Introduction to Mobile Network Engineering E-Book

Alexander Kukushkin

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 650

Veröffentlichungsjahr: 2018

Beschreibung

Summarizes and surveys current LTE technical specifications and implementation options for engineers and newly qualified support staff Concentrating on three mobile communication technologies, GSM, 3G-WCDMA, and LTE--while majorly focusing on Radio Access Network (RAN) technology--this book describes principles of mobile radio technologies that are used in mobile phones and service providers' infrastructure supporting their operation. It introduces some basic concepts of mobile network engineering used in design and rollout of the mobile network. It then follows up with principles, design constraints, and more advanced insights into radio interface protocol stack, operation, and dimensioning for three major mobile network technologies: Global System Mobile (GSM) and third (3G) and fourth generation (4G) mobile technologies. The concluding sections of the book are concerned with further developments toward next generation of mobile network (5G). Those include some of the major features of 5G such as a New Radio, NG-RAN distributed architecture, and network slicing. The last section describes some key concepts that may bring significant enhancements in future technology and services experienced by customers. Introduction to Mobile Network Engineering: GSM, 3G-WCDMA, LTE and the Road to 5G covers the types of Mobile Network by Multiple Access Scheme; the cellular system; radio propagation; mobile radio channel; radio network planning; EGPRS - GPRS/EDGE; Third Generation Network (3G), UMTS; High Speed Packet data access (HSPA); 4G-Long Term Evolution (LTE) system; LTE-A; and Release 15 for 5G. * Focuses on Radio Access Network technologies which empower communications in current and emerging mobile network systems * Presents a mix of introductory and advanced reading, with a generalist view on current mobile network technologies * Written at a level that enables readers to understand principles of radio network deployment and operation * Based on the author's post-graduate lecture course on Wireless Engineering * Fully illustrated with tables, figures, photographs, working examples with problems and solutions, and section summaries highlighting the key features of each technology described Written as a modified and expanded set of lectures on wireless engineering taught by the author, Introduction to Mobile Network Engineering: GSM, 3G-WCDMA, LTE and the Road to 5G is an ideal text for post-graduate and graduate students studying wireless engineering, and industry professionals requiring an introduction or refresher to existing technologies.

Leseprobe

Table of Contents

Cover

Dedication

Foreword

Acknowledgements

Abbreviations

Chapter 1: Introduction

Chapter 2: Types of Mobile Network by Multiple‐Access Scheme

Chapter 3: Cellular System

3.1 Historical Background

3.2 Cellular Concept

3.3 Carrier‐to‐Interference Ratio

3.4 Formation of Clusters

3.5 Sectorization

3.6 Frequency Allocation

3.7 Trunking Effect

3.8 Erlang Formulas

3.9 Erlang B Formula

3.10 Worked Examples

Chapter 4: Radio Propagation

4.1 Propagation Mechanisms

Chapter 5: Mobile Radio Channel

5.1 Channel Characterization

5.2 Worked Examples

5.3 Fading

5.4 Diversity to Mitigate Multipath Fading

5.5 Worked Examples

5.6 Receiver Noise Factor (Noise Figure)

Chapter 6: Radio Network Planning

6.1 Generic Link Budget

6.2 Worked Examples

Chapter 7: Global System Mobile, GSM, 2G

7.1 General Concept for GSM System Development

7.2 GSM System Architecture

7.3 Radio Specifications

7.4 Background for the Choice of Radio Parameters

7.5 Communication Channels in GSM

7.6 Mapping the Logical Channels onto Physical Channels

7.7 Signalling During a Call

7.8 Signal Processing Chain

7.9 Estimating Required Signalling Capacity in the Cell

References

Chapter 8: EGPRS: GPRS/EDGE

8.1 GPRS Support Nodes

8.2 GPRS Interfaces

8.3 GPRS Procedures in Packet Call Setups

8.4 GPRS Mobility Management

8.5 Layered Overview of the Radio Interface

8.6 GPRS/GSM Territory in a Base‐Station Transceiver

8.7 Summary

References

Chapter 9: Third Generation Network (3G), UMTS

9.1 The WCDMA Concept

9.2 Major Parameters of 3G WCDMA Air Interface

9.3 Spectrum Allocation for 3G WCDMA

9.4 3G Services

9.5 UMTS Reference Network Architecture and Interfaces

9.6 Air‐Interface Architecture and Processing

9.7 Channels on the Air Interface

9.8 Physical‐Layer Procedures

9.9 RRC States

9.10 RRM Functions

9.11 Initial Access to the Network

9.12 Summary

References

Chapter 10: High‐Speed Packet Data Access (HSPA)

10.1 HSDPA, High‐Speed Downlink Packet Data Access

10.2 HSPA RRM Functions

10.3 MAC‐hs and Physical‐Layer Processing

10.4 HSDPA Channels

10.5 HSUPA (Enhanced Uplink, E‐DCH)

10.6 Air‐Interface Dimensioning

10.7 Summary

References

Chapter 11: 4G‐Long Term Evolution (LTE) System

11.1 Introduction

11.2 Architecture of an Evolved Packet System

11.3 LTE Integration with Existing 2G/3G Network

11.4 E‐UTRAN Interfaces

11.5 User Equipment

11.6 QoS in LTE

11.7 LTE Security

11.8 LTE Mobility

11.9 LTE Radio Interface

11.10 Principle of OFDM

11.11 OFDM Implementation using IFFT/FFT Processing

11.12 Cyclic Prefix

11.13 Channel Estimation and Reference Symbols

11.14 OFDM Subcarrier Spacing

11.15 Output RF Spectrum Emissions

11.16 LTE Multiple‐Access Scheme, OFDMA

11.17 Single‐Carrier FDMA (SC‐FDMA)

11.18 OFDMA versus SC‐FDMA Operation

11.19 SC‐FDMA Receiver

11.20 User Multiplexing with DFTS‐OFDM

11.21 MIMO Techniques

11.22 Link Adaptation and Frequency Domain Packet Scheduling

11.23 Radio Protocol Architecture

11.24 Downlink Physical Layer Processing

11.25 Downlink Control Channels

11.26 Mapping the Control Channels to Downlink Transmission Resources

11.27 Uplink Control Signalling

11.28 Uplink Reference Signals

11.29 Physical‐Layer Procedures

11.30 LTE Radio Dimensioning

11.31 Summary

References

Chapter 12: LTE‐A

12.1 Carrier Aggregation

12.2 Enhanced MIMO

12.3 Coordinated Multi‐Point Operation (CoMP)

12.4 Relay Nodes

12.5 Enhanced Physical Downlink Control Channel (E‐PDCCH)

12.6 Downlink Multiuser Superposition, MUST

12.7 Summary of LTE‐A Features

References

Chapter 13: Further Development for the Fifth Generation

13.1 Overall Operational Requirements for a 5G Network System

13.2 Device Requirements

13.3 Capabilities of 5G

13.4 Spectrum Consideration

13.5 5G Technology Components

13.6 5G System Architecture (Release 15)

13.7 New Radio (NR)

13.8 Summary

References

Chapter 14: Annex: Base‐Station Site Solutions

14.1 The Base‐Station OBSAI Architecture

14.2 Common Public Radio Interface, CPRI

14.3 SDR and Multiradio BTS

14.4 Site Solution with OBSAI Type Base Stations

References

Index

End User License Agreement

List of Tables

Chapter 3

Table 3.1 Channel allocation in a 7 × 3 cluster.

