Zebra Workforce Connect: Voice Client Deploying VoWLAN Over Cisco Wireless Networks Best Practices Guide
DEPLOYING VOWLAN
OVER CISCO WIRELESS
NETWORKS
BEST PRACTICES GUIDE
DEPLOYING VOWLAN OVER CISCO WIRELESS
NETWORKS
BEST PRACTICES GUIDE
MN001146A02
Rev. A
May 2015
ii Deploying VOWLAN Over Cisco Wireless Networks Best Practices Guide
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Revision History
Changes to the original guide are listed below:
Change Date Description
-A01 Rev. A 12/2014 Initial release.
-A02 Rev. A 5/2015 Rebranding.
iii
iv Deploying VOWLAN Over Cisco Wireless Networks Best Practices Guide
TABLE OF CONTENTS
Revision History.............................................................................................................................. iii
About This Guide
Introduction..................................................................................................................................... vii
Chapter Descriptions ...................................................................................................................... vii
Notational Conventions................................................................................................................... vii
Related Documents ........................................................................................................................ viii
Service Information......................................................................................................................... viii
Chapter 1: Introduction
Coverage ....................................................................................................................................... 1-1
QoS ................................................................................................................................................ 1-3
Security .......................................................................................................................................... 1-4
General Wireless Network Best Practices ..................................................................................... 1-5
General Recommendations ..................................................................................................... 1-6
Other Recommendations ......................................................................................................... 1-6
Chapter 2: Cisco Lightweight Wireless – WLAN
WLAN ID .................................................................................................................................. 2-1
WLAN ID \ General .................................................................................................................. 2-1
WLAN ID \ Security .................................................................................................................. 2-2
WLAN ID \ Security \ AAA Servers .......................................................................................... 2-2
WLAN ID \ QOS ....................................................................................................................... 2-2
WLAN ID \ Advanced ............................................................................................................... 2-3
WLAN ID \ DHCP ..................................................................................................................... 2-3
WLAN ID \ Management Frame Protection .............................................................................. 2-4
WLAN ID \ DTIM Period (beacon intervals) ............................................................................. 2-4
WLAN ID \ Load Balancing and Band Select ........................................................................... 2-4
WLAN ID \ Off Channel Scanning Defer .................................................................................. 2-4
vi Deploying VOWLAN Over Cisco Wireless Networks Best Practices Guide
Chapter 3: Cisco Lightweight Wireless – Global 5 GHz
Network .................................................................................................................................... 3-1
Data Rates ............................................................................................................................... 3-2
CCX Location Measurement .................................................................................................... 3-2
RRM ......................................................................................................................................... 3-2
TPC .......................................................................................................................................... 3-3
DCA ......................................................................................................................................... 3-3
Coverage ................................................................................................................................. 3-4
General \ Profile Threshold for Traps ....................................................................................... 3-4
General \ Noise / Interference / Rogue Monitoring Channels .................................................. 3-4
General \ Monitor Intervals ....................................................................................................... 3-5
General \ Pico Cell ................................................................................................................... 3-5
General \ Client Roaming ......................................................................................................... 3-5
General \ Voice ........................................................................................................................ 3-5
General \ Video ........................................................................................................................ 3-6
General \ EDCA Parameters .................................................................................................... 3-6
General \ DFS (802.11h) .......................................................................................................... 3-7
General \ High Throughput ...................................................................................................... 3-7
Chapter 4: Cisco Lightweight Wireless – Global 2.4 GHz
Network .................................................................................................................................... 4-1
Data Rates ............................................................................................................................... 4-2
CCX Location Measurement .................................................................................................... 4-3
RRM ......................................................................................................................................... 4-3
TPC .......................................................................................................................................... 4-3
DCA ......................................................................................................................................... 4-3
Coverage ................................................................................................................................. 4-4
General \ Profile Threshold for Traps ....................................................................................... 4-4
General \ Noise / Interference / Rogue Monitoring Channels .................................................. 4-4
General \ Monitor Intervals ....................................................................................................... 4-5
General \ Pico Cell ................................................................................................................... 4-5
General \ Client Roaming ......................................................................................................... 4-5
General \ Voice ........................................................................................................................ 4-5
General \ Video ........................................................................................................................ 4-6
General \ EDCA Parameters .................................................................................................... 4-6
General \ High Throughput ...................................................................................................... 4-7
Chapter 5: Cisco Lightweight Wireless – QoS
QOS Profiles ............................................................................................................................ 5-1
Per-User Bandwidth Contracts ................................................................................................ 5-1
Per-SSID Bandwidth Contracts ................................................................................................ 5-2
WLAN QOS Parameters .......................................................................................................... 5-2
Wired QOS Protocol ................................................................................................................ 5-2
ABOUT THIS GUIDE
Introduction
This guide provides best practices when deploying VOWLAN over a Cisco® wireless network.
