Mobile Communication Systems

During the past decade there has been a dramatic change in the nature of mobile communications technology and its impact on the general communic­ ations environment. In the 1970s, mobile radio was a minority activity in communications, based on relatively unsophisticated technology. The 1980s, however, have seen the emergence of analogue cellular systems and the definition of future digital systems, and the predicted demand for these services is such that investigations into the use of higher frequency bands have already begun. It is predicted that, by the late 1990s, the 'personal communications' world will have resulted in the majority of adults in Europe and North America being dependent on radio-connected terminals of various kinds for more than 50% of their total telecommunications needs. The technology which will form the basis of this revolution has now been defined, at least in outline, and the fixed and mobile equipment that will be used in systems of the future will bear little resemblance to that available even ten years ago. It is impossible within the confines of a single, relatively short book to cover all the subject areas needed for a study of this exciting and expanding field of technology. We have, perforce, been selective and have chosen those topics which we believe to be of primary importance at the present time.

1 Introduction to mobile communications.- 1.1 Background.- 1.2 Mobile radio system fundamentals.- 1.2.1 The operating frequency.- 1.2.2 Modulation.- 1.3 A simple mobile radio system.- 1.4 Practical communication systems.- 1.4.1 Links.- 1.4.2 Repeaters.- 1.4.3 Talk-through.- 1.4.4 Communication with selected mobiles.- 1.4.5 Continuous tone controlled signalling system (CTCSS).- 1.4.6 Selective calling.- 1.5 Paging.- 1.5.1 Simple paging systems.- 1.5.2 Voice paging system.- 1.5.3 Overlay paging system.- 1.5.4 Wide-area paging.- 1.6 Portables.- 1.7 Dialling systems.- 1.8 Radiophone services.- 1.9 Channel sharing.- 1.9.1 Trunking.- 1.10 Area coverage techniques.- 1.10.1 Alternative techniques.- 1.10.2 Cellular schemes.- 1.11 Present and future use of mobile radio.- References.- 2 Multipath characteristics in urban areas.- 2.1 Introduction.- 2.2 The nature of multipath propagation.- 2.3 Short-term fading.- 2.3.1 The scattering model.- 2.3.2 Angle of arrival and signal spectra.- 2.3.3 Fading envelope statistics.- 2.3.4 Level-crossing rate.- 2.3.5 Average fade duration.- 2.3.6 Spatial correlation of field components.- 2.3.7 Random FM.- 2.4 Frequency-selective fading.- 2.5 Channel characterization.- 2.6 Channel sounding techniques.- 2.7 Practical channel sounders.- 2.7.1 Data processing.- 2.8 Small-area characterization.- 2.8.1 Statistical characterization.- 2.9 Large-area characterization.- 2.9.1 Distribution of the channel parameters.- 2.10 Conclusions.- References.- 3 Propagation and signal strength prediction.- 3.1 Introduction.- 3.2 Fundamentals of VHF and UHF propagation.- 3.2.1 Propagation in free space.- 3.2.2 Propagation over a reflecting surface.- 3.2.3 The effect of surface roughness.- 3.3 Propagation over terrain obstacles.- 3.3.1 Fresnel zones.- 3.3.2 Diffraction over rounded objectacles.- 3.4 Multiple knife-edge diffraction.- 3.4.1 The Bullington equivalent knife-edge method.- 3.4.2 The Epstein-Peterson diffraction loss method.- 3.4.3 The Japanese atlas method.- 3.4.4 Picquenard’s method.- 3.4.5 The Deygout method.- 3.4.6 Comparison of the diffraction models.- 3.5 Propagation prediction models.- 3.6 Signal strength prediction in urban areas.- 3.6.1 Allsebrook’s method.- 3.6.2 Ibrahim’s method.- 3.7 Discussion.- 3.8 Signal variability.- 3.8.1 Statistical analysis of the signal.- 3.9 Large area statistics.- 3.10 Building penetration losses.- 3.10.1 Interference effects.- References.- 4 Modulation techniques.- 4.1 Introduction.- 4.2 Amplitude modulation.- 4.2.1 Reduced carrier modulation.- 4.2.2 Single-sideband modulation.- 4.3 Angle modulation.- 4.3.1 Bandwidth of angle-modulated signals.- 4.3.2 Criteria for determining bandwidth.- 4.3.3 Carson’s rule.- 4.3.4 Narrowband modulation.- 4.4 Implementation of AM systems.- 4.5 Single-sideband implementation.- 4.5.1 Filter method.