On the Universality of Sequential Slotted Amplify and Forward Strategy in Cooperative Communications

TL;DR

This paper demonstrates that the sequential slotted amplify and forward (SSAF) strategy is universally optimal across cooperative multiple access, broadcast, and relay channels, achieving the best diversity-multiplexing tradeoff in all cases.

Contribution

The paper extends the SSAF strategy to cooperative broadcast and multiple access channels and proves its optimality for all three classical models, establishing universal optimality.

Findings

SSAF achieves the DMT upper bound for CMR.

Proposed CBC-SSAF asymptotically reaches the DMT upper bound with many users.

CMA-SSAF exactly achieves the DMT upper bound for any number of users.

Abstract

While cooperative communication has many benefits and is expected to play an important role in future wireless networks, many challenges are still unsolved. Previous research has developed different relaying strategies for cooperative multiple access channels (CMA), cooperative multiple relay channels (CMR) and cooperative broadcast channels (CBC). However, there lacks a unifying strategy that is universally optimal for these three classical channel models. Sequential slotted amplify and forward (SSAF) strategy was previously proposed to achieve the optimal diversity and multiplexing tradeoff (DMT) for CMR. In this paper, the use of SSAF strategy is extended to CBC and CMA, and its optimality for both of them is shown. For CBC, a CBC-SSAF strategy is proposed which can asymptotically achieve the DMT upper bound when the number of cooperative users is large. For CMA, a CMA-SSAF strategy is proposed which even can exactly achieve the DMT upper bound with any number of cooperative users. In this way, SSAF strategy is shown to be universally optimal for all these three classical channel models and has great potential to provide universal optimality for wireless cooperative networks.