System for low noise aggregation in DOCSIS contention slots in a shared upstream receiver environment

• US 20080170853A1
• Filed: 06/04/2004
• Published: 07/17/2008
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Shlomo Selim Rakib, Yehuda Azenkot
• Inventors: Azenkot, Yehuda, Rakib, Shlomo Selim
• Granted Patent: US 7,548,548 B2
• Time in Patent Office: Days
• US Class Current: 398/26
• CPC Class Codes: H04L 12/2801 Broadband local area networks

Abstract

A cable modem termination system is disclosed with flexible mapping of upstreams to downstreams and flexible mapping of downstreams to optical nodes and optical nodes to upstream receivers and the ability to add singe upstreams or downstreams as needed for load balancing. Multiple downstreams can share the same upstream. Multiple receivers can be coupled to the same upstream. Monitoring of upstream performance for overperforming or underperforming modems can be carried out, and new upstreams with higher and/or lower throughtput can be created to service the overperformers and/or underperformers. Modems can be grouped into logical groups with different performance levels and serviced by different upstreams or different upstream logical channels on the same upstream physical channel. An upstream linecard with a digital crosspoint switch is disclosed with the switch operated during contention intervals to allow reception with or without aggregation of noise where multiple upstream share the same receiver.

Claims

1. A method for receiving DOCSIS upstream bursts during contention intervals in an upstream linecard in a cable modem termination system having one or more PHY receivers, said upstream linecard coupled to a plurality of optical nodes, said reception carried out without aggregation of noise, comprising the steps:

(1) determining when a DOCSIS contention interval exists;

(2) determining how many PHY receivers are available during said contention interval to receive upstream DOCSIS bursts from said plurality of optical nodes;

(3) sensing energy of incoming DOCSIS bursts at inputs of said upstream linecard coupled to said optical nodes;

(4) determining if any PHY receiver is available to receive a DOCSIS burst which is creating said energy which was sensed;

(5) if no PHY receiver is available to process a burst whose energy was sensed, ignoring said burst;

(6) if a PHY receiver is available to process the incoming burst whose energy is being sensed and said contention interval is still occurring, picking an available PHY receiver and switching a crosspoint switch to coupled an input at which is arriving said burst whose energy was sensed to an output coupled to said available PHY receiver.

3. The process of claim 1 wherein step (1) is carried out by receiving DOCSIS upstream MAP message data pertaining to a plurality of DOCSIS upstreams from a plurality of optical nodes all of which are coupled to one or more shared upstream receivers (hereafter an upstream group), said MAP message data indicating when contention intervals are in said group.

4. The method of claim 1 wherein step (2) is carried out by polling said receivers to determine which receivers are available to receive upstream bursts during contention intervals.

5. The method of claim 1 wherein step (2) is carried out by receiving information from said receivers which indicates which receivers are available to receive upstream bursts during contention intervals.

6. The process of claim 1 wherein step (2) further comprises the step of constructing a table or database of receiver availability from availability information sent by the receivers, and wherein step (4) further comprises the step of updating the table or database built by step (2) with the latest availability information and then reading said table to find an available receiver, if any, and further comprising a step for building a mapping table using a discovery process carried out during contention intervals using reception of IUC 3 and IUC 4 bursts, said mapping table containing entries which associate each cable modem with an input to said switch at which upstream bursts from said cable modem will arrive.

7. The process of claim 1 wherein step (6) is accomplished by reading information sent to said crosspoint switch by a PHY receiver which indicates when said contention interval starts and when it stops or when said contention interval starts in terms of an upstream minislot number and the duration in minislots of said contention interval.

8. The process of claim 6 wherein step (7) is accomplished by the crosspoint switch reading the receiver availability table after it has been updated with the latest information on availability sent by said receivers and, if a receiver is available, automatically switching the input at which energy has been sensed to couple said input to an output of said crosspoint switch to which said available receiver is coupled.

