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  1. 1. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029 Qualitative Evaluation Of Cross-Layer Protocol For Proficient Communication In Wireless Sensor Networks N.Venkateswaran *, V.Kishore** *(Department of Computer Science & Engineering, Jyothishmathi Institute of Technology and Science,JNT University,Hyderabad,AP,INDIA) ** (Department of Computer Science & Engineering, Vaageswari, JNT University, Hyderabad, AP, INDIA)ABSTRACT This paper provides a qualitative analysis its energy efficiency has better performance thanof cross-layer protocol for proficient typical 802.11 based MAC protocols [1], S-MAC hascommunication in wireless sensor networks. The high delay problem in many-to-one (or few) multi-simplified and energy efficient protocol should be hop communication pattern of WSNs and it stilldesigned in order to maximize the network brings about energy waste due to the fixed duty cyclelifetime because of its inflexible resource scheme. TMAC is a timer based protocol inspired byconstraints, ultra power limitation, and tiny S-MAC and its duty cycling can allow T-MAC toembedded devices. We propose an enhanced adjust to fluctuations in the dynamic network traffic.cross-layer protocol for proficient communication Although, T-MAC shows better results underin wireless sensor networks by integrating variable traffic loads, it still undergoes the samemedium access control and routing protocol. Our delay and energy wastage problems as S-MAC. As inproposed protocol utilizes a synchronous medium the case of MAC protocols, the several routingaccess control scheme by using the adaptive duty protocols, such as Ad hoc On-demand Distancecycling technique to improve energy efficiency Vector (AODV) [4] and Dynamic Source Routingand solve long end-to-end delay problem. We also (DSR) [5], have been developed and suggested fordesign a tree-based energy aware routing WSNs. These protocols are on-demand routingalgorithm to prolong the network lifetime in our algorithms in which routes are only discovered whenprotocol. Simulation results show that the they are actually needed. Thanks to ultra energyproposed protocol outperforms other existing limitation and inefficient repairing scheme againstalgorithms in terms of energy efficiency and data delivery in dynamic network topology changeslatency. of WSNs, these routing protocols cannot be appropriately adapted for WSNs. In this paper, weKeywords - cross-layer protocol; duty cycle; propose an Enhanced Cross-Layer Protocol, soenergy efficiency; MAC; wireless sensor network; called ECLP, for energy efficiency in wireless sensor networks by integrating MAC and routing protocol.I. INTRODUCTION For reducing energy wastage due to idle listening and Research in wireless sensor networks. overhearing and for alleviating long delay, ourUnlike general purpose computer networks, these proposed protocol uses an adaptive duty cyclenetworks are primarily designed with a specific scheme with the adaptive time-out and RRTSsensing task in mind. Moreover, energy is a prime (Reservation Request-to-Send). Moreover, a treeconcern, since the nodes operate with exhaustible based energy aware routing algorithm is developed inbatteries; and the quality of data and the network’s ECLP to maximize the network lifetime but minimizelifetime depend on the power consumption of the the control overhead required for data II. THE PROPOSED PROTOCOL In recent years, since the ultra power and ECLP is an integrated MAC and routingresource limitation of wireless sensor networks protocol for energy efficient data delivery to the sink(WSNs), there has been a great interest in the study node with adaptive duty cycling and tree-basedof maximizing the lifetime of WSNs and a lot of energy aware routing algorithm while minimizingresearch efforts have been made to improve energy overhead cost and latency. The basic MAC operationefficiency in medium access control (MAC) and of ECLP is based on AD-MAC [7][8] in which werouting protocols for WSNs. S-MAC [2] and T-MAC have previously proposed. In this paper, we have[3] have been proposed for WSNs to decrease the extended AD-MAC to enhance the performance ofwasteful energy expenditure and they share the MAC by adopting the adaptive time-out schemeschedule information that specifies the cycle of active considering both energy efficiency and latency. Theand sleep period, called duty cycle, through a SYNC operation of ECLP protocol will be particularlyor beacon packet to improve energy efficiency. While described in the following subsections. 1021 | P a g e
