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Network Models
For
Converged Fixed And Mobile Telephony
Dual-mode phones combining cellular and WiFi/Bluetooth connectivity with voice over IP require appropriate network solutions to benefit fully from their new capabilities
As communications services are evolving, user are increasingly faced with a confusion of devices, subscriptions and numbers; they are crying out foe simplicity. Many users have a fixed line telephone at home, a phone in the office and a mobile phone, but most want just one phone for fixed and mobile telephony with a common directory, a common voice mailbox and a common set of services when at home, at work or traveling, They don't want to have to worry about what network is available, which tariff they should select or have to carry multiple devices for every eventuality
New technology combining Voice over Internet Protocol (VoIP ) and dual-mode phones, with both cellular and WIFI connectivity, can offer a sophisticated service to users in a very simple and easy to understand package. To benefit fully from these new services, the network solutions must perform some essential functions, including seamless roaming between enterprise or home networks and any public Wireless Local Area Network (WLAN) hotspots or any cellular network when on the move.
This article focuses on the solutions that realize seamless mobility between access networks for voice connections. These are the first step towards a common set of fixed-mobile solutions, which will be fully realized with the IP Multimedia Subsystem (IMS) architecture IMS is opening up new opportunities for a wide range of advanced services, such as videotelephony, which can be developed quickly within the service delivery environment and delivered with the IMS application server.
Terminal and Service Evolution
In the enterprise, the wireless extension to the LAN offers a convergent acces infrastructure for both voice and data, allowing digital wireless phones – Digital Enchanced Cordless Telecommunications (DECT) and Personal Wireless Telecommunications (PWT) – to be replaced by Voice over WLAN (VoWLAN) phones. In most cases, these will not be simply VoWLAN phones, but will also incorporate WiFi and cellularconnectivity.
Residential users subscribing to a VoIP service using a Session Initiation Protocal
“In June 2004, ABI Research predicted that dual-made phones will lead the VoWLAN handset market in 2008 with more than 30 million handsets being sold per year, comparaed with roughly 6 million softphones and around 1 million VoWLAN-only phones intended for use in specific vertical markets with dedicated onsite only mobility solution”
( SIP ) based call server, can use the first VoWLAN SIP phones on the market. These phones enable them to make and receive phone calls within the WLAN coverage area of their homes. As in the enterprise, the pure VoWLAN phon will be progressively replaced by a dual-mode phone.
In June 2004, ABI Research predicted that dual-mode phones will lead theVoWLAN handset market in 2008 with more than 30 million handsets being sold per year, compared with roughly 6 million softphones ( software installed on laptop and on personal digital assstants ) and around 1 million VoWLAN-only phones intended for inspecific vertical markets with dedicated on-site oly mobility solutions ( e.g. hospitals, warehouses[1] ) .
Although the situation is evolving rapidly, mobile phones with Bluetooth / cellular connectivity are currently far more common and cheaper than WiFi / cellular handsets. These phones can also be used to carry voice over Bluetooth if they support the Cordless Telephony Profile ( CTP ) standard.
Two main solutions can be envisaged to make these dual-mode phones work seamlessly. The first solution, which is based on Unlicensed Mobile Access ( UMA ) technology, allows real-time handover between access networks. However, it is only suited to mobile operators, or possibly Mobile Virtual Network Operators ( MVNO ) ; it can be used for residential users, both at home and within public hotspots, and for enterprise ( IP ) Centrex solutions. The second solution, based on SIP, is the Alcatel Intelligent Mobile Redirect
solution |
UMA |
IMR |
Control protocol |
UMA |
SIP |
LAN access technology |
WiFi/Bluetooth |
WiFi/Bluetooth |
Cellular access technology |
GSM/GPRS |
All(GSM,CDMA.ect…) |
IMS support |
Yes |
Yes |
Coverage extension |
All services |
Voice only (other mobile services through regular cellular access |
( IMR ) . This solution can be deployed by all operators and used by everyone, including large enterprises.
IMR and UMA allow a user to be reached on one device using one phone number regardless of where he or she is located. Both solutions accomplish this by:
• Automatic selection of the most convenient access network ( e.g. cellular access network or WiFi / Bluetooth access network ) which generally includes a broadband network using VoIP.
