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    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475 A Quick Over View Of Wireless Sensor Networks, Routing Protocols And Security Constraints M. L.S. N. S. Lakshmi *, S.Gopi Krishna** *(Department of Electronics, KONERU LAKSHMAIAH University, Vaddeswaram.,Vijayawada,Andhra Pradesh,India ** (Department of Electronics, KONERU LAKSHMAIH University,Vaddeswaram,Vijayawada,Andhra Pradesh,India.ABSTRACT The recent advances and the convergence mechanism at node for robust communication of highof micro electro-mechanical systems technology, priority messages. Once deployed, the sensors areintegrated circuit technologies, microprocessor expected to self-configure into a wireless network.hardware and nano technology, wireless Sensor networks consist of a large number of sensorcommunications, Ad-hoc networking routing nodes that collaborate together using wirelessprotocols, distributed signal processing, and communication and asymmetric many-to-one data.embedded systems have made the concept of Indeed, sensor nodes usually send their data to aWireless Sensor Networks (WSNs) and the specific node called the sink node or monitoringadvances in wsns have led to many protocols station, which collects the requested information. Thespecifically designed for sensor networks. Sensor limited energy budget at the individual sensor levelnetwork nodes are limited with respect to energy implies that in order to ensure longevity, thesupply, restricted computational capacity and transmission range of individual sensors is restricted,communication bandwidth. Most of the attention, perhaps of the order of a few meters. In turn, thishowever, has been given to the routing protocols implies that wireless sensor networks should besince they might differ depending on the multihop. An important difference between wirelessapplication and network architecture. To prolong sensor networks and conventional networks is thatthe lifetime of the sensor nodes, designing sensor nodes do not need node addresses (e.g.,efficient routing protocols is critical. Even though medium-access control (MAC) address and Internetsensor networks are primarily designed for protocol (IP) address). In conventional networksmonitoring and reporting events, since they are (e.g., Internet), the node address is used to identifyapplication dependent, a single routing protocol every single node in the network. Variouscannot be efficient for sensor networks . This communication protocols and algorithms are basedpaper surveys and gives explanatory details about on this low-level naming. However, wireless sensorwsn (wireless sensor networks) ,its protocols and networks are information-retrieval networks, notsecurity constraints and protocols for restriction point-to-point communication networks. That is,of unauthorized authentication recent routing wireless sensor network applications focus onprotocols for sensor networks and presents a collecting data, rather than on providingclassification for the various approaches pursued. communication services between network nodes. Node address is not essential for sensor networkKeywords – sensor network,multi hop,routing applications. Wireless sensor networks are a specialprotocol,security,data case of ad hoc networks. However, there are severalaggregation,centralized,.localised major differences between wireless sensor networks and ad hoc networks.1. INTRODUCTION Wireless sensor networks (WSNs) are being 2. ARCHITECTUREused in a wide variety of critical applications such as A sensor network is a network of many tinymilitary and health-care applications. WSNs are disposable low power devices, called nodes, whichdeployed densely in a variety of physical are spatially distributed in order to perform anenvironments for accurate monitoring. Therefore, application-oriented global task. These nodes form aorder of receiving sensed events is important for network by communicating with each other eithercorrect interpretation and knowledge of what actually directly or through other nodes. One or more nodesis happening in the area being monitored. Similarly, among them will serve as sink(s) that are capable ofin intrusion detection applications (alarm communicating with the user either directly orapplication), response time is the critical performance through the existing wired networks. The primarymetric. On detection of intrusion, alarm must be component of the network is the sensor, essential forsignaled within no time. There should be a monitoring real world physical conditions such as 1462 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475sound, temperature, humidity, intensity, vibration, limited with respect to energy supply, restrictedpressure, motion, pollutants etc. at different locations. computational capacity and communicationThe tiny sensor nodes, which consist of sensing, on bandwidth. The ideal wireless sensor is networkedboard processor for data processing, and and scalable, fault tolerance, consume very littlecommunicating components, leverage the idea of power, smart and software programmable, efficient,sensor networks based on collaborative effort of a capable of fast data acquisition, reliable and accuratelarge number of nodes. Figure 1 shows the structural over long term, cost little to purchase and required noview of a sensor network in which sensor nodes are real maintenance.shown as small circles. Each node typically consists The basic goals of a WSN are to:of the four components: sensor unit, central  determine the value of physical variables atprocessing unit (CPU), power unit, and a given location,communication unit. They are assigned with different  detect the occurrence of events of interest,tasks. The sensor unit consists of sensor and ADC and estimate parameters of the detected(Analog to Digital Converter). The sensor unit is event or events,responsible for collecting information as the ADC  classify a detected object, andrequests, and returning the analog data it sensed.  track an object.ADC is a translator that tells the CPU what the sensor Thus, the important requirements of a WSN are:unit has sensed, and also informs the sensor unit what  use of a large number of sensors,to do. Communication unit is tasked to receive  attachment of stationary sensors,command or query from and transmit the data from  low energy consumption,CPU to the outside world. CPU is the most complex  self organization capability,unit. It interprets the command or query to ADC,  collaborative signal processing, andmonitors and controls power if necessary, processesreceived data, computes the next hop to the sink, etc.  querying ability.Power unit supplies power to sensor unit, processingunit and communication unit. Each node may also 3. WIRELESS SENSOR NETWORKSconsist of the two optional components namely To begin, the nodes of a wireless sensorLocation finding system and Mobilizer. If the user network are generally densely deployed (e.g.,requires the knowledge of location with high hundreds or thousands of sensors may be placed,accuracy then the node should pusses Location mostly at random, either very close or inside thefinding system and Mobilizer may be needed to move phenomenon to be studied). Also, the number ofsensor nodes when it is required to carry out the nodes is typically not the same: while there areassigned tasks. hundreds or thousands of sensors, the number of nodes (laptops, personal digital assistants (PDAs), palmtops, etc.) in an ad hoc network normally ranges from tens to hundreds. The sensors have a larger failure rate and feature lower data reliability, and are subject to stringent limitations in the energy budget, computing capacity, and memory. The nodes of an ad hoc network are normally distinguished by their IP addresses or other identifiers, while sensors are usually anonymous, lacking fabrication-time identifiers. Consequently, they are being addressed and named using various strategies that either endow sensors with temporary IDs or else rely on data or position-driven naming. While ad hoc networks normally rely on topological information in their operation (e.g., knowledge of one-hop and often times 2-hop neighbors), such information may not be available in wireless sensor networks simply because of the lack of IDs at the individual sensor level. In Fig 1: Structural view of sensor network some cases, however, the sensors benefit from a Instead of sending the raw data to the nodes sense of relative geographic position with respect