Abstract: In the method of dynamically setting at least one threshold at an access point in a wireless local area network, signals from other access points are sensed, and a carrier detect threshold is determined based on the received signal strength of at least one of the sensed signals.

Abstract: Medium access control device (301) for a mobile network station (3, 4, 5) or an access point (AP1) in a wireless local area network (1), having controlling means (302), processing means (303) and transmitting and receiving means (304); the controlling means (302) being arranged to control transmission and reception of radio frequency data signals containing data symbols; the transmitting and receiving means (304) being arranged for transmission and reception of electromagnetic data signals; the processing means (303) being arranged for detecting a first signal portion and a second signal portion in the received data signal, the second signal portion following the first signal portion and having a signal coding differing from a signal coding of the first signal portion.

Abstract: A network system comprising a plurality of access points, wherein each access point can be used for wireless communication with at least one station, wherein each access point is arranged:

Abstract: A communication system with a plurality of access points (AP1, AP2, AP3) and at least one network station (5, 6), the network station (5, 6) being arranged to communicate with one of said plurality of access points (AP1, AP2, AP3) through a wireless communication protocol, each access point (AP1, AP2, AP3) is able to:

Abstract: The present invention relates to a wireless local area network station comprising means for signal processing, carrier detect sensing, defer behavior sensing, and memory.

Abstract: Method and device for communicating at least one packet of data with a predetermined packet size over a communication channel from a transmitter to a receiver, the transmitter having a memory for storing a common set of data rates, the method comprising the steps of fragmenting the at least one packet into a number of frames with a predetermined frame size by the transmitter, automatically selecting a combination of frame size and one of the common set of data rates by the transmitter such that the transmission time of each of the frames is limited to a predefined value, and transmitting each frame over the communication channel by the transmitter.

Abstract: A method and system of operating a wireless local area network station adapted to transmit and receive a signal within a communication cell. The method includes the steps of establishing a carrier detect threshold level, establishing a defer threshold level, and transmitting a signal when the signal level detected by the network station is above the defer threshold level. Additionally, the method further includes the step of receiving a signal transmission intended for the network station when the power of the received signal transmission is above the carrier detect threshold level.

Abstract: A receiver, and a method for operating the receiver, for a station in a wireless local area network using a common wireless communication channel and employing a CSMA/CA (carrier sense multiple access with collision avoidance) protocol includes various modes. In normal mode, the receiver follows typical states in order to detect a message and demodulate data from the message properly. Meanwhile, a process implements a message-in-message (MIM) mode when an energy increase above a specified level is detected. While in the MIM mode, if a carrier is detected, the energy increase is caused by a new message; otherwise, the energy increase is caused by an interfering station. If the carrier is detected, the receiver begins retraining so that it can start receiving the new message as soon as the first message ends. If no carrier is detected, the receiver waits a specified time to detect a carrier or for the end of the first message, after which the receiver returns to the beginning of the normal mode.

Abstract: For use in a direct sequence spread spectrum ("DSSS") receiver adapted to receive a differential phase shift keyed ("DPSK") packet on a channel, the DPSK packet having a training preamble and a data portion, a system to improve detection of the packet under degraded channel conditions, comprising: (1) a detection circuit that derives phase information from symbols in the packet and a weight that is a function of an estimated power profile for the channel and (2) a computation circuit that computes a weighted average for the phase information using the weight, the weighted average being power profile-based to allow the receiver to detect the data contained in the packet more reliably under the degraded channel conditions.

Abstract: The encoding/transmission of information in an OFDM system is enhanced by using complementary codes. The complementary codes, more particularly, are converted into phase vectors and the resulting phase vectors are then used to modulate respective carrier signals. The modulated result is then transmitted to a receiver which decodes the received signals to recover the encoded information.

Abstract: A wireless LAN includes first stations adapted to operate at a 1 or a 2 Mbps data rate and second stations adapted to operate at a 1,2,5 or 8 Mbps data rate. The 1 and 2 Mbps rates use DBPSK and DQPSK modulation, respectively. The 5 and 8 Mbps rates use PPM/DQPSK modulation. All four data rates use direct sequence spread spectrum (DSSS) coding. All transmitted messages start with a preamble and header at the 1 Mbps rate. The header includes fields identifying the data rate for the data portion of the message, and a length field. For a 2 Mbps transmission the length field identifies the number of bytes in the data field. For a 5 or 8 Mbps the length field identifies the number of bytes in the data field which, if transmitted at 2 Mbps, would take the same transmission time of the data field, and is thus a fraction 2/5 or 2/8 of the actual number of the bytes. With this arrangements, all the stations are interoperable in a co-existent manner in the LAN.

Abstract: A system for transmitting information over an OFDM channel using phase shift keying encoding employs a bit mapping encoder to reduce the crest factor (ratio of peak voltage to RMS voltage). For a 16 subchannel OFDM system using QPSK encoding, a first set of four symmetrically positioned pairs of subchannels is used to encode two bits of information on each subchannel. A second set of four symmetrically positioned pairs of subchannels is used to encode only one bit of information on each subchannel, with the resultant phasor for each pair of the second set of pairs of subchannels being orthogonal to the resultant phasor for one of the pairs of the first set of subchannels. With this arrangement, the crest factor is reduced.

