3g/4g mobile communications systems

Dr. Stefan BrückQualcomm Corporate R&D Center Germany

3G/4G Mobile Communications Systems

Chapter XI: Current and Future Trends in 3GPP – HSPA+ and LTE-Advanced

2

3GPP – HSPA+ and LTE-Advanced

Slide 2

HSPA+ (HSPA Evolution) Background

� For operators deploying HSPA, there is the need to continue enhancing the HSPA technology� 3GPP Long Term Evolution (LTE) being standardized now, but not backwards

compatible with HSPA

� Investment protection needed for current HSPA deployments

� HSPA+ effort introduced in 3GPP in March 2006

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� HSPA+ effort introduced in 3GPP in March 2006� Initiated by 3G Americas & the GSMA

� HSPA+ defines a broad framework and set of requirements for the evolution of HSPA� Rel.-7: improvements mainly in downlink

� Rel.-8: further uplink enhancements

Slide 3

Selected HSPA+ Features

� Multiple Input Multiple Output (MIMO) � Rel. 7 introduced 2x2 MIMO for the downlink (HSDPA)

� Higher Order Modulation� Rel. 7 introduced 64QAM for the downlink (HSDPA) and 16QAM for the uplink

(HSUPA)

� Dual Cell HSDPA� Rel. 8 introduced 2 x 5 MHz adjacent carrier operation

4

� Rel. 8 introduced 2 x 5 MHz adjacent carrier operation

� MIMO with 64QAM� Rel. 8 removed separation of either 64QAM or MIMO

� Dual Cell HSUPA� Rel. 9 introduced dual cell operation for HSUPA

� Dual Cell HSDPA with MIMO� Rel. 9 introduced dual cell operation together with MIMO

� Four Carrier HSDPA� Rel. 10 introduced 4 x 5 MHz operation with MIMO

Slide 4

HSPA+ Goals

� Based on the importance of the HSPA-based radio network, 3GPP agreed that HSPA+ should:� Provide spectrum efficiency, peak data rates & latency comparable to LTE in

5 MHz� Exploit full potential of the CDMA air interface before moving to OFDM

� Allow operation in an optimized packet-only mode for voice and data� Utilization of shared channels only

� Be backward compatible with Release 99 through Release 6

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� Be backward compatible with Release 99 through Release 6

� Offer a smooth migration path to LTE/SAE through commonality, and facilitate joint technology operation

� Ideally, simple infrastructure upgrade from HSPA to HSPA+

� HSPA evolution is two-fold� Improvement of the radio

� Architecture evolution

Slide 5

Higher Order Modulations (HOMs)

BPSK 2 bits/symbol

16QAM 4 bits/symbol

64QAM 6 bits/symbol

Uplink Downlink

6

� Increases the peak data rate in a high SNR environment� Very effective for micro cell and indoor deployments

Slide 6

HSPA+

(64QAM & 2x2 MIMO*)The use of Higher Order Modulations significantly increases the theoretical peak rates of HSPA

Provides data rate benefits for users in very good

HSPA+

(16 QAM & 2x2 MIMO)

21.1

28.0

Downlink Mb/s

42.2

Equal to LTE peak rates in 5 MHz2x2 SU-MIMO + 64 QAM in DL

16-QAM in UL**

HOM Peak Rate: DL 64-QAM & UL 16-QAM

7

for users in very good channel conditions (e.g. quasi-static or fixed users close to the cell center, lightly loaded conditions)

HSPA+ (64QAM)

HSDPA (16QAM)

14.0

21.1

HSPA+ (16QAM)

HSUPA (BPSK)

11.5

5.74

Uplink

Theoretical Max Peak Rates In Perfect RF Conditions*Part of 3GPP Rel-8

**Using 2 resource blocks for PUCCH and max prime factor restriction = 5 Slide 7

HSDPA 64-QAM – Hotspot Deployment

~30% throughput increase for top 10% users

Key assumptions: 500m inter-site distance and 6dB attenuation from non-serving cells (models site-to-site isolation)

Results from 3GPP R1-063415

8

2 Rx Antenna, Equalizer

Without 64-QAM With 64-QAM Gain

Sector Throughput 10 Mbit/s 11.3 Mbit/s 13%

90%-tile Throughput (normalized for 1 user per sector)

12 Mbit/s 15.6 Mbit/s 30%

Slide 8

16QAM for E-DCH

� 16QAM being considered in the uplink for HSPA Evolution, for use with the 2ms TTI and with 4 multi codes (2xSF2 + 2xSF4)� Increases peak rate from 5.76 Mbps to 11.52 Mbps