toresponsible for the fusion, sensor nodes use their the monitored environment and/or with respect to aprocessing abilities to locally carry out simple sink. Thus, positional information may be essential incomputations and transmit only the required and some applications of sensor networks, although itpartially processed data. The sensor nodes not only may not be essential for ad hoc networks.collect useful information such as sound, Depending on the application, differenttemperature, light etc., they also play a role of the architectures and design goals/ constraints have beenrouter by communicating through wireless channels considered for wireless sensor networks. We attemptunder battery-constraints. Sensor network nodes are 1463 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475to capture architectural design issues and highlight models, the transmission of data is triggered when antheir implications on the network infrastructure. event occurs or when a query is generated by theThere are three main components in a sensor sink. Some networks apply a hybrid model using anetwork. These are the sensor nodes, the sink, and the combination of continuous, event-driven, and query-monitored events. Aside from the few architectures driven data delivery. The routing and MAC protocolsthat utilize mobile sensors, most of the network are highly influenced by the data delivery model,architectures assume that sensor nodes are stationary. especially with regard to the minimization of energyOn the other hand, supporting the mobility of sinks, consumption and route stability. For instance, it hasclusterheads (CHs), or gateways is sometimes been concluded in that for a habitat monitoringdeemed necessary. Routing messages from or to application where data are continuously transmittedmoving nodes is more challenging, since route to the sink, a hierarchical routing protocol is the moststability becomes an important optimization factor, in efficient alternative. This is due to the fact that suchaddition to energy, bandwidth, and the like. The an application generates significant redundant datasensed event can be either dynamic or static that can be aggregated en route to the sink, thusdepending on the application. For instance, in a target reducing traffic and saving energy. In addition, in thedetection/ tracking application, the event continuous data-delivery model time-based medium(phenomenon) is dynamic, whereas forest monitoring access can achieve significant energy saving, thefor early fire prevention is an example of static since it will enable turning off sensors’ radioevents. Monitoring static events allows the network receivers. Carrier sense multiple access (CSMA)to work in a reactive mode, simply generating traffic medium-access arbitration is a good fit for event-when reporting. Dynamic events in most applications based data-delivery models, since the data arerequire periodic reporting, and consequently generate generated sporadically.significant traffic to be routed to the sink. In a wireless sensor network, different An important design consideration is the functionalities can be associated with the sensortopological deployment of nodes. This is usually nodes. In the early work on sensor networks, allapplication-dependent and affects the performance of sensor nodes are assumed to be homogenous, havingthe communication protocol. The deployment is equal capacity in terms of computation,either deterministic or self-organizing. In communication, and power. However, depending ondeterministic situations, the sensors are manually the application a node can be dedicated to a particularplaced and data are routed through predetermined special function, such as relaying, sensing, andpaths. In addition, collision among the transmissions aggregation, since engaging the three functionalitiesof the different nodes can be minimized through the at the same time on a node might quickly drain theprescheduling of medium access. However, in self energy of that node. . While some networks haveorganizing systems, the sensor nodes are scattered selected CHs from the deployed sensors in otherrandomly, creating an infrastructure in an ad hoc applications a CH is more powerful than the sensormanner. In that infrastructure, the position of the sink nodes in terms of energy, bandwidth, and memory. Inor the CH is also crucial in terms of energy efficiency such cases, the burden of transmission to the sensorand performance. When the distribution of nodes is nodes in terms of energy, bandwidth, and memory. Innot uniform, optimal clustering becomes a pressing such cases, the burden of transmission to the sink andissue to enable energy efficient network operation. aggregation is handled by the CH.During the creation of an infrastructure, the processof setting up the network topology is greatly 4. DATA AGGREGATION IN WIRELESSinfluenced by energy considerations. SENSOR NETWORKS Since the transmission power of a wireless When data are measured or arrive from aradio is proportional to distance squared or even neighbor, the sensor needs to decide whether or nothigher order in the presence of obstacles, multihop they are important enough to forward them. Therouting will consume less energy than direct coding techniques used need to minimize the numbercommunication. However, multihop routing of forwarded bits. The new data may also beintroduces significant overhead for topology combined with other received data, in order tomanagement and MAC. Direct routing would minimize the number of bits to forward. Such dataperformed well enough if all the nodes were very aggregation (also referred to as fusion) from multipleclose to the sink. Most of the time sensors are sensors is important, because of severe energy andscattered randomly over an area of interest, and bandwidth limitations as well as for numerous othermultihop routing becomes unavoidable. Arbitrating reasons, including reliability. The reliability ofmedium access in this case becomes cumbersome. individual measurements bandwidth or delayDepending on the application of the wireless sensor guarantees. Therefore, the transport control protocolsnetwork, the data-delivery model to the sink can be designed for wired networks or for other kinds ofcontinuous, event-driven, query-driven, and hybrid. wireless networks cannot be used for wireless sensorIn the continuous-delivery model, each sensor sends networks. When an event occurs, there is usually adata periodically. In event driven and query-driven multiple correlated data flow from the event to sink. 1464 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475A spatial correlation exists among the data reported. to random placement, where the sensors are dispersedSeveral reports may arrive at the sink, or several randomly by plane, artillery, humans, or robots.reports can be combined at intermediate nodes to Further, the initial deployment may be followed byreduce communication (data fusion). The sink makes later redeployment, as necessary. Wireless sensora decision on the event based on these reports, which network self-organization includes a time component.has a certain degree of collective reliability. The One aspect of the problem is the time at which eachtransport- layer problem in wireless sensor networks sensor starts to operate. In many protocols, therecan be defined concisely as follows: to configure the exists an implicit assumption that all sensors start toreporting rate to achieve the required event detection operate at the same time, which could bereliability at the sink with minimum resource preprogrammed, or may be externally decided andutilization. communicated. The later option is avoided because sensors6. QUERY PROCESSING IN WIRELESS need to be in the idle state to receive any instruction,NETWORKS which is much more energy-consuming compared to In other types of networks, queries are the sleep state (when receivers are turned off). Sensornormally address-centric in the sense that they are network operation may require time synchronizationsent to an individual node using, for example, IP- (covered in Chapter 7 in this book), whether or not allbased routing. By contrast, the anonymity of sensors sensors follow the same time or at least havesuggests that in wireless sensor networks queries be synchronized time slots. Time synchronization can beeither location-centric or data-centric. Queries are provided by a global positioning system (GPS), byaddressed to a geographic region rather than to collaborative efforts, or can be