1、 Report ITU-R BT.2215(05/2011)Measurements of protection ratios and overload thresholds for broadcast TV receiversBT SeriesBroadcasting service(television)ii Rep. ITU-R BT.2215 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of th
2、e radio-frequency spectrum by all radiocommunication 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 Regio
3、nal Radiocommunication Conferences and 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 submi
4、ssion of patent statements and licensing 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 Re
5、ports (Also available online at http:/www.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 r
6、elated satellite services P Radiowave propagation 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 ap
7、proved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R BT.2215 1 REPORT ITU-R BT.2
8、215 Measurements of protection ratios and overload thresholds for broadcast TV receivers (2011) TABLE OF CONTENTS Page 1 Executive summary 2 2 Abbreviations . 2 3 Useful definitions . 3 3.1 Radio frequency signal-to-interference ratio (C/I) . 3 3.2 Radio frequency protection ratio (PR) 3 3.3 Receive
9、r (front-end) overloading threshold 3 3.4 Adjacent channel leakage power ratio 3 3.5 “Can” tuners 3 3.6 “Silicon” tuners . 3 4 References 4 4.1 Broadcasting technology characteristics . 4 4.2 Mobile technology characteristics 4 5 Measurement methodology 4 5.1 Example test set-up . 4 5.2 Wanted signa
10、l levels . 7 5.3 Frequency offsets between interfering signal and wanted signal . 7 5.4 Measurements in the presence of a time varying interfering signal . 7 5.5 UMTS uplink 7 5.6 LTE downlink 7 5.7 LTE uplink . 7 5.8 Interferer reference power level 8 5.9 Characterization of the interfering signal
11、. 8 5.10 Failure point assessment methods 8 5.11 Method for determining protection ratios and overloading thresholds. 8 2 Rep. ITU-R BT.2215 Page 6 Conclusions and further work required 14 Annex 1 DVB-T receiver performance in the presence of interfering signals from DVB-T, UMTS and LTE 15 1 Executi
12、ve summary This Report documents measurements of protection ratio (PR) and overloading threshold (Oth) against interference from other broadcasts or mobile broadband services in the 800 MHz band. The types of interference used in the tests and the actual tests themselves varies with the different br
13、oadcasting system and mobile technologies used around the world. The aim of the Report is to establish test procedures together with measurement results to assist in network planning and sharing studies for the co-existence of TV broadcasting, with either mobile services, or other services and appli
14、cations. The original test details and measurement data, together with information on which particular Recommendation and its version number was updated with this data are contained in the individual annexes. 2 Abbreviations BS Base station OthOverloading threshold PR Protection ratio TPC Transmit p
15、ower control UE User equipment the mobile handset RB Resource block a unit of data transmission in LTE, represented by a certain number of carriers in a uplink or downlink symbol in the frequency domain. FDMA Orthogonal frequency-division multiplex access a multi-carrier modulation system used for t
16、he LTE downlink. SC-FDMA Single carrier frequency division multiplex access a multi-carrier modulation system used for the LTE uplink. 3 Useful definitions 3.1 Radio frequency signal-to-interference ratio (C/I) It is the ratio, generally expressed in dB, of the power of the wanted signal to the tota
17、l power of interfering signals and noise, evaluated at the receiver input (see Recommendation ITU-R V.573). Rep. ITU-R BT.2215 3 The power of the wanted signal is measured in a bandwidth equal to the wanted signal bandwidth, while the total power of interfering signal and noise is measured in a band
18、width equal to the interfering signal bandwidth. 3.2 Radio frequency protection ratio (PR) It is the minimum value of the signal-to-interference ratio required to obtain a specified reception quality under specified conditions at the receiver input (note that this differs from the definition in Reco
19、mmendation ITU-R V.573). In this Report, the “specified reception quality” and the “specified conditions” have been defined separately by each entity that has undertaken measurements. Usually, PR is specified as a function of the frequency offset between the wanted and interfering signals over a wid
