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7925G Series
Deployment Manual
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Cisco 7925G Series Deployment Manual

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Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 1
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide
This guide provides information and guidance to help the network administrator deploy the Cisco Unified Wireless IP Phone 7925G Series successfully in a wireless LAN environment.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 2
Revision History
Date
Comments
10/13/2008
Initial Version
11/17/2009
1.3(3) Release
5/3/2010
1.3(4) Release
8/30/2010
1.3(4)SR2 Release and 7925G-EX
12/15/2010
1.4(1) Release
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 3
Contents
Requirements for the Cisco Unified Wireless IP Phone 7925G Series.................................................................................................6!
Site Survey...............................................................................................................................................................................................6!
RF Validation..........................................................................................................................................................................................6!
Call Control ............................................................................................................................................................................................7!
Supported Protocols................................................................................................................................................................................ 7!
Supported Access Points .........................................................................................................................................................................7!
Supported Antennas ................................................................................................................................................................................9!
Phone Models and Localization .............................................................................................................................................................10!
Phone Models........................................................................................................................................................................................ 10!
7925G-EX Certifications.......................................................................................................................................................................11!
Atmospheres Explosibles (ATEX) Zone 2/Class 22 Certification ...................................................................................................11!
Canadian Standards Association (CSA) Class I/Division II Certification........................................................................................11!
World Mode (802.11d)..........................................................................................................................................................................12!
Supported Countries..........................................................................................................................................................................12!
Language Support ................................................................................................................................................................................. 13!
Radio Characteristics..............................................................................................................................................................................13!
Bluetooth ..................................................................................................................................................................................................14!
Bluetooth Profiles..................................................................................................................................................................................14!
Coexistence (802.11b/g + Bluetooth) ...................................................................................................................................................15!
Wireless Security ..................................................................................................................................................................................... 15!
Extensible Authentication Protocol - Flexible Authentication via Secure Tunneling (EAP-FAST) .....................................................16!
Extensible Authentication Protocol – Transport Layer Security (EAP-TLS) .......................................................................................17!
Protected Extensible Authentication Protocol (PEAP).........................................................................................................................19!
Cisco Centralized Key Management (CCKM)...................................................................................................................................... 20!
EAP and User Database Compatibility ................................................................................................................................................21!
Voice Security ..........................................................................................................................................................................................21!
Power Management.................................................................................................................................................................................22!
Protocols ...............................................................................................................................................................................................23!
Unscheduled Auto Power Save Delivery (U-APSD)........................................................................................................................23!
Power Save Poll (PS-POLL).............................................................................................................................................................23!
Active Mode......................................................................................................................................................................................23!
Delivery Traffic Indicator Message (DTIM).........................................................................................................................................23!
Scan Modes ...........................................................................................................................................................................................24!
Quality of Service (QoS) .........................................................................................................................................................................24!
Configuring QoS in Cisco Unified Communications Manager ............................................................................................................24!
Configuring QoS Policies for the Network ...........................................................................................................................................25!
Configuring Cisco IOS Access Points..............................................................................................................................................25!
Configuring Cisco Switch Ports........................................................................................................................................................25!
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 4
Configuring Switch Ports for Wired IP Phones ................................................................................................................................26!
Sample Voice Packet Capture...........................................................................................................................................................27!
Call Admission Control......................................................................................................................................................................... 27!
Pre-Call Admission Control..............................................................................................................................................................28!
Roaming Admission Control ............................................................................................................................................................29!
Traffic Classification (TCLAS) .............................................................................................................................................................29!
Roaming ...................................................................................................................................................................................................30!
Interband Roaming................................................................................................................................................................................ 30!
Channel Parking................................................................................................................................................................................30!
Multicast...................................................................................................................................................................................................31!
Designing the Wireless LAN for Voice..................................................................................................................................................31!
Planning Channel Usage ......................................................................................................................................................................31!
5 GHz (802.11a)................................................................................................................................................................................32!
Using Dynamic Frequency Selection (DFS) on Access Points....................................................................................................32!
2.4 GHz (802.11b/g) .........................................................................................................................................................................33!
Signal Strength and Coverage...........................................................................................................................................................34!
Configuring Data Rates ........................................................................................................................................................................37!
Call Capacity ........................................................................................................................................................................................37!
Dynamic Transmit Power Control (DTPC) .......................................................................................................................................... 38!
Multipath...............................................................................................................................................................................................39!
Verification with Site Survey Tools.......................................................................................................................................................40!
Cisco 792xG Neighbor List ..............................................................................................................................................................40!
Cisco 792xG Site Survey .................................................................................................................................................................. 40!
Configuring Cisco Unified Communications Manager .......................................................................................................................43!
Phone Button Templates .......................................................................................................................................................................43!
Softkey Templates.................................................................................................................................................................................. 43!
Security Profiles....................................................................................................................................................................................44!
G.722 Advertisement .............................................................................................................................................................................45!
Product Specific Configuration Options............................................................................................................................................... 45!
Configuring the Cisco Unified Wireless LAN Controller and Access Points .................................................................................... 50!
SSID / WLAN Settings ...........................................................................................................................................................................51!
Controller Settings ................................................................................................................................................................................ 53!
802.11 Network Settings........................................................................................................................................................................55!
Auto RF.............................................................................................................................................................................................56!
EDCA Parameters.............................................................................................................................................................................59!
DFS (802.11h)...................................................................................................................................................................................59!
Call Admission Control Settings...........................................................................................................................................................60!
Configuring QoS Basic Service Set (QBSS)..........................................................................................................................................63!
Configuring Auto-Immune ....................................................................................................................................................................64!
Configuring the WLAN Controller EAP-Request and EAPOL-Key Timeouts......................................................................................65!
Configuring Proxy ARP ........................................................................................................................................................................66!
Configuring TKIP Countermeasure Holdoff Time................................................................................................................................66!
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 5
VLANs and Autonomous Access Points ................................................................................................................................................67!
Configuring the Cisco Unified Wireless IP Phone 7925G Series ........................................................................................................67!
Configuring the Network Profile Parameters.......................................................................................................................................68!
Installing Certificates............................................................................................................................................................................72!
Using Templates to Configure Phones..................................................................................................................................................78!
