Now that it’s had time to review the details, the Bluetooth Special Interest Group (SIG) says it has a number of concerns when it comes to Globalstar’s revised proposal to use 11.5 megahertz of licensed mobile satellite service (MSS) spectrum for low-power terrestrial broadband services.
When it announced the revised proposal earlier this month, Globalstar said it “should resolve all remaining interference-related concerns in this proceeding,” as well as policy issues related to use of the 10.5 megahertz of unlicensed ISM spectrum. At the time, the Bluetooth SIG said while the new proposal appeared to eliminate any special rules for Globalstar, it was still evaluating whether the new proposal resolved interference concerns or raised new ones.
Their evaluation did indeed unearth more concerns. “The revised proposal suggests using 2 different specifications for out of band emissions (‘OOBE’), one for the top of the band at 2495 MHz and a completely different one for the bottom of the band at 2483.5 MHz,” Bluetooth SIG Executive Director Michael Powell wrote in a Nov. 22 filing (PDF) with the commission. “We are also concerned that the specifications proposed for these OOBE would result in swamping the receivers of devices particularly at the proposed 6dBW power level. In addition it is concerning that no specific technology has been identified for operation, which makes it difficult to properly assess the technical issues.”
”Shouldn’t the same specification be used at both ends of the band? Shouldn’t both blocks of adjacent spectrum be protected in the same way? The Bluetooth SIG’s view is that the proposal be revised so that there is a single specification for OOBE equally protective of spectrum below 2483.5 MHz as it is protective of spectrum above 2495 MHz,” Powell wrote in the filing.
That’s not the only issue, however. Because Globalstar’s not identifying the technology that it plans to deploy, “the precise specification of any OOBE mechanism asserting to appropriately protect the users of adjacent spectrum cannot be confirmed,” Powell wrote. “While we have not completed our technical investigations, what we have learned so far is that a transmission in the 2483.5-2495 MHz band at a 6dBW power level would produce sufficiently high OOBE to affect users of spectrum at the top end of the ISM band.”
The Wi-Fi Alliance, which also objected to Globalstar’s previous proposal, said in its Nov. 22 filing (PDF) that the revised plan appears, on its face, to alleviate many of the interference concerns that the alliance expressed. However, it still has some concerns as well, saying, for example, that Globalstar needs to submit into the record the precise rules that it would like to see adopted.
“The Commission should ensure that Globalstar does not ‘bond’ or ‘aggregate’ its spectrum with frequencies below 2483.5 MHz in an attempt to provide a combined ATC [Ancillary Terrestrial Components]/Part 15 service,” wrote Wi-Fi Alliance CEO and President Edgar Figueroa. “Allowing bonded or aggregated service will eliminate the beneficial components of Globalstar’s proposal and effectively permit the provision of service in a way to which Wi-Fi Alliance and others objected. The Commission can prevent that from occurring by clarifying that any service Globalstar offers conform to the provisions of Sections 15.205 and 15.209 of the rules.”
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Globalstar had originally petitioned the FCC in 2012 for the ability to use its satellite spectrum to offer a terrestrial low-power service (TLPS), which it said would be in the public interest, but critics said it would end up interfering with Bluetooth and Wi-Fi devices, a charge that Globalstar consistently denied. But in order to get something moving on the matter, Globalstar earlier this month introduced the revised plan in an attempt to eliminate objections.
The Wireless Internet Service Providers Association (WISPA) is one entity that has since tempered its objections. The organization said that by narrowing Globalstar’s earlier proposal to confine TLPS to licensed spectrum at 2483.5-2495 MHz, WISPA’s interference concerns were addressed.
The Bluetooth SIG plans to complete its investigation and post results in the record. But in the meantime, it doesn’t want regulators to proceed with undue haste. “It makes no sense to have different OOBE specifications, neither of which may be sufficient to protect ISM band users from a relatively high power level proposed,” the group said. “Nor does it help to not know which technology is proposed to be deployed.”