Building High-Performance Networks with 802.11ac - Xirrus

Building High-Performance Networks with 802.11ac - Xirrus


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.


1GigE Port




1Gbps Pipe

1.3Gbps Pipe





13Mbps Single

User Capacity

Single User

Multiple Users

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.

802.11ac Overview

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.

IEEE Standard


First Available



802.11n (Phase I)

July 2009 Mid 2013




Mid 2013


2007 2012 TBD

Max Data Rate 450Mbps 1.3Gbps 6.9Gbps


150Mbps 433Mbps 2.3Gbps


Channel Width


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

to 6.9Gbps.

• 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,

September 2012.


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

(1x2.4G, 1x5G)

User Bandwidth Dedicated Shared

Uplinks 4 GigE 1 GigE

Capacity Limiting



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.

Xirrus802.11ac 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

vital components:

• 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.



Wireless Array

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

5GHz spectrum.

802.11ac Deployment


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

this dynamic.

• 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.

About Xirrus

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

+1.805.262.1600 Sales

+1.805.262.1601 Fax

2101 Corporate Center Drive

Thousand Oaks, CA 91320, USA

To learn more visit: or


© 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

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