AN EFFECTIVE CONTROL OF HELLO PROCESS FOR ROUTING PROTOCOL IN MANETS

International Journal of Computer Networks & Communications (IJCNC) Vol.13, No.5, September 2021
DOI: 10.5121/ijcnc.2021.13503 37
AN EFFECTIVE CONTROL OF HELLO PROCESS
FOR ROUTING PROTOCOL IN MANETS
Dhirendra Kumar Sharma and Nitika Goenka
School of Computer Science, University of Petroleum and Energy
Studies Bidholi Dehradun, 248007, India
ABSTRACT
In the mobile ad hoc network (MANET) update of link connectivity is necessary to refresh the neighbor
tables in data transfer. A existing hello process periodically exchanges the link connectivity information,
which is not adequate for dynamic topology. Here, slow update of neighbour table entries causes link
failures which affect performance parameter as packet drop, maximum delay, energy consumption, and
reduced throughput. In the dynamic hello technique, new neighbour nodes and lost neighbour nodes are
used to compute link change rate (LCR) and hello-interval/refresh rate (r). Exchange of link connectivity
information at a fast rate consumes unnecessary bandwidth and energy. In MANET resource wastage can
be controlled by avoiding the re-route discovery, frequent error notification, and local repair in the entire
network. We are enhancing the existing hello process, which shows significant improvement in
performance.
KEYWORDS
Hello process, link change rate, hello interval, energy-saving application, neighbour table, virtual
neighbour table, AODV routing protocol
1. INTRODUCTION
A mobile ad hoc network (MANET) is an infrastructure-less network where it can easily
configure the whole network for communication. These applications are useful in military, rescue
operations, and low-cost small-scale network setup [1]. In multi-hop architecture, intermediate
nodes are involved to establish the path from source and destination node. Due to mobility, the
position of the intermediate nodes with the source and destination keeps changing [2].
In this paper, we have only considered the reactive routing, protocol for our study and
implementation of the proposed algorithm. In reactive routing source node establishes a route-by-
route discovery process by broadcasting of Route Request (RREQ) packets in the network and
after the certain time interval, destination unicast RREP packets to the source node. A route has a
fixed lifetime, which is maintained by the route maintenance process [3].
However, the Ad Hoc On-demand Distance Vector (AODV) routing protocol has some
disadvantages [4], in terms of bandwidth consumption. This phenomenon results in degradation
of performance of a routing protocol with respect to increased overhead, end-to-end delay, less
throughput, and packet delivery ratio. It occurs due to the transmission of additional control
packets for the successful delivery of data packets. Importance of the hello process is to monitor
the status of active route.

