A Wireless Architecture for a Multimedia World

Mike Short and Fred Harrison A Wireless Architecture for a Multimedia World

This article provides an overview of a mobile GSM). This article summarises some of the wireless architecture as it evolves to serve application demand drivers, the architectural elements of devices, services, and networks, applications anywhere, such that voice and takes us towards an all IP world, and applications innovation are more fully enabled in concludes with the relationship with wireless the data world. LAN technology. Market Introduction The cellular world should serve over The wireless industry is rapidly moving 1 billion customers before the middle of from voice to data services, from a verbal 2002, but what is very significant is the to a visual world of applications with proportion of customers that are GSM increasing mobility of services—a world of based and the growing interest in non-voice applications anywhere. services. A recent forecast by Strategy Whilst these services are facilitated by Analytics for the UK forecast a five-fold roaming, the cellular GSM roadmap also growth in non-voice revenues between 2001 needs to maintain international economies and 2006 (see Figure 1). of scale and scope. With over 700 million Many of these services may be advanced GSM customers worldwide in 175 coun- forms of messaging, mobile entertainment tries, the benefit of shared research and and location-based services, but it is clear development is likely to be maintained for that the potential for a wide range of years to come, as GSM evolves into the applications needs to be supported by third generation (3G) of mobile and robust and open standards and a clear provides for greater interoperability with architecture roadmap. This is all the more new technologies such as wireless LAN. important as the role of application The international approach to mobility developers and third-party wholesalers will also requires a focus on an open wireless need clear business interfaces in order to architecture and standards, to enable deliver these services to market. applications anywhere, as we move from 2G Evidence of the initial uplift in demand (GSM) to 2½G (general packet radio service for non-voice mobile services can be seen

The authors are with mmO2. (GPRS) or packet GSM) to 3G (multimedia from Figure 2. The Mobile Data Association (MDA) releases the UK total monthly SMS Figure 1 Applications, applications, applications... figures. This illustrates how the UK short message service (SMS) totals have grown UK mobile data applications forecast 2000–2006 from 22 million per day to 44 million per day from December 2000 to February 2002 12 respectively. The MDA forecast for the UK Messaging is 60 million per day for December 2002. Information 10 Services The growth in mobile data will repre- LBS sent some key interoperability challenges if Entertainment we do not work to consistent standards and 8 Other clear interfaces for the wide range of M-Commerce applications foreseen. One of the key 6 Advertising lessons learnt with SMS growth was that working with competitors and third-party US$ Billions US$ 4 channels helps to grow the overall market for mobile data, more than one party can achieve on its own. 2 Technology Roadmap 0 2000 2001 2002 2003 2004 2005 2006 The traditional standards-based technology Source: Strategy Analytics, 2001 roadmap in second-generation digital can be seen in accordance with Figure 3.

14 The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 Figure 2 Text messaging growth (SMS): Devices Architecture UK GSM network operator totals The first element of the end-to-end architec- 50 ture addresses the mobile device architecture. It is critical to accept that mobile thin clients may have some limitations in terms 40 of memory, processing power, display, and battery life, but these can be compensated for through added utility, mobility and 30 functionality. The technological break- Million throughs foreseen also should enable many Messages enhancements, illustrated in Figure 5. per Day 20 This is a significant evolution from the initial GSM devices which included a highly standardised physical layer and a 10 common basic service set of voice and messaging. A more open architecture is emerging where applications and content 0 can be added in a customised way. Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb The timing of these features will depend 00 01 01 01 01 01 01 01 01 01 01 01 01 02 02 on many industry supply factors, but the Source: UK Mobile Data Association capabilities of mobile devices moving www.text.it towards more variety and new personal

The mobile data revolution has been Figure 3 Technology roadmap significantly enhanced with the addition of 2½G or packet GSM technologies across the

O2 footprint. This phase of market development clearly adds many new devices, UMTS (3G) applications and revenues that cannot be fully Multimedia Services foreseen from a standards viewpoint alone. All-IP Networks The third-generation stage of our industry is one characterised by multimedia Information Services GPRS services and plans for ‘all IP’ networks. This Product will encourage many more new devices, Developments multimedia applications and further Mobile WAP interoperability challenges. The additional VPN spectrum coupled with ‘all IP’ networks will also allow for more capacity and cost GSM reduction potential, in addition to offering Voice/Data more applications. The emphasis on high speed should not be seen as the only 1996 1998 2000 2002 2004 2006 Time characteristic of this third-generation stage.

