<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">WSN</journal-id><journal-title-group><journal-title>Wireless Sensor Network</journal-title></journal-title-group><issn pub-type="epub">1945-3078</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/wsn.2017.91003</article-id><article-id pub-id-type="publisher-id">WSN-73723</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Computer Science&amp;Communications</subject></subj-group></article-categories><title-group><article-title>
 
 
  Location-Based Routing Protocols for Wireless Sensor Networks: A Survey
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Arun</surname><given-names>Kumar</given-names></name><xref ref-type="aff" rid="aff1"><sup>1</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hnin</surname><given-names>Yu Shwe</given-names></name><xref ref-type="aff" rid="aff2"><sup>2</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kai</surname><given-names>Juan Wong</given-names></name><xref ref-type="aff" rid="aff3"><sup>3</sup></xref></contrib><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Peter</surname><given-names>H. J. Chong</given-names></name><xref ref-type="aff" rid="aff4"><sup>4</sup></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib></contrib-group><aff id="aff2"><addr-line>School of Electrical and Electronics Engineering, Nanyang Technological University, Singapore</addr-line></aff><aff id="aff1"><addr-line>School of Electrical and Computer Engineering, National University of Singapore, Singapore</addr-line></aff><aff id="aff4"><addr-line>Department of Electrical and Electronic Engineering, Auckland University of Technology, Auckland, New Zealand</addr-line></aff><aff id="aff3"><addr-line>Information and Communications Technology, Singapore Institute of Technology, Singapore</addr-line></aff><author-notes><corresp id="cor1">* E-mail:<email>peter.chong@aut.ac.nz(PHJC)</email>;</corresp></author-notes><pub-date pub-type="epub"><day>17</day><month>01</month><year>2017</year></pub-date><volume>09</volume><issue>01</issue><fpage>25</fpage><lpage>72</lpage><history><date date-type="received"><day>November</day>	<month>3,</month>	<year>2016</year></date><date date-type="rev-recd"><day>Accepted:</day>	<month>January</month>	<year>20,</year>	</date><date date-type="accepted"><day>January</day>	<month>23,</month>	<year>2017</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  Recently, location-based routings in wireless sensor networks (WSNs) are attracting a lot of interest in the research community, especially because of its scalability. In location-based routing, the network size is scalable without increasing the signalling overhead as routing decisions are inherently localized. Here, each node is aware of its position in the network through some positioning device like GPS and uses this information in the routing mechanism. In this paper, we first discuss the basics of WSNs including the architecture of the network, energy consumption for the components of a typical sensor node, and draw a detailed picture of classification of location-based routing protocols. Then, we present a systematic and comprehensive taxonomy of location-based routing protocols, mostly for sensor networks. All the schemes are subsequently discussed in depth. Finally, we conclude the paper with some insights on potential research directions for location-based routing in WSNs.
 
</p></abstract><kwd-group><kwd>Location-Based Protocol</kwd><kwd> Geographic Routing</kwd><kwd> Wireless Sensor Networks</kwd><kwd> Energy Conservation</kwd><kwd> Routing</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>In recent years, location-based routing has emerged as the prominent area of research in the field of wireless sensor networks (WSNs). Sensor nodes may not have the internet protocol (IP) addresses; therefore, IP-based protocol cannot be used for the sensor networks. Building an efficient, scalable and simple protocol for WSN is very challenging due to limited resources and the dynamic nature of sensor networks. In location-based routing, the node does not need to make complex computations to find the next hop, as routing decisions are taken using the location information. Location-based protocols are very efficient in terms of routing data packet as they take the advantage of pure location information instead of global topology information. This paper presents a survey and taxonomy of location-based routing for sensor networks.</p><p>In location-based routing, a node that has a packet to send (Source) adds a destination location (Sink) in each data packet. Intermediate nodes in the path receive this packet and send it to next one-hop neighbours which are geographically closest to the destination. The process is continued until the data packets are received by the destination node. In location-based routing, the state required to be maintained in each node is minimum, because of the locality. It has low communication overhead because advertisements of routing tables, like in traditional routing protocols, are not needed. Location-based routing thus does not require the establishment or maintenance of routes. Therefore, Location-based routing conserves both energy and bandwidth since route request and state propagation are not required after one-hop distance.