Final Policy and Licensing Procedures for the Auction of the 24 and 38 GHz Frequency Bands
4. Technical Considerations
The following sections outline the technical aspects of the licensing of the 24 and 38 GHz frequency bands.
The spectrum auction process assigns blocks of spectrum within prescribed geographical areas. Licensees may deploy a range of point-to-point and point-to-multipoint equipment. The department will minimize technical regulations as they pertain to operation of licensees' systems. Industry Canada will place limits on certain system parameters in order to meet international regulations and to mitigate interference to/from other systems. The customer premises equipment, and possibly hub station equipment, will require a technical acceptance certificate to ensure maximum radio frequency compatibility between equipment types.
There may be situations where co-channel assignments are made in directly adjacent areas, and/or adjacent channel assignments are made within the same service areas. Such situations may lead to interference between systems and consequently will require effective coordination between operators. To minimize the potential for interference there must be communication between the licensees prior to system implementation. The following sections outline the various aspects of the coordination process including the required communications between licensees.
4.2 Coordination Process
4.2.1 Arrangements Between Licensees
Licensees are encouraged to enter into mutually beneficial frequency usage agreements that would ensure service is available in the boundary areas. Operators will be expected to take full advantage of interference mitigation techniques such as antenna discrimination, polarization, frequency offset, shielding, site selection, or power control to facilitate co-existence with systems of other service providers, at both design and implementation stages. Boundary arrangements between licensees will serve as the primary mechanism for coordinating systems that could potentially cause interference to an operator in an adjacent service area. In addition, operators serving the same area using adjacent frequency blocks should consult each other to avoid interference problems caused by transmitters and receivers being too close together (near/far problem).
4.2.2 Coordination Process in Lieu of Boundary Arrangement Between Operators
In the event two licensees cannot arrive at a mutually acceptable boundary arrangement, or where one operator needs to deploy before an arrangement can be concluded, it will be necessary to have a default process in place.
In the consultation document the department proposed that coordination between licensees can be initiated in several ways, such as using distance or power flux density (pfd) as a criterion. If the trigger criterion is distance, this distance needs to be sufficiently large to ensure minimum interference between systems. Similarly, if the trigger criterion is pfd, this pfd level needs to be sufficiently low to ensure minimum interference between systems. Some respondents were in favour of a "keyhole" distance mechanism to trigger coordination between point-to-point systems. Although this alternative has its advantages, it may not be optimal for handling point-to-multipoint systems. The department believes that the use of pfd limits as coordination triggers may be the most practical approach, provided that reasonable levels can be adopted. In addition, it is possible to use conservative culling distances in order to identify adjacent service areas where coordination is required.
The allowable pfd at a boundary to minimize interference to receivers within the area will depend on the susceptibility of base station and customer receivers. The calculation methods to determine the compliance with a pfd are typically based on worst case propagation conditions since the specific path profiles to all receivers are not usually known.
Pfd triggers will be set at appropriately conservative values to minimize the potential for interference to adjacent systems, since outside these values, licensees can operate without the requirement to communicate with neighboring licensees. Practical experience for services in many frequency bands has demonstrated that once communication between licensees has been triggered, actual systems can be implemented in much closer proximity than the worst case values would indicate. The department will develop suitable pfd trigger limits in consultation with industry.Footnote 15
4.3 Interference Considerations
Interference between broadband wireless systems primarily occurs through the following mechanisms:
- co-channel emission levels into adjacent areas (Co-Channel, Adjacent-Area); and,
- adjacent channel emission levels within the same service area (Adjacent-Channel, Same-Area).
These are discussed below.
4.3.1 Co-Channel, Adjacent-Area Systems
The potential for one system to interfere with another system typically extends for distances much greater than the desired link length. It will be extremely difficult to accommodate Co-Channel, Adjacent-Area systems in close proximity without knowing the characteristics of both systems.