Architecture Overview Figure 4 End-to-end architecture

The emphasis on open, international and non-proprietary standards is vital for the Network Infrastructure Service Layer evolution of our industry. The benefits Application Tier arising from these standards include: Applications • shared research and development; Third-Party Applications • economies of scale for networks, devices Portal and applications; APIs • roaming—both internationally and nationally; Middle Tier • variety of devices; Radio Access RAN/UTRAN Core Network Core

• applications diversity; and IP Service Access Information Repository

• cost reduction. Clients Devices/Thin Mobile However, these benefits would be lost if Service Enabling Tier a coherent architecture was not maintained based on standards. Operators in the O2 footprint have adopted the architecture OSS based on an end-to-end format as shown in BSS Figure 4.

The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 15 Figure 5 Mobile device architecture

digital assistant (PDA) formats should not be underestimated. Examples of new devices can be seen from the montage of thin clients in Figure 6. The characteristics of these devices include many new categories and Radio Service EnablingTier form factors; some multi-application devices for example, SMS, Air interfaces, multi-band, and some optimised for specific services (for location info, IN User Interface multi-mode, codecs example, mobile banking); and many with for example, display added functionality and complexity! control bar Packet GSM devices are already Middle Tier Content Core available on the market so the visions of Interactions with core for example, for example, MP3 file network elements; terminals shown in Figure 7 are being WAP gateways, web forexample, USSD replaced by real O2 business products. optimisation Applications for pre-pay The O RIM Blackberry includes ‘always for example, media 2 player, browser on’ GPRS capability, reaching potential Portal IP Service Access speeds equivalent to ISDN (subject to the APIs GPRS bearer service, application and network load) includes an for example, for example, physical, Access to Internet and web browsers SDKs integrated suite of applications, and is corporate intranets Service Core based on an open programming environ- TM for example, voice, ment (JAVA ). The services include: mmO and Third- IP/GPRS stack Corporate Network • push email, contacts, calendar; 2 Party Applications Operating System Access • Exchange/Outlook; for example, Corporate email, intranet • Lotus Notes; for example, pocket PC, Symbian Access; for • cradle synchronisation; and push content, pull data example, Blackberry RIM Software • triple DES security. for example, This has already attracted over 250 Operational Supportcodecs Business Support corporate customers. for example, Hardware for example, charging The O Handspring Treo has been status and event logs 2 for example, information Service management, developed by O in partnership with radio, memory 2 QoS negotiations Handspring. It is the first European integrated Palm OS Wireless Communica- tor. It covers three models the Treo 180, 180G and 270 colour model. The services

Figure 6 Wireless thin clients/mobile devices

16 The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 Figure 7 Packet GSM devices include mobile phone, wireless email, SMS, and Internet access. Microsoft Outlook and Lotus Notes capability. The GPRS device roll-out starts in Q2 2002.

The O2 XDA has been developed by O2 together with Microsoft as a GPRS PDA. Based on Microsoft Pocket PC 2002, it has a colour screen and offers mobile phone, email, fax, and Internet browser functionality. It includes over-the-air synchronisation, Outlook for calendar/contact/email, and RIM Blackberry Handspring Treo XDA will synchronise with Word, Excel and Packet PC. The roll-out of XDA devices will start in Q2 2002. It has already had great Figure 8 Service layer architecture trade press reviews including PC World: ‘one of the best products I have seen in a while’. Service Layer

Service Layer Application Tier

Architecture Third-Party Applications Applications To support the diversity of applications as Portal well as devices it is important for O2 to work on a common service layer architecture (see APIs Figure 8) to help assure customers of consistent service across the O footprint. 2 OSA Gateways API Gateways Web Ser vice This architecture also provides a common Platform set of interfaces for applications, which will support a volume and variety of applications that will not be achieved efficiently with a bespoke design for each service. The approach has been to adopt a flexible SMSC VMS MLC WAP MMS UM architecture with common building blocks to support direct and indirect channels, and applications that are voice or data orientated. Our approach to open application programming Core Core Core Core interfaces (APIs) is particularly to stimulate Network Network Network Network third-party applications and content, including the wholesaling of services to third parties for Access Access Access Access onward sale. This already applies in the SMS Network Network Network Network arena and is likely to extend in future with OUK OIreland O Netherlands OGermany multimedia messaging (MMS). Areas such as 2 2 2 2 voicemail and location (VMS and MLC) are all likely to require some tailoring for third parties, as we already have done for WAP content. Figure 9 Messaging Our intention is also to ensure we can develop applications once, and to multiple operators, in order to maximise both economies of scale and speed to market. Time to revenue is a critical factor in today’s service design. The applications layer also requires a consistency based on standards that support network and portal based applications, which require monitoring of network standards (3GPP and IETF) as well as application based standards (for example, GSM Association and WAP Forum). Our long experience in the mobile Internet arena since the launch of www.genie.co.uk in September 1997 has helped maintain O2’s credentials in mobile data leadership, with over 5 million subscribers to Genie across Europe today. Multimedia Messaging (MMS) Instant Messaging/Multimedia Messaging New products (Figure 9) that have been

