Research Article Energy Efficient Interest Forwarding in NDN-Based Wireless Sensor Networks

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1 Moble Informaton Systems Volume 2016, Artcle ID , 15 pages Research Artcle Energy Effcent Interest Forwardng n NDN-Based Wreless Sensor Networks Shua Gao, 1 Hongke Zhang, 1 and Bechuan Zhang 2 1 School of Electronc and Informaton Engneerng, Bejng Jaotong Unversty, Bejng , Chna 2 The Unversty of Arzona, Tucson, AZ 85721, USA Correspondence should be addressed to Shua Gao; gaoxlh@gmal.com Receved 7 January 2016; Accepted 10 March 2016 Academc Edtor: Xaohong Jang Copyrght 2016 Shua Gao et al. Ths s an open access artcle dstrbuted under the Creatve Commons Attrbuton Lcense, whch permts unrestrcted use, dstrbuton, and reproducton n any medum, provded the orgnal work s properly cted. Recently there has been a new emergng trend n ntegratng Named Data Networkng (NDN) and wreless sensor networks (WSNs) together to mplement real data-centrc Internet of Thngs (IoT). However, the man solutons n current lterature lack energy effcent desgn to meet the severely lmted energy resources n WSNs. In ths paper, we propose a dual mode Interest forwardng scheme (called DMIF n short) for NDN-based WSNs. The DMIF conssts of two combned forwardng modes, n whch several energy effcent mechansms ncludng flexble mode shft, floodng scope control, broadcast storm avodance, packet suppresson, and energy weght factors are desgned to save and balance the energy consumpton. We extend the ndnsim to support wreless multhop communcaton to valdate the proposed scheme. Smulaton experments show that the DMIF outperforms the baselne schemes n terms of total energy consumpton, energy equlbrum rate, and network lfetme. 1. Introducton Startng as a futurstc concept, the dea of wreless sensor networks (WSNs) has come a long way n past decades. Meantme, routng desgn s always one of the most mportant research topcs n WSNs communty [1, 2]. In earler stage of WSNs research, data-centrc routng protocols play mportant roles, n whch the snk sends Interests to the network and wats for data from the sensors wthout awareness of the dentty of the sensors n advance. The basc dea of the data-centrc routng s decouplng the sensed content from the sensor dentty. However, such data-centrc schemes are basedonstand-alonesolutonsforroutng[3],ratherthana comprehensvesolutonforthewholeinternetandinternetof Thngs (IoT). In addton, there are no detaled and standard namng schemes for varous and complex applcatons n the lterature [1]. All these factors lmt the deployment of the data-centrc approaches n practce for WSNs. Fortunately, as an emergng future Internet archtecture, Named Data Networkng (NDN) [4] has been proposed anddevelopedbasedonnformatoncentrcnetworkngn recent years. The NDN adopts a recever-based servce model and changes the communcaton paradgm from tradtonal host-centrc communcaton to named data-centrc communcaton. In the NDN, forwardng of Interest and Data packets s performed based on a dstrbuted way, rather than centralzed name resoluton and content dscovery, whch naturally meets the requrements of WSNs and IoT well. The emergence of the NDN provdes a good opportunty to rethnk how to desgn real data-centrc WSNs. Recently, some researchworkshavebeennvestgatedonhowtoapplythe NDN to WSNs [3, 5 9] and how the WSNs ft much more naturally nto the emergng NDN archtecture compared to conventonal TCP/IP based technologes. Nevertheless, there are stll some open ssues left for research [10], ncludng namng, routng and forwardng, securty, cachng, transport control, and deployment mode, snce orgnal NDN s desgned amng at a whole Internet archtecture, rather than WSNs. In ths paper, we focus on Interest forwardng and routng ssues for NDN-based WSNs. Regardng routng and forwardng, there have been few works n ths area. In the lterature [3], a routng scheme nspred by the drected dffuson (DD) [11] and coupled wth several antcollson tmers s proposed to meet the requrements of perodcal montorng applcatons. In [5], the authors desgn a one-hop forwardng

2 2 Moble Informaton Systems and routng protocol for multsource data retreval n NDNbased IoT. A vanlla Interest floodng scheme and a reactve optmstc name-based routng scheme are proposed n [6]. However, these proposed routng schemes work wthout consderaton about controlled floodng scope and energy awareness, so that they are not sutable for WSNs wth severely lmted energy and computaton resources. In addton, some research works [10] have dealt wth forwardng and routng schemes n NDN-based wreless ad-hoc networks. Due to the challenges on the moblty and resource lmtaton n ad hoc networks, reactve floodng s usually adopted to dscover potental content provders, rather than proactve routng, whch needs too much cost to mantan the routng reachablty for wreless ad hoc networks. Accordng to the survey n [10], the reactve forwardng n named data wreless ad hoc networks can be classfed nto two categores: blnd forwardng and aware forwardng. In the blnd forwardng, each node broadcasts Interest packets to dscover the content sources. To avod broadcast storm and mprove source dscovery effcency, some tmer-based packet suppresson schemes [12, 13] are proposed to control the blnd broadcast of Interest forwardng. On the other hand, the basc dea of the aware forwardng s selectng the next-forwarders [14 16] or content provders [12, 17, 18] n the Interest forwardng based on awareness of related network nformaton, such as transmsson dstance, message redundancy, geographcal locaton, and data retreval rate. However, all the prevous solutons about the Interest forwardngarebasedonwrelessadhocnetworksandlackof consderatons about severely lmted energy resources and more challengng envronment n WSNs. Inthspaper,basedonprevousworksnthelterature, we propose an energy effcent dual mode Interest forwardng approach (named DMIF n short) for NDN-based WSNs. The DMIF conssts of two forwardng modes: floodng mode and drectve mode. In the floodng mode, three schemes ncludng scope control, packet suppresson, and broadcast storm avodance based on an energy weght factor are desgned to support controlled floodng and reduce the network overhead. In the drectve mode, the Interest forwardngsgudednanenergyawarenesswaybasedonthe lookup results at the Forwardng Informaton Base (FIB) mantaned by the passng Data packets along the reverse paths, thus mprovng the Interest forwardng and content transfer effcency. The two modes n the DMIF work n a combned way and mode shft s allowed at any relay nodes f necessary. In addton, we extend ndnsim [19, 20] to support wreless multhop communcaton and conduct smulaton experments, the results of whch valdate the proposedschemeandshowthatthedmifschemecanreduce and balance total energy consumpton and prolong network lfetme sgnfcantly n contrast wth the baselne schemes. The remander of ths paper s organzed as follows. Secton 2 revews the related work. Secton 3 descrbes the concerned applcaton scenaros and a three-dmensonal namng scheme. Secton 4 s devoted to a detaled desgn of the energy effcent Interest forwardng based on two combned modes. Secton 5 presents our smulaton results and Secton 6 concludes the paper. 2. Related Work 2.1. NDN: An Overvew. As one promsng ICN archtecture, NDN [4] replaces the IP addresses wth content chunks at the narrow wast of current Internet s hourglass model. A recever-drven and content centrc communcaton paradgm s defned n the NDN-based on the exchange of two types of packets: Interest and Data, whch carres herarchcallystructurednames.eachndnroutermantansthree data structures: () a FIB ndexed by the content name prefxes andusedtogudetheinterestpacketstothecontentsources; () a Pendng Interest Table (PIT) storng all Interests that are not yet satsfed and gudng the Data packets along the reverse path; () a content store (CS) whch temporarly caches the ncomng Data packets to satsfy future Interests. To retreve a content, a consumer sends an Interest packet carryng the name of the desred content nto the network. When a NDN router receves an Interest from a downstream neghbor, t makes a lookup n local CS by matchng the contentnameatfrst.ifthematchhts,therouterwllsendthe Data back towards the consumer. If the match n the CS fals andamatchnthepitsfound,theinterestwllbedscarded. Otherwse, a new PIT entry wll be created and the Interest wll be further forwarded to the upstream neghbor(s) based on the FIB nformaton. When a NDN router receves Data, t forwards the Data along the reverse path taken by the Interest based on the PIT. Meanwhle, the router caches the content carred n the Data packet and the related PIT entres are removed. Thus, the Data packet returns to the requestng consumer fnally. In general, the NDN uses dfferent nterfaces at a node to dscrmnate the upstream neghbors and downstream neghbors. In the NDN, a node can forward the ncomng Interest to the upstream neghbors by sendng out the packet over all the network nterfaces except the one from whch the Interest arrves. In wreless multhop communcaton envronment consdered n ths paper, there s only sngle wreless network nterface at a node, whch poses a challenge n the desgn of the Interest forwardng strategy for wreless NDN NDN-Based Wreless Sensor Networks. The receverbased servce model n the NDN fts naturally nto datacentrc WSNs. Recently, some research works [3, 5 9] have shown that WSNs can beneft from basc dea of the NDN desgn. In [7], a wreless rechargng system for WSNs s proposed based on the NDN to valdate that the herarchcal namng structure fts n naturally wth energy aggregaton requrements and ts nherent moblty supportng ablty s very attractve for moble rechargng system. In order to meet the memory and computatonal constrants of WSNs, a lght-weght content centrc networkng protocol [8] wth smplfed message format and flexble namng strategy s proposed for WSNs. In [9], the authors analyze the benefts (e.g., securty, data aggregaton, and moblty) by applyng the NDN nto IoT applcatons and provde a hgh-level NDN archtecture that specally meets the IoT challenges. However, there are no Interest forwardng strateges for WSNs dscussedntheabovelterature[7 9].

