Technical Frequency Assignment Criteria
For fixed point-to-point radio services with digital
modulation operating in the frequency range 51.4 to 52.6 GHz
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Technical Frequency Assignment Criteria
For fixed point-to-point radio services with digital
modulation operating in the frequency range 51.4 to 52.6 GHz
|
RA381 is also available in
(204 KB)
Foreword
It is required by the Wireless Telegraphy Acts, 1949 and 1998 that no radio apparatus shall be installed or used in the United Kingdom, except under the authority of a licence granted by the Secretary of State. It is a condition of such a licence that the performance of the radio equipment meets certain minimum standards laid down in the UK Interface Requirement 2000 document.
This document details the frequency assignment criteria and principles that will be employed by the RA in the selection of frequencies for use by fixed point-to-point, digital radio equipment operating in the band or frequency range specified.
These assignment criteria are subject to updating and amendment, and intending operators / manufacturers should consult the latest version of this document complete with any amendments. Single copies of this document are available free from the RA library at the address below:
ADDRESS:
Radiocommunications Agency
Library Services
Wyndham House
189 Marsh Wall
London E14 9SX.
Switchboard and 24 hour
enquiry service:
Telephone: 020 7211 0211
Library:
Telephone: 020 7211 0502/0505
Fax: 020 7211 0507
www.radio.gov.uk
1. General
1.1 Introduction
This document outlines the frequency assignment criteria and principles that will be employed by the RA in the selection of frequencies for use by fixed point-to-point digital radio services operating in the frequency range 51.4 to 52.6 GHz.
The channel plan shall be in accordance with that given in Clause 5.
This document is generated to take into account the equipment standard ETS 301 786 V1.1.1. The RA will currently license the following classes:
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Class 2 - |
Equipment performances based on typically 4-state modulation schemes (E.g.: 4-FSK, 4-PSK or equivalent). |
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Class 3 - |
Equipment performance based on typically 8-state modulation schemes (e.g. 8 PSK or equivalent). |
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Class 4 - |
Equipment performance based on typically 16 or 32-state modulation schemes (e.g. 16-QAM, 32 QAM or equivalent). |
The RA will only assign links meeting the assignment criteria given in this document.
1.2 Licensee's responsibility
The Foreword of this document states that the establishment, use or installation of transmitting or receiving apparatus is subject to the issue of a licence by the Secretary of State. The licensee must ensure that equipment conforms with and is maintained to the standard set out in the relevant UK Interface Requirement document.
1.3 Link Length Policy
For the 52 GHz Band there is no minimum path length. Modification to this policy will, in the first instance, be reviewed within the Radio Systems Working Group.
2 Transmitting and receiving installations
2.1 General
The transmitting and receiving installations shall conform to Clauses 2.2 and 2.3 below. The installations shall be implemented in accordance with good engineering practice.
2.2 Antenna directivity
The antenna installation at the licensed premises shall be such that the antenna pattern will not exceed the co-polar RPE given in the appropriate Technical Regulation with the zero degree datum being the boresight path between the two stations.
2.3 Antenna polarisation
The allocated plane of polarisation of emissions for radio links in this frequency band will be vertical. Operators who elect to use horizontal polarisation must inform and obtain approval from the RA assignment engineer.
The antenna alignment surface shall be aligned as precisely as possible. Misalignment shall be no greater than 3° .
2.4 Equivalent isotropically radiated power (EIRP)
The assigned value of EIRP will be stated in the licence and must not be exceeded although a tolerance of ± 3 dB on this assigned value will be allowed in practice. The maximum EIRP normally assigned will be 30dBW and this value is not to be exceeded under any circumstance.
3. Principles of assignment and EIRP derivation.
3.1 Normal assignment
A normal frequency assignment for a single or multi-section bi-directional link shall comprise a pair of radio frequencies of corresponding channel number, one from each of the low and high frequency groups.
3.1.1 Normal Assignment Flow Diagram
Annex C shows a flow diagram for the normal assignment process.
3.2 Multi-section links
In the case of a multi-section link the direction of transmission of the two frequencies shall alternate for successive repeater sections so that the transmitter frequency assigned to any station shall be taken from only one of the frequency groups in the lower or upper half of the band.
