IS Sr.l
`
`The uDSM
`
`&$ys
`
`> ystem for
`Mobile
`Communications
`
`Ex.1030
`APPLE INC. / Page 1 of 21
`
`

`

`Y-a7- ee
`
`The GS M
`S ystem for
`Mobile
`Communications
`
`
`
`Michel MOULY
`Marie-BernadettePAUTET
`
`
`
`Ex.1030
`APPLEINC./ Page 2 of 21
`
`Ex.1030
`APPLE INC. / Page 2 of 21
`
`

`

`This book is published by the author’s company, Cell & Sys.
`Correspondence,
`in particular for the orders, but also for comments,
`should be mailedto:
`
`CELL & SYS
`4, rue Elisée Reclus
`F-91120 PALAISEAU
`FRANCE
`
`Telephone: + 33 1 69 31 03 18
`
`Facsimile : + 33 1 69 31 03 38
`
`Website : http :/ /perso.wanadoo.fr/cell.sys/
`
`Copyright © 1992, Michel MOULYand Marie-Bernadette PAUTET
`All rights reserved. Nopart of this book may be reproduced,translated, or
`utilised in any form or any means,electronic or mechanical, including
`photocopying, recording, or any information storage orretrieval system,
`without permission in writing fromthe authors.
`All drawingsare original, and all correspondingrights reserved.
`
`communications”) are registered.
`
`The name and logo GSM (and “Global System for Mobile
`
`International Standard Book Number: 2-9507190-0-7
`
`
`
`
`Ex.1030
`APPLEINC./ Page 3 of 21
`
`Ex.1030
`APPLE INC. / Page 3 of 21
`
`

`

`CONTENTS
`
`Foreword, by Thomas Haug
`Contents
`
`Preface
`
`Chapter 1 - Setting the Scene
`1.1. A Little Bit of History
`1.1.1. B.G. (Before GSM)
`1.1.2. The Genesis of a Standard
`1.1.3. Organisation of the Work
`1.1.4. The GSM MoU
`1.1.5. Technical Choices
`1.1.6. The GSM Technical Specifications
`1.2. Cellular Systems
`1.2.1. General Aspects
`1.2.2. Cellular Coverage
`1.2.3. Radio Interface Management
`1.2.4. Consequences of Mobility
`1.2.5. Roaming
`1.3. GSM Functionalities
`1.3.1. GSM: a Multiservice System for the User
`1.3.2. GSM: a System for the Operator
`Specifications Reference
`
`/
`
`7
`11
`
`17
`
`23
`24
`24
`28
`29
`32
`33
`37
`39
`39
`40
`43
`44
`46
`47
`47
`72
`75
`
`|
`
`
`
`79
`Chapter 2 - Architecture
`80
`2.0.1. The three Description Axes
`2.0.2. Frontiers of the System: Where are the Borders of GSM?=84
`2.0.3.
`Internal GSM Organisation
`87
`2.1. Sub-Systems
`89
`2.1.1. The Mobile Station (MS)
`89
`2.1.2. The Base Station Sub-System (BSS)
`94
`2.1.3. The Network and Switching Sub-System (NSS)
`100
`2.1.4. The Operation Sub-System (OSS)
`105
`
`
`
`Ex.1030
`APPLEINC./ Page 4 of 21
`
`Ex.1030
`APPLE INC. / Page 4 of 21
`
`

`

`2.2. Functional Planes
`
`2.2.1. Layer Modelling
`2.2.2. Transmission
`2.2.3. Radio Resource Management(RR)
`2.2.4. Mobility Management (MM)
`2.2.5. Communication Management (CM)
`2.2.6. Operation, Administration and Maintenance (OAM)
`2.3. Interfaces and Protocols — An Overview
`Specifications Reference
`
`Chapter 3 - Transmission -
`
`3.1. Modelling Principles
`3.2. An End-to-End View of Transmission
`
`3.2.1. Speech
`3.2.2. Non Speech Services
`3.3. Transmission inside GSM
`3.3.1. Architecture
`
`3.3.2. Speech
`3.3.3. Data
`Specifications Reference
`
`108
`109
`113
`114
`114
`115
`116
`118
`121
`
`125
`
`126
`128
`128
`132
`149
`149
`154
`166
`184
`
`187
`
`188
`189
`190
`191
`195
`197
`217
`227
`231
`238
`248
`249
`258
`
` 12
`
`Chapter 4 - The Radio Interface
`4,1. The Needs
`4.1.1. User Data Transmission
`
`4.1.2. Signalling
`4,1.3.
`Idle Mode
`4,2. The Multiple Access Scheme
`4.2.1. The Time Axis
`4.2.2. The Frequency Axis
`4.3. From Source data to Radio Waves
`4.3.1. The Bursts
`4.3.2.
`Interleaving and Channel Coding
`4.3.3. Ciphering
`4.3.4. Modulation
`Specifications Reference
`
`
`
`Ex.1030
`APPLEINC./ Page 5 of 21
`
`Ex.1030
`APPLE INC. / Page 5 of 21
`
`

`

`R)
`‘M)
`Aaintenance (OAM)
`—
`
`on
`
`g
`
`108
`109
`11S
`14
`ha
`116
`118
`121
`
`125
`126
`128
`128
`132
`149
`149
`154
`166
`184
`
`187
`188
`iBe
`iol
`195
`oT
`on”
`731
`ve
`249
`258
`
`|
`
`
`
`|
`
`|
`
`Chapter 5 - Signalling Transfer
`5.1. The Needs
`5.1.1. Contiguous Entities
`5.1.2. Relaying
`5.1.3. Protocol Interworking
`oie LG
`5.2.1. Structuring in Frames
`5.2.2. Segmentation and Re-Assembly
`5.2.3. Error Detection and Correction
`5.2.4. Multiplexing
`5.2.5. Flow Control
`5.2.6. LAPD and LAPDm Frames: a Summary
`5.2.7. RLP Characteristics
`:
`5.3. Networking
`5.3.1. Networking in the BSS
`5.3.2. Networking in the NSS
`5.3.3. Networking for Supplementary Services Management
`5.3.4. Networking for Point-to-Point Short Messages
`Specifications Reference
`3
`Chapter 6 - Radio Resource Management
`6.1. RR Functions
`6.1.1. The Concept of RR-Session
`6.1.2.
`Initialisation
`6.1.3. Transmission Management
`6.1.4. Handover Preparation
`6.1.5. Power Control and Timing Advance
`6.1.6. Radio Channel Management
`6.2. Architecture and Protocols
`6.3. RR Procedures
`6.3.1.
`Initial Procedures: Accessand Initial Assignment
`6.3.2. Paging Procedures
`6.3.3. Procedures for Transmission Mode
`and Cipher Mode Management
`6.3.4. Handover Execution
`6.3.5. Call Re-Establishment
`6.3.6. RR-Session Release
`6.3.7. Load Management Procedures
`6.3.8. SACCH Procedures
`6.3.9. Frequency Redefinition
`6.3.10.General Information Broadcasting
`Specifications reference
`
`261
`262
`263
`264
`266
`one
`269
`270
`272
`277
`279
`280
`281
`283
`284
`294
`299
`301
`305
`
`309
`312
`313
`317
`321
`327
`342
`350
`362
`366
`367
`382
`
`385
`396
`412
`415
`418
`420
`424
`424
`429
`
`
`
`Ex.1030
`APPLEINC./ Page 6 of 21
`
`Ex.1030
`APPLE INC. / Page 6 of 21
`
`

`

`Chapter 7 - Mobility and Security Management
`7.1. Location Management
`7.1.1. The Factors Determining the Service
`7.1.2. Cell and PLMNSelection
`7.1.3. Architecture
`7.1.4. The Location Updating Procedures
`7.2. Security Management
`7.2.1. The Needs
`7.2.2. The Functions
`7.2.3. Architecture and protocols
`7.2.4. The Signalling Mechanisms
`7.3. Miscellaneous MM Functions
`Specifications Reference
`
`433
`434
`435
`446
`459
`465
`477
`477
`478
`485
`487
`493
`498
`
`
`
`564
`
`Chapter 8 - Communication Management
`8.0.1. The Communication
`8.0.2. Management Functions
`8.1. Call Control
`8.1.1. The Routing of Mobile Terminating Calls
`8.1.2. Architecture
`8.1.3. The Mobile Originating Call Establishment Procedure
`8.1.4. The Mobile Terminating Call Establishment Procedure
`8.1.5. The Interrogation Procedures
`8.1.6. Call Release
`8.1.7.
`In-Call Functions
`8.2. Supplementary services management
`8.2.1. Architecture
`8.2.2. Procedures
`8.3. Short messages
`8.3.1. Architecture
`8.3.2. Mobile Originating Short Messages
`8.3.3. Mobile Terminating Short Messages
`Specifications Reference
`
`501
`503
`507
`510
`510
`528
`530
`539
`543
`545
`
`547
`552
`353
`554
`556
`557
`559
`560
`
`
`
`Ex.1030
`APPLEINC./ Page 7 of 21
`
`Ex.1030
`APPLE INC. / Page 7 of 21
`
`

