Research Of The Deployment Of Relays Assisted Public Safety Broadband Networks

Even with today’s seemingly ubiquitous wireless access, the cellular networks may not be sufficient to support the elevated traffic at incident or disaster areas. Many areas and corners are not fully covered by cellular networks, such as the basement level of large buildings and remote unpopulated areas. The existing cellular infrastructure may also be knocked out of service for periods of times in areas hit by disasters. This is a great threaten to the public safety, and a Public Safety Broadband Networks should be established to provide temporary wireless coverage for saving life and property.This dissertation takes relays as a means of establishing the Public Safety Broad-band Networks. Models, analytical results, and algorithms are proposed to study the optimal relays deployment problem, where the relays are deployed at the optimal place for optimizing the quality of service (QoS) or minimizing the number of relays subject to the QoS requirement. The main results are summarized as follows:For the scenes of mine and tunnel accidents, it is proposed that relays are deployed to establish a one-dimensional relays networks. With the location information of the base station and the user, the optimal relays deployment and resources allocation opti-mizes the QoS. Without the location information of the base station and the user, the optimal relays deployment and resources allocation maximizes the reach of the cover-age subject to the QoS requirement. When the QoS metric is the outage probability, only the relays deployment should be optimized. The optimization problems are con-vex, which could be efficiently solved by convex optimization theory. When the QoS metric is the data rate, the relays deployment and resources should be jointly optimized. The optimization problems are non-convex. After analyzing the resources allocated to each hop with respect to the hop distance, an efficient algorithm is proposed to solve the optimization problems. The proposed algorithms achieves the global optimal solutions with low complexity.For the scenes of fire accident and arrest event, it is proposed that a base station and multiple mobile relays are placed to establish a two-dimensional mobile relays net-works. The optimal base station deployment maximizes the minimum signal-to-noise-ratio (SNR) over the target area. Without placement restriction, the base station could be deployed anywhere, where the optimization problem is convex. With placement restriction, the base station could be deployed on the boundary or outside the target area, where the optimization problem is non-convex. Based on geometric analysis, ef-ficient algorithms are proposed to compute the global optimal solutions. The optimal relays deployment and resources allocation minimizes the maximum outage probabil-ity or maximizes the minimum data rate of multiple users. When the QoS metric is the outage probability, only the relays deployment should be optimized. The optimization problem is non-convex. A greedy algorithm is proposed to compute one local optimal solutions, whose system performance almost overlaps that of the global optimal solu-tions obtained by exhaustive searching method. And the complexity of the proposed greedy algorithm is much lower than that of the exhaustive searching method. When the QoS metric is the data rate, the relays deployment and resources should be jointly optimized. The optimization problem is non-convex. Each user will only choose the link with the highest resource efficiency. A centralized algorithm is proposed, which traverses the link selections to obtain the global optimal solutions. Another distributed algorithm is proposed based on users classification, which obtain one local optimal so-lutions. The system performance of the two proposed algorithms are almost the same, but the complexity of the distributed algorithm is much lower than that of the centralized one.For the scenes of earthquake and tsunami disasters, it is proposed that a base station and multiple randomly distributed relays are deployed to establish a two-dimensional randomly distributed relays networks. Relays and users are randomly distributed. The minimum number of relays is studied to minimize the system cost subject to the rescue delay requirement. The rescue delay is defined as the delay for the typical user transmit-ting or receiving one packet to or from its nearest relay. Stochastic geometry is utilized to analyze the rescue delay, while taking the modulation and coding schemes into con-sideration. The routing scheme is studied to establish the relay links between the base station and each relay. With the limitation of retransmission count of each hop, the op-timal routing optimizes the transmit power of each hop and minimizes the end-to-end energy consumption to energy residual ratio. Advanced optimized link state routing (OLSR) protocol is proposed and Dijkstra algorithm is utilized to select the optimal routing, which reduces the system complexity.All the proposed models, analytical results, and algorithms are the significant guid-ance to the design of relays assisted Public Safety Broadband Networks.