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  1. 1. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 6, August 2012 A Cooperative Multi-Hop Clustering Protocol for Energy Saving of Mobile Devices P. Narasimhaiah M.Sc (M. Tech), Mrs. S. Vasundra M. Tech. (Ph. D)Abstract— Wireless local area network (WLAN), or IEEE Because of the limited power Bluetooth supports low802.11, has become a most popular because of its sufficient bandwidth of 2mbps for range of 10 meters. This workbandwidth and well-constructed infrastructures. But, a serious presents the idea of using the co-existence of WLAN andproblem of WLAN is its considerable energy consumption. Bluetooth in a single mobile platform to solve the energyMobile devices are driven by limited battery power, so it is consumption problem of WLAN interface.essential to reduce the power consumption due to WLANinterface without degrading its performance. This can be Previous several works used Bluetooth asachieved by using the co-existence of WLAN and Bluetooth in a secondary radio to reduce the energy consumption [3], [4],single mobile platform to solve the power consumption [5]. Mainly Bluetooth is used as a connected channelproblem in WLAN based communication systems. This work is between mobile devices and the WLAN access points (AP).based on Multi-Hop Clustering proposed to increase the life In On-Demand paging [3], and wake on wireless [7],time of network. This protocol selects the cluster head Bluetooth is used as a wake up channel. Bluetooth is alsoconsidering three factors, maximum energy, the number of used as a data communication channel when applicationneighbouring nodes, and distance to the access point. In thispaper, a cluster is a Bluetooth Personal Area Network (PAN), need low data rates to prolong the power off time of thewhich consists of one cluster head and several regular nodes WLAN. This requires the hardware and software.The cluster head acts as gateway between the PAN and the modification to Wireless infrastructures. Clustering makeWLAN and enabling the regular nodes to access the WLAN. the nodes share their WLAN interfaces with each other, andThis paper presents a Cooperative Multi-Hop Clustering Clustering performed periodically in a distributed mannerProtocol, which dynamically reforms clusters according to the based on the energy usage and bandwidth need of nodes.each nodes bandwidth requirement, energy use, and Clustering is performed independent of WLAN APs,application type. This protocol does not require the therefore there is no need to made changes to the existingmodifications of existing wireless infrastructures. This protocol infrastructures.simulated for large network more than 200 nodes. But resultsdemonstrate that, this approach is effective in reducing the Compare to the previous works, this approach ispower consumption of the WLAN. based on Multi-Hop Clustering. Clustering is commonly used in sensor networks for load balancing [10],[12], orKeywords—Bluetooth, bandwidth, communication system, energy efficiency [8], [9], [12]. In this work clustering makeenergy consumption, Multi-Hop. nodes that share their WLAN with each other. A cluster is Bluetooth Personal Area Network (PAN) [13] as shown in I. INTRODUCTON Fig. 1(a), that can consist of one cluster head (CH) and several regular nodes (RNs). CH coordinates the nodesWireless local area network (WLAN) [11], or IEEE 802.11 within the cluster, and forward the packets from PAN to theis well-known because of its well developed infrastructures WLAN APs, and vice-versa. CH keep their WLAN interfaceand sufficient bandwidth. But a serious problem with the on to provide links to the WLAN AP, and allow RNs to useWLAN interface of mobile devices is, it consume more only Bluetooth and turn WLAN interface off in order topower relative to the other devices like processor, memory, save energy. Clustering is performed periodically in adisplay and disk. The relative power consumption of the distributed manner based on the energy usage andWLAN interface depends on mobile devices and it varies bandwidth need of the node.from 5-10% in laptops and, more than 50% in PDAs [4], [6].Mobile devices are driven by limited battery power. It is In this work clustering is performed independentlynecessary to device a solution to reduce the energy of WLAN APs. Therefore, this approach does not requireconsumption of WLAN interface without reducing the any changes to the existing infrastructures. Because of theperformance and modifying hardware and software large difference between the communication range WLANinfrastructures. and Bluetooth, only devices close to the CH can use the low-power radio to communicate CH and RN, and vice- The Bluetooth is mainly designed for low energy versa. On the other hand, in this case most devices are notconsumption, requires only 10% of the WLAN energy [6]. needed to connect CH directly and each device in the cluster 46 All Rights Reserved © 2012 IJARCSEE
