1、 Report ITU-R BT.2143-2(10/2010)Boundary coverage assessmentof digital terrestrial televisionbroadcasting signalsBT SeriesBroadcasting service(television)ii Rep. ITU-R BT.2143-2 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of t
2、he 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 Regi
3、onal 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 subm
4、ission 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 R
5、eports (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
6、related 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 a
7、pproved 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.2143-2 1 REPORT ITU-R B
8、T.2143-2 Boundary coverage assessment of digital terrestrial television broadcasting signals* (Question ITU-R 31/6) (2009-2010) Foreword This Report contains information gathered from Radiocommunication Study Group 6 and Radiocommunication Working Party 6A. The development of the report has been dri
9、ven by the fact that the measurement and verification of the planned coverage is of the utmost importance after the planning of digital broadcasting services. TABLE OF CONTENTS Page 1 Coverage . 3 2 Assessment of the coverage 3 3 Comparison with planned values 4 4 The different reception ways 4 5 Pa
10、rameters to be evaluated . 4 6 The model for coverage assessment . 5 Appendix 1 The results of experimental estimation of DVB-T system work stability under a multibeam signal 7 1 Introduction 7 2 Parameters of DVB-T transmission station 7 3 Parameters of experimental paths and test stations (see Fig
11、. 1) . 7 4 Measurement equipment 8 5 Methods and the results of the measurement 8 6 Conclusions 8 *It should be noted that the findings in this Report might not be applicable to countries signatory to the GE-06 Agreement. 2 Rep. ITU-R BT.2143-2 Page Appendix 2 The usage of a spectrum analyzer for fi
12、eld-strength measurements . 11 1 Introduction 11 2 Digital signal voltage measurement technique . 11 Appendix 3 The impact of signal parameters variation on DVB-T reception quality 13 1 Low or not present external interference conditions 13 2 Presence of external interference 14 Appendix 4 The impac
13、t of mountainous area conditions on reception quality of digital TV broadcasting . 17 1 The impact of propagation path on useful signal field strength . 17 2 The impact of reflected signals on reception quality 21 3 Estimation of digital set-top boxes work in multipath conditions 30 Attachment 1 to
14、Appendix 4 Detailed information on measurements 32 1 Measurement location 32 2 Measurement technique 32 2.1 Measurement of received signal level 32 2.2 Measurement of S/N . 32 2.3 Measurement of BER . 33 2.4 Determination of reception quality . 33 3 Description of transmitting network . 33 4 Measuri
15、ng equipment . 36 Appendix 5 Digital terrestrial television broadcasting reception conditions in the urban environment 38 1 The impact of the propagation path on useful signal field strength . 38 2 Conclusions 46 Attachment 1 to Appendix 5 Detailed information on measurements 47 1 Measurement locati
16、on 47 2 Measurement technique 47 2.1 Measurement of received signal level 47 2.2 Determination of reception quality . 47 3 Measurement routes 49 Rep. ITU-R BT.2143-2 3 1 Coverage The term “coverage” is typically used in this Report to represent all the points where the electromagnetic field strength
17、 is higher than the minimum theoretical required value and the interference signal level is lower to that indicated as protection ratio parameters in ITU-R Recommendations. Both wanted field strength and the potential unwanted interfering signals can be evaluated by means of theoretical calculations
18、 or by measurements. However, the extension of the coverage area for DTTB depends on several additional factors: a) the channel model adopted as reference (i.e. Rayleigh, Rice, ANWG, etc.); b) the modulation configuration adopted (which includes more than one hundred possibilities); c) the kind of t
19、he network implemented (SFN vs. MFN); and d) the reception types (fixed, portable, mobile, indoor), continuous and troposphere interferences, man made noise, and so on. It is clear that, when the electromagnetic field strength exceeds the minimum theoretical value, evaluated at reference clutter hei
20、ght, it should be protected against interference through the normal frequency coordination process. However, it is also possible to have good reception also with the electromagnetic field strength lower than the minimum theoretical value. In terms of theoretical evaluation, in the ITU-R DTTB Handboo
21、k, Edition 2002, both time and location variability of field strength have been defined. In particular for each reception condition a three-level approach has been defined: Level 1: single point reception. A point can be considered served if the minimum field strength required to guarantee a service
22、 is exceeded for more than 99% of the time. Level 2: small coverage area (100 100 m). It is necessary to introduce the level of the coverage. Coverage is defined as “good” if at least 95% of the points included in the area are covered. Coverage is defined as “acceptable” if at least 70% of the point
23、s included in the area are covered. Level 3: coverage area of transmitter. The global “good” and “acceptable” area of transmitter coverage is given respectively by the sum of all little areas. Coverage assessment of the transmitter is given by verification of the coverage area boundary in comparison
24、 with a theoretical one. As mentioned above, each result obtained using the three-level approach method is valid for a specific reception condition. It is necessary to specify for which reception condition (Level 1, 2 or 3) the evaluation has been done. 2 Assessment of the coverage The coverage of a
25、 specific area, as determined by a prediction method, should be verified by “in-field” measurements in order to assess prediction results. The digital terrestrial television reception system works on the basis of a “threshold” and the coverage depends on three factors: a) the access to the service,
26、b) the time availability, c) the location availability. 4 Rep. ITU-R BT.2143-2 The service can be defined available at the boundary, under Level 1 conditions, if the following two statements are true: BER (bit error rate) after Viterbi is less than 2 104(QEF) and measured field strength is higher th
27、an the minimum needed field strength, indicated for the considered transmitter configuration and channel type (i.e. Ricean, Rayleigh). The service “time availability” can be defined if the above-mentioned statements are verified for any time interval. Time availability is evaluated taking into accou
