1、 Rep. ITU-R BT.2035-2 1 REPORT ITU-R BT.2035-2 Guidelines and techniques for the evaluation of digital terrestrial television broadcasting systems including assessment of their coverage areas (Question ITU-R 31/6) (2003-2004-2008) CONTENTS Page 1 Introduction 2 2 Laboratory test plans 2 3 Field test
2、 plans 5 3.1 Recommended practices for developing field test plan 6 3.2 Coverage measurement procedures 12 3.3 Service measurement procedures . 16 3.4 Capture of channel characteristics 20 3.5 Analogue broadcast television measurements 22 3.6 Guidelines for comparative DTTB field tests. 24 3.7 Field
3、 survey methodology for fixed measurement of digital television reception . 25 3.8 Field survey methodology for nomadic measurement of digital television reception . 31 4 Representative equipment and costs. 37 5 System descriptions 38 Annex 1 Field test summary chart 41 Annex 2 Minimum DTTB comparat
4、ive field test summary chart 44 Annex 3 PN test sequences . 45 Annex 4 Multipath ensembles. 45 Annex 5 Laboratory test results 46 Appendix 1 Test transmission characteristics. 76 Appendix 2 DTTB site measurement data profile 77 Appendix 3 Recommended reference testing equipment . 79 Appendix 4 DTTB
5、coverage field study flow chart 80 2 Rep. ITU-R BT.2035-2 1 Introduction The objective of digital terrestrial television broadcasting (DTTB) testing and trials is to evaluate the performance of an available system or systems in a variety of transmission configurations and reception conditions. These
6、 may include: urban, suburban, and rural conditions; indoor as well as rooftop reception; reception on portable and mobile receivers in a variety of circumstances. The range of possible operational requirements is summarized in Table 1, together with the key factors and parameters that affect perfor
7、mance in the various operational circumstances. These requirements form the basis for the derivation of the laboratory and field trial programmes described in 2 and 3, as well as for providing the framework for the brief description of the three ITU-R recommended DTTB systems briefly described in 5.
8、 TABLE 1 While tests and measurements may be planned and conducted for specific reasons and objectives, others may analyse the resultant data with different reasons and objectives. Consequently, it is recommended that all tests, measurements and data-gathering herein documented be conducted accordin
9、g to these sets of principles and general procedures, in order that the resulting analysis and conclusions concerning different tests are consistent and meaningful. 2 Laboratory test plans The following procedures are intended to verify the performance of the DTTB modulators and receivers. These tes
10、ts include measurements of receiver performance in the presence of: random noise; input RF signal dynamic range; Operational requirement Primary factors affecting operational requirements Indoor fixed reception Multipath, non-line of sight, building penetration loss (on-frequency repeater) Outdoor f
11、ixed reception Multipath (static), low signal strength Portable reception Multipath (static and dynamic), low signal strength (on-frequency repeater) Mobile reception Multipath (dynamic), signal fading (single frequency network (SFN) Receiving modes Personal reception Multipath (static and dynamic),
12、 signal fading, penetration loss Channel bandwidth (6, 7 or 8 MHz) Determined by regulatory and/or licensing authority SFN Strong static and low-speed multipath distortion On-frequency repeaters (gap fillers) Static multipath Multimode operation Different types of modulation and coding, hierarchical
13、 transmission Maximum coverage System C/N requirement UHF only or UHF and VHF operation Sensitivity to impulse noise at VHF Rep. ITU-R BT.2035-2 3 static multipath interference; dynamic multipath interference; co-channel interference; lower and upper adjacent channel interference; impulse noise; pha
14、se noise. 2.1 Random noise impairment The purpose of these tests is to determine the DTTB receivers robustness to random noise impairment. The DTTB desired signal shall be adjusted at four different RF levels: very strong (15 dBm), strong (28 dBm), moderate (53 dBm) and weak (68 dBm). The noise leve
15、l shall be increased until the threshold of visibility (TOV) is reached and the C/N value shall be recorded. The signal levels in brackets are suggested typical signal levels. In the scope of laboratory tests, the TOV is considered to be reached when trained observer is able to detect some kind of a
16、rtefact on the image after ONE minute of observation. 2.2 Input RF signal dynamic range The ability of receivers to receive very strong to very weak signals shall be tested. The maximum and minimum RF signal level shall be determined by increasing and decreasing respectively the RF power signal leve
17、l at the receivers input until the TOV level is reached. At the maximum and minimum RF signal level, the noise level shall be increased until the TOV is reached and the C/N value shall be recorded. It is recommended that this test be performed at the lower, middle and upper parts of the VHF and UHF