Table 3.2 Erlang B table.

Chapter 4

Table 4.1 Pre‐set values for correction coefficients in semi‐empirical equation for propagation loss.

Chapter 5

Table 5.1 Tabularized LNF margin in a function of location probability at cell border.

Chapter 6

Table 6.1 Standard deviation of lognormal distribution in different environments.

Table 6.2 Typical values of building penetration loss.

Chapter 7

Table 7.1 Functionalities of the base station and controller.

Table 7.2 GSM frequency bands.

Table 7.3 GSM characteristics.

Table 7.4 Erlang capacity of the cell versus number of TRX.

Chapter 8

Table 8.1 EGPRS modulation coding schemes [1].

Table 8.2 The relationship between carriers, time slots, voice traffic and Erlang capacity [2].

Chapter 9

Table 9.1 Example of allocation of channelization codes in the cell [4].

Table 9.2 Main parameters of WCDMA.

Table 9.3 Comparison of GSM and WCDMA in air‐interface technology.

Table 9.4 Spectrum allocation for 3G FDD WCDMA.

Table 9.5 Traffic classes.

Table 9.6 Mapping traffic class to RAB.

Table 9.7 UTRA logical channels.

Table 9.8 Common transport channels.

Table 9.9 Different types of physical channels in UTRA‐FDD.

Table 9.10 Transport channel parameters.

Table 9.11 Multiplexing the DTCH and DCCH onto a single DPDCH [12].

Table 9.12 DPDCH fields [15].

Chapter 10

Table 10.1 HSPDA channels.

Table 10.2 CQI mapping for UE category 1–6 [4].

Table 10.3 CQI mapping for UE category 10 [4].

Table 10.4 Enhanced uplink physical channels.

Table 10.5 Typical assumptions for the mobile station.

Table 10.6 Typical assumptions for the base station.

Table 10.7 Example of the maximum available channel resources with pole capacity (100% load).

Chapter 11

Table 11.1 LTE UE equipment categories.

Table 11.2 Standardized QCI characteristics [4].

Table 11.3 UTRAN and E‐UTRAN differences in mobility [10].

Table 11.4 LTE channel arrangement.

Table 11.5 Layer mapping.

Table 11.6 Transmission bandwidth configuration

N

RB

in E‐UTRA.

Table 11.7 Channel coding scheme and coding rate for Transport Channels (TrCHs).

Table 11.8 Channel coding scheme and coding rate for control information.

Table 11.9 Codeword‐to‐layer mapping for spatial multiplexing [16].

Table 11.10 Codeword‐to‐layer mapping for transmit diversity.

Table 11.11 Codebook for transmission on antenna ports {0,1} [16].

Table 11.12 Large‐delay cyclic delay diversity [16].

Table 11.13 Multi‐antenna technique for physical channels.

Table 11.14 Root indices for the primary synchronization signal [16].

Table 11.15 Supported PDCCH formats [16].

Table 11.16 Modulation and TBS index table for PDSCH [19].

Table 11.17 Modulation, TBS index and redundancy version table for PUSCH [20].

Table 11.18 Transport‐block size table in bits versus number of the scheduled PRB and TBS index [20].

Chapter 12

Table 12.1 E‐UTRA operating bands [1].

Table 12.2 Possible carrier aggregation options.

Chapter 13

Table 13.1 Standardized SST values.

Table 13.2 RRM functional split between gNB‐CU and gNB‐DU.

Table 13.3 Supported transmission numerologies.

Table 13.4 Frame structure with scalable transmission numerology.

Table 13.5 Minimum and maximum number of resource blocks.

Table 13.6 Supported PDCCH aggregation levels.

Table 13.7 Resources within an SS/PBCH block for PSS, SSS, PBCH and DM‐RS for PBCH.

List of Illustrations

Chapter 2

Figure 2.1 Common multiple‐access schemes.

Chapter 3

Figure 3.1 Model of a cellular network with frequency reuse. Shadowed hexagons represent cells with the same set of allocated frequencies.

Figure 3.2 Frequency reuse and cluster formation.

Figure 3.3 Sectorization.

Figure 3.4 Antenna patterns for a cell site with three 120° sectors.

Figure 3.5 Illustration of

frequency reuse cluster.

Figure 3.6 Illustration of the trunking effect.

Figure 3.7 Blocking an incoming call.

Chapter 4

Figure 4.1 Path loss examples with different clutter loss factors.

Figure 4.2 Path loss in a mixed environment.

Figure 4.3 Three components in path loss.

Figure 4.4 Basic components of link budget.

Chapter 5

Figure 5.1 Multipath propagation.

Figure 5.2 Beating diagram in a two‐ray channel model.

Figure 5.3 Power delay profile.

Figure 5.4 Phasor diagram in the narrowband channel.

Figure 5.5 Inter‐symbol interference in the wideband channel.

Figure 5.6 Inter‐symbol interference.

Figure 5.7 Average total BER versus SNR for different values of delay spread in Rayleigh channel: the solid line corresponds to a delay spread of 0.1‐bit duration, +s to 0.05 and

s to 0.01, respectively; horizontal lines (dashes) correspond to irreducible BER values.

Figure 5.8 Projection of velocity vector |

v

| onto the direction of propagation

k

.

Figure 5.9 Probability density function of signal variations normalized at the global mean.

Figure 5.10 Effect of slow fading/shadowing on estimation of the cell range.

Figure 5.11 The Q function.

Figure 5.12 Illustration of fading margin and accessibility.

Figure 5.13 Rayleigh fading.

Figure 5.14 Geometry of scattering.

Figure 5.15 Channel coding with repetition.

Figure 5.16 Noisy two‐port network.

Figure 5.17 Cascade network.

Chapter 6

Figure 6.1 Base‐station antenna system with a two‐port dual band cross‐polarization antenna and diplexer for combining 900 and 1800 MHz RF paths.

Figure 6.2 Base‐station antenna system with a four‐port dual band cross‐polarization antenna and MHA for 1800 MHz.

Chapter 7

Figure 7.1 GSM System architecture.

Figure 7.2 GSM system hierarchy.

Figure 7.3 Connection to the public telephone network.

Figure 7.4 Principle of subscriber authentication.

Figure 7.5 Generation of the cipher key Kc.

Figure 7.6 Combining payload data stream and ciphering stream.

Figure 7.7 Cell structure with cluster size 3 × 3.

Figure 7.8 The multiple‐access scheme in GSM.

Figure 7.9 Burst schedule at the BS. Time slot 2 is assigned to mobile user.

Figure 7.10 Duplex arrangement with three frequency channels allocated to a sector/cell. Total number of available channels is 3 × 8 = 24 channels.

Figure 7.11 The GSM channel models [2].

Figure 7.12 Structure of training sequence.

Figure 7.13 Equalizer window versus delay spread.