  2. 2. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029A. Network Model R_costi = ET_i / Er_i α (1 – perr_i)β (1) A wireless sensor network (WSN) ismodeled as an directed graph G(V,E), where V = S where, ET i is the unit packet transmission∪ N is the number of sensor nodes in the network, S is cost of node I (e.g., ET = Erecv + Etrans, Erecv is thethe number of sink nodes, N is the number of sensor consumed energy for packet reception and Etrans isnodes, and E is the number of links in the network. the consumed energy for packet transmission), Er i isThere can be multiple sink nodes in WSNs but each the residual energy of node i, and perr i is the packetsensor node is assigned to only one sink node since error probability of the link between node i and j.asymmetric communication paradigm generally Also, α and β are nonnegative weighting factors foroccurs in many nodes-to-one sink communication setting the relative between link cost and node cost inpattern. We assume that the network comprises the range [0, 1]. Calculating and choosing thisrandomly distributed nodes with here. We also minimum routing cost function (1) is equivalent toconsider that all the sensor nodes have the same choosing a minimum cost path from node i to thetransmission range and initial power capability. sink node. This routing cost function is fully localized, distributed and computed with only itsB. Tree-based Routing Algorithm neighbor nodes from a node. In ECLP, a tree-based energy aware routing In ECLP, there are three steps for choosingalgorithm is executed. It is formed by the SYNC and the next relaySY NCreply packet. node (parent node) for routing destined for In synchronous MAC protocols, such as S- the sink node. First, a node checks its residualMAC and TMAC, the SYNC packet is used only for energy. If the residual energy of the node is less thansynchronization. However, the SYNC of ECLP is the energy threshold of its Danger state (ThD), whichapplied to not only routing configuration and implies that the node has no more energy to takemanagement but also synchronization. The SY more transmission jobs with other nodes, the nodeNCreply of ECLP is exploited to confirm the tree simply discards the received request. Secondly, thepath configuration and recognize the total number of node received SYNCs from its neighbor nodes checkshops from the sink node on each branch node of the the r_lth in the SYNCs. Then, it chooses one neighbortree network. In the following subsections, the node having the smallest value of r_lth in the SYNCrouging algorithm of ECLP as the next relay node. Finally, if there are theis presented in more detail. multiple nodes with the same r_lth value, it next1) Determining the Next Forwarding Node: To compares the r cost in the SYNCs among the multipleselect the next forwarding node (parent node) for nodes. Then, it selects one neighbor node with thetree-based energy aware routing path to the sink minimum value of r cost as the next relay node. Afternode, ECLP uses the routing cost supplied with the next forwarding node (parent node) isinformation such as transmission cost (link cost) and determined, it adds the chosen relay node to itsenergy cost (node cost) together. A routing algorithm neighbor management table with the r_lth value. Theusing only hop count cannot optimize the energy smallest value of r_lth means the minimum hopconsumption across the network, especially in non- count needed to reach the sink node. The minimumuniform traffic conditions. Thus, maximizing the value of r_cost implies the minimum energy cost fornetwork lifetime is the primary goal of our algorithm increase energy efficiency. Routing algorithm basedand we adopt the routing cost function, r_cost with on global information may provide the optimizedr_lth. In the case of WSNs, the resultant path with path from the source to destination pair, but it canmany short-range links may perform worse than a result in long configuration latency and highpath with fewer long-range links in terms of latency overhead cost for routing management. Based on thisas well as energy consumption. This is because the local information, ECLP may not provide the optimalpath with many short-range links would cause more path but it can select the next forwarding nodelink errors that result in more retransmissions [6]. In (parent node) through which the overall energy costthis case, the link layer retransmissions on a specific destined for sink node is minimized. Therefore,link essentially ensure that the transmission energy ECLP can prolong the network lifetime and reducespent on the other links in the path is independent of the overhead cost.the error rate of that link. In ECLP, the link error rate 2) Path Set-up Phase: In ECLP, the SYNC and SYparameter is employed as the link cost and the energy NCreply packet are used for setting-up the tree-basedcost parameter provided by the packet energy aware routing path in the network. The SYNCreceiving/transmitting energy and residual energy is of ECLP has five new fields compared with theexploited as the node cost together. Since the number SYNC in SMAC: {r_lth, r _cost, thresholds, parent,of transmission on each link is independent of the status}, indicating the sensor node’s routing length,other links and is geometrically distributed, the its routing cost, its energy thresholds, its parent noderouting cost of node i, r_costi is defined in ECLP as in the branch tree, and its status. The SY NCreply offollows: ECLP is exploited to confirm the tree path configuration and recognize the total number of hops 1022 | P a g e
