Abstract: Systems and methods are provided for signaling control information in a communication of data. The method includes overwriting a portion of a frame in a sequence of frames with control information. The control information has a low bit size, and the overwriting is performed at a frequency of less than about 20% of the frames. The system includes a spread spectrum transmitter that includes a channel coder, an interleaver and framer unit, and an insertion unit. The insertion unit is configured to overwrite a portion of a frame in a sequence of frames with control information and is further configured to overwrite at a frequency of less than about 20% of the frames.

Abstract: A wireless network (100) includes a number of definable radio systems (102) in communication with one another via a wideband backbone (108). Each of the systems (102) includes a first software programmable transceiver (200) for extra-network communication using a narrowband channel defined by a radio frequency capability (106). Each of the radios (102) further includes a second transceiver for intra-network communication using wideband backbone (108). Methods for operating the network (100) enable the radios (102) to engage in communication over narrowband channels to carry a signal between multiple radios (102) and an extra-network location, and for communicating the signal as distinct bitstreams between the radios (102) and another of the radios (102) using the wideband backbone (108).

Abstract: Apparatus are provided for a communication signal processing apparatus having a channel estimator configured to generate a first channel estimation at a first time point, a linear predictor coupled to the channel estimator, and an adaptive filter coupled with the linear predictor. The linear predictor is configured to predict a second channel estimation based on a second time point and a channel frequency. The second time point is concurrent or subsequent to the first time point. The second channel estimation includes a first coefficient. The linear predictor includes a first predictor having a sample time point. The first predictor is configured to generate the first coefficient of the second channel estimation based on the sample time point and the second time point. The sample time point is prior to the second time point. The adaptive filter is configured to recursively determine the second channel estimation.

Abstract: A programmable modem (20) for processing a waveform includes a general purpose processor (GPP) engine (34) and special purpose programmable signal processing engines (22) in communication with the GPP engine (34). Each of the special purpose engines (22) executes a special purpose software program (80) to process a portion of the waveform under one of a plurality of communications standards in response to control signals from the GPP engine (34). A power manager engine (56) is in communication with the GPP engine (34) and the signal processing engines (22). The power manager engine (56) responds to the control signals from the GPP engine (34) to power currently used ones of the special purpose engines (22) and to discontinue power to unused ones of the special purpose engines (22). The programmable modem is implemented on a single CMOS integrated circuit (66).

Abstract: In an embodiment, a receiver includes an antenna configured to receive a communication frame. The communication frame may include an acquisition code symbol sequence, which in turn may include a plurality of acquisition code symbols. In an embodiment, an acquisition code symbol includes a subcode sequence having a plurality of subcodes. A receiver also may include a correlation calculator coupled to the antenna. The correlation calculator may be configured to determine a correlation between the subcodes of the received communication frame and a stored version of the subcodes. The correlation may be used in determining a timing offset for further processing of the communication frame.

Abstract: Embodiments include methods and apparatus for verifying the detection of a correlation peak, which may represent an acquisition of a received acquisition code symbol sequence. The method includes determining a series of coherently-aligned peaks from a series of correlation peaks. Determining the plurality of coherently-aligned peaks includes correcting a frequency offset and a phase offset for each of the plurality of correlation peaks. A coherent match filter process is performed on the plurality of coherently-aligned peaks. A detection of the correlation peak may be verified when the match filter result exceeds a threshold.

Abstract: An RF receiver (12) includes a channel estimator (52). The channel estimator (52) includes a channel estimation filter (82), error signal generator (84), and normalized Least-Mean-Square (NLMS) filter-definition generator 36. The filter (82), error generator (84) and NLMS filter-definition generator (86) function together as an adaptive estimator. An error signal (90) is formed with a received signal (48). The filter (82) filters an estimated transmit signal (74) constructed from lower confidence decision data (66) and higher confidence known preamble data (30?). .An adaptive filter definition (94) is formed in a feedback, loop which minimizes correlation between the estimated transmit signal (74) and the error signal (90). A convergence signal (122) is modulated in synchronism with the changes between lower and higher confidence data in the estimated transmit signal (74).