9. The process of claim 1 wherein normal operation of step (8) is accomplished by performing the following steps:

(A) generating DOCSIS UCD and MAP messages contain Information Element data in an upstream media access control process and sending said UCD and MAP messages downstream to said cable modems, said MAP message data defining when each cable modem coupled to an optical node can transmit and what type of burst it can transmit during DOCSIS non contention intervals;

(B) examining said Information Element data to determine when each burst will be arriving from each optical node during non contention intervals;

(C) for each burst, determining receiver availability and picking a receiver to process said burst;

(D) sending MAP data and UCD data pertaining to each burst to the receiver to which said burst has been assigned;

(E) in each said receiver which has been assigned to process a burst and which has received pertinent MAP and UCD data, setting up to process said burst and using said MAP data to search a lookup table which indicates upon which RF section said burst will be arriving and using said MAP data regarding when said burst will be arriving and data found from said lookup table to generate a switch control command or data for said crosspoint switch which will cause said crosspoint switch to couple at an appropriate time an input at which said burst will be arriving to an output to which said receiver is coupled such that sample data of said burst reaches said receiver.

10. An upstream linecard apparatus, comprising:

means for determining when a DOCSIS contention interval exists;

means for determining how many PHY receivers are available during said contention interval to receive upstream DOCSIS bursts from said plurality of optical nodes;

means for sensing energy of incoming DOCSIS bursts at inputs of said upstream linecard coupled to said optical nodes;

means for determining if any PHY receiver is available to receive a DOCSIS burst which is creating said energy which was sensed;

means for ignoring said burst whose energy was sensed if no PHY receiver is available to process said burst;

means for determining if the contention interval is still occurring if a PHY receiver is available and energy of an incoming burst during a contention interval is sensed;

means for picking an available PHY receiver and switching a crosspoint switch to coupled an input at which is arriving said burst whose energy was sensed to an output coupled to said available PHY receiver if a contention interval exists, a PHY receiver is available and energy of an incoming burst is sensed and for sampling said burst to digitize it, processing said samples and recovering data encoded in said burst; and

means for returning to normal operation when no contention interval is active wherein any burst which is arriving during a non contention interval is known via DOCSIS MAP data and said crosspoint switch is switched so as to couple said burst to an output to which is coupled a PHY receiver which has been assigned to receive it and for receiving digital samples of said burst and recovering data therefrom.

11. A method for receiving DOCSIS upstream bursts during contention intervals in an upstream linecard in a cable modem termination system having one or more PHY receivers, said upstream linecard coupled to a plurality of optical nodes in one or more hybrid fiber coaxial cable systems and wherein each cable modem for a group of cables belongs to an upstream logical channel, comprising the steps:

(1) determining when a DOCSIS contention interval exists;

(2) responding to start of a DOCSIS contention interval by grouping upstream logical channels from different optical nodes into groups, each group having the same MAC domain and the same UCD and IUC type;

(3) selecting a group to process;

(4) switching a switch to couple each input coupled to a hybrid fiber coaxial cable system optical node in said selected group to an output coupled to a DOCSIS compatible PHY receiver for a fixed or programmable time so as to sum all upstream signals from said optical nodes in said group;

(5) determining if the contention interval is over;

(6) a step for receiving upstream bursts from cable modems in said group and which do not collide, and for determining if all groups have been processed during said contention interval and attempting to process each group during said contention interval to receive non colliding bursts from each group in turn; and

(7) if step 5 determines the contention interval is over, returning to normal processing.

12. The process of claim 1 further comprising the following step following step (5):

if a PHY receiver is available to process an incoming burst whose energy was sensed, determining if the contention interval is still occurring;

and further comprising the following step following step (6);

if said contention interval is not still occurring, returning to normal operation wherein the burst which is arriving is known via DOCSIS MAP data and said crosspoint switch is switched so as to couple said burst to an output to which is coupled a PHY receiver which has been assigned to receive it.

and wherein step (1) is carried out by receiving information from one or more PHY receivers in an upstream line card indicating when DOCSIS contention intervals start and stop in a plurality of DOCSIS upstreams from a plurality of optical nodes all of which are coupled to one or more shared upstream receivers (hereafter an upstream group) and further comprising the step of sending DOCSIS MAP data for at least said upstream group from an upstream media access control process to one or more PHY receivers which are assigned to process upstream bursts from said upstream group, said MAP message data indicating when contention intervals are in said group.

12-1. An apparatus comprising:

means for determining when a DOCSIS contention interval exists;

means for responding to start of a DOCSIS contention interval by grouping upstream logical channels from different optical nodes into groups, each group having the same MAC domain and the same UCD and IUC type;

means for selecting one of said groups to process;

means for switching a switch to couple each input coupled to a hybrid fiber coaxial cable system optical node in said selected group to an output coupled to a DOCSIS compatible PHY receiver for a fixed or programmable time so as to sum all upstream signals from said optical nodes in said group, and for receiving any upstream burst which does not collide with another burst and recovering data therefrom;

means for receiving any upstream burst during said contention interval which does not collide with another burst and recovering data therefrom and attempting to receive upstream bursts from each logical group in turn during said contention interval; and

means for carrying out normal processing to receive and recover data from scheduled bursts from said optical nodes without noise aggregation during non contention intervals.

13. A process comprising the steps:

(1) determining when a DOCSIS contention interval exists;

(2) responding to start of a DOCSIS contention interval by determining how many PHY receivers are available to receive bursts during said contention interval;

(3) dividing upstream logical channels received at inputs of an upstream line card into one or more groups, each group of upstream logical channels having the same MAC domain, UCD type and IUC type, and then dividing each group into a number of subgroups equal to the number of PHY receivers available to process bursts from cable;

(4) coupling inputs at which are received upstream logical channels of each subgroup of a selected group to an output of a crosspoint switch which is coupled to one of said available receivers assigned to receive bursts from said subgroup for a fixed or programmable time, and receiving digital samples of bursts and recovering data from non colliding bursts of said subgroup and ignoring colliding bursts within said subgroup;

(5) attempting to receive non colliding bursts from cable modems in other groups during said contention interval.

14. An apparatus comprising:

means for determining when a DOCSIS contention interval exists;

means for responding to start of a DOCSIS contention interval by determining how many PHY receivers are available to receive bursts during said contention interval;

means for dividing upstream logical channels received at inputs of an upstream line card into one or more groups, each group of upstream logical channels having the same MAC domain, UCD type and IUC type, and then dividing each group into a number of subgroups equal to the number of PHY receivers available to process bursts from cable;

means for coupling inputs at which are received upstream logical channels of each subgroup of a selected group to an output of a crosspoint switch which is coupled to one of said available receivers assigned to receive bursts from said subgroup for a fixed or programmable time, and receiving digital samples of bursts and recovering data from non colliding bursts of said subgroup and ignoring colliding bursts within said subgroup;

means for determining whether said contention interval is over, and, if not, incrementing the group number and repeating step (4) and this step (5) until it is determined that said contention interval is over, and when said contention interval is over, returning to normal processing.

15. An upstream linecard comprising:

a plurality of RF amplifier sections, each having an input for coupling to an optical node of a hybrid fiber coaxial cable system and an output each having an gain control input;

a plurality of analog-to-digital (A/D) converters, each having an input for receiving amplified signals from said output of an RF amplifier section, and each having a sample output;

a digital crosspoint switch having a plurality of inputs and one or more outputs, each said input coupled to an output of one of said A/D converters, and having a switch control input, for switching so as to couple one or more inputs to an output under control of data or signals received at said switch control input;

one or more DOCSIS compatible receivers, each having an input coupled to an output of said crosspoint switch, and each having a switch control output coupled to said switch control input of said crosspoint switch, and each having a UCD and MAP data input for receiving DOCSIS UCD and MAP data for upstream logical channels coupled to said plurality of RF amplifier sections, and each having a gain control output coupled to a gain control input of an RF amplifier section, each said receiver functioning to generate switch control signals which control switching of said crosspoint switch based upon said MAP data such that scheduled bursts during non contention intervals get coupled to an input of a PHY receiver during non contention intervals such that said receiver recovers data encoded in said burst-without noise aggregation caused by summing of signals of more than one said upstream logical channel sharing a PHY receiver, and for causing said crosspoint switch to go into contention mode processing when contention intervals occur so as to receive contention burst transmitted during contention intervals on one or more upstream logical channels coupled to one or more inputs of said crosspoint switch.

