Research Article A Service-Based Selfish Routing for...

Research ArticleA Service-Based Selfish Routing for Mobile Social Networks

Lingfei Yu12 and Pengfei Liu1

1School of Computer Science and Engineering University of Electronic Science and Technology of China Chengdu 611731 China2School of Computer Engineering Nanyang Technological University Singapore 639798

Correspondence should be addressed to Lingfei Yu linphie163com

Received 7 August 2014 Accepted 25 September 2014

Academic Editor Haigang Gong

Copyright copy 2015 L Yu and P Liu This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Routing in mobile social networks is a challenging task due to the characteristic of intermittent connectivity especially when thenodes behave selfishly in real world Selfish behaviors of node always influence its altruism to provide forwarding service for othersand degrade network performance strongly In this paper to address the selfishness problem in MSNs we propose a service-basedselfish routing protocol SSRWhenmaking forwarding decision SSR employ user altruism and the amount of service that the relaynodes provide User altruism is determined by the social selfishness and the individual selfishness The services include pairwiseservices and social services which is also considered as the incentives to stimulate node to be more cooperative The more servicesthe node provides themore chance the node has to be servedThenodewith higher altruism and fewer services is the preferred relaynode Simulation results show SSR achieves better performance when the user altruism is low and demonstrate the effectiveness ofthe service-based scheme

1 Introduction

The portal devices such as smart phone laptop and tabletcomputer have been very popular in the world with the rapiddevelopment of the technologies of wireless communicationand integrated circuit These devices with the wireless capa-bilities such as Bluetooth WiFi or 3G are often carried bypeople and cooperate with each other to form an ad hocnetwork for exchanging and sharing data Social behavioranalysis has been introduced to resolve the routing issueswhen nodes are attached to the human or vehicles and couldachieve better performance by using social relationship inreal life environment Hui et al [1] named the network pocketswitched networks (PSNs) a typical type of delay tolerantnetworks (DTNs) [2] Because there have been some inherentsocial features in the network it is also called mobile socialnetworks (MSNs)

Some institutes try to find social properties of the mobilesocial networks in the real world based on the data setcollected from the portable devices attached to human forexample Reality Mining [3] Infocomrsquo05 [4] and Infocomrsquo06[5] And there have been lots of routing strategies for mobilesocial networks such as LABEL [6] BUBBLE [7] and

SimBet [8] which all employ the social network properties tohelp message forwarding However in the previous routingtechniques there is a common assumption that all nodes inthe network are unselfish and cooperative That is each nodeis willing to receive and relay the packets sent by other nodesUnfortunately in the real world most people are selfish andthere would be some selfish nodes dominated by rationalhuman For example the node would be reluctant to deliverthe packet for others because of the limited resources (energybuffer bandwidth etc)

Obviously node selfishness affects node behaviors anddegrades the network performance To stimulate selfishnodes to forward packets many incentive protocols such asreputation-based credit-based and TFT-based for ad hocnetwork have been proposed [9ndash12] The goal of these incen-tives is to handle the individual selfishness assuming that thestatus of nodes is equal However in a real social networkthe social relations or social ties of nodes are different anda node is more willing to relay packets for those who havesocial relations or social ties with it Li et al [13] call it socialselfishness They propose a social selfishness aware routing(SSAR) algorithm to allow user selfishness and provide betterrouting performance in an efficient way However SSAR

Hindawi Publishing CorporationInternational Journal of Distributed Sensor NetworksVolume 2015 Article ID 910635 8 pageshttpdxdoiorg1011552015910635

2 International Journal of Distributed Sensor Networks

quantifies the nodersquos willingness to evaluate its forwardingcapability based on the social ties which is not enough toreflect the real willingness of the node to relay the packetsBesides social ties the residual resources of the node also haveimpacts on userrsquos willingness to relay the packets For exam-ple a node has strong social relation with other nodes butits resources are scarce (eg very low energy of the battery)Though it is very willing to serve for other nodes it cannotdo it because it lacks the resources

In this paper we propose service-based selfish routingprotocol for mobile social networks which consider the useraltruism to relay packets and the amount of service of nodeThe main contributions of the paper are as follows

(1) Classify user altruism into social altruism and indi-vidual altruism Social altruism is decided by thesocial selfishness while individual altruism is deter-mined by the current resources of the node

(2) Propose a service-based incentive scheme in whichthe service made by the node is considered as theincentive to the node Different from other works itquantifies the services of the node based on its altru-ismThe services of the node include the pairwise ser-vices between the two given nodes and their servicesfor the whole network

(3) Propose a routing protocol based on the amount ofservices of the relay node and demonstrate the effec-tiveness of the protocol via simulation

The remainder of this paper is organized as followsSection 2 discusses the related works Section 3 presents thesystem model and describes the problems Section 4 givesthe detailed design Section 5 introduces simulations anddiscusses the results The last section concludes the paper

2 Related Works

21 Routing in Social Network Hui and Crowcroft haveproposed a routing algorithm called LABEL [6] which takesadvantage of communities for routing messages LABELpartitions nodes into communities based on only affiliationinformationThen each node in the network has a label tellingothers about its affiliation A node only chooses to forwardmessages to destinations or to the next-hop nodes belongingto the same group (same label) as the destinations LABELsignificantly improves forwarding efficiency over obliviousforwarding using their data set but it lacks a mechanism tomove messages away from the source when the destinationsare socially far away

