Performance Enhancements in a Frequency Hopping GSM Network / Edition 1

by Thomas Toftegaard Nielsen, Jeroen Wigard

Overview

Due to the explosive global growth in the number of mobile subscribers, as well as the growth predicted in the mobile data segment, the need for improved spectrum efficiency on the radio interface becomes more and more important. Frequency hopping (FH) is an effective method for improving the spectrum efficiency. One of the advantages of FH is that it can be combined with other spectral efficiency improving features like power control, handover and reuse partitioning.
Performance Enhancements in a Frequency Hopping GSM Network covers FH and some of the additional features in detail. It begins with an in-depth description of the basic concept of FH on link level as well as on system level. Different methods have been used for analysis, such as link level simulations, network level simulations and classic tele-traffic theory.
Special features of Performance Enhancements in a Frequency Hopping GSM Network:

• Combines the practical experiences of operator and vendor with more theoretical research methods. An in-depth treatment of prevailing problems in GSM networks;
• Presentation of a new method, computer-aided network design (CAND), which has been developed to analyse the complex network structures of a GSM network. CAND provides the possibility for more realistic performance evaluations than conventional methods;
• Provides GSM-specific analysis of functionality improvements in power control, discontinuous transmission, and several handover algorithms;
• Explanation of the quality and capacity gains of features like the combination of FH and reuse partitioning, referred to as intelligent frequency hopping;
• A frequency planning method for FH GSM networks is presented. This method exploits the benefits from FH directly in the allocation process, increasing the overall frequency plan.

Product Details

ISBN-13:	9780792378198
Publisher:	Springer US
Publication date:	04/30/2000
Edition description:	2002
Pages:	334
Product dimensions:	6.10(w) x 9.25(h) x 0.03(d)

Read an Excerpt

Chapter 1: Introduction

The ability to exchange information becomes more and more important in today's society. This is reflected in the effort that is being put into research of the different telecommunication fields. Due to an enormous progress in the field of semiconductors, telecommunication today is relatively cheap with examples such as the telegraph, the telephone, digital mobile telephones, the Internet add various satellite communication systems being some of the landmarks in the development of electronic communication systems.

1. Evolution Of Digital Systems

The common drive in the research of communication systems,' is the need for faster exchange of information, i.e. the need for exchange of increasing amounts of information per time unit. Some of the goals of research within this field are to make communication less expensive and more efficient. The efficiency involves, among other parameters, the ability to be mobile while communicating. This has over the last couple of years become possible, enabling a commercial success of digital speech systems. The need for capacity has therefore increased enormously. Some digital examples are the European GSM-900 and GSM-1800, which have both become world-wide spread. These types of systems are generally referred to as 2nd generation Personal Communication Service systems, PCS [158]. In recent years Europe has witnessed a massive growth in mobile communications, where some northern European countries, such as Finland, have experienced penetration rates of more than 55 % [93]. On the way towards new 3rd generation mobile systems, such as the European Universal Mobile Telecommunications System (UMTS), Wireless Local Area Networks (WLAN) and Mobile Broadband Systems (MBS), allowing broadband data transmission (see Figure 2), it is therefore necessary to deal with the capacity problem of the existing 2nd generation systems. Along with the increasing capacity requirements, requirements to the network performance increase the need for enhanced 2nd generation systems even further.

In the case of 3rd generation systems a large effort is currently put into specifying, designing and standardising the individual systems. For 2nd generation systems this has previously been done, and therefore a large effort is now put into research/development of features and methods to optimise the performance of the individual system. Such features are in particular related to network algorithms of the 2nd generation system, but can in many cases correspondingly be used in 3rd generation systems. The two different research "branches" in the area of digital wireless communication are shown in Figure 3.

This book deals with improvements to 2nd generation systems. In order to be able to design relevant performance features it has been chosen to limit the description to deal with one specific system and GSM has been chosen.

The term 'performance' is quite complex and linked closely to different network parameters such as capacity and quality. Part of this book treats the search for features/algorithms to enhance the network performance of the radio communication part of a GSM network, the BSS network. In order to clarify this statement the term performance, as defined in relation to this book, is described in the following.