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The existing routing protocols [5], transmit hello packets periodically, with a fixed time interval.
In dynamic topology, high density of neighbor nodes requires a fast rate of hello packet
transmission to maintain the neighborhood relationship. Similarly, a node having very few
neighbours should transmit hello packets with a higher time interval. This dynamic change in the
rate of transmission is not handled by any of the existing routing protocols. In [6] authors modify
the rate according to the mobility factor of a node. Although it introduces the idea of a
dynamically changing transmission rate, it still has the shortcomings of not considering the
neighbor density. The authors propose a method in [7, 11] based on link change rate estimation
for dynamic change the hello timer for reduction of the routing overhead.
In [8], wireless network updated link connectivity information gives best effort route discovery
and route maintenance. A route has a fixed lifetime and expires when data transfer is interrupted
or delayed due to link failure. In [9], a comparison has been performed to extract the
neighbourhood information by the network layer (HELLO process) and link layer (link layer
(LLF)) mechanism, which are the important parts of the route maintenance scheme.
Hello, process provides the link connectivity or neighbor node information by periodic exchange
of hello messages. Link failure detection technique [10, 11, 12], has been developed to find link
breaks on the active routes by counting the number of received hello messages from neighbour
nodes. Slow response of the hello process is inadequate for active links and outdated links, which
invokes huge packet, drops. Thus, an efficient technique is required in hello process, which helps
to maintain link lifetime, neighbor table, routing table entries. In our proposed method, we
consider the RSSIth value to adjust the refresh rate, which overall gives a good result
Contribution
 We have enhanced the existing Dynamic Hello/timer adjustment by cross-layer parameter,
 Link change rate (LCR) adjustment on the basis of virtual neighbour table (VNT),
 Route discovery process based on the basis Received Signal Strength Indicator (RSSI),
 Route maintenance works on availability of backup routes and position of link break.
2. RELATED WORK
As the hello packets are meant only for link connectivity management [13] and link failure
detection [10]. In [14], reactive routing protocols, timers are used to control the routing
mechanism, expiry of timers arise from the interruption of communication. Hello, process is a
type of timer which is periodically initialized by node; its periodicity helps to extract
neighborhood information. It is clear that complete restriction on the hello process causes the
expiry of timers in hop-by-hop routing where routes are completely based on routing table and
neighbour table. Source routing [15], is a beacon less and it updates their route cache by transfer
of data packets when traffic increases in the network then huge contention increases the packet
drop. This problem arises due to lack of neighborhood information which causes packet drop
problems and it can be overcome by route repair techniques.
In [16], RSSI and link life time based reliable routing has been proposed to reduce the latency
and overhead and packet drop ratio. In [17], a link lifetime prediction technique shows better
performance in static or less mobility area. In dynamic topology better maintenance techniques
are required to improve the performance of network.
A study over multi-hop route shows the performance of routing protocol become less effective
due to unstable route; the route discovery greatly works in shortest route (2 to 3 hops). A simple

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signal strength-based technique helps to find the cause of the failure of the routing protocols in
the unreliable networks [18]. Such type of neighbor discovery process helps to increase the
performance of routing protocol in the certain scenarios. To increase the routing protocols
consistency better maintenance approach is required.
A neighbor monitoring mechanism (NMM) [19], monitors the status of neighbor node's
information by exchange of hello messages at a fixed rate. This method solves the unidirectional
link problem in MANET. This scheme works better in static topology to monitor the various
metrics of neighbour nodes. We found several advancement has done over protocols development
for MANET. Main contributory work focused on performance improvement with lifetime
enhancement [31, 32, 33].
In [20], a performance comparison has been done between a link layer feedback mechanism and
neighbor discovery mechanism. These mechanisms are used to find the neighborhood
information at a different layers. Link layer feedback mechanism gives only active neighbour
nodes information and it is not used to update the lifetime of all links. neighbor discovery
mechanism is used to obtain the neighbor hood information; it helps to gain the lifetime of all
links and routes. Hello, process has an overhead problem but it can be controlled by different
methods. In a static scenario hello process is controlled by assuming a large hello interval
(2000ms) and result from less overhead. In AODV RFC [21], only active nodes are allowed to
invoke the hello process so hello is controllable in some scenarios. We can understand the rest of
the nodes are not allowed to start hello process; hence there is a huge improvement in the
throughput and the lifetime of the network. Using original AODV, our implementation allows
only the nodes, which have a routing table and alternate route table, to exchange hello messages.
As the neighbor of all the nodes of an active route must have either received or forwarded RREQ
or/and RREP packets, a routing table is created for them to keep the entries of
forwarding/backward routes. Hence, all the members of an active route along with their
neighbors are allowed to exchange hello packets and not others. Keeping track of the neighbors
by the intermediate nodes helps in local repairs and hence reduces the number of rerouteing
discoveries. This helps in reducing further the flow of other control packets, thereby reducing the
routing overhead and improving the performance. If a node does not receive a control packet
from a neighbor within a stipulated time, it assumes the loss of connectivity with it. Hence, a
node always sends a HELLO packet every such time period if it has not sent any other control
packet. HELLO_INTERVAL is the maximum time interval between two successive control
packets. ALLOWED_HELLO_LOSS is the maximum number of hello intervals that a node waits
to receive a hello packet from a neighbor before it confirms a loss of connection with it. In
AODV, HELLO_INTERVAL is set with a value of 1000ms (1 sec) and
ALLOWED_HELLO_LOSS with a value of 3. The utility of hello/beaconing is used to update
the geographical position of mobile nodes in MANET. A greedy perimeter stateless routing
(GPSR) [23], a periodic beaconing technique used to maintain the geographical position of
neighborhood and helps to improve the routing decision.
In [11], a dynamic hello timer adjustment adjusts the hello timer on the basis of link change rate
(LCR). The link LCR is computed by observation of neighbour table entries in which neighbor
nodes are categorized into two parts; new neighbor, lost neighbor. Network awareness [22],
information is required to monitor the overall network status; its objective is to highlight the self-
adaptation strategies, of routing protocols for dynamic topology. In awareness strategies link
duration and node density-based metric has been observed for adaptation in mobility. In the
papers [29, 30], the authors show the utility of the hello message for wireless sensor network
management. It is used for authentication and localization techniques.