3 Moble Informaton Systems 3 In [5], a comprehensve framework for relable retreval from multple wreless sources s proposed based on Data suppresson, collson avodance, and Exclude feld carred n the Interest packets. However, the proposed framework s only sutable for one-hop wreless scenaros. Interest forwardng based on multhop mesh networks s dscussed n [3, 6]. A blnd floodng based on a deferred tmer s desgned to dscover potental content provders n [3]. In addton, nspred by the DD protocol [11], each NDN node mantans a drecton state durng the Data packet forwardng n the blnd floodng phase to facltate future Interest forwardng. Smlarly, a vanlla Interest forwardng (VIF) and a reactve optmstc name-based routng (RONR) are proposed n [6] to support basc blnd and stateful forwardng, respectvely. In our paper, the proposed DMIF combnes two Interest forwardng modes together and supports flexble mode shft when needed, whch s dfferent from the related two Interest forwardngschemesn[3,6]workngnaparallelway. In addton, energy consumpton and controlled scope are ntegrated nto the blnd forwardng phase to mprove the energy effcency of the system n ths paper. In [21], the authors extended the deferred tmer calculaton n [3] to let the nodes wth hgher energy level forward Interest packets wth hgher prorty. However, there s no weght factor between resdual energy and transmsson dstance consdered n the tmer calculaton. Moreover, the energy effcent stateful forwardng s not supported n [21] Interest Forwardng n NDN-Based Wreless Ad Hoc Networks. Compared wth WSNs, more research works have been nvestgated n NDN-based wreless ad hoc networks, mostly focusng on vehcular communcatons. Accordng to the survey n [10], the reactve forwardng n named data wreless ad hoc networks can be classfed nto two categores: blnd forwardng and aware forwardng. In the blnd forwardng, some tmer-based packet suppresson schemes [12, 13] are proposed to control the blnd broadcastoftheinterestforwardngandavodthebroadcast storm. In [13], the authors develop a collson preventon soluton based on a unform random tmer to support NDNbased V2V traffc nformaton dssemnaton. In addton, a proactve data pushng scheme through actve overhearng s proposed n [13] to speed up the Data propagaton, whch s dfferent from the recever-based servce model n orgnal NDN desgn. Smlarly, a set of tmers and packet suppresson solutons are proposed n [12, 17, 18] to avod packet collson n NDN-based vehcular envronment. The deferred tmer for Interest s longer than the one for Data, whch gves hgher access prorty to Data over Interest packets. The above blnd forwardng schemes are based on unform random tmers, whereas the deferred tmer n ths paper s based on transmsson dstance and resdual energy at ntermedate nodes andmakesthefloodng-basedforwardngnottooblnd. On the other hand, the basc dea of the aware forwardng s selectng the next-forwarders [14 16] or content provders [12, 17, 18] n the Interest forwardng based on the awareness of related network nformaton, such as transmsson dstance, message redundancy, geographcal locaton, and data retreval rate. In [14], a drecton-selectve forwardng scheme s proposed to choose the farthest node n each quadrant as the forwarder by nformaton exchangng among Interest senders and recevers wth two extended types of messages. The dedcated nformaton exchangng for choce of the relay nodes may ncrease the system complexty. In the proposed DMIF, the deferred tmer based on transmsson dstance gves the farther nodes wth hgher prorty n the Interest forwardng wthout extra nformaton exchangng. In the neghborhood-aware Interest forwardng (NAIF) scheme [15], the relay nodes are chosen n a probablstc way based on two mportant hstorcal factors, data retreval rate and forwardng rate. The former s the rato of the number of Data packets successfully retreved to the number of Interest packets sent, and the latter reflects the fracton of the ncomng Interest packets that a gven node wll forward. In [16], a gossp algorthm named BlooGo s developed to dssemnate messages throughout the wreless NDN network wth a mnmum number of transmssons. The basc dea s that a relay node forwards the message only f ts neghborhood s not strctly ncluded nto the one of the sender. The comparson of the neghborng relatonshp s performed based on a bloom flter. In a word, the above aware forwardng schemes need extra algorthms to obtan the related nformaton for choce of the relay nodes, whereas the awareforwardngnthedmifsbasedonthenformaton left by the passng Data packets wthout extra overhead. In the lterature [12, 17, 18], the authors desgn a provderaware forwardng (PAF) scheme to gude the Interest forwardng after the blnd floodng. Each node mantans a dstance table recordng the dstance nformaton between local node and potental content provders. After recevng multple Data packets repled from potental content provders,theconsumerschoosethenearestoneamongthem andcarrytheprovderidanddstancenformatonnfuture Interest packets. The relay nodes forward the Interests to thedrectonoftheselectedprovderbasedonthedstance table.thebascdean[12,17,18]ssmlartotheproposed DMIF. In our paper, we are concerned about energy effcent forwardng for Interest packets. Specfcally, the hop and resdual energy metrcs are carred n Data packets along the reverse paths to mantan the FIB and assst n future Interest forwardng n order to balance energy consumpton and prolong network lfetme. In addton, the provderaware forwardng and blnd forwardng are two parallel modes n [12, 17, 18], whch means the content consumer needs to restart the blnd forwardng after the provder-aware forwardng fals n the relay nodes. In the DMIF, the two modes work n a combned way and mode shft s allowed at any relay nodes when needed. 3. Scenaro Descrpton and Namng Scheme In ths paper, we are concerned about a NDN-based WSN applcaton n whch multple snks are actng as content consumers that send perodc Interests to query the related nformaton (e.g., temperature, humdty) sensed by the statc sensorsactngascontentprovdersnspecfcareas.the snks are powerful devces, but the sensor nodes are resource lmted devces, ncludng energy, computng, and memory,