</p><p>Location-based routing uses the location information for nodes to provide higher efficiency and scalability. It requires three facts: first, each node in the network must know its own location information by GPS or by any other methods [<xref ref-type="bibr" rid="scirp.73723-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref3">3</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref4">4</xref>] . Second, each node must be aware of its neighbour node’s location which is one-hop away from it. Third, the source must be aware of the location of destination node.</p><p>Location-based routing requires the correct location information, which can be obtained using some localization mechanism. Location information is essential for many wireless network applications, so it is expected that each wireless sensor node in the network will be equipped with some localization devices. Several techniques [<xref ref-type="bibr" rid="scirp.73723-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref3">3</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref4">4</xref>] exist for location sensing based on proximity or triangulation using radio signals, acoustic signals, or infrared. These techniques differ in their localization granularity, range, deployment complexity and cost. Most of the location mechanisms utilize the flooding [<xref ref-type="bibr" rid="scirp.73723-ref5">5</xref>] to spread the sink’s location up to all other nodes, which is undesirable for the large-scale WSNs, especially when the multiple mobile sinks and sources exist.</p><p>Location-based routing usually uses a greedy forwarding mechanism to forward a data packet from source to destination. Greedy approach forwards packets to the neighbour, which is closest to the destination. It assumes that the network is sufficiently dense; each node has its own accurate location information, its neighbours’ locations, and high link reliability. Dense sensor deployment [<xref ref-type="bibr" rid="scirp.73723-ref6">6</xref>] and reasonably accurate location information may be acceptable in some WSN applications. But the high link reliability is not acceptable in any realistic deployment. Because recent studies [<xref ref-type="bibr" rid="scirp.73723-ref7">7</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref8">8</xref>] show that wireless links can be highly unreliable and have to deal with the higher-layer protocols.</p><p>Many forwarding strategies [<xref ref-type="bibr" rid="scirp.73723-ref9">9</xref>] are proposed to improve the performance of geographic routing. These forwarding strategies can be broadly divided into two categories: distance-based and reception-based. While the nodes need to know only the distance to their neighbours in distance-based strategy, the nodes also know the packet reception rates of their neighbours in reception-based strategy. Both strategies use the greedy-like forwarding to choose the next hop in the forwarding process.</p><p>In order to understand localtion based routing in WSN, we begin with an overview on WSN. The overview includes common architectures of sensor networks, available protocols and application areas in WSN. We then provide a taxonomy of localtion-based routing protocols for WSN. A table comparing different location-based routing protocols is given at the end of this paper. In addition, we discuss the available ad-hoc routings in WSN. To the best of our knowledge, there is no paper to give a survey on location-based routing for WSNs. With this article, readers can have a more thorough and delicate understanding of location-based routing for WSNs and the research trend in this area.</p></sec><sec id="s2"><title>2. Wireless Sensor Networks</title><sec id="s2_1"><title>2.1. Architecture of WSNs</title><p>WSNs have attracted many researchers in this field of research in the past few years. The advancement in the field of micro electro mechanical systems (MEMS) has open the way to develop low-cost, low-power, multi-functional, tiny sensor nodes [<xref ref-type="bibr" rid="scirp.73723-ref10">10</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref11">11</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref12">12</xref>] . These tiny nodes are capable to sense the environment, perform data processing and having the capability to communicate with other nodes in the network over short distances. A typical architecture of WSN is shown in <xref ref-type="fig" rid="fig1">Figure 1</xref>.