achieved by someindividual sensors. Since, as we discussed, the other means. Some applications benefit or evensensors do not have unique IDs, routes are created require that the sensory data collected by sensors bebased on the nature and value of data collected by supplemented with location information, whichsensors. An example of data-driven routing is the encourages the development of communicationresponse to a query that is asking to report all sensor protocols that are location aware and perhaps locationreadings with temperature over 408C. Queries can be dependent. The practical deployment of many sensordistinguished along several orthogonal axes. networks will result in sensors initially beingSpatially, queries may be global and be sent to the unaware of their location: they must acquire thisentire deployment area, or area-specific, in which information post deployment.case they are addressed to a geo casting region In fact, in most of the existing literature, the(where only sensors inside a geographic region are sensors are assumed to have learned their geographicasked to report), or to multi geo casting regions position. The location-awareness problem is for(where all sensors located inside several geographic individual sensors to acquire location informationregions are asked to report). In terms of the reporting either in absolute form (e.g., geographic coordinates)mechanism there are several possible types of or relative to a reference point. The localizationqueries. We only mention the following three: event- problem is for individual sensors to determine, asdriven, on-demand, and persistent. In an event-driven precisely as possible, their geographic coordinates inquery, the sensor itself decides when it has something the area of deployment. One simple solution to theto report (for instance, when it measures high localization problem is to use a GPS, where sensorstemperature, which may indicate incipient fire). In an receive signals from several satellites and decide theiron demand query, the request comes from the end position directly. However, for tiny sensors suchuser via the sink. In a persistent query, the end user direct position learning may not be possible or mayexpresses a long-term interest in an event or a not be sufficiently accurate enough (if a GPS signal isdisjunction of events. The various sensors tasked not provided with sufficient accuracy) for thewith answering the persistent query report whenever assigned task. However, due to limitations in forma trigger event occurs during the lifetime of the factor, cost per unit, and energy budget, individualinterest sensors are not expected to be GPS enabled. Moreover, in many occluded environments, including6. STRATEGIES OF WIRELESS SENSOR those inside buildings, hangars, or warehouses,NETWORKS satellite access is drastically limited. Since direct There are several strategies for deploying reliance of GPS is specifically proscribed, in order towireless sensor networks. The sensors can be obtain location awareness individual sensorsembedded in the ambient environment, be embedded exchange messages to collaboratively determine theirin the asphalt covering streets and highways, in the own geographic position (absolute or relative) in thewalls of building, in trees, and so on. They can be network. The vast majority of collaborative solutionsplaced deterministically by humans or robots, or to the localization problem are based on multiincorporated in the paint coating walls, or deployed lateration or multiangulation. These solutions assumein a purely random fashion. Most research is devoted the existence of several anchors that are aware of their geographic position (e.gsinks or specialized 1465 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475sensors that can engage in satellite communication). characterized by their ad hoc nature that lack preBy exchanging messages with their neighbors, deployed infrastructure for computing andindividual sensors can conceivably measure signal communication. Both share some characteristics likestrengths and/or time delays in communication. Some network topology is not fixed, power is an expensiveapproaches are based on hop-count distances to resource and nodes in the network are connected toreference points. Sensors receiving location messages each other by wireless communication links. WSNsfrom at least three sources can approximate their own differ in many fundamental ways from MANETS aslocations In some other applications, exact mentioned below.geographic location is not necessary: all that  Sensor networks are mainly used to collectindividual sensors need is coarse-grain location information while MANETS are designedawareness. There is an obvious trade-off; coarse- for distributed computing rather thangrain location awareness is lightweight, but the information gathering.resulting accuracy is only a rough approximation of  Sensor nodes mainly use broadcastthe exact geographic coordinates. One can obtain this communication paradigm whereas mostcoarse-grain location awareness by a training MANETS are based on point-to-pointprotocol that imposes a coordinate system onto the communications.sensor network. an interesting by product of such a  The number of nodes in sensor networks cantraining protocol is that it provides partitioning into be several orders of magnitude higher thanclusters and a structured topology with natural that in MANETS .communication paths. The resulting topology will  Sensor nodes may not have globalmake it simple to avoid collisions between identification (ID) because of the largetransmissions of nodes in different clusters, between amount of overhead and large number ofdifferent paths, and also between nodes on the same sensors.path. This is in contrast with the majority of papers  Sensor nodes are much cheaper than nodesthat assume routing along spanning trees with in a MANET and are usually deployed infrequent collisions. In the training protocol the thousands.deployment area is endowed with a virtual  Sensor nodes are limited in power,infrastructure to make the presentation self- computational capacities, and memorycontained, however, we now outline the idea. The where as nodes in a MANET can becoordinate system divides the sensor network area recharged somehow.into equiangular wedges. In turn, these wedges are  Usually, sensors are deployed once in theirdivided into sectors by means of concentric circles or lifetime, while nodes in MANET movecoronas centered at the sink. The task of training the really in an Ad-hoc manner.wireless sensor network involves establishing  Sensor nodes are much more limited in theircoronas The deployment area is covered by coronas computation and communication capabilitiesdetermined by concentric circles centered at the sink . than their MANET counterparts due to theirWedges: The deployment area is ruled into a number low cost.of angular wedges centered at the sink. Individualsensors can acquire the desired coarse-grain locationawareness by learning the identity of the corona and 8. APPLICATIONS OF SENSORthe wedge to which they belong. As it turns out, the NETWORKStraining protocol is lightweight and does not require In the recent past, wireless sensor networkssensors to have IDs; moreover, sensors are not aware have found their way into a wide variety ofof their neighbors within the same sector. It is worth applications and systems with vastly varyingnoting that location awareness is modulo the sector to requirements and characteristics. The sensorwhich the sensor belongs. Since accurate position networks can be used in Disaster Relief, Emergencyinformation is unreliable because of shadowing, Rescue operation, Military, Habitat Monitoring,scattering, multi paths, and time synchronization Health Care, Environmental monitoring, Homeproblems, training provides a viable alternative. networks, detecting chemical, biological, radiological, nuclear, and explosive7. COMPARISON OF MANETS AND material etc. as summarized in table 1.SENSOR NETWORKS MANETS (Mobile Ad-hoc networks) andsensor networks are two classes of the wirelessAdhoc networks with resource constraints. MANETStypically consist of devices that have highcapabilities, mobile and operate in coalitions. Sensornetworks are typically deployed in specificgeographical regions for tracking,monitoring andsensing. Both these wireless networks are 1466 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475TABLE 1 such differences, many new algorithms have been SOME APPLICATIONS FOR DIFFERENT