| The Internet of Things (IoT) is a recently emerged technology concept on networking. It is proposed to take advantage of modern communications, net-working and electronic technology, for each of the objects of the physical world, given the intelligence and the ability to communicate. We are able to automate the physical objects through accessing to the information technology. IoT can be an important aspect for further development of information technology.This thesis performs detailed investigation on Radio Frequency Identification (RFID) technology. RFID plays an important part of IoT related network tech-nologies. It is widely used in object identifications and information access. RFID systems use a simple star topology which contains severe scalability problems. In applications with high throughput, RFID systems suffer from insufficient capacity and are difficult in expanding throughput. In this thesis, a key issue of the RFID system-multi-label multiplexing problem is studied.Besides, this thesis also proposes an IoT model that combines a hierarchical architecture of IoT and master-slave senor networks. The network is divided into a layer of sensor networks and a layer of wide area networks. The sensor networks are used to aggregate data from sensors. When a master node of the sensor networks have fetched enough data, the master node directly accesses the WAN servers through, for example, a wired link or mobile telecommunication networks.IoT has recently become a hot spot in research. This thesis tries to build a computer simulation model for the proposed architecture of IoT. This model can be used to evaluate the proposed hierarchical architecture as well as the relationship between the network performance and its scale, parameter configurations. The result information can provide reference to real systems.The main contributions of this thesis include:(1) A multi-reader joint detection scheme is proposed to solve the limited capacity of RFID systems. This detection scheme can provide multi-antenna di-versity and higher throughput by joint detection among multiple readers. It can improve system capacity through adding more readers in dense RFID systems.(2) To reduce the severe collisions in dense RFID networks, an Interleaver Division Multiple Access (IDMA) scheme is proposed. This system scheme can enable simultaneous decoding of multiple tag signals by means of encoding and interleaving. IDMA is a variant of Code Division Multiple Access (CDMA) system-s. With the inheritance of the quadrature signal separation capability of CDMA systems, it can also reduce the requirements on system complexity. This thesis provides the adaption method of IDMA on dense RFID network and discusses several problems during the adaption.(3) Investigations on the implementation issues of IDMA in RFID networks, including modulations, interleaver realizations, synchronization and channel esti-mation. Computer simulations are conducted to evaluate the scheme performance.(4) Besides, an overall architecture of IoT and hierarchical WAN-sensor net-works is studied. The sensor networks within work in master-slave mode. The master nodes in the sensor network also work as a LAN gateway to send data directly to server systems through WAN access.(5) Network simulations in OMNeT++to investigate the communication load and quality in proposed networks. The simulations model the master-slave sensor nodes and WCDMA/GPRS network protocols. Studies on relationship between network delay, throughput, number of nodes and distribution are provided. |
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