3.3 Go - Return separation
The frequency difference between a pair of corresponding go and return frequencies shall be 616 MHz.
3.4 Parallel links operating over the same path
In assessing the interference potential between parallel links operating over the same path, it is assumed that the wanted and interfering signals suffer correlated fading. Therefore, protection from interference is derived from frequency separation. To be classed as operating over the same path, the stations located at the sites at each end of the links must be within 10m of each other in the horizontal plane and within 2m in the vertical plane.
Table 1 lists the minimum frequency separations for like systems operating under these conditions. For mixed systems, the appropriate minimum separations are derived by the sum of half of the individual minimum separations given. The assignment software identifies available channels that meet the minimum frequency separation criteria, in accordance with the channel plan defined in Clause 5.
Table 1. Frequency separations.
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Minimum capacity(Grade) |
Spectrum Efficiency Class (Ref. Clause 1.1) |
Minimum separation between carriers on a parallel route operating over the same path. |
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2 Mbit/s |
2 |
3.5 |
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4 Mbit/s |
2 |
3.5 |
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8 Mbit/s |
2 |
7.0 |
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16 Mbit/s |
2 |
14.0 |
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34 Mbit/s |
2 |
28.0 |
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51 Mbit/s |
3 |
28.0 |
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8 Mbit/s |
4 |
3.5 |
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16 Mbit/s |
4 |
7 |
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34 Mbit/s |
4 |
14 |
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51 Mbit/s |
4 |
14 |
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140/155 Mbit/s |
4 |
56 |
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3.5 Antenna discrimination
In assigning frequencies for links which are in the same geographical area due consideration shall be taken of the antenna discrimination. When available, data derived from a manufacturer' guaranteed RPE will be used and where not available the appropriate RPE specified in the UK Interface Requirement 2000 document will be assumed.
3.6 Path Clearance
It will usually be assumed that each hop has a clearance from obstructions of not less than 0.577F between the transmitting and receiving antennas at the two stations, under conditions corresponding to values of the ratio K greater than 0.7.
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F : |
First Fresnel Zone Clearance |
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K : |
Ratio of effective earth radius to real earth radius |
3.7 Path Loss
3.7.1 Median Path Loss
The median path loss between two stations will be equal to the free space path loss plus the atmospheric gaseous absorption:
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Path Loss = 92.45 + 20log(d) + 20log(f) + Gaseous Absorption. |
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where: |
d = distance between
the stations in km. |
3.7.2 Gaseous Absorption
The link budget shall include contributions from gaseous absorption in addition to the path free space transmission loss. Gaseous absorption is based on oxygen and water vapour data obtained from ITU-R Rec. PN.676-1 Figure 1. At 52.6 GHz a gaseous specific attenuation of 0.87 dB/km shall be assumed, based on ground level, 15° C and a water vapour density of 10g/m3.
3.8 Availability
Availabilities greater that 99.99 % are to be agreed with the RA on a case-by-case basis.
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NOTE: |
Throughout this document, availability will be taken to mean propagation availability. |
3.9 Receiver Input Levels
Table 2. Receiver median signal levels.
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Capacity & Bandwidth |
Class |
Rx Median Signal Level |
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2 Mbit/s in 3.5 MHz |
2 |
-110 dBW + M |
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4 Mbit/s in 3.5 MHz |
2 |
-107 dBW + M |
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8 Mbit/s in 7 MHz |
2 |
-104 dBW + M |
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16 Mbit/s in 14 MHz |
2 |
-101 dBW + M |
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34 Mbit/s in 28 MHz |
2 |
-98 dBW + M |
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51 Mbit/s in 28 MHz |
3 |
-95 dBW + M |
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8 Mbit/s in 3.5 MHz |
4 |
-100 dBW + M |
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16 Mbit/s in 7 MHz |
4 |
-97 dBW + M |
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34 Mbit/s in 14 MHz |
4 |
-94 dBW + M |
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51 Mbit/s in 14 MHz |
4 |
-93 dBW + M |
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140/155 Mbit/s in 56 MHz |
4 |
-90 dBW + M |
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Note 1: M = Fade Margin. See Clause 3.10 Note 2: Minimum Fade Margin of 10 dB will be allocated. Note 3: In the case of protected equipment an extra allowance, agreed on a case by case basis with the RA, may be allowed for receiver input level. Note 4: All levels are referenced to Point C on the system block diagram in EN 301 786. |
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The RA will in general examine applications for the use of radio links on the assumption that the median signal level of the receiver input is as detailed in Table 2 and a transmitter power shall be assigned accordingly.