• Rerouting of incoming calls to the appropriate access network.
Table 1 summarizes the main features of both solutions.
Real-time Handover with UMA Technology
UMA is a flexible, fully open fixed/mobile convergence solution that can be used to extend GSM/GPRS coverage in residential markets ( home and public hotspots ) and the Small Office / Home Office ( SOHO ) market. Call are delivered to the user via WiFi ( or Bluetooth ) access points and mobile handsets equipped with WiFi ( or Bluetooth ) . UMA established a standard for seamless hand-off and roaming between a cellular network ( e.g. GSM/GPRS ) and fixed IP-based wireless networks ( e.g. WiFi or Bluetooth, or even DSL ) . This is applicable for data, but the important application is voice. The UMA specification has been transferred to the Third Generation Partnership Project ( 3GPP ) standardization body under the name Generic Access Network ( GAN ) .
Solution description
As show in Figure 1, this solution is based around the Generic Access Network Controller ( GANC ) , which mimics the role of a Base Station Controller ( BSC ) . The mobile core network is not affected by the UMA solution; the GANC is seen as a standard BSC that is connected via the standard A and Gb interfaces. The detailed architecture of Alcatel's UMA solution is show in Figure 2.
Voice and data GSM/GPRS services, including the Shot Message Service ( SMS ) , Multimedia Message Service ( MMS ) , Wireless Application Protocal ( WAP ) and location-based services, are provided in a seamless manner whatever the radio technology. This also enables GSM/GPRS indoor coverage to be extended using a low cost DSL modem with WiFi / Bluetooth access points ( at home or public hotspots ) . Moreover, the GANC connected to WiFi / Bluetooth access point via the Internet or any IP network, provides simultaneous access to circuit and packet domain services, like the Dual Transfer Mode ( DTM ) feature expected in GSM/GPRS networks by the end of 2005.
When a user with a dual-mode handset moves within range of an unlicensed network(WiFi), the device contacts the GANC over the IP access network. First the user is authenticated and authentication, Authorization and Accounting(AAA) server using Home Location Register(HLR) data from the GSM network. The user is then authenticated and authorized for GSM/GPRS services by the core network via the standard GSM security protocol based on the Subscriber Identity Module(SIM), in a transparent manner for the GANC. Signaling and user data are routed through the GANC to and from the device, rather than through the cellular network, using an IP Security (IPSec) tunnel that provides data integrity and ciphering.
Handsets
To enhance the user experience and meet the requirement for seamless mobility in an optimal way, the user terminal is equipped with an intelligent software client. This client automatically selects the preferred access technology while in idle mode (roving) and performs seamless handover between the available access mode according to the operator's / user's preference and policies
Access point
The access point, which can be Bluetooth or WiFi, is generally connected to the GANC over the public Internet. It has no specific GAN-related features nor configuration data, and is fully transparent to the GSM/GPRS user and signaling data
Generic Access Network Controller
The GANC manages and security all subscriber access to mobile voice, data and multimedia services from various WLAN locations. In addition, it facilitates automatic seamless roaming and handover between mobile radio access networks (GSM/GPRS) and a WLAN. It provides the following functionality:
• Interworking between the IP access network (e.g. DSL) and the mobile GSM/GPRS core network through the existing A and Gb interfaces.
• User access security and registration for GAN access.
• Tunneling of GSM information (voice data and signaling) to/from the user terminal (e.g. bearer establishment, management) via a secured IPSec tunnel.
Evolution toward IMS
IMS is access independent, enabling it to be used with fixed, cellular and WiFi access networks like UMA that combine technologies. When IMS services are available on the cellular network, the same IMS services (videotelephony, instant messaging, etc) are also available unchanged in UMA.
Universal SIP-based Solution with IMR
Alcatel's IMR solution is a flexible , fully open fixed-mobile convergence solution that can be used to build new services for both the enterprise and residential markets. The principles of the solution are illustrated in figure 3, while the detailed architecture is shown in figure 4.
