Short MAC Header Packet Number Management in Wireless LAN
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Solution Overview
Problem
In wireless communication systems, particularly in WLANs, managing Sequence Numbers (SN) for short Medium Access Control (MAC) headers is challenging, especially in Machine-to-Machine (M2M) communication scenarios where power conservation and preventing STA malfunction are critical, due to the intermittent and low-rate data transmission from a large number of devices.
Innovation Solution
A method for receiving frames at a Station (STA) involves using a Sequence Control (SC) field to determine Packet Numbers (PN), performing decryption after block Acknowledgment (ACK) reordering, and incrementing the partial PN value when the sequence number of the received frame is smaller than the previous sequence number, utilizing a transceiver and processor configured to manage SN and configure encrypted data units within short MAC headers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a short MAC header is used to reduce overhead in M2M communication, then transmission efficiency is improved, but Sequence Number management becomes complex and may cause STA malfunction
Solution Approach 1:
The 48-bit Packet Number (PN) is segmented into two parts: the upper 16 bits are stored in the STA's buffer as a baseline, and the lower 16 bits are transmitted in the short MAC header's Sequence Control field. This segmentation allows the header to remain short while the full PN can be reconstructed by combining the stored upper bits with the received lower bits, thus managing sequence numbers efficiently without increasing header overhead.
Solution Approach 2:
The STA pre-stores the upper 16 bits of the Packet Number in its buffer before receiving frames. This preliminary action enables the STA to reconstruct the complete 48-bit PN by combining the stored upper bits with the lower 16 bits received in each frame's SC field, eliminating the need to transmit the entire 48-bit PN in the header and avoiding management complexity while maintaining transmission efficiency.
2Reliability
If the STA continuously monitors and manages Sequence Numbers for decryption, then security is maintained, but power consumption increases
Solution Approach 1:
The patent extracts only the necessary 16 bits of the Packet Number (the lower bits that change with each frame) to be transmitted in the short MAC header, while the upper 16 bits are stored locally in the STA. This extraction reduces the amount of data that needs to be processed and transmitted, thereby reducing power consumption while maintaining the ability to reconstruct the full 48-bit PN for secure decryption.
Solution Approach 2:
Instead of transmitting or processing the complete 48-bit Packet Number in every frame, the patent uses partial action by transmitting only the varying lower 16 bits in the short MAC header. The STA combines this partial information with the stored upper 16 bits to reconstruct the full PN when needed for decryption, reducing power consumption while maintaining security.
3Use of energy by moving object
If the MAC header is shortened to accommodate low-rate M2M traffic, then power efficiency is improved, but the ability to manage encrypted data units with full Packet Numbers is compromised
Solution Approach 1:
The patent applies the nested doll principle by nesting the 16-bit transmitted Packet Number segment within the context of the 32-bit stored Packet Number segment. The short MAC header contains only the necessary varying portion (lower 16 bits), which is nested within the broader context of the full 48-bit PN reconstructed by combining it with the stored upper 16 bits. This nesting allows the short header to convey sufficient information for security while maintaining power efficiency.
Solution Approach 2:
The STA's buffer acts as an intermediary, storing the upper 16 bits of the Packet Number. This intermediary storage mechanism bridges the gap between the short MAC header (which can only carry 16 bits) and the full 48-bit Packet Number required for security. The intermediary buffer enables reconstruction of the complete PN without requiring the header to carry all 48 bits, thus maintaining both power efficiency and information integrity.
Data Source
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AI summary
The present invention relates to a wireless communication system and, more particularly, to a method and an apparatus for transmitting and receiving a frame supporting a short MAC header in a wireless LAN system. A method for receiving a frame by a station (STA) in a wireless communication system in accordance with one embodiment of the present invention may comprise the steps of: receiving the frame including a sequence control (SC) field; determining a packet number (PN) using the value of the SC field and a partial PN value stored in the STA; and performing decryption for the frame using the PN. When the decryption is performed after reordering a block ACK for the frame, an operation can be performed to increase the partial PN value stored in the STA by 1 if the sequence number value of the SC field of the received frame is less than the previous sequence number value.