The Impact of Signal Strength over Routing Protocols in Wireless Networks

www.ijemr.net ISSN (ONLINE): 2250-0758, ISSN (PRINT): 2394-6962
126 Copyright © 2018. IJEMR. All Rights Reserved.
Volume-8, Issue-4, August 2018
International Journal of Engineering and Management Research
Page Number: 126-130
DOI: doi.org/10.31033/ijemr.8.4.15
The Impact of Signal Strength over Routing Protocols in Wireless
Networks
Dr. Reem Jafar Ismail
Assistant Professor, Department of Computer Science, Cihan University-Erbil, ERBIL-IRAQ
Corresponding Author: reem.jafar@cihanuniversity.edu.iq
ABSTRACT
In ad hoc routing protocols the source node
may need an intermediate nodes to transmit the packets into
the destination if the destination is not within transmission
range of the source. This paper studies the impact of signal
strength of nodes over ad hoc routing protocols and explains
an important effect of signal strength on ad hoc routing
protocols in four different directions including the routes and
the nodes. As a result the study give an important
improvement in ad hoc routing protocols when using signal
strength compared to other ad hoc routing protocols without
considering signal strength.
Keywords-- Signal strength, Ad hoc routing protocol, Link
reliability, Route optimization, Routing metric
I. INTRODUCTION
Ad hoc network has many mobile nodes that are
moved without specific topology this makes failure when
sending packets in ad hoc routing protocols. One of the
important parameters that has been considered in ad hoc
routing protocols is signal strength of the nodes in ad hoc
network. Many applications of ad hoc networks are based
on signal strength like: real time communication, security
and wireless sensor networks.
The following sections of the paper is organized
as follows. Section 2 describes related work, section 3
provides a detailed explanation of four important effect of
signal strength on ad hoc routing protocols and finally,
section 4 gives the conclusions of the study.
II. ELATED WORKS
Signal strength in ad hoc networks has been used
as metric in ad hoc routing protocols. In [1], Min-Gu and
Sunggu lee proposed a route selection based on
differentiated signal strength (DSS). DSS indicates
whether the nodes are getting closer or getting farther
apart. If the signal strength is getting stronger, the link is
considered to be stable and if the signal strength is getting
weaker in case of node moving away it is considered to be
unstable link.
According to [2] the route discovery for the
intermediate nodes use one parameters in order to replay
for the node that send the packet which is the signal
strength of the node that send the packet where it must be
more than threshold value.
In [3] the route discovery for the intermediate
nodes use two parameters in order to replay for the node
that send the packet:
 The first is the signal strength of the node that
send the packet where it must be more than
threshold value.
 The second is the energy level of the node that
send the packet where it must be more than
threshold value.
III. SIGNAL STRENGTH IN WIRELESS
AD HOC ROUTING PROTOCOL
In wireless ad hoc routing protocols the signal
strength is important to be considered in routing since it
effect on the rout discovery of nodes in the network.
According to the importance of signal strength we
recognize two main used of it related to the link between
node or the nodes itself. The following sections will
describe signal strength implementation in ad hoc routing
protocol.
3.1 Route Optimization
Route optimization work by eliminate flooding
storm of packets and control parameter. The (Dynamic
Source Routing) DSR protocol is a reactive routing
protocol used in multi hop wireless ad hoc networks. Two

