1、163 (1986) CCIR VOLUME*VIII 90 W 4855232 0531435 7 Rec. 626 RECOMMENDATION 626 EVALUATION OF THE QUALITY OF DIGITAL CHANNELS IN THE MARITIME MOBILE SERVICE (Question 42/8) The CCIR, CONSIDERING (a) that the administrations of numerous countries are developing different types of equipment for the tra
2、nsmission of digital information on radio channels of the maritime mobile service; (b) that specific technical Recommendations shoud be adopted on the basis of a comparative analysis of the overall final results of laboratory or field tests performed on the equipment offered by various administratio
3、ns; (c) that, however, it is generally difficult to carry out joint tests on different types of equipment; (d) ,that owing to the variations in the probabilistic characteristics of radio channels in the maritime mobile service, the conditions of the various tests may differ considerably, which may m
4、ake it difficult to provide a basis of comparison for the evaluation of the final results; (e) that equipment performance is seriously affected by inadequate radiocommunication conditions, CONSIDERING FURTHER: the need to provide a standard method for the evaluation of the conditions and final resul
5、ts of tesfs (f) conducted on equipment used in digital radio channels of the maritime mobile service, UNANIMOUSLY RECOMMENDS 1. that the main parameter adopted to characterize the effectiveness of equipment proposed by administra- tions for use in digital maritime radio channels should be the gain i
6、n channel quality, relative to a reference system operated just before the start of each test; Note. - The reference system consists of a standard character generator, e.g. a pseudo-random generator connected to a modulator of the same type as used in the equipment to be tested, or a CCIT standard m
7、odem for the data speed to be tested where applicable. 2. that the most practical method of assessing the quality of such channels is based on the statistical (probabilistic) characteristics (parameters) obtained (or calculated) before and during the operation of the new equipment. These parameters
8、may be applied for the comparative evaluation of different equipment without any joint tests; 3. that the main parameter adopted to characterize initial channel quality (before the operation of the equipment), i.e. the test conditions, should be the value of the character error probability. For test
9、 purposes, the range of variation inthis value during the experiment may be from lo- to 4. 5. should be in the range from 100 to 150; 6. also be the character error probability; 7. integral distribution; 8. - mean link setting-up time; - 9. that in principle, the difference between th final and init
10、ial character error probabilities should define the effectiveness of the equipment. However, for the analysis of performance to be complete, account must also be taken of the additional indicators given under 8 8 of this Recommendation, as well as of the technical characteristics (power, selectivity
11、, antenna losses, etc.) of other radiotechnical plant and systems contributing to the formation of the digital radio channel. that the duration of a single test period (session) should, as a rule, be 10 to 12 min; that the number of test periods sufficient for the statistical (probabilistic) evaluat
12、ion of the final results that the main parameter adopted to characterize channel quality during operation of the equipment should that the mean character error probability obtained (or calculated) should, as a rule, be represented as its that other indicators characterizing channel quality in the use of the equipment should be as follows; operational information processing rate (mean information transmission rate); I P .- -l. - COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