Abstract: A symbol synchronizer (100) is provided for a software-defined communications system (10). The symbol synchronizer (100), when integrated into either a pre- or post-detection diversity signal combiner (108, 208), enables highly accurate signal synchronization with minimal added system complexity. The symbol synchronizer (100) includes a single complex sliding window-matched filter (102) for filtering an input digital signal with a match filtering function based on predetermined signal transfer function characteristics to average out receiver noise from the signal. A signal delay bank (84) includes a plurality of delay blocks each for delaying the digital signal filtered by the single matched filter for a predetermined number of samples. A complex correlator (88) correlates the digital signal filtered by the single complex sliding window matched filter (102) and delayed by the complex correlator (88) with a correlator reference signal, and selects an index of a path having a peak correlator value.

Abstract: A communication network (22) includes a central node (30) loaded with a trusted key (26) and key material (56) corresponding to an asymmetric key agreement protocol (48). The network (22) further includes vulnerable nodes (32) loaded with key material (69) corresponding to the protocol (48). Successive secure connections (68, 70) are established between the central node (30) and the vulnerable nodes (32) using the key material (56, 69) to generate a distinct session key (52) for each of the secure connections (68, 70). The trusted key (26) and one of the session keys (52) are utilized to produce a mission key (39). The mission key (39) is transferred from the central node (30) to each of the vulnerable nodes (32) via each of the secure connections (68, 70) using the corresponding current session key (52). The mission key (39) functions for secure communication within the communication network (22).

Abstract: An embodiment of a method for parameterizing an input signal includes non-linearly transforming the input signal, removing higher order terms by passing the input signal through a low pass filter to produce a linear combination of data symbols and DC components, solving for the DC components, separating a plurality of mixed baseband signals from the input signal, and coordinate transforming each of the separated signals from polar coordinates to Cartesian coordinates. An embodiment of a receiver includes a non-linear transform operator receiving a digitized input signal and adapted to produce a linear combination of data symbols, DC components, and carrier effects; a low-pass filter for removing higher order terms; a separator unit for separating the plurality of mixed baseband signals; and a coordinate transform for converting the separated signals from polar coordinates to Cartesian coordinates.

Abstract: A programmable electronic device (10) stores a number of cipher-text software modules (14) to which access is granted after evaluating a user's token (55, 80, 82), a software-restriction class (58) for a requested software module (14), and/or a currently active access-control model (60). Access-control models (60) span a range from uncontrolled to highly restrictive. Models (60) become automatically activated and deactivated as users are added to and deleted from the device (10). A virtual internal user proxy that does not require users to provide tokens (80, 82) is used to enable access to modules (16) classified in a global software-restriction class (62) or when an uncontrolled-access-control model (68) is active. Both licensed modules (76) and unlicensed modules (18,78) may be loaded in the device (10). However, no keys are provided to enable decryption of unlicensed modules (18,78).

Abstract: A feed assembly (26) for an antenna system (38) includes a first feed element (30) that propagates a first beam (32) and a second feed element (34) that propagates a second beam (36). The second feed element (34) is collocated with, but displaced vertically from, the first feed element (30) to achieve angular diversity in elevation. Each of the feed elements (30, 34) has an elongated conical shape and is formed from a dielectric material. The feed assembly (26) operates within the Ku-band frequency range to yield high gain, collimated, independent first and second beams (32, 34). The feed assembly (26) can be implemented in a tropospheric scatter communication system (38) in conjunction with a reflector (22) to provide concurrent transmit and receive capability via the two independent, angularly separated first and second beams (32, 36).

Abstract: Systems and methods for increasing bandwidth capability of an envelope elimination and restoration (EER) transmitter. A frequency response of a power supply modulator of the transmitter is approximated. An inverse response is applied to the envelope signal prior to digital-to-analog conversion (DAC) and before the signal reaches the power supply modulator to pre-emphasize the signal thereby counteracting distorting affects of the modulator. The filter is implemented using any of a variety of different digital techniques including programmable logic, DSP, etc.

