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Intelligent Management and Control for Wi-Fi Small Cells

出版	Universitat Politècnica de Catalunya. Escola d'Enginyeria de Telecomunicació i Aeroespacial de Castelldefels, 2016 (Grau en Enginyeria Telemàtica), 2016
URL	http://books.google.com.hk/books?id=9CALywEACAAJ&hl=&source=gbs_api

註釋In order to face the exponential growth of mobile data transmissions, it has been long since the concept of small cells is in the table, which provides high density deployments of small cells so as to provide a high capacity to a large number of users. The SENSEFUL project, being directed by a research team in the I2CAT foundation, studies the use of small cells with Wi-Fi technology, where both the access network and the backhaul share the same radio resource. The deployment of this new paradigm requires a deep study of improvements on the performance of access networks in terms of mobility while, at the same time, trying to improve the behaviour of the backhaul network by means of new techniques to access the shared medium. SENSEFUL has been granted the funding of the WiSHFUL open call, started up by a collective of entities and universities, of which we have mainly worked with the Technische Universität Berlin, due to the use we have made of their testbed, the TWIST. Using new techniques and technologies, such as the Software Defined Networking paradigm, an intelligent network is deployed, which can manage the network resources dynamically according to the requirements of the system. Regarding both of the fronts of SENSEFUL, the performance in the backhaul network and the mobility in the access network, the techniques that were applied are the following: For the backhaul network, an innovative proposal of a shared medium access mechanism has been studied. It is not yet standardized, because there are many research teams trying to achieve a functional system that can be applied to multiple scenarios. In this thesis, the Hybrid TDMA is studied, a Wi-Fi radio medium access protocol that uses a hybrid of carrier sense (CSMA) and time division (TDMA) in order to benefit from both systems. The main advantages that HTDMA brings are a better management of the quality of service in wireless networks, while solving some of the endemic problems of Wi-Fi, such as the hidden node or the exposed node. So as to work in this direction, first of all, a precise synchronization among the devices that will use this medium access mechanism is required; that is why the usual synchronisation mechanisms in Wi-Fi networks is one of the main topics that this thesis deals with. Regarding mobility in the access network, a new technique is used, which, despite being out of the scope of this thesis, it is indeed interesting and innovative. The BigAP unifies several access points under a shared BSSID, providing a seamless handover for the clients by making only a change on the transmission channel. Working in different environments and scenarios, this project studies the best synchronisation mechanisms for this field. Moreover, the HTDMA system is installed in a small test scenario so as to begin with the analysis of the operation of this hybrid mechanism and its performance under different conditions, as compared to the legacy CSMA.