3900 MHz NCLL cross-border best practices

The cross-border requirements listed in Section 10 of SRSP-521 can be summarized as follows:

• NCLL operators may not deploy stations that exceed a power flux density level of -114.5 dBW/m²/MHz at the Canada/U.S. border. Power flux density (pfd) is a measure of how much power from a radio signal is spread over a specific area. It indicates the amount of signal power that reaches a certain location, e.g., a certain point along the Canada/U.S. border.
• NCLL stations must not cause harmful interference to U.S. registered fixed satellite earth stations operating in the 4000–4200 MHz band.

The following sections provide guidance on the cross-border requirements for Canadian licensed systems with respect to U.S. flexible use systems (see Section 2.1), and U.S. registered earth stations (see Section 2.2).

2.1 Co-existence with U.S. flexible use systems

NCLL operators are expected to either comply with the pfd limit of -114 dBW/m²/MHz or reach a mutually acceptable commercial coordination arrangement with impacted U.S. flexible use licensee(s) before exceeding the limit. A station that exceeds the pfd limit must not be placed into operation until a coordination agreement has been reached between the relevant Canada/U.S. licensees. Please note that ISED does not get involved in commercial coordination agreements. Licensees that have entered into such an arrangement are expected to collaboratively address and mitigate interference issues.

Commercial coordination agreements typically take significant time and effort to finalize, particularly given the larger licenced areas in the U.S., which may require U.S. licensees to coordinate with multiple NCLL operators. As such, ISED encourages NCLL operators to meet the pfd limit, as this allows for quicker NCLL deployments and operation.

Based on the current permissible operating parameters of NCLL stations, ISED recommends that NCLL operators review the pfd limits if they are within:

• 38 km of the Canada/U.S. border when operating under a Medium Power licence
• 11 km of the Canada/U.S. border when operating under a Low Power licence

In the event that a U.S. flexible use system is receiving cross-border interference from a Canadian NCLL system, ISED may direct the NCLL operator to reduce its pfd level at the border or impose additional measures such as Time Division Duplex (TDD) synchronization to resolve the interference issues.

In the event that a Canadian NCLL system is receiving cross-border interference, the NCLL operator can request assistance from ISED by contacting the nearest regional ISED district office (see RIC 66 - Addresses and Telephone Numbers of District Offices).

2.1.1 Determining the PFD level

The following example illustrates how the pfd level at the Canada/U.S. border may be determined through calculation. This example is for illustration purposes only, and assumes line‑of‑sight (LoS) conditions, free-space path loss, and an omni-directional antenna.

Example station parameters are provided in Table 1.

1. Note that the example assumes LoS conditions. Where LoS does not apply, an appropriate propagation model that takes the non-line-of-sight situation into account should be used. This may require expressing antenna height above average terrain (HAAT) instead of AGL.

2. The example assumes an omni-directional antenna and applies the maximum gain toward the Canada/U.S. border. Please note that the pfd limit is applicable to all points along the Canada/U.S. border. Consequently, it is imperative that the NCLL base station complies with this limit in any direction. Therefore, for directional antennas, the NCLL operator should take into account the transmitter antenna gain in the specific direction towards the Canada/U.S. border when calculating the pfd.

3. Since the example assumes LoS and an omni-directional antenna, the worst-case distance for this example would be the shortest distance from the NCLL base station to the Canada/U.S. border. This may not be the case for non-LoS or NCLL base stations using directional antennas.

Figure 1: Example deployment scenario near the Canada/U.S. border

For this example, the pfd level can be calculated as follows:

P_T'
= P_T − 10 log B_MHz
= (-5 − 10 log (10)) dB(W/MHz)
= -15 dB(W/MHz)

P_border
= P_T' + G_T – Path Loss
= (P_T' + G_T − 20 log F_MHz − 20 log D_km − 32.4) dB(W/MHz)
= (-15 + 5 − 20 log (3935) − 20 log (5) − 32.4) dB(W/MHz)
= (-15 + 5 – 71.90 – 13.98 − 32.4) dB(W/MHz)
= -128.28 dB(W/ MHz)

Then, the power flux density in dB(W/m²) in 1 MHz may be calculated as follows:

pfd
= P_border − 10 log (λ² / (4π))
= (-128.28 – 10 log ((0.076239 )² / (4π)) m²
= (-128.28 − 10 log (462.53 x 10^-6 m²)) dB(W/m²) in 1 MHz
= (-128.28 − (-33.35)) dB(W/m²) in 1 MHz
= -94.93 dB(W/m²) in 1 MHz

In this example, the preliminary analysis shows that the station exceeds the pfd limit since -94.93 dBW/m²/MHz is greater than the pfd limit of -114.5 dBW/m²/MHz.

