Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1998-06-24
2004-03-23
Baker, Stephen M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
Reexamination Certificate
active
06711709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system and method for checking the integrity of data files transferred at high speeds in compressed format.
2. Description of the Prior Art
Some systems for transferring very large files using multiplex communications are classified in class 370, subclasses 260+, 465+ and 536+. One such system is shown described in my U.S. Pat. No. 5,680,400 assigned to same assignee as the present invention. The system described therein splits data to be transferred into a plurality of streams for asynchronous transmission for the purpose of increasing the speed of the transfer over parallel lines, cables or phone links.
Another method of increasing the speed of data transmission is to compress the data without loss so that data being transmitted is in a format up to one-tenth its original size. Theoretically this would increase the speed of transmission by one order of magnitude. Data compression, while desirable, carries with it a loss of computer time during processing and other problems which are usually ignored. State of the art mainframe computers can easily format one million or more bytes per second. Data links and high speed networks presently used for high speed data transfer are capable of exceeding this data rate. Thus, data files whether compressed or not can be transferred over such data links at a minimum of time. Such transmission links are not always available in all locations of the world and it often becomes desirable to increase the rate of transmission of data over lines and links by employing data compression of the data files before transmission. It is not generally known that compressed data in compressed format is not fault tolerant and that the older and slower transmission lines and data link are more prone to causing transmission errors in the transmission path. Numerous data files concerning financial data, manufacturing data and inventory data are being transmitted over such lines. A typical example will illustrate the point. More and more world wide manufacturing and sales companies desire to transmit data concerning manufacturing needs, inventory and sales from all remote locations to a central location which has an enterprise computing system. The central system is usually capable of updating all data on a daily basis and generating reports and issuing orders and calculating data to maintain a balance of incoming parts with outgoing sales without depletion of sales items at any one location.
Accordingly, it would be most important that the data generated at remote locations is reproduced without error at the central location at a minimum of cost and time. When data compression is employed to increase the amount of data transferable in a given unit of time, the occurrence of errors in transmission can corrupt the compressed data to the point to where it is useless and/or meaningless in its decoded format.
It would be desirable to provide a method and apparatus for transferring large data files such as inventory and sales data from points all over the world to a central enterprise host system over various available communication lines and data links in compressed format which would ensure a very high degree of integrity of the data received and decoded.
SUMMARY OF THE INVENTION
It is the principal object of the present invention to provide a method and apparatus for enhancing the integrity of compressed and transmitted data.
It is a principal object of the present invention to provide a method and means for checking compressed data that has been transmitted to a receiver for decoding.
It is a principal object of the present invention to provide a method and means for checking compressed data that is virtually without cost of any kind to the system.
It is an object of the present invention to provide a method and apparatus for efficiently compressing and decoding data being transferred between remotely located computers.
It is an object of the present invention to provide an apparatus and a method for generating and inserting a novel block check code in a compressed data stream which is transparent to the encoder and decoder.
It is an object of the present invention to provide a novel block check code which can be cryptically inserted in a compressed or noncompressed data stream at low cost to prevent interception of confidential and proprietary data.
It is an object of the present invention to provide a block code generator for inserting a block check code after a predetermined large number n of fixed-length N-byte blocks so to be easily recognized by position.
It is the general object of the present invention to provide a method of checking transmitted data on the fly in one step.
According to these and other objects of the present invention there is provided a method for enhancing the validity of transmitted data files which comprises reading the data from a data file and formatting the data into alpha numerical characters which may be compressed by a known compression code which produces a variable length data stream. The new data stream is then divided into n blocks of N bytes where N represents an integer. A check code is inserted for each n blocks of N bytes to provide a data stream with a validity code enhancement embedded in the data stream.
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Baker Stephen M.
Sowell John B.
Starr Mark T.
Unisys Corporation
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