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“There is a demonstrable need in the United States for use of the TETRA standard,” said the request. “While a number of manufacturers stand ready to produced TETRA-based devices in this country, a waiver of the FCC rules is necessary to make this technology available.”
The association seeks a waiver of Section 90.209(b)(5), authorizing operations at an occupied bandwidth of up to 21.5 +/- 0.5 kHz. The filing said TETRA marginally fails the Part 90 occupied bandwidth requirement. TETRA employs adaptive selection of modulation and coding according to propagation characteristics, and there are agreed upon schemes for links at the edge of coverage (4 QAM), moderate speeds (16 QAM), high speeds (64 QAM) and common control channel (II/4 DQPSK). Channel bandwidths can be 25, 50, 75 or 100 kilohertz. The European Telecommunications Standards Institute (ETSI) TETRA standard does not set occupied bandwidth limits. Rather, it sets standards for adjacent channel power and for unwanted emissions at different offsets.
The TETRA Association also requested a waiver of the rules governing emissions masks B, C, and G in Section 90.210 to allow for up to 5 dB excursions. The filing said the TETRA standard comes close to meeting but does not meet the Part 90 emissions mask requirements. The standard does not establish channel bandwidth limits via emission masks, but rather sets standards for adjacent channel power and for unwanted emissions at different offsets. Three Part 90 emissions masks are considered appropriate for TETRA technologies: masks B, C and G. TETRA just fails to meet the Part 90 requirements by up to 5 dB around 10 kilohertz offset from the center frequency, typically somewhere in the range 8 – 12 kilohertz.
The filing also seeks a waiver of the FCC’s permissive change rules to allow TETRA manufacturers that have received interim equipment authorizations using a modified TETRA standard to upgrade to the TETRA standard without requiring a new application or FCC ID.
As an interim measure, certain TETRA manufacturers are seeking FCC certification of radios using a modified TETRA standard — essentially reducing power to levels that will permit compliance with existing Part 90 rules. This is being done to meet critical, immediate demand for TETRA-style radios while the waiver request is being processed. Assuming that the waiver request is granted, the effected manufacturers will modify the radios produced using the interim standard to make them consistent with the worldwide TETRA standard.
Generally, the FCC does not allow certain changes to certificated equipment, including changes to the maximum power, without application and authorization of new grant of equipment certification. Finally, the association seeks a waiver of this rule to allow the TETRA manufacturers that have received authorizations for interim TETRA equipment, as described above, to upgrade to standard TETRA upon grant of this waiver request without having to go through the process of filing new equipment authorization applications and requesting new FCC ID numbers. The group said granting the request would serve the public interest, ensuring that both manufacturers and FCC staff will not have to undergo the equipment certification process twice.
The association attached an analysis of the potential performance of TETRA equipment in the United States. Using adjacent channel power ratio (ACPR) to measure the quantification of interference, the analysis demonstrates that TETRA offers adjacent channel protection that is no poorer than, and often better than, other narrowband systems currently operating in the LMR bands.
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