Part 7-B3G and 4G - University of Hong Kongsdma/elec6040_2008/Part 7-B3G and 4G.pdf · Part 7. B3G...

ELEC6040 Mobile Radio Communications, Dept. of E.E.E., HKUp. 1

Part 7. B3G and 4G Systems


Roadmap

HSDPA HSUPA

AIE

HSPA+HSPA+

LTE

AIE

IMT

-Adv

ance

d (4

G)


HSPA Standardization3GPP Rel'99: does not manage the radio spectrum efficiently whendealing with bursty trafficNeed for even better spectral efficiency, improved user experience and new services => High Speed Packet Access (HSPA)HSPA: High Speed Downlink Packet Access (HSDPA) +

High Speed Uplink Packet Access (HSUPA)

Source: H. Holma and A. Toskala, “HSDPA/HSUPA for UMTS,” JohnWiley and Sons, LTD..


Based on WCDMA network: either on the same carrier (f1) or usinganother carrier (f2)Why using another carrier: a high capacity and high bit rate solutionHSPA and WCDMA share all the network elements in the core network and the radio network. Upgrade from WCDMA to HSPA: no core network impacts, new software package, some new pieces of hardware in the BS and RNC to support the higher data rates and capacityUpgrading cost: very low compared with building a new standalone data network

HSPA DeploymentSource: H. Holma and A. Toskala, “HSDPA/HSUPA for UMTS,” JohnWiley and Sons, LTD..


Korea: May 2006, SK Telecom, the world's first commercial HSDPA service, data rate 1.8Mbps

Hong Kong: June 2006, SmarTone-Vodafone, HSDPA service at 1.8Mbps; Sept. 2006, enhanced 3.6Mbps HSDPA full-coverage network; 2008: support 14.4Mbps downloading (HSDPA) and 2Mbps uploading (HSUPA)

SmarTone: Mobile Broadband, provides high speed access to Internet with your PC or Laptop

Commercial HSPA Network

USB modem for desktops and laptops

Express card for laptops


HSDPA - High Speed Downlink Packet Access


IntroductionHSDPA is a UMTS packet air interface (add-on solution on top of 3GPP R99/R4 architecture) that allows up to 3.6 Mbps peak data rate for a Category 6 Mobile per user with a classical Rake receiver and up to 14.4 Mbps peak data rate for a Category 10 mobile per user with advanced receiver solutions.

HSDPA: offers significantly higher data capacity (at least twice per cell) and data-user speed, lower latency (70ms round trip delay), fully backward compatible with Rel'99 (WCDMA)– A new downlink shared transport channel (HS-DSCH) with shorter

frame size (2ms)– A fast link adaptation controlled by the Node B (BTS): dynamic

adaptive modulation and coding– A fast scheduler– A fast physical layer retransmission and transmission combining

Source: Nortel, “HSDPA and beyond,” White paper.


New Channels (1)

New channel types: HS-DSCH (Downlink Shared Channel), HS-SCCH (Shared Control Channel), HS-DPCCH (Dedicated Physical Control Channel)HS-DSCH: High Speed Downlink Shared Channel– shared by all users of a sector by a number of SF 16 codes and time– within each 2 ms TTI, up to 15 parallel code channels can be used for

the HS-DSCH: may all be assigned to one user, or may be split among several users

– no more power control, HS-DSCH is transmitted at a constant power– the modulation, the coding and the number of codes are changed to

adapt to the variations of radio conditions– difference between HS-DSCH and DSCH in WCDMA: the

scheduling of HS-DSCH is done at the Node B (BS) rather than the RNC



New Channels (2)

Only TurboConvolutional or TurboChannel coding

QPSK and 16QAMQPSKModulation

YesNoBTS-based scheduling and link adaptation

Yes, and also at RLC layerNo, only at RLC layerPhysical layer retransmission

Yes, extendedYesMulti-code operation

YesNoAdaptive modulation and coding

NoYesFast power control

No and SF=16No and SF=4~512Variable spreading factor

HS-DSCH (HSDPA)DCH (WCDMA)Features

Comparison of fundamental properties of the DCH and HS-DSCH



New Channels (3)



New Channels (4)

HS-DSCH channel coding chain

New functions



New Channels (5)Why is bit scrambling needed?– HSDPA: QPSK and 16QAM are used

– to recover 16QAM symbols: phase and amplitude (power level) information is required