NOTE Screens and windows pictured in this guide are samples and can differ from actual screens.
Chapter Descriptions
Topics covered in this guide are as follows:
•
Chapter 1, Introduction provides information for deploying VOWLAN over a Cisco wireless network.
•
Chapter 2, Cisco Lightweight Wireless – WLAN provides information for setting up a Cisco Lightweight
wireless WLAN.
•
Chapter 3, Cisco Lightweight Wireless – Global 5 GHz provides information for setting up a Cisco
Lightweight wireless 5 GHz WLAN.
•
Chapter 4, Cisco Lightweight Wireless – Global 2.4 GHz provides information for setting up a Cisco
Lightweight wireless 2.4 GHz WLAN.
•
Chapter 5, Cisco Lightweight Wireless – QoS provides information for configuring Quality of Service.
Notational Conventions
The following conventions are used in this document:
•
Italics are used to highlight the following:
• Chapters and sections in this and related documents
• Icons on a screen.
viii Deploying VoWLAN Over Cisco Wireless networks Best Practices Guide
•
Bold text is used to highlight the following:
• Dialog box, window, and screen names
• Drop-down list and list box names
• Check box and radio button names
• Key names on a keypad
• Button names on a screen.
•
Bullets (•) indicate:
• Action items
• Lists of alternatives
• Lists of required steps that are not necessarily sequential
•
Sequential lists (e.g., those that describe step-by-step procedures) appear as numbered lists.
Related Documents
•
Cisco CUCM Administrator Configuration Guide, p/n MN001147Axx
•
Cisco CME Technical Guide, p/n MN001148Axx
For the latest version of this guide and all guides, go to: http://www.zebra.com/support.
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Serial number of the unit (found on manufacturing label)
•
Model number or product name (found on manufacturing label)
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CHAPTER 1 INTRODUCTION
Voice over Wireless LAN (VoWLAN) delivers the functionality of an enterprise telephone system in a wireless
handset. The handset is a wireless client device, and it shares the wireless network with laptops and other
hand-held devices. For enterprise use, the handset is functionally equivalent to a wired desk phone, giving
end-users all the features they are used to in a wired office telephone. The benefits of VoWLAN can result in
substantial cost savings, leveraging Wi-Fi infrastructure and eliminating recurring charges associated with the
use of cell phones, while significantly improving employee mobility.
There are two types of mobility, being mobile and 100%-connected mobility. To help explain this, think of the
marketing manager working on a presentation and saving it on a network share. He later wants to give that
presentation in the boardroom. If he picks up his laptop, closes the lid, and walks to the boardroom, opens the
laptop, connects to the wireless network, and gives his presentation - that is being mobile. His laptop may have
disconnected from the wireless network in between his office and the boardroom, but he never noticed. The
same manager starting a call on his VoWLAN handset while in his of fice, remaining on that call as he walked to
the elevator, traveled up several floors, and then walked to the boardroom – that is true mobility. If his V oWLAN
handset had disconnected during that call, he would have noticed.
