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WCDMA/HSPA basics for UMTS

Kari AhoProject 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 latest information from official sources like 3GPP specs (http://www.3gpp.org/Specification-Numbering)

Material represents the views and opinions of the trainer and not Material represents the views and opinions of the trainer and not necessarily the views of their employers or customers

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

2 © 2010 Magister Solutions Ltd

Trainer and Company Introduction


Trainer and Company Introduction


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 of

Jyväskylä

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

Jyväskylä

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 and Development Partner Research and Development Partner 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 customer’s 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


Magister Solutions – Case Tokyo (1/3)

Goal: Performance benchamarking between 3G HSDPA

and next generation LTE system

Challenges:It i h d t ll t d d t ti ti f It is hard to collect needed statistics from commercial networks

It is not affordable to build large enough test networks

In relation to LTE, there are only limited commercial products available



Simulation based approach was selected Like many vendors, operators as

well as the scientific communities do for studying the wireless cellular network performance

Digital network planning data over Tokyo map was used in the simulator Realistic conditions through non-

regular network layout and propagation



Achievements Extensive report of the bechmarking study in realistic network Customer knowledge improvement to better support standardization International publications


Defining and

planningStart-

up Simulations Result analysis Reporting

2 months0.5 month 0.5 month

Schedule and Practical Issues


Schedule and Practical Issues


Course schedule

Introductory WCDMA technology overview Standardization Market and performance situation

Rel’99 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 Rel’99 WCDMA when HSPA is introduced

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


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. Sköld 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 Management

For Practical Engineering Tasks – J. Lempiäinen, M. Manninen


WCDMA Technology Overview


WCDMA Technology Overview

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 and flexible utilization of the spectrum


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

FDMAWastes time

resources

Wastes frequency resources

q y Example Global System for Mobile Communication (GSM)

Code Division Multiple Access (CDMA) Same frequency and time but users are separated from each

other with codes Example WCDMA/UMTS


Code

Frequency

Time

12

N…

CDMA

Can exploit both 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 information

bandwidth 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 secure

communication Reduces the impact

of interference (and jamming)

Po

wer

den

sity

(W

atts

/Hz) Received signal

after despreading butbefore filtering

Received despred signal

Interference


Frequency

PP

ow

er d

ensi

ty (

Wat

ts/H

z)

Frequency

Received signalafter despreading andafter filtering

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 timeUL d DL h t 5 MH f b d UL and DL have separate 5 MHz frequency bands

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

WCDMA is the most common radio interface for UMTS systems including 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

q

In theory with PC received power levels

would be equal


Soft handover Improves coverage, decreases interference


UE1BS 1BS 2


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

l l f d ff h d ff Multiplexing of different services with different QoS require on a single physical connection Real-time, (voice, video telephony) Streaming (video and audio) Interactive (web-browsing) Background (e-mail download)


Standardization


Standardization

Standardization (1/2)

WCDMA was studied in various research programs in the military, industry and universities First publications: late 40s First applications: Military from the 50s Rake receiver patent 1956 Cellular applications proposed late 70s Cellular applications proposed late 70s Investigations for cellular use 80s IS-95 standard 1993 (2G)

WCDMA was chosen as 3G technology in late 1997/early 1998 by many 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 and

not likely to arrive to identical specifications globally The same discussion e.g. in ETSI and ARIB sometimes ended

up to different conclusionsW k l i i USA d K Work was also on-going in USA and Korea

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


Third Generation Partnership Project (1/2)

Members Founding members

ETSI – EU ARIB – Japan Telecommunications Technology Committee (TTC) – Japan Telecommunications Technology Association – Korea Wireless Technologies and Systems Committee (T1P1) USA Wireless Technologies and Systems Committee (T1P1) – USA

China Communications Standard Association (CCSA) – China later Different companies, like Nokia, are members through their

respective standardization organization

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


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

RAN2 covers, for instance, 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)

RAN3 covers, for instance, 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

RAN4 covers, for instance, Requirements for radio link, Radio Resource Management (RRM)

performance and accuracy of measurements Radio system scenario analysis and simulation

RAN5 covers, for instance, Development of UE conformance test specifications


Commercial HSUPA

networks

Commercial HSDPA

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 major milestone by

3GPP

Japan launched first commercial

Rel’99 3G network

Commercial networks in

Europe

WCDMA HSDPA HSUPA HSPA Evolutions (HSPA+)

