GPS Re-Radiators1 GPS Re-Radiator Issues Dr. A.J. Van Dierendonck AJ Systems For the US GPS Industry Council

GPS Re-Radiators2 Topics Comments on commercial applications of Section of NTIA Manual of Regulations and Procedures for Federal Frequency Management Suggested Regulatory Categories Possible Licensing Criteria for Commercial Entities

GPS Re-Radiators3 Comments on Section Section provides US agencies and their contractors adequate means of using re- radiators in furtherance of USG requirements NTIA/IRAC rules and FCC experimental licensing achieves this goal Additional considerations are needed when authorizing commercial entities to operate GPS re-radiators

GPS Re-Radiators4 Proposed Regulatory Categories of Commercial Use of GPS Re-Radiators

GPS Re-Radiators5 Regulatory Category I Category I: Commercial Entities Having Controlled Public Access E.g., GPS industrial operations, universities, research institutes Operate re-radiators for test purposes In facilities having controlled public access Within a pre-determined zone to ensure no degradation of the public use of GPS FCC Part 5 experimental licenses only

GPS Re-Radiators6 Regulatory Category II Other commercial entities Do not operate re-radiators for test purposes Entities that are open to the public Within a pre-determined zone that requires additional mitigation to ensure no degradation to the public use of GPS Can this category be authorized? If mobile public use of GPS can be protected, then only as a Part 5 experimental authorization The Council is working with the re-radiator community on possible approaches to the licensing of this type of use At this time, however, the Council does not see how to adequately protect mobile GPS users in open access facilities from this category of re-radiators

GPS Re-Radiators7 Issues for Consideration when Licensing Commercial Entities

GPS Re-Radiators8 Impact of GPS Re-Radiators on GPS Users GPS Re-Radiators do not cause classical noise interference Except maybe in a rare case GPS Re-Radiators can cause multipath errors in non-participating GPS Receivers If re-radiator is not adequately controlled If the environment is not adequately controlled If power levels are not controlled, GPS re-radiators could cause loss-of-lock and capture GPS Receiver tracking loops

GPS Re-Radiators9 User Receiver Multipath Error Envelope (±0.5 Chip Spacing) Re-radiated signal amplitude = one- half direct signal amplitude in example Error proportional to ratio of amplitudes Multipath delay = Re-Radiator signal delay relative to direct signal

GPS Re-Radiators10 Re-Radiator/Non-Participating GPS User Operational Environment

GPS Re-Radiators11 Potential Impact on Non- Participating GPS Users from Re-radiators in an Uncontrolled Environment E.g., using -140 dBm Re-Radiated 100 Feet Multipath error based upon error envelope

GPS Re-Radiators12 Potential Impact … (cont’d) Error is proportional to ratio (  ) of re-radiated signal amplitude to desired signal amplitude Based upon nominal desired signal (-125 dBm),  = 0.178, so reduce error in chart by 0.178/0.5 = Total re-radiated signal delay  300 feet (0.3 C/A chips  0.3 microseconds) Results in an envelope error on the order of  50 feet This is a significant error that could occur in an uncontrolled environment

GPS Re-Radiators13 Proposed Commercial License Criteria for Category I FCC Part 5 Experimental License Application to include engineering analysis that can be used to evaluate impact on non-participating GPS users Variables include re-radiated signal power, range to possible GPS user, re-radiated signal delay at GPS user and, possibly, any re-radiated signal attenuation, natural or added Multipath errors can then be evaluated and above variables could be modified until errors are below a specified level If error criteria can be met with a reasonable re- radiator/GPS user environment, license could be granted