4 4 Moble Informaton Systems Interest Content store Data M Forwardng mode? DM ForwarderID s me? N Drop FM Y Pendng Interest table (PIT) M M FIB Forward n FM Drop Forward n DM M Lookup mss Lookup ht Fgure 1: Dual mode Interest forwardng for NDN-based WSNs. requrng that the process of the content query and retreval should be energy effcent. Data namng s one of the most mportant technologes n the NDN archtecture, whch may affect the desgn of the Interest forwardng and routng. In the concerned applcaton, there are three-dmensonal attrbutes to descrbe a content name: tme dmenson, space dmenson, and type dmenson. Therefore, based on the readable and herarchcal rules of NDN namng, we propose the followng threedmensonal namng for the raw data n ths applcaton, n whch WSNs s a dedcated prefx to dentfy the proposed namng scheme. /WSNs/type/... /space/... /tme/... () Type: type of the nformaton sensed by the deployed sensor nodes, for example, /type/temperature, /type/humdty. () Space: the locaton attrbute of the sensed content. It can be expressed as natural granularty, lke a buldng ID or a room number. Another way s usng a granularty confgured manually for more general purpose. For example, we can dvde the montored area nto several subareas based on the requrements of the applcaton. And we use the subarea ID to descrbetheattrbuteofspace,lke /space/areaa. We assume that each node knows where t locates and the content name of the raw data generated locally. () Tme: the granularty n the tme dmenson s 1 mnute n ths paper. In other words, the raw data s generated every mnute. Therefore, the format of the tme dmenson s expressed as /tme/date/mnute ndex. (a) Date:we use the format /year/month/day/, for example, /2015/12/04. (b) Mnute ndex: 1, 2,..., n,..., 1440; here,n denotes the tme perod {n 1, n} mnute wthn one day. For example, /2015/12/04/1000 denotes the tme perod from 16:39 to 16:40 on December 4, The above namng format conssts of three components {space, tme, type} that descrbe the content from three parallel dmensons. For each component, a herarchcal name s used to support flexble granularty and can be aggregated freely. The namng scheme here provdes a recommended format. The order and the granularty of the three dmensons can be adjusted based on system requrements n practce. 4. Dual Mode Interest Forwardng (DMIF) In ths paper, we propose a dual mode Interest forwardng strategy based on the followng consderatons. (1) Reactve routng s more effcent than proactve rout ng n resource lmted WSNs based on NDN [22]. Therefore, floodng mode s the smplest way to dscover the potental content provders. (2) The flow of Data packets along the reverse paths leaves a tral of breadcrumbs [23], whch can help fnd the content sources more quckly at less cost. Based on ths, another Interest forwardng mode, drectve mode, may be adopted to gude the Interest forwardng more effcently. The above two modes are not two parallel modes, whch can be ntegrated together nto the NDN forwardng plane andshftedtoeachotheraccordngtothefiblookupresults. IntheproposedDMIF,acontentconsumerchecksthe FIB at frst before sendng out an Interest packet. If the FIB lookup hts successfully, the Interest wll be sent n the drectve mode (DM). Otherwse, the Interest wll be sent n the floodng mode (FM). In the DM mode, an extended feld (named as ForwarderID) about the unque ID of the nexthop forwarder s carred n the Interest packet to desgnate a neghbor node as the forwarder of the Interest. A node recevng the Interest packet wll check local content store as specfed n orgnal NDN desgn. If the content store lookup fals,thenodewllperforminterestforwardngbasedon the proposed DMIF llustrated n Fgure 1. If the ncomng Interest s n the FM mode, the node should contnue theinterestforwardngftherearenoduplcatedinterests receved before. If the ncomng Interest s n the DM mode

5 Moble Informaton Systems 5 FIB lookup mss Floodng mode (FM) FIB lookup ht FIB lookup mss FIB lookup ht Drectve mode (DM) Fgure 2: Interest forwardng mode shft n the DMIF scheme. andthenodesthesameastheonedesgnatedbythe ForwarderID feld, the node wll perform the forwardng. Regardng the forwardng, a node needs to check local FIB andchoosesutableforwardngmodeshownnfgure1based on the results of the FIB lookup. Note that t s not guaranteed that sngle mode lke the FM or the DM can be performed for Interest forwardng n an end-to-end path. Durng the forwardng n the DM mode, the FIB lookup at an ntermedate node may fal due to some uncertanreasons,lkenodefalureorentrytmeout.ifso,the DM mode can shft to the FM mode drectly. In the lterature [12, 17, 18], f there s a lookup mss n an ntermedate node, the content consumer needs to choose another content provder or choose to flood Interest after the Interest tmes out. In the DMIF, the two Interest forwardng modes can be combned together and mode shfts are allowed at any ntermedate nodes when needed based on the FIB lookup results shown n Fgure Floodng Mode (FM). In case of FIB lookup mss, the floodng mode (FM) s used to dssemnate the Interest packets. In the FM mode, the content consumer or the ntermedate forwarders broadcast the Interest packets through the wreless lnk to dscover potental content provder(s). The key pont of the FM mode s how to mplement controlled floodngtoreduceenergyconsumptonandmprovedscover effcency. Here, three schemes are adopted to support controlled floodng: scope control, broadcast storm avodance, and packet suppresson Scope Control. Interest floodng wthout controlled scope wll contnue untl t goes throughout the network arrvng at the network edge, even f the content provders have already been dscovered. Uncontrolled floodng wll cause severe waste of bandwdth and energy resources. To address ths ssue, a new feld about TTL (Tme To Lve) s added nto the Interest packet to control the dssemnaton scope of an Interest. Frstly, the Interest s flooded wth the TTL values set to TTL START. The TTL value s reduced by 1 at each forwardng node n the FM mode. If the Interest tmes out, the content consumer wll ncrease the TTL value by TTL INCREMENT to restart thecontentdscoveryprocess.thechoceofttlstart and TTL INCREMENT s dependent on the network scale and performance requrements on energy consumpton or dscover delay Broadcast Storm Avodance. In related lterature, a deferred tmer s often adopted n the Interest floodng to avod or allevate the effects of broadcast storm. The deferred tmer s generally based on a random counter, whch lacks enough control on the path selecton. In wreless sensor networks, unbalanced energy consumpton may lead to energy depleton too early and shorten the network lfetme. Here, we desgn an energy effcent Interest floodng scheme wth a deferred tmer based on transmsson dstance and resdual energy. Upon recevng an Interest packet wth a content name c k from node n j,anoden needs to wat for a deferred tmer T c k before broadcastng the Interest packet. The deferred tmer T c k s a parameter per Interest rather than per node. Each Interest packet has a dfferent deferred tmer. We use e r and e max to denote the resdual energy and ntal maxmum energy at node n. Gven the relatve transmsson dstance between n and n j, d j,andthemaxmumtransmssonrange d max, the deferred tmer for the Interest forwardng T c k can be calculated as follows: T c k =T basc (1+α e max e r e max + (1 α) d max d j d max ), (1) where T basc s a basc constant tme slot for the calculaton and α s a weght factor to trade off the effects of resdual energy and communcaton dstance n the tmer calculaton. We have 0 α 1. When the weght factor α=0,further neghborhasahgherprobabltytobechosentoforward Interest packets. Wth the ncrease of the α value, resdual energy plays more mportant role n the deferred tmer calculaton, whch helps balance the energy consumpton. In (1), the calculaton of the deferred tmer T c k s dependent on the relatve dstance and the resdual energy. Here, t s assumed that the relatve dstance can be obtaned by some tradtonal methods. One lght-weght soluton s based on the RSSI (Receved Sgnal Strength Indcaton) parameter to estmate the relatve dstance. Another more accurate but costly soluton s usng GPS nformaton to calculate the relatve dstance. However, the detaled dstance calculaton soutofscopeofthspaper. Regardng the Data packet, the deferred tmer T c k d for the Data forwardng wth a content name c k canbecalculatedas follows: T c k d = rand [0, T basc]. (2) Smlarly, the deferred tmer T c k d s also a parameter per packet rather than per node. Each Data packet has a dfferent deferred tmer. The key dea n (2) s that Data packets have hgher prorty n the forwardng than the Interest packets. Based on ths, we gve the Data packets shorter deferred tmers than the Interest packets. Thus, some Interest packets n the deferred queue may be matched by ncomng Data packet wth a shorter deferred tmer, whch may avod redundant packet forwardng and reduce energy consumpton Packet Suppresson. The deferred tmer for the Interest and Data forwardng s a new concepton n the NDN

6 6 Moble Informaton Systems Table 1: Actons when an ncomng packet matches a deferred packet. Tmer type Interest Data Incomng packet type Data Interest Data Interest Actons Cancel T c k Cancel T c k Cancel T c k d Keep the T c k d and Interest forwardng and then forward the Data based on local PIT table and Interest forwardng after the number of the same ncomng Interests reaches a threshold and Data forwardng after the number of the same ncomng Data packets reaches a threshold and dscard the ncomng Interest even though ts cache lookup hts successfully n 2 : cancel Interest transmsson n 2 n 2 : cancel Interest transmsson n 1 n 1 n 4 n 4 Interest path Data path n 3 n 3 Fgure 3: Interest suppresson n floodng mode. forwardng paradgm. How a NDN router should act after recevng Interest or Data before the deferred tmer of the correspondng Interest or Data expres s not defned n the NDNarchtecture[4]andtheNDNforwardngppelne [24]. In [3, 12], the authors propose an Interest suppresson scheme to avod the waste of bandwdth resources. However, Data suppresson s not consdered n the lterature. Table 1 presents several packet suppresson rules to deal wth the ncomng packet matchng wth a packet n the deferred watng queue. As presented n Table 1, durng the watng tme of the Interest deferred tmer T c k, f a NDN router overhears the requested Data packet, the tmer and the Interest n the watng queue wll be canceled. In the left pcture of Fgure 3, acontentconsumern 1 s requestng a content located at node n 4.Noden 2 and node n 3 are two neghbor nodes of node n 1 and node n 4. It s assumed that node n 3 has a shorter deferred tmer than node n 2 for the Interest floodng. And the Data deferred tmer s always shorter than the Interest deferred tmer. Therefore, the Interest packet may be stll deferred n the watng queue at node n 2 when the Data packet returns to node n 2 from node n 4 n the left pcture of Fgure 3. In ths way, node n 2 wll cancel the Interest transmsson n the watng queue and forward the ncomng Data based on local PIT ncomng records accordng to the packet suppresson scheme proposed n Table 1. Thus, the Data from the content provder n 4 wll return to the content consumer n 1 along two reverse paths n Fgure 3. In addton, durng the T c k watng tme,fandnrouteroverhearsthesameinterestforspecfc number of tmes, θ, theinterestnthewatngqueuewllbe canceled. The threshold of θ s set to 1 n dense networks accordng to the lterature [3, 12]. In the rght pcture of Fgure 3, we have the smlar applcaton assumpton wth the left pcture. The dfference s that the dstance between n 2 n 2 : cancel Data transmsson n 2 n 2 : dscard Interest from n 3 n 1 n 1 n 4 n 4 n 2 n 3 n 3 Interest path Data path Fgure 4: Data suppresson n floodng mode. node n 2 and node n 3 s closer so that node n 2 can receve the Interest packet forwarded by node n 3.Inthsway,noden 2 wll receve the same Interest query twce from node n 1 and node n 3. Therefore, node n 2 wll cancel the Interest transmsson n the watng queue after recevng duplcate Interests from node n 3 accordng to Table 1. Regardng the Data deferred tmer T c k d,fandnrouter overhears the same Data for specfc number of tmes, θ, the deferred Data n the watng queue wll be canceled. Smlarly, the threshold of θ canbesetto1 n dense networks. The applcaton assumpton n the left pcture of Fgure 4 s the same as the one n the rght pcture of Fgure 3. After node n 4 returns the Data packet, node n 2 and node n 3 wll receve the Data packet at the same tme. It s assumed that node n 3 has a shorter deferred tmer than node n 2 for the Data floodng. Thus, node n 2 wll receve duplcate Data packets from node n 3. Then node n 2 wll cancel the deferred Data packet n the watng queue. In addton, durng the T c k d watng tme, the ncomng Interest may match the deferred Data packet. In ths case, the broadcastng Data packet after the tmer expres wll meet the request of the ncomng Interest. Therefore, the NDN router wll dscard the newly ncomng Interest and wllnotforwardtfurther.intherghtpctureoffgure4, acontentconsumern 1 requested a content located at node n 4 at frst. Durng the deferred tmer of the Data packet at node n 2, another content consumer n 3 starts to request the same content matchng wth the deferred Data at node n 2.Inths case, the ncomng Interest from the content consumer n 3 wll be dropped. And the Data packet broadcasted by node n 2 wll reach node n 3 automatcally later FIB Mantenance. The floodng mode of Interest packets s costly n energy consumpton, even wth the help of the

7 Moble Informaton Systems 7 Forward Calculate aggregated metrcs Pendng Interest table (PIT) Add M FIB Data Content store M Dscard Data Update Fgure 5: NDN data forwardng process wth FIB mantenance. controlled floodng proposed n Secton 4.1. Actually, the purpose of the Interest floodng s dscoverng potental content provders to assst n future Interest forwardng at a lower cost. The key pont here s how to dynamcally mantan the FIB to gude the Interest forwardng n the DM mode. Inspred by the breadcrumbs routng n the lterature [23], we propose to mantan the FIB wth the passng Data packets n a passve way. The FIB status left by the Data packets along the reverse paths s helpful to speed up the subsequent content dscovery n the DM mode at less cost. To support energy effcent Interest forwardng n the DM mode, each entry n the FIB has a format of the followng fve-tuple Prefx, ForwarderID, Hop, Energy, Tmer, ndexed by the content name prefx and the ForwarderID. () Prefx:nameprefxofthecontent. () ForworderID: ID of the node from whch the Data comes. () Hop: hop factor of the path from local node to the content source. (v) Energy: resdual energy factor of the path from local node to the content source. (v) Tmer: lfetme of ths forwarder entry. In an ad hoc mesh topology, t s possble that broadcasted Interests arrve at the content provders along multple paths. Orgnal NDN desgn adopts one Interest-one Data mode n whch only one Data packet arrvng frstly wll be accepted fnally even f there are more returned Data packets. In order to provde the capablty of the selecton among more paths n the DM mode, we let the FIB mantan multple entres for each name prefx to support multpath selecton, whch s not contradctory wth one Interest-one Data mode. In the multpath scheme, the Data packets arrvng later wll be used to update the status of the correspondng FIB entres, even though they cannot be forwarded further due to the mssng of the PIT entres. Therefore, the FIB may mantan multple entres wth dfferent ForwarderIDs for each name prefx. Each entry n the FIB has a tmer denotng the lfetme that s reset whle recevng correspondng Data packet or Interest packet. A FIB entry wll be deleted once the tmer expres, whch s helpful n deletng the obsolete forwardng nformaton and mprovngthescalablty.inthedmmode,thettlvaluewll not be reduced n the Interest forwardng n order to mprove the effcency of the content retreval. In ths paper, each content source reples Data packets carryng ntal hop and resdual energy nformaton as follows: h source =1; e source = e max e r. Fgure 5 llustrates the extended NDN data forwardng process wth FIB mantenance. When a content router receves a Data packet from an upstream node j,twllfrstly check whether there has been an entry wth the same name prefx and ForwarderID stored n local FIB. If not, the content router wll add a new entry wth metrcs (denoted as h(, j) and e(, j)) carred n the ncomng Data packet. If yes, the contentrouterwllupdatethemetrcsoftherelatedentry. Then, the content router wll perform normal NDN process. If the PIT lookup hts, the Data packet wll be forwarded towards the downstream node(s). Because there may exst multpleentresforthesamecontentprefxnlocalfib, Algorthm1wllbeperformedtocalculatetheaggregatedhop metrc h() and energy metrc e() carred n the Data packet n a probablstc way Drectve Mode (DM). Thanks to the FIB mantenance n Secton 4.2, the drectve mode canbeusedtogudethe Intereststowardsthedscoveredcontentprovdersatlesscost. As llustrated n Fgure 1, the DM mode wll be actvated once the FIB lookup hts successfully. Sncetheremayexstmultpleentresforthesamecontent prefx n local FIB, the content consumer or ntermedate content routers have multple choces for the neghbor forwarder selecton. To balance energy consumpton and prolong network lfetme, we propose a least cost forwardng based on the tradeoff between the hop and the energy metrcs shown n Algorthm 2. In Algorthm 2, β s a weght factor to balance the tradeoff between total energy consumpton and network lfetme. In Secton 5, we wll observe the mpacts of dfferent weght factors on energy effcency. Note that the proposed DMIF s only applcable for the Interest forwardng. The Data forwardng process s always the same regardless the selecton of Interest forwardng mode. EventheDMmodeschosen,theDataforwardngprocesss performed n the same way defned n Secton 4.2. (3)

8 8 Moble Informaton Systems Input: m entres for the same content prefx n the FIB; the hop and the energy metrcs of the entry j are denoted as h(, j) and e(, j); (1) Calculate the proporton about the hop and the energy nformaton of each entry; 1/h(, j) p hop(, j) = m k=1 1/h(, k) ; p energy(, j) = 1/e(, j) m k=1 1/e(, k) (2) Calculate the aggregated metrcs h()and e() for hop and energy; m h() = p hop(, k) h(, k); k=1 m e() = p energy(, k) e(, k) k=1 Algorthm 1: Aggregated metrc calculaton at node. Input: m entres for the same content prefx n the FIB; the hop and the energy metrcs of the entry j are denoted as h(, j) and e(, j); (1) Calculate the aggregated metrc m(, j) for each entry; m(, j) = β e(, j) + (1 β) h(, j), 0 β 1 (2)TheForwarderIDoftheentryj wth the least aggregated metrc s chosen as the neghbor forwarder: m(, j) = mn m(, k), k [1,k] Algorthm 2: Least cost Interest forwardng at node Routng Loop Consderaton. Thanks to the Nonce feld carred n the Interest packet of the NDN, the Interest forwardng s naturally routng loop free. In detal, every Interest carres a random Nonce and each node recevng the Interest can remember the seen Nonces at the PIT table. The ncomng Interest wth a duplcate Nonce feld wll be dropped to avod the routng loop durng the Interest forwardng. Accordng to orgnal desgn of the NDN, the Data forwardng wll not loop snce t s performed along the reverse paths of the Interest from upstream nodes to downstream nodes. However, somethng new needs to be consdered n wreless envronment wth multpath capablty. Frst, each node has only sngle wreless nterface to send and receve the NDN packets. Therefore, there s no way to dscrmnate the conceptons about upstream nodes or downstream nodes n wreless envronment. Second, multpath capablty requres anodetoreceveandprocessmultpledatapacketsfrom dfferent neghbors to remember multple path nformaton, even though only the frstly arrvng Data s forwarded. In addton, there s no any nformaton about the sender ID carred n the Data packet n orgnal NDN desgn. In ths case, the sender of a Data packet may receve the same Data and store the nformaton from ts neghbors, thus causng routng loop problem. For example, n Fgure 6, node n 3 receves a Data packet from node n 5. It s assumed that the PIT lookup hts locally at node n 3 andtwllforwardthedatapacketthroughthe wreless broadcast lnk. In ths case, not only the downstream node n 2 butalsotheupstreamnoden 5 can receve the Data n 1 n 2 IDLst {n 5,n 3,n 4,n 2 } Interest path Data path IDLst{n 5,n 4 } n 4 n 3 IDLst{n 5,n 3 } n 5 IDLst{n 5 } Fgure 6: Routng loop avodance n the Data forwardng. packet from node n 3. In other words, node n 5 receves the same Data packet sent by tself before and routng loop happens. To address the routng loop problem of the Data forwardng, we add a new feld named IDLst n the Data packet. The IDLst contans the IDs of all nodes along the forwardng path of the Data packet. Upon recevng a Data packet, the node wll frstly check whether ts ID has been lsted n the IDLst. If yes, routng loop happens and the ncomng Data wll be dropped. If no, the path nformaton carred n the ncomng Data wll be used to update local FIB as descrbed n Secton 4.2. Fgure 6 presents an example to llustrate how the IDLst works. In Fgure 6, node n 5 wll dscard the Data packet from node n 3 snce ts ID s lsted n the IDLst. Smlar routng loop detecton s performed at the rest nodes to avod routng loop n the Data forwardng. The IDLst scheme may

9 Moble Informaton Systems 9 n 8 M FM FM M FM n 7 M n 6 Interest path Data path n 1 DM DM n 3 M n 2 M FM M FIB lookup mss FIB lookup ht Fgure 7: An example for mode shft between the FM and the DM. not scale well n large scale networks. More effcent routng loop detecton schemes may be nvestgated as future work. 4.5.ExampleforModeShftntheDMIF. Fgure 7 provdes an example to llustrate how the mode shft works between the FM mode and the DM mode to mprove the Interest forwardng.infgure7,tsassumedthatnoden 1 quered the content located at node n 5 prevously along the path n 1 -n 3 - n 5. Accordng to the FIB mantenance rules, a tral of breadcrumbs s left along the reverse path. Now, node n 8 squeryngthesamecontent.basedontheproposeddmif scheme, the Interest s frstly forwarded n the FM mode untl t arrves at node n 1. After the FIB lookup hts successfully at node n 1, the Interest s broadcasted n the DM mode wth the ForwarderID set as node n 3. Let us assume that the FIB entry at node n 3 wasdeletedduetosomereasons.thus,the forwardng mode wll shft back to the FM mode at node n 3, whch broadcasts the Interest to the fnal destnaton. Wth the shft between the FM mode and the DM mode, nodes n 2 and n 4 wll not be nvolved n the Interest forwardng orgnated by node n 8, whch helps reduce the resource consumpton and mprove the network effcency. 5. Performance Evaluaton 5.1. Smulaton Settngs. Ths secton evaluates the performance of the Interest forwardng scheme DMIF mplemented n ndnsim 2.0 [19, 20], whch s extended to support wreless multhop communcaton and the forwardng strateges proposed n ths paper. In the smulaton experments, there are 100 sensor nodes deployed n a 400 m 400 m area n Fgure 8 n whch all the black nodes on the border are chosen as the content producers that generate the raw data about temperature wthn ts subarea every mnute. For example, the raw data name generated by node n 0 at 16:40 on December 4, 2015, s /type/temperature/space/area0/tme/2015/06/04/1000, accordng to the namng scheme n Secton 3. The whte nodes n Fgure 8 are chosen as the snk nodes (content consumers) that send perodc Interests to query the nterested content about several subareas every fve mnutes. Every tme, 12 nterested areas are randomly chosen among the 36 content producers. The grey nodes are NDN routers that can relay packet and cache contents as specfed n the NDN. The n 5 n 4 Table 2: Smulaton parameters. Parameter Value Interest sze 50 bytes Data sze 100 bytes T basc 7ms Wreless nterface IEEE Rado coverage range 100 m Grd topology sze Grd topology step 45 m Number of nodes 100 Number of content producers 12 out of 36 Number of content consumers 1 5 Intal energy 5 Joule Energy consumpton per bt e 0.5 μj/bt Smulaton tme 3600 s number of the snks s changed from 1 to 5 n the experments. For example, at 16:40 on December 4, 2015, a snk sends the followng Interests to query the temperature about subarea0 n the past fve mnutes: WSNs/type/temperature/space/area0/tme/2015/12/04/996 WSNs/type/temperature/space/area0/tme/2015/12/04/997 WSNs/type/temperature/space/area0/tme/2015/12/04/998 WSNs/type/temperature/space/area0/tme/2015/12/04/999 WSNs/type/temperature/space/area0/tme/2015/12/04/1000 In the experments, t s assumed that each node sends and receves packets wth fxed transmsson and recepton power. Therefore, the energy consumpton s ndependent of the transmsson dstance through a wreless lnk. Based on ths, we adopt the followng energy model [25, 26] to evaluate the power consumpton n the smulaton experments: c e (b r +b t ), (4) where c denotes the total energy consumpton of one node for recevng b r bts and transmttng b t bts and e s a factor ndcatng the energy consumpton per bt at the recever crcut. In order to support more effcent forwardng, we let the FIB mantan multple entres and update the metrcs dynamcally, whch may brng more cost n the FIB memory and energy consumpton. The ndnsim platform used n ths paper can smulate almost real experment envronment because t adopts NFD (Named Data Networkng Forwardng Daemon) as the forwardng kernel. In other words, the extra overhead caused by supportng multpath capablty can be ncluded n the energy consumpton automatcally. The smulaton parameters are lsted n Table Smulaton Methodology. As analyzed n Secton 2, the lterature [3, 12] proposes two Interest forwardng strateges ncludng blnd forwardng (BF-RD) and provder-aware forwardng (PAF), whch are chosen as the baselne schemes for comparson n the smulaton experments. () BF-RD: the Interest s always forwarded n the floodng mode based on a randomly deferred tmer.

10 10 Moble Informaton Systems n 90 n 91 n 92 n 93 n 94 n 95 n 96 n 97 n 98 n 99 n 80 n 81 n 82 n 83 n 84 n 85 n 86 n 87 n 88 n 89 n 70 n 71 n 72 n 73 n 74 n 75 n 76 n 77 n 78 n 79 n 60 n 61 n 62 n 63 n 64 n 65 n 66 n 67 n 68 n 69 n 50 n 51 n 52 n 53 n 54 n 55 n 56 n 57 n 58 n 59 n 40 n 41 n 42 n 43 n 44 n 45 n 46 n 47 n 48 n 49 n 30 n 31 n 32 n 33 n 34 n 35 n 36 n 37 n 38 n 39 n 20 n 21 n 22 n 23 n 24 n 25 n 26 n 27 n 28 n 29 n 10 n 11 n 12 n 13 n 14 n 15 n 16 n 17 n 18 n 19 n 0 n 1 n 2 n 3 n 4 n 5 n 6 n 7 n 8 n 9 Fgure 8: Smulaton scenaro: grd topology. () PAF: the content consumer ncludes the nformaton about the nearest provder nto the Interest so that t can be forwarded to specfc drecton after the BF-RD s performed. In ths paper, we propose an energy effcent strategy named DMIF, whch conssts of a floodng mode and a drectve mode for Interest forwardng. For more ntutve comparson wth the baselne schemes, we name the floodng mode n the DMIF as BF-ED correspondngly due to ts energy effcent deferred tmer calculaton. In the BF-ED, the Interest s always forwarded n the floodng mode based on a deferred tmer proposed n (1). In addton, the other energy effcent schemes ncludng scope control and packet suppresson presented n Secton 4.1 are also used n the BF-ED. In other words, the BF-ED s a subset of the DMIF scheme. We observe the followng metrcs to evaluate the performance of the DMIF scheme. () Total energy consumpton s total energy consumed by all sensor nodes. () Energy equlbrum rate (EER) s defned as the varance of the energy consumpton of each node. The EER denotes the balance of the energy consumpton of the whole network and reflects the network lfetme ndrectly. () Hop count s the average hop count of the content retreval for each Interest request. (v) Network lfetme s defned as the tme length from the begnnng of the smulaton to the frst node s energy exhauston Smulaton Results Performance of BF-ED. Frst, we evaluate the mpacts of the weght factor α n (1) on the performance of the BF-ED. In Fgures 9 and 10, when the weght factor α=0,only the dstance value between adjacent nodes s consdered n the deferred tmer calculaton. In ths way, further neghbor hasahgherprobabltytobechosentoforwardinterest packets durng the blnd floodng, whch wll help reduce the hop count and the energy consumpton. Wth the ncrease of the α value, the dstance between adjacent nodes plays less mportant role n calculatng the Interest deferred tmer and then the total energy consumpton and average hop count rses gradually. What s more mportant s the mpacts of the α on energy equlbrum rate shown n Fgure 11, n whch the energy equlbrum rate decreases wth the ncrease of the α value. The key dea of (1) s tryng to balance the energy consumpton by adjustng the weght factor α. Inthe proposed BF-ED, bgger α value denotes that resdual energy plays more mportant role n the deferred tmer calculaton. In other words, choosng the node wth more resdual energy to forward Interests wll help balance the energy consumpton, whch s consstent wth the results n Fgure 11. InFgures12,13,and14,wecomparetheperformanceof the proposed BF-ED wth the baselne scheme BF-RD [3, 12]

11 Moble Informaton Systems 11 Total energy consumpton (Joule) consumer 2 consumers 3 consumers Weght factor α 4 consumers 5 consumers Fgure 9: BF-ED: mpact of weght factor α on total energy consumpton. Energy equlbrum rate consumer 2 consumers 3 consumers Weght factor α 4 consumers 5 consumers Fgure 11: BF-ED: mpact of weght factor α on energy equlbrum rate Average hop count Total energy consumpton (Joule) consumer 2 consumers 3 consumers Weght factor α 4 consumers 5 consumers Fgure 10: BF-ED: mpact of weght factor α on average hop count BF-ED (α =0) BF-ED (α = 0.5) Number of consumers BF-ED (α =1) BF-RD Fgure 12: Comparson between BF-ED and BF-RD: total energy consumpton. bychangngthenumberofthecontentconsumersfrom1 to 5. More content consumers means more Interest requests consumng more energy n Fgure 12 and then causng bgger varance of the energy consumpton n Fgure 14. Note that the experments wth more consumers exhbt better performance than the ones wth less consumers n terms of average hop count n Fgure 10, thanks to n-network cachng adoptednthendnarchtecture.itcanbeobservedthat the BF-RD exhbts medum performance compared wth two border condtons under the BF-ED wth α=0and α=1. In a summary, the weght factor α has mportant mpacts on the performance of the BF-ED scheme. In practce, a sutable α value needs to be chosen to trade off the energy consumpton and the energy equlbrum rate accordng to actual applcaton requrements. For smplcty, the α value s chosen as 0.5 n the followng experments Performance of DMIF. Fgures 15 and 16 show the mpacts of the wegh factor β n Algorthm 2 on total energy consumpton and average hop count. It can be observed that the wegh factor β exhbts smlar mpacts wth the weght factor α as presented n Secton Wth the rse of the β value, the hop count plays less mportant roles n choosng the Interest forwarder, whch results n the ncrease of total energy consumpton and average hop count for content retreval. On the other hand, wth the change of the β value

12 12 Moble Informaton Systems Average hop count Total energy consumpton (Joule) BF-ED (α =0) BF-ED (α = 0.5) Number of consumers BF-ED (α =1) BF-RD Fgure 13: Comparson between BF-ED and BF-RD: average hop count. Energy equlbrum rate Number of consumers BF-ED (α =0) BF-ED (α = 0.5) BF-ED (α =1) BF-RD Fgure 14: Comparson between BF-ED and BF-RD: energy equlbrum rate. from 0 to 1, the content consumers and the ntermedate nodes would rather choose the neghbor wth hgher resdual energy as the Interest forwarder. In other words, the resdual energy outperforms the hop count n Algorthm 2 wth the ncrease of the β value, whch helps balance the energy consumpton from the vewpont of the whole network and leads to the descendng trend of the energy equlbrum rate n Fgure 17. Next, we compare the performance of the proposed DMIF and the PAF by changng the number of the content consumers from 1 to 5. In Fgure 18, the total energy consumpton n both the DMIF and the PAF ncreases when more content consumers send more Interests to request the contents. In contrast wth the PAF, the DMIF has better Weght factor β 1 consumer 2 consumers 3 consumers 4 consumers 5 consumers Fgure 15: DMIF: mpact of weght factor β on total energy consumpton (α = 0.5). Average hop count Weght factor β 1 consumer 2 consumers 3 consumers 4 consumers 5 consumers Fgure 16: DMIF: mpact of weght factor β on average hop count (α = 0.5). performance n terms of total energy consumpton, snce the DMIF supports flexble mode shft for the Interest forwardng accordng to the results of the FIB lookups. In the PAF scheme, the blnd floodng phase and the provder awareness phase are two parallel phases. The nformaton about the content provder carred n the Interest s only added by the content consumer after the blnd floodng phase. In ths case, the blnd floodng mode wll contnue tll the content provders even though an ntermedate node has already FIB nformaton for the requested content. When the PAF forwardng fals due to the mss of the FIB lookup, the content consumer needs to restart the floodng phase throughout the

