Long lived path routing with received signal strength for ad hoc networks

The AODV-RSS algorithm power consuming rate [22, 23] and suffer more path broken uses the received signal strength, RSS, and the received signal frequency.. Simulation results show that

Long-lived Path Routing With Received Signal

Ruay-ShiungChang+and Shing-JiuanLeu++

+Departmentof Computer Science and InformationEngineering

NationalDong HwaUniversity, Shoufeng,Hualien,Taiwan,ROC

email:rschanggmail.ndhu.edu.tw 'Department of Information Management Tung NanInstitute ofTechnology,Taipei,Taiwan, ROC Abstract-Routing paths in mobile ad hoc networks are easily otherpaths inreal distance Itishighly probablethat the spatial

disrupteddue to themobilityof nodes.Therefore,it is desirable to distance between intermediate nodesontherouteislarger than find arouting path such that alledges in thepathare long-lived, another path The actually longer distance between neighboring Based on theAdhocOn-demand Distance VectorRouting(AODV) nodes may give rise to path maintenance cost, reduce the

Signal Strength) routing protocol such that connectivities of links quait cof su rasch low packett mio rate,bhigh

in the route found can sustainlonger The AODV-RSS algorithm power consuming rate [22, 23]) and suffer more path broken

uses the received signal strength, RSS, and the received signal frequency The whole systemperformance will be affected by strength changing rate, ARSS, to predict the link available time, the inferior routing path.

LAT Using the LAT as a constraint, our method will find out a In this paper we propose a routing scheme to improve the

satisfying routing path Simulation results show that our routing quality ofedge connection time in therouting path found for

algorithm can greatly improve thequality of the routing path in mobile ad hoc networks This protocol is called AODV-RSS route connection time,and route reestablishmentfrequency (AODV with Received Signal Strength) Our method is based Keywords: Ad HocNetworks, ReceivedSignalStrength,Ad on the received signal strength, RSS, and the received signal hocOn-demand Distance Vectorrouting strength changing rate, zIRSS. We use these parameters to

forecast the link available time (LAD between two mobile

I INTRODUCTION nodes Then we can find a minimum hop count routing path

that satisfies a minimum LATconstraint This method isvery Wireless networks provide mobile users with ubiquitous useful in the multimedia communication environment where communication and information access capabilities regardless there are real time flows and best effort flows A real time flow

of their locations Thereare currentlytwovariations of mobile needs QoS guarantees, such as packet delay bound, delayjitter, wireless networks The first is known as infrastructured bandwidth, etc Though a larger LAT does not necessarily networks, i.e., networks with fixed and wired gateways A translate into better QoS guarantees, it is a good start for typical network is the cellular personal wireless finding such a path Using the LAT constraint, at least our communication system The second type of mobile wireless routing protocol will produce a more long-lived and stable network is the infrastructureless mobile networks, commonly routing path for the real time flows

known as a Mobile Ad Hoc NETwork, or MANET [1]. The The remainder of this paper is organized as follows Section infrastructureless network has no fixed routers. Each mobile 2describes some of the routing protocols for ad hoc networks node operates not only as a host but also as a router, which Section 3 describes the AODV-RSS routing protocol In discovers and maintainsroutes toother nodes inthis network Section 4, the simulation environment and the results of Example applications of ad hoc networks are emergency comparing theperformanceofour method and related work are search-and-rescueoperationsand dataacquisition operations im presented Section 5 concludes this paper.

inhospitable terrains

hosts make the design ofrouting protocols challenging. Many

protocols have been proposed, such as DSDV [2], CGRS [3], In an ad hoc network environment, the routing protocol WRP [4], AODV [5, 25], DSR [6], TORA [7], ZRP [8], etc. must keep up with the changing topology So, the routing Among them, AODV (Ad hoc On-demand Distance Vector) algorithm is more complex then the other network environment routing protocol is one of the most frequently mentioned It Various routing schemes have been proposed inresent years In

chooses a minimal hop-count path to be the routing path. this section, we review some ad hoc routing protocols and However, a path having the minimal hop-count does not categorize these researches into four types

always mean that it is the optimal routing path in various 1) Table-driven protocols

respects Even the smallest hop-count path may be longer than 2) On-demand driven protocols

