Building High Performance Networks with
High Performance Wireless Networks
Building High Performance
Networks with 802.11ac
Millions of new wireless devices are activated
every day. The volume of application traffic
generated by these devices on wireless
networks will overtake the total traffic on wired
networks by 2014. 1 The emerging 802.11ac
standard will enhance these wireless networks
by delivering much greater performance than
today’s 802.11n standard.
Wireless has become the preferred and often the only form
of access. But while the 802.11ac standard is a significant
improvement in performance it is not enough to provide end
users with the application performance and user experience
they have come to expect from their 1GB and 10GB wired-
Ethernet networks. With the adoption of 802.11ac, theoretical
throughput for Wi-Fi will go from 450Mbps with 802.11n to
1.3Gbps. However, in the real world with protocol overhead and
interference, actual throughput will be closer to 433Mbps.
Wired networks have moved from shared hubs to dedicated multiport
switches, but the same architectural shift has not happened
for wireless. Wi-Fi network capacity must play catch up to replace
wired systems. Doing so will require utilizing not only 802.11ac but
also multi-radio systems. With the multi-radio Array and 802.11ac,
Xirrus is uniquely positioned to provide the performance needed
to credibly replace the wire once and for all.
Wireless has become the primary access to the network.
Many consumers are now carrying two, three, or four devices.
That ratio of wireless devices will continue to explode as it
reaches a 7:1 by 2016. 2 Over 1 million smartphones are
activated daily with tablets forecasted to outsell desktops by
late 2013. 3 Unlike wired users, mobile users expect to connect
anytime, anywhere – at home, in the office, in classrooms, and at
conferences. Dependency on mobile applications and cloudaccess
are now business-critical. To help meet the exploding
need for more wireless performance, the industry is about to
release the next Wi-Fi standard: 802.11ac.
Existing 802.11n networks will eventually be replaced by
802.11ac. A key characteristic of 802.11ac is that it operates
only in the 5GHz band. This band provides seven times the
channel bandwidth and has less interference compared to the
previously more popular 2.4GHz band. To simplify network
migration, 802.11ac will maintain backward compatibility with
existing 802.11n equipment.
The following table summarizes the key characteristics of 802.11ac.
802.11n (Phase I)
July 2009 Mid 2013
2007 2012 TBD
Max Data Rate 450Mbps 1.3Gbps 6.9Gbps
150Mbps 433Mbps 2.3Gbps
20, 40 20, 40, 80 20, 40, 80,
Spatial Streams Up to 3 Up to 4 Up to 8
RF Bands 2.4GHz, 5GHz 5GHz 5GHz
Max Modulation 64-QAM 256-QAM 256-QAM
Ratification of the IEEE 802.11ac standard and testing by the
Wi-Fi Alliance is expected in 2013. Many leading consumergrade
Wi-Fi vendors have begun shipping products based on
this new standard, showing confidence in the imminent passage
of the standard.
To achieve higher performance, 802.11ac uses several
technology advancements to triple (and more) the throughput
compared to 802.11n:
• Enhanced modulation techniques push beyond 64QAM (used by
802.11n) to 256QAM, making spectrum usage 30% more efficient.
• Increased channel bandwidth from 20MHz or 40MHz (used by
802.11n) to 80MHz widens the channel, increasing capacity.
• Support for up to 8 spatial streams and 160MHz channels in
future versions of 802.11ac takes the maximum data rates up
• Moving from MIMO (multiple-input and multiple-output)
technology in 802.11n to advanced Multi-User MIMO (or
MU-MIMO) will add the ability for multiple devices to connect
to each other simultaneously on the same radio.
3 Zeus Kerrvala Research, BYOD Requires New Network Strategies,
802.11ac WHITE PAPER // 2
Is 802.11ac Enough?
The increase in performance offered by 802.11ac is critical to
the success of wireless. However, is it enough to make wireless
the primary connection to the network?