20、e frequency range. In this Report, PR specified in this way is referred to as “PR curve”. PR curves show the ability of a receiver to discriminate against interfering signals on frequencies differing from that of the wanted signal. 3.3 Receiver (front-end) overloading threshold Overloading threshold
21、 (Oth) is the interfering signal level expressed in dBm, above which the receiver begins to lose its ability to discriminate against interfering signals at frequencies differing from that of the wanted signal (i.e., the onset of strong non-linear behaviour). Therefore, above the overloading threshol
22、d the receiver will behave in a non-linear way, but does not necessarily fail immediately depending on the receiver and interference characteristics. 3.4 Adjacent channel leakage power ratio Adjacent channel leakage power ratio (ACLR) is the ratio of the filtered mean power centred on the assigned c
23、hannel frequency to the filtered mean power centred on an adjacent channel frequency. The requirements shall apply whatever the type of transmitter considered (single carrier or multi-carrier). It applies for all transmission modes foreseen by the manufacturers specification. For a multi-carrier bas
24、e station (BS), the requirement applies for the adjacent channel frequencies below the lowest carrier frequency transmitted by the BS and above the highest carrier frequency transmitted by the BS for each supported multi-carrier transmission configuration. The requirement applies during the transmit
25、ter ON period. 3.5 “Can” tuners “Can” tuners are classical superheterodyne tuners housed in a metal enclosure containing discrete components. Classically, there are fixed and tunable circuits made up from discrete inductors and transistors usually with varactor diode frequency control. The metal enc
26、losure should minimize RF interference and eliminate crosstalk and stray radiation. 3.6 “Silicon” tuners “Silicon” tuners are IC-based tuners integrating all tuner circuitry into a small package directly to be fitted onto main boards. The tuned circuits may be completely absent or can be integrated
27、onto the silicon. The silicon chip may be protected from external electromagnetic interference by a metallic cover. Silicon tuners have different characteristics to can tuners and their performance can be better and worse at some frequency offsets compared to can tuners. This technology is still dev
28、eloping. 4 Rep. ITU-R BT.2215 4 References 4.1 Broadcasting technology characteristics The following references explain the characteristics of the different broadcast systems including transmitter spectrum masks. DVB-T system characteristics: Recommendation ITU-R BT.1306, ETSI EN 300 744 DVB-T2 syst
29、em characteristics: Recommendation ITU-R BT.1877, ETSI EN 302 755 ISDB-T system characteristics: Recommendation ITU-R BT.1306, ARIB STD-B31 ATSC system characteristics: Recommendation ITU-R BT.1306, ATSC A/53 DTMB system characteristics: Recommendation ITU-R BT.1306, GB20600-2006. 4.2 Mobile technol
30、ogy characteristics The following references explain the characteristics of the different mobile broadband systems. UMTS system characteristics: ETSI TS 125.101, ETSI TS.125.104 LTE system characteristics: ETSI TS 136.101, ETSI TS.136.104. 5 Measurement methodology 5.1 Example test set-up An example
31、 basic test setup for protection ratio and overloading threshold measurements is depicted in Fig. 1. FIGURE 1 Report BT.2215-01DVB-TreceiverInterferingsignal generatorCombinerInterfering signal pathWanted signal pathAdjustableband-passfilterDVB-T signalgeneratorMPEG-2/4video sourceIsolatorObserverSp
32、ectrumanalyzerVariableattenuatorImpedancematching(50 /75)Rep. ITU-R BT.2215 5 It is necessary to insert an adjustable band-pass filter between the interfering signal generator and the combiner. The objective of this filter is to eliminate the noise generated by the interfering signal generator and a
33、djust the interfering signal to the correct interference transmission mask and adjacent channel leakage ratio (ACLR) values. In fact, most of the RF signal generators have a wide frequency range (from several hundred of kHz to several GHz) prohibiting the use of an internal adjustable RF channel fil
34、ter over their whole frequency range. Consequently, depending on the generated signal level, a non-negligible wideband noise may be observed at the generator output. The higher the generated interfering signal level, the higher the noise level. The reduction of the undesired wideband noise by filter
35、ing at the output of interfering signal generator is shown in Fig. 2. If this noise is not reduced by filtering, it is impossible to measure the actual protection ratios of the receiver under test. This is due to the wideband noise generated by the interfering signal generator, falling into the want
