umts key technologies.ppt

8/10/2019 UMTS Key Technologies.ppt

http://slidepdf.com/reader/full/umts-key-technologiesppt 1/48

Key Technologies of UMTS



Course Objectives

At the end of this course, you will be able to:

Master key technologies of UMTS

Master characteristic of UMTS system capacity



Power Control

Handover

Rake receiver

Call Admission Control & traffic control

Intelligent Antenna and MUD

Capacity of UMTS system

Content



Why Power Control?

All CDMA users occupy the same frequencyat the same time! Frequency and time arenot used as discriminators.

CDMA operates by using CODES todiscriminate between users.

CDMA interference comes mainly fromnearby users

Each user is a small voice in a roaring crowd-- but with a uniquely recoverable code.

Transmit power on all users must be tightly controlled so their signals

reach the base station at the same signal level and at the absolute

minimum power level necessary to ensure acceptable service quality.

Power Control



Overpowered by strong signals Block the whole cell

Power

f

Near-Far Effect

Power Control



Power control

Power

f

Power

f

Nearby terminals havehigher probability of success

Power control tech reduce theinterference among each UEs

and increase system capacity

Power Control



Power Control

Overcome Near-Far effect and fading compensation

Reducing multi-address interference, ensuing network capacity

Prolonging the working time of cell phone

DL power control

Cell transmitting power

Transmitting power control bit

UE signal

Power control order

UL power control

Power Control



RX vs TX ower

RX power

TX power

Channel Fading



Three methods of power control

Open loop:

measure received signal level and adjust transmitting power

Inner-loop (closed loop):Frequency:1500HZ

Measured SIR> Target SIR, lower transmitting power

Measured SIR< Target SIR, increase transmitting power

Outer-loop (closed loop): Measure BLER, adjust target SIR

Power Control



Power control

UE

RNC

Node B

Open loop power control（no feedback ）

Closed loop power control（feedback ）

UE Node B

RNCOuter-loop

Inner-loop

Power Control



Open loop power control

If received signal is stronger,then

UE can speak softer

Node

BNode

B

1

2

1

2

problem：

Unbalanced for UL/DL signal, not accurate, only used in initial stage

Open loop

If received signal is weaker,then UE

can speak louder

Power Control



Closed loop power control

Inner-loop power control is fast

Inner-loop according to SIR estimation,Node-B control UE transmission power.conducted every 0.66ms (1500Hz )

Outer-loop： according to BLER measurement estimation RNC control

and adjust SIR target

Node B

...

”Power down”

Power up command

”Power ...” SIR estimation

SIR estimationRNCSIR target ”Power up”

TPC:1500HzBLER tar SIR tar

Power down command

Power Control



Closed loop power control

Inner Loop Power control UL/DL (fast)

UE or Node-B will use:

Signaling channel, TPC,

Continuously @ rate 1500 times/s,

To relatively changes (up or down) the power to reach the

SIR target.

Outer loop Power control (Slow) If the BLER measured is below/above the target,

UE/RNC increase/reduce SIR target.

Use the new target for the Inner loop PC.

Power Control



The Effect of Power Control

The purpose of DL power control:

Saving power resource of NodeB, reducing interference to other

NodeB.

The purpose of UL power control:

Overcoming Near-Far effect, save power of UE

Power Control



Power Control

Handover

Rake receiver




Content



Handover

Handover refers to the process in which when a UE

moves from one Node B to another during calling.

Purpose: Keep service continuity.

In the UMTS system, handover is divided into soft

handover and hard handover.

Handover

H d



Type of handover

Intra-RNC, inter-Node B

Inter-RNC

Soft handover

Same Node B, Inter- sector

Softer handover

Intra-frequency handover Inter-frequency handover

Inter-system (3G&2G)

Inter-mode (FDD&TDD)

Hard handover

UMTS system support

multi handover technology

Handover

H d



Hand-over

Hard Handover

Soft Handover

Handover

H d



Soft/Softer Hand-over

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Handover

H d



Soft/Softer Handover

The soft/softer handover allows to swap from one cell to

another without call interruption or without deleting all old radio

links (by opposition to hard HO).

It also allows the UE to be connected to more than one cell

simultaneously and take benefit from macro-diversity.

Soft Handover Softer Handover

CN CN

Iur

The two Node Bsmay belong to the

same RNC

The two Node Bs may

belong to the Same RNC


SRNC DRNC

CN

Node B

SRNC

CN


Node B

CN

Handover

Handover



Hard Handover

The hard handover procedure is used in case of

service quality degradation or for traffic

distribution management.

During the hard handover procedure, all the old

radio links with the UE are abandoned before

new ones are established.

Hard handover may occur in the following

main cases :

When the UE is handed over another UTRAN

carrier, or another technology mode.

