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| --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
"spatial stream" is defined as follows: spatial stream: One of several streams of bits or modulation symbols that might be transmitted over multiple spatial dimensions that are created by the use of multiple antennas at both ends of a communications link. "modulation symbol" is not defined and nor is plain "symbol". Mark -- Mark RISON, Standards Architect, WLAN English/Esperanto/Français Samsung Cambridge Solution Centre Tel: +44 1223 434600 Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601 ROYAUME UNI WWW:
http://www.samsung.com/uk From: Dick Roy [mailto:dickroy@xxxxxxxxxxxx]
“space-time stream: A stream of modulation symbols created by applying a combination of spatial
and temporal processing to
a spatial stream of modulation symbols.” Without defining a “spatial stream” and “modulation symbol”, none of this makes much sense it seems to me. And defining “spatial stream” is going to
be a challenge because it’s an oxymoron of sorts. Streams are temporal things; space is “stationary”. Secondly, defining “modulation symbol” is going to also be a challenge because symbols are objects that arise as a consequence of modulation of an RF carrier.
How does one “spatially and temporally process a spatial stream” to create anything meaningful?
In short, the above text is confusing at best, and not really meaningful. My two cents … RR From: ***** 802.11 REVm - Revision Maintainance List ***** [mailto:STDS-802-11-TGM@xxxxxxxx]
On Behalf Of Mark Rison We had a discussion a couple of teleconfs ago on the definition of a space-time stream, since the spec currently only defines space-time streams (plural): space-time streams: Streams of modulation symbols created by applying a combination of spatial and temporal processing to one or more spatial streams of modulation symbols. The question was whether it was: space-time stream: A stream of modulation symbols created by applying a combination of spatial and temporal processing to
one or more spatial streams of modulation symbols. or whether it was necessarily: space-time stream: A stream of modulation symbols created by applying a combination of spatial and temporal processing to
a spatial stream of modulation symbols. I have consulted PHY colleagues here, and the conclusion was that Spatial streams and Space-time Streams are the same except when an STBC encoder is applied (the STBC encoder expands both space and time) When STBC is applied a single spatial stream is mapped to two space-time streams. and that for example for HT the possible mappings are: For 1SS -> 2 STS via 2x2 STBC coding For 2SS -> 3 STS via 2x2 STBC for 1st SS and 1:1 mapping for 2nd SS For 2SS -> 4 STS via 2x2 STBC for 1st SS and 2nd SS For 3SS -> 4 STS via 2x2 STBC for 1st SS and 1:1 mappings for 2nd and 3rd SS Therefore I think the following definition is correct: space-time stream: A stream of modulation symbols created by applying a combination of spatial and temporal processing to
a spatial stream of modulation symbols. Mark -- Mark RISON, Standards Architect, WLAN English/Esperanto/Français Samsung Cambridge Solution Centre Tel: +44 1223 434600 Innovation Park, Cambridge CB4 0DS Fax: +44 1223 434601 ROYAUME UNI WWW:
http://www.samsung.com/uk _______________________________________________________________________________
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