Director of Spectrum and Radio Services Industry Canada Room 1611A 300 Slater Street Ottawa, Ontario, K1A 0C8 Canada Gazette, Part I February 27, 2004 Consultation on Allocation Changes and Revision to Spectrum Utilization Policy and Technical Rules in the 5GHz Band Notice No. DGTP-005-04 Submitted via email: June 1, 2004 COMMENTS OF THE INFORMATION TECHNOLGY INDUSTRY COUNCIL The Information Technology Industry Council (ITI) hereby submits comments in response to the Industry Canada Notice No. DGTP-005-04, Consultation on Allocation Changes and Revision to Spectrum Utilization Policy and Technical Rules in the 5GHz Band. A U.S. industry association, ITI represents the leading providers of information technology (IT) products and services. ITI is the voice of the high tech community, advocating policies that advance industry leadership in technology and innovation; open access to new and emerging markets; promote e-commerce expansion; protect consumer choice; and enhance the global competitiveness of its member companies. ITI believes that the unlicensed band use, such as RLAN, has been one of the few recent success stories in fostering broadband access to the Internet and in driving productivity of the enterprise segment. Industry Canada (IC) is serving the needs of residential and business customers in Canada by implementing the World Radio Conference s resolution with respect to unlicensed use in the 5 GHz band.
Discussion ITI not only supports the IC s proposal to permit RLAN devices to use the 5.470-5.725 GHz band but also supports -- with a few minor caveats and clarifications -- the IC s proposed revisions to its 5 GHz RLAN rules. ITI urges the IC to expeditiously adopt the appropriate revisions to its rules. I. Proposed Changes to the Table of Frequency Allocations ITI fully supports the IC s proposal to amend the Table of Frequency Allocations consistent with 5 GHz allocation changes adopted at WRC-03. 1 Specifically, the IC should adopt its proposal to allow RLAN devices to operate in the 5.470-5.725 GHz band. ITI also supports the IC s allocation proposal for the radiolocation, earth exploration-satellite and space research services. Adding the 5.470-5.725 GHz band to the 5 GHz frequencies already available for use by RLAN devices will help address the need for additional spectrum to support the phenomenal growth in the market for wireless broadband networking technology. Further, adding this additional 255 MHz to the existing RLAN spectrum will better enable RLAN devices to successfully co-exist with the Radiolocation, Earth Exploration- Satellite and Space Research services that will also use 5 GHz frequencies. The RLAN industry and government engineers as well as the international community spent months developing the technical solutions that will now permit a multitude of important services to share 5 GHz frequency bands globally. Those solutions all contemplate the availability of this additional spectrum. 1 Among other changes to the International Table of Frequency Allocations, WRC- 03 adopted primary Mobile allocations ( for wireless access systems, including RLANs ) in the 5.150-5.250 GHz, 5.250-5.350 GHz and 5.470-5.725 GHz bands. See Final Acts of the World Radiocommunication Conference (Geneva, 2003). 2
II. Proposed Changes to the RLAN Rules In the months before WRC-03, government and private sector engineers worked together to develop technical solutions that would allow RLAN devices to share 5 GHz frequencies with radiolocation and other services. The modeling they performed showed that there were two key solutions to the sharing problem: Dynamic Frequency Selection (DFS) and transmit power control (TPC). A. Dynamic Frequency Selection ITI supports the IC s proposal to require the use of DFS in the 5.250-5.350 GHz and 5.470-5.725 GHz bands. ITI also supports the DFS detection threshold levels and technical parameters as presented in the proposed rule appendix to the NPRM. 2 These levels and parameters are the same as those adopted as an ITU Recommendation 3 and, as a result, are likely to be adopted globally. It only makes sense for these thresholds to be adopted in Canada. The IC has also proposed that, where multiple devices are under the direction of a central controller, only the central controller is required to have DFS. ITI fully supports this proposal. Since in many wireless network architectures remote devices (such as a laptop) are associated under the control of a central controller (i.e., an access point), requiring DFS in both the access point and its associated remotes would be redundant. Such redundancy increases both the cost and complexity of the remote units. It also increases the likelihood of network disruption operation because it increases the false alarm rate for radar detection. 3 See Annex 1 to ITU-R Recommendation M.1652 Radiocommunications Assembly (Geneva 2000). 3
The IC also noted that DFS threshold levels adopted by ITU are keyed to a 1 MHz bandwidth and, therefore, seeks comment on whether a bandwidth correction factor is necessary for RLAN devices with a receive bandwidth less than 1 MHz. 4 ITI is unaware of any attempts to model the interference potential of systems using less than a 1 MHz channel, and thinks the IC should be hesitant to adopt a correction factor in the absence of a widely-vetted analysis. In addition, the IC notes that the ability of DFS to reliably detect a radar s presence depends on the pulse characteristics of the radar. Therefore, it seeks comment on the minimum number of radar pulses and observation time needed for reliable detection of radar signals. 5 The proposed DFS thresholds for a 1-microsecond pulse are so sensitive that a single radar pulse that is not masked by other interference and that exceeds the threshold will be detected by RLANs with very high probability. This is because, like an RLAN packet, a radar pulse is characterized by a power rise at its start, and it is this property that is exploited in an RLAN to maximize sensitivity to incoming packets. In normal operation, an RLAN receiver is on hair-trigger alert to detect packets with high probability at incoming power levels as low as 82 dbm. The probability of detection increases strongly at greater incoming power levels and is very high at the proposed DFS threshold levels, which are some 20 db above the 82 dbm level. Masking effects, of course, can complicate further analysis. But based on the work already done, ITI believes that any further refinement of these parameters is best done in the course of developing DFS compliance testing procedures. Codifying these parameters before the work on compliance testing procedures is completed could lead to 4