BUBBLE [7] combines knowledge of the communitystructurewith knowledge of node centrality tomake forward-ing decisions Centrality in BUBBLE is equivalent to popu-larity in real life which is defined as how frequently a nodeinteracts with other nodes People have different popularitiesin the real life so that nodes have different centralities inthe network Moreover people belong to small communi-ties like in LABEL When two nodes encounter the nodeforwards the message up to the node with higher centrality(more popular node) in the community until it reaches the

same level of centrality as the destination node Then themessage can be forwarded to the destination community atthe same ranking (centrality) level

SimBet presented in [8] makes routing decisions by cen-trality and similarity of nodes Centralitymeans popularity asin BUBBLE More specifically the centrality value captureshow often a node connects nodes that are themselves notdirectly connected Similarity is calculated based on thenumber of common neighbors of each node SimBet routingexchanges the preestimated centrality and locally determinedsimilarity of each node in order to make a forwarding deci-sionThe forwarding decision is taken based on the similarityutility function (SimUtil) and betweenness utility function(BetUtil) When nodes contact with each other the nodeselects the relay node with higher SimBet utility for a givendestination

In [14] Fabbri and Verdone propose a sociability-basedDTN routing which is based on the idea that nodes with highdegrees of sociability (frequency encounteringmany differentnodes) are good forwarding candidates They defined thesociability indicator metric to evaluate the forwarding abilityof a node The routing strategy forwards packets to the mostsociable nodes only

In [15] authors propose a fuzzy-assisted social-basedrouting (FAST) protocol that takes the advantage of socialbehavior of humans on the road to make optimal and securerouting decision FAST uses prior global knowledge of real-time vehicular traffic for packet routing from the source tothe destination In FAST fuzzy inference system leveragesfriendship mechanism to make critical decisions at intersec-tions which is based on prior global knowledge of real-timevehicular traffic information

22 Handle Selfishness Since selfish behavior of the nodedegrades the performance of routing protocol many incen-tive mechanisms have been studied to stimulate individualselfish node to be cooperative The incentive strategies canbe classified into three categories reputation-based credit-based and TFT-based approach

In reputation-based schemes forwarding services areprovided to nodes depending on their reputation When anode provides services for other nodes it gets good reputa-tion Nodes with good reputations can receive services fromother nodes On the contrary misbehaving nodes get badreputations and will be denied participation in the networkThe fear of detection and punishment motivates nodes tocooperate Mei and Stefa [9] proposed a reputation-basedincentive scheme (Give2Get) for DTN routing which candetect misbehaving nodes and remove them from networkrouting They proved that their proposed scheme achievesNash equilibria

The credit-based schemes introduce some form of creditor virtual currency to regulate the packet-forwarding rela-tionships among different nodes Nodes earn virtual currencyby forwarding packets for othersThese credits can be used toobtain forwarding service from any node in the network Forevery forwarding request the virtual bank charges the senderan extra amount of virtual currency and the intermediatenodes redeem their rewards at the bank after successful

International Journal of Distributed Sensor Networks 3

delivery SMART (secure multilayer credit-based incentive)scheme [10] uses credits to provide incentives to selfish nodesSuch scheme adopts a novel layer concatenation techniqueto withstand cheating actions of selfish nodes MobiCent [11]assumes that each mobile device is capable of operating intwo modes a long-range low-bandwidth radio to maintainan always-on connection and a short-range high-bandwidthlink to opportunistically exchange a large amount of datawith peers in its vicinity MobiCent provides a credit-basedalgorithmic mechanism design approach to address selfishattacks

In TFT-based schemes every node forwards as manymessages for a neighbor as the neighbor forwards for it In thisway a node autonomously lowers services to a neighbor if itdetects that the neighbor ismisbehaving Shevade et al in [12]proposed the use of pairwise tit-for-tat (TFT) as a simple androbust incentivemechanism forDTN routingThis incentive-aware routing protocol allows selfish nodes tomaximize theirown performances without any significant degradation ofsystem-wide performance Rather than attempting to detectmisbehavior it focuses on detecting good behaviors by usingTFT

Li et al [13] introduce the social selfishness problem intoDTNs and proposes a routing algorithm SSAR following thephilosophy of design for user SSAR allows user selfishnessand improves performance by considering user willingnessresource constraints and contact opportunity when selectingrelays User willingness is quantified by the social relationsamong nodes which is used to evaluate its forwardingcapability

Based on the regularity of human behavior authorspropose a hot-area-based selfish routing protocol (HASR)tailored for mobile social networks Data transmission isbased on the active degree of the node which is calculatedby the weight of hot areas that nodes will visit when thereare no selfish nodes When nodes behave selfishly routingdecision is made by the contribution index that indicates thecontributions to data transmissions of the network made bynodes Moreover they present a social contribution-basedrouting protocol for selfish vehicular network in [16] Whenmaking forwarding decision the protocol considers boththe delivery probability to the destination and the socialcontributions of the relay node

