Abstract: An ODS-CDMA communications system is disclosed with at least one hub station and a plurality of user terminals. Each user is assigned a code which is orthogonal to all of the other user codes. The orthogonal code period is chosen such that the code repeats an integer number of times in a data symbol time and the code is synchronized with the symbol transitions so that no data transitions occur within the code. Thus, the selection of an orthogonal code book which enables a high rate data to be spread using shorter code words, and conversely, low data rate to be spread using longer code words, all of which remain mutually orthogonal.

Abstract: A fast algorithm for performing maximum likelihood detection of data symbols transmitted as phases of a carrier signal.

Abstract: The invention is a cellular radio system for terminals with narrowbeam antennas that provides demand assignment multiple access channel assignment under a guaranteed channel quality criterion. The invention features an efficient channel assignment algorithm that utilizes a database of measured the co-channel interference characteristics of subscriber terminals to eliminate significant co-channel interference in assigned channels. The use of measured terminal interference characteristics eliminates the occurrence of unexpected random occurrence of large co-channel interference in channel assignments thus permitting the use of more spectrally efficient cellular frequency reuse patterns.

Abstract: A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDMA channels.

Abstract: A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDMA channels.

Abstract: The invention relates to a threshold extension block phase estimator (TEBPE) which estimates phase in the presence of noise. Threshold and sector slips are controlled by an iterative calculation. This can be of crucial advantage in coded systems. Another attribute of the TEBPE is it can be configured as a hybrid feedback loop incorporating characteristics of both the BPE and the PLL. This gives a high degree of flexibility with very fast acquisition times at high signal-to-noise ratio (SNR), and improved threshold performance at low SNR.

Abstract: A method and apparatus for taking advantage of diverse signals. Trellis decoding takes advantage of multiple symbol noncoherent detection and diversity combining. Accordingly, combination of diverse signals effectively occurs pre-detection. Tracking loops are not necessary to set weights for each channel. In a QPSK embodiment employing a rate 1/2 convolutional code, an improvement in effective SNR of 1-3 dB may be achieved as compared with non-diverse reception.

Abstract: A spread spectrum OCDMA communication system in which multiple base stations or beams from a satellite are deployed in a “cellular” coverage structure, system capacity is increased by dividing the available spectrum into non-overlapping frequency segments which are assigned to different cells in a frequency reuse pattern to provide greater system capacity than full frequency reuse in each cell.

Abstract: The invention is a cellular radio system for terminals with narrowbeam antennas that provides demand assignment multiple access channel assignment under a guaranteed channel quality criterion. The invention features an efficient channel assignment algorithm that utilizes a database of measured the co-channel interference characteristics of subscriber terminals to eliminate significant co-channel interference in assigned channels. The use of measured terminal interference characteristics eliminates the occurrence of unexpected random occurrence of large co-channel interference in channel assignments thus permitting the use of more spectrally efficient cellular frequency reuse patterns.

Abstract: A networking method for a wireless point base station to a plurality of users where the users are stationary and which utilizes time-division multiplexing in the downstream direction of the base station to the user, including downstream frame timing, comprising providing time-division multiple access in the upstream direction of the user to the base station. Medium access is achieved by actively controlling assigning frame time slots in the upstream direction to accommodate varying demands for bandwidth by multiple users. The upstream frame time slots are synchronized to the downstream frame timing, the time slots carrying individual ATM cells, the first time slot of the downstream frame carries a frame start ATM cell. Upstream time slot synchronization is maintained to within ±2 modulation symbols through timing control from the base station to the user.

Abstract: A point-to-multipoint star configured terrestrial radio communication system having at least one base station transmitting to and receiving RF communication signals from a plurality of associated subscriber stations in the 0.3-300 GigaHertz (GHz) range. The system includes means for reducing frequency uncertainty, drift or error of the RF transmissions from each of the subscriber stations to the base station. Each subscriber station has a low cost local reference oscillator, and the system incorporates a reference broadcast signal of high frequency precision from the base station and at each subscriber station there is means for measuring frequency error and compensating for frequency drift/error in the low-cost oscillator at the subscriber station.

