The document provides an overview of the 802.11ac wireless standard, highlighting its features such as support for 5 GHz frequencies, multi-user MIMO capabilities, and increased data rates through advanced modulation techniques. It discusses the advantages and limitations of 802.11ac in real-world deployments, particularly in environments with multiple access points, and emphasizes the need for updated hardware for full compatibility. The document also outlines different waves of 802.11ac and the expected performance enhancements associated with each.

1. RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL
Ruckus on 802.11ac
April 2013

2. 802.11ac - An Overview
RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL2
5 GHz Only
Optimistic
Specs
Multi-user MIMO
(MU-MIMO)
o Breaks “gigabit” barrier
o Max of 6.9 Gbps
o “Gimmick” specs that drive
data rates very high
o Many features not practical
for real-world enterprises
o Encourages 5G adoption
o Focuses on capacity-rich,
low-interference spectrum
o Benefits entire Wi-Fi
ecosystem
Up to 8 spatial
streams
A
P
o N-fold efficiency
improvement
o Increases radio complexity,
power draw, and cost
o Requires client-side support
o Not possible today
o Simultaneous downlink Tx to
single-stream clients
o Multiples network capacity
o Key differentiator from
802.11n
5G
2.4G
256-QAM
o More efficient modulation
o 33% data rate gains
o Very short ranges only
o Requires 11ac clients
80/160 MHz
channels
o Very wide channels
o Primary reason for 11ac’s
very high data rates
o Ineffective use of spectrum
in multi-AP environments
o Decreases total capacity
160
4
0
2
0
8
0

3. o 11ac supports 5 GHz
frequencies only
o Dual-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
3
5 GHz Only
RUCKUS PROPRIETARY AND CONFIDENTIAL
480 MHz
25 channels
83.5 MHz
3 channels
Capacity

4. 4
80 and 160 MHz Channels
RUCKUS PROPRIETARY AND CONFIDENTIAL
o 11ac devices must support 80 MHz
channel width
o Optional support for 160 MHz
o Contiguous or non-contiguous (80+80)
o Boosts maximum 802.11ac specs
o 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
Pros
o Max data rate is more than doubled
o Boosts throughput in networks with few APs
o Improves backup, file transfer speeds
o Sub-optimal spectral reuse in multi-AP deployments
o Max of 5 non-overlapping 80 MHz channels
o Increases neighbor interference and contention
o Likely decreases aggregate capacity in enterprise

5. 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 Business
o Increases AP/client cost
o Increases AP/client size
o Decreases aesthetic appeal
o 2x2 APs often meet the business need
o Technical
o Short range for 4+ streams
o 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

6. 6
256-QAM
RUCKUS PROPRIETARY AND CONFIDENTIAL
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 SNR
o Beneficial near the AP
o Efficiency gain from modulation does
not increase linearly
o Requires 802.11ac AP and client

7. 7
Multi-User MIMO (MU-MIMO)
RUCKUS PROPRIETARY AND CONFIDENTIAL
o Transmit simultaneous downlink frames to different receivers
o 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
4x4:4
Access Point
Multi-User MIMO
Multiple downlink Tx at same time
Single-User MIMO
Single downlink Tx at a time
o DataA to StaA o DataB to StaB o No DataA to StaB o No DataB to StaA

8. Payload
MAC
Header
PHY
Header
Interframe
Space
Random
Backoff
Interframe
Space
ACK
Overhead Effective Overhead
Time
*Note: Diagrams are not to scale and are conceptual only
Payload
MAC
Header
PHY
Header
Interframe
Space
Random
Backoff
Interframe
Space
ACK
Overhead Effective Overhead
Payload
MAC
Header
PHY
Header
Interframe
Space
Random
Backoff
Interframe
Space
ACK
Overhead Effective Overhead
Why throughput does not equal data rate…
8
Large(r) Frame Size
RUCKUS PROPRIETARY AND CONFIDENTIAL
The Solution: increase payload size
o Every data frame in 802.11ac is an A-MPDU
o Better spectrum efficiency enables larger frame sizes
without adverse impact from interference
o Use of large frames depends on high rates
PHY Aggregation
Max
Bytes
(Layer 2)
Max Bytes
(Layer 1)
11b
N (fragmentation
often used)
2,304 ~2,336
11a/g N 2,304 ~2,336
11n Y 7,935 65,535
11ac Y 11,454 1,048,575

9. 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.
9
FAQ
RUCKUS PROPRIETARY AND CONFIDENTIAL
A:
Q:
A:
Q:
A:

10. 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

11. Better 11ac with Ruckus
Making the most of next-generation Wi-Fi
11 RUCKUS WIRELESS PROPRIETARY AND CONFIDENTIAL

12. 12
Maximizing 256-QAM
RUCKUS PROPRIETARY AND CONFIDENTIAL
BPSK
DPSK
16-QAM
64-QAM
256-QAM
o With per-packet adaptive antenna control, polarization diversity, and active channel
selection techniques, Ruckus APs maximize the potential of 256-QAM with 11ac
o Greater SNR/SINR increases the useful downlink range of 256-QAM
o Adaptive PD-MRC and higher uplink receive sensitivity increase uplink range of 256-QAM
o APs select channels with more capacity and less noise and interference
Them Us

13. 13
BeamFlex-Enhanced MU-MIMO
RUCKUS PROPRIETARY AND CONFIDENTIAL
Antenna 2 to Client 2Antenna 1 to Client 1
Antenna 3 to Client 3
3x3 MU-MIMO
3 clients concurrently communicate
with AP, each on a dedicated spatial
stream (and antenna)
MU-MIMO enhanced with BeamFlex
Directional antenna element for each client
o Better signal separation
o Higher sustained data rates
o Increased AP capacity
Standard MU-MIMO
All clients hear all antennas
o Poor signal isolation per client
o Lower SNR per link = lower data rates
o Marginal benefit to capacity