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required and the amount of network overhead, espe-
cially when scaling to very large MANETs.
It is hoped that by using signal strength, along
with incorporating relative distance information for
cost calculations and studying various cost calculation
equations for different environments, the new proto-
col can improve the MANET performance under vari-
ous scenarios where other common protocols perform
poorly or fail. The main metric that is targeted is the
time needed for routing change, therefore reducing
the amount of time to establish a new route when a
link is broken. Other targeted metrics are reducing
latency and increasing bandwidth.
When controlling a swarm of robots, some of the
robots are normally autonomous. With only one op-
erator normally, only one robot can be controlled at
a time, the others must act autonomously, or remain
idle. The issue of controlling the autonomous robots,
with the scope of optimizing the MANET, is also a
main goal of this research.
4 STATE OF THE ART
Routing based on signal strength has been discussed
since the first uses of MANETs, however, most of the
common wireless routing protocols do not make use
of this information. The proposed routing protocols
are rarely implemented and are usually only studied
in simulations.
The Signal Strength based Adaptive Routing
(SSA) Protocol is described in (Dube et al., 1997).
The protocol is a reactive protocol that selects routes
based on their continuous link connectivity duration
and the average signal strength of the connection.
SSA is composed of two separate protocols. The
Static Routing Protocol (SRP) is used to retrieve and
record the signal strength information in the signal
stability table. The second part, the Dynamic Rout-
ing Protocol (DRP), maintains the routing table.
Using the beacons sent by the wireless adapters
firmware, the signal strength is simply classified as
either strongly or weakly connected. The length of
time that the beacons have been continuously received
over that link is also stored. When a node attempts
to forward a packet, it first searches for a route in the
routing table maintained by DRP. If the route does not
exist, a route search is initiated. When a route is bro-
ken, the node that is attempting to forward the packet
will notify the source node, which will then search for
another route. If the notification of the broken route
is unable to arrive to the source, the source will send
a request for a new route after a timeout period.
The route selected will use only strongly con-
nected links when possible. If a route consisting
solely of strongly connected links is unavailable, it
will search for a route that includes weakly connected
links.
The SSA routing protocol is simulated and com-
pared with a simple routing algorithm that chooses
the smallest number of hops. It is determined that the
SSA routing protocol significantly reduced the num-
ber of route reconstructions vs. the simple hop min-
imizing algorithm. The usefulness of the continuous
connectivity lifetime is found to vary greatly depend-
ing on the scenario and must be configured properly
for each case. It does not seem that this protocol has
been implemented outside of a simulation environ-
ment.
A mechanism to improve TCP performance in ad-
hoc networks using signal strength is proposed by
(Klemm et al., 2005). It is found that the causes
of 802.11 link performance degradation can be at-
tributed to congestion of the shared channel medium
or to the mobility of the nodes. The paper‘s objectives
are to reduce the packet losses due to the mobility of
nodes in MANETs.
Suggestions to reduce link failures are made to re-
act to the loss of a link. When a link failure is de-
termined to be due to a node moving out of range,
the transmission power of the network adaptor is tem-
porarily increased and a search for a new route is ini-
tiated. Care is taken not to include routes of links that
have temporarily increased transmission power. By
using signal strength information, it is possible to de-
termine when a route is approaching failure and then
pro-activelysearch for a new route. If the route degra-
dation is due to congestion and it is determined that
the neighbour is most probably in range from prior
signal strength data, the node will persist overa longer
period of time to communicate with its neighbour in-
stead of searching for better routes.
A problem is found that signal strength degrades
as the networks channel becomes congested. To de-
termine if the links degradation is due to congestion
or due to the node moving out of range, the number
of packets overheard by the node is counted. If the
count is large, then the degradation can be attributed
to channel congestion. Care must be taken not to in-
crease transmission power in this case as it can lead
to further deterioration of the communication link.
It is determined through simulations using net-
work simulator 2 that under low load, the TCP per-
formance is increased by up to 75%. On a congested
network under heavy load, TCP performance is in-
creased by 14-30%. TCP performance is determined
from the number of packets lost.
In the above papers, by using simulations, the use
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