Abstract: A communication device according to the present invention includes a header compressor (121) which measures a time from a start of communications with a communication partner and changes a compression ratio of a header of a packet to a compression ratio lower than a present compression ratio each time that a time represented by a timer value elapses, and a controller (12) which controls the timer value based upon at least one information from among channel quality information of the communication device and channel quality information received from the communication partner.

Abstract: Downlink control information including uplink control information can be transmit efficiently. That is, a base station apparatus that configure a communication system includes changing means. The changing means changes a component carrier as a mapping target on which downlink control information including control information about uplink is mapped based on a predetermined processing procedure, among a plurality of component carriers having mutually different frequency bands within a frequency band used for downlink.

Abstract: A communication device according to the present invention includes a header compressor (121) which measures a time from a start of communications with a communication partner and changes a compression ratio of a header of a packet to a compression ratio lower than a present compression ratio each time that a time represented by a timer value elapses, and a controller (12) which controls the timer value based upon at least one information from among channel quality information of the communication device and channel quality information received from the communication partner.

Abstract: A frequency offset correction system includes a phase shift estimation unit and correction unit. The phase shift estimation unit estimates a pilot phase shift from pilot signal data for a plurality of bits, and estimates a data phase shift of data from the pilot phase shift for each bit when the frequency offset of a received signal having data of an in-phase component whose bit rate is variable, and pilot signal data of a quadrature component is small. The correction unit sequentially adds data phase shifts and pilot phase shifts estimated by the phase shift estimation unit, and performs frequency offset correction of the received signal using a phase shift obtained by selectively inserting the estimated pilot phase shifts in the added estimated data phase shifts. A frequency offset correction method is also disclosed.

Abstract: A signal from a local oscillator is separated by a 90.degree. phase sifter into an in-phase component and an orthogonal component. Each of the components is multiplied by a received IF signal in a mixer to perform pseudo-synchronous detection. The pseudo-synchronously detected signals are subjected to A/D conversion in an A/D converter, and preamble portions are integrated in integrating circuits. The integrated signals are latched in latch circuits. The timing of the latch is controlled by a timing circuit. A power detector detects the power of the latched signal, and the maximum value is detected in a maximum value detector to determine timing at which the power becomes maximum in selectors. A phase (.theta.) is determined from the inverse tangent of the maximum value, and is used as an initial value of a voltage controlled oscillator (VCO) in a demodulator.

Abstract: The spread spectrum communication system of the present invention is intended to equalize link capacity by taking deterioration of link quality so as to enable reliable communication which enhances the frequency diversity effect even if it is affected by the frequency selective fading or the like. Then, between a base station and a mobile station in a code division multiple access communication system which multiplexes the hopping frequencies by varying them with hopping series different for each channel, a same frequency band is used for a forward-link and a reverse-link, and the number of hopping frequencies and/or the number of hops per one data symbol being assigned is varied according to line quality. There is provided means for performing communication by multiplexing the forward- and reverse-links using the different hopping frequencies for transmission and receiving, so that the link capacity is equalized for the forward- and reverse-links.

Abstract: A communication system comprises a master station 21 and a plurality of slave stations 22-1 to 22-N each of which communicates with the master station through a radio channel carrying a communication signal by using time division multiple access. The slave stations are similar in structure to one another. The master station is similar in structure to each of slave stations. Each of the slave stations selectively transmits a speech signal and an image signal to the master station. On transmitting the speech signal, the speech signal is converted into an ADPCM signal. On transmitting the image signal, the image signal is converted into a PCM signal. The master station receives the communication signal which is transmitted from each of the slave stations. The master station detects whether or not the communication signal is representative of the ADPCM signal to selectively produce the speech signal and the image signal.