SP 5150 MHz — Spectrum Utilization Policy for Licence-exempt Wireless Local Area Networks in the 5 GHz Range (Issue 2)

4. Policy Provisions for Licence-exempt Wireless Local Area Networks

4.1 General Discussion and Policy Provisions

The use of the frequency bands 5150–5250 MHz, 5250–5350 MHz and 5725–5825 MHz for LE-LANs has been governed by SP 5150 MHz, issued October 1999.

LE-LANs can be characterized as local transmission devices which provide a wide range of applications for high-speed, broadband, digital distribution applications comprising voice, video and data. These systems promise to provide high-speed connectivity for computers and multimedia neighbourhoods and will mainly consist of point-to-point and point-to-multipoint high-speed digital wireless services.

A number of respondents believe that globally harmonized spectrum use, technical rules and deployment flexibility are essential for rapid 5 GHz broadband deployment. Many respondents urged the Department not to adopt "unique" technical restrictions which could result in higher production costs. On the other hand, incumbent licensed operators stressed the importance of their operations and the need for appropriate technical rules for LE-LANs to protect their licensed operations.

Industry Canada recognizes the importance of harmonized technical requirements with the international community, in accordance with the decisions of WRC-03 and the benefits of economies of scale for consumer products. Furthermore, the Department recognizes the need to protect licensed services from potential harmful interference. Therefore, the Department generally supports globally harmonized spectrum use when possible and strives to provide a solution set that will protect incumbent services, while imposing minimum technical restrictions on licence-exempt devices.

Hence, it is appropriate to permit the operation of licence-exempt wireless local area networks in the band 5470–5725 MHz, in addition to the bands 5150–5250 MHz, 5250–5350 MHz and 5725–5825 MHz which are currently available. Similarly, it is appropriate that LE-LANs be operated based on not interfering with, nor claiming protection from, licensed services.

Licence-exempt devices may constitute transmission facilities as defined in the Telecommunications Act. The use of such devices in providing telecommunications services to the public for compensation could be subject to the provisions of the Act including those pertaining to Canadian ownership and control requirements.

Operators of these licence-exempt transmission links may be subject to the requirements for seeking approval for antennas and their supporting structures. The Department has instituted procedures for users of the radiofrequency spectrum which give consideration to the following three areas: (i) the environment; (ii) Health Canada's Limits of Human Exposure to Radiofrequency Electromagnetic Fields in the Frequency Range from 3 kHz to 30 GHz, Safety Code 6; and (iii) land-use consultation. Details of the responsibilities associated with antenna tower placements can be found in Client Procedures Circular 2-0-03.

The following sections provide discussion, spectrum policy provisions and technical provisions for each sub-band. 

4.2 Discussion and Provisions for the Band 5150–5250 MHz

4.2.1 Co-existence issues

The band 5150–5250 MHz is currently allocated on a primary basis to the aeronautical radionavigation service, and to the fixed-satellite service (FSS) in the Earth-to-space direction. Use of the FSS in this band is limited to feeder links for non-geostationary systems in the mobile-satellite service. WRC-03 added a global allocation to the mobile service in the band for wireless access systems including RLANs on the basis that stations in the mobile service shall not claim protection from earth stations in the fixed-satellite service. In addition, technical limits were imposed on the mobile service in order to ensure compatibility with other services.

International studies have concluded that, with appropriate power levels as well as technical and regulatory provisions, the sharing of spectrum among LE-LAN devices, existing aeronautical radionavigation service, and FSS feeder links for non-geostationary mobile-satellite service networks is feasible.

In the consultation, the Department proposed that the existing rules contained in Radio Standards Specification-210, Low Power Licence-Exempt Radiocommunication Devices (All Frequency bands) (RSS-210) be maintained. These rules are consistent with the WRC-03 decisions and ensure that incumbent operation will continued to be protected. The Department notes the indoor-only operational restriction on LE-LANs is necessary and will continue to apply in order to ensure compatibility with the FSS. Power limits currently specified in the RSS are consistent with those adopted by the WRC. In addition, provisions to allow mobile-satellite service operators to monitor emissions from LE-LAN devices in the band, are included in RSS-210 and continue to apply.

Some respondents requested that the Department remove the requirements for integral antenna and unique connectors on LE-LAN devices operating in this band. These issues will be dealt with in the development or revision of an appropriate Radio Standard Specification document.

4.2.2 Spectrum Policy Provisions

The band 5150–5250 MHz, allocated to the mobile service on a primary basis, is designated for use by LE-LANs, on the basis that such devices cannot claim protection from other radio systems and cannot cause harmful interference to licensed radio services.

4.2.3 Technical and Operational Provisions

In the band 5150–5250 MHz, the maximum e.i.r.p. of a LE-LAN device shall be limited to 200 mW (further limited to 10 mW in any 1 MHz). The operation of the LE-LANs is restricted to indoor-only. These requirements will be reflected in an appropriate Radio Standards Specification.

