1 RLAN and C Band Weather Radar Interference Studies* Paul Joe 1, John Scott 1, John Sydor 2, Andre Brandao 2, Abbas Yongacoglu 3 1 Meteorological Service of Canada, 2 Communications Research Centre, 3 University of Ottawa *Study supported by Industry Canada

2 Outline ITU Resolution R 229 RLANs and RLAN signal The Experiment (Internal, External) Simulation of RLANs in Urban Environment Radar Examples Summary

3 International Telecommunication Union World Radiofrequency Conference 03 RESOLUTION 229 [COM5/16] (WRC-03) Use of the bands MHz, MHz and MHz by the mobile service for the implementation of wireless access systems including radio local area networks

4 ITU-R Resolution 229 / WRC03 (highly condensed and edited) MHz allocated on a primary basis to WAS, RLAN MHz is allocated on a primary basis to the radiodetermination service; MHz, ground-based meteorological radars are extensively deployed and support critical national weather services Must protect existing primary services Dynamic Frequency Selection (DFS) for mitigation by RLAN

5 Experimental Setup RLAN TX DFS Detector Collaborative study with Industry Canada/Communication Research Centre; Previous work was theoretical, simulations Inject RLAN signals directly into the radar receiver to determine effect on weather radars of different power outputs, modulations Introduce RLAN signals in a “typical” rural/urban environment taking into propagation and terrain effects (not comprehensive) Simulations

6 RLAN Spectrum Single packet (Agilent signal generator) 18 MHz and many peaks 10 channels of 18 MHz wide for RLAN (5625 MHz)) Compared to 1MHz wide for radar ( MHz) RLAN looks like white noise to the weather radar – no preferred frequencies within 18 MHz RLAN are Wireless LANs using Radiofrequencies Send sequence of information packets; typical 750 usec in length; 18 MHz bandwidth, 30 dBm erip Point to point or isotropic

7 Input of signal processor Propagation compensated - predetermined Packet Modulations Frequency Test Interference Modes Off-Axis Backscatter Direct

8 Dynamic Frequency Selection RLAN Mitigation Strategy DFS – a device to detect weather radar interference and shift DFS detects weather radar, must vacate channel for 30 minutes and then can use frequency immediately again (and interfere). Q: Sensitivity, reaction time? Channel vacate algorithm is unknown? Canadian proposal on the channel visit algorithm: additional 10 minutes of monitoring (without transmission) before using the channel. Proposal led by Industry Canada. Otherwise, intermittent (mutual) interference every 30 minutes. Adopted in several jurisdictions. Sensitivity Range of DFS to weather radar DFS detector can see weather radar easily! (not shown)

9 RLAN Simulation Urban Environment What happens with a network of RLANS? Distribution of RLANS Remaining RLANS with DFS ITU specification of distribution. King City/Toronto – worse case in Canada Theoretical simulations used London UK. One Realization of a monte carlo simulation

10 Effect of Network of RLANS on the Weather Radar as a function of the DFS Detection Threshold MDS of Wx Radar DFS Sensitivity 0.65 o beamwidth antenna has greater sensitivity 1.0 o beamwidth antenna sees more RLANS DFS must have at least this detection sensitivity

11 Low Level PPI of RLAN Interference Example for RLAN at 500m and 10 km 500 m 10 km

12 RHI’s through the Intereference Example for RLAN at 500m and 10 km 500 m 10 km

13 Sidelobe Detection 4.1 o elevation Main Sidelobe

14 Cross-section Perpendicular to Radial/Beam Pattern

15 RLANS and the King City Environment RLANS are licensed now! Non-licensed use in the future! Artifacts are out of band RLAN interference radar is very sensitive Radar rx needs to filter 24 hr Rainfall Accumulation

16 Summary Spectrum sharing is the reality Must adopt collaborative mitigation strategies  10 minute additional monitor without transmit strategy in DFS  Filtering out of band in wx radar (tx/rx) Experiments show RLAN as white noise and manageable (for now) Simulations show that DFS will mitigate RLANS  Urban sprawl may change the situation;  Increased use of RLAN’s and… DFS can see weather radar  No commercial DFS’ yet, Specification enforcement?,  Non-licensed, No import restrictions  Vacate algorithms unknown? Other frequencies at risk too; particularly passive microwave Ultrawideband next, support your ITU rep – communications, avoidance radars Lightning, UAV not even considered yet