  3. 3. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029(hop count) from the sink node on each branch node their neighbor nodes. The node received the SYNCsof the tree network. The SY NCreply of ECLP is similar rom its neighbor nodes first checks the r_lth values into the SYNC of ECLP but it has two different fields the SYNCs and selects the node with the r_lth valuefrom the SYNC of ECLP: {r_lthtotal, r_cost, of 1 as its parent node. If there are multiple nodesthresholds, sink, status}, indicating the total number with the r_lth of 1, the node next checks the r_costof the branch tree’s routing length (hop count of the value in the SYNCs among them. Then, it selects oneleaf node), its routing cost, its energy thresholds, its node with the minimum value of r_cost as its parentroot node (sink node) in the branch tree, and its node. After its parent node is found, it adds its parentstatus. The length of all new fields is one byte node to its neighbor management table with the r_lthrespectively, except the length of the status field is of 1 for primary routing. Moreover, it adds the nodestwo bits. Thus, the status field shows four states, which has the same r_lth of 1 but has the different{intermediate node, (larger) value of r_cost or which has the different leaf node, Danger state, Emergency state}. (larger) r_lth value to its neighbor management tableIntermediate node and leaf node indicate that the with r_lth of 1 for alternative routing. Any node actsnode plays the part of the intermediate node and the on only the first SYNC with the same ID and ignoresleaf node on the branch tree. Danger state means the any subsequent SYNCs. In addition, the noderesidual energy of a node is less than the energy calculates its own r_cost values and stores its ownthreshold of its Danger state (ThD). So, the node in r_cost in the SYNCs. Afterward, it increments theDanger state does not participate in data transmission r_lth value in the SYNC by one (e.g., the r_lth valuejobs with its neighbor nodes. It just sends its own of 2) to update and broadcasts the SYNC to itssensed data to the sink node. Emergency state neighbor nodes like the first step. This r_lth updatesignifies process is repeated and the local routing information the broken node has occurred and the with the parent-to-child node pair (to the sink node)routing path has lost. Thus, the local path recovery is madephase is executed in this case. The local pathrecovery phase will be described in the followingsubsection. The thresholds field is comprised of twovalues of the energy thresholds, ThR and ThD. ThR isused for the adaptive time-out mechanism. When theresidual energy of a node is larger than the energythreshold of its Relief state (ThR) in the SYNC packet,the node sets its adaptive timer (TA) to Tmin forprolong energy efficiency. The more detaildescription of this function will be explained inSection II.C. ThD is used for the participation of anode’s data transmission and local path recoveryphase. ThR and ThD are pre-determined in the SYNCand they are dependent on the applications of WSNs.(e.g., ThR = 50% of the initial node energy, ThD =15% of the initial node energy) Initially, all nodes arerandomly deployed and have both the r_lth of 255and the r cost of 255 in the SYNC while the sink nodehas the r_lth of 0 and the r_cost of 255 in the SYNC.Actually, r_lth and r_cost are one byte, respectively Figure 1. Tree-based energy aware routing algorithmin the SYNC so that they have the maximum value of in ECLP255, respectively. In the first step, the routing pathconfiguration is developed between the sink node and in the neighbor management table. In theits neighbor nodes. The sink node periodically final step, a leaf ode sends the SY NCreply to the sinkbroadcasts the SYNC to its neighbor nodes with the node through each node on the branch tree in order toinitial r_lth and r_cost value. When the neighbor confirm the tree path configuration and recognize thenodes receive the SYNC from the sink node, they first total number of hops (hop count) from the sink nodeadd the sink node to their neighbor management table on each branch tree. The more detail description ofwith the r_lth of 0 as their parent node. Secondly, this function will be presented in Section II.C.they calculate their own r_cost values and store them Consequently, the tree-based energy awarein the SYNCs. Afterward, they increment the r_lth routing path configuration is completely establishedvalues in the SYNCs by one to update. Then, they from the sink node to leaf nodes across the wholebroadcast the SYNCs to their neighbor nodes. In the network. In the final step, Note that only localsecond step, the routing path configuration is information and neighbor managementdeveloped between the nodes with the r_lth of 1 and 1023 | P a g e