Guan et al [17] study the impact of individual and socialselfish behaviors in DTNs Based on analysis it is concludedthat social selfishness leads the internal threats in DTNs Themain reason of internal threats is that some nodes have lesssocial relations and difficulty to participate in the forwardingprocessWhen these nodes cannot afford the forwarding costthey will be isolated by the network and become maliciousnode To avoid the internal threats authorsmeasure the socialwealth distribution of the DTNs by using Gini coefficient anddesign the taxation strategy to redistribute the social wealth

3 System Models and Problem Statement

In this section we first define the user altruism and thenformalize the network model Finally the problem is statedand analyzed

31 User Altruism User altruism means the user willingnessto relay packets for other nodes and is related to the userselfishness As mentioned before the user selfishness couldbe classified into social selfishness and individual selfishnessCorrespondently there are also social altruism and individualaltruism Social altruismbetween twonodes depends on theirsocial relation The stronger their social relation is the largertheir social altruism is and the more chance the two nodesforward packets for each other Let SA denote the socialaltruism

However social altruism to relay the packets for othersjust reflects the social relations among nodes It may notreflect the real willingness of an individual rational entity Todifferentiate from the social altruismwe introduce individualaltruism denoted by IAThe current resources of node wouldaffect the individual altruism If a node has limited resourcessuch as low energy or low buffer it is not willing to relaypackets for others even if its social altruism is highThemorethe resources of the node the larger the IA

32 Network Model We model the mobile social network asa directed contact graph 119866 = (119881 119864) where 119881 consists ofall the nodes and 119864 represents opportunistic contact edgesOnce two nodes encounter each other therewould be an edgebetween them The contact graph reflects the social relationsor social ties amongnodesThemore frequent twonodes con-tact each other the more they are willing to forward packetsbetween them Each edge on graph has a weight representingthe strength of social relation (social altruism) between twonodes to forward packets for others Individuals with higherSA are more likely to meet other people and forward packetsfor other nodes The social altruism SA could be achievedby the method in [13] SA is a real number with [0 1]SA = 0 denotes no social relationship between two nodes andthey are not willing to forward packets for each other largerSA represents a stronger relationship and the node is morewilling to relay packets for the other one

As for individual altruism it is determined by the residualresources of nodeThe residual resources of node change overtime with the consumption of the resources so that the IAis variable IA could be calculated by the current resourcesof nodes Without loss of generosity we compute IA basedon the residual energy of node that is IA is equal to thepercentage of the residual energy

Moreover we assume that nodes are honest and trusteach other There are no malicious nodes in the network andnodes never drop packets intentionally We do not considerthe buffer issue in this paper for the handheld nodes graduallyhave more and more storage size and the bandwidth ishigh enough to allow the exchange of all messages betweennodes at encounter times These assumptions are reasonablebecause capabilities of todayrsquos handheld node are strongerand are also used commonly in some studies [18]

33 Problem Statement In mobile social networks self-ish behaviors of node pose great challenges for data for-warding Both social selfishness and individual selfishnesshave impacts on routing decision SSAR [13] allows socialselfishness and improves performance by considering user


willingness and contact probability when selecting the relaynodes User willingness is used to calculate its forwardingcapability However user willingness is only quantified bythe social relations among nodes It does not reflect the realwillingness of nodes which should consider the individualaltruism The IA should be taken into account to evaluaterelaying capability combining with social altruism SA

On the other hand incentive is an effective method tostimulate selfish nodes to cooperate with each other Theexisting incentive methods such as reputation-based andcredit-based need infrastructure (eg trust authority or vir-tual bank) which is not scalable and requires higher invest-ment In our opinions when two nodes 119894 and 119895 meet eachother the reason node 119894 relaying packets for node 119895 is howmuch services that node 119895 provided for it or for the networkMore services mean more contributions In the rest of thispaper service and contribution are used interchangeablyThe more services (or contributions) node 119895 provides themore probability node 119894 relays packets for it It sounds likeTFT-based method Different from TFT-based method theservices the node provides include pairwise services andsocial services which are the services provided for the wholenetwork For any two given nodes when they serve eachother they make pairwise services Traditional TFT-basedmethod just considers pairwise contributions when relayingpackets but it is unfair to those who serve more for othernodes For example node 119895 has relayed many packets fromother nodes except node 119894 then node 119894 will refuse to relaypackets from node 119895 according to pairwise principle So thesocial services also should be considered to make forwardingdecision Moreover the pairwise services of traditional TFTmethod are evaluated by the amount of data exchangedbetween two nodes But in social selfish network userselfishness to forwarding packets is different from each otherTo stimulate the node with lower altruism to be cooperativeit should get more rewards if it relays packets from othersThe lower the altruism the more the rewards For those withhigher altruism especially social altruism they will get lessreward than those with lower altruism Because they havestronger social relations among the network they have morechance to serve for other nodes and get enough rewards Sothe services of the node should be calculated based on itsaltruism

4 Detailed Design

In this section we present the details of SSR protocol At firstwe define some notations to make the presentation clear

SA119894119895 the social altruism between nodes 119894 and 119895

determined by the strength of social relation betweennodes 119894 and 119895 Assume that social willingness issymmetric that is SA

119894119895= SA

119895119894 The larger the

SA119894119895is the more probability the two nodes provide

forwarding services for each otherIA119894 the individual altruism of node 119894 decided by the

residual resources of node 119894119860119894119895 the altruism of node 119894 to relay packets to node 119895

