Abstract: A terrestrial Rf telephone system provides a plurality of voice signal channels on a plurality of forward direction carrier frequencies, each carrier frequency having an associated predetermined bandwidth which is designed to accommodate one analog voice signal, and each carrier frequency containing a plurality of slots. The system includes a base station having a plurality of circuit paths for receiving a plurality of forward direction digitized voice signals; a plurality of compressors for compressing the voice signals; a processor for assigning each of the compressed voice signals onto a dynamically assigned frequency/slot; a plurality of channel controllers, each for sequentially combining the compressed digitized voice signals into a single transmit channel bit stream, with each compressed voice signal occupying a respective repetitive sequential time slot in the transmit channel bit stream; and a plurality of modulators for modulating the carrier frequencies.

Abstract: Data as may be employed in telecommunication is segmented into blocks, each block having associated therewith a metric of distortion as a function of the number of bits in the block to represent the quality of the data contained in the block. Within the blocks, bits are ordered according to significance. The blocks are then ranked according to the distortion metric, then the lowest significant bits of blocks having the lowest distortion metrics are dropped and bits are allocated to other blocks having the highest distortion metrics in order to redistribute the quality or distortion of each of the blocks for transmission (or subsequent compressed storage). Each of the blocks can thus be transmitted at substantially the same level of distortion within a channel which is bandwidth restricted compared to the maximum possible resolution of the data, thus minimizing imbalances in quality among the blocks of data and maximizing channel efficiency.

Abstract: A non-coherent digital receiver of a spread spectrum communication system for baseband synchronizing of a reference pseudo-noise sequence with a received pseudo-noise sequence modulated in a received spread spectrum signal.

Abstract: A receiver used in a system having a transmitter (10) that sends an exciting signal to a remote transponder (18) is configured to receive a relatively weak signal from the transponder and to cancel out relatively high level interference from the transmission itself. A received frequency shift keying signal is fed to a tuned amplifier (22) for preliminary analog signal conditioning, and thence fed to an analog to digital converter (24). The output of the analog to digital converter is integrated (26) over a selected number of clock pulses and then dumped into a quarter rate quadrature demodulator (60) that multiplies the integrated signal by the same signal delayed by one clock interval. Undesired artifacts generated in the demodulator (60) are removed by a cascade of comb filters (70), and the demodulated digital output is available as the desired output of the receiver.

Abstract: The invention relates to a method for associating an information unit from a limited set of various/different information units with a signal sector of given length of a data signal transmitted in a signal transmission system and including superimposed disturbances. The transmission of data takes place by a time-succession of the information units in the data signal. The various information units are coded in each case by a typical curve of the data signal in the corresponding signal sector. On the receiver side of the signal transmission system, different partial areas are determined for each signal sector under the curve of the received data signal. The various partial areas are assigned to rating numbers in accordance with their size. Based on the rating numbers, the decision is made as to which information unit has been transmitted in the relevant signal sector.

Abstract: At a transmit site of a spread spectrum communication system, a header is produced containing integers M and N (where M>1 and N.gtoreq.0) and a frame is assembled with symbol bits. The header is converted to I and Q signals having a predetermined number of signal points in a signal constellation, which are spread with a predetermined pseudorandom sequence, and quadrature-modulated and transmitted. Using integers M and N, (M+N) data bits in a symbol are separated into M- and N-bit portions. The M-bit portion of each symbol is converted to I and Q signals having 2.sup.M signal points in the signal constellation, which are spread with one of 2.sup.N pseudorandom sequences according to the N-bit portion of each symbol, quadrature-modulated and transmitted. At a receive site, the transmitted header is converted to I and Q signals which are despread with the predetermined PN sequence to detect the integers M and N. The transmitted frame is converted to I and Q signals, which are sequentially despread with 2.sup.