Calls are delivered to the user via WiFi (or Bluetooth) access points and mobile handsets equipped with WiFi (or Bluetooth ) access points and mobile handsets equippeb with WiFi ( or Bluetooth) Presence within the WLAN ( or Bluetooth )coverage area is managed using standard SIP messages to the service control point. These SLP messages can be generated either by the Enterprise mobility server ( EMS ) , by a specific access point or by the mobile handsets.
Solution description
Handsets
The handset has two air interfaces; one for communicating with the home / office network. The architecture does not depend on the handset radio technologies; it supports second and third generation mobile communications as well as WiFi ( or Bluetooth ) for short range wireless communications. Although early implementations will be based on Bluetooth, WiFi will be the preferred interface and is therefore described here.
The handset must be equipped with embedded software to allow VoIP communications over the short-range wireless protocol.
Enterprise/home network
The enterprise or home network acts as the gateway between the handset's short-range wireless protocol and the rest of the network. In its simplest form, the home/office network is a DL modem with the handset. The network intelligence is informed of the user's presence by a SIP message sent from the handset when a user enter(through WiFi) and leaves (through cellular) the home network.
In the enterprise, the deployment of multiple access points to ensure coverage throughout the site requires fast handover mechanisms (to be standardized in IEEE 802.11r in future). Also, the large number of user requires support for Quality of Service (QoS) mechanisms, such as WiFi MultiMedia(WMM), which is to be standardized in IEEE 802.11e. In any case, security is ensured using WiFi Protected Access (WPA/WPA2), which has been standardized in IEEE 802.11i. In addition an IPSec tunnel provides data integrity and ciphering between the enterprise and carrier network[2].
A mobility server is required in the enterprise to manage user presence, via SIP, in the enterprise WLAN.
Network intelligence
The network intelligence part of the architecture is made up of the Alcatel 8690 Open Service Platform (OSP) and a softswitch, such as the Alcatel 5020 Softswitch. The OSP is responsible for number translation and routing the call to the correct network based on the whereabout of the user, as well as for making routing decision based on the dialed number and presence information. This implies that the OSP, MSC, public Switched Telephone Network (PSTN) switch and softswitch communicate during call setup
Flexible numbering plan
One of the most useful aspects of IMR is that a user only needs to cive out one number to family friends and collegagues. This is possible by having two or even three numbers associated with the handset one the user knows about (visible number) and the others the user doesn't know about (invisible numbers) .The visible number is the one that is called,allowing it to be captured by the OSP and routed,while the invisible numbers correspond to a fixed location and a mobile location .IMR is completely flexible ,allowing both the visible and the invisible numbers to be associated with any of fixed , mobile or non-geographic specific numbers.depending on the needs of the operator. This feature is important since it support different potions for interconnecting and terminating calls on other provider's networks
Evolution to IMS
IMR allows the service to evolve step-by-step as a result of its multiple deployment scenarios. The service provider can start by deploying the solution over the existing PSTN, redirecting mobile calls to the PSTN usijng PSTN-based access points. Once the service concept has become established,evolution to a broadband service becomes a logical next step. This allows the provider to take intermediate steps toward a more homogeneous SIP-based architecture for which IMS is the reference.
All providers can deploy IMR knowing that they are deploying a forward-looking architecture that will support the move towards a converged IMS-compliant infrastructure (see Figure 5 ) IMS opens up new opportunities for a wide range of additional service ,including videotelephony video on demand and instant messaging of the radio access technology, ims will facilitate the introduction of new radio technologies such as WiMax
Residential users
A dual-mode terminal offers the convenience of the a single device that supports all services: single voice mailbox,single directory,single list of missed calls ,access to the same services(SMS,MMS,etc ) .In addition,IMR and UMa solutions extends the reach of the mobile phon into areas not correctly covered by GSm .Both IMR and UMA automatically select the most suitable network (usually the one offering the cheapest tariff) and provide all the required security mechanisms (authenticaton, confidentiality,etc)
Enterprise users
IMR and UMA solutions reduce the total cost of ownership for telecom services as only a single handset has to be provided and maintained instead and maintained instead of two. Optimize routing also helps to reduce an enterprise,phon bills.
