N-DCF: MAC overhead reduction using narrow channel contention in wireless networks

Jungmin So,Ayinebyona Eliab

doi:10.1186/s13638-018-1241-z

Jungmin So, Ayinebyona Eliab

Open Access

https://doi.org/10.1186/s13638-018-1241-z

Copy DOI

Abstract

This paper presents a medium access control protocol for wireless networks that improves system spectral efficiency using multiple channels. Use of multiple narrow channels has already been proposed as a solution to reduce MAC overhead, but merely dividing a wide channel into narrow channels cannot mitigate the negative effect of packet collisions especially when the network is densely populated. The proposed protocol, called N-DCF, adds protocol support to reduce packet collisions and improve channel utilization. The main idea is to let each node contend on one of the multiple channels and give the node privilege to access other channels when it successfully finishes transmission on its contention channel. When a node gains privilege to a channel, it can access the channel without contention. Privilege is gained probabilistically so that other nodes can have chance to win the channel and obtain privilege for other channels as well. N-DCF reduces channel idle time by conducting random backoff only on one of the narrow channels and reduces packet collisions by assigning contention channel randomly. Idle channels are not wasted because nodes can access other channels once the node wins its contention channel. Performance evaluation shows that the proposed scheme achieves higher throughput than 802.11 DCF without harming the fairness, regardless of node density, packet size, and number of radios.

Highlights

IEEE 802.11 Distributed coordination function (DCF), a medium access control used in current-day wireless Local area network (LAN), uses random backoff mechanism to mitigate packet collisions [1]
Frame aggregation techniques included in recent WLAN standards can reduce channel idle time, but the negative effect of packet collisions remains and significantly affects system spectral efficiency
Using multiple narrow channels has similar benefits with frame aggregation, which reduces the percentage of time spent on random backoff and interframe spacing

Summary

Introduction

IEEE 802.11 DCF, a medium access control used in current-day wireless LANs, uses random backoff mechanism to mitigate packet collisions [1]. A node picks a random number from a range called contention window and waits for a duration of time according to the selected number. The purpose of random backoff is to have a single node begin transmission, it is still possible that multiple nodes transmit simultaneously, resulting in a packet collision. Once a node starts transmitting, other nodes sense the channel as busy and wait until the channel becomes idle again. The overhead of this random access protocol consists of channel idle time (duration of time when all nodes are waiting and no one is using the channel) and loss from packet collisions.

Methods

Results

Conclusion