FCC and Congress Look For New Frequency Bands For Expanded WiFi Use
Recent interest in unlicensed wireless operations using the 802.11 standard, often called “WiFi,” has led both the FCC and Congress to identify additional spectrum where WiFi operations might be possible. The FCC recently issued a Notice of Inquiry (NOI) proposing two bands—including the one currently used for over-the-air television broadcasting—where unlicensed operations could be permitted. Comments on the NOI are due by April 7, 2003. Reply comments may be submitted through May 6, 2003.
In addition, several bills have already been introduced in Congress this session that would require the FCC to allocate a significant amount of additional spectrum for WiFi purposes. These include S.159, known as the Jumpstart Broadband Act, HR.363, and HR.340. FCC Notice of Inquiry— Comments Due April 7, 2003 (Replies Due by May 6).
The FCC issued its NOI on Dec. 20, 2002, as another step in the FCC’s comprehensive review of spectrum policy conducted by the its Spectrum Policy Task Force. In the NOI, the FCC recognized the need to allow unlicensed devices to operate in additional frequency bands beyond those where such operations are currently authorized (which are the 900 MHz band, 2.4 GHz band, and 5.8 GHz bands). The FCC also said, that, due to low power levels and other technical restrictions it imposes on unlicensed devices, such devices might be able to operate without interfering with the licensed users of these bands. The frequency bands under consideration for this purpose are the VHF and UHF television broadcast bands (54-72 MHz, 76-88 MHz, 174-216 MHz, and 470-806 MHz) and the 3650-3700 MHz band.
Comments on the FCC’s NOI are due by April 7, 2003. Replies to these comments may be submitted through May 6, 2003. By announcing these proposals in a NOI, rather than in a Notice of Proposed Rulemaking, the FCC is giving itself the flexibility to issue a more formal proposal before it adopts rules in this area. However, by proposing specific frequency bands for additional unlicensed operations, the FCC is providing more specifics about its tentative direction than it usually gives in an NOI.
In starting this inquiry, the FCC said that its rules permitting unlicensed transmitters “have been a tremendous success,” based on the rapid development and widespread use of equipment operating under these rules. The FCC attributes this success primarily to three reasons: (1) because the bands currently used for unlicensed operations are licensed primarily for Industrial, Scientific, and Medical (ISM) equipment, which are not as directly impacted by interference from unlicensed devices, these devices can operate using significantly higher power levels than would be possible in other frequency bands; (2) the ISM bands have enough spectrum to permit wide bandwidth uses allowing for video and high speed data transmissions and to allow multiple users to share the bands; and (3) the FCC imposes no restrictions on the types of devices that may operate in these bands, thereby encouraging the development of new and innovative uses for unlicensed transmitters. In identifying other frequency bands for unlicensed operations, the FCC seeks to find bands having similar attributes.
The FCC believes it could achieve this goal by allowing unlicensed operations in the frequency bands that are used for television broadcasting. As a result of the FCC’s allocation scheme for television stations, many television channels are not being used by either analog or digital television stations in each geographic area, because such stations could not operate without interfering with nearby co-channel or adjacent channel stations. However, the FCC believes that unlicensed transmitters might be able to operate on vacant channels that cannot be used by higher power television stations due to interference concerns, provided the unlicensed equipment complies with strict limits on power, operating frequency, and location.
The FCC also identified the 3650-3700 MHz frequency band as another potential band for expanded unlicensed operation. This band has been the subject of reallocation in recent years and is currently authorized for use by the base stations of fixed and mobile terrestrial services and government radiolocation on a mixed-use basis, with fixed satellite service operations licensed on a secondary basis. Furthermore, the FCC has proposed rules for licensing this band that allow for flexible spectrum use, geographic area licensing, and band managers. Part of this band could be also used to satisfy a congressional requirement to auction an additional 15 MHz of government spectrum for fixed terrestrial services.
Nonetheless, the FCC believes the 3650 MHz band could potentially be used for unlicensed operations because: (1) it offers a contiguous 50 MHz block of spectrum; (2) there is sufficient spectrum to permit wide bandwidth applications such as high speed data; and (3) the band is not heavily used in most parts of the country. According to the FCC, it may be possible to allow unlicensed devices to operate in this band with minimal restrictions except those needed to avoid interference with existing users, perhaps by requiring frequency agility. It may also be possible to allow wideband operations with high gain antennas in this band at power levels greater than the 1 watt maximum permitted for other unlicensed devices.
FCC Seeks Comments On These Questions
The FCC’s NOI invites comment on a number of questions that can be grouped into two categories:
1. The first set of questions concerns the use of TV broadcast bands by unlicensed devices, the technical standards that should apply to assure non-interference with authorized users, and any requirements for unlicensed users to monitor frequencies for use before beginning operations.
- Should new unlicensed devices be allowed to operate within any portions of the TV bands, and if so, which portions?
- Should unlicensed devices be prohibited to use certain channels, such as: (1) channel 37 which is allocated for radio astronomy operations and the Wireless Medical Telemetry Service; (2) channels 2, 3 and 4 which are used for, or are adjacent to, the output channels of VCRs and other set-top boxes, or (3) channels 52-69 which has been reallocated and will be licensed for new services? Should unlicensed operations be permitted in the reclaimed spectrum?
- Should there be geographic restrictions on where unlicensed operation in the TV bands is permitted, such as in areas where co-channel or adjacent channel television, Private Land Mobile Radio Service or Commercial Mobile Radio Service is present, or in border areas near Canada and Mexico?
- What restrictions, if any, should be placed on the applications or numbers of unlicensed devices that are permitted in the TV broadcast bands and why would such restrictions be needed? Should unlicensed applications be limited to fixed uses?
