National Weather Service 1 Results of Operational Compatibility Studies between ASR, Meteorological Radars and IMT Systems Operating in the – MHz Band Presented By: Robert Leck NOAA’s National Weather Service (QSS Group Inc. for NOAA/NWS) January 2007

National Weather Service 2 ARS and Meteorological Radars Overview Meteorological Radar Frequency Band Meteorological Radar Coverage ASR Coverage MHz Band Utilization

National Weather Service 3 Overview The MHz Band is used on a global basis by both ASR and meteorological radars NOAA operates a wide network of meteorological Radars. Interference to meteorological radars from IMT systems degrades the radars performance. Simulations verify potential problems and establish if compatibility between systems is possible.

National Weather Service 4 ASR and Meteorological Radar MHz Band Radio Regulations Footnote In the band MHz, ground based radars used for meteorological purposes are authorized to operate on a basis of equality with stations of the aeronautical radionavigation service.

National Weather Service MHz Band Utilization NOAA NWS NEXRAD Network

National Weather Service MHz Band Utilization FAA Radar Network

National Weather Service MHz Band Utilization Current Radar and Potential Base Station Deployment ASR Radar Deployment Meteorological Radar Deployment Typical Base Station Deployment

National Weather Service MHz Band Utilization RF Survey Frequency Domain Representation of the MHz Band within an Urban Environment (Los Angeles, California)

National Weather Service 9 Meteorological Radars Base Products Interference Criteria Effects of Interference Upon Radar Performance

National Weather Service 10 Meteorological Radar Base Products Modern meteorological radars measure reflectivity, velocity and spectrum width – Reflectivity: return signal level used to measure total water in sample volume – Velocity: measure of speed and direction of movement of the atmosphere – Spectrum Width: measurement used to determine turbulence and wind shear

National Weather Service 11 ASR and Meteorological Radar Interference Protection Criteria The ITU-R has established an I/N of -10 dB for ASR and meteorological radars. (ITU-R Recommendation M.1464) Additional testing to determine if an I/N of -14 dB can be justified is being planned for 2007.

National Weather Service 12 Effects of Interference on Radar Performance Presence of interference: – Raises the radar noise floor making it less sensitive to very weak return signals – Increases intensity of reflectivity measurement resulting in overestimation of atmosphere moisture content and rainfall – Corrupts base data products used for measuring wind – velocity, turbulence, wind shear, and tornado detection

National Weather Service 13 Example of Interference on Radar Operations No Interference Interference

National Weather Service 14 IMT Systems What is IMT ?

National Weather Service 15 What is IMT? IMT encompasses both IMT-2000 and IMT-Advanced Systems – Intended to provide seamless worldwide mobile – telecommunications (voice and high speed data) – Use one band plan worldwide – Use a common radio standard for worldwide mobility Worldwide compatibility standards development being led by ITU Seeking spectrum in various frequency ranges including the 1-3 GHz range

National Weather Service 16 Simulations Study/Simulation Objectives Simulation Criteria IMT Cell Topologies

National Weather Service 17 Study/Simulation Objectives To combine and summarize the results of several different studies regarding sharing of the – MHz band between various radar (ASR and meteorological) and IMT systems. To conduct new simulations that provide insight into the feasibility of sharing the – MHz band between ASR and meteorological radars and IMT systems. Based upon the results of those studies, develop conclusions regarding the compatibility of those systems when jointly operated within the MHz band.

National Weather Service 18 Simulation Criteria The simulation was conducted using propagation characteristics and terrain modelling simulations that were based upon a software implementation of ITU Recommendation ITU-R- P IMT system characteristics were taken from ITU Recommendation ITU-R M.2039 Radar characteristics were taken from ITU Recommendation ITU-R M.1464 and ITU-R M.1461

National Weather Service 19 Simulation Criteria The simulations were configured to closely approximate the operation of the radar. IMT topologies included macro, micro and pico cell deployments. The predominant interfering element in an IMT network is the IMT base station.

National Weather Service 20 Simulation Criteria The interference simulations were run under two scenarios. – The first scenario had the radar placed at the edge of the cell coverage area. – The second scenario varied the distance from which the radar was offset from the cell coverage area.

