ERA/RT/NT Patrik Karlsson Limited Internal Information Page 1Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

3GPP Air Interface- Radio Network Algorithms

Patrik Karlsson, Andreas AnderssonSystem engineer, Radio Access

System Design & Radio Network Product DevelopmentProduct Unit Wideband Radio Networks

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 2Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

UTRAN Radio Network - Outline

Introduction– System requirements

– UTRAN states

– Frequency reuse

System RN functionality– Mobility, handover

– Power control

– Capacity and coverage

– Channel switching

– Future enhancements

– Summary

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 3Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

The role of RN algorithms

The RN algorithms have two main tasks

– Maintaining the quality agreed upon when admitting the RAB (seen towards CN)

– Maximizing the capacity in the RN

To do this there is a need for supporting info

– Properties of the RABs (e.g. real time requirements)

– Measurements (e.g. RSCP, Ec/Io or Total DL Power)

RNalgorithms

L1 & L2

Control Measurements

RAB attributes-Traffic class-Error rate req.-…

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 4Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Requirements from end user services

End user services have different characteristics– Reflected by the RAB attributes

Speech ~90 sec.

WWW ~ 0.1-12 hours

MP3 download~ 0.5 hour

Coffee breakRead time

www-page

Read time

www-pageE-mail

Listen to music

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 5Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

UTRAN service states

Idle

Cell_FACH

Cell_PCH URA_PCH

Cell_DCH

RRC Connected Mode

Idle Mode

A UTRAN entityand connection is established

• UTRAN has no knowledge of the UE existence• Core Network controls the UE

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 6Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

UTRAN service states and usage - Example

Idle

Interactive RABConversational RABSignalling to CN

DCH 64/64 kbps

Idle Idle

Cell_DCH

Cell_FACH

Cell_PCH

URA_PCH

DCH 384/64 kbps

Cell_DCHCell_DCHCell_DCH

Cell_DCH

Service established

Signalling service(RRC) established

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 7Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

One cell reuse is typical for CDMA

In WCDMA, all cells use the same carrier frequency (frequency reuse = 1)

– makes soft handover possible

– requires efficient power control

– makes system load control more complex

FDMA/TDMA (reuse > 1) CDMA (reuse = 1)

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 8Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Mobility

Where is the UE?

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 9Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell Cell CellCell Cell CellCellCellCell CellCellCellCellCell

RA

LA - Location areaRA - Routing areaURA - UTRAN Registration area

LA

URA

CellCell Cell

Cell

Mobility areas

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 10Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Mobility - Handover functions

Idle

Cell_FACH

Cell_PCH URA_PCH

Cell_DCH

RRC Connected Mode

Idle Mode

UTRAN determineswhich cell the UE should be in

UE selects cell based on broadcast system information

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 11Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell re-selection

When UE is in state: Idle, Cell_FACH, Cell_PCH or URA_PCHThe UE selects one cell onlyNecessary system information is received on the BCH

– Neighbour cells, cell hysteresis, quality measure etc.

The UE performs measurements on the CPICH– Three different quality measurements

DL Ec/I0 Best Quality

DL RSCP Strongest received

DL Pathloss Closest Node-B

The UE selects the cell with the best quality– The UTRAN system can not reject a UE from selecting a cell– The system can bar a whole cell– Selects among all frequencies specified

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 12Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Paging

12 unused bits288 bits

10 ms

The way for the system to find the UE location on cell level The UE periodically listens to the PICH - Sleep mode (2[2-12]*10 ms) If bits equal to 1 listen to PCH and receive further information Several UEs can listen to the same PICH bits - paging group PICH size

– No. paging groups per frame = 18, 36, 72, or 144

Paging group

PICH

UE id, MsgS-CCPCH(PCH)

UE id, Msg

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 13Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

From Cell ACell A Cell B

From Cell B

Soft Handover

When the UE is in state Cell_DCH A UE communicates with several Node-B’s simultaneously Soft handover possible and necessary with a one-cell frequency reuse. Handover need to be very fast, since going a few dB into the neighbor cell

will cause severe capacity loss. Soft handover yields diversity gain less fast fading New cell adjusts timing of the new dedicated channel

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 14Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Quality estimate PurposeDL Ec/No Best qualityDL RSCP Received strongest DL pathloss Nearest Node-B

Soft Handover

Active set - Cells the UE is connected to– Size 1-4

Monitoring set - Cells UE performs measurements on– Union of all neighbor cells of the cells in active set

A UE need to detect and connect to a new good cell fast– Time constraints around 0.5 s

The terminal performs measurements on the CPICH– Three available quality estimates

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 15Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

= Active set

= Monitoring set

Soft Handover

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 16Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Timer

