Opinion for the Court filed by Circuit Judge ROGERS.
In
AT&T Wireless Services v. FCC,
I.
The background to the Commission’s decision to grant to AirCell, Inc. a waiver of the rules barring the use of analog cellular telephones in aircraft,
see
47 C.F.R. § 22.925 (2004), is set forth in
AirCell I,
The tests were conducted in rural areas, where such harmful interference is most likely because there is less background electromagnetic noise that a cellular call needs to overcome. This permits cellular calls in rural areаs to be of acceptable quality even with a relatively weak signal, but those weak signals are then more susceptible to interference than calls in suburban or urban areas, which are required to transmit at a higher strength. For the one day of test flights the Commission considered representative of how AirCell would operate in practice, July 10, 1997, AirToueh Communications submitted an analysis by Dr. William C. Y. Lee, who concluded that AirCell’s calls would cause
In
AirCell I,
the court remanded on the harmful interference threshold determination, holding that the Commission had failed “to justify adequately its choice of an interference threshold,”
On remand, the Commission reaffirmed its prediction that AirCell would not cause harmful interference with ground-based cellular systems and explained its rejection of Dr. Lee’s conclusion to the contrary. See Remand Order, 18 F.C.C.R. 1926. It explained that it had derived the -117 dBm figure by starting from the strength of the weakest ground-based call that could still be considered acceptable quality in a rural area, which the Commission claimed was - 100 dBm, and subtracting a 17 dB “buffer,” which is the industry, standard for the amount by which a cellular call must exceed other signals in order to be effective. It reasoned that the -124 dBm figure used by Dr. Lee had been derived by assuming a -129 dBm environmental noise floor in quiet locations and stipulating that AirCell would cause interference with ground systems once it exceeded the noise floor by 4.76 decibels. The Commission stated that this method was erroneous because it assumed too low a noise floor and failed to justify its premise that interference to ground-based calls would become harmful at 4.76 decibels above the noise floor. The Commission also stated that even if Dr. Lee’s conclusions about the relative signal strengths were corrеct, it would show at most that AirCell’s systems could cause interference, but not necessarily harmful interference, because Dr. Lee had wrongly assumed that all interference above his - 124 dBm threshold would be harmful. The Commission reasoned that the 17 dBm buffer was “significantly more buffer than is necessary to prevent harmful interference,” and that an AirCell signal would not cause harmful interference until it “seriously degrades, obstructs, or repeatedly interrupts” a ground-based call, which, the Commission stated, would not occur until a “very substantial (e.g., 7 dB or more) excess over an [interference threshold].” Id. at 1935-36.
II.
The sole question now before the court is whether the Commission’s order satisfies the remand in
AirCell I.
The court is generally the authoritativе interpreter of its own remand,
see FCC v. Pottsville Broad. Co.,
The Commission, on remand, provided what the court requested: an explanation of “why the Commission considered one interference threshold preferable to another.”
AirCell I,
The Commission similarly explained its reason for rejecting the -124 dBm threshold proposed by AirTouсh Communications in the report of Dr. Lee. Dr. Lee’s analysis was based on an environmental noise floor in rural areas of -129 dBm, -127 dBm when noise from AirTouch’s system is factored in, and assumed that AirCell would cause harmful interference if its signal exceeded that level by more than a “reliability factor” of 4.76 dB. Dr. Lee’s calculations showed that an AirCell signal would exceed the noise floor by the required amount if it reached a strength of - 124 dBm. The Commission did not consider Dr. Lee’s premise of a -127 dBm noise floor credible; he assumed “zero environmental noise,” which the Commission found was “not reflective of the typical noise environment in which cellular carriers operate,” and his assumption of only two decibels of system noise relied on high-fidelity receiver equipment that was neither “universal or standard practice for the cellular industry, even in rural areas.” Remand Order, 18 F.C.C.R. at 1933-34. Second, the Commission explained that the premise behind Dr. Lee’s analysis — that AirCell wоuld cause interference whenever it exceeded the level of background noise by a 4.76 dB “reliability factor” —■ had not been shown to have “any link” to cellular call quality. See id. at 1935. Under the Commission’s reasoning, what matters is the ratio between AirCell’s signal strength and the signal strength of terrestrial calls. See id. AirCell’s signal might be undetectable if it falls below the noise floor, but it does not need to; it can exceed the noise floor without causing interference so long as it remains at leаst seventeen decibels less powerful than any acceptable ground-based call on the same channel.
Nothing in the explanation in the
Remand Order
deviates impermissibly from the Commission’s reasoning in the
Initial Order.
