Wcdma Hspa Basics 001

8/12/2019 Wcdma Hspa Basics 001

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WCDMA/HSPA basics for UMTS

Kari Aho

Project and Business Development Manager

[email protected]

Disclaimer

Effort has been put to make material as correct as possible,however, it is still suggested that reader confirms the latestinformation from official sources like 3GPP specs(http://www.3gpp.org/Specification-Numbering)

necessarily the views of their employers or customers

Use/reproduction of this material is forbidden without apermission from the author

2 2010Magister Solut ions Ltd




2/47

Trainer introduction

Work history

01/2009 Project and business development manager at Magister

01/2008 12/2008 Senior research scientist at Magister

01/2006 12/2007 Researcher / Research trainee at University ofJyvskyl

Education

Ph.D. 2009-2010, L.Sc. 2007-2009, M.Sc. 2003-2006, University ofJyvskyl

International publications

20 conference papers

2 journal articles


Magister Solutions (1/2)

Strong background in wireless network research 2 Professors, 9 Doctors, 16 Masters of Sciences / Ph.D students, and

2 Masters Degree students

Over 100 academic publications and several patents

Research to support standardization and implementation

Technology road mapping

Technology training

References

R&D co-operation with largest mobile and network manufacturers

Leadership and membership on customers R&D project teams


Magister Solutions (2/2)

Technology competence Second generation cellular systems

GSM, GPRS, EDGE

Third generation cellular systems WCDMA, TD-(S)CDMA, HSDPA / HSUPA, HSPA+

Next generation cellular systems LTE, LTE-A

WiMAX, Flash-OFDMA

Special areas of interest Voice over IP

Radio resource management development

System level performance analysis

Mobility management



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10 2010Magister Solutions Ltd

Course schedule

Introductory

WCDMA technology overview

Standardization

Market and performance situation

Rel99 WCDMA

Codes

Power Control

Mobility

Multimedia Broadcast Multicast Service

HSPA

HSDPA

HSUPA

Continuous Packet Connectivity

Internet HSPA


Motivation and Goals

Main things to learn

Architecture (elements, data flow)

Power control (fast, slow)

Mobility (soft, softer, hard handover)

What changes in Rel99 WCDMA when HSPA is introduced

All of the issues form a basis for HSPA and HSPA+ systems andthose are still in use



5/47

Readings related to the subject

General readings

WCDMA for UMTS H. Holma, A. Toskala

HSDPA/HSUPA for UMTS H. Holma, A. Toskala

3G Evolution - HSPA and LTE for Mobile Broadband - E. Dahlman, S.Parkvall, J. Skld and P. Beming,

Network planning oriented

Radio Network Planning and Optimisation for UMTS J. Laiho, A.Wacker, T. Novosad

UMTS Radio Network Planning, Optimization and QoS ManagementFor Practical Engineering Tasks J. Lempiinen, M. Manninen



Why new radio access system for UMTS (1/2)

Need for universal standard

Universal Mobile Technology System (UMTS)

Support for packet data services

IP data in the core network

IP radio access

New services in mobile multimedia need higher data rates andflexible utilization of the spectrum



6/47

Why new radio access system for UMTS (2/2)

Frequency Division Multiple Access (FDMA)

Different frequencies for different users

Example Nordic Mobile Terminal (NMT) systems

Time Division Multiple Access (TDMA)

Same frequency but different timeslots for different users

TDMA

FDMAWastestime

resources

Wastesfrequencyresources

Example Global System for Mobile Communication (GSM)

Code Division Multiple Access (CDMA)

Same frequency and time but users are separated from eachother with codes

Example WCDMA/UMTS


Code

Frequency

Time

1

2

N

CDMA

Can exploitboth time and

frequency

WCDMA Systems (1/3)

Wideband CDMA (WCDMA) means that

Bandwidth is not dependent of the information signal

Transmission bandwidth is much larger than the informationbandwidth i.e. transmitted signal is spread


Frequency

Despread narrowband signal, i.e, original data signal

Spread wideband signal which will be sent

Transmitted signalbefore spreading

WCDMA Systems (2/3)

Benefits

More securecommunication

Reduces the impactof interference (and

jamming) owerdensity(Watts/Hz) Received signal

after despreading butbefore filtering

Received despred signal

Interference


Frequency

Powerdensity(Watts/Hz)

Frequency

Received signalafter despreading andafter filtering


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WCDMA Systems (3/3)

Wide bandwidth, 3.84 Mcps (Megachips per second)

Maps to 5 MHz due to pulse shaping and small guard bands between

the carriers

Users share the same 5 MHz frequency band and time

an ave separate z requency an s

Users are separated from each other with codes and thus frequencyreuse factor equals to 1

