DCAP: A Multichannel Protocol for Single Interface 802.11 Wireless Mesh Networks

Abstract

Wireless ad hoc networks are gaining popularity as quick and inexpensive methods of connecting computers. In particular, Wireless Mesh Networks (WMNs) are becoming a viable method of offering Internet access to entire neighborhoods. One reason WMNs are attractive is because of their use of inexpensive 802.11 wireless hardware. However, using 802.11 standard compliant hardware has a major limitation: the 802.11 standard does not support the use of multiple channels in the same network. Because of this limitation, wireless 802.11 networks are not able to achieve the traffic throughput possible when utilizing all the available channels.

To increase the throughput in WMNs, this paper proposes a novel protocol allowing the use of multiple channels with a single wireless 802.11 interface. This protocol, Distributed Channel-switching Accessory Protocol, or DCAP, requires no modifications to the 802.11 MAC layer. DCAP defines the methods wireless nodes use to send and receive traffic across multiple channels with a single wireless interface. The key concept of our approach is Home Channels. A node's Home Channel is the only wireless channel on which the node receives data. By requiring the sender to change to the receiver's Home Channel to transmit a packet, all nodes know on which channel to transmit each packet. Once on the receiver's Home Channel, the transmission of the packet follows the 802.11 standard.

In this work, DCAP is implemented in the ns-2 event simulator to evaluate its performance. DCAP is implemented as a separate protocol immediately above the 802.11 MAC layer in ns-2. The implementation of DCAP makes no modifications to the 802.11 MAC protocol. A series of performance evaluation tests are performed to compare DCAP's performance against a single channel 802.11 network. These tests compare the throughput of the two networks in a variety of different network traffic conditions and network topologies. The simulation results show the network with the DCAP protocol achieves significantly higher throughputs than the single channel 802.11 network (up to four times in a network with three channels).