proposed for the problem of routing data in sensorAREAS networks. These routing mechanisms have considered the characteristics of sensor nodes alongArea Applications with the application and architecture requirements. Military situation awareness. Almost all of the routing protocols can be classifiedMilitary Sensing intruders on basis. as data-centric, hierarchical or location based Detection of enemy unit although there are few distinct ones based on network movements on land and sea. flow or quality of service (QoS) awareness. Data- Battle field surveillances centric protocols are query-based and depend on the naming of desired data, which helps in eliminatingEmergency Disaster management. many redundant transmissions. Hierarchical protocolsSituations Fire/water detectors. aim at clustering the nodes so that cluster heads can Hazardous chemical level and do some aggregation and reduction of data in order to fires. save energy. Location based protocols utilize the Environmental monitoring of position information to relay the data to the desired water and soil. regions rather than the whole network. The lastPhysical World Habitual monitoring. category includes routing approaches that are based Observation of biological and on general network-flow modeling and protocols that artificial systems. strive for meeting some QoS requirements along with Sensors for blood flow, the routing function, in this paper, we will explore the respiratory rate, ECG routing mechanisms for sensor networks developed Medical and (electrocardiogram),pulse in recent years. Each routing protocol is discussedhealth oxymeter, blood pressure and under the proper category. Our aim is to help better oxygen measurement. understanding of the current routing protocols for Monitoring people’s location and wireless sensor networks and point out open issues health condition. that can be subject to further research. Factory process control andIndustrial industrial automation. 10. ROUTING PROTOCOL Monitoring and control of Routing protocols work on the assumption industrial equipment. that every node is aware of its own position in the Home appliances, location network; via mechanisms like GPS or distributed Home awareness (blue tooth). localization schemes and that the physical topologyNetworks Person locator. of the network is a good approximation of the Tire pressure monitoring. network connectivity. In other words, these routingAutomotive Active mobility. protocols assume that if two nodes are physically Coordinated vehicle tracking. close to each other, they would have radio connectivity between them, which is true in most cases. Hence the protocols use node location9. ROUTING information to route packets from source to Routing in sensor networks is very destination. Every node having its locationchallenging due to several characteristics that information is a fair assumption in most sensordistinguish them from contemporary communication networks since application data frequently needs toand wireless ad hoc networks. First of all, it is not be annotated by location information. One bigpossible to build a global addressing scheme for the advantage of geographic routing schemes is the factdeployment of sheer number of sensor nodes. that there is no need to send out route requests orTherefore, classical IP-based protocols cannot be periodic connectivity updates. This can save a lot ofapplied to sensor networks. Second, in contrary to protocol overhead and consequently, energy of thetypical communication networks almost all nodes. This is an important consideration for sensorapplications of sensor networks require the flow of networks where the network size could be on thesensed data from multiple regions (sources) to a order of thousands of nodes, but each node hasparticular sink. Third, generated data traffic has extremely limited memory capacity to store routingsignificant redundancy in it since multiple sensors tables.may generate same data within the vicinity of aphenomenon. Such redundancy needs to be exploited 10.1.Localized versus centralized protocolsby the routing protocols to improve energy and Due to a number of factors, the topology ofbandwidth utilization. Fourth, sensor nodes are wireless sensor networks changes frequently and selftightly constrained in terms of transmission power, organization must be adaptive to local changes.on-board energy, processing capacity and storage and Centralized protocols require global networkthus require careful resource management. Due to information at each sensor (sink only, respectively, 1467 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475with sink making decisions) for making sensor being requested through queries, attribute baseddecisions. This includes the use of topological naming is necessary to specify the properties of data.structures, such as minimal spanning tree (MST), Here data is usually transmitted from every sensorwhose local links cannot be locally determined. node within the deployment region with significantThere are a number of combinatorial optimization redundancy. In location aware routing nodes knowformulations of sensor network design problems with where they are in a geographical region. Locationlinear programming solutions. These protocols can information can be used to improve the performanceperform well only when sensor networks are small. of routing and to provide new types of services. InWe do not discuss centralized approaches further, QoS based routing protocols data delivery ratio,since we believe in and assume large-scale wireless latency and energy consumption are mainlysensor networks where centralized protocols do not considered. To get a good QoS (Quality ofwork well. Localized protocols only require local Service),the routing protocols must possess more dataknowledge for making decisions, and a limited delivery ratio, less latency and less energy(usually constant) amount of additional information consumption.(e.g., the position of the sink). Some localized Routing protocols can also be classifiedprotocols may require preprocessing, such as based on whether they are reactive or proactive. Aconstructing a suitable topology for further operation. proactive protocol sets up routing paths and statesOne typical example is setting up a cluster structure. before there is a demand for routing traffic. Paths areIn addition to localized protocol operation, it is also maintained even there is no traffic flow at that time.important to consider the maintenance cost of such In reactive routing protocol, routing actions aretopology. For instance, if the cluster structure is triggered when there is data to be sent andadopted, what happens when CHs move or fail? Does disseminated to other nodes. Here paths are setup onthe update procedure remain local, and, if so, what is demand when queries are initiated. Routing protocolsthe quality of the maintained structure over time? are also classified based on whether they areSome maintenance procedures may not remain local. destination-initiated (Dst-initiated) or source-initiatedThis happens when local change triggers message (Src-initiated). A source-initiated protocol sets up thepropagation throughout the network. Of course, routing paths upon the demand of the source node,localized maintenance is preferred, meaning that and starting from the source node. Here sourcelocal topology changes should be performed by a advertises the data when available and initiates theprocedure that always remains local, involving only data delivery. A destination initiated protocol, on thethe neighborhood of the affected sensors. other hand, initiates path setup from a destination A number of protocols in the literature are node. Routing protocols are also classified basedlocalized, but use an excessive number of messages sensor network architecture some WSNs consist ofbetween neighboring sensors. For instance, some homogenous nodes, whereas some consist oftopology control and position determination protocols heterogeneous nodes. Based on this concept we canrequire over a dozen (sometimes even thousands of ) classify the protocols whether they are operating on amessages to be exchanged between neighbors. flat topology or on a hierarchical topology. In FlatBecause of the severely limited bandwidth and routing protocols all nodes in the network are treatedenergy budget and medium-access problems caused equally. When node needs to send data, it may find aby excessive messaging, messages between route consisting of several hops to