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IEEE Communications Magazine • December 201036 0163-6804/10/$25.00 © 2010 IEEE

This work was supportedin part by Enterprise Ire-land’s Innovation Part-nership Programme andDisney Research.

INTRODUCTION

The convergence of wireless communications,digital media, and information technologies onmobile devices has created an avalanche of excit-ing new applications and user experiences. Aug-mented reality is a great example of thistechnology convergence. Take the example of anaugmented reality travel guide as seen in Fig. 1.This application uses the mobile device’s GPS,digital compass, and accelerometer for locationand orientation. Information on nearby points ofinterest is gathered from online sources via radiocommunications. The mobile device’s cameraand touch screen display are used to present theinformation overlaid on the camera view, creat-ing an augmented reality.

The potential to design even more creativeapplications exists in large controlled environ-ments such as entertainment parks, sports stadia,municipalities, universities, and business campus-

es. In the case of entertainment parks, they areoften the size of a small city and just as popu-lous. These parks already provide an exciting vis-itor experience, entertaining guests with an arrayof events, attractions, parades, concerts, exhibi-tions, and rides. Given the controlled nature ofthe environment, the potential for a mobiledevice to provide further interaction with thealready interactive surroundings is compelling. Adedicated device could be provided to users onentry. The device would support new experi-ences in creative ways that are not possible withexisting wireless devices such as the newestsmart phones.

We have stated, and have seen with augment-ed reality, that the new wave of mobile applica-tions require advanced wireless connectivity. Adedicated device as described above would alsorequire connectivity throughout the entertain-ment park. In such a scenario, however, it wouldnot be acceptable to have to pay a mobile phoneprovider for connectivity as for normal mobiledevices. Alternatives to communication in thelicensed spectrum used by mobile phone pro-viders must be sought for the device.

Radio communication based on the well-known Wi-Fi standard IEEE 802.11 (wirelesslocal area network [WLAN]) utilizes the unli-censed spectrum in the 2.4 GHz and 5 GHz fre-quency bands, allowing free wirelesscommunication at high data rates. Free high-data-rate wireless communications using WLANwould allow the power of mobile applications tobe harnessed on the device. For WLAN to workover a large controlled environment such as anentertainment park, it is necessary to have fullcoverage across the target environment as wellas reliable communications, all at low cost andlow complexity. Given the large crowds, reason-able data throughput for large numbers ofdevices in the same location would also be arequirement.

This article discusses the challenges in pro-viding WLAN connectivity to mobile devices ona large mobile phone network scale. Althoughwe are focusing on WLAN in the following,complementary standards for wireless metropoli-tan area networks (WMANs) exist and are not

ABSTRACT

The functionality of mobile devices has grownexponentially in recent times. This has led tosmart phones and the mobile Internet becominga big success story. IEEE 802.11 wireless localarea network, known as Wi-Fi, has become astandard feature on these devices and representsa viable alternative to using a mobile phoneprovider’s network for connectivity. Users cansurf the web, make VoIP calls, and more fromtheir home WLAN networks or public hotspots.At present WLAN has too many outstandingissues to universally replace existing mobilephone networks. However, WLAN is ready toprovide universal coverage for mobile devices inlarge controlled environments such as universityand business campuses, sports stadia, and enter-tainment parks. In this article we outline thechallenges in such a deployment and describehow the state of the art in WLAN can meetthese challenges. Outstanding issues and areasrequiring improvement are highlighted. With aview to overcoming these hurdles, some poten-tial solutions and promising research directionsare outlined.

CONSUMER COMMUNICATIONS AND NETWORKING

Kevin Collins, Dublin City University

Stefan Mangold, Disney Research Zurich

Gabriel-Miro Muntean, Dublin City University

Supporting Mobile Devices withWireless LAN/MAN inLarge Controlled Environments

COLLINS LAYOUT 11/18/10 10:54 AM Page 36

IEEE Communications Magazine • December 2010 37

meant to be excluded in our discussion. Usecases that involve offering good quality to wire-less-communication-based services within enter-tainment parks are discussed in the next section.These use cases are not restricted to entertain-ment parks and hence can be generalized to anylarge controlled environment. Where challengesare being met by the state of the art in WLAN,this is highlighted. Outstanding issues and areasrequiring improvement are investigated. With aview to overcoming such hurdles, potential solu-tions and promising research directions are indi-cated.

