Multicast; Designing The Wireless Lan For Voice; Planning Channel Usage - Cisco 7925G Deployment Manual

Multicast

When enabling multicast in the wireless LAN, impacts on battery life, performance, and capacity must be considered.
The Cisco Unified Wireless IP Phone 7925G uses the DTIM period to receive the queued broadcast and multicast packets.
If there are many packets queued up, then they client may have to stay awake longer thus potentially reducing battery life.
With multicast, there is no reliability that the packet will be received the by the client.
The multicast traffic will be sent at the highest basic data rate enabled on the access point, so will want to ensure that only the
lowest enabled rate is configured as the only basic rate.
The client will send the IGMP join request to receive that multicast stream. The client will send the IGMP leave when the
session is to be ended.
The Cisco Unified Wireless IP Phone 7925G supports the IGMP query feature, which can be used to reduce the amount of
multicast traffic on the wireless LAN when not necessary.
Ensure that IGMP snooping is also enabled on all switches.
Note: If using Coexistence where 802.11b/g and Bluetooth are being used simultaneously, then multicast voice is not
supported.

Designing the Wireless LAN for Voice

You must consider these network design areas to insure adequate call capacity, signal strength and coverage for mobile wireless
phones.
For more information about these topics, refer to the "VoWLAN Design Recommendations" chapter in the Enterprise Mobility
Design Guide at this URL:
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns279/c649/ccmigration_09186a00808d9330.pdf

Planning Channel Usage

Cisco Unified Wireless IP Phone 7925G Deployment Guide 26