the sink. Aneighbors to construct/maintain topology, determine hierarchical routing protocol is a natural approach toposition, or perform any other operation should be take for heterogeneous networks where some of theminimized, possibly avoided entirely . nodes are more powerful than the other ones. The hierarchy does not always depend on the power of10.2. Classification Of Routing Protocols nodes. In Hierarchical (Clustering) protocols The design space for routing algorithms for different nodes are grouped to form clusters and dataWSNs is quite large and we can classify the routing from nodes belonging to a single cluster can bealgorithms for WSNs in many different ways. combined (aggregated).The clustering protocols haveRouting protocols are classified as node centric, data- several advantages like scalable, energy efficient incentric, or location-aware (geo-centric) and QoS finding routes and easy to manage.based routing protocols. Most Ad-hoc networkrouting protocols are node-centric protocols where 10.3 Design Issues Of Routing Protocolsdestinations are specified based on the numerical Initially WSNs was mainly motivated byaddresses (or identifiers) of nodes. In WSNs, no military applications. Later on the civilian applicationdecentric communication is not a commonly domain of wireless sensor networks have beenexpected communication type. Therefore, routing considered, such as environmental and speciesprotocols designed for WSNs are more data-centric monitoring, production and healthcare, smart homeor geocentric. In data-centric routing, the sink sends etc. These WSNs may consist of heterogeneous andqueries to certain regions and waits for data from the mobile sensor nodes, the network topology may be assensors located in the selected regions. Since data is simple as a star topology; the scale and density of a 1468 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475network varies depending on the application. To meet occurs. In query driven models, the transmission ofthis general trend towards diversification, the data is triggered when query is generated by the sink.following important design issues of the sensor Some networks apply a hybrid model using anetwork have to be considered. combination of continuous, event-driven and query driven data delivery.10.3.1) Fault Tolerance Some sensor nodes may fail or be blocked 10.3.7) Data Aggregation/Fusiondue to lack of power, have physical damage or Since sensor nodes might generateenvironmental interference. The failure of sensor significant redundant data, similar packets fromnodes should not affect the overall task of the sensor multiple nodes can be aggregated so that the numbernetwork. This is the reliability or fault tolerance of transmissions would be reduced. Data aggregationissue. Fault tolerance is the ability to sustain sensor is the combination of data from different sources bynetwork functionalities without any interruption due using functions such as suppression (eliminatingto sensor node failures. duplicates), min, max and average. As computation would be less energy consuming than10.3.2) Scalability communication, substantial energy savings can be The number of sensor nodes deployed in the obtained through data aggregation. This techniquesensing area may be in the order of hundreds, has been used to achieve energy efficiency and trafficthousands or more and routing schemes must be optimization in a number of routing protocolsscalable enough to respond to events. 10.3.8) Quality Of Service (QoS )10.3.3) Production Costs The quality of service means the quality Since the sensor networks consist of a large service required by the application, it could be thenumber of sensor nodes, the cost of a single node is length of life time, the data reliable, energyvery important to justify the overall cost of the efficiency, and location-awareness, collaborative-networks and hence the cost of each sensor node has processing. These factors will affect the selection ofto be kept low. routing protocols for a particular application. In some applications (e.g. some military applications) the data10.3.4) Operating Environment should be delivered within a certain period of time We can set up sensor network in the interior from the moment it is sensed.of large machinery, at the bottom of an ocean, in abiologically or chemically contaminated field, in a 10.3.9) Data Latency And Overheadbattle field beyond the enemy lines, in a home or a These are considered as the importantlarge building, in a large warehouse, attached to factors that influence routing protocol design. Dataanimals, attached to fast moving vehicles, in forest aggregation and multi-hop relays cause data latency.area for habitat monitoring etc. In addition, some routing protocols create excessive overheads to implement their algorithms, which are10.3.5) Power Consumption not suitable for serious energy constrained networks. Since the transmission power of a wirelessradio is proportional to distance squared or even 10.3.10) Node Deploymenthigher order in the presence of obstacles, multi-hop Node deployment is application dependentrouting will consume less energy than direct and affects the performance of the routing protocol.communication. However, multi-hop routing The deployment is either deterministic or self-introduces significant overhead for topology organizing. In deterministic situations, the sensors aremanagement and medium access control. Direct manually placed and data is routed through pre-routing would perform well enough if all the nodes determined paths. However in self organizingwere very close to the sink. Sensor nodes are systems, the sensor nodes are scattered randomlyequipped with limited power source (<0.5 Ah creating an infrastructure in an Ad-hoc manner.1.2V).Node lifetime is strongly dependent on itsbattery lifetime. 11. SECURITY IN WSN A distributed Wireless Sensor Network10.3.6) Data Delivery Models (WSN) is a collection of n sensors with limited Data delivery models determine when the hardware resources. Sensors can exchange messagesdata collected by the node has to be delivered. via Radio Frequency (RF), whose range usuallyDepending on the application of the sensor network, covers only a limited number of other sensors. Anthe data delivery model to the sink can be interesting problem is how to implement secure pair-Continuous, Event driven, Query-driven and Hybrid . wise communications among any pair of sensors in aIn the continuous delivery model, each sensor sends WSN. A WSN requires completely distributeddata periodically. In event-driven models, the solutions which are particularly challenging due totransmission of data is triggered when an event the limited resources and the size of the network. 1469 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475Moreover, WSNs can be subject to several security In particular, this is a pre-requisite for thethreats, including the physical compromising of a implementation of secure routing. Also, it can besensor. Hence, any solution for secure pair wise useful for the establishment of secure groupcommunications should tolerate the collusion of a set communications as well. The native technique forof corrupted sensors. a probabilistic model and two implementing secure pair-wise communication is toprotocols to establish a secure pair-wise assign a set of secret keys to each component of thecommunication channel between any pair of sensors group, each key of the set being shared with only onein the WSN, by assigning a small set of random keys other member of the group. This solution requiresto each sensor. We build, based on the first Direct each member to store n-1keys, where n is the size ofProtocol, a second Co-operative Protocol. The Co- the group, with n(n-1)/2 different keys in the group.operative Protocol is adaptive: its security properties We focus on confidentiality, and provide models andcan be dynamically changed during the life-time of protocols to allow any pair of sensors of the WSN tothe WSN. Both protocols also guarantee implicit and establish a confidentially secure communicationprobabilistic mutual authentication without any channel (secure channel in the following) whileadditional overhead and without the presence of a loading each sensor with a small set of keys. Webase station. The performance of the Direct Protocol devise a first protocol, the Direct Protocol, whichis analytically characterized while, for the Co- establishes a pair-wise communication channel that isoperative Protocol, we