- •1.1 Introduction
- •1.2 Cellular Fundamentals
- •1.2.1 Communication Using Base Stations
- •1.2.1.1 A Call from a Mobile
- •1.2.1.2 A Call to a Mobile
- •1.2.1.3 Registration
- •1.2.2 Channel Characteristics
- •1.2.2.1 Fading Channels
- •1.2.2.2 Doppler Spread
- •1.2.2.3 Delay Spread
- •1.2.2.4 Link Budget and Path Loss
- •1.2.3 Multiple Access Schemes
- •1.2.3.1 Frequency Division Multiple Access Scheme
- •1.2.3.2 Time Division Multiple Access Scheme
- •1.2.3.3 Code Division Multiple Access Scheme
- •1.2.3.4 Comparison of Different Multiple Access Schemes
- •1.2.3.5 Space Division Multiple Access
- •1.2.4 Channel Reuse
- •1.2.5.1 Macrocell System
- •1.2.5.2 Microcell Systems
- •1.2.5.3 Picocell Systems
- •1.2.5.4 Overlayed System
- •1.2.6 Channel Allocation and Assignment
- •1.2.6.1 Fixed Channel Allocation Schemes
- •1.2.6.2 Dynamic Channel Allocation Schemes
- •1.2.6.3 Hybrid Channel Allocation Schemes
- •1.2.7 Handoff
- •1.2.7.1 Network-Controlled Handoff
- •1.2.7.2 Mobile-Controlled Handoff
- •1.2.7.3 Mobile-Assisted Handoff
- •1.2.7.4 Hard Handoff and Soft Handoff
- •1.2.8 Cell Splitting and Cell Sectorization
- •1.2.9 Power Control
- •1.3 First-Generation Systems
- •1.3.1 Characteristics of Advanced Mobile Phone Service
- •1.3.2 Call Processing
- •1.4 Second-Generation Systems
- •1.4.1 United States Digital Cellular (Interim Standard-54)
- •1.4.2 Personal Digital Cellular System
- •1.4.4 Pan European Global System for Mobile Communications
- •1.4.5.1 Multiple Access Scheme
- •1.4.5.2 Common Channels
- •1.4.5.3 Burst Format
- •1.4.5 Cordless Mobiles
- •1.5 Third-Generation Systems
- •1.5.3 Planning Considerations
- •1.5.3.1 Radio Access
- •1.5.3.2 Spectrum Requirements
- •1.5.3.3 Security
- •1.5.3.4 Intelligent Networks
- •1.5.3.5 Regulatory Environments
- •1.5.4 Satellite Operation
- •References
Network services — These services are provided by IMT-2000 [67]:
1.Voice telephony (ITU-T E105)
2.Program sound
3.Message handling (ITU-T F400)
4.Teletex (ITU-T F200)
5.Paging (open loop, closed loop, user acknowledged)
6.Telefax (ITU-T F160 and F180)
7.Point to multipoint
8.Data
9.Video services using MPEG derived algorithms [68]
10.Short messages
11.Location monitoring
12.Multimedia
Supplementary services — The following services may be provided by IMT-2000:
1.Separation of answering from alerting: Currently, the alerting function resides in the same device used for answering. In IMT-2000, the alerting device may be a pager and the answering device may be a terminal of the user’s choice.
2.Advice of charging: Parties to a call should be able to receive charging information before, during, and after the call.
1.5.3 Planning Considerations
In defining IMT-2000, several factors required consideration: radio access, spectrum requirements, security, network issues, and regulatory environments.
1.5.3.1 Radio Access
IMT-2000 provides access, by means of one or more radio links, to a wide range of services in a wide variety of operating environments. High data rates are required to provide users with the necessary quality of service for multimedia communications, ranging from a few tens of kilobits per second for image transfer, to a couple of hundreds of bits per second for peak Internet transfers, to 2 Mbps for video. The bearers for IMT-2000 are therefore defined as 384 kbps for full area coverage and 2 Mbps for local area coverage.
It is essential to optimize third-generation techniques to cater for variable bit rate and packet capabilities because many multimedia applications are packet oriented. Similarly, multimedia support implies flexibility to handle services with different bit rates and Eb/N0 requirements [69].
