458 results about "Spread spectrum modulation" patented technology

Methods and apparatus are described for marine asset security and tracking (MAST). A method includes transmitting identification data, location data and environmental state sensor data from a radio frequency tag. An apparatus includes a radio frequency tag that transmits identification data, location data and environmental state sensor data. Another method includes transmitting identification data and location data from a radio frequency tag using hybrid spread-spectrum modulation. Another apparatus includes a radio frequency tag that transmits both identification data and location data using hybrid spread-spectrum modulation.

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station, and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The system and method transmits from the base station, a synchronization channel having a chip-sequence signal used by the plurality of subscriber units for synchronization. A first subscriber unit receives the synchronization channel, and determines timing from the synchronization channel. In order to initiate communications with the base station, the first subscriber unit transmits an access signal. The access signal has a plurality of power levels, which typically ramp up. The base station receives the access signal at a particular-power level. The base station then transmits to the first subscriber unit an acknowledgment signal. The first subscriber unit receives the acknowledgment signal, and transmits to the base station, a spread-spectrum signal.

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station (BS), and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The improvement method for adaptive reverse power control (APC) from a subscriber unit (SU) to a base station (BS), comprises the steps of sending from the subscriber unit, using spread-spectrum modulation, a SU-spreading code on a reverse channel. The base station despreads the SU-spreading code on the reverse channel as a despread signal, determines a first power level Pd which includes power of the despread signal plus noise and a second power level PN, which includes despread-noise power. The base station determines a first error signal e1, from the first power level Pd, the second power level PN, and a required signal-to-noise ratio SNRREQ for service type, and a second error signal e2, from a measure of total received power Prt at the base station, and an automatic gain control (AGC) set point Po. The base station forms a combined error signal from the first error signal e1, the second error signal e2, a first weight a1, and a second weight a2, and hard limits the combined error signal to form a single APC bit. The APC bit is transmitted to the subscriber unit. In response to the APC bit, the subscriber adjusts transmitter power to the base station.

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station (BS), and a plurality of subscriber units (SUs). The signals transmitted between the BS and SU use spread-spectrum modulation. The apparatus for maintaining control of power from an SU to a BS, comprises sending from the SU, using spread-spectrum modulation, a SU-spreading code, and detecting at the base station, the SU-spreading code from the SU. In response to detecting the SU-spreading code at the BS, a BS-spreading code is sent to the SU, using spread-spectrum modulation. At the SU, if the BS-spreading code is detected, then transmit power of the SU is reduced. If the BS-spreading code is not detected at the SU, then transmit power of the SU is increased.

A self-organizing backhaul radio (SOBR) and related arrangements are disclosed. A “primary” link between an first SOBR enabled radio and a second SOBR radio includes a secondary transmission link, referred to as a signature control channel (SCC), as a spread spectrum modulated signal embedded within and transmitted simultaneously with the primary link. The SCC transmissions from the first SOBR radio may be utilized by other SOBR enabled radios to determine an interference level to or from the first SOBR radio's primary link. The SCC transmission may be utilized to allow transmit beam forming between SOBR-enabled radios without damaging other friendly SOBR radios within the propagation distance of the transmitted signals based upon the detection of the SCC transmissions.

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station, and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The system and method transmits from the base station, a synchronization channel having a chip-sequence signal used by the plurality of subscriber units for synchronization. A first subscriber unit receives the synchronization channel, and determines timing from the synchronization channel. In order to initiate communications with the base station, the first subscriber unit transmits an access signal. The access signal has a plurality of power levels, which typically ramp up. The base station receives the access signal at a particular-power level. The base station then transmits to the first subscriber unit an acknowledgment signal. The first subscriber unit receives the acknowledgment signal, and transmits to the base station, a spread-spectrum signal.