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The $20 Billion Question:

Can Satellite and Terrestrial Wireless

Co-Exist in C-band?

David Hartshorn

Secretary General

GVF

www.gvf.orgWhy Is SatCom Important in C-band?

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• Spectrum:

– ITU table of allocations allows FSS only in selected bands– Bandwidth requirements for traditional FSS applications need to be met in the selected

band– Civilian Use

• Industry Supply, User Demand:

– Many satellites available– Well established, increasingly inexpensive technology– Widely used for a multitude of satellite services like:

• TV broadcast to cable networks• TV broadcast to individual receivers• VSAT networks• Internet providers• Point-to-multipoint links• Satellite News Gathering• MSS feeder links

Why Is Satcom Operating in C-band?

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Newcomers in C-band downlinks

Band commonly used by FSS satellitesAdditional band

(FSS, feederlinks for MSS, …)

Future mobile phone networks(IMT Advanced, 4G, ….)

Broadband Wireless Access (BWA), WiMax, FWA, ….

Is being considered by ITUIs being considered by ITUIs currently being introduced Is currently being introduced country by country worldwidecountry by country worldwide

BWA or IMT in ANY part of satcom C-band downlink will have an impact on FSS reception in ALL of the band

3.43.4 3.53.5 3.63.6 3.73.7 3.83.8 3.93.9 4.04.0 4.14.1 4.24.2Std. CStd. CEtx. CEtx. C

www.gvf.orgImpact on FSS Reception

• In-band interference

• Interference from unwanted emissions (outside the signal bandwidth)

• Overdrive of LNB’s

Exclusion zones around earth stations are required if these terrestrial wireless services are to operate in the band

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Exclusion Zones: A Viable Solution?

Example of calculated exclusion zone around an earth station to counter interference from a single IMT base station in each cell

(From French study to ITU Working Party 8F (Document WP 8F/868))

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Exclusion zone

Example of exclusion zone with a radius of 20 km around an earth station in Singapore

www.gvf.orgUSE OF 3625 – 4200 MHz BY THE FSS IN BRAZIL

Brazilian Contribution at June CITEL Meeting (OEA/Ser.L/XVII.4.2CCP.II-RADIO/doc. 974/06):

No Better Band to Address Rain Attenuation

Exclusion Zones Unworkable in Nations with High-Density Satcom Deployment

Developing Countries Can’t Afford Equipment Changeout

Conclusion: 3625-4200 & 4500 – 4800 MHz Should Not Be Considered for IMT

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Exclusion zones

• May be enforced for base stations with respect to specific earth stations

• Cannot be applied with respect to user terminals

• Will require user terminals which do not emit any signals when they are not in contact with a base station

• Cannot be applied with respect to unlicensed earth stations or earth stations at unknown locations

• Exclusion zones around earth stations may block large areas for BWA or IMT and prohibit effective and economically viable operation

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In-band interference

Noise increase due to a single in-band BWA station

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

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90.0

100.0

0 40 80 120 160 200 240 280 320 360 400

Distance (km)

dT

/T (

%)

Base station (100W) (line-of-sight)

Base station (4W) (line-of-sight)

User terminal (2W) (line-of-sight)

Base station (100W) with 18.5dB blocking loss

Base station (4W) with 18.5dB blocking loss

User terminal (2W) with 18.5dB blocking loss

dT/T = 6%

Example of calculated exclusion zone around an earth station to counter interference from a single IMT base station

(From AsiaSat study to ITU Working Party 4A (Document WP 4A/304))

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Unwanted emissions

BWA band

Signals appear at the input of the LNB with a much higher power density than the satellite signals

How much suppresion of out-of-band components can one realistically expect from BWA or IMT equipment?Appendix 3 of the Radio Regulations provide limits for spurious emissions

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Noise increase due to out-of-band emissions from a single BWA station (base station or user terminal)

(using Radio Regulations AP3 (-43 dBW/MHz)

0.0

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30.0

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0 2 4 6 8 10 12 14 16 18 20

Distance (km)

dT

/T (

%)

Radio Regs AP3 limits(aggregated)

Radio Regs single entry

dT/T = 6%

Example of calculated exclusion zone around an earth station to counter spurious emissions in accordance with the levels

prescribed by Appendix 3 of the Radio Regulations (From AsiaSat study to ITU Working Party 4A

(Document WP 4A/304))

Unwanted emissions

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Overdrive of LNB

BWA band

BWA or IMT signals can produce much higher powers than the satellite signals at the LNB input and can thus overdrive the LNB or bring it into non-linear operation

Normal LNB bandwidth

X

LO

LNA

LNB

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Distortion of received FSS spectre by BWA signal

B

Att 0 dB*

RBW 300 kHz* VBW 10 kHzSWT 65 ms

*

Ref -35 dBm

Center 1.425 GHz Span 100 MHz10 MHz/

3 PKVIEW

1 PKVIEW

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

-35

Date: 12.JUN.2006 12:42:16

Overdrive of LNB B

Att 0 dB*Ref -35 dBm

100 MHz/Center 1.35 GHz Span 1 GHz

*

*

RBW 300 kHzVBW 10 kHzSWT 340 ms

3 PKVIEW

2 PKVIEW

-85

-80

-75

-70

-65

-60

-55

-50

-45

-40

-35

1

Marker 1 [T2 ] -31.03 dBm 1.648000000 GHz

Date: 12.JUN.2006 12:49:04

Intermodulation products BWA

carrier

3.3 GHz4.3 GHz

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Overdrive of LNB

1. BWA signal off 3. BWA EIRP 1.6 W

2. BWA EIRP 0.5 W 4. BWA EIRP 5 W

Example of gain compression and intermodulation of LNB by single BWA base station

(BWA signal at 3.505 GHz (bandwidth 3.5 MHz), spectrum plots 3.775-3.675 GHz)

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Overdrive of LNB

Earth station received power level

-80.0

-70.0

-60.0

-50.0

-40.0

-30.0

-20.0

0.01 0.1 1 10 100

Distance to BWA terminal (km)

Re

ce

ive

d p

ow

er

(dB

m)

One signle base station (100W)

One single base station (4W)

One single user terminal (2W)

6 cell 50/50 base station (4W)/user terminal

-50 dBm (1 dB compression point)

-60 dBm (non-linear operation)

Example of calculated exclusion zone around an earth station to avoid overdrive or non-linear operation of the LNB

(From AsiaSat study to ITU Working Party 4A (Document WP 4A/304))

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RF waveguide bandpass filter

• Only helps against overdrive of LNB

• Cannot mitigate in-band interference

• Cannot mitigate unwanted emissions

• Only provides limited reduction of overdrive effects

• For many antennas, in particular receive only antennas, LNB and antenna feedhorn are molded together in one unit and no filter can be inserted in between

• Expensive (~ USD 1000.-). Inserting such in all receive installations becomes a significant cost

X

LO

LNA

LNBAntenna feedhorn

Waveguide BP filter

Waweguide flanges

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Conclusions

• BWA or IMT in a part or all of the FSS C-band downlink will be incompatible with general FSS reception in any part of C-band in the same geographical area

• BWA or IMT in a part of C-band may be compatible with FSS reception by a small number of earth stations if:– Appropriate exclusion zones around each of the earth stations are

established

– User terminals are designed not to emit any signals when not in contact with a base station

• Introduction of BWA or IMT by one country can block FSS reception in another country

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Alternative frequency bands

• S-band (e.g. 2.29 – 2.4835 GHz)

• 7 GHz band

• Spectrum refarming

• FSS uplink bands (frequencies > 6.425 GHz less used)