– bit scrambling is introduced to avoid having long sequences of '1s' or '0s'. Otherwise, the terminal would have difficulties with HS-DSCH power level estimation



New Channels (6)

HS-SCCH: HSDPA Shared Control Channel– enables the UE to identify which codes of the HS-DSCH contain its

dataHS-DPCCH: HSDPA Dedicated Physical Control Channel– responsible of Uplink signaling– provides Channel Quality Indicator (CQI), ACK and NACK

CQI: reflects the signal to Interference Ratio (SIR)– provides real time (every 2ms) knowledge of the radio conditions for

each user. Based on CQI, BTS may change every 2ms the modulation, coding and the number of codes

– makes HSDPA match the exact throughput of the radio bandwidth available for each user

– higher average throughput and higher spectrum efficiency



New Channels (7)

Dynamic behavior of HSDPA



Fast Link Adaptation (1)

Fast link adaptation at BS: Adaptive modulation and coding (AMC) (TTI: 2ms)Principle of AMC: change modulation and coding format in accordance with variations in the channel conditions which leads to a higher data rate for users in favorable positions and reduced interferenceEnables bursty traffic => higher average throughput, three to five times higher than that without HSDPAReduces the interferences variation – link adaptation based on variations in the mod./coding scheme instead

of variations of the transmit power



Fast Link Adaptation (2)

Example of link adaptation Source: H. Holma and A. Toskala, “HSDPA/HSUPA for UMTS,” JohnWiley and Sons, LTD..


Fast Retransmission (1)

Fast Retransmission:Hybrid Automatic Request

3GPP R'99: ARQ in RLC layer; HSDPA: ARQ in physical layer

BTS retransmission handling

Source: H. Holma and A. Toskala, “HSDPA/HSUPA for UMTS,” JohnWileyand Sons, LTD..



HSDPA: Stop-and-Wait (SAW) => simplest

Waiting for ACK from the receiver Retransmission due to timer expiry


Fast Retransmission (3)3GPP R'99: Selective Repeat (SR) => most complex and most efficient


HSDPA: Why SAW instead of SR? – SR: complex, need high memory, sequence information, high

signaling bandwidth– SAW: simple, need less memory, no sequence information, less

signaling bandwidth => suitable for UE – Improved SAW: Dual-Channel SAW


HSDPA: Retransmission combining: Two combining schemes–Chase combining: BT resends the same packet–Incremental redundancy: BT provides additional coding by sending the parity bits in the retransmission, requires more memory, used with high coding rate



Example of Chase combining




Example of Incremental Redundancy



Fast Scheduling (1)

Fast scheduling: Placed in the Node B in order to quickly respond to the changes in channel conditions.


L1: physical layer


Time

Rec

eive

d C

/Ifo

r ea

ch u

ser

#1 #2 #3

TTI

Scheduling algorithm: A compromise between a Round Robin and a Max C/I scheduler will be used.

Fast Scheduling (2)

Max C/I Scheduler


Fast Cell Selection

Fast cell selectionSoft handoff is impossible for HSDPAA hard handoff is used for HS-DSCH: the UE indicates the best cell which should serve it through uplink signalingWhile multiple cells may be members of the active set, only one of them transmits at any time, potentially decreasing interference and increasing system capacity



Terminal Capability Categories



HSUPA - High Speed Uplink Packet Access


Introduction (1)Why HSUPA: a complement of HSDPAHSDPA: provide high speed (up to 14.4Mbps) data transmission in downlink, increase data usage => the uplink throughput should beincreased accordinglyHSUPA: also called as Enhanced DCH, defines a new radio interface for the Uplink communication. The overall goal is to improve the coverage and throughput as well as to reduce the delay of the uplink dedicated transport channels.Enhancement of HSUPA over 3GPP R'99 (3GPP Study)- 50-70% improvement in UL capacity- 20-55% reduction in end user packet call delay- Around 50% in user packet call throughput- max 5.76 Mbps (one UE/cell), typical about 2 Mbps (several UEs/cell)


Introduction (2)

HSUPA

new uplink transport channel

uplink Hybrid ARQ

10ms TTI (mandatory)2ms TTI (optional)

SF=2~256

multicodetransmission

Node B controlled scheduling

New Features in HSUPA

Note: HSUPA does not support adaptive modulation because it does not support any higher order modulation schemes. Reason: more complex modulation schemes require more energy per bit to be transmitted than simply going for multicodetransmission using simple BPSK modulation.