`

`agement
`
`vice
`
`es
`
`ent
`
`.
`ing Calls
`
`ablishment Procedure
`tablishment Procedure
`
`it
`
`ges
`ages
`
`433
`434
`435
`446
`459
`465
`477
`477
`478
`485
`487
`493
`498
`
`501
`503
`507
`
`510
`
`510
`528
`
`530
`539
`543
`545
`547
`552
`553
`554
`556
`557
`559
`560
`564
`
`Chapter 9 - Network Management
`9.1. Subscriber Management
`9.1.1. Subscription Administration
`9.1.2. Billing and Accounting
`9.2. Maintenance
`9,3. Mobile Station Management
`9.4. System Engineering and Operation
`9.4.1. Cellular Planning
`9.4.2. Cell Configuration
`9.4.3. Network Engineering
`9.4.4. Observations
`9.4.5. Network Change Control
`9.5. Architecture and Protocols
`9.5.1. Management Network Architecture
`9.5.2. Operation and Maintenance in
`the Traffic Handling Protocols
`9.5.3. The BTS Managementprotocol
`9.5.4. The GSM Q3 Protocol
`vee
`gs
`Specifications Reference
`
`TheList of the GSM Specifications
`
`Bibliography
`Index
`Message Index
`‘
`Indexof Figures
`
`|
`|
`|
`
`|
`
`567
`568
`569
`572
`578
`585
`591
`593
`613
`622
`627
`628
`633
`633
`
`637
`638
`640
`646
`
`649
`
`667
`673
`693
`697
`
`
`
`Ex.1030
`APPLEINC./ Page 8 of 21
`
`Ex.1030
`APPLE INC. / Page 8 of 21
`
`

`

`
`THE RADIO INTERFACE 217$$___________NEMADIOINTerrace.CCT.
`
`
`
`
`148 supertrames
`33s 760ms
`
`
`
`
`4.2.2. THE FREQUENCY AXIS
`
`4.2.2.1. The Available Frequencies
`
`GSM wasfirst devised as a cellular system in a specific 900 MHz
`band, called “the primary band’. This primary band includes two sub-
`bands of 25 MHz each, 890-915 MHz and 935-960 MHz (see figure
`4.16). This does not mean that the whole primary band must be used for
`GSMin a given country, especially at the start of the system. Moreover, a
`given operatoris rarely given morethan a portionofthis band, since most
`countries have several operators. However, every mobile station must be
`able to use the full band, in order notto impose constraints upon roaming
`users,
`
`In 1990, upon request of the United Kingdom,a second frequency
`band was specified for being used with the Specifications. This band
`includes the two domains 1710-1785 MHz and 1805-1880 MHz,
`twice 75 MHz:
`three times as much as the primary 900 MHz band.
`Mobile stations using this band are different from those using the primary
`band: using the same mobile equipment for roaming between the two
`variants of the system, GSM900 and DCS1800, althoughnot ruled out, is
`not envisaged in the nearfuture.
`Another extension of the primary band is forescen. It should
`consist of the band which is directly “below” the primary band. For
`instance, an 8 MHz extension would raise the 900 MHz bands to 882-
`915 MHz and 927-960 MHz,i.e., twice 33 MHz.
`
`
`
`
`
`45 MHz
`
`>
`
`<
`
`910 920
`900
`890
`< 25 MHz >
`
`960
`930 940 950
`< 25 MHz >
`
`f
`
`
`
`__| uplink (Mobile to Base)
`
`[> downlink (Base to Mobile)
`
`Figure 4.16 — GSMprimary band
`
`
`
`x 51 multiframes
`
`'s) cr
`
`
`
`
`
`
`
`
`
`51 multiframe
`>
`(#235 ms)
`
`
`erarchy of frames
`
`dle of both the 51 TDMAframecycle
`TA frame cycle for dedicated channels.
`ich serves as the basis for frame numbering.
`
`‘rame multiframe” is defined as a
`1 corresponds to the 51 x 8 BP cycle
`and of the common channels.
`
`sion of 51 x 26 TDMA frames (6.12
`ie
`smallest
`cycle
`for which the
`ed. Note that this repetition abstracts
`nstance the SACCH coding period is
`‘ould then be 4 superframes), neither
`‘CH (which in some cases does not
`ne which will now bedefined).
`
`is
`It
`period.
`numbering
`he
`to say exactly 12533.760 seconds, or
`d 760 milliseconds. It is obviously a
`cles, and determines in fact all the
`\o path. It is in particular the smallest
`ciphering.
`
`The GSM primary bandincludes two 25 MHz sub-bands around 900 MHz.
`
`
`
`Ex.1030
`APPLEINC./ Page 9 of 21
`
`Ex.1030
`APPLE INC. / Page 9 of 21
`
`

