Interference Control: Problems & Examples

Euntaek Lim

Samsung Electronics

Contents

Mobile Spectrum Allocation Overview Current Allocation

LTE Spectrum Trends

Interference Case

Mitigation techniques Interference Scenarios

Mitigation

Concluding Remarks

Mobile Spectrum Allocation

(MHz)

Korea

EU

US

CELLULAR PCS IMT-2000

Japan

China

800 1000 1700 2000

824

900 2200

869

849

894

880

925

915

960

1750

1850

1780

1880

1805

17851710

1880

1850 19101920

1990

1920 1980 2110 2170

1893 1919

1500

810 828

843 846 898 901

860 885 915 958 1429 1453

1477 1501

1805

17201710

1815

824

869

849

915

960935

824 849

869 894

1920 1980

1920

1980

2110 2170

2110 2170

1920 1980 2110 2170

2500 2700

WARC-92

WRC-2000

1885 2025 2110

140MHz 90MHz

154MHz 175MHz 190MHz

806 960 17102690

BWA

AWS AWS

Almost spectrum under 3GHz is allocated to mobile

Trends in Spectrum

LTE Spectrum Portfolio

Lower Spectrum: Coverage Digital Dividends: Mobile-DTV Interference

Higher Spectrum: Capacity 2.6GHz: 140MHz FDD 50MHz TDD

3.4-3.6GHz: FDD-TDD Optional & Fixed Satellite Service

Re-allocations in existing mobile bands LTE GSM or CDMA interference

New Spectrum may be possible but required to protect existing services in same or adjacent channels

New Spectrum in Other Areas

EU

Further Spectrum in C-bands: EU designated 3.4~3.8GHz spectrum for mobile BWA under EC Decision xxxx

Digital Dividends Phase II is investigated in Digital Agenda

US

1675-1710 MHz Weather satellite

1755-1780 MHz Federal (Satellite and other operations)

2075-2110 MHz broadcasting service

2155-2175 MHz AWS-3 band under FCC pending discussion

2175-2180 MHz AWS-2 band under FCC pending discussion

Interference Case

Interference with adjacent incumbent services E.g., DTV-Mobile, Satellite-Mobile

Interference between different region Satellite-Mobile cross-border

DTV-Mobile cross-border

Interference between mobile bands FDD-TDD interference

CDMA-GSM bands interference

In-band migration interference

Digital Dividends

Interference to DTV Receiver is still problem US: No guard band but regional allocation

APT: 5/9MHz guard but UE to DTV Receiver Interference

EU: Only 1MHz guard

45MHz (UP)

703

DTV

698

45MHz (Down)

748 758 803

18MHz (UP)

69818MHz

(Down)

11MHz

(Down)

716 722 746 757D block

& PS

11MHz

(UP)

D block

& PS

758775

776787

788806

Medi

aFL

PPDR

806

AWG

Plan

US

Plan

EU

Plan30MHz

(Down)

790

DTV

791

30MHz

(UP)

832821 862

DTV

EU Digital Dividends Interference Impact

UK Research 6~8.5% of households have influence in DTV receiver

Additional filter with polarization can reduce the interference

DTV channel Mitigation % Households lost Area

CH 58

Rx filter: Type-3

(-19dB@796MHz)

No filter, Polar discr. = 3dB 5.87% Waltham

-Total served

household

: 726,195Filter, Polar discr. = 3dB 0.14%

No filter, Polar discr. = 16dB 1.39%

Filter, Polar discr. = 16dB 0.03%

CH 60

Rx filter: Type-1

(-1dB@796MHz)

No filter, Polar discr. = 3dB 8.68% Oxford

-Total served

household

: 388,430 Filter, Polar discr. = 3dB 5.90%

No filter, Polar discr. = 16dB 3.15%

Filter, Polar discr. = 16dB 2.48%

Interference between Mobiles

Introduction of new system in the adjacent band Sufficient guard band is required to mitigate interference

839-849

Operator B @ 850 MHz

(LTE service)

Operator A @ 900 MHz

(LTE service)

11 MHz of guard band

884-894

905-915

950-960

Special out-of-band emission limits are regulated for mobile

terminal of Operator A and BS of Operator B

3.4-3.6GHz in Asia Pacific

Because of Interference from Mobile to Satellite, only 8 countries among Asia Pacific identified the band for IMT. SUIRG Measurement: In worst case with 1km separation distance, I/N

is range of 20 to 42dB

Satellite Signal

Mobile BS

Interference from

mobile

About 1 km

FSS Earth Station

I/N at receiver

Cross Border Interference

Example of Interference CDMA BS to EGSM MS Interference or

GSM MS to CDMA MS Interference

MS MS

CDMA BS GSM BS

Administration 1Neighboring

Administration 2

Interference

Cellular Spectrum in APT

Cross border interference between countries using CDMA and countries using EGSM900

