MNP Class 5·is one of the error correction and
data compression protocols developed by the modem manufacturer Microcom.
MNP Class
5 provide a data compression protocol that can increase
throughput by up to 200%.
MNP Class 5 yields data
compression rations of between 1.3:1 and 2:1 using two data
compression algorithms:
Huffman encoding is used to re-encode ASCII characters. Frequently
used characters such as a, e, and s are encoded
using only 4 bits, whereas rarely occurring characters such as
x or z are encoded using as many as 11
bits. Overall, the effect of Huffman encoding is that more
characters are transmitted using fewer bits.
Run-length encoding examines a data
stream in search of repeating characters. When a character repeats
more than three times, the algorithm replaces the entire string
of repeated characters with only three repetitions of the character
followed by a count field indicating how many times the
character is actually repeated. For example, 10 repeated characters would
be sent as 4 characters (3 characters + 1-byte count).
Other topics in our resources on Modems related to MNP Class 5 include: