HYMN: AN INTEREST-BASED MULTIMEDIA PROVIDING SYSTEM FOR HYBRID WIRELESS NETWORKS

Transcription

1 HYMN: AN INTEREST-BASED MULTIMEDIA PROVIDING SYSTEM FOR HYBRID WIRELESS NETWORKS Adran Andronache 1 ), Matthas R. Brust 2 ), Steffen Rothkugel 3 ) Abstract The concept of self-organzaton already exsts n the feld of ad-hoc networks. The nherent lmtatons of pure ad-hoc networks can be overcome by ntroducng uplnks to the Internet backbone. In ths paper, we present HyMN, a prototypcally mplemented hybrd wreless network system optmzed for multmeda content provdng. In the ad-hoc network, adequate devces are elected to keep uplnks to a backbone, whch provdes multmeda news from certan sports events lke Football Champonshps, Olympc Games etc. 1. Introducton Ad-hoc networks emphasze flexblty and survvablty of the whole system. However, centralzed approaches e.g. for group management and nformaton provsonng do not work well n such settngs. Moreover, due to frequent topology changes, connectvty of devces cannot be generally guaranteed. In partcular, ths makes t hard to dssemnate nformaton n a relable way. We overcome these lmtatons nherent to pure ad-hoc networks by (a) establshng local groups of communcatng devces n a self-organzng manner and (b) ntroducng dedcated uplnks to a backbone nfrastructure. Such uplnks are used for accessng resources avalable n the Internet. Addtonally, they are employed to drectly nterconnect dstant devces, ether wthn a sngle partton and partcularly also across dfferent parttons. In our work we envsage an envronment that s composed of moble users operatng dfferent knds of moble devces, rangng from smartphones over PDAs to Tablet PCs and notebooks. The envronment mght be augmented by statonary machnes, but ths should be consdered as an excepton to the rule. All devces are supposed to be equpped wth wreless communcaton adapters. However, dfferent technologes are supposed to be used n conjuncton, ncludng for nstance W-F and Bluetooth. Devces also mght have the ablty to connect to a backbone network usng for nstance cellular networks, satelltes, or va W-F hotspots. In terms of communcatons, the envronment can be consdered as beng hybrd wreless and t provdes the potental for combnng the advantages of both ad-hoc as well as nfrastructure-based networks. The communcaton paradgms supported hence are pure ad-hoc, together wth the potental ablty of creatng backbone lnks. 1 adran.andronache@un.lu, Unversty of Luxembourg, 6 rue Coudenhove-Kalerg, Luxembourg 2 matthas.brust@un.lu, Unversty of Luxembourg, 6 rue Coudenhove-Kalerg, Luxembourg 3 steffen.rothkugel@un.lu, Unversty of Luxembourg, 6 rue Coudenhove-Kalerg, Luxembourg

