The GSM Network: GPRS Evolution: One Step Towards UMTS - Softcover

Tisal, Joachim

Softcover

ISBN 10: 0471498165 ISBN 13: 9780471498162

Verlag: Wiley, 2001

Inhaltsangabe

Thoroughly revised and updated, the second edition of GSM Cellular Radio Telephony, offers guidance through the evolving field of GSM networks. By presenting the GSM standard it describes the varied aspects of this technology including international scale compatibility, spectral frequency usage, availability, adaptability, cost quality, access potentials and proposed services.
? Provides an essential introduction into the most recent developments in terms of standardisation and service range
? Examines internet access through GPRS (General Packet Radio Service)
? Discusses the advances towards UMTS (Universal Mobile Telecommunication Services)
? Features numerous new topics including SMS (Short Message Service), EDGE (Enhanced Data Rates for GSM Evolution) and WAP (Wireless Applications Protocol)
The GSM Network provides an instructive insight into recent progress in this area and will have great appeal to telecommunications engineers and consultants as well as network and telecommunications managers.

Über diesen Titel

Über die Autorin bzw. den Autor

Joachim Tisal is the author of The GSM Network: GPRS Evolution: One Step Towards UMTS, 2nd Edition, published by Wiley.

Von der hinteren Coverseite

Thoroughly revised and updated, the second edition of GSM Cellular Radio Telephony, offers guidance through the evolving field of GSM networks. By presenting the GSM standard it describes the varied aspects of this technology including international scale compatibility, spectral frequency usage, availability, adaptability, quality and costs, access potentials and proposed services.
The GSM Network provides and instructive insight into recent progress in this area and will have great apppeal to telecommunicatiosn engineers and consultants as well as network and telecommunications managers.
* Provides an essential introduction into the most recent developments in terms of standardisation and service range
* Examines internet access through GPRS (General Packet Radio Service)
* Discusses the advances towards UMTS (Universal Mobile Telecommunications System)
* Features numerous new topics including SMS (Short Message Service), EDGE (Enhanced Data Rates for GSM Evolution) and WAP (Wireless Applications Protocol)

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Chapter Two - Cellular Concepts

Frequency Re-use

This chapter sets out the constraints arising from three network aspects; subscriber mobility within the network, the reach of the network, and the characteristics of radio propagation. It then describes the solutions to these problems adopted in cellular networks.

Limitations imposed by subscriber mobility have an impact on the characteristics of subscriber terminals. The subscriber terminal must be intrinsically mobile in respect of its use in a vehicle (e.g. boat, car or motorbike), or as a handheld instrument. This means that the terminal must be of restricted size and weight so that it is easy to carry and manoeuvre. However, a compact and lightweight unit implies a power supply of limited capacity, which is an important factor if a reasonable duration of stand-alone operation is desired. Other important aspects of mobility concern the network, including the need to locate subscribers, the ability to follow their movements, and the capacity to monitor their accessibility (a subscriber who turns off his handset disappears from the network). A final important characteristic of mobile terminals is their performance in noisy environments - city streets are rarely quiet places.

The radio beam is the link between the subscriber's mobile terminal and the fixed infrastructure of the network. The fixed network terminals containing transmitters and receivers are known as 'base stations'. Since the output power of the subscriber terminal is limited by its battery supply capacity, the emitted radio power is weak. Moreover, it should be borne in mind that the attenuation of a radio signal is proportional to the fourth POW distance between the transmitter and receiver. If the emitted power is limited, the range Of the signal will also be limited. For a significant coverage area, with subscriber terminals having low transmitter power, it is therefore necessary to have a substantial number of base stations. The corollary of this is that, given that the weak transmitted power limits the coverage area, it is possible to re-use the same frequency in zones separated sufficiently far apart without suffering from co-channel interference.

In radio telephony, the zone covered by a base station is known as a 'cell'; hence the title of 'cellular' radio telephony for networks engineered for the best performance within the given limitations. Frequency re-use is an important concept in public radio telephony because the frequency spectrum is a scarce resource and this type of 're-cycling' optimises its usage.

In cellular radio, there is a direct relationship between the number of available frequencies and the number of calls possible at any given time. The numberof frequencies available determines the traffic capacity of the network. In a given zone, the smaller the cell size, the greater is the number of simultaneously usable frequencies. This fact is exploited to the full in urban areas where the traffic density is high.

In a network, the cell is the basic element used in the architecture of a zone which uses a group of frequencies. To use any one of these frequencies in two different cells C1 and C2, it must be arranged that they are at least two cell diameters apart in order to limit co-channel interference. Figure 2.1 shows a cell architecture, with the cells represented as hexagons.

In a GSM network, a cell pattern made up of nine cells is defined with which to structure the geographical area for cellular telephony. This is shown in Figure 2.2. In general, the base stations are located at the intersection of three cells in order to optimise their number. Figure 2.2 shows the ideal use in which a base station at the intersection of cells A1, A2 and A3 can serve the three cells.

A cluster is the logical grouping unit of one or more cells between which bearer handover takes place.

2.2 Mobility

The freedom of users to move imposes the following requirements:

* locating subscribers in the network
* monitoring subscriber movement in the network;
* maintaining the link between the network and the subscriber while the user changes cell.

When the network perceives that the subscriber who is conducting a call will cross the boundary between two cells, it transfers the call between the two cells in a way that disrupts the call as little as possible. This intercellular transfer, known as handover, is technically complex.

Handover is the process of switching a call in progress from one physical channel to another. Two forms of handover exist - intra-cell handover and inter-cell handover. Intra-cell handover is the transfer of a call in progress on a physical channel of one cell to another physical channel of the same cell. Inter-cell handover involves transferring the call between two cells.

In analogue cellular networks, when the mobile terminal changes cell, communication is first interrupted in the active cell, before being re-established in the new cell. In a GSM network, the mobile terminal is equipped with several demodulators, and it can thus stay in contact with two base stations simultaneously, in such a way as to avoid breaking the link to the fixed network, and this is the first main advantage. The second advantage follows from the first in that the ping-pong effect, resulting from a mobile terminal moving in an area along the boundary between two cells, is avoided.

Roaming is the movement of the mobile terminal from one part of the network coverage area to another part, whilst retaining the network capability to make or receive calls in both areas.

The attach process is the way in which a mobile station within the network coverage area in which it has rights notifies the network that it is operative. The reverse process is detach, in which the mobile terminal reports that it is inoperative.

Details zur Ausgabe

• Verlag: Wiley
• Erscheinungsdatum: 2001
• Sprache: Englisch
• ISBN 10: 0471498165
• ISBN 13: 9780471498162
• Einband: Taschenbuch
• Auflage: 2
• Anzahl der Seiten: 239
• Kontakt zum Hersteller: Wiley-VCH GmbH; product_safety@wiley.com; ; Boschstrasse 12; Weinheim; 69469; Deutschland