  4. 4. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029table is utilized in ECLP and the global tree structure neighbor management table, another path recoveryis not maintained by any node. Fig. 1 shows one mechanism is performed. A PERR (Path ERRor)example of initial path configuration in ECLP. The control packet is used for the path recovery in ECLP.tree-based path configuration process with the SYNC The PERR is almost same as a SYNC of ECLP and itand SY NCreply is depicted in Fig. 1. In Fig. 1, the indicates the PERR’ sender lost the link. Thesolid lines mean the primary difference between the PERR packet and SYNCrouting path and the dashed lines signify the packet is to point out the lost node’s ID in the field ofalternative routing path. Also, the solid-circles mean the control packet. If the broken node is only oneintermediate nodes parent node destined for the sink node, the child nodeand the dashed circles imply leaf nodes in the branch changes its state to Emergency state of the statustree. Note that during the tree-based energy aware field in the PERR indicating the broken node’s IDrouting path construction. ECLP only requires each and broadcasts the PERR packet. In Emergency state,node to broadcast once to avoid wastefully the nodes cannot send any data and they have theoverlapping SYNCs. r_lth of 255. In this case, only SYNCs from other neighbor nodes can release this Emergency state3) Data Forwarding Phase: ECLP is a kind of table since the SYNCs from others have reliable the treedriven approach and the routing table is established routing information with r_lth, r_cost and parent the path set-up phase as the neighbor management Then, the nodes received PERRs compare their r_lthtable. In the neighbor management table, only local values with the r_lth of PERRs and check theirinformation from SYNC packets between a node and residual energy. If the r_lth value of the PERR isits neighbor nodes is utilized. The tree-based routing larger and their residual energy is larger than thetable indicating the parent and child node pair energy threshold of its Danger state (ThD), the PERRinformation is exploited for data delivery from a is ignored and the node having the larger r_lthsensor node to the sink node. Once the routing tree broadcasts the SYNC with its tree routing table. Thehas been built, a node which has data to the sink node node having the larger r_lth implies that it has thejust sends them to its parent node and the data are alternative routing path (parent node) destined for thefinally delivered to the sink node through the sink node. Therefore, the new tree routing path isconstructed routing tree. If the residual energy of the found and the broken path is recovered in the end.node is less than the energy threshold of its Danger Otherwise, in other words, if the r_lth value of thestate (ThD), which implies that the node has no more PERR is smaller or the node’s residual energy is lessenergy to take part in for more transmission jobs with than the energy threshold of its Danger state (ThD), itother nodes, the node simply discards the received means that the nodes received the PERR have lost therequest. Then, the node changes its state to Danger routing path to the sink node likewise.state of the status field in the SYNC and it sends theSY NCreply packet to the sink node in order to indicate while (data forwarding is needed) doit becomes the leaf node on the branch tree from the 1 if (node i finds an upper node’s link lost)sink node. In other words, the node (leaf node) only 2 if (node i has another (alternative) uppersends its own sensed data to the sink node. node _ receives a new SYNC) /* Problem Solved */4) Path Recovery Phase: Due to a node’s mobility 3 turns off Emergency state;or breakdown, when a link on the active branch route 4 sends a SYNC to its neighbor nodes;is broken, the node tries to locally repair the broken elselink. When a child node starts to send data to its /* Repair the lost link */parent node, it first sends a RTS to its parent node. If 5 sends a PERR to its neighbor nodes;the child does not receive a CTS from its parent node 6 turns on Emergency state;for sending a RTS three times, the child node can be 7 waits a SYNC from its neighbor nodes;aware that its parent node has been lost. Then, the 8 if (node j receives a PERR)child node begins the local path recovery process. 