Abstract: A system for despreading and/or demodulating spread spectrum codes is provided. A data signal is encoded using an M-ary transmission technique, wherein predefined symbol codes are associated with a particular series of data bits. A receiver comprises a plurality of delay elements or a shift register with a plurality of taps configured to recognize one or more the predetermined symbol codes. Delayed representations of the received signal are generated and combined to produce a known output sequence, such as a string of consecutive one or consecutive zeroes, when a recognizable spread spectrum code is received. The receiver shift register may be preloaded such that recognition may occur starting with the first received chip. More than one set of taps may be coupled to the same shift register, so that more than one of the M spreading codes may be recognized by the same shift register.

Abstract: An apparatus and method for receiving spread spectrum signals, and, further, for decoding phase encoded information from such signals, requires correlation of input signals into real and imaginary components and determination of the phase angles of the received signal. A transmitter can divide an input signal into a plurality of data streams, independently modulate these streams, and then superpose the plurality of resultants for transmission. A receiver can receive the superposed signal and separate it into real and imaginary parts. In one embodiment, the receiver uses a plurality of spread spectrum codes to generate a plurality of real correlation signals and a plurality of imaginary correlation signals. A transmitter may also generate a differentially phase encoded signal. Phase encoding of a signal generally involves the imposition of known phase changes in the transmitted signal at selected intervals. Decoding of the phase changes at the receiver allows recognition of the phase encoded information.

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A transmitter divides a signal data stream 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 interleaves the correlated I and Q data streams into a unified signal data stream. In one embodiment, the receiver separates the received spread spectrum signal into real and imaginary parts, attempts to correlate both real and imaginary parts for a plurality of chip sequences, and combines the real I, real Q, imaginary I, and imaginary Q signals into a unified signal data stream.

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A spread spectrum transmitter includes a chip sequence generator for generating a chip sequence from a data stream, a switch for dividing said chip sequence into an odd chip sequence and an even chip sequence, and a modulator for generating and transmitting a continuous phase modulated signal from said odd chip sequence and said even chip sequence. A spread spectrum receiver comprises a plurality of non-coherent serial CPM correlators, each generating a correlation signal. In a preferred embodiment, the chip sequence generator of the transmitter comprises a table of symbol codes, each symbol code comprising a series of chips corresponding to a unique series of bits in said data stream, and each non-coherent serial CPM correlator is configured to detect one of the symbol codes.

Abstract: A system for time division multiplexed communication over a single frequency band in which guard time overhead is reduced by active adjustment of reverse link transmission timing as a function of round trip propagation time. In one embodiment, during a first portion of a time frame, a base station issues a single burst segmented into time slots comprising data directed to each user station. After a single collective guard time, the user stations respond, one by one, in allocated time slots on the same frequency as the base station, with only minimal guard times between each reception. In order to prevent interference among the user transmissions, the base station measures the round trip propagation time for each user station and commands the user stations to advance or retard their transmission timing as necessary.

Abstract: A receiver system for antenna diversity employing a single backhaul cable. A single backhaul cable couples a receiver to a plurality of antennas. The signals from the antennas are combined onto the single backhaul cable using frequency offsets, spread spectrum code division, time division, or a combination thereof. At the receiver, the signals from the antennas are decoupled. In the case of frequency offsets, the antenna signals are decoupled by splitting the backhaul signal into a plurality of duplicate signals, frequency shifting selected ones of the duplicate signals, and correlating said frequency shifted signals. In the case of spread spectrum code division, the antenna signals are decoupled by splitting the backhaul signal into a plurality of duplicate signals and demultiplexing each of the duplicate signals with a different spread spectrum code. One or more antennas may be selected for communication in response decoupling the antenna signals.

Abstract: A system for publishing data on shared broadcast channels using spread-spectrum techniques, which may comprise a spread-spectrum encoder capable of receiving data and placing it in a spread-spectrum signal format and a transmitter operating on a shared communication channel or frequency band, such as might be allocated to terrestrial point-to-point or broadcast communications. The shared communication channel may comprise a cellular system, in which data may be transmitted using spread-spectrum techniques using the transmitters and repeaters of the cellular system simultaneously with voice and other transmissions associated with the cellular system. A subscriber station may be capable of receiving using a plurality of different communication channels or frequency bands, such as a first receiver capable of cellular reception and a second receiver capable of satellite reception, at least one of which uses spread-spectrum techniques.

Abstract: A method for establishing communications between a master unit and a plurality of node units. Of the plurality of node units, K node units are assumed to have established communications with a master unit. A first (K+1) node unit of the plurality of node units, desires to establish communications with the master unit. The method includes transmitting from the master unit, a base-station spread spectrum signal having a common signalling chip code, transmitting from the first node unit a second spread spectrum signal with a first identification code using the common-signalling chip code, transmitting from the master unit a third spread spectrum signal with a master unit identification code, using the common-signalling chip code. The method further includes generating at the first node unit using the master unit identification signal, a master unit chip code for transmitting spread spectrum signals to the master unit.

