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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
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