  2. 2. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 6, August 2012connected to the CHs indirectly through the other nearby guarantee that node is more than d hops away from thedevices. This increases the range of PAN and most devices leader, where d is a value selected for heuristic. The maincan obtain the benefit of energy saving as shown in Fig. objectives of this protocol are:1(b). 1. Elects cluster heads in such a manner as to favour their re-election in future rounds.. 2. Cluster heads are well distributed. 3. Energy efficiency of wireless network is improved by exploiting Bluetooth. 4. Clusters are dynamically configured to meet the bandwidth need of all nodes. 5. Provide the load balancing among cluster heads to insure a fair distribution among cluster heads. 6. Reduce the transition over heads. A Cooperative Multi-Hop Clustering Protocol simulated for large networks and evaluates the performance. This result demonstrates that Cooperative Multi-Hop clustering protocol is effective in reducing the power Fig. 1(a). A Single-Hop Clustering. consumption of WLAN-based communication system. II. SYSTEM MEODL The mobile devices considered in this paper are popular user terminals like the smart phones. Here mobile device simply referred as a node. The following properties are assumed about the nodes: 1. Each node should capable of measure its energy. 2. Each node has one WLAN interface and one Bluetooth interface. 3. There is at least one WLAN AP in the field. 4. The WLAN AP do not have Bluetooth interface. 5. All Bluetooth interfaces have the same range of communication. 6. Each node must know the total bandwidth need, and free bandwidth of the Bluetooth link. Fig. 1(b). A Multi-Hop Clustering. The main goal of this protocol is to reduce the energy In this approach mobile devices are arbitrarily consumption in wireless networking applications. Tocontrolled by their users, this needs consideration of node achieve this goal design a general clustering protocol. Themobility as well as a large variance of bandwidth need for essential operation in clustering is to select a set of clustervarious applications. However, because all devices have heads from the set of nodes in the network. Cluster headsequal importance, changing the role of CH among all are responsible for coordinating the nodes within the cluster,devices is necessary to distribute the energy consumption. and aggregation of the data from cluster members, and sendNodes also can be turned off at any time and powered again the data to the APs. Clusters are formed to meet the userdepending on the user‟s need, which require the requirements and the following requirements:consideration of unexpected link failure. 1. To minimize the number of cluster heads. This paper presents a distributed Cooperative 2. To minimize the number, and size of the dataMulti-Hop Clustering Protocol. This work started with the structures need.aim of generalizing the clustering heuristics so that a node is 3. Clustering should be completely distributed.either a CH or a regular node atmost d-hops away from the 4. For each cluster the sum of bandwidthCH. A new distributed leader election heuristic proposed to requirements of all regular nodes within the 47 All Rights Reserved © 2012 IJARCSEE
  3. 3. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 6, August 2012 cluster must not exceed maximum data rate of The power consumption of anode using either Bluetooth. WLAN or Bluetooth interface with data transfer rate „r‟ can 5. Communication between CHs and APs is be defined as fallows single-hop. 𝑟 𝑟 6. At the end of the clustering process, each node PW ( r ) = PWA + PWi (1— ) (1) 𝑅𝑊 𝑅𝑊 should be either cluster head or atmost d hops 𝑟 𝑟 away a cluster head. PB ( r ) = PBA + PBi ( 1— ) (2) 𝑅𝐵 𝑅𝐵 7. Clustering should be efficient in terms of processing complexity and message exchange. Where RW is rate of WLAN and RB is rate of Bluetooth. 8. Re-elects CHs when possible. 