Abstract: An integrated communication system supporting multiple TDMA or TDD communication protocols whereby both protocols are supported within the same geographic region. Each protocol defines time frames and/or time slots of a different duration, from which is derived a composite time frame having a predefined timing structure. A first base station unit communicates in a first set of time slots of the composite time frame according to a first TDMA or TDD protocol, and a second base station unit (which may be collocated with the first base station unit) communicates in a second set of time slots of the composite time frame according to a second TDMA or TDD protocol. Coordinating electronics (such as a GPS receiver in one or both base station units) are provided so as to prevent collisions between communications occurring between each base station unit and its respective users. In a particular embodiment, a first protocol is a GSM protocol, and a second protocol is a TDD protocol utilizing spread spectrum techniques.

Abstract: A method for communicating using a plurality of spread spectrum codes. A plurality of spreading codes are generated by use of one or more linear feedback shift registers configured with feedback taps. The spreading codes may be maximal or non-maximal. A plurality of code portions are selected, one from each of the spreading codes. The code portions each have the same length and are selected for low cross-correlation and favorable auto-correlation and spectral properties. Each of the code portions is associated with a data symbol representing a unique group of data bits. An input data stream is divided into groups of data bits and, in response thereto, the code portion associated with each group of data bits is transmitted. At the receiver, the transmitted signal is captured in one or more receive shift registers.

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: A technique for spread-spectrum communication which uses more than one mode and more than one frequency band. Selectable modes include narrowband mode and spread-spectrum mode, or cellular mode and microcellular mode. Selectable frequency bands include both licensed and unlicensed frequency bands, particularly frequency bands including the 902-928 MHz, 1850-1990 MHz, and 2.4-2.4835 GHz frequency bands. Spread-spectrum communication channels are 10 MHz or less in width. The frequency band onto which spread-spectrum signals are encoded may be changed upon a change in environment or other control trigger, such as establishment or de-establishment of communication with a private access network. A multi-band transmitter comprises a single frequency synthesizer and a frequency source (e.g., a local oscillator), coupled to a selectable band pass filter.

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 system for efficient time division duplex communication between a base station and a plurality of user stations over multiple frequency bands whereby guard time overhead is reduced through use of an interleaved frame structure and active adjustment of reverse link transmission timing as a function of round trip propagation time. A time frame is divided into a plurality of time slots. A user station transmits a preamble over a user frequency band. The base station receives the preamble and transmits, in a given time slot, a forward link message over a base frequency band to a user station. The user station responds with a reverse link message over the user frequency band in a subsequent time slot. While the base station is transmitting to a first user station over the base frequency band, it receives messages from another user station over the user frequency band, using the time slot differential between forward and reverse link messages for round trip propagation.

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: A simple and flexible over-air protocol for use with a mobile telephone system, having hand-held telephones in a microcell or other type of cellular communication system. A method in which user stations communicate with one or more base stations to place and receive telephone calls, in which the user stations are provided a secure voice or data link and have the ability to handoff calls between base stations while such calls are in progress. Each base station has a set of "air channels" to which it transmits in sequence. The air channels supported by each base station are called that base station's "polling loop". A user station receives general polling information on an unoccupied air channel, transmits responsive information to the base station, and awaits acknowledgment from the base station. Each base station may therefore simultaneously maintain communication with as many user stations as there are air channels in its polling loop.

Abstract: A pulse position modulation detector divides a timing window into a plurality of pulse position windows, determines the peak magnitude of a signal level received during each pulse position window, compares the peak magnitudes of the signal detected during each pulse position window to determine during which pulse position window the greatest peak magnitude is detected, and generates a bit sequence corresponding to the pulse position window wherein the greatest peak magnitude was detected within the current timing window.

Abstract: A technique for demodulating CPM spread spectrum signals and variations thereof. A receiver receives a CPM spread spectrum signal, splits it into two signals, demodulates the signals (either coherently or non-coherently) and simultaneously attempts to correlate for a plurality of chip sequences (e.g., I and Q or even and odd), ultimately combining the results into a unified correlation signal. A plurality of A/D converters quantize the demodulated signals into multi-bit digital signals prior to correlation, and multi-bit correlators operate on the multi-bit digital signals to produce correlation signals that are combined to form a unified correlation signal for detection.

Abstract: A method of pulse-position modulation in a spread-spectrum communication system, which is capable of transmitting more than one bit per received and recognized chip sequence in a system in which an entire chip sequence is required to produce a correlation pulse. A framing pulse window in which a framing pulse may be received, and a plurality of data pulse windows in which a data pulse may (or may not) be received. The delay between the framing pulse window and the first data pulse window may comprise an entire chip-sequence duration, while the delay from one data pulse window to the next may be less. A method of pulse-position modulation with more than one spread-spectrum code. A second transmission medium (such as a second spread-spectrum code) on which a data pulse may (or may not) be received. Each possible choice, for the data pulse, of delay time and transmission code may represent a separate set of multiple data bits.

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A transmitter divides a signal data stream 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 interleaves the correlated I and Q data streams into a unified signal data stream. In one embodiment, a spread spectrum transmitter comprises a plurality of lookup tables for storing spread spectrum code chip sequences, at least one preamble code chip sequence, and at least one fill code chip sequence. An output from each of the tables is provided to a selection circuit (e.g.