Specifications

Installation and Operation Manual Chapter 1 Introduction
IPmux-24 Ver. 1.5 Functional Description 1-17
When the first packet is received, or immediately after an underrun, the buffer is
automatically filled with conditioning pattern up to the PDVT level in order to
compensate for the underrun. Then, IPmux-24 processes the packet
(packetization delay) and starts to empty out the jitter buffer to the TDM side.
See
Figure 1-14 for the illustration of the PDVT buffer operation.
The PDVT (jitter) buffer is designed to compensate for network delay variation of
up to 180 msec.
Packets arriving from the PSN side are stored in the jitter buffer before being
transmitted to the TDM side, adding a delay to the TDM traffic. The delay time
equals to the PDVT size configured by the user.
PDVT (Jitter) Buffer Depth
Normal Operation
(No PDV)
Maximum Jitter Buffer Size
(2 PDVT + 2 PCT + 1 msec)
PDVT Buffer + Packet Creation Time
Figure
1-14. Jitter Buffer Operation
The maximum jitter buffer size is 2 × PDVT + PCT + 1 msec.
Packet Creation Time (PCT)
When IPmux-24 builds a frame, a packetization delay is introduced. The packet
creation time is different for the different payload encapsulation methods. It is
calculated according to the following formulas:
TDMoIP
PCT (ms) =
TS
0.125N 47
×
×
Where:
N =
48
ebytes/framTDM
TS = number of assigned timeslots (in unframed mode= 32 for E1, 24 for T1)
For a bundle that contains a few timeslots (i.e. 1 to 3), the recommended
number of TDM bytes/frame is 48 in order to prevent excessive PCT.
CESoPSN
PCT (ms) = N × 0.125
Where:
N = Number of TDM frames in packet
Note