Chapter 6
Evolution of GSM and cdmaOne to
3G Systems.
Chapter
6
Evolution of GSM and cdmaOne to
3G Systems
6.1 Introduction
The previous chapters have concentrated on the two leading second generation (2G) cellular
systems: GSM and IS-95. These systems are deployed in many parts of the world and will
continue to operate and evolve during the next decade as third generation (3G) systems are
rolled out. We may expect that the new 3G systems will be harmonised with their evolved
2G counterparts, and that slowly 2G spectra will be refarmed to provide extra 3G spectra.
No 3G systems are currently deployed, although trials are in progress. As a consequence,
this chapter, which deals with systems that are about to be deployed, is treated in a qual-
itative manner, describing how they will work rather than quantifying their performances.
Before getting into detail, let us briefly review how cellular communications arrived at to-
day’s position.
6.1.1 The generation game
There is no doubt that there was pent-up demand for public mobile telephony networks,
and when they arrived in the 1980s as the so-called first generation (1G) analogue cellular
networks, they grew at phenomenal rates. These networks initially offered only telephony,

game from the beginning [6]. Paralleling the European Union (EU) RACE initiative, ITU
formed task group TG8/1, originally under the auspices of CCIR. This committee referred
to their 3G system as the future public land mobile telecommunications system (FPLMTS).
Europeans were, of course, also members of TG8/1, and with commercial and political pres-
sures a long way in the future, FPLMTS and UMTS seemed synonymous in terms of aims
and objectives. The important difference between TG8/1 and the happenings in Europe,
was that in Europe there was an actual research and development (R&D) 3G programme in
process, while TG8/1 was more like a forum.
The Americans did not launch concerted national R&D programmes, neither for 2G nor
3G systems. Their advanced mobile phone service (AMPS) 1G system did evolve into the
2G IS-136, and became dual-mode with IS-95. The United States also introduced the iDEN
system with its ability to offer both cellular and dispatch services. It then auctioned a large
part of its 3G spectrum for PCS licenses, and allowed GSM to enter the United States in
the form of PCS1900. This auctioning of the 3G spectrum meant that there were significant
advantages if existing 2G networks could evolve into 3G ones, preferably in a seamless
manner.
A big factor, not just in the United States, but in the world, was the advent of IS-95 [7–11].
It arrived late compared with GSM, and some engineers argued that it was a 2.5G system.
It had to fight to be born because of the lack of spectrum, and the quasi-religious attitudes
406
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
of engineers towards methods of multiple access. The meagre spectrum of 1.25 MHz at the
top of the AMPS band was just about adequate for cellular CDMA, which was just as well
because that was all there was available. CDMA entered the cellular world with a host of
technical problems, not made easier as the transceivers from day one had to be dual-mode
with AMPS. Its advocates were clear in that CDMA has a high spectral efficiency and is
well suited to the 3G multiservice environment. The real significance of IS-95 is that it won
the technical argument in that the UMTS and the Japanese Association of Radio Industries
and Businesses (ARIB) proposals have CDMA radio interfaces, albeit of wider bandwidth
systems as more bandwidth is available for 3G networks. We therefore agree that IS-95 is a

tions (DECT) system.
6.2. EVOLUTION OF GSM
407
In the authors’ opinion, the truly 3G systems are the IMT DS, IMT MC and IMT TC
systems.
6.1.2 IMT-2000 spectrum
The World Administration Radio Congress (WARC) in March 1992 assigned 200 MHz in
the 2G frequency band to IMT-2000 for world-wide use [3]. The actual frequency bands
are 1885–2025 MHz and 2110–2200 MHz. Unfortunately some parts of these bands are
already used for other services. Figure 6.1 shows a diagram of the IMT-2000 spectrum, and
the current use of this spectrum in Europe, the United States, and Japan.
The IMT-2000 spectrum may be partitioned into seven segments. The frequency of each
segment is shown in Table 6.1
Part of Segment 1 is currently used for DECT in Europe, and is also used for PHS, PCS
and DECT in other parts of the world. Segment 2 is used at present for PCS and PHS in the
United States and Japan, respectively. Segments 3 and 6 form 60 MHz frequency division
duplex (FDD) bands. Mobile satellite services (MSS) are in Segments 4 and 7, providing
30 MHz FDD bands. Segment 4 supports the earth-to-space links; while segment 7 provides
the space-to-earth links. The 1980–1990 MHz band in Segment 4 is currently used for PCS
in the United States. Segments 1, 2 and 5 are unpaired and are suitable for time division
duplex (TDD) operation. Segment 5 may be used in the United States for earth-to-space
MSS services.
6.2 Evolution of GSM
The GSM system was initially designed to carry speech, as well as low speed data. Much
has already been discussed regarding speech, so we will concentrate here on data. The user
data rate over the radio interface using a single physical channel, i.e. a single timeslot per
Table 6.1: IMT-2000 spectrum and its segments (MSS stands for mobile satellite services).
Segment Frequency Comment
number band (MHz)
1 1885–1900 Unpaired

