Real-time and reliable radio communication is essential for wireless control systems (WCS). In WCS, preambles create significant overhead and affect the real-time capability since payloads are typically small. To shorten the preamble transmission time in OFDM systems, previous works have considered adopting either time-direction extrapolation (TDE) or frequency-direction interpolation (FDI) for channel estimation which however result in poor performance in fast fading channels and frequency-selective fading channels, respectively. In this work, we propose a subcarrier-selectable short preamble (SSSP) by introducing selectability to subcarrier sampling patterns of a preamble such that it can provide full sampling coverage of all subcarriers with several preamble transmissions. In addition, we introduce adaptability to a channel estimation algorithm for the SSSP so that it conforms to both fast and frequency-selective channels. Simulation results validate the feasibility of the proposed method in terms of the reliability and real-time capability. In particular, the SSSP scheme shows its advantage in flexibility as it can provide a low error rate and short communication time in various channel conditions.

This paper presents a design of the software and hardware modules of an embedded board with both a sensor and an interface circuit which not only control home light-emitting diode (LED) lighting appliances but also reduce their differences in brightness caused by luminous decay. This design consists of four parts: an automatically adjusted LED driver, environment illumination detection, a wireless remote control unit and an automatic brightness control.

This paper discusses the reduction of the amount of transmitted information for the efficient use of frequency resources in wireless feedback control systems, and clarify the effect of the reduction of the amount of transmitted information. As a typical example of the underactuated controlled object, a rotary inverted pendulum is considered. We propose a reduction method for state information fed back from the controller to the controlled object. It estimates angle or velocity state from the previous state. In addition, we propose a reduction method that temporally omits less important control information and state information. Numerical examples clarify the effect of the reduction methods on the control quality. And we show that the reduction methods achieve large reduction of the amount of transmitted information with small disadvantage of the control quality.

This paper discusses a wireless control system for cooperative motion of multiple machines, and clarifies the influence of packet losses on the system behavior. We focus on the synchronization of the motion of the machines, and using the nature of wireless, we propose a new wireless control scheme for maintaining the synchronization performance under packet loss conditions. In the proposed scheme, each controlled object (plant) utilizes control information destined for all plants, and the main controller also utilizes state information of all plants. The additional information of the other controller-plant pairs is used to compensate lost information. As an example of the controlled plants, rotary inverted pendulums, which move synchronously with wireless connections in their control-feedback loops, are considered. Numerical examples confirm the superiority of the proposed scheme from the view-point of the synchronization of the motion of the plants.

In this manuscript, a layered macro/micro diversity scheme is introduced at the receiver side of a MIMO STBC wireless control system under fading and shadowing environment. The combination of the outputs of micro diversity is based on soft-decision values, while the macro diversity branches are combined based on hard decision values. As a measure of the reliability of the system, the outage probability of frame-error rate is employed. The performance of the proposed system is analytically and numerically evaluated and the impact of the macro diversity in the outage probability is clarified.