2.1.2 Reducing the PFD level

If the analyses (e.g., measurements, calculations, etc.) conclude that the pfd limit is not met, NCLL operators may consider using various techniques to reduce the pfd level, including, but not limited to, lowering the power towards the Canada/U.S. border by changing antenna directivity/orientation, adding shielding, changing station location, reducing power, etc.

Note that the above calculation in section 2.1.1 uses the free-space path loss propagation model. This model can be overly conservative in estimating potential for interference in some cases as it does not take into account factors such as terrain and clutter that could decrease the signal strength at the receiving location (i.e. Canada/U.S. border). NCLL operators should consider using other propagation models that most closely resemble the propagation environment involved.

NCLL operators may also wish to seek assistance from a professional, such as a qualified radio frequency engineer, to determine compliance with the pfd limit according to their individual deployment scenarios and parameters.

NCLL operators are advised to keep all relevant analyses on file as ISED may require operators to demonstrate compliance with the pfd limit set forth in the SRSP.

2.1.3 Coordination with impacted U.S. flexible use licensees

If an NCLL operator's base station would exceed the pfd limit, the NCLL operator must coordinate with potentially impacted U.S. flexible use licensees prior to operating its base station.

To identify impacted U.S. flexible use licensees, NCLL operators can perform a "License Search" on the FCC's Advanced License Search tool.

Steps on how to use FCC's Advance License Search tool are provided below:

In the "Call Sign & Radio Services" section, for Service Group,

• Select "MidBand"
• Select "PM- 3.7 GHz Service"

In the "Frequencies" section, for Frequency,

• Select the range from 3900 MHz to 3980 MHz

Press the "Geosearch" button. This brings up a second search screen where you can limit results to a particular geographic area. Enter the appropriate U.S. State(s) and county(ies) where the pfd limit will be exceeded.

Press the "Search" button to obtain a list of results.

To find the contact information for an individual result, click on its lease ID.

Please note that the above instructions pertain to a third-party website not managed by ISED and could change without notice.

If the above steps are no longer applicable, the NCLL operator may contact the relevant regional ISED district office (see RIC 66 - Addresses and Telephone Numbers of District Offices) for assistance.

2.2 Co-existence with U.S. registered fixed satellite service earth stations

As noted above, NCLL operators near the Canada/U.S. border must not cause harmful interference to U.S. registered FSS earth stations operating in the 4000-4200 MHz band. Harmful interference, as defined in the Radiocommunication Act, means an adverse effect of electromagnetic energy from any emission, radiation or induction that:

1. endangers the use or functioning of a safety-related radiocommunication system; or
2. significantly degrades or obstructs, or repeatedly interrupts, the use or functioning of radio apparatus or radio-sensitive equipment.

As a best practice, ISED encourages NCLL operators who are planning to deploy, operate, or modify a base station within 10 km of the Canada/U.S. border to check whether there is a nearby U.S. registered FSS earth station within 10 km of the NCLL base station. Please see FCC's Updated C-Band Incumbent Earth Station List for the location of U.S. registered FSS earth stations. It is noted that regardless of the distance between an NCLL station and a U.S. FSS earth station, the same cross-border provision with regards to harmful interference applies.

In the event that there is a nearby U.S. registered FSS earth station, NCLL operators may wish to contact the relevant earth station licensees to ensure that their stations do not cause harmful interference.

In the event of cross-border interference, ISED will require the NCLL operators to take necessary steps (e.g., changing antenna directivity, adding shielding, changing station location, reducing power, shut down of specific station etc.) to mitigate the interference. It is the NCLL operator's responsibility to ensure there is no negative impact to U.S. registered FSS earth stations. NCLL operators may wish to seek assistance from a professional, such as a qualified radio frequency engineer, in evaluating and addressing any interference issue.

Note that U.S. registered FSS earth stations only receive signals in the 4000-4200 MHz band. They do not transmit signals in this band and therefore, will not cause interference to an NCL licensee's base station.