Abstract: An apparatus for decoding a received spread spectrum signal having a data signal modulated with a pseudo-noise code and transmitted as an RF spread spectrum signal. A first reference register holds a first pseudo-noise signal, a second reference register holds a second pseudo-noise signal, and a receive-register holds a received spread spectrum signal. A first modulo adder adds each chip of the received spread spectrum signal with each respective chip of the first pseudo-noise signal, thereby generating a first plurality of chip-comparison signals. A first summer adds the first plurality of chip-comparison signals, generating a first correlation signal. The comparator compares the correlation signal to an upper threshold level and a lower-threshold level, and respectively generates a first data-symbol signal or a second data-symbol signal.

Abstract: This invention is a decoding method for a special class of trellis codes which have large free distances. The encoding of the trellis code to be decoded can be implemented by employing a single binary convolutional code followed by more than one processor. The decoding can be implemented by using the trellis of the binary convolutional code and additional processors.

Abstract: The invention is used to shape noise in time domain and frequency domain coding schemes. The method advantageously uses a noise weighting filter based on a filterbank with variable gains. A method is presented for decoding an encoded signal based on received side information and on a masking matrix derived from the masking properties of speech. In particular, the encoded signal is separated into subband signal components, each of which is multiplied by a corresponding gain value based on the masking matrix. These multiplied subband signal components are then combined to produce a decoded signal.

Abstract: A printed circuit board intended to be placed within a card slot of a personal computer that allows the personal computer to receive information directly from a satellite communication network. The adaptor card operates in slave mode to a CPU of the personal computer. The CPU receives demodulated signals from a demodulator of the adaptor card via a bus interface on the adaptor card. The CPU also receives status information for the demodulator and a tuner and controls the operation of the demodulator and tuner via the bus interface. A DC-DC converter receives power from a power supply of the personal computer via the bus interface and provides power for the adaptor card circuitry. Moreover, the DC-DC converter powers a low noise block (LNB) of an antenna of the satellite communication network.

Abstract: A digitally modulated signal is conditioned, such as to facilitate amplification (500). The digitally modulated signal is derived from a digital information stream which is mapped onto a symbol constellation to generate a sequence of channel symbols. From a signal envelope representing the sequence of channel symbols, signal envelope minimum values are determined for the signal envelope as it transitions through successive channel symbols of the sequence (510). A modified sequence of channel symbols is generated by adjusting at least some channel symbols of the sequence, preferably based on response characteristics of a spectral shaping filter, to avoid signal envelope minimum values below a threshold value, thereby conditioning the digitally modulated signal (515, 520, 530, 540, 545, 555).

Abstract: A method and device for processing a signal are described, wherein an estimate of a multipath-induced contribution to a demodulated navigation signal is calculated and subtracted from said demodulated navigation signal to obtain an estimated line of sight contribution to said demodulated navigation signal, and a propagation time .tau..sub.0 is calculated from the thus calculated line of sight contribution to said demodulated navigation signal, such that a very accurate propagation time .tau..sub.0 of said navigation signal can be calculated.

Abstract: A method and apparatus for phase encoding and decoding a CPM spread spectrum signal. A transmitter divides a data stream into a data symbol portion and an associated phase information portion. The data symbol portion is used to select one of a plurality of spread spectrum codes for transmission from a symbol table. The phase information portion is used to differentially phase encode the data symbol prior to transmission. The transmitter divides the phase encoded spread spectrum codes into a plurality of data streams (such as I and Q data streams), independently modulates the I and Q data streams using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and simultaneously attempts to correlate for a plurality of chip sequences (such as I and Q chip sequences), and derives a real correlation signal and an imaginary correlation signal.

Abstract: A method and apparatus at a transmitter (800) initializes (904) pseudonoise (PN) sequence generators (302, 306, 320) to predetermined initial states and thereafter generates (906) time-synchronized PN sequences. A spread spectrum signal is then transmitted (908) by utilizing the PN sequences to encode information. At a receiver (600, 700) a predetermined one of the PN sequences is acquired and tracked (1002), and one of the predetermined initial states is predicted and tracked (1004). A PN sequence generator (608, 714, 722, 730) of the receiver is adjusted (1006, 1014) to generate a selected PN sequence time-synchronized with the predetermined one, and a corresponding one of the PN sequences is despread (1008) by utilizing the selected PN sequence to decode the information.