9. Provides load balancing among cluster heads. By monitoring the idle time of WLAN and Bluetooth channels during the period of time T, each node III. THE MULTI-HOP COOPERATIVE CLUSTERING can estimate its FreeBWW and FreeBWB using a moving PROTOCOL OPERATION average with weight α ∈ [0, 1] as follows: 𝑇𝑊Several Multi-Hop Clustering algorithms are there. Among FreeBWW = α FreeBWW + (1—α) RW—R mar (3) 𝑇them, the authors of [2] propose a heuristic to form a d-dominating set. Within the cluster messages are exchanged 𝑇𝐵 FreeBWB = α FreeBWB + (1—α) R B — R mar (4) 𝑇among the nodes via Bluetooth. When a node is newlybooted up, it becomes a CH and uses the Bluetooth for Where RW and, RB are the transmission rates of WLAN,advertising its resource information periodically (say, every Bluetooth respectively. Rmar is a predefined constant used to200 ms). The advertisement message contains the clustering maintain the free bandwidth to be slightly lower than thecost, amount of bandwidth available for packet forwarding, actual available bandwidth.ID, and the network address. Each node manages a set SCH,which stores the information advertised by neighbouring Each CH waits for join request from other nodesCHs. The nodes wait for a specific amount of time for CH for short time (say, 1second). The join message of a nodeannouncement (cluster joining offer) during the cluster includes the amount of required bandwidth, up on receivingformation phase shown in Fig. 2. Hearing upon these offers, a join message, the CH compares its free bandwidth with theeach node selects the best-offer using the information required band width. If the CH has a sufficient amount ofreceived from the CH. The nodes that lie outside 1-hop free bandwidth for the sender, it will accept the request.range of the CHs cannot hear any announcement directly.They, however , receive offers from existing CMs to join a When there is no request, the CH counts thecluster. number of RNs within the cluster. If there is at least one RN, then CH keep continuous its current role. This allows the RNs to select their next CH by themselves, which is necessary for network stability. If the CH has no RNS, then for saving energy it select the next CH by itself, The CH selection process of Multi-hop Clustering cooperative protocol executes the following Max-Min D-Cluster Formation procedure. Each node initiates 2d rounds of flooding. Each node maintains a logged entry of the results of each flooding round. The rounds are segmented in to the 1st d rounds and the 2nd d rounds. The 1st d rounds are a flood max to propagate the largest node Ids. After completion of the 1st d rounds of flooding the 2nd d rounds of flooding begin, using the values that exist at each node after the 1st d rounds. The 2nd d rounds of flooding are a flooding to allow the smaller node Ids to reclaim some of their territory. After completion of 2nd d rounds each node looks at its logged entries for the 2d rounds of flooding. The following rules explain the logical steps that each node runs on the logged entries. Fig. 2. A Multi-Hop Cluster Formation. Rule 1: Each node check to see if it has received its own original node Id in the 2nd d rounds of flooding. If it has then it can declare itself as a CH 48 All Rights Reserved © 2012 IJARCSEE
  4. 4. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 6, August 2012 and skip the rest of the phase, otherwise proceed to uniformly dispersed into a 70×70 meters field. Because it is rule 2. unrealistic to assume that all 100 nodes have the same purpose of prolonging the group life time and consider Rule 2: Each node looks for node pair, once a node individual networking in this solution. An ordinary WLAN has identified all node pairs; it selects the minimum AP is located at (0, 0). Here assume that the WLAN and node pair to be the CH. If node pair does not exist Bluetooth communication ranges are 100 and 10 meters for a node then proceed to rule 3. respectively. Therefore, all nodes can communicate with the access point anywhere in the field using their WLAN Rule 3: Elect the maximum node Id in 1st d rounds interface. f flooding as the CH for the node. A. EFFECT OF NODE DENSITY ON ENERGY Floodmax- Each node locally broadcast its winner value to all of its 1-hop neighbours. After all the Vary the number of nodes in the field from 10 to 100 to neighboring nodes have been heard from for a study how Cooperative Multi-Hop Clustering protocol single round, the node chooses the largest value works. Fig. 3. Show the effect of node density on among its own winner value and the value communication energy consumption. In Cooperative Multi- received in the round as its new winner. This Hop Clustering protocol energy consumption decreases as process continues for d rounds. the node density increases, because more nodes can be grouped into a cluster and share WLAN interface. A node Floodmin-This follows Floodmax and also last d belongs to a larger cluster can spend more time as RN. rounds. It is the same as floodmax except a node chooses smallest rather than the largest value as its new winner. Node Pairs: A node pair is any node Id that