1、 Report ITU-R SM.2156(09/2009)The role of spectrum monitoring in support of inspections SM SeriesSpectrum managementii Rep. ITU-R SM.2156 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spectrum by all radio
2、communication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication Conferences and
3、Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statements and licensin
4、g declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Reports (Also available online at http:/w
5、ww.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave p
6、ropagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in English by the Study Group un
7、der the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2009 ITU 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R SM.2156 1 REPORT ITU-R SM.2156 The role of spectrum monitoring in
8、support of inspections (2009) TABLE OF CONTENTS Page 1 Scope 2 2 Introduction 2 2.1 Effective radiated power and field strength 2 2.2 Measurement of spurious emissions . 3 2.3 Mask measurements 4 2.4 Frequency measurements 4 Annex 1 Example of monitoring used in inspections planning in the Netherlan
9、ds 5 1 Comparison of field-strength measurements with calculated values . 5 2 Trends . 7 3 Bandwidth . 8 4 Measurement schedule . 9 5 Summary . 10 Annex 2 Example of mobile monitoring to select candidates for PLT network inspections in Brazil . 10 1 Introduction 10 2 Mobile monitoring station used 1
10、0 3 Device under test configuration 11 4 Reference documents 11 5 Measurements . 11 6 Comparing loop antenna plus spectrum analyser vs. mobile monitoring station . 12 7 Conclusion 20 2 Rep. ITU-R SM.2156 1 Scope This Report discusses the role of spectrum monitoring in support of inspections, support
11、ed with examples. Where the link of spectrum monitoring with inspections is very strong or direct we can speak of monitoring in support of inspections. To avoid misunderstanding it needs to be clarified that this support and “on site inspections” are not interchangeable but could be complementary in
12、 the total inspection process. The Report also contains national examples of prototypes and operational monitoring mechanisms in the form of annexes. The task of conducting spectrum monitoring in support of inspections is not new but superior results are obtained due to improvements in automatic con
13、trol of monitoring equipment. A technique discussed is the use of common monitoring/measurement equipment for triggering an inspection by recording the same parameters that would be recorded during an inspection. Monitoring results obtained with this equipment can be used to select candidates for an
14、 “on site” inspection. These monitoring processes do not form a replacement for on site inspections but can be used to save money in situations where otherwise a large number of expensive and sometimes unique measurement setups would be required. 2 Introduction Remote inspections are not new but due
15、 to the availability of automation the form of such an inspection nowadays may outperform the results gathered with traditional spectrum monitoring techniques. To place the remote inspections in their right perspective something needs to be said about accuracy and measurement uncertainty. Measuremen
16、t uncertainty is influenced by both the used methodology and equipment limitations. A few of the basic parameters to be measured are discussed here along with an indication of their limitations. A thorough understanding of the limitations of using monitoring tasks to assist inspections is essential
17、for efficient coordination between the monitoring services and inspection services, and for the effectiveness of such programs. 2.1 Effective radiated power and field strength When observing several different methods to obtain e.r.p. we can identify some associated accuracies as the result of the me
18、thodology that is used. Table 1 shows the most common ones for e.r.p. measurement/estimation. Each method has its own advantage and obtainable accuracy. TABLE 1 Type e.r.p. result Accuracy (2 )(dB) Independence Monitoring along a route e.r.p. and antenna diagram 8 dB Yes Long term monitoring 1 or 2
19、directions 5 dB Yes On site inspection Max. e.r.p. only 2 dB No (extra uncertainty is 7 dB) Helicopter measurement e.r.p. and diagram 1.4 dB Yes Rep. ITU-R SM.2156 3 We can see that for an on site inspection an additional uncertainty is added. The reason for this is that most large transmitting stat
20、ions have combiners, filters and large synthesized antenna structures with no physical access to their individual components. Attenuation values can only be measured during installation of the station and are therefore only known with a reasonable accuracy to the operator of the station. For small s
21、tations with access to all components this additional uncertainty does not apply. Instead of visiting transmitter sites and carry out physical inspections or measuring with mobile monitoring units, transmitters can also be measured from fixed (remote) stations. In many countries monitoring services
22、have remote monitoring stations available that can be used to measure basic transmitter parameters from different angles and compare the results with theoretical values obtained with planning tools. By automating these measurements, the data processing and the presentation of results this is not tim
23、e consuming anymore. If automation is applied well it can be brought back to a fully administrative process, a technical capable monitoring engineer however should always take the final responsibility in quality assurance and interpreting the results. The end results of a measurement could be plots
24、from every channel and a list presenting a green/red situation for all transmitters. The management of the monitoring station or enforcement department can decide what the follow up of these results should be. It should be noted that for obtaining the typical accuracy noted in the Table the monitori
25、ng units need to be placed at distances where field strength variations due to propagation effects are within reasonable limits. The measurement uncertainty of the monitoring setup and the number of monitoring stations used to obtain a value are factors to take into account. Usually a monitoring rec
26、eiver has a field strength indicator but lack both sufficient accuracy and linearity. Another factor is the antenna, the common monitoring antennas are broadband but do not have a well defined antenna pattern and gain over the whole frequency range. The described method therefore is not a replacemen
27、t for a helicopter measurement or a physical inspection with true measurement equipment but can make the selection of candidates for further inspection easier. 2.2 Measurement of spurious emissions In addition to remote e.r.p. and field strength measurements it is also possible to perform remote spu
