VLR++: VLR with LZW Compression for Communications

These notes are written for investors, developers and decision makers.

Useful links for more information on the LZW lossless compression:

Compress (Unix)
V.42bis (1)
V.42bis (2)

LZW for communications:

Generally, the LZW algorithm is used in frame by frame compression, in streaming or for the files. In frame by frame compression, if the frames are too short, the compression rates are very low. It may even be expansions.
To make this algorithm used for the communications, we use a dictionary built with the frames previously transmitted, and we do a complete flush of data to transmit at the end of each frame.

It remains some tasks to do, including:
   - Apply the algorithm on the residuals: for each frame and for all types of elements (positions, magnitudes and phases), make the difference between the most frequent element and the current element, or make the difference between the current element and the previous element.
   - Manage the packet loss. With the VLR protocol, the receiver knows if it is in phase with the transmitter or not. If case of desynchronization, one must send a resynchronization frame (every second for example, as there is no confirmation of receipt) and wait for a confirmation of reception, so that the two corresponding reset their dictionaries.
There is no resynchronization if there is no packet loss (files or TCP/IP protocol for example).

Shortly after the start, one can hope to divide by two (up to four) the bitrate compared to the version without additional compression. The average bitrate will be significantly below 1200 bps, without loss of quality.

Contacts and Comments: