Microwave power transfer provides power wirelessly by converting electromagnetic waves emitted by an antenna to DC power using a rectifying antenna (rectenna). We are developing a distributed cooperative power transfer system that intentionally generates constructive interference on a device by applying appropriate phase control to microwaves emitted from each antenna to improve the efficiency of the power supply. This paper proposes a novel phase optimization method to find the optimal phase that maximizes the received power of the device. The proposed method obtains the optimal phase by performing nonlinear curve regression based on the received signal strength indication (RSSI) feedback of the device. Experimental evaluations showed that the proposed method improved the stability of the supplied power and reduced the time of phase optimization in both feedback models.

Future networks require a high degree of flexibility over wide areas to enable many services that require higher quality wireless networks such as remote control of cars and remote surgery. Therefore, the network technology must combine high capacity, low latency, and flexibility. To deal with these requirements, we developed Software-Defined Radio over Fiber (SD-RoF), which is an architecture that tightly couples light and radio at a low cost. SD-RoF offers the following two key features: elastic wireless service and elastic bidirectional passthrough. The elastic wireless service provides users with access to wireless services that they need at any time in any place. The elastic bidirectional passthrough connects two remotely located points via RoF through radio waves and enables allowing for bidirectional radio communication between devices at each location. In this study, we design and prototype implementation of SD-RoF, and conduct a basic evaluation of the implemented circuit and demonstration experiments on elastic bidirectional passthrough. Through demonstration experiments, we found the feasibility and the challenges of SD-RoF. In addition, the deployment of SD-RoF, application scenarios, and operational issues are discussed.

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