</p><p>WSN consists of at least one sink node (or base station) and a (large) number of sensor nodes deployed in the network field. Sensor nodes in the field sense and collect raw data from the environment to do some local processing, communicate with each other to perform aggregation in necessary, and then route the aggregated data to the sink. Sink or base station serves as a destination node for the sensor nodes. User can access the data from the sink by internet or satellite.</p><fig id="fig1"  position="float"><label><xref ref-type="fig" rid="fig1">Figure 1</xref></label><caption><title> Architecture of wireless sensor network</title></caption><graphic mimetype="image"   position="float"  xlink:type="simple"  xlink:href="http://html.scirp.org/file/3-9501509x2.png"/></fig><p>A large-scale WSN consists of thousands of sensor nodes deployed according to the application [<xref ref-type="bibr" rid="scirp.73723-ref13">13</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref14">14</xref>] . Wireless sensor nodes are small devices that have three basic components. First, a sensing device for data acquisition from the physical surrounding environment. Second, a processing unit for local data processing and storage. Third, a wireless communication device for data transmission. An archi- tecture of typical wireless sensor node [<xref ref-type="bibr" rid="scirp.73723-ref15">15</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref16">16</xref>] and a berkeley Mote (Real-life sensor node) [<xref ref-type="bibr" rid="scirp.73723-ref17">17</xref>] is shown in <xref ref-type="fig" rid="fig2">Figure 2</xref> and <xref ref-type="fig" rid="fig3">Figure 3</xref> respectively.</p><p>These sensor nodes have several resource constraints such as limited memory, battery power, signal processing, computation and communication capabilities. These nodes are mainly deployed in remote areas and intended to work for WSN research interest. Many research prototype sensor nodes such as UCB motes [<xref ref-type="bibr" rid="scirp.73723-ref18">18</xref>] , uAMPS [<xref ref-type="bibr" rid="scirp.73723-ref19">19</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref20">20</xref>] , MICA [<xref ref-type="bibr" rid="scirp.73723-ref21">21</xref>] and PC104 [<xref ref-type="bibr" rid="scirp.73723-ref22">22</xref>] have been designed many years so lifetime extension of sensor networks play an important role in and manufactured. Energy efficient MAC [<xref ref-type="bibr" rid="scirp.73723-ref23">23</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref24">24</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref25">25</xref>] , and different routing schemes are implemented and evaluated for the real life application of WSNs.</p><p>WSNs require sensor nodes to communicate with each other frequently depending on the application, making data dissemination a challenging task in large networks. During data dissemination in WSNs, data transmission consumes more energy than data processing in a sensor node. The energy required to transmit a single bit is comparable to the amount required to process a few</p><fig id="fig2"  position="float"><label><xref ref-type="fig" rid="fig2">Figure 2</xref></label><caption><title> Architecture of a typical sensor node</title></caption><graphic mimetype="image"   position="float"  xlink:type="simple"  xlink:href="http://html.scirp.org/file/3-9501509x3.png"/></fig><fig id="fig3"  position="float"><label><xref ref-type="fig" rid="fig3">Figure 3</xref></label><caption><title> Berkeley mote [<xref ref-type="bibr" rid="scirp.73723-ref17">17</xref>] </title></caption><graphic mimetype="image"   position="float"  xlink:type="simple"  xlink:href="http://html.scirp.org/file/3-9501509x4.png"/></fig><p>thousands operations in a typical sensor node [<xref ref-type="bibr" rid="scirp.73723-ref26">26</xref>] . Sensing subsystem energy consumption depends on the sensor type. In some cases, it is negligible when compared with processing and transmission energy. But on the other hand, data sensing may be comparable to, or even greater than, the energy needed for data transmission.</p><p>Mainly, energy-saving techniques focus on network subsystem and sensing subsystem. In networking subsystem, energy management is taken into account in the operations of each single node, as well as in the design of networking protocols. In sensing subsystem, techniques are used to reduce the amount or frequency of energy-expensive samples. The lifetime of the sensor network can be prolonged by applying different energy conservation techniques. However, the main energy consumption components are CPU radio, even if they are idle. Therefore, different power management schemes are used to switch off the node components that are temporarily not necessary. Conserving the energy of the nodes can prolong the lifetime of the whole network.