9 if (r lth of itself < r lth of PERR &&First of all, if the child node has another parent node the residual energy of node j is largerdestined for the sink node in its neighbor than the energy threshold of node j’smanagement table (as alternative routing path), it Danger state (ThD)simply changes the new parent node and tries to send /* Problem Solved */data to the new parent node. At this moment, the Step 3;r_lth value of the broken node is edited to 255 else(namely, unreachable) in the neighbor management /* Repair the lost link */table. In this case, there is no additional signal Step 5;overhead and fast path recovery is possible. done However, if there are no alternative parent nodes Figure 2. Local path recovery algorithmin the 1024 | P a g e
  5. 5. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029In the same manner, they edit the r_lth value of the the next forwarding node. A node received the FRTSbroken node to 255 in their neighbor management packet should be awake by the next time totable and they can recognize which node has gone communicate with the prior node. It resultsfrom the broken node’s ID designated in the PERR. in wasteful energy consumption. Secondly, the RRTSThen, they also try to find the alternative parent node packetdestined for the sink node repeatedly. If it succeeds, includes the value of a new time-out so thatthey broadcast the SYNC and the lost path finally has this new value can be adapted to the next forwardingbeen recovered. However, if they cannot find the nodes to change a time-out threshold (TA) foralternative parent node, they go to the Emergency reducing delay for the next data communication. Thisstate with the r_lth of 255 and broadcast PERRs to technique can adapt to traffic fluctuations and havetheir neighbor nodes again until they obtain the good influence on dealing with trafficalternative parent node in a certain period. If they fail condition for shortening repair the lost link in the certain period, they stop To solve the early sleeping problem whichthe path recovery scheme and wait the initial path was explained in T-MAC, the interval TA must beconfiguration process by the sink node. During this long enough to receive at least the start of the CTSsituation, any node in the Emergency state stops data packet and the decision of TA is presented as followsdelivery and store them. When the node obtained the [3]:new alternative parent node to the sink node, it TA > Ct + R + T (2)directly broadcasts a SYNC to update the new path where, Ct is the contention interval, R is theconfiguration. After all nodes in the Emergency state length of a RTS packet, T is the very short guardreceive the SYNC, they change their old paths into the time. In ECLP, we adopt the adaptive time-outnew detour path to reach the sink node and the tree scheme based on r_lth that implies the hop countrouting is finally reconfigured in the tree network. (distance) from the sink node. In short, the adaptiveThe basic local path recovery algorithm is presented timer, TA is employed in proportion to r_lth in ECLP,in Fig. 2. namely, the smaller the r_lth, the smaller value of the timer (TA). It means that the nodes closer to the sinkC. Adaptive Synchronous MAC Scheme node have the larger values of the timer (TA) and they ECLP performs the adaptive synchronous have longer waiting time for data delivery. ThisMAC scheme. In ECLP, the active period ends when scheme can decrease the end-to-end delay but spendno activation event has occurred for a time-out period more energy. So, this algorithm is only performed(TA). In other hands, if there are no data to send or when the residual energy of a node i is larger than thereceive until the timer’s expiration, the node goes to energy threshold of its Relief state (ThR) in the SYNCsleep to reduce the unnecessary time and energy packet. Initially, the sink node broadcasts a SYNCwasted in idle listening. The MAC operation of packet to nodes in the network and the tree-routingECLP is based on AD-MAC (Adaptive Duty cycling path is built up. Nodes can obtain the distance (hopsynchronous MAC) [7][8] and it is enhanced by count) from the sink node from the r_lth value in theusing RRTS (Reservation Ready-to-Send) and the SYNC. However, they cannot know the total hopadaptive time-out mechanism in ECLP. ECLP allows count of the branch tree. If thenon-intended recipients to avoid overhearing byreturning to sleep immediately when they catch thecontrol packets such as a RTS, CTS, and RRTS. Inunidirectional multi-hop communication pattern fromnumerous nodes to the sink, the per-hop latency canbe increased. This long latency problem can besolved by using a RRTS