Meteorological Radar Radio Spectrum Issues Presented by: David Franc U.S. National Weather Service October 8, 2002

2 Meteorological Radars This section of the workshop covers ground-based radars used or monitoring the atmosphere with the exception of wind profiler radars

3 Outline Bands for meteorological radar operations Interference protection criteria Effects of interference Proposed changes to bands used by meteorological radars –IMT-2000 in MHz –New allocations to multiple services in MHz Strategy to defend meteorological radar spectrum requirements

4 Purpose of Briefing The information contained in this briefing is intended to prepare workshop participants with necessary information on meteorological radar issues to interact with their representatives to ITU meetings and conferences The information presented is consistent with WMO views of the subject matter and promotes protecting meteorological operations The information does not necessarily reflect the positions of the United States

5 Meteorological Radar Bands Three allocations exist in the Radio Regulations specifically for meteorological radars – MHz- ground based radars – MHz- ground based radars – MHz- ground based and airborne radars Allocation by footnote Depending on type of use, aeronautical radionaviagtion and radiolocation bands can also be used

6 Meteorological Radar Bands MHz 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

7 Meteorological Radar Bands MHz Radio Regulations Footnote Between 5600 and 5650 MHz, ground based radars used for meteorological purposes are authorized to operate on a basis of equality with stations of the maritime radionavigation service

8 Meteorological Radar Bands MHz Radio Regulations Footnote The use of the band MHz by the aeronautical radionavigation service is limited to airborne weather radars and ground-based radars. … In the band MHz, ground-based radars used for meteorological purposes have priority over other radiolocation services.

9 Comparison of The Bands System Cost: Highest MHz Lowest MHz System Complexity: Highest MHz Lowest MHz Operating Distance:~450 km MHz <200 km MHz <75 km MHz Severe Weather Highest MHz Performance:Lowest MHz

10 Comparison of The Bands (cont) System cost, complexity and operating range are all limitations that can be addressed through additional engineering and funding Severe weather performance is a physical limitation that can not be addressed through additional engineering or funding

11 Comparison of the Bands Severe Weather Performance The ability of a meteorological radar to measure high wind speeds at its outer operational range is limited by the frequency of operation. v * r 1/f Therefore, as frequency increases, the maximum range or maximum observable velocity, or both must decrease. Maximum velocity Maximum range Frequency

12 Meteorological Radar Interference Protection Criteria Interference Protection Criteria: The highest interference level that does not degrade the system performance beyond performance requirements

13 Interference-to-Noise Ratio I/N is specified as a interference signal level relative to the radar noise floor Interference is added to receiver noise to produce a higher noise + interference level Higher noise + interference level masks and corrupts weak but vital returns

14 Meteorological Radar Interference Protection Criteria The ITU-R has historically used I/N= -6 dB for meteorological radars Discussions have been held in the ITU during the last year on making the criteria more stringent –Proposals for I/N = -10 dB… no technical basis provided –U.S. has proposed a value of –14 dB should be used for MHz radars… based on testing –Testing is still required for MHz and MHz

15 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

16 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 detection tornadoes

17 Example of Interference on Radar Operations No InterferenceInterference

Proposed Changes to Frequency Bands Used for Meteorological Radar Operations MHz MHz

MHz and IMT-2000 In 1999 the ITU-R identified the band MHz as a candidate expansion band for IMT-2000 –WRC-2000 considered proposals to create a mobile service allocation in the band for use by IMT-2000 –WRC-2000 concluded insufficient technical studies had been complete to support the proposed allocation –WRC-2000 created a preliminary agenda item for WRC-05/06 –Studies have been ongoing in the ITU-R to evaluate compatibility between meteorological radars and IMT-2000

20 WRC-05/06 Agenda Item Agenda Item 3.1:to consider results of ITU-R studies on the feasibility of sharing in the band MHz between the aeronautical radionavigation service, meteorological radars and the mobile service, and to take appropriate action on this subject;

21 What is IMT-2000? Also known as 3G: Third Generation Mobile Telecommunications 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 the 1-3 GHz range

22 Background: MHz and IMT-2000 Two ITU Working Parties involved –Working Party 8B: Represents radar interests –Working Party 8F: Represents IMT-2000 interests Preliminary studies showed the two systems are not compatible –Co frequency operation would result in harmful interference –Radars would have to be removed from the band if it were to be used for IMT-2000

23 Current Work: MHz and IMT-2000 More in-depth studies are underway for evaluating compatibility –Some studies show separation distances as great as several hundred km are required to prevent interference –Other studies show some IMT-2000 systems can withstand radar interference but do not address interference into the radars Support of this proposed use is decreasing The CPM Report (Ch. 7) to WRC-03 states that studies show incompatibility and WRC-03 may consider deleting the WRC-05/06 agenda item

24 Last Working Party 8F Meeting: September 25 - October 2 At the last Working Party 8F meting a decision was made to suspend any further studies in WP 8F until WRC-03 confirms or suppresses the WRC-05/06 agenda item on MHz –If agenda item is suppressed WP 8F will discontinue work indefinitely –If agenda item confirmed, WP 8F will restart work on the compatibility studies

25 Working Party 8B Work on MHz Independent of the final decision taken by WRC-03 on the agenda item for WRC- 05/06, Working Party 8B will continue general compatibility work between meteorological radars and other radio services –Finalize radar protection criteria –Improve methodology for evaluating compatibility with radars

26 Working Party 8B Work on Protection Criteria Working Party 8B approved a revision of ITU-R Recommendation M.1464 at its most recent meeting –Revision changes the meteorological radar protection criteria from a I/N = -6 dB to I/N = -14 dB based on testing –Revision of M.1464 will be on agenda for approval at February 2003 Study Group 8 Meeting

27 Near Future: MHz and IMT-2000 The Conference Preparatory Meeting (CPM) will review and possibly modify or delete the text in Chapter 7 of the CPM Report. WRC-03 will evaluate the need for the current agenda item on the WRC-05/06 agenda.

