The graduate school of Ajou university. Tel: +82-31-2191892, Fax: +82-31-219-1891. E-mail: {chahs, ricman, kkim86, swyoo}@ajou.ac.kr. AbstractâA wireless ...
Efficient Relay Node displacement mechanism for improvement of lifetime in WSN Hyun-Soo Cha, Jea-Tek Ryu, Ki-Hyung Kim, Seung-Hwa Yoo The graduate school of Ajou university Tel: +82-31-2191892, Fax: +82-31-219-1891 E-mail: {chahs, ricman, kkim86, swyoo}@ajou.ac.kr
In Pan et al. studied a two-tiered network model where the sensor nodes are grouped into clusters, each covered by an application node[3]. There are some problems in earlier work on Relay Node displacement mechanisms. One of the problems is that they did not consider the energy consumption of each sensor node. In earlier work, they calculated the energy consumption in entire network then derive the number of relay node. And the other one is that they consider the case of sensor nodes and relay nodes have different transmission range. They assumed that the relay node has longer transmission range than common node. So we propose an efficient relay an optimal solution o node displacement mechanism which consider before two problems.
Abstract—A wireless sensor network consists of many lowpower, low-cost nodes which can perform sensing, computing, and send short messages over short distance. In respect that
sensor nodes are powered by batteries, energy would be very important for wireless sensor work. In this paper, we proposed an efficient relay node displacement mechanism which considers each node’s energy consumption and analysis the lifetime per unit cost.
I.
INTRODUCTION
A wireless sensor network consists of many low-power, low-cost nodes which can perform sensing, computing, and send short messages over short distance. In respect that sensor nodes are powered by batteries, energy would be very important for wireless sensor work. So there have been extensive studies focusing on the lifetime of wireless sensor network[1,2,3,4] Network lifetime is usually defined as the time for the first sensor node to die, or as the time for a certain percentage of nodes to die. One of approaches which can prolong the lifetime of wireless sensor network is deploying several additional relay nodes in the network. Lifetime per unit cost, defined as the network lifetime divided by the number of sensors deployed in network, it can be used to measure the utilization efficiency of sensors [5]. This paper is composed as follows. Section 2 we presented other related works. Section 3 explains the mechanism of relay no displacement. Section 4 present evaluation results, and finally we conclude this paper in Section 5 with some future works. II.
III.
In this paper, we propose an efficient relay node displacement mechanism which considers the energy consumption of each node and the case of relay node and sensor node have same transmission range. To do this, we define several sets as follows. S {S1 , S 2 , S 3 ...} Sensor nodes
R {R1 , R2 , R3 ...} Relay nodes N {N1 , N 2 , N 3 ...} Node with high energy consumption E {E1 , E2 , E3 ...} Energy consumption of S
These sets are used in equations which calculate the positions of relay nodes. The relay node’s positions are derived by follow two steps.
RELATED WORK
STEP1 Find sensor nodes which spend more energy
Cheng et proposed a relay node displacement mechanism which deploys a minimum number of relay node in WSN so that, between every pair of sensor nodes, there is a connecting path consisting of relay and/or sensor nodes and such that each hop of the path is no longer than the common transmission range of the sensor nodes and the relay nodes. This problem is exactly the Steiner minimum tree with minimum number of Steiner points and bounded edge length problem (SMT-MSPBEL)[1]. Errol et studied the single-tiered relay node placement problem and the two-tiered relay node placement problem in a wireless sensor networks[2].
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PROPOSED METHOD
If a node spends more energy, it becomes a member of set N and removed in S. Repeat until all nodes are checked
Calculate the average energy consumption A Compare A and E n If E n > A then S n become a member of Nr
STEP2 Calculate the position of relay node
If N1 is a member of set N, find nodes which are deployed in N1’s transmission range. These nodes become a member of a group. Repeat this process until all members in the set N are belonged in any group.
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The position of relay nodes (X, Y) is
E1 E2 Xn X1 X 2 ..... E1 E2 E3 .... E1 E2 E3 ....
(1)
E1 E2 Y1 Y2 ..... E1 E2 E3 .... E1 E2 E3 ....
