Communications Satellite Corporation

Other

Hughes Network Systems, LLC

Lin-nan Lee

Mustafa Eroz

Peter Hou

Shyue-Ching Lu

Victor Liau

Russell J Fang

Glenn Robins

Ming-I Weng

Mustafa Rawala

Sarah Xie

Communication terminals, systems and methods are disclosed herein. In an embodiment, a method for improving communication throughput when experiencing periodic blockages includes generating at least one outer code block including a plurality of sync data elements, writing the sync data elements from the at least one outer code block to a same column of at least one interleaver including a plurality of rows and a plurality of columns, and writing additional data elements from the outer code block to other columns of the at least one interleaver.

Systems and methods for improving communication throughput

Communication terminals, systems and methods are disclosed herein. In an embodiment, a method for improving communication throughput when experiencing periodic blockages includes reading a plurality of data elements into an interleaver in one of a quasi-reverse order and a consecutive order, reading the plurality of data elements out of the interleaver in the other of the quasi-reverse order and the consecutive order, and. transmitting the plurality of data elements via a communication channel that experiences periodic blockages.

In a secure communications system, a key number which is changed periodically, e.g. monthly, and a random number from a random number generator are combined and used as a seed to reset a PN sequence generator, with the output of the generator being used to control encryption of transmission data in a signal processor. The key is also provided to a first encipherer to encipher the random number for transmission with the encrypted data. At the receiver, the key is provided on common to a decipherer for deciphering the random number and a PN sequence generator which is periodically reset by the combination of the key and random number in the same manner as in the transmitter. The PN sequence is then used to decrypt the information. User identification codes are stored in the transmitter and are used to encipher the key, with each employing its ID code to decipher the key. The user ID codes are known only to the system operator, so that not even a particular user can know the key.

Security system for SSTV encryption

A codec consists of an encoder and decoder. The encoder provides 12 information bits, 11 parity bits generated according to the polynomial for the (23, 12) Golay code, and an overall parity bit to a transmitter at selected transmit times to form a 24-bit block of data. The decoder is separated into two independent list decoders, a comparator, and common clock generator and output buffers. Each list decoder is divided into a syndrome generator and an overall parity check generator, a syndrome error pattern table, an input buffer, error correction logic, and four-error detection logic. The error pattern table includes a pair of read only memories storing the most likely 12-bit error patterns at each ROM address corresponding to each syndrome. An additional 4-bit output is used to indicate the number of errors in the associated error pattern. The comparator compares the number of errors detected in the two independent decoders and chooses the decoder having the fewer number of errors to provide the corrected data.

Weighted erasure codec for the (24, 12) extended Golay code

A method of protecting communications through encryption is disclosed which is particularly useful for multiplexed communications. On the transmit side, each message is multiplied by an enciphering key corresponding to its destination, and the products are all added together to form a cryptogram. Each receiving station divides the entire cryptogram by its own deciphering key to obtain the message intended for that station.

Multiple-destinational cryptosystem for broadcast networks

A public encryption key (c.sub.1, c.sub.2, r) in which r is the product of two relatively prime numbers, and in which c.sub.1 and r, as well as c.sub.2 and r, are relatively prime numbers, is used in an encryption algorithm

Simple and effective public-key cryptosystem

The strength of a cryptosystem is increased by providing multiple characters for one or more of the characters being encoded to thereby reduce redundancy.

Reduction of message redundancy by multiple substitution: a message

The integrated data enciphering and channel encoding system consists of a message expansion function F, a convolutional encoder G.sub.e of code rate r.sub.e greater than the computational cutoff rate R.sub.comp, and an artificial noise generator emitting a noise sequence n. The expansion function F is the key to this integrated cryptosystem and can be any linear time varying or time invariant function, with or without memory. It can also be a block code or a convolutional code itself provided that the resultant concatenated convolutional code is non-catastrophic. The concatenation of the expansion function F with G.sub.e is equivalent to a new convolutional encoder G.sub.d .ident.FG.sub.e of code rate r.sub.d less than the computational cutoff rate R.sub.comp of the equivalent channel, but without knowledge of the expansion function F or the artificial noise n, the transmitted information rate appears to exceed R.sub.comp. Thus, an opponent can only attempt to intercept the original message by decoding the code G.sub.e, but the information rate r.sub.e exceeding R.sub.comp will prevent this. The output of the encoder plus the noise sequence n is the cryptogram x which is transmitted over a noisy channel characterized by the additive noise sequence z. The corrupted version of the cryptogram y which is received at the receiving end is regarded as the output of the equivalent convolutional encoder G.sub.d plus noise e equivalent to the sum of the artificial noise n and the channel noise z. Therefore, the integrated channel decoder and deciphering system simply consists of a sequential decoder for G.sub.d =FG.sub.e.

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Germantown, MD, United States of America

Lin-nan Lee