The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 17 Figure 10 Network infrastructure architecture launched include instant messaging (IM) in PSTN/ISDN 2G January 2002 which offers a full IM link Circuit-Switched MSC with Microsoft MSN Instant Messaging, MSC Domain capability for conversational short Radio HLR messaging, PC and mobile IM client, and a Access live address book. This represented the Network IP Network GPRS ● Public UK’s first fully integrated IM solution. Packet-Switched Domain GGSN ● Private In Q1/2 2002 we are trialling multime- SGSN IP network dia messaging (MMS) to include a per- 2.5G message billing/revenue model and person-to-person (for example, photo) messaging. The service will be dependent on handset availability expected Q3 2002. Figure 11 ManxTelecom—3G showcase applications As part of the requirements for third- party involvement and assuring applica- Video telephony Online games Live and archive video tions anywhere we have set up Source O2 to support applications partnerships with ●●●Point-to-point video Download Short clips O2. This facility provides for interoperability services ●Rentals ●Information testing and prototyping, as well as being a ●Review and ●Entertainment front door and development facility in its tips/cheats own right. More details can be seen on www.sourceO2.com. Network Architecture

The traditional GSM architecture was enhanced with packet capability (2½G) Location services Information services Mobile office based on 3GPP standards. mmO was the 2 ●Push information ●Games ●Corporate intranet first to launch GPRS worldwide in June ●Pull information ●Email services 2000, and reached national coverage by the ●E- and m-commerce ●Sports ●Mobile workforce end of the summer that year. This reached ●Location-specific ●News advertising ●Public transport a full O2 Western European footprint by the spring of this year. Figure 10 brings out the ●Entertainment/gambling main differences between the circuit- and ●Job adverts packet-switched domains. The evolution to 3G will not be driven by the hype associated with spectrum auctions, but in particular will be driven by: • general availability of dual mode (GPRS/ Figure 12 3G R99: UMTS launch architecture 3G) handsets, • availability of compelling applications, and GSM HLR • deployment and stability of 3G infrastruc- Radio ture (network and billing safety). Packet-Switched Domain: IP Network ● Public Our experience on the Isle of Man with Cellular GGSN ● Private the Manx Telecom 3G trial has been very SGSN IP Network successful in many respects. It is the first network outside Japan to launch 3G worldwide and it has provided valuable lessons on this new technology; it has also Circuit-Switched PSTN/ISDN Domain MSC enabled customers to trial the new services. MSC Most of all it has provided a very fertile test ATM/64K Network bed to trial new applications generating UMTS strong partnership lessons for the future Radio and hopefully a lot of goodwill. Some of these applications can be seen in Figure 11. The 3G launch architecture is shown in risk. However, successful launch will be (largely based on standards agreements set Figure 12. This is based on 3GPP Release dependent on the availability of dual-mode in 1999), the first enhancement is termed 99 standards. The initial release builds on 2G/3G terminals. release 4. The major enhancements the GSM and GPRS core network platform envisaged are to the packet-switching and adds a new air interface using Futureproofing 3G Mobile capability, particularly the addition of wideband code-division multiple access enhanced quality of service for sustainable (CDMA) technology. This approach Further enhancements to the 3G architec- real-time sessions. Some enhancements to leverages the GSM core technology and ture have been envisaged. Whilst the the circuit-switch area include the addition roaming capabilities and reduces launch launch architecture is termed release 99 of a media switching gateway and more

