Specifications
Table Of Contents
- Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0 and Later
- Contents
- Preface
- An Overview of the Cisco Unified Wireless IP Phone 7921G
- An Overview of the Voice Over IP Wireless Network
- Understanding the Wireless LAN
- Components of the VoIP Wireless Network
- Voice Over IP Wireless Network Configuration
- Site Survey Verification
- Setting Up the Cisco Unified Wireless IP Phone 7921G
- Before You Begin
- Installing the Cisco Unified Wireless IP Phone 7921G
- Powering On the Cisco Unified Wireless IP Phone 7921G
- Understanding the Phone Startup Process
- Using the Cisco Unified Wireless IP Phone 7921G Web Pages
- Using the USB Connection for Initial Phone Configuration
- Updating Phones Remotely
- Configuring Network Profiles
- Configuring USB Settings
- Configuring Trace Settings
- Using System Settings
- Configuring Settings on the Cisco Unified Wireless IP Phone 7921G
- Accessing Network and Phone Settings
- Configuring Network Profile Settings
- Changing Phone Settings
- Configuring the Security Certificate on the Phone
- Changing the USB Configuration
- Configuring Features, Templates, Services, and Users
- Configuring Cisco Unified Wireless IP Phones in Cisco Unified CallManager
- Telephony Features Available for the Phone
- Specific Configuration Options for the Cisco Unified Wireless IP Phone 7921G
- Configuring Softkey Templates
- Modifying Phone Button Templates
- Setting Up Services
- Configuring Corporate and Personal Directories
- Adding Users to Cisco Unified CallManager
- Managing the User Options Web Pages
- Creating Custom Phone Rings
- Viewing Security, Device, Model, and Status Information on the Phone
- Monitoring the Cisco Unified Wireless IP Phone Remotely
- Troubleshooting the Cisco Unified Wireless IP Phone 7921G
- Resolving Startup and Connectivity Problems
- Resolving Voice Quality and Roaming Problems
- General Troubleshooting Information
- Erasing the Local Configuration
- Providing Information to Users By Using a Website
- Supporting International Users
- Physical and Operating Environment Specifications
- Checklist for Deploying the Cisco Unified Wireless IP Phone 7921G
- Index
Chapter 2 An Overview of the Voice Over IP Wireless Network
Understanding the Wireless LAN
2-4
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
OL-10802-02
• Direct-Sequence Spread Spectrum (DSSS) technology—To help prevent
interference, DSSS technology was developed to spread the signal out over
the frequency range or bandwidth. DSSS technology multiplexes chunks of
data over several frequencies so that multiple devices can communicate
without interference. Each device has a special code that it uses to identify its
data packets and to ignore all others. The Cisco wireless 802.11b/g products
use DSSS technology to support multiple devices on the WLAN.
• Orthogonal Frequency Division Multiplexing (OFDM) technology—OFDM
is a physical layer encoding technology for transmitting signals through the
RF. This method breaks one high-speed data carrier into several lower-speed
carriers that transmit in parallel across the particular RF spectrum. OFDM,
when used with various modulation types such as 802.11g and 802.11a, is
capable of supporting data rates as high as 54 Mbps.
Table 2-1 provides a comparison of the Wi-Fi standards and their features.
Connecting to the Wireless Network
The critical components in the wireless network are the access points that provide
the wireless links or “hot spots” to the network. Cisco requires that the access
points supporting voice communications must run Cisco IOS Version 12.3(8)JA
or later. Cisco IOS provides features for managing voice traffic. For more
information about access points, see the
“Voice Over IP Wireless Network
Configuration” section on page 2-27.
Each access point has a hard-wired connection to an Ethernet switch, such as a
Cisco
Catalyst 3750, that is configured on the LAN. The switch provides access
to gateways and the Cisco Unified
CallManager server to support wireless IP
telephony (WIPT).
Ta b l e 2-1 Comparing Wi-Fi Standards Features
Item 802.11b 802.11g 802.11a
Data Rates 1, 2, 5.5, 11 Mbps 6, 9, 12, 18, 24, 36, 48, 54
Mbps
6, 9, 12, 18, 24, 36, 48, 54
Mbps
Non-overlapping
Channels
3 (Japan uses 4) 3 (Japan uses 4) Up to 23
Wireless
Modulation
DSSS DSSS, ODFM ODFM