LARGE CONTROLLEDENVIRONMENTS: THEENTERTAINMENT PARK

When providing connectivity for large numbersof dedicated mobile devices, there will be uniquechallenges specific to distinct large controlledenvironments. The applications and require-ments will vary for sports stadia, municipalities,business campuses, and so on. In this section weexamine some of the unique characteristics andrequirements of an entertainment park.

The largest entertainment parks comparewith a big city in scale. The Walt Disney WorldResort in Florida, for example, spans over 100km2, an area greater than that covered by theCalifornia state capital, Sacramento. With tensof thousands of employees and millions of visi-tors each year, such a resort is as densely popu-lated as a city. The parallels do not stop there;entertainment parks include other city elementssuch as busy streets and roads, and mass trans-portation including buses, trains, and even watertaxis. The reasons people visit entertainmentparks, however, tend to be different from thereasons most people spend time in the city:mainly leisure as opposed to work.

One use of a dedicated mobile device for thisenvironment is to make it available to parkguests to enhance their visit. Many park patronsalready carry electronic devices such as digitalcameras, smart phones, and game consoles withthem. Unofficial entertainment park relatedsmart phone software applications already exist,including entertainment park guides and applica-tions that offer information on attraction waittimes. Entertainment park applications for theNintendo DS have also been trialed. For exam-ple, a DS with a park guide/GPS add-on, usingthe existing WLAN capabilities of the DS, pro-vides an interactive entertainment park guidewith up-to-the-minute information on wait times.

It is not a huge leap to envision a dedicateddevice for guests providing a park guide with arange of information services kept up to date viawireless communications. If communications arefree, there is no limit to the amount of commu-nication-based applications the device can run.Potential applications include device-to-devicemessaging, video streaming, attraction interac-tion, and multiplayer gaming. This would suggestusing a communications technology such as Wi-Fi/WLAN, which operates in the unlicensedspectrum.

No assumptions should be made about users,as visitors to entertainment parks encompassevery demographic. A single family group maycontain elderly grandparents and young children.Thus, it is important that a dedicated device canbe used intuitively by anyone. To aid ease of use,connectivity must be seamless and hidden fromusers in a similar fashion to that of a mobilephone. It would not be acceptable for a visitor tohave to stop and search for a new wirelesshotspot just because they have stepped off astreet and into a building.

For each of the dedicated devices, but alsofor the overall system infrastructure, the requiredcommunication capacity and quality of service(QoS; e.g., throughput, delay) demands areapplication-dependent and difficult to predict. Itis however reasonable to assume that demandswill increase over time, when more and moresophisticated and useful applications will findtheir way onto the devices. It is therefore impor-tant to select a network and communicationinfrastructure that scales: it must be commercial-ly feasible to incrementally increase systemcapacity by investing into the infrastructurewhere and when needed.

The entertainment park is clearly a challeng-ing environment: there is a large coverage area;there are a large number of users, so the net-work must have high capacity; communicationsshould be free, and visitors must be able to roamwith seamless connectivity. Exact bandwidthrequirements are hard to quantify for such adiverse environment, but a number of usage sce-narios can be envisioned. Next, four specific sce-narios encountered by the device within theenvironment are examined. The challenges theypose for wireless communications are explored.

SCENARIO 1: VISITORS WAITING IN LINEA large number of visitors are waiting in line fora park ride. To entertain waiting guests, a multi-player game is played. To do this, a waitingguest’s dedicated device will interact with the

Figure 1. An augmented reality travel guide for Dublin, Ireland.


devices of nearby guests and a nearby interactiveattraction such as a large screen. There are anumber of interesting aspects from a communi-cations perspective: there is a very high densityof users, users move slowly but are in a constantstate of flux (groups arriving and leaving theline), and the device is used for game controlbut not display (volumes of data exchanged arenot large, but exchanges are frequent and time-sensitive).