packet with the adaptivetimer (TA) to adapt traffic conditions in ECLP. TheRRTS packet is similar to the FRTS (Future Requestto Send) packet in T-MAC [3] but there are twodifferences. First, the RRTS packet lets other nodesknow there are remaining data to deliver. If a nodeoverhears a CTS packet destined to another node, itimmediately sends a RRTS packet to the nextforwarding node. The RRTS packet contains theinformation about the duration of data Figure 3. Adaptive duty cycle scheme in ECLPcommunication so that the node received the RRTSpacket can go to sleep until the previous data total hop count from the sink node and atransmission is completed. Then, it wakes up and node’s hop count information on the branch tree isreceives data from the backward node (child node). recognized, the node can set up the adaptive timerIn T-MAC, if a node overhears a CTS packet (TA) in proportion to the hop count. The procedure ofdestined to another node, it sends a FRTS packet to acquiring the total hop count value is the following. 1025 | P a g e
  6. 6. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029After receiving the SYNC for the first time, a node i Assuming that node 1 sends data to route node 4sets up its timer to Ti. Ti counts down when the through node 2 and node 3, in other words, the tree-channel is idle. When the timer Ti times out, the node based routing path has already been constructed andi increases its r_lth (hop count) by one and broadcasts data are destined for the sink in the end, node 1the SYNC. If a node k receives a SYNC from node i operates as typical contention-based MAC protocols.indicating that its parent node is node k, then k marks When node 3 overhears a CTS packet from node 2, ititself as a intermediate node. Otherwise, the node knows the next forwarding node (parent node) itselfmarks itself as a leaf node. This process continues so that it can go to sleep until finishing the previousuntil each node broadcasts once. If a node becomes a data transmission. Afterward, node 3 directly initiatesleaf node, it signifies its r_lth is the total hop count data transferring unlike typical contention-basedfrom the sink node in the branch tree. Then, a leaf MAC approaches. That is, node 3 directly sends anode sends the SY NCreply to the sink node through CTS packet to node 2 after overhearing an ACKeach node on the branch tree to let them know the packet from the previous node, node 2 and thentotal hop count (r_ lthtotal) of the branch tree. Finally, receives data from node 2. This mechanism reduceseach node from the sink node and leaf nodes can the overhead cost of control packets and alsoperceive the total hop count (r_ lthtotal) from the sink improves energy efficiency compared to S-MAC andnode and their hop count. Afterward, each node on T-MAC. On the other hand, when node 3 overhears athe branch tree sets up the adaptive timer, (TA) in CTS packet, it immediately sends a RRTS packet andproportion to this information. The adaptive timer of goes to sleep until the previous data communicationnode i, (TA i) is expressed in ECLP as follows: completion. Node 4 can recognize there are data destined for itself and the duration of the { Tmin + γ(Tmax − Tmin) × (1 – r_ communication so that it can go to sleep until lthi+1 / r_lthtotal), i ≤ r lthtotal − 2 completing the previous data transmission. Note thatTA_i = (3) when node 4 wakes up, it directly sends a CTS packet Tmin, like the previous procedure. Consequently, this otherwise mechanism enhances energy efficiency and alsowhere, Tmin = Ct + R + T, Tmax = Duty cycle in the decreases the per-hop latency and the controlSYNC packet, γ is the proportional constant in the overhead cost as well.range [0, 1] to alleviate energy consumption. Ingeneral, the leaf node and its parent node do not need III. PERFORMANCE EVALUATIONto set up the adaptive timer because these two nodes The ECLP was implemented in ns-2 [9] toare the start point in the multi-hop data validate and evaluate the performance of thecommunication from the leaf node to the sink node. proposed protocol in comparison with IEEE 802.11So, the leaf node and its parent node just set up their MAC and AODV/DSR routing protocols pair and S-timer to Tmin. γ is used for reduce the impact of the MAC and AODV/DSR protocols pair. Theadaptive timeout mechanism for expand energy simulation was carried out with 20 or 50 nodes andefficiency. Note that this algorithm is only randomly chosen one node moved away in everyaccomplished when the residual energy of a node i is Parameter Valuelarger than the energy threshold of its Relief state Number of nodes 20 or 50 nodes(ThR) in the SYNC packet. It results in minimizing Data transmission speed 20 kbpsenergy wastage of the adaptive timer. As we have Transport layer UDPdiscussed, the relationship between