Bluetooth Configuration........................................................................................................................................................................78!
Upgrading Phone Firmware.................................................................................................................................................................79!
Wavelink Avalanche..............................................................................................................................................................................80!
Using the Bulk Deployment Utility .......................................................................................................................................................87!
Default Export...................................................................................................................................................................................90!
Bulk Export.......................................................................................................................................................................................90!
Pushing Configuration Files to the Cisco 792xG..............................................................................................................................91!
Configuring the Local Phone Book and Speed Dials............................................................................................................................91!
Increased Font ......................................................................................................................................................................................93!
Using Phone Designer ..........................................................................................................................................................................94!
IP Phone Services ....................................................................................................................................................................................96!
Extensible Markup Language (XML)....................................................................................................................................................96!
Java Mobile Information Device Profile (MIDP).................................................................................................................................97!
Troubleshooting.......................................................................................................................................................................................97!
Stream Statistics....................................................................................................................................................................................97!
Network Statistics..................................................................................................................................................................................99!
Wireless LAN Statistics .......................................................................................................................................................................101!
Traffic Stream Metrics (TSM).............................................................................................................................................................101!
Phone Logs.......................................................................................................................................................................................... 102!
Trace Modules.................................................................................................................................................................................103!
Trace Levels.................................................................................................................................................................................... 104!
Radio Status Indicator.........................................................................................................................................................................104!
Hardware Diagnostics ........................................................................................................................................................................105!
Firmware Recovery.............................................................................................................................................................................105!
Restoring Factory Defaults ................................................................................................................................................................. 106!
Capturing a Screenshot of the Phone Display .................................................................................................................................... 106!
Healthcare Environments.....................................................................................................................................................................106!
Cleaning the Phone................................................................................................................................................................................107!
Phone Accessories..................................................................................................................................................................................107!
Additional Documentation....................................................................................................................................................................109!
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 6
Requirements for the Cisco Unified Wireless IP Phone 7925G Series
The Cisco Unified Wireless IP Phone 7925G Series are IEEE 802.11a/b/g wireless IP phones that provide voice communications.
The wireless LAN must be validated to ensure it meets the requirements to deploy the Cisco Unified Wireless IP Phone 7925G Series.
Site Survey
Before deploying the Cisco Unified Wireless IP Phone 7925G Series into a production environment, a site survey must be completed by a Cisco certified partner with the advanced wireless LAN specialization. During the site survey the RF spectrum can be analyzed to determine which channels are usable in the desired band (2.4 GHz or 5 GHz). Typically there is less interference in the 5 GHz band as well as more non-overlapping channels, so 5 GHz is the preferred band for operation and even more highly recommended when the Cisco Unified Wireless IP Phone 7925G or 7925G Series is to be used in a mission critical environment. The site survey will include heatmaps showing the intended coverage plan for the location. The site survey will also determine which access point platform type, antenna type, access point configuration (channel and transmit power) to use at the location. See the “Designing the Wireless LAN for Voice” section for more information.
Refer to the Steps to Success website for additional information.
http://www.cisco.com/go/stepstosuccess
RF Validation
In order to determine if VoWLAN can be deployed, the environment must be evaluated to ensure the following items meet Cisco guidelines.
Signal
The cell edge should be designed to -67 dBm where there is a 20-30% overlap of adjacent access points at that signal level.
This ensures the 7925G Series phone always has adequate signal and can hold a signal for at least 5 seconds in order to roam seamlessly.
Channel Utilization
Channel Utilization levels should be kept under 50%.
If using the 7925G Series phone, this is provided via the QoS Basic Service Set (QBSS), which equates to around 105.
Noise
Noise levels should not exceed -92 dBm, which allows for a Signal to Noise Ratio (SNR) of 25 dB where a -67 dBm signal should be maintained.
Packet Loss / Delay
Per voice guidelines, packet loss should not exceed 1% packet loss, otherwise voice quality can be degraded significantly.
Jitter should be kept at a minimal (< 100 ms)
Retries
802.11 retransmissions should be less than 20%.
Multipath
Multipath should be kept to a minimal as this can create nulls and reduce signal levels.
Many different tools and applications can be used to evaluate these items in order to certify the deployment.
Cisco Spectrum Expert
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 7
AirMagnet (Survey, WiFi Analyzer, VoFi Analyzer, Spectrum Analyzer)
Cisco Wireless Control System (WCS) for Unified Wireless LAN management
Call Control
For call control, the Cisco Unified Wireless IP Phone 7925G Series supports only Skinny Client Control Protocol (SCCP) on the following applications:
• Cisco Unified Communications Manager 4.3, 5.1, 6.0, 6.1, 7.0, 7.1, 8.0 and later
• Cisco Unified Communications Manager Express 4.3 and later (Minimum of 12.4(15)T7)
• SRST 4.3 and later (Minimum of 12.4(15)T7)
Device Support in Cisco Unified Communications Manager
Cisco Unified Communications Manager requires a device package to be installed or service release update in order to enable Cisco Unified Wireless IP Phone 7925G Series device support.
Cisco Unified Communications Manager 5.1 or higher requires signed COP files.
Device packages for Cisco Unified Communications Manager are available at the following location.
http://www.cisco.com/kobayashi/sw-center/sw-voice.shtml
Supported Protocols
Supported voice and wireless LAN protocols include these:
• Real Time Protocol (RTP)
• G.711u-law, G.711a-law, G.729a, G.729ab, G.722, iLBC
• Real Time Control Protocol (RTCP)
• Cisco Discovery Protocol (CDP)
• Syslog
• CCX v4
• Wi-Fi MultiMedia (WMM)
• Traffic Specification (TSPEC)
• Traffic Classification (TCLAS)
• Unscheduled Auto Power Save Delivery (U-APSD)
• Power Save Poll (PS-POLL)
Supported Access Points
The Cisco Unified Wireless IP Phone 7925G Series are supported on both the Cisco Unified and Autonomous solutions.
• Cisco Unified Wireless LAN Controller
Minimum = 5.2.193.0
Recommended = 7.0.98.0 or later
• Cisco IOS Access Points (Autonomous)
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 8
Minimum = 12.3(8)JEA2 or later
Recommended = 12.4(10b)JA3 or later (does not apply to 1100, 1200, 1230)
Note: VoWLAN is not currently supported in conjunction with outdoor MESH technology (1500 series).
