Harris Corporation

Alan J Michaels

David Bruce Chester

Robert C Peach

Chester B David

System () and methods () for improving packet loss due to fast optical power fades in an FSO communication link (). The methods involve: obtaining Channel Fade Statistics ('CFSs') for the FSO communication link; and analyzing CFSs to determine if Redundant Packet Transmission ('RPT') is required to mitigate fast optical power fading. If RPT is required, then first operations are performed at a data link layer () of a protocol stack () to generate first packets (). Each packet has a sequence number () disposed between a data link layer header () and a network layer header (). If RPT is not required, then second operations are performed at the data link layer to generate a second packet absent of the sequence number or alternatively having a sequence number equal to zero. Thereafter, the packet(s) is transmitted over the FSO communication link one or more times.

Dynamic packet redundancy for a free space optical communication link

Systems () and methods for selectively controlling access to data streams communicated from a first communication device (FCD) using a timeslotted shared frequency spectrum and shared spreading codes. Protected data signals () are modulated to form first modulated signals (). The first modulated signals are combined with first chaotic spreading codes to form digital chaotic signals. The digital chaotic signals are additively combined to form a protected data communication signal (PDCS). The PDCS () and a global data communication signal (GDCS) are time division multiplexed to form an output communication signal (OCS). The OCS () is transmitted from FCD () to a second communication device (SCD) over a communications channel. The SCD () is configured to recover (a) only global data from the OCS, or (b) global data and at least some protected data from the OCS.

Permission-based TDMA chaotic communication systems

Systems () and methods () for Pulse Rotation Modulation. The methods involve: generating First Segments ('FSs') of a Numerical Sequence ('NS') based on a First Data Symbol Sequence (&#x201c;FDSS&#x201d;); and encoding FDSS within NS. The encoding is achieved by: (a) shifting positions of numbers contained in each FS &#x201c;X&#x201d; positions to the right or left; and (b) moving a last &#x201c;X&#x201d; numbers of the FSs to a beginning of a respective segment thereof or moving a first &#x201c;X&#x201d; numbers of the FSs to an end of the respective segment. X&#x201d; is defined as an integer value represented by a respective portion of FDSS. Thereafter, the NS having FDSS encoded therein can be used to spread a Second Data Signal (&#x201c;SDS&#x201d;) over a wide intermediate frequency band. SDS has second data symbols, that are different then FDSS, phase and/or amplitude encoded therein.

Systems and methods for pulse rotation modulation encoding and decoding

A method for encrypting data is provided. The method includes formatting data represented in a weighted number system into data blocks. The method also includes converting the data blocks into a residue number system representation. The method further includes generating a first error generating sequence and inducing errors in the data blocks after converting the data blocks into a residue number system representation. It should be understood that the errors are induced in the data blocks by using the first error generating sequence. After inducing errors into the data blocks, the data of the data blocks is formatted into a form to be stored or transmitted. The method also includes generating a second error generating sequence synchronized with and identical to the first error generating sequence and correcting the errors in the data blocks using an operation which is an arithmetic inverse of a process used in inducing errors.

Encryption via induced unweighted errors

Embodiments of the present invention provide a system and method for further reducing cyclostationarity and correspondingly energy density in a chaotic spread spectrum data communication channel, by digitally generating a first chaotic sequence of values to form a spreading code. The spreading code is then used to form a digital IF spread spectrum signal having a uniform sampling interval. The digital IF spread spectrum signal is converted to a sampled analog IF spread spectrum signal at a conversion rate substantially equal to the uniform sampling interval. The duration of the sampling interval is then selectively varied in accordance with a first pseudo-random sequence, thereby introducing a known dither in the analog IF spread spectrum signal. After introducing the known dither, the analog IF spread spectrum signal is upconverted to an analog RF spread spectrum signal. The first pseudo-random sequences may be designed to be a chaotic sequence.

Continuous time chaos dithering

A system for communicating a sequence of information symbols using a chaotic sequence spread spectrum signal. The system includes a transmitter () for transmitting a signal including the information symbols, the information symbols encoded into the signal using a first chaotic sequence of chips generated at the transmitter. The system also includes a receiver () configure to receive the signal and extract the information symbols from the signal, the information symbols extracted using a second chaotic sequence of chips generated at the receiver. In the system, the first and the second chaotic sequences are identical and synchronized in time and frequency, each of the sequence of symbols is associated with a randomly generated threshold symbol energy value, and the portion of chips in the first and the second chaotic sequences associated with each of the plurality of information symbols is selected based on the associated threshold symbol energy value.

Symbol duration dithering for secured chaotic communications

Systems and methods for code-division multiplex communications. The methods involve forming orthogonal or statistically orthogonal chaotic spreading sequences (CSC, CSC), each comprising a different chaotic sequence. The methods also involve generating an offset chaotic spreading sequence (CSC, CSC, . . . , CSC, CSC, . . . , CSC) which is the same as a first one of the orthogonal or statistically orthogonal chaotic spreading sequences, but temporally offset. Spread spectrum communications signals (SSCs) are each respectively generated using one of the orthogonal or statistically orthogonal chaotic spreading sequences. Another SSC is generated using the offset chaotic spreading sequence. The SSCs are concurrently transmitted over a common RF frequency band.