Abstract: A system for the wireless transmission of multiple information signals utilizing digital time division circuits between a base station and a plurality of subscriber stations. The subscriber stations may be fixed or movable. The number of time division circuits is determined by the transmission quality of the signals. The base station is interconnected with an external information network, which may be analog and/or digital. The information signals are selected from the group consisting of voice, data, facsimile, video, computer and instrumentation signals. The modulation level of the signals and the power applied to the system are adjusted in accordance with signal error detection in the system. The system is provided with spatial diversity by using a plurality of antennas selectively spaced from each other to provide relatively high signal reception despite signal fading. The base station operates over a plurality of RF channel pairs.

Abstract: A method and apparatus for transmitting and receiving a direct sequence spread spectrum signal encoded using two or more chip sequences to encode an information signal. The encoded information signal is received using a bank of matched filters (501a-501l), a bank of threshold comparators (505a-505l), a non-frequency locked bit clock circuit (509, 509') and a bit detector (510). Frequency locking is avoided by performing correlation on both the I- and Q- baseband signals and by logically combining the correlation results to recover the bit clock. In one embodiment, the method and apparatus uses binary phase shift keying to modulate the direct sequence spread spectrum signal with a carrier. In another embodiment, quadrature phase shift keying is used.

Abstract: An apparatus and method for synchronizing a spread spectrum receiver comprises a preamble matched filter and a plurality of symbol code correlators for receiving and correlating to a received spread spectrum signal. The preamble matched filter is preferably non-coherent in nature and outputs a correlation signal including a correlation pulse of variable width. The pulse is converted to a square wave having a duration of a discrete number of chip periods. The correlation pulse is used as a timing reference for the symbol code correlators, which are also non-coherent in nature. A center seeking circuit provides an offset to the timing reference according to the width of the correlation pulse. In a preferred TDMA system, a timing window is used for a subsequent time frame for defining a period of time in which the correlation signal output from the preamble matched filter can yield a valid correlation pulse.

Abstract: Methods and systems for receiving signals in spread spectrum communications are described. In CDMA systems, for example, signature sequences used to generate correlations with received signals may not have ideal autocorrelation properties. In such cases, the correlations determined by the receiver may include errors which are propagated through channel tap estimates to the demodulated and decoded information symbols. To reduce or eliminate such self-interference or inter-ray interference, the correlations are decorrelated by, for example, matrix multiplying them with values related to values of the autocorrelation function for the signature sequence of interest.

Abstract: This contribution involves the generation, transmission, propagation and selective reception of electrical, magnetic or electromagnetic energy in the form of a halfwave sinusoidal pulse signal, from one location to another, whereby intelligence input for transmission is recovered from one sinusoidal pulse, or from a plurality of sinusoidal pulses. In a transmitter embodiment, one or more sinusoidal halfwave pulse generators are provided, where each pulse signal may be generated asynchronously, with varying polarity, duration and amplitude on a continuous serial sampled information basis. Complementary pulse signal filtering and recovering of transmitted intelligence is provided in a signal receiver embodiment. Another transmitter embodiment includes a software-driven signal synthesizing capability, wherein a plurality of timed sinusoidal halfways pulses are linearly summed as elementary signal components of an information-carrying propagable signal.

Abstract: A split frequency band signal digitizer (10) includes a first mixer (18) for translating a split-band signal (200) about a multiple of the sampling frequency. The split-band signal so translated is then communicated to an analog-to-digital converter (26). The digitized signal is then analyzed to recover an original portion of the split-band signal and a second portion of the signal aliased into a single Nyquist band.