WCDMA is the most common radio interface for UMTS systemsincluding HSPA and HSPA+


WCDMA Key Features (1/4)

Fast power control (PC)

Reduces the impact of channel fading and minimizes the interference

UE1 UE2

Without PC received

power levels would

be unequal


UE3

UE1

UE2

UE3

UE1 UE2 UE3

In theory with PC

received power levels

would be equal


Soft handover

Improves coverage, decreases interference


UE1BS 1

BS 2


8/47


Robust and low complexity RAKE receiver

Utilizes multipath diversity



Considerably higher bit rates than with 2G systems

With Release 99 theoretically 2 Mbps

The highest implemented is however 384 kbps

Support for flexible bit rates

Mu tipexing o i erent services wit i erent QoS require on asingle physical connection

Real-time, (voice, video telephony)

Streaming (video and audio)

Interactive (web-browsing)

Background (e-mail download)




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Standardization (1/2)

WCDMA was studied in various research programs in themilitary, industry and universities

First publications: late 40s First applications: Military from the 50s

Rake receiver patent 1956

ll l l lll l l l

Investigations for cellular use 80s

IS-95 standard 1993 (2G)

WCDMA was chosen as 3G technology in late 1997/early 1998 bymany forums like

European Telecommunications Standards Institute (ETSI)

Association of Radio Industries and Business (ARIB, Japan)


Standardization (2/2)

During 1998 parallel work proceeded (mainly) in ETSI and ARIB

Resource consuming for companies with global presence andnot likely to arrive to identical specifications globally

The same discussion e.g. in ETSI and ARIB sometimes endedup to different conclusions

or was a so on-go ng n an orea

At end of 1998 Third Generation Partnership Project (3GPP) wasfounded


Third Generation Partnership Project (1/2)

Members Founding members

ETSI EU

ARIB Japan

Telecommunications Technology Committee (TTC) Japan

Telecommunications Technology Association Korea i l l i ii l l i i

China Communications Standard Association (CCSA) China later

Different companies, like Nokia, are members through theirrespective standardization organization

Original scope was to produce Technical Specifications (TS) andTechnical Reports (TR) for a 3G Mobile System but later themaintenance and development of GSM including evolved radioaccess technologies (e.g. GPRS and EDGE) was also included



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Third Generation Partnership Project (2/2)

3GPP work is divided into Technical Specification Groups (TSG)

GSM EDGE Radio Access Network (GERAN)

Radio Access Network (RAN)

Service & System aspects (SA)

Core network & terminals (CT)


3GPP RAN (1/2)

RAN1 covers, for instance,

Physical channel structures and mappings

Physical layer multiplexing, and channel coding and error detection

Spreading, modulation and other physical layer procedures

Measurements and their provision to the upper layers


Radio interface architecture and protocols between UE and RAN

Services offered by the physical layer to upper layers

Cell selection and re-selection procedures

UE capabilities for UE - RAN interface

Definition of RRM strategies to be supported by RAN


3GPP RAN (2/2)


Overall UTRAN and E-UTRAN architecture

Synchronization in UTRAN and E-UTRAN

Interface protols for Radio Network Controller (RNC) RNC (Iur),NodeB RNC (Iub) and RNC Core Network (Iu) communication


Requirements for radio link, Radio Resource Management (RRM)performance and accuracy of measurements

Radio system scenario analysis and simulation


Development of UE conformance test specifications



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CommercialHSUPA

networks

CommercialHSDPA

networks

Timeline

1999 2002 2005 2006 2007 2008 2009 2010 2011

R99 Rel-4 Rel-5 Rel-6 Rel-7 Rel-8 Rel-9 Rel-10Standard

First majormilestone by

3GPP

Japan launchedfirst commercial

Rel99 3Gnetwork

Commercialnetworks in

Europe

WCDMA HSDPA HSUPA HSPA Evolutions (HSPA+)

LTE LTE-Advanced 4G3G

3.5G

3.75G

Technique

Naming


Market and performance situation (1/5)

In Finland alone there are over 8 million GSM and WCDMA-HSPAmobile subscriptions

World wide over 4.7 billion subscriptions

3G (incl. HSPA) Over 650 million 3G subscriptions

Commercially launched by 383 operators in 156 countries

Network peak data rates

247 commercial HSPA networks, i.e 65%, support 7.2 Mbps (peak DL) orhigher

58 HSUPA networks support up to 5.8 Mbps peak UL and another 5networks support 11.5 Mbps peak



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Device peak data rates (excl. notebooks, e-book readers)

2,221 (out of 2922) devices support 3.6 Mbps peak or higher

1,435 devices support 7.2 Mbps peak or higher

Operating band

27 commercial UMTS900 operators launched in 20 countries (i.e. HSPAlaunched in the 900 MHz band; some have launched HSPA+)