True mobility and enterprise-grade VoWLAN requires wireless networks designed to provide the highest audio
quality throughout the facility. VoWLAN handsets require continuous, reliable connections as a user moves
throughout the coverage area. Voice applications have a low tolerance for network errors and delays,
deteriorating with just a few hundred milliseconds of delay or 1% of packet loss.
Coverage
Most data communication protocols provide a mechanism for retransmission of lost or corrupted packets, thus
delays caused by retransmissions are not discernable. The real-time nature of a telephone conversation
requires that voice packets be received correctly within 100ms of transmission. Lost or corrupted packets are
discarded after limited retries. In areas of inadequate wireless coverage, the audio quality of real-time voice
will suffer.
Moving handsets make the determination to roam in less than half the overlapping coverage area from a
neighboring access point. That Assessment Area must be large enough to allow the handset time to discover,
associate with, and connect to the next access point before the signal on the currently connected access point
becomes too weak. Understanding what impacts RF coverage, cell size, and overlap is essential to properly
design and configure a wireless network for voice usage.
The usable cell size of an access point is dictated by the frequency, signal power level, minimum data rate,
number of channels used, and objects that attenuate the signal. A properly designed wireless network
1 - 2 Deploying VoWLAN Over Cisco Wireless Networks Best Practices Guide
positions access points with sufficient overlapping coverage to ensure there are no coverage gaps between
them. 20% overlapping coverage between access points will result in seamless hand-offs and excellent voice
quality at the average walking speed of 3 mph. If the speed of the moving user is greater (golf cart, fork lift or
running/jogging), a larger overlap percentage may be necessary.
Dynamic Channel Assessment (DCA) is generally performed between the transmission of voice and control
packets to learn about neighboring access points. It takes approximately 250 ms to process each channel in
the channel list. To determine the size of access point Cell Overlap, determine the number of feet covered per
second for the average walking speed of 3mph:
•
5,280 feet per mile * 3mph = 15,840 feet per hour
•
15,840 feet per hour / 60 = 264 feet per minute
•
264 feet per minute / 60 = 4.4 feet per second
Then apply that distance to the duration of the DCA Cycle for each band/channel configuration. The
Assessment Area is approximately ¾ of the Coverage Overlap Area. Overlap Percentage is based on access
points located 60 feet apart.
The following table shows the results of those calculations for various channel configurations:
Band
2.4 GHz 3.00 250.00 0.75 3.30 4.40 7%
5 GHz 8.00 250.00 2.00 8.80 11.70 20%
5 GHz 12.00 250.00 3.00 13.20 17.60 29%
5 GHz 23.00 250.00 5.75 25.30 33.70 56%
Failure to complete the DCA cycle within the assessment area can lead to loss of connectivity, choppy audio,
or a dropped call. Give careful consideration to the number of channels deployed in 5 GHz for a VoWLAN
environment to avoid this.
There are unique requirements for the various types of WLAN implementations. A data-only implementation
does not require significant cell overlap as 802.11 clients typically step down their rate to accommodate the
transition to another access point. Typical thresholds for a data-only implementation are a Signal Strength of
-82 dBm and a Signal-to-Noise Ratio (SNR) of 10 dB.
The voice-data implementation generally requires a Signal Strength of -65 dBm, a Signal-to-Noise Ratio (SNR)
of 25 dB or better, and a Cell Overlap of 20%. The Cell Overlap ensures that a VoWLAN handset can detect
and connect to alternative access points before it reaches its current cell boundary . The Signal Strength target
of -65 dBm at the cell edge results in more access points running at lower power levels. A same channel
separation of 19 dB is necessary to diminish co-channel interference. In a voice-data implementation, a low
noise background is as important as high energy density. Transient conditions will make themselves more
evident in a voice-data implementation. The actual target minimum Signal Strength depends on the 802.11
frequency band it is operating in, modulation used, data rates enabled on the access point, and data rate used
by the handset at any particular time.
Number
Channels
Duration
(ms)
DCA Cycle
(seconds)
Assessment
Area
Coverage
Overlap
Overlap
percentage
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