Performance Analysis of Effect of Transmission Power in Mobile Ad hoc Network

Manoranjan Das1, Banoj Kumar panda2, Benudhar sahu3

1,2Konark Institute of Science and Technology, Bhubaneswar, India3Rajdhani Engineering College, Bhubaneswar,India

{mr_dasbiet@rediffmail.com1, bk_panda2001@yahoo.com

2, bdsahu66@yahoo.com

3}

Abstract- The increase in users of mobile electronic gadgets with communication facilities day by day all around the world is resulting growth in research on multi hop wireless network getting exponential in past few years. Mobile ad hoc network is the suitable one for providing communication between these users (known as nodes) in a network as far as the application and physical structure of the network is considered. The mobile ad hoc network being infrastructure less is flexible to form. However the existence of the network for a long duration depends on the lifetime individual nodes belongs to that network. The life time of a node depends on the battery power. Most of the power consumed in a node is because of transmission. Therefore it is important to know the effect of transmission power on the performance of network so that for specific applications the transmission power of nodes can be decided based on the network area and the number of possible nodes that to work in the network which can work for long duration. In this paper we have described the analysis of the effect of transmission power on the performance of network such as packet delivery fraction, routing load, average energy consumption per node and hop count. The analysis is made for a network with different number of sources and different transmission power of nodes for a fixed network area.

Keywords- MANET, Transmission power, AODV

I. INTRODUCTION

Mobile ad hoc network (MANET) [1] is a network that comprises of wireless mobile nodes which moves freely and self organizes them to form a temporary network without the involvement of any base station. Thus such a network helps people using the mobile electronic gadgets with communication facility such as cell phones, laptops to communicate between themselves even in areas where it is not possible to establish an infrastructure for the network. This leads to an increase in the application area of such networks last few years and become a good research topic in current times. In MANET there is a frequent change in network topology due to the random movement of nodes which creates more than one path of packet transmission between source and destination nodes. Further the limited battery power of individual nodes restricts their functionality which indirectly affects the performance of MANET [2]. Under such a scenario the transmission range

and the computations related to the nodes must be taken care so as to obtain a better performance of the network. This is because in MANET the consumption of battery power at each node is mainly due to data computation and wireless transmission and reception [3]. Among them the consumption of battery power due to transmission and reception is more in compare to computation. Again the transmission and reception power consumption directly depends on the radio range of the nodes. Thus in order to have a better network connectivity among the nodes so as to improve the performance the transmission range can be increased because by this the number of hops between source and destination will decrease. Simultaneously this will lead to an increase in probability of collision and also the life of node will reduce since it requires more power to transmit over a greater range. Similarly if the transmission range will be decreased may be the life of the node will increase but a more number of nodes will be required to cover a greater geographical area which may not be possible for certain applications in remote areas. Therefore it is required that the transmission range must to be chosen such a value that the performance of MANET will be better and the nodes must function throughout the application time without fail. In order to have the knowledge of this we have analyzed the performance of MANET for different transmission range for different number of nodes with different number of sources in a fixed network area. The routing protocol we have used for the network is AODV.

The rest of the paper is organized as follows. In section II we have given a brief overview of the radio model that wehave considered for MANET. Section III presents a list of parameters that we have chosen for simulation. The different performance metric based on which we have made the analysis of the performance has also listed in section III. In section IV we have presented a detail analysis of the variation in performances under different environment. Finally section V expresses our conclusion related to the work.

II. OVERVIEW OF RADIO POWER MODEL

In our simulation we have chosen a simplified radio power model in which the energy expended towards

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transmission of one data packet from source to destination is a function of radio range and number of hops between source and destination. In order to simplify the analysis we have assumed that the routing nodes in between source and destination are equally spaced maintaining a distance ‘r’ between them which is equal to the transmission range of individual node. Hence the distance between source and destination (say ‘l’) is always divisible by ‘r’ which is equal to ‘k’ that means there lays ‘k-1’ number of routing nodes between source and destination. Now the total energy consumed for transmission of one data packet from sourceto a destination present at a distance of ‘l’ from source at any time can be expressed as

� �total k trans receive discardE E E E� � � �� (1)

Where

transE = Energy consumed by a node for

transmission/forwarding of a data packet to a node present at next hop in the route between source and destination

receiveE = Energy consumed by a node for reception of

data packet transmitted from a node present in the previous hop in the route between source and destination

discardE = Energy consumed by the overhearing node

We have chosen ‘k’ as the multiplying factor because besides the ‘k-1’ number of intermediate or routing nodes between source and destination source can be considered as one node who can only transmit the data packet and destination is one node who can only receive the data packet.