2,183 HSPA devices (90%) operate in 2100 MHz band

817 tri-band HSPA devices 850/1900/2100 MHz

Source: Global mobile Suppliers Association (GSA) surveys



One Song

Whole Album

DVD-Movie

HD-Movie



Source: Ficora Telecommunication Markets in the Nordic Countries


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Almost 10- foldwhen compared

Unit Magnitude

Exabyte 1,000,000,000,000,000,000

Petabyte 1,000,000,000,000,000

Terabyte 1,000,000,000,000

o yearGigabyte 1,000,000,000

Megabyte 1,000,000

Kilobyte 1,000


(WCDMA)

Contents

Codes

UMTS Architecture

Power Control

Handovers



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Codes in WCDMA (1/4)

Channelization Codes (=short codes)

Defines how many chips are used to spread a single information bit

and thus determines the end bit rate Length is referred as spreading factor

Used for:

Downlink: Separation of downlink connections to different users within onecell

Uplink: Separation of data and control channels from same terminal

Same channelization codes in every cell / mobiles

additional scrambling code is needed



Scrambling codes (=long codes)

Very long (38400 chips), many codes available

Does not spread the signal

Used for

Downlink: to separate different cells/sectors

li i illi i il

The correlation between two codes (two mobiles/NodeBs) is low



Channelization

codes separate

different

connections

Channelization

codes separate

data/control

channels

Downlink

Scrambling

codes separate

cells/sectors

Uplink

Scrambling codes

separate different

mobiles



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Spreading

Factor (SF)

Channel

symbolrate(kbps)

Channel

bit rate(kbps)

DPDCH

channel bitrate range(kbps)

Maximum user

data rate with -rate coding(approx.)

512 7.5 15 36 13 kbps

256 15 30 1224 612 kb sHalf rate speech

Symbol_rate =Chip_rate/SF

Bit_rate =Symbol_rate*2

Control overhead User_bit_rate =Channel_bit_rate/2

128 30 60 4251 2024 kbps

64 60 120 90 45 kbps

32 120 240 210 105 kbps

16 240 480 432 215 kbps

8 480 960 912 456 kbps

4 960 1920 1872 936 kbps

4, with 3parallel

codes

2880 5760 5616 2.3 Mbps

Full rate speech

144 kbps

384 kbps

2 Mbps


Questions

To what purpose channelization codes are used in the downlink?

To what purpose scrambling codes are used in the uplink?


UMTS Terrestrial Radio Access Network (UTRAN)Architecture (1/3)

New Radio Access networkneeded mainly due to newradio access technology

Core Network (CN) is

based on GSM/GPRS

RNC

NodeBUECN

Uu interfaceIub interface

Radio Network Controller(RNC) corresponds roughlyto the Base StationController (BSC) in GSM

Node B correspondsroughly to the Base Stationin GSM

NodeB

NodeBRNC

UE

Iur interface

UTRAN



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RNC

Owns and controls the radio resources in its domain

Radio resource management (RRM) tasks include e.g. the following Mapping of QoS Parameters into the air interface

Air interface scheduling

Handover controll

Outer loop power control

Admission Control

Initial power and SIR setting

Radio resource reservation

Code allocation

Load Control



Node B

Main function to convert the data flow between Uu and Iubinterfaces

Some RRM tasks:

Measurements

Innerloop power control


Questions

Name three main elements in the UMTS architecture

What would be the responsibility of UEs



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Power Control in WCDMA (1/4)

The purpose of power control (PC) is toensure that each user receives andtransmits just enough energy to prevent:

Blocking of distant users (near-far-effect)

Exceeding reasonable interference levelsUE1 UE2

Without PC received

power levels would

be unequal


UE3

UE1

UE2

UE3

UE1 UE2 UE3

In theory with PC

received power levelswould be equal


Power control can be divided into two parts:

Open loop power control (slow power control)

Used to compensate e.g. free-space loss in the beginning of the call

Based on distance attenuation estimation from the downlink pilot signal

Closed loop power control (fast power control)

Used to eliminate the effect of fast fading li i i

Applied 1500 times per second



Closed loop power control can also be divided into two parts:

Innerloop power control

Measures the signal levels and compares this to the target value and ifthe value is higher than target then power is lowered otherwise power isincreased

Outerloop power control Adjusts the target value for innerloop power control

Can be used to control e.g. the Quality of Service (QoS)



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Example of inner looppower control behavior:

With higher velocitieschannel fading is more

control may not besufficient


WCDMA Handovers (1/7)

WCDMA handovers can be categorized into three different typeswhich support different handover modes