New Channels

for scheduling control

E-DPDCH: E-DCH Dedicated

Physical Data Channel

E-DPCCH: E-DCH Dedicated

Physical Control ChannelE-AGCH: E-DCH Absolute Grant Channel

E-RGCH: E-DCH Relative Grant Channel

E-HICH: E -DCH HARQ

Acknowledgement Indicator Channel

E-DCH



E-DCH

24 bits0, 8, 12, 16, 24 bits


E-DPDCH (1)E-DPDCH: similar structure to DPDCH- support variable spreading factor, multi-code transmission, BPSK modulation, fast power control loopDifference between E-DPDCH and DPDCH- E-DPDCH supports fast physical layer HARQ, fast Node B based scheduling, spreading factor of 2

Physical channel bit rates for DPDCH and E-DPDCH


E-DPDCH (2)Difference between E-DPDCH and DPDCH (Con't)- E-DPDCH supports TTI of 2ms

E-DPDCH frame structure


E-DPCCH (1)E-DPCCH and DPCCH- both deliver the information needed to decode corresponding data channel transmission- DPCCH also provides common information related to channel estimation and power controlE-DPCCH- fixed spreading factor: 256- (30,10) Reed-Muller coding, 10 information bits every 3 slotsE-TFCI: 7 bits, E-DCH transport format combination indicator, telling the receiver the transport block size coded on the E-DPDCHRSN: 2bits, retransmission sequence number, initial transmission RSN=0, the first with RSN=1, the second with RSN=2, all subsequent RSN=3Happy bit: 1 bit, whether the UE is content with the current data rate orrelative power allowed to be used for E-DPDCHs


E-DPCCH (2)

E-DPCCH frame structure

(30, 10) Reed Muller coding


E-DPCCH (3)Why use two TTI lengths?- 2ms: potential delay benefit- 10ms: needed for range purpose to ensure cell edge operation.

At the cell edge, signaling using a 2-ms period starts to consume a lot of transmission power, especially at the BTS end. HSDPA: the number of active users is relatively small. HSUPA: a large number of active users


Comparison

2No

Yes

Yes

Yes

YesNo

No

Turbo

HS-DSCH (HSDPA)

10, 280, 40, 20, 10TTI length (ms)YesYesSoft handover

Turbo (1/3)Convoultional (1/2 or 1/3) and Turbo (1/3)

Channel coding

YesNoBTS-based scheduling

YesNoPhysical layer retransmission

YesYesMulti-code operation

NoNoAdaptive modulation and coding

YesYesFast power control

YesYesVariable spreading factor

E-DCH (HSUPA)

Uplink DCH (WCDMA)

Features


Fast HARQFast physical layer retransmission (Hybrid ARQ)- basic principle is the same as that for HSDPA- both Chase combining and Incremental Redundancy are permittedHARQ and soft handover- special for HSUPA, similar rules to those for uplink power control: single ACK from the active set => successful transmission

HSUPA ARQ operation in soft handover


Fast SchedulingBTS based fast scheduling- scheduling is moved from RNC to Node B, small latencyPrinciple different to HSDPA- HSDPA: one to many scheduling. All the cell power can be directed to a single user for a short period of time and reach very high data rates, then to another user- HSUPA: many to one scheduling. Users have their own power resource that cannot be shared. The shared source of uplink is the uplink noise rise, or the total received power seen in the Node B.Tasks for uplink scheduler- avoid overload- use as much of the uplink capacity as possible without the risk of the cell becoming overloaded


HSUPA Terminal Categories


Summary of HSPA

HSDPA employs mainly four measures to increase the packet data rate: new channel HS-DSCH; fast link adaptation; fast scheduler; fast retransmission and combinations.HS-DSCH: comparison to DCH in WCDMA; new function blocks needed to generate signals on HS-DSCH.Advantages of fast link adaptationFast retransmission: HARQ schemes employed in HSDPA; combining schemesAdvantages of fast schedulerHSUPA: only BPSK supported, no adaptive modulation and codingReason for E-DPCCH in HSUPA supporting two TTI lengths, 10ms and 2ms.


