摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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. Furthermore, by observing the estimated positions of the mobile earth station obtained as a plurality of solutions at proper time intervals, comparing with one another the movements of the respective estimated positions occurring with the local time proceeds and selecting the estimated position of the minimum movement, the estimated position of the mobile earth station is uniquely determined relative to its true position.
摘要:
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. Thus, all the element channels are synchronized with one another because of the use of a single common PN code, and receive level of signal of each element channel is uniform, irrespective of a number of communication stations, and therefore, high quality communication with no interference is obtained in a relatively narrow frequency band.
摘要:
A spread spectrum communications system includes at least one communication station for transmitting a plurality of digital information data sequences via a plurality of communication channels by using the same PN code sequence. The communication station spreads the respective digital information data sequences by the PN code sequence to provide spread spectrum signals, modulates the spread spectrum signals by respective carriers having different frequencies from each other to provide modulated signals, and then transmits the modulated signals via the communication channels respectively. A frequency interval of the carrier frequencies is determined to an even-numbered multiple of a symbol rate of the transmitted digital information data sequences.
摘要:
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.