利用裝置與裝置通訊技術的資源與鄰近裝置搜尋演算法

Abstract

In Device-to-Device (D2D) communications, devices can communicate with each other directly. Although industry and academia are actively pursuing research in D2D communications, a frequently asked question is that why operators should buy in the idea of D2D communications because operators may loss control of devices. In this thesis, we propose an efficient resource discovery algorithm to demonstrate the benefit of D2D communications in 3GPP networks. The algorithm first dynamically groups devices. We then apply Distributed Hash Table (DHT) to reduce the resource discovery time. When a device needs a resource, it discovers the resource in its own group first. If the resource is found in the group, the device does not need to query servers in core network to get the resource. After a device finds the resource, the resource will be cached in the group. Therefore, other devices in the group can find the resource immediately. If the resource is not found in the group, the device has to query server to get the resource. It will make the resource discovery time longer than query server directly. Therefore, we propose to analyze the performance to help network operators to make decision whether the devices should query the resources in the group first. The proposed algorithm and performance analysis are verified by using extensive simulations. D2D communications also can be used in pedestrian collision avoidance. Based on our prior work, we have proposed a Wi-Fi pedestrian collision avoidance system. In the system, pedestrian's device acts as an WiFi AP and periodically sends beacons which include GPS and time information. The car which receives the beacon will detect whether there are pedestrians on its way. If there are, the system will warn the driver. Therefore, the system can avoid pedestrian collision. We analyze the performance which is validated by extensive simulations.

In Device-to-Device (D2D) communications, devices can communicate with each other directly. Although industry and academia are actively pursuing research in D2D communications, a frequently asked question is that why operators should buy in the idea of D2D communications because operators may loss control of devices. In this thesis, we propose an efficient resource discovery algorithm to demonstrate the benefit of D2D communications in 3GPP networks. The algorithm first dynamically groups devices. We then apply Distributed Hash Table (DHT) to reduce the resource discovery time. When a device needs a resource, it discovers the resource in its own group first. If the resource is found in the group, the device does not need to query servers in core network to get the resource. After a device finds the resource, the resource will be cached in the group. Therefore, other devices in the group can find the resource immediately. If the resource is not found in the group, the device has to query server to get the resource. It will make the resource discovery time longer than query server directly. Therefore, we propose to analyze the performance to help network operators to make decision whether the devices should query the resources in the group first. The proposed algorithm and performance analysis are verified by using extensive simulations. D2D communications also can be used in pedestrian collision avoidance. Based on our prior work, we have proposed a Wi-Fi pedestrian collision avoidance system. In the system, pedestrian's device acts as an WiFi AP and periodically sends beacons which include GPS and time information. The car which receives the beacon will detect whether there are pedestrians on its way. If there are, the system will warn the driver. Therefore, the system can avoid pedestrian collision. We analyze the performance which is validated by extensive simulations.