RAD Data comm IPmux-16 Pdvt Jitter Buffer, Intrinsic PDV, Pdvt Buffer Effect on Delay

Chapter 1 Introduction IPmux-16Installation and Operation Manual

Packets Leaving IPmux-16 t

Packets Arriving

t

PDV

Figure 1-10. Packet Delay Variation

PDVT (Jitter) Buffer

IPmux-16 is equipped with a Packet DVT (Delay Variation Tolerance) buffer. The PDVT buffer or jitter buffer is filled by the incoming IP packets and emptied out to fill the E1/T1 stream. The buffer begins to empty out only after it is half full in order to compensate for packet starvation from the Ethernet side. The time it takes for half of the buffer to empty out is the maximum DVT time. Delay Variation Tolerance is configurable. The PDVT (jitter) buffer is designed to compensate for packet delay variation caused by the network.

It supports a delay variation of up to E1: 32 ms, T1: 24 ms.

➤To configure jitter buffer depth:

Estimated or Measured PDV introduced by the network + intrinsic PDV (if it exists) introduced by the module as a result of configuring the

TDM bytes / frame > 48 (see explanation of calculating intrinsic PDV, below).

Intrinsic PDV

If TDM bytes/frame is greater than 48, there is an intrinsic delay variation (intrinsic PDV). The intrinsic PDV introduced by the module is a function of n>1 in TDM bytes/frame configuration as follows:

I.PDV (ms) = ((n – 1) x 1000) / (frames per second ⋅ n)

Where n = configured TDMbytes/frame (n=1 – 8).

48

PDVT Buffer Effect on Delay

The PDVT buffer is on the TDM path. This means that it adds to the total end-to-end delay (see delay calculation, below).

1-12 Functional Description