Abstract: A system in which a sending node sends modulated waveform signals to a receiving mode can include the capability to change the waveform type of the modulated waveforms from a current waveform type to a new waveform type. The sending node can generate and send to the receiving node a variable length header that provides the receiving node sufficient information for the receiving node to demodulate modulated waveform signals modulated in accordance with the new waveform type. The variable length header can identify the parameters in a parameter set defining the new waveform type that have different values as compared to the current waveform type.

Abstract: The present invention is generally directed to using code division multiplexing (CDM) on the beacon and traffic channels while lowering the power of the beacon channel so that it rides under the traffic channel and becomes very difficult to detect. In this way, the beacon channel can contain sensitive information for decoding the traffic channel while remaining hidden from unintended recipients. By hiding the beacon channel, the CDM technique can be particularly beneficial in adaptive waveform systems where sensitive traffic channel acquisition information is regularly transmitted to the receiver.

Abstract: A digital electronic message comprising datawords to be transmitted in a communications system can be encoded prior to transmission using an asymmetric error detection coding scheme. The coding scheme is asymmetric because the coding scheme includes multiple codeword groups each with a different minimum coding distance. The codewords in a group having a greater minimum coding distance can correspond to datawords that have a relatively high susceptibility to transmission errors. The codewords in a group having a lesser minimum coding distance can correspond to datawords that have a relatively low susceptibility to transmission errors.

Abstract: A spectral sensing demodulator can include a programmable filter bank and a reconfigurable processor coupled to the programmable filter bank. The programmable filter bank can frequency demultiplex a plurality of frequency division multiplexed channels from a frequency band into a plurality of demultiplexed channels. The reconfigurable processor can include a plurality of reconfigurable resources. Each resource can be alternatively be configured to demodulate a demultiplexed channel and to monitor a demultiplexed channel.

Abstract: A spectral sensing demodulator can include a programmable filter bank and a reconfigurable processor coupled to the programmable filter bank. The programmable filter bank can frequency demultiplex a plurality of frequency division multiplexed channels from a frequency band into a plurality of demultiplexed channels. The reconfigurable processor can include a plurality of reconfigurable resources. Each resource can be alternatively be configured to demodulate a demultiplexed channel and to monitor a demultiplexed channel.

Abstract: A self-synchronizing cryptographic device can be shared among a plurality of communications links. Blocks of data can be transferred to the cryptographic device, wherein each block of data includes a head portion which is the tail portion of a previous block of data for the same communication link. The head/tail portion is sufficient to reestablish cryptographic synchronization of the cryptographic device.

Abstract: A sensing system includes integrated sensor locating capability. Sensors can transmit spread spectrum encoded data pulses which are received at mobile nodes. Based on time of arrival information and known locations of the mobile nodes, locations of the sensors can be determined.

Abstract: Wireless terminals, systems, and methods use interlaced diplexers. A first diplexer can provide a first pair of bands separated by a first separation band, and a second diplexer can provide a second pair of bands separated by a second separation band. The first separation band and the second separation band can overlap. Transceivers (comprising transmitters and receivers) can be coupled to the diplexers to provide frequency-division duplex communications using one or both of the pairs of bands.

Abstract: A method and apparatus for mitigating multi-user interference in reception of a code division multiple access (CDMA) signal is described. The CDMA signal has a plurality of spread user symbol streams, each spread by a corresponding one of a plurality of spreading codes. Estimated symbols are iteratively improved by forming a reconstructed signal from the estimated symbols, subtracting the reconstructed signal from the CDMA signal to create a difference signal, and adjusting the estimated symbols based on a combination of the difference signal and the estimated symbols.

Abstract: In one exemplary embodiment of the invention, a device includes: a first frequency search engine configured to receive input values and determine a frequency of a signal to be within a first frequency band; a second delay component configured to store at least a portion of the plurality of input values; and a second frequency search engine configured to determine the frequency of the signal to be within a second band that is a subset of the first band. The first frequency search engine includes: a shift register configured to store bits of the input values; a combining circuit configured to combine bits of the plurality of input values; a first delay component configured to serially store a plurality of accumulator values; and a feedback circuit configured to add a function of the first delay component output to a next accumulator value to obtain a modified next accumulator value.