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We have studied the dynamic hello timer adjustment, and proposed a technique to enhance its
performance in terms of hello timer, refresh rate (hello interval, and neighbor expiry by
monitoring the status of neighbor nodes. Link change rate (LCR) has been used to estimate the
refresh rate and neighbor expiry in dynamic topology. Its control over hello is lost when node
density increases along the active routes and adjusts a very low refresh rate (0.000002s) along
active route. Thus, all nodes invoke the exchange of hello message, which interrupts the
communication. In [27, 28], the authors describe the significance of hello message for finding the
link failure in the network which helps to avoid excessive packet loss.
Our proposed method overcomes such type of problem by using a cross-layer design (CLD). Our
work is based on the original AODV routing protocol and we have made a modification to the
hello process.
3. OVERVIEW OF LINK CONNECTIVITY MANAGEMENT AND PROBLEM
DESCRIPTION
In link connectivity management, neighborhood information is exchanged by the hello process
which is shown in figure 1. This process is useful to find the link failure in the network [10].
Routing/neighbor table entries are expired due to high contention in data transfer and timer
expiry. Generally routing entries are updated by data transfer; heavy congestion and contention
interrupt the update of link connectivity information. Neighbour table entries are periodically
updated, this mechanism is not adequate for dynamic topology because nodes are not fixed at
their position. Slow exchange of link connectivity information cause a high packet drop ratio in
each attempt thus this occurrence results in degradation of performance in a network.
Figure 1: Hello process
In a network, the hello process is used for link connectivity management. It is initialized at a
fixed rate and works better in static topology. In dynamic topology, a fixed refresh rate is not
suitable to increase the lifetime of node entries in the neighbor table. A dynamic hello timer

41
adjustment [11] method has been proposed to adjust the hello timer by adjusting the refresh rate
and the link change rate (LCR). This dynamic adjustment of hello timer produces the significant
results in low-density network. In a network, node density is non-uniform along the active route,
in dynamic topology mobile nodes move, hence there is non-uniform node density distributed
along the active route. Non uniform distribution of node density causes the a very low refresh rate
at any point to overcome such type of problem we are proposing an algorithm to efficiently adjust
the refresh rate. We are considering the basic concept of dynamic hello timer adjustment and
assuming the RSSI range for node selection and refresh rate evaluation. In figure 2, a cross-layer
design (CLD) technique shows the RSSI (physical layer metric) to network layer which is used in
proposed algorithm.
Figure 2: Cross-layer design; Exchange of Physical layer metric (RSSI) to network layer
4. SYSTEM MODEL
This section describes the utility of the overhearing process for the formation of an alternate route
table (ART). In the proposed work we have considered ART entries are formed by overhearing
unicast RREP packets and update by data transfer. We are using the CLD technique to enhance
the hello process by use of physical layer metrics. By link change rate (LCR) we are monitoring
and evaluating the neighbor nodes and refresh rate.
4.1. Cross-Layer Design
In multi-hop route timers (route, neighbor) expiry affects the overall performance which can be
improved by cross-layer design (CLD) (as shown in figure 2). In [26], cross layer design
technique has been proposed for access point selection to enhance the performance of the
network. CLD technique motivates us and designs an efficient technique for the hello process
which is used to overcome route timeout, packet life timeout, neighbor table entries timeout
issues.