Intra-frequency handover

WCDMA handover within the same frequency and system. So f t , so f t e r

and h ard h an d ov ersupported

Inter-frequency handover

Handover between different frequencies but within the same system.Only h ard h an d ov ersupported

Inter-system handover

Handover to the another system, e.g. from WCDMA to GSM. Only h ardh an d ov ersupported



Soft handover Handover between different

base stations

Connected simultaneously tomultiple base stations

The transition betweenthem should be seamlessl l

Downlink: Several Node Bstransmit the same signal tothe UE which combines thetransmissions

Uplink: Several Node Bsreceive the UEtransmissions and it isrequired that only one ofthem receives thetransmission correctly


UE1BS 1

BS 2


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Softer handover

Handover within the

coverage area of one basestation but betweendifferent sectors

Procedure similar to softhandover


UE1BS 1

BS 2


Hard handover

The source is released first and then new one is added

Short interruption time

Terminology

Active set (AS), represents the number of links that UE is connectedto

Neighbor set (NS), represents the links that UE monitors which arenot already in active set



Handover parameters

Add window

Represents a value of how much worse a new signal can be compared tothe best one in the current active set in order to be added into the set

Adding link to combining set can be done only if maximum number of

links is not full yet (defined with parameter). Moreover a new link is added to the active set only if the difference

between the best and the new is still at least as good after the add timeris expired. Timer is started when the signal first reaches the desiredlevel.

Drop window

Represents a value of how much poorer the worst signal can be whencompared to the best one in the active set before it is dropped out

Similarly to adding, signal which is to be dropped needs to fulfill the dropcondition after the corresponding drop timer is expired.



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Replace window

Represents a value for how much better a new signal has to be compared

to the poorest one in the current active set in order to replace its place Replace event takes place only if active set is full as otherwise add event

would be applied

Similarly to add and drop events, also with replace event there exist al il i



Exercises: Replace Threshold_1, Triggering time_1, etc with correct handover

parameter names.

Which event is missing from the example?

BS1Triggering time_1 Triggering time_2

Receivedsignal

strengthBS2

BS3

Threshold_1Threshold_2

BS2 from the NS reachesthe threshold to be added

to the AS

BS1 from the AS reachesthe threshold to be

dropped from the AS

BS1 dropped from the AS


Questions

To which parts can the fast i.e. closed loop power control bedived into?

To how many base stations UE is connected to when it makes ahard handover?



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Multimedia Broadcast Multicast Service(MBMS) Background

Before MBMS broadcast and multicast transmissions were dealtwith using somewhat inefficient techniques

Cell Broadcast Service (CBS)

Only message-based services with low bit rates

IP Multicast Service (IP-MS)

No ca abilit to use shared radio or core network resourcesili i

Nowadays clear need for efficient group transmission method


Digital Video Broadcast - Handheld (DVB-H) / Digital MultimediaBroadcasting (DMB)


MBMS Introduction (1/3)

Allows different forms of multimedia content to be deliveredefficiently by using either broadcast or multicast mode

Mobile TV, weather reports, local information,

The term broadcast refers to the ability to deliver content to allusers who have enabled a specific broadcast service and find

themselves in a broadcast area

Multicast refers to services that are delivered solely to users whohave joined a particular multicast group. Multicast group can be, forexample, a number of users that are interested in a certain kind ofcontent, such as sports



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More efficient use of network resources and capacity fordelivering identical multimedia content to several recipients in

the same radio cell

Built on top of the existing 3G network

All MBMS services can be provided with cellular point-to-point(p-t-p) or with point-to-multipoint (p-t-m) connections

Optimizing the usage of radio resources

Users receives the data with fixed bit rate

e.g. 64, 128 or 256 kbps



MBMS has so called co unting

methods to indicate when the

transition from p -t-p to p-t-m mode is

reasonable

p-t-p p-t-m


MBMS Quality of Service (1/4)

Lack of uplink traffic with MBMS leads to not having

Feedback information available

Individual retransmissions

In order to improve the reliability of MBMS transmissionsper o c repet t ons o content can e use

Repetitions are not precluded by the lack of uplink traffic becausethe service provider can transmit them without feedback from theUE

Periodical repetitions are done on RLC level with identical RLCsequence numbers and Protocol Data Unit (PDU) content



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MBMS Quality of Service (2/4)

As data loss is required to be minimal also during cell change,there has been made effort to achieve this e.g. by using soft and

selective combining MBMS is most likely to be available through large parts of the

network thus macro diversity combining i.e. combining theinformation coming from different NodeBs could be utilized

Moreover, also antenna diversity techniques can be consideredas an option to improve the reliability

Multiple transmit (Tx) and/or receive (Rx) antennas


Multimedia Broadcast Multicast Service(MBMS) Quality of Service (3/4)


Multimedia Broadcast Multicast Service(MBMS) Quality of Service (4/4)



24/47

MBMS performance in WCDMA networks

Cell throughput with 2-

antenna terminal and soft

combining 1500-2500 kbps =

12-20 x 128 kbps TVchannels

-

terminal and soft combining

600-1000 kbps = 5-8 x 128 kbps

TV channels


Questions

What does multicast mean?

