Method and apparatus for flexibly filtering scheduling messages in a communication system
View Patent ↗A method and apparatus for flexibly filtering upstream scheduling messages in a communication system is described. The inventive method and apparatus uses software to rapidly filter a MAP message comprising a plurality of information elements. In accordance with the inventive method, a communication device inputs a MAP message and outputs a filtered MAP message comprising upstream transmission information relevant only to the communication device. The communication device stores data relevant to its upstream transmit opportunities. This data is derived from information elements that are associated with the communication device. In one embodiment, the communication device stores a transmit time. In another embodiment, the communication device stores a transmit time and a transmit duration. In yet another embodiment, the communication device stores a transmit time, a transmit duration and an IUC.
1. A method of filtering upstream scheduling messages in a data communication system that includes a headend and at least one subscriber unit, wherein the system has an upstream and a downstream transmission path, the method comprising:
obtaining a scheduling message from the headend, the scheduling message including a MAP message having a plurality of information elements (IE's), at least one IE including a service identifier (SID), an Interval Usage Code (IUC), a Minislot offset and a Minislot length value;
filtering the MAP message to identify a plurality of IEs that correspond to a selected subscriber unit, and to generate a filtered MAP message having a plurality of data fields, where the MAP message includes at least one Null IE; and
storing an information set based upon the plurality of IEs obtained in the step of filtering the MAP message into a filtered scheduling message that includes the following sub-steps:
(1) before encountering Null IE, storing the information using a first process;
(2) when encountering the Null IE, storing the information using a second process; and
(3) after encountering the Null IE, storing the information using a third process.
2. The method of filtering upstream scheduling messages as set forth in claim 1 wherein the MAP message flier includes at least one Real IE.
3. The method of filtering upstream scheduling messages as set forth in claim 1 , wherein the MAP message further includes at least one Real IE and at least one Acknowledgement IE.
4. The method of filtering upstream scheduling messages as set forth in claim 3 , wherein the first process comprises Real IE processing.
5. The method of filtering upstream scheduling messages as set forth in claim 4 , wherein the Real IE processing process comprises the following sub-steps:
storing the SID in a 16-bit SID field;
storing the IUC in an 8-bit IUC field;
storing the Minislot offset in a 16-bit Minislot offset field;
calculating a Minislot length; and
storing the Minislot length in a 16-bit Minislot length field.
6. The method of filtering upstream scheduling messages as set forth in claim 1 , wherein the second process comprises Null IE processing.
7. The method of filtering upstream scheduling messages as set forth in claim 6 , wherein Null IE processing comprises the following sub-steps:
storing a value of Zero in a 16-bit SID field;
storing a value of 7 in an 8-bit IUC field;
storing the Minislot offset in a 16-bit Minislot offset field; and
storing a value of zero in a 16-bit Minislot length field.
8. The method of filtering upstream scheduling messages as set forth in claim 1 , wherein the third process comprises Acknowledgment IE processing.
9. The method of filtering upstream scheduling messages as set forth in claim 8 , wherein Acknowledgement IE processing comprises the following sub-steps:
storing the SID in a 16-bit SID field;
storing the IUC in an 8-bit IUC field;
storing the Minislot offset in a 16-bit Minislot offset field; and
storing a value of zero in a 16-bit Minislot length field.