IEEE Wireless Communications • October 20104

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INTRODUCTIONFacing an explosion in traffic demand, driven by the evolutionof smart mobile devices exploiting a flat charging model, theinfrastructure supporting mobile devices is presented withformidable challenges, but also creative opportunities, whichwill help manifest the potential of present and future mobilenetworks. In this short column we explore, at a high level, anumber of the challenges and opportunities associated withthe mobile infrastructure. In our broad definition, we considerhere as part of the mobile infrastructure all the wired net-working, storage, and computing elements required to delivera modern user experience to smart mobile devices (e.g., frombase station processing elements, to the high-end IP routers inthe core, to the centers supporting content delivery and appli-cation processing).

KEY REQUIREMENTS FOR THE FUTURE MOBILE INFRASTRUCTUREAs we consider our recent, extraordinary experience withsmart mobile devices, as well as our frustrations with theirperformance and unrealized potential, we can identify a num-ber of areas where much technical focus should be concen-trated. However, progress in the areas we highlight hererequire more than pure technical breakthroughs, but alsoadvances at the business and regulatory levels.

A short list of interesting areas of investigation andprogress, implying new and more sophisticated requirementfor the future mobile infrastructure, includes the following:• Support for broader (Internet) mobility• More effective traffic offloading• More advanced and flexible identity management• Lower latency• More distributed application awareness• More distributed application processing

Most of these requirements are motivated by the need foran improved traditional mobile user experience, but also bythe evolving demands of sensor networks at the fringes of thecurrent mobile network and the foreseen expansion of vehicu-lar connectivity. In the next subsections we explore therequirements listed above in further detail.

MOBILITY SUPPORTThe current generation of mobile devices, together with thecurrent infrastructure, are far from supporting a broadernotion of mobility, including seamless transition across non-homogeneous wireless technologies, such as third genera-tion (3G) and WiMA, sometimes defined as true Internetmobility.

For a number of reasons, the current architectures supporta somewhat seamless connectivity and some dimensions ofapplication continuity only for cellular networks, via a some-what centralized set of data centers, and through the notionof roaming. Enterprise networks also support, through theirwireless controllers, a similar notion of mobility (at layer 2 ofthe open systems interconnection [OSI] stack). Furthermore,Session Initiation Protocol (SIP) supports a notion of mobilityat the application level.

However, seamless movement from cellular to other net-works is not happening, even in the case of femtocells. Thus,the achievement of the promise of pervasive seamless mobilityacross non-homogeneous networks still requires much work.

We see promise in the Internet Engineering Task Force(IETF) work on Mobile IP (in particular, Mobile IPv6, DualStack Mobile IP) [1, 2], and the work on the Mobile LISPProtocol [3].

A key functionality required in this area relates to connec-tion management, which involves features residing at both theclient and infrastructure levels. An intelligent connectionmanager can ensure connection continuity and optimization,thus greatly improving user experience.

A strong connection manager is especially needed to satis-fy future requirements in the connected vehicle space.

EFFECTIVE TRAFFIC OFFLOADINGWithout doubt, the intense growth in traffic demand we havewitnessed in recent years will continue into the future. It willbe difficult for the mobile infrastructure to meet such explo-sive demand, even with the adoption of fourth-generation(4G) technologies and usage-based charging. For this reason,various approaches to traffic offloading will need to beexplored. These will include, besides the femtocell approach,more widespread use of WiFi access in the home, enterprise,as well as public spaces. In particular, future roadside accesspoints may provide efficient offloading for connected vehicles.Other wireless technologies may play a role complementary oralternative to WiFi (e.g., 60 GHz wireless).

The extent of service provider control over mobile usertraffic as it spans multiple wireless networks is an interestingopen issue.

Another very important offloading approach will involvemore local communications, such as peer-to-peer communica-tion at the periphery of the network (Nokia Paper) or moresuccessful exploration of ad hoc networking.

ADVANCED AND FLEXIBLE IDENTITY MANAGEMENTThe mobile infrastructure should try to expand its support foridentity beyond the current well tried models, based on bothhardware (i.e., SIM cards) or software (e.g., in code-divisionmultiple access [CDMA]) approaches. There need to be bet-ter, more flexible ways to associate an identity with a userwho may, for example, want to use the same identity to oper-ate, interchangeably, a smart phone, vehicular phone, mobiletablet device, and body sensor. This more flexible identitymanagement will open powerful opportunities, for example, inthe evolving world of machine-to-machine communications.Further requirements in the direction of innovative identitymanagement come from connected vehicles and the develop-ing world.

