Abstract: Ad-hoc networks employing cooperative signal processing are configured for detecting, identifying, and visualizing radio communication networks used by an adversary, such as enemy combatants or criminals. These networks are further configured for performing a non-passive tactical response to an adversary's communication capabilities. Such ad-hoc networks are particularly useful for identifying radio communication resources, establishing radio links, and subverting an adversary's communication capabilities in environments lacking available communication infrastructure, including battlefield environments, and locations where communication infrastructure is non-existent or has been compromised by natural disasters or terrorists attacks.

Abstract: Multiple-access codes are generated using an asymptotically optimal decoding algorithm, such as the Viterbi algorithm. A trellis may be constructed using a number of desired users, at least one code length, and a number of code-chip parameters. A fitness function is derived from a mathematical relationship between the multiple-access codes, and may include some measure of correlation of the codes. The multiple-access codes correspond to paths having optimal path metrics derived from the fitness function. Multiple iterations through the trellis may be performed to refine a selection of multiple-access codes.

Abstract: A method of communicating over a wideband communication channel divided into a plurality of sub-channels comprises dividing a single serial message intended for one of the plurality of communication devices into a plurality of parallel messages, encoding each of the plurality of parallel messages onto at least some of the plurality of sub-channels, and transmitting the encoded plurality of parallel messages to the communication device over the wideband communication channel.

Abstract: A redundently modulated multicarrier protocol known as Carrier Interference Multiple Access (CIMA) is used in an optical-fiber network having wireless links at network nodes. CIMA is a protocol that can be used to create wireless protocols (such as TDMA and CDMA) having enhanced capacity and reduced system complexity. A CIMA optical-fiber network uses dispersion to enhance signal quality and facilitate switching. CIMA achieves both diversity benefits and capacity enhancements by providing redundancy in at least one diversity parameter while providing orthogonality in another diversity parameter. This basic operating principle of CIMA may be combined with multi-user detection to achieve frequency reuse and improved power efficiency. In the wireless link, diversity may be used to reduce the effects of small-scale fading on interferometry multiplexing.

Abstract: Systems and methods for adjusting phase of a signal are provided. In one embodiment, the system includes a phase compensator configured for adjusting phase of the signal based on filtered and unfiltered representations of a first component of the signal and based on filtered and unfiltered representations of a second component of the signal. For example, the phase compensator may provide phase adjusted I and Q components of a complex signal through a plurality of multiplications of filtered and unfiltered I and Q components. The system also includes a detector that is communicatively coupled to the phase compensator. The detector is configured for combining the first and the second components with a code sequence to determine a complex amplitude of a channel.

Abstract: The present invention provides systems and methods for decreasing interference in a selected coded signal. The system includes a matrix generator for generating a matrix. The matrix may comprise vectors, the elements of which are formed from components of the interference. The interference may exist in the form of co-channel and/or cross channel interference, such as that found in CDMA telephony. The components of this interference may, therefore, be code components of the interference that are used to fill elements of the vectors. Each element of a vector may represent a code component of an interfering coded signal. A processor uses the matrix to substantially remove the interference from the selected coded signal. For example, the processor may generate a projection operator that projects the coded signal substantially orthogonal to the interference such that the impact of interference on the selected coded signal is substantially reduced.

Abstract: The architecture of the present invention is premised upon an algorithm involving integration of oblique correlators and RAKE filtering to null interference from other spread spectrum signals. The oblique correlator is based on the non-orthogonal projections that are optimum for nulling structured signals such as spread spectrum signals. In one configuration, space spanned by a first signal associated with a first emitter is orthogonal to an interference space associated with one or more signals of one or more other emitters. RAKE filtering is used to rapidly steer the beam of the multi-antenna system and to mitigate the effects of multipath.

Abstract: An optical processor for controlling a phased antenna array uses a frequency-shifted feedback cavity (FSFC), which includes a traveling-wave cavity. The FSFC incrementally delays and incrementally frequency shifts optical signals circulating in the traveling-wave cavity. Optical signals coupled out of the FSFC are separated by frequency, hence by delay, and processed to control either or both transmit and receive beam-forming operations. The FSFC provides a receiver with multiple receive signals which have incremental values of frequency. Each frequency corresponds to an incremental time sampling of optical signals input into the FSFC. Transmit signals coupled out of the FSFC have frequency and phase relationships that result in short time-domain pulses when combined. Controlling modulation and frequency of the transmit signals achieves carrier interference multiple access, a new type of spread-spectrum communications.

Abstract: Substantial improvements in frequency reuse in microwave communications systems is achieved by canceling co-channel interference and transmitter leakage. Interferometric beam-narrowing reduces beamwidth without reducing preak magnitude of the beam pattern. Frequency-dependent beam-shaping compensates for frequency-dependent distortions of the beam pattern thereby improving bandwidth. A spatial demultiplexing technique utilizes spatial gain distributions of received signals to separate signals, even from co-located transmit sources, and uses microwave lensing to enhance received spatial gain distributions. Predetermined cross-polarization interference is used to separate differently polarized receive signals. A reference branch provides a cancellation signal to a receiver to cancel transmitter leakage signals. An error signal controls an impedance-compensation circuit that is responsive to changes in antenna impedance but not to receive signals.

Abstract: A novel method and apparatus is provided for enabling the computation of a signal in a certain subspace, its projection that lies outside the subspace, and the orthogonal basis for a given matrix. More particularly, the present invention relates to the use of such a method or apparatus for real-time hardware applications since the method and apparatus may be utilized without matrix inversions or square root computations.

Abstract: Principles of quantum interferometry are used to create a signal architecture (known as carrier interferometry) for wireless and waveguide electromagnetic-wave communications. Carrier interferometry provides unprecedented bandwidth efficiency and enables substantial improvements in interference rejection, power efficiency, and system versatility. The carrier interferometry architecture also enables simpler transceiver designs that facilitate digital up-conversion and down-conversion.

Abstract: Spatial multiplexing techniques achieve substantial improvements in frequency reuse in microwave communications. The spatial demultiplexing techniques use amplitude and phase differences of received signals at spatially separated antennas to separate interfering signals. A set of complex weights is generated based on the differences of the received signals. The received signals are weighted and summed to cancel interference and separate the signals. Beamforming operations in an antenna array provide rejection of intersymbol interference and reduce the number of antennas needed to cancel interference. A spatial demultiplexing technique using multicarrier signals eliminates the requirement for multiple receiver antennas. The spatial demultiplexing technique is also applied to separating received signals that have polarization time, and frequency diversity.