Today, most Wi-Fi networks provide a fraction of the capacity
enjoyed by wired users. Most wired networks run Gigabit
Ethernet, delivering close to 100Mbps of bandwidth to the user
(accounting for uplink aggregation). In contrast, most Wi-Fi
networks provision 5Mbps or less per user based on design
guidelines by vendors and industry experts. This is unacceptable
if wireless is truly expected to be the primary access technology.
See the following table for an example comparison.
Total BW = 4Gbps
Total BW = 100M (5G) +
50M (2.4G) = 150Mbps
Number of Users 48 48
User Connections 48 GigE ports 2 radios
User Bandwidth Dedicated Shared
Uplinks 4 GigE 1 GigE
Capacity per User 4Gbps + 48 =
150Mbps + 48 =
Why should todays’ wireless users accept 5Mbps as good
enough? Either we are overprovisioning the wired or we are
under-provisioning the wireless. At Xirrus, we believe it is the
latter. Wired gigabit infrastructure has enabled networked
medical imaging, HD video services, life-size video telepresence,
and much more. The same high-capacity performance is needed
on our wireless networks to deliver these services.
802.11ac brings us another step up in performance but by itself is
not enough. 433Mbps of achievable throughput on an 802.11ac
radio shared between 30 users is still only about 15Mbps per user.
Such performance will not effectively replace wired networks.
More Radios is the
Real Xirrus Advantage
The most effective way to increase capacity on the wireless
network is to add more radios – more “ports”. While
802.11ac adds more capacity per radio, the actual increase
in performance for many clients will be less than one might
expect. While 802.11ac will provide throughput up to 433Mbps
per radio, most clients will never experience that performance.
Tablets and smartphones, for example, typically have only one
antenna and therefore do not support multiple data streams that
increase performance. For example, the iPhone 5 operates up to
150Mbps maximum data rate, well below the 802.11n maximum
of 450Mbps. Even when 802.11ac support is added to these
devices, they will not support the full speeds given their size,
form factor, and power restrictions.
In wired networks, supporting more users means adding more
switch ports. The same holds true with wireless viewing the
radio as a switch port. When you add more wireless users, you
need to add more radios. However you cannot deploy more
than three conventional dual-radio APs in a given area since
each supports a 2.4GHz radio. This is because co-channel
interference causes performance degradation. There must be
physical isolation between APs or the conflicting 2.4GHz radios
must be shut-off.
Xirrus solves this issue by designing a Wireless Array with
directional antennas and radio isolation to allow multiple radios
to coexist in the same chassis. This approach follows the same
architectural path that wired switches took with increasing port
counts. Xirrus Arrays support 2, 4, 8, 12, or 16 radios per Array.
Xirrus’ 802.11ac Solution
With an average wireless equipment refresh cycle of 4-5 years,
it is vital for customers purchasing new wireless systems today
to consider their plans to accommodate 802.11ac. The BYOD
(Bring Your Own Device) phenomenon will drive 802.11ac
adoption on corporate wireless networks as 802.11ac-enabled
devices reach the market.
Only Xirrus delivers a wireless solution that is truly 802.11acready.
Our modular, multi-radio architecture provides investment
protection and a smooth migration path for customers.
Pushing beyond traditional AP and controller architectures, the
innovative Wireless Array infrastructure integrates the following
• Multiple radio design with 2, 4, 8, 12, and 16 modular APs
per Array. In contrast, conventional enterprise APs have only
2 fixed radios similar to consumer grade Wi-Fi routers.
• Directional antennas providing 2X more range and 2-4X more
coverage than omni-directional antennas on traditional APs—
meaning 50-75% less equipment.
• Integrated controller that places network processing and
intelligence at the edge of the network – a better deployment
model than centralized controllers housed in the core network.
• Modular chassis-based design that enables capacity and
technology upgrades by adding new modules without forklift
replacement of any equipment.
1 Multiple Radios (2 to 16 per Array)
2 Directional Antennas
3 Integrated Controller
4 Modular Chassis-based Design
802.11ac WHITE PAPER // 3
This unique Xirrus Array architecture affords a number of key advantages
when migrating to 802.11ac.