Abstract: A local area network system (10) includes a host computer (14) connected in a wired LAN (12) with a plurality of bridges (18). The bridges (18) further connect with respective wireless LANs (100, 200, . . . , 600) which operate on a common wireless communication channel and contain respective pluralities of terminals (102, 202, . . . , 602). When a download operation is effected for initially starting up a new added terminal (e.g. 102-1), the bridges (18) are adapted to identify download message frames issued by the host computer (14) and retransmit each such frame (400) over the wireless communication channel in non-overlapping time intervals by applying respective different delays. Also, each download message frame is transmitted twice by each of the bridges (18).

Abstract: A local area network station (12) includes a transceiver (20) adapted to transmit and receive signals over a wireless communications link. The transceiver (20) is coupled to a CSMA/CD LAN controller device (22) and to a signal generator circuit (40) which is also coupled to the LAN controller device (22). If the station (12) desires to transmit a data frame but a carrier sense signal (CRS) indicates that the link is busy, transmission of the data frame is deferred, and after the carrier sense signal (CRS) becomes inactive, a collision is simulated by the signal generator circuit (40) providing a CDT signal to the LAN controller device (22) which goes into a backoff mode and attempts to retransmit the frame after a random backoff time. Thus, commercially available CSMA/CD chips can be utilized in a single wireless channel LAN environment using a CSMA/CA protocol, with a low risk of collisions.

Abstract: A local area network station (12) includes a transceiver (20) adapted to transmit and receive signals using electromagnetic radiation on a wireless communication link. The station (12) utilizes a CSMA/CD communications controller (22) in a CSMA/CA (collison avoidance) technique wherein deferred data frames are transmitted after a random number of backoff slots periods. A plurality of antennas (14, 16) is employed, with the antenna having the best receive conditions being selected for reception of a data frame. The antennas having a slotting control (200) which is synchronized with the backoff slotting to provide a short carrier detect time and hence high throughpout.

Abstract: A local area network (10) utilizes a wireless transmission link and has network stations (12) each having two differently polarized antennas (14, 16). Data transmission utilizes a spread spectrum code and in the receiver, correlator outputs are utilized in an integrator and registers circuit (54) to provide correlator output sample values integrated over a plurality of symbol intervals. These values are stored in registers (156) the contents of which are utilized to determine a peak value and a total value which are applied to a spike quality determination circuit (78) including a look-up table (200). The resultant spike quality output value represents the quality of the received signal and is utilized for carrier detection and for antenna selection.

Abstract: A data modem communication system includes a data modem transmitter adapted to transmit data on a main channel at a relatively high bit rate and to transmit data at a relatively low bit rate on a secondary channel. At the receiver, a single analog-to-digital converter (54) supplies digital signals via a notch filter (58) to the main channel receiver (60) and to the secondary channel receiver (62) wherein a single IIR low-pass digital filter (110) is utilized for processing at three different sample rates to eliminate the main channel signal with frequency conversion taking place between processing at the first and second sample rates. The invention enables the provision of a reliable secondary channel while using a minimum amount of circuitry for complex-valued digital signal processing.

Abstract: In a data modem receiver (80) the received signal is digitized in an A/D-converter (84), the output of which is applied to notch filter means (88, 96) which eliminates secondary channel signals, and which applies an output signal to a pair of IIR filters (112, 116), responsive to the frequency components present in a training signal. The values of the IIR filter output sigals are determined and compared with a pair of threshold levels provided by a threshold setter circuit (152) responsive to the peak received signal level to detect the receipt of a training signal. In response to the detection of a training signal, DFT calculations are initiated for timing recovery and modem address identification, using samples stored in a buffer shift register (206). A gain control circuit (220) is located subsequent to a band-pass filter (212) coupled to the buffer shift register (206).

Abstract: In a phase perturbation compensation system for use in a data modem receiver, the signal from an equalizer is fed to a phase and amplitude correction circuit which is connected to a decision circuit providing a data output signal and a phase error output signal which is applied to a phase jitter compensation determination circuit. The phase jitter compensation determination circuit includes a tapped delay line the output taps of which are applied to multipliers fed with adaptive weighting coefficients to provide values which are summed to provide a phase error prediction signal. The weighting coefficients are generated in integrator circuits which include respective delays. The values generated in the delays during an initial training sequence and stored in a storage device are retrieved for use in subsequent training segments, whereby fast phase jitter adaptation is achieved and hence stort training sequences can be utilized.

Abstract: A multipoint data modem communication system (10) includes a master modem (12) and a plurality of remote modems (14, 16 and 18). During an initial, remote-to-master transmission, a relatively long training sequence is transmitted and receiver parameter and equalizer coefficients are stored in a storage unit (156) in the master modem (12). During subsequent transmissions a relatively short training sequence which synchronizes the master modem receiver timing and also identifies the transmitting remote modem is applied. In the master modem an interpolation filter based on a ninth order Lagrange interpolation formula is located between an analog-to-digital converter (84) and a band-pass filter (92). Coefficients for the interpolation filter are calculated using a residual time shift value which is computed using a DFT calculator (96) which is coupled to a phase segment detector (142) and a phase-to-time-shift converter (146).