Also the energy consumed per second towards transmission is given as

� ntrans t d rE E E B� � � (2)

Where

tE = Energy consumed for transmission of one bit

by the transceiver

dE = Energy dissipated by the amplifier circuits

present in the transceiver before feeding to antenna for transmission

r = Transmission range

n = Power index for the channel path loss of

antenna (generally between 2 and 4)

B = Bit rate of the radio for transmission and reception

Similarly the energy consumed per second for receiving the data packet is given as

receive rE E B� � (3)

Where rE = Energy consumed for reception of one bit by the transceiver

In order to decrease the energy consumption at each node and thus increase the life time of a node in the network it is required that the transmission range of the node must be small. This means a long distance between source and destination can be divided into several shorter ones which in turn increase the requirement of more number of routing nodes. However, if the number of routing nodes is very large then the energy consumption per node is dominated by the term tE .

III. SIMULATION ENVIRONMENT AND PERFORMANCE

METRICS

A. Simulation Environment

We have used Global Mobile Simulator (GloMoSim) as the network simulator [5] for the performance analysis. The mobility model we have chosen is Random Way Point model [6, 7]. The other parameters that we have chosen for the network in the simulator are as listed below in the TABLE I.

TABLE I

PARAMETERS USED FOR SIMULATION

Parameters Value/Specification

Terrain Area 1500Mx300M

Number of Nodes 50

Node Mobility model Random Waypoint

Number of sources 10 ,15 and 25

Maximum Speed 10 M/S

Pause time 0 S

Simulation Time 15 M

Transmission Power 10 dBm, 15 dBm and 20 dBm

Mac Protocol 802.11

Routing Protocol AODV

Packet size 512 bytes

Data rate 2 Mbps

Type of Data traffic CBR (Constant Bit Rate)

The simulation has done for 900 sec. Each simulation corresponds to a seed. For 5 different seeds the simulation has been carried out. To get a point related to a performance metrics in the plot the average of 5 seeds are taken.

B. Performance Evaluation Metrics:

We have considered the following metrics for analyzing the performance of the network under different transmission range scenario.

a) Packet delivery fraction: The ratio between the number of packet delivered to the destination and the total number of packet generated at the CBR sources.

b)Normalized routing load: Normalized routing load is the ratio between total number of routing control packets transmitted by nodes and the total number of packets received by all destinations.

c) Average energy consumption per node: The ratio between sum of total energy consumed by all the active nodes in a network (for both transmission and reception) and the number of nodes in the network.

d) Hop Count: This the sum of number of hops faced by the source nodes in the network for transmission of their information to the destination nodes throughout the simulation time.

IV. SIMULATION RESULT AND ANALYSIS

In this section we present the simulation results for different transmission powers for different number of sources (i.e. 10, 15 and 25). In order to make the analysis of the effect of variation in transmission power the mobility of the nodes we have chosen fixed (i.e.10 m/s). The analysis is based on the comparison of different metrics stated in the last section for different transmission range scenario corresponding to different transmission power.

Transmission Range Scenario:

The transmission range of a node usually refers to the average distance between two nodes in normal operating condition. The range can be changed by changing the transmission power of the node. In our simulations we have chosen three different transmission powers (i.e.10 dBm, 15 dBm and 20 dBm) which correspond to three different transmission ranges.

Fig. 1 indicates packet delivery fraction vs transmission power for 10, 15 and 25 sources. It is observed that a network with 10 sources shows a packet delivery fraction of 0.86 for transmission power of 10dBm. The packet delivery fraction increases to 0.94 with the increase in transmission power to 15dBm. This is due to the fact that an increase in transmission power increases the transmission range of nodes. This results to the decrease in number of link between source and destination. Hence the possible number of link breaks decreases and results to increase in packet delivery fraction. However, with further increase in transmission power to 20dBm, there is a decrease in packet delivery fraction to 0.89. This is due to the phenomena that with the increase in transmission power, more number of nodes comes within the transmission range of a transmitting node. 802.11 MAC stops the entire node within the transmission range from transmission. This results in a decrease in packet delivery fraction.

Fig. 1 Packet delivery fraction vs transmission power in a MANET of 50 nodes with 10, 15 and 25 sources

Similar trend in packet delivery fraction is observed for the network with 15 and 25 sources. Packet delivery fraction for 15 and 25 sources for 10dBm transmission power is 0.78 and 0.54 respectively. The decrease in packet delivery fraction with increase in number of sources is due to increase in congestion in the network [8]. It is interesting to observe that all the network results in highest packet delivery fraction for 15dBm transmission power.