119873119894119895 the number of forwarding that node 119894 provides for

node 119895119878119894119895 the amount of service that node 119894provides for node119895 per forwardingSI119894119895 the serving index of node 119894 in the pairwise

services of nodes 119894 and 119895120595 the set of nodes that node 119894 provides forwardingservice1205951015840 the set of nodes that provides forwarding service

for node 119894NS119894 the amount of services that node 119894 provides for

all the nodes that it servesNS1015840119894 the amount of services that other nodes provide

for relaying packets from node 119894SI119894 the serving index of node 119894 for the network

It reflects the services that node 119894 provides for thenetworkCI119894119895 the contribution index of node 119894 to node 119895 It is

used to evaluate the forwarding capability of node 119894

41 Altruism to Forwarding In selfish mobile social networkthe altruism of the node to relaying packets for other nodesis essential to make routing decision The altruism is deter-mined by the social altruism and the individual altruismSocial altruism depends on the social relations among nodesThe stronger the social altruism between two nodes is thelarger the probability the two nodes encounter and the morethe willingness to provide forwarding services for each otherisThen a node should forward packets to the relay node withhigher social altruism for the destination node However thecapability of relaying packets is also constrained by the indi-vidual altruism If the individual selfishness of a node is lowerit will be reluctant to relay packets though it has strongersocial relations with destination node For example a nodehas high social altruism to forwarding packets for the destina-tion node but its energy of battery is not enough to supportto provide forwarding service And it has to refuse to relaypacket due to the large individual altruism The altruism ofnode 119894 to relay packet to node 119895 is

119860119894119895= SA119894119895sdot IA119894 (1)

When a node encounters several nodes it will choose thenodes with higher altruism to relay packets to the destinationnode as the next hop

42 Incentive Schemes To stimulate selfish node to behavemore unselfish incentives are effective method Intuitivelythe more service the node provides the more contributions itmakes and the more rewards it should achieve The rewardsthat the node gets are proportional to the amount of itsservice For simplicity let the rewards be the amount ofservice that the node provides Usually when a node relaysone packet from other node it provides 1 unit service forthe other node But in socially selfish network the node thathas small social strength to forward packet should get more


incentives if it provides forwarding services successfully inorder to stimulate it to be more cooperative Define theamount of service that node 119894 provides after it relays a packetfrom node 119895 as

119878119894119895=

IA119895

IA119894sdot SA119894119895

(2)

If node 119894 relays a packet from node 119895 then node 119894 provides119878119894119895unit service rather than 1 unit service And it will get119878119894119895unit rewards As in (2) if the strength of social relation

between node 119894 and node 119895 is weak (ie the smaller socialaltruism) the node should get more rewards Similarly if thenode with smaller individual altruism provides forwardingservice for the node with higher individual altruism it alsoshould get more rewards Noticeably 119878

119894119895is not the same when

node 119894 relays packets from node 119895 because the individualaltruism of the two nodes changes over the time

43 Contribution Index To indicate which one serves morethan the other for a pair of nodes define SI

119894119895as

SI119894119895=

sum119873119894119895119878119894119895

sum119873119894119895119878119894119895+ sum119873119895119894119878119895119894

=

sum119873119894119895(IA119895IA119894)

sum119873119894119895(IA119895IA119894) + sum119873119895119894(IA119894IA119895)

(3)

SI119894119895is the ratio of the amount of services node 119894 provides

for node 119895 and the sum of services that the two nodes providefor each other If SI

119894119895equals 05 it means they provide the

same service for each other If SI119894119895is close to 0 it means node 119894

provides less service than node 119895 As in (3) SI119894119895is only decided

by the individual altruism of the two given nodes and has norelation to the social altruism

However the services a node provides are not only fora given node it will relay packets for all the nodes in thenetwork if possible On the other side node 119894 also consumesservices provided by the nodes Define NS

119894and NS1015840

119894as

NS119894= sum

119895isin120595

sum

119873119894119895

119878119894119895

NS1015840119894= sum

119895isin1205951015840

sum

119873119894119895

119878119895119894

(4)

And let the serving index of node 119894 for the network be

NSI119894=

NS119894

NS119894+NS1015840119894

(5)

Thenwe design a contribution index for node 119894 to evaluatethe forwarding capability to node 119895 as

CI119894119895= SA119894119895SI119894119895+ (1 minus SA

119894119895)NSI119894 (6)

Contribution index has twofold implications (1) if thesocial altruism of nodes 119894 and 119895 is high the contribution index

(1) begin(2) Broadcast destinations of packets in the buffer(3) Get summary vectors from neighbors(4) for each destination 119896 of the packets in the(5) buffer of node 119894(6) for each neighbor 119895 of node 119894(7) calculate 119860

119895119896and CI

119895119894

(8) if (119860119895119896gt 119860119894119896) then

(9) 120593 = 120593 cup 119895

(10) end if(11) end for(12) choose node 119895 with the highest 119860

119895119896CI119895119894from 120593

(13) send packets that destination is node 119896 to node 119895(14) end for(15) end

Algorithm 1 Packet forwarding of node 119894

of node 119894 is mainly evaluated by the pairwise services that itprovides only for node 119895 (2) if the strength of social relationbetween nodes 119894 and 119895 is small the contribution index of node119894 is mainly determined by the services that it provides for theentire system

