Throughput analysis of single gateway association in wireless mesh network with multiple gateways

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Throughput analysis of single gateway association in wireless mesh network with multiple gateways. This scenario of multiple gateways leads to improvement in throughput of overall network. But some criteria is required based on which the nodes are to be associated to a gateway. Associating to the nearest gateway may not be always the best choice. We present here an algorithm for associating a node to one of several available gateways.
International Journal of Computer Networks and Communications Security
VOL. 3, NO. 12, DECEMBER 2015, 447–450
Available online at: www.ijcncs.org
E-ISSN 2308-9830 (Online) / ISSN 2410-0595 (Print)
Throughput Analysis of Single Gateway Association in Wireless
Mesh Network with Multiple Gateways
GEETA J. TRIPATHI1 and DR. A. R. MAHAJAN2
1 Research Scholar, Department of CSE, GHRCE, Nagpur (MS), India
2 Professor & Head, Department of IT, Government Polytechnic, Nagpur (MS), India.
E-mail: 1tripathi.geetaj@gmail.com, 2armahajan@rediffmail.com
ABSTRACT
Wireless mesh network (WMN) has become widely accepted technology in recent decade [1]. Low cost,
simplicity and availability of the Internet without actually getting directly connected to the broadband
services, are few of the advantages that can be counted on for popularity of WMN. Mesh nodes get access
to the Internet through a special device called Gateway. Even one gateway may be sufficient to provide
broadband facility to a number of nodes in its range. With addition of more gateways, the range of covering
more nodes is increased. This scenario of multiple gateways leads to improvement in throughput of overall
network. But some criteria is required based on which the nodes are to be associated to a gateway.
Associating to the nearest gateway may not be always the best choice. We present here an algorithm for
associating a node to one of several available gateways. Throughput is one of the key performance metrics
for many applications. In this paper we have analyzed the network on this performance metric for nearest
gateway scheme and for proposed scheme. The proposed scheme has shown better performance especially
for densely populated mesh nodes near gateway.
Keywords: WMN, Gateway, Mesh Node, End to End Delay, Throughput.
1
INTRODUCTION
gateway is available to a node, then decision
regarding to which gateway the node be associated
Wireless networks have never taken back seat
is to be taken. One of the major issues with WMN
since their introduction to the computer networks
are the resource sharing, i.e., sharing bandwidth of
area [1], [2]. Wireless network and the Internet has
the gateway [2]. As number of clients goes on
become a new life line showing health and progress
increasing, allocation of bandwidth becomes more
of a society. A node in wireless network can get
tedious. This may lead to more complex problems
access to the Internet through broadband services.
like
unfairness,
starvation,
congestion,
packet
With the advent of mesh technology, a node may
drops, delays and dropped throughput. Generally,
access
the
same
without
having
need
of
direct
the nodes get associated to the nearest gateway.
connection to the broadband services. Even if it is
This nearest gateway may be calculated on the
having one node, called the gateway node, with
basis of either hop count or end to end delay. When
direct access to backbone network, any node in the
nodes with different hop count or end to end delay
range of the gateway get the facilities of backbone
get associated to a gateway, the nearer one gets
access. This simplicity and low cost of WMNs
hold on the gateway than the farther one in the
make
them
more
popular
amongst
their
competition of gaining access. This may lead to
counterparts [2].
long waiting time on the part of nodes located at
comparatively
longer
distance
and
may
cause
2
MOTIVATION
starvation. It may also lead to unfairness as the
nodes nearer to gateway are most of the time
In WMN, a mesh node can access a gateway if
the gateway is in its range. If more than one
keeping gateway unavailable
located nodes. Many nodes
to the distantly
trying to access
448
G. J. Tripathi and A. R. Mahajan / International Journal of Computer Networks and Communications Security, 3 (12), December 2015
backbone
at
the
same
time
through
the
same
gateway may further cause congestion and packet
drops at the gateway which in turn may be the
reason for decreasing network throughput. This has
been a motivation to go for some scheme that may
do the better utilization of the resource i.e.,
gateway.
The decision of primary gateway is taken
at the runtime
The primary gateway may not be the same
designated one, but it may be changed
Even with the mobile nodes it may work
effectively with little modification
3
THE PRIMARY GATEWAY
Increased availability of gateway services
ASSOCIATION SCHEME
to nodes
In a WMN scenario with multiple gateways,
there may be two or more gateways in the range of
a node. A node will take decision to select a
gateway as its primary gateway. This can be done
by checking the delay from node to available
gateways. The gateway with the lowest delay from
the node may be assigned as primary gateway (PG)
for the node, as shown in table 1 below.