rules that are overly burdensome or that limit the flexibility for DFS implementations in particular devices. Instead, ITI recommends that these parameters once developed be written into compliance test procedures. B. Transmit Power Control. Again in accordance with the ITU Recommendation, the IC proposes a requirement that devices operating in the 5.470-5.725 GHz band employ Transmit Power Control ( TPC ) to reduce the potential for impact on EESS and SRS operations. ITI supports the imposition of a TPC requirement. However, the IC s proposal needs some clarification. The IC proposes in the text that, RLAN devices employ a TPC mechanism that will ensure a 6 db drop in power when triggered. However, the proposed rule says simply that a TPC mechanism is required. In a separate sentence the proposed rule states that, The RLAN device is required to have the capability to operate at least 6 db below the mean EIRP value of 30 dbm. 6 At best, the text and the proposed rule are unclear. The development of the WRC-03 position on DFS trigger levels included consideration of TPC when modeling how RLAN systems might affect radiolocation services. Noting that TPC was already planned for most RLAN systems, 7 the DFS modeling assumed an average 3 db drop in power due to TPC (referenced to a maximum EIRP of 1 watt). In other words, in the course of normal operation (with TPC), and without any non-system trigger, radar systems would see at least an average 3 db drop in 7 Manufacturers have every incentive to employ transmit power control to limit power to the minimum necessary to maintain a high-quality, reliable broadband link. Using more power than needed creates power consumption problems, raises system self-interference issues, and restricts the ability to optimize frequency reuse. 5
RLAN energy compared to an environment where RLANs constantly operate at maximum EIRP. Therefore, the IC s goal should be to create an RLAN environment that when viewed by radar should appear on average to be 3 db below 1-watt EIRP. 8 There are a variety of ways to accomplish this. One is to require, as reflected in the rule appendix, TPC for every device authorized. This approach would certainly result in a 3 db drop or more in the RLAN radiated power environment. However, another and better approach would be to require the requisite reduction in power due to TPC only in systems with an EIRP of 500 mw or more. The latter approach is more flexible and could reduce unnecessary circuitry and cost in lower power devices. This, of course, would result in lower consumer costs and faster adoption of wireless broadband devices. Consequently, ITI proposes that the IC clarify its proposal and rule to permit devices certified for use in systems with an EIRP of 500 mw or less to forego TPC. ITI also urges the IC not to specify specific algorithms and parameters for transmit power control mechanisms. Manufacturers have great incentives to employ TPC in their broadband systems and are already doing so. They have already developed a variety of algorithms and architectures to implement TPC. It would be both unnecessary and unwise for the IC to codify specific TPC parameters. C. Test Procedures. Even now, private sector and government engineers use an open and informal process to develop and propose compliance testing procedures that will ensure that future RLAN devices meet the DFS requirements. ITI hopes the test procedures resulting from 8 Though the pre-wrc U.S. technical investigations were primarily concerned with protecting radars, it is widely recognized that a reduction in RLAN energy attributable to TPC also benefits the space services. 6
this process will allow manufacturers to demonstrate that their devices are capable of detecting radar signals at the appropriate threshold, as codified in the IC s future rules. However, it is critical that test procedures not be more burdensome than necessary to protect radiolocation. If they are, the burden will fall not only on the manufacturers who will be forced to spend unnecessary time and money on testing, but also on the consumers -- since higher production and compliance certification costs are often translated into higher consumer costs. Therefore, we urge IC to adopt harmonized test procedures for DFS instead of developing a separate procedure for the industry. D. Transition Period for RLAN Equipment Operating in the 5.250-5.350 GHz Band The IC proposes that the DFS requirements for 5.250-5.350 GHz RLAN equipment become effective for devices submitted for certification beginning one year from the date of the Federal Register publication of the Report and Order in this proceeding. Further, the IC proposes that all 5.250-5.350 GHz RLAN devices that are imported or shipped in interstate commerce comply with DFS requirements two years after the above-referenced date. 9 ITI believes the IC should lengthen the transition period both because suitable compliance testing procedures have not yet been designed, and because pre-wrc product designs are just entering distribution. Moreover, and critically, lengthening the transition period will not have an adverse impact on radiolocation or other services. The proposed requirement for RLAN devices to implement DFS to protect other services is a new one. As noted, studies to develop appropriate compliance testing procedures to ensure DFS capabilities in RLAN devices are just beginning. To date, such studies have revealed little more than that the process to derive sensible, efficient test 7
