Abstract: A transmitter device comprises an OFDM transmission unit, a MC-CDMA transmission unit, and a control unit for selecting either the OFDM transmission unit or the MC-CDMA transmission unit at slot time assigned to a receiver device in response to propagation conditions for the receiver device. The propagation conditions are a distance from the receiver device and a CINR.

Abstract: A packet control apparatus connected between an interconnected network and a wireless apparatus includes a quality detection unit for detecting whether a quality of transmission toward the wireless apparatus is in a predetermined deteriorated state, and a packet filtering unit for deleting a link state watching packet received from the interconnected network, when the transmission quality is in the predetermined deteriorated state.

Abstract: A frequency error correction device for an OFDM receiver is proposed. The receiver receives an OFDM signal with a preamble section and a payload section including pilot carriers. The frequency error correction device includes a first frequency correction unit for correcting a relative phase error in a predetermined period of time based upon a frequency error in the preamble section of the OFDM signal in time domain, and a second frequency correction unit for correcting a remaining phase error in every predetermined period of time based upon the pilot carriers of the OFDM signal in frequency domain.

Abstract: A wireless LAN system comprising a plurality of wireless stations, and a switching apparatus for switching a frequency channel used between stations communicated with each other. The switching apparatus includes means for selecting the frequency channel to be used, and means for sending a switching request packet for specifying the selected frequency channel to the stations. Each of the stations include means for switching a current frequency channel to the frequency channel specified by the switching request packet received.

Abstract: An access point comprises a data table in which a correspondence relationship between a terminal ID specific to each mobile terminal and a virtual ID specific to a virtual LAN group to which each mobile terminal belongs, identifies a terminal. ID registered in a packet received from the mobile terminal, inserts a virtual LAN tag in the received packet, extracts the virtual ID corresponding to the terminal ID from the data table to register in the virtual LAN tag, and transfers it to switching means. The switching means selects an output port of the received packet based on the virtual ID registered in the virtual LAN tag of the received packet, and deletes the virtual LAN tag from the received packet and sends it.

Abstract: A radio LAN master station system which provides long distance communication and suffers from small interference by another system located inside and/or outside of a service area comprises a transceiver, and a plurality of directional antennas each directed to a respective section with some angular spacing, through a power distributor which couples said transceiver with said antennas. Polarization plane of any antenna is orthogonal to polarization plane of an adjacent antenna.

Abstract: An access point comprises a data table in which a correspondence relationship between a terminal ID specific to each mobile terminal and a virtual ID specific to a virtual LAN group to which each mobile terminal belongs, identifies a terminal. ID registered in a packet received from the mobile terminal, inserts a virtual LAN tag in the received packet, extracts the virtual ID corresponding to the terminal ID from the data table to register in the virtual LAN tag, and transfers it to switching means. The switching means selects an output port of the received packet based on the virtual ID registered in the virtual LAN tag of the received packet, and deletes the virtual LAN tag from the received packet and sends it.

Abstract: In each of communication stations, among all of spread spectrum signal waves having the carrier frequencies separated from each other in units of an integer multiple of the frequency amount R, all the spread spectrum signal waves having the carrier frequencies separated from each other in units of an even-number multiple of the frequency amount R are converged into a first group; all the spread spectrum signal waves that are adjacent to the aforementioned spread spectrum signal waves and that have the carrier frequencies separated in units of an even-number multiple of the frequency amount R are converged into a second group; and the first and the second groups of spread spectrum signal waves are simultaneously transmitted according to orthogonal polarized waves to perform information transmission.

Abstract: A transmitter device comprises an OFDM transmission unit, a MC-CDMA transmission unit, and a control unit for selecting either the OFDM transmission unit or the MC-CDMA transmission unit at slot time assigned to a receiver device in response to propagation conditions for the receiver device. The propagation conditions are a distance from the receiver device and a CINR.

Abstract: A packet control apparatus connected between an interconnected network and a wireless apparatus includes a quality detection unit for detecting whether a quality of transmission toward the wireless apparatus is in a predetermined deteriorated state, and a packet filtering unit for deleting a link state watching packet received from the interconnected network, when the transmission quality is in the predetermined deteriorated state.

Abstract: A receiver device adopting STTD MC-CDMA scheme, includes a plurality of receive antennas, a plurality of MC-CDMA receive units for respectively converting received signals from the plurality of receive antennas into parallel signals, for respectively performing FFT of the converted parallel signals, for respectively inversely spreading transformed signals, and for respectively equalizing and combining inversely spread signals, STTD decoding units for decoding in time direction and in space direction output signals from the plurality of MC-CDMA receive units, a parallel to serial conversion unit for converting output signals from STTD decoding units into serial signals, a de-mapping unit for de-mapping output serial signals from the parallel to serial conversion unit, and a decoding de-interleaving unit for de-interleaving output signals from the de-mapping means and for decoding de-interleaved data by performing error correction.

