Ad Hoc Networks : Technologies and Protocols - University of ...

Routing with Directional Antennas 221
However, the overhead still remains higher than in DSR using omni-directional
communications.
Figure 7.10. The Selective Forwarding Optimization
Finally, in [5], the authors find that the problems with deafness (a direct
consequence of DMAC) remain and the performance of the routing schemes
in terms of throughput seem to be poor with regular topologies. With random
topologies however, they observe significant gains in throughput in spite of the
increase in overhead due to sweeping.
7.4.3 A Joint MAC/Routing Approach
In [6], S.Roy et al design a new routing protocol that attempts to compute
multiple paths and balance the load across the multiple paths. Directional
antennas are assumed. Once the multiple paths are found, it becomes important
to choose the right path for a connection since one can get the maximum out of
the network if the interference zones created by the transmissions on the path
taken a connections were disjoint to the extent possible with the interference
zones created by other connections. In order to illustrate this point we refer
Figure 7.11. We have two sources and and these nodes want to establish
connections with nodes and respectively. For the connection from node
to node two distinct routes are feasible. The first is via nodes and
and the second via nodes and If the former route is chosen it creates
high levels of interference to the second connection that is being routed via
nodes and This problem of two paths that can create severe levels of
interference to each other is called route coupling. Link state information (in
the form of lists) are exchanged in order to facilitate an awareness of the routing