Contribution index is used to evaluate the capabilityto relay packets It is natural that the node with smallercontribution index is the preferred candidate for providingrelay service The node with smaller contribution index hasto provide service for others so that it could get more rewardsto increase its contribution index

44 Packet Forwarding Packets forwarding in SSR is basedon the altruism to relay packets for the destination and thecontribution index of the relay nodes The node with higheraltruism and smaller contribution index will be the candidatefor relaying packet The pseudocode of packet forwardingcarried out by each node is presented in Algorithm 1

When node 119894 encounters some neighbors it firstly broad-casts the information of the packets such as the destination ofthe packets The neighbor 119895 computes its willingness to relaythe packet to the destination node 119896 that is 119860

119895119896 and echoes

a summary vectors to node 119894 The vectors include 119860119895119896 119860119894119895

and CI119895119894of node 119895 According to the information node 119894 puts

the neighbor with higher 119860119895119896than itself into a set 120593 Then it

chooses the neighborwith the highest119860119895119896CI119895119894among the set

120593 The higher the 119860119895119896and the lower the CI

119895119894are the higher

the value of 119860119895119896CI119895119894is Then node 119895 with highest 119860

119895119896CI119895119894

is the preferred next hop of node 119894 to relay the packets fordestination node 119896

5 Performance Evaluation

In this section we evaluate the performance of the proposedSSR protocol using a Java based simulator For comparisonwe also implement SSAR [13] and SimBet [8] protocols


3 6 9 12 15 18 21

Time (hour)

0

10

20

30

40

50

60

70

80D

elive

ry ra

tio (

)

SSRSSARSimBet

(a) Infocomrsquo05 data set

0

10

20

30

40

50

60

70

80

Deli

very

ratio

()

3 6 9 12 15 18 21

Time (hour)

SSRSSARSimBet

(b) Infocomrsquo06 data set

Figure 1 The impact of individual altruism caused by the residual energy

51 Simulation Setups The simulation is based on two realtraces referred to as Infocomrsquo05 [4] and Infocomrsquo06 [5] Inthese traces there were 41 and 78 participants carrying smalldevices to log contacts of the mobile devices for 3 days inConference Infocom 2005 and 2006 respectively Infocomrsquo05trace logs more than 20 thousand contacts with each otherand average contacts for two given nodes are about 45 per dayand Infocomrsquo06 trace logs about 190 thousand contacts with65 average contacts per pair per day Each contact includesthe two contact entities the begin-time and the end-timeWe use the contacts to perform trace-driven simulations Insimulation we assume that if any two nodes have contacthistory they have social relation with each other The morethey contact the stronger social relation is and the highersocial altruism could be

In the simulation each node generates 2 packets per hourand selects a destination node randomly The packet has acertain TTL Once TTL expires the packet will be droppedTo demonstrate the impact of individual willingness causedby the limited energy we design a simple scheme for energyconsumption though it is not practical According to thestudy of [19] a typical handheld node (ie smart phone)usually exhausts its energy in 21 hours if it is in regularusage pattern (ie calling and messaging) We assume theenergy decreases linearly with a loss rate 1mAh per minuteand it will consume 001mAh when sending or receiving thepacket The initial energy of node is randomly selected from1200 to 1600mAh The threshold 119864th is set to 30 Oncethe residual energy of node is less than the threshold theindividual altruism IA is set to 0 and the node is no longerto relay packets

52 Simulation Results For fair comparison we extend SSARand SimBet with individual altruism IA For SSAR whencalculating packet priority it should be multiplied by IA ForSimBet the node should relay the packet with the probabilityof IA

Firstly we investigate the impact of individual altruismdetermined by the residual energy of node on data delivery

ratio We assign each node with an initial energy randomlyselected from 1200 1300 1400 1500 and 1600mAh and eachnode consumes 1mAh per minute When the energy of thenodes is less than 119864th the individual altruism IA is set to zeroFigure 1 shows the simulation results

As seen from Figure 1 data delivery ratio of all algorithmsincreases first and then decreases when it reaches a certainvalue This is because more and more energy consumptionleads to lower individual altruism decreasing the probabilityto relay packets Moreover SSAR outperforms SSR at thebeginning After a period of time the delivery ratio of SSARdrops more quickly than that of SSR The reason is thatwhen the energy of node is high the nodes in SSAR relaypackets with high probability and deliver more packets Astime elapses the residual energy is lower and lower andthe probability to relay packets decreases When the residualenergy is less than 119864th the node will not relay packets anymore For SSR the incentive scheme simulates more nodes torelay packet in which the energy of nodes is consumed moreevenly than SSAR So SSR performs better than SSAR in thelong term For example SSR outperforms SSAR by 15 after18 simulation hours in Infocomrsquo05 data set

Figure 2 shows the percentage of nodes providing relay-ing services to other nodes The percentage of relay nodeincreases because there are more and more nodes participat-ing in packets relaying More nodes in SSR join in forwardingfor the incentives stimulate nodes to bemore cooperative andthe node with less contribution has to relay packets so thatits packets could be relayed by other nodes On the otherhand the nodes with larger social altruism (stronger socialrelation for SSAR or higher centrality for SimBet) are thepreferred next hop to relay packets and the nodes with weaksocial relations or lower centrality are not easy to be a relaynode That is to say the incentive scheme of SSR is effectiveto stimulate the node to be more cooperative

