French Military Mission to Poland and 8b/10b encoding: Difference between pages

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In [[telecommunication]]s, '''8B/10B''' is a [[line code]] that maps [[8-bit]] symbols to [[10-bit]] symbols to achieve [[Direct current|DC]] balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery. This means that there are just as many "1"s as "0"s in a string of two symbols, and that there are not too many "1"s or "0"s in a row. This is an important attribute in a signal that needs to be sent at high rates because it helps reduce "[[intersymbol interference]]". The code was described in 1983 by Al Widmer and Peter Franaszek in the [[IBM]] Journal of Research and Development. IBM was issued a patent for the scheme the following year.

The '''French Military Mission to Poland''' was an effort by [[France]] to aid the nascent [[Second Polish Republic]] after it achieved its independence in November, [[1918]], at the end of the [[First World War]]. The aim was to provide aid during the [[Polish-Soviet War]] ([[1919]]-[[1921]]), and to create a strong Polish military to serve as a useful ally against Germany. It was an advisory body consisting of about 400 French officers attached to staffs of Polish units at various levels. Although the French mission was small numerically, its effect was substantial in improving the [[organisation]] and [[logistics]] of the [[Polish army]]. It worked in parallel with the smaller [[British Military Mission to Poland]].

As the scheme name suggests, 8 [[bit]]s of data are transmitted as a 10-bit entity called a ''Symbol'', or ''Character''. The low 5 bits of data are encoded into a 6-bit group and the top 3 bits are encoded into a 4-bit group. These code groups are concatenated together to form the 10-bit Symbol that is transmitted on the wire. The ''Data Symbols'' are often referred to as Dxx.y where xx ranges from 0-31 and y from 0-7. Standards using the 8B/10B encoding also define ''Special Symbols'' (or ''Control Characters'') that can be sent in place of a ''Data Symbol''. They are often used to indicate end-of-frame, link idle, skip and similar link-level conditions. They are referred to as Kxx.y and have different encodings from any of the Dxx.y symbols. Because 8B/10B encoding uses 10-bit symbols to encode 8-bit words, each of the 256 possible 8-bit words can be encoded in two different ways, one the bit-wise inverse of the other. Using these alternative encodings, the scheme is able to affect long-term DC-balance in the serial data stream, allowing links to be capacitively coupled.

It was commanded by French General [[Paul Prosper Henrys]], previously the commander of French forces in the [[Balkans]]. The French mission commanded considerable respect and influence through the activities of its 400 officer-instructors. These men, distributed among the cadres of the Polish Staff, were entrusted with the task of training the officer corps in the art of military science and in the use of French army manuals. The French effort was vital in improving the organisation of the newly formed Polish army, which up till 1919 used various manuals, organisation structures and equipment, mostly from the former [[partitions of Poland|partitioners]] armies.

Among the French offcers was future President of France, [[Charles de Gaulle]].

The encoding is normally done entirely in hardware based on lookup tables. Upper levels of the software stack should be unaware that this encoding is being used.

This mission should not be confused with the '''[[Interallied Mission to Poland]]''', an improvised effort launched by [[David Lloyd George]] on [[July 21]], [[1920]], at the height of the crisis before the [[Battle of Warsaw (1920)|Battle of Warsaw]]. The purpose of this mission was to send a number of high level personnages from Britain and France to Poland in an attempt to influence Polish policy, possibly through effecting a change in

government. They included French diplomat, [[Jean Jules Jusserand]], [[Maxime Weygand]], chief of staff to Marshal [[Ferdinand Foch]] (the Supreme Commander of the victorious Entente), and the British diplomat, Lord [[Edgar Vincent D'Abernon]]. The crucial battle of Warsaw was won in the early days of August, before the mission could achieve anything of importance. The only tangible result was the installation of Weygand as an advisor the Polish General Staff, where his role was negligible. Nevertheless, soon after the battle and for various political reasons, a myth arose that Weygand was the author of the Polish victory in the battle of Warsaw.

Among the areas in which 8B/10B encoding finds application are [[Fibre Channel]], [[Gigabit Ethernet]], [[InfiniBand]], [[XAUI]], and audio storage devices such as the [[Digital Audio Tape]] and [[Digital Compact Cassette]] (DCC). The related [[Eight-to-Fourteen Modulation]] is used in the [[Compact Disc]] standard. The encoding scheme used in [[10 Gigabit Ethernet]]'s 10GBASE-R [[Physical Media Dependent]] (PMD) interfaces, 64B/66B, while similarly created with consideration of DC balance, maximum run length, transition density, electromagnetic emissions, and the like, is considerably different in design.

== See also ==

* [[Blue Army]]

* [[Western betrayal]]

==External links==

[[Category:Polish-Soviet War]]

*[http://domino.research.ibm.com/tchjr/journalindex.nsf/0/b4e28be4a69a153585256bfa0067f59a?OpenDocument Original paper by Franaszek and Widmer].

[[Category:History of France]]

*[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/search-bool.html&r=1&f=G&l=50&co1=AND&d=ptxt&s1=4486739.WKU.&OS=PN/4486739&RS=PN/4486739 US Patent 4,486,739], the relevant document at the US Patent and Trademark Office's site.

[[Category:History of Poland]]

[[Category:Computer and telecommunication standards]]

[[Category:Polish-SovietLine Warcodes]]

[[fr:Encodage 8b/10b]]