`

`
`
`
`
`
`218
`
`THE GSM SYSTEM
`
`(carrier number)
`
`;
`
`200 kHz
`<>
`
`GSM band
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`The central frequencies of the frequency slots are spread evenly
`every 200 kHz within these bands, starting 200 kHz away from the band
`borders (see figure 4.17). 124 different frequency slots are therefore
`defined in 25 MHz, and 374 in 75 MHz. The modulation spectrum is
`somewhat wider than 200 kHz, resulting in some level of interference
`between bursts on simultaneousslots or on adjacent frequencyslots. This
`is a nuisance mainly near the band borders, since this interference could
`disturb non-GSM applications in adjacent bands. The border frequencies
`are therefore usually avoided. The normal practice is not to use the
`frequency slots at the border (those numbered 0 and 124), except when a
`special agreement has been reached with the users of the adjacent band.
`As a consequence, the number of frequency slots which can be used in
`25 MHzis usually limited to 122.
`
`Figure 4.17 — Carriers at the border of the GSM band
`Carrier spacing is equal to 200 kHz.
`A guard band of 200 kHz betweenthe edge ofthe band
`and thefirst carrier is neededat the bottom of eachof the sub-bands;
`the carrier numbered0is often not used in practice.
`
`4.2.2.2. Frequency Hopping
`slow frequency hopping.
`The radio interface of GSM uses
`Frequency Hoppingconsists in changing the frequency used by a channel
`regular
`intervals. The origin of
`this
`technique lies
`in military
`at
`transmission systems, where it was introduced to ensure secrecy and
`combat jamming. Publications in that domain distinguish Fast Frequency
`
`
`
`
`
`Ex.1030
`APPLEINC./ Page 10 of 21
`
`Ex.1030
`APPLE INC. / Page 10 of 21
`
`

`

`(carrier number)
`
`border of the GSM band
`
`qual to 200 kHz.
`ween the edgeof the band
`bottom of each of the sub-bands;
`ften not used in practice.
`
`frequency slots are spread evenly
`arting 200 kHz away from the band
`srent frequency slots are therefore
`MHz. The modulation spectrum is
`iting in some level of interference
`or on adjacent frequency slots. This
`orders, since this interference could
`acent bands. The border frequencies
`normal practice is not
`to use the
`umbered 0 and 124), except when a
`with the users of the adjacent band.
`equency slots which can be used in
`
`slow frequency hopping.
`M uses
`zing the frequency used by a channel
`of
`this
`technique lies
`in military
`3
`introduced to ensure secrecy and
`t domain distinguish Fast Frequency
`
`frequency
`
`
`
`
`
`
`Figure 4.18 — Slow Frequency Hopping in the time-frequency domain
`
`Frequency for a given channel may change at each burst,
`and remains constant during the transmission of a burst
`
`than the
`frequency changes quicker
`Hopping (FFH), where the
`modulation rate, from Slow Frequency Hopping (SFH). In GSM,the
`transmission frequency remains the same during the transmission of a
`whole burst; GSM belongs therefore clearly to the slow hopping case.
`Figure 4.18 shows an example of a time-frequency diagram: for a
`frequency hopping channel.
`Slow frequency hopping was introduced in GSMfor two main
`reasons. Thefirst reason is frequency diversity. As shall be explained
`later, error-correcting codes are introduced in the transmission chain.
`Such codes are based on redundancy: the data is made redundantin such
`a waythat, even with a certain amountoferrors, the original data may be
`reconstructed from what remainsin the received flow. This redundancyis
`spread over several bursts. SFH therefore ensuresthat this information is
`sent on several frequencies, and this improves transmission performance.
`To explain this, a digression concerning propagation is needed.
`term
`Mobile radio transmission is subject
`to important short
`amplitude variations when obstacles are involved; these variations are
`called Rayleigh fading.
`In most cases,
`the emitting and receiving
`antennas are not within direct sight one with the other, and the received
`signal is the sum of a number of copies of one signal with different
`phases. For instance,if the path includesa reflection on an obstacle, there
`
`
`
`Ex.1030
`APPLEINC./ Page 11 of 21
`
`Ex.1030
`APPLE INC. / Page 11 of 21
`
`