O-7803-9410-O/06/$20.OO ©2006IEEE

3) Location aided protocols The location aided protocols are base on the knowledge of 4) QoSsupported routing protocols mobile host's location by using the global position system The table driven routing protocols (also known as proactive (GPS) Most related researches of location aided routing are protocols) attempt to maintain consistent, up-to-date routing focus on reducing the complexity of routing procedure and information from each node to every other node in the network saving the routing message The most famous and original These protocols require every node to maintain one or more scheme is the Location AidedRouting (LAR)[9].Accordingto routing tables and have to propagate its routing table contents the destination mobile host's location and moving speed, LAR throughout the network in order to have a consistent network computes the destination's excepted zone (a circle at view for every node In Destination-Sequenced destination'snow location with radios speed multiply excepted Distance-Vector Routing (DSDV) [2] routing protocol, every time) A routing request zone is drawn as a rectangle from mobile node maintainsarouting table inwhich all the possible source's locationtothe exceptedzone Only these nodes inthe destinations in the network and the number ofhops to each routing request zone can forward theroutingrequest message, destination are recorded The contents ofrouting table are sotheroutingmessage is restrictedintheroutingrequestzone. exchanged periodically The Clusterhead Gateway Switch The routing message is saved Location Aided Knowledge Routing (CGSR) [3] is acluster basedDSDVrouting protocol Extraction Routing (LAKER)[10]usesguiding-routetoreduce

Acluster head controls a set of mobile nodes In acluster, the the complexity of ad hoc routing LAKER inherits the route DSDVrouting protocol is usedtomaintain the routing path A strategy from DSR A forwarding-route in DSR is a series of gateway is the bridge oftwo or more cluster heads In the nodeIDsfromsource todestination.Aguiding-route isaseries Wireless Routing Protocol (WRP) [4], each node in the oflocations of the forwarding-route Using the guiding-route network is responsible for maintaining four tables: (a) distance message, LAKER attempts to learn the information about the table, (b) routing table, (c) link-cost table, and (d) message networktopology and forward the routingrequest to theright retransmission list (MRL) table Mobile nodes send update way to be near to the destination A Location-Aided messages after processing updates from neighbors ordetecting Power-Aware Routing (LAPAR) [11] protocol is proposed by

a change in a linkto a neighbor The neighbors then update Xue and Li This method used location aided to reduce the their distance table entries and check for new possible paths routingmessage overhead In order to save power consuming, through other nodes Any new paths are relayed back to the power aware try to select a route with distance of any two original nodes,sotheycanupdate their tables accordingly mobile nodes is shorter

The on-demand routing protocols (also known as reactive Generally speaking, the topics ofQuality of Service (QoS) protocols) create routes only when desired by the sourcenode may be related to bandwidth, throughput, packet delay, delay When a node requires a route to a destination, it initiates a jitter, etc. Havingno fixed networkinfrastructure, QoSsupport route discovery process within the network Ad-hoc in ad hoc network reveals more difficulties in many manners On-demand Distance VectorRouting (AODV) [5, 25] protocol In order to discover a more stable path, the degree of builds ontheDSDValgorithm Itisapureon-demandprotocol, association stability opinion is used in Associativity-Based

asnodes thatare not on aselectedpath donotmaintainrouting Routing (ABR) protocol [12] Theessence ofABRlies on the informationorperform routing table exchanges Whena source fact that amobile host's association with itsneighbor changes node wants to send a message to some destination node and as it ismigrating Its transiting periodcanbe identified by the does not have a valid route to that destination, it broadcasts associativity "ticks" There are stable and unstable ticks The route request (RREQ) packets to its neighbors The Signal Stability Routing (SSR) protocol [13], which selects intermediate nodes re-broadcast the RREQ packet until the routes based on the signal strength between nodes and on a destination node receives the RREQ Upon receiving the node's location stability This method maintains a routing RREQ packet, the destination node sends the route reply tables and the signal stability table The signal strength (RREP) packet back to the neighbor from which it first recorded inthe signal stability table is characterizedas strong received the RREQ Except carry a series of node IDs, the orweakby theaveragereceivedsignal strengthinthepastfew Dynamic Source Routing (DSR) [6] routing procedure isvery beacons A Core-Extraction Distributed Ad Hoc Routing similartoAODV DSRallows nodestokeep multipleroutes to Algorithm (CEDAR) [14] uses three key components: a) the

