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Tokihiko YOKOI Yoshimitsu IKI Jun HORIKOSHI Katsuji MIWA Yoshio KARASAWA Akira FUKUDA Jun-ichi TAKADA Yuichi KURODA Takayasu SHIOKAWA Yukitsuna FURUYA Shigenari SUZUKI Yasuhiro SENBA Yoshihide YAMADA Hiroshi HARADA Yasuo SUZUKI Kiyomichi ARAKI
It is expected that software receivers will be widely available for radio communication, broadcasting and radio monitoring applications because they are able to be equipped with multimode, multirate and multiband functions in a single hardware platform. This paper describes the basic techniques required for software receivers for both hardware and software. The evaluation items and methods were studied and some evaluations done with an experimental software receiver model fabricated for radio monitoring applications. Future concepts in radio communication, broadcasting and radio monitoring applications where software receivers are thought to be suitable, were studied, and problems for realization identified.
Yoshihiko AKAIWA Eiji OKAMOTO Yukitsuna FURUYA
With popularity of radio communication, voice scrambling has received increased attention for communication privacy. It has been known that pre-emphasis at the transmit side and de-emphasis at the receive side improves the received signal to noise power ratio (SNR) both for scrambled and nonscrambled signals. In this paper, optimum pre- and de-emphasis are theoretically investigated for FM and PM transmission including frequency-domain scrambling for voice security. Using a linear system model, the optimum frequency-characteristics for pre- and de-emphasis filter are given as a function of a voice signal spectrum, demodulator output noise spectrum, and the scrambling method. Comparisons of the maximum attainable SNR are made for various case including plain voice (non scrambling) and secured voice scrambled by spectrum inversion, reverberation and FFT spectrum transformation, assuming simple voice and noise spectra.
Susumu YOSHIDA Fumiyuki ADACHI Jun HORIKOSHI Masahiro UMEHIRA Shingo OHMORI Yasutaka OGAWA Takahiko OGINO Tadashi FUJINO Yukitsuna FURUYA Koichi HONMA Yasushi YAMAO Yoshihide YAMADA Fumio WATANABE
Kazuhisa KAEDE Shuji SUZUKI Tomoki OHSAWA Yukitsuna FURUYA
A passive double star (PDS) optical subscriber system which employs a newly proposed flexible access and frequency division duplex transmission system has been reported. For the flexible access and efficient channel usage in subscriber PDS system, a modified pipe-line polling with a call-by-call basis channel assignment has been proposed. This access system has a wide covering range which exceeds 10km or more. A newly proposed pulsed PSK transmission and a baseband transmission are used for a single wavelength bi-directional transmission for to and from the central office. A pulsed FM single subcarrier transmission system is also proposed for the analog CATV distribution system, which is overlaid with wavelength division multiplexing on the bi-directional transmission system. The equipments for the pulsed PSK and the pulsed FM transmission can be realized with all digital circuits. Moreover, the pulsed signal's modulation nature has eased the requirement for the laser diode characteristics, such as linearity and RIN. These features are effective for the compact and cost effective transmission systems.
Kojiro HAMABE Yukitsuna FURUYA
This paper reviews Dynamic Channel Allocation (DCA) in TDMA cellular systems. The emphasis is on distributed DCA, which features decentralized control and adaptability to interference. Performance measures are discussed not only from a theoretical viewpoint but also from a practical viewpoint. Major techniques to enhance the capacity of cellular systems are channel segregation, reuse-partitioning, and transmitter power control. In addition to the performance of conventional cellular systems, differing performance in microcellular systems and multi-layer cellular systems is also discussed.
Ryuji KOHNO Kazuo TSUBOUCHI Peter JUNG Masakazu SENGOKU Tetsushi IKEGAMI Hisao TACHIKA Yukitsuna FURUYA Yoshiharu TOZAWA Takaaki HASEGAWA Shigenobu SASAKI Hiromasa HABUCHI
Yukitsuna FURUYA Yoshihiko AKAIWA
A new channel allocation algorithm named "Channel Segregation" is proposed for small cell mobile radio systems. The proposed scheme in principle requires no effort in the cell design and is highly adaptive to the change of propagation conditions. Channel allocation is determined in each base station in a distributed manner, without measuring propagation conditions in advance. By learning from statistical data of carrier sense results, each base station makes its favorite channel independently so that unnecessary interferences will not occur. As a result, each base station captures its favorite channels for dedicated use. Simulation results show that channel segregation actually takes place by a distributed control. Performances are measured in two criteria, interference probability due to carrier sense error and total blocking probability. Compared with a system without segregation, the proposed sheme decreases interference probability by 1/10-1/100, and increase channel utilization efficiency by 28% for a 2-dimensional interference model.
Masao NAKAGAWA Ryuji KOHNO Shin'ichi TACHIKAWA Taka-aki HASEGAWA Tetsushi IKEGAMI Eisuke FUKUDA Yukitsuna FURUYA Shuzo KATO Masashi SATOH Hisao TACHIKA Yoshihiro TANADA Kazuo TSUBOUCHI
Yoshihiko AKAIWA Shuzo KATO Masao NAKAGAWA Ryuji KOHNO Shinsuke HARA Nobuo NAKAJIMA Yukitsuna FURUYA Kouichi HONMA Eisuke FUKUDA
Masao NAKAGAWA Yukitsuna FURUYA Toshikazu KODAMA Ryuji KOHNO Yoichi SAITO Yoshinori SAKAI
Kenkichi HIRADE Hiroshi SUZUKI Hideichi SASAOKA Hiroshi NAKAMURA Yukitsuna FURUYA
Kazuhiro OKANOUE Akihisa USHIROKAWA Hideho TOMITA Yukitsuna FURUYA
This paper presents an adaptive MLSE (Maximum Likelihood Sequence Estimator) suitable for TDMA cellular systems. The proposed MLSE has two special features such as handling wide dynamic range signals without analogue gain controls and fast channel tracking capability. In order to handle wide dynamic range signals without conventional AGCs (Automatic Gain Controller), the proposed MLSE uses envelope components of received signals obtained from a non-linear log-amplifier module which has wide log-linear gain characteristics. By using digital signal processing technique, the log-converted envelope components are normalized and converted to linear values which conventional adaptive MLSEs can handle. As a channel tracking algorithm of the channel estimator, the proposed MLSE adopts a QT-LMS (Quick-Tracking Least Mean Square) algorithm, which is obtained by modifying LMS algorithm to enable a faster tracking capability. The algorithm has a fast tracking capability with low complexity and is suitable for implementation in a fixed-point digital signal processor. The performances of the MLSE have been evaluated through experiments in TDMA cellular environments with π/4-shifted QPSK, 24.3k symbol/sec. It is shown that, under conditions of 65dB amplitude variations and 80Hz Doppler frequency, the MLSE successfully achieves less than 3% B.E.R., which is required for digital cellular systems.