Recently, quality-of-service (QoS)-aware cyclic sleep controllers for optical network units (ONUs) have been proposed to guarantee the QoS and energy efficiency in passive optical networks (PONs). Proportional-integral-derivative (PID)-based cyclic sleep controllers can maintain the average downstream queueing delay in an optical line terminal (OLT) at a constant level. However, conventional PID-based controllers generate errors between a target queueing delay and an actual delay because of the nonlinear characteristics of the cyclic sleep mechanism. This letter proposes a feedback controller with a disturbance observer (DOB) that includes a linearized cyclic sleep model to improve the QoS in terms of the average downstream queueing delay. Simulations confirm that the proposed DOB-based controller can reduce errors effectively compared with a PID-based controller.

In order to obtain near-metal-insensitive antenna for closed-space wireless communications, the impedance characteristics of U-shaped folded monopole antenna is investigated in detail. In this Letter, the near-metal-insensitive means antenna VSWRs are hardly influenced by the near object, especially metal. The simulated and measured results show that the proposed higher impedance model has stronger near-metal-insensitiveness than the conventional middle impedance model. The simulated and measured results show that the antenna gains of higher impedance models are 3 dB greater at maximum than those of middle impedance models, when metal plane approaches.

In terrestrial digital TV broadcasting in Japan, OFDM is utilized as a modulation scheme. However, the communication quality could be seriously deteriorated at the high speed mobile reception (Ex. vehicle). Furthermore, most of the mobile reception system, 4 antennas are mounted on a vehicle (Front: 2 antennas, Rear: 2 antennas).

The authors proposed a new combing method (Incoming waves separating system by adaptive array antenna). In this paper, the performances in case of 4 directional antennas are evaluated. Furthermore the performance in more complicated environment is evaluated. From experimental results, it is clarified that the BER performances of the proposed system are superior to the conventional system.