Unlicensed Mobile Access Technology - Deepak Menghani | Gsm
C C ESS: NEX T G ENERATIONOF MOBILE NETWORK TECHNOLOGY
D eepak M enghani
B.Tech. (Hons.),Electronics and Com munication Rajasthan Technical University, Kotadeepak.firstname.lastname@example.org
This paper covers the discussi on on a cutting edge technology in Telecommunications to deliver voice, messaging and multimedia content over a wireless IP Network, known asU nlicensed Mobile Acc ess (U MA). U MAprovides access to Global System for Mobile Telecommunication (GSM) and GeneralPacket Radio Service (GPRS) mobile services using unlicensed spectrum technologies (such as Bluetooth, IEEE 802.11standard WLAN technology, DSL, etc). By implementing UMA,servic e providerscan all ow their subscri berbase to roam and perform handover operations between licensed cellular network and public and private unlicensed wireless networksusing a dual-mode mobile terminal. GSM subscribers canexperience all-the-time voice and data service even if service provider has no cellularnetwork coverage in some area or at the time of N etwork Busy H our.In additio n,U MAprovides a consi derably higher throughput than G SMsystems. E volution of highly stable digital circuit switched network has taken place fromthe old incompatible analogue system. The next major trend in telecom network evolution will be based upon packet switched network implemented using UM A.
UMA, GAN,GSM,WLAN, Blue tooth
Unlicense d Mobile Access (UMA)aims to offer mobil e, fixed andinternet telephony on a single mobile terminal and provideseamless handover between these services using Wi-Fi orBluetooth technology, etc. UMA uses IP tunneling to transmit anycontent a mobile subscriber can receive over the GSM or UMTSnetwork i.e. existing voice, data and IMS services. UMA-enabledhandset connects to any IP-based service and wraps the standardGSM content in an IP packet. The packet is then transmitted toUMA Network Controller (UNC) over local area network orinternet. At the UNC, it is unwrapped and routed further towardsmobile service provider’s Core Mobile Network.Essentiall y UMA offers high speed delivery of standard GSM/UMTS content to mobile service provider’s Core Mobile Network: “avideo streaming service could be from 1-4 frames per second overa cellular network and jump to 20 frames per second over UMA-supported W-Fi connections”. It is expected to resolve the issues of modern mobile telephony such as limited signal strength indoorsand limited ba ndwidth. It o pens a widerange of o pportunities both for the telecom consumers and operators. It allowssubscribers to enjoy the benefits of better indoor coverage usingprivate or public WL AN radio access. Itserves to give op eratorsthe ability to fully leverage their cellular assets via alternativeradio access methods where they are unable to provide cellularnetwork d ue to low r evenue gene ration or othe r cost-cuttingfactors or at the time of Network Busy Hour where call congestionmay occur.Itis a cost-effectiv e way to expand ce llular cover age for voice and data services to homes and enter priseswhere it might be too difficult or expensive to buildcellular covera ge indoors. The technical measurements of UMA performance providedevidence that the solution really works. The handoversbetween UMA and GSM are similar to typical inter-BSChandovers in the GSM system. Therefore, UMA is at its best inextending the cellular network operator’s current network coverage in indoor lo cationsin current ma rket trends wheresubscriber’s expectation is very high.
2.1 UM A: BRIEF HISTORY & OV ERV IEW
Currently, the definitions of standards allowing transparent handover between different radio technologies (verticalhandover) are an area of intense activity. A number of standards inthis domain have been app roved and are under investigation, for example, the IEEE 802.21 standard isespecially true for 802.11 and cellular technologies, aiming toexploit the rapid deployment of broadband and the use of wireless LAN (WLANs) within homes, offices and hot-spots.UMA is a concrete example in providing a high bandwidth andlow-cost wireless access network, which is further integratedinto operator’s core network, enabling roaming and handoveroperationsbetweenitself a nd orig inallylicensedmobile network.In this context, the UMAC (Unlicensed Mobile AccessConsortium) was formed by leading companies within thewireless industry to promote UMA technology and to developits specifications. The initial specification of UMA waspublished on 2
September 2004, which details the use of thesame device over a licensed radio spectrum connection (GSM)when users are outside the UMA coverage and using anunlicensed radio spectrum (Bluetooth or Wi-Fi) when beinginside the UMA coverage. 3GPP defined UMA as a part of 3GPP release 6 (3GPP TS 43.318)under the name of Ge neric Access Network (GAN).
