Abstract: Methods and systems for tone hopping are provided. In one embodiment, a method for an orthogonal frequency division multiplexing (OFDM) multipoint-to-point communications system comprises: establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration; transmitting up to a plurality of tones from the first remote unit modulated with upstream information using OFDM; adjusting at least one characteristic of the up to a plurality of tones such that when any tones are transmitted from the first remote unit and at least one other remote unit of the plurality of remote units, the orthogonality of the tones received at the host unit is improved; and dynamically switching modulation between tones of the up to a plurality of tones based on an error-rate history of at least one of the tones.

Abstract: A method to compensate for variances in signal path delays for a plurality of radar return processing channels is described. The method comprises providing a signal in the signal path between an antenna and a corresponding receiver of each radar return processing channel, receiving a reflection of the provided signal from each antenna at the corresponding receiver, measuring phase variances between the reflected signals processed by each receiver, and adjusting compensation algorithms for each radar return processing channel based on the measured phase variances.

Abstract: A navigation system is described which includes a navigation processor, an inertial navigation unit configured to provide a position solution to the navigation processor, and a digital elevation map. The described navigation system also includes a radar altimeter having a terrain correlation processor configured to receive map data from the digital elevation map and provide a position solution based on radar return data to the navigation processor. A map quality processor within the navigation system is configured to receive map data from the digital elevation map and provide a map quality factor to the navigation processor which weights the position solution from the terrain correlation processor according to the map quality factor and determines a position solution from the weighted terrain correlation processor position solution and the position solution from the inertial navigation unit.

Abstract: The invention relates to the field of gun-launched guidance systems and to a navigation system based on inertial sensors mounted in a spinning projectile using at least one rotation sensing device with input components perpendicular to the spinning body's longitudinal axis, and an appertaining method for upfinding. The phase of the sinusoidal angular rate as detected by a phase-locked loop or correlator is used to determine the local vertical orientation. This invention may be used to align the inertial navigation system in spinning projectiles in ballistic trajectories, which can include artillery shells, satellites or underwater torpedoes.

Abstract: A training premable in multipoint-to-point communication using orthogonal frequency division multiplexing (OFDM) is provided. In one embodiment, a system comprises a host unit and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using OFDM. The host unit sends an adjustment signal to at least one of the remote units instructing the at least one remote unit to adjust the timing of transmissions from the remote unit to improve orthogonality of an OFDM waveform received at the host unit. The host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units. At least one remote unit transmits a training sequence in at least one upstream OFDM signal to the host unit and the host unit uses the training sequence to assist in demodulating the upstream OFDM signal of the at least one remote unit.

Abstract: Methods and systems for adaptive modulation are provided. In one embodiment, a method for a plurality of remote units of an orthogonal frequency division multiplexing multipoint-to-point communications system comprises: establishing communication between a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration; transmitting a plurality of tones from the plurality of the remote units such that tones from more than one remote unit are simultaneously received at the host unit, the plurality of tones modulated with upstream information using orthogonal frequency division multiplexing; modulating up to a plurality of tones using a first modulation scheme when transmitting a first type of upstream information; and modulating up to a plurality of tones using a second modulation scheme when transmitting a second type of upstream information.

Abstract: Methods and systems for forward-looking tone allocation are provided. In one embodiment, a method for an orthogonal frequency division multiplexing (OFDM) multipoint-to-point communications system comprises: establishing communication between a plurality of remote units and a host unit, the remote units communicatively coupled to the host in a multipoint-to-point configuration; transmitting a plurality of tones from the remote units, such that tones from more than one remote unit are simultaneously received at the host, the tones modulated with upstream information using OFDM; adjusting at least one characteristic of at least one tone at least one remote unit, in response to adjustment commands from the host, such that the orthogonality of the simultaneously received tones is improved as received at the host unit; and dynamically switching modulation from at least a first tone of the plurality of tones to a second tone based on an error-rate history of the second tone.

Abstract: An articulating sonobuoy is provided. The articulating sonobuoy comprises a plurality of section, and a plurality of joints connecting each of the plurality of section to adjacent sections, wherein each of the plurality of sections self-aligns by rotating about one or more of said plurality of joints changing the shape of the buoy from a stowed configuration to a streamlined deployed configuration.

Abstract: An apparatus and methods for disambiguating data elements transmitted by exception over a multi-path, multi-tiered communications network of nodes from at least one originating node to a destination node. A method includes the steps of receiving counter data from each node operable to originate data elements, receiving a data element name, evaluating counter data from nodes forming at least one possible path between the named data element's originating node and said destination node; and indicating as unambiguous data associated with the data element name if each of the nodes forming the possible path are transmitting counter data to the destination node. The apparatus includes a processor coupled to the destination node and to a source of data element names, a memory containing a path database and instructions for searching the database for paths of the named data element and to update the database with data relating to counter data reception.

Abstract: A system to determine unwanted noise produced by simulation equipment. In one embodiment, an angular rotation noise measuring system comprises a stable body, a laser, at least one interferometer and at least one mirror. The laser is adapted to generate a primary laser beam and is mounted to the stable body. The at least one interferometer is adapted to split the primary laser beam into two or more out of phase secondary laser beams. Moreover, the interferometer is coupled to the stable body. The at least one mirror is coupled to a fixture on a vibration generating device. The fixture is adapted to hold a device under test. Each mirror is adapted to reflect an associated secondary laser beam back to the interferometer such that an interference pattern is formed with the secondary laser beams. Changes to the interference pattern determine the angular rotation noise caused by the vibration generating device.

Abstract: A wireless distribution system includes a number of remote units distributed in a coverage area to receive wireless signals and to provide the signals through the distribution system to input ports of a node where the signals are combined, a number of input power monitors operatively connected to one or more of the input ports to determine power levels of signals received at the input ports, variable gain controllers to control signals received at some or all of the input ports, a node to combine a plurality of signals from the plurality of input ports, and a controller to provide control signals to control one or more of the variable gain controllers.