Figure 7.14 Frequency hopping concept.

Figure 7.15 Baseband frequency hopping.

Figure 7.16 RF synthesizer frequency hopping.

Figure 7.17 TDMA frame length constraints.

Figure 7.18 Timing alignment.

Figure 7.19 Logical channels. The abbreviations TCH/H and TCH/F correspond to full‐ and half‐rate traffic channels, respectively. The numbers 9.6, 4.8 and 2.4 refer to specific data service rates over circuit switch traffic channels.

Figure 7.20 Utilization of logical channels during call setup.

Figure 7.21 GSM frame formats.

Figure 7.22 TDMA structure for traffic channels, a 26‐frame multiframe.

Figure 7.23 Example of signalling channel allocation in a 51‐multiframe.

Figure 7.24 Mapping the control channels onto broadcast carrier with signalling over Time Slot 0.

Figure 7.25 Mobile‐initiated call setup.

Figure 7.26 Signalling on dedicated downlink control channel during the call setup.

Figure 7.27 Sliding frames [4].

Figure 7.28 Handover decision.

Figure 7.29 Transmit receive chain.

Figure 7.30 Channel coding.

Figure 7.31 Reordering and interleaving for TCH allocated to a user in TS2.

Figure 7.32 SDCCH configuration: (a) combined configuration and (b) separate SDCCH.

Chapter 8

Figure 8.1 GPRS/EDGE network.

Figure 8.2 GPRS interfaces.

Figure 8.3 GPRS procedures.

Figure 8.4 GPRS mobility management states.

Figure 8.5 PDP context activation procedure.

Figure 8.6 PDP states/phases.

Figure 8.7 GPRS MS: network reference model [1].

Figure 8.8 GPRS transformation data flow.

Figure 8.9 Radio block structure for GPRS data transfer.

Figure 8.10 Multiframe structure for PDCH [1].

Figure 8.11 MS initiated DL TBF establishment.

Figure 8.12 Downlink TBF assignment, MS monitors CCCH.

Figure 8.13 CS‐PS borders in the BS transceiver.

Chapter 9

Figure 9.1 UMTS architecture.

Figure 9.2 Modular functionality split in the UMTS.

Figure 9.3 Modular architecture of UE [2].

Figure 9.4 WCDMA timing arrangement.

Figure 9.5 Combining data and spreading sequences with SF = 4.

Figure 9.6 Spreading with OSVF codes.

Figure 9.7 OVSF code tree.

Figure 9.8 Spreading and scrambling for a single data stream.

Figure 9.9 Channelization code tree example with control channels allocated in the cell.

Figure 9.10 Outer‐loop power control.

Figure 9.11 Closed‐loop power control.

Figure 9.12 Closed‐loop power control compensates for a fading channel.

Figure 9.13 Softer handover.

Figure 9.14 Soft handover.

Figure 9.15 Discontinuous transmission during compressed mode.

Figure 9.16 Channel estimation and recovery of the multipath component of the signal.

Figure 9.17 RAKE receiver with MRC [7].

Figure 9.18 UMTS QoS architecture [8].

Figure 9.19 Logical role of the RNC for one UE UTRAN connection.

Figure 9.20 Air‐interface protocol reference architecture [9].

Figure 9.21 Example of mapping services to radio interface channels [10].

Figure 9.22 Multiplexing the transport channels.

Figure 9.23 Transport channel multiplexing structure for the uplink [11].

Figure 9.24 Complex‐valued scrambling for the physical channel.

Figure 9.25 I/Q multiplexing with complex scrambling [5].

Figure 9.26 Spreading for uplink DPCCH/DPDCHs [14].

Figure 9.27 Modulation process [14].

Figure 9.28 Composition of DPDCH and DPCCH in the uplink direction [15].

Figure 9.29 Power control and variable bit‐rate transmission in the uplink direction.

Figure 9.30 Spreading for all downlink physical channels except SCH [14].

Figure 9.31 Combining downlink physical channels [14].

Figure 9.32 Frame structure for the common pilot channel [15].

Figure 9.33 Structure of the synchronization channel [16].

Figure 9.34 RRC states and state transitions including GSM and E‐UTRA [16].

Figure 9.35 RRC connection establishment.

Figure 9.36 Service establishment process between the UE and core network.

Figure 9.37 Network‐initiated state transition.

Figure 9.38 Estimation of load increase caused by the admission of additional traffic.

Figure 9.39 Initial UE radio access.

Chapter 10

Figure 10.1 HSDPA mapping to physical channels with a fixed spreading factor [1].

Figure 10.2 Sharing by means of time multiplex as well as code multiplex [1].

Figure 10.3 Channel‐dependent scheduling.

Figure 10.4 Packet retransmission principle in NodeB.

Figure 10.5 Protocol architecture of HS‐DSCH, configuration with MAC‐c/sh [2].

Figure 10.6 Protocol architecture of E‐DCH [3].

Figure 10.7 HARQ retransmission and soft combining.

Figure 10.8 Principle N‐channel stop‐and‐wait HARQ (N = 4) [1].

Figure 10.9 UTRAN side MAC architecture/MAC‐hs details [2].

Figure 10.10 Fractional DPCH [4].

Figure 10.11 Link adaptation based on CIR.

Figure 10.12 Use of power control commands for DL channel‐quality report adjustment [1].

Figure 10.13 Enhanced Uplink scheduling.

Chapter 11

Figure 11.1 EPS architecture for 3GPP accesses.

Figure 11.2 Non‐roaming architecture within EPS using S5, S2a, S2b.

Figure 11.3 E‐UTRAN and EPS with S1‐flex interface [1].

Figure 11.4 LTE bearer services architecture [1].

Figure 11.5 3GPP LTE security architecture.

Figure 11.6 Mobility anchor points.

Figure 11.7 Inter‐eNB handover with an X2 interface.

Figure 11.8 User‐plane switching in handover with an X2 interface.

Figure 11.9 Inter‐eNB handover without an X2 interface.

Figure 11.10 Orthogonal Frequency Division Multiple Access concept.

Figure 11.11 Subcarrier shape in time and frequency domains.

Figure 11.12 OFDM modulator [11].

Figure 11.13 Basic principle of OFDM demodulation [11].

Figure 11.14 OFDM modulation by means of IFFT processing [11].

Figure 11.15 Architecture of an OFDM transceiver.

Figure 11.16 CP insertion.

Figure 11.17 CP role in a multipath environment.

Figure 11.18 Cell‐specific reference‐symbol arrangement in the case of normal CP length for one antenna port.

Figure 11.19 Transmitter RF spectrum [13].

Figure 11.20 OFDM as a user multiplexing/multiple‐access scheme.

Figure 11.21 Block diagram of a SC‐FDMA transmitter [14].

Figure 11.22 Physical‐layer processing: downlink link‐OFDMA and uplink‐SC‐FDMA.

Figure 11.23 Basic principle of DFTS‐OFDM demodulation [14].

Figure 11.24 Uplink user multiplexing in the case of DFTS‐OFDM.

Figure 11.25 MIMO principle with a 2 × 2 antenna configuration.

Figure 11.26 Cyclic delay diversity.

Figure 11.27 LTR radio interface user‐plane protocol stack [1].

Figure 11.28 LTE radio interface control plane protocol stack [1].

Figure 11.29 Downlink channel mapping [1].

Figure 11.30 Uplink channel mapping [1].

Figure 11.31 Mapping between downlink transport channels and downlink physical channels [1].

Figure 11.32 Mapping between uplink transport channels and uplink physical channels [1].

Figure 11.33 Frame structure of FDD LTE [16].

Figure 11.34 Downlink resource grid [16].

Figure 11.35 Definition of the channel bandwidth and transmission bandwidth configuration for one E‐UTRA carrier [17].

Figure 11.36 OFDMA transmission time‐frequency grid.

Figure 11.37 Transport block processing for DL‐SCH, PCH and MCH channel coding [18].

Figure 11.38 Physical‐layer processing [16].

Figure 11.39 Mapping of downlink reference signals to the resource grid (normal cyclic prefix) [16].

Figure 11.40 Time‐domain position of PSS and SSS for FDD.

Figure 11.41 Definition and structure of PSS.

Figure 11.42 Frequency domain structure of secondary synchronization signal in FDD LTE.

Figure 11.43 Mapping of synchronization signals to a resource grid.

Figure 11.44 PBCH structure and mapping to resource grid [12].

Figure 11.45 Example of mapping of PCFICH to a resource grid.

Figure 11.46 Illustration of a LTE downlink resource grid.

Figure 11.47 PHICH signal construction [12].

Figure 11.48 Transport‐block processing for UL‐SCH [18].

Figure 11.49 Mapping of UCI to PUSCH [19].

Figure 11.50 Uplink physical channel processing [16].

Figure 11.51 Mapping to physical resource blocks for PUCCH format 2/2a/2b [16].

Figure 11.52 Random access with PRACH [16].

Figure 11.53 Uplink subframe configuration with an SRS symbol.

Figure 11.54 Multiplexing of SRS transmissions from different terminals [11].

Figure 11.55 Sounding RS symbol structure with RPF = 2 [12].

Figure 11.56 UL power control with variable data rate [19].

Figure 11.57 Timing diagram of the downlink HARQ [12].

Figure 11.58 Timing diagram of the uplink HARQ [12].

Chapter 12

Figure 12.1 Intra‐band versus inter‐band carrier aggregation: contiguous and non‐contiguous.

Figure 12.2 Uplink carrier aggregation.

Figure 12.3 Layer 2 structure for DL with CA configured [2].

Figure 12.4 Layer 2 structure for UL with CA configured [2].

Figure 12.5 RF coverage with inter‐band carrier aggregation.

Figure 12.6 MIMO DL with precoding and reference signal for demodulation. DM‐RS is UE and data stream specific signal.

Figure 12.7 DM‐RS pattern for rank 3 and 4 [4].

Figure 12.8 Scenario 1: Homogeneous network with intra‐site CoMP [5].

Figure 12.9 Scenario 2: Homogeneous network with high Tx power RRHs.

Figure 12.10 Scenario 3/4: Network with low‐power RRHs within the macrocell coverage.

Figure 12.11 Joint transmission CoMP.

Figure 12.12 Uplink CoMP reception.

Figure 12.13 Relay configuration.

Figure 12.14 Overall E‐UTRAN architecture supporting relay node [2].

Figure 12.15 Functional entities in relaying architecture [7].

Figure 12.16 User‐plane protocol stack [7].

Figure 12.17 Packet delivery with relay architecture [7].

Figure 12.18 Control‐plane protocol stack in relay architecture [7].

Figure 12.19 Signalling connection in relay architecture.

Figure 12.20 Relay Node DL radio frame configuration: normal subframes (left) composed with reference, control signals and user data, and gap in transmission to UE on Uu in declared MBSFN subframes (right). This gap is used for reception of Un by RN from DeNB [8].

Figure 12.21 Resource allocation for PDCCH and E‐PDCCH.

Chapter 13

Figure 13.1 Planned frequency spectrum allocation for 5G.

Figure 13.2 Concept of successive interference cancellation.

Figure 13.3 Downlink NOMA power allocation.

Figure 13.4 Concept of NOMA.

Figure 13.5 General AAS BS radio architecture [12].

Figure 13.6 Active Antenna System architecture [12].

Figure 13.7 Beamforming in the elevation plane with an Active Antenna System.

Figure 13.8 5G network slices implemented on a common infrastructure.

Figure 13.9 5G stand‐alone system architecture [21].

Figure 13.10 Overall architecture [22].

Figure 13.11 Functional split between NG‐RAN and 5GC [22].

Figure 13.12Figure 13.12 NG interface architecture.

Figure 13.13 NG interface protocol stack [22].

Figure 13.14 Xn protocol stack: (a) user plane and (b) control plane [22].

Figure 13.15 NG‐RAN gNB architecture [23].

Figure 13.16 Interface protocol structure for F1 [23].

Figure 13.17 User‐plane protocol stack [22].

Figure 13.18 Control plane protocol stack [22].

Figure 13.19 Downlink layer 2 structure [22].

Figure 13.20 Uplink layer 2 structure [22].

Figure 13.21 Inter‐subcarrier interference.

Figure 13.22 Resource grid and resource block [25].

Figure 13.23 MgNB Bearers for Dual Connectivity [22].

Figure 13.24 SgNB Bearers for Dual Connectivity [22].

Figure 13.25 Control plane architecture for EN‐DC [30].

Figure 13.26 Control plane architecture for MR‐DC with 5GC [30].

Figure 13.27 Radio Protocol Architecture for MCG, MCG split, SCG and SCG split bearers in MR‐DC with EPC (EN‐DC) [30].

Figure 13.28 Radio Protocol Architecture for MGC, MCG split, SCG and SCG split bearers in MR‐DC with 5GC (NGEN‐DC, NE‐DC) [30].

Figure 13.29 U‐plane connectivity for EN‐DC (left) and MR‐DC with 5GC (right) [30].

Chapter 14

Figure 14.1 Typical GSM site solution.

Figure 14.2 OBSAI BTS reference architecture [2].

Figure 14.3 Logical structure of RP3–01 interface [3].

Figure 14.4 Generalized modular SDR architecture [7].

Figure 14.5 OBSAI base‐station architecture with separate RF and system modules [8].

Figure 14.6 Feederless site solution example with OBSAI architecture.

Figure 14.7 SFP, a small form factor pluggable optical transceiver.

Figure 14.8 Compact Nokia RF module site solutions [9].

Figure 14.9 Integration of RF modules into an antenna array forming an Active Antenna System (AAS) [9].

Figure 14.10 Centralized (Cloud) RAN architecture.

Guide

Cover

Table of Contents

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Introduction to Mobile Network Engineering

GSM, 3G-WCDMA, LTE and the Road to 5G

Alexander Kukushkin

PhD, Australia

Copyright

This edition first published 2018

© 2018 John Wiley & Sons Ltd

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Library of Congress Cataloging-in-Publication Data

Names: Kukushkin, Alexander, author.