a destination in their cache Ifa link on route is broken, the establishment and maintenance of a self-organizing routing source node can select another valid route to the destination infrastructure; b) the propagation of the link state of high without re-start route discovery procedure Base on the link bandwidth and stable links; and c) a QoS-route computation reversal concept, Temporally-Ordered Routing Algorithm algorithmto supportthe QoS routing in ad hoc networks The (TORA) [7] uses a "height" metric to establish a directed Flow OrientedRouting Protocol(FORP) [15]usesthe mobile's acyclic graph (DAG) rooted at the destination Arouting path moving direction, speed, and transmissionrangeto predict the from source todestination is foundbyDAG TheZoneRouting linkexpiration time, and thenfindout a routepath accordingto Protocol (ZRP) [8] is for the re-configurable, large scale, and thislinkexpiration time.Depending onthelinkexpiration time highly mobile ad hoc networking environment Through the concept, QoS support bybandwidth reservation is proposed in use of the zone radius parameter, the scheme exhibits [16] If the available bandwidth on the path can't fit the adjustable hybrid behavior of proactive and reactive routing bandwidth requirement, the connection request will be rejected

Route Selection (AODV-RRS) [17] introduces the concept of between nodeBand nodeA So the receivedsignal at timet1, stablezone andcautionzone to discover a more stablerouting RSSBc(t]), is greater than RSSA,B(tl) at first But node B is path in ad hoc networks For improving network stability and moving toward node A, and node C is leaving from node B total throughput, multiple pathsrouting protocolsareproposed The received signal strength between B and C is decreasing

[18, 19] The total bandwidth of thosepaths cannotjust besum over the time On the contrary, the received signal strength

up because of "interference" The paper [20] discussed the between A and B is increasing After a few minutes, the

"available bandwith" network capacity and "interference" received signal strength ofRSSA,B(t2) is larger thanRSSB,C(t2).

accordingtodifferent MediaAccess Control(MAC)protocols In our research, we are interest in using the received signal

The Race-Free Bandwidth Reservation Protocol [21] is strength, RSS, and the received signal strength changing rate, proposed forparallel bandwidth reservation inad hoc networks ARSS, to calculate the LAT (Link Available Time) between two For high-throughput and low power consuming, the excepted mobilenodes

transmissioncount(ETC) [22] and medium time metric(MTM)

[23] were proposed The ETX is defined as the inverse of RS

packet forward probability (df) multiply ack reverse

probability (dr) The MTM value was assigned by packet

transmission rate. Apath has a high packet transmission rate

will assign low MTM value Arouting path with low ETX

ti t2

III. RECEIVEDSIGNAL STRENGTHROUTING ALGORITHM Fig 1 Moving direction and RSS

Let t1 be the time when node i and nodej first detect the Minimum-hop count routing is the spirit ofmost routing presence of each other With this understanding, we can algorithms But some researches [15, 16, 17, 22, 23] showed simplify ARSS, j(t1,t2) to ARSS,J (t2). Therefore, without the minimum-hop count routing path will be an unstable, loss of generality, we use ARSS (t) to denote the RSS

present arouting schemeto find out astableroutingpathinad changing rate between time t and the time node i and nodej hoc network Basedonthe Ad hoc On-demand DistanceVector first met

(AODV) routing protocol, our scheme will tryto find a route To calculate the link available time, let D,j (t) denote the such that links in the route are long-lived This new routing distance between node i and nodej at time t and Sjj(t) protocol is called AODV-RSS (Ad hoc On-demand Distance denote the relative speed. Assume TR is the radio transmission Vectorwith ReceivedSignal Strength)routing protocol

The receivedsignal strengthwill be largerwhen the distance ir j a I ,

oftwo mobile nodes is closer Our long-lived path routing node iand nodej are movingtoward each other, as shown in algorithm uses the Received Signal Strength, RSS, and Fig 2(a). The time needed before they are at their closest Received Signal Strength changing rate, ARSSto predict the points (Fig 2(b)) canbe approximated by D,(t) After the

denote the received signalstrength seenbynodejwithrespect closest points, they will leave away from each other Their

to node i at time t. Assume a symmetric wireless network connection will be broken when each is at the border of the Then RSSi,j(t)=RSSj,i(t). Define transmission range of the other (Fig 2(c)) The time for them ARSS (t1,t2)= RSSJJ(t2)- RSSj (tl) , t2 >tl ARSSj J(t, ,t2) to move from the position in Fig 2(b) to that of Fig 2(c) can

canbeseen astheRSSchangingratefrom timet,tot2 Since Sj(t)