`

`
`
`
`
`
`Figure 4.19 — Typical amplitude variations due to Rayleigh fading
`(the time unit is the time to move through one wavelength,
`e.g., 24 msat 50 km/h for 900 MHz)
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`are usually many other reflected paths, in particular whenthe reflector is
`irregular and of a scale greater than the wavelength (buildings meet these
`criteria). The sum of a lot of phase-shifted signals with a random
`distribution of phases has
`an
`envelope
`following the Rayleigh
`distribution. Figure 4.19 shows an exampleof the variation in time of the
`envelope of a Rayleigh affected signal.
`Now,the fading incurred by signals at different frequencies are not
`the same, and become more and more independent whenthe difference in
`frequency increases. With frequencies spaced sufficiently apart
`1 MHz), they can be considered completely independent. With frequency
`hopping,all the bursts containing the parts of one code word are then not
`damagedin the same wayby Rayleigh fading.
`the difference
`When the mobile station moves at high speed,
`betweenits positions during the reception of two successive bursts of the
`same channel(i.e., at least 4.615 ms) is sufficient to decorrelate Rayleigh
`fading variations on the signal. In this case Slow Frequency Hopping
`does no harm, but it does not help much either. However, when the
`mobile station is stationary or moves at slow speeds, SFH allows the
`transmission to reach the level of performance of high speeds. The gain
`
`
`
`Ex.1030
`APPLEINC./ Page 12 of 21
`
`Ex.1030
`APPLE INC. / Page 12 of 21
`
`

`

`| SYSTEM
`
`e variations due to Rayleigh fading
`movethrough one wavelength,
`) km/h for 900 MHz)
`
`aths, in particular when the reflector is
`n the wavelength (buildings meet these
`phase-shifted signals with a random
`envelope
`following the Rayleigh
`example of the variation in time of the
`gnal.
`; signals at different frequencies are not
`iore independent when the difference in
`iencies spaced sufficiently apart (say
`ompletely independent. With frequency
`the parts of one code word are then not
`leigh fading.
`the difference
`moves at high speed,
`eception of two successive bursts of the
`ms) is sufficient to decorrelate Rayleigh
`In this case Slow Frequency Hopping
`help much either. However, when the
`noves at slow speeds, SFH allows the
`f performance of high speeds. The gain
`
`has been evaluated to be around 6.5 dB. This advantage is of prime
`importance for a system where a high proportion of handhelds is sought,
`since hand-held users are usually moving at a slow pace or not moving at
`all.
`
`interferer
`frequency hopping is
`second advantage of
`The
`diversity, a property associated with Code Division Multiple Access
`(CDMA). In high traffic areas, such as large cities, the capacity of a
`cellular system is limited by its own interferences caused by frequency
`reuse. The relative interference ratio (C/I) may vary a lot between calls: C
`(the Carrier level) changes with the mobile station position relative to the
`base station, with the amount of obstacles between them, ctc.; J (the
`Interference level) changes depending on whether the frequency is being
`used by anothercall in some nearby cell, and it also varies according to
`the distance with the interfering source,its level, etc. .
`Since the aim of a system is usually to satisfy as many customers
`as possible, its maximum capacity is calculated based on a given (small!)
`proportion of calls subject to a noticeable decrease in quality due to
`interferences. Because of this concept of “worst case”, the capacity of a
`system is better when, for a given mean C/I value, the statistical spread
`around this mean value is as small as possible. Let us consider a system
`where the interference level perceived by a call
`is the mean of the
`interference level caused by many other calls;
`then,
`the greater this
`numberofinterferers for a given total sum, the better the system. This is
`how interferer diversity operates.
`In a system such as the current analog ones, a call potentially
`receives interference from a small number of other calls (typically 2 to 6,
`depending on the reuse pattern). At
`the other extreme,
`in a CDMA
`system—very fashionable these days West of the Atlantic—all calls
`interfere a little with all others. For the same mean interference value in
`the two systems, a call in the conventional system will cither have a very
`good quality or be completely jammed, whereas a call in the CDMA
`system will always have some low level ofinterference, rarely so bad that
`transmission would fail. Thus the interferer diversity can be used to
`increase system capacity.
`The major drawback of CDMAsystems is that their design usually
`leads to calls interfering in the same cell and in adjacent cells. What is
`good for reducing the spread around the mean value causes the same
`mean value to decrease! GSM hasbeen devised to avoid collisions inside
`one cell and between a certain number of adjacent cells. It allows
`however to spread the interference between many calls of a potential
`interferer cell, instead of a single one as in conventional systems.
`
`
`
`Ex.1030
`APPLEINC./ Page 13 of 21
`
`Ex.1030
`APPLE INC. / Page 13 of 21
`
`

