802.11ac overview
DESCRIPTION
Overview of the upcoming 802.11ac standard and what to expect from wave 1 and wave 2 products. Customer expectations vs. the real features which are going to be available in "wave 1" and "wave 2" products. To avoid the unnecessary frustration...TRANSCRIPT
RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL
Ruckus on 802.11acApril 2013
802.11ac - An Overview
RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL2
5 GHz OnlyOptimistic Specs
Multi-user MIMO (MU-MIMO)
o Breaks “gigabit” barriero Max of 6.9 Gbpso “Gimmick” specs that drive
data rates very higho Many features not practical
for real-world enterprises
o Encourages 5G adoptiono Focuses on capacity-rich,
low-interference spectrumo Benefits entire Wi-Fi
ecosystem
Up to 8 spatial streams
AP
o N-fold efficiency improvement
o Increases radio complexity, power draw, and cost
o Requires client-side supporto Not possible today
o Simultaneous downlink Tx to single-stream clients
o Multiples network capacityo Key differentiator from
802.11n
5G
2.4G
256-QAM
o More efficient modulationo 33% data rate gainso Very short ranges onlyo Requires 11ac clients
80/160 MHz channels
o Very wide channelso Primary reason for 11ac’s
very high data rateso Ineffective use of spectrum
in multi-AP environmentso Decreases total capacity
160
40
20
80
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o 11ac supports 5 GHz frequencies onlyoDual-band devices will
support 11n in 2.4 GHz
o Focuses on spectrum with more bandwidth, less interference, and better scalability and capacity
o Encourages client device suppliers to adopt 5 GHz, to benefit from 11ac marketing, leaving 2.4 GHz as “best effort” spectrum
5 GHz Only
5G2.4G
480 MHz25 channels
83.5 MHz3 channels
Cap
acity
4 RUCKUS PROPRIETARY AND CONFIDENTIAL
80 and 160 MHz Channels
o 11ac devices must support 80 MHz channel width
o Optional support for 160 MHzo Contiguous or non-contiguous (80+80)
o Boosts maximum 802.11ac specso Appeal is for consumers with 1 AP
20 MHz
40 MHz
80 MHz
160 MHz
160 MHz (80+80)
114
38 46 54 62 102 110 118 126 134 151 159
42 58 106 122 155
50
36 40 44 48 52 56 60 64 100
104
108
120
112
116
124
128
132
136
140
153
157
161
165
149
5170 MHz
5330 MHz
5490 MHz
5730 MHz
5835 MHz
5735 MHz
UNII-1 UNII-2 UNII-2e UNII-3/ISM
802.11a/b/g
802.11n
802.11ac
Red channels are not permitted in some regions
25
12
6
2
2
Total
9
4
2
0
1
144
142
138
DFS
OVERVIEW
Cons
Proso Max data rate is more than doubledo Boosts throughput in networks with few APso Improves backup, file transfer speeds
o Sub-optimal spectral reuse in multi-AP deployments
o Max of 5 non-overlapping 80 MHz channelso Increases neighbor interference and contentiono Likely decreases aggregate capacity in enterprise
Artificially bloats max data rates of 802.11ac
5
Spatial Streams
RUCKUS PROPRIETARY AND CONFIDENTIAL
8x8:8 (MIMO) 8x8:8 (MIMO)
Bandwidth 1ss 2ss 3ss 4ss … 8ss
20 MHz 78 156 260* 312 … 624
40 MHz 180 360 540 720 … 1440
80 MHz 390 780 1170 1560 … 3120
256-QAM, 800 ns GI
o Businesso Increases AP/client cost o Increases AP/client sizeo Decreases aesthetic appealo 2x2 APs often meet the business need
o Technical o Short range for 4+ streamso More streams require RF “differentiation”
(difficult with 4+ streams)o Adds power draw on APs (PoE power
budget) and clients (battery life)
Real-World Barriers
802.11ac defines up to 8 spatial streams
802.11n defined up to 4 spatial streams
Flagship devices today support up to 3SS
Enterprises often prefer cost/performance of 2x2 APs
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256-QAM
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)
o 256-QAM improves efficiency by 33%o Higher-order modulation adds
complexity, which requires higher SNRo Beneficial near the AP
o Efficiency gain from modulation does not increase linearly
o Requires 802.11ac AP and client
