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V.90 Modems. Telephone Bandwidth is Limited (Chapter 4) Bandwidth limits speed Limits speed to about 35 kbps When you transmit , limited to 35 kbps. 35 kbps. V.90 Modems. Telephone Bandwidth is Limited Limits occur when you transmit in analog to the phone company

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V.90 Modems

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V 90 modems

V.90 Modems

  • Telephone Bandwidth is Limited (Chapter 4)

    • Bandwidth limits speed

    • Limits speed to about 35 kbps

    • When you transmit, limited to 35 kbps

35 kbps


V 90 modems1

V.90 Modems

  • Telephone Bandwidth is Limited

    • Limits occur when you transmit in analog to the phone company

      • Analog-to-digital converter (ADC) at the telephone company limits you to about 35 kbps

Telephone

Network

PC

V.34

modem

ADC

33.6 kbps


V 90 modems2

V.90 Modems

  • Receive at 56 kbps

    • ISP connects with digital line to the Telco

    • Sends at 56 kbps

    • No analog-to-digital converter to limit speed

Digital

Link

Telephone

Network

PC

ISP

56 kbps

modem

DAC

No

ADC!

56 kbps


V 90 modems3

V.90 Modems

  • Receive at 56 kbps

    • 56 kbps digital channels inside phone network

    • Only local loop is analog today

    • Trunk lines and switches support 56 kbps transmission

Digital Switches and Trunk Lines

Telephone

Network

PC

ISP

56 kbps

modem

DAC

56 kbps


V 90 modems4

V.90 Modems

  • Receive at 56 kbps

    • Telephone company transmits in analog to subscriber at 56 kbps

    • Digital to audio converter (DAC) does not limit speed to less than 56 kbps

Digital

Link

Telephone

Network

PC

ISP

56 kbps

modem

DAC

56 kbps


V 90 modem

V.90 Modem

  • Telephone Company Does Not Have to Do Anything Differently

    • ADCs and DACs are already in place for ordinary voice service

    • Lack of change in phone system allowed fast implementation

Digital

Link

ADC

Telephone

Network

PC

ISP

56 kbps

modem

DAC


V 90 modem1

V.90 Modem

  • ISP Does Have to Do Things Differently

    • Digital line to telephone network

    • Special equipment at ISP

    • Does not use a V.90 modem

    • If used V.90 modem, could only send at 33.6 kbps

Digital

Link

Telephone

Network

PC

ISP

56 kbps

modem

DAC

No

V.90

Modem!


V 90 modem2

V.90 Modem

  • User Needs a V.90 Modem

    • Does not need a new phone line

    • Not all phone lines will work, but it is never worth the cost to install a new line for V.90 modems


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