How the lack of uplink transmissions with MBMS can becompensated so that the QoS is improved?




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Conclusion (1/4)

Need for universal standard and improved packet datacapabilities were among the key factors towards a new radio

network interface, Wideband Code Division Access (WCDMA)

3GPP is currently the main standardization body in charge of

Market share for WCDMA is growing rapidly

More than 650 million subscribers (incl. HSPA)

Fueled by various services (facebook, twitter, youtube, etc.)


Conclusion (2/4)

Codes in WCDMA Channelization Codes

Spreads the information signal

Separates of downlink connections (DL) or data and control channelsfrom same terminal (UL)

Scrambling codes i l i l

Separates different cells/sectors (DL) or different mobiles (UL)

UTRAN Needed mainly due to new radio access technology

Node B responsible of handling connections to and from the UE

RNC responsible of radio resource management


Conclusion (3/4)

Fast power control (PC)

To ensure that each user receives and transmits with just enoughenergy

Open loop PC for the connection setup and fast closed loop PC forthe actual connection

WCDMA Handovers

Intra-, interfrequency and intersystem handovers

Soft(er) handover for seamless hand-off

Hard handovers with small interruption time when HO is made



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Conclusion (4/4)

MBMS was introduced to more efficient utilization of limited radionetwork resources with multimedia content provision

Improved even further with macro diversity combining and diversitytechniques




Contents

Introduction

HSDPA

HSUPA

Continuous Packet Connectivity

I-HSPA Conclusion

2010Magister Solutions Ltd


27/47

79 2010Magister Solut ions Ltd2010Magister Solutions Ltd

High Speed Packet Access (1/3)

There were number of pushing forces to improve the packet datacapabilities of WCDMA even further, e.g.

Growing interest towards rich multimedia content in the wireless domain

Competitive technologies such as WIMAX

High Speed Packet Access (HSPA) evolution introduced first downlinkcounterpart of the evolution called High Speed Downlink Packet Access(HSDPA) in Release 5

Uplink evolution followed later in Release 6 by the name of High SpeedUplink Packet Access (HSUPA)

HSPA was originally designed for non-real time traffic with hightransmission rate requirements



HSPA features/properties include e.g.

Higher order modulation and coding

Higher throughput and peak data rates

In theory up to 11.4 Mbps in the uplink and 28 Mbps in the downlinkwithout Multiple Inputs and Multiple Outputs (MIMO) in Release 7

system Multiple Inputs and Multiple Outputs (MIMO)

Roughly speaking equals to additional transmitter and receiver antennas

Enables simulaneous spatially separated data streams -> multiplied datarates!

2x2 DL MIMO in Release 7 doubles the theoretical data rate to 56 Mbps

Fast scheduling in the Node B

Possibility to take advantage of channel conditions with lower latency



28/47


Link adaptation in downlink

Possibility to adjust the used modulation and coding scheme in order to beappropriate for current radio channel conditions

Improved retransmission capabilities

Newly introduced layer one retransmissions called as Hybrid Automatic RepeatRequest (HARQ) => reduced delay

Radio Link Control (RLC) level retransmissions still possible

Shorter frame sizes and thus Transmission Time Intervals (TTI)

With HSDPA 2ms and with HSUPA 10ms and 2ms

Multicarrier HSPA (Rel. 8-10)

Two or more 5 Mhz carriers in use simultaneously


CommercialHSUPA

networks

CommercialHSDPA

networks

Timeline

1999 2002 2005 2006 2007 2008 2009 2010 2011

R99 Rel-4 Rel-5 Rel-6 Rel-7 Rel-8 Rel-9 Rel-10Standard

First majormilestone by

3GPP

Japan launchedfirst commercial

Rel99 3Gnetwork

Commercialnetworks in

Europe

WCDMA HSDPA HSUPA HSPA Evolutions (HSPA+)

LTE LTE-Advanced 4G3G

3.5G

3.75G

Technique

Naming

Questions

Why were the packet data capabilities of WCDMA improved evenfurther?

For what kind of services was HSPA originally designed?