28、rious measurement but the limitations are different. Spurious is usually presented as an x dB down value and consists of out of band emissions, noise, harmonics etc. A factor influencing the measurement is the antenna of the transmitting station under test. Specially the antenna pattern is of concer
29、n. Spurious signals relatively far from the wanted signal are transmitted with a completely different antenna pattern than the wanted signal. This depends of course on the bandwidth and other properties of the transmitting antenna but the uncertainty is undeterminable in most cases. Figure 1 gives a
30、 graphical presentation of the problem. The blue antenna pattern is for the wanted signal and the red for one of the spurious components. In the main lobe the spurious seems to be 20 dB down and at an azimuth of 285 there is 10 dB more spurious than the wanted signal. We can conclude that multiple m
31、easurement points are needed to conclude something about the absolute value of a spurious emission using remote measurement sites. It is very unlikely that a single remote monitoring station can be used perform an adequate spurious measurement. An indication of the presence of measurable spurious is
32、 possible specially when measured from different locations (under different angles). 4 Rep. ITU-R SM.2156 FIGURE 1 Transmitter antenna pattern for wanted and spurious signal Report SM.2156-0110dB90051015202530354027030033003060240 120210 15018020dB2.3 Mask measurements Mask measurements are used to
33、measure bandwidth or conformity of the emitted spectrum to a standard or reference. Usually a spectrum analyser or measurement receiver with scanning capabilities is used for this type of measurement. For certain measurements a defined scanning or processing speed is needed due to the dynamic behavi
34、our of the signal. Monitoring receivers however can mimic some functions of a spectrum analyser with the right software. The measurement accuracy and scanning capabilities of such a system should be observed in relation to the observed deviations from the mask and the results only be used to trigger
35、 follow up inspections. 2.4 Frequency measurements A standard monitoring receiver usually does not have the capability to perform very accurate frequency measurements. Most of this inaccuracy comes from temperature changes at the receivers location and the lack of a frequency standard such as an ove
36、n controlled reference oscillator. A true frequency counters is also not present in most cases, instead of this a frequency discriminator or similar solution is used. All this together leads to a relative unstable frequency measurement setup. A possibility to perform indicative measurements is howev
37、er to use an external stable frequency source in the same frequency range as the signal to be tested. This can be a stable broadcasting transmitter or a local reference source such as a from GPS-derived frequency standard. Calibration needs to be performed before each critical measurement. The resul
38、ts will have a large measurement uncertainty and can therefore again only be used to trigger follow up inspections. Rep. ITU-R SM.2156 5 Annex 1 Example of monitoring used in inspections planning in the Netherlands Often national administrations are responsible for planning and enforcement of the FM
39、 BC band. National frequency management uses planning tools to calculate coverage and field strength based on technical parameters, such as power, antenna height, antenna patterns from stations. These technical parameters are included in the licence conditions. There is a good correlation between th
40、eoretical and practical values so the same planning tools using measured values from monitoring stations as input could be used to determine the technical parameters of the transmitting stations to some extent. This example sets this principle and treat the investigation of the FM broadcasting band
41、(in Region 1: 87.5-108 MHz). The principle is of course also applicable for other services. 1 Comparison of field-strength measurements with calculated values Monitoring stations are as already said relatively inaccurate when it comes to measuring field strength and frequency. Trends and relative me
42、asurement values can however be determined quite well. In this practical example, data from a measured frequency band 87.500-107.500 MHz (107.480) is converted in two plots. One is a common spectrogram the other shows processed data with min/max/median values. For both plot the same data is used. Lo
43、ng-term (24 h) plots reveal the on and off switching of stations but also the main field strength with reasonable accuracy. FIGURE 2 Spectrogram and min/med/max plot including calculated values Report SM.2156-022010588 90 92 94TSO96 98f = 20 kHz Frequency (MHz)100 102 104 106dB(V/m)20406080100015TSO
44、 spectrogram lelystad, date: 24/04/04Time (h)Time (h)Frequency (MHz)100402088 90 92 94 96 98 100 102 104 10660TSO spectra NERA, date: 30/01/05 To = 0 h, = 23.8 hTEdB(V/m)MaxMedianMinTSO f = 20 kHz8006 Rep. ITU-R SM.2156 On every 100 kHz channel a min/max/median plot and also a pink line with a rhomb
45、ic on top is plotted, representing the theoretical calculated value obtained from a planning tool. The calculated value can be derived from the distance of the transmitter to the monitoring station and the allowed e.r.p. value in the licence using the proper planning model. This enables the user to
46、compare between measured and predicted (licence) field strengths. To estimate the effects of time variance of the signal a time plot over 24 h is produced showing the theoretical calculated value by a dotted line and a distribution plot over the same period. The coloured plot represents a moving ave
47、rage plot ion the channel under test and the adjacent channels. This information is used for two reasons: The first one is the stability of the monitoring system. Variations in measured values of a reference signal can be used to have an idea about the maximum achievable accuracy. The second is the
48、actual variation of the measured signal due to propagation which also influences the accuracy. FIGURE 3 Field strength over time, distribution and spectrum Report SM.2156-030TSO NERA 06/03/05 Freq: 97.6 MHzFieldstrength(dB(V/m)(Rotterdam Chir. (61.6 dB( V/m)City FM Freq: 97.61 0008006004002000100805
49、04020010060503070906030109080704020(dB(V/m)E5 10 15 20 20 40 80 10060 97.4 97.6 97.8Stddev = 4.6Gem = 62.310% = 67Median = 6390% = 56Modus = Plots as above are available for all channels on each remote station but accessing this information needs a management tool which is designed around a web interface. Figure 4 shows the interface which has the form of a spectrogram. To have access to all channel plots one can select the appropriate measurement day, remote station, the wanted channel by moving the cursor over the spectrogram and then click. The