3GPP Long Term Evolution (LTE) and System Architecture Evolution


Introduction With HSPA, UTRA will remain highly competitive for several yearsThreat from WiMAX to cellular systems– WiMAX provides high speed wireless data services: up to 20Mbps– Advantage of WiMAX: high speed, low cost to construct, various

services including voice over IP, video, multimedia transmission, etc.– Vendor strategy: Leading 3G vendors backing LTE, vendors that are not

3G leaders using WiMAX as an end around– WiMAX: big threat to 3G

Current 3GPP standards should be further developed to maintain the competitiveness of 3G in long term future

700kbps2.2MbpsAverage UL Throughput2Mbps2.3MbpsAverage DL Throughput

2.3Mbps5.0MbpsPeak UL Throughput

3.6Mbps20.1MbpsPeak DL Throughput

HSPAWiMAX


3GPP LTE and SAELTE focuses on– enhancement of the Universal Terrestrial Radio Access (UTRA)– optimization of the UTRAN architecture

SAE focuses on– enhancement of Packet Switched technology to cope with rapid

growth in IP traffic– higher data rates– lower latency– packet optimized systemthrough– fully IP network– simplified network architecture– distributed control


Targets of LTE (1)

3GPP has concluded a set of targets and requirements for LTE– Peak data rates exceeding 100 Mbps for the downlink direction and 50

Mbps for the uplink direction– Mean user throughput improved by factors 2 and 3 for uplink and

downlink respectively– Cell-edge user throughput improved by a factor 2 for uplink and

downlink– Uplink and downlink spectrum efficiency improved by factors 2 and 3

respectively– Significantly reduced control-plane latency– Reduced cost for operator and end user– Spectrum flexibility, enabling deployment in many different spectrum

allocations


Targets of LTE (2)


New Technologies for LTEThe reference system of LTE is a basic WCDMA system– new radio transmission technologies are neededDownlink: OFDM with frequency domain adaptation– OFDM supports varying spectrum allocations, ranging from 1.4MHz to

20MHz– OFDM is suitable for broadcast services– Channel-based adaptation in frequency domainUplink: Single carrier FDMA with dynamic bandwidth– to satisfy the requirement for uplink transmission: power-efficient user-

terminal transmission to maximize coverage– the base station assigns a unique time-frequency interval to the terminal

for the transmission of user data– Channel-based adaptation in frequency domainMulti-Antenna solutions– to increase data rates, improve coverage and capacity


Further Agreement on LTE

Currently no more macro diversity – no soft handover required

Security– Control Plane: Ciphering and Integrity provided by enhanced Node B

(BTS), RLC and MAC provided directly in the enhanced Node B– User plane: Ciphering and integrity in the enhanced Access Gateway

functionality


4G ScenariosPeople’s Expectation on 4G Mobile Communications– High-data-rate transmission: up to 100Mbps and 1Gbps for macro and hot

spot areas– High mobility– A wide coverage area and seamless roaming among different systems– 4G will be a mixture of different communication systems, such as cellular

systems, wireless LANs, personal communication systems, etc.– Higher capacity and lower cost per bit– Expected to be at least 10 times of that of 3G in capacity– Wireless QoS controlFeatures of 4G– New mobile access scheme– New spectrum for 4G with broader band, e.g., 100MHzKey 4G technologies– LTE uses 4G technologies on 3G systems, key 4G technologies similar to

LTE: OFDM, Multiple Antenna


Layered Architecture of 4G

DistributionLayer

Digital audio/video broadcasting (DAB, DVB), Satellite comm.

Cellular Layer

Hot-SpotLayer

GSM, 3G, 4G-cellular

WLANs

PersonalNetwork

Layer

Fixed (Wired)Layer

Bluetooth, DECTHandover


Summary

HSDPA employs mainly four measures to increase the packet data rate: new channel HS-DSCH; fast link adaptation; fast scheduler; fast retransmission and combinations.HS-DSCH: comparison between HS-DSCH and DCH in WCDMA; new function blocks needed to generate signals on HS-DSCH.Fast link adaptation: principle of AMC; advantages of fast link adaptationFast retransmission: HARQ schemes employed in HSDPA; combining schemesAdvantages of fast schedulerHSUPA: only BPSK supported, no adaptive modulation and codingReason for E-DPCCH in HSUPA supporting two TTI lengths, 10ms and 2ms.

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