physical channel has since been increased to 14.4 kb/s by reducing the power of the channel
coding on the full rate traffic channel by means of code symbol puncturing. Apart from
increasing the level of puncturing still further, the other ways to increase the user data rate
beyond 14.4 kb/s are either to allow an MS to access more than an one timeslot per TDMA
frame or to use a higher level modulation scheme (e.g. quadrature amplitude modulation,
QAM) to increase the amount of information that can be transmitted within a single timeslot.
Two new services have been introduced as part of GSM Phase 2+ which allow the user
data rate to be increased by permitting an MS to access more than one timeslot per TDMA
frame. These new services are the high speed circuit switched data (HSCSD) service and
the general packet radio service (GPRS). The HSCSD service allows an MS to be allocated
a number of timeslots per TDMA frame on a circuit-switched basis, i.e. the MS has exclu-
sive use of the allocated resources for the duration of a call [12]. In contrast, GPRS uses
packet-orientated connections on the radio interface (and within the network) whereby a
user is assigned one, or a number of traffic channels only when a transfer of information
is required [13]. The channel is relinquished once the transmission is completed. In the
following sections we will describe these two services in more detail.
6.2. EVOLUTION OF GSM
409
The second approach to increasing the user data rate by employing a higher level modu-
lation scheme is currently being studied under the Enhanced Data Rates for GSM Evolution
(EDGE) project [14]. The basic principle behind EDGE is that the modulation scheme used
on the GSM radio interface should be chosen on the basis of the quality of the radio link. A
higher level modulation scheme is preferred when the link quality is ‘good’, but the system
reverts to a lower level modulation scheme when the link quality becomes ‘poor’. At the
time of writing it appears that EDGE will use the existing Gaussian minimum shift keying
(GMSK) modulation scheme in poor quality channels and eight-level phase shift keying (8-
PSK) in good quality channels. EDGE will also include link adaption functions to allow the
MS and BS to assess the link quality and switch between the different types of modulation
as necessary.
Once developed, the EDGE technology will enhance the range of services offered by

AMR technology is that the speech coding rate and the degree of channel coding should
be chosen according to the channel quality. For example, in ‘good’ channels a lower rate
speech coder can be used in an HR traffic channel thereby increasing the system capacity.
However, if the link quality is ‘poor’ FR then a traffic channel will be used and the level of
channel coding increased. At the time of writing the candidate AMR codecs have not yet
been chosen.
6.2.1 High speed circuit-switched data
The HSCSD service [12] is a natural extension of the circuit-switched data services that
were supported in earlier versions of GSM. No changes to the physical layer interfaces be-
tween the different network elements are required for HSCSD. At the higher layers the MS
and the network support the additional functionality required to multiplex and demultiplex
a user’s data onto a number of traffic channels for transmission over both the Abis interface
and the radio interface. Additional functionality is also included at the radio resource man-
agement level to handle the new situation where a number of different traffic channels are
associated with the same connection. For example, when an HSCSD user is handed over
between two cells, there must be a mechanism to ensure that sufficient traffic channels are
available in the new cell before the handover occurs. An HSCSD connection is, however,
limited to a single 64 kb/s circuit on the A interface.
On call set-up the MS provides information to the network which defines the nature of the
HSCSD connection. The multislot class of the MS is used by the network to determine the
maximum number of timeslots that may be accessed by the MS, and the amount of time that
must be allowed between timeslots, e.g. for the purposes of neighbour cell measurements.
This information is used to define the MS’s capabilities for both the HSCSD and GPRS
services. The multislot classes are listed in Table 6.2 along with their associated parameters
[17].
Multislot MSs can be either type 1 or type 2 and this information is shown in the right-
hand column of Table 6.2. Type 2 MSs are required to be able to transmit and receive
simultaneously, whereas type 1 MSs are not. The ‘Rx’ and ‘Tx’ columns give the maxi-
mum number of receive and transmit timeslots that the MS may occupy per TDMA frame,
respectively. The ‘Sum’ column gives the total number of transmit and receive timeslots

