Managing Interference Correlation Through Random Medium Access

TL;DR

This paper investigates how increasing randomness in medium access control, such as FHMA and ALOHA, can mitigate interference correlation effects in wireless networks, providing analytical results and optimal parameters for reducing local delay.

Contribution

It derives closed-form expressions for mean and variance of local delay under FHMA and ALOHA, introducing optimal parameters and regimes to improve network performance.

Findings

Optimal parameters minimize mean local delay.

Variance differs significantly between protocols.

Tradeoff between delay and jitter analyzed.

Abstract

The capacity of wireless networks is fundamentally limited by interference. However, little research has focused on the interference correlation, which may greatly increase the local delay (namely the number of time slots required for a node to successfully transmit a packet). This paper focuses on the question that whether increasing randomness in the MAC, such as frequency-hopping multiple access (FHMA) and ALOHA, helps to reduce the effect of interference correlation. We derive closed-form results for the mean and variance of the local delay for the two MAC protocols and evaluate the optimal parameters that minimize the mean local delay. Based on the optimal parameters, we propose the definitions of two operation regimes: correlation-limited regime and bandwidth-limited regime. Our results reveal that while the mean local delays for FHMA with N sub-bands and for ALOHA with transmit probability p are the same when p=1/N with thermal noise ignored, significant difference exists between the variances. At last, we evaluate the mean delay-jitter tradeoff and the bounds on the tail probability of the local delay, which shed key insights into the system design.