16. An apparatus comprising:

means for determining when a DOCSIS contention interval exists;

means for responding to start of a DOCSIS contention interval by determining how many PHY receivers are available to receive bursts during said contention interval;

means for switching a crosspoint switch so as to couple bursts arriving during one or more contentention intervals on one or more upstream logical channels to one or more PHY receivers; and

one or more shared PHY receivers for receiving contention intervals bursts.

17. A method for receiving DOCSIS upstream bursts during contention intervals and non contention intervals in an upstream linecard in a cable modem termination system having one or more PHY receivers, said upstream linecard coupled to a plurality of optical nodes, comprising the steps:

(1) determining when a DOCSIS contention interval exists;

(2) when a contention interval is occurring, for a switch having at least one output coupled to a PHY receiver and having a plurality of inputs coupled to a plurality of optical nodes in a hybrid fiber coaxial cable system generating suitable control signals to control said switch to sum all inputs signal appearing at said inputs and couple the result to an output coupled to a PHY receiver;

(3) receiving an IUC 3 burst during said contention interval and identifying the cable modem which sent said IUC 3 burst;

(4) sending a message to the cable modem identified in step 3 ordering said cable modem to send an IUC 4 burst, and generating control signals to control said switch to pick just one input for coupling to said output coupled to said PHY receiver;

(5) if no IUC 4 burst from said cable modem identified in step 3 is heard, generating control signals to control said switch to select another single input for coupling to said output coupled to said PHY receiver and sending a command to said cable modem identified in step 3 ordering it to send another IUC 4 burst;

(6) if no IUC 4 burst is heard, repeating steps 5 and 6 until an IUC 4 burst is heard

(7) when an IUC 4 burst is heard, making an entry in a mapping table associating the cable modem which sent said IUC 4 burst with the optical node coupled to the input upon which said IUC 4 burst is heard; and

(8) after said contention interval is over, using information in said mapping table and information in DOCSIS MAP messages to determine upon which input each scheduled non contention burst will be arriving and using that information to generate control signals to control switching by said switch so as to avoid noise aggregation in receiving bursts by a shared DOCSIS receiver coupled through said switch to multiple optical nodes.

18. A method for receiving DOCSIS upstream bursts during contention intervals and non contention intervals in an upstream linecard in a cable modem termination system having one or more PHY receivers, said upstream linecard coupled to a plurality of optical nodes, comprising the steps:

(1) determining by notification or MAP data when a DOCSIS contention interval is active;

(2) enable energy sensors on each input of switch;

(3) sensing energy of an incoming DOCSIS IUC 3 burst at an input of said switch, and controlling switch to couple IUC 3 burst to PHY receiver and receive burst and carry out DOCSIS training protocol;

(4) determining from energy detector which input IUC 3 burst arrived upon and determining from IUC 3 burst which cable modem sent burst;

(5) making a mapping table entry associating cable modem which sent IUC 3 burst to the input and/or optical node to which said cable modem is coupled;

(6) using mapping table and MAP data to control switch to receive non contention bursts without noise aggregation.

19. A method for receiving DOCSIS upstream bursts during contention and non contention intervals, in an upstream linecard in a cable modem termination system having one or more PHY receivers, said upstream linecard coupled to a plurality of optical nodes, comprising steps for:

determining when a contention interval is active, and, when a contention interval is active, operating a switch to sum all inputs to an input of a PHY receiver;

receiving an IUC 3 burst and identifying the cable modem which sent said IUC 3 burst and performing DOCSIS training with said cable modem;

sending a message to said cable modem inviting said cable modem to send one or more IUC 4 bursts and controlling said switch to carry out a successive approximation process to listen for the IUC 4 bursts on ever smaller groups of inputs until a single input is found;

after said single input is found, making a mapping entry in a mapping table associating said cable modem which sent said IUC 4 burst which was heard on a single input with said input and/or optical node to which said cable modem is coupled;

using said mapping table and MAP message data to control said switch to receive scheduled non contention bursts without noise aggregation.