# Presentation: 661015

## GPS Re-Radiator Issues

- Dr. A.J. Van Dierendonck
- AJ Systems
- For the US GPS Industry Council

- GPS Re-Radiators

- 10-28-2005

## Topics

- Comments on commercial applications of Section 8.3.28 of NTIA Manual of Regulations and Procedures for Federal Frequency Management
- Suggested Regulatory Categories
- Possible Licensing Criteria for Commercial Entities

- GPS Re-Radiators

- 10-28-2005

## Comments on Section 8.3.28

- Section 8.3.28 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-Radiators

- 10-28-2005

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

- GPS Re-Radiators

- 10-28-2005

## 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-Radiators

- 10-28-2005

## 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-Radiators

- 10-28-2005

## Issues for Consideration when Licensing Commercial Entities

- GPS Re-Radiators

- 10-28-2005

## 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-Radiators

- 10-28-2005

## 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-Radiators

- 10-28-2005

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

- GPS Re-Radiators

- 10-28-2005

## Potential Impact on Non-Participating GPS Users fromRe-radiators in an Uncontrolled Environment

- E.g., using -140 dBm Re-Radiated Signal @ 100 Feet
- Multipath error based upon error envelope

- GPS Re-Radiators

- 10-28-2005

## 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 = 0.356
- 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-Radiators

- 10-28-2005

## 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

- GPS Re-Radiators

- 10-28-2005