Osamu Kagami

Concept and Feasibility Study of Wide Area Ubiquitous Network for Sensors and Actuators

The wide area ubiquitous network (WAUN), which is used for transmitting and receiving information for sensors and actuators, is proposed and the feasibility study of a new wireless network for the WAUN is described. The WAUN is designed to satisfy the requirements of many new applications using sensors and actuators, which are wirelessly connected to the IP network. One of the basic requirements for the wireless system of the WAUN is wide coverage larger than several km with low wireless terminal output power of 10 mW To meet this requirement, an experimental wireless system, which uses a powerful FEC and the diversity technique, for use in WAUNs is designed, and its feasibility is evaluated by field experiments. The experimental results demonstrate the feasibility of the WAUN. That is, the 10 mW transmission power wireless terminal communicates with the access point (base station) 5 km away

Wireless access system for Wide Area Ubiquitous Network

This paper introduces a wireless access system for the Wide Area Ubiquitous Network (WAUN), which is a large cell-based public sensor network, and provides feasibility study results gained through field tests. The wireless access system uses several key technologies to accommodate widely dispersed small simple terminals. First, to realize the large cell radius of several kilometers, space and site diversity technique based on digital radio over optical fiber (DROF) is developed. Second, an intelligent multiple access control scheme, a combination of demand assignment and random access, is employed to effectively accommodate tens of thousand of wireless terminals (WTs) per cell. Finally, techniques that yield low power consumption are introduced to create the long WT lifetimes needed. The system performance realized by the above-mentioned technologies is confirmed by field tests.

Inter-eigenbeam interleaving scheme for eigenbeamspace division multiplexing in OFDM system

This paper proposes an inter-eigenbeam interleaving scheme for the eigenbeam-space division multiplexing (E-SDM) in orthogonal frequency division multiplexing (OFDM) systems. It changes the assignment of eigenbeams to each data stream under the rule of cyclic sub-carrier selection, and the signal error created by eigenbeams with small eigenvalues can be corrected by a forward error correction (FEC) scheme that involves the eigenbeams with large eigenvalues. We evaluate the throughput performance of the proposed scheme and compare it with adaptive bit loading and transmission power control (ABL/TPC), which is a conventional E-SDM scheme. The simulation results show that the proposed scheme offers more stable throughput performance than ABL/TPC under fast Doppler fading environments. Keywords-component; MIMO, SDM, Eigenbeam, OFDM

Analysis and measurement of effects of SCM technique in WLL systems

We are studying the application of a subcarrier multiplexing (SCM) transmission technique to the wireless local loop (WLL). In this paper, the signal-level compression (SLC) method is proposed, which can be used to extend the optical transmission length or increase the number of multiplexed subcarriers on an optical fiber. The theoretical analysis of this method is described and the validity of the analysis is experimentally clarified. The results show that the number of subcarriers increases eightfold and the permissible optical transmission loss is improved by 10 dB when the level compression gain is 20 dB. As a result, the accuracy of the theoretical analysis and the effectiveness of the proposed SLC method are experimentally confirmed.

A non-regenerative repeating digital microwave radio system

The authors present a nonregenerative repeating system using digital quadrature amplitude modulation (QAM) signals. The difference in cumulative degradation characteristics between regenerative and nongenerative repeating systems is discussed. In addition, the bit error rate performance of a repeater transmission is presented using 16-QAM signals at a 12.5-Mb/s transmission rate. Multirelay degradation factors and countermeasures against interference noise are considered, which are self-interference passing adjacent channels and cross-polarization interference. Calculated and experimental results using adjacent 16-QAM signals and dual-polarization 256-QAM signals are presented.<<ETX>>

A Burst Modulation/Demodulation Method for Narrowband Ubiquitous Communication Systems

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.

Design and experiments of wide area wireless network for sensors and actuators

A new wireless network for the wide area ubiquitous network (WAUN), which is used for transmitting and receiving information for sensors and actuators, is studied. The wireless network for the WAUN needs to have wide cell coverage with a low transmission rate to support new applications economically using low-end wireless terminals. The transmission power of the wireless terminal of the WAUN must be very low to enable a very long battery lifetime. To meet the above requirements, an experimental wireless system, which uses a powerful FEC and the diversity technique, for use in WAUNs is designed, and its feasibility is evaluated by field experiments. The experimental results demonstrate the feasibility of the WAUN. That is, the 10 mW transmission power wireless terminal communicates with the access point 5 km away.

Coherent non-regenerative repeater digital microwave radio system field test

The first field test results of a coherent nonregenerative repeater digital microwave radio (CNR-DMR) system are presented. Among the cumulative degradation factors in fading state on nonregenerative repeating, self interference caused by passing adjacent channels (S-IPAC) and cross polarization interference are the main factors. The S-IPAC becomes intersymbol interference and cumulative cross polarization interference is changed to diverse multipath interference, since a coherent relationship between transmitter and receiver devices or between vertical and horizontal devices is maintained constant. These interference signals can be easily removed by equipping the terminal station with a decision feedback equalizer and a transversal filter type diverse cross polarization interference canceller. From the compensating effect obtained in the field test by using two nonregenerative repeaters with the equalizer and the canceller, it is clarified that the transmission quality of the CNR-DMR system is just as high as that of a regenerative repeater system.<<ETX>>