2 Ths paper presents the prototypcally mplemented HyMN (Hybrd Multmeda Network) system, whch s desgned for users nterested n lve multmeda news from certan events lke e.g. Football Champonshps, Olympc Games etc. For nstance moble devces of football fans create an nterest group n a local ad-hoc network partton. Multple such groups co-exst lke football fans n pubs, those watchng another match, travelng ones, and more. In each of these cases, a consderable number of devces have shared nterests and mght jon forces n a local settng. The devces n the ad-hoc network runnng HyMN organze themselves n clusters, where the clusterheads mantan uplnks to a backbone network n order to receve multmeda news related to the nterests of the adhoc members. Thus, the football fans wll receve nformaton such as small vdeos, pctures or text messages each tme somethng nterestng s happenng durng the match. The multmeda fles receved reman stored on the moble devces and wll be provded to further devces jonng the nterest group later on. In order to optmze the multmeda provdng process, the HyMN backbone splts the multmeda fles nto chunks, whch are sent concurrently to dfferent clusterheads wthn a sngle ad-hoc network partton. After reachng such an ad-hoc network partton, the chunks are exchanged among the nterested devces untl all devces receve the complete fle. The chunks are dssemnated over a wreless connecton lke W-F or Bluetooth to the nterested devces. These connectons have the advantage to be free of charge. Moreover, these technologes allow hgher bandwdth compared to GSM or 3G cellular connectons. The remander of the paper s organzed as follows. In Secton 2 related work s descrbed. Secton 3 shows the prototypcal mplementaton of the HyMN system. In Subsecton 3.1 the nterest-based hybrd network model s specfed and Subsecton 3.2 presents the system archtecture. Subsecton 3.4 descrbes the clusterhead afflaton algorthm requred for concurrent chunk provdng. The paper concludes wth a dscusson of results and future work. 2. Related Work Moble wreless networks are manly lmted n bandwdth and connectvty. A hybrd settng, such as a hybrd wreless network, s a vable networkng soluton to tackle these problems. There are a wde range of approaches to establsh hybrd networks that make use of dfferent communcaton technologes. The CAR approach [1] s bult upon the vew to support cellular base statons by ntroducng addtonal relay statons that work n ad-hoc mode. For ths, these relay statons are equpped wth two nterfaces, one for ad-hoc communcaton (WLAN) and one for communcaton wth base statons. The major objectve of CAR s to balance the traffc load between cells. Load s forwarded to free cells va ad-hoc relay statons. Addtonally, ad-hoc relay statons provde CAR wth ncreased coverage area. UCAN [2] also combnes cellular and ad-hoc networks (CDMA/HDR and IEEE b). UCAN uses mult-hop routng to mprove the throughput. In contrary to CAR t s assumed that nodes are completely under the coverage of one base staton. As UCAN, the Hybrd Wreless Network (HWN) archtecture [3] tres to optmze the throughput. Thereby HWN requres geographcal postons of moble devces n order to decde f a cell has to be managed n a sngle-hop or mult-hop ad-hoc mode.

3 A-GSM [4] focuses on provdng connectvty to dead spot areas for ad-hoc networks. Devces are equpped wth both, a GSM nterface and an ad-hoc communcaton nterface. Whle one nterface s workng, the other one s able to check for an alternatve connectvty mode. Ratanchandan et al [5] focuses on hybrd networks wth Moble IP capablty and Internet Gateways to communcate wth wred correspondent nodes. Andreads [6] descrbes a smlar arrangement. It s used a fxed Internet Gateway as for example an access pont to provde Internet connectvty to the entre moble ad-hoc network. The hybrd settng of Sun et al [7] conssts of base statons that are nter-connected and moble devces that can connect locally va an ad-hoc mode or to a base staton f near enough to t. Two routng schemas are ntroduced to deal wth dfferent applcaton requrements. Sun et al research ponts out that the effcency of the chosen communcaton mode strongly depends on the applcatons runnng n the overall network. Fujware et al. [8] proposes a routng protocol and MAC protocol for a mult-hop hybrd wreless network n case of emergency communcaton. In [9] further protocols for hybrd networks are presented and dscussed. He et al. [10] proposes a centralzed peer-to-peer vdeo streamng over hybrd wreless network. The approach s to delver the base layer of the vdeo from the server va WLAN, whle the enhancement layers uses multple paths n ad-hoc mode. None of the mentoned approaches and archtectures here deals wth chunkng ssues of the requested nformaton or parallel njecton of nformaton to selected devces. 3. The HyMN System In ths secton we descrbe a hybrd wreless network model and the nterest-based nformaton dstrbuton. As one proof of concept HyMN (Hybrd Multmeda Network) has been mplemented prototypcally on top of the JANE smulaton envronment [11]. JANE s desgned to support applcaton and protocol desgn n the feld of ad-hoc networks. One dstnct feature of JANE s that applcatons can be executed on top of smulated devces (cf. Fg. 1) as well as n so-called platform mode on real hardware. 3.1 Interest-based Hybrd Network Model We assume the system model as descrbed n the ntroducton where the ad-hoc network devces organze themselves n clusters. The clusterheads are n charge of keepng track of local devces and ther nterests. Clusterheads are chosen accordng to ther weght that s calculated by a heurstc weght functon (cf. Secton 3.3). Parameters lke avalable power, sgnal strength to the backbone network, topologcal relatons etc. are taken nto account by means of ths functon. Clusterheads can act as njecton ponts [12]. Injecton ponts mantan a connecton to the backbone network and request nformaton related to the common nterests shared by the devces n the cluster. An nterest can refer to a sngle data tem such as a specfc vdeo. Interest mght also have a more permanent nature, lke for nstance n case of stock market nformaton. Hence, multple data tems mght be of nterest and forwarded to the user over tme. The nformaton about avalable

