CATV digital transmission with bandpass sampling
Methods and systems capable of improving the transmission of data along an upstream path of a Hybrid Fiber-Coaxial Cable Network, from a transmitter in a node to a receiver in a Cable Modem Termination System.
1. A method for sending a signal on an upstream path in a CATV network, the method comprising:
receiving an input electrical signal comprising upstream data from at least one cable modem of a CATV consumer;
combining the input signal to form a single continuous upstream spectrum including a plurality of channels including at least a first wideband orthogonal frequency division multiple access (OFDM) channel bounded by the lowest frequency in the continuous upstream spectrum and a second wideband OFDM channel bounded by the highest frequency value of the continuous upstream spectrum;
sampling and digitizing only a selective portion of the continuous upstream spectrum, the selective portion including the first OFDM channel and the second OFDM channel;
converting the digitized signal to an optical signal; and
sending the optical signal to a CMTS in a head end of the CATV network.
2. The method of claim 1 where the signal on an upstream path is sent at a throughput exceeding 1 Gbps.
3. The method of claim 1 where the signal on an upstream path is sent at 1024 QAM.
4. The method of claim 1 having a guardband located on the continuous upstream spectrum between the first OFDM channel and the second OFDM channel, the guardband not sampled and digitized.
5. The method of claim 1 including amplifying both the first OFDM channel and the second OFDM channel.
6. The method of claim 1 where the selective portion is sampled and digitized at a rate at least equal to the Nyquist rate.
7. The method of claim 1 where all information in the continuous upstream spectrum is retained.
8. The method of claim 1 including at least one bandpass filter configured to exclude guardbands within the continuous upstream spectrum from being sampled.