42
4.2. Overhearing
In a network, an overhearing region is one where neighbors nodes are able to easily overhear the
packets to form the alternate route table. To illustrate the overhearing region we are assuming a
mathematical model to describe the region where node effectively overhears the packets without
any loss. An the analytical model, we are simply using a trigonometric formula for illustration of
the overhearing region.
Figure 3: Overhearing region
Above figure 3, shows that routing starts from source node A to destination node D on selected
path, which is a set of nodes (A, B, C, D). We assumed that all nodes have equal transmission
range and multi-hop routing is used to deliver the data packets. As shown in the figure we
consider that node E starts the overhearing along the active route (A to D). Here neighbors node
E has alternate paths and updates its timeout by overhearing of data packets as discussed in Ad
Hoc On-Demand Distance Vector Backup Routing (AODV-BR) [24]. The Use of alternate paths
does not provide assurance of delivery of packets, because neighbor node may be standalone and
start to drop the packets. We observe one of the serious problems is to keep the order of nodes in
neighbor table. The normal update process only adds and resets the timeout of the existing entries
in neighbor table. This type of method is successful for updating the timeout of entries, but does
not give assurance for effective neighbor nodes, that handle the delivery of packets in link break
situations.
We observe that overhearing happens when node E resides in the red colored region (assumed to
be twice the area of the triangle). In the figure, at point F we observe that node E is able to
overhear from nodes A, B, C simultaneously. The blue shaded region is the maximum
overhearing region in the above figure.
In figure 3, we assume that connection of nodes form an equilateral triangle and AB, BC and CA
are sides of triangle. The overhearing area
,
A B
OH
A
is calculated as:

43
2 2 2 2 4 4 4
,
1
( ) 2( )
4
2
A B
OH
ABC AE AB BE AE AB BE
A ABC
      
  , Heron’s formula [25] (1)
For equilateral triangle,
2
,
3
4
2
A B
OH
r
ABC
A ABC
 
  (2)
2 2
, 2 2
( , ) , , ,
( )
( / , 0 ) ,
4
,
4
2( / ) 4 1
th
A B
OH
if BE AE r and AB r for isosceles triangle
let AE BE r and ABisthen part of r
AB r n n finite number then
AB AE AB
Area of ABC
A r n n
 
 
  

 
 
4.3. Example
We assume a network where all mobile nodes are randomly placed and can move in any
direction. A mobile node starts the data transmission when routes are available otherwise starts
route discovery. Route discovery and route maintenance processes are considered in reactive
routing protocols. In the further section, we are describing the processing of route reply (RREP)
packets at the source node. Route maintenance process is shown in the flowchart of figure 12,
which clearly shows the use of backup routing, local repair, and re-route discovery process.
Figure 4: Data transfer over multi-hop route from source node 1 to destination node 10
In figure 4, source node 1 establishes route of 9 hops to destination node 10, all selected
intermediate nodes are green and neighbour nodes are blue. In link failure, upstream node selects
the neighbour node from their neighbour table to continue the data transfer.
Table-I. LCR and refresh rate as figure 4
Node
Id
Neighbour node
Id
Number of
neighbour node
Maximum average Link
change rate (LCRmax)
Initial Refresh
rate (r)
1 2, 12, 14 3 6 1 s
2 1, 2, 11, 13, 14 5 10 1 s