mation includes the fixed network user rate, i.e. the data rate that the MS would like to
achieve over the fixed network, the channel coding schemes supported by the MS, and the
maximum number of traffic channels to be used during the connection. This final param-
eter allows the user to control the call cost by limiting the number of traffic channels that
will be occupied. The final multislot configuration is chosen by the network based on the
MS capabilities and the requirements imposed by the services, e.g. whether neighbour cell
measurements are required. The HSCSD service can support both symmetric transmissions,
i.e. the same number of up-link and down-link timeslots, or asymmetric transmissions, i.e.
more timeslots are allocated in one direction. However, in the case of HSCSD connections,
only down-link biased asymmetry is allowed and the up-link timeslot numbers must be a
subset of the down-link timeslot numbers.
6.2.2 The general packet radio service
Many services do not require a continuous bi-directional flow of user data across the radio
interface. To illustrate this, consider the example of a user browsing the Worldwide Web
(WWW) on her lap-top computer using a dial-up connection via a cellular network. Once
a page of information has been downloaded, there will be a pause in the information flow
between the MS and the network as the user reads the information and before more infor-
mation is requested. Using circuit-switched connections for ‘bursty’ services of this nature
represents an inefficient use of the radio resources because a user will continue to occupy a
radio channel for the duration of a call (or browsing session) even though this channel may
only be utilised for a small fraction of the time. Inefficiencies of this type can be overcome
by carrying these services using packet-orientated connections.
The GSM system was initially designed to support only circuit-switched connections at
the radio interface level with user data rates of up to 9.6 kb/s. However, the Phase 2+
412
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
Table 6.2: The MS multislot classes.
Multislot Maximum number of slots Minimum number of slots Type
class Rx Tx Sum T
ta

25 8 3 NA 3 b 2 c 1
26 8 4 NA 3 b 2 c 1
27 8 4 NA 2 b 2 c 1
28 8 6 NA 2 b 2 c 1
29 8 8 NA 2 b 2 c 1
NA = Not Applicable
a
=
(
1 if frequency hopping is used
0 if frequency hopping is not used
b
=
(
1 if frequency hopping is used or there is a change from Rx to Tx
0 if frequency hopping is not used and there is no change from Rx to Tx
c
=
(
1 if frequency hopping is used or there is a change from Tx to Rx
0 if frequency hopping is not used and there is no change from Tx to Rx
6.2. EVOLUTION OF GSM
413
specifications now include provision for the support of a packet-orientated service known
as the general packet radio service (GPRS) [13, 18–20]. GPRS attempts to optimise the
network and radio resources, and strict separation between the radio subsystem and the
network subsystem is maintained, although the network subsystem is compatible with the
other GSM radio access procedures. Consequently, the GSM MSC is unaffected. The
allocation of a GPRS radio channel is flexible, ranging from one to eight radio interface
timeslots in a TDMA frame. Up-link and down-link timeslots are allocated separately. The

414
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
MS BTS BSC
MSC/
VLR
Um Abis
A
SGSN
Gb
GGSN
Gn
HLR
GcGrGs
GGSN
Gp
SGSN
Other GSM networks
D
SMS-GMSC
SMS-IWMSC
Gd
E
C
EIR
Gf
Gn
SM-SC
Gi
PDN
Signalling Interface

In the BSS the relay function relays LLC PDUs between the radio interface Um and the
Gb interface. In the SGSN the relay function relays packet data protocol (PDP) PDUs
between the Gb and the Gn interfaces. The BSS GPRS protocol (BSSGP) conveys routing
and quality-of-service (QoS) information between a BSS and an SGSN. It does not perform
error control. The network service (NS) layer transports BSSGP PDUs. The radio link
control (RLC) provides a radio dependent reliable link, while the medium access control
(MAC) controls the access signallings, both request and grant, for the radio channel; and
the mapping of the LLC frames onto the GSM physical channel. GSM RF is the GSM
physical layer.
6.2.2.3 High-level functions required for GPRS
Network access control function An access protocol has a set of procedures, such as
registration, authentication and authorisation, admission control, charging and so on, that
allow a user to use the services and facilities the network provides. A user may make an
access attempt, or the user may be paged. The fixed network interface, Gi, may support, at
the discretion of the PLMN operator, multiple access protocols to external networks such
as X.25 and IP.
Anonymous access The idea of anonymous access has also been introduced into GPRS
whereby an MS can access the network without being authenticated and without air-interface
encryption being required. There is also no requirement for the MS to supply its IMSI or
IMEI, although there is provision for the network to request these. One example of an ap-
plication that could make use of this facility is automatic road-tolling, whereby a road user
could use a pre-paid card, inserted into a GSM terminal, automatically to make payment as
she approaches a toll booth.
Packet routing and transfer functions A route consists of an originating network node,
and if required, relay nodes, and finally a destination node. Routing is the transmission
of messages within and between PLMNs. A node forwards data received to the next node
using the relay function. The routing function determines the network GPRS support node
416
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
Application

