1
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2
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- sending voice information in digital form
- very cost-effective,
- promoting technology convergence
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3
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- PC to PC
- PC to Phone
- Phone to Phone
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4
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- PCM
- DSP
- Voice Activity Director (VAD) detects and removes silence
- CODEC; tone
- Microprocessors-> packets
- Router ; Switch ; QoS
- At the destination, the reverse process takes place
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5
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- Accumulation Delay (sometimes called algorithmic delay) - collect a
frame of voice samples
- Processing Delay - CODEC
- Network Delay: This delay is caused by the physical medium and by the
jitter buffers
- Echo - caused by signal
reflections generated by the hybrid circuit that converts between a
4-wire circuit (a separate transmit and receive pair) and a 2-wire
circuit .- echo canceller
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6
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- A jitter buffer in the DSP allows several packets to be queued so th=
at
the playout occurs at a steady rate
- To compensate for lost packets , will replay the last successfully
received packet
- Out-of-order packets:deleted
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7
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- the roles of gateways and remote access servers in the transmission =
and
reception of voice, fax, and modem data.
- the type of incoming call, be it voice, fax, or modem.
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8
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- To connect these TDM circuits over an Internet Protocol (IP) network,
gateway functionality is required. The gateway adapts the
circuit-switched call to a packet-switched environment. A gateway
emulates a central office, and provides signaling, conversion to pac=
ket
network, encoding/compression, echo cancellation, and quality of ser=
vice
(QoS).
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9
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- Telogy's Golden Gateway :
- special handling -- primarily from the delays introduced by the netw=
ork
- "Spoofing" allows the two fax machines to operate "as
if" the network delay were virtually zero and keeps the fax call
alive. A fax gateway emulates the central office and the remote fax
machine.
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10
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- The PC modem data is connected to the central office, as in all anal=
og
telephony calls, and is routed to a RAS accordingly
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11
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- is a single piece of equipment
- conversion to be performed dynamically on a call by call basis
- reduces the additional equipment costs incurred by having discrete
trunks and idle equipment
- Channels don't end up underutilized and result in calls not being
answered because of limitation of resources
- type of call coming in is a voice, fax or data modem call
- GoldenPort is the first standards-based software solution
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12
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- Implementing a Voice/Fax/Data over packet solution is far from merely
adding a codec between the telephone and the packet network.
- All kinds of interoperability issues exist, such as telephony
interfaces, test conformance, codec specifications, network protocol=
- Must address complex quality of service issues
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13
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- echo cancellation
- Performance with high background noise
- pass out of band, the DTMF tones
- Fax spoofing
- Comfort Noise Generation
- V.90 modem Interoperability (56k)
- New APIs
- Built-in testing
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14
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- access and gateway markets
- high density carrier and infrastructure products
- It is important to select a vendor supporting the full spectrum – it
improves time to market, interoperability and implementation time
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15
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- Remote branch office users can now interface to the home office PBX =
via
a packet network
- trunking between two or more PBXs
- Available bandwidth is shared between voice and data applications
- Call routing : VoIP / PSTN<=
/li>
- PSTN: increasing the effective capacity
- CATV =3D TV + IP + VoIP + Fax-oIP
- xDSL=3DIP + VoIP + Fax-oIP
- IP phones - connect directly to the enterprise LAN
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