Contention Intensity based Distributed Coordination for V2V Safety Message Broadcast

TL;DR

This paper introduces a distributed coordination scheme for V2V safety message broadcast that estimates channel contention to improve channel access, reducing collisions and delays compared to 802.11p.

Contribution

It proposes a novel contention intensity based distributed coordination (CIDC) scheme that estimates contention and deterministically sets back-off counters, improving V2V broadcast performance.

Findings

Lower collision probability than 802.11p

Reduced contention delay in simulations

Effective contention estimation even with errors

Abstract

In this paper, we propose a contention intensity based distributed coordination (CIDC) scheme for safety message broadcast. By exploiting the high-frequency and periodical features of the safety message broadcast, the application-layer design of the CIDC enables each vehicle to estimate the instantaneous channel contention intensity in a fully distributed manner. With the contention intensity information, the MAC layer design of CIDC allows vehicles to adopt a better channel access strategy compared to the 802.11p. This is because CIDC selects the initial back-off counter for each new packet deterministically, i.e., based on the contention intensity, instead of randomly. The proposed CIDC is modeled, and key performance indicators in terms of the packet collision probability and average contention delay, are derived. It is shown that the proposed change in the initial counter selection leads to a system model completely different from the classic Markov chain based model. Moreover, the proposed CIDC, fully distributed and compatible with the 802.11p, can achieve both a much lower collision probability and a smaller contention delay compared with 802.11p at the cost of a small communication and computation overhead. Extensive simulation results demonstrate the effectiveness of the CIDC in both of the accurate and the erroneous contention intensity estimation scenarios.