2.2UM AAR C HITEC TUREOV ERV IEW
UMA technology allows subscribers to seamlessly roambetween mobile and home wireless networks or Wi-Fi Hot spots. Subscriber s performhandover opera tion between twonetworks and continue to receive mobile voice and dataservice in a consistent manner. A mobile user can takeadvantage of potentially faster data services through avoidingthe bandwidth constraint in the GSM network.As illustrated in Figure 1, connection to the fixedunli cens ednetw ork occ urs au toma tical ly whe na mobil e subscriber with a UMA enabled handset moves within itsrang e.Upon con nect ing, the ha ndse t contac ts the UMANetwork Controller (UNC) over broadband IP access network to get authenticated foraccessing GSM andGPRS services v iaunlicensed wireless network.After getting authorized, the subscriber’s new locationinformatio n is stored in th e corenetwork e lement “Hom eLocation Register” and from this point, all mobile voice and
Unlicensed Mobile Access-Research Paper Vol ume 2.1, January, 201 3
data traffic is routed to the handset via the UMA network insteadof licensed cellular network.The UNC presen ts itself tothe mobile core n etwork as a standa rd cellular Base Station Controller (also it is virtually created in NSScore network elem ent –Mobile Switching Cen ter/Visitor Locatio n Register). The mobile terminal communicates with UNC usingstandard GSM / UMTS existing protocols, thus when it moves froma GSM / UMTS network to 802.11 network, it appears to the corenetwork as if it is simply on a different base station connectedwith core elements.
F igure 1 -UMA Arch itec ture
2.3UM ASE RV IC ES
UMA offers under mentioned services:
Seamless mobility between licensed & unlicensed mobileaccess networ k forproviding voice & data ca ll continuity
Mobile users are able to make use of existing as well asnew data services in a seamless manner withconsiderabl y higher throughput
Bandwidth-intensive mobile services such as internet gaming, audio & video streaming do not have to endwhen the end user goes home
Multimedia Services over IMS such as push-to-talk (PTT),Voice-Over-IP (VOIP), etc are also available
2.4BENE FITS OF UM A FO R SERV ICEPROVIDERS
Following benefits a service provider can achieve by implementingUMA in its network:-
GSM radio network can be optimized by using alternativelower-cost and higher-bandwidth access network
Direct investment can be minimized in cellular network expansion in the areas of low revenue generation or at the time of
Netw ork Busy Hour o r at the time of festiveseason
Delivering advanced reach as well as improved voicequality over IP network
Bringing increased usage and allowing new services to
be oﬀered along with existing ones
Greatly increasing the use of mobile voice and dataservices in locations where usage was discouraged dueto cost or network coverage
2.5MO DES O F OPERATION S IN UM A
The original Release 6 GAN specification supported a 2G (A/Gb)connection from the UNC into the mobile core network (MSC/GSN).Today all commercial GAN dual-mode handset deploymentsare based on a 2G connection and all GAN enabled devices aredual-mode 2G/Wi-Fi. The specification, though, definedsupport for multimode handset operation. Therefore,3G/2G/WI-Fi handsets are supported in the standard. Thefirst 3G/UMA devices were announced in the second half of 2008.A typical UMA/GAN handset has four modesof operations:-
Uses only cellular networks
uses cellular networks if available , otherwise the 802.11 radio
uses a 802.11 connection if anaccess point is in range, otherwise the cellularnetwork
usesonly the802.11 connectio nIn all cases, the handset scans for GSM cells when it first turnson to determine its location area. This allows carrier to routethe call to the nearest UNC, set the correct rate plan andcomply with existingroaming agre ements. At the end of 2007, the GAN specification was enhanced tosupport 3G (Iu) interfaces from the UNC to the mobile corenetwork (MSC/GSN). This native 3G interface can be used fordual-mode handset as well as 3G femtocell service delivery.TheGAN re lease8 docum entationdescribesthesenewcapabilities.The foll owing fu nctionalblock inthe Mob ile Station (MS) supports end-user access to telecommunicationservices:
AnMTu provides a ccess via UTR AN
An MTm provides access via GERAN
An MTp provides access via UMA network
UM AIMPLEM EN TATION
The UMA solution does not need much direct investment. Themost critical block in UMA implementation is UMA Network Controller (UNC) which provides authentication andtunneling setup. In the UNC, operators can also specify otherrestrictions for the access, such as access point SSID or MACspecifications. Therefore, the cellular network operator (whoalso runs the UMA solution) can specify who can use UMAand how they can use it in connecting to the operator’s corenetwork.The generic structure of UMA access system is illustrated inFigure-2.
