03-12-2012, 01:54 PM
A Bidirectional Routing Abstraction for Asymmetric Mobile Ad Hoc Networks (IEEE)
Abstract:
Wireless links are often asymmetric due to heterogeneity in the transmission power of devices,
non-uniform environmental noise, and other signal propagation phenomenon. Unfortunately,
routing protocols for mobile ad hoc networks typically work well only in bidirectional networks.
This paper first presents a simulation study quantifying the impact of asymmetric links on
network connectivity and routing performance. It then presents a framework called BRA that
provides a bidirectional abstraction of the asymmetric network to routing protocols. BRA works
by maintaining multi-hop reverse routes for unidirectional links and provides three new abilities:
improved connectivity by taking advantage of the unidirectional links, reverse route forwarding
of control packets to enable off-the-shelf routing protocols, and detection packet loss on
unidirectional links. Extensive simulations of AODV layered on BRA show that packet delivery
increases substantially (two-fold in some instances) in asymmetric networks compared to
regular AODV, which only routes on bidirectional links.
Existing System:
AODV avoids any unidirectional links in its paths. It achieves this by tracking the unidirectional
links in a black list. Nodes discover unidirectional links and add them to the black list whenever
an RREP sent along the reverse path fails to return an expected acknowledgment. Once added,
a unidirectional link is retained in the black list for a short lifetime. Nodes do not forward RREPs
to any node in their black list.
Proposed System:
Improved connectivity by taking advantage of the unidirectional links
Reverse route forwarding of control packets to enable off-the-shelf routing protocols
Detection packet loss on unidirectional links.