The petitioners contend that the -117 dBm threshold was initially predicated, as was Dr. Lee’s -124 dBm threshold, on reasoning “up” from the electromagnetic noise floor, and that the Commission’s explanation on remand, which reasons “down” from the strength of an acceptable ground-based call, is an attеmpt to evade record evidence that the noise floor at the test site was -127 dBm, such that reasoning “up” would have resulted in an interference threshold less permissive than -117 dBm. Petitioners misread the initial order, however, for it does not suggest that the Commission derived the -117 dBm figure by reasoning “up” from the noise floor. Indeed, the court remanded because the Commission did not explain the origin of the -117 dBm figure, which the initial order simply stated was “more realistic for typical analog systems.” 15 F.C.C.R. at 9631 n. 67. While counsel for the Commission at oral argument in
Air-Cell I
did represent to the court that the - 117 dBm figure was chosen because it was
The petitioners also challenge the merits of the Commission’s explanation on remand for the -117 dBm threshold. First, they point out that the record showed an actual noise floor of -127 dBm at the test site, confirming Dr. Lee’s figure that the Commission considered too conservative. If there was any such error, it was harmless. As explained, the actual location of the electromagnetic' noise floor is mostly irrelevant to the interference threshold under the Commission’s reasoning; rather, what matters is the ratio between terrestrial cellular calls and AirCell’s signal.
Second, the petitioners object to the Commission’s use of -100 dBm as the starting point acceptable call from which to reason “down” to the interference threshold. The Commission explained its choice of the -100 dBm figure on the basis that some petitioners in the initial AirCell proceeding used the -100 dBm figure, and that technical literature uses -100 dBm as the signal strength at which a call becоmes so weak that cellular sites in rural areas will “attempt to continue carrying a call only if there were no cell site with better reception to which to hand it off.” Remand Order, 18 F.C.C.R. at 1932. The petitioners, however, dispute the relevance of the technical literature cited by the Commission, and contend that record data show that many- ground-based cellular calls at the test site were weaker than -100 dBm, and that absent any interference from AirCell, these calls would funсtion properly so long as they remain at least 17 decibels above the measured noise floor, i.e, -110 dBm. Thus, the Commission’s - 100 dBm starting point effectively denies interference protection to these weaker calls.
Whatever the merits of these objections might be, they are not properly before the court. The only issue before the court is to determine whether the Commission has complied with the remand, not to review generally the merits of the remand order where petitioners failed to petition for rehearing, for the court may not consider any argument that “relies on questions of fact or law upon which the Commission,, or designated authority within the Commission, has been afforded no opportunity to pass.” 47 U.S.C. § 405(a). The petitioners’ objections to the -100 dBm figure do not address whether the Commission on remand explained its decision based on the record. Indeed, their counsel conceded at oral argument that thе petitioners, by failing to seek rehearing, have waived any
The petitioners also contend that the Commission’s explanation on remand, despite lip service to the -117 dBm figure, actually relies on a -110 dBm threshold. This miscomprehends both the purpose of the remand and the Commission’s response. The court remanded so that the Commission could explain “why [it] considered one interference threshold preferable to another,”
AirCell I,
The Commission’s review on remand of the July 10 test flight data showed that AirCell’s mean signal strength exceeded - 117 dBm only on one of the 24 test flights, and then only by .62 decibels, a trivial amount. It concluded, therefore, that Air-Cell was unlikely to cause harmful interference. See id. at 1937. This reasoning aligns with, and further elaborates upon, the Commission’s conclusion in the initial order. It differs only in the acknowledgment that one of the test flights did show a signal strength slightly exceeding -117 dBm, as contrasted with its conclusion in the initial order that AirCell would cause harmful interference “0% of the time.” Initial Order, 15 F.C.C.R. at 9631 n. 67. Later in the order, the Commission also noted that even if AirCell had exceeded the -117 dBm threshold, the interference it would cause would not necessarily become harmful until it reached a higher level somewhere close to -110 dBm. See Remand Order, 18 F.C.C.R. at 1935-36. But the Commission explained that Air-Cell’s signal would not еxceed the -117 dBm level in the first place. See id. at 1937. The context of the Commission’s discussion makes clear that it is discussing a hypothetical. Dr. Lee’s -124 dBm thx-eshold assumed that AirCell would cause harmful interference as soon as its signal, by rising above the electromagnetic noise floor, was strong enough to be detectable. The Commission was explaining that Dr. Lee’s analysis provided more buffer than was necessary because not all detectable interference is so sеvere that it can be considered harmful. See id. at 1935-36.
The petitioners have not, however, waived their related contention that the Commission’s use of mean signal strength disregards the terms of the court’s remand, but that objection is easily disposed of. They contend that irrespective of whether it was arbitrary and capricious, use of mean rather than peak signal strength is an attempted end-run around the court’s instruction that the Commission demonstrate “how it was able, in the absence of a probability study, to translate the raw signal data from the July 10, 1997, field test” into a determination of noninterference.
See AirCell I,
Finally, there was nothing “counterintui-tive,” Petitioners’ Br. at 32, much less an abuse of discretion, in the Commission’s decision to rely on the record in the original proceeding and to reject for filing the petitioners’ comments on the court’s remand instruction. The Commission rejected a filing of comments by AT&T Wireless, Cingular Wireless and CellCo addressing the remand instruction, explaining that it “need not consider” the comments because it “neither solicited nor granted leave to file additional pleadings” in the case, and that the existing record was “a sufficiently adequate base on which to rest the Commission’s decision” because the Commission was “merely explaining]” its earlier decision. 18 F.C.C.R. at 1927. This is consistent with the court’s remand, which sought an explanation from the Commission based of the administrative record of the initial order.
See AirCell I,
Accordingly, because the
Remand Order
provides an adequate explanation in re-' sponse to the remand in
Aircell I,