`

`
`
`
`
`
`
`
`
`
`
`
`
`An example should help to illustrate this principle. Let us consider
`a cell using 4 frequencies (cell A), and 2 potentially interfering neighbour
`cells (see figure 4.20). Each one of the latter two also uses 4 frequencies,
`two of them being part of the 4 frequencies used in the first cell. The
`figures listed in table 4.2 give an example of the interference levels
`experienced by a mobile station in cell A whentraffic is maximum. A
`call is deemed jammed when the sum ofall interferences amounts to a C/I
`ratio of less than 5.0 (7 dB). Without frequency hopping,
`the mobile
`station has an even chance to receive correctly the signal (if the allocated
`frequency is fj or f), whereas with frequency hopping, the quality is
`correctin all cases. This example is not a deliberate choice of a rare case,
`such situations arise quite often and frequency hopping really creates a
`significantstatistical gain.
`
`'
`i
`
`'
`\
`
`.
`
`
`
`iy
`
`‘joe oo8e
`) e 5)
`3
`\f
`f
`15] fg,
`:
`;
`3) eo
`
`\
`
`\
`
`x
`
`Figure 4.20 — Example ofinterfering cells with Slow Frequency Hopping
`quencies, but with decorrelated hopping sequences,
`lead to interferer diversity.
`
`Cells using the samefre
`‘
`
`Ex.1030
`APPLEINC./ Page 14 of 21
`
`Ex.1030
`APPLE INC. / Page 14 of 21
`
`

`

`interference level
`
`(C/l=10 dB)
`
`(C/I=8.5 dB)
`
`.
`
`(C/l=5.5 dB)
`
`0.19 (C/I=7.2 dB)
`
`0.10 (C/L=10 dB)
`
`0.28 (C/l=5.5 dB)
`
`0.19 (C/l=7.2 dB)
`
`Mobile to base
`interferencelevel
`on the frequency
`
`Mobile to base
`average
`interference level
`
`Base to mobile
`interference level
`on the frequency
`
`Base to mobile
`average
`
`ustrate this principle. Let us consider
`id 2 potentially interfering neighbour
`he latter two also uses 4 frequencies,
`squencies used in the first cell. The
`example of the interference levels
`cell A when traffic is maximum. A
`1 of all interferences amounts to a C/I
`1out frequency hopping,
`the mobile
`2 correctly the signal (if the allocated
`th frequency hopping, the quality is
`not a deliberate choice of a rare case;
`1 frequency hopping really creates a
`
`
`
`ig cells with Slow Frequency Hopping
`
`it with decorrelated hopping sequences,
`ferer diversity.
`
`Table 4.2 — Interference levels for 4 calls in each cell of figure 4.20
`
`(without powercontrol; levels relative to wanted signal level)
`Without frequency hopping, performance can be compared with the first and third lines;
`with frequency hopping, it can be compared with the secondandlastlines.
`Interferer diversity helps to improve capacity for a given mean quality.
`
`4.2.2.3. Hopping Sequences
`
`GSM allows a wide diversity—indeed almost an infinity—of
`different channels, when both time and frequency parameters are taken
`into account. A hopping sequence—i.e., the sequence of couples (TN,
`frequency)
`allocated to a channel—may use up to 64 different
`frequencies. Of course,
`the
`single frequency list
`is possible:
`corresponds to a fixed frequency channel, which appears here as a
`“degenerate” frequency hopping channel.
`
`Hopping sequences are described for channels using one slot every
`8 BPs. A hopping sequence is then a function of the timeslot number
`modulo 8. For a channel using less than one slot every 8 BPs,
`the
`hopping frequencies are calculated by applying the same function. For
`example, if a TACH/F usesthe following hopping sequence:
`1
`2
`3
`#4
`1
`2
`3
`4
`
`Then the
`sequences:
`
`corresponding TACH/H shall use
`
`the
`
`following
`
`sub-TN 0:
`
`1
`
`3
`
`1
`
`sub-TN I:
`
`2
`
`4
`
`2
`
`4 E
`
`x.1030
`APPLEINC./ Page 15 of 21
`
`Ex.1030
`APPLE INC. / Page 15 of 21
`
`