energy efficiency CBR (Constant bit rate) 2 ∼ 0.02 packet/secand latency is trade-off so it depends on the PHY (Physical layer) IEEE 802.11applications or requirement of WSNs. However, this Antenna Unit antenna Unit antenna rangeadaptive time-out mechanism with the energy range 36 mWthreshold (ThR) and γ can improve the MAC Energy consumption in 14 mWperformance of ECLP in terms of both energy transmitting 14 mWefficiency and latency. Furthermore, if a node Energy consumption in 0.15 μWoverhears a CTS packet from its child node receiving 20 frames(backward node) or receives a RRTS packet from its Energy consumption in 50%child node, the node goes to sleep until the active state 0 ∼ 0.25completion of the previous data transmission and Energy consumption inthen it wakes up and directly sends CTS to receive sleep statedata from its child node. In ECLP, the tree routing SYNC packet cyclepath has already been set up so that this mechanism Duty cycle in S-can be executed and useful to reduce the delay of MAC/ECLPdata transmission as well as the control overhead Link error ratecost.Fig. 3 briefly shows the adaptive synchronous MAC Table I : SIMULATION PARAMETERSoperation of ECLP compared with S-MAC. experiment. This method was considered in order to evaluate mobility effect. In our evaluation, the uncast 1026 | P a g e
  7. 7. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029traffic and asymmetric communication is considered,like in many nodes-to-one sink traffic pattern. Also,energy consumption by the radio turn on/off ismainly focused and not considered by processing orsensing data in our experiment. The average energyconsumption is the sum of the average energyconsumption in each state: transmitting, receiving,idle listening and sleep respectively. In transmittingand receiving state, data packets and control packetsof MAC and routing are included. The basicsimulation parameters are shown in Table I.A. Energy Consumption In ECLP, the average energy consumption isthe sum of data transmitting, receiving, idle listeningand sleep state per each node. Therefore, the average Figure 4. Average energy consumption with 20 nodesenergy consumption of IEEE 802.11 based protocolsisE802 11 = Etrans + Erecv + Eidle (4) Where, Etrans is the average energy spent fortransmitting data and Erecv is the average energy spentfor receiving data. Also, Eidle is the average energyspent for idle listening and Esleep is the average energyspent for sleep period. In S-MAC and ECLP, dutycycling technique is utilized for reducing unnecessaryenergy wastage caused by idle listening. The averageenergy consumption of S-MAC and ECLP isESMAC/ECLP = Etrans + Erecv + Eidle + Esleep (5) Figure 5. Average energy consumption with 50 nodes Fig. 4 and Fig. 5 show the average energyconsumption with different number of nodes and It uses only local SYNC packets for tree-varying packet rates. IEEE 802.11 based MAC based energy aware routing path configuration andprotocols typically waste unnecessary energy because management by exploiting r_lth, r_cost andof idle listening. This approach always turns on its thresholds metrics. Consequently, ECLP outperformsradio to wait data transmission and reception. In much better than both S-MAC based protocols andaddition, with low mobility and node density, the IEEE 802.11 based consumption of DSR and AODV is similar.On the other hand, S-MAC uses the duty cycling B. End-to-End Delaytechnique to reduce energy wastage caused by idle Fig. 6 and Fig. 7 show the average end-to-listening so that S-MAC based protocols (DSR and end delay with different number of nodes and varyingAODV) have better energy efficiency than IEEE packet rates. In our simulation, AODV slightly has802.11 based approaches. In ECLP, however, the less delay and provides better performance than DSR.adaptive synchronous MAC scheme effectively However, the relative performance of both protocolsexecutes the adaptive duty cycling by using the RRTSand adaptive timeout mechanism with energythresholds. ECLP also decreases the control overheadcost and idle listening. Moreover, 1027 | P a g e