The levels in Table 2 are derived using the methodology shown in Annex A.
3.10 Fade margin
3.10.1 General
The two main factors considered, that cause the wanted signal to fade are multipath clear air fading and rain fade. Multipath clear air fading is considered dominant below about 10GHz and rain fade is dominant above about 15GHz. Consequently only rain fade effects are considered for the 52 GHz band.
3.10.2 Rain Fade Margin
The rain fade margin M1, for a given availability, depends on the path length, polarisation and geographical location. UK rain rates are shown in Annex E for each UK grid square for 99.99% availability (0.01% of average year).
The rain fade is derived as follows:
Values of regression coefficients k and a are given in Table 3 below. These have been derived by interpolation between the values in Table 1 of ITU-R Rec. PN.838, for the top frequency of the band:
Table 3. Regression Coefficients
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Frequency |
kV |
aV |
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52 GHz |
0.510 |
0.858 |
The path reduction term r is given in ITU-R PN Rec. 530-7 as:
The effective path length Le is found by multiplying the actual physical path length L, by the reduction term r found above.
The path attenuation exceeded for 0.01% of time is given by Equation 43 of ITU-R PN Rec. 530-7
The attenuation Ap exceeded for other time percentages p (over the range 0.001% to 1%) can be deduced from equation 44 of ITU-R PN Rec. 530-7:
3.11 Equivalent Isotropically Radiated Power calculation
The licence schedule will detail the assigned EIRP for each transmitting station. This is based on the following calculation:
EIRP = RX Median signal level + RX station feeder losses - RX antenna gain + Path Loss
Where the RX Median signal level is the receiver minimum input level plus the fade margin. The maximum CO-polar gain figure for the receiving antenna is used.
4. Interference assessment
4.1 General
The link to be assigned is co-ordinated with all other links in the same frequency band within a co-ordination zone radius of 70km around each site. The size of the co-ordination zone may be reviewed from time to time as operational experience is gathered. Interference to and from the proposed link is assessed taking into account the path profile between the two stations. Use is made of antenna radiation patterns to obtain the gain of antennas in the direction of unwanted signals.
The interference evaluation considers two conditions:
a) Median wanted signal against the unwanted signal enhanced by clear-air effects.
b) Faded wanted signal against median unwanted signal.
The combination producing the highest interference signal is taken.
The procedures followed are in line with ITU-R PN. Rec. 452 and outlined in the flow diagram shown in Annex D.
4.2 Interference Limits
The interference limits are derived as follows:
Interference limit = Reference sensitivity for BER = 10-6 (See Annex A) - W/U ratio.
4.3 Co and Adjacent channel limits
The maximum CO-channel and adjacent channel interference, at the receiver input, from a single unwanted source is shown in Tables 4 and 5. W/U ratios for single-entry interferers, relating to mixed capacity digital systems, are given by the matrices in Annex B, for frequency separations up to 3 times the wanted channel spacing. The above limits are set on the basis that the wanted signal is at the reference sensitivity level for BER = 10-6 detailed in Annex A.
The adjacent channel interference limits given in Table 5 do not apply to links operating on a parallel path over the same hop. Under these circumstances fading is assumed correlated with interference protection offered by frequency discrimination. See clause 3.4.