provide both analytical secure with a fixed probability. We then build on thisevaluations and extensive simulations. For example, protocol a second one that allows to trade off thethe results show that, assuming each sensor stores desired level of security with the protocol overhead.120 keys, in a WSN composed of 1024 sensors with The Co-operative Protocol is adaptive: its security32 corrupted sensors the probability of a channel parameters can be dynamically changed in such acorruption is negligible in the case of the Co- way to guarantee a fixed security level even when theoperative Protocol. A Wireless Sensors Network number of corrupted sensors in the WSN grows(WSN) is a collection of sensors whose size can during the WSN life-time. We achieve this goal at therange from a few hundred to a few hundred price of an increase in the communication overhead.thousands and possibly more sensors. The sensors do Note that the overhead for establishing thenot rely on any pre-deployed network architecture, communication channel is paid only once for anythey thus communicate via an ad-hoc wireless channel set up. The security of both approaches isnetwork. Distributed in irregular patterns across analytically described, and these results have beenremote and often hostile environments, sensors validated with extensive simulations. We also showshould autonomously aggregate into collaborative, that both protocols guarantees implicit andpeer-to-peer networks. Sensor networks must be probabilistic mutual sensor to sensor authenticationrobust and survivable despite individual sensor with scaling properties.failures and intermittent connectivity (due, forinstance, to a noisy channel or a shadow zone). 12. METHODS PROVIDING SECURITYWSNs are often infrastructure-less, and the power Several recent research works focus on keysupply of each individual sensor is provided by a establishment protocols in dynamic peer groups. Inbattery, whose consumption for both communication particular, deals with the problem of key agreementand computation activities must be optimized. A in dynamic peer groups and recognizes that keyWSN can be deployed in both military and civil agreement, especially in a group setting, is thescenarios. For instance, it could be used to provide a stepping stone for all the other security services. Therelay network for tactical communication in a paper also presents a concrete protocol suite,battlefield, collect data from a field in order to reveal CLIQUES, which offers complete key agreementthe presence of a toxic gas, facilitate rescue services. CLIQUES is based on multi-partyoperations in wide open hostile areas, fulfill extensions of the well known Diffie-Hellman keyperimeter surveillance duties, operate for commercial exchange method. The protocols are provably securepurpose in severe environmental constrained against passive adversaries. In the above protocolsscenarios (for instance, to measure the concentration are enhanced to provide services like authenticatedof metals such as nodules of manganese on the ocean key agreement in dynamic peer groups with thebed). Moreover, a WSN can be used to enforce emphasis on efficient and provably secure keyphysical access control by checking secure access to authentication, key confirmation and integrity.a building. Each person should carry a sensor which However, the protocols in and use public keycontains some sort of encrypted personal information. cryptography. As it was pointed out in public keyThis information is exchanged with other sensors cryptography is not well-suited for securing WSNs.distributed across the building, and can be used to Indeed, the memory of a sensor is typicallyauthenticate, to assign the appropriate clearance to insufficient to hold the long keys necessary tothe users, and to trace their movements in the guarantee secure asymmetric cryptographic.building. Establishing secure pair-wise Moreover, sensors are usually equipped with a lowcommunication can be useful for many applications. power processor which requires too long and too 1470 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475much energy to compute the modular exponentiations will provide a key deployment schemeinvolved in the implementation of public key describing how the sensors are loaded withcryptography. Among research specifically focused the keys a key discovery procedure whichon a security subsystem for a limited wireless sensor enables an arbitrary pair of sensors tonetwork platform. The system assumes the presence compute the set of keys they share a securityof base stationsacting as gateways for inter-sensor adaptive channel establishment procedure, acommunications. Being abase station more powerful mechanism to enable an arbitrary pair of(we can think of it as a workstation), it is reasonable sensors to agree on a common key to beto assume it can easily implement public key used to secure the channel.cryptography. By assuming the base stations trustedcomputing bases, can relax the assumption of tamper- 14.1. The Key Deployment Schemeresistance of sensors. The security subsystem is Assume an n sensor Wireless Sensorshown to support a few security functions, such as Network. The random key pre-deployment strategyauthenticated and confidentiality communications as proposed is composed of the following steps:well as authenticated broadcast. In, a key 1. a pool of P random keys {v1P……………..Vpp} ismanagement scheme is proposed which periodically generated;updates the symmetric keys employed by the sensors. 2. for each sensor a in the WSN, a setHowever, neither forward nor backward secrecy is Va={V1a………Vka}. of k distinct keys is randomly drawnguaranteed. Different schemes for key establishment from the pool and assigned to a.in WSN are examined and a couple of new schemes If the above key deployment scheme is used,are proposed. the corresponding channel establishment procedure could be quite time and energy consuming. Even if13 THREAT MODEL IN WSNS two sensors a and b are in their communication range Generally two types of attacks: (1) passive and share some keys, to discover which keys theyattacks; (2) active attacks. In passive attacks, we actually share is not efficient. Indeed, sensor a isassume that an eavesdropper can constantly monitor supposed to broadcast messages ,EVia(α), i = 1; : : : ;kthe whole WSN. We consider two types of passive where αis a challenge. The decryption of EVia(α ) withattacks that an adversary can perform: (1) cipher text the proper key by sensor b would reveal the challengeattack, that is, given the cipher text, the adversary and the information that b shares that key with a. Thistries to recover the encryption key; and (2) chosen key discovery procedure requires k2 decryptions onplain text attack, that is, the adversary can feed the the receiver side and k encryptions on the sendersensor with known data and then observe the side. Moreover, at least k messages have to be sentencrypted message sent by the sensor. Therefore, we and received.consider confidentiality and authenticity of data of As observed in, a pseudo-random keyparamount importance. In active attacks, we assume deployment scheme allows a more efficient keythe attacker can capture a sensor, collecting all the discovery procedure than a random scheme. Given ainformation and the keys the sensor is loaded with. sensor a, the idea is to generate the indexes of theMoreover, we consider a worst case scenario, that is keys that will be assigned to a pseudo-randomly. Thewe assume that all the compromised sensors in the generator is initialized with a publicly known seedWSN are compromised by the same attacker and thus dependent on a. Once the seed is known, the kcollude to compromise the network. Finally, we indexes of the keys assigned to a can be computed byassume that the environment in which the sensors anyone. Note that this key discovery procedureoperate is untrusted. Each sensor trusts itself, while reveals only the indexes of the keys given to sensor a,sensors do not trust each other. To overcome these and does not leak any information on the keysdifferent protocols are introduced. themselves. The above pseudo-random method requires a limited amount of additional storage per14. DIRECT PROTOCOL sensor in comparison with the key assignment. The constraints that make the task of Indeed, each sensor has to store, along with the keys,securing a channel between any pair of sensors not also the index of each key. However, the new keytrivial include: a limited amount of memory