4 nterests s provded by the backbone va the clusterheads to all devces n an ad-hoc network. The moble devces regster the nterests selected by ther users at the clusterhead, thus allowng keepng track of local nterest groups. As soon as the backbone can provde fresh nformaton related to a partcular nterest, t s njected nto the mult-hop ad-hoc network by sendng t to all njecton ponts of that partton. Updates of nformaton are also njected as long as the njecton pont keeps the connecton to the backbone. The njecton pont wll forward the receved nformaton to all nterested devces n the cluster. Fgure 1. The HyMN System n smulaton mode. 3.2 HyMN Archtecture The prototypcal mplementaton of the HyMN system conssts of two man components: the backbone and the clent for the moble devces. The backbone keeps track of regstered njecton ponts and ther nterests. Durng the runtme the lst of avalable nterests can be changed and njected to the ad-hoc network. Addtonally, fles afflated to certan nterests can be added to the njecton queue. In order to optmze the njecton process, the backbone multmeda fles are splt nto chunks. These chunks are njected concurrently to dfferent njecton ponts wthn a sngle ad-hoc network partton. Thus, the bandwdth for njectng data nto a sngle partton s ncreased and the fles reach the ad-hoc network faster. Detals about the chunk njecton process are presented n Subsecton 3.4. After reachng the network, the chunks are exchanged among the nterested devces untl all devces receve the complete fle. In case of parttonng durng the njecton process, the devces can

5 request the potental new clusterhead to gather the mssng chunks from the backbone. Ths process s not descrbed further n ths paper. The clent servce provdes mechansms for local network communcaton, usng the Bluetooth or W-F nterface, and for backbone communcaton, usng a 3G or satellte nterface. Ths servce contans also two mportant modules: clusterhead electon module and network meda module. The clusterhead electon module s n charge of reactng on network changes and decdng whch neghbor s the responsble clusterhead. Ths s done based on local nformaton only (cf. Subsecton 3.3). The network meda module keeps track of meda fles avalable on the own devce and exchanges the lst wth the neghbor devces. If updates arrve, the nformaton about the own and the known network meda fles are sent to the graphcal user nterface. 3.3 Ad-hoc Network Topology The HyMN ad-hoc network s organzed n clusters. For ths, a clusterng algorthm, namely WACA, whch uses a heurstc weght functon, was desgned [13]. The WACA algorthm bulds an ad-hoc network topology that fts the needs of the applcatons runnng on partcpatng devces. One objectve of WACA s to avod network communcaton overhead durng the clusterhead electon and clusterng process. Therefore, the electon of a local clusterhead s based solely on nformaton avalable locally. In order to acheve ths, each devce calculates ts own weght based on ts devce parameters lke remanng power, backbone sgnal strength and topologcal attrbutes. The weght s recalculated when changes of attrbutes occur. Each devce propagates ts own weght as part of the beacon, whch s a perodcally broadcasted message used n ad-hoc networks to detect devces n communcaton range. The algorthm only consders so-called neghbor devces,.e. devces that mutually see each other. The devces run the algorthm each tme the set of neghbor devces changes, e.g. when devces enter or leave the communcaton range, or when weghts are updated. Usng the nformaton about the neghborhood, each devce elects the neghbor devce wth the hghest weght value as ts clusterhead. Ths clusterhead n turn also nvestgates ts one-hop neghborhood, also electng the devce wth the hghest weght as ts clusterhead. Ths process termnates n case of a devce electng tself as ts own clusterhead, due to the fact of havng the hghest weght among all ts neghbors. We call all ntermedary devces along such clusterhead chans sub-heads. Hence, n each network partton, multple clusterheads mght co-exst. Only clusterheads mght serve as njecton ponts, dependng on current nterests of the cluster members. Informaton wll be njected to clusterheads only. The sub-heads n turn are responsble for further forwardng the data to other cluster members. 3.4 Clusterheads Afflaton Novel moble phone technologes for backbone uplnks are usng packet swtchng, whch optmzes the use of the bandwdth avalable n a network. Ths mnmzes the transmsson latency and also ncreases robustness of network communcaton. The elementary method for the backbone to provde requred nformaton to a network partton s njectng data to each clusterhead, whch wll multcast t to all nterested devces n the cluster (Fgure 2a). The sub-heads n turn wll further multcast the nformaton receved from the

