Cisco SPA501G Administration Guide - Page 32

Getting Started Ensuring Voice Quality 1 Codec G.729 and G.729A G.723.1 G.722 Complexity and Description G.729A low-medium complexity. G.729 medium complexity. MOS 4 G.729A requires about half the processing power of G.729. The G.729 and G.729A bit streams are compatible and interoperable, but not identical. High complexity. Cisco SPA IP phones support 3.8 the use of ITU G.723.1 audio codec at 6.4 kbps. Up to two channels of G.723.1 can be used simultaneously. For example, Line 1 and Line 2 can use G.723.1 simultaneously, or Line 1 or Line 2 can initiate a three-way conference with both call legs using G.723.1. G.723.1 is not supported on the Cisco SPA525G or Cisco SPA525G2 or Cisco WIP310 phones. Only one G.722 call at a time is allowed. If a 4.3 conference call is placed, a SIP re-invite message (approx) is sent to switch the calls to narrowband audio. Not supported on the Cisco WIP310. Bandwidth Requirements Depending on how you have your IP phones configured, each call requires 55 to 110 kbps of the bandwidth in each direction. For example, using G.729 with an average business-grade broadband Internet connection supporting 1.5 Mbps downstream and 384 kbps upstream, a total of seven (7) simultaneous conversations can be reliably supported with adequate bandwidth available for file downloads. We recommend using Cisco SPA IP phones with QoS-capable networking equipment that can prioritize the VoIP traffic. A QoS-enabled device prioritizes the packets going upstream to the ISP. Cisco Small Business SPA300 Series, SPA500 Series, and WIP310 IP Phone Administration Guide 31