A Diversity-Multiplexing-Delay Tradeoff of ARQ Protocols in The Z-interference Channel

TL;DR

This paper investigates the fundamental tradeoff between diversity, multiplexing, and delay in ARQ protocols for the Z-interference channel, proposing new strategies and analyzing their performance improvements.

Contribution

It characterizes the three-dimensional tradeoff for ARQ protocols in ZIC, introduces a cooperative approach with dynamic decoding, and derives closed-form expressions for the tradeoff.

Findings

Cooperative ARQ protocols significantly enhance diversity.

Dynamic decoders outperform static ones in the tradeoff.

Optimal message splitting improves communication reliability.

Abstract

In this work, we analyze the fundamental performance tradeoff of the single-antenna Automatic Retransmission reQuest (ARQ) Z-interference channel (ZIC). Specifically, we characterize the achievable three-dimensional tradeoff between diversity (reliability), multiplexing (throughput), and delay (maximum number of retransmissions) of two ARQ protocols: A non-cooperative protocol and a cooperative one. Considering no cooperation exists, we study the achievable tradeoff of the fixed-power split Han-Kobayashi (HK) approach. Interestingly, we demonstrate that if the second user transmits the common part only of its message in the event of its successful decoding and a decoding failure at the first user, communication is improved over that achieved by keeping or stopping the transmission of both the common and private messages. We obtain closed-form expressions for the achievable tradeoff under the HK splitting. Under cooperation, two special cases of the HK are considered for static and dynamic decoders. The difference between the two decoders lies in the ability of the latter to dynamically choose which HK special-case decoding to apply. Cooperation is shown to dramatically increase the achievable first user diversity.