L1
SGSN GGSN
IP/X.25
GTP
UDP/
TCP
IP
L2
L1
Gn
Gi
Figure 6.3: GPRS transmission plane [18–20].
(GSN) where the message is sent using the destination address in the message. The routing
function also selects the transmission path to the next GSN along the route. Address transla-
tion is needed to convert one address to another when packets are routed between PLMNs.
Encapsulation is the addition of address and control information to the PDU for routing
within and between PLMNs. Encapsulation, and its reverse, are performed between the
GGSN nodes of PLMNs, and between the SGSN and an MS. The tunnelling function (see
the transmission plane) is the transfer of encapsulated PDUs within and between PLMNs
from where they are encapsulated to where they are decapsulated. There is a compression
function that removes as much overhead information as possible, prior to radio transmis-
sion. The ciphering function provides confidentiality of a user’s data, while the domain
name server function is a standard IP function that resolves any name for GSNs and other
6.2. EVOLUTION OF GSM
417
GPRS nodes within the GPRS backbone networks.
GPRS mobility management and the MS states Mobility management describes the
processes in the mobile radio system that are associated with tracking the movements of
subscribers as they travel around a network. The non-GPRS GSM system uses location
areas and location update procedures to ensure that it always knows the whereabouts of its

data activity over the logical link.
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CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
Radio resource management functions Allocation and maintenance of radio communi-
cation channels are provided by these functions. The GSM radio resources are dynamically
shared between the circuit mode and GPRS. The GPRS radio resource management is con-
cerned with the allocation and release of timeslots for a GPRS channel; monitoring GPRS
channel utilisation; congestion control; and the distribution of GPRS channel configuration
information that is broadcast on the common control channels.
Network management functions These support operation and management functions for
GPRS.
6.2.2.4Low-level functions
The radio interface functions for GPRS are the medium access control (MAC) and radio
link control (RLC) that operate above the physical layer. The MAC function arbitrates be-
tween MSs attempting to transmit at the same time. It is therefore concerned with collision
avoidance, detection, and recovery following a collision. The MAC function may let a sin-
gle MS use several physical channels simultaneously. The multiplexing of data and control
signalling on both links is affected by the MAC function, as well as by priority scheduling.
The GPRS RLC function supports the transfer of logical link control layer PDUs (LLC-
PDU) between the LLC and MAC entities, the segmentation and reassembly of LLC-PDUs
into RLC data blocks, and backward error correction for the retransmission of uncorrectable
code words.
Packet data logical channels Although circuit switched and GPRS services use the same
physical channels, they have different logical channels. The physical channel dedicated to
packet data is called a packet data channel (PDCH). The logical channels for common con-
trol signalling for packet data are carried by the packet common control channel (PCCCH),
and there is also the packet random access channel (PRACH), an up-link-only channel used
by MSs to initiate data or signalling packet transmission. The other PCCCHs are all down-
link ones. There is the packet paging channel (PPCH) that uses paging groups of MSs
to enable discontinuous reception (DRX) to be used. PPCH can be used for both circuit