SCENARIO 2: VISITORS ON A PARK RIDEVisitors exchange data with park infrastructureto record stats while on a ride. During a ride vis-itors move at high speed (Fig. 2) and undergorapid accelerations through a changing environ-ment. Challenges include sharp bends, suddenchanges of altitude, tunnels, and water hazards.The data volume is not the concern here, butrather supporting communications in the rideenvironment.

SCENARIO 3: STREET CROWDVisitors on a crowded street are using the dedi-cated device for location-based applications suchas a park guide with navigation. A Street Crowdscenario (Fig. 3) is characterized by an averagedensity of users who are highly mobile (movingat walking speed). In this case the challenge issupporting interactive applications that exchangesmall amounts of data frequently but sometimesrequire support for more data-intensive serviceslike video streaming.

SCENARIO 4: SEATED AUDIENCEA seated audience is found in locations such asnovelty restaurants, theatres, and similar arenas.Applications may include interactive menus forremote orders and audience participation duringlive shows (e.g., devices are used for voting in anask the audience segment). In this scenario thereare a number of important aspects from a com-munications standpoint: there is a very high den-sity of users in a large area; these users are,however, stationary, but may be in an indoor

location; and the volumes of data exchanged aresmall, but frequent and time-sensitive.

It is clear that the entertainment park envi-ronment poses even more challenges than firstthought. Potential requirements include the abil-ity to support communications at high speed, theneed for very high capacity or a large number ofclosely coexisting access points (APs) to supportdense crowds, and QoS support for delay-intol-erant applications. The next section deals ingreater detail with the technical challenges ofdeploying such a network. The elements of theWLAN standard that meet these challenges arealso discussed.

CHALLENGES IN LARGE WIRELESSLAN/MAN NETWORKS

There are a host of challenges involved indeploying a large WLAN/WMAN capable ofsupporting rich communication-based serviceson a large number of mobile devices. In this sec-tion we discuss those challenges from the topdown.

In an infrastructure-based IEEE 802.11deployment, a fixed wired station with expandedcapabilities provides network connectivity to enduser stations: this is an AP. To provide ubiqui-tous wireless connectivity across a large con-trolled environment such as an entertainmentpark, a dense deployment of IEEE 802.11 APs isneeded. Just as in cellular networks, there mustbe a standardized method for the individual cells(AP sites) to coexist/combine so as to provideseamless connectivity to end users. The complex-ity of the network structure is hidden from endusers, who see it as a single large network.

The IEEE 802.11s1 draft standard amend-ment, which defines how wireless devices caninterconnect to create a mesh network, is suitedto this purpose. Wireless mesh networks havebeen widely deployed to provide ubiquitous cov-erage in municipalities worldwide. They are usedto cover metropolitan areas, entire cities, andeven whole counties. The biggest advantage of802.11s is that it dramatically reduces the cost ofnetwork deployment. The prohibitive cost of net-work deployment is that of the wired infra-structure required to interconnect APs. 802.11sremoves this barrier by allowing APs to intercon-nect wirelessly; however, there are a number ofoutstanding issues if the technology is to scalesuccessfully.

For wireless devices to coexist in close prox-imity, they must communicate on orthogonalchannels. Orthogonal channels are communica-tion channels that reside in non-overlappingregions of the frequency spectrum. A typicalWLAN channel occupies 20 MHz of the fre-quency spectrum. As illustrated in Fig. 4a,devices operating at the same frequency causeinterference preventing communication, whereasdevices operating on orthogonal channels cancommunicate without interference (Fig. 4b). Thenumber of APs capable of coexisting per unitarea will affect the scalability of a large wirelessLAN/MAN network. Consequently, the avail-ability of orthogonal channels affects the scala-bility of the network. The number of orthogonal

IEEE Communications Magazine • December 201038

Figure 2. Rides like rollercoasters and park transport move at speed.

1 IEEE P802.11/D4.02:Mesh Networking (DraftStandard), Mar. 2010.

COLLINS LAYOUT 11/18/10 10:54 AM 8


channels increases with the width of the regionof frequency spectrum available for use.

