Design and Analysis of an Asynchronous Zero Collision MAC Protocol

TL;DR

This paper introduces ZC, a distributed, collision-free MAC protocol that operates without control messages or synchronization, supporting variable-length packets and real-time applications, with proven efficiency and robustness.

Contribution

The paper presents ZC, a novel asynchronous MAC protocol that achieves zero collision without control messages, supporting variable-length packets and dynamic network conditions.

Findings

ZC achieves collision-free operation in steady state.

ZC outperforms CSMA and TDMA at various loads.

ZC maintains efficiency with node mobility and clock drift.

Abstract

This paper proposes and analyzes a distributed MAC protocol that achieves zero collision with no control message exchange nor synchronization. ZC (ZeroCollision) is neither reservation-based nor dynamic TDMA; the protocol supports variable-length packets and does not lose efficiency when some of the stations do not transmit. At the same time, ZC is not a CSMA; in its steady state, it is completely collision-free. The stations transmit repeatedly in a round-robin order once the convergence state is reached. If some stations skip their turn, their transmissions are replaced by idle $20 \mu$-second mini-slots that enable the other stations to keep track of their order. Because of its short medium access delay and its efficiency, the protocol supports both real-time and elastic applications. The protocol allows for nodes leaving and joining the network; it can allocate more throughput to specific nodes (such as an access point). The protocol is robust against carrier sensing errors or clock drift. While collision avoidance is guaranteed in a single collision domain, it is not the case in a multiple collision one. However, experiments show ZC supports a comparable amount of goodput to CSMA in a multiple collision domain environment. The paper presents an analysis and extensive simulations of the protocol, confirming that ZC outperforms both CSMA and TDMA at high and low load.