25th May 2000
SPWG/RSWG
Date:
Meeting:
Document Reference: R 0300 0016 00
Working Paper: RSWG (00) 16
Radiocommunications Agency (Fixed Links)
Contact: Brian Harrison Tel. 0207 211 0292
e-mail. Harrisonb@ra.gtnet.gov.uk
Radio Systems Working Group
Date: 30 May 2000
Title: Proposed TM4 paper addressing relaxation of transmission spectral mask for discrete unwanted
signals.
Objective: To obtain UK approval for the submission of TM4 paper attached as Annex A.
Introduction
RSWG paper R 0100 0004 00 was reviewed by the committee in January and approved, with minor
changes, for onward transmission to Dr Macchi, the ETSI TM4 chairman. The document raised a series
of issues relating to the proposed relaxation of limits for discrete unwanted signals transmitted within
250% of channel spacing. As a result of the issues raised the limits were revised. These revised limits
were circulated to members (Paper R 0200 0010 00) and reviewed at the March meeting. Members
were asked to submit their comments on the revised limits and, if possible, conduct tests to determine
the level of discrete interference that FS receiver’s, particularly those using high modulation orders,
could tolerate. No comments have been forthcoming although limited testing has been possible with the
co-operation of two companies. This paper combines a theoretical analysis of tolerable levels of
interference with data gathered from an equipment test at 23 GHz to determine the probability of a
degradation in FS system performance resulting from the proposed relaxation in transmission mask
limits.
2. Results of the 23 GHz, 16 QAM, receiver test.
System Parameters:
Frequency Band
Modulation.
Receiver Bandwidth
Receiver Sensitivity
23 GHz.
16 QAM.
50 MHz
-66 dBm
Note: Receiver reference sensitivity quoted in EN 300 198 = -66.5 dBm.
Comments
Co-channel
Centre Frequency
Frequency (GHz)
23.280
23.290
23.300
23.310
23.320
23.330
23.340
Level of Interfering CW signal
relative to the RSL for BER 10-5
(dB)
+29.0
-9.0
-12.0
-13.0
-12.0
-7.0
+24
Note: Worst case adjacent channel W/U ratio = +29 dB. Occurred at the image frequency with an offset
of 70 MHz.
3 Analysis of Results.
It can be assumed that the highest levels of transmitted spectrum power density in any FS frequency
band will be transmitted by systems operating on the narrowest channels. At 23 GHz the narrowest
channel 3.5 MHz. Therefore, the highest absolute discrete unwanted powers will occur when the
2
frequency of the unwanted signal is within 0 dB spectrum mask reference level. The analysis below is
based on this scenario.
Theoretical Co-channel W/U Ratio = C/N + Degradation in Noise Floor + N/I Ratio + System
Allowance + Multiple Interference Allowance.
= (20.5 + 1 + 6 + 2.5 + 4) dB
= 34 dB.
Maximum theoretical spectrum power density of interfering system, referenced to measurement
bandwidth, w.r.t. reference sensitivity = Tx mean power – 10log Cn/Bwe
where Cn = Narrow BW. Bwe = Measurement BW.
 Theoretical maximum discrete interference level referenced to Rx reference sensitivity level
= Co-channel W/U ratio + 10log Cn/Bwe - Level of relaxation
permitted.
= (34 + 10log 3.5 MHz/30 kHz - 7.7) dB where 7.7 dB is the
maximum permitted by ETSI for a 3.5 MHz transmission.
= 34 + 20 - 7.7 = 46.3 dB
It is worth noting that that discrete unwanted emissions must be spaced by a difference in frequency not
less than the minimum channel spacing.
4. Conclusion
The analysis in the preceding section indicates that for 23 GHz equipment the probability of
interference occurring as a result of the proposed relaxation is extremely remote. In theory the discrete
power level will be somewhere in the order of 46 dB below the reference sensitivity. Indications are
that a 16 QAM receiver operating in the 23 GHz band will experience a 1 dB degradation in
performance when subjected to discrete interference approximately 13 dB below reference sensitivity
level. For the case illustrated there is a safety region, between discrete interferer and critical level of
interference, of somewhere in the order of 30 dB. Even allowing for the limitations in this study it
would appear that there is a negligible threat to system performance as a result of this proposed change
to ETSI FS standards. It is recommended that the paper attached as Annex A be approved as a UK
submission to the forthcoming ETSI TM4 Plenary in Jersey.
RA2/FTSLU
31/5/2000
Attached: Annex A – Input paper to ETSI TM4.
3
Annex A to R 0300 0016 00
European Telecommunications Standards Institute
ETSI
ETSI STC TM4
TM4 Plenary, Jersey, 12 June to 23 March 2000
Date:
30 May 2000
Source:
Radiocommunications Agency
Title:
Proposal for resolving the CW spectral lines issue.
Purpose:
Discussion within Drafting Group
WG:
WP 1 - WI (REN/TM-4075, REN/TM-4111)
1.
TM4__ _td0--
Introduction.
At the Interim TM4/WP1 meeting, held in Paris between the 27 th and 29th March 2000, paper WP 105,
drafted by Roberto Macchi of Siemens, proposed changes to the limits, originally proposed at the
preceding plenary, for spectral lines exceeding the transmission mask. At the preceding TM4 plenary,
held during December 1999 in Sofia Antipolis, the Radiocommunications Agency had expressed
concern about the proposed relaxation. The main concern centred on the mixed system environment
where the possibility existed of a narrow-band transmission radiating an unwanted discrete signal
which, by coincidence, was co-channel to another system sharing the same spectrum.
2.
Summary and Recommendation.
As agreed with ETSI TM4 the Radiocommunications Agency organised tests on FS equipment to
determine the level of discrete interferer that FS receivers, operating to ETSI criteria, will tolerate
before performance degrades to unacceptable levels. Results from these tests have demonstrated that
the revised limits, now referenced to the measured spectrum power density of a transmitted wanted
signal, will not degrade the performance of systems operating in a mixed environment. The Agency
thanks TM4 membership for their co-operation and withdraws its opposition to this generic relaxation.
RA/FTSLU
31/5/2000