Wi-Fi MPDU CRC Selection for Legacy-Compatible Large Packets
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Solution Overview
Problem
The existing IEEE-CRC-32 polynomial limits the maximum size of MAC Protocol Data Units (MPDUs) to 11,454 bytes, restricting throughput in Wi-Fi communications, and newer protocols like Wi-Fi-7 do not support larger MPDUs, leading to inefficiencies in error detection and inter-operability issues with legacy devices.
Innovation Solution
Implementing a factorable polynomial for larger MPDUs (e.g., 64 kilobytes) and a prime polynomial for smaller MPDUs, allowing devices to advertise and negotiate maximum sizes, enhancing error detection and maintaining compatibility with legacy devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the IEEE-CRC-32 polynomial is used for error detection, then compatibility with legacy devices is maintained, but the maximum MPDU size is limited to 11,454 bytes
Solution Approach 1:
The system dynamically selects between the IEEE-CRC-32 polynomial and the factorable polynomial based on the MPDU size. For MPDUs up to 11,454 bytes, the IEEE-CRC-32 polynomial is used to maintain compatibility with legacy devices. For larger MPDUs, the factorable polynomial is used to enable extended size support. This dynamic adaptation resolves the contradiction by allowing the system to optimize for either compatibility or size capability depending on the specific operational context.
Solution Approach 2:
The invention changes the polynomial parameter used for CRC calculation based on the MPDU size requirement. By switching from the IEEE-CRC-32 polynomial to the factorable polynomial when MPDU size exceeds 11,454 bytes, the system enables larger packet transmission while maintaining backward compatibility for smaller packets. This parameter change allows the system to overcome the inherent limitation of the IEEE-CRC-32 polynomial without sacrificing legacy compatibility.
2Productivity
If the MPDU size is increased beyond 11,454 bytes, then throughput is improved, but error detection performance deteriorates with the IEEE-CRC-32 polynomial
Solution Approach 1:
The system changes the polynomial parameter when MPDU size exceeds the 11,454-byte threshold. The factorable polynomial is specifically designed to maintain effective error detection performance for larger MPDU sizes, preventing the deterioration of reliability that would occur if the IEEE-CRC-32 polynomial were used for extended packets. This parameter change enables both improved throughput and maintained reliability for large packet transmission.
3Reliability
If a factorable polynomial is used for larger MPDUs, then error detection for large packets is improved, but compatibility with legacy devices is reduced
Solution Approach 1:
The system dynamically adapts the polynomial selection based on the MPDU size and device capabilities. When communicating with legacy devices or transmitting smaller packets, the IEEE-CRC-32 polynomial is used to ensure compatibility. When larger MPDUs are transmitted, the factorable polynomial is activated to provide enhanced error detection. This dynamic behavior allows the system to maintain both reliability for large packets and compatibility for legacy devices simultaneously.
Solution Approach 2:
The invention segments the MPDU size range into two categories: smaller packets (up to 11,454 bytes) handled with the IEEE-CRC-32 polynomial for legacy compatibility, and larger packets handled with the factorable polynomial for enhanced error detection. This segmentation allows different polynomial implementations to coexist without interfering with each other, resolving the compatibility-reliability contradiction by applying the appropriate tool for the specific size category.
4Device complexity
If the MAC layer is limited to 11,454 byte MPDUs, then protocol simplicity is maintained, but throughput optimization is restricted
Solution Approach 1:
The invention changes the polynomial parameter to enable larger MPDU sizes without fundamentally altering the MAC layer protocol structure. By introducing a conditional polynomial selection mechanism that activates the factorable polynomial for large packets, the system achieves throughput optimization while maintaining the overall simplicity and established architecture of the MAC layer protocol. This approach allows throughput enhancement without requiring complex protocol redesign.
Data Source
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AI summary
A device may advertise a first information element indicating a first maximum size for MAC protocol data unit, MPDU, frames for the first device (602). A device may select, based at least on the first maximum size, a first polynomial for a cyclic redundancy check, CRC, for an MPDU frame received from a second device (604, 606). A device may compute, using the selected first polynomial, a CRC for the received MPDU frame. A device may detect, based at least on the computed CRC, an error in the MPDU frame.