Wideband Modulation Technology Research In The Confined Space

Different from the open space, in the confined space, the radio is reflected and refracted by the wall so that the propagation of radio signal is more complex. And the coal mine laneway is a typical representation of the confined space. This paper aims at seeking a suitable communication system in the coal mine laneway which is able to improve the safe production in real underground mine.In order to establish an effective communication system in the coal mine laneway, based on the thoughts of "changing wideband for transmission distance", this paper focuses on the research about wideband modulation. At present, the most widely researched wideband technologies are CDMA spread spectrum technology and multicarrier CDMA technology. So this paper analyses and compares CDMA system and time domain spread spectrum multicarrier CDMA system (MC-DS-CDMA system and MT-CDMA system) in detail.First, coal mine laneway is an especial communication circumstance, it directly affects the received signal quality, so the investigate on the wireless channel of coal mine laneway is basic to develop the research on coal mine wireless communication system. By analysis, it is found that the radio is sensitive to multipath interference, Doppler frequency shift and impulse interference when it propagates in the coal mine laneway, so the paper mainly discusses the effect of the three channel characteristic on the signal.Next, based on the wireless channel model of coal mine laneway, the paper designs the proper coal mine DS-CDMA, MC-DS-CDMA and MT-CDMA communication system project respectively, mainly studies the damage degree of the performance of the three systems affected by that multipath interference, Doppler frequency shift and impulse interference in coal mine laneway, also compares the three systems at different communication frequency band 1.8GHz and 2.4GHz. At the same times the paper shows the change about theirs bit error ratio by MATALB, moreover observes the performance characteristic and different reaction of the three systems.Finally, the three communication systems are compared and analyzed synthetically with the multipath interfere, Doppler effect, impulse interfere and multi-user under the coal mine laneway, and theirs advantages and disadvantages is discovered...