Research On Multi-user Accessing And Adaptive Technology Of Private Networks In Cognitive Radio

Radio communication system on 230MHz has been used since the 1980s. As developing and expand-ing of business in electric power industry, more requests are made for radio communication system used in past years. So researching about communication systems of electric power wireless private network on 230MHz has been focused by domestic academic field and enterprises. Electric power wireless private net-work on 230MHz was authorized 40 distributed frequency points by China Radio Regulatory Commission. It has advantages of stable, easily to extend and maintain, flexible of networking, and costing less, while it has disadvantages that spectrum efficiency and transmission rate is very low,and remote communication and the alarm information can't been uploaded promptly. Distribution of frequency points authorized restricts broadband communication technology applied in electric power wireless private network on 230MHz. How-ever, the spectrum aggregation technology in cognitive radio can realize frequency points distributed being aggregated in continuous frequency band. On the basis above, we modeled and simulated on the condition of multipath channel on 230MHz, and then discussed transmission performance of HARQ, and in the last designed the scheme of multi-user accessing control. We solved the problems in the old communication sys-tem of electric power wireless private network that spectrum efficiency and transmission rate is very low,and remote communication and the alarm information can't been uploaded promptly.Firstly, we introduced technology of cognitive radio, background of wireless communication in electric power system, and present situation of the researching of electric power wireless private network. As the old electric power wireless private network communication system had limitations in production environment, we could use the technology of present mobile communication system for reference. Considering the fea-ture of communication of private network and disadvantages of old communication system, we proposed the improvement of wireless private network technology.Secondly, we introduced the basic situation of electric power wireless private network communication, and described the physical architecture of electric power information acquisition wireless communication system. Then we described the electric power wireless private network and its feature, and summarized the advantages, character and research significance of private network communication on 230MHz. We calcu-lated the link budget on the fields of urban, suburban and rural, and got the maximum path loss and cell coverage radius during different modulation. Basing on the characteristic and multipath channel parameters on 230MHz, we made a channel model of wireless multipath on VHF frequency band, analyzed and compared BER results of different modulation on base of channel model.Thirdly, we studied the application of spectrum sensing technology in electric power private network, which included the single-user detection methods of match filter detection, energy detection and the multi-user cooperative detection. By simulating and analyzing the detection performance in the case of AWGN, rayleigh and rice channel circumstance, we found that SNR and the number of samples are the influence factors in single-user detection, and the number of cooperative users affects the detection performance in the multi-user cooperative detection. On one hand, in the condition of OR-rule cooperative detection, as the number of cooperative users increases without SNR varying, the detection performance increases sharply, which means that OR-rule cooperative detection adapts to the systems requiring lowest undetected probability and fewer interferences. On another hand, in the condition of AND-rule cooperative detection, as the number of cooperative users increases without SNR varying, the detection performance has a increase, which means that AND-rule cooperative detection adapts to the systems requiring lowest false alarm probability and higher channel utilization rate. As the analysis above, OR-rule cooperative detection adapts to combining OR-rule cooperative detection adapts to is a better scheme to electric power private network.Fourthly, we studied HARQ technology applied in electric power private network. By simulating, we got the throughput and frame error rate curves of HARQ-? and HARQ-? on the condition of different modulation and different maximum transmission times. Based on the simulating results in different channel situation, we analyzed the influence of modulation and maximum transmission times to HARQ performance. The simulating results indicated the conclusion as follows. HARQ-? has a better performance than HARQ-?. The bigger the modulation order is, the better throughput performance we get, and the smaller the modulation order is, the better frame error rate performance we get. The bigger the maximum transmission times is, the higher throughput and lower frame error rate we get, but if maximum transmission times is above 3, the improvement of performance by adding maximum transmission times become very limited.Lastly, we studied the schemes of multi-user accessing control in electric wireless private network. After introducing background of electric wireless private network accessing, which included traditional technology and architecture of air interference, we designed physical frame structure and physical channel. Basing on the result of simulation we made the length of frame 25ms, and divided the authorized frequency points into accessing frequency points and business frequency points. We separated physical channel into PBCH?SCH? PDCCH?PRAC?PUCCH and PUSCH. After introducing and analyzing polling accessing, we designed the scheme of multi-user random access, which included cell searching, random access basing on competition and random access basing on non-competition.