LOWER LATENCYMore than increased bandwidth, long latency is a fundamentalchallenge for the mobile infrastructure, as explored by VictorBahl et al. [4]. Long latency is caused by a number of techni-cal factors, including:• Networking delays to and from a sparse set of mobile data

centers• A backhaul infrastructure based on a rather cumbersome

set of tunneling techniques and a large number of hops,involving long queuing and packet processing delays

• Delays involved in loss correction (i.e., retransmissions) inthe radio access network

• Data center processing delays

THE FUTURE MOBILE INFRASTRUCTURE: CHALLENGES AND OPPORTUNITIESFLAVIO BONOMI, CISCO SYSTEMS

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Long latencies in the mobile core inevitably lead to poorutilization of the available bandwidth, particularly for TCPconnections, and, eventually, to a frustrating mobile userexperience in many congested urban areas. It also limits thetypes of applications on smart devices that can make efficientuse of “cloud” resources, thus limiting the scope of supportedapplications, and even cloud processing support aiming atextending mobile battery life. This issue is well articulated byVictor Bahl et al. in [5].

In order to face the all important latency issue, the mobileinfrastructure should move quickly toward a more efficientnetwork architecture, with fewer gateways between differentnetworking technologies, tunneling levels, and hops. Moreeffective latency-aware congestion management needs to beadopted, together with a distribution of smaller mobile datacenters closer to the edge of the network. The adoption ofmore distributed, smaller data centers may also have positivecost implications [6].

More efficient transport models need to be explored, withthe goal of avoiding as much as possible the inefficiencies oflong end-to-end TCP connections. Advances in transport opti-mization will always be needed in order to take full advantageof the available bandwidth in the radio access network.

DISTRIBUTED APPLICATION AWARENESSThe mobile network needs to become more content- andapplication-aware, at various levels of its infrastructure (e.g.,mobile device, base station, gateway general packet radio ser-vice service node [GGSN], data center) in order to achievehigher functionality and efficiency. Content inspection andapplication classification can enable a higher degree of securi-ty, context-aware policies, quality of service, selective trafficoptimization, and load balancing. Video traffic, which consti-tutes an ever growing percentage of mobile traffic, will needto be recognized throughout the network and specifically han-dled.

Finally, application processing, as we describe in the nextsubsection, may take place in a more distributed fashion. Inorder to achieve this more pervasive processing, the mobilenetwork will need to become more application-aware.

DISTRIBUTED APPLICATION PROCESSINGMany are the motivations for the exploration of a muchmore distributed architecture for application processing infuture mobile networks. Among those motivations, we wouldinclude reduction of latency, more effective handling of sen-sor and emergency data, enabling new applications such asinteractive gaming, more optimized handling of video traffic,and the potential for closer support of mobile devices, withthe important goal of extending their battery life [5]. Movingin this direction will definitely not be an easy process, butmay prove extremely rewarding. More distributed mobileapplication processing will leverage virtualization, requirenew middleware evolution, and definitely be facilitated bythe diffusion of processors with homogeneous instructionsets from the cloud servers space to the embedded andhandheld space.

CONCLUSIONSIn this brief note we have listed and discussed a number ofbroad challenges and opportunities facing the future mobilenetwork infrastructure. Meeting these challenges will requirea deeply technical as well as regulatory and business effort.However, the results of progress on many of the items dis-cussed here will open new vistas and enable a deeper, evenmore positive impact of technology on society and the envi-ronment. A close partnership between academia and industrywill be required for more successful exploration of the issuesdiscussed here.

REFERENCES[1] http://www.ietf.org/rfc/rfc3775.txt and related docs.[2] http://tools.ietf.org/html/draft-ietf-mip6-dsmip-problem-01 and related

docs.[3] http://tools.ietf.org/html/draft-meyer-lisp-mn-03 and related docs.[4] J. Huang et al., “Anatomizing Application Performance Differences on

Smartphones,” ACM MobiSys 2010, San Francisco, California, June 2010.[5] E. Cuervoy et al., “MAUI: Making Smartphones Last Longer with Code

Offload,” ACM MobiSys 2010, San Francisco, California, June 2010.[6] K. Church, A. Greenberg, and J. Hamilton, “On Delivering Embarrassingly

Distributed Cloud Services,” ACM SIGCOMM Hotnets VII, Calgary Alber-ta, Oct.. 2008.

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