18 The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 Figure 13 R4: Enhanced UMTS architecture

Enhanced QoS for server-based control architecture. This SCP GSM sustainable real-time HLR release 4 architecture is shown in Fig- Radio sessions ure 13. Many of the network vendors IP Network already have release 4 solutions planned Cellular IP Network ● Public GGSN ● Private for early next year. SGSN The thrust towards IP multimedia is largely being handled in release 5 (see Figure 14). This supports real-time multimedia IP applications, but will require MSC Server PSTN/ISDN major changes to infrastructure. Also it Media offer significant cost savings and revenue Circuit Domain Gateway potential, but does still have some risks UMTS associated with it as the standards are not Server-based control Added switching Radio gateway yet complete. architecture ‘Many-to-many’ gateway As a release it is much more IP- to server linkage orientated whereby the call server for call and session control is via session initiation protocol (SIP). It also introduces a home switching or 2G (GSM) domain, with considered and discussed in the standards subscriber server (HSS), or evolved home services now based on IP protocols and community. The architecture option shown location register (HLR) for user information procedures. in Figure 15 includes: on roamers to GSM. Generally there is Future concepts such as an ‘all IP’ • wide area IP-based architecture, much less dependency on the circuit- mobile network architecture are now being • greater server usage,

Figure 14 R5: IP multimedia

Shared application control Call server for call/session Home Subscriber Multi-vendor platforms control via ‘SIP’ Server (HSS) Linkage to legacy network Evolved HLR IM User information GSM Application Roaming to GSM HSS Radio Server (HLR) Call Cellular Server IP Network ● IP Network Public GSN ● GPRS Elements Private

MSC Server and Gateway Media CS Domain Gateway PSTN/ISDN

UMTS Reduced role Media gateway Radio for CS platforms connections to legacy

Figure 15 All-IP mobile network architecture

Wide area IP-based IM Call architecture Application Server Greater server usage Server Radio HSS Access (HLR) Components IP Network RNC GSN IP-Based Node B ● Public Servers Mobility ● Private

BTS Media BSC PSTN/ISDN Gateway GSN Media IP-based RAN Servers procedures Gateway Wider usage of IP mobility mechanisms

The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 19 • wider usage of IP-based mobility Figure 16 WLANs in the wireless landscape mechanisms, • IP-based RAN procedures, and Wireless Wide Area Network (WWAN) • distributed service platforms. ● Metro/geographical area ● Ubiquitous public connectivity Wireless LANs with private virtual networks Wireless Local Area Network (WLAN) Mobility ● Public or private site or campus The role of wireless LANs will depend on ● Enterprise/premises application Vehicle market and regulatory factors in equal voice and data network extension measure. On the market side it is clear that GSM Wireless Personal Area Network Wireless LAN technology will offer some Walk GPRS (WPAN) Outside key data-rate advantages for low mobility Campus ● Personal or location specific market needs (see Figure 16); however, Fixed UMTS ● Proximity-based services/info

there are still come uncertainties around HiperLAN2 sync/cable replacement/voice spectrum pricing and availability, security, Walk DECT 802.11a and data interworking technology standards and product availabil- 802.11b

Within Fixed/ LAN ity. Campus Bluetooth 802.11 Desktop In O2 we see wireless LAN as a comple- mentary solution to both 2½G and 3G. In 0.1 1 10 100 Mbit/s particular wireless LAN high-speed access User Bit Rate, Datacommunication Services is an excellent low-mobility compliment to high-mobility wide area cellular. Market needs can be envisaged for hot spots such as high-speed access at airports, conference Figure 17 WLAN/GPRS integration scenarios centres, shopping malls, schools, libraries, and hospitals. By linking wireless LAN to cellular, mobile operators can however provide significant customer value in areas Circuit-Switched MSC PSTN/ISDN such as: Radio MSC Domain • authentication and billing relationships Access Network HLR (for example, single monthly bill and service support); GPRS IP Network • secure communications environment and ● Public Packet-Switched trusted relationship; GGSN ● Private • seamless roaming and hand off between SGSN IP Network wireless LAN and GPRS/3G networks; and • access to a wide range of applications/ services (for example, MMS). ● Loose-coupling scenario — The architecture for a wireless LAN/ Through AAA, HLR for authentication, authorisation, WLAN billing purposes GPRS scenario could include either a loose- AAA — Available today or tight-coupling scenario as shown in ● Tighter-coupling scenario Figure 17. — Through GGSN, SGSN for seamless roaming and hand-off Overall there are some technical — Expected to be available soon challenges that remain and some network integration choices that need to be made. These need to be based on market demand, We are seeing a challenging competitive http://www.text.it national regulatory policies, and the most world of communications based on http://www.mda-mobiledata.org relevant business models. However, we requirements of increased volume (of believe that wireless LANs will be comple- usage), value and variety of applications in 3 WAP Forum. http://www.wapforum.org mentary to GPRS and 3G in meeting overall the wireless world. Our architecture customer needs. evolution, and third-party initiatives 4 GSM Association.

