Intelligent node for improving signal quality in a cable modem network
Systems and methods are provided for improving the signal quality and performance in a cable operator's Hybrid Fiber Coax (HFC) plant by adding DOCSIS intelligence to components within the HFC plant. These intelligent DOCSIS devices, referred to here as DOCSIS Intelligent Nodes (DINs), intercept the upstream signal from cable modems and set top boxes, and perform various types of signal processing on the signals based upon knowledge of the signal characteristics obtained from CMTS control structures such as MAPs and Upstream Channel Descriptors (UCDs). The DIN functionality can be integrated into any type of device found in HFC networks such as RF amplifiers and fiber nodes.
1. A method of intelligently collecting and using DOCSIS control information in a cable modem communication network by an intelligent node to improve upstream signal transmissions on the network, said intelligent node being in communication with a cable modem termination system (CMTS), cable modems (CMs), and other devices, the method comprising:
the intelligent node obtaining CM identifier information for CMs and other devices on said network;
the intelligent node obtaining control information from said cable modem communication network, including at least one of a DOCSIS MAP or a DOCSIS UCD control structure;
the intelligent node synchronizing to a DOCSIS timestamp clock maintained by said cable modem communication network;
the intelligent node using said obtained control information and said CM identifier information to determine when a device is scheduled to transmits on an upstream communication link;
the intelligent node using the obtained control information to modify transmissions on the upstream communication link; and
the intelligent node receiving upstream data traffic from a sub-node, demodulating the received upstream data traffic from the sub-node, compressing the demodulated received upstream data traffic from the sub-node, re-modulating the compressed demodulated received upstream data traffic data, and re-transmitting the compressed data to the CMTS so as to reduce the bandwidth requirements on the section of an HFC network upstream of the sub-node.
2. The method of claim 1 , wherein the intelligent node uses the DOCSIS UCD control structure to determines the radio frequency (RF) characteristics of each burst transmission and wherein the intelligent node uses the RF characteristics of each burst transmission to modify the RF characteristics of an upstream transmission from a downstream device via signal processing.
3. The method of claim 1 , wherein the scheduling information is obtained by the intelligent node by monitoring DOCSIS MAP control messages sent by the CMTS that identify the time when a particular cable modem is transmitting using the DOCSIS service identifier (SID).
4. The method of claim 2 , wherein the RF characteristics of the burst transmissions are obtained by the intelligent node by monitoring the DOCSIS upstream channel descriptor (UCD) which includes the channel center frequency, channel width, and other parameters associated with different interval usage codes (IUCs) such as the type of modulation, preamble information, interleaving information, and Reed-Solomon (RS) Forward Error Correction (FEC) codes.
5. The method of claim 1 wherein DOCSIS service identifiers (SIDs) are assigned to a plurality of CMs belonging to a subnode such that the value of a SID uniquely identifies the CM as belonging to a given subnode.
6. The method of claim 1 , further comprising identification of an intelligent node network topology by tagging of upstream packets by an intelligent node with a unique identifier such that the CMTS is enabled to associate a CM device with a particular subnode.
7. The method of claim 1 , further comprising controlling at the intelligent node an amount of amplification provided to communications from a CM to a CMTS based upon a cable modem identifier.
8. The method of claim 1 , further comprising scheduling by the CMTS such that only devices on a given sub-node network transmit in a given time slot, such that other DINs in the HFC network are enabled to keep their corresponding devices isolated.
9. The method of claim 1 , further comprising the intelligent node filtering noise on channels other than the transmitting channel to remove interference with the upstream transmissions by CMs associated with other subnodes in the cable modem network.
10. The method of claim 1 , further comprising filtering of noise on the transmitting channel by demodulating and decoding a signal received from the CM, and then re-encoding and re-modulating the signal before it is sent upstream.
11. The method of claim 1 , further comprising calculating pre-equalization coefficients at the intelligent node for usage by at least one CM attached to a sub-node of the intelligent node in accordance with the DOCSIS pre-equalization specification.
12. The method of claim 4 , further comprising modifying a channel carrier frequency of at least one CM at the intelligent node.
13. The method of claim 12 , further comprising modifying a channel carrier frequency at an intelligent node from a first portion of spectrum above 15 MHz to a second portion of spectrum below 15 MHz to avoid the introduction of coupled household noise by at least one CM downstream of the DIN and make the second portion of spectrum usable for communications from the DIN to the CMTS.
14. The method of claim 12 , further comprising modifying a channel carrier frequency at an intelligent node from a frequency which lies within the frequency range supported by a CM to a frequency range which lies outside the CM supported range so as to expand the available spectrum for upstream transmission.
15. The method of claim 1 , further comprising independent configuration of channel carrier frequencies, channel widths, and other channel parameters on the CM and CMTS sides of the intelligent node.
16. The method of claim 15 further comprising independently scheduling the upstream channel transmissions for the CM-side and CMTS-side of the intelligent node.
17. The method of claim 16 wherein the scheduling entity for the CM side of the DIN resides within the intelligent node.
18. The method of claim 16 wherein the scheduling entity for the CM side of the DIN resides within the CMTS.
19. The method of claim 15 , further comprising configuring non-bonded channels on a sub-node of the intelligent node and bonded channels upstream of the intelligent node to convert non-bonded traffic to bonded traffic.
20. The method of claim 15 , further comprising configuring multiple narrower channels on a sub-node of the intelligent node to be combined to form a wider channel on the upstream interface of the intelligent node.
21. The method of claim 15 , further comprising configuring multiple channels with a lower QAM modulation order to be combined to form fewer channels with a higher QAM modulation order on the upstream interface of the intelligent node.
22. The method of claim 1 , further comprising gathering statistics on a downstream sub-node of the intelligent node, and communicating these statistics to the CMTS in order to provide fault isolation.
23. The method of claim 1 , wherein the intelligent node is integrated into a fiber node.
24. The method of claim 1 , wherein the intelligent node is integrated with at least one of a radio frequency (RF) line amplifier or a distribution amplifier.
25. The method of claim 1 , wherein the intelligent node is integrated with a radio frequency over glass (RFoG) optical network unit (ONU).