2. Performance Of A Mobile Network

Depending on the target group quite different parameters are of interest in determining the system performance. The two parties of interest, as considered here, are the network operator and the mobile user. Therefore the performance parameters considered are also seen from this perspective. The most essential parameters are:

Capacity - The GSM network operators have only a limited number of channels at their disposal. This means that the system capacity must be optimised with a fixed number of channels. The network should be designed to meet the requirements of capacity arising from the users. Intensive research on how to do this is continuously being conducted using different approaches. Different methods on how to enhance the GSM network capacity are proposed throughout this book, making capacity one of the most important parameters.

Quality - Throughout this book the term quality reflects the experience by the system end-user. Different quality measures are used, like the signal to interference ratio (C/I), the bit error rate (BER), the frame erasure rate (FER), the dropped call rate and the number of blocked calls. In some situations these quality measures are correlated, while in others some are more independent of each other. All of them are not necessarily correlated to the subjective quality experienced by the mobile user. Many different factors decide the network quality, making it another key parameter in this book.

Coverage - In order to have a high performance cellular mobile network, a certain level of coverage has to be provided. Since such a network is assumed, coverage becomes a secondary issue.

Cost - The impact of the price of a commercial communication system may never be underestimated. The mobiles, as well as the base stations including the rest of the cellular network infrastructure, have to be relatively cheap to ensure commercial success. However, in this book the cost issue is not treated any further.

New Services - The effect of offering new services to the subscribers becomes more important for network operators. Having lowered the air-time price as much as possible, one parameter that can be used to ensure the proper revenue is new services. By inventing new services that does not necessarily require a large amount of capacity, an income based on the functionality of the service can be generated. Since such new services can be operator specific, the individual operator can differentiate itself from the competing operators and thereby get more customers. Currently one of the new services for GSM is enhanced data-rates to introduce Internet applications from GSM. This subject is briefly introduced in Chapter 2.

Complexity/Flexibility - From the network operators' point of view a low network complexity is highly desirable. This is related to what is generally referred to as network maintenance and for a great part taken care of by the Operating and Maintenance Centre (OMC). From the radio network engineers point of view, especially frequency and parameter planning is important. A fairly large part of this book is concerned with the network complexity when considering the problem of frequency planning.

The six performance parameters introduced above all have some kind of an influence on each other making the overall network performance evaluation quite complex. Examples of such influences are the trade off between quality and capacity or between quality/capacity and cost.

Another way of illustrating this parameter interaction is by looking at the typical life cycle of the highest priority of these parameters, if specified by the operator. This is shown in Figure 4.

Coverage -- Capacity--Quality

Figure 4. The shift in primary performance parameter as a function of time.

Initially, during the roll-out of the network (stage 1), the primary aim is to provide as much coverage as possible in order to offer mobile telephony to as many people as possible. With increasing coverage the need for capacity becomes more and more important (stage 2). Furthermore, the various national operators compete about the customers, which increases the capacity requirements even further since the individual operator typically will do quite inventive things to get new customers. A very effective way to accelerate the movement towards stage 2 is when operators starts selling mobile phones at a very low cost (e.g. at the price of 1 DKr. as was the case in Denmark in 1997). At stage 2 the idea is typically to provide a satisfactorily quality, while increasing the network capacity substantially. After a certain period of time the number of potential new customers becomes smaller and the primary aim becomes to improve the network quality (stage 3). Of course the quality has to be as good as possible during all stages, but now it becomes the primary aim...

Table of Contents

Preface. Acknowledgements. 1. Introduction. 2. Performance Enhancing Strategies and Evaluation Methods. 3. A Brief Introduction to the GSM System. 4. Link Modelling and Link Performance. 5. Computer Aided Network Design. 6. Influence of FH on a GSM System. 7. Power Control and DTX in a FH GSM System. 8. Handover Algorithms in a GSM System. 9. Combining Reuse Partitioning and Frequency Hopping in a GSM Network. 10. Frequency Planning of Frequency Hopping Networks. References. Index.