Table 4. Single entry CO-channel interference limits
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Capacity (Mbit/s) |
System Class |
W/U (dB) |
Interference Limit |
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2 Mbit/s in 3.5 MHz |
2 |
27 |
-137 + M |
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4 Mbit/s in 3.5 MHz |
2 |
27 |
-134 + M |
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8 Mbit/s in 7 MHz |
2 |
27 |
-131 + M |
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16 Mbit/s in 14 MHz |
2 |
27 |
-128 + M |
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34 Mbit/s in 28 MHz |
2 |
27 |
-125 + M |
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51 Mbit/s in 28 MHz |
3 |
34 |
-129 + M |
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8 Mbit/s in 3.5 MHz |
4 |
34 |
-134 + M |
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16 Mbit/s in 7 MHz |
4 |
34 |
-131 + M |
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34 Mbit/s in 14 MHz |
4 |
34 |
-128 + M |
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51 Mbit/s in 14 MHz |
4 |
34 |
-127 + M |
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140/155 Mbit/s in 56 MHz |
4 |
34 |
-124 + M |
Table 5. Single entry adjacent channel interference limits
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Capacity (Mbit/s) |
System Class |
W/U (dB) |
Interference Limit |
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2 Mbit/s in 3.5 MHz |
2 |
3 |
-113 dBW + M |
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4 Mbit/s in 3.5 MHz |
2 |
6 |
-113 dBW + M |
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8 Mbit/s in 7 MHz |
2 |
6 |
-110 dBW + M |
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16 Mbit/s in 14 MHz |
2 |
6 |
-107 dBW + M |
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34 Mbit/s in 28 MHz |
2 |
6 |
-104 dBW + M |
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51 Mbit/s in 28 MHz |
3 |
5 |
-100 dBW + M |
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8 Mbit/s in 3.5 MHz |
4 |
5 |
-105 dBW + M |
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16 Mbit/s in 7 MHz |
4 |
5 |
-102 dBW + M |
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34 Mbit/s in 14 MHz |
4 |
5 |
-99 dBW + M |
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51 Mbit/s in 14 MHz |
4 |
5 |
-98 dBW + M |
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140/155 Mbit/s in 56 MHz |
4 |
5 |
-95 dBW + M |
4.4 Multiple interferers
In Table 4, Table 5 and Annex B the single-entry digital W/U ratios include allowances for multiple interferers. The allowances are 4dB for CO-channel interferers and 6 dB for adjacent channel interferers independent of bit-rate.
5. Channel Plan
5.1 Derivation of radio frequency channels for the band 51.4 to 52.6 GHz in the UK.
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The channel arrangements based on a 14 MHz raster and extracted from CEPT Recommendation T/R 12-11 are as shown below: |
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Let: fr be the reference frequency of 51,412 MHz for the 51.4 to 52.6 GHz band. |
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fn be the centre frequency of the radio-frequency channel in the lower half of the band. |
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Fn be the centre frequency of the radio-frequency channel in the upper half of the band. |
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TX/Rx separation = 616 MHz |
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Separation band =112 MHz |
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Individual channel frequencies are expressed by the following relationships with fo and fn in MHz: |
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a) |
For systems with a carrier spacing of 56 MHz: |
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lower half of the band: |
fn = (Fr + 56n) MHz |
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upper half of the band: |
fn' = (Fr + 616 + 56n) MHz |
where n = 1,2,3,... 9 |
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b) |
For systems with a carrier spacing of 28 MHz: |
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lower half of the band: |
fn = (Fr + 14 + 28n) MHz |
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upper half of the band: |
fn' = (Fr + 630 + 28n) MHz |
where n = 1,2,3,... 18 |
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c) |
For systems with a carrier spacing of 14 MHz: |
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lower half of the band: |
fn = (Fr + 21 + 14n) MHz |
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upper half of the band: |
fn' = (Fr + 637 + 14n) MHz |
where n = 1,2,3,... 36 |
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CEPT/ERC/REC 12-11 E does not currently define a channel plan for 3.5 MHz or 7 MHz channels. It is the intention of the RA to permit these channel spacings on national basis. The RA will also take steps to amend CEPT/ERC/REC 12-11 E to incorporate 3.5 MHz and 7 MHz channel spacings using the procedure detailed below: |
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d) |
For systems with a carrier spacing of 7 MHz: |
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lower half of the band: |
fn = (Fr + 24.5 + 7n) MHz |
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upper half of the band: |
fn' = (Fr + 640.5 + 7n) MHz |
where n = 1,2,3,...72 |
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e) |
For systems with a carrier spacing of 3.5 MHz: |
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lower half of the band: |
fn = (Fr + 26.25 + 3.5n) MHz |
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upper half of the band: |
fn' = (Fr + 642.25 + 3.5n) MHz |
where n = 1,2,3,... 144 |
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Figure 1 Channel Arrangement for the 51.4 to 52.6 GHz frequency band.