In the traditional scheme, primary gateway is a
designated gateway allotted to node depending
upon the hop count from the node to gateway. This
works well in case of wireless infra-structure mesh
networks, where the nodes are rather static and
accessing the backbone network wirelessly through
the gateway. So as long as the network exists, the
node has same gateway as its default or primary
gateway. If more number of active nodes populated
Table 1: Algorithm Primary Gateway Association
near a gateway, the performance of the overall
network goes on decreasing. On the other hand, the
Algorithm: Primary Gateway
Association
1. For each node
2. For each gateway in the range
3. Send hello from node
4. Find e2e delay and IFQ threshold
for this GW, save in a list
other gateway in the range of these active nodes
may be underutilized just because the hop-count
from nodes to this gateway is not the lowest one.
The freedom to choose best possible gateway at
runtime and if it is not available selecting the
second best as primary gateway assures maximum
time availability of gateway services in the
network. Once the list is sorted according to end to
5.
6.
7.
End for
Sort list to find lowest e2e delay
and higher IFQ threshold
Make gateway with lowest e2e and
higher IFQ threshold as Primary
gateway PG
end delay and IFQ threshold, it may be utilized to
take decision regarding the second or third best
gateway for a node in case the first best gateway is
overloaded.
If the data regarding end to end delay from the
node to every possible gateway in the range is
gathered whenever there is denial of service from
8.
End for
primary gateway to the node, this scheme may
9. If new load
10. Send request to PG
work effectively for wireless mesh network with
mobile nodes.
11. If ack received
12. Send load to PG
13. Else
14. //If PG Signal waiting
15. Pick up next suitable gateway as
PG from step 6 and 7
16. Perform step 10 onwards
17. End if
18. End if
The algorithm in table 1, is for single gateway
association, i. e., a node is associated to only one
gateway at a time. This scheme is different from
basic default gateway association in three ways:
Fig. 1. Experimental Scenario in NS-2
449
G. J. Tripathi and A. R. Mahajan / International Journal of Computer Networks and Communications Security, 3 (12), December 2015
4
RESULTS AND DISCUSSIONS
The
algorithm
is
implemented
in
network
simulator NS-2 which is widely accepted amongst
the researchers [3], [4]. As shown in figure 1, a 5X5
regular grid scenario is considered. The nodes are
assumed to be static. The association of nodes to
gateway using basic default association scheme is
as shown in table 2. As more number of nodes
associated to gateway G4, when the nodes try to
send
packets,
most
of
the
packets
are
dropped
whereas, these nodes might have approached other
gateways in the range. The scenario was observed
Fig. 2. Average Throughput using Default Scheme
for varying data rates. Throughput of the network
was analyzed. As shown in figure 2, for 200Kbps
CBR traffic, gateway G2 and gateway G3 have
better average throughput compared to gateway G1
and gateway G4. The reason is more number of
active nodes associated to gateway G1 and gateway
G4. Hence, there is competition for access and
more packet drops are there leading to lowered
throughput, especially at gateway G4 with eight
associated nodes.
Table 2: Association of nodes to gateways
Fig. 3. Average Throughput using Proposed Scheme
Gateway number
Associated node number
Figure 3 shows that gateway G4 has given
noticeably good improvement in throughput. Also
G1 (4)
2, 3, 8, 9,14
gateway G2 and G3 performed better in the
proposed scheme. These two gateways were
available to take load when gateway G1 and G4
G2 (20)
10, 15, 16, 21
were signaling wait. Hence, we have got better
network throughput with the proposed scheme.
G3 (24)
18, 19, 22, 23
5
CONCLUSION
G4 (6)
0, 1, 5, 7,10, 11, 12, 13
The proposed scheme of gateway association has
shown better throughput than the general scheme.
There are many other advantages of this scheme.
The same scenario is used for the proposed
scheme of association listed in table 1, and the
When a node is denied for service from gateway, it
does not sit idle starving. It tries to approach
another gateway. As the traffic is diverted from
results of throughput were plotted as shown in
figure 3. From figure 2 and figure 3, it can be
observed that the network throughput in case of
proposed scheme is better than the default scheme.
The proposed scheme responds better for increasing
data rate and also when the number of active nodes
busy gateway towards the comparatively less
burdened gateway, congestion is avoided, which in
turn may lower the packet losses. As the nodes are
getting chance to communicate through another
gateway, fairness is increased and better utilization
of resources is done.
is increased.
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Throughput analysis of single gateway association in wireless mesh network with multiple gateways. This scenario of multiple gateways leads to improvement in throughput of overall network. But some criteria is required based on which the nodes are to be associated to a gateway. Associating to the nearest gateway may not be always the best choice. We present here an algorithm for associating a node to one of several available gateways..

