Buffered Aloha with K-Exponential Backoff -- Part I: Stability and Throughput Analysis

TL;DR

This paper analyzes the stability and throughput of buffered Aloha networks using K-Exponential Backoff, showing that exponential backoff maintains stability even with infinitely many nodes, unlike geometric backoff.

Contribution

It introduces a unified method for analyzing stability and throughput of K-Exponential Backoff in buffered Aloha networks for any cutoff K.

Findings

Exponential Backoff maintains stability regardless of network size.

Geometric Backoff's stable region shrinks as the number of nodes increases.

Analytical results are validated through simulations.

Abstract

This two-part paper series studies the performance of buffered Aloha networks with K-Exponential Backoff collision resolution algorithms. Part I focuses on stability and throughput analysis and Part II presents the delay analysis. In Part I, the buffered Aloha network is modeled as a multi-queue single-server system. We adopt a widely used approach in packet switching systems to decompose the multi-queue system into independent first-in-first-out (FIFO) queues, which are hinged together by the probability of success of head-of-line (HOL) packets. A unified method is devised to tackle the stability and throughput problems of K-Exponential Backoff with any cutoff phase K. We demonstrate that a network with K-Exponential Backoff can be stabilized if the retransmission factor q is properly selected. The stable region of q is characterized and illustrated via examples of Geometric Retransmission (K=1) and Exponential Backoff (K=infinity). With an increasing number of nodes n, we show that the stable region of Geometric Retransmission rapidly shrinks, and vanishes as n goes to infinity. In contrast, the stable region of Exponential Backoff does not vary with the network population n, implying that a stable throughput can be achieved in networks with Exponential Backoff even with an infinite number of nodes. All the analytical results presented in this paper series are verified by simulations.