SpectrumTalk

Interesting Waiver Request
in 900 MHz ISM Band
Out for Public Comment

On March 26, The FCC's Office of Engineering and Technology released a public notice asking for comment on a pending waiver request. Often these requests are not put out for comment, but this one must have crossed the threshold for seeking input.

The PN summarizes the issue as follows:

Starkey Laboratories, Inc., (“Starkey Laboratories”) has filed a request for waiver of Part 15 of the Commission’s rules to permit a reduction in the 6 dB-bandwidth requirements under Section 15.247(a)(2) for unlicensed operation of systems using digital modulation techniques in the 902-928MHz (915 MHz) band. Starkey Laboratories states that its proposed system would facilitate audio enhancement capabilities for the hearing impaired via the use of digital audio equipped assistive listening devices (“ALDs”).

In a waiver request filed 11/12/08 by former FCC Commissioner Gloria Tristiani, Starkey asserts that it "has made a significant investment in low power RF communication devices ('low power devices') in the 902 to 928 MHz ISM band." Starkey seeks to sell advanced hearing aids with 2-way capabilities and say it can not do so in the existing 217 MHz band used for communications with hearing aids without the following rule changes:

Allow two-way voice and data communication;
Increase the occupied bandwidth up to 300 KHz;
3 MHz total bandwidth;
Max power spectral density of = 6 dBm/10 kHz; and
Max power of +20 dBm (This is no change from the present max power).

Instead of doing this, Starkey seeks a waiver of the ISM band spread spectrum rules, 15.247, to permit bandwidths of 100 kHz as opposed to the current minimum of 500 kHz while retaining the same power spectral density limit of 8 dBm/3 kHz (15.247(e)).

The request states

By granting the waiver Starkey Laboratories host devices will use a narrower bandwidth than the minimum bandwidth required under 15.247 thus reducing potential interference.

Readers are encouraged to review this and tell FCC whether they agree with this statement. If 902-928 MHz 15.247 devices were all operating at the maximum permitted power, then the 8 dBm/3kHz limit of 15.247(e) would be the determining factor in interference. However, I suspect that most operate at lower power due to battery limitations and RF safety/SAR issues. Thus the narrower bandwidth at comparable total power might increase interference. On the other hand the interference range may be so small that there is little likelihood of a close encounter resulting in actual interference.

The proposed enhanced hearing aids that Starkey wants to sell sounds like a great idea. The question is whether or not selling them in the 902-928 MHz band under the proposed waiver is a great idea. FCC has established Docket 09-38 for this issue.