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International Journal of Computer Networks and Communications Security VOL. 3, NO. 12, DECEMBER 2015, 447–450 Available online at: www.ijcncs.org E-ISSN 2308-9830 (Online) / ISSN 2410-0595 (Print) Throughput Analysis of Single Gateway Association in Wireless Mesh Network with Multiple Gateways GEETA J. TRIPATHI1 and DR. A. R. MAHAJAN2 1 Research Scholar, Department of CSE, GHRCE, Nagpur (MS), India 2 Professor & Head, Department of IT, Government Polytechnic, Nagpur (MS), India. E-mail: 1tripathi.geetaj@gmail.com, 2armahajan@rediffmail.com ABSTRACT Wireless mesh network (WMN) has become widely accepted technology in recent decade [1]. Low cost, simplicity and availability of the Internet without actually getting directly connected to the broadband services, are few of the advantages that can be counted on for popularity of WMN. Mesh nodes get access to the Internet through a special device called Gateway. Even one gateway may be sufficient to provide broadband facility to a number of nodes in its range. With addition of more gateways, the range of covering more nodes is increased. This scenario of multiple gateways leads to improvement in throughput of overall network. But some criteria is required based on which the nodes are to be associated to a gateway. Associating to the nearest gateway may not be always the best choice. We present here an algorithm for associating a node to one of several available gateways. Throughput is one of the key performance metrics for many applications. In this paper we have analyzed the network on this performance metric for nearest gateway scheme and for proposed scheme. The proposed scheme has shown better performance especially for densely populated mesh nodes near gateway. Keywords: WMN, Gateway, Mesh Node, End to End Delay, Throughput. 1 INTRODUCTION Wireless networks have never taken back seat since their introduction to the computer networks area [1], [2]. Wireless network and the Internet has become a new life line showing health and progress of a society. A node in wireless network can get access to the Internet through broadband services. With the advent of mesh technology, a node may access the same without having need of direct connection to the broadband services. Even if it is having one node, called the gateway node, with direct access to backbone network, any node in the range of the gateway get the facilities of backbone access. This simplicity and low cost of WMNs make them more popular amongst their counterparts [2]. 2 MOTIVATION In WMN, a mesh node can access a gateway if the gateway is in its range. If more than one gateway is available to a node, then decision regarding to which gateway the node be associated is to be taken. One of the major issues with WMN are the resource sharing, i.e., sharing bandwidth of the gateway [2]. As number of clients goes on increasing, allocation of bandwidth becomes more tedious. This may lead to more complex problems like unfairness, starvation, congestion, packet drops, delays and dropped throughput. Generally, the nodes get associated to the nearest gateway. This nearest gateway may be calculated on the basis of either hop count or end to end delay. When nodes with different hop count or end to end delay get associated to a gateway, the nearer one gets hold on the gateway than the farther one in the competition of gaining access. This may lead to long waiting time on the part of nodes located at comparatively longer distance and may cause starvation. It may also lead to unfairness as the nodes nearer to gateway are most of the time keeping gateway unavailable to the distantly located nodes. Many nodes trying to access 448 G. J. Tripathi and A. R. Mahajan / International Journal of Computer Networks and Communications Security, 3 (12), December 2015 backbone at the same time through the same gateway may further cause congestion and packet drops at the gateway which in turn may be the reason for decreasing network throughput. This has been a motivation to go for some scheme that may do the better utilization of the resource i.e., gateway.  The decision of primary gateway is taken at the runtime  The primary gateway may not be the same designated one, but it may be changed  Even with the mobile nodes it may work effectively with little modification 3 THE PRIMARY GATEWAY ASSOCIATION SCHEME  Increased availability of gateway services to nodes In a WMN scenario with multiple gateways, there may be two or more gateways in the range of a node. A node will take decision to select a gateway as its primary gateway. This can be done by checking the delay from node to available gateways. The gateway with the lowest delay from the node may be assigned as primary gateway (PG) for the node, as shown in table 1 below. Table 1: Algorithm Primary Gateway Association Algorithm: Primary Gateway Association 1. For each node 2. For each gateway in the range 3. Send hello from node 4. Find e2e delay and IFQ threshold for this GW, save in a list 5. End for 6. Sort list to find lowest e2e delay and higher IFQ threshold 7. Make gateway with lowest e2e and higher IFQ threshold as Primary gateway PG 8. End for 9. If new load 10. Send request to PG 11. If ack received 12. Send load to PG 13. Else 14. //If PG Signal