1、QUESTION ITU-R 229-1/3Prediction of sky-wave propagation conditions, signal intensity, circuitperformance and reliability at frequencies between about 1.6and 30 MHz, in particular for systems usingdigital modulation techniques(2002-2009)The ITU Radiocommunication Assembly,consideringa) that accurate
2、 quantitative predictions of ionospheric propagation are important for planningoptimum spectrum utilization;b) that the methods for prediction of basic and operational MUFs and ray paths(see Recommendation ITU-R P.1240) are required for predicting HF sky-wave propagationcharacteristics and merit fu
3、rther improvement;c) that a method for predicting HF sky-wave propagation characteristics is given inRecommendation ITU-R P.533, and that this now includes procedures for digital systems in theEquatorial region;d) that Recommendation ITU-R P.842 provides a method for the computation of reliabilityan
4、d compatibility of HF radio systems;e) that radio system performance is influenced by variations of the amplitude and dispersionof the wanted signals, and of the background noise and interference, and this influence varies withthe type of emission, particularly between analogue and digital;f) that t
5、he available prediction methods are intended primarily for use for narrow-band oranalogue systems;g) that many HF systems use digital modulation techniques, including those which utilize fastsignalling speeds or which require phase or frequency stability;h) that a method needs to be developed for ot
6、her parts of the world, particularly at highlatitudes, to estimate the performance of digital broadcasting,decides that the following Questions should be studied1 What improvement may be made to the methods given in Recommendation ITU-R P.1240for the long-term prediction of basic and operational MUF
7、s and ray paths, and their variability,from predicted ionospheric characteristics?- 2 -2 What improvements may be made to the method for the long-term estimation of sky-wavepropagation conditions, signal intensity, circuit performance and reliability using predictedionospheric characteristics?3 What
8、 are the characteristics of time delay spread, frequency spread (multipath and Dopplershifts) and frequency correlation of HF sky-wave signals, including fading characteristics?4 What values of a time-delay and frequency power profiles are characteristic of theionosphere at different locations and t
9、imes, and how may the prediction of these characteristics beincluded within a comprehensive method?further decides1 that the available information should be prepared as new Recommendations, or as revisionsto existing Recommendations;2 that the methods described in the Recommendations should be available as a softwarepackage for use within the Radiocommunication Bureau and by those concerned with the planningand operation of HF systems and networks;3 that the above studies should be completed by 2011.Category: S1