36、ed signal channel, which cannot be reduced by the receiver filter. In this particular case, the receiver loses its ability to discriminate against interfering signals on frequencies differing from that it is tuned to. This phenomenon is shown in Fig. 3. It is also advisable to insert an isolator bet
37、ween the combiner and the DVB-T signal generator to keep the power from the interfering signal generator returning to the DVB-T signal generator output. FIGURE 2 The benefit of band-pass filtering at the interfering signal generator output Report BT.2215-0290807060504030600 610 620 630 640 650 660 6
38、70 680Frequency (MHz)Useful DVB-T signalUseful DVB-T signal + unfiltered interfering signalUseful DVB-T signal + filtered interfering signal100110120psd(dBm/10kHz)6 Rep. ITU-R BT.2215 FIGURE 3 The benefit of band-pass filtering at the output of the interfering signal generator (wanted signal level =
39、 Rx sensitivity +10 dB) Report BT.2215-038070605040302070 60 50 40 30 20 10 0 10 20 30 40 50 60 70 80Frequency offset in MHz (fi-fw)Measurements conducted without filterMeasurements conducted with a filterCI/ (dB)805.2 Wanted signal levels Protection ratios and overloading thresholds of a receiver a
40、re derived from its C(I) curves (see 5.11). The measurements should be carried out by using different wanted signal levels to cover the range from weakest to strongest signals. The following wanted signal levels are advised as a possible range: receiver sensitivity +5, +10, +20, +30, +40, +50, +60,
41、+70 and +80 dB. This range could be extended if the overloading threshold of the receiver is not reached. At low wanted signal levels the protection ratio limit is usually reached before the overloading threshold. Therefore it is necessary to use higher wanted signal levels to reach the onset of ove
42、rload. 5.3 Frequency offsets between interfering signal and wanted signal It is usual to use the following frequency offsets: 0, N, (N+BWI), (N+2 BWI), (N+3 BWI), (N+4 BWI), and 9 BWW(image channel). Where: N = (BWW+ BWI)/2 BWW: wanted signal bandwidth BWI: interfering signal bandwidth However, regi
43、onal specific frequency offsets could also be used, and smaller steps where more detailed investigation is required. Rep. ITU-R BT.2215 7 5.4 Measurements in the presence of a time varying interfering signal An important difference between existing interference by other broadcast signals, and mobile
44、 signals is that in many cases the mobile signal power can exhibit significant time variation which can degrade the PR and Othperformance of some DTT receivers due to interfering with automatic gain control (AGC) and channel estimation algorithms. It is important to test against such types of interf
45、erence. Time variation occurs in (at least) the following circumstances: 5.5 UMTS uplink The UE can use transmit power control (TPC) to improve performance in mobile reception conditions where the channel can be rapidly changing. The effect of this is for the UE to vary its transmit power rapidly ov
46、er time in response to feedback messages from the BS. 5.6 LTE downlink The Base station output power can vary over time if only some resource blocks (RB) are used in each OFDMA symbol, or if some OFDMA symbols are completely empty. This tends to happen when the BS traffic loading is zero or at low l
47、evels. Consequently, in the presence of a BS interfering signal, it is recommended to carry out the measurements with different network traffic loadings of 0%, 50% and 100%. 5.7 LTE uplink The uplink signal can vary considerably in both the time and frequency domains depending upon the traffic loadi
48、ng required. In the frequency domain the number of RBs allocated for each SC-FDMA symbol can vary rapidly. In the time domain, there can be long periods where the UE does not transmit at all, leading to an irregular pulse like power profile. Consequently, in the presence of a UE interfering signal,
49、it is recommended to carry out the measurements with different data rates on the uplink. The modes should include both fully loaded continuous operation and time division multiplexed i.e. pulsed operation. 5.8 Interferer reference power level Signal level variation can be from level reductions or time division occupancy. In order to be able to see the degradations caused by time variation in the interfering signal, it is necessary to set the appropriate rms power or power spectral density (psd) of the activ