6 Conclusions

In this paper we have proposed a service-based data for-warding scheme Firstly we classify user altruism to relay


0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet


Figure 2 The percentage of nodes participating relaying service

packets into social altruism and individual altruism Thenwe introduce service-based incentive scheme in which thecontributions the nodemakes are considered as the incentivesto the node The service consists of pairwise service betweentwo given nodes and social service for the entire systemMaking forwarding decision is based on the altruism toforwarding the packets and the contributions of the relaynodeThe node with higher altruism and lower contributionsis a preferred candidate for packet relaying Simulation resultsshow that SSR performs better than SSAR and SimBet whenthe altruism of node is low and demonstrate the effectivenessof incentive scheme of SSR

Conflict of Interests

The authors declare that they have no conflict of interestsabout the paper

Acknowledgments

This work is supported in part by National Science and Tech-nology Support Program of China (2012BAI22B05) NationalScience Foundation of China under Grants nos 6110322661103227 61170256 61173172 and 61370151 and the Funda-mental Research Funds for the Central Universities underGrant no ZYGX2013J067

References

[1] P Hui A Chaintreau J Scott R Gass J Crowcroft andCDiotldquoPocket switched networks and human mobility in conferenceenvironmentsrdquo in Proceedings of the ACM SIGCOMM Work-shops Conference on Computer Communications pp 244ndash251ACM Press Philadelphia Pa USA August 2005

[2] K Fall ldquoA delay-tolerant network architecture for challengedinternetsrdquo in Proceedings of the ACM SIGCOMM Conferenceon Applications Technologies Architectures and Protocols forComputer Communications pp 27ndash34 August 2003

[3] N Eagle and A Pentland ldquoReality mining sensing complexsocial systemsrdquo Personal and Ubiquitous Computing vol 10 no4 pp 255ndash268 2006

[4] J Scott R Gass J Crowcroft P Hui C Diot andA ChaintreauldquoCRAWDAD Trace Cambridgehaggleimoteinfocom (v2006-01-31)rdquo 2006 httpcrawdadorgsimcrawdaddownloadcambridgehaggle

[5] J Scott R Gass J Crowcroft P Hui C Diot and A Chain-treau CRAWDADTrace Cambridgehaggleimote (v 2009-05-29) 2009 httpcrawdadorgsimcrawdaddownloadcambridgehaggle

[6] P Hui and J Crowcroft ldquoHow small labels create big improve-mentsrdquo in Proceedings of the 5th Annual IEEE InternationalConference on Pervasive Computing andCommunicationsWork-shops (PerCom Workshops rsquo07) pp 65ndash70 White Plains NYUSA March 2007

[7] P Hui J Crowcroft and E Yoneki ldquoBUBBLE rap social-basedforwarding in delay tolerant networksrdquo in Proceedings of the 9thACM International Symposium on Mobile Ad Hoc Networkingand Computing (MobiHoc rsquo08) pp 241ndash250 May 2008

[8] EMDaly andMHaahr ldquoSocial network analysis for routing indisconnected delay-tolerantMANETsrdquo in Proceedings of the 8thACM International Symposium on Mobile Ad Hoc Networkingand Computing (MobiHoc rsquo07) pp 32ndash40 September 2007

[9] A Mei and J Stefa ldquoGive2Get forwarding in social mobilewireless networks of selfish individualsrdquo in Proceedings of the30th IEEE International Conference on Distributed ComputingSystems (ICDCS rsquo10) pp 488ndash497 Genoa Italy June 2010

[10] H Zhu X Lin R Lu Y Fan and X Shen ldquoSmart a securemultilayer credit-based incentive scheme for delay-tolerant net-worksrdquo IEEE Transactions on Vehicular Technology vol 58 no8 pp 4628ndash4639 2009

[11] B B Chen andMC Chan ldquoMobiCent a credit-based incentivesystem for disruption tolerant networkrdquo in Proceedings of the29th IEEE International conference on Computer Communica-tions (INFOCOM rsquo10) March 2010

[12] U B Shevade H H Song L Qiu and Y Zhang ldquoIncentive-aware routing in DTNsrdquo in Proceedings of the 16th IEEE Inter-national Conference on Network Protocols (ICNP rsquo08) pp 238ndash247 Orlando Fla USA October 2008


[13] Q Li S Zhu and G Cao ldquoRouting in socially selfish delaytolerant networksrdquo in Proceedings of the 29th IEEE Internationalconference on Computer Communications (INFOCOM rsquo10) pp1ndash9 San Diego Calif USA March 2010

[14] F Fabbri and R Verdone ldquoA sociability-based routing schemefor delay-tolerant networksrdquo EURASIP Journal on WirelessCommunications and Networking vol 2011 Article ID 2514082011

[15] R H Khokhar R M Noor K Z Ghafoor C Ke and M ANgadi ldquoFuzzy-assisted social-based routing for urban vehicularenvironmentsrdquo EURASIP Journal on Wireless Communicationsand Networking vol 2011 article 178 2011

[16] H Gong L Yu and X Zhang ldquoSocial contribution-basedrouting protocol for vehicular network with selfish nodesrdquoInternational Journal of Distributed Sensor Networks vol 2014Article ID 753024 12 pages 2014