In additions ,the introduction of VoWLAN in the enterprise reduces cabling requirements (only WiFi access points need to be connected), and voice and data service a share a single infrastructure. Wireless phones also eliminate the modifications required when employees are relocated from one office to another.
Operator Benefits
Converged fixed-mobile solutions make it possible to offer services bundles that are targeted at strategic market segments (e.g. high-end residential ,students or specific enterprise segments) .allowing
- Increased customer stickiness (reduced churn)
- Increased market share in the target segment.
- Cross-selling of services (i.e. selling mobile services to an existing user of the operator's fixed network)
The solutions helps protect margins by using optimized routing to the operator,s benfit routing calls on the most efficient network (taking into account the change of tariff, incremental operating expenses,and the cost and revenie from interconnection fees) .In addition, it allows arditraging of tariff distortions ,for instance ,generating revenue from incoming calls through higher interconnection fees.
More importantly ,combined fixed-moblie solutions allow operators to move into the VoIP business, making it unnecessary for their customers to move to an alternative solutions .There is a risk of a lowering of revenue from some subscribers,but this can usually be avoided by detailed segment analysis to isolate profitable and unprofitable service users
Business case analysis shows that the value proposition (see Table 2) depends om a lage number of parameters, including
• service provider's position: market share,presence in fixed and mobile (own operation or through MVNO deal)
• Taget segment: high-end or low-end residential, type of enterprise (single or multiple sites, large lage or small, heavy mobile usage or not)
• Tariff policy: subsidization or not of access point and terminals, service subscriptions
• Regulations : possibility to merge fixed and mobile activities,to create bundles to subsidize access to the service
• Interconnection conditions between network and operators.
• Competitive situation
Overall, the value sometimes lost by providing lower cost calls can be offset by the increased stickiness of the user which in turn increases customer lifetime value
Conclusion
Dual-mode phones comblining cellular and WiFi/Bluetooth connectivity with VoIP require appropriate network solutions to realize their full benefits. Depending on the targeted user (residential or enterprise )and the nature of the operators (fixed,mobile,MVNO) various solutions are possible these can be divided into two main families:
• UMA-based solutions for residential and small office Zsoho) customers of mobile and MVNO operators
• IMR-based solutions with different flavors for all users and all operators.
All these solutions are now available with current wireless access technologies (mostly WiFi) and will evolve to take into account new technologies such as WiMax. The introduction of these new radio accesses will be facilitated by the IMS architecture, which offers a consistent set of services that are independent of the access technology
Alcatel can offer these solutions today thanks to its expertise in fixed,mobile IP and enterprise network.this expertise was recongniZed by BT who selected Alcatel as prime contractor for its BT Bluephone project, which will see Europe's first launch of a service that will enable users equipped with just one phone to roam across both fixed and mobile networks accessing a range of converged broadband services
BT Bluephone Project
On 18 may 2004 alcatel announced that the seven company consortium,of which it is head and prime contractor,has been selected to launch BT's groundbreaking “Proect Bluephone”
Admire contractor to the consortium, Alcate is drawing on its global project management expertise to act as solution intwgrator to the project andto u nite all seven companies behind a smooth roll out and implementation.
BT's Projct Bluephone is the first stage of BT's fixed-moblie convergence aspirations.The pioneering attempt,set for launch in 2005, will see BT offer customers a handset that will hook onto its own fixed-line system when used at home or fixed- mobile system system used at home or in the office but switch automatically to Vodafone's wireless network when on the move.
Refernces
1 P.Solis: Voice over WiFi ,ABI Research,2 nd Quarter 2004.
2 J-m Lauriol et al: “WLAN, a converged data and voice mobility solution for enterprise'' Alcatel technology white paper, Novermber 2004.
Philippe Laine is network stratrgy Manager in the Alcatel Network strategy Group,paris ,France.
( Philippe. laine@alcatel.fr )
Nicolas Drevon is an End-to-end mobile Network Solutions Architect in the Alcatel MCG/CTO,velize, france (Nicolas. Drevon@alcatel.fr )
Jean-Marc Cannet is Director, product and solutions Marketing, in the Alcatel Fixed solutions Division, Velizy,france
(Jean-Marc. Cannet@alcatel.fr )
