Application Of Spectrum Shared Technology In Emergency Communications

With the rapid development of the wireless communication,the spectrum resource of the wireless communication becomes increasingly scarce. Currently deployed wireless emergency networks and commercial cellular networks are facing the similar problem which is the low efficiency of spectrum utilization. Because multiple wireless emergency networks may share the limited spectrum resources, the resource blocks will have higher probability of collision. New technology of spectrum allocation needs to be considered in the physical layer and media access layer. The main work of this thesis is to study the application of the latest development of spectrum sharing technology in a specific wireless emergency communications. In the second chapter of this thesis, conception of emergency communication system, characteristics and the involved new technologies are described. In the subsequent two chapters of this thesis, the low complexity static and semi-static subcarrier allocation techniques are studied based on the resource sharing of OFDMA.The static resource allocation has the problem of low spectrum utilization, to deal with this problem, in this thesis, a semi-static resource allocation policy is proposed based on OFDMA system. For the purpose of reducing the mutual interference between systems, a Poisson judge mechanism is introduced to control the probability of accessing the spectrum sharing for different systems and enhance the overall transfer rate. Firstly, the simple scene of a primary user and a secondary user is analyzed from three aspects that are network, signal model and signal interference ratio. Then, the algorithm of semi-static subcarrier allocation strategy is introduced. Finally, the simulation is done based on this algorithm, and the simulation results show that the spectrum allocation scheme can effectively improve the system spectrum efficiency, avoid rate declined sharply caused by the directly collision between the primary and secondary users, which ensures the stability of the system.The secondary users'scheduling scheme is studied based on multiple secondary users. The users'scheduling is studied firstly, and then a new scheme is provided by the combination of proposed algorithm with current classical packet scheduling algorithm-RR, Max C/I and PF algorithm. We join the users'scheduling in the semi-static algorithm, at last, the simulation parameter is given and the simulation is performed, which shows the best performance.