4.3 Discussion and Provisions for the Band 5250–5350 MHz

4.3.1 Public Interest Considerations

As with any new service allocation, the Department recognizes the importance to protect licensed services from potential harmful interference. It also recognizes the advantage to be gained from globally harmonized spectrum, technical rules and flexibility to ensure successful deployment of new services.

The Canadian Space Agency (CSA) currently operates satellite RADARSAT-1 in the band 5250–5350 MHz, which provides imagery data services to customers around the world. There are more than 32 types of applications supported by CSA including agriculture, cartography, disaster management (floods, hurricanes, search and rescue), forestry, hydrology, sea and land ice, defence and intelligence. Future applications may require higher bandwidth to improve the resolution.

Interference from a single LE-LAN device into the EESS may not be significant. However, as wireless consumer devices become more and more affordable, the potential increase in the number of these devices internationally could lead to an increase of the potential for harmful interference. The Department endeavours to balance the needs of all parties by establishing rules for successful co-existence. These rules are discussed below.

4.3.2 Co-existence Issues

The band 5250–5350 MHz is currently allocated to the Earth exploration-satellite (active), radiolocation, and space research (active) services on a primary basis. This band has been designated in Canada for both indoor and outdoor LE-LAN products since 1999. Outdoor LE-LAN products have been used to provide broadband wireless access to customers for high-speed Internet applications. Prior to WRC-03, Canada was active in the international scene in ensuring that outdoor LE-LAN applications were accommodated while providing protection to the operation of other services in this band. A number of technical and operational restrictions were required in order to achieve this objective.

The CSA operates a RADARSAT satellite in this band, which provides imagery data services to customers around the world.

The band 5250–5350 MHz is also used globally by radiolocation systems.

As discussed, WRC-03 made a global allocation to the mobile service in this band for wireless access systems including RLANs. Under the WRC provisions, stations in the mobile service shall not claim protection from the radiolocation, Earth exploration-satellite (active) and the space research (active) services. In addition, technical limits were imposed on the mobile service in order to ensure compatibility with other services.

The decisions of the WRC-03 represent a compromise among the various competing spectrum needs within the international community. Specifically, due to the potential for interference into sensitive international Earth exploration-satellite instruments, there were strong representations from many countries to restrict the operation of LE-LAN to indoor use only. A number of other countries were of the view that other mitigation techniques could be used to ensure compatibility between systems in the Earth exploration-satellite service and LE-LAN devices. These techniques include the use of an e.i.r.p. elevation angle mask.

Studies have shown that the e.i.r.p. elevation angle mask can be an effective mitigation technique to ensure compatibility with the EESS. Technologies such as the use of tilt sensors that vary the output power as a function of tilt angle of the device have demonstrated success in ensuring compliance with the e.i.r.p. elevation angle mask.

Technical compatibility studies conducted by the International Telecommunication Union, in which Canada was an active participant, have shown that sharing between LE-LAN devices and systems in the radiolocation service is possible provided certain technical constraints on the LE-LAN devices are adopted. These constraints include the use of dynamic frequency selection, as well as emission limits on LE-LANs. These constraints were adopted by WRC-03 in ITU Resolution 229 (WRC-03) as shown in Appendix 2 of this document.

The Department is of the view that the decisions made at WRC-03 represent a well-balanced compromise among the competing spectrum needs. Of particular importance to Canada is the provision to allow the use of outdoor LE-LANs. The Department is of the view that the capability for LE-LANs to operate outdoors will be essential to connect rural and remote communities. At the same time, the Department recognizes that LE-LANs shall not cause harmful interference into other licensed services, such as the Earth exploration-satellite service and radiolocation service operating in the same band. With all elements of sharing considered, the Department believes that the decision made at WRC-03 will protect the incumbent services appropriately while allowing LE-LANs to operate in indoor and outdoor environments.

Respondents to the consultation document indicated that the majority of the equipment currently being developed or marketed will not be able to comply with the e.i.r.p. elevation angle mask. The Department notes that the majority of LE-LANs will operate with low power (i.e. an e.i.r.p. of less than 200 mW). As stated in Recommendation ITU-R M.1652, the ITU-R expects that only 5 percent of all LE-LAN equipment will operate with e.i.r.p. greater than 200 mW. In the case of LE-LANs operating with e.i.r.p. less than 200 mW, no e.i.r.p. elevation angle mask is necessary, that is approximately 95 percent of all LE-LAN equipment will be able to operate without the mask. By imposing the mask on higher power LE-LAN equipment, the potential to cause interference into the operation of a primary service will be lowered. It should be noted that higher-power LE-LAN equipment can be deployed in other 5 GHz bands (e.g. 5470–5825 MHz) without the restriction of an e.i.r.p. mask.