3rd party access points are not supported, as there is no interoperability testing performed against 3rd party access points.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 9
The table below lists the modes that are supported by each Cisco access point.
Cisco AP Series
802.11a
802.11b
802.11g
802.11n
Autonomous
Unified
500
No
Yes
Yes
No
Yes
Yes
1100
No
Yes
Optional
No
Yes
Yes
1130AG
Yes
Yes
Yes
No
Yes
Yes
1140
Yes
Yes
Yes
Yes
Yes
Yes
1200
Optional
Yes
Optional
No
Yes
Yes
1230AG
Yes
Yes
Yes
No
Yes
Yes
1240AG
Yes
Yes
Yes
No
Yes
Yes
1250
Yes
Yes
Yes
Yes
Yes
Yes
1260
Yes
Yes
Yes
Yes
No
Yes
3500
Yes
Yes
Yes
Yes
No
Yes
Supported Antennas
Some of the Cisco Access Points require external antennas.
Please refer to the following URL for the list of supported antennas and how these external antennas should be mounted.
http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 10
3rd party antennas are not supported, as there is no interoperability testing performed against 3rd party antennas including Distributed Antenna Systems (DAS) and Leaky Coaxial Systems.
Please refer to the following URL for more info on Cisco Wireless LAN over Distributed Antenna Systems.
http://www.cisco.com/en/US/prod/collateral/wireless/ps5678/ps6973/positioning_statement_c07-565470.html
Note: The Cisco 1130, 1140 and 3502i series access points are to be mounted on the ceiling as they have omni-directional antennas.
Phone Models and Localization
Phone Models
Cisco manufactures four Cisco Unified Wireless IP Phone 7925G models and one Cisco Unified Wireless IP Phone 7925G-EX model.
The regulatory domain can be identified by navigating to Settings > Model Information > WLAN Regulatory Domain and then referencing the Regulatory Domain number in the table below.
The Cisco Unified Wireless IP Phone 7925G-EX is configured like the Cisco Unified Wireless IP Phone 7925G –W model, which requires an 802.11d enabled access point.
Use the following tables to identify specific phone versions that support these regulatory domains for use around the world:
7925G
Part Number
Regulatory Domain
Regulatory Domain Number
Band Range
Available Channels
Channel Set
CP-7925G-A-K9
FCC (Americas)
1050
2.412 – 2.462 GHz
5.180 – 5.240 GHz
5.260 – 5.320 GHz
5. 500 – 5.700 GHz
5.745 – 5.805 GHz
11
4
4
8
4
1-11
36,40,44,48
52,56,60,64
100-140
149,153,157,161
CP-7925G-E-K9
ETSI (Europe)
3051
2.412 – 2.472 GHz
5.180 – 5.700 GHz
13
19
1-13
36-48,52-64,100-140
CP-7925G-P-K9
Japan
4157
2.412 – 2.472 GHz
2.412 – 2.484 GHz
5.180 – 5.700 GHz
13 (OFDM)
14 (CCK)
19
1-13
1-14
36-48,52-64,100-140
CP-7925G-W-K9
Rest of World
5252
Uses 802.11d to identify available channels and transmit powers
7925G-EX
Part Number
Regulatory
Band Range
Available
Channel Set
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 11
Domain Number
Channels
CP-7925G-EX-K9
5252
2.412 – 2.484 GHz
5.180 – 5.240 GHz
5.260 – 5.320 GHz
5. 500 – 5.700 GHz
5.745 – 5.805 GHz
14
4
4
11
4
1-14
36,40,44,48
52,56,60,64
100-140
149,153,157,161
Note: 802.11j (channels 34, 38, 42, 46) and channel 165 are not supported.
7925G-EX Certifications
The Cisco Unified Wireless IP Phone 7925G-EX has both Atmoshpheres Explosibles (ATEX) Zone 2/Class 22 and Canadian Standards Association (CSA) Class1/Division II certifications in order to allow it to be used in hazardous and explosive environments.
Atmospheres Explosibles (ATEX) Zone 2/Class 22 Certification
Organizations in the European Union must follow the ATEX directives to protect employees from explosion risk in areas with an explosive atmosphere.
• ATEX 95 equipment directive 94/9/EC
Equipment and protective systems intended for use in potentially explosive atmospheres.
• ATEX 137 workplace directive 99/92/EC
Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres.
Areas classified into zones (0, 1, 2 for gas-vapor-mist and 20, 21, 22 for dust) must be protected from effective sources of ignition. Equipment and protective systems intended to be used in zoned areas must meet the requirements of the directive. Zone 0 and 20 require Category 1 marked equipment, zone 1 and 21 required Category 2 marked equipment and zone 2 and 22 required Category 3 marked equipment. Zone 0 and 20 are the zones with the highest risk of an explosive atmosphere being present.
Certification ensures that the equipment is fit for its intended purpose and that adequate information is supplied with it to ensure that it can be used safely.
Canadian Standards Association (CSA) Class I/Division II Certification
Laws and regulations in most municipalities, states, and provinces in North America require certain products to be tested to a specific standard or group of standards when they are to be deemed intrinsically safe when used in an explosive environment.
In North America, hazardous locations have traditionally been defined by the following combination of Class and Division:
• Class I - A location where a quantity of flammable gas or vapor, sufficient to produce an explosive or ignitable
mixture, may be present in the air.
• Class II - A location made hazardous by the presence of combustible or electrically conductive dust, including Groups
E (metal dust), F (coal dust) and G (grain dust).
• Class III - A location made hazardous by the presence of easily ignitable fibers in the air, but not likely in sufficient
quantities to produce ignitable mixtures.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 12
• Division 1 - A location where a classified hazard is likely to exist.
• Division 2 - A location where a classified hazard does not normally exist but is possible under abnormal conditions.
Internationally (and more recently in North America, for Class I hazardous locations), areas where explosive gas atmospheres are likely to be present are divided into three IEC-defined Zones:
• Zone 0 - An area in which an explosive gas atmosphere is continuously present or present for long periods.
• Zone 1 - An area in which an explosive gas atmosphere is likely to occur in normal operation.
