Contact: MR. TIM HEWITT
Chair, Regulator Working Group WiMAX Forum
Tel: Fax: Email: [email protected]
ASIA-PACIFIC TELECOMMUNITY The 7th Meeting of the APT Wireless Forum (AWF-7) Document
AWF-7/INF-06 23 – 26 September 2009, Phuket, Thailand 23 September 2009
CROSS-BORDER COORDINATION FOR BROADBAND WIRELESS ACCESS
by
WiMAX Forum
Copyright 2009 WiMAX Forum. All rights reserved. “WiMAX”, “Mobile WiMAX,” “Fixed WiMAX,” “WiMAX Forum,” “WiMAX Forum Certified,” and the WiMAX Forum and WiMAX Forum Certified logos are trademarks of the WiMAX Forum. All other trademarks are the properties of their respective owners.
Cross-border coordinationfor Broadband Wireless Access
APT Wireless Forum, Phuket, 25th-29th September 2009
Tim HewittDirector, Regulatory & Spectrum PolicyChairman, Regulatory Working Group
Contents
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
AWF-7/INF-06
Page 1 of 16
Copyright 2009 WiMAX Forum. All rights reserved3
Most areas of the World have potential cross-border co-ordination issues...
“CEPT Europe” is a small region with 48 Countries and many borders
Germany, for example, has 9 international borders:-• Austria• Belgium• Czech Republic• Denmark• France• Luxembourg• Netherlands• Poland• Switzerland
Copyright 2009 WiMAX Forum. All rights reserved
A study commissioned by the WiMAX Forum• The European Task Group of the
WiMAX Forum recently commissioned a study of cross-border co-ordination in order to be able to contribute constructively to the development of cross-border co-ordination regulation and recommendations for Broadband Wireless systems– The Consultants were UK-based
Analysys-Mason Ltd• We believe that this work is also
relevant to other regions around the world
AWF-7/INF-06
Page 2 of 16
Copyright 2009 WiMAX Forum. All rights reserved
The European band plan for the 2.6 GHz band is based on ECC Decision (05) 05 and subsequent EC Decision• ITU World Radio Conference in 2000 originally identified 2.6GHz as expansion
spectrum for terrestrial IMT-2000/UMTS in Europe and other world regions• Central to European regulators’ plans for the assignment of 2.6 GHz spectrum was
the ECC Frequency Plan set down in March 2005 under Decision ECC/DEC/(05)05.– This designates the entire frequency band to terrestrial IMT-2000/UMTS
systems and recommends a harmonised spectrum plan for the 2.6 GHz band in order to facilitate terminal economies of scale and global roaming.
• Since 2005, policy and technology developments have shifted towards flexibility, including service and technology and usage neutrality
• The ITU IMT-2000 technology family now includes WiMAX (OFDMA TDD WMAN).
2.6 GHz Band - Fixed Designation in ECC/Dec/(05)05
2500 2570 2620 2690 MHz
Paired – FDD (Uplink) Paired – FDD (Downlink)Unpaired – TDD
Copyright 2009 WiMAX Forum. All rights reserved
The EC 2.6 GHz decision allows flexibility between FDD and TDD use
• The EC has now identified 2.6 GHz band as a technology neutral spectrum band• National market demand will determine the split of FDD/TDD spectrum.
– The ECC(05)05 fixed designation might change if market demand exists for additional unpaired (TDD) blocks.
– This initiative has some implications on spectrum management in border areas
• An example of a flexible implementation, allocating more spectrum to be available for TDD technology is shown below.
2.6GHz Band - Additional Flexibility
Paired – FDD (Uplink) Paired – FDD (Downlink)Unpaired – TDD
2500 2570 2620 2690 MHz
Additional unpaired blocks
AWF-7/INF-06
Page 3 of 16
Copyright 2009 WiMAX Forum. All rights reserved
Flexibility potentially introduces the need for coordination in border areas between FDD and TDD systems
• If one or more European countries allocates additional spectrum to TDD then cross border coordination of co-channel interference between FDD and TDD systems may need to be undertaken.
