Payload Indication in 802.11n Last OFDM Symbol
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Solution Overview
Problem
The error-prevention performance of IEEE 802.11ac/ax/be is compromised due to excessive padding bits, leading to inefficiencies in payload indication, whereas 802.11n's reduced padding bits result in better performance but at the cost of significant overhead in the Physical Layer Convergence Procedure (PLCP) Service Data Unit (PSDU) due to 16-bit payload length indication.
Innovation Solution
The proposed solution involves indicating the number of payload bytes in the last OFDM symbol using fewer bits, such as 3 or 4 bits, and refining the indication by dividing the last OFDM symbol into multiple segments to reduce overhead and improve error prevention performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If 16-bit payload length indication is used in the PHY header, then payload size can be accurately indicated, but overhead increases significantly consuming 16 bits out of 34-bit PHY header
Solution Approach 1:
The patent segments the payload indication into two parts: a fixed-length field (e.g., 4 bits) for the most significant portion of the payload length, and a variable-length field for the least significant portion. This segmentation allows accurate payload size indication while reducing the fixed overhead in the PHY header, as only the necessary bits are always present in the header while additional bits can be appended as needed.
Solution Approach 2:
The patent implements a dynamic payload indication mechanism where the number of bits used for payload length varies based on the actual payload size. The indication field can expand from a fixed 4 bits to additional bits as needed, allowing the system to adapt to different payload lengths without always consuming the full 16 bits in the header, thus reducing average overhead while maintaining accuracy.
2Reliability
If reduced number of padding bits is used, then error-prevention performance improves, but payload length indication requires more bits consuming significant overhead
Solution Approach 1:
The patent changes the parameter of payload length indication from a fixed 16-bit field to a variable-length field that adapts to the actual payload size. By using a more efficient encoding scheme that only allocates the necessary number of bits for indication, the system reduces the overhead consumption while maintaining the ability to accurately indicate payload lengths, thereby preserving the benefits of reduced padding bits for error prevention.
3Device complexity
If more padding bits are used, then payload indication overhead is reduced, but error-prevention performance deteriorates
Solution Approach 1:
The patent segments the padding and indication bits into functional components where the payload length indication is separated from the padding bits. This allows the system to use minimal indication bits in the PHY header while maintaining accurate payload size information, and separately manage padding bits only where necessary, thereby avoiding the trade-off between overhead reduction and error prevention performance.
Data Source
AI summary
A method and device for providing payload length indication in IEEE 802.11 wireless communications are disclosed. The last OFDM symbol of a transmission is divided into multiple symbol segments and a number of medium access control layer (MAC) and physical layer (PHY) symbol segments are then allocated. The allocated number of MAC symbol segments is indicated using a field in the SIGNAL field or MAC frame body. Mapping between MAC and PHY symbol segments is provided as is additional puncturing for OFDM symbol usage.