Wireless Network Design: Optimization Models and Solution ...

9 Routing in Mobile Ad Hoc Networks 211
Fig. 9.6 Route discovery flooding
MPR Node Non MPR Node
9.4.3.2 TBRPF (Topology Dissemination Based on Reverse-Path Forwarding)
As with OLSR, TBRPF is a proactive protocol that seeks to reduce the use of bandwidth
by control messages. As opposed to OLSR, which maintains a partial topology
of the network (using MPR), all mobiles in TBRPF have a knowledge of the
complete topology of the network. Such knowledge is more expensive but allows
the use of multiple paths or paths with a certain quality of service. For the network
topology, each node will maintain a tree of shortest paths (it may be possible to use
a different metric) to all other nodes. The tree is unique to each mobile. When a
mobile detects a state change at one of its neighboring links, it sends an update on
its associated tree. Each internal node in the tree forwards the update message. The
trees themselves are constructed according to the update messages: when a node
receives such a message, it computes the tree related message initiator. The update
messages are sent only when detecting a status change (appearance or disappearance
of a link). Only the neighbor discovery messages are sent periodically.
9.5 Quality of Service in Ad Hoc Networks
For the last several years, there has been a significant increase of interest in supporting
QoS constraints in multi-hop mobile ad hoc networks (MANET). The specificity
of MANETs make existing solutions for wireline networks unsuitable and a broad
range of novel approaches have been studied. When considering QoS support, there
are several aspects that must be taken care of:
1. One must choose a QoS model, i.e., the eventual goals one wants to achieve.
The goals are tightly related to the applications that are to take advantage of the
QoS support. Real-time audio/video applications require constant bandwidth and
little delay, whereas FTP transfers can go with no more than classical best-effort.