TDD to TDD (without synchronisation BS to BS is most significant but alsoBS to MS)
TDD BS to FDD BS
FDD BS to TDD BS
Country A
Country B
Paired FDD Block
Unpaired TDD Block
Paired - FDD (Uplink)Paired - FDD (Uplink) Paired –FDD (Downlink)Paired –FDD (Downlink)
Interference paths studied
Copyright 2009 WiMAX Forum. All rights reserved
Need for Cross Border Coordination
Ideal Outcome
International Border
Undesirable Outcome
No coverage due to compliance with International Interference limits
xx dB�V/m/5MHz
International Border
Country B
Country A
xx dB�V/m/5MHz
Country A
Country B
yy dB�V/m/5MHz
yy dB�V/m/5MHz
AWF-7/INF-06
Page 4 of 16
Copyright 2009 WiMAX Forum. All rights reserved
Contents
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
Introduction (Europe Cross Border Coordination)
� Mobile WiMAX, HSPA and 3G LTE technologies might all be deployed in the 2.6 GHz spectrum band. It can also be assumed that services in this band will be data oriented rather than voice.
� This study attempts to find the efficient cross border coordination trigger threshold levels for TDD-TDD and TDD-FDD scenarios between two or more countries, to facilitate successful network operation in border areas
� Two case studies were produced to test the revised trigger levels in real scenarios (Basle and Maastricht).
Maastricht
Basle
AWF-7/INF-06
Page 5 of 16
Copyright 2009 WiMAX Forum. All rights reserved
Approach taken for the Study
• The study was undertaken in 2 phases
• Phase 1 consisted of a single interferer-victim path using “smooth earth” propagation curves in representative urban, suburban and rural environments. The objective was to review the trigger values recommended in CEPTs earlier co-ordination guidelines for 3G systems – (CEPT/ERC Recommendation (01)01
• Phase 2 of the study considered several European cross-border scenarios and considered multiple interferer-victim paths, representing deployment scenarios that might occur in practice in European border areas. The objective was to determine the practical impact on network deployment in border areas.
Approach to Study (Phase 1)
• Phase 1analyses Base Station (BS) to Base Station interference as the BS is more sensitive to interference than the Mobile Station (MS).
• Step 1: Link budgets for HSPA and two WiMAXdeployments, Hand Held and Notebook mobile stations, were constructed. The Carrier-to-Interference (C/I) ratios for a range of modulation schemes were calculated.
• Step 2: The cell size of the interfering base station was calculated using the appropriate link budget depending on the technology being considered. We determined the cell size by using the lowest data rate available and the slow fade margin required to satisfy fading at 75% cell edge (90% cell area).
• Step 3: Interference from the base station is predicted for a border test point at 3m above ground level using propagation predictions based on Rec. ITU-R P.1812, 50% locations and 10% time.
Impact on the Interfering Cell
MSBS Tx
Interfering Cell
BS Tx
Interfering Cell
InternationalBoundary
1. BS EIRP fromlink budget
2. Calculate cell size with Extended Hatafor mobile at 1.5m
3. Predict interference from BS at border with ITU-R P.1812 with 50% locations, 10% time at 3m
Test Pointat 3m
AWF-7/INF-06
Page 6 of 16
Approach to Study (Phase 1)
• Step 4: The minimum distance between the interfering base station and border test point is calculated to achieve compliance with a range of coordination thresholds from 0 to 100 dB�V/m. A graph of coordination threshold against minimum separation distance is plotted.
• Step 5: The throughput of a mobile station at 1.5m on the border was also calculated depending on the C/I ratio and modulation schemes. A graph of throughput against coordination threshold was plotted from this.
BS Tx
Interfering Cell
Mobileat 1.5m
MS
4. Plot minimum separation distance to achieve compliance with a range of thresholds from 0 to 100 uV/m
5. Plot throughput as a function of coordination threshold for a mobile on the border at 1.5 m
InternationalBoundary
Approach to Study (Phase 1)
An interfering base station is placed at a distance equal to its cell radius away from the international border. • Step 1: The coordination threshold
was varied at the 3m test point on the border, and the EIRP of the interfering base station was varied to comply with each value of coordination threshold considered.
• Step 2: The interference was predicted at the victim base stationusing Rec. ITU-R P.1812, for 50% locations and 10% time.
• Step 3: The throughput of the victim base station was calculated based on the C/I achieved for the minimum carrier power allowed for in the link budget, and is plotted as a function of coordination threshold as shown in the figure.
