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GSM-R system electromagnetic environment of the test solution-GSM-R, the electromagnetic environment - Communications Industry
0 Introduction Recent years, Qinghai Radio Communicate Faster development of the cause, various types of radio stations increased rapidly. Radio technology in the economic and social development in Qinghai Province play a very important role, particularly as the economic expansion in the trunk of the Qinghai-Tibet Railway system plays a fundamental role.
Train to Tibet for the effective protection of the radio communication clear, the radio station launched in Qinghai Province Qinghai-Tibet railway line budongquan - Tanggula section of GSM-R base station electromagnetic environment testing, and in-depth analysis of monitoring data. The test on the maintenance of order in the wave along the Qinghai-Tibet Railway, the scientific use of radio spectrum resources planning and has an extremely important role.
1 Introduction Electromagnetic Environment National standard GB/T4365-1995 on the electromagnetic environment is described: the electromagnetic environment is present in a given place the sum of all electromagnetic phenomena. This definition has two meanings: First, the electromagnetic environment for limited regional scope; Secondly, the electromagnetic environment is in a given area to the sum of all the electromagnetic environment, including natural electromagnetic phenomena and man-made electromagnetic phenomena.
Electromagnetic environment will directly affect the operation of radio equipment effectiveness. Harsh electromagnetic environment will lead to the radio device is not working, this is what we often say that the electromagnetic noise. Electromagnetic noise is clearly not time-varying electromagnetic transmission of information phenomena, it may be superimposed or combined with the useful signal.
Radio environment is within the scope of radio frequency electromagnetic environment, especially a given place in a working condition of all the electromagnetic fields generated by radio transmitters the sum of electromagnetic phenomena are man-made (artificial devices generate electromagnetic phenomena) and are .
2 test basis and purpose The test based on "900MHzTDMA digital public land system of cellular mobile communications network technology" in order to fully test the Qinghai-Tibet railway station GSM-R system electromagnetic environment, and identify various types of interference sources of interference signal strength. Meanwhile, the benchmark analysis of base stations and base stations, base station and the train between the radio frequency interference, and determine whether the technical requirements of the base station to provide the technical basis for Jianzhan units. The tests include the following aspects:
(1) GSM-R system and the test frequency, adjacent channel and interference from other GSM systems.
"900MHzTDMA digital public land cellular mobile communication network technology system provides that" clearly states: For the GSM digital mobile communication site, requiring the co-channel interference protection ratio (project value) should be C / I 9dB, adjacent channel interference protection ratio (engineering values) should be C / I -9dB, 400kHz frequency interval than when the interference protection (project value) should be C / I -38dB.
(2) calculation of the carrier / interference ratio (C / I).
General, GSM base station receiver when operating parameters are: the base station receiver sensitivity level Pr is-104dBm, the base station receiver required C / I is 9dB, the base station receiver noise level is-116dBm.
GSM system, the actual design, usually to consider environmental noise and multipath interference on the impact of the base station (usually the minimum to take 3dB). Therefore, GSM minimum available power C = Pr +3 =- 101dBm. As the GSM carrier to interference ratio C / I = 9dB, GSM system, the maximum allowable interference level for the I = CC / I =- 110dBm.
3 electromagnetic environment Test Equipment Electromagnetic environmental testing of equipment and need special testing system to complete. Electromagnetic environment is different from the communication receiver testing equipment. Communications receiver for reproduction of a radio signal, the signal at the receiving process, the sensitivity and speed is the key. Electromagnetic environmental test equipment is used to test electromagnetic noise, radio signal interference level value, and whether other indicators.
General, electromagnetic environmental test equipment required:
(2) NSMI-0118 spectrum automatic test system;
(3) 0.6-meter parabolic Antenna (0.7GHz ~ 4GHz), Dipole antenna;
(4) 0.7GHz ~ 4GHz Low Noise Amplifiers (50dB);
(5) GPS locator.
Which, NSMI-0118 system, the connections shown in Figure 1. The system needs to select appropriate low-noise amplifier and antenna, used to prevent input overload and calibrated before the test.
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