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Get the latest Cisco news in this December issue of the Cisco Small Business Monthly Newsletter

UC 500 DSP: Conference and Transcoding Capabilities/Limitations

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[toc:faq]

Definitions

Software Conference: Default conference option for UC500. Software conferencing enables 3-party ad-hoc conferencing capabilities and is enabled by default for a maximum of 8 conferences (8x3).


Hardware Conference: Conferencing option that makes use of a DSP for audio mixing. Two types are available on the UC500, ad-hoc and meet-me. When hardware conferencing is enabled on the UC500, ALL conferencing sessions (including 3-way calls) will be hardware-based.

  • An Ad-hoc conference is an unscheduled conference. It occurs when a third party is added into any conversation by the participants by use of the conference softkey or access code.  The ad-hoc initiators can add/delete/drop participants to/from the conference.  The conference falls back into a normal call when there are only two parties in the conference. A maximum of 8 users can be in a hardware ad-hoc conference or less depending on how configured.
  • A Meet-Me conference is a conference that is initiated by a conference initiator by using the meet-me softkey. Only an IP Phone user can start a meet-me conference.  Once the conference is initiated, anyone is allowed to join the conference by dialing into the conference number (internal DN or external DID). Additionally, the meet-me conference initiator is allowed to add or delete parties to/from the conference. A maximum of 32 users allowed in a meet-me or less depending on how configured.

DSP or Digital Signal Processor: A DSP is a dedicated Hardware component used to process digital voice for a variety of functions, such as codec conversion (also known as "transcoding", for example G.711 to G.729 conversion), audio mixing (for conferencing), voice quality processing (echo cancellation, jitter buffers, etc.), fax signal demodulation (for fax to fax transmissions and also fax to email/email to fax implementations) and voice packetization (for transport over packet network technologies, such as VoIP).

Packet Voice Digital Signal Processor (DSP) Module (PVDM2):  Microprocessor included with every UC500. The DSP module on a UC500 is a non-replaceable part. The PVDM2 included with the UC500 has the following characteristics:

Table 1: Available DSPs Per Platform

PlatformPVDM2Number of DSPs
UC520 8/16U1x PVDM2-322
UC520 24/32/48U1x PVDM2-644
UC5401x PVDM2-644
UC5602x PVDM2-648

Hardware Conferencing

When hardware conferencing is enabled CCA statically allocates the following number of DSPs for conferencing:

Table 2: Available DSPs For Conferencing

Platform

Number of Configured

Voice T1/E1's

DSPs Allocated for

Conferencing

UC520 8/16U1Not supported
UC520 8/16U01
UC520 24/32/48U11
UC520 24/32/48U02
UC54011
UC54002
UC56004
UC56014
UC56023

Meet-Me

For Meet-me conferencing each DSP can support a maximum of 64 G.711 conference streams (single-mode) or 16 G.711/G.729a/G.729 conference streams (mixed-mode). The maximum number of conference participants in a single Meet-me conference call is 32. Here are the following configuration options:

Table 3: Single-Mode (G.711) Meet-me Conference

Maximum

Multi-Party Sessions

Maximum

Meet-Me Partipants

1 DSP
23264 streams
41664 streams
68*48 streams
8864 steams

*A configuration of 6 conference sessions with a maximum of 8 participants each would be  underutilizing the DSP resource

Table 4: Mixed-Mode (G.711/G.729a/G.729) Meet-me Conference

Maximum

Multi-Party Sessions

Maximum

Meet-Me Participants

1 DSP
11616 streams
2816 streams

For a UC500 platform that has more than 1 DSP for hardware conferencing (refer to Table 2) the number of sessions would increase by the number of DSPs available. E.g. A UC560 with two voice T1’s in single-mode (G.711) can support up to 6 simultaneous conference sessions (2 sessions x 3 DSPs) of a maximum of 32 participants in each conference. Note that the maximum number of Meet-me participants remains unchanged.

Ad-hoc

For Ad-hoc conferencing the maximum number of conference participants is 8. This value is not configurable as in the case of Meet-me conferencing. Keeping in mind that a single DSP can support a maximum of 64 G.711 conference streams (single-mode) or 16 G.711/G.729a/G.729 conference streams (mixed-mode), we have the following options:

Table 5: Single-Mode (G.711) Ad-hoc Conference

Maximum

Conference Sessions

Maximum

Ad-hoc Participants

1 DSP
8864 streams

Table 6: Mixed-Mode (G.711/G.729a/G.729) Ad-hoc Conference

Maximum

Conference Sessions

Maximum

Ad-hoc Participants

1 DSP
2816 streams