6.2.2.5 The GPRS MS classes
There are three classes of MS as far as the GPRS is concerned and these are based on
the ability of the MS to support the simultaneous use of packet-based and circuit-switched
services. The Class A MSs are able to support the simultaneous transfer of both packet-
based and circuit-switched traffic using different timeslots within the GSM TDMA frame
structure. The Class B MSs can be simultaneously ‘attached’ to both the circuit switched
and packet-based services, e.g. they can receive pages for either service; however, they
cannot transfer packet-based traffic and circuit-switched traffic at the same time. If, for
example, a Class B MS is engaged in a packet-based data transfer and a circuit-switched
connection is established, the transfer of packet data will be suspended for the duration of
Figure 6.4: Multiframe structure for PDCH.
420
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
the circuit-switched connection. However, in this example there is no requirement for the
GPRS to be deactivated for the particular MS. Class C MSs do not support any simultaneous
use of circuit-switched and packet-based services. A Class C MS can be viewed as operating
in two distinct modes, the GPRS mode and the circuit-switched mode, and it can only be
in one mode at a particular time. For example, if the class C MS is in GPRS mode (i.e. it
is engaged in a packet-based data transfer) and a circuit-switched call arrives at the PLMN
for this particular MS, then the MS will be considered ‘not reachable’ as far as the circuit-
switched call is concerned. It should be noted that the GPRS class of an MS and its multislot
class (see Table 6.2) are separate parameters and there is no direct correlation between the
two.
6.2.2.6 The GPRS quality-of-service
There are four different quality-of-service (QoS) profiles supported in GPRS and these are
dependent on the type of service. For example, an email transaction can tolerate greater de-
lays than, say, an interactive video service, and the QoS profile will be chosen appropriately
in each case. The MS and the network will agree on a particular QoS profile during the
initial service negotiation stages and, as far as possible, the network will attempt to deliver
this QoS to the MS. The QoS service profile is made up of a number of factors, including

be accommodated. In indoor environments, the maximum bit rate would be 4.7 Mb/s. For
136 HS the carrier spacing is 200 kHz (as in GSM) for outdoor/vehicular environments, and
1600 kHz for offices.
The 136 HS (outdoor/vehicular) with its 200 kHz carrier spacing, eight slots per frame,
FDD, with multilevel modulation was part of the UWC-136 IMT EDGE proposal. The
evolution of GSM to EDGE and IS-136 to EDGE is now undertaken jointly by ETSI and
the UWC Consortium. Consequently, EDGE will be compatible with both GSM and IS-
136. The plan [14] is to deploy GPRS, then enhanced GPRS (EDPRS) and enhanced circuit
switch data (ECSD). Then the high level of modulation will be deployed to realise 3G
EDGE services.
EDGE radio interface The radio interface will continue to have GMSK available, but
will be able to use 8-PSK which has three bits per symbol instead of the one-bit type symbol
of GMSK. Since the symbol rate is 271 ksymbols/s then the gross bit rates per slot (includes
overhead) is 22.8 and 69.2 kb/s for GMSK and 8-PSK, respectively. The pulse shape for
8-PSK is such that the 8-PSK spectrum fits within the GMSK spectrum mask. The normal
burst format for EDGE is the same as for GSM, except the two sets of 58 symbols now have
three bits per symbol.
Packet switched transmission The EDGE concept has both packet switched and circuit
switched modes. Indeed, EDGE is more like the grand evolutionary plan of GSM that in-
cludes both GPRS and HSCSD. The enhanced GPRS (EGPRS) differs from GPRS because
with multilevel modulation the channel coding must be improved because it is more vul-
nerable to interference and noise. Accordingly a link adaption scheme regularly estimates
link quality and selects GMSK or 8-PSK and the appropriate channel coding to provide the
highest user bit rate. At the time of writing various schemes are being considered for stan-
dardisation. The coding rate is determined by the amount of puncturing. The rate per time
slot for GMSK is 11.2, 14.5, 16.7 and 22.8 kb/s for code rates of 0.49, 0.64, 0.73, and 1.0,
respectively. For 8-PSK the rate per time slot is 22.8. 34.3, 41.25, 51.6, 57.35 and 69.2 kb/s
for code rates of 0.33, 0.50, 0.60, 0.75, 0.83 and 1.0, respectively.
The enhanced circuit switched (ECSD) mode has the data interleaved over 22 TDMA
frames. For GMSK modulation the rate per time slot is 3.6, 6, 12 and 14.5 kb/s for a code