28 New Allocations in MHz WRC-2000 created a WRC-03 Agenda Item for possible allocation changes in the range MHz –Agenda Item 1.5: to consider, in accordance with Resolution 736 (WRC-2000) regulatory provisions and spectrum requirements for new and additional allocations to the mobile, fixed, Earth exploration- satellite and space research services, and to review the status of the radiolocation service in the frequency range MHz, with a view to upgrading it, taking into account the results of ITU-R studies.

29 What does Agenda Item 1.5 mean? ITU to conduct studies determining the effect of: –New and expanded allocations to mobile, fixed, Earth exploration-satellite and space research services –Upgrade of radiolocation service from secondary to primary status WRC-03 to consider creating new and additional allocations in the frequency range MHz WRC-03 to consider upgrading the radiolocation service to primary status

30 Potential Impact to Meteorological Radar Operations The radiolocation upgrade will probably have minimal impact since radiolocation systems already exist in the band on a secondary basis Introduction of fixed and mobile services could result in harmful interference to meteorological radars Introduction of Earth exploration satellite service and space research service will most likely have no impact on meteorological radar operations

31 Radiolocation Upgrade Radiolocation means radars… radars can generally share well with other radars The only potential problem is meteorological radars losing equal status with all other services in the band MHz per footnote –If radiolocation is upgraded to primary status, the words and radiolocation should be inserted in footnote 5.452

32 Introduction of Fixed and Mobile Services To be used for wireless access systems (WAS) such as wireless local area network (LAN) devices The level of interference to meteorological radars is dependent on WAS deployment and distance from radar –As density of WAS increases, interference levels increase –Devices close to radar will result in higher interference levels than devices at a large distance

33 Introduction of Fixed and Mobile Services (cont) There are proposals to use technology for the WAS to detect radar signals and avoid those frequencies… called DFAS. The ability of DFAS to reliably detect a radar is questioned by many –Radar signals are pulsed and the antenna is rotating making detection very difficult –Radars are not always in operation… DFAS could miss a radar going into operational mode

34 Introduction of Fixed and Mobile Services (cont) There is no way to control WAS deployment to prevent operation near a radar or at a high density

35 EESS and SRS Allocation The Earth Exploration Satellite Service and Space Research Service are seeking a primary allocation up to 5570 MHz The allocation for meteorological radars is MHz- does not overlap EESS and SRS proposals should not impact meteorological radar operations

Strategies for WRC-03 to Promote Protection of Meteorological Operations

37 Recommended Strategy for MHz IMT-2000 operation in MHz will place unacceptable operational restrictions on meteorological radar operations and result in harmful interference to the radars Encourage your CPM delegation to support retaining text in section 7.2 of the CPM Report Encourage your WRC-03 delegation to propose/support deleting the WRC-05/06 agenda item

38 Recommended Strategy for MHz (cont) The revision to ITU-R Recommendation M.1464 will be considered for adoption at the February Study Group 8 Meeting The revision tightens the protection criteria of meteorological radars in the band Encourage your Study Group 8 delegation to support adoption of Revised recommendation M.1464

39 Recommended Strategy for Agenda Item 1.15 ( MHz) Radiolocation upgrade should have little impact on meteorological radar operations with exception that footnote needs to now include a reference to the radiolocation service –5.452 Between MHz, ground based radars used for meteorological purposes are authorized to operate on a basis of equality with stations of the maritime radionavigation and radiolocation services

40 Recommended Strategy for Agenda Item 1.15 ( MHz) (cont) The EESS and SRS allocations should present no problems for meteorological radar operations EESS allocations often benefit meteorological operations Encourage your CPM delegation to support text in the CPM report favorable to creating the EESS and SRS allocations Encourage your WRC-03 delegation to support creation of the EESS and SRS allocations

41 Recommended Strategy for Agenda Item 1.15 ( MHz) (cont) WAS devices pose a significant risk to meteorological operations Encourage your CPM delegation to support CPM text that protects meteorological radar operations Encourage your WRC-03 delegation to only support allocation changes if meteorological radar operations are protected –No allocation to fixed and mobile services is best solution –Regulatory text ensuring protection of radars is an alternative

42 Recommended Strategy for Agenda Item 1.15 ( MHz) (cont) The necessary protection criteria for radars operated in this band should be studied and the ITU-R Recommendation should be modified –Current recommendation on met radars operated in MHz specifies an I/N = -6 dB –The value of -6 dB randomly selected based on other radars and not based on testing or analysis

43 Future Protection of Meteorological Radar Operations The ITU-R defines certain systems and radio services to perform safety-of-life functions The users of meteorological radars may wish to consider having meteorological radars classified as safety-of-life –Provides meteorological radars special consideration in cases where interference may occur