LTE LTE-Advanced 4G3G

3.5G

3.75G

Technique

Naming

Market and performance situation


Market and performance situation

Market and performance situation (1/5)

In Finland alone there are over 8 million GSM and WCDMA-HSPA mobile 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) or higher

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



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. HSPA

launched 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”


Almost 10- fold when compared

t 2010

Unit MagnitudeExabyte 1,000,000,000,000,000,000

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

Terabyte 1,000,000,000,000

to year 2010Gigabyte 1,000,000,000

Megabyte 1,000,000

Kilobyte 1,000

Wideband Code Division Multiple Access


Wideband Code Division Multiple Access (WCDMA)

Contents

Codes UMTS Architecture Power Control Handovers


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 one o Sepa a o o do o e o s o d e e use s o e

cell 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 Uplink: to separate different mobiles Uplink: to separate different mobiles

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


Codes in WCDMA (3/4)Channelization codes separate

different connections

Channelization codes separate

data/control channels

Downlink

Scrambling codes separate

cells/sectors

Uplink

Scrambling codes separate different

mobiles



SpreadingFactor (SF)

Channelsymbol

rate(kbps)

Channelbit rate(kbps)

DPDCHchannel bitrate range

(kbps)

Maximum userdata rate with ½-

rate coding(approx.)

512 7.5 15 3–6 1–3 kbps256 15 30 12–24 6–12 kbps Half rate speech

Symbol_rate =Chip_rate/SF

Bit_rate =Symbol_rate*2

Control overhead User_bit_rate =Channel_bit_rate/2

256 15 30 12 24 6 12 kbps128 30 60 42–51 20–24 kbps64 60 120 90 45 kbps32 120 240 210 105 kbps16 240 480 432 215 kbps8 480 960 912 456 kbps4 960 1920 1872 936 kbps

4, with 3parallelcodes

2880 5760 5616 2.3 Mbps

Full rate speech

144 kbps384 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 network needed mainly due to new radio access technology

Core Network (CN) is based on GSM/GPRS

RNC

NodeBUECN

Uu interfaceIub interface

Radio Network Controller (RNC) corresponds roughly to the Base Station Controller (BSC) in GSM

Node B corresponds roughly to the Base Station in GSM

NodeB

NodeB RNC

UE

Iur interface

UTRAN



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 controlHandover control 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 Iub

interfaces Some RRM tasks:

Measurements Innerloop power controle oop po e o o


Questions

Name three main elements in the UMTS architecture What would be the responsibility of UEs


Power Control in WCDMA (1/4)

The purpose of power control (PC) is to ensure that each user receives and transmits just enough energy to prevent: Blocking of distant users (near-far-effect) Exceeding reasonable interference levels

UE1 UE2

Without PC received power levels would

be unequal


UE3

UE1

UE2

UE3

UE1 UE2 UE3In theory with PC

received power levels would 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 fadingUsed to eliminate the effect of fast fading 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 if the value is higher than target then power is lowered otherwise power is increased

Outerloop power control Adjusts the target value for innerloop power control Can be used to control e.g. the Quality of Service (QoS)



Example of inner loop power control behavior:

With higher velocities channel fading is more rapid and 1500 Hz power rapid and 1500 Hz power control may not be sufficient


WCDMA Handovers (1/7)

WCDMA handovers can be categorized into three different types which support different handover modes Intra-frequency handover

WCDMA handover within the same frequency and system. Soft, softerand hard handover supported

Inter-frequency handoverq y Handover between different frequencies but within the same system.

Only hard handover supported Inter-system handover

Handover to the another system, e.g. from WCDMA to GSM. Only hardhandover supported



Soft handover Handover between different

base stations Connected simultaneously to

multiple base stations The transition between

them should be seamlessthem should be seamless Downlink: Several Node Bs

transmit the same signal to the UE which combines the transmissions

Uplink: Several Node Bs receive the UE transmissions and it is required that only one of them receives the transmission correctly


UE1BS 1BS 2


Softer handover Handover within the

coverage area of one base station but between different sectors

Procedure similar to soft handover


UE1BS 1BS 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 connected

to Neighbor set (NS), represents the links that UE monitors which are

not already in active set



Handover parameters Add window

Represents a value of how much worse a new signal can be compared to the 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 timer’ is expired. Timer is started when the signal first reaches the desired level.

Drop window Represents a value of how much poorer the worst signal can be when

compared 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 drop

condition after the corresponding drop timer is expired.