� Simulation results showed:� 16QAM requires very high SNR at the receiver

� 16QAM can be used only in case of one single HSUPA active user per cell

9

BPSK

BPSK

BPSK

BPSK

SF2

SF2

SF4

SF4

I

Q

I

Q

SF2

SF4

16 QAM

I

Q

16 QAM

I

Q

Slide 9

Coding/Modulation/

Weighting/Mapping

Basic MIMO Channel

Weighting/Demapping

Demodulation/Decoding

M Tx N Rx

10

� The MIMO channel consists of M Tx and N Rx antennas

� Each Tx antenna transmits a different signal

� The signal from Tx antenna j is received at all Rx antennas i

� Channel capacity can increase linearly

CMIMO ≤ min{M,N} • CSISO

Slide 10

MIMO in HSPA+ (Rel. 7)

� Release 7 MIMO for HSDPA� 2x2� D-TxAA, Mode 1� HS-DPCCH-only feedback (CQI and PCI reported on HS-DPCCH)� PARC Algorithm with support for dual stream and single stream

V11Stream 1

Antenna 1

11

EncodeChannel interleave

Modulator(16QAM, QPSK)

EncodeChannel interleave

Modulator(16QAM, QPSK)

V22

V12

V21Stream 2

Antenna 1

Antenna 2

Slide 11

MIMO Performance Benefits

� 2x2 D-TxAA MIMO scheme doubles peak rate from 14.4 Mbps to 28.8 Mbps

� 2x2 D-TxAA MIMO provides significant experienced peak, mean & cell edge user data rate benefits for isolated cells or noise/coverage limited cells

� 2x2 D-TxAA MIMO provides 20%-60% larger spectral efficiency than 1x2

1.75

2

Dat

a R

ate

Gai

n of

MIM

O v

s.

SIS

O fo

ran

Isol

ated

Cel

l SISO (1x1)100

Spe

ctra

l Effi

cien

cy G

ain

(%) o

f 2x2

12

0

0.25

0.5

0.75

1

1.25

1.5

1.75

Near Cell Center Average CellLocation

Cell Edge

Dat

a R

ate

Gai

n of

MIM

O v

s.

SIS

O fo

ran

Isol

ated

Cel

l SISO (1x1)

MIMO (2x2)Note: All gains normalized to Near Cell Center SISO Data Rate

0

20

40

60

80

Interference LimtedSystem

Isolated Cell

Spe

ctra

l Effi

cien

cy G

ain

(%) o

f 2x2

M

IMO

ove

r 1x2

LM

MS

E

Slide 12

Dual Cell Operation in Rel. 8 (DC-HSDPA)

� The dual cell operation only applies to downlink HS-DSCH

� Uplink traffic is carried in one frequency

� The two cells belong to the same Node-B and are on adjacent carriers

� The two cells operate with a single TX antenna

� MIMO excluded of dual carrier operation → max two streams per user

� The two cells operate in the same frequency band� 850/1900 and 900/2100 MHz combinations are not allowed

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� 850/1900 and 900/2100 MHz combinations are not allowed

Multi-carrier HSDPA

Node-B

F1

UEF2

DLDL

5 MHz 5 MHz

UL

5 MHz

2.1 GHzUL

UTRAN configures one of the cell as the

serving cell for the uplink

Slide 13

Dual Cell HSDPA Operation for Load Balancing

� Dual Cell HSDPA can optimally balance the load on two HSDPA carriers by scheduling active users simultaneously or on least loaded carrier at given TTI

Avg cell throughput is 3 Mbps in

loaded condition (incl multi

user gain)

Avg Transfer size : 1000 kbytes

Avg Time between transfers :

Dual Cell HSDPA operation versus Two legacy HSDPA c arriers

6000

7000

8000

Avg user throughput (2 HSDPA carriers)

Avg Sector throughput (2 HSDPA carriers)

Avg user throughput (Dual Cell HSDPA operation)

Avg Sector throughput (Dual Cell HSDPA operation)

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Avg Time between transfers :

60 sec

No gain at very high load (full

buffer) with this simple model

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 50 60

Nb of users in sector footprint

Thr

ough

put i

n kb

ps

Slide 14

DC-HSDPA with MIMO

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� In Rel. 9 DC-HSDPA can be combined together with MIMO

