| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
| --- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Ah ha … I now think I see the
problem. The “S” in SDMA stands for “spatial”, but NOT
the space most people are used to thinking about. It’s not the Newtonian
[x,y,z] coordinate space in which we live (actually the Lorenzian [x,y,z,ict]
is more appropriate but is still not the correct space). Yes, the term “space”
is overloaded here, however that can’t be changed. The relevant space is
the M-dimensional (M is the # of antennas) vector space of array manifold
vectors over the field of Green’s functions generated by the laws of
physics (cf. James Clerk Maxwell, Helmholtz, and others). The multiple
dimensions over which streams are transmitted are NOT (some combination of) the
three dimensions of the coordinate space in which we live; they are the
dimensions of the array manifold vector space, and while the structure of that
space is a function of the Lorenz coordinates of the “stuff” in our
more familiar coordinate space, the two spaces are entirely different. Note
that while multiple antennas [e.g. MxN] can be used “on both ends of a
link”, spatial streams are created upon transmission and do NOT require
multiple antennas at “both ends”. Fixing this in the document may
take some doing unfortunately. As for fixing “modulation symbol”,
that shouldn’t be too hard I would think. Just replacing the term with “symbol”
pretty much everywhere should do the trick (but I haven’t looked at all
occurrences ether:^))) For more info, search on SDMA, MUSIC,
ESPRIT, array manifold(s), array manifold vectors. Happy Holidays, RR From: Mark Rison
[mailto:m.rison@xxxxxxxxxxx] "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 ROYAUME
UNI
WWW: http://www.samsung.com/uk From: Dick Roy
[mailto: “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 ROYAUME
UNI
WWW: http://www.samsung.com/uk _______________________________________________________________________________
IF
YOU WISH to be Removed from this reflector, PLEASE DO NOT send your request to
this CLOSED reflector. We use this valuable tool to communicate on the issues
at hand. SELF
SERVICE OPTION: Point your Browser to - http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-TGM
and then amend your subscription on the form provided. If you require removal
from the reflector press the LEAVE button. Further
information can be found at: http://www.ieee802.org/11/Email_Subscribe.html
_______________________________________________________________________________ IF YOU WISH to be Removed from this reflector, PLEASE DO NOT send your request to this CLOSED reflector. We use this valuable tool to communicate on the issues at hand. SELF SERVICE OPTION: Point your Browser to - http://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-TGM and then amend your subscription on the form provided. If you require removal from the reflector press the LEAVE button. Further information can be found at: http://www.ieee802.org/11/Email_Subscribe.html _______________________________________________________________________________ |