Abstract: Spaced-apart communication controllers connected to a cable-based network place a portable device in communication with the network for transfer of data packets. Each controller communicates with the portable device with packet transmissions through air, and requires registration of the portable device before offering packet transferring services. The registration process involves transmitting a packet from the portable unit requesting a response from controllers, transmitting a response packet from each controller receiving the request, selecting one of the responding controllers at the portable unit according to criteria that enhance data transfer, and transmitting from the portable unit a packet identifying the selected controller to complete registration. The selected controller transmits to other controllers via the network cable a packet confirming the registration.

Abstract: In a wireless local area network in which data packets are spread spectrum encoded, method and apparatus are provided for determining phase values that synchronize noise codes at network stations with received data packets. A synchronizing packet is first transmitted from a source station to various network stations. Each network station performs a wide-range search for a phase value that synchronizes the noise code of the station with the synchronizing packet. Thereafter, each network station performs narrow-range searches for phase values synchronizing the noise code of the station with subsequently received network packets. The stations switch to the wide-range search mode whenever a synchronizing phase angle has not been detected for predetermined period of time and switch to a narrow-range search mode whenever a synchronizing phase angle is detected.

Abstract: A wireless packet communication system is operable in a frequency band occupied by other transmission sources. The system includes a base station and several remote stations. Each remote station has a transceiver for transmitting and receiving data packets on electromagnetic carriers. The carrier frequency of the transceiver is selected in a pseudorandom manner from a predetermined set of carrier frequencies prior to transmission of each packet or in response to detection of transmission errors. Each carrier frequency may be associated with a unique pseudorandom noise code used to spread spectrum encode packets. The base station has a number of transceivers which operate simultaneously at the different carrier frequencies and which generate different noise codes for spread spectrum encoding and decoding. The base station records data for each remote station identifying the transceiver which last received a data packet and transmits packets addressed to each remote station with the identified transceiver.

Abstract: A local area network permits wireless transfer of digitized data among data processing machines in the interior of a building. The network includes a base station which may commonly be associated with shared network resources such as a host computer, print servers and file servers and a plurality of local stations each associated with a data processing machine such as a dumb terminal dependent on the host computer. The base station polls each local station to initiate a transmission of data to the base station. All data including request for data is transmitted as temporally spaced-apart packets spread spectrum modulated according to a pseudo-random noise code common to all stations and encoded onto an RF carrier which is common to all stations. The transmitted data packets include a synchronization code which permits proper spread spectrum decoding without loss of relevant data.

Abstract: Circuitry for receiving and demodulating a spread spectrum signal integrates signal acquisition and tracking functions and also accommodates signal drift. Two data decoding signals are generated which correspond to the pseudo noise code used to modulate the received signal and which are phase-shifted by a half-chip interval. Two correlators use the decoding signals to demodulate the received signal, both during acquisition and tracking, producing two data signals. A summer combines the two data signals to produce a signal whose strength is less dependent on the degree of synchronization of each data decoding signal with the received signal. Tracking error circuitry periodically compares the two demodulated data signals and incrementally phase shifts the two data decoding signals, the magnitude of the increment being one-quarter chip and the polarity being selected to strengthen the weaker of the two data signals. This causes the circuitry to track the received signal despite gradual signal drift.