Upstream channel bonding in a cable communications system
View Patent ↗A method for increasing upstream bandwidth per cable modem user in a cable communications system that includes a cable modem termination system (CMTS) and a plurality of cable modems is provided. The method permits a cable modem to transmit data to the CMTS on multiple upstream channels simultaneously using a technique called “channel bonding.” Channel bonding allows smaller bandwidth upstream channels to be bonded together to create a larger bandwidth pipe.
1. A method in a cable modem for high-throughput transmission in a cable network, comprising:
requesting bandwidth to transmit packets in an upstream queue;
receiving a multichannel grant from a cable modem termination system (CMTS), wherein the multichannel grant allocates the requested bandwidth as a plurality of minislots across a plurality of bonded upstream channels;
concatenating the packets in the upstream queue;
filling the multichannel grant by dividing the concatenated packets into a plurality of segments, wherein a size of each segment corresponds to a contiguous subset of the allocated minislots in one of the upstream channels; and
transmitting the segments to the CMTS.
2. The method of claim 1 , wherein when the allocated bandwidth exceeds the requested bandwidth, the concatenating step comprises continuously concatenating the packets in the upstream queue such that packets already in the upstream queue are concatenated with newly arriving packets until the multichannel grant is filled.
3. The method of claim 2 , further comprising padding out the multichannel grant with padding bytes when the upstream queue is empty.
4. The method of claim 2 , wherein the filling step comprises filling the multichannel grant with the concatenated packets without using DOCSIS concatenation headers.
5. The method of claim 1 , wherein the filling step comprises fragmenting at least one of the concatenated packets such that the fragmented packet spans more than one of the segments, the method further comprising inserting into the segments segment headers that assist in packet demarcation within the segments.
6. The method of claim 5 , wherein the inserting step comprises inserting into a segment a pointer to a first DOCSIS header within the segment.
7. The method of claim 5 , wherein the inserting step comprises clearing a pointer valid bit in a segment header for a segment when there is no first DOCSIS header for the segment.
8. The method of claim 5 , wherein the inserting step comprises inserting into the segments segment headers that have a fixed amount of overhead.
9. The method of claim 8 , wherein the requesting step comprises requesting an unburdened amount of bandwidth, and wherein the multichannel grant from the CMTS includes an additional amount of bandwidth to accommodate the fixed amount of overhead associated with each of the segment headers.
10. The method of claim 5 , further comprising using a DOCSIS request/transmission policy to enable and disable the segment headers.
11. The method of claim 10 , further comprising piggybacking a request for additional bandwidth using at least one of a DOCSIS baseline privacy interface (BPI) extended header (EHDR) or a DOCSIS request EHDR only when the segment headers are disabled.
12. The method of claim 5 , wherein the inserting step includes inserting into a segment a segment header having a piggyback field that accommodates a bandwidth request from the cable modem.
13. The method of claim 12 , wherein the receiving step comprises receiving a grant pending from the CMTS in the multichannel grant, the method further comprising requesting additional bandwidth for newly arrived packets in the upstream queue using the piggyback field in the segment header.
14. The method of claim 12 , wherein the receiving step comprises receiving no grant pendings from the CMTS in the multichannel grant, the method further comprising re-requesting for previously requested bandwidth using the piggyback field in the segment header when a request time is earlier than an acknowledgement time in the multichannel grant.
15. The method of claim 14 , further comprising requesting additional bandwidth for newly arrived packets in the upstream queue.
16. The method of claim 1 , wherein the requesting step comprises requesting additional bandwidth in a subsequent request upon receiving an acknowledgement that the CMTS received a previous bandwidth request.
17. The method of claim 16 , wherein the requesting step comprises requesting additional bandwidth in the subsequent request upon receiving at least one of a grant or a grant pending from the CMTS for the previous bandwidth request.
18. The method of claim 1 , further comprising, before the filling step, performing baseline privacy interface (BPI) encryption on each of the concatenated packets.
19. A method in a cable modem termination system (CMTS) for high-throughput bandwidth allocation in a cable network, comprising:
receiving from a cable modem a bandwidth request to transmit packets in an upstream queue;
issuing a multichannel grant that allocates the requested bandwidth as a plurality of minislots across a plurality of bonded upstream channels;
receiving from the cable modem a plurality of segments comprising a concatenation of the packets in the upstream queue, wherein a size of each segment corresponds to a contiguous subset of the allocated minislots in one of the bonded upstream channels; and
reconstructing the upstream queue of packets from the received segments.
20. The method of claim 19 , wherein the received segments further comprise at least one fragmented packet that spans more than one of the plurality of segments, the reconstructing step further comprising reconstructing the upstream queue of packets based on information in segment headers inserted into each of the plurality of segments.
21. The method of claim 20 , wherein the reconstructing step further comprises reconstructing the upstream queue of packets based on a pointer to a first DOCSIS header within a segment.
22. The method of claim 20 , wherein the issuing step comprises issuing a multichannel grant that includes additional bandwidth to accommodate a fixed amount of overhead associated with each of the segment headers.
23. The method of claim 19 , further comprising allocating a number of request opportunities on one of the bonded upstream channels, wherein the number of allocated request opportunities is a multiple of a number of minislots required to transmit a request on the bonded upstream channel.
24. The method of claim 23 , further comprising receiving from the cable modem a request for bandwidth in at least one of the allocated request opportunities on the bonded upstream channel.
25. A high throughput cable network, comprising:
a cable modem termination system (CMTS); and
one or more cable modems residing on the cable network,
wherein the CMTS issues a multichannel grant responsive to a bandwidth request from a cable modem of the one or more cable modems to transmit packets in an upstream queue, the multichannel grant allocating the requested bandwidth as a plurality of minislots across a plurality of bonded upstream channels, and
wherein the cable modem transmits to the CMTS a plurality of segments comprising a concatenation of the packets in the upstream queue, wherein a size of each segment corresponds to a contiguous subset of the allocated minislots in one of the bonded upstream channels.
26. A cable modem termination system (CMTS), comprising:
a bandwidth allocation controller configured to allocate bandwidth to a cable modem as a plurality of minislots across a plurality of bonded upstream channels in response to a bandwidth request from the cable modem;
a downstream physical layer modulator (DS PHY) configured to issue a multichannel grant to the cable modem, wherein the multichannel grant assigns the allocated bandwidth across the plurality of bonded upstream channels; and
an upstream physical layer demodulator (US PHY) configured to receive from the cable modem a plurality of segments comprising a concatenation of packets, wherein a size of each segment corresponds to a contiguous subset of the allocated minislots in one of the bonded upstream channels.