Remove threshold

CPICH 1

CPICH 2

CPICH 3

Time

QualityAdd threshold

CPICH 1 CPICH 1 & 2 CPICH 2&3

Soft Handover margins

Handover events - Add, remove, exchange cell in ASTo stabilize decisions - Hysteresis and timers

AS- max = 2 CPICH 2

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 17Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Radio Network Controller

Soft/Softer Handover - Diversity

Downlink: Maximum Ratio Combining (MRC) in UE, one RAKE!Uplink: In RNC selective combining, CRC on transport block

In Node-B, one RAKE and MRC in respective Node-B

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 18Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

: Micro-cell, carrier-frequency f1

: Macro-cell, carrier-frequency f2

HCS-scenario

:High-traffic cell, carrier-frequencies f1 + f2

: Low-traffic cell, carrier-frequency f1

Hot-spot scenario

Inter-Frequency and Inter-System HO

Why inter-frequency HO?

Why inter-system HO?– Initially e.g. GSM has a more built out coverage

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 19Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power Control

Which power level should be used?

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 20Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power allocation - Physical channels

Common Control Channels - Fixed power– CPICH, P-SCH, S-SCH, P-CCPCH (BCH), S-CCPCH (PCH), PICH

– Several UEs anywhere in the cell simultaneously uses these channels

– Therefore the channels should provide good quality in the whole cell

– Forward Access Channel (FACH) can have power control

Downlink Shared Channel (DSCH) - Power control– No own power control commands (TPC)

– The power control have the possibility to follow the power control of the associated dedicated channel.

Dedicated Channels - Power control– One UE per DPCH channel

– The power can be set optimal for this individual radio link

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 21Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control - Why?

L1

L2

L1 >> L2 PRX,2 >> PRX,1

PTX,2 PTX,1

PRX,2

PRX,1

Several UEs transmit on the same frequencyUplink power control to fight pathloss and fast fadingDownlink power control mostly to fight fast fadingLimitations in hardware (MCPA), UE power consumption

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 22Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control - Uplink

Δquality New SIR target

Qualitytarget

up/downSend TPCto UE Receive TPC

adjust pwr

Measure received SIR

Measure qualitye.g. BLER

RNC Node-B UE

Outer loop Inner loop

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 23Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control - Outer loop

SIR-target

CRC error

CRC Check:

SIR target change

CRC correct - δ*ΔP dBΔP = 1/(-1+1/BLER-target)E.g. 2% 1/(-1+1/0.02) = 1/49

CRC error + δ dB

Measure the actual BLER (Block Error Rate) of the service Estimate the SIR which will give target quality (BLER) and set this as SIR

target for the inner-loop - ”Jump algorithm” CRC is determined every (TTI) 10/20/40/80 ms

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 24Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control - Inner loop

Measure the actual SIR & Compare with SIR-target– SIR > SIR-target Decrease power

– SIR < SIR-target Increase power

TPC power step size– Uplink +/- 1 dB

– Downlink + 1 dB or +/- 0.5 dB

TPC is sent in every timeslot (1500 Hz) – Compensate for fast fading

TPC command (2 bits in UL, 2-8 bits in DL) is not protected by coding

– Protecting every TPC command would create to much information overhead

– Delay requirements, 1-2 timeslots

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 25Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power combats fast fading

TX power TX power

RX power RX power

t

t t

t

Without power control With power control

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 26Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Sir Estimation

User dataPilot

Timeslot

SIR is measured on the pilot power since it is independent of the user data rate.

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 27Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

BLER %

SIR-measured

SIR-target

New environment

Pdl

(Bad)

(Good)

Q - fast increase

Q - slow decrease

Fast PC

New interferer

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 28Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control during soft handover - Uplink

TPC = 1

TPC = 1& 0

TPC from cell to UEOne inner loop in respective Node-BOne separate TPC from each cell in the active set

– All “increase” increase UE power– At least one “decrease” decrease UE power– Only consider TPC with sufficient quality

TPC = 0

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 29Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power control during soft handover - Downlink

1

TPC = 1 TPC = 0

TPC from UE to cell Initial cell power is set equal for all cells in the active setOne and same TPC from UE to all cells in the active setNode-B power drift is likely

– Independent BER per link different interpretations of received TPC in different cells can occur

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 30Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Power drift degradation solution

Solution - Power offset setting – Each cell periodically performs a power jump towards a reference level. To

decrease impact on system the jump is distributed in time.– Jump α*(P-Preference), α = [0,1]– Jump every time T

Power reference

Power

Power jump

Time

Cell 1

Cell 2

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 31Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity

How is system capacity controlled?

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 32Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity limiting resources in WCDMA

Node-B Hardware– In the Node-B a limiting amount HW exists, RAKES, processors, spreaders..

