phases and delays, leading to severe performance loss. For most denoising and decoding methods, precise estimation of the delay is required by the relay and end users, which is usually unavailable when strong noise is present. Using the ergodic property of chaotic signals and the fact that the sum of two signals over a given period is invariant with respect to their temporal alignment, we propose to address the asynchronous problem using chaos modulation. In particular, we use ergodic chaotic parameter modulation (ECPM) and guarding intervals (GIs) to remove the requirement for precise time synchronization and complex iterative decoding. The theoretical bit-error-rate (BER) performance is analyzed and verified by simulations. A relay selection method is also proposed for two-way relay systems with multiple relays to use part of the relays to achieve improved performance compared to using all relays. It is shown that the relay selection method can increase the normalized throughput in low signal-to-noise ratio (SNR) scenarios.