Research On Disaster Relief Techniques Based On Mobile Communication

Human societies have been suffering from natural disasters, and disaster relief techniques with high efficiency and high reliability are always in desperate need. With the rapid development of information technology, mobile phone has become indispensable in daily life. In view of the high popularity and high signal strength of mobile communication, the phone-based localization system has drawn worldwide attention these years. However, suffering from the inadequate research on communication sytem design, channel modeling and localization algorithm, the phone-based disaster relief techniques fail to meet the practical requirements. Given all this, this dissertation carries on indepth analysis and innovative research on the aforementioned three aspects, and the following achievements have been obtained:1) Towards the design of the disaster relief base station (BS), passive implementation approaches of the key communication techniques, such as the cell reselection, user registration, signal induction and frequency hopping, are presented based on an indepth study of GSM system. Furthermore, to alleviate the disadvantages of low positioning accuracy, high cost, low efficiency, strong interference and unnecessary resource waste, localization system with high performance for disaster relief is studied, and a novel cooperative communication system based on a handheld device is proposed.2) The radio propagation channel between disaster relief BS and mobile station (MS) is investigated. A channel modeling method based on the space smoothing estimating signal parameters via rotational invariance techniques (SS-ESPRIT) algorithm is proposed. By conducting measurements in ruins scenarios, a statistical disaster channel model is built, and the channel characteristics are analyzed. Simulation and experimental results validate that the proposed approach has the advantages of high resolution, low model order, low computational burden and good anti-noise performance for channel modeling.3) Employing empirical path loss model, this dissertation presents an elaborate description of the radio channel with low BS antenna for pedestrian rescue in ruins. Based on extensive measurements, a detailed analysis and modeling of the large-scale fading and the small-scale fading is performed, and the effect of different antenna heights, different polarizations, line-of-sight (LOS) and non-line-of-sight (NLOS) circumstances, are investigated. Besides, the attenuation due to common obstacles in ruins, including human body, is characterized.4) In view of the difficulty in localization due to unknown channel parameters and strong noise in disaster scenarios, a semidefinite programming algorithm based on multi-anchor method and path loss model is proposed in this dissertation. In this algorithm, the traditional maximum likelihood problem is transformed into a convex optimization problem by utilizing semidefinite relaxation techniques. Simulation results validate the effectiveness of the proposed method by comparison with the Cramer-Rao lower bound, which shows good convergence performance and high precision. Moreover, the accuracy degradation caused by the estimation error of the excess loss is analyzed as well as the coexistence of LOS and NLOS propagations.