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3 2, 4, 16, 17 4 8 1 s
4 3, 5, 15, 17, 18 5 10 1 s
5 4, 6, 18, 19, 20 5 10 1 s
6 5, 7, 20, 21 4 8 1 s
7 6, 8, 21, 22, 23 5 10 1 s
8 7, 9, 23, 24 4 8 1 s
9 8, 10, 24, 25, 26 5 10 1 s
10 9, 25, 26 3 6 1 s
4.4. Link Change Rate
In [11], the authors explain the evaluation of link change rate (LCR) and assume that its
measurement reflects the mobility. There are two types of counters (new-link counter and lost-
link counter) assumed in neighbor table (NT) that find the number of new neighbor nodes and
lost neighbor nodes. An average LCR value has been computed by the EWMA filter method to
control the maximum changes in refresh rate (r). In multi-hop route such type of process causes
the contention problem and increases the delay. It works better in case of low node density and
mobility. An Increase in node density at any point (hop) of the route extensively affects the
overall performance of MANET. Our proposed method uses the physical layer metric for control
of LCR which gives better response in highly dense network and multi-hop routs.
Figure 5: High node density around active node 16
Our proposed method objective is to control the LCR value by advantage of the cross-layer
design. We have taken the range of RSSIth value for the selection of mobile nodes to forward the
packets. We assume that a node can transmit up to maximum distance but after that distance
RSSI becomes weak and the receiver cannot receive from the sender site.
In figure 6, RSSI range determination has a valid reason, a weak link has a possibility to be
broken in less time. High RSSImax node selection provides the high data transfer up to a fixed
rate but it increases the length of the route, such type of scenario already explained in the route
discovery process. RSSImax only works better when the destination node exists inside the
transmission area of the source node. We have considered RSSI rage for the evaluation of
proposed methods.

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Received Signal Strength Indicator (RSSI):
RSSI stands for Received Signal Strength Indicator which indicates the received signal quality.
This RSSI value between any two nodes indicates the receiving capacity. This parameter is
exchanged by the exchange of hello messages to update the status of neighbor nodes. By using a
cross-layer approach, an exchange of RSSI has been performed to network layer which improve
update of neighbor table entries so, there is a selection of nodes on the basis of RSSIth and
RSSImax.
Table-II: RSSI values
Figure 6: RSSI range for node selection
5. DESCRIPTION OF LCR CALCULATION
Our proposed method uses the existing LCR technique, which selects neighbor nodes by
measuring RSSI value. We are using the LCR technique of dynamic the hello timer adjustment
[11], by assuming the RSSIth, which is exchanged by hello process. In figure 8, 9, and 10, we
have modified the header of the hello message format to exchange the RSSI value and update in
the virtual neighbour table (VNT) and neighbor table (NT). The complete hello process is shown
in the flowchart of figure 7.
The proposed algorithm assumes the RSSI of mobile node for node selection in neighbour table
entries.
1. Receive Hello message
2. Check Node_ID and RSSI
2.1 if RSSI < RSSImin
2.1.1 Stop
2.2 else
2.2.1 if RSSI > RSSIth
2.2.1.1 Node_ID and RSSI stored in VNT
2.2.1.1.1 if old node
Quality of Link RSSI (dB)
High/Strong -55
Medium/threshold -75
Weak -85

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2.2.1.1.1.1 Increment counter c and store RSSI
2.2.1.1.2 calculate LCR
2.2.2 else
2.2.2.1 Node_ID and RSSI stored in NT
Figure 7: Flow chart of hello process to update neighbour table
Figure 7, shows neighbor table update process when the mobile node receives a hello message,
which has RSSI value. This value is checked by neighbor node before updating the NT. Less
RSSI value compare to minimum RSSI value for selection of neighbor node in NT. If RSSI value
is very low then NT will not updated with low RSSI node Id, because it will cause loss during
data transfer.
Figure 8: Hello packet header format
Figure 9: Virtual neighbour table (VNT)
Figure 10: Modified neighbour table (NT)

