In this blog, we will discuss the salient features of Cisco PVDM and Cisco DSP.
Digital signal processing (DSP)
This is the study of signals in a digital representation and the processing methods of these signals. It does analogue to digital conversion and digital to analogue as well. In technical terms, it has three major subfields
- Audio Signal Processing
- Digital Image Processing
- Speech Processing
It is a huge subject to discuss and a plethora of books have been written on Digital Signal Processing. This document will help you to understand how we use Digital Signal Processing in Cisco VoIP Technology.
Related- Commonly used VoIP Terms and Concepts
Packet Voice DSP Module (PVDM)
Cisco provides DSP resources in ISR routers to provide voice termination, transcoding, conferencing and connectivity capabilities for IP telephony Solutions. Cisco has created a DSP module called PVDM, It stands Packet Voice DSP module. Each PVDM is equipped with a number of cisco DSPs chip on the core, the higher the number of DSP, the greater the processing power of that Cisco PVDM.
Types of PVDM
There are 2- types available to support first Generation (2800 series and 3800 series) and second Generation of routers (2900 series and 3900 series). The Cisco 2800 and 3800 series platform only supports PVDM-2 but Cisco 2900 and 3900 platform supports PVDM-2 and PVDM-3 as well. The PVDM3 modules provide higher density (up to 4 times higher) than the PVDM2s. They also provide improved performance in terms of the number of conference and transcoding sessions supported.
Related- Introduction to Network Routers
Table 1 lists the PVDM-2 models.
Table 2 lists the PVDM-3 models.
By referring above table it is understood what do the numbers 8, 16, 32, 64 etc in the PVDM-2 and PVDM-3. The number of channels supported on PVDM-2 and PVDM-3 is entirely depending on the codec-complexity. There are 3 flavours of codec-complexity refer below table.
Table -3 lists of Codec Supported in PVDM2 and PVDM3
Table -4 lists the number of voice channels supported by the PVDM2
Table -5 lists the number of voice channels supported by the PVDM3.
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