Enhanced multichannel routing protocols in MANET

Abstract

Utilising multiple non-overlapping channels in MANET networking can improve performance and capacity. Most multichannel MAC and routing protocols rely on an extra radio interface, a common control channel or time synchronisation to support channel selection and routing, but only at the expense of hardware and power consumption costs. This thesis considers an alternative type of multichannel wireless network where each node has a single half-duplex radio interface and does not rely on a common control channel or time synchronisation. Multichannel MAC and routing protocols that adopt the Receiver Directed Transmission (RDT) communication scheme are investigated to assess their ability to implement a multichannel MANET. A novel multipath multichannel routing protocol called RMMMC is proposed to enhance reliability and fault-tolerance in the MANET. RMMMC introduces new route discovery and recovery processes. The former establishes multiple node and channel disjointed paths in different channels and accumulates them to acquire a full multi-hop path to each destination. The latter detects broken links and repairs them using pre-discovered backup routes. To enhance communication reliability, a novel cross-layer multichannel MAC mechanism called RIVC is proposed. It mitigates transmitting/rerouting data packets to a node that does not have an updated route information towards a destination and only allows data packets with valid routes to occupy the medium. The optional access mode in the MAC protocol is modified to early detect invalid routes at intermediate nodes and switchover to an alternative path. A new cross-layer multichannel MAC mechanism called MB is proposed to reduce contention in a busy channel and enhance load balancing. MB modifies the MAC back-off algorithm to let a transmitter node invoke an alternative path in the alternative channel when the retry count threshold is reached. The proposed multichannel protocols are implemented and evaluated by extensive NS2 simulation studies.