International Civil Aviation Organization
ACP-WG S/Web
Meeting 6 IP-01
2/6/14
INFORMATION PAPER
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
2nd JUNE WEBMEETING OF THE WORKING GROUP S (SURFACE)
Agenda Item x:
SPECTRAL MASK SPECIFICATION
(Proposed by Hitachi)
SUMMARY
This document provides information about Spectral Mask Specification
measurement method and some actually measured waveform data of emission
1.
INTRODUCTION
To avoid the unnecessary interference for other system, the transmission power should be
regulated as Spectral MASK. This MASK specification has been derived from “The Spectrum
Mask requirement is taken from Title 47 CFR section 90.210.”. However, this measurement is not clearly
defined and may have several ways of measuring method.
2-1 SPECTRAL MASK Definitions
In SARPs 3. 5 SPECTRAL MASK AND Emissions, It is described as follows. 3.5.1 The power
spectral density of the emissions must be attenuated below the output power of the transmitter as follows:
a) On any frequency removed from the assigned frequency between 0–45% of the
authorized bandwidth (BW): 0 dB.
b) On any frequency removed from the assigned frequency between 45–50% of the
authorized bandwidth: 568 log (%of (BW)/45) dB.
c) On any frequency removed from the assigned frequency between 50–55% of the
authorized bandwidth: 26 + 145 log (% of BW/50) dB.
d) On any frequency removed from the assigned frequency between 55– 100% of the
authorized bandwidth: 32 + 31 log (% of (BW)/55) dB.
e) On any frequency removed from the assigned frequency between 100–150% of the
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authorized bandwidth: 40 +57 log (% of (BW)/100) dB.
f) On any frequency removed from the assigned frequency between above 150% of the
authorized bandwidth: 50 dB.
g) The zero dB reference is measured relative to the highest average power of the
fundamental emission measured across the designated channel bandwidth using a
resolution bandwidth of at least one percent of the occupied bandwidth of the
fundamental emission and a video bandwidth of 30 kHz. The power spectral density is
the power measured within the resolution bandwidth of the measurement device divided
by the resolution bandwidth of the measurement device. Emission levels are also based
on the use of measurement instrumentation employing a resolution bandwidth of at least
one percent of the occupied bandwidth.
This is derived from originally from “The Spectrum Mask requirement is taken from Title 47 CFR section
90.210.” and is based upon emission mask “M” .
However, for OFDM system such as AeroMACS, which adopt IEEE802.2009, ,the measurement
description g) and emission MASK description a) and b) , two issue should be considered for actual
system,
2-2 SPECRAL emission Measurement
When we compile the measuring method by g) description, the waveform and MASK is measured as
shown in figure 1.
Figure 1 Tx Spectral MASK for DL preamble
Spectral MASK, which described in SARPs is shown as purple line. The actual measurement data is
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shown as yellow line.
One of the issues is that the description of g) is not clear.
It is described as “The zero dB reference is measured relative to the highest average power”,
To define the average power for TDD transmission system, following conditions should be cleared to get
the same data for every measurement system. .
・average condition (number of data for average, average duration)
・detector setting
・modulation method
・data subcarrier condition (data configuration)
Or it should be defined as spectral power density not average power.
2-3 SPECTRAL MASK Specifications
This spectral mask is mapped by actual frequency bandwidth of 5MHz for a) to as table 1.
The spectral mask complied with this specification is shown as figure2.
Table 1 Specral mask for frequecy
Offset frequency from center
frequency(MHz)
±0～2.25
±2.25～2.5
±2.5～2.75
±2.75～5
±5～7.5
±7.5～
Attenuation (dB)
Figure 2 Tx Spectral MASK
0
0～26
26～32
32～40
40～50
50
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When the measurement, which define that the average power would be the average transmitting power,
MASK ranged to 4.5 to 5 MHz , condition b) should be considered.
WiMAX spec based on IEEE802.16 2009, transmission spectrum is configurated by OFDMA
subcarriers. And the preamble of DL transmission the number of subcarriers which have effective data is
429, which is complied as 8.4.6.1.1 Preamble as follows. The maximum bandwidth for DL should be
defined at preamble .
In this specification, Sub carrier interval : 10.94KHz
429 is derived as 512 - 41- 42 = 429
Therefore the effective data bandwidth should be as follows.
10.94kHz * (429-1) = 4.68MHz
In this case, 4.68MHz should be occupied as effective channel bandwidth.
The detail subcarrier configuration is shown in Figure 3.
±45%
Sub-carrier interval
Null sub-carrier
Sub-carrier 429
10.94 kHz
・・・・
・・
Effective Channel bandwidth
・・・・
・・
4.68MHz
Channel bandwidth 5MHz
Figure.3 Configuration of effective sub-carrier of preamble of DL transmission
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Although BW=5MHz of downlink transmission should have at least 4.68MHz bandwidth, Spectrum
Mask which compiled current specification only allow 45% offset = 2.25MHz offset .(4.5MHz)
This MASK specification shall cause contradiction to this transmitting specification as red circle of figure
2 shown like in figure 4.
Figure 4 Tx Spectral MASK for DL preamble
If this spectral mask complied with current specification of SARPs 3.5.1, the measured data would be
shown in Figure 4, and frequency edge at red line should be considered.
The actual data of figure1, spike is shown, on the condition of detector setting, as average detector in 045%, and is peak detector in 45-50%, because we considered 45-50% is spurious area.
For UL side, the number of subcarrier is 409.
Tthe effective data bandwidth should be as follows.
10.94kHz * (409 - 1) = 4.46MHz
In this UL case, current Spectral MASK can be applied..
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2.4 Proposal for Spectral MASK
1) Proposal 1
In OFDM system specification, it is not normal to define the attenuation inside the system
frequency band-width of 5MHz .It is proposed to define attenuation after 50% offset.
That is, it is proposed that Spectral MASK of SARPs 3.5, a) should be proposed to changed
like as follows.
a) On any frequency removed from the assigned frequency between 0–50% of the authorized bandwidth
(BW): 0 dB. b ) should be delegated. No change for c) to f)
This spectral mask is mapped by actual frequency as table 2
The figure of new proposed spectral MASK is shown in figure 5.
Table 2 Proposed Specral mask for frequecy
Offset frequency from center
frequency(MHz)
±0～2.5
±2.5～2.75
±2.75～5
±5～7.5
±7.5～
Attenuation (dB)
0
26～32
32～40
40～50
50
0
5
Attenuation [dB]
10
15
20
25
30
35
40
45
50
55
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
Offset Freq [MHz]
Figure 5 proposed Tx Spectral MASK for DL PUSC
WiMAX specification does not define the attenuation in-side the system band-width.
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2) Proposal 2
From IEEE802.2009 8.5.2, TX spectral MASK is defined as follows.
It has 20 and 10MHz, although, this specification is only specified to Wireless HUMAN
（Wireless High-speed Unlicensed Metropolitan Area Networks）, but is proposed 5MHz
spectral MASK for enlargement of this specification.
Figure.6 TX Spectral MASK for 10,20MHz defined by IEEE802.2009
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3. ACTION BY THE MEETING
ACP WG-S is invited to consider
SPECTRAL MASK specification should be reviewed according to the WiMAX transmission
specification and other OFDMA system specifications.
The choice would be
1) Proposed MASK description as proposal1
2) New MASK description as proposal2
3) Should use the MASK description based on Title 47 CFR section 90.210.
The detail of measurement condition should be also considered if new proposed specification
would adopt.