• Zone 2 - An area in which an explosive gas atmosphere does not normally exist.
World Mode (802.11d)
If using the Cisco Unified Wireless IP Phone 7925G World (-W) model, the Cisco Unified Wireless IP Phone 7925G-EX model, then it is required to enable 802.11d. The Cisco Unified Wireless IP Phone 7925G Series gives precedence to 802.11d to determine the channels and transmit powers to use and inherits its client configuration from the associated access point.
Enable World Mode (802.11d) for the corresponding country where the access point is located.
If 802.11d information is not available from the access point, then the Cisco Unified Wireless IP Phone 7925G (-A, -E, -P) model uses the locally configured regulatory domain. If the Cisco Unified Wireless IP Phone 7925G Series -A, -E or -P model is taken to another country, where the access point uses a different regulatory domain, then 802.11d will be required for the Cisco Unified Wireless IP Phone 7925G Series to operate successfully.
When using 802.11a, enable 802.11d to discover which channels can potentially be used in the network. Specifically, for
802.11h support, the phone passively scans some of the 5 GHz channels (DFS) first before actively scanning any network channels.
If using 2.4 GHz (802.11b/g) and 802.11d is not enabled, then the Cisco Unified IP Phone 7925G Series can attempt to use channels 1-11 and reduced transmit power.
Note: World Mode is enabled automatically for the Cisco Unified Wireless LAN Controller.
World Mode must be enabled manually for Cisco Autonomous Access Points using the following commands:
Interface dot11radio X
world-mode dot11d country US both
Supported Countries
Below are the countries and their 802.11d codes that are supported by the Cisco Unified Wireless IP Phone 7925G Series.
Argentina (AR)
India (IN)
Poland (PL)
Australia (AU)
Indonesia (ID)
Portugal (PT)
Austria (AT)
Ireland (IE)
Puerto Rico (PR)
Belgium (BE)
Israel (IL)
Romania (RO)
Brazil (BR)
Italy (IT)
Russian Federation (RU)
Bulgaria (BG)
Japan (JP)
Saudi Arabia (SA)
Canada (CA)
Korea (KR / KP)
Singapore (SG)
Chile (CL)
Latvia (LV)
Slovakia (SK)
Colombia (CO)
Liechtenstein (LI)
Slovenia (SI)
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 13
Costa Rica (CR)
Lithuania (LT)
South Africa (ZA)
Cyprus (CY)
Luxembourg (LU)
Spain (ES)
Czech Republic (CZ)
Malaysia (MY)
Sweden (SE)
Denmark (DK)
Malta (MT)
Switzerland (CH)
Estonia (EE)
Mexico (MX)
Taiwan (TW)
Finland (FI)
Monaco (MC)
Thailand (TH)
France (FR)
Netherlands (NL)
Turkey (TR)
Germany (DE)
New Zealand (NZ)
Ukraine (UA)
Gibraltar (GI)
Norway (NO)
United Arab Emirates (AE)
Greece (GR)
Oman (OM)
United Kingdom (GB)
Hong Kong (HK)
Panama (PA)
United States (US
Hungary (HU) Iceland (IS)
Peru (PE) Phillipines (PH)
Venezuela (VE) Vietnam (VN)
Note: Compliance information is available on the Cisco Product Approval Status web site at the following URL:
http://tools.cisco.com/cse/prdapp/jsp/externalsearch.do?action=externalsearch&page=EXTERNAL_SEARCH
Language Support
The Cisco Unified Wireless IP Phone 7925G Series currently supports the following languages.
Bulgarian
English
Japanese
Serbian
Catalan
Finnish
Korean
Slovak
Chinese
French
Norwegian
Slovenian
Croatian
German
Polish
Spanish
Czech
Greek
Portuguese
Swedish
Danish
Hungarian
Romanian
Dutch
Italian
Russian
The corresponding locale package must be installed to enable support for that language. English is the default language on the phone.
Download the locale packages from the Localization page at the following URL:
http://www.cisco.com/kobayashi/sw-center/telephony/callmgr/locale-installer.shtml
Radio Characteristics
The following table lists the data rates, ranges, and receiver sensitivity info for Cisco Unified Wireless IP Phone 7925G Series.
802.11a
Data Rate
Range
Receiver Sensitivity
Max Tx Power is 16 dBm
6 Mbps
604 ft (184 m)
-91 dBm
9 Mbps
604 ft (184 m)
-90 dBm
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 14
12 Mbps
551 ft (168 m)
-88 dBm
18 Mbps
545 ft (166 m)
-86 dBm
24 Mbps
512 ft (156 m)
-82 dBm
36 Mbps
420 ft (128 m)
-80 dBm
48 Mbps
322 ft (98 m)
-77 dBm
54 Mbps
289 ft (88 m)
-75 dBm
802.11g
Data Rate
Range
Receiver Sensitivity
Max Tx Power is 16 dBm
6 Mbps
709 ft (216 m)
-91 dBm
9 Mbps
650 ft (198 m)
-90 dBm
12 Mbps
623 ft (190 m)
-87 dBm
18 Mbps
623 ft (190 m)
-86 dBm
24 Mbps
623 ft (190 m)
-82 dBm
36 Mbps
495 ft (151 m)
-80 dBm
48 Mbps
413 ft (126 m)
-77 dBm
54 Mbps
394 ft (120 m)
-76 dBm
802.11b
Data Rate
Range
Receiver Sensitivity
Max Tx Power is 17 dBm
1 Mbps
1,010 ft (308 m)
-96 dBm
2 Mbps
951 ft (290 m)
-85 dBm
5.5 Mbps
919 ft (280 m)
-90 dBm
11 Mbps
902 ft (275 m)
-87 dBm
Note: Receiver sensitivity is the minimum signal needed to decode a packet at a certain data rate.
See the “Designing the Wireless LAN for Voice” section for more information on signal requirements.
Bluetooth
The Cisco Unified Wireless IP Phone 7925G Series supports Bluetooth Class 2 technology allowing for wireless headset communications.
Bluetooth enables low bandwidth wireless connections within a range of 30 feet, however it is recommended to keep the Bluetooth device within 10 feet of the phone.
Up to five headsets can be connected, but only the last one connected is used as the default.
