A Peek at 5G

F a n g X i eC h i n a M o b i l e R e s e a r c h I n s t i t u t e

Outline

• Challenges and Requirements

• TDD: An efficient transmission mode for 5G

• C-RAN: Centralized/Cooperative/Cloud/Clean RAN

• Beyond Cellular Generation

• LTE-Hi: Small cell enhancement for Hotspot/indoor

• Summary

1. Traffic grows explosively but not the revenue

Mobile data traffic will increase 1000 times in 10 years

Profit per bit will continuously decrease in the future years

2. Traffic distribution appears as unbalanced

Imbalance between the terminal type: in 2010, smart phone’s global penetration rate is 13%, while it

contribute 78% traffic load from the terminal

Geographic imbalance: in 2009, more than 50% mobile service happened at home/office; while this

percentage is 63% in China. Most of the data service happens in low mobility indoor and dense urban

Home access Internet

Office access Internet

On-road access Internet

USA 37.8% 19.6% 42.6%UK 45.6% 17.8% 36.6%Germany 43.4% 15.3% 41.3%France 33.1% 21.7% 45.2%Italy 39.6% 21.4% 39.0%South Africa 48.6% 21.4% 30.0%

Mexico 28.2% 27.6% 44.2%Brazil 36.7% 24.7% 38.6%Korea 33.7% 31.7% 34.6%India 45.9% 30.4% 23.7%China 30.1% 32.7% 37.2%

3. Spectrum has been fragmented and used up

Surging power consumption 

The majority of power consumption from RAN 

4. Power consumption plays an important role in OPEX

High CAPEX/OPEX of RAN result from BS equipment room 

Summary of Challenges and Requirements for future

Explosive growth of mobile data traffic

Spectrum Fragmentation

Unbalanced DL and UL traffic

low‐band spectrum used up

Higher date rateHigher Spectrum Efficiency

Efficient utilization of un‐paired spectrum

Flexible adaptation of DL/ UL traffic

More usable spectrum

Huge power consumption Better energy saving

Challenges Requirements

Outline

• Challenges and Requirements

• TDD: An efficient transmission mode for 5G

• C-RAN: Centralized/Cooperative/Cloud/Clean RAN

• Beyond Cellular Generation

• LTE-Hi: Small cell enhancement for Hotspot/indoor

• Summary

Promising Features of TDD

• Channel Reciprocity

– Advanced MIMO/Beamforming

• Flexible allocation of DL/UL resource

– Traffic adaptation

– Energy saving

• Unpaired frequency usage

– Flexible deployment

– Suitable for higher band and large bandwidth

TDD based downlink CoMP: Joint Transmission

1,92,54

2,47

5,46

2,81

6,15

3,01

6,58

0

2

4

6

8

2Tx�(X)/2Rx 8Tx(XXXX)/2Rx

Cell average spectrum efficiency

0,0560,098

0,047

0,183

0,078

0,227

0,101

0,266

0,00

0,10

0,20

0,30

2Tx�(X)/2Rx 8Tx(XXXX)/2Rx

Cell Edge spectrum efficiency 25%

SU-BF MU-BF Intra-Site�CoMP 3�site/9�cells�CoMP

SU-BF MU-BF Intra-Site�CoMP 3�site/9�cells�CoMP

TDD based 3D-MIMO

• High frequency lead to feasible antenna array size

• Active antenna array technology makes it feasible to achieve cost effective implementation

• TDD promises more accurate CSI by UL sounding to exploit the potential gains of CSIT

Feasibility of TDD 3D-MIMO

• System capacity improvement• Small intra-cell interference• High beamforming gain• High spatial multiplexing gain

• Energy efficiency improvement

What can be achieved?

