WCA, WiMax Forum, SIA Seek Reconsideration of 3.6 GHz Order

The FCC has allocated 50 MHz of spectrum at 3650-3700 MHz to promote deployment of wireless broadband services, such as WiMax. The order provides for nationwide, non- exclusive licensing of terrestrial operations, utilizing a contention-based protocol requirement and mandatory registration of fixed and base stations with an obligation to avoid interference to new entrants. With a contention- based protocol, several users can share the same spectrum, since the protocol keeps transmitters from interfering with one another while accessing the same channel. Such a protocol could consist of procedures for initiating new transmissions, determining whether a channel is available and managing transmissions in case the channel is unavailable.

“We are opposed to contention-based protocol in any scenario,” WiMax Forum Regulatory Working Group Chair Margaret LaBrecque told us. WiMax targets “wide area networks,” she said: “There is no history of contention- based protocols working over long ranges to manage interference… There is no evidence that could be done.”

In “less congested” areas, the WiMax Forum supported the FCC approach to license spectrum on a non-exclusive but registered basis. But it said “there is no need to specify a contention-based protocol” in non-congested areas: “Such a protocol will be problematic and spectrally inefficient when applied across multiple, non- interoperable technologies, including WiMax.”

“We don’t want to delay opening the band” in non- congested areas, LaBrecque said: “We'd like to see the FCC proceed immediately with opening the band by using non-exclusive licensing approach in non-congested areas” without the requirement of a contention protocol. The Forum, whose members include Intel, Motorola, Lucent, Nokia, Ericsson and Cisco, supports the fixed and base station registration requirements for improved sharing of the band by operators.

In “more congested” areas, the contention-based protocol wouldn’t provide the required QoS new wireless broadband providers must be able to offer to compete with wireline broadband providers, WiMax Forum said. The Forum didn’t offer any recommendations on how to handle “more congested” urban and high density suburban areas. “At WiMax Forum, we couldn’t get consensus on what that policy should be,” LaBrecque said: “Some members wanted [spectrum there] to be exclusively licensed, others wanted to have non-exclusive licensing but we couldn’t agree on how to prevent interference.” Intel suggested the FCC should exclusively license spectrum in top 50 MSAs. “We don’t know any other way on how to deal with that problem,” said LaBrecque, who also represents Intel. Similar to the WiMax Forum, Intel supported prescribing non-exclusive licensed use without the contention-based protocol in rural areas.

The WiMax Forum also asked the FCC to raise power levels for fixed or mobile subscriber stations to 5 w. EIRP over a 25 MHz. The FCC imposed a peak power limit of 25 w. per 25 MHz bandwidth for fixed stations, and a 1 w. maximum peak EIRP over a 25 MHz bandwidth for mobile operations. But the Forum said increasing power levels would enable “sufficient link budget for indoor or nomadic end user devices to communicate back to a base station located (potentially) several kilometers away.” The existing limit of 40 milliwatts in any 1-MHz slice of spectrum is “burdensomely low and not necessary,” it said. The Forum also asked the Commission to explore power limit considerations for point-to-point links in general, and within the exclusion zones for FSS Earth Stations in particular.

WCA urged the FCC to modify its licensing regime for the 3650-3700 MHz band. The Commission should auction a 25 MHz block based on MSA/RSA to meet growing demand for high QoS, while retaining the non-exclusive licensing regime for the remaining 25 MHz of spectrum for those “willing to accept the risk associated with non-exclusive operations,” WCA said. The WiMax Forum didn’t take a position on that issue. Intel said it prefers spectrum in more congested areas have exclusive licenses.

With respect to spectrum subject to non-exclusive licensing, WCA asked the FCC to clarify that the order does “not require that ‘industry’ must agree upon a single ‘contention-based’ protocol before the 2650-2700 MHz band can be utilized.” While Wi-Fi devices based on the IEEE 802.11 standard use “listen before talk” protocol, WiMax technologies using the IEEE 802.16 standard use a different protocol to avoid interference among competing users, WCA said: “A mandated single protocol, assuming it is possible, would result in significant delay and foreclose use of the band for sometime.” Such a requirement could also “deter equipment manufacturers from developing products acceptable for the U.S. market,” since other govts. don’t impose a single-protocol requirement on this band, WCA said.