waiting 15. Pick up next suitable gateway as PG from step 6 and 7 16. Perform step 10 onwards 17. End if 18. End if The algorithm in table 1, is for single gateway association, i. e., a node is associated to only one gateway at a time. This scheme is different from basic default gateway association in three ways: In the traditional scheme, primary gateway is a designated gateway allotted to node depending upon the hop count from the node to gateway. This works well in case of wireless infra-structure mesh networks, where the nodes are rather static and accessing the backbone network wirelessly through the gateway. So as long as the network exists, the node has same gateway as its default or primary gateway. If more number of active nodes populated near a gateway, the performance of the overall network goes on decreasing. On the other hand, the other gateway in the range of these active nodes may be underutilized just because the hop-count from nodes to this gateway is not the lowest one. The freedom to choose best possible gateway at runtime and if it is not available selecting the second best as primary gateway assures maximum time availability of gateway services in the network. Once the list is sorted according to end to end delay and IFQ threshold, it may be utilized to take decision regarding the second or third best gateway for a node in case the first best gateway is overloaded. If the data regarding end to end delay from the node to every possible gateway in the range is gathered whenever there is denial of service from primary gateway to the node, this scheme may work effectively for wireless mesh network with mobile nodes. Fig. 1. Experimental Scenario in NS-2 449 G. J. Tripathi and A. R. Mahajan / International Journal of Computer Networks and Communications Security, 3 (12), December 2015 4 RESULTS AND DISCUSSIONS The algorithm is implemented in network simulator NS-2 which is widely accepted amongst the researchers [3], [4]. As shown in figure 1, a 5X5 regular grid scenario is considered. The nodes are assumed to be static. The association of nodes to gateway using basic default association scheme is as shown in table 2. As more number of nodes associated to gateway G4, when the nodes try to send packets, most of the packets are dropped whereas, these nodes might have approached other gateways in the range. The scenario was observed for varying data rates. Throughput of the network was analyzed. As shown in figure 2, for 200Kbps CBR traffic, gateway G2 and gateway G3 have better average throughput compared to gateway G1 and gateway G4. The reason is more number of active nodes associated to gateway G1 and gateway G4. Hence, there is competition for access and more packet drops are there leading to lowered throughput, especially at gateway G4 with eight associated nodes. Table 2: Association of nodes to gateways Fig. 2. Average Throughput using Default Scheme Fig. 3. Average Throughput using Proposed Scheme Gateway number G1 (4) G2 (20) Associated node number 2, 3, 8, 9,14 10, 15, 16, 21 Figure 3 shows that gateway G4 has given noticeably good improvement in throughput. Also gateway G2 and G3 performed better in the proposed scheme. These two gateways were available to take load when gateway G1 and G4 were signaling wait. Hence, we have got better network throughput with the proposed scheme. G3 (24) 18, 19, 22, 23 5 CONCLUSION G4 (6) 0, 1, 5, 7,10, 11, 12, 13 The same scenario is used for the proposed scheme of association listed in table 1, and the results of throughput were plotted as shown in figure 3. From figure 2 and figure 3, it can be observed that the network throughput in case of proposed scheme is better than the default scheme. The proposed scheme responds better for increasing data rate and also when the number of active nodes is increased. The proposed scheme of gateway association has shown better throughput than the general scheme. There are many other advantages of this scheme. When a node is denied for service from gateway, it does not sit idle starving. It tries to approach another gateway. As the traffic is diverted from busy gateway towards the comparatively less burdened gateway, congestion is avoided, which in turn may lower the packet losses. As the nodes are getting chance to communicate through another gateway, fairness is increased and better utilization of resources is done. 450 G. J. Tripathi and A. R. Mahajan / International Journal of Computer Networks and Communications Security, 3 (12), December 2015 6 REFERENCES [1] W.I.F. Akyildiz, X. Wang, “Wireless mesh networks: A survey,” in Computer Networks Journal 47 (Jan.) (2005) 445–487. [2] M. L. Sichitiu, “Wireless mesh networks: opportunities and challenges”, in Proceedings of World Wireless Congress (May) (2005). [3] S. Tajima, T. Higashino, N. Funabiki, S. Yoshida, “An internet gateway access-point selection problem for wireless infrastructure mesh networks”, Seventh International Conference on Mobile Data Management (MDM’06), 2006, pp. 112–118. [4] P. Owczarek and P. Zwierzykowski, “Review of Simulators for Wireless Mesh Networks”, Journal of Telecommunications and Information Technology, March 2014. [5] The network simulator ns-2 manual online available at http://www.isi.edu/nsnam/ns/

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