13 Moble Informaton Systems Energy equlbrum rate Weght factor β Average hop count Number of consumers 1 consumer 2 consumers 3 consumers 4 consumers 5 consumers Fgure 17: DMIF: mpact of weght factor β on energy equlbrum rate (α = 0.5). 250 DMIF (β = 0) DMIF (β = 0.5) DMIF (β = 1) PAF Fgure 19: Comparson between DMIF and PAF: average hop count (α = 0.5) Total energy consumpton (Joule) Energy equlbrum rate DMIF (β = 0) DMIF (β = 0.5) Number of consumers DMIF (β = 1) PAF Fgure 18: Comparson between DMIF and PAF: total energy consumpton (α = 0.5) Number of consumers DMIF (β = 0) DMIF (β = 0.5) DMIF (β = 1) PAF Fgure 20: Comparson between DMIF and PAF: energy equlbrum rate (α = 0.5). whole network after the Interest tmes out. In the proposed DMIF, the drectve mode can shft to the floodng mode locally, whch helps reduce the energy consumpton greatly n Fgure 18. As analyzed n Secton 5.3.1, the requested Interests may be satsfed by the ntermedate nodes rather than the content provders, thanks to the n-network cache technology n the NDN archtecture. Therefore, the average hop count for the content retreval drops wth the ncrease of the number of the content consumers n Fgure 19. It also can be observed that theaveragehopcountnthepafsshorterthantheproposed DMIF, snce the content consumers always choose the nearest provder as ts destnaton n the PAF. In the DMIF, the weght factor β=0means only hop count s consdered n choosng the Interest forwarder. However, the DMIF wth β=0stll has a lttle more average hop count than the PAF, because the hop count calculaton n Algorthm 1 s based on the weghts of all hop metrcs. In Fgure 20, the proposed DMIF gans better energy equlbrum rate and more balanced energy consumpton than the PAF due to the followng three reasons: (1) the average energy consumpton n the DMIF s lower than the one n the PAF; (2) the metrc aggregaton n Algorthm 1 sbasedonweghtsofthemetrcsfromeachneghbor;(3) the weght factor β helps avod choosng the nodes wth lttle

14 14 Moble Informaton Systems Total energy consumpton (Joule) DMIF PAF BF-ED Number of consumers Fgure 21: Comparson between DMIF and BF-ED: total energy consumpton (α = 0.5; β = 0.5). Network lfetme (s) DMIF PAF BF-ED Number of consumers Fgure 22: Comparson between DMIF and BF-ED: network lfetme (α = 0.5; β = 0.5). resdual energy for the Interest forwardng. On the other hand, there s no consderaton about flexble mode shft andenergyconsumptonbalancenthepaf,thusleadngto hgher energy equlbrum rate than the DMIF Comparson between DMIF and BF-ED. Fnally, we compare the DMIF and the BF-ED proposed n ths paper n terms of total energy consumpton and network lfetme n Fgures21and22,nwhchtheweghtfactorsα and β are both set as 0.5. Here, the network lfetme s defned as the tme length from the begnnng of the smulaton to the frst node s energy exhauston. Actually, the nformaton about Fgure 21 has been presented n Fgures 12 and 18. In ths secton, we make an ntutve fgure to llustrate the advantage of the DMIF about total energy consumpton. It can be observed that the BF-ED wth only floodng mode has the most energy consumpton and the shortest network lfetme. Wth the help of the flexble mode shft and energy aware neghbor selecton, the DMIF scheme can reduce the total energy consumpton and prolong the network lfetme sgnfcantly compared wth the BF-ED and the PAF n Fgures 21 and Concluson In ths paper, we propose an energy effcent Interest forwardng scheme called DMIF for NDN-based WSNs. In the DMIF, two combned forwardng modes (floodng mode and drectve mode) can be shfted flexbly based on the FIB lookupresultssothatthenetworkoverheadcanbereduced greatly. In addton, several energy effcent mechansms ncludng floodng scope control, broadcast storm avodance, packet suppresson, and energy weght factors are proposed to save and balance the energy consumpton. Smulaton experments under the ndnsim show that the DMIF scheme outperforms the baselne schemes n terms of total energy consumpton, energy equlbrum rate, and network lfetme. As future work, we plan to conduct theoretcal analyss and real experments to evaluate the proposed schemes. Competng Interests The authors declare that they have no competng nterests. Acknowledgments ThsworkssupportedbytheNatonalBascResearchProgram of Chna (973 Program) under Grant no. 2013CB329100, the Fundamental Research Funds for the Central Unverstes under Grant no. 2015JBM004, the Natonal Hgh Technology Research and Development Program (863) of Chna under Grant no. 2015AA011906, Bejng Nova Program under Grant no. Z , Bejng Hgher Educaton Young Elte Teacher Project under Grant no. YETP0532, and the Natonal NSF of Chna under Grants nos and References [1] K. Akkaya and M. Youns, A survey on routng protocols for wreless sensor networks, Ad Hoc Networks, vol. 3, no. 3, pp , [2] J. N. Al-Karak and A. E. Kamal, Routng technques n wreless sensor networks: a survey, IEEE Wreless Communcatons, vol. 11,no.6,pp.6 28,2004. [3] M. Amadeo, C. Campolo, A. Molnaro, and N. Mtton, Named data networkng: a natural desgn for data collecton n wreless sensor networks, n Proceedngs of the IFIP Wreless Days Conference (WD 13), pp. 1 6, Valenca, Span, November [4] L.Zhang,A.Afanasyev,J.Burkeetal., Nameddatanetworkng, ACM SIGCOMM Computer Communcaton Revew, vol. 44,no.3,pp.66 73,2014.

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16 Journal of Advances n Industral Engneerng Multmeda The Scentfc World Journal Appled Computatonal Intellgence and Soft Computng Internatonal Journal of Dstrbuted Sensor Networks Advances n Fuzzy Systems Modellng & Smulaton n Engneerng Submt your manuscrpts at Journal of Computer Networks and Communcatons Advances n Artfcal Intellgence Internatonal Journal of Bomedcal Imagng Advances n Artfcal Neural Systems Internatonal Journal of Computer Engneerng Computer Games Technology Advances n Advances n Software Engneerng Internatonal Journal of Reconfgurable Computng Robotcs Computatonal Intellgence and Neuroscence Advances n Human-Computer Interacton Journal of Journal of Electrcal and Computer Engneerng