| Since the radio frequency resource is owned by the state, being a special resource, it has been paid attention by governments. All countries have put a lot of manpower and effort to enhance the radio management work for the building of organization, infrastructure construction and regulation construction. This will make the radio management work accommodate to the economic development and the trend of communication globalization. In order to enhance the management of the frequency spectrum resource, obviate the systemic interference of the wireless, insure the frequency spectrum resource to be utilized adequately, Wireless management institutes at all levels have built up hundreds wireless monitor stations, which most of them are the UHF/VHF ultrashort wave monitor ones. With the rapid development of the urbanization and the needs of the radio management, we strongly believe that more and more monitor stations will appear in the near future. Because the electric wave within the ultrashort wave frequency band can be easily influenced, different type wireless launcher has different working mechanism and speciality, the diversity lies in the monitor system equipment's speciality, all of these lead to the radio management work sets foot in the research about the ultrashort wave monitor system coverage area.The work is focused on the simulation computing of the monitor coverage. At first, we study several transmittal models with the principle of the theory research, which are applied to the ultrashort wave frequency band. They are ITU—RP. 1546 model, Okumura-Hata model and Egli model. Then we choose the transmittal model, which is fit for the monitor coverage computing, through the fixed spot testing and movable testing. This will provide the theoretical direction for the monitor coverage computing. With the typical figure computing method, we carry out the emulation computing of the coverage radii for different type radio broadcasting stations. And also, we do the computing and evaluating for the coverage of the Jilin Province and Changchun City Radio Monitor Station with the support of the special monitor data analysis software and the geography information data.According to the result of the fixed spot testing, for the Okumura-Hata model, i.e. the medium & small city model, and the P. 1546 model i.e. the urban 30 m model, the simulation computing result is close to the practical testing one in the urban and suburban environment, which the error figure is less than 6dB. What should be noticed is, regardless of the building density, the computing result is nearly the same for the Okumura-Hata model of medium & small city model and Okumura-Hata model of big city. So it is the same for the medium & small city model and big city model in this report. Under the movable testing condition, in order to improve the testing rate, we can test more spots at the same time. According to the testing data, we can find out that in most cases the computing result is similar for the P. 1546 model and the Okumura-Hata model. In the case of the terrains are complex, P. 1546 model can provide more accurate data. From the analysis of P. 1546 model, we can find out that P. 1546 is the very same as the Okumura-Hata model, i.e. the big city model, when the building density is considered. The transmittal loss is higher than the medium & small city model. But all of these are considered for the transmitting antenna is high and receiver antenna is low. When it comes to the transmitting antenna is low and receiver antenna is high, from the computing result, we can find out that the path loss is bigger for the transmitting antenna-high & receiver antenna-low, compared with the transmitting antenna-low & receiver antenna-low. Therefore in this experiment for the P. 1546 model, i.e. the urban 30 meter model, the computing result is similar as the Okumura-Hata model, i.e. the medium & small city model, with the computing mode of the transmitting antenna-high & receiver antenna-low.The maximum distance between the transmitter and the monitor station is about 10 km, if the distance is farther than 10 km; the receiving signal is approaching the system base noise, so the experiment hasn't been done. That is to say, for the receiver and transmitter's distance is beyond 10 km, whether it accords with the P. 1546 model i.e. the urban 30m model and Okumura-Hata model, this experiment didn't carry on the verify check.Considering the above analysis, we come to the following conclusions.In this experiment, the maximum distance between the transmitter and the monitor station is 10km, for the distance is father than 10km, we didn't make the practical verify check. In the condition of the transmitting antenna is approaching the ground, the Okumura-Hata formula, ITU-R P. 1546 model simulation result is fitting well with the practical testing data. In the condition of the terrains are complex, P. 1546 model can compute more accurate than the Okumura-Hata model, it can indicate the rise and fall of the terrain very well. Considering the density of the buildings in China city, the P. 1546 model, i.e. 30m model, is also applicable, such as the small city like Jing Yue. P. 1546 model, i. e. the 30m model is applicable in the suburb, where the buildings are low and sparse. For some testing spots, we can measure them with some long time by the stable testing method to get the basic results. And then we can test some more spots in a relatively short time with the movable testing method to verify the former results.To identify the transmittal model in the simulation computingConsidering the monitor stations' coverage to the radio transmitting stations, for the different radio stations which are working in the different models, the simulation coverage computing should be considered respectively, such as the working characteristics and transmitting specialities. For the operational stations, Vehicle mounted stations, which the antennas are far away from the ground, with the local digital map, we can adopt the P. 1546, i. e. 30m model, which is recommended by ITU-R. If the transmitting stations are located in the suburb area or they are the high-altitude stations, we can adopt the 10m model. This can accurately display the terrain influence over the transmitting, but the computing is complicated. If there's no digital map, or at the plain area, Okumura-Hata model can be adopted, i.e. the medium & small city model. For the mobile communication base station, relay station, normally, they are located on the top of the buildings; actually, they might be screened because the buildings are at different height. When there's no city buildings height distribution information, we still adopt P. 1546 model, to compute, i.e. 30m model, For the broadcasting stations, which they have the very high antennas, there might be the line-of-sight propagation between the broadcasting stations and the monitor stations, we use the free-space transmitting model and the additional loss to compute. Considering the practical condition of the monitor station coverage computing, the following suggestions are about this kind of work and fixed station spot choosing. Every monitor station's coverage should be computed according to the special situation. Because of the influence of the electromagnetism environment, the sensitivity of the monitor system facilities might be different from the marked value. The coverage should be computed according to the actual conditions. In the condition of the transmitting antenna is approaching the ground, the ITU-R P. 1546 model, i.e. the 10m model, is recommended to be used. When the monitor station is located in the suburb area where the buildings are low and sparse, P. 1546 model, i.e. the 10m model is recommended. As for the terrain data are unknown, Okumura-Hata formula is recommended. In the condition of the transmitting antenna is high, ITU-R P. 1546 model, i.e. the 30m model, is recommended to be used.Considering the influence of the electromagnetism environment to the monitor system, testing and evaluation should be done before the monitor station is built, meanwhile it can be corrected with the help of the testing data provided by the monitor stations, which have been built. After building the monitor station, the evaluation for the monitor scope can be carried out by the fixed testing, movable testing and the testing from the built stations. Fixed testing, movable testing and monitor system base noise management method, all of these can be used as the auxiliary tools for the monitor station coverage computing and evaluation.With the limitation of the monitor station's sensitivity and the complex terrains, this experiment hasn't carry on the practical monitor verify check for the transmitter and receiver's distance beyond 10km. Only tested in Changchun, the testing area should be expanded if possible. For the stations with the high antenna, it should be measured by the present monitor station. According to the testing data, we adopt the transmit model to do the verify check for the high antenna. |
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