doc.: ieee 802.22-07/0254r0 submission may 2007 sai shankar n qualcommslide 1 aggregate interference...

May 2007

Sai Shankar N QualcommSlide 1

doc.: IEEE 802.22-07/0254r0

Submission

Aggregate Interference at DTV Receiver

Date: 2007-05-14

Name Company Address Phone E-mail Sai Shankar N Qualcomm 5775 Morehouse Dr

San Diego, CA 92121 (858) 651 4218

[email protected]

Steve Shellhammer Qualcomm 5775 Morehouse Dr San Diego, CA 92121

(858) 658 1874

[email protected]

Authors:

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May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Abstract

• This is a method of calculating the aggregate interference seen by the DTV receiver– Supported by simple analytical model and realistic

data from the working group

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Outline

• How is interference calculations used in determining the keep-out region in IEEE 802.22 WRAN?

• Effect of individual interferer as well as multiple tiers of WRAN cells on the keep-out region

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Model of the network

• Consider a 2-D grid– Using the F(50,90) curve the TV receiver is kept at the 134.2 km

from the DTV transmitter

– The keep-out region from simulation model doc is 16.1 km beyond the nose limited contour [1]• This translates into a keep-out radius of 150.3 km from the DTV

transmitter

• Is this calculation of the keep-out region correct?– Consider that the DTV receiver has omni directional antenna (Case 1)

– Then consider that the DTV receiver has a directional antenna with the front to back ratio of 14 dB as specified in IEEE 802.22 draft (Case 2)

• Let us look at the geometry in the next slide….

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Determination of Number of Interferers• We define the primary radius as R

– The noise limited contour has a radius x

– The distance from edge of noise limited contour to WRAN transmitter is y

– We define R=x+y

• Let r be the radius of the WRAN cell

• We have to determine how many green circles can be fit around the white circle of radius R

x

y

R=x+y

x

y

R=x+y

r

x

y

R=x+y

r

If the BS is only transmitting and there is no traffic in the reverse link then this figure makes sense

If the CPE is transmitting then this figure makes sense

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Determination of Number of Interferers

• To do this we resort to Pythagoras theorem– We need to determine theta

– Theta is give by:

Rr

θ

Rr

r1sin Compare it with our and competitive

technology

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Determination of Number of Interferers

• Number of Interferers is given by:

• In IEEE 802.22 context– R=134.2 km: r=10km, NINT =45

Rrr

N INT1sin2

360

R r NINT

1 1 6.00

1 0.5 9.24

1 0.25 15.60

1 0.1 34.51

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Omni Directional Antenna at DTV Receiver• Interference effect due to a single WRAN BS with radius = 10 km

– Assume forward link interference from the WRAN system

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doc.: IEEE 802.22-07/0254r0

Submission

Omni Directional Antenna at DTV Receiver

• First cut at the analysis– Subsequent analysis will consider directional ATSC

antennas

• Calculate interference due to different WRAN radius– Small WRAN radius results in more WRAN cells fit

around the ATSC noise protected contour

– More WRAN cells results in more interference

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doc.: IEEE 802.22-07/0254r0

Submission


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doc.: IEEE 802.22-07/0254r0

Submission


• A distance y of 18.26 km is sufficient to guarantee that there will not be any interference at the DTV receiver.

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doc.: IEEE 802.22-07/0254r0

Submission

Results using ITU Curves

• The previous results were obtained using simple path loss models

• We will now apply the ITU curves and employ the directional antennas at the DTV receiver

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doc.: IEEE 802.22-07/0254r0

Submission


• The performance is better than the simple path loss model but the aggregate interference reduces the D/U ratio at the DTV receiver– Performance of the DTV receiver can be increased

by increasing the existing keep-out region by additional 1 km (See next page)

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doc.: IEEE 802.22-07/0254r0

Submission


May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Results using ITU Curves• Distance y = 17.1 km

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

Results using ITU Curves• Distance y = 18.1 km

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doc.: IEEE 802.22-07/0254r0

Submission

Conclusions• A simple method to analyze the aggregate

interference• The aggregate interference depends on the

radius of the WRAN. – Smaller WRAN radius results in larger interference

– Similar effect was seen when using the ITU curves and directional antenna

• As a recommendation the keep-out radius should be a function of the WRAN radius.– Larger WRAN radius results is less interference

compared to smaller radius for the same fixed EIRP

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doc.: IEEE 802.22-07/0254r0

Submission

Next Steps

• Add a directional antenna model for ATSC receiver

• WG to discuss best method of modeling aggregate interference– Typical WRAN cell size

– What is likelihood of multiple WRAN cells operating on the same channel

– Should aggregate interference be considered in keep-out region calculations

May 2007


doc.: IEEE 802.22-07/0254r0

Submission

References

1. Steve Shellhammer, Victor Tawil, Gerald Chouinard, Max Muterspaugh and Monisha Ghosh, Spectrum Sensing Simulation Model, IEEE 802.22-06/0028r10, August 2006

doc.: ieee 802.22-07/0254r0 submission may 2007 sai shankar n qualcommslide 1 aggregate interference...

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