• Upgradability. With a Xirrus system, there will be no need
to uninstall existing hardware when 802.11ac radio modules
become available. Simply add the new 802.11ac modular radios
in the chassis’ slots. Simplify installation and upgrades, and lower
costs by maintaining existing chassis, cabling, and switches.
• Technology Migration. The modular, multi-radio design of the
Array operates with different wireless client types (802.11a/b/
g/n/ac) without compromising performance. Individual radios
can be dedicated to operate with slower 802.11bgn (2.4GHz)
clients, faster 802.11an (5GHz) clients, or the new fastest
802.11ac clients – all within a single Array. Legacy 2-radio
APs will run slower in 5GHz given they are unable to separate
slower 802.11an clients from faster 802.11ac clients.
• 5GHz Evolution. Every radio within a Xirrus Array can be
configured to operate in either the 2.4GHz or 5GHz spectrum.
With the ability to assign radios to bands based on actual
client mix, the Xirrus Array provides far more flexibility
compared to conventional enterprise dual-radio APs, which
are fixed with a single radio in 2.4GHz and another in 5GHz.
Remember that 802.11ac advances are only available in the
In anticipation of 802.11ac, Xirrus recommends the following:
• Migrate clients from 2.4GHz to 5GHz whenever possible.
2.4GHz is becoming an unusable spectrum given limited
available channels and congestion from overuse.
• Separate faster and slower clients. Slower wireless clients will
slow down the performance of faster wireless clients when
operating together on the same wireless network, much like
slow moving vehicles on a highway. Look at segmenting clients
so that faster clients operate together on radios independent
of slower clients. Design your network to direct faster multistream
clients such as laptops to their own channels, while
connecting slower, single-stream clients such as smartphones
and tablets to separate channels. The more radios you have
in your infrastructure, the easier it will be to segregate clients,
thus provisioning the network with more radios is essential.
• Site Survey. Most Wi-Fi networks were designed for coverage
and not capacity. Consider a new site survey when installing
new 802.11ac APs. The minimum signal level criteria should
be -65dBm in both 2.4GHz and 5GHz for full support of
smartphones, tablets, VoWiFi phones, etc.
• Ensure sufficient uplink capacity to APs. At a minimum,
Gigabit Ethernet ports should be wired to each 802.11ac AP
location and in some cases, two cables should be considered.
The capacity limitation of wireless today is typically in the
number of radios, not the uplinks, but 802.11ac can change
• Review backend infrastructure. Is your firewall, NAC, or other
inline network infrastructure capable of handling the faster
speeds of 802.11ac and the impact of BYOD? What about
your Internet connection? A review of the current installation
end-to-end is required for any upgrade.
While 802.11ac provides definite performance improvements
for Wi-Fi, implementation alone will not solve the gap between
wired and wireless networks. The industry continues to sell
traditional two-radio AP solutions, conceptually equal to a twoport
wired switch. These two-radio APs do not offer enough
capacity to provide wired-equivalent performance.
While 802.11ac improves performance, its throughput per user
will still be far below wired networks. A large percentage of
clients on today’s wireless networks (tablets and smartphones)
have RF limitations that will not allow them to support anywhere
close to the maximum data rates promised by 802.11ac. To
approach wired-equivalent performance per user, multi-radio
architectures must be adopted by the industry.
Xirrus is the leader in high performance wireless networking. The enterprise-grade Xirrus Wi-Fi Array enables wireless connectivity
for small businesses to the Fortune 500. Headquartered in Thousand Oaks, CA, Xirrus is a privately held company that designs and
manufactures its family of wireless products in the USA.
High Performance Wireless Networks
1.800.947.78.71 Toll Free in the US
2101 Corporate Center Drive
Thousand Oaks, CA 91320, USA
To learn more visit:
© 2012 Xirrus, Inc. All Rights Reserved. The Xirrus logo is a registered trademark of Xirrus, Inc.
All other trademarks are the property of their respective owners. Content subject to change without notice. SOLUTION BRIEF // 4