The existing WLAN standards 802.11a [1]and 802.11g [1] operate in the 5 GHz and 2.4GHz regions of the frequency spectrum. 802.11b[1] is not considered as it has been supersededby 802.11g. 802.11a typically offers 19 non-over-lapping channels, while 802.11g offers just 3 non-overlapping channels. The 802.11y [2]amendment to the standard allows communica-tion in the 3.6 GHz region; this mode of opera-tion is, however, limited to the United States atpresent, and must also be licensed. In a deploy-ment where the 22 channels offered by 802.11aand 802.11g are insufficient, additional spectrumusage must be considered; one potential solutionis the use of TV white space.

In November 2008 the FCC opened up TVwhite space for use by unlicensed devices [3].Four bands of frequency are allocated for broad-cast television in what is known as the VHF andUHF regions of the radio spectrum (54–72 MHz,76–88 MHz, 174–216 MHz, and 470–806 MHz).TV white spaces are regions of this spectrum

that are not used locally. There are likely to bemore of these TV white spaces as televisionmakes the shift from analog to digital. Anamendment to the standard has been proposedin order to take advantage of this newly avail-able unlicensed spectrum, 802.11af.2 By operat-ing in this spectrum, it is expected that 802.11afcan provide as many as 50 5-MHz channels. Thenumber of new channels available varies in dif-ferent geographical regions depending on localTV broadcast activities. Any additional capacityhelps scale a wireless LAN/MAN to support richcommunication-based services for a large num-ber of end users.

As well as having sufficient orthogonal chan-nels to scale, the network must allow users tomove between AP sites without interruption.This type of mobility support is taken for grant-ed on mobile phone networks and allows usersto communicate while travelling at high speed invehicles or trains. There are a number of stan-dard amendments that are relevant when build-ing support for mobility. The IEEE 802.11k [4]standard amendment provides for radio resource

Figure 3. Trying to provide connectivity on a busy entertainment park street.

Figure 4. Devices operating on orthogonal channels do not interfere.

Orthogonal channels

Frequency 1

A. B.

Frequency 2

Frequency 3

Frequency 4

2 IEEE 802.11af: WirelessLAN in the TV WhiteSpace, 2010 (Proposed)


measurement. This makes information based onmeasurements of the state of the radio environ-ment available to the upper layers in the com-munications stack. Such information is usefulwhen making decisions such as when to transi-tion from one AP to another. The 802.11r [5]standard amendment allows for a fast transitionbetween APs, and maintains both security andQoS.

Providing mobility support becomes more dif-ficult as the end user’s speed increases. Devicesmoving at speed create new challenges for thewireless network due to a rapidly changing radioenvironment and the short duration of commu-nication times with AP sites. The 802.11p [6]draft amendment for wireless access in the vehic-ular environment (WAVE) addresses theseissues by speeding up the mechanism for associ-ating with APs, and improving the radio’s immu-nity to the destructive effects of high speed byenhancing the standard at the physical layer. Itmay be necessary to use IEEE 802.11p in anenvironment like an entertainment park if con-nectivity is required while on high-speed rides orpark transport.

Security across the network is another veryimportant concern, especially in corporate envi-ronments where a denial of service attack couldmean loss of revenue, and data theft may haveserious implications. The early iterations of theWLAN standard had notoriously poor securitymechanisms. The ease with which hackers couldintercept transmissions and gain unauthorizedaccess to wireless networks was well documentedat the time. Since then the issue of security hasbeen addressed with amendments to the stan-dard. The 802.11i [1] enhanced security amend-ment brings 802.11 security up to date withgovernment-strength encryption using theAdvanced Encryption Standard (AES). For cor-porate-level security the encryption can be cou-pled with an authentication process. One means

of providing authentication is to use a RemoteAuthentication Dial In User Service (RADIUS)authentication server with a suitable authentica-tion method. Security was further enhanced bythe 802.11w [7] protected management framesamendment. Prior to this amendment, manage-ment frames were unprotected, and systemscould be disrupted by attacks impersonatingvalid equipment and disseminating false infor-mation. The 802.11w amendment closes thisavenue of attack by properly securing manage-ment frames.