Impact on the Victim Cell
BS Rx
Victim Cell
1. Vary coordination trigger level onborder at 3m
3. Plot throughput of the victim BS as a function of coordination threshold
BS Tx
Interfering BS
2. Predict interference from interfering BS to victim BS using ITU-R P.181250% locations and 10% time
InternationalBoundary
AWF-7/INF-06
Page 7 of 16
Approach to Study (Phase 2)Phase 2 Objective: To determine the impact on deployment in border areas for networks designed for HSPA, WiMAX Handheld and WiMAX Notebook reception using revised trigger values found in Phase 1.
• Basle and Maastricht border scenarios were chosen because they contain a good mixture of geo-types (urban, suburban and rural) on either side of the international border – these two scenarios can be assumed to represent the most challenging cross border coordination situations in Europe.
• ATDI ICS Telecom v.9.1.4 and Microsoft Access were used to carry out the simulations.
Approach to Study (Phase 2)
• Step 1: A 50m resolution digital terrain map from SRTM data for the selected border regions was obtained.
• Step 2: Reference network in each country based on the technology being used was designed. These networks were designed using the link budget parameters summarised in the main report.
• Step 3: Reference network coverage was verified for each of the networks to ensure that our modelling was representative of likely coverage (at least 90% area coverage) strategies that operators might deploy in these areas in practice.
AWF-7/INF-06
Page 8 of 16
Approach to Study (Phase 2)• Step 4: Test points at 3m above
ground level along the international border were created in order to predict the field strength at each of these test points.
� Step 5: Interference analysis from base stations to these test points were carried out.
Approach to Study (Phase 2)• Step 6: The most significant interfering sites from
any group of sites that collectively breached the coordination threshold at any test point were removed. Bonn Summation algorithm was used to calculate the aggregated co-channel interference.
• Step 7: Interference analysis between interfering and victim base stations was performed to confirm that the calculated C/I value for each technology was not breached.
• Step 8: Some interference mitigation techniques were used and the scenario was simulated with each technique applied. Graphs of % of sites requiring coordination vs aggregated trigger level and Aggregated Interference vs CDF of Victim BS were plotted.
• Step 9: Repeat for each of the following scenarios:
– WiMAX HH (Ger) – WiMAX NB (Swi)– WiMAX HH (Ger) – HSPA (Fra)– WiMAX NB (Swi) – HSPA (Fra)– WiMAX NB (Swi) – WiMAX HH (Ger)– HSPA (Fra) – WiMAX NB (Swi)– HSPA (Fra) – WiMAX HH (Ger)
AWF-7/INF-06
Page 9 of 16
Contents
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
Interference Mitigation Techniques• For cross border coordination, only co-channel interference need be
considered• Interference Mitigation techniques include:
– TDD Synchronisation (WiMAX to WiMAX only): Removes BS to BS interference by ensuring that interfering and victims BS do not transmit and receive at the same simultaneously. Requires both network operators near the border to agree the same downlink/uplink ratios.
– Partial Frequency Re-use (WiMAX to WiMAX only): Careful design of frequency assignments along the border can be used to reduce the amount of co-channel interference received at the victim BS.
– Reduced EIRP: reducing EIRP decreases the signal field strength at the victim BS.– Increased Antenna downtilt: Reduces the amount of interference exported; also increases
resilience to incoming interference.– Suppression of secondary lobes: suppressing the secondary lobes on the upper half of
the elevation pattern reduces the amount of interference exported; also increases resilience to incoming interference.
– Consideration of Antenna Azimuth: care is taken to avoid antennas pointing directly towards BS on the other side of the border.
– Site Placement : Knowledge of precise BS locations and predicted level of interference may be shared to the network operators concerned before sites are built.
