OFDMA CID Encoding to Cut DL/UL MAP Overhead
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Solution Overview
Problem
Fixed length encoding in OFDMA based IEEE 802.16 networks results in inefficient use of resources due to transmission of unnecessary leading zero bits and redundant CID information in MAP IEs and MAC headers, leading to higher overhead when the number of users is less than the maximum capacity.
Innovation Solution
Eliminating the transmission of unnecessary leading zero bits of CIDs in DL/UL MAP IEs and removing redundant CID information from both MAP IEs and MAC headers, using a flag to indicate the removal of leading zeros and allocating CIDs in ascending order to optimize resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed length encoding is used for CIDs, then the encoding is simple and consistent, but the overhead increases when the number of users is less than maximum capacity
Solution Approach 1:
The patent applies variable-length encoding where the number of bits used to encode CIDs dynamically adjusts based on the actual number of active users. When fewer users are active, fewer bits are used, making the encoding length adaptive rather than fixed. This resolves the contradiction by allowing simple encoding structure while reducing overhead through dynamic bit allocation.
Solution Approach 2:
The patent changes the parameter of encoding length from a fixed value to a variable value that depends on the number of active users. By modifying this parameter dynamically, the system achieves both simplicity (through consistent encoding rules) and reduced overhead (through shorter encoding lengths when users are fewer).
2Ease of operation
If leading zero bits are transmitted for all CIDs, then the encoding is uniform and simple, but unnecessary bits increase the frame overhead
Solution Approach 1:
The patent extracts and removes unnecessary leading zero bits from CID encodings. Instead of transmitting all bits uniformly, the system identifies and eliminates the redundant leading zeros that do not carry information, thereby reducing frame overhead while maintaining encoding simplicity through consistent removal rules.
Solution Approach 2:
The patent discards unnecessary leading zero bits that do not contribute to user identification. The receiver can still correctly identify users by interpreting the remaining significant bits, effectively discarding redundant information while preserving the essential identification function.
3Reliability
If CID is included in both MAP IEs and MAC headers, then user identification is redundant for verification, but the redundant information increases overhead
Solution Approach 1:
The patent merges the CID identification function into a single location (MAP IEs) and removes the redundant CID from MAC headers. The MAC headers can still be associated with users through the MAP IE references without needing to repeat the CID, thereby combining the identification function efficiently while reducing overhead.
Solution Approach 2:
The MAP IE serves multiple functions: it provides user identification (CID) and establishes the reference for MAC header association. By making the MAP IE multi-functional, the system eliminates the need for separate CID fields in MAC headers, reducing overhead while maintaining reliable user identification through the universal MAP IE reference.
Data Source
AI summary
An embodiment of the present invention provides a method, comprising reducing overhead in OFDMA based Wireless Networks by determining the highest CIDs to be transmitted in a particular DL/UL MAP and determining the number of leading zero bits of the highest CID and removing the leading zero bits from each CID prior to transmission. Further, an embodiment of the present invention provides removing the CID field in the header of the message identified by a particular CID.