When soft handover is not permitted (if O&M

constraint)

Hard Handover

Node B

SRNC

RNC or

BSC

CN

Node B or

BTS

Handover

Handover



Basic concepts

Active Set:

The set of cells connected with UE;

User information is transmitted from these cells.

Monitor Set:

The set of cells not within the active set but being monitored

by a UE according to the adjacent node list allocated by

UTRAN.

Detect Set:

The set of cells in neither the active set nor the monitor set.

Handover

Handover



Soft handover process

Measurement

The RNC sends a measurement control message to UE.

UE should perform measurement as required and report the measurement

result.

Generally, the measured quantity is the common pilot’s Ec/No.

Decision

The RNC stores data of different cells according to the measurement

results.

The RNC makes preliminary decision according to the event decision

method.

e.g.

When the event is reported and the target cell is acceptable, send an

active set update command to add/delete the cell into/from the active set.

Execution

The RNC sends an active set update command to UE and UE starts

handover.

Handover

Handover



Soft handover event

Event Description

1A

Quality of target cell improves, entering a

report range of relatively activating set

quality add

1B Quality of target cell decreases, depart froma report range of relatively activating set

quality delete

1C

The quality of a non-activated set cell is

better than that of a certain activated set cell

replace

1D Best cell generates change

1EQuality of target cell improves, better than

an absolute threshold

1FQuality of target cell decreases, worse than

an absolute threshold

Handover



Example of soft handover

Handover



Soft handover Case

In especially urban

environment, the

handover region

between two cells might

be too small.

If the UE passes such an

area in a very quick

speed, the call might be

dropped.

Handover



Power Control

Handover

Rake receiver




Content

Rake receiver



RAKE Receiving

d1 d2

t t t

d3

transmitting ReceivingRake

combination noise

Rake receiver

Rake receiver



Multi-finger receiver

receivertransmitter

coding decoding

Direct signal

Reflect signal

Dispersive time < 1 chip length

Multi-finger receiver can’t supply multi-finger diversity

decodingDirect signal

Reflect signaltransmitter receiver

Dispersive time > 1 chip length

Multi-finger receiver can supply multi-finger diversity, improve signal gain

coding

Rake receiver

Rake receiver



RAKE Receiving

RAKE overcome multi-finger interference，improve receive capability

receiver

Single

receiving

Single

receiving

Single

receiving

searcher calculate

combining

t t

s(t) s(t)

signal

Rake receiver

Rake receiver



Multi-finger receiver

Maximal ratio combining(MRC)

at each time delay phase shifting by adding

Finger 1

Finger 2

Finger 3

Rake receiver



Power Control

Handover

Rake receiver




Content




Call Admission Control

When user initiates a call, RRM decides weather access

or deny this call according to the resource situation.

When accessing, network allocate resource (such as

OVSF, Scramble code)

Ca d ss o Co t o & t a c co t o




Traffic control

When traffic surpass system

threshold, traffic control begin.

To accept as many as possibleservices while keep the stability of

the system.




Example for load control

Breath effect of cell

With the increase of activated terminals,

interference increase

the increase of high speed service,the

increase of interference

The shrink of cell coverage area

Coverage blind spot occurs

Drop of call will happen at the edge of cell Coverage andcapacity are

relative



Power Control

Handover

Rake receiver




Content




Intelligent Antenna

user

Interference

g




Omni-cell cell with Three sector Cell with smart attenna

Intelligent Antenna




Intelligent Antenna




Multi-user Detection Principle



Power Control

Handover

Rake receiver




Content




System capacity and QoS can be interconverted

Different

combination of

service has

different capacity

Soft Capacity




Capacity of UMTS System

=

=

=

Under the circumstance of single services:




Capacity of UMTS System

…...

Under the circumstance of mixture of services：

Y Z + +




Coverage and Capacity

UMTS performance is determined by such factors as：

Number of users

Transmission rate

Mobile rate

Wireless environment

indoors

Outdoors

The sizes of cell depend on such factors as:

Local radio conditions (local interference)

Traffic in neighbouring cells (distanced interference)

Cell Radius decrease according to the Increase of user

number




Coverage/capacity vs Data Rate

Higher rate needs higher power

High data rate transmission is only available nearby the

station

>12.2 kbps

>64 kbps

>384 kbps

>144 kbps

Coverage decrease

Subscriber

num

increase




DL transmission diversity (Tx Div)

high power amplifier(TEU 50 W)

UL

tower mounted amplifier (TMA)

4RxDiv

OTSR

DL/UL:

Add carrier

six sectors

Smart antenna

Add basestation

“last choice”

Coverage and Capacity

In order to overcome cell breath caused by increasedtraffic and different requirement for capacity and coverage

in different environment ,such solution supplied:

umts key technologies.ppt

Documents