The Bluetooth device does not need to be within direct line-of-sight of the phone, but barriers, such as walls, doors, etc. can potentially impact the quality.
Bluetooth utilizes the 2.4 GHz frequency just like 802.11b/g and many other devices (i.e. microwave ovens, cordless phones, etc.), so the Bluetooth quality can potentially be interfered with due to using this unlicensed frequency.
Bluetooth Profiles
The Cisco Unified Wireless IP Phone 7925G Series supports both the Bluetooth Headset and Handsfree Profiles.
With a Bluetooth Headset Profile capable headset, the following call functions can be performed.
-Ring
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 15
-Answer a call
-End a call
-Volume Control
With Bluetooth Handsfree Profile (HFP) support, the following features can also be available if supported by the Bluetooth headset.
-Last Number Redial
-Call Waiting
-Divert / Reject
-3 way calling (Hold & Accept and Release & Accept)
For more information, refer to the documentation from the Bluetooth headset manufacturer.
Coexistence (802.11b/g + Bluetooth)
If using Coexistence where 802.11b/g and Bluetooth are used simultaneously, then there are some limitations and deployment requirements to be considered as they both utilize the 2.4 GHz frequency.
Capacity
When using Coexistence (802.11b/g + Bluetooth), call capacity is reduced due to the utilization of CTS to protect the 802.11g and Bluetooth transmissions.
Multicast Audio
Multicast audio from Push To Talk (PTT), Music on Hold (MMOH) and other applications are not supported when using Coexistence.
Data Rate Configuration
It is recommended to only enable 802.11g (OFDM) data rates (i.e. > 12 Mbps) to prevent from engaging in CTS for 802.11g protection when using Coexistence, which can impact voice quality.
Note: It is highly recommended to use 802.11a if using Bluetooth due to 802.11b/g and Bluetooth both utilizing 2.4 GHz, but also due to the above limitations.
Wireless Security
When deploying a wireless LAN, security is essential.
The Cisco Unified Wireless IP Phone 7925G Series supports the following wireless security features.
Authentication
• WPA (802.1x authentication + TKIP encryption)
• WPA2 (802.1x authentication + AES encryption)
• WPA-PSK (Pre-Shared key + TKIP encryption)
• WPA2-PSK (Pre-Shared key + AES encryption)
• EAP-FAST (Extensible Authentication Protocol – Flexible Authentication via Secure Tunneling)
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 16
• EAP-TLS (Extensible Authentication Protocol – Transport Layer Security)
• PEAP (Protected Extensible Authentication Protocol)
• LEAP (Lightweight Extensible Authentication Protocol)
• CCKM (Cisco Centralized Key Management)
• Open and Shared Key
Encryption
• AES (Advanced Encryption Scheme)
• TKIP / MIC (Temporal Key Integrity Protocol / Message Integrity Check)
• WEP (40-bit and 128-bit Wired Equivalent Protocol)
Extensible Authentication Protocol - Flexible Authentication via Secure Tunneling (EAP-FAST)
This client server security architecture encrypts EAP transactions within a Transport Level Security (TLS) tunnel between the access point and the Remote Authentication Dial-in User Service (RADIUS) server such as the Cisco Access Control Server (ACS).
The TLS tunnel uses Protected Access Credentials (PACs) for authentication between the client (phone) and the RADIUS server. The server sends an Authority ID (AID) to the client (phone), which in turn selects the appropriate PAC. The client (phone) returns a PAC-Opaque to the RADIUS server. The server decrypts the PAC with its master-key. Both endpoints now have the PAC key and a TLS tunnel is created. EAP-FAST supports automatic PAC provisioning, but it must enable don the RADIUS server.
To enable EAP-FAST, a certificate must be installed.
The Cisco Unified Wireless IP Phone 7925G Series currently supports only automatic provisioning of the PAC, so enable “Allow anonymous in-band PAC provisioning” on the RADIUS server as shown below.
Both EAP-GTC and EAP-MSCHAPv2 must be enabled when “Allow anonymous in-band PAC provisioning” is enabled.
EAP-FAST requires that a user account be created on the authentication server.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 17
If anonymous PAC provisioning is not allowed in the product wireless LAN environment then a staging Cisco ACS can be setup for initial PAC provisioning of the Cisco Unified Wireless IP Phone 7925G Series.
This requires that the staging ACS server be setup as a slave EAP-FAST server and components are replicated from the product master EAP-FAST server, which include user and group database and EAP-FAST master key and policy info.
Ensure the production master EAP-FAST ACS server is setup to send the EAP-FAST master keys and policies to the staging slave EAP-FAST ACS server, which will then allow the Cisco Unified Wireless IP Phone 7925G Series to use the provisioned PAC in the production environment where “Allow anonymous in-band PAC provisioning” is disabled.
When it is time to renew the PAC, then authenticated in-band PAC provisioning will be used, so ensure that “Allow authenticated in-band PAC provisioning” is enabled.
Ensure that the Cisco Unified Wireless IP Phone 7925G Series has connected to the network during the grace period to ensure it can use its existing PAC created either using the active or retired master key in order to get issued a new PAC.
Is recommended to only have the staging wireless LAN pointed to the staging ACS server and to disable the staging access point radios when not being used.
Extensible Authentication Protocol – Transport Layer Security (EAP-TLS)
Extensible Authentication Protocol Transport Layer Security (EAP-TLS) is using the TLS protocol with PKI to secure communications to the authentication server.
TLS provides a way to use certificates for both user and server authentication and for dynamic session key generation.
Either the internal Manufacturing Installed Certificate (MIC) or a user installed certificate can be used for authentication.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 18
EAP-TLS provides excellent security, but requires client certificate management.
Ensure that “Certificate CN Comparison” is selected when enabling EAP-TLS.
EAP-TLS also requires that a user account be created on the authentication server matching the common name of the certificate imported into the Cisco Unified Wireless IP Phone 7925G Series.
It is recommended to use a complex password for this user account.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 19
See the “Installing Certificates” section for more information.
Protected Extensible Authentication Protocol (PEAP)
Protected Extensible Authentication Protocol (PEAP) uses server-side public key certificates to authenticate clients by creating an encrypted SSL/TLS tunnel between the client and the authentication server.