6 clusterhead to nterested cluster members. Ths method s very sutable for provdng small data tems that ft nto the network packets. Provdng multmeda fles mples dealng wth larger amounts of data. Fgure 2. (a)injecton nonepece toalclusterheads.(b)concurentnjectonofchunks. The HyMN backbone s desgned to beneft from data chunkng n order to optmze the data provdng process. The backbone njects concurrently dfferent chunks of a data tem to dfferent clusterheads n a network partton (Fgure 2b). Thus, the data tem flows faster trough the downlnks from backbone to the ad-hoc network, whch means an ncrease of the njecton bandwdth to the partton. Also, the tem wll be sent only once n peces to the network partton nstead of once for each clusterhead. Ths also optmzes bandwdth usage of the downlnks. In order to enable concurrent backbone njecton of data chunks, sutable clusterheads need to be dscovered. Clusterheads that ft the requrements of concurrent njecton are called afflated clusterheads throughout ths paper. The apponted mnmal requrements for the afflaton of two clusterheads are: (a) the membershp of the same partton and (b) the topologcal proxmty. The requrements assure that the clusterheads can exchange the concurrent njected chunks locally. The probablty that the partton splts before the chunks are exchanged s reduced at the same tme. In ths work we consder two clusterheads to be afflated f they are belongng to the same partton and they have at least one common one-hop neghbor (Fgure 3b and 3c). Fgure 3. Afflaton of clusterheads CH1 and CH2: (a) not sutable, (b) and (c) sutable. In order to enable the backbone to buld afflatons groups, each clusterhead sends the lst of ts neghbors to the backbone and updates t each tme the neghborhood changes. For the afflaton process the clusterhead afflaton algorthm (CHA) was desgned. The pseudo code of the algorthm s shown n Fgure 4. CHA requres as nput a set of clusterheads and the sets contanng each clusterheads neghbors. The algorthm returns an afflaton set for each clusterhead. In order

7 to fnd afflated clusterheads, CHA checks for each clusterhead f t has common neghbors wth other clusterheads. If the neghbor s dscovered n the neghbor set of another clusterhead, the respectve clusterhead wll be added to the afflaton set. The backbone executes the CHA algorthm each tme a clusterhead sends new neghborhood nformaton, thus keepng the afflaton groups up-to-date for the njecton process. Input : Output : 1: 2: C : Set of clusterheads D... D : Sets of neghbors of the clusterheads 1 D: the set of neghbors of clusterhead c A... A : Sets of afflated clusterheads 1 n n A : the set of afflated clusterheads of c 1 3: for each D { D... D }\ D 4: 5: for each c for each d f 6: return A... A c d t C j n j do D do t 1 n D A t then do Fgure 4. Pseudo code of the Clusterheads Afflaton Algorthm (CHA). 3.5 User authentcaton and data encrypton Some multmeda provder mght requre mechansms for user authentcaton and data encrypton. A possble soluton s to use a publc-key encrypton system, such as e.g. Pretty Good Prvacy (PGP), whch s popular for transmttng nformaton va the Internet. On the bass of the keys, the clusterhead can authentcate the cluster members va a publc key nfrastructure n the backbone. Moreover, the multmeda can be cryptographcally secured usng a sesson key. The sesson key can be forwarded n an encrypted fashon ndvdually to each authorzed ad-hoc network devce. In ths work we are not dealng drectly wth both encrypton of the multmeda data respectvely user authentcaton. However, these mechansms are planned to be ntegrated n a subsequent verson. 4. Concluson and Future Work Ths paper s a work-n-progress report regardng our novel approach for dealng wth multmeda content n hybrd wreless networks. A prototypcal system, namely HyMN, has been mplemented as a proof of concept. Throughout ths paper, we ponted out dfferent aspects of HyMN. On the sde of the backbone an autonomous nterest management s establshed. On the sde of the ad-hoc communcaton the clusterng algorthm WACA [13] has been appled. In conjuncton, nterest-based dstrbuton patterns together wth clusterhead afflaton optmze the nterface between backbone and ad-hoc nfrastructure.

