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
2-3
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
OL-10802-02
Chapter 2 An Overview of the Voice Over IP Wireless Network
Understanding the Wireless LAN
The 802.11 Standards for Wireless LAN Communications
Wireless LANs must follow the Institute of Electrical and Electronics Engineers
(IEEE) 802.11 standards that define the protocols that govern all Ethernet-based
wireless traffic. The Cisco
Unified Wireless IP Phone 7921G supports these
standards:
• The 802.11b standard was the first standard in wireless LAN
communications, which is commonly called Wi-Fi.The 802.11b standard
specifies the radio frequency (RF) of 2.4 GHz for both transmitting and
receiving data.
• The 802.11g standard uses the same unlicensed 2.4 GHz band as 802.11b, but
extends the data rates to provide greater performance by using Orthogonal
Frequency Division Multiplexing (OFDM) technology.
• The 802.11a standard uses the 5 GHz band that provides more channels and
improved data rates by using OFDM technology.
Radio Frequency Ranges
Wireless LAN communications uses these two radio frequency ranges:
• 2.4 GHz radio frequency range—This open RF range does not require
licensing. To reduce interference within this band, WLANs transmit on
non-overlapping channels, which are typically limited to three channels,
although Japan uses four channels. Many devices operate in this bandwidth
including cordless phones and microwave ovens; consequently, wireless
communication is susceptible to interference or noise. Interference does not
destroy the signal, but can impede the transmission speed and reduce an 11
Mbps signal all the way down to a 1Mbps signal. In addition, RF interference
can reduce the voice quality over the wireless network.
• 5 GHz radio frequency range—This band has been divided into several
sections called Unlicensed National Information Infrastructure (UNII) bands
which have four channels each. The channels were spaced at 20 MHz thereby
providing non-overlapping channels. As a result, 802.11a provides more
channels.
Wireless Modulation Technologies
Wireless communications uses these two methods for carrying data and signals: