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: 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 spread spectrum CDMA communication system in which a base station communicates with a plurality of subscriber terminals and the base signal transmitted by the base station is comprised of a set of substantially orthogonal functions which are overlaid with a pseudo-noise (PN) sequence forming a coded spreading sequence for an information signal, each orthogonal function of the set carries data for a single user in the system. Information signals are modulated onto the carrier to form a transmit signal and the coded spreading sequence on the transmit signal for broadcasting, each subscriber terminal having a receiver for coherently demodulating the base station signal. A plurality of correlators, each respectively tuned to different functions of the orthogonal signal set, are each followed by an appropriate nonlinearity for removing the data modulation. The summed output of the correlators is used to improve the estimate of carrier phase over that obtained with a single correlator.

Abstract: A spread spectrum CDMA communication system in which a station transmits a short synchronization signal to allow a second station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data. The rapid acquisition channel (RAC) includes a burst signal comprising of an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN) sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence.

Abstract: A satellite network communication system in which a plurality of subscriber handset terminals communicate with a ground hub station on traffic frequency channels using spread spectrum orthogonal CDMA transmissions. The hub station includes a control generator for generating a net entry control channel for communicating synchronization correction signals (timing, frequency and power) to subscriber handset terminals and a return link receiver. Each subscriber handset terminal has a subscriber unit control channel receiver for receiving the control channel synchronization correction signals and a subscriber unit return link transmitter connected to receive the synchronization correction signals so that signals from all subscriber handset terminals arrive at the hub station in time, power and frequency synchronism. The subscriber unit return link transmitter includes frequency hopped spread spectrum carrier such that none of the signals occupies the same frequency bin at the same time.

Abstract: A modulator system for generating a plurality of individual modulated RF signals and combining them and transmitting them in different frequency channels. The invention provides a practical method and apparatus for generating and combining a multiplicity of CDMA signals in several radio channels using digital circuitry. Further, several such band segments can be generated in parallel and combined to cover a large bandwidth. The invention generates this multiplicity of signals and combines them at baseband using all digital techniques. The advantage of this approach is a great simplification in hardware and improvement in reliability, as well as flexibility.

Abstract: The hub station of a network receives a multiplicity of signals in different frequency channels and possibly on different antennas. The individual signals to be demodulated may coexist in a radio frequency channel using FDMA, TDMA, or CDMA or other signal types or combinations thereof. The received frequency band is divided into subbands which are all translated to baseband and distributed to the backplane of one or more demodulator chassis (each of which contains many demodulators). In this way, any demodulator may be connected to any signal. Relatively large segments of the input bandwidth are translated to baseband. These segments are then digitized and further band segmentation is performed digitally. In this way, the digitation and switching functions are almost all done with digital hardware. This affords considerable advantage in hardware cost, size, and reliability.