Improve VOIP traffic in WRT54G

Requirement:
WRT54G Router,
DD-WRT 24 Sp1 firmware.
To improve VOIP traffic in the network, I put VOIP adapter mac address into the QoS features.
* Under ‘MAC Priority’, enter the MAC Address of the device
* Click ‘add’
* click ‘Save changes’
I put my SPA-2002 VOIP adapter at Premium priority.
After one week using, I fell the VOIP telephone/ conversion has better quality without jiggly.