umts basic

6All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

1.1 UMTS Basics

UMTS network architecture(1)

Iu

PLMN, PSTN,

ISDN, ...

IP

networks

External Networks

USIM

ME

Cu

UE

Uu

(air)

User

Equipment

Node B

Node B

Iur

UTRAN

RNC

RNC

Node B

Node B

Iub

RNS

RNS

UMTS Radio

Access Network

MSC/VLR

CN

GMSC

GGSN

HLR

SGSN

Iu-CS

Iu-PS

Core Network

Entities and interfaces

Iub


1.1 UMTS Basics

UMTS network architecture(2)

Alcatel OMC-UR architecture

A9100

MBS

UTRAN

A9140

RNC

Iub

RNS

RNS

LAN

A1353 OMC-UR

RNO

NM

ItfB

ItfR

A9155

RNP tool

Radio Network Optimizer

Network Performance Analyzer

Network Manager (used to

perform supervision and

configuration of the UTRAN)

RNO

NPA

NM

Note: NM is provided from R3 onwards. In R2, the NM

function are implemented in two separate servers EM

(Element Manager) and SNM (Sub-network Manager)

+

NPA

A9140

RNC

A9100

MBS

A9100

MBS

A9100

MBS

Note: the

Alcatel

NodeB is

called

A9100 MBS

(Multi-

standard

Base

Station)

from R2

onwards


1.1 UMTS Basics

3GPP: the UMTS standardization body

Members:ETSI (Europe) ARIB/TTC (Japan) CWTS (China)T1 (USA) TTA (South Korea)

UMTS system specifications: Access Network

WCDMA (UTRAN FDD) TD-CDMA (UTRAN TDD)

Core Network Evolved GSM All-IP

Note: 3GPP has also taken over the GSM recommendations (previously written by ETSI)

Releases defined for the UMTS system specifications: Release 99 (sometimes called Release 3) Release 4 Release 5

In the following material we will only deal with UMTS FDD R99.

(former Release 2000)


1.1 UMTS Basics

3GPP UMTS specifications

3GPP UMTS specifications are classified in 15 series (numbered from 21 to 35), e.g. the serie 25 deals with UTRAN aspects.

Note: See 3GPP 21.101 for more details about the numbering scheme and an overview about all UMTS series and specifications.

Interesting specifications for UMTS Radio Network Planning:

3GPP TS 25.101: "UE Radio transmission and Reception (FDD)"

3GPP TS 25.104: "UTRA (BS) FDD; Radio transmission and Reception

3GPP TS 25.133: "Requirements for support of radio resource management (FDD)"

3GPP TS 25.141: "Base Station (BS) conformance testing (FDD)

3GPP TS 25.214: "Physical layer procedures (FDD)".

3GPP TS 25.215: "Physical layer - Measurements (FDD)

3GPP TS 25.942: "RF system scenarios".


1.1 UMTS Basics

Alcatel UTRAN releases

Alcatel UTRAN equipment (RNC, NodeB and OMC-UR) is designed by a joint-venture between Alcatel and Fujitsu, called Evolium.

Note: the Alcatel UMTS equipment is called EvoliumTM 9100 MBS, EvoliumTM

9140 RNC and EvoliumTM 1353 OMC-UR

Relationship between Evolium UTRAN releases and 3GPP releases:

Evolium UTRAN releases 3GPP releases

R1 (former 3GR1)

R99 (Technical Status December 2000)

R2 R99 (Technical Status June 2001)

R3 R99 (Technical Status March 2002)

R4 R4

R5 R5

Prevision

Stand:

June 2004


1.1 UMTS Basics

UMTS main radio mechanisms(1)

Sector/Cell/Carrier in UMTS

Sector and cell are not equivalent anymore in UMTS:

A sector consists of one or several cells

A cell consists of one frequency (or carrier)

Note: a given frequency (carrier) can be reused in each sector of each

NodeB in the network (frequency reuse=1)


1.1 UMTS Basics


CDMA (called W-CDMA for UMTS FDD) as access method on the air a given carrier can be reused in each cell (frequency reuse=1)no FDMA all active users can transmit/receive at the same timeno TDMA As a consequence, there are inside one frequency:

Extra-cell interference: cell separation is achieved by codes (CDMA) Intra-cell interference: user separation is achieved by codes (CDMA)

Multiple frequencies (carriers)

first step of UMTS deployment: a single frequency (e.g. frequency 1) is used for the whole

network of an operator

second step of UMTS deployment: additional frequencies can be used to enhance the capacity of

the network: an additional frequency (e.g frequency

2) works as an overlap on the first frequency.

