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Chapter 1 An Overview of the Cisco Wireless IP Phone 7920
Understanding the Voice Wireless Network
1-4
Cisco Wireless IP Phone 7920 Administration Guide for Cisco CallManager Release 3.3 or Later
OL-3930-02
Understanding the Voice Wireless Network
Voice over IP (VoIP) telephones use a hard-wired connection to the network for
transmitting call control messages and voice packets. With the introduction of
wireless communication, mobile wireless IP phones provide similar
communication features within the corporate wireless local area network
(WLAN). Use the following topics to understand your voice wireless network:
• Overview of a Wireless LAN, page 1-4
• The 802.11 Standard for Wireless LAN Communications, page 1-5
• Wireless Access Points, page 1-6
• Security, page 1-7
Overview of a Wireless LAN
In a traditional LAN, phones and computers use cables to transmit messages and
data packets over a wire conductor. Wireless LANs use radio waves to carry the
messages and data packets. WLANs require access points that receive and
transmit radio signals. Cisco Aironet series access points including the 1200,
1100, and 350 series models support voice on a WLAN. Figure 1-2 shows a
typical WLAN topology that incorporates both wireless data with laptop
computers and wireless IP telephony (WIPT) with Cisco Wireless IP Phone 7920.
When a wireless device powers on, it immediately searches for and becomes
associated with an access point. As users move from one location to another
within the corporate WLAN environment, the wireless device roams out of range
of one access point and into the range of another. Data and voice calls are
transmitted from the access point to the switch and router by using the wired,
Ethernet network. Phone calls are sent to the Cisco CallManager server for call
processing and routing.