
Upstream Data Channel in
Cable Modem Physical Layer
• Upstream
– Data flowing from the cable modem to the CMTS
– It is always in bursts
– Many modems can transmit on the same frequency
• Modulation formats
– QPSK (2 bits per symbol) and 16 QAM (4 bits per symbol)
• Bandwidth per channel
– 2 MHz for a 3 Mbps QPSK channel
• Frequency
– 5-65 MHz
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