Abstract: A frequency error correction device for an OFDM receiver is proposed. The receiver receives an OFDM signal with a preamble section and a payload section including pilot carriers. The frequency error correction device includes a first frequency correction unit for correcting a relative phase error in a predetermined period of time based upon a frequency error in the preamble section of the OFDM signal in time domain, and a second frequency correction unit for correcting a remaining phase error in every predetermined period of time based upon the pilot carriers of the OFDM signal in frequency domain.

Abstract: The invention offers a repeater for radio communication system for eliminating a blind zone in a closed space in the radio communication system, which transmits information between a base station and a mobile station over a radio transmission medium. The repeater comprises a base station-directed unit equipped with a function of transmitting a radio signal to and receiving a radio signal from said base station, and a mobile station-directed unit equipped with a function of transmitting a radio signal to and receiving a radio signal from said mobile station. The base station-directed unit and the mobile station-directed unit are connected via a radio transmission medium over which an electromagnetic wave signal is transmitted.

Abstract: A surface acoustic wave-matched filter is disclosed which comprises: an input transducer provided on a piezoelectric substrate surface; a first output transducer, that is, a forward output transducer encoded in correspondence to a pseudo-noise code sequence for spectrum spreading and provided on the substrate surface; and a second output transducer, that is, a backward output transducer encoded in correspondence to the pseudo-noise sequence code and provided on the substrate surface at the succeeding to the forward output transducer by the length of the pseudo-noise code sequence as viewed from the input transducer. With the use of the surface acoustic wave-matched filter, it is possible to realize a differential detector for demodulating spread spectrum signals.

Abstract: A radio LAN master station system which provides long distance communication and suffers from small interference by another system located inside and/or outside of a service area comprises a transceiver, and a plurality of directivity antennas each directed to respective section with some angular spacing, through a power distributor which couples said transceiver with said antennas. Polarization plane of any antenna is orthogonal to polarization plane of an adjacent antenna.

Abstract: A wireless LAN system comprising a plurality of wireless stations, and a switching apparatus for switching a frequency channel used between stations communicated with each other. The switching apparatus includes means for selecting the frequency channel to be used, and means for sending a switching request packet for specifying the selected frequency channel to the stations. Each of the stations include means for switching a current frequency channel to the frequency channel specified by the switching request packet received.

Abstract: In each of communication stations, among all of spread spectrum signal waves having the carrier frequencies separated from each other in units of an integer multiple of the frequency amount R, all the spread spectrum signal waves having the carrier frequencies separated from each other in units of an even-number multiple of the frequency amount R are converged into a first group; all the spread spectrum signal waves that are adjacent to the aforementioned spread spectrum signal waves and that have the carrier frequencies separated in units of an even-number multiple of the frequency amount R are converged into a second group; and the first and the second groups of spread spectrum signal waves are simultaneously transmitted according to orthogonal polarized waves to perform information transmission. In addition, the communication station performs the transmission of the signal waves according to a time division multiple access (TDMA).

Abstract: A method is disclosed for uniquely determining the position of a mobile earth station in a mobile satellite communication system which employs a non-geostationary satellite with a multi-spot beams. A given point of a preknown position on the earth surface is defined as the center coordinate of a three-dimensional coordinate axis, information on the measured distance and Doppler shift amount between a mobile earth station of an unknown position and a non-geostationary satellite is used to repeat the estimation of the position of the mobile earth station a plurality of times, thereby obtaining the position of the earth station with high accuracy.

Abstract: A timing recovery and tracking method and apparatus with respect to data signal in a digital communication system is provided. The method includes a step of setting a time window for making a decision based upon a predetermined threshold level, the time window having a time period corresponding to a transmission data rate in the digital communication system, a step of detecting a time duration positioned within the time window, a level of a received signal being higher than the predetermined threshold level during the time duration, a step of assuming a substantially middle point of the time duration as an optimum decision point of the received signal, and a step of updating the time window so that the updated time window has its center at a position of the assumed optimum decision point.

Abstract: A combined channel or a composite channel is to be transformed into a plurality of element channels. The composite channel may be either shared by a plurality of communication stations on time division multiplex basis, or used by a single communication station. In a transmit side, a serial data information which is called a composite channel is transformed to parallel form associated with a plurality of element channels, each of which is spread by using a single common PN code. Each spread element channels are frequency converted to radio frequency so that the center carrier frequency is offset from that of adjacent element channel by an integer multiple of information transmission rate of each element channel, and frequency band occupied by spread element channels overlap with one another. Each element channels thus spread and frequency converted are combined on frequency axis, and transmitted to a receive side.