Eimatsu Moriyama

2.6 Ghz Band Multipath Characteristics for Urban Microcellular Telecommunication Systems

L O Summary Measurement of multipath delay profile characteristics in the 2.6 GWz band has been carried out within a 2 x 1.5 km area in metropolitan Tokyo to investigate the feasibility of a high speed digital micro-cellular portable radio system. The measurement system has time resolution of 40 ns. In this paper we present the spatial variations of the power delay profile and the delay-Doppler spectra, and we show the cumulative distribution of the delay spread and the error rate caused by multipath in the micro-cellular propagation environment.

Measurement And Modeling Of 2GHz-Band Out-of-Sight Radio Propagation Characteristics Under Microcellular Environments

On the bases of the measurement results gained in Tokyo metropolitan areas, this paper discusses the 2GHz band propagdion charucteristics of out-of-sight areas under microcellular environment. The measured results show that the received signul power is totally dominuted b y building-wallreflected waves in out-of-sight areas. Based on the analysis of the results, the paper proposes a calculation model for the line-of-sight roads using only wall-reflected waves. The proposed model well explain the phenomena; (a) that, the wider the out-of-sight pei-pendiculur roads, the larger the path loss on such roads; (b) that, if the distance from a base station to a turning corner becomes longer, the received signul comes to suffer from the larger attenuation b y turning the corner into out-of-sight areas; and (c) that, when the corner becomes more distant from a base station, the propagation path loss slope after turning the comer becomes larger.

Multicarrier/QAM-level-controlled adaptive modulation for land mobile communication systems

A multicarrier and an adaptive modulation combined system, where a suitable level of quadrature amplitude modulation (QAM) is selected for each carrier and time-slot using a QAM-level selection scheme, is proposed for digital land mobile communications. The advantages of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory to limit a transmission delay time. The QAM-level of each carrier is also controlled collectively according to the amount of the stored data bits in the memory. We confirmed the bit error rate (BER) performances of the system using computer simulation and we found that the system provided a noticeable BER improvement over frequency-selective fading channels and that the selection scheme was effective for a low maximum Doppler frequency and a small size of the memory.

2.6 GHz band multipath characteristics measurement in a residential area for micro-cellular systems

Multipath characteristic measurement in the 2.6 GHz band was carried out within a 0.8*2 km area in Tokyo to evaluate the feasibility of high-bit-rate digital portable personal radio communication systems in the microcellular propagation environment. In these measurements, microcellular propagation is realized by using a base station with an antenna lower than the surrounding buildings. The measurement area is a typical Japanese residential area where houses are densely built, located near an urban city center. Houses lining the test route have a mean height of two stores. The measurement system has a time resolution of 40 ns. The authors present the spatial variations of the power delay profile and the delay-Doppler spectra, and show the cumulative distribution of the delay spread and the error rate caused by multipath in microcellular environments.<<ETX>>

Implementation and performance of an adaptive QAM modulation-level-controlled system for land mobile communications

An adaptive modulation system for land mobile communications that can select one of the quadrature amplitude modulation levels as a suitable modulation for the propagation conditions is described. The main characteristics of the system are a mode in which information cannot be transmitted under adverse propagation conditions and a buffer memory for maintaining the data transmission rate. We confirmed the basic performance of the adaptive modulation system using the equipment we developed and we found the measured performance was consistent with computer simulation results. We also found that the adaptive modulation system provided a noticeable improvement in the spectral efficiency and transmission quality.

2.6 GHz multipath characteristics measurement in a shielded building

The measurement of multipath delay profiles in a shielded room is described. The aim of this measurement is to investigate the feasibility of high-bit-rate digital radio communication systems. The following results have been obtained: (1) power delay profiles can be simulated by a wall reflection model; (2) in shielded buildings, the delay spread is less than 160 ns over 90% of the area, whereas for outdoor urban systems with low base station antennas, the delay spread is less than 3.91 mu s over 90% of the area; (3) with two-branch diversity, at a data rate of 10/sup 5/ symbol/s, the error rate is better than 10/sup -4/ over 100% of the measurement area; and (4) partitioning can achieve an attenuation of about 20 dB, but does not offset the delay spread.<<ETX>>

Transmission experiments on slow-FH/16QAM system for land mobile communications

Field and laboratory experiments of a slow frequency hopping/16-ary quadrature amplitude modulation (SFH-16QAM) system for land mobile communications are presented. For interference diversity with high quality and high capacity on 16QAM, the system uses an FH scheme with a interference immunity decoding to further enhance immunity from co-channel interference, The laboratory experimental results show the effectiveness for reducing the bit error rate (BER) under strong interference. Field experiments have been conducted to demonstrate the BER performance in suburban Tokyo. The results show that the obtained BER is close to that of laboratory experiments and that the system can provide better performance than a system without FH.

Reduction of errors due to random FM noise

This paper proposes a technique for reducing errors caused by random FM noise in land mobile communication systems. With this technique, we do not need the pilot or preamble signals that up to now have been indispensable. Changing the received signal by using this technique reduces the effect of random FM noise even in currently available radio systems without any change in signal format standards. Computer simulation results with DPSK, QDPSK, and 16-star QAM demonstrated the feasibility of this technique. Errors were reduced to about 1/100 of the conventional level for QDPSK when f/sub D/T was 0.012 (where f/sub D/ is the maximum Doppler frequency and T is the symbol duration).

High bit rate /spl pi//4-QPSK modem with a new equalizer based on sequence estimation for mobile communications

This paper proposes a new type of greatly reduced-complexity sequence estimation in which stronger power delay waves are selected and combined. The proposed method has a similar BER performance and a greatly reduced complexity than MLSE. A high-bit-rate transmission system with a rate of 10 Mbit/s, /spl pi//4-QPSK/TDM for multimedia data transmission in land mobile communications is implemented. In adopting a 4-channel TDM, a user bit rate of 2 Mbit/s can be achieved. The system can compensate for delayed waves of up to 1.8 /spl mu/sec and sustains a maximum Doppler frequency (f/sub d/) of 240 Hz.