Annex A : Receiver input levels and interference levels.
Receiver input levels and maximum permitted interference levels for digital systems operating in the frequency band 51.4 to 52.6 GHz.
Table A.1: Example noise budget and interference calculations for Class 2 systems.
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Channel Bandwidth: |
3.5 MHz |
3.5 MHz |
7 MHz |
14 MHz |
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Minimum Bit Rate: (Mbit/s) |
2 |
4 |
8 |
16 |
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Assumed modulation: |
4-PSK |
4-PSK |
4-PSK |
4-PSK |
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Thermal Noise KT (dBW/Hz) |
-204 |
-204 |
-204 |
-204 |
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RX Bandwidth B (dBHz) |
60.5 |
63.5 |
66.5 |
69.5 |
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Receiver Noise KTB (dBW) |
-143.5 |
-140.5 |
-137.5 |
-134.5 |
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Noise Figure (Note 3) (dB) |
13 |
13 |
13 |
13 |
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C/N for BER=10-6 without coding gain (Note 4) |
13.5 |
13.5 |
13.5 |
13.5 |
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C/N for BER=10-6 with coding gain (Note 4) |
- |
- |
- |
- |
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Fixed System Losses (dB)(Note 2) |
6 |
6 |
6 |
6 |
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Interference Margin (dB) |
1 |
1 |
1 |
1 |
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Reference Sensitivity for BER 10-6 (dBW) |
-110 |
-107 |
-104 |
-101 |
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Sensitivity for BER 10-3 (dBW) |
-114 |
-111 |
-108 |
-105 |
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Median RX Input Level (dBW)(Note 1) |
-110+ M |
-107+ M |
-104+ M |
-101+ M |
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Planned CO-channel Interference limit (dBW) |
-137 |
-134 |
-131 |
-128 |
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NOTE 1: M is fade margin, dependent on path length and availability required. NOTE 2: Includes modulation/demodulation losses, other implementation factors and Branching network losses for single channel to points C, C'. NOTE 3: Referred to point C. NOTE 4: Reference ITU-R Recommendation F1101. |
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Table A.2: Example noise budget and interference calculations for Classes 2, 3 and 4 systems.
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Channel Bandwidth: |
28 |
28 |
3.5 |
7 |
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Minimum Bit Rate: (Mbit/s) |
34 |
51 |
8 |
16 |
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Assumed modulation: |
4-PSK |
8-PSK |
16 QAM |
16QAM |
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Thermal Noise KT (dBW/Hz) |
-204 |
-204 |
-204 |
-204 |
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RX Bandwidth B (dBHz) |
72.5 |
70.2 |
63.5 |
66.5 |
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Receiver Noise KTB (dBW) |
-131.5 |
-133.8 |
-140.5 |
-137.5 |
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Noise Figure (Note 3) (dB) |
13 |
13 |
13 |
13 |
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C/N for BER=10-6 without coding gain (Note 4) |
13.5 |
18.8 |
20.5 |
20.5 |
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C/N for BER=10-6 with coding gain (Note 4) |
- |
- |
- |
- |
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Fixed System Losses (dB)(Note 2) |
6 |
6 |
6 |
6 |
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Interference Margin (dB) |
1 |
1 |
1 |
1 |
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Reference Sensitivity for BER 10-6 (dBW) |
-98 |
-95 |
-100 |
-97 |
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Sensitivity for BER 10-3 (dBW) |
-102 |
-99 |
-104 |
-101 |
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Median RX Input Level (dBW)(Note 1) |
-98 + M |
-95 + M |
-100 + M |
-97 + M |
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Planned CO-channel Interference limit (dBW) |
-125 |
-122 |
-127 |
-124 |
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NOTE 1: M is fade margin, dependent on path length and availability required. NOTE 2: Includes modulation/demodulation losses, other implementation factors and Branching network losses for single channel to points C, C'. NOTE 3: Referred to point C. NOTE 4: Reference ITU-R Recommendation F1101. |
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Table A.3: Example noise budget and interference calculations for Class 4 digital systems.
