移动通信简答（Use the mobile communication）.docVIP

移动通信简答（Use the mobile communication） What are the main interference with the mobile station? What disturbances are unique to the cellular system? Answer: intermodulation interference; Adjacent channel interference; Same frequency interference; peculiar to a cellular system Multiple access interference. How many ways does mobile communication work? Which way is the cellular mobile communication system adopted? Answer: the simplex communication; Duplex communication (cellular mobile communication system adopts this mode); Single duplex communication; Mobile relay mode. The correlation time is the statistical average of the channel impulse response maintained at constant intervals. The two fading signals near the frequency interval have different delays, which allows the two signals to become correlated, a frequency interval called correlation bandwidth. The width broadening of a pulse in a received signal due to multipath effects is known as delay spread. Due to multipath fading and Doppler effect, the power spectrum of the received signal is broadened and expanded, i.e., Doppler expansion under the influence of the Doppler effect. What are the requirements for modulation mode selection in mobile communications? Answer: the frequency band utilization rate is high, the power efficiency is high, has adjusted the signal constant envelope, easy to demodulate the band radiation: the general request achieves -60 to -70dB What is the guiding principle of diversity receiving technology? A: the received multiple fading independent signals are processed, and the quality of the received signals is improved by reasonably utilizing the energy of these signals. What are macro diversity and micro diversity? What are the micro diversity commonly used in mobile communications? Macro diversity: used to combine two or more long time logarithmic normal signals that receive signals from two or more different antennas from different base stations via independent fading paths. Microscopic d