Downlink code tree– Is of fixed size, different users occupy different size of the code tree

Downlink power– A cell has a fixed maximum power level (MCPA)– Different users will require different amount of power depending on

environment, service, system load

Uplink interference– Each user generate interference, how much depend on how the SIR-target– The interference will depend on environment, service, system load etc.

Several independent resource pools exists

Which is the limiting pool can differ from time to time

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 33Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell load - Unpredictable mobility

Planned coverage

True coverage

Case A Case B

Case B

Case A

Node-B Power

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 34Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell load - Unpredictable mobility cont.

Time

UL interference

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 35Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity load

Users

Node-B Power

Users

Interference

Nu

Downlink Uplink

Nd

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 36Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell load - Resource usage example

Time

DL power [W]

20

Time

DL power [W]

20

2

18 usersPmax = 1 W 36 users

Pmax = 1 W

Guaranteed mobility Not guaranteed mobility

2CC CC

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 37Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity control functions

Admission Control– Monitor the load of the cell - slow, periodic measurements– Accept or reject requests for a DCH– Tries to estimate the load achieved if the DCH request is accepted

Congestion control– Monitor the load of the cell - faster, event based measurements– Take actions to maintain the cell load below the critical level– Take actions to stabilizing the cell load when congestion has occurred

No admission or congestion control on the common channels– Has a fixed maximum air interface load– Priority is used when input data is larger than output data

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 38Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell load control - Strategy

A system/cell needs to guarantee full mobility – End user judge the system quality by the dropping occurrence

– A cell has to limit the load of services that require full mobility at a level that is much lower than the maximum possible cell load

Should minimize SHO failure– SHO denial will only export the problem to other cells

High cell capacity is achieved by using spare capacity when available

– Need to be able to disconnect services from dedicated channel without service is being dropped - best effort!

SHO add load to all cells in the active set– Located at the cell border

– Fast fading per cell is independent

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 39Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Downlink power - efficient resource usage

Power

Maximum power

Time

Non guaranteed service users

Guaranteed service users

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 40Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity management - DL Power measure

DL power [W]

PMCPA

- Admission level - Reject new or increased DCH requests

- SHO level - Reject DCH/SHO requests

- Congestion level - Take actions to decrease the load

- Maximum power level - Automated power limitations in RBS

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 41Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity management - UL interference measure

Uplink interference - Only one high congestion level – Uplink interference measure is too inaccurate +/-3 dB– Changing background environment - How judge coverage or capacity

limited?

UE back off strategy– The UE knows its own situation best

Used powerRetransmission rate

– Transport Channels with multiple rates are used

300 bits 150 bits

Eb/I0: 0 dB 3 dB 4 dB 4 dBBLER: 60% 10% 5% 5%Max Rate: 64 kbps 32 kbps 10 kbps 64 kbps

Example: UL channel 50 bits 300 bits………….

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 42Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity management - ASE measure

DL ASE

- Reject DCH

- Reject DCH/SHO

ASE (Air-interface Speech Equivalent) is an upper load limitSwitch down ASE to keep below levels

- Reject BE DCH/SHO

- Reject BE DCH

UL ASE

- Reject BE DCH

- Reject DCH

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 43Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Possible Capacity control actions

The load will always be close to overload!!Fast and efficient congestion actions are required

– Downlink:– Bar the cell for new DCH requests– Switch down high rate interactive users to lower rates– Uplink:– Decrease SIR-target for users (uplink)– Decrease power for all users (downlink)

Selective actions– Remove soft handover legs (downlink)– Remove users– Handover users to other frequencies or systems– Schedule (delay) data packet users– Switch down in rate user rates (uplink/downlink)

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 44Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Cell breathing - Uplink

Power

UE has limited power UE transmitting on its maximum power can not increase its

power can not achieve its SIR when the interference is increased e.g. by new users

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 45Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity and Coverage enhancement

384 kbps 128 kbps 64 kbps

Different service rates result in different maximum coverage In downlink it is a trade-off between power and user rate

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 46Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity enhancing - Scheduling

Power Power

Schedule

Packet data is very bursty and not time critical Schedule users in time

Schedule users onto a common channel

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 47Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Channel Selection & Channel Switching

Which channel rate should be used for the user?

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 48Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Packet data in radio network

NACK, 2

Data 1, 2, 3, 4, 5

Re-transmission– Interactive and background services are not real time critical, as

opposed to speech

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 49Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Packet data - Capacity/Throughput

ƒ cap

SIR

Too much re-transmission

Too few users

logToo little re-transmission

There exists an optimal rate of re-transmission– Delay sensitive

– System capacity

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 50Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Capacity enhancing - Channel switching

User data

DCH

FACH/RACH

PCH/RACH

Time

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 51Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Packet data - on wire TCP/IP

RouterR1

RouterR4

RouterR3

RouterR2

Rec

eive

rR

ecei

ver

Sen

der

Sen

der

Seg

men

t 24

Ack

1A

ck 2

Ack

3A

ck 4

Ack

5

Ack

6

Ack

7

Ack

8 Ack

9

Ack

10

Ack

11

Ack

12

Seg

men

t 23

Seg

men

t 22

Seg

men

t 21

Seg

men

t 16

Seg

men

t 15

Seg

men

t 14

Seg

men

t 13

Seg

men

t 20

Seg

men

t 19

Seg

men

t 18

Seg

men

t 17

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 52Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

TCP/IP Flow control

Bandwidth (= Data speed ) =# Segments in the round trip * bits per segment

Round trip timeRTT - Round Trip TimeRTO - Re-transmission TimeoutTCP controls the data speed by controlling the # segments in

the round tripPrimary parameters

– Sliding window size and estimated round trip time

Goal: Prevent overflowing ( re-transmissions) in the buffers– Not primary aim: Collision resolution

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 53Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Slow start - slightly simplified

cwind

Time [round trip times]1 2 543

Set cwind = 1 and send one segment – cwind = sliding window size

For every ACKed segment, increase cwind by one Yields a window size (and data speed) that grows exponentially in time

5101520253035

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 54Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Congestion avoidance mode (Simplfied)

cwind

Time [round trip times]

1

1

4

3

2

2

5

543

7

8

6

6 987

Congestion avoidanceSlow start

Congestion means buffer overflow For every ACK:ed segment, increase cwind with 1/cwind If ACK not received within the “re-transmission timeout” (RTO)

– Set cwind = cwind/2– Re-transmit the not ACK:ed segments

The window size (and data speed) grows linearly in time

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 55Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Channel switching conclusions

The goal is to make channel switching adapt to TCP/IP - within the available resources

– Slow start tries to estimate the available bandwidth (+ buffer size and RTT)

– When switching down in channel rate TCP/IP will retransmit due to time out (RTT > RTO), and TCP/IP adapts to the new available rate

There is a risk that channel switching forces TCP/IP to adapt instead

– If RTTfirst_segment > RTOinitial_value (large latency) TCP goes into congestion avoidance mode immediately => inefficient usage of the channel

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 56Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Code tree - Downlink

Code limitation All codes within the tree are orthogonal

Spreading factor1

2

4

8

16

32:

C(1,1) C(1,-1)

C(1,1,1,1)

C(1,1,-1,-1)C(1,1,1,1,1…)

C(1,1,1,1,-1,-1,-1,-1)

C(….) C(….)

C(1)

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 57Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Code tree cleaning

Clean

SF 8: 1SF 16: 2

SF 4: 1or

SF 8: 1SF 16: 2

SF 8: 2or

= Busy

= Idle

Resolve the fragmentation of the tree Enable more high rate users

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 58Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

RRC connection supervision

Uplink– Each Node-B supervise the quality of its Radio link set

– When lost synchronization Cell start to send periodic TPC pattern N*(01)+1

– If the received quality of all radio link sets are too low, RNC disconnects the radio bearer

Radio link

Radio link set

RNC

Radio bearer

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 59Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

RRC connection supervision cont.

Downlink– The UE estimates the received quality and disconnects the radio link

set after a system defined time if the received quality is too low

– The UE tries to re-establish the radio link during a time

RAB supervision– If the quality of the service is too low, free resources by disconnecting that

service– Different time constraints for different services

Speech e.g. 3 secondsE-mail e.g. 1 hour

– Today RAB supervision is up to the core network or UE

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 60Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Future enhancements

Transmit diversity– Open loop transmit diversity

WCDMA-E– High Speed Data Packet Access (HSDPA) is one channel shared by

many users. Adapts the modulation per user to its radio condition

– Faster acknowledge and re-transmission

Interference cancellation– Zero out the interferer(s)

Adaptive antennas– Decrease the interfering space

ERA/RT/NT Patrik Karlsson Limited Internal Information Page 61Doc. No.: ERA/RT:00-540

Product UnitWideband Radio Networks

Summary

UTRAN needs to support a wide flavor of services with different behavior and needs.

– Have to interact with their external protocols e.g. TCP/IP.

UTRAN uses frequency re-use of one– Users and cells are all on the same frequency– UTRAN is interference limited and sensitive. Any RN function that decreases

the transmitted interference will increase the capacity.

RN functions– Trade-off: Capacity - Coverage - Quality– The system need to support full UE mobility - regardless of service– Power control - Fast and optimizes the quality per user.– Soft handover - UE is connected to several cells at the same time– Power control and Soft handover are essential in a UTRAN system.– Stable capacity surveillance and control is a key functionality