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Figure 11: Refresh rate calculation (α>1, β<1) [11]
Figure 11, illustrates about the estimation of refresh rate (r), which starts as first calculating the
link change rate (lcr) then compared to lcr threshold (thlcr). An Increase in thlcr value proceeds to
update the refresh rate for updating the hello interval. In another way refresh rate (r) is reduced
by dividing it with β. Overall figure 11 shows the adjustment of refresh rate, which is used in the
proposed method. We have modified the hello message to exchange the RSSI value of the mobile
node. We have not increased the size of the hello message to exchange the RSSI value. These
values are in neighbor table, during backup routing and local repair process. We consider α>1,
β<1 from the existing dynamic hello method for evaluation [11].
5.1. Route Discovery and Route Maintenance
In our work route is established by broadcasting of RREQ packets to nodes which are available in
neighbour table and virtual neighbour table. It means RREQ packets are broadcasted to RSSIth
and RSSImax nodes.
The route maintenance process is initialized when a route may be broken or expired due to
topological changes and huge back-off. Usually, an error notification process is used that
initializes the re-route discovery [21]. This error notification system is only significant for short-
span networks. In a large scale network, better route maintenance techniques are required which
have the capability to locally repair [63] the broken route in stipulated time. Our proposed route
maintenance improves the existing method and gives better results in a long-hop multi-hop route.
In link break situation we are using the backup routing, local repair and error notification as
shown in figure 12. The Backup routing process is initialized when neighbor table nodes have
alternate route for the destination node. Local repair is started when alternate routes are not
available and neighbor table have new entries. When backup routing and local repair process fail
then an error notification is initialized by the upstream node to inform source node.

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Figure 12: Improved route maintenance process in MANET
Figure 13 (a) Node selection for route discovery

49
Figure 13(b): Multi-hop route discovery in MANET
Example:
Figure 13(a), shows the detailed description of RSSI quality which helps for node selection,
process. In this section we are describing the route discovery process on the basis of our proposed
methods. Basically, the route discovery process is modified by introducing a RSSI (RSSIth,
RSSImax) parameter for forwarding of control packets. When a source node wants to send the
data to the destination node then it starts the route discovery process as shown in figure 13(b).
Mobile nodes directly discard Low an RSSI packets; this mechanism reduces flooding of control
packets in the network. The source node only receives single-hop RSSImax RREP packet from
destination node, otherwise receives multi-hop RSSIth unicast RREP packet. This type of RREP
packet processing decreases the route length in MANET, which is clearly shown in figure 13(b).
6. PERFORMANCE EVALUATION
We have used the original AODV [21], routing protocol to study the effect of the proposed
algorithm. The Proposed method hello process gains better performance in MANET. We have
performed extensive simulations by network simulator (ns2.34) to measure the performance of
our proposed method in multi-hop route and compared to the existing method of routing
protocols (AODV-BR [24], AODV [21]). We have taken two scenarios where the route length is
10 hops and 15 hops for data transfer. We have considered IEEE standard 802.11 MAC layer
protocol for data transfer.
Table III: Simulation parameter
Parameter Value
Simulation time 1200s
Topology size 1200*800 m2
Number of mobile nodes 100
MAC type MAC 802.11
Radio propagation model Two ray ground
Transmitter Range 100m
Size of packet 512 Bytes
Transmitter power 0.281W
Receiver threshold 7.69113*10-8
W
Traffic type CBR (2Mbps)
No of CBR 5

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Initial Hello interval 1000msec
Speed 1 to 10 m/s
Mobility pattern Random way point
Route length 10 and 15 hops
6.1. Result and Discussion
In this section we are describing the simulation result; we have observed the effect of the
proposed method by considering the AODV routing protocol. We have implemented the
proposed algorithm and compared it to the existing routing protocols method. We have analyzed
the results by considering the following parameters which are compared with existing methods;
available backup routes, no of the error message generated by the upstream node on a route,
number of route repair attempts, link failure probability, number of link breaks, and performance
metric as throughput.
Figure 14. Comparison of Number of backup routing Vs Link failure probability
Scenario 1:
In this scenario, we have to assume a route length of 10 hops in which the size of the packet 512
Byte and there is a random number of link breaks on active route. In the simulation scenario
source node starts a data transfer with data rate of 2 Mbps. The available backup routes are
compared with respect to link failure probability and number of link breaks. the Figure shows the
significant improvement of the proposed method over the AODV-BR [11] routing protocol in
which the number of available backup routes with respect to link failure probability and the
number of link breaks [10].