With respect to registered base stations, WCA asked the FCC to revisit non-exclusive licensees’ rights and obligations. “The Commission not only subjects established facilities to interference from newcomers, but appears to have imposed on those who are first to deploy an obligation to modify their facilities to accommodate newcomers,” it said: “This formulation is not likely to give comfort to potential system operators that require interference protection.”

The FCC also should permit spectrum manager leasing by 3650-3700 MHz licensees and “de facto transfer leasing” by exclusive-use licensees, WCA said. And the Commission should modify its rules on protection of grandfathered fixed satellite service to provide for 3rd-party frequency coordination of point-to-point links within the 150 km radius FSS coordination zones in the same way that governs spectrum sharing under Part 101, it said.

The contention-based protocol and the new rule ambiguities will lead to “squatting by competing providers” and “inefficient use of the 3650 MHz band,” Intel, Redline Communications and Alvarion said in a joint petition. They said the Commission should remove the contention protocol from all markets and set the signal strength limit at 47 dB V/m to facilitate “the effective resolution of interference issues and allow for the co- existence of exclusive and non-exclusive licensed use in adjacent areas.”

BRN Phoenix asked the FCC to designate the AAS standard, based on AAS methods using OFDMA modulation as the contention-based protocol for fixed terrestrial systems operating in the 3.6 GHz band, and permit an increase of EIRP for sectorized and narrowbeam antennas. Alternatively, it said, the FCC should grant BRN Phoenix a waiver to allow for those changes.

Satellite Officials Concerned

The Satellite Industry Assn. (SIA), citing concerns about interference in the satellite spectrum neighboring 3.6 GHZ, said it wants the Commission to revisit an order to protect Fixed Satellite Services (FSS) networks. The 3700-4200 MHz band adjacent to 3.6 GHZ is used intensively by FSS as the principal downlink allocation for C-band satellites. And, the SIA noted, the C-band is the primary distribution vehicle for all major TV programming in the U.S. The SIA told the FCC it’s concerned about interference from both in-band and out-of-band wireless Internet service provider (WISP) sources that would harm FSS earth station receivers in a way that “would be devastating to the satellite industry, the broadcast industry, and the general public,” SIA Exec. Dir. David Cavossa told us.

In comments filed June 10, the SIA asked the Commission to reconsider 2 parts of the 3.6 GHZ order to protect C-band FSS networks in the 3700-4200 MHz band. First, the SIA wants the Commission to keep out-of-band emissions down to -71.25 dBW/MHz, or at a limit no greater than it proposed for unlicensed devices. The order currently establishes the limit at -43 dBW/MHz. According to the SIA, as HDTV and other bandwidth-intensive C-band applications increase, the advanced modulation schemes used by FSS networks will make receive signals even more sensitive to interference. The out-of-band interference limit set in the 3.6 GHz order isn’t enough to protect sensitive HDTV transmissions from WISP interference and the result “could be quite detrimental to the proliferation of HDTV,” SIA said.

SIA also wants the Commission to address saturation of C-band earth station low-noise block-downconverters (LNBs) by WISP transmissions. The SIA said the 3.6 GHz order fails to address the issue of LNB saturation. LNBs are amplification devices used in FSS earth stations. The SIA claims that if LNBs must operate near their level of saturation, the receive signal is distorted. The SIA told the FCC it’s concerned that a single WISP device could saturate the LNB of a C-band earth station. To protect LNBs, they asked the Commission to reduce the 25 w power limit for WISP devices or to limit full-power WISP transmissions to the lover half of the 3.6 GHz band. “LNB saturation is a serious problem, and the lack of discussion of LNB saturation in the Order is a significant omission,” the SIA said: “However, reasonable and adequate minimization of this risk would be neither difficult or costly."