Networking Reference
In-Depth Information
depend on the greedy selection which just considers the distance to the destination.
This approach for routing selection lacks the consideration of some real physical
conditions such as fading and interference which may affect reception of the
packets by the selected recipient. Other selection metrics should be taken into
consideration to provide more efficient routing decisions. Such metrics can be
merged with the greedy approach by optimization solutions, (2) As VANET
applications will include real time communications, for example, sharing videos
and playing games on the move among passengers of many neighboring vehicles,
QoS support should be considered by new VANET routing protocols to satisfy the
requirements of these types of communications, (3) With the advances of the built-
in VANET communication modules, many interfaces and technologies will be
available for transmitting the packets. The availability of these multiple radios and
technologies should be considered by the routing protocols to provide the most
efficient transmission over the highly available communication technologies,
(4) Routing should be aware of the higher-layer requirements and generated traffic
to better assist the application operation. This leads to what is known as content-
based routing in which the contents of the messages should be taken into con-
sideration for providing the optimal routing functionalities and decisions. For
example, in the case of an accident or health emergency, packets should be routed
to the nearest ambulance in addition to the neighboring vehicles, (5) One of the
most enabling factors in VANET communications is the inclusion of the infra-
structure. Most of the VANET routing protocols ignore infrastructure exploitation
for the message transmissions. Depending on the infrastructure, it can help in
handling the intermittent connectivity and expediting the transmission times,
hence, reducing the delay. So routing protocols that exploit the existence of the
infrastructure need to be proposed. A few infrastructure-based protocols were
proposed in the literature and presented in Chap. 3 but more proposals are needed
to make use of the benefits gained from considering the infrastructure as a relay,
(6) Network coding can be considered as an efficient mechanism for reducing the
number of transmissions and utilizing network resources efficiently, (7) The
number of delay-tolerant routing protocols is limited compared to the number of
non-delay-tolerant ones. So further research is needed in the area of routing for
delay-tolerant VANETs, (8) As VANETs can operate in many scenarios and traffic
conditions and support different applications, VANET routing protocols should be
adaptable to these different application requirements and be scalable to various
network sizes at different times of the day.
In addition, as a common opportunity for all wireless multi-hop networks, the
introduction of cognitive radios and their integrations with wireless multi-hop
networks will open many research issues for wireless multi-hop routing. Cognitive
radios add some challenges with their intermittent connectivity and bandwidth
availability that should be handled and taken into consideration by the routing
functions.
With the current focus on the integration of heterogeneous networks, a network
may consist of multiple different wireless multi-hop network paradigms integrated
together for cooperatively providing a designated service. Examples of such
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