[17] X Guan C Liu M Chen H Chen and T Ohtsuki ldquoInternalthreats avoiding based forwarding protocol in social selfishdelay tolerant networksrdquo in Proceedings of the IEEE Interna-tional Conference on Communications (ICC rsquo11) pp 1ndash6 KyotoJapan June 2011

[18] C Liu and JWu ldquoAn optimal probabilistic forwarding protocolin delay tolerant networksrdquo in Proceedings of the10th ACM Inter-national Symposium on Mobile Ad Hoc Networking and Com-puting (MobiHoc rsquo09) pp 105ndash114 May 2009

[19] A Carrol and G Heiser ldquoAn analysis of power consumption ina smartphonerdquo in Proceedings of the USENIX Annual TechnicalConference pp 21ndash35 2010

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

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Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

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Advances inOptoElectronics


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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



quantifies the nodersquos willingness to evaluate its forwardingcapability based on the social ties which is not enough toreflect the real willingness of the node to relay the packetsBesides social ties the residual resources of the node also haveimpacts on userrsquos willingness to relay the packets For exam-ple a node has strong social relation with other nodes butits resources are scarce (eg very low energy of the battery)Though it is very willing to serve for other nodes it cannotdo it because it lacks the resources

In this paper we propose service-based selfish routingprotocol for mobile social networks which consider the useraltruism to relay packets and the amount of service of nodeThe main contributions of the paper are as follows

(1) Classify user altruism into social altruism and indi-vidual altruism Social altruism is decided by thesocial selfishness while individual altruism is deter-mined by the current resources of the node

(2) Propose a service-based incentive scheme in whichthe service made by the node is considered as theincentive to the node Different from other works itquantifies the services of the node based on its altru-ismThe services of the node include the pairwise ser-vices between the two given nodes and their servicesfor the whole network

(3) Propose a routing protocol based on the amount ofservices of the relay node and demonstrate the effec-tiveness of the protocol via simulation

The remainder of this paper is organized as followsSection 2 discusses the related works Section 3 presents thesystem model and describes the problems Section 4 givesthe detailed design Section 5 introduces simulations anddiscusses the results The last section concludes the paper

2 Related Works

21 Routing in Social Network Hui and Crowcroft haveproposed a routing algorithm called LABEL [6] which takesadvantage of communities for routing messages LABELpartitions nodes into communities based on only affiliationinformationThen each node in the network has a label tellingothers about its affiliation A node only chooses to forwardmessages to destinations or to the next-hop nodes belongingto the same group (same label) as the destinations LABELsignificantly improves forwarding efficiency over obliviousforwarding using their data set but it lacks a mechanism tomove messages away from the source when the destinationsare socially far away

BUBBLE [7] combines knowledge of the communitystructurewith knowledge of node centrality tomake forward-ing decisions Centrality in BUBBLE is equivalent to popu-larity in real life which is defined as how frequently a nodeinteracts with other nodes People have different popularitiesin the real life so that nodes have different centralities inthe network Moreover people belong to small communi-ties like in LABEL When two nodes encounter the nodeforwards the message up to the node with higher centrality(more popular node) in the community until it reaches the

same level of centrality as the destination node Then themessage can be forwarded to the destination community atthe same ranking (centrality) level

SimBet presented in [8] makes routing decisions by cen-trality and similarity of nodes Centralitymeans popularity asin BUBBLE More specifically the centrality value captureshow often a node connects nodes that are themselves notdirectly connected Similarity is calculated based on thenumber of common neighbors of each node SimBet routingexchanges the preestimated centrality and locally determinedsimilarity of each node in order to make a forwarding deci-sionThe forwarding decision is taken based on the similarityutility function (SimUtil) and betweenness utility function(BetUtil) When nodes contact with each other the nodeselects the relay node with higher SimBet utility for a givendestination

In [14] Fabbri and Verdone propose a sociability-basedDTN routing which is based on the idea that nodes with highdegrees of sociability (frequency encounteringmany differentnodes) are good forwarding candidates They defined thesociability indicator metric to evaluate the forwarding abilityof a node The routing strategy forwards packets to the mostsociable nodes only

In [15] authors propose a fuzzy-assisted social-basedrouting (FAST) protocol that takes the advantage of socialbehavior of humans on the road to make optimal and securerouting decision FAST uses prior global knowledge of real-time vehicular traffic for packet routing from the source tothe destination In FAST fuzzy inference system leveragesfriendship mechanism to make critical decisions at intersec-tions which is based on prior global knowledge of real-timevehicular traffic information

22 Handle Selfishness Since selfish behavior of the nodedegrades the performance of routing protocol many incen-tive mechanisms have been studied to stimulate individualselfish node to be cooperative The incentive strategies canbe classified into three categories reputation-based credit-based and TFT-based approach

In reputation-based schemes forwarding services areprovided to nodes depending on their reputation When anode provides services for other nodes it gets good reputa-tion Nodes with good reputations can receive services fromother nodes On the contrary misbehaving nodes get badreputations and will be denied participation in the networkThe fear of detection and punishment motivates nodes tocooperate Mei and Stefa [9] proposed a reputation-basedincentive scheme (Give2Get) for DTN routing which candetect misbehaving nodes and remove them from networkrouting They proved that their proposed scheme achievesNash equilibria