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Figure 15: Comparison of Number of Error message generate Vs Link failure probability
Figure 15 shows the comparison of the number of the error messages generated when link failure
probability and the number of link breaks increases. In figure we obtain that proposed method
generated smaller number of error messages with respect to AODV-BR and AODV routing
protocols.
Figure 16: Comparison of Number of route repair Vs Link failure probability
Figure 16 shows the functionality of route the repair that is only enabled in the proposed method
because existing method only works when the link breaks closest to the destination node. In our
proposed work, a route repaired because of the position of the link break. Figure 16 shows the
proposed method behavior with respect to link failure probability and the number of route repairs
over the active route.
Figure 17: Comparison of Throughput Vs Link failure probability

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Figure 17 shows the improvement in throughput of proposed method over 10 hop multi-hop
route, and AODV-BR and AODV have less throughput.
Scenario 2
In this scenario, we have to consider route length 15 hops in which the size of the packet is a
change to 512 Byte and there is a random number of link breaks on the active route. In the
simulation scenario source node starts the data transfer with data rate 2 Mbps.
Figure 18: Comparison of Number of backup routing Vs Link failure probability
Figure 18, shows the significant improvement of proposed method when route length increased to
15 hops. It is compared to AODV-BR routing protocol by considering following parameters;
number of available backup routes with respect to link failure probability and number of link
breaks.
In figure 19, shows the comparison of number of error message generated by proposed method
and AODV-BR and AODV routing protocols. There is significant reduction in error message
generation by proposed method which is due use of fresh backup routes.
Figure 19: Comparison of Number of Error message generate Vs Link failure probability
In figure 20, shows use of the route repair process by the proposed method it only happens due to
the unavailability of backup routes. Here it shows behavior with respect to number of routes the

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repair and link failure probability. Local route repair invokes when backup routes are not
available. It only happens when neighbour nodes density along active routes are very low.
Figure 20: Comparison of Number of route repair Vs Link failure probability
Figure 21: Comparison of Throughput Vs Link failure probability
The results in figure 21, show the improvement of throughput by the proposed method and
compared to the AODV-BR and AODV routing protocol. We have observed that in a dense
network the performance of the proposed method.
7. CONCLUSIONS
In mobile ad-hoc network link connectivity information is obtained by the hello process. Link
timeout or neighbour timeout, route timeout are the problems which that degrade the overall
performance of the network. These timeout issues can be overcome by applying various
techniques at layer 2 (Data Link) and layer 3 (Network). In general, a link indicates the existence
of neighbour node inside the coverage area of the node. Hello process is an important part of
route maintenance, which is followed in several routing protocols. Its periodicity shows the
utilization in a network to obtain the up-to-date neighbour node's information. In dynamic
topology, existing hello process lacks the update of the link lifetime (neighbour lifetime) and
route lifetime. In this work, we have considered the existing work, which is the dynamic
adjustment of hello timer. The Major limitation of dynamic the hello is very low refresh rate
(hello interval) which is evaluated based on high link change rate (LCR) value. The reason
behind high LCR is due to consideration of all neighbour nodes, which are in proximity, and
exterior area of a node. We have the proposed an algorithm based on of RSSIth to control the

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LCR and achieve efficient refresh rate. Implementation of proposed method has been done in
AODV routing protocol and compared to the existing schemes. Our results show the a significant
improvement over existing routing protocols (AODV-BR and Original AODV).
CONFLICTS OF INTEREST
The authors declare no conflict of interest.
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AUTHORS
Dhirendra Kumar Sharma working as Assistant Professor-SG at SCS, University of
Petroleum and Energy Studies Dehradun. He did Ph.D (CSE) from Indian Institute of
Technology (ISM) in 2016. His research interest in protocols development for ad hoc
networks, wireless sensor networks, UAV communication.
Nitika Goenka working as Assistant Professor at SCS, University of Petroleum and
Energy Studies Dehradun. Her area of Specialization Software Development (JAVA,
Web Services) and Testing (Groovy), Compute vision.

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