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| --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
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:
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