DSP In IP Telephony

Voice over Internet Protocol, how it works

Homes were connected to Internet through circuit switched telephone networks with slow connection speeds in the past. Nowadays telephony services are more and more build on top of Internet. One example of this are third generation mobile networks, conventional phone calls are converted from circuit switched systems to packet networks. VOIP has become a commodity because of services like Skype and Google Talk.

The key components of an IP Telephony Solution is Digital Signal Processors (DSP).The words we speak are in a form of a sine wave (analog), ranging from 300 hertz to 3200 hertz. It requires a type of conversion that can only be done by DSPs to allow our voice to travel across an IP network. DSP convert our word from analog to digital and vice versa, this transformation is impossible without DSP. DSP is a processor for processing and generation of real-world signals such as video, voice, and music. Digital Signal Processors embedded in every mobile phone, or CDplayer.

a DSP reside on a module called Packet-Voice-Data-Module (PVDM-2) in a Cisco IP Telephony solution. The more DSPs on a PVDM means the more sessions available for trannscoding, conferencing, and voice calls. PVDM resides in a voice gateway on a Cisco High-Density Digital Voice Network Module (HM-HDV). It must be configured with DSPfarms, a pool DSP resources. DSP resources on the Cisco gateway, for example, Catalyst 4000 WS-X4604-GWY, Cisco 2600XM, Catalyst 6000 WS-6608-T1 or WS-6608-E1, Cisco 2691, Cisco 3660, Cisco 3745, Cisco 3620, Cisco 3640, Cisco 2600, or Cisco VG200, offer hardware support for IP telephony features named Cisco CallManager. These features include hardware-based MTP support for supplementary services, hardware-enabled voice conferencing, and transcoding services.

DSP components functionality usually overlooked compared by CallManager Servers and Voice gateways during IP deployment. The worker don’t know about the importance of DSP. IP Telephony Solution would have difficulties in providing voice services if the worker ignore it. An ICND training will fix this problem.

April 23, 2008 | Filed Under Internet, VOIP 

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