The ensuing exchange of authentication information is then encrypted and user credentials are safe from eavesdropping.
MS-CHAP v2 is the current supported inner authentication protocol (GTC is not supported).
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 20
PEAP (MS-CHAPv2) requires that a user account be created on the authentication server.
The authentication server can be validated via importing a certificate into the Cisco Unified Wireless IP Phone 7925G Series.
See the “Installing Certificates” section for more information.
Cisco Centralized Key Management (CCKM)
When using 802.1x type authentication, it is recommended to implement CCKM to enable fast roaming. 802.1x can introduce delay during roaming due to its requirement for full re-authentication. CCKM centralizes the key management and reduces the number of key exchanges. WPA and WPA2 introduce additional transient keys and can lengthen roaming time.
When CCKM is utilized, roaming times can be reduced from 400-500 ms to less than 100 ms, where that transition time from one access point to another will not be audible to the user.
As of the 1.3(4) release, the Cisco Unified Wireless IP Phone 7925G Series supports CCKM with WPA2 (AES or TKIP), WPA (TKIP or AES) and 802.1x (WEP) authentication.
Authentication
Key Management
Encryption
EAP-FAST
802.1x, WPA, WPA2
AES, TKIP, WEP (40 or 128 bit)
EAP-TLS
802.1x, WPA, WPA2
AES, TKIP, WEP (40 or 128 bit)
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 21
PEAP
802.1x, WPA, WPA2
AES, TKIP, WEP (40 or 128 bit)
LEAP
802.1x, WPA, WPA2
AES, TKIP, WEP (40 or 128 bit)
AKM
802.1x, WPA, WPA2
AES, TKIP, WEP (40 or 128 bit)
CCKM was not supported with WPA2 in release 1.3(3) or earlier.
WPA Version
Cipher
Prior to 1.3(4)
1.3(4) and later
TKIP
Supported
Supported
WPA
AES
Not Supported
Supported
TKIP
Not Supported
Supported
WPA2
AES
Not supported
Supported
EAP and User Database Compatibility
The following chart indicates which EAP and database configurations are supported by the Cisco Unified Wireless IP Phone 7925G Series.
Database
LEAP
EAP-TLS
PEAP
(MS-CHAPv2)
EAP-FAST
(Phase Zero)
ACS
Yes
Yes
Yes
Yes
Windows SAM
Yes
No
Yes
Yes
Windows AD
Yes
Yes
Yes
Yes
LDAP
No
Yes
No
No
ODBC (ACS for Windows only)
Yes
Yes
Yes
Yes
LEAP Proxy RADIUS Server
Yes
No
Yes
Yes
All Token Servers
No
No
No
No
Voice Security
The Cisco Unified Wireless IP Phone 7925G Series supports the following voice security features.
• Certificates
• Image authentication
• Device authentication
• File authentication
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 22
• Signaling authentication
• Secure Cisco Unified SRST
• Media encryption (SRTP)
• Signaling encryption (TLS)
• Certificate authority proxy function (CAPF)
• Secure profiles
• Encrypted configuration files
• Settings Access (can limit user access to configuration menus)
• Locked network profiles
• Administrator password
Power Management
The Cisco Unified Wireless IP Phone 7925G Series has an option for a standard or extended battery.
The standard battery can provide up to 180 hours standby time or up to 9.5 hours talk time.
The extended battery can provide up to 240 hours standby time or up to 13 hours talk time.
When the access point supports the Cisco Client Extensions (CCX) proxy ARP information element, the idle battery life will be optimized.
When on call U-APSD, PS-POLL, or active mode can be utilized depending on the Cisco Unified Wireless IP Phone 7925G Series and Access Point configuration.
To extend on call battery life, the Cisco Unified Wireless IP Phone 7925G Series can use U-APSD or PS-POLL power save methods.
The Cisco Unified Wireless IP Phone 7925G Series will use either U-APSD or PS-POLL when in idle (no active phone call).
There can be up to 40-50% reduction of battery life when on call and using Coexistence (802.11b/g + Bluetooth).
The table below lists the maximum on call and idle times for each 802.11 mode and battery type.
802.11 Mode
Call State
Standard
Battery
Extended
Battery
2.4 GHz
On Call
9.5
13
On Call + Bluetooth
5.5
7
Idle
180
240
Idle + Bluetooth Enabled
165
200
5 GHz
On Call
9
11
On Call + Bluetooth
7
10
Idle
180
240
Idle + Bluetooth Enabled
165
200
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 23
If the access point does not support CCX or proxy ARP is not enabled, then the idle battery life will be up to fifty percent less. See the “Configuring Proxy ARP” section for more information.
Protocols
Unscheduled Auto Power Save Delivery (U-APSD)
The Cisco Unified Wireless IP Phone 7925G Series will use U-APSD (Unscheduled Auto Power Save Delivery) for power save when in idle mode or when a phone call is active if WMM is enabled, where U-APSD is supported.
U-APSD helps optimize battery life.
Below is a sample packet sequence when using U-APSD.
Power Save Poll (PS-POLL)
If Wi-Fi MultiMedia (WMM) is disabled, which will disable U-APSD support, or U-APSD support is not available on the access point, then the Cisco Unified Wireless IP Phone 7925G Series will use PS-POLL for power save when in idle mode and when a phone call is active.
Below is a sample packet sequence when using PS-POLL.
Active Mode
If the “Call Power Save Mode” is set to “None”, then the phone will use active mode and no power save will be used, which will reduce the battery life.
Delivery Traffic Indicator Message (DTIM)
Increasing the DTIM period can also increase the battery life. The Cisco Unified Wireless IP Phone 7925G Series can use the DTIM period to schedule wakeup periods to check for broadcast and multicast packets as well as any unicast packets.
For optimal battery life and performance, we recommend setting the DTIM period to “2” with a beacon period of “100 ms”.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 24
The DTIM period is a tradeoff between battery life and multicast performance.
Broadcast and multicast traffic will be queued until the DTIM period when there are power save enabled clients associated to the access point, so DTIM will determine how quickly these packets can be delivered to the client. If using multicast applications, a shorter DTIM period can be used.
Scan Modes
When using only one access point, select Single Access Point Mode on the phone to reduce scanning and optimize battery life for phones that do not roam.