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Channel Bandwidth: |
14 |
14 |
56 |
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Minimum Bit Rate: (Mbit/s) |
34 |
51 |
140/155 |
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Assumed modulation: |
16 QAM |
16QAM |
16QAM |
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Thermal Noise KT (dBW/Hz) |
-204 |
-204 |
-204 |
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RX Bandwidth B (dBHz) |
69.5 |
71.5 |
77.4 |
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Receiver Noise KTB (dBW) |
-134.5 |
-132.5 |
-126.6 |
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Noise Figure (Note 3) (dB) |
13 |
12 |
12 |
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C/N for BER=10-6 without coding gain (Note 4) |
20.5 |
20.5 |
- |
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C/N for BER=10-6 with coding gain (Note 4) |
- |
- |
17.6 |
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Fixed System Losses (dB)(Note 2) |
6 |
6 |
6 |
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Interference Margin (dB) |
1 |
1 |
1 |
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Reference Sensitivity for BER 10-6 (dBW) |
-94 |
-93 |
-90 |
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Sensitivity for BER 10-3 (dBW) |
-98 |
-97 |
-94 |
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Median RX Input Level (dBW)(Note 1) |
-94 + M |
-93 + M |
-90 + M |
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Planned CO-channel Interference limit (dBW) |
-121 |
-120 |
-117 |
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NOTE 1: M is fade margin, dependent on path length and availability required. NOTE 2: Includes modulation/demodulation losses, other implementation factors and Branching network losses for single channel to points C, C'. NOTE 3: Referred to point C. NOTE 4: Reference ITU-R Recommendation F1101. |
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Annex B: Wanted to unwanted levels.
Tables B1a to B11c give the Wanted to Unwanted (W/U) ratio for all frequency offsets up to three times the wanted channel spacing.
The figures in the Annex B tables have been derived on the following basis:
CO-channel and adjacent channel W/U ratios for like with like systems have been linked to tables 4.4 and 4.5 and therefore to the appropriate equipment standard. W/U ratios for all other combinations have been derived from the filter discrimination plots detailed in document RSWG (97) 13 Rev.1 available through the Radiocommunications Agency Radio Systems Working Group.
Important Note:
When the wanted and unwanted channels of digital systems are not equal Step
1 in the Wanted to Unwanted tables is equal to 1/2 the narrowest bandwidth.
Thereafter the step sizes are equivalent to the narrowest bandwidth. When the
wanted and unwanted channels are the same all step sizes are equal to the bandwidth
of these systems. Shaded regions indicate a Wanted to Unwanted Ratio of -40
dB.
Wanted System 2 Mbit/s in 3.5 MHz
Wanted System 4 Mbit/s in 3.5 MHz
Wanted System 8 Mbit/s in 7 MHz
Wanted System 16 Mbit/s in 14 MHz
Wanted System 34 Mbit/s in 28 MHz
Wanted System 51 Mbit/s in 28 MHz
Wanted System 8 Mbit/s in 3.5 MHz
Wanted System 16 Mbit/s in 7 MHz
Wanted System 34 Mbit/s in 14 MHz
Wanted System 51 Mbit/s in 14 MHz
Wanted System 140/155 Mbit/s in 56 MHz
Annex C: Normal Assignment Process- Flow Diagram
Note: the following diagram is based on P.452-7 (1995 P Series Fascicle), but there are no differences between recent versions in the high-level structure of the method.
Annex D: High-level flow diagram for Recommendation ITU-R P.452
Annex E: UK Rain Rates in mm/hr for 99.99% availability by National Grid Square
History
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Document History |
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19th January 2001 |
381p 0001 00 |
First publication following drafting and approval within the RA's Radio Systems Working Group (RSWG). |
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Document Information: |
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Title: |
Frequency Assignment Criteria |
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Technical Editor: |
Brian Harrison |
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Working Filename: |
381p 0001 00 |
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RA
381 |
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