Chapter 1 An Overview of the Cisco Wireless IP Phone 7920
Understanding the Voice Wireless Network
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 products use DSSS technology to support multiple devices on the WLAN.
Wireless Access Points
The critical components in the wireless network are the access points (APs) that provide the “hot spots” or wireless links to the network. Cisco requires that Cisco IOS is running on the APs that support voice calls since Cisco IOS provides features for managing voice traffic. The minimum version of IOS you can use is 12.2(15)JA. The Cisco Aironet APs that support IOS include the following AP series:
•Cisco Aironet AP 350
•Cisco Aironet AP 1100
•Cisco Aironet AP 1200
Each AP has a
APs transmit and receive RF signals over channels within the 2.4 GHz frequency band. Regulatory domains determine the number of channels that wireless communications can use within the 2.4 GHz frequency band. The Cisco Aironet APs support up to 11 communication channels in North America, 13 channels in Europe (ETSI) and 14 channels in Japan. An access point broadcasts on a specific channel within the available channel range. To provide a stable wireless environment and reduce channel interference, you must specify
The AP has a transmission range or coverage area that depends on its type of antenna and transmission power. The access point coverage range is from 500 to 1000 feet with effective isotropic radiated power (EIRP) output that scales at 1, 5, 20, 50, and 100mW. To provide effective coverage, access points need a range overlap of approximately 20 percent to allow uninterrupted connections as phone users roam from one access point to another.
| Cisco Wireless IP Phone 7920 Administration Guide for Cisco CallManager Release 3.3 or Later |