  8. 8. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029with respect to delays is very similar.Figure 6. Average end-to-end delay with 20 nodes Figure 8. Control overhead cost C. Control Overhead Cost The Control overhead cost is defined as the energy spent for control packets from MAC and routing protocol which are MAC signals (SYNC, SY NCreply, RTS, CTS, ACK, RRTS) and routing signals (RREQ, RREP, RERR, PERR), except data. The cumulated control overhead cost is shown in Fig. 8. In Fig. 8, the simulation is performed with randomly deployed 20 nodes. The green bar means MAC signaling overhead cost, the red one depicts ARP signaling overhead cost, and the blue one describes routing overhead cost. The control overhead of MAC generally occupies much larger than other parts. The averaged results indicate that the control overhead in IEEE 802.11 based AODV/DSR protocols is much larger than that of ECLP. The reason why ECLP hasFigure 7. Average end-to-end delay with 50 nodes much smaller the control overhead cost than that of other schemes is that first, ECLP is the integrated In general, the duty cycling schemes can protocol by combining MAC and routing protocol.improve energy efficiency but they suffer from long Secondly, it utilizes the effective control packetend-to-end delay because of the periodical active and scheme (RRTS and Direct CTS technique). Thirdly,sleep state’s repetition resulted in the per-hop long only local information is used for tree routingdelay. Therefore, there is the trade-off relationship configuration and management and thus ECLPbetween energy efficiency and latency in IEEE reduces the overhead cost. The control overhead cost802.11 based approaches and duty cycling of S-MAC based protocols may be smaller thanmechanisms. The results reveal that S-MAC based 802.11 based protocols because of massage passingprotocols typically underperform compared with scheme and overhearing avoidance but S-MACIEEE 802.11 based protocols. The long end-to-end basically has the same mechanism, RTS-CTS-ACKdelay has occurred in S-MAC based approaches with 802.11 MAC. Therefore, ECLP definitely hasbecause of their duty cycles. However, ECLP has lower control overhead cost than SMAC basedmore significant improvements since the adaptive schemes and IEEE 802.11 MAC based schemes.duty cycling scheme utilizes the enhanced RRTStechnique with the adaptive time-out scheme, whichcan avoid overhearing and reduce the long end-to-end IV. CONCLUSION AND FUTURE WORKdelay compared with SMAC based protocols. In In this paper, we propose an enhanced cross-addition, due to nodes’ mobility or failure, ECLP layer protocol for energy efficiency in wireless sensorachieves the fast and effective local path recovery networks. Both energy efficiency and latency areprocess so that it alleviates the long delay problem in considered for efficient data delivery in ourthe multi-hop wireless network. algorithm. In our protocol, the advanced adaptive duty cycling technique with the adaptive timeout and thresholds reduces long delay and ameliorates energy efficiency. Furthermore, the proposed tree-based energy aware routing algorithm can minimize overhead cost and lengthen the network lifetime. 1028 | P a g e
  9. 9. N.Venkateswaran, V.Kishore / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.1021-1029Simulation results have shown that the proposedECLP has more significant improvement than otherschemes, such as IEEE 802.11 and SMAC withAODV and DSR in terms of energy consumption, theend- to- end delay, and the control overhead cost. The future work involves a more detailedanalysis with traffic conditions and extendedsimulation with other parameters, such as successratio, various mobility, link error rate, and networkdensity. Also, we are implementing our algorithm topractical tiny- OS based sensor nodes to evaluate theperformance in detail under the real environment.REFERENCES [1] Wireless LAN Medium Access Control (MAC) and PhysicalLayer (PHY) Specification, IEEE Std. 802.11-1999 edition. [2] W. Ye, J. Heidemann, and D. Estrin, ”Medium Access Control with Coordinated Adaptive Sleeping for Wireless Sensor Network,” IEEE/ACM Transactions on Networking, vol. 12, no. 3, pp. 493-506, Jun. 2004. [3] T. V. Dam and K. Langendoen, ”An Adaptive Energy Energy-Efficient MAC Protocol for Wireless Sensor Networks,” in Proc. ACM Conference on Embedded Networked Sensor Systems, Los Angeles, USA, Nov. 2003, pp. 171-180. [4] C. Perkins, E. B. Royer, and S. Das, ”Ad hoc On-Demand Distance Vector (AODV) Routing,” Mobile Ad-hoc Networks (MANET) Working Group, IETF RFC 3561, 2003. [5] D. Johnson, Y. Hu, and D. Maltx, ”The Dynamic Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for IPv4,” Mobile Ad-hoc Networks (MANET) Working Group, IETF RFC 4728, 2007. [6] S. Banerjee and A. Misra, ”Minimum Energy Paths for Reliable Communication in Muiti-hop Wireless Networks,” in Proc. ACM International Symposium on Mobile Ad Hoc Networking & Computing, Lausanne, Switzerland, Jun. 2002. [7] J. H. Kim, J. S. On, S. G. Kim, and J. Y. Lee, Performance of Evaluation Synchronous and Asynchronous MAC Protocols for Wireless Sensor Networks,” in Proc. International Conference on Sensor Technologies and Applications, Cap Esterel, France, Aug. 2008. [8] J. H. Kim, J. Y. Lee, and S. G. Kim, ”A Cross-Layer Approach for Efficient Delivery in Wireless Sensor Networks,” in Proc UKC 2008, San Diego CA, USA, Aug. 2008. [9] Ucb/lbnl/vint network simulator— ns (version 2). [Online] Available: 03.25.2009 1029 | P a g e