layman’s guide to txbf, mimo and mu-mimo
DESCRIPTION
From: www.cwnp.com/uploads/gt-hill-txbf.pdfTRANSCRIPT
RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL
Layman’s Guide to TxBF, MIMO and MU-MIMO
GT HillChief Big Dog
Ruckus Wireless
@gthill
◦ Poor adoption with 802.11n◦ 802.11ac focuses on one implementation
◦ Universal industry focus
◦ NDP Sounding with explicit immediate compressed feedback
2x2
Access Point 1x1
Client
Signal
Quality
TxBF
3
4
+3dB
5
+4.7dB
6
+6dB
7
12
8
12
9
12
10
12
o 3 / 4.7 / 6 dB gain vs. additional spatial streamoEach antenna can either
reinforce the signal (TxBF) or
add more data (spatial
multiplexing) but never both at
the same time.
oEach additional spatial stream
adds significantly more speed
o3dB adds <10% more speed
oRequires client feedbackoDoes not work with 11a/b/g/n
and only some 11ac clients
11
Problem
AP
Conventional 11ac
TxBF Pattern
(symmetric)
How to optimize signal
for client location?
Client Direction
TxBF
Client
1 B
itCan you hit this target?
2 B
its
How about one of these?
4 B
its
6 B
its
8 B
its
o Improves efficiency by 33%
oAdds complexity, requires higher
SNR
oEfficiency gain from modulation
does not increase linearly
256-
QAM64-QAM16-QAM
QPSKBPSK
0 1
01 11
00 10
100% gain (2x)
100% gain (2x) 50% gain (1.5x) 33% gain (1.3x)
18
Uses only ONE antenna for transmit and receive
802.11a/b/g
Go Get Certified!
19
802.11n/ac
Can use multiple antennas for transmit and receive
Go
Get
Certified!Tx Rx : SS
3 x 3 : 3
20
802.11n/ac
Can use multiple antennas for transmit and receive
Go
Get
Certified!Tx Rx : SS
3 x 3 : 3
21
oIncreasing the difference in “perspective” between each stream
oHorizontal vs. vertical polarization
oMultipath
22
oRequires 11ac client(s) with TxBF feedback/support
oCreates new challenges related to signal steering and isolation
4x4:4
Access Point
4x4:4
Access Point
Multi-User MIMOmultiple clients at the same time
Single-User MIMOone client at a time
oPeak to Average Power Ratio
oTransmit power equalization
oRate selection
oDelayed Acknowledgment (block ack)
oData Queuing
oSelecting MU groups
oMaking the process efficientoSame size frames
oSame data rate clients