Transmission Planning

This section describes the basic concepts of transmission planning. The basic concepts are used in the assessment procedure described in the next section, see Implementation Assessment.

IP telephony has become an essential part of media transmission in private networks but it also introduces new challenges. Even familiar impairment such as delay and echo causes more significant impact on the speech quality than in a traditional TDM oriented transmission environment. Thus a successful deployment of MX-ONE, an IP-PBX communication system, requires a careful transmission planning to achieve high level of speech quality.

The E-Model (Ref [1]) is a computational model to use for estimation of the end-to-end voice quality. The transmission planning guideline in this section describes the concept and the use of E-Model and explains important parameters that must be taken into planning consideration. The followings are key quality impairments that have major impact on MX-ONE IP telephony features.

• Speech compression (VoIP vocoder) and transcoding
• Delay, including packet delay variation
• Speech level - sender/receiver/overall loudness ratings
• Level and loss plan (related to loudness rating)
• Packet loss
• Echo impairments deployment

It is important to assess all those transmission parameters listed above studying all connection scenarios and the combined effect is evaluated prior to the system deployment.

The transmission plan must consider the combined effect of all parameters to ensure that MX-ONE achieves the overall level of speech transmission quality as perceived by the user (end-to-end speech quality).