So, by combining the functionalities shown in Fig. 4.1 and choosing a suitable
selection metric, an ideal wireless multi-hop routing protocol can be designed.
As we have seen throughout this brief, a considerable number of routing pro-
tocols have been proposed for the various wireless multi-hop networks. With these
protocols available in the literature, there are still many open issues that need to be
covered in the area of wireless multi-hop routing. Most of the open issues are
related to WMNs and VANETs considering that these are the most recent wireless
multi-hop network paradigms; however, a few open issues are still there for
routing in MANETs and WSNs.
MANETs are the oldest multi-hop networks and many routing protocols were
proposed for use in MANETs in the past decade. Those protocols presented a
variety of functionalities handling most of the challenges of MANET operation.
However, some researchers are currently interested in applying some optimization
and intelligent techniques in MANET routing and testing the potential improve-
ments. Examples of such techniques are those utilizing soft computing and arti-
ficial intelligence. Some of these intelligent protocols were presented in Chap. 3 .
This trend for designing intelligent, optimized protocols is of interest in the design
of routing protocols for all wireless multi-hop network paradigms; not only for
The WSN paradigm is considered relatively old compared to the WMN and
VANET ones with many routing protocols proposed in the literature to cover its
multimedia sensor networks is currently gaining interest from researchers. Few
protocols have been proposed to serve the needs of this paradigm and it is still
considered an open issue for researchers. Such protocols should consider QoS
requirements while keeping energy efficiency as the main goal.
Although there are tens of WMN routing protocols proposed in the literature,
there are still some open issues that need to be covered to improve the efficiency of
the WMN routing function: (1) Extensive testing for the various routing metrics is
needed to determine the most accurate and efficient metric or combination of
metrics, (2) Proposing passive techniques for measuring metric parameters instead
of depending on exchanging control packets for the sake of reducing the overhead
and utilizing network resources efficiently, (3) Studying the impact of the active
measurement techniques on increasing the self-interference problem, (4) Many
protocols depend on the use of Dijkstra's algorithm for calculating the best path.
The use of such an algorithm hinders the network scalability. Other approaches
should be investigated for the optimal path computation, (5) Further exploration on
the impact and the benefits of network coding strategies. Currently, only a few
WMN routing protocols utilize these coding opportunities.
For VANETs, although there are many new protocols introduced for routing
functionalities, routing is still considered one of the hottest topics in the VANET
research area. There are some open issues and opportunities that can be handled
and considered by the researchers to improve the performance of message routing
and pave the road to many new applications and services to be supported by
VANET communications, among them: (1) Most VANET routing protocols