1. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 1 Aggregate Interference at DTV Receiver Date: 2007-05-14 Authors: Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org.patcom@iee.org >

2. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 2 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

3. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 3 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

4. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 4 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….

5. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 5 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 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

6. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 6 Determination of Number of Interferers To do this we resort to Pythagoras theorem –We need to determine theta –Theta is give by: Compare it with our and competitive technology

7. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 7 Determination of Number of Interferers Number of Interferers is given by: In IEEE 802.22 context –R=134.2 km: r=10km, N INT =45 RrN INT 116.00 10.59.24 10.2515.60 10.134.51

8. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 8 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

9. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 9 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

10. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 10 Omni Directional Antenna at DTV Receiver

11. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 11 Omni Directional Antenna at DTV Receiver A distance y of 18.26 km is sufficient to guarantee that there will not be any interference at the DTV receiver.

12. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 12 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

13. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 13 Results using ITU Curves 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)

14. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 14 Results using ITU Curves

15. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 15 Results using ITU Curves Distance y = 17.1 km

16. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 16 Results using ITU Curves Distance y = 18.1 km

17. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 17 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

18. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 18 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

19. doc.: IEEE 802.22-07/0254r0 Submission May 2007 Sai Shankar N QualcommSlide 19 References 1.Steve Shellhammer, Victor Tawil, Gerald Chouinard, Max Muterspaugh and Monisha Ghosh, Spectrum Sensing Simulation Model, IEEE 802.22-06/0028r10, August 2006