29/47


(HSDPA)


Contents

Introduction to HSDPA

Link Adaptation

Fast Retransmissions

Downlink Scheduling

HSDPA Mobility


Introduction to HSDPA

HSDPA Improvements for packet data performance both in termsof capacity and practical bit rates are based on

The use of link adaptation,

Higher order modulation,

Fast scheduling,

ll ,

Physical layer retransmission

HSDPA operates on top of Rel99 and is not a stand alone system

HSDPA does not support Rel99 features like fast power controlor soft handover



30/47

Link Adaptation (1/3)

UE informs the Node B regularly of its channel quality by CQImessages (Channel Quality Indicator)



Adaptive modulation and higher order modulation (16/64QAM)with HSDPA

810121416

usEsNo[dB]


0 20 40 60 80 100 120 140 160-2

0

24

Time[ number of TTIs]

QPSK1/4

QPSK2/4

QPSK3/4

16QAM2/4

16QAM3/4

Instantane

Link

adaptation

adjusts the

mode within

few ms based

on CQI


Link adaptation is not used in uplink, though

More complex modulation schemes require more energy per bit tobe transmitted than simply going for transmission with multipleparallel code channels, thus HSUPA benefits more from usingmultiple codes as PC keeps the signal levels quite good anyway



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Fast Retransmissions (1/3)

PacketRetransmisson

Packet

Rel 99 HSPA

RNC

Radio Link Control (RLC) layer ACK/NACKs also possible with HSPA


RLC ACK/NACK

Layer 1

ACK/NACK

Retransmisson

NodeB

UE


RNCNodeBUE


ser ata

RLC

MAC-d

Layer1

MAC-hs

HARQ (N)ACK

(Re)transmission

RLC (N)ACK

(Re)transmission


Layer 1 signaling indicates the need of retransmission which leads tomuch faster round trip time that with Rel 99

Retransmission procedure with layer 1 retransmissions (HARQ) is doneso that decoder does not get rid of the received symbols if the

transmission fails but combines them with new transmissions

Retransmissions can operate in two ways:

Identical retransmissions (soft/chase combining)

Non-identical retransmissions (incremental redundancy)



32/47

Questions

What is CQI?

What does link adaptation do?

Which entity initiates RLC re-transmissions?

Which entity initiates HARQ re-transmissions?


Downlink scheduling (1/5)

NodeB has certain amount of users connected to it and it needsto schedule the different users for transmission in differentfractions of time (Transmission Time Intervals)

Certain fairness for scheduling time for each user should bemaintained

Resources should be utilized in optimal mannerl l l

There exists different ways that users can be scheduled indownlink, e.g.

Round Robin

Proportional Fair



Round Robin (RR)

Simplest scheduling algorithms

Assigns users in order i.e. handling all users without priority

Positive sides

Easy to implement

ll ll

Negative sides

No channel conditions are taken into account and thus resources mightbe wasted



33/47


Proportional Fair (PF) Compromise-based scheduling algorithm

Based upon maintaining a balance between two competing interests Maximize network throughput i.e. users are served in good channel

conditions

Allowing all users at least a minimal level of service



PF is assigning each user a scheduling priority that is inverselyproportional to its anticipated resource consumption High resource consumption => low priority



In general priority metric for certain user can be defined as follows

,r

dpriority

where instantaneous data rate, d, is obtained by consulting the link adaptation

algorithm and average throughput, r, of the user is defined and/or updated as

,otherwise,*)1(

servedisuserif,**)1(

old

old

ra

darar


follows

where is so called forgetting factor. Hence, equals the equivalent averaging

period in a number of TTIs for the exponential smoothing filter

a 1a


34/47

Mobility with HSDPA (1/4)

Handovers are roughly tradeoff between two issues

When channel conditions are getting worse, handover to better cell

should be made so that packets wont get lost due to poor channelconditions

However, each time when the (inter-site) handover is made,transmission buffers in the Node B are flushed resulting to additionaldelays from RLC level retransmission or disruption of service

When regarding HSDPA, the user can be connected only to oneserving HSDPA Node B at the time

Leading to hard handover when the handover between HSDPA NodeBs is required in contrary to DCH soft handover



Even though there is only one serving HSDPA cell, the associatedRel99 channels can be in soft(er) handover and maintain theactive set as in Rel99

Node B,

Serving HSDPA


DCH

UE

Node B,

Part of DCH active setHS-SCCH

DCH/HSDPA

DCH

DCH


HSDPA handover procedure includes following steps

Serving cell change procedure is initiated when a link in (Rel99)active set becomes higher in strength and stays stronger for certainperiod of time, referred as time-to-trigger

If the condition mentioned above is met then the measurement

report is sent from the UE to the Node B, which forwards it to theRNC

If e.g. the admission control requirements are met the RNC can thengive the consent for the UE to make the handover by sending socalled Signaling Radio Bearer (SRB) (re)configuration message



35/47


In the case of intra Node B handover, the HARQ processes(transmissions) and Node B buffers can be maintained and thus

there is only minimal interruption in data flow However, with inter Node B handover i.e. between Node Bs, the

Node B packet buffers are flushed including all unfinished HARQprocesses which are belonging to the UE that is handed off


Questions

How does Round Robin allocate resources for the users?