The credit-based schemes introduce some form of creditor virtual currency to regulate the packet-forwarding rela-tionships among different nodes Nodes earn virtual currencyby forwarding packets for othersThese credits can be used toobtain forwarding service from any node in the network Forevery forwarding request the virtual bank charges the senderan extra amount of virtual currency and the intermediatenodes redeem their rewards at the bank after successful


















4 Detailed Design




119894119895= SA














119860119894119895= SA119894119895sdot IA119894 (1)





119878119894119895=

IA119895

IA119894sdot SA119894119895

(2)






119894119895as

SI119894119895=

sum119873119894119895119878119894119895

sum119873119894119895119878119894119895+ sum119873119895119894119878119895119894

=

sum119873119894119895(IA119895IA119894)

sum119873119894119895(IA119895IA119894) + sum119873119895119894(IA119894IA119895)

(3)








119894and NS1015840

119894as

NS119894= sum

119895isin120595

sum

119873119894119895

119878119894119895

NS1015840119894= sum

119895isin1205951015840

sum

119873119894119895

119878119895119894

(4)


NSI119894=

NS119894

NS119894+NS1015840119894

(5)


CI119894119895= SA119894119895SI119894119895+ (1 minus SA

119894119895)NSI119894 (6)



119895119896and CI

119895119894

(8) if (119860119895119896gt 119860119894119896) then

(9) 120593 = 120593 cup 119895


119895119896CI119895119894from 120593







119895119896 and echoes








119895119896CI119895119894





3 6 9 12 15 18 21

Time (hour)

0

10

20

30

40

50

60

70

80D

elive

ry ra

tio (

)

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

Deli

very

ratio

()

3 6 9 12 15 18 21

Time (hour)

SSRSSARSimBet










6 Conclusions



0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet






Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation


























4 Detailed Design




119894119895= SA














119860119894119895= SA119894119895sdot IA119894 (1)





119878119894119895=

IA119895

IA119894sdot SA119894119895

(2)






119894119895as

SI119894119895=

sum119873119894119895119878119894119895

sum119873119894119895119878119894119895+ sum119873119895119894119878119895119894

=

sum119873119894119895(IA119895IA119894)

sum119873119894119895(IA119895IA119894) + sum119873119895119894(IA119894IA119895)

(3)








119894and NS1015840

119894as

NS119894= sum

119895isin120595

sum

119873119894119895

119878119894119895

NS1015840119894= sum

119895isin1205951015840

sum

119873119894119895

119878119895119894

(4)


NSI119894=

NS119894

NS119894+NS1015840119894

(5)


CI119894119895= SA119894119895SI119894119895+ (1 minus SA

119894119895)NSI119894 (6)



119895119896and CI

119895119894

(8) if (119860119895119896gt 119860119894119896) then

(9) 120593 = 120593 cup 119895


119895119896CI119895119894from 120593







119895119896 and echoes








119895119896CI119895119894





3 6 9 12 15 18 21

Time (hour)

0

10

20

30

40

50

60

70

80D

elive

ry ra

tio (

)

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

Deli

very

ratio

()

3 6 9 12 15 18 21

Time (hour)

SSRSSARSimBet










6 Conclusions



0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet






Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











119878119894119895=

IA119895

IA119894sdot SA119894119895

(2)






119894119895as

SI119894119895=

sum119873119894119895119878119894119895

sum119873119894119895119878119894119895+ sum119873119895119894119878119895119894

=

sum119873119894119895(IA119895IA119894)

sum119873119894119895(IA119895IA119894) + sum119873119895119894(IA119894IA119895)

(3)








119894and NS1015840

119894as

NS119894= sum

119895isin120595

sum

119873119894119895

119878119894119895

NS1015840119894= sum

119895isin1205951015840

sum

119873119894119895

119878119895119894

(4)


NSI119894=

NS119894

NS119894+NS1015840119894

(5)


CI119894119895= SA119894119895SI119894119895+ (1 minus SA

119894119895)NSI119894 (6)



119895119896and CI

119895119894

(8) if (119860119895119896gt 119860119894119896) then

(9) 120593 = 120593 cup 119895


119895119896CI119895119894from 120593







119895119896 and echoes








119895119896CI119895119894





3 6 9 12 15 18 21

Time (hour)

0

10

20

30

40

50

60

70

80D

elive

ry ra

tio (

)

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

Deli

very

ratio

()

3 6 9 12 15 18 21

Time (hour)

SSRSSARSimBet










6 Conclusions



0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet






Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










3 6 9 12 15 18 21

Time (hour)

0

10

20

30

40

50

60

70

80D

elive

ry ra

tio (

)

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

Deli

very

ratio

()

3 6 9 12 15 18 21

Time (hour)

SSRSSARSimBet










6 Conclusions



0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet






Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

10

20

30

40

50

60

70

80

90

100

2 4 6 8 10 12

Time (hour)

Rela

yers

()

SSRSSARSimBet


0

10

20

30

40

50

60

70

80

90

100

Rela

yers

()

2 4 6 8 10 12

Time (hour)

SSRSSARSimBet






Acknowledgments


References























RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation



















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Research Article A Service-Based Selfish Routing for...

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