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 a

replace timerreplace timer



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

Received signal strength

BS2

BS3

Threshold_1Threshold_2

BS2 from the NS reaches the threshold to be added

to the AS

BS1 from the AS reaches the 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 be dived into?

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


Multimedia Broadcast Multicast Service


Multimedia Broadcast Multicast Service

Multimedia Broadcast Multicast Service (MBMS) – Background Before MBMS broadcast and multicast transmissions were dealt

with using somewhat inefficient techniques Cell Broadcast Service (CBS)

Only message-based services with low bit rates IP Multicast Service (IP-MS)

No capability to use shared radio or core network resourcesNo capability to use shared radio or core network resources

Nowadays clear need for efficient group transmission method Multimedia Broadcast Multicast Service Digital Video Broadcast - Handheld (DVB-H) / Digital Multimedia

Broadcasting (DMB)


MBMS – Introduction (1/3)

Allows different forms of multimedia content to be delivered efficiently by using either broadcast or multicast mode Mobile TV, weather reports, local information, … The term broadcast refers to the ability to deliver content to all

users who have enabled a specific broadcast service and find themselves in a broadcast area

Multicast refers to services that are delivered solely to users who have joined a particular multicast group. Multicast group can be, for example, a number of users that are interested in a certain kind of content, such as sports



More efficient use of network resources and capacity for delivering 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 counting 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 transmissions i di titi f MBMS t t b d periodic repetitions of MBMS content can be used

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

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


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 the information coming from different NodeBs could be utilizedg

Moreover, also antenna diversity techniques can be considered as 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)


MBMS performance in WCDMA networks

Cell throughput with 2-antenna terminal and soft

combining 1500-2500 kbps = 12-20 x 128 kbps TV

channels

Cell throughput with 1 antennaCell throughput with 1-antenna 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 be

compensated so that the QoS is improved?


WCDMA Conclusion


WCDMA Conclusion

Conclusion (1/4)

Need for universal standard and improved packet data capabilities 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 WCDMA and its evolutionsWCDMA and its evolutions

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 channels

from same terminal (UL) Scrambling codes

Does not spread the signal Does not spread the signal 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 enough

energy Open loop PC for the connection setup and fast closed loop PC for

the 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


Conclusion (4/4)

MBMS was introduced to more efficient utilization of limited radio network resources with multimedia content provision Improved even further with macro diversity combining and diversity

techniques


HSPA evolutions


HSPA evolutions


Contents

Introduction HSDPA HSUPA Continuous Packet Connectivity I-HSPA Conclusion

© 2010 Magister Solutions Ltd

Introduction


Introduction


High Speed Packet Access (1/3)

There were number of pushing forces to improve the packet data capabilities 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 downlink g p ( )counterpart 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 Speed Uplink Packet Access (HSUPA)

HSPA was originally designed for non-real time traffic with high transmission 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 downlink

without 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 data

rates! 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



Link adaptation in downlink Possibility to adjust the used modulation and coding scheme in order to be

appropriate for current radio channel conditions Improved retransmission capabilities

Newly introduced layer one retransmissions called as Hybrid Automatic Repeat Request (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


Commercial HSUPA

networks

Commercial HSDPA

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 major milestone by

3GPP

Japan launched first commercial

Rel’99 3G network

Commercial networks 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 even further?

For what kind of services was HSPA originally designed?


High Speed Downlink Packet Access


High Speed Downlink Packet Access(HSDPA)


Contents

Introduction to HSDPA Link Adaptation Fast Retransmissions Downlink Scheduling HSDPA Mobility


Introduction to HSDPA

HSDPA Improvements for packet data performance both in terms of capacity and practical bit rates are based on The use of link adaptation, Higher order modulation, Fast scheduling, Shorter frame size (or transmission time interval) and Shorter frame size (or transmission time interval), and Physical layer retransmission

HSDPA operates on top of Rel’99 and is not a stand alone system

HSDPA does not support Rel’99 features like fast power control or soft handover


Link Adaptation (1/3)

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



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

68

10121416

ous

EsN

o [d

B]


0 20 40 60 80 100 120 140 160-20246

Time [number of TTIs]

QPSK1/4

QPSK2/4

QPSK3/4

16QAM2/4

16QAM3/4

Inst

anta

neo

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 to

be transmitted than simply going for transmission with multiple parallel code channels, thus HSUPA benefits more from using multiple codes as PC keeps the signal levels quite good anyway