and a discovery procedure now requires no messagelimited battery power available to each sensor. exchange, at most k applications of the pseudo-Henceforth, we want to design a protocol that is, random generator, and k look-ups in the local  Memory efficient: only a limited amount of memory. memory is required to store crypto keys; In the following we adopt this pseudo- random, seed-based key deployment strategy, and for  Energy efficient: low computation and this strategy we are interested in evaluating its main communication overhead; properties: (1) the channel establishment effectiveness between any two sensors; (2) the  Resilient to the coalition of corrupted efficiency of the channel establishment procedure; sensors. To match these requirements, we (3) the resilience of the channel against node 1471 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475capture. degree of security. The degree of security achieved depends on parameters k, P according to14.2. Channel Existence methodology. The main drawbacks of the Direct Given two sensors a and b loaded with sets Protocol are the following the Direct Protocol is notof keys Va and Vb according to the seed-based adaptive to changes in the threat (for instance, thestrategy, it is important to assess the probability that a number of corrupted sensors overcomes the valuechannel exists between two sensors in the WSN. assumed as an upper bound in the design project of A communication channel (channel in the following) the WSN), or in the security requirements (forexists between sensors a and b if and only if Va Vb instance, a higher security level is desired due to the=6 that is a and b share at least one key. temporary management of more sensitiveFrom Definition, the probability that a channel exists information), for a fixed sensor key ring size k, thebetween sensors a and b is equal to the probability probability of channel corruption can bethat a and b share at least one key of the pool. Let E unsatisfactory even for small values of the number ofbe the event: ”There is at least one key shared by a corrupted sensorsand b”. Pr[E] can be directly computed asCooperative protocol. TABLE 2 Pseudo code of the Co-operative Protocol for the pair wise key establishment assuming 16 corrupted sensor, the best (lowest) channel corruption probability is reached around k =Fig 2: Channel existence probability for different 100 and is above 15%).values of P and k. To overcome the above drawbacks, we propose a scheme where, with an increase in the Note that channel existence scales with the communication overhead, the key establishmentWSN size. Indeed, the probability of channel phase is made co-operative. If sensor a wants toexistence is independent from n, being dependent establish a secure channel with sensor b, sensor aonly on k and P. In Fig 2 we plot the probability of chooses a set C = {c1; : : : ;cm} of co-operatingchannel existence between sensors a and b as a sensors such that a;b € C and m ≥ 0. Then, a sends afunction of the per sensor number of keys k and for request of co-operation to each of the sensors in C.three values of the pool size P. It is remarkable that, The request sent to c ε C is encrypted with ka,c andeven with a small number of keys loaded on the carries the ID of b. Each cooperating sensor csensors, the channel has high probability of existence. transforms its original channel key with b, kc;b, as follows: first, kc;b is built according to the Direct15. THE COOPERATIVE PROTOCOL Protocol; then, a share is created by hashing kc;b with15.1. The Protocol the id of a As it has been shown the Direct Protocolallows two sensors to communicate with a certain 1472 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475 finally, the share is sent back to a encrypted  sensor failure resistance: if a sensor in C iswith key ka;c. When all the shares are received, sensor not available for any reason (for instance,a computes ka;b and combines it with all the shares to the sensor is destroyed or its batteryobtain a cooperative channel key kC a;b exhausted), the protocol will not fail or deadlock; moreover, if some sensors do not answer to the request of co-operation within a certain time-out, sensor a can choose to add other sensors to C, in order to achieve aSensor a sends the list of sensors in C (encrypted satisfactory level of security.with key ka;b) to sensor b along with H (kC a;b).  no information leakage: since co-operatingSensor b, once this message is received, has all the sensors provide a with a transformed, not-information required to locally compute kC a;b, invertible image of their channel with b, nowithout sending or receiving any other message, and information on the effective channels kci;b isto double check the resulting key with H (kC a;b). revealed;Note that, when m = 0, the Direct and Co-operative  adaptiveness: if no information is availableProtocol are equivalent. on the set of corrupted sensors but an upperTable 3 shows in detail the pseudo code of the Co- bound on set C can be chosen in such a wayoperative Protocol. In Figure 3, we show a simplified to secure all channels with the desiredinstance of the messages exchanged by the Co- probability;operative Protocol in the case there is only one co-operating sensor (c1). In step (1), sensor a sends the  load balance: the work-load generated by therequest of co-operation to sensor c1; once c1 has Co-operating Protocol is equally distributedreceived such a request, it computes kc1;b according among all the sensors in C, i.e. one messageto the Direct Protocol and sends a transformed and per sensor in C. Only sensor a has to sendnot-invertible image of such a value to a, as shown in m+1 messages (one for each of the co-step (2). Finally, sensor a computes kCa;b according operating sensors in C and one to b). Theto Equation, and sends this value to b, together with total cost for the WSN is thus 2m+1the set of sensors (c1) that co-operated in building the potentially multi-hop messages. However,channel (step (3)). Note that it is mandatory for this cost is incurred only once, during thesensor a to send, in step (3), the list of sensors in C, channel set up. Finally, note that sensor botherwise b would not be able to compute kCa;b. does not need to send any message to buildSuch a list is at most mlogn bits long. up the cooperative channel. In general, it is possible that corrupted sensors are chosen as co-operators in the Co-operative Protocol. This is explicitly considered in the analysis of the previous section and in the experiments, which shows that channel confidentiality can be probabilistically guaranteed. However, it is interesting to explore all possible attacks from a cooperating sensor against other properties of the protocol. Assume ὼi 2 C W is a corrupted sensor included into the set of cooperators for the channel set up from a to b. When ὼi is asked by a to provide its share, i can behave asFig 3: Example of co-operative approach with one follows:cooperating sensor 1. Sensor ὼi does not respond; Set C can be chosen according to several 2. sensor ὼi sends a correct key kὼi ;b;policies. A first energy preserving option is to include 3. sensor ὼi sends a bogus key ˜kὼi ;b.only relatively nearby sensors in C. For example, Case 1 is equivalent to the case when a co-only sensors within one or two hops. This choice operating sensor is not available anymore, foryields a more efficient key setup phase, though the instance it has been destroyed or its battery has runprotocol can be weaker against geographically out. After the time-out ∆defined in Table 3, sensor alocalized attacks. A second option is to choose C can decide to involve other sensors if the number ofrandomly, giving more security at the price of a cooperating sensors is too low to guarantee itslarger communication overhead especially in large security requirements. Case 2 is the best choice if thenetworks. With this second option, the protocol attacker aims at breaking the channel confidentiality.would support both random and geographically Indeed, the channel is set up, and the attacker maylocalized attacks. Third, sensors can be chosen have enough keys to recover kCa;b. Since this paperaccording to individual properties, like tamper- focuses on confidentiality, in both the analysis andresistance, giving a potentially more secure channel. the experimental evaluation we assume this is theThe Co-operative Protocol shows the following default behavior of corrupted sensors. Note that thefeatures: presence of malicious