Australia

Bangladesh

China

Mongolia

India

Indonesia

Korea

Japan

Malaysia

Myanmar

New Zealand

Taiwan

Afghanistan

Vietnam

Thailand

Cambodia

GSM 900 + CDMA800

EGSM 900 + CDMA800

Interference Mitigation

Filtering & In-band Power limit: Block edge mask Spectrum efficiency loss

Limitation in Mobile Terminal

Site Design / Shielding

Opportunistic Channel Access with Database

Harmonization for cross-border

Block Edge Mask

Block Edge Mask defines out-of-band emission and in-band emission to protect adjacent channels EU 2.6GHz Block Edge Mask ( ): Imposing ACLR of 99dB to BS

EU Digital Dividends (EC Decision 2010/267/EU )

Up to BS ACLR of 49/59dB to protect DTV

Situation Case

Condition on base

station e.i.r.p.

(dBm/10MHz)

Maximum

mean out-of-

block EIRP

Measurement

bandwidth

AFor TV channels where

broadcasting is protected

P 59 dBm 0 dBm 8MHz

44 dBm P < 59 dBm P-59 dB 8MHz

P < 44 dBm -15 dBm 8MHz

B

For TV channels where

broadcasting is subject to an

intermediate level of

protection

P 59 dBm 10 dBm 8MHz

44 dBm P < 59 dBm P-49 dB 8MHz

P < 44 dBm -5 dBm 8MHz

CFor TV channels where

broadcasting is not protectedNo condition 22 dBm 8MHz

Site Design

Antenna Separation Antenna separation is the mean to separate two BSs antennas

operating in adjacent CH, horizontally or vertically at site.

The point is whether such antenna separation can ensure more than 56dB isolation in addition to the isolation secured by guard band.

Installation Illustration

Vertical Separation Horizontal Separation

Performance of Site Design

Summary of Antenna Configurations

Antenna Configuration Expected Isolation

Horizontal separation 2m / 8m 55dB / 61dB

Horizontal separation 1m / 2m

with (+) 15face-to-face angle rotation56dB / 60dB

Horizontal separation 1m / 8m

with 4electrical down-tilt70 / 80dB

Vertical separation 0m 70dB

Vertical separation with different antenna pole 77dB

Vertical separation 0.5m

with 4electrical down-tilt83dB

Shielding

ITU-R WP5D is developing the technical report on Mitigation technique of mobile systems to protect FSS. Site Shielding example

c

d interference

h

hW

interference

Mesh grid step Attenuation (dB)

Single mesh grid with step a=1 cm 12 dB

Single mesh grid with step a=5 mm 18 dB

Single mesh grid with step a=2 mm 26 dB

Double mesh grid(separation of 10 cm) with step a=2 mm

2x26 dB

Barrier

Mesh Grid

Cross-Border Coordination

Methods of Cross Border Coordination Triggering Site Specific Method: Recommendation ITU-R P.452

Site General Model: Recommendation ITU-R P.1546

Specific Procedure for Mobile Networks

Predict Interference at

the border

Calculated Interference level from interfering

cell

Calculated victim performance with

various interference level

Define affected interference level

(Trigger values)

Need practical methods of performance evaluation

WiMAX Example (WiMAX Forums Study)

Trigger level based on real scenarios TDD to TDD Interference (with no-synchronization) based on site

general model: -4.4 dBV/m/5MHz

Aggregated trigger levels with real scenarios

Information on the study is available at

http://www.apt.int/sites/default/files/INF-06WiMAX_Forum-Cross-border-8.pdf

ScenariosAggregated Trigger level

(dBV/m/5MHz)

No Synchronization 30

TDD Synchronization 58

Preferential Sub-carriers 65

Cognitive Radio Concept

CR Terminal

CR BS

Primary

Device

Primary

Device

Spectrum Sensing

Sensing Report

Spectrum Usage

Indication

Spectrum

Manager

Spectrum Share

Protocol

Other CR Systems CR System

1 Primary system in operation

CR system detects the primary

transmission by sensing techniques

2

Terminals report sensing results to BS3

4 BS makes decision on choosing the

operational spectrum based on the

sensing information, or the spectrum

sharing protocols with other CR system,

and informs terminals of any change.

The CR system coordinates with other

CR system on spectrum sharing with

dedicated protocols, if any

5

NTIA DefinitionA Radio or system that senses its operational electromagnetic environment and can dynamically and autonomously adjust its radio operating parameters to modify system operation, such as maximize throughput, mitigate interference, facilitate interoperability, access secondary markets.

Concluding Remarks

Additional mobile spectrum is required based on current mobile traffic analysis & trends

However, there are less available spectrum for additional mobile spectrum Interference between blocks or separated locations are getting

increased.

Diverse interference mitigation is available but most important control mechanism is harmonized spectrum usage. E.g., cross-border interference is dramatically decreased when two

countries are coordinating.