Frequency 1

Frequency 2


1.1 UMTS Basics


Channelization and scrambling codes (UL side)

2chc

1chc

scramblingc

air

interfaceModulator

3chc

UE

Ph

ysic

al

ch

an

nels

Channelization codes (spreading codes)

short codes (limited number, but they can be reused with another scrambling code)

code length chosen according to the bit rate of the physical channel (spreading factor)

assigned by the RNC at connection setup

Scrambling codes

long codes (more than 1 million available)

fixed length (no spreading)1 unique code per UE assigned by the RNC at connection setup

Bit rateA

Bit rateB

Bit rateC

3.84 Mchips/s

3.84 Mchips/s

3.84 Mchips/s3.84 Mchips/s

.

.

.


1.1 UMTS Basics


Channelization and scrambling codes (DL side)

2chc

1chc

scramblingc

air

interfaceModulator

3chc

NodeBsector

Ph

ysic

al

ch

an

nels

Channelization codes (spreading codes)same remarks as for UL sideNote: the restricted number of channelization codes is more problematic in DL, because they must be shared between all UEs in the NodeB sector.

Scrambling codes

long codes (more than 1 million available, but restricted to 512 (primary) codes to limit the time for

code research during cell selection by the UE)

fixed length (no spreading)1(primary) code per NodeB sector defined by a code planning: 2 adjacent sectors shall have

different codes (see 5)Note: it is also possible to define secondary

scrambling codes, but it is seldom used.

Bit rateA

Bit rateB

Bit rateC

3.84 Mchips/s

3.84 Mchips/s

3.84 Mchips/s3.84 Mchips/s

.

.

.


1.1 UMTS Basics


Physical channels Physical channels are defined mainly by:

a specific frequency (carrier) a combination channelization code / scrambling code

used to separate the physical channels (2 physical channels must NOT have the same combination channelization code / scrambling code)

start and stop instants physical channels are sent continuously on the air interface between

start and stop instants

Examples in UL: DPDCH: dedicated to a UE, used to carry traffic and signalling between UE and

RNC such as radio measurement report, handover command

DPCCH: dedicated to a UE, used to carry signalling between UE and NodeB such as fast power control commands

Examples in DL: DPCH: dedicated to a UE , same functions as UL DPDCH and UL DPCCH

P-CCPCH: common channel sent permanently in each cell to provide system- and cell-specific information, e.g. LAI (similar to the time slot 0 used for BCCH in GSM)

CPICH: see next slide


1.1 UMTS Basics


CPICH (or Pilot channel)

DL common channel sent permanently in each cell to provide:

srambling code of NodeB sector: the UE can find out the DL scrambling code of the cell through symbol-by-symbol correlation over the CPICH (used during cell selection)

power reference: used to perform measurements for handover and cell selection/reselection (function performed by time slot 0 used for BCCH in GSM)

time and phase reference: used to aid channel estimation in reception at the UE side

Pre-defined symbol sequence

Slot #0 Slot #1 Slot #i Slot #14

Tslot = 2560 chips , 20 bits = 10 symbols

1 radio frame: Tf = 10 ms

The CPICH contains:

a pre-defined symbol sequence (the same for each cell of all UMTS networks) scrambled with the NodeB sector scrambling code

at a fixed and low bit rate (Spreading Factor=256): to make easier Pilot detection by UE


1.1 UMTS Basics


Power control Near-Far Problem: on the uplink way an overpowered mobile phone

near the base station (e.g. UE1) can jam any other mobile phones far from the base station (e.g. UE2).

Node

B

UE1

UE2

an efficient and fast power control is necessary in UL to avoid near-far effect

power control is also used in DL to reduce interference and consequently to increase the system capacity

Power control mechanisms (see Appendix for more details): open loop (without feedback information) for common physical

channels

closed loop (with feedback information) for dedicated physical channels (1500 Hz command rate, also called fast power control)


1.1 UMTS Basics


RNC

Node B

Soft/softer Handover (HO)

a UE is in soft handover state if there are two (or more) radio links between this UE and the UTRAN

it is a fundamental UMTS mechanism (necessary to avoid near-far effect)

only possible intra-frequency, ie between cells with the same frequency

Note: hard handover is provided if soft/er

handover is not possible

A softer handover is a soft handover between different sectors of the same

Node B

Soft handover(different sectors of different NodeBs)

Softer handover(different sectors of the same NodeB)

RNC

Node BNode B

UE

UE


1.1 UMTS Basics


Active Set (AS) and Macro Diversity Gain

All cells, which are involved in soft/softer handover for a given UE belong to the UE Active Set (AS):

usual situation: about 30% of UE with at least 2 cells in their AS. up to 6 cells in AS for a given UE

The different propagation paths in DL and UL lead to a diversity gain, called Macro Diversity gain: UL

one physical signal sent by one UE and received by two different cells

soft handover: selection on frame basis (each 10ms) in RNC softer handover: Maximum Ratio Combining(MRC) in NodeB

DL two physical signals (with the same content) sent by two

different cells and received by one UE

soft/softer handover: MRC in UE

umts basic

Documents

alcatel umts equipment

umts series

umts radio network planning

umts fdd r99

alcatel nodeb

abaa wbzza

network fr

evolium utran releases