18、bands. 2.3 Static multipath interference The performance of the DTTB receiver for diverse combinations of multipath representative of various reception environments shall be measured. The purpose of multipath testing is to measure the DTTB receivers robustness in the presence of multipaths with and
19、without random noise. For each test the noise level shall be increased until the TOV is reached and the C/N value shall be recorded. All the multipath tests shall be done with the DTTB signal RF level adjusted to the moderate level (53 dBm). Note that for consistence on the C/N values, signal power
20、level shall be the result of the combination of the main and the echo signals. Single echo: A single echo test shall be done, including pre and post-echo, with and without phase rotation. This test verifies the robustness of the receiver to decode the signal satisfactorily over a wide range of time
21、delays (negative and positive) with and without phase rotation. Suggested values are delays in the range of 80 s to 80 s and phase rotation in the range of 0 to 5 Hz. Multiple echoes: In previous tests in different locations and by different organizations various multipath ensembles have been used.
22、Examples of such ensembles are given in Annex 4. 2.4 Dynamic multipath interference The purpose of this test is to measure if the DTTB receivers robustness in the presence of a combination of multipath that are representative of various dynamic receiving conditions. Much of the experience gained abo
23、ut the performance of DTTB receiver was derived from experiments using urban mobile channel developed for GSM and for UMTS tests. 4 Rep. ITU-R BT.2035-2 It is appropriate to leave the development of specific dynamic channel profiles tailored for DTTB to an expert group that would be tasked to develo
24、p a detailed test plan. 2.5 Co-channel interference The purpose of this test is to determine the DTTB receivers performance under analogue TV and DTTB co-channel interference. Analogue TV to DTTB: The interference level (D/U) at TOV shall be recorded for three typical undesired analogue TV test sign
25、als and at least one should be a dynamic signal. The suggested interference signals are the dynamic Zoneplate and the colour bars at 75% saturation. These tests shall be done with the DTTB signal RF level adjusted to moderate level (53 dBm). DTTB to DTTB: The interference level (D/U) at TOV shall be
26、 recorded for one undesired DTTB signal with and without frequency offset of 10 kHz. These tests shall be done with the DTTB signal RF level adjusted to moderate level (53 dBm). 2.6 Lower and upper adjacent channel interference The purpose of this test is to determine the DTTB receivers performance
27、under analogue TV and DTTB lower and upper adjacent channel interference. Analogue TV to DTTB: The interference level (D/U) at TOV shall be recorded for three typical undesired analogue test signals and at least one should be a dynamic signal. The suggested interference signal is the dynamic Zonepla
28、te. These tests shall be done with the DTTB signal RF level adjusted to moderate level (53 dBm). Note that for lower adjacent channel interference test, the audio deviation shall be set to the maximum allowed, for example, complete BTSC (Broadcast Television Systems Committee) signal (stereo + secon
29、dary audio program (SAP) + professional audio channels (PRO). DTTB to DTTB: The interference level (D/U) at TOV shall be recorded for one undesired DTTB signal. These tests shall be done with the DTTB signal RF level adjusted to moderate level (53 dBm). 2.7 Impulse noise The purpose of this test is
30、to determine the DTTB receivers robustness to impulse noise impairment. Adding thin pulses of white noise to the RF signal may simulate the effect of impulse noise. For similarity with real conditions it is important to produce pulses of white noises, which varies in amplitude, repetition rate and p
31、ulse width. For each pulse width the noise level shall be increased until the TOV is reached. This test will be made in conformance with the following technical points: Due to practical difficulties in generating high-level gated Gaussian noise the wanted signal level should be 60 dBm. The gated noi
32、se signal should be divided into elements of approximately 250 ns. E.g. a 1 s test is made up of four consecutive 250 ns pulses, with random separations, contained within one orthogonal freguency division multiplexing (OFDM) symbol and within the ATSC frame. Despite the fact that such segmentation m
33、akes no difference to an ordinary receiver, real impulsive noise is like this after band limiting in the receiver, and it may lead to a difference in performance in receivers designed to provide countermeasures to impulse interference. It will also prevent receivers being designed to pass a simpler