How intra- and inter-Node B handovers differ from each other?



(HSUPA)



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Contents

Introduction to HSUPA

Multicodes with HSUPA

Uplink Scheduling

HSUPA Mobility


Introduction to HSUPA (1/2)

Roughly three years later when HSDPA was introduced uplinkcounterpart of the high speed packet access evolution wasintroduced in Release 6

In 3GPP original name was not HSUPA but Enhanced DedicatedChannel (E-DCH)

The obvious choices for uplink evolution was to investi ate thel ltechniques used for HSDPA and, if possible, adopt them for theuplink as well

Improvements in HSUPA when compared to Rel99

Layer 1 Hybrid ARQ (HARQ) i.e. fast retransmissions

Node B based scheduling


Introduction to HSUPA (2/2)

Easier multicode transmissions

Shorter frame size, 10ms mandatory for all HSUPA capable devicesand 2 ms as optional feature

Higher order modulation (Release 7)

,basic features of the WCDMA Rel99

Cell selection and synchronization,

random access,

basic power control loop functions,

basic mobility procedures (soft handover), etc.



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Multicodes with HSUPA

Even though Rel99 supports in theory multicode transmissionsin practice only HSUPA can support multicode transmissions and

thus higher bitrates In theory Rel99 can use 6xSF4

HSUPA can in practice support 2xSF2 + 2xSF4

The reason why Rel99 does not support multicodes is that thescheduling is controlled by RNC and thus rather slowlycontrollable

Potentially wasted resources due to changing channel conditions andslow adjustment

Also, the lack of HARQ with Rel99 means lower packet error targetfor the system and thus higher resources for UE


Questions

What new features on top of multicodes and shorter frame sizesdo HSUPA offer?

Is DCH part of the HSUPA?

Why does not DCH support multicodes in practice?


Uplink scheduling (1/5)

With HSDPA all the cell power can be directed to a single user fora short period of time

Very high peak data rates achievable for certain UE and all theothers can be left with a zero data rate

However, in the next time instant another UE can be served and so

on

With HSUPA HSDPA type of scheduling is not possible

HSUPA is a many-to-one scheduling

The uplink transmission power resources are divided to separatedevices (UEs) which can be used only for their purposes and notshared as with HSDPA



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The shared resource of the uplink is the uplink noise rise(*), or thetotal received power seen in the Node B receiver

Typically, one UE is unable to consume that resource alone completelyand it is very beneficial for the scheduler to know at each time instanthow much of that resource each UE will consume and to try to maintainthe interference level experienced close to the maximum


(*)ratio between the total power received from all of the UEs at the base station and the thermal noise


Two different scheduling schemes are defined for HSUPA traffic

Scheduled transmissions controlled by Node B which might notguarantee high enough minimum bit rate. In addition each requestrequires time consuming signaling

Non-scheduled transmissions (NST) controlled by radio networkcontroller (RNC) which defines a minimum data rate at which the UEcan transmit without any previous request. This reduces signalingoverhead and consequently processing delays



Scheduled transmissions

The scheduler measures the noise level and decides whether

Additional traffic can be allocated

Should some users have smaller data rates

The scheduler also monitors the uplink feedback

Transmitted on E-DPCCH in ever TTIi i

Referred to as happy bits

Tells which users could transmit at a higher data rate both from thebuffer status and the transmission power availability point of view



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Depending on possible user priorities given from the RNC, thescheduler chooses a particular user or users for data rate

adjustment The respective relative or absolute rate commands are then send on the

E-RGCH or E-AGCH

UE in soft handover receives only relative hold/down commandsrom o er an servn o e


Questions

What is the shared resource in the uplink if power is in thedownlink?

What kind of scheduling possibilities HSUPA offer?


Mobility in HSUPA (1/2)

HSUPA supports the soft(er) handover procedure similar toWCDMA Rel99

The HARQ operation in HSUPA soft handover situation is done in

following manner any o e n t e act ve set sen s an , t en t e n ormat ongiven to the Medium Access Control (MAC) layer is that an ACK hasbeen received and the MAC layer will consider the transmissionsuccessful



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Mobility in HSUPA (2/2)

RNC

NodeBCorrectly

received

Packet

reordering


Data

Layer 1

ACK/NACK

UE

NodeB

Layer 1

ACK/NACKpacket

Questions

Which logical entity handles packet reordering and initiates RLCretransmissions if necessary

If UE is in a two-way soft handover how does the HARQ operate?