Abstract: A communications waveform format is provided for a satellite-based telecommunications system. The waveform format includes forward and return link waveforms between the satellite, earth stations and terminals. The forward and return links use orthogonal direct-sequence code division multiple access (ODS-CDMA) to minimize interference between users. The forward and return link spectrum may be divided into channels, the frequencies and spacing of which are adjustable to compensate for Doppler effects, thereby maintaining synchronization. The spectrum of the terminal links may be divided into multiple subbands (e.g., 38), each of which may support multiple (e.g., 80) ODS-CDMA channels.

Abstract: A network protocol for the delivery of wireless broadband integrated services digital network (ISDN) using asynchronous transfer mode (ATM).

Abstract: Positioning system for locating a mobile body comprising a plurality of earth based spread spectrum (SS) broadcasting stations arranged geographically in a cellular pattern. Each SS broadcasting station include a modulator providing a channel signal structure which is substantially orthogonal with respect to adjacent stations in the cellular pattern, each channel signal including navigation beacon data including a unique beacon identification, station latitude and longitude, time.sub.-- slot and phase characterizations and selected parameters of adjacent stations. In one embodiment, each modulator provides a chirped SS signal in which the navigation beacon is a frequency tone that is repeatedly swept over a selected frequency band for each station. In a further embodiment, each modulator provides a GPS like direct sequence SS signal in which the navigation beacon is a PN coded broadcast.

Abstract: A spread spectrum CDMA communication system in which base stations communicate with a plurality of subscriber terminals located in different beams of a multi-beam satellite relay system. A base station transmits a signal for each beam which is comprised of a set of orthogonally spaced subcarriers, each of which is modulated by a set of orthogonal functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal. Each orthogonal function carries data for a single user in the beam. Selected carrier signals are modulated with information signals onto the subcarriers to form a beam signal. The available frequency spectrum is divided into non-overlapping segments which are assigned to different beams in a 1:N.sub.ru frequency reuse pattern. Each subscriber terminal has a receiver which coherently demodulate the base station signal. A PN spreading code, P2, with chipping rate N.sub.ru .chi.R.sub.

Abstract: A receiver for tracking and acquisition of the split spectrum PN GPS C/A signal constellation from an earth-orbiting satellite for radiolocation includes an RF front end for receiving and downconverting the split spectrum PN GPS C/A signals from the earth-orbiting satellite to an IF signal. The total power in the split spectrum PN GPS C/A signal is compressed and the compressed split spectrum PN GPS C/A signals are supplied to a utilization device.

Abstract: A multiple access RF communication system in which a plurality of mobile user transceivers communicate with a central hub transceiver through an earth orbiting satellite, and wherein groups of mobile user transceivers in close proximity with each other share a common multi-access inbound (to hub) frequency F.sub.l and a common outbound channel (from hub) frequency F.sub.o. Each said mobile user transceiver includes a continuously listening receiver for the outbound channel and a half-duplex transceiver on the inbound channel, determining the busy or idle status of the common inbound frequency F.sub.1, and a device to indicate the status of the carrier outbound channel, which controls the ability to transmit on the inbound channel.

Abstract: A Kronecker product code structure for a synchronization word is presented which permits the use of dual-mode sequential matched filter. This matched filter permits a large reduction in acquisition time since the number of frequency bins that must be searched is greatly reduced when there is a large frequency uncertainty. In the first mode of operation the output of a filter matched to the high rate code is non-coherently integrated in a post-detection integrator to obtain reliable but ambiguous acquisition of the synchronization word. In the second mode of operation the ambiguity is resolved.

Abstract: A system for providing a signal structure for code-division multiplexed radio positioning comprises a coherent signal source from which carrier frequency and all lower frequencies used in code definition are derived through frequency synthesis. A radio frequency (RF) carrier approximately centered in the available band is provided.

Abstract: A laser satellite communication system which avoids atmospheric, wind and turbulence effects. A satellite or high altitude platform communication system includes an earth-orbiting satellite or high altitude platform carrying a laser communications receiver and an acknowledgement transmitter. A ground terminal having a laser communications transmitter which is caused to continuously transmit large data block signals. When one block of data signals is received at the satellite or platform, an acknowledgement signal is sent to earth from the satellite or platform. The ground terminal receives the acknowledgement signal and causes the ground terminal laser communication transmitter to continuously transmit the next succeeding large block data signals. This process is repeated until all of the data has been received by the earth-orbiting satellite or high altitude platform, whereby all of the large data block signals are received by the laser communication receiver through scintillation windows in the atmosphere.