- 4.5.2 Outphasing methods.- 4.5.3 Problems in SSB implementation.- 4.6 Demodulation.- 4.6.1 Coherent demodulation.- 4.6.2 Non-coherent (envelope) detection.- 4.7 Generation of FM signals.- 4.7.1 Direct methods.- 4.7.2 Indirect methods.- 4.8 FM demodulators.- 4.8.1 Frequency discriminators.- 4.8.2 Pulse-counting discriminators.- 4.8.3 Phase-locked loops.- 4.8.4 Quadrature detection.- 4.9 The effect of noise on AM systems.- 4.9.1 Noise performance of DSBSC and SSB.- 4.9.2 Noise performance of AM.- 4.9.3 Comparison of the modulation methods.- 4.10 The effect of noise on FM systems.- 4.10.1 The SNR-bandwidth interchange and FM threshold.- 4.10.2 Pre-emphasis and de-emphasis.- 4.11 The effects of multipath propagation.- 4.11.1 Practical SSB systems.- 4.12 Demodulation of data signals.- 4.13 Differentially encoded PSK (DPSK).- 4.14 The effect of noise in data communication systems.- 4.15 Carrier transmissions.- 4.16 The influence of multipath fading on data transmissions.- 4.16.1 Non-coherent FSK and DPSK.- 4.16.2 Coherent systems.- 4.17 System performance.- 4.18 The fully digital approach.- 4.18.1 The principal compromises.- 4.18.2 Quadrature amplitude modulation.- 4.18.3 Frequency modulation schemes.- References.- 5 Man-made noise.- 5.1 Introduction.- 5.2 Characterization of pulses.- 5.3 Characterization of impulsive noise.- 5.4 Measuring equipment.- 5.4.1 Bandwidth.- 5.4.2 Dynamic range.- 5.4.3 Sensitivity and noise figure.- 5.4.4 Impulse response considerations.- 5.5 Practical measuring systems.- 5.6 Measurement of noise amplitude distribution.- 5.7 Statistical characterization of noise.- 5.8 Impulsive noise measurements.- 5.9 Summary.- 5.10 Performance prediction techniques.- 5.10.1 The assessment of receiver performance.- 5.10.2 Prediction methods using APD.- 5.10.3 Prediction methods using NAD.- 5.10.4 The Bello and Esposito technique.- 5.10.5 Application to other receivers.- References.- 6 Diversity reception.- 6.1 Introduction.- 6.2 Basic diversity methods.- 6.2.1 Selection diversity.- 6.2.2 Maximal-ratio combining.- 6.2.3 Equal-grain combining.- 6.3 Improvements obtainable from diversity.- 6.3.1 Envelope probability distributions.- 6.3.2 Level-crossing rate and average fade duration.- 6.3.3 Random FM.- 6.4 Switched diversity.- 6.4.1 Cumulative probability distribution.- 6.5 The effect of diversity on data systems.- 6.6 Practical diversity systems.- 6.7 Predetection diversity.- 6.7.1 Phase-sweeping or ‘mode averaging’ diversity.- 6.8 Diversity systems using special receivers.- 6.8.1 Pilot-tone systems.- 6.8.2 Systems without pilot-tone.- 6.9 Switched diversity.- 6.10 Comparison.- 6.11 Postdetection diversity.- 6.11.1 Use of a modified phase-correction loop.- 6.11.2 Unified analysis of postdetection diversity.- 6.11.3 Postdetection selection and switched diversity.- 6.12 Time diversity.- 6.13 Discussion and conclusions.- References.- 7 Using the radio channel in cellular radio networkgs.- 7.1 The radio channel as a system component.- 7.2 Wideband versus narrowband.- 7.3 Cellular radio fundamentals.- 7.3.1 Why ‘cellular’?.- 7.3.2 Frequency re-use strategies.- 8 Analogue cellular radio systems.- 8.1 Channel structures.- 8.2 Specifications for the radio equipment.- 8.2.1 RF power levels.- 8.2.2 Modulation.- 8.2.3 Spectrum and channel designation.- 8.3 Network control activity.- 8.3.1 Dedicated control channels.- 8.3.2 Protecting data messages.- 8.3.3 Signalling formats.- 8.3.4 Supervision.- 8.4 System operation.- 8.4.1 Principal functions.- 8.4.2 Mobile scanning.- 8.4.3 Registration.- 8.4.4 Call origination.- 8.4.5 Call receipt.- 8.4.6 Hand-off.- 8.4.7 Call termination.- 8.5 Some system comparisons.- 9 Digital cellular radio systems.- 9.1 Digital versus analogue for second-generation cellular systems.- 9.2 Choice of basic system architecture.- 9.2.1 Single channel per carrier, FDMA.- 9.2.2 Time division multiple access.- 9.3 Essential techniques for digital implementation.- 9.3.1 Speech coding.- 9.3.2 Channel coding.- 9.3.3 Channel equalization.- 9.3.4 Frequency hopping.- 9.4 Example systems.- 9.4.1 An asymmetrical system—MATS-D.- 9.4.2 A wideband TDMA system—CD900.- 9.4.3 The GSM system—narrowband TDMA.- 9.5 Postscript.