When using multiple access points where roaming is required, “Single AP Mode” should not be enabled. Instead use the auto (default) or continuous scan mode, which will allow for seamless roaming.
Continuous scan mode can be optionally enabled to allow for better location tracking.
Quality of Service (QoS)
Quality of Service enables queuing to ensure high priority for voice traffic. To implement appropriate queuing for voice traffic, use the following suggestions:
• Ensure that WMM is enabled on the access point.
• Create a QoS policy on the access point giving priority to voice (RTP) and call control (SCCP) traffic and apply that
profile to the desired interfaces.
Traffic Type
DSCP
802.1p
WMM UP
Voice (RTP)
EF (46)
5
6
Call Control (SCCP)
CS3 (24)
3
4
• Be sure that RTP packets have the proper QoS markings and other protocols are not using the same QoS markings.
• Select the “Platinum” QoS profile for the voice wireless LAN when using Cisco Unified Wireless LAN Controller
technology and set the 802.1p tag to “6”.
• Enable Differentiated Services Code Point (DSCP) preservation on the Cisco IOS switch and/or use a QoS policy to set
DSCP to EF for RTP traffic (UDP port range 16384-32767) on the Cisco IOS router.
For more information about TCP and UDP ports used by the Cisco Unified Wireless IP Phone 7925G Series and the Cisco Unified Communications Manager, refer to the Cisco Unified Communications Manager TCP and UDP Port Usage document at this URL:
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/port/7_1_2/CCM_7.1.2PortList.pdf
Configuring QoS in Cisco Unified Communications Manager
The SCCP DSCP values are configured in the Cisco Unified Communications Manager enterprise parameters. Cisco Unified Communications Manager uses the default value of CS3 to have devices set the DSCP marking for SCCP packets as shown in the Enterprise Parameters Configuration page.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 25
Configuring QoS Policies for the Network
Set up QoS policies and settings for the following network devices.
Configuring Cisco IOS Access Points
Use the following QoS policy on the Cisco IOS access point (AP) to enable DSCP to CoS (UP) mapping. This allows RTP packets to be placed into the voice queue, if those packets are marked correctly, when received at the access point level.
class-map match-all RTP
match ip dscp ef
class-map match-all SCCP
match ip dscp cs3
!
policy-map Voice
class RTP
set cos 6
class SCCP
set cos 4
!
interface dot11radioX
service-policy input Voice
service-policy output Voice
Configuring Cisco Switch Ports
Configure the Cisco access point switch ports and uplink switch ports for DSCP trust.
mls qos
!
interface X
mls qos trust dscp
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 26
Note: When using the Cisco Unified Wireless LAN Controller, DSCP trust must be implemented or trust the UDP data ports used by the Cisco Unified Wireless LAN Controller (LWAPP = 12222 and 12223; CAPWAP = 5246 and 5247) on all interfaces where wireless packets will traverse to ensure QoS markings are correctly set. Versions prior to 5.2 use LWAPP, where versions 5.2 and later use CAPWAP.
Configuring Switch Ports for Wired IP Phones
Enable the Cisco wired IP phone switch ports for Cisco phone trust
mls qos
!
Interface X
mls qos trust device cisco-phone
mls qos trust dscp
If DSCP markings are not preserved, then the below configuration can be used to set the DSCP based on the TCP or UDP port to map RTP and SCCP correctly.
Ensure the following QoS policy is not applied to an interface where wireless traffic traverses.
If using non-secure SCCP, then TCP port 2000 is used. TCP port 2443 is used for secure SCCP.
ip access-list extended SCCP
permit tcp any eq 2000 any
permit tcp any any eq 2000
permit tcp any eq 2443 any
permit tcp any any eq 2443
!
ip access-list extended RTP
permit udp any range 16384 32767 any
permit udp any any range 16384 32767
!
class-map match-all SCCP
match access-group name SCCP
class-map match-all RTP
match access-group name RTP
!
policy-map Voice
class RTP
set dscp ef
!
class SCCP
set dscp cs3
!
interface X
service-policy input Voice
service-policy output Voice
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 27
Sample Voice Packet Capture
This packet capture below shows that RTP packets bound for the Cisco Unified IP Phone 7925G over the air should be marked with DSCP = EF and UP = 6.
Call Admission Control
Inbound and outbound call admission control can be enabled on the access point.
• Enable Call Admission Control / Wi-Fi MultiMedia Traffic Specifications (TSPEC)
• Set the desired maximum RF bandwidth that is allocated for voice traffic (default = 75%)
• Set the bandwidth that is reserved for roaming clients (default = 6%)
The minimum PHY rate can be configured for which the phone is to use when Call Admission Control (CAC) is enabled.
• Enable a data rate that is enabled on the access point. (Default setting is 12 Mbps)
• Cisco Access Points will only accept a minimum PHY rate of 5.5, 6, 11, 12 or 24 Mbps, so ensure that one of these
rates are enabled.
As of the 1.3(3) release, the Cisco Unified Wireless IP Phone 7925G Series will auto-negotiate the minimum PHY rate to be used for TSPEC. By default it will try the locally configured minimum PHY rate (i.e. 12 Mbps) first, but if that data rate is not enabled on the access point, then it will try the next highest enabled data rate on the access point. If there is not a higher data rate enabled, then it will then try the next lowest data rate as the minimum PHY rate.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 28
In releases prior to 1.3(3), the Cisco Unified Wireless IP Phone 7925G Series would use the static minimum PHY rate configured locally.
If 12 Mbps is not enabled on the access point, then the next highest enabled data rate must be 24 Mbps. For example, if 12 Mbps is disabled but 18 Mbps is enabled, the phone will try the next highest rate of 18 Mbps and fail because that minimum PHY rate for CAC is not supported by the Cisco access point.
The dynamic minimum PHY rate is useful for deployments that require higher capacity where 24 Mbps and higher data rates are only enabled. For this high capacity deployment configuration and with release 1.3(3), the minimum PHY rate would be adjusted to 24 Mbps automatically even if the phone is configured statically for a minimum PHY rate of 12 Mbps. In releases prior to 1.3(3), the minimum PHY rate would have to be changed to 24 Mbps manually from the default of 12 Mbps in order for CAC to work correctly for this deployment configuration.