Communications system employing orthogonal chaotic spreading codes

The invention concerns a chaotic communications system, method and apparatus having a transmitter configured to spread an input data signal over a wide intermediate frequency band, by digitally generating a first chaotic sequence of values to form a spreading code. The spreading code is then used to form a digital IF chaotic spread spectrum signal having a uniform sampling interval. The duration of the sampling interval is then selectively varied in accordance with a first pseudo-random sequence, thereby introducing a known dither in the digital IF chaotic spread spectrum signal. After introducing the known dither, the digital IF chaotic spread spectrum signal is converted to an analog RF spread spectrum signal at a conversion rate that exceeds the sampling interval of the chaotic spread spectrum signal. A corresponding receiver recovers the input data from the spread transmitted signal. This spreading may utilize a chaotic sequence employing discrete time chaos dithering.

Discrete time chaos dithering

Systems () and methods () for selectively controlling access to multiple data streams which are communicated using a shared frequency spectrum and shared spreading codes. The methods involve generating a first product signal (FPS) by spreading first symbols of a first amplitude modulated (AM) signal using a first spreading code (SC). The methods also involve generating a second product signal (SPS) by spreading second symbols of a complimentary AM signal using a second SC. The FPS () and SPSare combined to form a protected data communication signal (PDCS) including first data recoverable by a receiver (). A global data communication signal (GDCS) is combined with PDCS () to form an output signal () having a spread spectrum format. The GDCS is generated using a digital modulation process and includes second data recoverable by a plurality of receivers ().

Permission-based multiple access communications systems

Methods for code-division multiplex communications. The methods involve generating orthogonal or statistically orthogonal chaotic spreading codes (CSC, . . . , CSC) using different sets of polynomial equations (f(x(nT)), . . . , f(x(nT))), different constant values (C, C, . . . , C) for the polynomial equations, or different sets of relatively prime numbers (p, p, . . . , p) as modulus (m, m, . . . , m) in solving the polynomial equations. The methods also involve forming spread spectrum communications signals using the orthogonal or statistically orthogonal chaotic spreading codes, respectively. The method further involve concurrently transmitting the spread spectrum communications signals over a common RF frequency band.

A communications system includes RF hardware () configured for receiving an input data signal includes a modulated carrier encoded with information symbols and modulated using a sequence of discrete time chaotic samples. The system also includes a chaotic sequence generator () configured for generating the sequence of discrete-time chaotic samples and a correlator (). The correlator is configured for synchronizing the input data signal with the sequence of discrete-time chaotic samples and obtaining normalization factor values for each of the information symbols based on comparing a received symbol energy for the information symbols and a symbol energy of the discrete-time chaotic samples associated with the duration of transmission of the information symbols.

Symbol estimation for chaotic spread spectrum signal

Systems () and methods for selectively controlling access to multiple data streams which are communicated using a shared frequency spectrum and spreading code. The methods involve forming a global data communication signal () by amplitude modulating a global data signal () comprising global data symbols and forming a phase modulated signal () by phase modulating a protected data signal. The phase modulated signal represents protected data symbols. The methods also involve forming a protected data communication signal () by changing phase angles of the protected data symbols using a variable angle &#xd8; determined by a random number source and combining the protected data signal with a spreading sequence (CSC). The methods further involve combining the global and protected data communication signals to form an output communication signal () having a spread spectrum format. The output communication signal is transmitted over a communications channel ().

Permission-based secure multiple access communication systems

A spread spectrum communication system includes a channel encoder configured for modulating a carrier signal with data to form an information signal. A spreading sequence generator is configured for generating a spreading sequence having a phase angle dependent upon a chaotic sequence and contiguously distributed over a predetermined range. The chaotic sequence also has a magnitude which is selectively dependent upon the pseudo-random number or chaotic sequence. The invention also includes a multiplier configured for forming a spread spectrum signal by multiplying the information signal by the spreading sequence. The spreading sequence generator is responsive to a magnitude control signal for controlling the selective dependency of said magnitude. The magnitude can be constant to form a constant amplitude zero autocorrelation signal. Alternatively, the magnitude can be allowed to vary in selectively controlled chaotic or pseudo-random manner to vary a peak to average power ratio.

Anti-jam communications having selectively variable peak-to-average power ratio including a chaotic constant amplitude zero autocorrelation waveform

Systems () and methods () for providing a communications link with a power-limited communication transmitter () positioned remotely from an intended receiver system (). The methods involve channel encoding a carrier signal with data provided at the power-limited communication transmitter to form an information signal. The methods also involve generating a chaotic spreading sequence based on a chaotic number sequence. The chaotic spreading sequence has a magnitude that is constant and a variable arbitrary phase angle comprising phase values which are uniformly distributed over a predetermined range of angles. A spread spectrum signal is formed by multiplying the information signal by the chaotic spreading sequence. The spread spectrum signal has an adjustable amplitude characteristic and a zero autocorrelation. The spread spectrum signal is transmitted from the power-limited communication transmitter to the intended receiver system.

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West Melbourne, FL, United States of America

Alan J Michaels