� This allows achieving a peak rate of 84 Mbps in 10 MHz

Slide 15

Four Carrier HSDPA

16

� In Rel. 10 Four Carriers for HSDPA can be combined

� This allows achieving a peak rate of 84 Mbps in 20 MHz

Slide 16

HSDPA – UE Physical Layer CapabilitiesHS-DSCH category

Codes TB size / HSDSCH

Aggregated cells

Modulation w/o MIMO, w/o agg. cells

Modulation w/ MIMO, w/o agg. cells

Modulation w/o MIMO, w/ agg. cells

Modulation w/ MIMO, w/ agg. cells

Category 1 5 7298 1

QPSK, 16QAM

Not applicable (MIMO not supported)

Not applicable (aggregated carriers operation not

supported)Not applicable (simultaneous

aggregated carriers and MIMO operation not

supported)

Category 2 5 7298 1Category 3 5 7298 1Category 4 5 7298 1Category 5 5 7298 1Category 6 5 7298 1Category 7 10 14411 1Category 8 10 14411 1Category 9 15 20251 1Category 10 15 27952 1Category 11 5 3630 1

QPSKCategory 12 5 3630 1Category 13 15 35280 1

QPSK, 16QAM, 64QAMCategory 14 15 42192 1Category 15 15 23370 1

QPSK, 16QAMCategory 16 15 27952 1

Now

17 Slide 17

supported)Category 16 15 27952 1

Category 17 NOTE 2

1535280 1 QPSK, 16QAM, 64QAM –

23370 1 – QPSK, 16QAM

Category 18 NOTE 3

1542192 1 QPSK, 16QAM, 64QAM –

27952 1 – QPSK, 16QAMCategory 19 15 35280 1


- -QPSK, 16QAM

Category 22 15 27952 2Category 23 15 35280 2


- - -QPSK, 16QAM

Category 26 15 27952 2Category 27 15 35280 2

- - -QPSK, 16QAM, 64QAM

Category 28 15 42192 2

Category 29 15 42192 3 - - QPSK, 16QAM, 64QAM -

Category 30 15 42192 3 - - QPSK, 16QAM, 64QAM

Category 31 15 42192 4 - - QPSK, 16QAM, 64QAM -

Category 32 15 42192 4 - - QPSK, 16QAM, 64QAM

Rel. 7

Rel. 8

Rel. 9

Rel. 10

E-DCH – UE Physical Layer CapabilitiesE-DCH category Maximum number

of E-DCH codes transmittedper transport block

Minimum spreading

factor

Support for 10 and 2 ms TTI EDCH

Maximum number of bits of an E-DCH transport block

transmitted within a 10 ms E-DCH TTI

Maximum number of bits of an E-DCH transport block

transmitted within a 2 ms E-DCH TTI

Category 1 1 SF4 10 ms TTI only 7110 -

Category 2 2 SF4 10 ms and2 ms TTI

14484 2798



20000 5772

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� UEs of Categories 1 to 6 support QPSK only� UEs of Category 7 supports QPSK (2 ms TTI, 10 ms TTI) and 16QAM (2 ms TTI)� UEs of Category 8 support only QPSK in Dual Cell E-DCH operation� UEs of Category 9 support QPSK and 16QAM in Dual Cell E-DCH operation

Slide 18



20000 11484

Category 7 4 SF2 10ms and 2 ms TTI 20000 22996

Category 8 4 SF2 2 ms TTI - 11484

Category 9 4 SF2 2 ms TTI - 22996

NOTE: When 4 codes are transmitted in parallel, two codes shall be transmitted with SF2 and two with SF4

LTE-Advanced

� The evolution of LTE� Corresponding to LTE Release 10 and beyond

� Motivation of LTE-Advanced� IMT-Advanced standardisation process in ITU-R

� Additional IMT spectrum band identified in WRC07

� Further evolution of LTE Release 8 and 9 to meet:� Requirements for IMT-Advanced of ITU-R

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� Requirements for IMT-Advanced of ITU-R

� Future operator and end-user requirements

Work Item phaseWork Item phaseStudy Item phaseStudy Item phase

First submission

Final submission

LTE release 10 (”LTE-Advanced”)

2009 20102008

ProposalsProposalsCircular Letter

3GPP WSIMT-Advanced

SpecificationSpecification

IMT-Advanced recommendation

EvaluationEvaluation

3GPP

ITU

Slide 19

Evolution from IMT-2000 to IMT-Advanced

IMT-2000

Mobility

High

EnhancedIMT-2000

Enhancement

IMT-2000

Mobility

High

EnhancedIMT-2000

Enhancement

IMT-Advanced will encompass the capabilities of previous systems New capabilities

of IMT-Advanced

New Mobile Access

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Interconnection

Low

1 10 100 1000Peak useful data rate (Mbit/s)