`

`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Since the number of bursts in the uplink direction derives
`conventionally from the one in the downlink direction by a delay of
`3.BPs,
`the hopping sequence (i¢.,
`the function which associates a
`frequency to each TN modulo 8) in the uplink direction derives from the
`one in the downlink direction by simply adding 45 MHz.
`For a set of n given frequencies, GSM allows 64 xn different
`hopping sequences to be built. They are described by two parameters, the
`MAIO (Mobile Allocation Index Offset) which may take as many values
`as the numberof frequencies in the set, and the HSN (Hopping Sequence
`Number) which may take 64 different values. Two channels bearing the
`same HSN but different MAIOs never use the same frequency on the
`same burst. On the opposite, two channels using the same frequency list
`and the same TN,but bearing different HSNs,interfere for 1/n th of the
`bursts, as if the sequences were chosen randomly. The sequences are
`indeed pseudo-random, exceptfor the special case of HSN =0, where the
`frequencies are used one after
`the other
`in order. Pseudo-random
`sequences have been chosen because they have statistical properties
`similar to random sequences.
`Usually, channels in one cell bear the same HSN and different
`MAIOs:it is desirable to avoid interference between channels inside a
`cell. Adjacent cells are not interfering either, since they use disjointed
`frequencysets.
`In distant cells using the same frequency set, different HSNs
`should be used in order to gain from interferer diversity. If this gain is
`sought,
`it
`is best to avoid HSN =0, which leads to poor interferer
`diversity, even with non-identical frequencysets.
`
`4.2.2.4. The Case of Common Channels
`
`There exists a restriction to the use of frequency hopping: common
`channels (FCCH, SCH, BCCH, PAGCH and RACH) must use a fixed
`frequency. This constraint
`is meant
`to ease initial
`synchronisation
`acquisition (described on page 214): once the mobile station has found an
`FCCHburst, it will look for an SCH burst on the same frequency. Since
`this burst is too small to contain the description of a hopping sequence for
`the BCCH,the simplest way is to put the BCCH on the same frequency
`as the SCH.If the PAGCH and the RACH were hopping channels, their
`hopping sequences could be broadcast on the BCCH. This would
`however increase system complexity for little gain. The choice was that
`common channels on TN 0 never hop andall use the same frequency.
`
`Ex.1030
`APPLEINC./ Page 16 of 21
`
`Ex.1030
`APPLE INC. / Page 16 of 21
`
`

`

`n the uplink direction derives
`ownlink direction by a delay of
`he function which associates a
`uplink direction derives from the
`adding 45 MHz.
`es, GSM allows 64 xn different
`» described by two parameters, the
`t) which may take as many values
`and the HSN (Hopping Sequence
`values. Two channels bearing the
`‘r use the same frequency on the
`nels using the same frequency list
`t HSNs, interfere for 1/n th of the
`sen randomly. The sequences are
`special case of HSN = 0, where the
`other
`in order. Pseudo-random
`e they have statistical properties
`
`bear the same HSN and different
`ference between channels inside a
`g either, since they use disjointed
`
`ne frequency set, different HSNs
`| interferer diversity. If this gain 1s
`0, which leads to poor interferer
`luency sets.
`
`1 Channels
`
`use of frequency hopping: common
`3CH and RACH) must use a fixed
`nt
`to ease initial
`synchronisation
`once the mobile station has found an
`burst on the same frequency. Since
`lescription of a hopping sequence for
`it the BCCH onthe same frequency
`RACH were hopping channels, their
`dcast on the BCCH. This would
`; for little gain. The choice wasthat
`iop and all use the same frequency.
`
`Similarly, extension sets of common channels are also forbidden from
`hopping anduse the same frequency as the primary group, so that there is
`no need to transmit the description of their frequency organisation on the
`BCCHof TN 0.
`the
`that
`is
`Another peculiarity related to common channels
`frequency they use must be emitted continuously, even if no information
`needs to be conveyed on some bursts. This is needed because mobile
`stations in neighbouring cells continuously perform measurementson this
`frequency, in order to determinethe best cell they should listen to or to
`report measurements
`for handover preparation. When there is no
`information transfer request, a specific pattern is emitted (the fill frames).
`Because of these special roles of the frequency carrying the FCCH, we
`will refer it by a special name, the “beacon frequency”ofthe cell (in the
`Specificationsit is in some places referred to as the BCCH frequency).
`
`4.2.2.5. Channel Organisation in a Cell
`
`The description of the channels has been up to now focused on the
`description of one channelat a time, a point of view close to that of the
`mobile station. The point of view ofa base station is somewhat different.
`We have seen in the time domain description that channels have
`been designed so as to use as well as possible a transmitter which is
`limited to one burst per burst period. This introduces the notion of TRX,
`which is the natural unit to measure the capacity of a base station (this
`unit is so natural it appears in the procedures between the BTS and the
`BSC). A TRX has then the capacity of 8 TACH/F, or 16 TACH/H,or 64
`TACH/8 grouped by 8, or a lot of other combinations. It is perfectly
`possible to build equipments with smaller capacities, but it secms they
`have no commercial interest, and the TRX is a concept used by all
`manufacturers.
`Another reason for this concept is the frequency allocation. A cell
`is usually allocated an integral number n of frequencies, and the
`maximum capacity of such a cell corresponds to the capacity of n TRXs.
`This does not mean that there is a one to one relationship between
`frequencies and TRXs:this would be true only if frequency hopping was
`not used. But in most applications, a cell is equipped with exactly as
`many TRXsas allocated frequencies. In fact, it may happen that a cell is
`equipped with less TRXs, for economy reasons, but this raises a specific
`problem that will be dealt with later.
`
`
`
`Ex.1030
`APPLEINC./ Page 17 of 21
`
`Ex.1030
`APPLE INC. / Page 17 of 21
`
`