Example: 8*8 = 64

• Background– Current Systems are Interference-

Limited– Interference Suppression by MIMO is

limited to 2-Dimension– New AAS design facilitating the

exploitation of elevation dimension

Promising Features of TDD

• Channel Reciprocity

– Advanced MIMO/beamforming

• Flexible allocation of DL/UL resource

– Traffic adaptation

– Energy saving

• Unpaired frequency usage

– Flexible deployment

– Suitable for higher band and large bandwidth

Dynamic TDD achieves better spectrum & energy efficiency

Fast DL/UL switching

Higher throughput by fast adaptation to

instantaneous traffic

Fast switching off of DL transmission to

save energy

• Semi-static TDD:DL/UL resource allocation based on TDM in the same carrier

Asymmetric DL/UL resource allocation adapts to asymmetric DL/UL traffic

Promising Features of TDD

• Channel Reciprocity

– Advanced MIMO/Beamforming

• Flexible allocation of DL/UL resource

– Traffic adaptation

– Energy saving

• Unpaired frequency usage

– Flexible deployment

– Suitable for higher band and large bandwidth

TDD becomes dominate for wide band allocation

• Fragmented spectrum• Difficult to find wideband paired spectrum (low

to medium frequency)• Future system is expected to be wideband

Current situations

• Use un-paired spectrum• Easy to allocate wideband, e.g. 100MHz• Better utilization of spectrum

TDD: A better choice 

Outline

• Challenges and Requirements

• TDD: An efficient transmission mode for 5G

• C-RAN: Centralized/Cooperative/Cloud/Clean RAN

• Beyond Cellular Generation

• LTE-Hi: Small cell enhancement for Hotspot/indoor

• Summary

…

RRU

RRU

RRU

RRU

RRU

RRU

RRU

Virtual BS Pool

Distributed RRU

High bandwidth optical transport

network

Real-time Cloud for centralized

processing

…Centralized Control and/or Processing• Centralized processing resource

pool that can support 10~1000 cells

Collaborative Radio• Multi-cell Joint scheduling and

processingReal-Time Cloud • Target to Open IT platform• Consolidate the processing

resource into a Cloud• Flexible multi-standard operation

and migrationClean System Target• Less power consuming• Lower OPEX• Fast system roll-out

C-RAN Concept

Soft base-station – seamlessly scalable and upgradable

C-RAN Benefits

Lower CAPEX and OPEXSave up to 15% CAPEX and 50% OPEX compared to distributed BTS 3G network*

0 100 200 300

Faster system roll outDue to simpler remote radio site, system roll out can save up to 1/3 the time*

Lower energy consumptionSave up to 71% of power compared to traditional RAN system*

*Source: Base on China Mobile research on commercial networks

• Traditional Cellular Network is coverage-based and is not energy efficient, especially when traffic is low

• Data traffic growth densifies BS• Beyond cellular generation

– On-off small cells (AP)– Signaling and data decoupling– Uplink and downlink decoupling

Enhanced Macro BS

Densed BS

Ericsson soft-cell GreenTouch BCG2

Hetnet

Beyond Cellular Generation

19

BCG structure

signaling

data

downlink

uplink

downlink Zzzz…

Zzzz…

LTE-Hi Motivations

Currently, 60% Voice Traffic & 70% Data Traffic Happen Indoor

In Future, 90% Indoor/Hotspot Traffic Estimated

To Accommodate Explosive Growth Of Data Traffic In Such Cases, The Followings Means Need To Be Considered:

– Denser Network (But Difficult For Macro Layers)– Easy-to-deploy Low Power Node– Larger Bandwidth– New Techniques To Improve The Spectrum Efficiency & Throughput

These Motivates The So-called LTE-Hi (Hotspot & Indoor) To Ensure The Competitiveness Of 3GPP In Local Area

Characteristics

• High Data Rate Needed• Low Mobility• Rich Scattering• Low Multi-Path Latency• Discontinuous Coverage• High Degree Of Isolation

Between Cells

EnhancementEnhancement

• Physical Layer:• New transmission technology, e.g.

NCT, dynamic TDD, 256QAM

• Denser Network:• Hetnet, Multi-Type/Easy-to-deploy

Nodes for Indoor/Hotspot

• Larger Bandwidth:• Expand to higher spectrum for

larger bandwidth.

Characteristics & Possible Enhancements

Summary

• Challenges and Requirements for 5G

• Promising features of TDD makes it a most efficient transmission mode for Beyond 4G system– Channel Reciprocity makes it a sufficient way to utilize advanced

MIMO/Beamforming– Dynamical TDD adapts to asymmetrical traffic and lead to higher

capacity and energy efficiency – Unpaired frequency usage utilizes the limited spectrum in most

efficient way and lead to flexible deployment

• C-RAN: Centralized/Cooperative/Cloud/Clean RAN

• Beyond Cellular Generation

• LTE-Hi: Small cell enhancement for Hotspot/indoor

If you can imagine it You can achieve it

Thank you