Introduction

Activities towards next generation mobile communication are up to now technology driven. But, especially from an operator’s point of view, a system B3G has to deal with various aspects like user preferences, system requirements, network architecture, business model, security, and standardisation.
Mobile technologies are dominating the modern communication world. Third generation mobile systems are currently being rolled out. So far, most vision documents and discussions about B3G are focusing on wireless transmission technology issues. And in fact, generations were mainly characterized by the air interface in the past. But, the provisioning of mobile communication means more than just maintenance of the air interface. Various user expectations have to be met. Innovative services have to be developed to distinguish the operator’s offer from competitors. Complex value chains require reconsideration of business models and alliances. New technologies, especially in software technology, allow a more flexible reaction on changing market demands.

The wireless industry has grown at an awesome pace over the past decade. Consequently, more than half a billion subscribers to cellular services are now enjoying the benefits of staying connected while on the move. Most of these people use the Global System for Mobile Communication (GSM) or one of its close derivatives DCS 1800 or PCS1900 and therefore also benefit from personalized services with a high level of security as well as the possibility of worldwide roaming.
Internet is another branch of the telecommunication industry to have enjoyed similar dramatic growth, with the result that today an ever growing range of services is available through World Wide Web. This “network of networks” is accessed by users through a wired infrastructure operated by the traditional telecom or cable TV companies.
The introduction of mobile Internet brought about by the convergence of these two technologies is the future objective of industry professionals. At the same time, multiple enhancements are being implemented in both cellular mobile systems and Internet networking. The progressive introduction of the General Packet Radio Services (GPRS), Enhanced Data rates for GSM Evolution (EDGE) and the third generation of Universal Mobile Telecommunications Systems (UMTS) clearly illustrated this evolution.

Concepts for the Roadmap towards B3G
Mobile users have already outnumbered fixed users – at least in (Western) Europe – and this trend is expected to continue. These expectations and the experiences made in the industry by the 3G licensing underline the importance of having a realistic view on a roadmap towards the future. The industry players are developing possible roadmaps from their individual perspectives. An example of such a roadmap developed is given in the following figure.

Besides the technology-oriented approach, several other areas complement a complete B3G vision: Business model, user expectations, service and applications, networking, terminals and air interface. High attention should be paid to the services that are provided by B3G systems. It is the traditional role of the operator to bring these services to the customers. In this respect, a B3G system has to put the user and his or her services into the focus, not only the technology supporting it. The vision developed is “It is simple, it works, it is personalised”, combining the quality of the Telecom world (“it works”) with the possibilities of the IT world (“It is simple”). Personalisation to reflect the user preferences and the user context is the third issue.

A number of interesting observations can be made at this point. First, several major technological transitions occurred between the first and third generation systems. The cellular mobile industry has gradually moved from:
 High volume speech services to high volume/high speed data services
 Only circuit mode to circuit+packet mode transmission
 Isolated networks to interworking between networks
All these advances have resulted from the network centric and technology centric approaches adopted by the cellular industry. The access network first evolved from GSM to EDGE and then to UMTS, while the core network moved only from circuit mode to circuit and packet mode operation.

It could thus be conjectured that:
 The time has come to start looking “ Beyond 3G”
 The technology and service perspectives of the fourth generation (4G) and the regulatory aspects, like spectrum availability, should be clarified. Additionally, the accelerating pace of technology development may make it possible to introduce 4G systems within the normal ten year timeframe. New 4G may coexist alongside 3G networks at a time when the latter will be undergoing enhancements.
 The “network centric” evolution should be complemented by a “user centric service implementation”.

Key Drivers

Subscribers on the move currently benefit from seamless “person to person” communication and access to voice, data and some multimedia services. However, future generation wireless communication systems will have to support:
 An extraordinary large number of users seeking to network with one another. In fact, the present concept of “person to person” networking to exchange information needs to be extended to include “person to machine” and “machine to machine” networking.
 Availability of intelligent spaces (i.e. a space in which information is being radiated using radio signals which can be easily captured by suitable devices), and hence the ability to implement Personal Area Networks (PAN) of intelligent appliances, as well as interworking between PANs and their immediate local, residential and/or professional environments.
 Ubiquitous connectivity to real-time and transactional services, as well as high speed access to multimedia (e.g. video streaming)
 Wireless access to location based and context related information for work and leisure.
Several technologies for the wireless transmission of information are currently available, including:
 Direct Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB) for wide area broadcasting.
 GSM, GPRS, EDGE and WCDMA for wide cellular networks.
 Local Multipoint Distribution Service (LMDS) and Microwave Multipoint Distribution Systems (MMDS) for fixed wireless access.
 IEEE 802.11, 11a, 11b and HIPERLAN2 for wireless local area networking based on cellular operation or on peer to peer networking. The latter mode is offered by Bluetooth for short range communications and PAN implementation.
Nearly all these technologies include arrangements for accessing Internet services.
As shown in the following figure, each of these technologies has been optimized for operation over a particular range of service bit rate vs. user speed of mobility. Wide area cellular systems have reached a higher level of maturity than short range systems.

In this varied environment, “Beyond 3G” solutions must provide ubiquitous connectivity of/for slow and fast moving users. One promising implementation could be based on a common Internet Protocol (IP) core network interworking with multiple access networks for broadcast, wide area cellular and short range communications.

Rather than to come up with yet another general vision, we have identified several scenarios for key drivers of systems beyond 3G:

• Personalisation
• Seamless Access
• Quality of Service
• Intelligent Billing

The following is a non-exhaustive list of technology and regulatory issues related to the introduction of “Beyond 3G systems”.

Technology issues
 Protocol mechanisms have to be designed to allow ad hoc networking between appliances with varying capabilities.
 The advantage of mobility offered by wireless is somewhat circumvented by additional security problems. Mechanisms need to be designed for user authentication, call privacy and non-repudiation guarantees. The use of appliances with varying capabilities at different locations complicates this issue.
 Implementation of horizontal handover (between cells of networks with the same radio characteristics) and vertical handover is essential to provide seamless connectivity for multi-mode appliances. The design of handover algorithms might have to include Quality of Service (QoS) criteria, such as the availability of a higher bit rate bearer in a new cell.
 IP protocols will need to be enhanced to meet the expectations of wireless system designers. IP header compression and the tuning of Transmission Control Protocol (TCP) parameters for data streaming over the wireless interface are just two examples.
 Considering the differences in user densities in different environments, it might be difficult to manage the interaction between the mechanisms for radio resource management in wide area cellular systems and those for campus networks.
 Multi-mode appliances will have to implement software configurable hardware architectures.

Conclusion
In view of the explosive growth of wireless communication over recent decades and the lead time required for the introduction of new technologies, the time has come to develop a clear perspective of “Beyond 3G” wireless systems and services. This “Beyond 3G” vision should exploit two complementary approaches: one based on “evolution through a network centric view” and the other based on the recently introduced “user centric view”. The “person to person” communication concept needs to be enhanced to include “person to machine” and “machine to machine” networking for ubiquitous connectivity to Internet services.
Interworking between access networks implementing enhanced versions of current technologies for broadcast, cellular and short-range communications should provide a good first solution for “Beyond 3G services”. This technology map can be extended to include access technologies for transmission at more than 50Mbps for fast moving users as well as ultra wide band systems for wide area coverage. However, several interesting technological challenges and regulatory issues need to be addressed before the “Beyond 3G” vision becomes a reality.