Yasuyuki Nishibayashi

Compressed Block Ack, an efficient selective repeat mechanism for IEEE802.11n

The standardization of IEEE802.11n which aims to achieve 100 Mbps at MAC-SAP (medium access control - service access point) is under work in IEEE802.11, wireless LAN standardization committee. The frame aggregation scheme in which MAC (medium access control) frames are aggregated into one PHY (physical) frame is proposed for IEEE802.11n, because it decreases MAC overhead. In this paper, we propose the compressed block ack mechanism as a selective repeat mechanism to be adapted to the frame aggregation scheme. We present simulation results to compare performance of the compressed block ack mechanism and the legacy block ack of IEEE802.11e and show that the proposed method improves the total throughput by 10% than the conventional method

Development of autonomous power electronics products with communication middleware

In this paper, we introduce a communication middleware and its implementation on two kinds of inverters. This middleware provides services of an automatic and dynamic network configuration (plug-and-play) and operation mode/master switching for distributed cooperative control of electric facilities. Energy end-nodes such as photovoltaic (PV) or batteries are clustered by the middleware to form a larger power conversion system. We made two types of prototypes and compared them. The first implementation was based on an embedded processor of a commercial inverter and the other was based on an ARM/Linux control board that will be attached on the aforementioned inverter. Though both worked well, Linux and its powerful, free software offered certain advantages in terms of design and operation. Loosely coupled design was applied to an abstraction layer of an open-source framework ZeroMQ, and a standardized message format JSON with its library JSON-C were employed for the middleware. They contribute flexibility for various applications in the smart grid. A demonstration with five prototype inverters showed that our concept and implementation work well.