The individual AP sites are the basic buildingblock of the network. The wireless capacityavailable at each of these will greatly influencescalability. IEEE 802.11a and 802.11g both offeran over-the-air throughput of 54 Mb/s resultingin an estimated maximum throughput of 25 Mb/sat the medium access control (MAC) service AP[8]. This means less than 25 devices can be sup-ported with individual throughputs of 1 Mb/s asadditional throughput is lost when separatedevices contend for the medium. If the maxi-mum throughput can be increased, the numberof devices that can be supported at each AP sitealso increases. As data rates increase, individualusers occupy less airtime on communicationchannels, which increases the capacity of theentire network. The 802.11n [9] amendment tothe standard provides enhancement for higherthroughputs. Using techniques such as multiple-input multiple-output (MIMO) and increasingchannel width from 20 MHz to 40 MHz, over-the-air throughputs of up to 600 Mb/s are achiev-able with 802.11n. MIMO uses multiple antennasto transmit and receive more information than ispossible with a single antenna. If existing stan-dards cannot provide enough bandwidth, twoworking groups, 802.11ac,3 Very High Through-put at less than 6 GHz, and 802.11ad,4 VeryHigh Throughput at 60 GHz, are promising topush WLAN throughput beyond the 1 Gb/s bar-rier. These developments will make possible newapplications such as the wireless transmission ofdigital cinema [10], but may also allow a greatmany more mobile users to be supported at APsites.

To support the next generation of digitalmedia application, it is not simply enough toincrease throughput; applications such as voiceover IP (VoIP), video streaming, massively mul-tiplayer online (MMO) games, and other com-munication-based rich media services have strictdelay tolerances that must be serviced. Take, forexample, video streaming; if delays become toogreat, the video playback becomes jittery or stilt-ed and is unwatchable. To avoid the problem,applications of this nature require QoS guaran-tees. The WLAN standard provides support forQoS via the 802.11e [1] standard amendment.With 802.11e, traffic may be prioritized based onfour categories: voice, video, best effort, andbackground. For QoS to be successfully imple-mented on the wireless network, it must bebacked up by support for QoS on any associatedwired network through the IEEE 802.1p Class ofService field provided by the 802.1Q [11] virtualbridged local area networks amendment to theEthernet standard.

In Fig. 5 we can see all the IEEE 802.11 solu-


Figure 5. IEEE 802.11 solutions mapped to the entertainment park scenario.

1. Waiting in line

Heterogeneity802.11s

Security802.11i802.11w

Mobility802.11p802.11r

QoS support802.11e

Data transfer802.11a/b/g/n802.11ac/af

Management802.11k

2. Visitor on Park Ride

3. Street crowd

4. Seated audience

3 IEEE 802.11ac: VeryHigh Throughput <6GHz, 2010 (Proposed)

4 IEEE 802.11ad: VeryHigh Throughput 60GHz, 2010 (Proposed)



tions discussed mapped to the entertainmentpark scenario. IEEE 802.11i and w provide thesecurity needed for this type of corporate envi-ronment. IEEE 802.11p can support the kind ofmobility found on park rides and transportation.It can be seen that many of the challenges indeploying a wireless LAN/MAN to serve a largenumbers of end users are being met by existingelements of the 802.11 standard. Further chal-lenges are being tackled by draft and proposedamendments to the standard, there are still out-standing problems, however. These issues andpotential solutions are discussed in the next sec-tion.

OUTSTANDING PROBLEMS ANDAPPROACHES TO

IMPROVE PERFORMANCE

There are many obstacles to overcome in aWLAN/WMAN deployment that supports com-munications for a dedicated mobile device in alarge controlled environment. This section is notintended to be an exhaustive list of these issuesbut rather a cross section of the wide variety ofareas where problems may be encountered.Potential solutions in today’s research are dis-cussed where appropriate.

When installing a WLAN/WMAN infra-structure to cover a large area, IEEE 802.11swireless mesh has a number of distinct advan-tages. By replacing wired links with wireless, theinstallation cost is reduced. The dynamically self-organizing and self-configuring nature of meshnetworks also further reduces the complexityand cost of installation, and makes the networkrobust to the failure of single AP sites. Thereare, however, some problems with mesh net-works. A large number of APs must coexistacross a target environment in order for a wire-less LAN/MAN infrastructure network to scale.In a wireless mesh wireless links that are inrange of each other on a multihop route cannotbe active on the same frequency at the sametime, or interference occurs. This must be solvedby either scheduling or multifrequency approach-es. Scheduling introduces delays, which seriouslyhamper scalability, so multifrequency approachesare preferable.

