Showing papers in "IEICE Transactions on Communications in 1996"

A Frequency and Timing Period Acquisition Technique for OFDM Systems

Abstract: Symbol Pattern Abstract This paper introduces a frequency and timing period acquisition technique for orthogonal frequency division multiplexing (OFDM) systems. The proposed technique estimates both the frequency and timing pesiod offsets at the time by using only one pilot symbol with its suitable frequency assignment. Pseudo noise (PN) sequences are introduced to assign these frequencies of the pilot symbol so that the acquisition range can be widened. Numerical examples are given to show the estimate variances for both additive white Gaussian noise (AWGN) and multipath fading channels.

Pilot Symbol-Assisted Coherent Multistage Interference Canceller Using Recursive Channel Estimation for DS-CDMA Mobile Radio

Abstract: A pilot symbol-assisted coherent multistage interference canceller using recursive channel estimation is proposed for DS-CDMA mobile radio cellular system. Since the channel variation caused by fading is recursively estimated at each interference cancelling stage, the accuracy of channel estimation is improved successively. Computer simulation results show that the required E/sub b//N/sub 0/ at the average BER of 3/spl times/10/sup -2/ is improved by /spl sim/3.5 dB compared to the matched filter receiver for 10 users and two paths with equal power, and where f/sub d/T=10/sup -3/ (f/sub d/: fading maximum Doppler frequency, T: data symbol duration).

A Circularly Polarized Omnidirectional Antenna

Abstract: A circularly polarized omnidirectional antenna consisting of a vertical sleeve dipole and three pairs of tilted parasitic elements set around it is proposed. The antenna has a simple structure and no feeding network for radiating circular polarization. The authors describe the idea of the proposed antenna, some experimental approaches and the evaluation of the antenna by using the moment method.

Experiments on coherent multicode ds-cdma

Abstract: Direct sequence code division multiple access (DS-CDMA) is a promising candidate for 3rd generation mobile communications systems. We propose a coherent multicode DS-CDMA (CM-CDMA) scheme. The major features of the proposed access scheme are application of pilot symbol-aided coherent RAKE, traffic-adaptive transmit power control, orthogonal multicode transmission, and concatenated channel coding. A series of laboratory and field tests have been conducted. The measured results for the pilot symbol-aided coherent RAKE, transmit power control based on SIR measurements and multicode transmission are presented.

Adaptive Modulation System with Punctured Convolutional Code for High Quality Personal Communication Systems

Abstract: This paper proposes an adaptive modulation system with a punctured convolutional code for land mobile communications to achieve high quality, high bit rate, and high spectral efficient data transmission in multipath fading environments. The proposed system adaptively controls the coding rate of the punctured convolutional code, symbol rate, and modulation level according to the instantaneous fading channel conditions. The performance in fading environments is evaluated theoretically and by computer simulation. The results show that the proposed system can realize higher quality transmission without the degradation in average bit rate compared to conventional adaptive modulation systems.

A family of single-switch ZVS-CV DC-to-DC converters

Abstract: A family of single-switch ZVS-CV (zero voltage switching and clamped voltage) DC/DC power converters, i.e., buck, boost, buck/boost, Cuk, Zeta, and Sepic, are presented. Each power converter is realized by employing a commutation inductor circuit which is connected in parallel with either a transistor or a freewheeling diode in a conventional PWM power converter. The steady-state characteristics of these converters are analyzed, including the voltage conversion ratio, the ZVS condition and the input and output current ripple characteristics. These analytical results are confirmed by experiments. The proposed technique is quite simple and output voltage control is easy.<>