F igure 2 –UMA Acc es sto cellul ar network
Unlicensed Mobile Access-Research Paper Vol ume 2.1, January, 201 3
UMA TECHNOLOGY SPECIFICATIONS
4.1 HOW UMA TECHNOL OGYWORKS?
UMA technology provides alternativ e access to GSM and GPRS core network services via IP-based broadband connections. In order todeliver a seamless user experience, the specifications define a newnetwork element (the UMA Network Controller, UNC) andassociated protocols that provide for the secure transport of GSM/GPRS signalling and user plane traffic over IP. The UNCinterfaces into the core network via existing 3GPP specified A/Gbinterfaces.1.A mob ile s ubsc ribe r wi th a U MA en able d dua l-mo de ha ndse t moves within range of an unlicensed wireless network (It isassumed that handset is allowed to connect to UMA network).2.Uponconn ectin g,hand setcont actstheUMAnetw ork controller (UNC) over the broadband IP access network forauthentication and authorization to access GSM voice anddata services via unlicensed wireless network.3.Uponsucce ssfu l a uthen ticat ion,thesubs crib er’scurr ent location is updated in core network elemen ts (Home Location Register). All the mobile voice and data traffic is routed to thehandset via UMA network rather than cellular radio accessnetwork (RAN).4.
When a UMA enabled subscriber moves outsidethe range of an unlicensed wireless network, the UNC and thehandset facilitate roaming back to the licensed outdoornetwork.5.
If a subscriber is on active GSM Voice call orGPRS data session, when they come within the range (or out of the range) o f an unlicense d wireles snetwork, tha t voicecall or data session can automatically handover betweenaccess networks with no discernible service interruption.Handovers are completely transparent to the subscriber.
4.2 UMAFUNC TIONAL A RCHITECTURE
The UMA network consists of one or more access points (APs) andone or more UMA Network Controller (UNC) interconnectedthro ugh a bro adba nd IPnetw ork. T he basi c elem ents a srepresented in Figure 3 are classified as:
M obile S tation (MS )
versus Mobile Terminal (MT)
Access Point (AP)
-TheAP pr ovid es th e ra dio l ink t o the mobile station using unlicensed spectrum
F igure 3–UMA F unctional Archi tecture
UMA Network Controller (UNC) -
The UNC appears to thecore network as a GERAN Base Station Subsystem (BSS). It includes a Security Gateway (SGW) that terminates secureremote access tunnels from the MS, providing mutualauthentication, encryption and data integrity forsignaling, voice and data traffic
broadband IP network
provides connectivitybetween the AP and the UNC. The IP transport connection extends all the way from the UNC to the MS,through anAP. A singleinterface,the Up inter face, is defined between the UNC and the MS
Co-existence with the
G SM /G PRS Radio A ccessNetwork (GERAN)
and interconnection with the GSMCore Network (CN) via the standardized interfacesdefined for GERAN: A-interface for circuit switchedservices [TS 48.008]
for packet switched services [TS 48.018]
4.3FUN C TIONA L E NTITIES
The MS must have dual mode capability to switchbetween licensed cellular network and public andprivate un licensednetwork. It mustsupporteitherBlue tooth o r 802.11 WLA N stand ards .It must al sosupport an IP interface to access points.
A ccess Points
The Access Points provides radio link towards themobi le sta tion u sing u nlice nsed s pectr um.-It con nectsto the UNC through broadband IP network. The APprovides Bluetooth or 802.11 access point functionality.The AP doesn’t provide any UMA-specific gatewayfunctions, and any generic AP can be used tointerconnect the MS to the UNC via the broadband IPnetwork.The UMA cell is analogous to a GSM base stationcontroller (BSC ). For this reaso n, it is perceived as suchby the cellular network and roaming between UMA andGSM is considered an inter-BSC handover. From the BSCperspective the UNC is just another BSC. In theory, if theUNC is in the BSC neighbors list, it is possible to performa handover. However, the individual Wi-Fi cells areindependent from the UMA system. Regardless of thesimilarities between the UNC and the BSC, the cell sizedoes not directly correlate.