Normalized routing load vs transmission power for the network with 10, 15 and 20 sources is presented in Fig.2. It is observed that the normalized routing load of a network with 10 sources at 10dBm transmission power is 1.1. With increase in transmission power to 15dBm, the normalized routing load decreases to 0.8 due to decrease in number of hops between sources and destination pair. A further increase in transmission power from 15dBm to 20dBm results in more reduction in the number of hops between sources and destination pair. Thus results in the decrease of normalized routing load. Similar trend in the normalized routing load is observed for the network with 15 and 20 sources. The normalized routing load for 15 and 25 sources at 10dBm transmissions power is 1.3 and 3 respectively. The increase in normalized routing load for 15 and 25 sources is due to the increase in the network congestion [8]. One of the important observations is that the normalized routing load for network with 10, 15 and 25 sources is lowest at 20dBm transmission power. This is due to the presence of less number of hops at 20dBm transmission power.

Fig. 2 Normalized routing load vs transmission power for a MANET of 50 nodes for 10, 15 and 25 sources

The variation in average energy consumption per node due to the variation of transmission power of nodes in a network with different number of sources is shown in fig.3.It is seen that the energy consumption per node for a network with 10 sources at 10dBm transmission power is 67.8mWHr. This energy consumption per node increases to 68mwHr at 15dBm transmission power. The increase in energy consumption is due to increase in transmission power to reach hops of longer distance. Further increase in transmission power to 20dBm also increases the energy consumption per node to 68.9mWHr. The large transmission power per hop results in larger energy consumption per node even though the packet delivery fraction reduces a little.

Fig. 3 Average energy consumption per node vs transmission power for a MANET of 50 nodes for 10, 15 and 25 sources

Similar trend of increase in energy consumption per node with increase in transmission power from 15dBm to 20dBm is observed for the network with 15 and 20 sources. The decrease in energy consumption per node for a network with

15 and 20 sources is due to decrease in successful packet transmission between source and destination pair.

Fig. 4 presents the hop count vs transmission power for a MANET with 10, 15 and 25 sources.

Fig. 4 Hop count vs transmission power in a MANET of 50 nodes with 10,

15 and 25 sources

It is observed that the hop count for a network with 10 sources is 95 at 10dbM transmission power. The hop count decreases to 52 with increase in transmission power to 15dBm. The number of hops between source and destination pair decreases with increase in transmission power. This results in the likely hood of decrease in link failure. So,decrease in hop count is due to decrease in the number of hops between source and destination pair. Further increase in transmission power reduces the hop count further to 20due the same reason.

Similar trend is seen for a MANET with 15 and 25 sources. The number of hop count for a MANET with 20dBm transmission power is observed to have lowest hop count.

V. CONCLUSIONS

Using the network simulator the various performance parameters (as mentioned in section III above) related to the AODV routing protocol for different transmission power of nodes are calculated and analyzed. It is observed from the plots that the performance of the network will be better only for a specific transmission power (i.e. 15dBm) for the nodes not all which also depends on the network load (i.e. 15 source).

REFERENCES

[1] Charles E. Perkins “Ad-hoc Networking” Text book, Addison-wesley-2001[2] B.Venkatalakshmi and S.Shanmugavel, “Transmission range

effects of On-Demand Multicast Routing Protocol multicast communication for MANET” 2009 World Congress on Computer Science and Information Engineering, IEEE , pp 332-337.

[3] Jing Deng, Yunghsiang S. Han, Po-Ning Chen and Pramod K. Varshney, “Optimal Transmission Range for Wireless Ad Hoc Networks Based on Energy Efficiency” IEEETRANSACTIONS ON COMMUNICATIONS, VOL. 55, NO. 9, pp 1772-1782, September 2007.

[4] C.E Perkins, E.M. Royer and S.R.Das, “Ad hoc on Demand Distance Vector Routing” IETF internet draft (draft – ietf- manet- aodv-06.txt), July 2000.[5] L. Bajaj, M. Takai, R. Ahuja, K. Tang,R. Bargodia and M.

Gerla, GlomoSim: A Scalable Network SimulationEnvironment,CSD Technical report, University of Californiaat LosAngles, 1997.

[6] N. Adam, M. Y. Ismail and J. Abdulla, “Effect of node density on performance of three MANET routing protocols”,in proc. International conference on Electronic Devices, Systems and applications (ICEDSA-2010), pp. 321-325, Malaysia,April 2010.

[7] K. Amjad and A. J. Stocker, “Impact of node density and mobility on performance of AODV and DSR in MANET” in proc. 7th International symposium on Communication Systems networks and Digital Signal Processing (CSNDSP-2010), pp. 61-65, University of Northumbria, U.K. ,July 2010.