RSS1J(t)=~RSSi(t), we have ARSSJ(ti~2) =ARSSji (t, t2),If link between node i and nodejto be effective is D, (t) +TR.

time t2 thanthey were attime t, On the contrary, a negative Similarly, if ARSSij(t) is negative, node i and nodej are ARSSij(tl,t2) meansthat nodeiandnodejareleaving away leaving away from each other The time needed for them to from each other Usually, RSS1,1(t) depends on the distance lose contact can be approximated by TR-D,(t). Combining

how fast nodeiandnodejaremovingrelatively Therefore,we the above results, the link available time between node i and can use xRSSJ J(t,I,t2) as an indication of the relative speed nodej, LATj (t),can bedefinedas:

betweennodeiland node Alarge (t, ,t2) meansnode (1)if AIRSSJ(t) is positive, L ( Di.j(t)+TR; else

other quickly Its concept is illustrated in Fig 1 The distance (2)if tRS (t) isnegative,=

J TR 1 the other hand, the routing path discovered byAODV will be

AODV is A-B-C-E-F, it will suffer from more frequent path

Fig 2 The relative position of two approaching nodes

doesnothave the valuesof Di,j(t) and Sj (t)9. From[24],

S(t)oc D3ARSS ARSS Using the above reasoning, discovery procedure, AODV-RSS algorithm just sends the

LATj(t) canbe redefinedas: the LAT constraints If a RREP (Route Reply) packet is not

(1)if ARSS1j(t) is positive, received within the path discovery time, this connection

request isrejected Onthecontrary, thepacket is sentthrough

(RSS/ ,(t)) 2 +TR ; else the routing path until the path is broken due to the mobile

receiver within atime period, the sourcenode will re-send the (2)if ARSSij(t) is negative, RREQpackettore-establisha newpath.

TR-(RSS 1(t))~ In order to assess the performance of our algorithm,

LAT, (t)= TR-(RSS,j (t)) 2 simulations are done to compare with AODV algorithm The

Since RSS,j(t) and ARSSij(t) can be estimated in each IV PERFORMANCE EVALUATIONS

node withoutextrainformation,thelinkavailable timecanthus

becomputed The calculatedLAT representsa measurement of 4.1Simulation Environments

howlongtwonodes cankeepconnected Assumeaconnection We evaluate the proposed AODV-RSS protocol by wantstotransmitMbytes andalink's data transmissionrate is simulation and compare the performance with that of AODV

N bits per second, the whole data transmission time for this protocol The link breakage is detected by the feedback of connection will beM*81N seconds TheAODV-RSS algorithm MAC layer in both protocols No additional network layer canusethe data transmission timeinthe routing pathdiscovery mechanism is used And the bandwidth limitation of each procedure as anLATconstraint Intuitively, ifwe set theLMT mobile node is not taken into consideration to simplify the constraint to the data transmission time, it means that simulationmodel.

AODV-RSS algorithm can find out a routing path that can In our simulation model, we generate 100 mobile nodes in a transmit the entire data without suffering any broken routing 1500*1500 square meters area The sides of the square are path Thatis, a connectionusing data transmission time asthe wrapped around The moving direction of each mobile node is LATconstraint will have a good service quality However, a a random variable of 0 degree to 360 degree The mobile higher LAT constraint will suffer from a higher connection node's transmission range is 240 meters [17] The data rejection probability This is because a higher LATconstraint transmission time of each connection is an exponential needs a longer link available time between any two mobiles distribution with mean 50 seconds. Themobility patterns are The number of availablepaths for ahigher LATconstraint will 12 different speeds (1, 2, 3, 4, 9, 10, 11, 12 meters per

be less than others To decrease the route discoverytime and second) The node traversal time is aconservative estimate of increase the route discovery probability, less rigid LMT the time that a packet spent before being retransmitted It

Using the aboveLATconstraint, our long-lived path routing transfer times The same as [25], the node traversal time is set algorithm will find out aminimumhop-count routing paththat to 40millisecondsin oursimulations.