- Are temporary restrictions needed to ensure that unlicensed devices do not impact the transition of television from analog to digital service? How can the FCC ensure that unlicensed operation does not cause interference when stations make such changes or when new DTV stations begin operating?
- How would new unlicensed devices affect the ability of broadcasters to provide ancillary services such as data after the digital transition?
- What power and/or field strength limits are needed for unlicensed transmitters within the TV bands to prevent interference to TV reception? Could unlicensed devices operate in TV bands with a power greater than the 1 watt maximum permitted for Part 15 devices in the ISM bands or with power greater than the general Part 15 limit?
- What separation distances or D/U ratios should be established between unlicensed devices and the service of analog, digital, Class A and low power TV and TV translator stations? What assumptions should be used to determine these protection criteria? Should TV stations be protected only within their grade B or noise limited service contours, or should unlicensed devices be required to protect TV reception from interference regardless of the received TV signal strength? Is protection necessary only for co-channel and adjacent channel stations? What special requirements, if any, are necessary to protect TV reception in areas where a station’s signal is weak? Would minimum performance standards for receivers facilitate the sharing of TV spectrum with unlicensed devices?
- What technical requirements are needed to protect other operations in the TV bands, including operations in the Public Land Mobile Radio Service (PLMRS) and Commercial Mobile Radio Service (CMRS) in the areas where they operate on TV channels and low power auxiliary stations such as wireless microphones and wireless assist video devices? Could technical limits allow unlicensed devices to co-exist with new licensed services on former TV channels 52-69? Should unlicensed transmitters be required to protect unlicensed medical telemetry transmitters operating on TV channels 7-46 from interference?
- What requirements are needed to prevent interference to coaxial cable or other multi-channel video service providers using the TV bands or to prevent interference to TVs, VCRs and set-top boxes caused by direct pickup of signals from unlicensed devices?
- Should antenna requirements be imposed? Can technologies such as “smart antennas,” which automatically change their directivity as necessary, assist unlicensed devices in sharing the TV bands? Should unlicensed devices be required to use an integrated transmitting antenna and be prevented from using external amplifiers and antennas?
- What specific capabilities should an unlicensed transmitter have to successfully share spectrum with licensed operations in the TV broadcast band without interference? Can transmission protocols enable efficient sharing of spectrum, such as a “listen-before-talk” approach?
- Could GPS or other location techniques be incorporated into an unlicensed device so it could determine its precise location and identify licensed users in its vicinity by accessing a database? Would such an approach be reliable and could it be combined with other methods to prevent interference to licensed services? What specific methods could be used to protect low power auxiliary stations such as wireless microphones that are not listed in a database?
- Once an unlicensed device begins transmissions on an open frequency, how can it ensure that interference will not be caused to a licensed user of that frequency who wants to begin transmissions? Is there a way to avoid such “collisions” or mitigate their effect? For example, should these devices have limited “duty cycles” in a given frequency band?
- Is frequency agile equipment, as well as the protocols to enable efficient frequency sharing, feasible in the near-term?
- How can the FCC enforce rules for unlicensed devices to ensure that such devices do not cause interference to authorized users of the TV bands?
- Is it necessary to establish standards to allow sharing between unlicensed users of the TV bands? If so, how should the FCC arrive at standards and what process should be put in place to make certain that the standards remain current and support innovation?
2. The FCC also posed numerous questions concerning permitting unlicensed operation in the 3650 MHz band:
- What are the potential benefits and drawbacks of allowing unlicensed operation in this band, subject only to the minimum rules needed to avoid interference to licensed users?
- Is it viable to license fixed operations in this spectrum as proposed and permit operation of Part 15 devices in unused portions on a non-interference basis?
- Could power levels greater than 1 watt be permitted for such operations without causing interference to authorized users within the band? If so, what is the maximum power level that could be permitted? Are restrictions needed on antenna gain or directivity?
- What other requirements are needed to protect FSS and federal government operations in the 3650 MHz band from interference? Are geographic restrictions needed on where an unlicensed device could operate, and how could these be enforced? Could GPS be incorporated into a device so it could determine its precise location and distance from licensed users and if so, would such an approach be necessary or reliable?
- What other requirements would be needed to prevent interference to other authorized services, such as out-of-band emission limits? What types of licensed services could share the 3650 MHz band with unlicensed devices?
- Is it necessary to establish any standards to allow sharing between unlicensed users of the 3650 MHz band? If so, how do should the FCC arrive at standards?
- Are there any other bands where unlicensed operation with minimal rules could be permitted without causing interference to authorized services? What other bands should be considered and what are the advantages of each?
Sen. George Allen (R., Va.) and Sen. Barbara Boxer (D., Calif.) introduced a bill on Jan. 14, 2003, known as the Jumpstart Broadband Act (S. 159). Like the FCC’s NOI, this legislation is designed to increase the amount of spectrum available for unlicensed uses such as WiFi. Within six months of enactment the bill would require the FCC to allocate at least 255 MHz of contiguous spectrum in the 5 GHz band for use by unlicensed broadband devices. Within a year of enactment the FCC would also be required to adopt minimal technical and device rules for the allocated spectrum. The bill would also require all wireless broadband devices operating within this spectrum band and manufactured after these rules become effective, to be capable of two-way digital communications and to meet interference standards protecting incumbent government users of the spectrum. The bill has been referred to the Senate’s Committee on Commerce, Science and Transportation. A companion bill was introduced in the House on Jan. 27 by Rep. Michael M. Honda (D., Calif.), identified as H.R. 363. On the same day, Rep. Darrell Issa (R., Calif.) introduced H.R. 340, which requires the FCC to allocate additional spectrum for WiFi purposes within 18 months of enactment.