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 20µ-second mini-slots that enable the other stations to keep track of their order. To claim the right to transmit, a station selects one of the idle mini-slots in one round and transmits in that mini-slot in the next round. If multiple stations select the same mini-slot, they collide and repeat their random selection in a subsequent round. A station loses its right to transmit after being idle in a given number of successive rounds. The number of transmissions per round can be adapted to the number of active stations in the network. 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.
In ZC REF , each station notes all the idle slots in a cycle.
Design and Analysis of an Asynchronous Zero Collision MAC Protocol
ArXiv
ArXiv
Computer Science