Ligado Says Testing Shows that LTE Network Won’t Interfere with GPS

Testing commissioned by Ligado Networks LLC (formerly LightSquared) shows that LTE signal levels agreed to by Ligado will not impact GPS user performance for tested Garmin International, Inc., Samsung Electronics, and Motorola Solutions, Inc., devices, Ligado and its engineering consultants told reporters.  Ligado submitted the test results from its engineering consultant, Roberson and Associates LLC, to the FCC late yesterday. The company shared the results with representatives of the Department of Transportation, Department of Defense, and National Telecommunications and Information Administration during a Feb. 5 meeting at the Roberson and Associates testing lab in Herndon, Va.

 Roberson and Associates launched the testing last year and modified its work in the wake of spectrum use agreements that Ligado reached with GPS companies Garmin, Trimble Navigation Ltd., and Deere & Company. Under the spectrum use agreements, Ligado has agreed to reduced power levels and out-of-band emissions limits to protect GPS operations in adjacent bands. It has asked the FCC to modify its licenses to conform with the agreements (TRDaily, Jan. 4).

The test results discussed today were released in response to a question by a DoT representative at a Jan. 11 meeting about whether the operational limitations that Ligado has agreed to “were in fact protective of Garmin’s consumers,” noted a Ligado cover letter submitted yesterday in IB dockets 12-340 and 11-109 with the test results.

 The results covered testing on seven Garmin devices, a Motorola public safety laptop, and the Samsung Galaxy S5 and S6 smartphones. The following bands were tested: 1526-1536 megahertz, 1627.5-1637.5 MHz, 1646.5-1656.5 MHz, and 1670-1680 MHz.

 Ligado stressed in its cover letter that the results show that (1) “[t]he Garmin and non-Garmin general navigation devices tested showed no degradation in performance at the operating levels contained in the settlement agreements and reflected in the license modification applications;” (2) “[s]martphones tested showed no degradation, and in fact have become more resilient over time;” and (3) “the metric the DoT has proposed to use in its testing of adjacent bands—a 1 dB rise in the carrier to noise ratio (the ‘1 dB proposal’)—is fatally flawed because it does not accurately predict impact of adjacent band signals on GPS device positioning performance.

“Indeed, the testing demonstrated that average carrier to noise ratio value reported by the receiver (averaged over all GPS satellites) showed small, random variations that can exceed 1dB in the absence of adjacent band signals,” Ligado added.

 “Preliminary results from other testing are consistent with these results for Garmin devices, and the RAA [Roberson and Associates] testing and analysis is entering the final phase,” Ligado said in its cover letter. “We expect to share the complete results and analysis from the testing as necessary and appropriate.”

 Ken Zdunek, Roberson and Associates’ chief technology officer, said during a call with reporters this afternoon that the testing of the 28 total devices is nearly complete and that the company is now analyzing “a mountain of results.”

 “There was a lot of skepticism … when we filed the original test plan back in the later summer … about the ability to test GPS adjacent-band performance with user performance metrics, and specifically we’re talking about position error,” he said.  “I think we’ve definitely answered the question.”

 Gerry Waldron, an attorney for Ligado, told reporters that he is not sure when the analysis of the testing on the remaining GPS devices, including those of Trimble and Deere, might be completed. He hedged when asked whether Ligado plans to release all the raw test results, while stressing that it has offered the results discussed today to DoT and GOP companies. Mr. Waldron said that Ligado wants the FCC to issue a public notice soon seeking comments on the license modifications, but he said it does not know when the agency will do that. “In that context, we expect to share … the helpful data that will give the policymakers the information they need,” he said.

 When asked if the company planned to release all of the raw data, he replied, “I’m not prepared to address that today.” But he added, “I think we have been as transparent and open as any person in this saga, frankly, over the years in terms of showing exactly what we’re doing and how we’re doing it.” He finally said that if the FCC wants all the results submitted into the record, Ligado would do so.

 Mr. Waldron was also asked how the test results discussed today compare with any results of testing done under existing operating parameters, rather than the reduced levels agreed to by Ligado in its agreements with Garmin, Trimble, and Deere.

 “We actually don’t think it’s sort of a very interesting point,” he replied, adding that Ligado is obligated by contract to operate under the new parameters and noting it has asked the Commission to modify its licenses consistent with those levels.

 Garmin did not respond to a request for comment today on the Ligado results. – Paul Kirby,

Courtesy TRDaily