important mechanisms in DSR are Route Discovery and
Route Maintenance. Nodes discover and maintain routes
through the network using these mechanisms [4].
In route discovery phase, flooding of control
packets produces significant traffic load, wastage of
bandwidth and increase the number of collisions. In case
of high mobility and intensive topology changes flooding
can provoke broadcasting storm.
the proposed cross-layer ad hoc routing protocol
the search space in route discovery phase is optimized by
selecting partial neighbor nodes of the transmitting node
instead of selecting all neighbor nodes for broadcasting
ROUTE REQUEST messages according to the signal
strength of nodes [5]..
Then the procedure of Route Discovery Phase
will be:
Read the signal strength from the ROUTE
REQUEST message packet format that is send by the
sender node.
If Signal strength="low" or Signal strength="very low" or
Signal strength="excellent"
Then Drop ROUTE REQUEST Message
Else Forward ROUTE REQUEST Message
End If
Where the proposed protocol discards the
following neighbor nodes order to obtain reliable link:
 The neighbor nodes that have excellent signal
strength are too close to the transmitting node.
 The neighbor nodes that have low and very low
signal strength are too far to the transmitting
node.
The routing protocol need to have a new ROUTE
REQUEST message option format is constructed by
adding the "Signal Strength of the current Node" field in it,
as shown in figure (1).
Figure 1. The New ROUTE REQUEST Message Option Format
As a result, the optimized flooding percentage is
reduced to 22% -34% when compared to DSR routing
protocol. This percentage depends on the total number of
nodes in ad hoc network and the current topology of the
nodes which have different arrangement across the
network with different signal strength compared to the
transmitting node [5].
3.2 Routing Metric
Signal strength parameter has been used as link
quality metrics in many routing protocols for wireless
networks.
Punnoose et al. [6] convert the signal strength into
a link quality factor, which is then used to assign weights
to the links. For a route consisting of M hops, the link
quality factor of the route is estimated as L:
∏ ( (( ) )) …(1)
where Q(x) is the standard Q-function, is
the theoretically predicted power received by the ith
node
from the (i - 1)th
node, is the receiving threshold and σ
is the variance of signal variations, which are assumed to
be normally distributed.
The link quality factor is the product of
probabilities computed for each hop that at a certain time
in the future the signal level will be above the receiving
threshold. The theoretically predicted power is calculated
as follows: using linear position extrapolation based on the
input data from GPS positioning and velocity information,
estimates for the positions of all nodes one second in the
future are calculated. These positions, along with some
propagation model are used to obtain, while the default
values for the variance of signal is σ = 6 dB and for the
receiving threshold = 60 dBm [6].
3.3 Indicator of Link Reliability and Stability
Since the nodes in ad hoc network (MANET) is
mobile that makes topology constantly changing so the
nodes that are selected as route nodes are not stable and
have a high mobility, data transmission route is broken
quickly. Therefore, the method can be considered in the
routing that from the nodes are between source and
destination, nodes that are more stable, are selected as
intermediate nodes. In [7] propose a novel routing metric
for MANETs that is called Signal Strength Based
Reliability (SSBR), by measuring signal strength changes
of neighbor nodes, to identify nodes that have a lot of
mobility and can cause link failure. Thus, we don't select
them as route nodes. Advantage of this scheme is by
selecting reliable nodes we can create a stable route that it
has long lifetime.
Ad hoc On-demand Distance Vector Routing
(AODV) [8, 9, 10]. The Ad-hoc On-Demand Distance
Vector protocol is a very simple, efficient and effective
routing protocol for mobile Ad-hoc networks which do not
have fixed topology. All the node in the network will be a
router and the routes are obtained, which makes the
Option Type Opt. Data Len ID Target Address Signal Strength of the
Node
Path List

network specified its structure. In this protocol the routing
will be on demand and does not require to obtain it
periodically by using the available bandwidth that will be
less compared to other protocols.
This protocol uses sequence number counter that
is maintained and increased by each node. The route
discovery process needs a route-request message (RREQ)
and this RREQ will be broadcasted to all other nodes in the
network. When the node has discovered a valid route to the
destination, it replies with a route-reply (RREP) message.
The destination node uses the reverse route entry in its
routing table starting from the last node, which contains
the number of hops to source node, address of the source
node, and the address of the node from which it receives
the message i.e. the next hop’s address. Coping up with
dynamic topology and broken links: When the nodes in the
network move from their places and the topology is
changed or the links in the active path are broken, the
intermediate node that discovers this link breakage
propagates an RERR packet and the source node starts the
path discovery again if it still desires the route. This
ensures quick response to broken links that happen in
routing.
SSBR schema is used in AODV, leading to
SSBR-AODV as a result routing control overhead is
decreased and packet delivery ratio is increased compared
to number of nodes in the networks as shown in figure 2
and figure 3, respectively [7].
Figure 2. Routing control overhead vs. number of nodes
Figure 3. Packet delivery ratio vs. number of nodes
3.4 Localize the Unknown Node
Signal strength in ad hoc networks can be used as
a parameter to measure distance between nodes in ad hoc
networks. In ad hoc routing protocol the connectivity of
the network will depend on available received signal
strength (RSS) measurements and a predefined RSS
threshold to find the location of the node.
DV-HOP (distance vector-hop), propose to have
anchors to localize the unknown node by exchanging hop-
count values between anchors and unknown nodes and
find the distance based on the computed average size of a
hop (hop-distance) [11, 12], as shown in figure 4.

Figure 4. Performance of DV-HOP in practical environment
In order to localize unknown node in DV-HOP
must the network must be fully connected in which all
nodes can reach each other via a direct link and all
unknown nodes are 1-hop away from all anchors.
In [13] proposed a formula to determined the
signal strength threshold RSSth to ensure that all the nodes
in the network are connected means that every node in the
network is within the radio range of every other node,
where:
if RSS < RSSth (not connected)
if RSS ≥ RSSth (connected)
The formula is derived as a function of the total
number of nodes and the network size.
IV. CONCLUSION
The signal strength for the nodes in wireless
networks is important as indicator in route as optimization
and metric, and in nodes as stability and connectivity.
The performance of standard wireless routing protocols
like, DSR are increased when signal strength is consider as
a parameter in routing.
As a result the routing in wireless network had
prevented link breakages and routing failure so the packet
delivery increased.
REFERENCES
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