Communication of active data flows between a transport modem termination system and cable transport modems
View Patent ↗Multiplexing of information from a plurality of information flows into fixed-length packets such as, but not limited to, MPEG packets allows efficient utilization of bandwidth and also can be used to reduce transmission latency. In addition, utilizing MPEG packets and transport streams for octet multiplexing allows the packets carrying octet-multiplexed data to easily be integrated with other MPEG packets for other services that are commonly found in cable transmission networks of all coax, hybrid fiber coax, and/or all fiber. The multiplexing/demultiplexing of octets using MPEG packets generally is described by mappings that specify the use of octets in MPEG packets. Changes to allocations in a map generally should be propagated in a way that reliably ensures that both the transmitter and receiver have a consistent view of the octet mappings.
1. A method of ensuring consistent communication of map allocations between a first device and a second device, the method comprising:
receiving an active map from the first device at the second device, wherein the active map comprises at least one active data flow associated with the second device;
storing active data flow changes to the map in an inactive map;
receiving the inactive map at the second device; and
receiving, at the second device, a command to switch from the active map to the inactive map;
wherein each of the active and inactive maps specify at least two packet identifiers for at least one frequency channel, and each of the active and inactive maps specify, for each of the at least two packet identifiers, blocks of data that are used by the second device from the at least one active data flow and blocks of data that are unused by the second device from the at least one active data flow, such that packets with the at least two packet identifiers can be received by the second device, wherein each of the blocks of data is a proper subset of a packet.
2. The method of claim 1 , wherein the at least one frequency channel comprises two different frequency channels.
3. The method of claim 1 , wherein the at least one frequency channel provides frequency division multiplexing and the at least two packet identifiers provides time division multiplexing.
4. The method of claim 1 , further comprising:
activating the inactive map and deactivating the active map; and
retrieving from the inactive map the active data flow changes.
5. The method of claim 4 , further comprising: transmitting a command indicating receipt of the inactive map; and transmitting a final command indicating that the inactive map was activated.
6. The method of claim 1 , wherein the second device has a partial active map of a complete map.
7. The method of claim 6 , further comprising receiving partial active maps associated with each of a plurality of second devices.
8. An apparatus that ensures consistent communication of map allocations between a first device and a second device, the apparatus comprising:
the second device, the second device being configured to:
receive changes to a map from the first device at the second device;
store changes to the map in an inactive map; and
receive a command to switch from an active map to the inactive map;
wherein each of the active and inactive maps specify at least two packet identifiers for at least one frequency channel,
each of the active and inactive maps specify, for each of the at least two packet identifiers, blocks of data that are used by the second device from at least one active data flow and blocks of data that are unused by the second device from the at least one active data flow, such that packets with the at least two packet identifiers can be received by the second device, wherein each of the blocks of data is a proper subset of a packet.
9. The apparatus of claim 8 , wherein the second device is further configured to communicate a command to the first device indicating receipt of the command to switch from the map to the inactive map.
10. The apparatus of claim 8 , wherein the second device is further configured to communicate a second command to the first device indicating the switch to the inactive map is complete.
11. The apparatus of claim 8 , wherein the map comprises at least one active data flow associated with the second device, and the inactive map comprises at least one active data flow change.
12. The apparatus of claim 8 , wherein the at least one frequency channel comprises two different frequency channels.
13. The apparatus of claim 8 , wherein the second device has a partial map of a complete map.
14. A system for ensuring consistent communication of map allocations, the system comprising:
a first device for generating and transmitting at least a portion of a complete active map, wherein the complete active map comprises data flows for each of a plurality of second devices, wherein, when at least one of the data flows change, the first device for generating and transmitting at least a portion of a complete inactive map indicating the data flow changes, wherein the complete active map specifies at least two packet identifiers for a frequency channel and the complete inactive map specifies that the at least two packet identifiers are for at least two different frequencies, and wherein each of the complete active and complete inactive maps specify, for each of the at least two packet identifiers, blocks of data that are used from the data flows and blocks of data that are unused, wherein each of the blocks of data is a proper subset of a packet; and
the first device is further for transmitting to at least one of the plurality of second devices a command to switch from the at least a portion of the complete active map to the at least a portion of the inactive map.
15. The system of claim 14 , wherein, when the at least one of the plurality of second devices receives the command to switch, the at least one of the plurality of second devices transmits a command indicating receipt of the at least a portion of the inactive map.
16. The system of claim 14 , wherein, when the at least one of the plurality of second devices switches maps, the at least one of the plurality of second devices transmits a command indicating that the at least a portion of the inactive map was activated.
17. The system of claim 14 , wherein the complete active map comprises data flows for each of the plurality of second devices.
18. The system of claim 14 , wherein the frequency channel specified in the complete active map provides frequency division multiplexing.
19. The method of claim 1 , wherein the at least one active data flow comprises at least two different active data flows, and wherein the each of the active and inactive maps further specify that a first packet identifier of the at least two packet identifiers receives data blocks from each of the at least two different active data flows.
20. The method of claim 14 , wherein the complete inactive map further specifies that a first packet identifier of the at least two packet identifiers receives data blocks from two different data flows of the data flows.