(TSGs) responsible for the core network, the radio access networks, services and system
aspects, and terminals. Each TSG has a number of working groups. There will be a roll-out
of the specifications; the initial release of the specifications is Phase 1 Release 99. New
capabilities and services will be introduced according to annual specification releases.
The UMTS terminology introduces a number of new terms, and re-names some familiar
ones. Many of these new terms will be defined as they appear in the text, but to assist the
reader give a list of UMTS abbreviations in Table 6.3. We also draw the reader’s attention
to some familiar GSM terms that are different in UMTS. These are presented in Table 6.4
6.3. THE UNIVERSAL MOBILE TELECOMMUNICATION SYSTEM
423
Table 6.3: UMTS abbreviations.
ACLR Adjacent channel leakage power ratio
AI Acquisition indicator
AICH Acquisition indication channel
BCH Broadcast control channel
CCPCH Common control physical channels
CPCH Common packet channel
CPICH Common pilot channel
DPCCH Dedicated physical control channel
DPDCH Dedicated physical data channel
DCH Dedicated channel
FACH Forward access channel
FBI Feedback information
FDD Frequency division duplex
GMSC Gateway MSC
GGSN Gateway GPRS support node
I
uCS
Interface between an RNC and an MSC
I

TFCI Transport format combination indicator
TPC Transmit power control
UARFCN UTRA absolute radio frequency channel number
UE User equipment
UMTS Universal mobile telecommunication system
USIM Universal subscriber identity module
UTRA UMTS terrestrial radio interface
The UMTS network architecture block diagram is displayed in Figure 6.5. The core net-
work is encased by a dotted line. The mobile switching centre (MSC) and gateway MSC
(GMSC) are for circuit-switched GSM networks. Because GSM Phase 2+ will also ac-
commodate GPRS, and therefore handle packet data, there is a serving GPRS support node
(SGSN) and a gateway GPRS support node (GGSN). The other core network elements to do
with authentication, home and visitor location registers and equipment identity registers are
essential to support both circuit-switched and packet data networks. Thus, the core network
is architecturally a GSM Phase 2+ core network that is powered up so that it can also handle
the higher volume, higher bit rate, UMTS traffic.
Shown below the core network in Figure 6.5 are two GSM base station subsystems (BSSs)
and two UMTS radio network subsystems (RNSs). The A-interface is between a base sta-
tion controller (BSC) and a mobile switching centre (MSC), and there is an I
uPS
between
a BSC and SGSN, where the subscript uPS signifies a packet switch interface. The A
bis
interface between a BTS and a BSC is also shown.
The UMTS network uses the same core network as GSM, and has interfaces between
the RNC and MSC, SGSN and RNC of I
uCS
,I
uPS
and I

HLR = Home Location Register
VLR = Visitor Location Register
EIR = Equipment Identity Register
= Traffic and Signalling
MSC = Mobile Switching Centre
SGSN = Serving GPRS Support Node
GGSN = Gateway GPRS Support Node
= Signalling Only
Modified from 3GPP TS 23.002 Version 3.1.0
Core
Network
To external networks To external networks
A
I
ubis
A
bis
I
ur
I
uCS
I
uPS
Figure 6.5: UMTS network architecture.
426
CHAPTER 6. EVOLUTION OF GSM AND CDMAONE TO 3G SYSTEMS
represents circuit-switched. The equivalent of the A
bis
in UMTS is I
ubis

that a UE and a BS transmit at optimum power levels; and handover, the mechanism that
switches a serving cell to another cell during a call.
6.3.1 The UTRA FDD mode
The UMTS terrestrial radio interface (UTRA) frequency duplex (FDD) mode is the W-
CDMA radio interface of the UMTS, and is designated by the ITU as IMT DS. Referring to
Table 6.1, the UTRA FDD mode uses segment 3 for up-link transmission, and segment 6 for
down-link transmission, i.e. from node B to UE communications. These two segments are
6.3. THE UNIVERSAL MOBILE TELECOMMUNICATION SYSTEM
427
Transport
Channel
Data From
Higher
Layers
CRC
Attachment
Block
Concatenation/
Segmentation
Channel
Coding
1
st
Interleaving
Radio Frame
Segmentation
Rate
Matching
Traffic Channel
Multiplexing

for the up-link and down-link, respectively, will always be an integer because
of the raster frequency of 0.2 MHz. Note that the radio channels in the UTRA FDD are not
necessarily paired as they are in GSM.
Transmitted spectrum The CDMA chip rate is 3.84 Mchips/s, and the transmitted spec-
trum must conform to, i.e. be within, a spectrum mask [23]. As an example, the mask for a
BS with a maximum output power of

43 dBm is shown in Figure 6.7. The abscissa is the
frequency offset,
4
f , from the carrier. The carrier is at
4
f
=
0, not shown in the figure,
and the adjacent carrier would be positioned at
4
f
=
5 MHz. The lightly shaded part of
the figure corresponds to the left-hand ordinate, which is the power measured by a spectral