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Multi-User MIMO (MU-MIMO)o Transmit simultaneous downlink frames to different receiverso Significant capacity enhancements in environments with many single-
stream devices (tablets, smartphones)o Requires 11ac client(s) with TxBF feedback/support o Creates new challenges related to signal steering and isolation
o How to get…
4x4:4 Access Point Stream 1
Stream 2Stream 3
Stream 4
4x4:4 Access Point
Stream 1
Multi-User MIMOMultiple downlink Tx at same time
Single-User MIMOSingle downlink Tx at a time
o DataA to StaA o DataB to StaB o No DataA to StaB o No DataB to StaA
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PayloadMAC Header
PHY Header
Interframe Space
RandomBackoff
Interframe Space
ACK
Overhead Effective Overhead
Time*Note: Diagrams are not to scale and are conceptual only
PayloadMAC Header
PHY Header
Interframe Space
RandomBackoff
Interframe Space
ACK
Overhead Effective Overhead
PayloadMAC Header
PHY Header
Interframe Space
RandomBackoff
Interframe Space
ACK
Overhead Effective Overhead
11a/g
11n
11ac
Why throughput does not equal data rate…
Large(r) Frame Size
The Solution: increase payload sizeo Every data frame in 802.11ac is an A-MPDUo Better spectrum efficiency enables larger frame sizes
without adverse impact from interferenceo Use of large frames depends on high rates
PHY AggregationMax
Bytes (Layer
2)
Max Bytes (Layer 1)
11b N (fragmentation often used) 2,304 ~2,336
11a/g N 2,304 ~2,33611n Y 7,935 65,53511ac Y 11,454 1,048,575
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Q: Is it be backward compatible with 11a/n?Yes. 11ac is fully backward compatible with 802.11a/n, using protection mechanisms with 11a/n frame formats.
What about 2.4 GHz? Initially, dual-band APs will be 802.11n in 2.4G and 802.11ac in 5G. 11ac may eventually be introduced to 2.4G for benefits from added spatial streams or 256-QAM.
Will it require new hardware?Yes. For every supplier, all APs and clients will need new hardware, whether complete AP replacement or modular radio add-ons. Controllers or management software may be software upgradeable.
FAQ
A:
Q:A:
Q:A:
11ac in Waves
10
Net gain Slight efficiency improvement, most benefits are for 802.11ac devices
Wave 1 – Q3, 2013 256-QAM 33% gain at very short range
80 MHz channels Twice the capacity of 40 MHz 802.11n(but not recommended for multi-AP deployments)
3 spatial streams Already supported by 802.11n (3x3)
Net gain Multiples aggregate network capacity and efficiency, ALL devices benefit
Wave 2 – Late 2014 Wave 1+ Includes all Wave 1 features, with additional chip
improvements
80 / 160 MHz channels Twice the capacity of 80 MHz 802.11ac(but not recommended for multi-AP deployments)
3+ spatial streams Likely 4 spatial streams. N-fold throughput gain for high-end clients, more flexibility/capacity for MU-MIMO
MU-MIMO Up to 4x capacity boost, multiplies aggregate capacity
Better 11ac with RuckusMaking the most of next-generation Wi-Fi
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Maximizing 256-QAMBPSKDPSK16-QAM64-QAM256-QAM
o With per-packet adaptive antenna control, polarization diversity, and active channel selection techniques, Ruckus APs maximize the potential of 256-QAM with 11aco Greater SNR/SINR increases the useful downlink range of 256-QAMo Adaptive PD-MRC and higher uplink receive sensitivity increase uplink range of 256-QAMo APs select channels with more capacity and less noise and interference
Them Us
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BeamFlex-Enhanced MU-MIMO
Antenna 2 to Client 2Antenna 1 to Client 1
Antenna 3 to Client 3
AP
3x3 MU-MIMO3 clients concurrently communicate with AP, each on a dedicated spatial stream (and antenna)
MU-MIMO enhanced with BeamFlexDirectional antenna element for each cliento Better signal separationo Higher sustained data rateso Increased AP capacity
Standard MU-MIMOAll clients hear all antennaso Poor signal isolation per cliento Lower SNR per link = lower data rateso Marginal benefit to capacity