This paper presents a wireless burst modulation/ demodulation method for narrowband ubiquitous communication systems. This method especially suits those systems, whose traffic is especially dominated by short frame bursts. The proposed modulation method provides a preamble-less frame structure with training symbols, which improves both transmission efficiency and burst synchronization performance. Moreover, the proposed demodulation method achieves superior burst synchronization performance in low carrier-to-noise power ratio (CNR) environments by applying a synchronization method that includes symbol timing recovery, slot synchronization, carrier frequency correction and channel tracking. In addition, this paper presents the result of experiments on hardware prototypes of the proposed modulator and demodulator. The basic operation and practical performance of the proposed method is confirmed through testbed studies.

A new broadband space diversity (B-SD) combining method, which is a key technique in the growth of digital microwave radio system, is proposed. In this B-SD combining method, two received signals, whose bandwidths are 280 MHz, are combined. To develop this combining method, an optimum control algorithm is developed that monitors power levels of all primary carriers and controls the endless phase shifter so that the higher level signal is decreased and the lower level signal is increased. This paper describes the proposed B-SD combining method which effectively operates over a wide bandwidth. Performance evaluations based on simulations and theoretical estimations are given. It is proven that this combining method offers the same performance obtained by the conventional narrowband SD combining method and can be applied to over 50% cases of the propagation paths observed in Japan. The suitability of the proposed combining method and the calculation methods adopted is demonstrated experimentally.

The wireless LAN standards of HiperLAN2 and HiSWANa provide wireless access with high data rates in the 5 GHz band. The specifications of these standards include connection control procedures but do not define them in detail. In this paper, practical procedures and additional functions of connection control are described, such as efficient DUC bandwidth control for unicast and multicast, non-authenticated multicast, and authentication with the AAA server. These procedures and functions exceed the scope of HiperLAN2 and HiSWANa standards. Ways of implementing these connection control procedures efficiently are also provided.

It is well known that energy loss brings a serious problem in the optical information transmision systems with the quantum state control at transmitter. This letter presents proposal of a new system for the application of the quantum state control, which copes with the energy attenuation problem, and shows the numerical properties of performances.