Mixed Noisy Network Coding and Cooperative Unicasting in Wireless Networks

TL;DR

This paper introduces Mixed Noisy Network Coding (MNNC) and its layered extension for cooperative unicast in wireless networks, improving communication efficiency and robustness in noisy, fading environments by allowing relays to decode or forward messages dynamically.

Contribution

The paper proposes MNNC and Layered MNNC schemes that generalize existing methods, enabling relays to decode or forward adaptively, and introduces Selective Coding Strategy for better performance in uncertain channel conditions.

Findings

MNNC improves bounds in AWGN networks with proper relay selection.

Layered MNNC enhances multi-hop communication efficiency.

SCS outperforms traditional schemes in slow-fading relay networks.

Abstract

The problem of communicating a single message to a destination in presence of multiple relay nodes, referred to as cooperative unicast network, is considered. First, we introduce "Mixed Noisy Network Coding" (MNNC) scheme which generalizes "Noisy Network Coding" (NNC) where relays are allowed to decode-and-forward (DF) messages while all of them (without exception) transmit noisy descriptions of their observations. These descriptions are exploited at the destination and the DF relays aim to decode the transmitted messages while creating full cooperation among the nodes. Moreover, the destination and the DF relays can independently select the set of descriptions to be decoded or treated as interference. This concept is further extended to multi-hopping scenarios, referred to as "Layered MNNC" (LMNNC), where DF relays are organized into disjoint groups representing one hop in the network. For cooperative unicast additive white Gaussian noise (AWGN) networks we show that -provided DF relays are properly chosen- MNNC improves over all previously established constant gaps to the cut-set bound. Secondly, we consider the composite cooperative unicast network where the channel parameters are randomly drawn before communication starts and remain fixed during the transmission. Each draw is assumed to be unknown at the source and fully known at the destination but only partly known at the relays. We introduce through MNNC scheme the concept of "Selective Coding Strategy" (SCS) that enables relays to decide dynamically whether, in addition to communicate noisy descriptions, is possible to decode and forward messages. It is demonstrated through slow-fading AWGN relay networks that SCS clearly outperforms conventional coding schemes.