CEPT
STG(10)72
ECC
Electronic Communications Committee
STG #24
WGSE - SEAMCAT Technical Group
ECO, Copenhagen
8 December 2010
Date Issued: 1 November 2010
Source : ECO
Subject: #428 ACLR -> to add a new field for the edge channel
Document: for discussion
Summary
The ACLR interface has been enhanced to allow the channel edge to be set by the
user.
This feature is for testing in 3.2.3 beta1.
Proposal
STG is invited to consider the text as a proposal of explanation to the new feature
for the online manual and handbook.
Background ACLR model is used extensively in the mobile cellular community for compatibility
analysis. SEAMCAT uses the spectrum mask for its calculation. SEAMCAT display
has been modify for the users to have an information of the resulting ACLR when
setting the spectrum mask.
ACLR usage in SEAMCAT
1
Introduction
SEAMCAT does not use the ACIR (and consequently the ACLR) in its calculation. The ACLR is only
displayed as information to the user when setting the spectrum mask of the interferer.
When the victim system is CDMA or OFDMA only, the spectrum mask at the interferer will
automatically display the ACLR.
2
ACLR interface
Figure 1: ACLR interface – default value
When the ACLR display is activated, the Interfering Transmitter Emissions Mask dialog box is composed of
3 important parts

Part #1 corresponds the usual set of the spectrum mask

Part #2 corresponds to setting the ACLR parameters:

Adjacent channel (MHz) (default value = 1 MHz)

Emission bandwidth (MHz) (default value = 1.25 MHz)

Update display button

Part #3 corresponds to the display of the spectrum mask and the ACLR
When the user enters the mask, the ACLR is automaticaly calculated with the default ACLR setting
parameter values.
Figure 2: ACLR interface – with a spectrum mask – Step 1
For this example, assuming that the first adjacent channel starts at 4.5 MHz and the interfering emission
bandwidth of the system is 9 MHz, the user has to set the parameters as shown in Figure 3. The green
bars represents for information the various ACLR depending on each of the adjacent channels (see Figure
4 for a zoom of the display). On the right hand side the axis represent the normalized ACLR in dB.
Figure 3: ACLR interface – with a spectrum mask – Step 2
Figure 4: Zoom of the display
3
ACLR for OFDMA UL as interferer
Note that for an OFDMA UL interfering system of 10 MHz, where there is 5 active users to simulate, the
spectrum mask to set in SEAMCAT is defined over 2 MHz (10MHz / 5), but the ACLR is computed for the
full system emission bandwidth. Therefore the user would need to set:
4

Adjacent channel = +1 MHz (if the victim frequency is higher than the interferer) or -1 MHz (if the
victim frequency is lower than the interferer).

Interfering Emission Bandwidth = 10 MHz
Usage requirement
SEAMCAT allows the user to define the spectrum as part of a spectrum range which can be strictly above
or below the centre offset as shown in Figure 5.
Figure 5: Portion of spectrum mask definition (i.e. excluding the center offset)
This flexibility creates a restriction in the ACLR display. It is because the ACLR display algorithm is
normalized to the in-band power. Therefore, in order to generate the ACLR display it is necessary to have
the spectrum mask being defined within the range of the system emission bandwidth (centered to the
zero offset).
By default, in the case where a user would set the mask so that the ACLR would fail to compute, SEAMCAT
will automatically disable the ACLR display functionality as shown in Figure 6.
Figure 6: ACLR display functionality disabled due to the specific definition of the spectrum