Fast Retransmissions (1/3)

Packet

Retransmisson 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

U d t


User data

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 to much faster round trip time that with Rel ‘99

Retransmission procedure with layer 1 retransmissions (HARQ) is done so 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)


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 needs to schedule the different users for transmission in different fractions of time (Transmission Time Intervals) Certain fairness for scheduling time for each user should be

maintained Resources should be utilized in optimal mannerResources should be utilized in optimal manner

There exists different ways that users can be scheduled in downlink, 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 Each user gets served equally Each user gets served equally

Negative sides No channel conditions are taken into account and thus resources might

be wasted



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 inversely proportional 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(

served isuser if ,**)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

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 won’t get lost due to poor channel conditions

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

When regarding HSDPA, the user can be connected only to one serving HSDPA Node B at the time Leading to hard handover when the handover between HSDPA Node

Bs is required in contrary to DCH soft handover



Even though there is only one serving HSDPA cell, the associated Rel’99 channels can be in soft(er) handover and maintain the active set as in Rel’99

Node B,Serving HSDPA


DCH

UE

Node B,Part of DCH active set

HS-SCCH

DCH/HSDPA

DCH

DCH


HSDPA handover procedure includes following steps Serving cell change procedure is initiated when a link in (Rel’99)

active set becomes higher in strength and stays stronger for certain period 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 the RNC

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



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 HARQ processes 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?


High Speed Uplink Packet Access


High Speed Uplink Packet Access(HSUPA)


Contents

Introduction to HSUPA Multicodes with HSUPA Uplink Scheduling HSUPA Mobility


Introduction to HSUPA (1/2)

Roughly three years later when HSDPA was introduced uplink counterpart of the high speed packet access evolution was introduced in Release 6 In 3GPP original name was not HSUPA but Enhanced Dedicated

Channel (E-DCH) The obvious choices for uplink evolution was to investigate the The obvious choices for uplink evolution was to investigate the

techniques used for HSDPA and, if possible, adopt them for the uplink as well

Improvements in HSUPA when compared to Rel’99 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 devices

and 2 ms as optional feature Higher order modulation (Release 7)

HSUPA is not a standalone feature but requires many of the HSUPA is not a standalone feature, but requires many of the basic features of the WCDMA Rel’99 Cell selection and synchronization, random access, basic power control loop functions, basic mobility procedures (soft handover), etc.


Multicodes with HSUPA

Even though Rel’99 supports in theory multicode transmissions in practice only HSUPA can support multicode transmissions and thus higher bitrates In theory Rel’99 can use 6xSF4 HSUPA can in practice support 2xSF2 + 2xSF4

The reason why Rel’99 does not support multicodes is that the scheduling is controlled by RNC and thus rather slowly controllable Potentially wasted resources due to changing channel conditions and

slow adjustment Also, the lack of HARQ with Rel’99 means lower packet error target

for the system and thus higher resources for UE


Questions

What new features on top of multicodes and shorter frame sizes do 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 for a short period of time Very high peak data rates achievable for certain UE and all the

others 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 separate

devices (UEs) which can be used only for their purposes and not shared as with HSDPA



The shared resource of the uplink is the uplink noise rise(*), or the total received power seen in the Node B receiver Typically, one UE is unable to consume that resource alone completely

and it is very beneficial for the scheduler to know at each time instant how much of that resource each UE will consume and to try to maintain the 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 not

guarantee high enough minimum bit rate. In addition each request requires time consuming signaling

Non-scheduled transmissions (NST) controlled by radio network controller (RNC) which defines a minimum data rate at which the UE can transmit without any previous request. This reduces signaling overhead 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 every TTI Transmitted on E DPCCH in every TTI Referred to as happy bits Tells which users could transmit at a higher data rate both from the

buffer status and the transmission power availability point of view



Depending on possible user priorities given from the RNC, the scheduler 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 commands

f th th i HSUPA N d Bfrom other than serving HSUPA Node B


Questions

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

What kind of scheduling possibilities HSUPA offer?