occurs at least once a winner in both 1st and 2nd d rounds of flooding for an individual node.The heuristics has three logical stages, first the propagationof larger node Ids via floodmax, second propagation ofsmaller node Ids via floodmin, and third the determinationof cluster heads. The proposed heuristic provides an optimalsolution, when largest nodes Id are spaced d distance apart. It is necessary to rotate the CH role regularly tobalance the energy consumption among all nodes. For this,each RN has a timer, RN-timer, which expires in every TRN Fig. 3. The effect of node density on the communicationseconds. When timer expires, the RN calls the CH selection energy consumption.process to select its next CH. Fig3. Illustrate the relation between the node density energy Due to the mobility of nodes, the distance between consumption. It shows that as the number of nodes increasesthe Ch and RN and its neighbour becomes longer than the in the cluster, energy consumption decreases compare to theBluetooth range, and if the inbetween nodes turned off the single Hop. As in Cooperative Multi-Hop Clustering as theBluetooth. In these cases, the RN immediately changes its number of nodes increases from 10 to 100 the energyCH. consumption decreases to 57%. The nodes considered here have a large variety of B. EFFECT OF NODE DENSITY ON THROGHPUTapplications resulting in time-varying bandwidthrequirements with huge variations. Therefore, Nodes should As shown in Fig. 4. the number of nodes in the cluster areselectively use either Bluetooth or WLAN depending on the increases, the through put decreases. But here in comparisonrequirement. If the RN bandwidth requirement is not to the previous Single-Hop system in our Multi-Hop systemsatisfied by the CH and it finds new CH. throughput increases slightly.IV. SIMULATION AND PERFORMANCE EVALIATIONTo evaluate the performance of Cooperative Multi-HopClustering Protocol for large scale mobile networks viaextensive simulation. Here assume that 100 nodes are 49 All Rights Reserved © 2012 IJARCSEE
  5. 5. ISSN: 2277 – 9043 International Journal of Advanced Research in Computer Science and Electronics Engineering Volume 1, Issue 6, August 2012 Fig. 4. Effect of Number of nodes on throughput. C. EFFECT OF PACKET DELAY Fig. 6. Effect of number of packets on energy consumption.As shown in the Fig. 5. as the number of nodes in thecluster increases, the number of packets to be send also V. CONCLUSION AND FEATUREWORKincreases. As the number of packets increases the packet In this paper presented Cooperative Multi-Hop Clustering, adelay also increases. But in comparison to Single-Hop in energy efficient multi radio mobile network. CooperativeMulti-Hop system the packet delay is less. Multi-Hop Clustering uses Bluetooth to reduce the power consumption of WLAN in mobile devices. It dynamically reconfigures the cluster based on the bandwidth requirement of application without degrading performance. The Cooperative Multi-Hop Clustering uses the Max-Min D- Cluster formation for cluster head election. The Cooperative Multi-Hop clustering also provides load balancing among cluster heads and efficient in terms of processing complexity and message exchanges. We can easily extend to other interfaces such as WiMAX/Bluetooth. VI. REFERENCES [1] Jong-Woon Yoo, Kyu HoPark, “Cooperative Clustering Protocol for Energy Saving of Mobile Devices with WLAN and Bluetooth Interfaces”, IEEE Transactions on Mobile Fig. 5. Effect of number of packets on packet Computing, VOL. 10, NO.5, APRIL 2011. delay. [2] A. D. Amis. R. Prakash, T.P. H. Vuong and D. T. Hyunh, “Max-Min D-Cluster Formation in D. EFFECT OF PACKET DELAY Wireless Ad hoc Networks”, Proc. IEEE Infocom, PPP .32-41, 2000.As the number of nodes in cluster increases the number of [3] Y. Agarwal, C. Schurgers, and R. Gupta,packets to be sends also increases. As the number of packets “Dynamic Power Management Using on Demand Paging for Networked EmbeddedSystems,” Proc.increases the total energy consumption increases. As shown Asia South Pacific Design Automation Conf., vol.in the Fig. 6. in comparison to the Single system in our 2, pp. 755-759, 2005.Multi-Hop system energy consumption is reduced by 35%. [4] T. Pering, Y. Agarwal, R. Gupta, and R. Want, “CoolSpots: Reducing the Power Consumption of Wireless Mobile Deviceswith Multiple Radio Interfaces,” Proc. ACM MobiSys, pp. 220- 232,2006. [5] Y. Agrawal, T. Pering, R. Want, and R. Gupta, “SwitchR: Reducing System Power Consumption in a Multi-Client, Multi-Radio Environment,” Proc. IEEE Int‟l Symp. Wearable Computers, pp. 99- 102, 2008. 50 All Rights Reserved © 2012 IJARCSEE
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