A “fourth generation” of wireless systems, likely to appear after the successful deployment of the current third generation, is frequently debated these days. This article presents some of the results of the fourth generation wireless project (4GW) of the personal computing and communication. 4G is supposed to be an all IP network with higher bit rates, enhanced multimedia services, smooth streaming videos, worldwide access/roaming capability, intelligent software as driven technique. OFDM-UWB (orthogonal frequency division multiplexing – ultra wide band) as representative standard FDMA, TDMA,CDMA as multi-access techniques, low cost and tight security network.
Mobile communications and wireless networks are developing at an astounding speed, with evidences of significant growth in the areas of mobile subscribers and terminals, mobile and wireless access networks, and mobile services and applications. The present time is just right to start the research of 4G mobile communications because of:
- Possibility, according to the historical indication of a
generation revolution once a decade, and now we are
near the end of 3G standardization phase and the
beginning of 3G deployment.
- Necessity: according to 3G goals, 3G is necessary but
not sufficient to the mobile communication strategy, in
which many problems are only partly solved and there
are still many problems left to be solved in the next
generation, i.e. 4G.
There is plenty of related research on the next generation mobile communications [1-4], and the 4G topics are becoming hotter and hotter. However, most of the ongoing research can be classified into two different classes:
v Many of the related 4G research focuses mainly on one specific technical area, such as distributed computing, mobile agents, multimedia services, or radio air interfaces, etc.
v Some pieces of research are interested mainly in 4G scenarios from the standpoints of service provider or user, or a market analyst, from a less or non-technical viewpoint.
II. Mobile Communications Review
The history and status of mobile communications are shortly listed in the following, together with the respective evaluations on the chief contributions.
- Traditionally, wireless systems were considered as an auxiliary approach that was used in regions where it was difficult to build a connection by wireline.
- 2.5G extended the 2G with data service and packet switching methods, and it was regarded as 3G services for 2G networks. Under the same networks with 2G, 2.5G brought the Internet into mobile personal communications. This was a revolutionary concept leading to hybrid communications.
- 3G is deploying a new system with new services instead of only providing higher data rate and broader bandwidth. Based on intelligent DSP techniques, various multimedia data communications services are transmitted by convergent 3G networks.
MOBILE COMMUNICATION HISTORY AND STATUS
|Driven Technique||Analogue signal processing||Digital signal processing||Packet switching||Intelligent signal processing|
|Representative Standard||AMPS, TACS, NMT||GSM, TDMA||GPRS,I-MODE, HSCSD, EDGE||IMT-2000(UMTS, WCDMA, CDMA2000)|
|Cellular Coverage||Large area||Medium Area||Medium Area||Small area|
|Core Networks||Telecom networks||Telecom networks||Telecom networks||Telecom networks, Some IP networks|
|Service Type||Voice Mono-service person to person||Voice, SMS Mono-media person-to-person||Data Service||Voice, Data some Multimedia person-to-person|
III. 4g Features
- Different 4G feature frameworks have been defined from the standpoints of service subscriber, service provider, researcher and engineer. In the following we give some representatives of 4G perspectives.
- Other than the words “more”, “any” and/or “all” are preferred over expressions used by some others, e.g. anyone can communicate with anyone else, anywhere and anytime, or enjoy any service of any network operator, through any network of any network service provider. These sentences are truly attractive from a subscriber’s viewpoint, and they sound quite like advertisements or word games.
- DoCoMo introduced the concept of MAGIC for the vision of 4G :Mobile multimedia; Anytime, anywhere, anyone; Global mobility support; Integrated wireless solution; and Customized personal service, which mostly focused on public systems and treat 4G as the extension of 3G cellular service.
- A broader, all-encompassing perspective of 4G was proposed in , according to which 4G will encompass all systems from public to private, operator-driven to ad-hoc, broadband to personal area and ad hoc networks, 2G systems to 3G systems. It focused mainly on personalized services.