around source O2 and APIs are all designed http://www.gsmworld.com Summary to support a wider range of applications solutions to meet future customer needs. 5 MANX Telecom. Our approach to technology architecture In a world of applications anywhere our http://www.manx-telecom.com puts a lot of emphasis on providing architecture is designed to be standards- services to GSM/GPRS customers today, based, flexible yet cost-effective, and 6 NTT DoCoMo. but retains an eye on the future. Through sufficiently robust to meet future needs http://www.nttdocomo.co.jp/english/ the architecture evolution illustrated in across the O2 footprint. this article we can see a clear evolution 7 The Future of Wireless Communications. into 3G and beyond into an all IP net- References Williams Webb, editor (plus authors), work world. Maintaining this view is Artech House. important in meeting current customer 1 3GPP. http://www.3GPP.org demands and providing cost effective 8 BT Technology Journal, Mobile Theme. Jan. network plans. 2 Mobile Data Association. 2001, 19(1).

20 The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 Acknowledgements Biographies

We thank our colleagues Dr Mehmet

Unsoy, Chief Wireless Architect, mmO2 and Alan Clapton, Head of Technology Assess-

ment, mmO2 for their contribution to the design and development of this architecture and above article. Mike Short Fred Harrison

mmO2 mmO2 Glossary

Mike Short is Vice President, Products and Fred Harrison works in mmO2, where he is

3GPP 3rd Generation Partnership Project Services Technology, mmO2. His career spans responsible for directing efforts on mobile API Application programmers interface 28 years in electronics and telecommunica- standards. He has been involved in the work CDMA Code-division multiple access tions, with the last 15 years in mobile of 3GPP, the IETF, WAP Forum, GSM CS Domain Circuit-switched domain communications. He was appointed Con- Association and the 3G.IP Focus Group. He GGSN Gateway GPRS switching node tracts Director of Cellnet in 1989, dealing studied Electronic Engineering at Southamp- GPRS General packet radio system with infrastructure investments and UK ton University, graduating in 1978. He GSM Global system for mobile communi- interconnect agreements. In 1993, the focus started his career with BT, working on the cations moved to establishing Cellnet’s GSM service. introduction of optical fibre and then later HLR Home location register He was elected Chairman of the GSM on microwave radio developments for short- HSS Home subscriber server Association for 1995/96, and served on its haul digital links. In 1990, he moved to IETF Internet Engineering Task Force Executive Board for 3 years. He also is a Cellnet, where he was responsible for the IM Immediate messaging member of UK SMAG (Spectrum-Ministerial overall design and planning of Cellnet’s radio IP Internet protocol Advisory Group) and chaired the GSM network. He then spent two years in BT ISDN Integrated services digital network Association Data Task Force 1999/2001. He Group Technology prior to the formation of LAN Local area network was also elected to the WAP Forum Board BT Wireless, subsequently demerged into

LBS Location-based services 2000/2, and as Chairman UK Mobile Data mmO2. In 1998/9, he took a major role in M-Commerce Mobile commerce Association in 1999 (renewed for 2002). He establishing the new third-generation MDA Mobile Data Association served as Vice President UK FEI 1998/2001 partnership project standards body (3GPP). MLC Mobile location centre and led FEI mobile/environmental commit- He is an active member of the IEE. He took a MMS Multimedia messaging service tees. He was appointed Vice President in July leading role in developing and presenting the MSC Mobile switching centre 2000. His focus today is on third-generation 1994/5 IEE Faraday Lecture Tour ‘Making OS Operating system (UMTS) cellular, mobile data and steering Waves’, and he is currently conference

OSA Open services architecture mmO2 technology assessment, industry committee chairman for the Third Interna- PDA Personal digital assistant relations and standards from GSM evolution tional Conference on Mobile Communication QoS Quality of service towards UMTS. Technologies 3G 2002. RAN Radio access network SDK Software developers toolkit [email protected] [email protected] SGSN Serving GPRS switching node SIP Session initiation protocol SMS Short message service SMSC Short message service centre UM Unified messaging UMTS Universal mobile telecommunica- tions systems VMS Voice messaging server VPN Virtual private network WAP Wireless application protocol

The Journal of The Communications Network ● Volume 1 Part 1 ● April–June 2002 21