Wireless devices can coexist by operating onorthogonal channels. For this to work in a wire-less mesh network, network nodes must be ableto operate at multiple frequencies rather thanjust one single fixed frequency. One approachtaken is to use a single radio capable of operat-ing on different channels, but only one at a timeat each network node. It is also possible to use asingle radio with multiple transceivers controlledby the same MAC mechanism to allow operationat several channels simultaneously. Maximumflexibility is achieved by using multiple radios.These radios can operate independently, and, intheory, each could be capable of operating onmultiple channels. The three approaches listedprogressively increase complexity, but also pro-vide additional capacity. The benefit of thesemultifrequency approaches is a reduction ininterference and latency in mesh networks. This

is achieved through greater flexibility in channelallocation, allowing nearby nodes to coexist onorthogonal channels, thereby increasing networkcapacity. Multifrequency approaches, however,increase complexity and pose some additionalproblems, especially for smaller handhelddevices.

The size of a mobile device is a major limit-ing factor to what is possible. A handheld devicehas limited battery life. Radios are one of themost power-hungry pieces of hardware on such adevice. This may threaten capacity-enhancingapproaches that propose multiple radios. Somemultiple-radio approaches are, however,designed to improve battery life. For example, alow-power radio can be used in conjunction witha high-power radio. The high-power device isshut down when idle, and the low-power radiomonitors whether data is available, waking upthe high-power radio when needed. Another fac-tor working against multiple-radio or multiple-antenna solutions (e.g., IEEE 802.11n MIMO) isantenna placement; it is difficult to place multi-ple antennas in a handheld device without expe-riencing crosstalk or other forms of interference.Even the proximity of the user’s hand must beconsidered, as an antenna obscuring hand maybe a major source of interference. On moderndevices with sophisticated displays that allowmultiple orientations (Fig. 6), hand position canbe a real issue for wireless communication; forexample, Apple’s iPhone 4 had a high profileproblem with antenna placement that led to lostconnections when the lower left side of thedevice was touched.

There are a number of potential developmentplatforms for a custom dedicated mobile device,and the choice of operating system is an impor-tant design consideration. Competing mobileoperating systems include Symbian, Maemo,MeeGo, iPhone, BlackBerry, and Android. If,for example, the Android operating system andsoftware stack is to be used, as with any of theother operating systems, there are benefits anddrawbacks to consider. This platform is based onthe Linux kernel, which is free and open sourceand, consequently, appealing to the researchcommunity. There are many benefits for devel-opers too; if you wish to develop with a newpiece of hardware, provided it has a Linux driv-er, porting to Android is a relatively simple pro-cedure. At present, however, the platform has aproblem working with WLAN networks: it is notpossible to set up proxy settings for a WLANnetwork (a documented bug since November2008). This lack of proxy support is a major con-cern, especially for corporate networks.

Proxy servers are used by corporations andinstitutions such as universities to improve secu-rity and enforce policies and restrictions (e.g.,preventing access to sites unsuitable for theworkplace). One way of overcoming this Androidproblem now is to create a custom build of theOS with proxy restrictions removed for WLAN,and then build a proxy setting App. The custombuild of the OS and the proxy App can then bedistributed to all devices. This way of overcom-ing the problem is not ideal, as it increases plat-form fragmentation and complicatesinteroperability. Ideally, proxy setting functional-

Some multiple radio

approaches are

designed to improve

battery life. For

example, a low

power radio can be

used in conjunction

with a high power

radio. The high pow-

ered device is shut

down when idle and

the low powered

radio monitors

whether data is avail-

able, waking up the

high power radio

when needed.



ity would be included in the standard AndroidOS in a more intuitive fashion (e.g., a config-urable parameter associated with known wirelessnetworks).