8 We plan to conduct extended smulatons to fnd out how HyMN performs n the context of dfferent ad-hoc network moblty models. The clusterhead afflaton s also subject to further nvestgatons n order to optmze the parallel chunk njecton process for dfferent network settngs. Summarzng, t was shown that there s an effcent way that combnes the benefts of ad-hoc communcaton wth that of a broadband backbone nfrastructure. 5. References [1] H. Wu, C. Qao, S. De, and O. Tonguz, "Integrated cellular and ad hoc relayng systems: CAR," Selected Areas n Communcatons, IEEE Journal on, vol. 19, pp , [2] H. Luo, R. Ramjee, P. Snha, L. E. L, and S. Lu, "UCAN: a unfed cellular and ad-hoc network archtecture," Proceedngs of the 9th annual nternatonal conference on Moble computng and networkng, pp , [3] H. Y. Hseh and R. Svakumar, "Performance comparson of cellular and mult-hop wreless networks: a quanttatve study," Proceedngs of the 2001 ACM SIGMETRICS nternatonal conference on Measurement and modelng of computer systems, pp , [4] G. Aggelou and R. Tafazoll, "On the Relayng Capacty of Next-Generaton GSM Cellular Networks," IEEE Personal Communcatons, vol. 8, [5] P. Ratanchandan and R. Kravets, "A hybrd approach to Internet connectvty for moble ad hoc networks," Wreless Communcatons and Networkng, WCNC IEEE, vol. 3, [6] G. Andreads, "Provdng Internet Access to Moble Ad-hoc Networks," Unversty College London, ee. ucl. ac. uk/lcs/papers2002/lcs, vol [7] Y. Sun and E. M. Beldng-Royer, "Applcaton-orented routng n hybrd wreless networks," Communcatons, ICC'03. IEEE Internatonal Conference on, vol. 1, pp , [8] T. Fujwara, N. Ida, and T. Watanabe, "A hybrd wreless network enhanced wth multhoppng for emergency communcatons," Communcatons, 2004 IEEE Internatonal Conference on, vol. 7, [9] R. S. Chang, W. Y. Chen, and Y. F. Wen, "Hybrd wreless network protocols," Vehcular Technology, IEEE Transactons on, vol. 52, pp , [10] Y. He, I. Lee, X. Gu, and L. Guan, "Centralzed Peer-to-Peer Vdeo Streamng Over Hybrd Wreless Network," Multmeda and Expo, ICME IEEE Internatonal Conference on, pp , [11] H. Frey, D. Görgen, J. K. Lehnert, and P. Sturm, "A Java-based unform workbench for smulatng and executng dstrbuted moble applcatons," n Proceedngs of FIDJI 2003 Internatonal Workshop on scentfc engneerng of dstrbuted Java applcatons, Luxembourg, [12] S. Rothkugel, M. R. Brust, and C. H. C. Rbero, "Inqurng the Potental of Evokng Small-World Propertes for Self-Organzng Communcaton Networks," n 5th Internatonal Conference on Networkng (ICN 06), Maurtus, [13] A. Andronache, M. R. Brust, and S. Rothkugel, "Multmeda Content Dstrbuton n Hybrd Wreless usng Weghted Clusterng," n 2nd ACM Workshop on Wreless Multmeda Networkng and Performance Modelng, Malaga, Span, 2006.