National Weather Service 21 Macro Cell Topology 75 km Separation Distance Radar Service Area Radar is Offset from a Macro Cell Service Area

National Weather Service 22 Micro Cell Topology Separation Distance d 10 km Radar Service Area Radar is offset from Micro Cell Service Area

National Weather Service 23 Pico Cell Topology Radar is offset from Pico Cell Service Area Separation Distance d Radar Service Area

National Weather Service 24 Simulation Results Meteorological IMT to Meteorological Radars Meteorological and Airport Surveillance Radars to IMT Systems Meteorological Multiple Meteorological and Airport Surveillance Radars to IMT Systems Conclusions

National Weather Service 25 Simulation Results IMT to Meteorological Radars

National Weather Service 26 Simulation Results IMT to Meteorological Radars Results have shown that a minimum separation distance of 500 km between Meteorological radars and IMT networks is necessary to protect radar operations – Even with separation distances in excess of 500 km, the meteorological radar I/N Protection Criteria as defined by the ITU cannot be met. Studies have shown that interference from IMT macro, micro and pico based topologies within the – MHZ band will impair Airport Surveillance Radars and Meteorological radar operations.

National Weather Service 27 Interference from radar pulses has the potential to degrade IMT receiver performance via a number mechanisms including – LNA overload – Saturation of the automatic gain control (AGC) – Interference to signal ratios beyond the dynamic range of the analog to digital converter (ADC) – Filter overload – Mixer overload. Simulation Results Meteorological and Airport Surveillance Radars to IMT Systems

National Weather Service 28 Simulation results showed co-channel operation interference can occur even with large separation distances between Airport Surveillance Radars, Meteorological Radars and IMT systems. Simulation Results Meteorological and Airport Surveillance Radars to IMT Systems

National Weather Service 29 Simulation Results Meteorological and Airport Surveillance Radars to IMT Systems The ITU specified interference protection criteria for IMT Base stations was shown to always be exceeded at distances below 100 miles 1. Simulations indicated that widespread jamming of mobile and base station units would take place within the operational range of the radars. (1) Propagation effects (multipath, fading, terrain, etc.) could result in received signal levels from the radar that are higher than those predicated by path loss extending this distance even further.

National Weather Service 30 Simulation Results Multiple Meteorological and Airport Surveillance Radars to IMT Systems The LNA in the handset will, at times, be operating at or above its 1 dB compression point. – This will result in the potential desensitizing of the IMT receiver and loss of service. Base and Mobile station receiver LNA's can, at times, be subjected to high levels of RF energy. – These levels can damage sensitive components in the base and mobile station receivers, effectively disabling multiple service areas.

National Weather Service 31 Potential IMT System Degradation Loss of service Dropped calls Damage to sensitive receiver electronics Poor quality of service Limited deployment potential

National Weather Service 32 Conclusions IMT to Meteorological and Airport Surveillance Radars RF emissions from IMT transmitters would necessitate separation distances in excess of 500 km in order to ensure that radar receiver protection criteria are not exceeded. Meteorological Even if large separation such distances could be tolerated, regions in which sharing could take place would be severely limited due to the widespread geographical deployment of multiple Meteorological and Airport Surveillance Radars..

National Weather Service 33 Conclusions Meteorological and Airport Surveillance Radars to IMT Systems Radar signals, when present at the input to the IMT receivers, can overload the receiver resulting in loss of service or, in some instances, damage to the base station and or mobile unit. – Even if the IMT service were offset in frequency from one radar system, the IMT systems would still be interfered with by other radar systems operating at different frequencies throughout the band. IMT receivers would be jammed, disabled or damaged by the aggregate RF effect of the radar systems operating in that band.

National Weather Service 34 Conclusions Meteorological and Airport Surveillance Radars to IMT Systems Current IMT interference mitigation techniques would not protect the IMT mobile or base station receivers from high power radar signals. In scenarios where the band use is limited to uni-directional (Base Station to Mobile Station) transmissions only, the separation distances required to protect the IMT receivers would make the deployment of such a network impossible due to the effect of the interference from the radars into the IMT mobile stations.

National Weather Service 35 Conclusions MHz Band Utilization Studies have shown that IMT systems cannot operate with radars in the same band. IMT operation in MHz will place unacceptable operational restrictions on meteorological radar operations and result in detrimental interference to the radars. IMT receivers would be jammed, disabled or damaged by the aggregate RF effect of the radar systems operating in that band. The required separation distances for sharing of the band preclude the effective deployment of IMT systems. The overall results of the study show that sharing of the – MHZ band with IMT systems is not feasible.

National Weather Service 36 Recommendation That IMT systems not operate within the same geographical region[1] as Airport Surveillance and Meteorological radars[1] [1] For purposes of this recommendation the same geographic area is defined as within a 500 km radius of a radar operating in the MHz band.

National Weather Service 37 Thank You !