procedures will be complicated and time-consuming. It is anticipated, for example, that field trials will not commence until mid-2004 and that subsequent analysis of the trial results and feedback into compliance recommendations would consume much of the remainder of 2004. It would make no sense at this time, therefore, to set a hard DFS compliance date with so much uncertainty surrounding the test procedures. Moreover, as the IC observes in the NPRM, RLAN devices with no DFS capability are already deployed and operating. 10 In addition, many manufacturers have non-dfs products in the pipeline that were designed and slated for production before DFS for protecting radiolocation became a key consideration. In light of these factors, ITI believes that a more prudent approach would be to key the transition periods to the availability of appropriate compliance testing procedures. While this will delay the implementation of DFS beyond the dates proposed in the NPRM, it will pose no danger to radiolocation or other services. The interference risk to other services from RLAN devices comes, of course, from ubiquitously deployed devices -- not from a relative handful. Postponing implementation of the DFS requirement for the relatively few devices that will be sold in the next several years will not cause injury to other services and will allow time for development of appropriate compliance testing procedures. E. Technical Requirements for the 5 GHz RLAN Bands ITI also supports, with just three exceptions, the IC s proposal to apply other technical parameters in the 5.250-5.350 GHz band to the 5.470-5.725 GHz band in 9 See NPRM 18 FCC Rcd 11581 at 26. 10 See id. 8
updated RSS-210 radio standard specifications. This proposal is consistent with the range of technical parameters adopted for this band by WRC-03. A key to the success of 2.4 GHz broadband wireless systems has been their reasonable cost for consumers, educational institutions, governments, and businesses. Cost will, of course, also play an important role in the success or failure of 5 GHz broadband wireless systems. There are, however, IC regulations now applicable to 5 GHz devices that add to manufacturing costs without providing a corresponding benefit. The IC should not import these rules into the new RLAN bands. It would make more sense to take this opportunity to eliminate these rules from the current bands. One such regulation is the requirement in RSS-210 of an integral antenna for a system operating in the 5.150-5.250 GHz band. There is a general industry consensus 11 that the restrictions in this band on antenna gain and transmit power -- along with the prohibition on outdoor use -- are sufficient to provide protection to MSS. This general consensus is correct. The integral antenna requirement, in practice, does not provide any additional protection to these services. It should now be eliminated rather than imported into the new RLAN band. The requirement of a unique connector should also be eliminated for RLAN systems rather than imported into the new band. In the age of e-commerce when once difficult-to-find items may be quickly located and easily bought, the need to constantly upgrade a connector to keep it truly unique or to restrict its re-engineering is both cost prohibitive and impractical. 11 See Comments of WFA and ITI (filed October 18, 2002) responding to FCC 02-266 (The IC Seeks Public Comment in the 2000 Biennial Review of Telecommunications Regulations Within the Purview of the Office of Engineering and Technology (rel. September 26, 2002). 9
The third issue we wish to address is the recommendation of the antenna emission mask, or additional restrictions in the 5250 MHz band, as adopted in the WRC2003 resolution Com 5/16 and in the CITEL IAP as an additional protection criteria for EESS. 12 However, the current Canadian regulations as stated in RSS-210 allow a maximum power of 1W EIRP and outdoor use in the 5250 5350 MHz band with no restrictions. The proposed adoption of the antenna mask was to provide added protection for Earth exploratory satellite services. Currently, these unlicensed systems operate on a non-interference basis and would be required to address the issue if interference occurred. However, under the current rules, outdoor use at 1W EIRP without the mask is currently allowed and the operation of these low cost systems has not impacted EESS. In our engineering reviews, we have determined that the mask would effectively limit the 5250-5350 MHz band to short range point-to-point use only. 13 This band would be limited to very narrow beam antennas with carefully designed amplitude and phase tapers and to elements which greatly reduce side lobes while increasing F/B ratios with transmitters set to very low output power to meet the emission mask. Further, we have determined that a majority of the antennas for the RLAN devices currently on the market would not comply with the proposed mask. Therefore, the low-cost advantage of these systems would be overshadowed by the higher cost of custom designed antennas. Further review suggests that the mask would limit or preclude the use of point-to- 12 This issue is still being debated in the CITEL 5GHz workgroups to address alternate proposals and WRC2003 resolution allows the adoption of other mitigation techniques to provide additional protection to EESS. 13 The issue of FWA was debated at WRC2003 for this band but only adopted for region 3 via a footnote. 10
multi-point systems in this band, due to client card antennas not meeting the mask. In fact, most if not all of the antennas used by the client card would fail to meet the mask. This would greatly hamper the mobile aspect of these systems. Figure 1 EIRP with Patch vs Canadian Mask Radio Output = 100 mw EIRP Density, dbw/mhz Figure 2 0-5 -10-15 -20-25 -30-35 -40-45 -50-180 -150-120 -90-60 -30 0 30 60 90 120 150 180 Elevation Angle, degs Patch Antenna (Approx 7 dbi) Canadian Mask 11