Title: Introduction to mobile network engineering : GSM, 3G-WCDMA, LTE and the road to 5G / by Alexander Kukushkin.

Description: Hoboken, NJ : John Wiley & Sons, 2018. | Includes bibliographical references and index. |

Identifiers: LCCN 2018012499 (print) | LCCN 2018021194 (ebook) | ISBN 9781119484103 (pdf) | ISBN 9781119484226 (epub) | ISBN 9781119484172 (cloth)

Subjects: LCSH: Mobile communication systems. | Wireless metropolitan area networks.

Classification: LCC TK5103.2 (ebook) | LCC TK5103.2 .K85 2018 (print) | DDC 621.3845/6-dc23

LC record available at https://lccn.loc.gov/2018012499

Cover design by Wiley

Cover image: © pluie_r/Shutterstock

Dedication

To my family

Foreword

From the 1990s to the present, three generations of mobile radio networks have been deployed in every country of the world. Those networks connect billions of customers and provide mobile communications services. Mobile radio communications have become ubiquitous throughout the world. People are getting used to the technology through commercial mobile phones. The mobile network infrastructure that enables communications has become a normal part of the urban environment in which people live. There is also a great number of other applications for mobile radio that are essential in the modern world and are used in navigation, transportation, machine‐to‐machine communications (M2M), robotics, emergency and low enforcement services, broadcasting, space exploration, the military, and so on. The mobile radio is, in fact, a part of a more widely defined wireless technology that, of course, includes wireless LANs (Wi‐Fi) with fixed and nomadic access.

The content of this book is limited to three major mobile communication technologies: GSM, 3G‐WCDMA and LTE with the major focus on Radio Access Network (RAN) technology. We introduce some basic concepts of mobile network engineering used in the design and rollout of mobile networks. Then we cover principles, design constraints and provide a more advanced insight into the radio interface protocol stack, operation and dimensioning for three major mobile network technologies; the Global System Mobile (GSM), third (3G‐WCDMA) and fourth generation (4G‐LTE) mobile technologies that have been recently deployed or are shortly to be deployed. Enhancements of fourth generation technology in LTE‐Advanced (LTE‐A) are described at the level of conceptual design.

The concluding sections of the book are concerned with further development towards the next generation of mobile networks (5G). The last section describes some key concepts that may bring significant enhancements in network operation efficiency and quality of services experienced by customers. A development of the fifth generation of mobile networks can be regarded as a mix of evolutionary advances in 4G LTE through LTE‐A and new radio technology likely operating in newly allocated spectrum bands. This development covers a broad area of applications and many different topics that require specifically dedicated study. Therefore, many interesting and important topics such as the Internet of Things, massive MTC, developments in new technology for emergency services based on LTE, integration of the mobile radio access network and Wi‐Fi are out of the scope of this book.

Since the standards for 5G are still in development, most of the features of the new radio technology are related to 3GPP Release 15. Some breakthrough technological advances are planned for further releases of 5G, such as a Full Duplex and self‐backhauling and are described as concepts rather than commercially available technology.

While many excellent books on mobile radio networking are available, I think many more will be published in the near future since the subject is continuously evolving. This book is intended to provide a generalist and compressed description of major technologies utilized in the radio access part of modern mobile networks. I envisage readers are engineers in relatively early stages of their careers in the mobile wireless industry. Some of them may be taking a post‐graduate course to enhance their knowledge. They may include operation support engineers, technical sale/presale engineers, technical and account managers who may need or wish to enhance or expand their knowledge of mobile network system engineering. Each major technology section of the book consists of introductory material, a more advanced part and a summary.

Alexander Kukushkin

Acknowledgements

I thank Professor Branka Vucetic, School of Electrical and Information Engineering, University of Sydney, for the invitation to teach at the University that led to the writing of this book. I wish to thank the reviewers of the book for their constructive comments that helped to improve and extend the content, especially on the 5G related topics.

Abbreviations

3G

Third Generation

3GPP

3rd Generation Partnership Project

5G

Fifth Generation of mobile networks

5GC

5G Core network

5G‐S

5G System

TMSI

Temporary Mobile Subscription Identifier

AA

Antenna Array

AAA

Authentication, Authorization & Accounting

AAS

Active Antenna System

ACK

ACKnowledgement

ADC

Analogue to Digital Converter

AF

Application Function

AGCH

Access Grant CHannel

AICH

Acquisition Indicator CHannel

AKA

Authentication and Key Agreement

AM

Acknowledged Mode

AMC

Adaptive Modulation and Coding

AMF

Access and Mobility Management Function

AMR

Adaptive Multi‐Rate (coding)