AWF-7/INF-06
Page 10 of 16
Contents
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
Phase 1 Results (Minimum Distance Graph)
• Trigger level against distance from Interfering BS to international border graphs, for a smooth earth, urban
• Note the difference between a 3m and 15m test point
Minimum BS to border distance vs Coordination Trigger Level FSITU-R P.1812 50% Locations, 10% Time
0
20
40
60
80
100
120
0 5 10 15 20 25 30
Distance (km)
FS
(dB
uV/m
/5M
Hz)
WiMax Handheld 58.0dBm EIRP, urban 3m Test PointWiMax Handheld 58.0dBm EIRP, urban 15m Test Point
AWF-7/INF-06
Page 11 of 16
Copyright 2009 WiMAX Forum. All rights reserved
Phase 1 Results (All Results)• Summary of Phase 1 Results
Scenario Environment Interferer VictimPhase 1 ITU 1812 Trigger Level (3m)
(dBuV/m/5MHz)
Max. Interfence FS allowed at BS
antenna(dBuV/m/5MHz)
1 urban UMTS HSPA WiMax Handheld -5.44 22.562 urban UMTS HSPA WiMax Notebook -3.44 22.563 urban WiMax Handheld WiMax Handheld -1.44 22.564 urban WiMax Handheld WiMax Notebook 1.56 22.565 urban WiMax Handheld UMTS HSPA 10.81 24.816 urban WiMax Notebook WiMax Handheld -4.44 22.567 urban WiMax Notebook WiMax Notebook -2.44 22.568 urban WiMax Notebook UMTS HSPA 6.81 24.819 suburban UMTS HSPA WiMax Handheld -2.44 22.5610 suburban UMTS HSPA WiMax Notebook -1.44 22.5611 suburban WiMax Handheld WiMax Handheld 8.56 22.5612 suburban WiMax Handheld WiMax Notebook 9.56 22.5613 suburban WiMax Handheld UMTS HSPA 14.81 24.8114 suburban WiMax Notebook WiMax Handheld 6.56 22.5615 suburban WiMax Notebook WiMax Notebook 7.56 22.5616 suburban WiMax Notebook UMTS HSPA 12.81 24.8117 rural UMTS HSPA WiMax Handheld 7.56 22.5618 rural UMTS HSPA WiMax Notebook 12.56 22.5619 rural WiMax Handheld WiMax Handheld 9.56 22.5620 rural WiMax Handheld WiMax Notebook 12.56 22.5621 rural WiMax Handheld UMTS HSPA 25.81 24.8122 rural WiMax Notebook WiMax Handheld 7.56 22.5623 rural WiMax Notebook WiMax Notebook 10.56 22.5624 rural WiMax Notebook UMTS HSPA 25.81 24.81
Phase 1 Results (Diagrammatic Representation)
TDD – TDD Coordination
TDD BS to FDD BS
Coordination
FDD BS to TDD BS
Coordination
Country A
Country B
Paired FDD Block
Unpaired TDD Block
6.8 dBµV/m/5MHz
- 4.4 dBµV/m/5MHz - 5.4 dBµV/m/5MHz
Trigger levels measured at 3m
AWF-7/INF-06
Page 12 of 16
Copyright 2009 WiMAX Forum. All rights reserved
Contents
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
Phase 2 Results (Interfering BS)• Phase 2 simulations have been carried out in
ADTI ICS Telecom v.9.1.4.• Within 40km of the border, the percentage of
sites (BS) requiring coordination is calculated for a range of trigger threshold values from 10 to 60 dB�V/m/5MHz.
• EIRP of the base stations is as per the link budgets and a 2-degree downtilt is used.
• Two mitigation techniques have been used: 6-degree downtilt and 3dB power reduction.
– 3dB power reduction can be achieved by several methods – e.g.reducing the EIRP directly, azimuth change, fractional frequency re-use, etc…
• Eight scenarios modelled, two are shown to the right
• Conclusion from graphs: Terrain has a significant effect on the number of BS that has to undergo coordination process.
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
-10 0 10 20 30 40 50 60
Coordination Trigger Threshold (dBuV/m/5MHz)
% o
f si
tes
requ
iring
coo
rdin
atio
n 2 degrees tilt
6 degrees tilt
3dB Tx PowerReduction
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
-10 0 10 20 30 40 50 60
Coordination Trigger Threshold (dBuV/m/5MHz)
% o
f si
tes
requ
iring
coo
rdin
atio
n 2 degrees tilt
6 degrees tilt
3dB Tx PowerReduction
UMTS to WiMAX Notebook (Basel region: France to Switzerland)
WiMAX HH to UMTS (Basel region: Germany to France)
AWF-7/INF-06
Page 13 of 16
Phase 2 Results (Victim BS)Interference Limit From Link Budget 95
%
� As we are predicting interference at full EIRP and for only 10% of time, it would be reasonable to select an aggregated trigger level that results in a small number of breaches at victim base stations – say 5%.