28、nt both transmitter status and channel conditions (interferences, reflections, propagation and so on). The service “spatial availability” can be defined if the above-mentioned items are verified under Level 2 conditions. In such cases the placement of receiving antennas is not critical. The coverage
29、 assessment criteria should be based on the described factors and should also take into account practical objectives such that: measurements should be repeatable in the conditions and in the results; measurement procedures should provide results in an efficient way; the methods do not necessarily ha
30、ve to be sophisticated and expensive. 3 Comparison with planned values The field strength and BER change continuously during the antenna positioning process up to clutter height above ground level. The observed values depend on the different path combinations and also on the effects of obstruction a
31、t low height of the receive antenna. Both wanted and unwanted interfering signal field-strength values should be calculated and used in the comparison process. As far as the measurements are made to the fixed high, the appropriate propagation prediction model is to be chosen for the comparison. 4 Th
32、e different reception ways The digital television signal can be received in different ways. The conventional method considered for planning for early DTTB service planning is based on fixed receiving antennas placed on the roof of buildings, as for analogue systems. Moreover, it needs to be consider
33、ed the same antennas are used which are already in place for analogue systems. The criteria proposed herewith are based principally on fixed reception conditions. For fixed reception, the channel conditions under Rice propagation mode can be assumed quite constant in time. Reception conditions based
34、 on mobile or portable systems are related to extremely variable context and further studies are needed. 4.1 In cities and forest park areas, propagation of a digital television signal can be the multibeam. It renders essential influence on an opportunity of decoding action of a signal. Variation of
35、 value of field strength of a digital television signal due to its multibeam propagation is shown in the Appendix 1. This variation reaches essential values for terminal conditions BER = 2 104. Appendix 2 describes the usage of a spectrum analyzer for field-strength measurements. 5 Parameters to be
36、evaluated As reported in the current version of Recommendation ITU-R SM.1682 at 2.6, the parameters to be evaluated are: field strength and BER after different decoding. The BER after Viterbi (VBER) is used to determine the threshold of QEF condition. One more parameter should also be recorded durin
37、g measurement activities. It is MER (modulation error ratio) at the transmitting site. MER represents a synthetic form of constellation analysis. If the MER value at the transmitting site is lower than an established value, e.g. 32 dB, the measurement activities should be stopped due to possible tra
38、nsmission failure. Rep. ITU-R BT.2143-2 5 Appendix 3 provides the results on evaluation of dependence of the DVB-T signal quality on the filed strength and BER after Viterbi decoder and after Reed-Solomon decoder. 6 The model for coverage assessment It is well known that field strength measured at r
39、eceiving sites varies with location. The variability, at fixed power flux-density, depends on amplitude and phase combination of several paths that reach the receiving antenna. Variability is more accentuated for CW signals than spread spectrum signals. The reflected paths can give either possible p
40、ositive (additive or subtractive) or negative contributions. Negative contributions are connected to the intersymbol interference that happens when the delay of one or more paths is greater than the guard interval. Possible positive contributions are generated when the paths delay is lower than the
41、guard interval. The presence of several paths falling into the guard interval frame can result in additive or subtractive contributions depending on implementation of Viterbi soft decision, fixed or moving research window and paths phase. The intrinsic non-linearity related to Viterbi soft decision,
42、 protection levels, temporal and spatial dispersion gives as a result a low correlation between field strength and BER. Existence of a correlation law is yet to be studied. As far as defining a planning method the coverage border line for E70and E95, in the coverage assessment is important to verify
43、 the real extension of border lines. For fixed reception, it is proposed the scale reported in Table 1 is used. TABLE 1 DTTB coverage assessment BER Field strength VBER 2 104VBER 2 104E 2 104. The diagram of BER in the function Eeq was schemed according to the results of the measurements. Measuremen
44、t results are given in Fig. 2. At this picture the numbers of curves correspond to the numbers of the paths; points enclosed in the brackets are places conditionally the device showed “BER 108” at the same time, because 108 is its lower-range value. 6 Conclusions Path 1 The threshold value Eeq comes
45、 to 38-40 dB for open single-beam paths (curves 1 and 2) whereas it amounts to 58 dB and more under multibeam (dispersed) signal Eeq. Path 2 In an open path, located, even partially (especially the end part of it), over a water surface, another beam comparable in strength to the direct one can be cr
46、eated by the water surface in the receiving point. Resulting from the accidentally unfavourable rate of Eeqphases, the summation of two antenna currents can cause a random value, which, in this case, will be slightly higher than the value of the currents on open land paths (curves 1 and 2). Path 3 T
47、he results show that multibeam transmission plays an important role in the DVB-T broadcasting zone. That is why when planning certain networks and estimating corrections value with respect to a minimum field strength of a signal Emin2in use it is better to pay attention to this fact. For the detaile
48、d information see Dotolev et al. 2002. 2The Chester 1997 Multilateral Coordination Agreement relating to Technical Criteria, Coordination Principles and Procedures for the introduction of Terrestrial Digital Video Broadcasting (DVB-T). Chester, 25 July 1997. Rep. ITU-R BT.2143-2 9 FIGURE 3 Razmetele
49、voPath 3Path 4Mobile stationStrelnaGulf of FinlandRazmetelevoMobile stationMobile stationMobile stationMoykaSestroretskPath 1Path 2SestroretskStrelnaGulf of Finland1234MoykaDVB-TtransmitterSt. PetersburgFrom DVB-T transmitter10 Rep. ITU-R BT.2143-2 FIGURE 4 ( )( )( )( )40 50 60BERPath 1Path 2Path 3Path 4BER = 2 x 10 410210410610810101012 (dB( V/m)References DOTOLEV, V. G., JILTSOV, A. U., KOLESNIKOV, C. V. et al. 2002 Some measurement results of digital ground-based broadcasting in the exper