The mode of delivery is via either terrestrial or satellite-based radio links, with the possibility of incorporating two or more radio links in tandem. Although it would be desirable for a common radio interface to be provided for the terrestrial and satellite components, this is unlikely to be practical because of spectral and power efficiency design constraints. Therefore, terminals will most likely be required to operate over more than one type of interface, with adaptation controlled by software using digital signal processing technology. Dual-mode handsets already exist to combine GSM at different frequencies, GSM/DECT, and GSM/satellite. The IMT-2000 design allows for the provision of competitive services to the user in each of these operating conditions [65].
The UMTS radio interface, called UMTS terrestrial radio access (UTRA) will consist of a number of hierarchical layers. The higher layer will use W-CDMA, where each user will be given a special CDMA code and full access to the bandwidth allocated. The macrolayer will provide basic data rates to 144 kbps. The lower layers will provide higher data rates of 384 kbps and 2 Mbps, through the use of a frequency division duplex. It may also be possible to use TDD through time division CDMA (TD-CDMA) for higher data rates by dividing the frequency allocation into time slots for the lower layers [69, 70].
© 2002 by CRC Press LLC
This compromise between the two competing standards of W-CDMA and TD-CDMA means that Europe will have a “family of standards.” TD-CDMA provides greater efficiency than GSM and offers reuse of the existing GSM network structure as well as efficient interworking with GSM. TD-CDMA has the same basic frame structure as GSM, each having eight time slots per frame length, but provides higher data rates, up to 2 Mbps indoors. The combination of different access methods is intended to provide flexibility and network efficiency, with the UTMS terminal adopting the access method that best seeks its environment.
1.5.3.2 Spectrum Requirements
The work of ITU on the IMT-2000 is aimed at the establishment of advanced global communication services within the frequency bands, 1885 to 2025 MHz and 2110 to 2200 MHz, identified by the World Administrative Radio Convention (WARC-92). Within this bandwidth, the bands 1980 to 2010 MHz and 2170 to 2200 MHz will be utilized by the satellite component [64]. It is important to note that although the WARC-92 frequencies were intended for IMT-2000, their use by other systems such as personal communication services (PCS) and UMTS is not precluded [71]. WARC-92 resolved that administrations implementing IMT-2000 should make spectrum available in the identified bands for system development and implementation and should use the relevant international technical characteristics that will be developed to facilitate worldwide use and roaming.
Although the intention was to reserve this bank of the spectrum on a worldwide basis for IMT-2000, the Federal Communications Commission (FCC) in the United States engaged in a spectrum auction in late 1994, which resulted in the allocation of large portions of bandwidth in North America to operators providing PCS. The European DECT service and the Japanese PHS service also have spectrum overlaps with the IMT-2000/WARC-92 allocation. The use of this spectrum for other than IMT 2000 services indicates that the allocated spectrum is not enough to meet the growing demand for additional spectrum to provide services such as mobile data services, mobile e-commerce, wireless Internet access, and mobile video services. It should be noted that this spectrum identified in 1992 for global communication services was based on a model where voice services were assumed to be the major source of traffic and the services indicated above were not foreseen. In the current climate where the number of users worldwide is expected to reach 2 billion by 2010 and there is a need to provide common spectrum for global roaming, the World Radio Communication Conference in June 2000 (WRC-2000) decided to increase the available spectrum for IMT-2000 use on a global basis.
This additional spectrum has been identified in three bands: one below 1 GHz (806–960 MHz), another at 1.7 GHz (1710–1885 MHz), and the third band at 2.5 GHz (2500–2690 MHz).
Even though these bands are made available on a global basis for countries to implement IMT-2000, a good degree of flexibility has been provided for operators to evolve towards IMT-2000 as per market and other national considerations. The flexibility allows the use of these bands by services other than those for which the spectrum has been made available. Furthermore, it not only enables each country to decide on timing of availability based on national needs, but also permits countries to select those parts of bands where sharing with existing services is most suitable.
1.5.3.3 Security
Because of the radiating nature of wireless communications, IMT-2000 needs to incorporate security measures to prevent easy reception by parties other than the intended recipient. In addition, because of the nature of mobile communications, security measures are also required to prevent fraudulent use of services [72]. The security provisions for IMT-2000 are defined with the objective of ensuring interoperability with roaming across international and national network boundaries. Virtually all security requirements and features are related to the radio interface. IMT-2000 security features are categorized as user-related or service provider related. Within these categories, they are further categorized as essential or optional [73].
© 2002 by CRC Press LLC