If an 802.11b AP is used, the highest available date rate would be 11 Mbps, so 12 Mbps can not be used as the minimum PHY rate. For this 802.11b (11 Mbps) deployment configuration and with release 1.3(3), the minimum PHY rate would be adjusted to 11 Mbps automatically even if the phone is configured statically for a minimum PHY rate of 12 Mbps. In releases prior to
1.3(3), the minimum PHY rate would have to be changed to 11 Mbps manually from the default of 12 Mbps in order for CAC to work correctly for this deployment configuration.
There is no support for load-based CAC or multiple streams on the autonomous access points therefore it is not recommended to enable CAC on autonomous access points.
If CAC is enabled on the autonomous access point, then SRTP and barge calls will fail.
Pre-Call Admission Control
If Call Admission Control (TSPEC) is enabled on the access point, the Cisco Unified Wireless IP Phone 7925G Series sends an Add Traffic Stream (ADDTS) to the access point to request bandwidth in order to place or receive a call. If the AP sends an ADDTS successful message then the Cisco Unified Wireless IP Phone 7925G Series establishes the call. If the call is rejected by the access point and the wireless IP phone has no other access point to roam to, then phone displays “Network Busy”. If the admission is refused, there is no messaging from the Cisco Unified Wireless IP Phone 7925G Series to inform the remote endpoint that there is insufficient bandwidth to establish the call, so the call can continue to ring out within the system until the remote user terminates the call.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 29
Roaming Admission Control
During a call, the Cisco Unified Wireless IP Phone 7925G Series measures Received Signal Strength Indicator (RSSI) and Packet Error Rate (PER) values for the current and all available access points to make roaming decisions.
If the original access point where the call was established had Call Admission Control (TSPEC) enabled, then the wireless IP phone will send an ADDTS request during the roam to the new access point.
For more information about Call Admission Control and QoS, refer to the “Cisco Unified Wireless Quality of Service” chapter in the Enterprise Mobility Design Guide at this URL:
http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/emob41dg/eMob4.1.pdf
Traffic Classification (TCLAS)
Traffic Classification (TCLAS) helps to ensure that the access point properly classifies voice packets.
Without proper classification, voice packets will be treated as best effort which will defeat the purpose of TSPEC and QoS in general.
TCP and UDP port information will be used to set the UP (User Priority) value.
The previous method of classification depends upon preservation of DSCP value throughout the network, where the DSCP value maps to a particular queue (BE, BK, VI, VO).
However, the DSCP values are not always preserved as this can be viewed as a security risk.
TCLAS is supported in the Cisco Unified Wireless LAN Controller release 5.1.151.0 and later.
Using port based QoS policies is inadequate as all data packets use the same UDP port (LWAPP = 12222; CAPWAP = 5246) and the access point uses the outside QoS marking to determine which queue the packets should be placed in.
With TCLAS, DSCP preservation is not a requirement.
Call Admission Control (TSPEC) must be enabled on the access point in order to enable TCLAS.
TCLAS will be negotiated within the ADDTS packets, which are used to request bandwidth in order to place or receive a call.
Cisco Unified Wireless IP Phone 7925G Series Deployment Guide 30
Roaming
When using 802.1x type authentication, it is recommended to implement CCKM to enable fast roaming. 802.1x can introduce delay during roaming due to its requirement for full re-authentication. CCKM centralizes the key management and reduces the number of key exchanges. WPA introduces additional transient keys and can lengthen roaming time.
As of the 1.3(4) release, the Cisco Unified Wireless IP Phone 7925G Series supports CCKM with WPA2 (AES or TKIP), WPA (TKIP or AES) and 802.1x (WEP) authentication.
Authentication
Roaming Time
WPA/WPA2 Personal
150 ms
WPA/WPA2 Enterprise
300 ms
CCKM
< 100 ms
Interband Roaming
Some deployments may use one band for indoor (i.e. 5 GHz) and the other for outdoor coverage (i.e. 2.4 GHz). In this case, set the phone to either Auto-a or Auto-b/g mode, depending on the preferred band.
For Auto-a and Auto-b/g modes, this is giving preference to one band over another. At power on, the Cisco Unified Wireless IP Phone 7925G Series will scan all 2.4 and 5 GHz channels then attempt to associate to an access point for the configured network using the preferred band if available. If the preferred band is not available, then the Cisco Unified Wireless IP Phone 7925G Series will try to use the less preferred band if available. If the phone roams out of coverage of the preferred band, where the less preferred band signal is available, then the phone will attempt to associate to that less preferred band.
As of the 1.3(4) release, seamless interband roaming between 5 Ghz and 2.4 Ghz bands is supported as both bands are now scanned simultaneously when on call.
In order for the Cisco Unified Wireless IP Phone 7925G Series to roam from the preferred band to the less preferred band (i.e. roam to 2.4 GHz when configured for Auto-a mode), all access points in the preferred band must have a signal low enough to match the less preferred band roam threshold and the RSSI differential threshold for roaming must be met. In order to roam back to the preferred band, there must be at least one access point with sufficient signal matching the preferred band roam threshold.
Prior to the 1.3(4) release, the Cisco Unified Wireless IP Phone 7925G Series would have to roam out of range of the current band before it would attempt to roam to the other band when configured for an Auto 802.11 mode (i.e. Auto-a, Auto-bg, Auto­RSSI), where the user may experience choppy audio with the weak signal, followed up with a small second audio gap before looking for the least preferred band. Then once it has failed over to a less preferred band (i.e. associated to 802.11b/g when phone configured for Auto-a), there was no mechanism in place to check to see if the preferred band is available again or not in order to roam back to the preferred band.
It is recommended to perform a spectrum analysis to ensure that the desired bands can be enabled in order to perform seamless interband roaming.
Channel Parking
Channel Parking is a sub-feature of interband roaming, which is designed to conserve idle battery life when the Cisco Unified Wireless IP Phone 7925G Series are configured for an Auto 802.11 mode and continuous scan mode is enabled in the Cisco Unified Communications Manager.
Continuous scan mode enables constant scanning of all channels regardless of call state, which can also help with location. When configured for auto scan mode, typically the phone is only scanning when on call and not in idle unless the current signal drops below a certain RSSI threshold.
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