ARFCN

Absolute Radio Frequency Channel Number

ARQ

Automatic Repeat reQuest

ATCA

Advanced Telecommunications Computing Architecture

AUC

AUthentication Centre

AUSF

Authentication Server Function

BALUN

BALanced to UNbalanced conversion

BBU

Base Band Unit

BCCH

Broadcast Control CHannel

BCH

Broadcast CHannel

BLER

BLock Erasure Rate

BMC

Broadcast/Multicast Control

BS

Base Station

BSC

Base Station Controller

BSIC

Base Station Identity Code

BSS

Base Station Subsystem

CA

Carrier Aggregation

CAC

Call Admission Control

CC

Component Carrier

CCCH

Common Control Channel

CCE

Control Channel Element

CCPCH

Common Control Physical Channel

CCTrCH

Coded Composite Transport Channel

CDD

Cyclic Delay Diversity

CDM

Code Division Multiplexing

CDMA

Code Division Multiple Access

CIR

Carrier to Interference Ratio

COMP

COordinated MultiPoint transmission and reception

CP

Cyclic Prefix

CPCH

Common Packet Channel

CPICH

Common Pilot Channel

CP‐OFDM

Cyclic Prefix‐OFDM

CPRI

Common Public Radio Interface

CQI

Channel Quality Indicators

C‐RAN

Centralized Radio Access Network

CRC

Cyclic Redundancy Check

CRNC

Controlling RNC

CRNTI

Cell Radio Network Temporary Identifier

CRS

Cell RS

CSCH

Compact Synchronization Channel

CSFB

Circuit Switched Fall Back

CSI

Channel State Information

CSI‐RS

Channel State Information Reference Signal

CTCH

Common Traffic Channel

DAC

Digital‐to‐Analogue Convertor

DC

Dual Connectivity

DCCH

Dedicated Control Channel

DCH

Dedicated Transport Channel

DCI

Downlink Control Information

DeNB

Donor eNB

DFT

Discrete Fourier Transform

DFTS‐OFDM

DFT Spread‐OFDM

DL PCC

Downlink Primary Component Carrier

DL SCC

Downlink Secondary Component Carrier

DLL

Data Link Layer

DL‐SCH

Downlink Shared CHannel

DMRS

DeModulation Reference Signal

DN

Data Network

DNN

Data Network Name

DPCCH

Dedicated Physical Control CHannel

DPCH

Dedicated Physical CHannel

DPD

Digital Pre‐Distortion

DPDCH

Dedicated Physical Data Channel

DRNC

Drift RNC

DRX

Discontinuous Transmission and Reception

DSCH

Downlink Shared Channel

DTCH

Dedicated Traffic Channel

e2e

End to End

E‐AGCH

E‐DCH Absolute Grant CHannel

ECCE

Enhanced Control Channel Element

ECM

EPS Connection Management

E‐DCH

Enhanced Dedicated Channel

EDGE

Enhanced Data rate for GSM Evolution

E‐DPCCH

E‐DCH Dedicated Physical Control CHannel

E‐HICH

E‐DCH Hybrid ARQ Indicator CHannel

EIR

Equipment Identity Register

eMBB

Enhanced Mobile Broadband

EN‐DC

E‐UTRA‐NR Dual Connectivity

EPC

Evolved Packet Core

EPDCCH

Enhanced Physical Downlink Control CHannel

EPS

Evolved Packet System

EREG

Enhanced Resource Element Group

E‐RGCH

E‐DCH Relative Grant Channel

E‐TFC

E‐DCH Transport Format Combination

ETSI

European Telecommunications Standards Institute

E‐UTRA

Evolved UMTS Radio Access

E‐UTRAN

Evolved UTRAN

FACCH

Fast Associated Control Channel

FACH

Forward Access Channel

FBI

Feedback Information

FCCH

Frequency Correction Channel

FDD

Frequency Division Duplex

FDM

Frequency Division Multiplexing

FDMA

Frequency Division Multiple Access

F‐DPCH

Fractional DPCH

FDPS

Frequency Domain Packet Scheduling

FEC

Forward Error Correction

FER

Frame‐Error Rate

FFT

Fast Fourier Transform

FN

Frame Number

FR

Full Rate

GBR

Guaranteed Bit Rate

GGSN

Gateway GPRS Support Node

GMSC

Gateway MSC

GMSK

Gaussian Minimum Shift Keying modulation

GPRS

GSM Packet Radio Service

GSM

Global System Mobile

GTP

GPRS Tunnelling Protocol

HARQ

Hybrid ARQ

HLR

Home Location Register

HR

Half Rate

HSDPA

High Speed Downlink Packet Access

HS‐DPCCH

High‐Speed Dedicated Physical Control CHannel

HS‐DSCH

High‐Speed Downlink Shared CHannel

HSS

Home Subscriber Server

HS‐SCCH

High‐Speed Shared Control Channel

HSUPA

High Speed Uplink Packet Access

HW

Hardware

iFFT

inverse FFT

IMEI

International Mobile Station Equipment Identity

IMS

IP Multimedia Subsystem

IMSI

International Mobile Subscriber Identity

IPsec

IP Security protocol

ISHO

Inter‐System Handover

ISI

Inter‐Symbol Interference

IWF

Interworking Function

LA

Location Area

LAC

Location Area Code

LAI

Location Area Identifier

LAN

Local Area Network

LLC

Logical Link Control

LNA

Low Noise Amplifier

LOS

Line Of Sight

LPMA

Lattice Partition Multiple Access

LTE

Long Term Evolution

M2M

Machine to Machine communications

MAC

Medium Access Control

MAHO

Mobile Assisted HandOver

MAPL

Maximum Allowable Path Loss

MCC

Mobile Country Code

MCG

Master Cell Group

MCS

Modulation Coding Scheme

MeNB

Master eNB

MgNB

Master gNB

MHA

Mast Head Amplifier

MIB

Master Information Block

MIMO

Multiple Input Multiple Output

MME

Mobility Management Entity

MMI

Man‐Machine Interface

MN

Master Node

MNC

Mobile Network Code

MRC

Maximum Ratio Combining

MR‐DC

Multi‐RAT Dual Connectivity

MS

Mobile Station (mobile phone)