Enhancement

Low

1 10 100 1000

Area Wireless Access

Enhancement

Digital Broadcast SystemsNomadic / Local Area Access Systems

New Nomadic / Local

Slide 20

System Performance Requirements � Peak data rate

� 1 Gbps data rate will be achieved by 4-by-4 MIMO and transmission bandwidth wider than approximately 70 MHz

� Peak spectrum efficiency� DL: Rel. 8 LTE satisfies IMT-Advanced requirement

� UL: Need to double from Release 8 to satisfy IMT-Advanced requirement

Rel. 8 LTE LTE-Advanced IMT-Advanced

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Peak data rateDL 300 Mbps 1 Gbps

1 Gbps (*)

UL 75 Mbps 500 Mbps

Peak spectrum efficiency [bps/Hz]

DL 15 30 15

UL 3.75 15 6.75

*“100 Mbps for high mobility and 1 Gbps for low mobi lity” is one of the key features as written in Circular Letter (CL)

Slide 21

How to achieve LTE-Advanced Requirements� Support wider bandwidth

� Carrier aggregation to achieve wider bandwidth

� Support of spectrum aggregation

� Peak data rate, spectrum flexibility

� Advanced MIMO techniques

� Extension to up to 8-layer transmission in downlink

� Introduction of single-user MIMO up to 4-layer transmission in uplink

� Peak data rate, capacity, cell-edge user throughput

� Coordinated multipoint transmission and reception (CoMP)

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� Coordinated multipoint transmission and reception (CoMP)

� CoMP transmission in downlink

� CoMP reception in uplink

� Cell-edge user throughput, coverage, deployment flexibility

� Relaying

� Type 1 relays create a separate cell and appear as Rel. 8 LTE eNB to Rel. 8 LTE UEs

� Coverage, cost effective deployment

� Further reduction of delay

� AS/NAS parallel processing for reduction of C-Plane delay

� Contention based uplink data

Slide 22

System

Carrier Aggregation

� Wider bandwidth transmission using carrier aggregation

� Entire system bandwidth up to, e.g., 100 MHz, comprises multiple basic frequency blocks called component carriers (CCs)

� Each CC is backward compatible with Rel. 8 LTE

� Carrier aggregation supports both contiguous and non-contiguous spectrums, and asymmetric bandwidth for FDD

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Frequency

System bandwidth, e.g., 100 MHz

CC, e.g., 20 MHz

UE capabilities

• 100-MHz case

• 40-MHz case

• 20-MHz case (Rel. 8 LTE)

Slide 23

Advanced MIMO Techniques

� Extension up to 8-stream transmission for single-user (SU) MIMO in downlink

� Improve downlink peak spectrum efficiency

� Enhanced multi-user (MU) MIMO in downlink

� Specify additional reference signals

Max. 8 streams

Higher-order MIMO up to 8 streams

CSI feedback

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� Specify additional reference signals (RS)

� Introduction of single-user (SU)-MIMO up to 4-stream transmission in uplink

� Satisfy IMT requirement for uplink peak spectrum efficiency

Enhanced MU-MIMO

Max. 4 streams

SU-MIMO up to 4 streams

Slide 24

Relaying

� Type 1 relay

� Relay node (RN) creates a separate cell distinct from the donor cell

� UE receives/transmits control signals for scheduling and HARQ from/to RN

� RN appears as a Rel. 8 LTE eNB to Rel. 8 LTE UEs

� Deploy cells in the areas where wired backhaul is not available or very expensive

25

eNB RNUE

Cell ID #x Cell ID #y

Higher node

Slide 25

Coordinated Multipoint Transmission/ Reception� Enhanced service provisioning, especially

for cell-edge users

� CoMP transmission schemes in downlink� Joint processing (JP) from multiple

geographically separated points

� Coordinated scheduling/beamforming (CS/CB) between cell sites

Coherent combining or dynamic cell selection

Joint transmission/dynamic cell selection

26

� Similar for the uplink� Dynamic coordination in uplink

scheduling

� Joint reception at multiple sites

Coordinated scheduling/beamforming

Receiver signal processing at central eNB (e.g., MRC, MMSE)

Multipoint receptionSlide 26

Principle Idea of Coordinated Transmission

� The system model can be written as

y = H⋅x + n

with H = (hij)NxM, x = (x1,…,xM)T

d = (d1,…,dN)T, x = A⋅d

� Example: Zero-forcing transmission achieved by pre-filtering

27

achieved by pre-filtering

� Let A = HH⋅(H⋅HH)-1 and x = A⋅d

� Instead of transmitting d the pre-filtered vector x can be transmitted

� The received signal then becomes

y = H⋅x + n

= H⋅ HH⋅(H⋅HH)-1 d + n

= d + n

Slide 27

Figure taken from M.K. Karakayali, G.J. Foschini, and R.A. Valenzuela. Network coordination for spectrally efficient communications in cellular systems. IEEE Trans. on Wireless Comms.,13(4):56–61, Aug. 2006.