`

`
`
`
`
`frequencies
`
`beacon frequency
`
`
`
`
`
`
`
`
`
`and so on...
`
`set of common channels + SCH + FCCH on beacon frequency
`set of 5 TACH/F, hopping on 5 frequencies
`set of 8 TACH/E + 5 TACH/F, hopping on 6 frequencies
`additional set of common channels on beacon frequency
`
`Figure 4.21 — Frequency/TN groups
`
`The GSM hopping sequencesare such that, for a given TN in a givencell,
`one may define channel groups hopping on the samesetof frequencies.
`In the case of group C (to take an example), if all channels are not allocated,
`the BTS muststill manage to emit on the beacon frequency in all slots of TN 1.
`
`Let us look at a typical cell with n frequencies and n TRXs. The
`channel organisation must include one common channel group with a
`FCCH and a SCH,consisting of either (FCCH + SCH + BCCH +
`PAGCH/F + RACH/F), or a group with combined TACH/8 (FCCH +
`SCH + BCCH + PAGCH/T + RACH/H). Other common channel groups
`may be added in the first case. These choices are determined by load
`considerations. The common channels are non-hopping channels,andall
`use the same frequency, the beacon frequency. The rest of the resources
`are distributed among TACHs, with a ratio between TACH/F and
`TACH/8 which dependson load considerations.
`The constraints on the hopping sequences are few. To show
`various possibilities, we will use the diagram in Figure 4.21. Such a
`diagram is based on the particularity that the channel configuration can
`be described independently for each TN, because no channelusebursts of
`
`
`
`Ex.1030
`APPLEINC./ Page 18 of 21
`
`Ex.1030
`APPLE INC. / Page 18 of 21
`
`

`

`els on beacon frequency
`
`ca
`
`ii
`
`o
`Pe
`fea
`as
`7
`
`|P
`
`a
`tang
`
`|a
`
`e
`bee
`6
`
`beacon frequency
`
`TN
`
`different TNs. For a given TN,the channels are grouped in the frequency
`domain in one or several sets including the channels which haveatleast
`one frequency in common.
`In fact,
`the GSM frequency hopping
`sequences are defined in such a waythat the only rational approachis that
`all the channels in a group use the same set of frequencies. Hence the
`diagrams, which show such frequency/TNsets.
`the bursts
`The consequence of these possibilities is that
`succession on the same frequency may belong to a lot of different
`channels, and that there is very little logic in the succession. This is why
`the notion of TDMA is somewhat misleading with frequency hopping.
`Channels are not sharing a frequency on a time division basis,
`channels in a same frequency/TN groupare sharing several frequencies.
`
`Substantial gains in frequency and interferer diversity are obtained
`when at least 4 frequencies, and preferably more (say 8), are used in a
`hopping sequence. This causes a problem in the cases where for capacity
`reasons a single TRX would be sufficient in a given cell. The operator
`may choose for
`the gain of frequency hopping to allocate more
`frequencies to that cell than the numberofinstalled TRXs.
`A small problem then arises
`from the necessity to emit
`continuously on the beacon frequency. In cells of small capacity,
`operator may choosecither to let the channels of TN other than 0 hop on
`only as many frequencies as there are TRXs (but the gain of frequency
`hopping is small), or on as many frequencies as available. In the latter
`case, an additional transmitter dedicated to the filling of the common
`channels frequency is needed. Because the frequency/TN groups are not
`fully used by the installed TRXs, the continuous emission of the beacon
`frequency is not guaranteed by these TRX alone. The role of the
`additional transmitter is to emit on the beacon frequency when it would
`have been used by one of the missing channels.
`
`4.3. FROM SOURCE DATA TO RADIO
`WAVES
`
`Up to this point, we have addressed only how transmission
`resources are organised to be shared between users, not how they are
`used. In the previous chapter, we have seen that, if we restrict our view to
`the radio interface, all needs for user data transmission can be fulfilled
`
`4+ FCCH on beacon frequency
`frequencies
`yopping on 6 frequencies
`
`quency/TN g