FCC: TETRA Authorization is Coming to Public Safety

The FCC released a Notice of Proposed Rule Making and Order Tuesday to modify rules permitting the certification and use of Terrestrial Trunked Radio (TETRA) equipment.  TETRA is spectrally efficient digital technology, but it does not comply with all Part 90 technical rules.  The TETRA Association (the Association, comprised of 150 organizations from 35 countries) recently filed a request for waiver for the Part 90 rules on occupied bandwidth limit, to allow implementation of TETRA technology in the United States.  Pending the outcome of the rulemaking proceeding, the Commission has granted the waiver request in part. 

The Association asserted that Part 90 technical rules were developed originally for analog equipment and technology.  Because digital technology operates more efficiently than analog, the rules are not always appropriate for digital technologies, therefore they should neither be applicable. 

TETRA offers a digital, trunked radio solution that operates with Time Division Multiple Access (TDMA) in four-slot channels utilizing 25 kHz bandwidth.  In a request filed in 2009, the Association held that:

• The TETRA standard (developed by the European Technical Standards Institute, or ETSI) is currently used worldwide, in coexistence with other technologies.
• Manufacturers are prepared to distribute interoperable TETRA devices in the United States, on various frequency bands.
• TETRA technology is more efficient, secure, and interoperable than alternative solutions.

TETRA's efficiency allows the devices to operate on 25 kHz of bandwidth, but without causing harmful interference to adjacent channels.  The ETSI standards set limits for adjacent channel power and unwanted emissions at different frequency offsets.  Despite concerned comments from filers stating TETRA causes interference, the Association has demonstrated research to the contrary.  The waiver request was accompanied by a TSB-88 analysis of the adjacent channel power ratio (ACPR) of a TETRA signal with a typical receiver, which indicated a lower interference potential from the TETRA signal. 

Although the waiver has been granted in part and under specificed conditions, the Commission agreed with commenters in the aspect that permanent authorization of TETRA technology must be achieved through the rulemaking process.  Therefore, the Commission has formally requested comment on multiple issues surrounding their rulemaking decision.