</p><p>Sensor networks can be broadly classified into two types; homogeneous and heterogeneous sensor networks. In homogeneous sensor network, all the sensor nodes are identical in terms of battery energy and hardware complexity. On the other hand, two or more different types of nodes with different battery energy and functionality are used in heterogeneous sensor network.</p><p>Sensor nodes do not have the IP address so, the queries are directed to a region containing a cluster of sensors rather than specific sensor addresses. We can say that sensor networks are predominantly data-centric rather than address-centric. Aggregation of the data is performed locally and a summary or analysis of the local data is prepared by an aggregator node within the cluster, thus reducing the communication bandwidth requirements. Dedicated routing protocol is required for dissemination of data packet through shortest path. Redundancy must be considered to avoid congestion when different nodes are sending and receiving the same information. However, redundancy must be exploited to ensure network reliability. Data dissemination can be query driven or based on continuous updates.</p></sec><sec id="s2_2"><title>2.2. MAC for WSNs</title><p>In past few years, several medium access control (MAC) layer protocols were proposed to improve the performance of the sensor network. MAC protocols basically prolong the network life time by switching on and off the sensor node components like the radio transceiver. B-MAC [<xref ref-type="bibr" rid="scirp.73723-ref27">27</xref>] is a low power and flexible MAC protocol based on CSMA. It provides basic operations and interfaces help dynamically change the parameter of the protocol to compromise with the varying communication environment. B-MAC also provides two-directional interface for routing protocol and MAC protocol to communicate with each other by calibrating the parameter of the interface. It utilizes the sleep and wakeup technique to save the energy of the node. It does not support multicast and thus messages have to wait for another cycle to forward the data.</p><p>RMAC is an energy efficiency duty cycle MAC protocol for WSN. RMAC uses sleep period to send/receive data between nodes and forward control packet along the route during one duty cycle. The control packet helps the receiver to calculate the exact wakeup time. It uses data period to transmit PION packet instead of data and calculates to forward data packet to more than one node along the route in sleep mode. It does not support broadcast mode and bust data mode.</p><p>Z-MAC is a hybrid adaptive MAC protocol. The main idea is to make of CSMA as the foundation and TDMA as the hint for protocol. Based on the B-MAC operation, Z-MAC proposed a flexible and adaptive MAC with the data in the network. Z-MAC easily adapt with the changing content of the sensor network. It is suitable for the application with medium to high, two-hop contention. The drawback of Z-MAC is that many algorithms were needed to initialize and maintain the status of the network such as DRAND to assign node slot, TPSN to synchronize the global clock.</p><p>T-MAC is a contention-based MAC protocol for WSN which uses the duty cycle (alternatively active/sleep node) to increase the life of the nodes. It proposed an adaptive duty cycle by dynamically ending the active part of it. This can reduce the energy consumption on idle listening, while giving a constant and reasonable throughput.</p><p>S-MAC [<xref ref-type="bibr" rid="scirp.73723-ref28">28</xref>] utilized three novel techniques to reduce energy consumption and support self-configuration. Nodes periodically sleep to save the energy wasted by idle listening. Neighbouring nodes form virtual clusters auto-syn- chronize on sleep schedules. S-MAC utilizes the message passing technique to reduce contention latency for sensor-network applications that require store- and-forward processing as data moves through the network. S-MAC has better energy conserving properties compared to the IEEE 802.11. It also has the ability to trade-off between energy and latency according to traffic conditions.</p></sec><sec id="s2_3"><title>2.3. Application of WSNs</title><p>A wireless sensor network is a wireless network consisting of spatially distributed autonomous devices with sensing, computation and wireless communication capabilities to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants at different locations. The development of the sensor network was originally motivated by military applications such as enemy tracking, tank and soldier surveillance and battle field surveillance. Today we can see a large number of application of WSNs, like industrial process monitoring and control [<xref ref-type="bibr" rid="scirp.73723-ref29">29</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref30">30</xref>] , environment observation and habitat monitoring [<xref ref-type="bibr" rid="scirp.73723-ref31">31</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref32">32</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref33">33</xref>] , healthcare