Nec Corporation

Hidenori Maruyama

Hideho Tomita

Yoshikazu Ikegami

A mobile communication apparatus including a transmission portion which transmits data after varying an amount of data to be transmitted under control of scheduling from at least a base station, including a schedule portion that stops an operation of an unnecessary circuit by controlling an operation rate of the transmission portion.

Mobile communication apparatus, mobile communication system, and power consumption reducing method for use therewith

An initial synchronization method in a DS-CDMA inter-base station asynchronous cellular scheme of transmitting a spreading code sequence, includes: a first stage that detects correlation power values between the common identification code and a received signal by using a correlator and performs a threshold determination; a second stage that detects a correlation value between the received signal and each long code group identification short code, sets a group having a maximum correlation sum as a group, detects a slot in which a head of the pattern is obtained as a start slot of a frame, and compares an arbitrarily set threshold with the maximum correlation sum; and a third stage that sequentially generates replica codes of long codes and short codes, performs correlation detection for the obtained synchronization timing, and performs long code correlation detection.

Initial synchronization method in DS-CDMA inter-base station asynchronous cellular scheme

An equalizer with a phase-locked loop comprising: a phase rotator which rotates a phase of a received signal to output a rotated signal; an impulse response detector which detects impulse responses of a transmission line through which the received signal has been transmitted on the basis of the rotated signal; a first region designator which designates a first region on the basis of the impulse responses; a second region designator which designates a second region on the basis of the impulse responses; an equalizer which estimates a sequence on the basis of the rotated signal by using the impulse responses in the first region; a replica generator which generates a replica of the received signal on the basis of the sequence by using the impulse responses in the second region; a phase detector which detects a phase difference between the replica and the rotated signal; and a circuit for controlling the phase rotator on the basis of the phase difference to decrease the phase difference.

Equalizer with phase-locked loop

A radio data communication terminal that includes a phase rotator for correcting a narrow-band modulation system, an equalizer for correcting a transmission path distortion of the frame signal corrected in phase, and a calculating circuit for calculating the phase error by using a preamble in the frame signal, he phase error is used for the phase error correction in the phase rotating means. The terminal further includes a transmission path distortion estimator for estimating the transmission path distortion by using the preamble in the frame signal corrected in phase and calculating tap coefficients necessary for the equalizer. A setter is provided for setting the tap coefficients to the equalizer and a first delay circuit delays the frame signal. A selection circuit selects an input or output of the first delay circuit and outputs the selected one to the phase rotator so that the calculating circuit and the transmission path distortion estimator operate while using the same portion of the preamble.

Radio data communication terminal

An automatic frequency control circuit includes a phase difference detection circuit, average value calculation circuit, weighting circuit, and phase correction circuit. The phase difference detection circuit obtains the phase difference between pattern signals per period on the basis of a quadrature-demodulated pattern signal component and a pattern signal component one period before the quadrature-demodulated pattern signal component. The average value calculation circuit calculates the average value of first phase differences between the pattern signals repetitively output from the phase difference detection circuit, thereby obtaining a second phase difference in units of symbols in the current burst. The weighting circuit weights the second phase difference from the average value detection circuit and a third phase difference up to the previous burst, thereby obtaining a fourth phase difference up to the current burst. The phase correction circuit corrects a demodulated received signal on the basis of the fourth phase difference from the weighting circuit.

Automatic frequency control circuit

Disclosed is an automatic frequency control circuit for correcting the influence of frequency offset in a radio data communication terminal of a scheme in which transmission path characteristics are obtained during the preamble period by narrow-band modulation to equalize the received signal. The automatic frequency control circuit includes, on the transmitter side, a unit for repeatedly transmitting the pattern of a predetermined pseudo noise (PN) signal serving as a preamble signal, on the receiver side, a unit for calculating the phase difference per PN cycle on the basis of the component (real and imaginary part amplitude values) of a PN signal one cycle before that is quadrature-modulated during a predetermined period of the preamble, and the component of a current PN signal, a unit for dividing the phase difference by the number of symbols of one PN cycle to obtain the phase difference (.DELTA..theta.) of the unit symbol, a unit for holding .DELTA..theta. during the burst period, a unit for integrating .DELTA..theta. in units of symbols during data demodulation, a unit for converting the integrated value into real and imaginary part amplitude values, and a unit for correcting the phase of the demodulated received signal on the basis of the obtained real and imaginary part amplitude values.

A phase-locked loop circuit, which is used in a radio data communication terminal of the type that obtains a transmission line characteristic during a preamble period in a narrow band modulation mode and equalizes received signals, that can correct an influence due to a phase error even in an environment of frequency selective multipath fading. The phase-locked loop circuit includes a phase rotation section, a replica signal generator, a phase difference detector, a division section, an integration circuit, and a vector converter. An equalizer obtains tap coefficients determined by transmission line characteristics and sets them to the equalizer and the replica signal generator. The equalizer starts to demodulate data and sequentially inputs the demodulated data to the replica signal generator to reproduce I and Q signal components input to the equalizer based on the demodulation data and tap coefficients. The phase difference detector determines a phase difference between a reproduced I signal component and an I signal component to be input to the equalizer adjusted in timing and a phase difference between a reproduced Q signal component and a Q signal component to be input to the equalizer adjusted in timing. The division section arbitrarily weights phase differences. The integration circuit integrates weighted phase differences in symbol units. Then the vector converter converts the integrated value into received signal components and inputs the converted value to the phase rotation section, so that phase errors are corrected.