� M single antenna base stations� N single antennas mobiles � hij: channel coefficient between base station i and terminal j � dk: data symbol to terminal k

Pros and Cons of Coordinated Transmission

� Interference from neighbor cells is avoided

� Additionally, the received power is increased significantly

� Large gains can be expected with low receiver compl exity

� Challenges to overcome are already visible in this simple model� x = A⋅d Base station i transmits (ai1,…,aiN)⋅ (d1,…,dN)T

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� x = A⋅d Base station i transmits (ai1,…,aiN)⋅ (d1,…,dN)� Each base station requires data to be transmitted to all mobiles

� A = HH⋅(H⋅HH)-1 Base station i knows all channel coefficients� E.g, base station i requires knowledge of the channel between base station k and mobile j

� H⋅ HH⋅(H⋅HH)-1 = I Base stations are synchronized , channel information is instantaneously available at transmitter

� These requirements impose big challenges both to th e lower and higher layers of the radio access network (RAN)

Slide 28

Pre-filterChannel

3GPP HSDPA CoMP Work Item

� 3GPP RP-111375, ‘HSDPA Multiflow Data Transmission’, Sept/Dec 2011

� Work Description:� Specify the following HSDPA Multiflow Data Transmission technique where all cells

reside in the same NodeB� Simultaneous HSDPA transmission from a pair of cells operating on the same carrier

frequency in any given TTI to a particular user (Single-Frequency Dual-Cell aggregation)

� Extension of above enabling operation in a dual carrier configuration with two cell pairs, each on their respective carrier frequencies (Dual-Frequency Quad-Cell aggregation)

� Functionality currently defined in DC-HSDPA and/or 4C-HSDPA for e.g. channel coding of CQI reports and CQI reporting measurement procedures should be reused where possible

29

CQI reports and CQI reporting measurement procedures should be reused where possible

� Specify the following HSDPA Multiflow Data Transmission technique where cells may reside in different NodeBs� Simultaneous HSDPA transmission from a pair of cells operating on the same carrier

frequency in any given TTI to a particular user (Single-Frequency Dual-Cell aggregation)

� The two cells in the cell pair may reside in different NodeBs

� Extension of above enabling operation in a dual carrier configuration with two cell pairs, each on their respective carrier frequencies (Dual-Frequency Quad-Cell aggregation)

� The cell pairs may reside in different NodeBs

� For HSDPA Multiflow Data Transmission technique where cells may reside in different NodeBs, the benefits of any technique should be weighed against the complexity of the network implementation required and special care must be taken to ensure complexity of network implementation is minimized

Slide 29

3GPP LTE CoMP Work Item

� 3GPP RP-111365, ‘Coordinated Multipoint Operation for LTE’, Sept 2011

� Work Description:� Specify the support of intra- and inter-cell downlink CoMP for homogenous and

heterogeneous configurations studied in the CoMP study item.

� The work for specifying CoMP support in Rel-11 should focus on� Joint transmission

� Dynamic point selection, including dynamic point blanking

� Coordinated scheduling/beamforming, including dynamic point blanking

� Specification in support of DL CoMP operation potentially including:

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� Specification in support of DL CoMP operation potentially including:

� Enhancements and requirements on downlink reference signals

� PDCCH extension and other enhancements on downlink control signalling

� UE feedback scheme and related measurements

� Specify L2/L3 protocols and procedures to support DL CoMP

� Investigate the extent to which specified support is needed for X2 interfaces and specify the X2 interface support in the identified areas

� Specify UE core requirements

Slide 30

Outlook

� Volume of data in mobile systems increases dramatically

� Interference becomes more and more the bottleneck

� All 3G/4G mobile systems are still optimized for single-cell operation

� Network Coordination is the next big step in Mobile Communications

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Communications

⇒⇒⇒⇒ 5G Mobile Communication Systems will come

Slide 31

3g/4g mobile communications systems

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