RAD Data comm Vmux-210 Specifications download pdf (Page 166)

Chapter 6 Troubleshooting and Diagnostics Installation and Operation Manual

6-24 Frequently Asked Questions Vmux-210 Ver. 1.1

In order to overcome this situation, the Vmux-210 uses the fragmentation

feature. The fragmentation function enables the Vmux-210 to halt the

transmission of a long, lower priority packet, and begin the transmission of a

higher priority packet without waiting to finish the transmission of the lower-

priority packet. The transmission of the lower priority packet is then resumed

automatically after the transmission of the higher priority packet is

completed. In essence, fragmentation allows the Vmux-210 to "chop" long

packets in order to give higher priority to voice packets.

The size of the fragment packets is user-selectable.

Q: What is the end-to-end processing delay contributed by the Vmux-210 when

working with different compression algorithms (Coders)?

A: The end-to-end processing delay contributed by the Vmux-210 is as follows:

 G723.1A (5.3/6.4 kbps) - 120-150 msec (depending on packet interval)

 G729.A/8 kbps - 70 msec

 G711.A/64 kbps - 45 msec

Please note that when used in an IP network, the Vmux-210 uses jitter

buffers in order to compensate for packet delay variation. The jitter buffers

are implemented in the Vmux-210 DSPs (Digital Signal Processors), and they

are adaptive to the packet delay variation. Each timeslot has its own jitter

buffer.

The size of the Vmux-210 jitter buffers is not user-configurable (with the

exception of jitter buffers for transparent timeslots). The jitter buffer size is

changed according to the packet delay variation, which is detected by the

DSP. Each voice packet that is sent out of the DSP includes a time stamp. The

DSP analyzes the time stamps on the received packets and controls the size

of the jitter buffer according to the delay between the received packets. The

delay variation tolerance is from 10 msec up to 300 msec.

Example: When using G.723.1 compression, the DSP expects to receive a

packet every 30 msec. If the delay between the received packets is higher

than 30 msec, the DSP will increase the size of the jitter buffer so that data

will not be lost.

Q: What files can be transferred to/from Vmux-210?

A: See the following table.

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RAD Data comm Vmux-210 Specifications Page 166