Phase-locked loop circuit with equalizer and phase locking method

A radio data communication device that can perform a packet communication with the packet configuration suitable for transmission of a large volume of data in packet communications utilizing a low rate transmission mode and a high rate transmission mode. The transmitter side transmits packets only in a low rate mode or in a high rate mode after transmission in a low rate mode or only in a high rate mode. The receiver side simultaneously demodulates packets in the low rate mode and the high rate mode to detect the synchronous signal for each mode and judges whether or not in which mode the data has been transmitted, thus selecting the successive receive mode.

Radio data communication device and radio data communication method

A correlator 1 and an amplitude detection section 2 detect a correlation value of a spectrum spread signal. A maximum value detection section 5 detects a maximum correlation value for each symbol, which is then sequentially added by an adder section 6. A carrier detection section 4 compares the added value with a threshold value so as to detect presence/absence of carrier.

Carrier detection unit and carrier detection method

In a radio transmitter-receiver, a single frequency conversion method is used at a side of transmission and a double frequency conversion method is used at a side of reception. The frequency for transmission is identical with that of reception. A common oscillator of an oscillation frequency f1 is used for a local frequency for transmission/reception-first frequency conversion. A reception second local frequency signal and a transmitter intermediate frequency signal are generated by independent oscillators with oscillation frequencies 2f2 and 2f3 respectively. These oscillators generate two times the frequency of the conventional example thereof, thus providing the signals with frequency of 1/2 times the frequency-division by the frequency dividers for the reception side second frequency converter and transmission side intermediate frequency converters respectively. The output signals of these two oscillators are mixed in the frequency converter before the output signals are divided into 1/2-times the frequency thereof by the frequency divider, thus generating a base band signal of �2f2+2f3!/2 (in which '+' means mixing of signals) with the same frequency as that of the second local frequency signal. In this constitution, during reception of the signals, it allows the operation of the frequency divider for a transmitter intermediate frequency signal to halt temporarily. For this reason, since interference to the intermediate frequency band at the reception side vanishes therefrom, it becomes unnecessary to shield the reception side and the transmission side from each other.

Radio transmitter-receiver adopting both a single frequency and a double

In a receiving apparatus for spread spectrum communications, a carrier detecting circuit for detecting a carrier in a spread spectrum modulated signal is intermittently operated in a standby mode.

Spread spectrum receiving apparatus with battery saving function

In a waiting mode after transmission, a radio receiver is operated to convert a radio frequency signal into an intermediate frequency signal of which a signal level is checked. When the signal level is higher than a predetermined level, a reception mode starts for spectrum-despreading the intermediate frequency signal to provide a spectrum-despread signal and demodulating the spectrum-despread signal.

Direct sequence SS LAN station with reduced power consumption and method

A terminal unit for a wireless communication network includes a wireless modem, a wire network controller, and a CPU. The modem can check whether a RTS signal is inputted or not during reception of communication data, and modulates communication data and performs wireless transmission of the data in response to the RTS signal when no communication data is being received, while it temporarily outputs a CTS signal and disables it thereafter in response to the RTS signal when communication data is being received. Upon reception of a data transmission request from the terminal unit, the controller outputs the RTS signal to the modem after completion of reception of communication data when the data is being received, or outputs the RTS signal to the modem when no communication data is being received. The controller determines interruption of data transmission and outputs a RTI signal when the CTS signal from the modem is temporarily input and disabled thereafter. The CPU requests the controller to perform data transmission, performs back-off processing upon reception of the RTI signal, and causes the controller to generate a RTS signal to the modem after a determined back-off period.

Terminal unit for wireless communication network

At a transmit site of a spread spectrum communication system, a header is produced containing integers M and N (where M&gt;1 and N.gtoreq.0) and a frame is assembled with symbol bits. The header is converted to I and Q signals having a predetermined number of signal points in a signal constellation, which are spread with a predetermined pseudorandom sequence, and quadrature-modulated and transmitted. Using integers M and N, (M+N) data bits in a symbol are separated into M- and N-bit portions. The M-bit portion of each symbol is converted to I and Q signals having 2.sup.M signal points in the signal constellation, which are spread with one of 2.sup.N pseudorandom sequences according to the N-bit portion of each symbol, quadrature-modulated and transmitted. At a receive site, the transmitted header is converted to I and Q signals which are despread with the predetermined PN sequence to detect the integers M and N. The transmitted frame is converted to I and Q signals, which are sequentially despread with 2.sup.N PN sequences determined by the detected integer N, and then stored in a memory. Correlations between the I and Q signals of the frame and the 2.sup.N PN sequences are detected and a maximum correlation is identified for each symbol. A modulo-2.sup.N count is incremented in response to each correlation to produce a series of modulo-2.sup.N counts, and one of which is selected that corresponds to the maximum correlation. N-bit data representing the selected count is produced to read I and Q signals from the memory. The read I and Q signals are converted to M-bit data using integer M, and the M- and N-bit data are converted to a serial form.

Multimode spread spectrum communication system tolerant to varying

The present invention is an art of spread spectrum modulation systems, wherein a binary serial data is divided into a first bit data and a second bit data, the first bit data is primarily modulated, a spread code corresponding to the second bit data is selected, and the modulated data is spread by multiplying the primarily modulated first bit data by the selected spread code. In reception side, the spread code used for spreading in transmitter is detected in correlator, the second bit data is specified and the first bit data is demodulated.

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Tokyo, Japan

Hidenori Maruyama