12-09-2014, 10:00 AM
THE ROLE OF INTERNET TECHNOLOGY IN FUTURE MOBILE DATA SYSTEMS
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Abstract
Mobile telephony and the Internet are the fastest growing businesses in the telecommunications market. This is why most operators and service providers are looking after the development of new services in both sectors and newcomers are expected to enter the arena. The mobile operators foresee an increasing share of their revenues coming from new data services, whilst Internet Service Providers (ISPs) are attracted from wireless technology and mobility services both to reduce costs within the last-mile segment and to enrich their market share providing ubiquitous access to the Internetobjective. The employment of the Internet technology, with its novel mobility and security extensions, seems to be the most attractive option for achieving that goal. In addition, the migration to a full IP network architecture even within each specific wireless domain will be another promising opportunity, already under consideration within several technical and standardization bodies.
INTRODUCTION
Mobile telephony and the Internet are the fastest growing businesses in the telecommunications market. This is why most operators and service providers are looking after the development of new services in both sectors and newcomers are expected to enter the arena. The mobile operators foresee an increasing share of their revenues coming from new data services, whilst Internet Service Providers (ISPs) are attracted from wireless technology and mobility services both to reduce costs within the last-mile segment and to enrich their market potential providing ubiquitous access to the Internet and corporate intranets.
IP SERVICES WITHIN MOBILE NETWORKS
Approaching the market of data communications, during the last few years the PLMN (Public Land Mobile Network) operators have begun to deliver data services to their customers. Currently available solutions for data transfer over the GSM network include the Short Message Service (SMS), that allows a basic e-mail exchange, and the traditional low speed Circuit Switched Data (CSD), that may be used to access Internet services. The main drawbacks of CSD are the very limited bandwidth capacity (9.6 kbps or 14.4 kbps depending on the employed coding scheme) and the sub-optimal use of the radio interface. A straightforward extension of CSD is the High Speed Circuit Switched Data (HSCSD) [1], which increases the transmission capacity by allocating to a single user up to 8 CSD channels. Anyway this solution still makes use of the radio resources in circuit switched mode and is therefore poorly optimized for the bursty traffic profile generated by most of Internet applications. Aiming to provide more bandwidth as well as a more efficient spectrum usage, most of GSM operators are about to deploy the General Packet Radio Service (GPRS), which is a fully packet oriented technology designed to support both IP and X.25. A further medium term evolution will be the migration to the 3rd generation mobile system (UMTS), which will include a new W-CDMA radio access and will be able to accommodate a wide range of data rates (from 144 kbps to 2 Mbps). This evolution will also encompass relevant changes in the user terminals technology. In the meanwhile, as a short-term approach to enable advanced data capabilities even on current technology mobile handsets, GSM operators are beginning to deliver WWW like services based on the WAP (Wireless Access Protocol) technology .
MOBILITY WITHIN THE INTERNET
The increasing diffusion of portable devices, such as laptops, PDAs and smart phones, have recently led to a growing demand for access to the Internet and corporate intranets independent of the technology and the point of attachment. Today's ISPs cope with these new user needs by offering a set of dial-up services including remote Internet access as well as secure access to corporate intranets established by means of tunneling protocols like PPP , L2TP and IPSec . Besides, most of current ISPs have joined together in confederations (e.g. iPass and GRIC ) to provide
ADVANCED IP MOBILITY PROTOCOLS
Mobile IP (MIP) [15] is the IETF proposed standard solution for handling terminal mobility among IP subnets and was designed to allow a host to transparently change its point of attachment to the Internet. MIP works at the network layer influencing the routing of datagrams and for this reason it can easily handle mobility among different media (LANs, dial-up links, wireless channels, etc.). As a main feature, MIP is completely transparent to applications in that no IP address changes are needed to allow mobility, but the mobile node (MN)
can communicate using its home address regardless of its
actual position in the Internet. This in turn also means that
every active TCP session survives to movements, thus allowing uninterrupted communications to wireless terminals.
The basic MIP protocol requires to assign two IP addresses to the MN: the first one is its home address (HAddr), which never changes and is used for identification purposes, and the other one is a care-of address (CoAddr), which is an address lent by the visited subnet used to determine the actual location of the mobile node. The CoAddr changes at every movement and is normally the address of a Foreign Agent (FA), e.g. a base station, acting as a local relay point for the MN. Packet routing with Mobile IP (Fig. 1) is based on the presence of a Home Agent (HA) within the home network that keeps trace of the MN CoAddr by means of a registration procedure and takes care of forwarding data traffic addressed to the MN while it is away from home.
EVOLUTIONARY TRENDS
The current development of innovative mobile data services is leading to the coexistence of several wireless overlay networks. On the other hand, the availability of advanced IP mobility protocols makes the Internet technology attractive for both the interworking between different networks and the definition of new wireless network architectures
OVERLAY NETWORKS
IP mobility services for wireless users are currently delivered over a variety of networks and technologies, including GSM, GPRS, satellite, wireless MAN (e.g. Metricom), WLAN and many others. However, none of these solutions can be considered really universal because each one is targeted to a specific set of services and applications and has therefore different characteristics in terms of geographical coverage, bandwidth, delay, etc. As a consequence, allowing transparent user roaming amongst different wireless networks will be the best way to deliver the widest range of services anywhere and in a cost effective way for both the user and the service provider. In particular it is expected that the same geographical region will be covered by several wireless overlay networks, so that it will be up to the user to decide when to switch from one wireless access to the other based on availability or cost/performance considerations [21]. For example, when in the office, the mobile user will typically perform data retrieval from the Internet through the local 10
INTERWORKING BETWEEN OVERLAY NETWORKS
Nowadays there is almost no integration between available mobile data networks, but each one has its own user authentication and mobility management procedures. Therefore seamless mobility among overlay networks cannot take place, but any user roaming to a new wireless domain is typically assigned a new identity (i.e. a new IP address) and any previously active communication session gets lost. To efficiently solve these problems, a common protocol for handling inter-domain user mobility has to be deployed and it is expected that in future mobile data systems the novel IP technologies described in section 4 will be used for that purpose. In particular it will be possible to deploy a common IP backbone to interconnect heterogeneous wireless IP networks and to rely on Mobile IP to manage user mobility among them.
A FULL IP PERSPECTIVE
A key role of IP in future mobile data systems will probably be the provision of efficient and cost effective interworking between overlay networks. Moreover, both cellular operators and ISPs, together with the relevant standardization bodies (mainly 3GPP [22] and IETF), are eagerly looking at the possibility of employing IP and its mobility and security extensions even within the specific wireless networks. Starting from traditional circuit switched data services on today’s PLMNs (e.g. GSM CSD), where there is no IP at all within the network, several architectural enhancements can be identified to end up with more IP oriented solutions.