applications [<xref ref-type="bibr" rid="scirp.73723-ref34">34</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref35">35</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref36">36</xref>] , home automation [<xref ref-type="bibr" rid="scirp.73723-ref37">37</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref38">38</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref39">39</xref>] , traffic control [<xref ref-type="bibr" rid="scirp.73723-ref40">40</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref41">41</xref>] and forecast systems [<xref ref-type="bibr" rid="scirp.73723-ref42">42</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref43">43</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref44">44</xref>] .</p><p>WSN applications typically involve the surveillance of physical phenomenon through the sampling of the environment situation. Accordingly, WSN applications can be classified as tracking and monitoring categories. Overall classification of sensor network applications is depicted in <xref ref-type="fig" rid="fig4">Figure 4</xref>.</p><p>Location-based routing plays a massive role in the military application, volcano monitoring, environment observation, traffic control, forecast system and so on. Location-based routing protocols are efficient for getting the information from a particular region. It is also very useful when the terrain is not accessible by human being like volcano monitoring. Many real life projects are running in the different parts of the world using the location-based routing in to consideration like Zebranet [<xref ref-type="bibr" rid="scirp.73723-ref45">45</xref>] , wildCENSE [<xref ref-type="bibr" rid="scirp.73723-ref46">46</xref>] , PinPtr [<xref ref-type="bibr" rid="scirp.73723-ref47">47</xref>] , CenWits [<xref ref-type="bibr" rid="scirp.73723-ref48">48</xref>] and volcanic monitoring [<xref ref-type="bibr" rid="scirp.73723-ref49">49</xref>] .</p></sec></sec><sec id="s3"><title>3. Ad-Hoc Routings</title><p>Many ad-hoc routing protocols were proposed to enhance the efficiency of ad-hoc network. Most well-known protocols are like DSR [<xref ref-type="bibr" rid="scirp.73723-ref50">50</xref>] , DSDV [<xref ref-type="bibr" rid="scirp.73723-ref51">51</xref>] , TORA [<xref ref-type="bibr" rid="scirp.73723-ref52">52</xref>] and AODV [<xref ref-type="bibr" rid="scirp.73723-ref53">53</xref>] . Both of Dynamic source routing (DSR) [<xref ref-type="bibr" rid="scirp.73723-ref50">50</xref>] and Ad-hoc on demand distance vector routing (AODV) [<xref ref-type="bibr" rid="scirp.73723-ref53">53</xref>] protocols flood the route request on-demand which help to save the bandwidth and also increase the battery power (not sending and receiving the message unnecessarily). Even if the link is broken, the AODV provides loop-free routes. On the other hand, temporally- ordered routing algorithm (TORA) [<xref ref-type="bibr" rid="scirp.73723-ref52">52</xref>] is from the family of “link reversal” algorithms. TORA is best to use in large, dense and mobile networks. TORA is an efficient and scalable protocol and shows a high degree of adaptively. Sensor networks require more energy and bandwidth saving than the Ad-hoc networks; and the communication in sensor networks is data-centric as opposed to address- centric in ad-hoc networks. And the communication in WSN is data-centric as opposed to address-centric in ad-hoc networks. Therefore the ad-hoc network</p><fig id="fig4"  position="float"><label><xref ref-type="fig" rid="fig4">Figure 4</xref></label><caption><title> Overview of sensor network applications</title></caption><graphic mimetype="image"   position="float"  xlink:type="simple"  xlink:href="http://html.scirp.org/file/3-9501509x5.png"/></fig><p>protocols are undesirable for sensor networks.</p><p>The few major differences between wireless sensor networks and ad-hoc networks are given below.</p><p>1) Sensor networks are mainly used to collect information while MANETs (Mobile Ad-hoc Networks) are designed for distributed computing rather than information gathering.</p><p>2) The number of sensor nodes in a sensor network can be several orders of magnitude higher than the nodes in an ad hoc network.</p><p>3) Sensor nodes are densely deployed.</p><p>4) Sensor nodes are prone to failures.</p><p>5) The topology of a sensor network changes very frequently.</p><p>6) Sensor nodes mainly use a broadcast communication paradigm, whereas most ad hoc networks use point-to-point communications.</p><p>7) Sensor nodes are limited in power, computational capacities and memory.</p><p>8) Unlike a node in ad-hoc networks, a node in sensor network may not have global Identification (ID) because of the large amount of overhead and large number of sensors.</p><p>9) Sensor nodes are much cheaper than nodes in ad hoc networks.</p><p>10) Usually, the data in sensor networks are bound either downstream to nodes from a sink or upstream to a sink from nodes, while in MANETs, the data flows are irregular.</p></sec>