Abstract: A multi-carrier communication system (400) groups subchannels (802) into different quality-of-signal (QoS) regions (804). An unconstrained optimization process (1200) is performed independently for the subchannels (802) of the different QoS regions (804) to allocate bit rates and power to the individual subchannels (802) so that the indicated QoS will result. Coders (504, 508, 512, 516, 1700) partition and error-correction encode source information using encoding schemes matched to the different QoS regions (804). A set (1100) of only a few directed QoS partition vectors (1102) direct the unconstrained optimization process (1200) to attempt bit-rate and power allocations on only a few promising groupings of subchannels (802) and QoS regions (804). An iterative process may take place between bit-rate and power allocation on one side and source information coding on the other for different directed QoS partition vectors (1102) to identify the best solution.

Abstract: A separation management system (32) for governing interaction between code within a code base (50) operable on a computer (30) determines a region in a memory (44) of the computer (30) in which the code base (50) resides and defines container boundaries (118, 124, 130, 135) in the region for a plurality of containers (95). Each of the containers (95) contains subsets of the code (120, 126, 132, 137) that cannot be trusted. A policy (94) is created that governs interaction between the subsets of the code in the containers (95). The code base (50) is executed in the computer (30) in accordance with the policy (94) such that the subsets of code within the containers (95) are prevented from accessing code outside of their respective containers (95) when access is disallowable as indicated by the policy (94).

Abstract: Systems and methods for DC offset correction in analog and digital direct conversion RF receivers. A time derivate and subsequent integration of in-phase and quadrature phase signal path components is performed to effectively remove DC offset from the resultant down converted baseband signal.

Abstract: A system (100) and method for the reception and despreading of a code-division multiple access (CDMA) global positioning system (GPS) signal (200), or other direct-sequence spread-spectrum (DSSS) signals, is provided. An antenna array (102) receives the DSSS signal (200) over a plurality of elements (116). A preprocessor (104) down converts and digitizes the DSSS signal (200) to produce a signal stream (202) in the time domain. An FFT (106) transforms the signal stream (202) to the frequency domain. A beam former (108) generates a reception beam (201) for the DSSS signal (200) in the frequency domain, and also implements a narrowband frequency notch, if desired. A despreader (110) despreads the transformed signal stream (204) in the frequency domain. An IFFT (112) transforms the despread signal stream (208) back to the time domain. And a postprocessor (114) converts the transformed despread signal stream (210) into a desired received signal stream (212) in the time domain.

Abstract: A multi-carrier communication system (400) groups subchannels (802) into different quality-of-signal (QoS) regions (804). An unconstrained optimization process (1200) is performed independently for the subchannels (802) of the different QoS regions (804) to allocate bit rates and power to the individual subchannels (802) so that the indicated QoS will result. Coders (504, 508, 512, 516) partition and error-correction encode source information using encoding schemes matched to the different QoS regions (804). A set (1100) of only a few directed QoS partition vectors (1102) direct the unconstrained optimization process (1200) to attempt bit-rate and power allocations on only a few promising groupings of subchannels (802) and QoS regions (804). An iterative process may take place between bit-rate and power allocation on one side and source information coding on the other for different directed QoS partition vectors (1102) to identify the best solution.

Abstract: A robust and flexible system for signal parameter measurements in the field of signal processing dynamically uses signal parameters from previous signal detections and parametric priorities to adaptively control and process the signal in an efficient and reliable manner. The system provides for improved fine grain signal parameter measurements through the use of adaptive arbitration to control signal processing. The system improves measurement accuracy for various signal characteristics including pulse width, amplitude, frequency and timing information. The system also provides signal parameter measurements while requiring less power, size, and weight than conventional systems.

Abstract: A method and system is disclosed for cross-correlating information between the domains of network management and network security. The present invention discloses a model representing the security domain that can be used to define relationship between devices and events in the security domain in the context of a managed network. With this model, a security topology of the network security domain can be created based on the current implementation of the network. This model and topology allows the present invention to correlate relevant network security information to diagnose problems as they occur by using events detected within the network. Using the disclosed method and system for correlating information in the network security, the present invention provides further enhancements over conventional methods by cross-correlating information between the network security and network management domains to aid in their detection and analysis of problems.