MSC

Mobile Switching Centre

MSISDN

Mobile Subscriber ISDN Number

MSRN

Mobile Station Routing Number

MT

Mobile Termination

MTC

Machine Type Communications

MTCH

Multicast Traffic Channel

MU‐MIMO

Multi‐User MIMO

MUST

Multiuser Superposition Transmission

NACK

Negative ACKnowledgement

NAS

Non‐Access Stratum

NB‐IoT

Narrow‐Band Internet of Things

NDC

National Destination Code

NE‐DC

MR‐DC with the 5GC

NEF

Network Exposure Function

NF

Network Functions

NFV

Network Function Virtualization

NGEN‐DC

NG‐RAN E‐UTRA‐NR Dual Connectivity

NGMN

Next Generation Mobile Network Alliance

NG‐RAN

New Generation Radio Access Network

NOMA

Non‐Orthogonal Multiple Access

NR

New Radio

NRF

NF Repository Function

NSS

Network Switching Subsystem

NSSAI

Network Slice Selection Assistance Information

NSSF

Network Slice Selection Function

OAM

Operation, Administration and Maintenance

OBSAI

Open Base Station Architecture Initiative

OFDMA

Orthogonal Frequency Division Multiple Access

OMC

Operation and Maintenance Center

OSI

Open System Interconnect

OSS

Operation Support Subsystem

OVP

Over Voltage Protection

OVSF

Orthogonal Variable Spreading Factor

PACCH

Packet Associated Control Channel

PAPR

Peak‐to‐Average Power Ratio

PCC

Primary Component Carrier

PCCCH

Packet Common Control Channel

P‐CCPCH

Primary Common Control Physical Channel

PCell

Primary Cell

PCF

Policy Control Function

PCFICH

Physical Control Format Indicator Channel

PCH

Paging Channel

PCPCH

Physical Common Packet Channel

PCRF

Policy Charging and Rules Function

PCU

Packet Control Units

PDCH

Packet Data CHannel

PDCP

Packet Data Convergence Protocol

PDP

Packet Data Protocol

PDSCH

Physical Downlink Shared CHannel

PDTCH

Packet Data Traffic CHannel

PDU

Packet Data Unit

P‐GW

Packet Data Network Gateway

PHICH

Physical Hybrid‐ARQ Indicator Channel

PICH

Paging Indicator Channel

PIN

Personal Identification Number

PLMN

Public Land Mobile Networks

PMI

Precoder Matrix Indication

PRACH

Physical Random Access Channel

PRB

Power Resource Block

P‐RNTI

Paging Group Identity

PSC

Primary Scrambling Code

P‐SCH

Primary Synchronization Channel

PSS

Primary Synchronization Signal

PSTN

Public Switching Telephone Network

PTCCH

Packet Timing advance Control Channel

PTCH

Packet Traffic Channel

PT‐RS

Phase‐Tracking Reference Signals

PUCCH

Physical Uplink Control CHannel

QCI

QoS Class Indicator

QoE

Quality Of user Experience

QoS

Quality of Service

RAB

Radio Access Bearer

RACH

Random Access CHannel

RAN

Radio Access Network

RAT

Radio Access Technology

RAU

Routing Area Update

RB

Resource Block

RDN

Radio Distribution Network

REG

Resource Element Group

RF

Radio Frequency

RI

Rank Indication

RLC

Radio Link Control

RN

Relay Node

RNC

Radio Network Controller

RP

Reference Point

RRC

Radio Resource Control

RRH

Remote Radio Head

RRM

Radio Resource Management

RRU

Remote Radio Unit

RS

Reference Signals

SACCH

Slow Associated Control Channel

SAE

System Architecture Evolution

SAW

Stop‐And‐Wait

SCC

Secondary Component Carrier

SCell

Secondary Cell

SC‐FDMA

Single Carrier FDMA

SCG

Secondary Cell Group

SCH

Synchronization Channel

S‐CPICH

Secondary Common Pilot Channel

SDCCH

Standalone Dedicated Control Channel

SDN

Software Defined Networking

SDR

Software Designed Radio

SDU

Service Data Unit

SF

Spreading Factor

SFN

System Frame Number

SFP

Small Form factor Pluggable

SgNB

Secondary gNB

SGSN

Serving GPRS Support Node

S‐GW

Serving Gateway

SIB

System Information Block

SIC

Successive Interference Cancellation

SIM

Subscriber Identity Module

SINR

Signal to Interference and Noise Ratio

SIP

Session Initiation Protocol

SIR

Signal to Interference Ratio

SM

System Module

SMF

Session Management Function

SMG

Special Mobile Group

SN

Subscriber Number

SecN

Secondary Node

SNDCP

Subnetwork Dependent Convergence Protocol

S‐NSSAI

Single Network Slice Selection Assistance Information

SON

Self‐Organizing Network

SRB

Signalling Radio Bearer

SRNC

Serving RNC

SRS

Sounding RS

S‐SCH

Secondary Synchronization Channel

SSS

Secondary Synchronization Signal

STR

Simultaneous Transmission and Reception

SU‐MIMO

Single User‐MIMO

SVD

Singular‐Value Decomposition

SW

Software

TA

Terminal Adapter

TAB

Transceiver Array Boundary

TAG

Timing Advance Group

TAU

Tracking Area Update

TB

Transport Block

TBF

Temporary Block Flow

TCH

Traffic Channel

TCP

Transmission Control Protocol

TDMA

Time Division Multiple Access

TE

Terminal Equipment

TF

Transport Format

TFC

Transport Format Combination

TFCS

Transport Format Combination Set

TFI

Temporary Flow Identifier

TM

Transparent Mode

TMA

Tower Mounted Amplifier

TMSI

Temporary Mobile Subscriber Identity

TPC

Transmit Power Control

TrCH

Transport Channel

TRXUA

Transceiver unit array

TS

Time Slot

TTI

Transmission Time Interval

UDM

Unified Data Management Function

UE

User Equipment

UL PCC

UpLink Primary Component Carrier

UL SCC

UpLink Secondary Component Carrier

UL‐SCH

UpLink Shared CHannel

UM

Unacknowledged mode

UMTS

Universal Mobile Telecommunication System

UPF

User Plane Function

URLLC

Ultra‐Reliable and Low Latency Critical Communications

USB

Universal Serial Bus

USF

Uplink State Flag

USIM

Universal Subscriber Identity Module

VAS

Value Added Services

VLR

Visited Location Centre

VoIP

Voice over Internet Protocol

WCDMA

Wideband Code Division Multiple Access

Wi‐Fi

Wireless local area networking

Chapter 1Introduction

Over the last few decades, mobile radio communications have become ubiquitous throughout the world. People have become accustomed to the technology through commercial mobile phones. The mobile network infrastructure that enables communications has become a normal part of urban environment in which people live.

There is also great number of other mobile radio applications essential in the modern world that are used in navigation, transportation, machine‐to‐machine communications (M2M), robotics, emergency and low enforcement services, broadcasting, space exploration, the military and so on. Mobile radio is, in fact, a part of more a widely defined wireless technology that, of course, includes wireless LANs (WiFi) with fixed and nomadic access.

Each application was developed on the basis of specific needs and, in some aspects, the mobile radio networks for emergency services and commercial mobile services are different. Nonetheless, the underlying principles in mobile communications, such as radio link design given performance constraints, separation of control and traffic channels, mobility support, principles of the channel allocation in the cell, radio network management and so on, have lots in common in many applications. Moreover, some of the commercial technologies, such as LTE, now appeared to support land mobile radio applications for emergency and public safety services.

This book is written as a modified and expanded set of lectures on the wireless engineering course I had privilege to teach at the University of Sydney, Australia for a couple of years. Most of the concepts of these lectures were adopted from published standards and also based on personal experience in the field as well as from some works of other authors. The course was delivered as post‐graduate study. The assumption was made that the fundamentals of digital communications were already known to attendees and the objective was to explain the subject using mathematical arguments as little as possible; that is, close to common practice in the commercial communications industry. The target audience are engineers who are involved in either network operations or technical pre‐sale. The content is limited to major three mobile communication technologies: GSM, 3G‐Wideband Code Division Multiple‐Access (WCDMA) and LTE with the major focus on radio access network (RAN) technology. The core part of the network is a complex subject on its own and is described only to discuss its role in e2e procedures and interfaces with the radio network.

Chapter 2Types of Mobile Network by Multiple‐Access Scheme

Mobile radio networks can be distinguished by operation modes, services and applications and multiple‐access schemes. A major influence on the development of commercial radio communication systems is the scarcity of radio spectrum available for utilization. An apparent objective is to assign the maximum number of users to an available radio frequency segment. This objective is achieved by using various multiple‐access schemes. Here, we list the four most common technologies:

frequency division multiple access (FDMA)

time‐division multiple access (TDMA)

code division multiple access (CDMA)

orthogonal frequency division multiple access (OFDMA)

Figure 2.1 illustrates the principles of multiple‐access schemes used in mobile communications.

Figure 2.1 Common multiple‐access schemes.

In FDMA, each mobile user (or user group) is allocated a frequency channel for the duration of the call, while in the TDMA scheme a group of callers use the same frequency channel but during different time intervals. Most of the systems using TDMA do, in fact, combine both schemes: FDMA and TDMA. In this approach, the system allocates a set of frequency channels to several groups of users, one frequency channel per group. One user in each group accesses an allocated frequency channel during a system assigned time slot. We will have a detailed look at the frequency‐time‐domain channel structure when considering the Global System Mobile (GSM) based on combined FDMA/TDMA multiple‐access technology.

In CDMA, all users occupy the same frequency channel and can transmit/receive at the same time. The information stream of each user is coded by a specific code ensuring orthogonality between users. It can be achieved by allocating additional frequency bandwidth to each user in excess of the bandwidth required for transmitting user source data. The third‐generation mobile system, WCDMA, utilizes this technology. The WCDMA system will be considered in Chapter 9.

In OFDMA, a large spectrum segment is allocated as a channel pool available to one or many simultaneous users. As seen in Figure 2.1, user allocated channel bandwidth and duration can be varied according to user service requirements and instant availability of common resource/channel pool. User channels are mapped on the set of orthogonal narrowband carriers, thus excluding mutual interference. The details of the OFDMA scheme will be discussed in the Chapter 11 discussion about LTE technology.