34、test. The total effective periods (sum of all elements) in tests should be, 0.25, 0.5, 1, 3, 5 or 10 s. Rep. ITU-R BT.2035-2 5 The impulse noise simulation should also include a similar test using fast edges instead of gated Gaussian noise. It expected that tests with fast edges would be effective f
35、or testing tuners and devices ahead of tuners. 2.8 Phase noise impairment The purpose of this test is to determine the DTTB receivers robustness to phase noise. Phase noise is an inherent part of the RF systems and might be of significant relevance in the case of multiple frequency conversions. The
36、phase noise is simulated by injecting an FM modulated white noise signal at the local oscillator used in the up-conversion (IF to RF) of the DTTB modulated signal. The DTTB signal is adjusted and measured as for interference testing. This test shall be done with the DTTB signal RF level adjusted to
37、moderate level (53 dBm). The phase noise is generated with an RF signal generator and a random noise generator. The output of the random noise generator feeds the external FM source input of the RF signal generator used as the local oscillator of the DTTB up-converter (IF to RF). By selecting differ
38、ent peak deviations (0-50 kHz), a phase noise is created on the carrier output of the RF signal generator. The phase noise shall be measured with a spectrum analyser, such as the HP8560E, with the phase noise measurement option. The phase noise level shall be increased until TOV is reached and measu
39、red in dBc/Hz at 100 Hz, 1 kHz, 5 kHz, 10 kHz and 20 kHz at either side of the peak carrier. 3 Field test plans This section presents the objectives, and general methodology for conducting field tests of over-the-air digital terrestrial television systems. Field test plans are useful tools to gather
40、 field data of digital television systems in order that useful conclusions about DTTB signal coverage, service receivability and channel characteristics can be obtained. 6 Rep. ITU-R BT.2035-2 Paragraph 3 is organized in six major sections. The first section contains a general description of a field
41、 test plan and applies to all field tests proposed. The following three sections detail the procedures that are specific to each kind of field test: coverage measurement, receivability evaluation and channel characterization. The fifth section comments on incorporating analogue television broadcast
42、signal for coverage and receivability comparison with DTTB systems. The last section provides guidelines to implement comparative DTTB field tests. The scope of the work includes reception, demodulation, and recovery of the transmitted data. The scope of the work herein is not concerned with the dec
43、oded data or analogue signals except when these signals are used as a means to determine that the data has been correctly recovered. 3.1 Recommended practices for developing field test plan 3.1.1 Use of normative references Normative references should be added to any test plan document developed. Re
44、ferences should be included to any measurement methods used that are established by regulating authorities or are in accordance with recognized standard-setting bodies. 3.1.2 Field testing objectives Test plan implementations may focus on certain aspects of the objectives depending upon the immediat
45、e requirements of the testing entity. Thus, plans developed using this Report, have one or more of the following objectives: identify the variables in the environment and recommend the minimum set of variables to be measured; measure actual “service” versus predicted “coverage”; to collect data usef
46、ul in improving the DTTB system performance; evaluate the receivability of DTTB systems for a broad range of different receiving modes. The goal is to provide a uniform series of test procedures whose results and data can be compared with results of other tests conducted by various organizations in
47、different locations, or at different times, or both. Testing may be conducted for specific goals and objectives that include but are not limited to the following: 0 Comparison of one digital transmission system to another 1 Comparison of a digital transmission system to an analogue system 2 Comparis
48、on of various transmission and receiving components 3 Comparison of different generations of components 4 Comparison of different environments 5 Statistical characterization of the RF environment. 3.1.3 Definitions 3.1.3.1 Coverage testing Coverage is defined as the determination of actual field str
49、engths measured for a given transmission facility. There are generally two purposes for coverage measurements: ascertain the proper functioning of the transmit antenna, and provide supplementary data for terrain propagation algorithms that could be used for spectrum allocation planning and estimation of potential interference. Rep. ITU-R BT.2035-2 7 Coverage measurements are conducted using standardized test methods which typically use antennas calibrated to a standard dipole and placed at 9.1 m (30 ft) heig