Mobility in HSUPA (1/2)

HSUPA supports the soft(er) handover procedure similar to WCDMA Rel’99

The HARQ operation in HSUPA soft handover situation is done in following manner

If N d B i th ti t d ACK th th i f ti If any Node B in the active set sends an ACK, then the information given to the Medium Access Control (MAC) layer is that an ACK has been received and the MAC layer will consider the transmission successful


Mobility in HSUPA (2/2)

RNC

NodeBCorrectly received

Packet reordering


Data

Layer 1 ACK/NACK

UE

NodeB

Layer 1 ACK/NACK

packet

Questions

Which logical entity handles packet reordering and initiates RLC retransmissions if necessary

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


Continuous Packet Connectivity


Continuous Packet Connectivity(CPC)


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 bit rate services like VoIP

Eliminates the need for continuous transmission and reception when data is not exchanged. Can be categorized into three feature 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 less

interference => more users can be connected UE power savings => increased talk time (VoIP) UTRAN resources are saved


UL discontinuous transmission (1/2)

Before 3GPP Rel’7, DPCCH was defined to be transmitted continuously regardless 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 that p g pit is not transmitting any data and activate the control channels just for the transmissions periods However, that could compromise, e.g., the fast power control which would be

then updated only during the times when the data is exchanged

Thus, in Rel’7 more elaborate solution for UL DTX was formalized Various cycles and timers quarantee non-compromising discontinuous

transmisson


UL discontinuous transmission (2/2)


DL discontinuous reception (1/2)

In DL, Discontinuous Reception (DRx) cycles allow an idle UE to power 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 of

time to yield a non 100 % receiver duty cycle Minimum monitoring/measurement possibilities to keep up with Minimum monitoring/measurement possibilities to keep up with

changes in UE’s 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 it

starts timer for staying active certain period of time


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 sent over HSDPA

Retransmissions are sent with HS-SCCH pointing to the initial transmission


VoIP performance with and without CPC

In general major performance enhancements visible if circuit switched voice over WCDMA 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. Malkamäki, K. Ranta-aho, C. Tao: “VoIP over HSPA with 3GPP Release 7”, PIMRC, 2006.

Questions

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

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


Internet HSPA


Internet HSPA(I-HSPA)


I-HSPA (1/3)

Internet-HSPA (I-HSPA) aims to provide competitive mobile internet access with much more simpler network architecture than 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)


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 <100 ms

HSUPA ~50 ms

InternetIu + coreRNC


0

20

40

60

80

100

Today HSDPA HSDPA+HSUPA

IubNode BAIUE

I-HSDPA+I-HSUPA

I-HSPA ~25 ms

Questions

Name at least one difference between normal HSPA and I-HSPA architectures

Name at least two benefits of the simplified architecture in I-HSPA


HSPA Conclusion


HSPA Conclusion


Conclusions (1/2)

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

HSPA offers much higher peak data rates, reaching in theory up to 56 Mbps in the downlink and 11.4 Mbps in the uplink (Release 7), in addition 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 rate services, like VoIP, even though it was not originally designed for that

Continuous Packet Connectivity (CPC) enhancements introduced in Release 7 improve performance of delay critical low bit rate in Release 7 improve performance of delay critical low bit rate services even more

I-HSPA was introduced to provide competitive internet access solution High data rates with low delay Reduced costs => flat rate could be possible


HSPA vs DCH (basic WCDMA)

Feature

Variable spreading factor

Fast power control

DCH

Yes

Yes

HSUPA

Yes

Yes

HSDPA

No

No

Multicode transmission Yes(No in practice)

Yes Yes


Adaptive modulation

BTS based scheduling

No

No

No

Yes

Fast L1 HARQ No Yes

Yes

Yes

Yes

Soft handover Yes Yes No(associated DCH only)

HSPA Peak Data Rates

5 codes QPSK

# of codes Modulation

1.8 Mbps

Maxdata rate

2 x SF4 2 ms

# of codes TTI

1 46 Mbps

Maxdata rate

Downlink HSDPA

Theoretical up to 56 Mbps

Initial capability 1.8 – 3.6 Mbps

Uplink HSUPA

Theoretical up to 11.4 Mbps

Initial capability 1.46 Mbps


5 codes QPSK

5 codes 16-QAM

10 codes 16-QAM

15 codes 16-QAM

15 codes 64-QAM

1.8 Mbps

3.6 Mbps

7.2 Mbps

14.4 Mbps

56 Mbps

2 x SF4 s10 ms

2 x SF2 10 ms

2 x SF2 2 ms

2 x SF2 +2 x SF4 2 ms

1.46 Mbps

2.0 Mbps

2.9 Mbps

5.76 Mbps

Rel 7 MIMO + 64QAM

2 x SF2 +2 x SF4 2 ms 11.4 Mbps

Rel 7 16QAM

Th k !


Thank you!

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