Hybrid all digital fiber to CATV cable system and method
Producing advanced HFC CATV cable systems while easing the burden of backward compatibility. The system improves CATV data carrying capacity by moving RF QAM modulators from the cable head end to various individually or group addressed optical fiber nodes supplying neighborhood CATV cables, and sending data from the cable head IP backbone to the nodes over optical fiber as IP data packets. For high backward compatibility, the system digitizes legacy RF waveforms, or demodulates legacy QAM waveforms to QAM symbols, also transmits these over the optical fiber as IP data packets, and then reconstitutes back to original waveforms as needed. The system is thus able to easily handle legacy NTSC, FM, QPSK waveforms and do partial (QAM symbol level) compression of legacy QAM waveforms to and from multiple nodes without requiring additional optical fiber wavelengths. The system may use non-standard upstream/downstream CATV frequency splits, filter bank receivers, and FPGA/DSP/ASIC methods.
1. A digital optical fiber node system for a Hybrid Fiber Cable (HFC) network, the system comprising:
a cable head end (CHE) for transmitting internet protocol (IP) data packets comprising Quadrature Amplitude Modulation (QAM) symbols over an optical fiber;
a digital optical fiber node for (i) receiving the IP data packets, (ii) generating downstream radio frequency (RF) signals that are modulated according to the QAM symbols carried by the IP data packets, and (iii) transmitting the generated downstream RF signals over a set of cable television (CATV) cables to a plurality of cable modems.
2. The system of claim 1 further comprising a plurality of digital optical fiber nodes that includes the digital optical fiber node, wherein each digital optical fiber node comprises a different address and received IP data packets are associated with the different address.
3. The system of claim 2 further comprising a multiple port switch for:
identifying each of the different addresses of the plurality of digital optical fiber nodes; and
directing IP data packets to a specific digital optical fiber node corresponding to an address associated with the IP data packets.
4. The system of claim 1 , wherein the QAM symbols are a first set of QAM symbols, wherein the system further comprises a downstream converter device for:
accepting a plurality of RF signals from the CHE;
digitizing a first set of RF signals from the plurality of RF signals into a set of digital samples for transmission over the optical fiber; and
demodulating a second set of RF signals from the plurality of RF signals into a set of data packets comprising a second set of QAM symbols for transmission over the optical fiber.
5. The system of claim 1 , wherein the generated downstream RF signals comprise a first set of downstream RF QAM signals, wherein the digital optical fiber node is further for:
receiving the set of digital samples and the set of data packets;
reconstituting the received set of digital samples into a set of downstream digitally reconstructed RF signals;
converting the second set of QAM symbols into a second set of downstream RF QAM signals; and
transmitting the set of downstream digitally reconstructed RF signals and the second set of downstream RF QAM signals over the set of CATV cables.
6. The system of claim 5 , wherein the set of downstream digitally reconstructed RF signals comprise at least one of analog National Television System Committee (NTSC) television channels, frequency modulation (FM) audio channels, and Quadraphase-shift keying (QPSK) channels, wherein the second set of RF QAM downstream signals comprise at least one of standard definition television channels and high definition digital television channels, wherein the first set of downstream RF QAM signals comprise at least one of data over cable service interface specifications (DOCSIS) channels, edge QAM channels, video on demand channels, and IP data streams.
7. The system of claim 5 , wherein the transmitting the set of downstream digitally reconstructed RF signals and the second set of RF QAM downstream signals comprises combining the first set of downstream RF QAM signals, the second set of downstream RF QAM signals, and the set of downstream digitally reconstituted RF signals for transmission over the set of CATV cables.
8. The system of claim 1 , wherein the digital optical fiber node is further for:
accepting upstream RF signals transmitted over the set of CATV cables from the set of cable modems; and
digitizing the upstream RF signals in order to produce digitally encoded upstream RF channel data for transmission over the optical fiber to the CHE.
9. The system of claim 8 , wherein the digital optical fiber node is further for enabling variable frequency cutoff between RF frequencies of upstream RF signals designated for transmission over the optical fiber and RF frequencies of generated downstream RF signals designated for transmission over the set of CATV cables.
10. The system of claim 8 , wherein the digital optical fiber node is further for decomposing the upstream RF signals into a plurality of subbands, wherein the upstream RF signals are digitized by using at least some of the plurality of subbands.
11. The system of claim 1 , wherein the IP data packets further comprise digitized RF samples, wherein the generated downstream RF signals further comprise RF waveforms that are reconstituted from the RF samples.
12. A method of transmitting data over a Hybrid Fiber Cable (HFC) network, the method comprising:
receiving, at a digital optical fiber node, internet protocol (IP) data packets from a cable head end (CHE) over an optical fiber, the IP data packets comprising Quadrature Amplitude Modulation (QAM) symbols; and
generating downstream radio frequency (RF) signals that are modulated according to the QAM symbols carried by the IP data packets; and
transmitting the generated downstream RF signals over a set of cable television (CATV) cables to a plurality of cable modems.
13. The method of claim 12 ,
wherein the digital optical fiber node is one of a plurality of digital optical fiber nodes, each digital optical fiber node comprises a different address,
wherein the received IP data packets are associated with a specific address that corresponds to an address associated with the digital optical fiber node.
14. The method of claim 12 further comprising:
accepting upstream RF signals transmitted over the set of CATV cables from the set of cable modems; and
digitizing the upstream RF signals in order to produce digitally encoded upstream RF channel data for transmission over the optical fiber to the CHE.
15. The method of claim 14 further comprising enabling variable frequency cutoff between RF frequencies of upstream RF signals designated for transmission over the optical fibers and RF frequencies of generated downstream RF signals designated for transmission over the set of CATV cables.
16. The method of claim 14 further comprising decomposing the upstream RF signals into a plurality of subbands, wherein the upstream RF signals are digitized by using at least some of the plurality of subbands.
17. The method of claim 12 , wherein the QAM symbols are a first set of QAM symbols and the generated downstream RF signals comprise a first set of downstream RF QAM signals, wherein the method further comprises:
receiving a set of digital samples and a set of data packets comprising a second set of QAM symbols;
reconstituting the received set of digital samples into a set of downstream digitally reconstructed RF signals;
converting the second set of QAM symbols into a second set of downstream RF QAM signals; and
transmitting the set of downstream digitally reconstructed RF signals and the second set of downstream RF QAM signals over the set of CATV cables.
18. The method of claim 17 , wherein transmitting the set of downstream digitally reconstructed RF signals and the second set of RF QAM downstream signals comprises combining the first set of downstream RF QAM signals, the second set of downstream RF QAM signals, and the set of downstream digitally reconstituted RF signals for transmission over the set of CATV cables.
19. The method of claim 17 , wherein the set of downstream digitally reconstructed RF signals comprise at least one of analog National Television System Committee (NTSC) television channels, frequency modulation (FM) audio channels, and Quadraphase-shift keying (QPSK) channels, wherein the second set of RF QAM downstream signals comprise at least one of standard definition television channels and high definition digital television channels, wherein the first set of downstream RF QAM signals comprise at least one of data over cable service interface specifications (DOCSIS) channels, edge QAM channels, video on demand channels, and IP data streams.
20. The method of claim 12 , wherein the IP data packets further comprise digitized RF samples, wherein the generated downstream RF signals further comprise RF waveforms that are reconstituted from the RF samples.