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Enhancing Wireless Network Performance and Security through Physical Layer Properties Open Access

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In wireless communications, the performance and security of the network are among the utmost important topics. To enhance the wireless network performance, two issues have been carefully studied; namely, the performance of the multicast communication scheme in the single frequency network, and the effective deployment of mobile base stations.The Multicast communication scheme has the inherent advantages in one-to-many trans- missions. The 3rd Generation Partnership Project (3GPP) standard specifies one particular scheme of multicast communication in the Long-Term Evolution (LTE) as the Multicast Broadcast Single Frequency Network (MBSFN). The extra signal gain from constructive signals of neighboring eNodeBs in the MBSFN area gives User Equipment (UE) better Signal-to-Interference-plus-Noise-Ratio (SINR), especially for UEs at the cell edge. How- ever, there are some drawbacks in the multicast scheme that limit its performance gain; for example, it can not employ the Multiple-Input Multiple-Output (MIMO) technology, and all UEs in MBSFN share an overall unique low Modulation and Code Scheme (MCS). The performance gain analysis of MBSFN relies on a thorough network system-level simulation. On the other hand, recent technologies regarding mobile base stations have developed quickly, especially in the area of Public Safety Networks (PSN), due to its fast deployment and high flexibility nature. The performance for various types of mobile base stations, with different coverage, capacity and mobility features, as well as the special requirements from First Responders (FRs) of priority and Guarantee Bit Rate (GBR) are investigated in the study. Lastly, the physical layer information for security purposes and the Golay error correction code are explored. The Channel Impulse Response (CIR) from a half- duplex reciprocal channel has the inherent advantage as the secrecy. However, due to the half-duplex channel and device capacities, the physical layer data obtained from mutually measured two sides may be not be identical, and thus mismatch mitigation is necessary in order to resolve the discrepancy.In this research, the above concerns are being addressed. An MBSFN capable system-level simulation is implemented. The simulation results show that relatively higher SINR values are to be obtained for UEs in MBSFN, than those for UEs in unicast, under the same settings. On the other hand, the aggregated throughput depends on the UE distribution and other factors, hence, analysis of various scenarios are conducted. In the static mobile base station placement scenario, the special requirement from the FRs, e.g. priority and GBR, are modeled, and thus the corresponding performance metric is designed. Upon the settings, two mobile base station placement algorithms are designed, and the results are compared with the those of the baseline algorithm. The performance of the FRs’ priorities and GBR weighted K-means algorithm is always better than the other two in the empirical results. In the dynamic mobile base station placement scenario, four kinds of UE mobility models are designed, including two random walk models, a role-oriented model and a location-oriented model. Three types of mobile base stations are modeled. The algorithm for dynamic placement of heterogeneous mobile base stations is designed. For authentication with physical layer information and the corresponding mismatch mitigation, an efficient and flexible authentication scheme with imperfect keys from physical layer information is designed. The authentication scheme can be parameterized for specific application scenarios to achieve the high performance with low computational complexity. The Golay code based mismatch mitigation algorithm is also designed for good practicality and simplicity in IoT environment.The contributions of this dissertation research include: network system-level simulation with MBSFN capability and its performance analysis, which is, to the best of our knowledge, the first of its kind. The simulation provides a platform for MBSFN performance exploration in various settings. The dynamic placement algorithm for heterogeneous mo- bile base stations presents an efficient deployment strategy for multiple mobile base stations with concerns on the special characteristics in public safety networks. The authentication scheme with physical layer information and mismatch mitigation provides practical and flexible way for physical layer secrecy.

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