� Six scenarios modelled, two are shown above. Reasons why trigger level increased from phase 1:
� (i) Real antenna pattern characteristics are included (tilt and azimuth), � (ii) Terrain losses are included, not just smooth earth losses, and � (iii) real propagation paths cross a complex mixture of geotypes
-60.00
-40.00
-20.00
0.00
20.00
40.00
60.00
0% 20% 40% 60% 80% 100%
CDF of sum of received interference (% of BS)
Su
m o
f re
ceiv
ed i
nte
rfer
ence
(d
Bu
V/m
Trigger Value 50dBuV/mTrigger Value 45dBuV/mTrigger Value 40dBuV/mTrigger Value 35dBuV/mTrigger Value 30dBuV/m
-60.00
-40.00
-20.00
0.00
20.00
40.00
60.00
0% 20% 40% 60% 80% 100%
CDF of sum of received interference (% of BS)
Su
m o
f re
ceiv
ed i
nte
rfer
ence
(d
Bu
V/m
Trigger Value 20dBuV/mTrigger Value 15dBuV/mTrigger Value 14dBuV/mTrigger Value 12dBuV/mTrigger Value 10dBuV/m
UMTS to WiMAX Notebook (France to Switzerland)
WiMAX HH to UMTS Notebook(Germany to France)
Summary of Phase 2 BS to BS results
Impact of selected trigger level on Interferer and Victim networks.
– 1. Percentage of sites requiring coordination within 40km of the boarder, without mitigation applied.
– 2. Percentage of Base Stations which receive more than the permitted level of interference from the interfering sites that do not require coordination (i.e. those sites that together comply with the trigger level).
Interferer Victim
SenarioPercentage of sites requiring coordination 1
Trigger Level (dBuV/m/5MHz)
Percentage of Base stations
Breached 2
UMTS to WiMAX Notebook (France to Switzerland) 32.7% 30 0.0%WiMAX HH to UMTS (Germany to France) 40.5% 14 0.0%WiMAX HH to WiMAX Notebook (Germany to Switzerland) 48.3% 30 3.6%WiMAX Notebook to UMTS (Switzerland to France) 33.8% 14 1.4%WiMAX Notebook to WiMAX Hand Held (Switzerland to Germany) 23.7% 30 5.0%UMTS Notebook to WiMAX Hand Held (France to Germany) 47.7% 30 0.0%UMTS to WiMAX Notebook (Belgium to Netherlands) 32.3% 30 - WiMAX Notebook to UMTS (Netherlands to Belgium) 71.8% 14 -
AWF-7/INF-06
Page 14 of 16
Contents
Introduction
Need for Cross Border Coordination
Approach to Study
Interference Mitigation Techniques
Phase 1 Results
Phase 2 Results
Conclusion
Conclusion - 1
• Our proposed aggregated trigger levels based on a site specific model in real scenarios are as follows:
� Please note that 30dB�V/m/5MHz is equivalent to 33dB�V/m in a typical 10MHz WiMAX channel.
Removes BS to BS Interference
Removes both BS to BS and BS to MS Interference
� Our initial trigger levels based on a site general model with a single interferer are as follows:
Scenario Additional CommentTrigger Level (dBuV/m/5MHz)
TDD WiMAX to TDD WiMAX No Synchronisation -4.4
TDD WiMAX to FDD HSPA 6.8FDD HSPA to TDD WiMAX -5.4
Scenario Additional CommentAggregated
Trigger Level (dBuV/m/5MHz)
No Synchronisation 30TDD Synchronisation 58Preferential Sub-carriers 65
TDD WiMAX to FDD HSPA 14FDD HSPA to TDD WiMAX 30
TDD WiMAX to TDD WiMAX
AWF-7/INF-06
Page 15 of 16
Conclusion - 2
30 dBuV/m/5MHzAggregated Trigger level
FDD-TDD and TDD-TDD(No Synchronisation and No Preferential
Subcarriers)
TDD-TDD using TDD Synchronisation
TDD-TDD using Preferential Subcarriers
and Synchronisation
58 dBuV/m/5MHz
Aggregated Trigger level
65 dBuV/m/5MHz
Aggregated Trigger level
Copyright 2009 WiMAX Forum. All rights reserved. “WiMAX”, “Mobile WiMAX,” “Fixed WiMAX,” “WiMAX Forum,” “WiMAX Forum Certified,” and the WiMAX Forum and WiMAX Forum Certified logos are trademarks of the WiMAX Forum. All other trademarks are the properties of their respective owners.
www.wimaxforum.org
Thank you!
AWF-7/INF-06
Page 16 of 16