(2)
Yn
mechanism considers each node’s energy consumption and same transmission range. And our mechanism increase a lifetime of network. Thus, it is able to become an optimal solution of relay node displacement mechanism.
We can calculate the relay node’s positions using (1) and (2). In these equations, X and Y mean the position of x, y axis. E means the energy consumption of the sensor nodes. The PAN coordinator receives each sensor node’s remaining energy level through the Hello message in LEACH routing protocol [9]. And then these two steps are repeated until all groups have at least one relay node. To measure the utilization efficiency of sensors, we define the lifetime per unit cost as the network lifetime L divided by the number of sensor node n, i.e., E[ L] (3)
Fig 1. Comparison of proposed mechanism and common case
n
Lifetime per unit cost Lifetime per unit cost shows the rate at which the network lifetime L increases with the number N of sensors. IV. PERFORMANCE EVALUATION
Fig 2 Lifetime per unit cost
In order to measure performance of proposed mechanism, we measured the energy consumption and lifetime per unit cost by using network simulator. Simulation is carried out in Qualnet 4.5 to demonstrate the increase life time of WSN due to additional relay node. The simulations consisted of 25 sensor nodes in 100m * 100M. And the PAN coordinator sends a request for data to sensor nodes every one second. Table 1 shows you simulation circumstances. All packets are transferred in multi-hop. And we assume that the PAN coordinator has not a limit of energy.
ACKNOWLEDGMENT This work was supported by the Ministry of Knowledge Economy, Korea [Industrial Source Technology Development Programs] REFERENCES [1] X. Cheng, B. Narahari, R. Simha, M.X. Cheng, and D. Liu, "Strong Minimum Energy Topology in Wireless Sensor Networks: NP-Completeness and Heuristics,” IEEE Trans. Mobile Computing, vol. 2, pp. 248-256, [2] Errol L. Lloyd and G.Xue "Relay Node Placement in Wiress Sensor network", IEEE Trans. Computer vol 56 [3] J. Pan, Y.T. Hou, L. Cai, Y. Shi, and S.X. Shen, “Topology Control for Wireless Sensor Networks,” Proc. ACM MobiCom ’03, pp. 286-299, 2003 [4] S. C. Ergen and P. Varaiya. Pedamacs "Power efficient and delay aware medium access protocol for sensor networks" IEEE Transactions on Mobile Computing, to appear in 2006. [5] Yunxia Chen, Chen-Nee Chuah, and Qing Zhao "Sensor placement for maximizing lifetime per unit cost in wireless sensor networks" IEEE Milcom 2005 [6] J. H. Chang and L. Tassiulas. "Maximum lifetime routing in wireless sensor networks" IEEE/ACM Transactions on Networking, 12(4):609–-619, 2004. [7] Q. Li, J. Aslam, and D. Rus, "Online Power-Aware Routing in Wireless Ad-Hoc Networks,” Proc. ACM MobiCom ’'01, pp. 97-107, 2001. [8] Y. T. Hou, Y. Shi, and H. D. Sherali. "On energy provisioning and relay node placement for wireless sensor networks" [9] W. Heinzelman, A. Chandrakasan, and H. Balakrishnan, “Energyefficient Communication Protocol for Wireless Micro Sensor Networks,” in Proc. of the 33rd Annual Hawaii International Conf. on System Sciences, 2000, pp. 3005–3014.
TABLE 1 Simulation circumstance Simulator Mac Protocol Routing Protocol Transmission range Terrain Energy model
Qualnet 4.5 802.15.4 LEACH 10 (m) 100 *100 (m) MICAZ
Fig 1 shows you the simulation result. Node 1 is the PAN coordinator and other nodes are sensing nodes. Sensing nodes send data to the coordinator every one second. In common case, all sensor nodes use more energy than our proposed mechanism except PAN coordinator. The reason of this result is relay nodes disperse traffic. So our proposed mechanism is able to become an optimal solution of relay node displacement mechanism. Fig 2 shows you the measured lifetime per unit cost in simulation. We compare our mechanism with common case. V.
CONCLUSION AND FUTURE WORK
In this paper proposed a mean of relay node displacement mechanism in wireless sensor network. Our proposed
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