satisfies the LAT constraint In Fig 3, the number above the The followingcharacteristics are taken intoconsiderationto link between two mobiles means the link available time measure the AODV and AODV-RSS routing protocols' Assume, the LAT constraint is 14 Because the LAT ofB-C perormance Thesecharacteristicsaredepictedas follows does not satisfy the LAT constraint, the RREQ (Route Request) * Average Route Discovery Time: The time period from packet will not be sent to node C in AODV-RSS algorithm. RREQ packet is sent from source node to the RREP packet is

So, our algorithm will select A-B-D-E-F as the routing path. received by source Its value means the latency of connection Every link of this routing path satisfies the LAT constraint On established A lower value is better

* Path Discovery Failure Probability: The path discovery 025

failure probability is theprobability that therouting path for a 02U

* Average Route Connection Time:Theaveragetime ofa l1

routing path from established to broken due to the node -005

mobility A larger value is better, which means the path can 0

delivery packet foralongtime,donotsufferanybreach 2 3 4 5 6 7 8 9 10 11 12

mobile node will lead to a broken routing path So arouting Fig 5 Average path discovery failure probability vs mobility

path will be re-established.Itsvalue indicates howmanytimes 0.n6

transmittedbythispathwithout suffer anybreach,but its value FAODV Ml R s S

Q:)-isalwayslarger than 1.However,avalueclosingto1 is better o

*Connection Broken Probability: Whentherouting path 1

Speed2 m79ec)

is broken, we finda newrouting path for this connection The Fig.6.Connection brokenprobabilityvs.mobility

connection brokenprobabilityis the probabilitywhere thenew Increase the path discovery latency and path discovery path isnot establishedinthe first re-routing discoverytime A failure probability, the goal of our method is to will find out a

The simulation program is written in SimScript. Each the average route continuing connected time for AODV-RSS simulation is executed fortwohours The simulation resultsare with different LAT constraint versus AODV routing protocol theaverageof5runs and these resultsareshownasfollows When moving speed is lower, our AODV-RSS algorithm is

doinga goodjob inmaintainingthe connection For example,

Fig 4 shows the average route discovery time per connection constraint will increase routeconnectiontime about 7 seconds.

as afunction ofmobility(speed) for theproposed AODV-RSS, But from this Fig 7's tendency, we can see the routing with 0.2, 0.4, 0.6 and 0.8 LAT constraint, and AODV The connected time is shorter when the moving speed is higher In averageroute discoverytime forAODV is about 0.28 second moving speed 12, AODV-RSS increases the routing connected According the trend of lines in Fig. 4, we see the route time about 1.5 seconds for all LATconstraints That is because

discovery time is increased by the higher moving speed and when the moving speed is high the LAT of any two nodes is higher LAT constraint At 12 moving speed of 0.8 LAT short in the whole network So, no matter how high the LAT constraint, the results showourprotocolwill increase theroute constraint is, the route connection time will not increase discovery time about 0.05 second Fig. 5 shows the path substantially The average frequency of route discoveries for

discovery failure probability. As all we know, a higher LAT each connection is shown in Fig 8 In moving speed 1, the constraint will suffer a higher failure probability. But it is frequency of AODV is about 2, and the AODV-RSS is about gratified, that thepath discoveryfailureprobability of0.2LMT 1.8, 1.7, 1.6, 1.6 in 0.2, 0.4, 0.6, 0.8 LAT constraint, constraint is almost the same as AODV Fig. 6 shows the respectively. For moving speed 12, the frequencyof AODV is connection broken probability. The broken probability about 6.4, and theAODV-RSS isabout 5.1,4.6, 4.1, 3.8 in0.2,

increases by the moving speed and LAT constraint In the 0.4, 0.6, 0.8 LATconstraint, respectively Due to the moving moving speed 6the AODV-RSS with 0.8 LATconstraint will speed increasing, the route discovery frequency of AODV increase the broken probability about 1.8% than the AODV increasing too, the moving speed 12 is about 3.2 (6.4 divides 2)

routing protocol In the worst case, the increasing broken times of the moving speed I's The frequencyincreasingrate of

frequency increasingrate.

- AODV

80.3 - ~AODV-R,-SQfJ.4)5

O~~~~~~~~~~~~25

~

~

Speed (M/sec)

Fig 4 Average route discovery time vs mobility 0 o

1 2 Xi 4 5 6 7 0 9 10 1 1 12

Speed (nJsec)

Fig 7 Average route connected time vs mobility

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