Iv. Key Challenges and their solutions
|Key challenges||Proposed solutions|
|Multimode User Terminal||To design a single user terminal that can operate in different wireless networks, and overcome the design problems such as limitations in device size, cost, power consumption, and backward compatibilities to systems.||A software radio approach can be used: the user terminal adapts itself to the wireless interfaces of the networks|
|Wireless System Discovery||To discover available wireless systems by processing the signals sent from different wireless systems (with different access protocols and incompatible with each other).||User- or system-initiated discoveries, with automatic download of software modules for different wireless systems|
|Wireless System Selection||Every wireless system has its unique characteristic and The proliferation of wireless technologies complicates the selection of the most suitable technology for a particular service at a particular time and place.||The wireless system can be selected according to the best possible fit of user QoS requirements, available network resources, or user preferences|
|Terminal Mobility||To locate and update the locations of the terminals in various systems. Also, to perform horizontal and vertical handoff as required with minimum hand over latency loss||Signaling schemes and fast handoff mechanisms are proposed in|
|Network Infrastructure and QoS support||To integrate the existing non-IP-based and IP-based systems, and to provide QoS guarantee for end-to-end services that involves different systems.||A clear and comprehensive QoS scheme for UMTS system has been proposed This scheme also supports interworking with other common QoS technologies|
|Security||The heterogeneity of wireless networks complicates the security issue. Dynamic reconfigurable, adaptive, and lightweight security mechanisms should be developed.||Modifications in existing security schemes may be applicable to heterogeneous systems. Security handoff support for application sessions is also proposed|
|Survivability||To minimize the failures and their potential impacts in level of tree-like topology in wireless networks.||Fault-tolerant architectures for heterogeneous networks and failure recovery protocols are proposed in|
|Multi Operators Accounting and billing System||To collect, manage, and store the customers’ information from multiple service providers. Also, to bill the customers with simple but detailed information.||Various billing and accounting frameworks are proposed in|
|Personal Mobility||To provide seamless personal mobility to users without modifying the existing servers in heterogeneous systems.||Personal mobility frameworks are proposed. Most of them use mobile agents, but some do not|
Mobile Station Multimode User Terminals
In order to use the large variety of services and wireless networks in 4G systems, multimode user terminals are essential as they can adapt to different wireless networks by reconfiguring themselves. This eliminates the need to use multiple terminals (or multiple hardware components in a terminal). Figure 1 shows the design of an ideal software radio. The analog part of the receiver consists of an antenna, a bandpass filter (BPF), and a low noise amplifier (LNA). The received analog signal is digitized by the analog/digital converter (ADC) immediately after the analog processing. The processing in the next stage (usually still analog processing in conventional terminals) is then performed by a reprogrammable baseband digital signal processor (DSP).
Wireless System Discovery
To use 4G services, multimode user terminals should be able to select the target wireless systems. In current GSM systems, base stations periodically broadcast signaling messages for service subscription to mobile stations.
In order to provide wireless services at any time and anywhere, terminal mobility is a must in 4G infrastructure. Terminal mobility allows mobile clients to roam across geographic boundaries of wireless networks. There are two main issues in terminal mobility: location management and handoff management. With location management, the system tracks and locates a mobile terminal for possible connection. Location management involves handling all the information about the roaming terminals, such as original and current located cells, authentication information, and QoS capabilities.
In addition to terminal mobility, personal mobility is a concern in mobility management. Personal mobility concentrates on the movement of users instead of users’ terminals, and involves the provision of personal communications and personalized operating environments. Figure 4 demonstrates the concept of personal communications using a personalized video message application. As shown in the figure, when there is a video message addressed to the mobile user, no matter where the user is located or what kind of terminal is being used, the message will be sent to the user correctly.
Adaptability will be one of the basic requirements to the development and delivery of new mobile services. Promising techniques and possible topics may include:
- Mobile application should refer to a user’s profile so that it can be delivered in a way most preferred by the subscriber, such as context-based personalized services. This also brings the applications with adaptability to terminals that are moving in varying locations and speeds. Micro-sensors and GPS receivers are the main driven techniques.
- Techniques such as adaptive multimedia and unified messaging take the terminal characteristics into account and ensure that the service can be received and run on a terminal with the most suitable form to the host type.
- Intelligent mobile software agent is a common
technique to all of the three targets, which act as a platform
for service development, delivery, and auto-configuration.
- Applications can negotiate with networks so that they
can be transferred with the most efficient channel, e.g. indoor
networks or WLAN or cellular systems in a wide area.
Services will be tailorable in order to fit the different network
environments and the varying traffic conditions.
VI. 4g Visions Summary
We present Table 3 as a summary of the discussion above, which is a continuum of Table 1 with visions of 4G features.
TABLE 3 4G VISIONS SUMMARY
|Driven Technique||Intelligent software Auto configuration|
|Representative Standard Radio||OFDM, UWB|
|Frequency (HZ) Bandwidth||3G-5G|
|(bps) Multi-address Technique||10M-20M|
|Cellular coverage Core||FDMA, TDMA, CDMA|
|Service type||Multimedia Machine-to-machineAll-IP networks|
This paper presents 4G visions from a technical perspective. After a brief review of the history and status of mobile communications, we propose a 4G feature framework, in which features of 4G mobile communications are defined. The framework is based on the key concept of integration, and it has the following characteristics:
- Targets in the framework include users, terminals, networks, and applications, which compass the entire technical domain and operating environment of 4G.
- Core features of 4G are described as diversity and adaptability of the targets, leading to seamless integration.
- The feature of diversity includes both external and internal diversity, in which adaptability is caused by external diversity and is solved by internal diversity.
Technical perspectives are presented for each of the features in the paper, in which also some promising techniques and possible research issues of 4G are introduced. The proposed framework provides a layout view on future communication systems, and challenging research topics are figured for guiding systematic research of 4G.
Nilaya Mitash Shanker