Chapter 3Cellular System

3.1 Historical Background

A scarcity of the available frequency spectrum is a major issue in the development of mobile networks. We consider a well quoted and quite convincing example of a GSM system. For example, only 25 MHz of the radio spectrum is available for the GSM system in the 900 MHz frequency range. That may allocate a maximum of 125 frequency channels each with a carrier bandwidth of 200 kHz. Within an eightfold time multiplex for each carrier, a maximum of 1000 channels can be realized. This number is further reduced by guard bands in the frequency spectrum and the overhead required for signalling.

Apparently, 1000 simultaneous users cannot produce sufficient revenue to justify the licence cost of 25 MHz of spectrum. In order to be able to serve several hundreds of thousands or millions of subscribers in spite of this limitation, frequencies must be spatially reused; that is, deployed repeatedly in a geographic area. In this way, services can be offered with a cost‐effective subscriber density and acceptable blocking probability.

3.2 Cellular Concept

The spatial frequency reuse concept led to the development of the cellular principle, which allowed a significant improvement in the economic use of frequencies. The essential characteristics of the cellular network principle are as follows:

The area to be covered is subdivided into cells (radio zones). These cells are often modelled in a simplified way as hexagons (

Figure 3.1

) with a base station located at the centre of each cell. Assume that the operator has a licence on a set of channels, called, for example, set

S

.

To each cell

i

a subset of the frequencies

is assigned from the total set (bundle), which is assigned to the respective mobile radio network. In the GSM system, the set of frequencies assigned to a cell is called the Cell Allocation (CA). Under normal circumstances the number of channels in a subset

is driven by traffic capacity requirements.

Neighbouring cells do not normally use the same frequencies since this would lead to severe co‐channel interference from the adjacent cells.

Only at distance

D

(the frequency reuse distance) can a frequency from the set

be reused (

Figure 3.1

); that is, cells with distance D to cell

i

can be assigned one or all of the frequencies from the set belonging to cell

i

. When designing a mobile radio network,

D

must be chosen to be sufficiently large, such that the co‐channel interference remains small enough not to affect speech quality.

When a mobile station moves from one cell to another during an ongoing conversation, an automatic channel/frequency change may occur (handover), which maintains an active speech connection over cell boundaries.

Figure 3.1 Model of a cellular network with frequency reuse. Shadowed hexagons represent cells with the same set of allocated frequencies.

The spatial repetition of frequencies is done in a regular systematic way; that is, each cell with the cell allocation sees its neighbours with the same frequencies again at a distance D (Figures 3.1 and 3.2). Therefore, exactly six such neighbour cells exist. The first ring in the frequency set always contains six co‐channel cells in frequency reuse system independent of the form and size of cells, not just in the hexagon model.

Figure 3.2 Frequency reuse and cluster formation.

3.3 Carrier‐to‐Interference Ratio

The signal quality of a connection is measured as a function of received useful signal power and interference power received from co‐channel cells and is given by the Carrier‐to‐Interference Ratio (CIR or C/I):

(3.1)

The intensity of the interference is essentially a function of co‐channel interference depending on the frequency reuse distance . From the viewpoint of a mobile station, the co‐channel interference is caused by base stations at a distance from the current base station, see Figure 3.1. A worst‐case estimate for the CIR of a mobile station at the border of the covered area at distance from the base station can be obtained by assuming that all six neighbouring interfering transmitters operate at the same power and are approximately equally far apart (a distance that is large compared with the cell radius ).

3.2

Finally, we find the worst‐case CIR as a function of the cell radius R, the reuse distance D and the attenuation exponent γ as

3.3

Therefore, in a given radio environment, the CIR depends essentially on the ratio . From these considerations, it follows that, for a desired or required CIR value at a given cell radius, one must choose a minimum distance for frequency reuse above which co‐channel interference falls below the required threshold.

3.4 Formation of Clusters

The regular spatial repetition of frequencies results in a clustering of cells. The cells within a cluster must each be assigned different sets of channels, while cells belonging to neighbouring clusters can reuse the channels in the same spatial pattern. The size of a cluster is characterized by the number of cells per cluster , which determines the frequency reuse distance when the cell radius is given. Figure 3.2 shows some examples of clusters. The numbers designate the respective frequency sets used within the single cells. For each cluster, the following holds:

A cluster can contain all of the frequencies of the mobile radio system.

Within a cluster, no frequency can be reused. The frequencies of a set

may be reused at the earliest in the neighbouring cluster.

The larger the cluster is, the larger the frequency reuse distance and the larger the CIR. However, the larger the values of

, the smaller the number of channels and the number of supportable active subscribers per cell.

The geometry of hexagons sets the relationship between the cluster size and the reuse distance as:

3.4

The CIR is then given by

3.5

assuming the propagation attenuation exponent , . For example, if the system can achieve acceptable quality provided the C/I is at least 18 dB, then the required cluster size is 6.5. Hence, a cluster size of would fit. Not all cluster sizes are possible due to the restrictions of the hexagonal geometry. The hexagon geometry results in following equation for cluster size

(3.6)

where are integers.

Possible values of include 3, 4, 7, 12, 13, 19 and 27. The smaller the value of C/I, the smaller the allowed cluster size. Hence the available channels can be reused on a denser basis, serving more users and producing an increased capacity. In the example here, had the path loss dependence on radius been slower (i.e. the propagation exponent was less than 4), the required cluster size would have been greater than 7, so the path loss characteristics have a direct impact on the system capacity. Another constraint on the value of cluster size is that each base‐station site often serves a cloverleaf of three cells. (This can be designated, for example, by specifying 21 cells as a cluster.) Commonly used cluster sizes are multiples of three.

3.5 Sectorization

One way to reduce cluster size, and hence increase capacity, is to use sectorization. The group of channels available at each cell is split into three cells (sectors), each of which is confined in coverage to one‐third of the cell area by the use of directional antennas, as shown in Figure 3.3.

Figure 3.3 Sectorization.

Interference now comes from just two rather than six of the first‐tier interfering sites, reducing interference by a factor of three and allowing cluster size to be increased by a factor of √ = 1.72 in theory.

Sectorization has some disadvantages:

Mobiles have to change channels more often, resulting in an increased signalling load on the system.

The available pool of channels has to be reduced by a factor of 3 (in a three‐sector site) for a mobile at any particular location; this reduces the trunking efficiency given same cell size.

Despite these issues, sectorization is used very widely in modern cellular systems, particularly in areas requiring high traffic density. More than three sectors can be used to further improve the interference reduction.

The effective radiated power and, consequently, CIR can be increased with directional antennas. In a three‐sector site the radiation pattern of sector antenna spans 120° in the horizontal plane, as shown in Figure 3.4. In fact, the horizontal lobe of the sector antenna extends over 120° creating overlapping regions between site sectors where a mobile can receive a signal from both sectors. These regions facilitate an intra‐sector handover; that is, they enable an MS travelling between sectors to be switched from one sector to another.

Figure 3.4 Antenna patterns for a cell site with three 120° sectors.

While sectorization does significantly increase the CIR, it often decreases the carried traffic in time‐division multiple access (TDMA) and frequency division multiple access (FDMA) systems. For example, an omnidirectional site is allocated frequency channels and carries a traffic Erlang with a defined probability of cell blockage. After sectorization, each sector may be allocated channels and may carry traffic of