Abstract: A technique for reducing memory usage during signal processing includes storing least significant portions of a plurality of intermediate results in a first memory. Most significant portions of a subset the plurality of intermediate results are stored in a second memory having a smaller length than the first memory. A data linkage is maintained between the most significant portions and corresponding least significant portions.

Abstract: The present invention relates to a towed wireless network communications subsystem for use in flight by a towing aircraft. The towed wireless network communications subsystem includes an aerodynamic enclosure having a tether attachment and configured to be towed by the towing aircraft. A directional antenna is disposed on the aerodynamic enclosure and is capable of forming one or more directional communications beams within a wireless network. A communications device is disposed in the aerodynamic enclosure and is coupled to the directional antenna(s). The communications device is configured to relay communications data between the towing aircraft and the wireless network.

Abstract: An emergency locating system can include emergency transceivers and locator transceivers. The emergency transceivers can be capable of transmission of spread-spectrum encoded messages, and can be actuated by a user to send a distress message. A locator transceiver can be capable of receiving the distress messages and performing two-way ranging to determine a distance between the locator transceiver and the emergency transceiver.

Abstract: Decreased capability for detection of communications signals by an adversary is provided by applying frequency hopping, frequency chirping, and direct sequence spreading to the signals. The frequency hopping and frequency chirping can be driven by pseudo random functions. The direct sequence spreading can use a pseudo random chip sequence.

Abstract: Entry of a terminal into a wireless communications network is facilitated for terminals which may operate in either frequency-division duplex or time-division duplex mode. Join request messages transmitted by the terminals include a duplex capability indicator defining a carrier frequency which can be used to response to the terminals.

Abstract: An apparatus and method for correlating a signal over a correlation interval while accommodating spreading code frequency offset is described. In one embodiment, the apparatus includes a plurality of correlators, where each correlator forms a correlation result corresponding to a unique code frequency offset hypothesis. Each correlator selects samples from a tapped delay line at a tap position moved along the delay line at a rate corresponding to the correlator unique code frequency offset hypothesis.

Abstract: A method of transmitting a spread spectrum signal in a single communication session between a transmitter and a receiver, stores a series of N unique waveform designs and a hopping sequence in a transmitter memory. A signal is transmitted to a receiver according to the hopping sequence using the plurality of N unique waveform designs. Preferably, each waveform design is characterized by a unique composite spreading code that is formed by at least some of a plurality of constituent code segments. Alternatively or additionally, the waveform designs may differ by any one or more of code length, symbol or chip timing or phase, frame or burst structure, chip offset, modulation, error control coding, encryption scheme, or scrambling code. A transmitter and receiver are also disclosed, as is the concept of appending chips between symbols to expand the universe of unique spreading codes without incurring an increase in processing gain.

Abstract: Entry of a terminal into a wireless communications network is facilitated for terminals which may operate in either frequency-division duplex or time-division duplex mode. Join request messages transmitted by the terminals include a duplex capability indicator defining a carrier frequency which can be used to response to the terminals.

Abstract: A method of transmitting a spread spectrum signal in a single communication session between a transmitter and a receiver, stores a series of N unique waveform designs and a hopping sequence in a transmitter memory. A signal is transmitted to a receiver according to the hopping sequence using the plurality of N unique waveform designs. Preferably, each waveform design is characterized by a unique composite spreading code that is formed by at least some of a plurality of constituent code segments. Alternatively or additionally, the waveform designs may differ by any one or more of code length, symbol or chip timing or phase, frame or burst structure, chip offset, modulation, error control coding, encryption scheme, or scrambling code. A transmitter and receiver are also disclosed, as is the concept of appending chips between symbols to expand the universe of unique spreading codes without incurring an increase in processing gain.

Abstract: Entry of a terminal into a wireless communications network is facilitated for terminals which may operate in either frequency-division duplex or time-division duplex mode. Join request messages transmitted by the terminals include a duplex capability indicator defining a carrier frequency which can be used to response to the terminals.