WRC-03 permits administrations to exercise some flexibility in adopting other mitigation techniques, provided that they develop national regulations to meet their obligations to achieve an equivalent level of protection to the EESS (active) and the SRS (active) based on their system characteristics and interference criteria as given in Recommendation ITU-R SA.1632.⁷ In the consultation, the Department asked for suggestions for alternate mitigation techniques accompanied with any sound technical analysis. While a few respondents indicated that other mitigation techniques are available, the Department did not receive any specific solution or technical studies to that effect.

The Department is of the view that the decisions adopted by the WRC-03 to impose an e.i.r.p. mask on higher-power LE-LANs are necessary in order to protect incumbent primary licensed users. However, the Department also recognizes that technical studies conducted to date are largely theoretical. To date, no interference from higher-power LE-LANs into the operation of EESS (active) has been reported, which could be due to the fact that the LE-LAN industry is still in its development stage. If in the future LE-LANs are as widely and densely deployed as the wireless industry predicts, the potential for aggregate interference from higher-power LE-LANs into EESS (active) could be realized. Therefore, in order to protect the interests of the primary licensed users, the Department is imposing the use of an e.i.r.p. mask on LE-LAN devices with e.i.r.p. greater than 200 mW. However, the Department recognizes that any changes to existing provisions will require a period of transition to phase out equipment that does not meet the new requirement. During this period, more practical experience will be gained in terms of actual interference and alternative mitigation techniques. Also, since the interference into other primary licensed users is of an aggregate nature, the interference effect will gradually increase as LE-LAN deployments increase; there will be time for further evaluation of the actual operating environment. Hence, a transition period will be introduced to phase out equipment that does not comply with the new technical provisions (described in Section 4.3.4). However, the Department may review these decisions in the future.

4.3.2.1 Transmitter Power Control

In the consultation document, the use of transmitter power control (TPC) was proposed and respondents to the consultation have generally supported the use of TPC. However, some respondents indicated that a 6 dB TPC requirement on each device may be excessive and that for devices with less than 500 mW, TPC should not be required.

The Department notes that in accordance with Resolution 229 (WRC-03), two options with respect to TPC are stated. The first option: if TPC is employed, it shall provide, on average, a mitigation factor of at least 3 dB on the maximum average output power of the system. The second option: if TPC is not in use, then the maximum permitted e.i.r.p. of each device shall be reduced by 3 dB.

Therefore, each LE-LAN device must have the capability to operate at least 6 dB below the maximum permitted e.i.r.p. in order to provide, on average, a mitigation factor of at least 3 dB on the maximum average output power of the system. Alternatively, if TPC is not used, then the maximum permitted e.i.r.p. shall be reduced by 3 dB. In the band 5250–5350 MHz, the maximum permitted e.i.r.p. limit is 1 W. Therefore, devices with maximum e.i.r.p. of less than 500 mW do not require TPC.

4.3.2.2 Dynamic Frequency Selection

The requirement to use Dynamic Frequency Selection (DFS) as a mitigation technique to ensure compatibility with the radiolocation service was adopted by WRC-03. The specific requirements are given in Recommendation ITU-R M.1652.⁸ An excerpt from this recommendation is provided in Appendix 3 of this document. In summary, the DFS mechanism has to be able to detect interference signals above a minimum detection threshold of -62 dBm for devices with a maximum e.i.r.p. of less than 200 mW, and -64 dBm for devices with a maximum e.i.r.p. of 200 mW to 1 W averaged over 1 µs. The LE-LAN device should be able to perform a channel availability check on a particular channel for 60 seconds to identify whether a radar is operating on that radio channel. The LE-LAN device should also be able to perform in-service monitoring to detect the presence of radars. As well, a channel that has been flagged as containing a radar signal, either by a channel availability check or in-service monitoring, is subject to a 30-minute non-occupancy period where it cannot be used by the LE-LAN device, in order to protect scanning radars.

Respondents to the consultation document generally supported the use of DFS. In addition to the detection thresholds and other parameters, the Department notes the importance of channel closing time ⁹, although not included in Recommendation ITU-R M.1652, as an additional effective measure to mitigate interference between LE-LANs and the radiolocation service. The Department also notes that other countries have already adopted a maximum limit on channel closing time of 260 ms.

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Footnotes

⁷ Recommendation ITU-R SA.1632: Sharing in the band 5 250–5 350 MHz between the Earth exploration-satellite service (active) and wireless access systems (including radio local area networks) in the mobile service.

⁸ Recommendation ITU-R M.1652: Dynamic frequency selection (DFS) in wireless access systems including radio local area networks for the purpose of protecting the radiodetermination service in the 5 GHz band.

⁹ Channel closing time is the aggregate duration of transmission of LE-LANs during the channel move time.