Avaya 555-245-600 manual Pcm, Cs-Acelp, Acelpmp-Mlq

Voice quality network requirements

Table 46 provides a comparison of voice quality considerations associated with some of the codecs supported by Avaya products.

Toll-quality voice must achieve a MOS (Mean Opinion Score) of 4 or above. The MOS scoring is a long-standing, subjective method of measuring voice quality.

Table 46: Comparison of speech coding standards (without IP / UDP / RTP overhead)

Standard	Coding Type	Bit Rate	MOS-LQO1,2
		(kbps)	(Mean Opinion Score -
			Listening Quality Objective)
G.711	PCM	64	4.37
G.729	CS-ACELP	8	3.94
G.723.1	ACELPMP-MLQ	6.3	3.78
		5.3	3.68

1.As predicted. Measured according to ITU-IT Recommendation P.862 (PESQ). See draft Recommendation P.862.2, application guide for PESQ.

2.Given MOS-LQO values for American English.

Because it does not use compression, G.711 offers the highest level of voice quality assuming proper operation of the IP network. Unfortunately, there is a trade-off with higher bandwidth usage. In situations where bandwidth is scarce, such as across WAN links, G.729 offers a good compromise with lower bandwidth usage, but still good fidelity audio.

In general, compression codecs use twice as many signal processing resources than the G.711 codec. On the TN2302AP (Media Processor) circuit pack (and on the G700 VoIP engine) there are 64 DSP resources. Thus, the number of calls supported by one Media Processor board or

G700 is:

●64 G.711 calls

●32 compressed calls (for example, G.729)

●Some number in-between for a call mix.

The formula for calculating the number of calls one Media Processor board supports is

(Number of uncompressed calls) + 2 ⋅ (Number of compressed calls) ≤ 64

The TN2602AP circuit pack supports:

●320 channels of G.711 (u/a-law)

●320 channels of G.729A/G.729AB

●320 channels of G.726 (32 kbps only)

●320 channels of T.38

252 Avaya Application Solutions IP Telephony Deployment Guide