(CPC)



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Contents

Introduction CPC

UL discontinuous transmission

DL discontinuous reception

HS-SCCH less

Performance example


Introduction to CPC (1/2)

Continuous Packet Connectivity (CPC) was released in Release 7

Designed to improve the performance of delay critical small bitrate services like VoIP

Eliminates the need for continuous transmission and receptionwhen data is not exchanged. Can be categorized into threefeature

UL discontinuous transmission

DL discontinuous reception

HS-SCCH less for HSDPA VoIP


Introduction to CPC (2/2)

Benefits

Connected inactive HSPA users need less resources and create lessinterference => more users can be connected

UE power savings => increased talk time (VoIP)

UTRAN resources are saved



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UL discontinuous transmission (1/2)

Before 3GPP Rel7, DPCCH was defined to be transmitted continuouslyregardless is actual user data or not

Highly loading the cell Draining the UE battery

An ideal solution would be to keep the UE silent during the periods thatit is not transmitting any data and activate the control channels just forthe transmissions periods

However, that could compromise, e.g., the fast power control which would bethen updated only during the times when the data is exchanged

Thus, in Rel7 more elaborate solution for UL DTX was formalized

Various cycles and timers quarantee non-compromising discontinuoustransmisson


UL discontinuous transmission (2/2)


DL discontinuous reception (1/2)

In DL, Discontinuous Reception (DRx) cycles allow an idle UE topower off the radio receiver for a predefined period so that

DL scheduling is still possible

UE is able to shut-off the receiver circuitry over some periods oftime to yield a non 100 % receiver duty cycle

llchanges in UEs active set due to mobility

When UE wakes up from inactivity

It listens predefined time for incoming transmissions

If it successfully decodes a new transmission during that time itstarts timer for staying active certain period of time



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DL discontinuous reception (2/2)


HS-SCCH less

HS-SCCH-less HSDPA operation in downlink

Initial transmission of small, periodic packets, such as VoIP packets,can be sent without High Speed Secondary Control Channel (HS-SCCH)

Eliminates the control channel overhead from small packets sentover HSDPA

Retransmissions are sent with HS-SCCH pointing to the initialtransmission


VoIP performance with and without CPC

In general major performance enhancements visible if circuit switched voice overWCDMA and VoIP over HSPA Rel 7 is compared

With Rel 99 CS voice capacity 60-70 users/cell

With Rel 7 VoIP capacity goes beyond 120 users/cell


H. Holma, M. Kuusela, E. Malkamki, K. Ranta-aho, C. Tao:VoIP over HSPA with 3GPP Release 7 , PIMRC, 2006.


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Questions

Name one benefit for the UE and one benefit for the network thatUL DTX brings along with it

What kind of constraints there are for configuring a DRX cycle?



(I-HSPA)


I-HSPA (1/3)

Internet-HSPA (I-HSPA) aims to provide competitive mobileinternet access with much more simpler network architecturethan it is in normal WCDMA/HSPA systems

Deployable with existing WCDMA base stations

Utilizes standard 3GPP terminals

Simplified architecture brings many benefits such as

Cost-efficient broadband wireless access

Improves the delay performance

Transmission savings

Enables flat rating for the end user

Works anywhere (compared to WLAN or WIMAX)



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I-HSPA (2/3)

UE

NodeB /E-NodeB

RNC

SGSN

GGSN

Internet /

Intranet


I-HSPA

I-HSPA (3/3)

Round trip time of 32-Byte packet

120

140

160

180

200

Release 99~200 ms

HSDPA


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Conclusions (1/2)

High Speed Packet Access evolution for WCDMA was introduced inRelease 5 and 6 for downlink and uplink, respectively

HSPA offers much higher peak data rates, reaching in theory up to 56Mbps in the downlink and 11.4 Mbps in the uplink (Release 7), inaddition to reduced delays

Key technologies with HSPA are

Fast Layer 1 retransmissions i.e. HARQ

Node B scheduling

Shorter frame size (2ms in DL and 2/10ms UL)

Higher order modulation and coding along with link adaptation in downlink

Support for multicodes in the uplink

In later releases MIMO & multi-carrier


Conclusions (2/2)

HSPA improves also the performance of delay critical low bit rateservices, like VoIP, even though it was not originally designed forthat

Continuous Packet Connectivity (CPC) enhancements introduced

services even more

I-HSPA was introduced to provide competitive internet accesssolution

High data rates with low delay

Reduced costs => flat rate could be possible



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Wcdma Hspa Basics 001

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