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 Analog-to-digital converter (ADC) at the telephone company limits you to about 35 kbps Telephone Network Telephone Network ADC PC V.34 modem 33.6 kbps

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 Telephone Network Telephone Network DAC PC 56 kbps modem ISP Digital Link No ADC! 56 kbps

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 Telephone Network Telephone Network DAC PC 56 kbps modem ISP Digital Switches and Trunk Lines 56 kbps

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 Telephone Network Telephone Network DAC PC 56 kbps modem ISP Digital Link 56 kbps

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 Telephone Network Telephone Network ADC PC 56 kbps modem ISP Digital Link DAC

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 Telephone Network Telephone Network DAC PC 56 kbps modem ISP Digital Link No V.90 Modem!

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