For most point-to-multipoint systems it is possible to cover an area with contiguous cells. A basic premise is that this should be attainable regardless of who actually owns or operates the individual cells. This applies particularly to systems which are similar in technical characteristics, deployment, intended service, and spectrum use (channelization, bandwidth, frequency pairing, etc.). The situation becomes more complex where the characteristics are different, particularly in power and spectrum use. Licensees attempting to implement systems in close proximity to each other and/or to a licence area boundary will require knowledge of both systems to allow the incorporation of mitigating design and deployment considerations to allow coexistence.
4.3.2 Adjacent-Channel, Same-Area Systems
Adjacent channel operation within the same area will have the potential for interference, particularly with respect to the near/far effect at the subscriber receiver when the transmitting hubs are not located in reasonably close proximity. Hubs receiving in adjacent spectrum could also be subject to the same near/far problems as subscriber terminals, especially when the hubs are not co-located.Footnote 16 An emission limit at the channel block edges will alleviate some of the potential for interference.
From an interference standpoint, co-location of hub transmitters may be desirable, but differences in power requirements, intended market, or business cases may make this unfeasible. The size of the area will also play a major role in the complexity of coordination since the larger the area, the greater the requirement for multiple hubs to provide service.
Out-of-block emission limits will be required to minimize inter-system interference. Point-to-multipoint systems are less constrained when the emission limits are applied to a block of spectrum rather than to individual channels within the block. Consideration may be given to the application of an absolute emission limit at the block edge, i.e. independent of carrier level and frequency tolerance.
4.4 Technical Acceptance Certification
Point-to-point and point-to-multipoint customer premises equipment, and possibly hub station equipment, will be required to meet certain minimum radio frequency standards such as out-of-block emission limits and frequency drift tolerance. The department will set reasonably stringent, technology-independent, out-of-block emission specifications at the licensed band edge. These standards will be developed in consultation with industry and the appropriate Radio Standard Specification (RSS) will be revised accordingly.Footnote 17 Vendors will be required to certify compliance to the revised RSS specifications for equipment under Industry Canada's technical acceptance certification process.
4.5 Sharing Issues at 24 GHz
The band 24.75-25.25 GHz is currently allocated to the Fixed Satellite Service (FSS) (Earth-to-space) and is intended for use by Broadcast Satellite Service (BSS) feeder links in support of the band 17.30–17.80 GHz. As per footnote C44 in the Canadian Table of Frequency Allocations, future earth stations will be permitted, provided that such installations do not cause interference to any fixed systems operating within the authorized service areas. The department will develop appropriate coordination criteria in consultation with industry.Footnote 18
4.6 International Coordination
Licensees will be expected to respect ITU Radio Regulations pertaining to the 24 and 38 GHz bands and abide by any future agreements established with other countries.
The deployment of point-to-point and point-to-multipoint systems near the Canada/U.S. border is subject to the sharing arrangements established between the two countries. Bilateral negotiations for the 24 and 38 GHz bands between Industry Canada and the Federal Communications Commission of the United States are on-going. It is the department's intention to develop a mechanism for cross-border coordination similar to the domestic process outlined in the previously mentioned Standard Radio System Plans (SRSPs).
- back to footnote reference 15 See the draft Standard Radio System Plans (SRSPs) Technical Requirements for the Fixed Radio Systems Operating in the Bands 24.25–24.45 GHz and 25.05–25.25 GHz (Provisional SRSP–324.25) and Technical Requirements for the Fixed Radio Systems Operating in the Band 38.6–40 GHz (Provisional SRSP-338.6), available on the Web site of the Radio Advisory Board of Canada (RABC) (http://www.rabc-cccr.ca/home.cfm?lang=en).
- back to footnote reference 16 The department will not mandate co-location of hub stations.
- back to footnote reference 17 See the draft Radio Standards Specification (RSS) Radio Standards Specification for Local Multipoint Communications Systems in the 28 GHz Band and Point-to-Point and Point-to-Multipoint Broadband Communication Systems in the 24 GHz and 38 GHz Bands (Provisional RSS-191), available on the Web site of the Radio Advisory Board of Canada (RABC) (http://www.rabc-cccr.ca/home.cfm?lang=en).
- back to footnote reference 18 These criteria will be made available on the department's Strategis Web site (http://strategis.ic.gc.ca/spectrum).
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