cooperators does not imply that 1473 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475the channel is corrupted. Case 3 may result in a each environment are different, further research isDenial of Service (DoS) on sensor a. Indeed, the necessary for handling these kinds of situations.channel built by sensor a with a bogus share does not The primary contribution of this work is to providematch the channel locally computed by sensor b. an brief analytic and quick review about sensorEven though the goal of this paper is to address networks, wireless sensor networks, routingconfidentiality, in the following we sketch a few protocols, design issues, and security constraints bycountermeasures that can be taken to mitigate this going through this paper an easier and brief review ofsort of DoS attack. A first countermeasure is to all wsns and the drawbacks of protocols which usingrandomly select another set C of co-operating sensors for providing security has also analyzed and theand to re-apply the co-operative protocol. In order to disadvantages are also mentioned… to continuebe an effective solution, set C should be chosen small forwarding the field of security in WSNenough to have Pr[C ∩W = ᶲ] > 1=t, for some small reprogramming protocols, proposing apositive integer t. In this way, after t iterations on the comprehensive security solution. We focus less onaverage, a good set of cooperators is found. Note that novel solutions for authentication and focus more onother subsets of cooperators can be added later to availability and confidentiality .in network scenariosstrengthen the same final cooperative channel. A needing security in the reprogramming process.second countermeasure is possible if a trusted Another contribution of this work is that we makechannel to the center is available. Each sensor can evident in our energy examination that radiostore an individual secret key shared with the center, operations are the most energy consuming operationswhich also knows all the secret keys of the pool. in update dissemination. This fact guided ourWhen sensor a finds that a channel key ˜k Ca ;b could decisions in proposing balanced availability andcontain a bogus share, sensor a sends it to the center confidentiality solutions.along with all the shares it used to build the key.Assuming that a is not corrupted, the center has all REFERENCESthe information to track down efficiently the cheating [1] A comparative analysis of routingsensors among C and b. Then, this is sent back to a. techniques for wireless sensor networksNote that the center is used only when a cheater is Raghunandan, G.H. Lakshmi, B.N.detected, and corrupted sensors are discouraged to Innovations in Emerging Technologygive bogus shares in this setting. Finally, even when a (NCOIET), 2011 National Conference onchannel to the center is not available, the presence of Digital Object Identifier:a bogus share gives the important information that 10.1109/NCOIET.2011the WSN is under attack. [2] The Novel Energy Adaptive Protocol for heterogeneous wireless sensor networksCONCLUSION Golsorkhtabar, M.; Nia, F.K.; Hosseinzadeh, Sensor Networks hold a lot of promise in M.; Vejdanparast, Y. Computer Science andapplications where gathering sensing information in Information Technology (ICCSIT), 2010 3rdremote locations is required. It is an evolving field, IEEE International Conference on Volume:which offers scope for a lot of research. Moreover, 2unlike MANETS, sensor networks are designed, in Digital Object Identifier:general, for specific applications. Hence, designing 10.1109/ICCSIT.2010.5563781 Publicationefficient routing protocols for sensor networks that Year: 2010 , Page(s): 178 - 182suits sensor networks serving various applications is [3] Tradeoffs among Delay, Energy andimportant. In this paper, we identified some of the Accuracy of Partial Data Aggregation inimportant design issues of routing protocols for Wireless Sensor Networks Wuyungerile Li;sensor networks and also compared and contrasted Bandai, M.; Watanabe, T. Advancedthe existing routing protocols. As our study reveals, it Information Networking and Applicationsis not possible to design a routing algorithm which (AINA), 2010 24th IEEE Internationalwill have good performance under all scenarios and Conference on Digital Object Identifier:for all applications. Although many routing protocols 10.1109/AINA.2010.137 Publication Year:have been proposed for sensor networks, many issues 2010 , Page(s): 917 – 924still remain to be addressed Other possible future [4] Methods of Sensors Localization in Wirelessresearch for routing protocols includes the integration Sensor Networks Chaczko, Zenon;of sensor networks with wired networks (i.e. Klempous, Ryszard; Nikodem, Jan;Internet). Most of the applications in security and Nikodem, Michal Engineering of Computer-environmental monitoring require the data collected Based Systems, 2007. ECBS 07. 14thfrom the sensor nodes to be transmitted to a server so Annual IEEE International Conference andthat further analysis can be done. On the other hand, Workshops on the Digital Object Identifier:the requests from the user should be made to the sink 10.1109/ECBS.2007.48through Internet. Since the routing requirements of [5] A reliable synchronous transport protocol for wireless image sensor networks 1474 | P a g e
    • M. L.S. N. S. Lakshmi, S.Gopi Krishna / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.1462-1475 Boukerche, A.; Yan Du; Jing Feng; Pazzi, R. Computers and Communications, 2008. ISCC 2008. IEEE Symposium on Digital Object Identifier: 10.1109/ISCC.2008.4625679 Publication Year: 2008 , Page(s): 1083 - 1089 [6] An implementation of wireless sensor Gopi Krishna.Seemala received network Soo-Hwan Choi; Byung-Kug Kim; B.S.C electronics degree from Andhra university Jinwoo Park; Chul-Hee Kang; Doo-Seop Visakhapatnam (Andhra pradesh) in 1999.and M.S.C Eom Consumer Electronics, IEEE electronics in 2001,and doctorate in Transactions on physics(phd)from same university in 2002.from Volume: 50 , Issue: 1 Digital Object 2002-2007 he worked as a senior research fellow in Identifier: 10.1109/TCE.2004.1277868 Andhra University under the Guidance of Publication Year: 2004 , Page(s): 236 - 244 PROF.P.V.S RAMA RAO Physics Dept, Andhra [7] W. Heinzelman, J. Kulik, H. Balakrishnan, University and from 2007 he worked as a research Adaptive protocols for information scientist in Institute For scientific research ,Boston dissemination in wireless sensor networks, college, Boston U.S.A. later he worked as a post in: Proceedings of the 5th Annual doctoral research scientist (2007-2009) in the same ACM/IEEE International Conference on college .having Hands on experience on Real time Mobile Computing and Networking monitoring TEC, and scintillations using the [8] Ian F. Akyildiz, Weilian Su, Yogesh LISN(low latitude ionospheric sensor Sankaraubramaniam, and Erdal Cayirci: A network)producing TEC maps and possible Survey on sensor networks, IEEE prediction of scintillations. He published more than Communications Magazine (2000) 20 research publications in terristial atmospheric, and [9] Al-Karaki,J.N,Al-Mashagbeh: Energy- oceanic sciences journal of geophysical research, Centric Routing in Wireless Sensor Journal of earth planets and sciences, journal of Networks Computers and Communications, atmospheric and solar terristial physics and presented ISCC 06 Proceedings, 11th IEEE papers on communication journals. Presently he is Symposium (2002). working as a associate professor in Koneru [10] Kay Romer, Friedemann Mattern: The Lakshmaiah university. Design Space of Wireless Sensor Networks, IEEE Wireless Communications, pp. 54-61 (December 2005) AUTHORS BIBILOGRAPHY M.L.S.N.S Lakshmi received herdiploma in Electronics and Communications in Govt.Polytechnic for Women Guntur (Andhra Pradesh) in(2008),B.Tech degree in Electronics AndCommunication Engineering from Vignan’sEngineering college affiliated to JNTU Kakinada, (in2011) and presently doing her M.Tech inCommunications and Radars from KoneruLakshmaiah University (KLU) situated inVaddeswaram near to Vijayawada (Andhra Pradesh).Currently she is doing research at the laboratories ofmobile and wireless communications in theDepartment of Electronics and CommunicationEngineering at KL University. Her research interestslie in channel allocation strategies, assignmentschemes, hand off techniques, call blockingprobabilities, access& queuing techniques, related tomobile and wireless communications. 1475 | P a g e