Exelis Inc.

Itt Manufacturing Enterprises, Inc.

Harris Global Communications, Inc.

Bruce Edward Reidenbach

Terrance Wayne Charbonneau

Gregory Thomas Barnett

John P Johnston

James Garland Grabill

Rodney Louis Wilson

Mark Alan Norden

Thomas Robertson Dickson, Ii

Gregory T Barnett

A technique for equalizing a distributed pilot OFDM signal with decision feedback involves correlating a received OFDM signal against a pilot reference to obtain a coarse channel estimate, where the received OFDM signal includes a distributed pilot signal and an OFDM data signal. The received OFDM signal is equalized based on the coarse channel estimate and the distributed pilot signal is removed to generate a coarse data signal estimate. The coarse data signal estimate is removed from the received OFDM signal using the coarse channel estimate to generate a residual pilot signal. The residual pilot signal can then be correlated against the pilot reference to obtain a fine channel estimate. The received OFDM signal is equalized based on the fine channel estimate, and the distributed pilot signal is removed to produce a fine data signal estimate from which data is recoverable.

Equalization of a distributed pilot OFDM signal

A technique for removing a band-limited distributed pilot signal from an orthogonal frequency division multiplexed (OFDM) signal involves converting a received OFDM signal, which includes a distributed pilot signal and an OFDM data signal, into a frequency domain signal having populated frequency bins containing respective subcarrier signals, each including a constituent data signal of the OFDM data signal and component pilot signal of the distributed pilot signal. An average magnitude of the populated frequency bins is determined based on the absolute values of the complex components of the populated frequency bins of the frequency domain signal, and the average magnitude of the populated frequency bins is used to estimate a pilot signal magnitude. The distributed pilot signal is removed from the frequency domain signal using a stored replica of the pilot signal scaled in conjunction with the pilot signal magnitude to yield the OFDM data signal.

Removal of a band-limited distributed pilot from an OFDM signal

An exponentiation circuit for computing an exponential power of a finite field element includes combinatory logic circuits that map input digits of a multi-digit field element &#x3b2; to output digits of an output multi-digit field element &#x3b2;. The exponentiation circuit is capable of computing a power of a field element without performing any multiplication operations and requires only exclusive-OR logic operations to generate the output exponential field element. A circuit for generating a multiplicative inverse of a finite field element can be constructed from a set of parallel exponentiation circuits, with each of the parallel exponentiation circuits generating a different multi-digit field element &#x3b2;directly from the input field element &#x3b2;. Multiplier circuits multiply together the outputs of the parallel exponentiation circuits to generate the multiplicative inverse of the field element &#x3b2;.

Circuits and methods for performing exponentiation and inversion of finite field elements

An encoder according to the present invention embodiments employs a key expansion module to expand an encryption key by using logic and available clock cycles of an encryption process or loop. The key expansion module generates control signals to enable key expansion data to be injected at appropriate times into the encryption loop (e.g., during available clock cycles of the encryption loop) to perform the key expansion, thereby utilizing the resources of the encryption loop for key expansion. The key expansion module dynamically accounts for varying key lengths, and enables the encryption loop to combine the data being encrypted with proper portions of the expanded key. The use of encryption logic and available clock cycles of the encryption loop for the key expansion reduces the area needed by the encoder on a chip and enhances encoder throughput.

Method and apparatus for key expansion to encode data

A programmable application specific integrated circuit (ASIC) for implementing operations that involve a plurality of computational functions. The programmable ASIC comprises a plurality of fixed functions and programmable switch logic. Each of the plurality of fixed functions is parameterized such that its operational characteristics are programmable using different operating parameters. In addition, each of the plurality of fixed functions inputs and outputs data in accordance with common interface rules. The programmable switch logic is configurable to link two or more of the fixed functions in a sequence to perform desired operations. The fixed functions are implemented using 'hard' or fixed digital logic gates such as those in an ASIC.

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Albion, IN, United States of America

Bruce Edward Reidenbach