Many upper-layer protocols required to sup-port applications on mobile devices were origi-nally designed for wired networks.Unfortunately, some of these do not performwell in wireless networks. For example, transportlayer protocols, including the popular TCP pro-tocol, were developed for wired networks. Wire-less links, especially in the presence of mobilityor ad hoc wireless networks, behave very differ-ently from wired links (in terms of packet lossand delay), and this invokes an inefficient reac-tion from the transport protocol. Congestioncontrol mechanisms may treat the packet lossgenerated by the error-prone wireless channelsas network congestion, and wrongly reduce theirtransmission rate. Similarly, an unreliable link inawireless ad hoc network may cause a packetretransmission over the entire path. This is high-ly inefficient, in terms of both delay and energyconsumption. Several link-layer solutions thataid higher-layer protocols (mainly TCP) to copebetter with link-layer QoS characteristics havebeen proposed. Such enhancements includeSnoop TCP [12] and SPLADE [13], the latterbeing designed for real-time multimedia applica-tions, which use buffering and local retransmis-sion techniques to shield the TCP layer from thewireless QoS variations.

Newly developed upper-layer protocolsdesigned specifically for wireless networks pro-vide the solution to this problem and will verylikely take over in wireless communications.Recently developed transport protocols includeStream Control Transmission Protocol (SCTP)[14] and Datagram Congestion Control Protocol(DCCP) [15], both of which support multihom-ing, a very important feature in the context ofmobility and wireless heterogeneous networks.One proprietary solution is the Venturi Trans-port Protocol (VTP), which transparentlyreplaces TCP to overcome its limitations overwireless networks. VTP is already used by anumber of wireless broadband service providersto speed up their networks.

There are a wide range of issues to considerwhen developing a custom mobile device sup-ported by WLAN infrastructure. We have high-

lighted some important considerations, includingthe limitations of the wireless network technolo-gy, restrictions of the device’s OS, problemsassociated with upper-layer protocols, and evenissues as simple as the space available on a handheld device.

SUMMARYThis article focuses on the feasibility of usingWLAN to support communication-based appli-cations on mobile devices in a large controlledenvironment. An entertainment park is taken asan example environment, and the particularchallenges for the entertainment park case arediscussed. Existing WLAN standards, draft stan-dards, and proposed standards that can meetthese challenges are summarized. Finally, abroad cross-section of the remaining obstaclesassociated with such a deployment are discussed.Problems relating to infrastructure, operatingsystems, limited space on handheld devices, andupper-layer protocols are highlighted to showthe scope of such an undertaking.

ACKNOWLEDGMENTSThe authors wish to thank Kevin McGuinnessfor his valuable comments and contributions tothis work. The authors also wish to thank Maur-izio Nitti of Disney Research, Zurich for his helpwith illustrations.

REFERENCES[1] IEEE 802.11-2007, “Wireless LAN Medium Access Con-

trol (MAC) and Physical Layer (PHY) Specifications,”2007.

[2] IEEE 802.11y, “3650–3700 MHz Operation in USA,”2008.

[3] FCC, “FCC Report and Order: Unlicensed Operation inthe TV Broadcast Bands, Additional Spectrum for Unli-censed Devices below 900 MHz and in the 3 GHzBand,” Nov. 2008.

[4] IEEE 802.11k, “Radio Resource Measurement Enhance-ments,” 2008.

[5] IEEE 802.11r, “Fast Basic Service Set (BSS) Transition,”2008.

[6] D. Jiang and L. Delgrossi, “IEEE 802.11p: Towards anInternational Standard for Wireless Access in VehicularEnvironments,” IEEE VTC, Singapore, 2008.

[7] IEEE 802.11w, “Protected Management Frames,” 2009.[8] Intel, “Intel and 802.11: Helping Define 802.11 and

Other Wireless LAN Standards,” Intel White Paper,2009.

[9] IEEE 802.11n-2009, “Enhancements for Higher Through-put,” 2009.

[10] Y. Hirata et al., “Digital Cinema Wireless Transmissionand its Windows Application.” IEEE Commun. Info.Tech., 2009, pp. 814–19.

[11] IEEE 802.11Q-2005, “Virtual Bridged Local Area Net-works,” 2005.