<sec id="s4"><title>4. Location-Based Protocols for WSNs</title>
<p>In this section, we survey the state-of-the-art location-based routing protocols for WSNs. Sensor nodes may not have the internet protocol (IP) addresses, therefore IP-based protocols cannot be used for the sensor networks. Building an efficient, scalable and simple protocol for WSN is very challenging due to limited resources and the dynamics nature of sensor network. In location-based routing, the node do not need to make complex computations to find the next hop, as routing decisions are taken using the location information. Location- based protocols are very efficient in terms of routing data packet as they take the advantage of pure location information instead of global topology information.</p>
<p>Location-based protocol uses the location information of nodes to provide higher efficiency and scalability. It requires three facts. First, each node in the network must know its own location information by GPS or by any other methods [<xref ref-type="bibr" rid="scirp.73723-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.73723-ref3">3</xref>] . Second, each node must be aware of its neighbour nodes’ location, which are one-hop away from it. Third, the source node must be aware of the location of destination node. Location-based routing protocols can be mainly categories as shown in <xref ref-type="fig" rid="fig5">Figure 5</xref>.</p>
<p>Most of the location-based protocols are using the greedy algorithms to forward the packets to the destination. These algorithms only differ in how they handle the hole communication problem.</p>
<p>The earliest work in location-based is done by Finn and Gregory G. [<xref ref-type="bibr" rid="scirp.73723-ref54">54</xref>] in 1987. In this report, they proposed a flat routing mechanism called Cartesian</p>
<fig id="fig5"  position="float"><label><xref ref-type="fig" rid="fig5">Figure 5</xref></label><caption><title> Categorization of location-based routing protocols</title></caption><graphic mimetype="image"   position="float"  xlink:type="simple"  xlink:href="http://html.scirp.org/file/3-9501509x6.png"/></fig>
<p>routing. The drawback of the mechanism was its difficulty in determining an appropriate scope for the search.</p>
<p>Greedy perimeter stateless routing (GPSR) [<xref ref-type="bibr" rid="scirp.73723-ref55">55</xref>] uses a planar graph to avoid this problem. Planar graph is derived from the original network graph. The packet follows the perimeter of the planar graph to circumvent holes. The de- rived planar graph is much sparser than the original one, and the traffic concen- trates on the perimeter of the planar graph in perimeter mode. Thus, the nodes on the planar graph tend to be depleted quickly. In addition, nodes are assumed to operate in promiscuous listening mode and consequently consume energy.</p>
<p>Location aided routing (LAR) [<xref ref-type="bibr" rid="scirp.73723-ref56">56</xref>] , was proposed for the ad-hoc network. It uses the location information (location information obtained by GPS) to find the new route. By using the location information, the LAR limits the search in a smaller region called “request zone”. Limiting the search in the request zone significantly reduces the number of search message. The request zone is estimated by the previous information of the location and mobility pattern of the nodes. In case, the mobility pattern is not accurate, the request zone can be extended up to the whole network field.</p>
<p>The categorization of location-based routing is shown in <xref ref-type="fig" rid="fig5">Figure 5</xref>. To present the protocols in this paper we have divided the protocols in two sections, ac- cording to mobile or static nodes present in the network. Each protocol in these sections states which method they use to acquire the location information. In both sections, we survey in detail the protocols that fall below the location-based routing in WSN. <xref ref-type="table" rid="table1">Table 1</xref> shows the detailed comparison among those location-based routing algorithms mentioned here. The properties chosen for comparison are mobility, energy-awareness, self-reconfiguration, negotiation, data aggregation, quality of service (QoS), state complexity, scalability, multipath, query-based, and GPS incorporation. Routing algorithms considering mobile nodes in the network are complex in nature as opposed to the static nodes. Due to limited energy of the tiny wireless sensor nodes, energy- awareness is an important characteristic for location-based routing protocols in WSN. As these protocols requires the location information, wireless sensor</p></sec></body>
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