[12] H. Balakrishnan, V. Padmanabhan, and R. Katz,“Improving Reliable Transport and Handoff Perfor-mance in Cellular Wireless Networks,” Wireless Net.,vol. 1, no. 4, 1995, pp. 469–81.

[13] I. Radovanovic, R. Verhoeven, and J. Lukkien, “Improv-ing TCP Performance over Last Hop Wireless Networksfor Live Video Delivery,” IEEE Trans. Consumer Electron-ics, vol. 54, no. 3, Aug. 2008, pp. 1139–47.

[14] R. Stewart, Q. Xie, and K. Morneault, “Stream ControlTransmission Protocol,” RFC 2960, Oct. 2000.

[15] E. Kohler, M. Handley, and S. Floyd, “Datagram Con-gestion Control Protocol (DCCP),” RFC 4340, 2006.

BIOGRAPHIESKEVIN COLLINS [M] ([email protected]) received his B.Eng.degree in digital media engineering from Dublin City Uni-versity in 2006. He subsequently joined the Performance

Figure 6. Hands cover different areas depending on device orientation.



Engineering Laboratory (PEL) at Dublin City University,where he studied for his Ph.D. as a full-time researcher. Hejoined CLARITY, the Centre for Sensor Web Technologies inDublin City University, as a post-doctoral researcher in Jan-uary 2010, and continues to work in collaboration with thePerformance Engineering Laboratory. His research coversmany aspects of wireless communication networks. Hisfocus is providing wireless access in challenged environ-ments; challenging characteristics of these environmentsmay include high interference, devices moving at highspeed, devices with complex mobility, very large numbersof devices, and very high data rate requirements. Otherresearch interests include intelligent transportation sys-tems, location-aware applications, and human-computerinteraction-and-music.

STEFAN MANGOLD ([email protected]) received hisdegrees in electrical engineering/telecommunications fromComNets RWTH Aachen University, Germany. He is a seniorresearch scientist at Disney Research, Zurich. In addition,he also enjoys working as a lecturer at ETH Zürich, Depart-ment of Computer Science, where he has been teachingmobile computing and wireless communications since2007. As an independent expert, he regularly consults forthe European Commission in Brussels with regard to overallresearch program funding. Before joining Disney Research,Zürich in October 2009, he worked at Swisscom(2005–2009) in various management positions in researchand business development, and with Philips ResearchU.S.A. (2003–2005) as a senior member of research staff.His research covers many aspects of wireless communica-

tion networks. His foci are wireless protocols and systemaspects for IEEE 802.11 wireless LAN, cognitive radio, andwide area networks such as cellular and WiMAX. Otherresearch interests include mobile computing, interactivetoys, cellular networks, and ontology engineering. He is co-author of two books, IEEE 802 Wireless Systems: Protocols,Multi-Hop Mesh/Relaying, Performance, and SpectrumCoexistence (Wiley, 2007) and Cognitive Radio and Dynam-ic Spectrum Access (Wiley, 2009). He holds various patentsand publications. He is a contributor to the standardizationbody of IEEE 802.11.

GABRIEL-MIRO MUNTEAN [M] ([email protected]) wasawarded his B.Eng. and M.Sc. degrees in software engi-neering from the Computer Science Department, “Politehni-ca” University of Timisoara, Romania in 1996 and 1997. Heobtained his Ph.D. degree from Dublin City University, Ire-land, for research in the area of quality-oriented adaptivemultimedia streaming in 2003. He is a lecturer with theSchool of Electronic Engineering and co-Director of thePerformance Engineering Laboratory at Dublin City Univer-sity. He has published over 100 papers in top-level interna-tional conferences and journals, authored a book and fivebook chapters, and edited two books. His research inter-ests include quality and performance-related issues ofadaptive multimedia delivery and personalized e-learningover wired and wireless networks with various devices. Heis an Associate Editor of IEEE Transactions on Broadcastingand a reviewer for important international journals, confer-ences, and funding agencies. He is a member of the IEEEBroadcast Society and the Rince Institute Ireland.


supporting mobile devices with wireless lan/man in large ...€¦ · like video streaming. scenario...

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