WLAN Preamble Frame Format for Cross-Protocol Coexistence
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Solution Overview
Problem
Wireless local area networks (WLANs) face challenges in allowing wireless terminals employing different communication protocols to share the same physical layer, leading to inefficiencies in data transmission and compatibility issues between various protocols.
Innovation Solution
The solution involves formatting data units with a preamble that allows client stations operating under different communication protocols to determine the duration and compatibility of the data unit, using specific fields and modulation schemes such as UHT-SIGA fields and CRC generation schemes to differentiate between protocols and ensure proper processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a data unit is formatted according to a first communication protocol, then the data transmission efficiency for devices using that protocol is improved, but compatibility with devices using other communication protocols deteriorates
Solution Approach 1:
The data unit is segmented into multiple parts: a preamble portion formatted according to a second communication protocol (accessible to all devices) and a data portion formatted according to the first communication protocol (optimized for specific devices). This segmentation allows legacy devices to access basic information while newer devices can utilize the full optimized data structure.
Solution Approach 2:
The preamble is designed with universal compatibility, containing fields that can be decoded by devices using different communication protocols. The L-SIG field and other preamble elements are structured so that both legacy devices (second protocol) and modern devices (first protocol) can interpret them, enabling the same data unit to serve multiple device types.
2Adaptability or versatility
If the preamble is formatted to be decodable by devices using a second communication protocol, then protocol compatibility is improved, but the ability to convey first protocol-specific information deteriorates
Solution Approach 1:
The patent adds an additional dimension to the data unit structure by including a third communication protocol format within the preamble or data portion. This allows the data unit to carry information in multiple protocol formats simultaneously, enabling first protocol devices to access their specific information while second protocol devices can still decode the universal preamble.
Solution Approach 2:
The L-SIG field acts as an intermediary that bridges different protocol requirements. It contains rate and length information that can be interpreted by both second protocol devices (for basic duration calculation) and first protocol devices (which can extract additional meaning or use it as a baseline for more sophisticated decoding).
3Measurement precision
If a CRC generation scheme specific to the first communication protocol is used, then error detection accuracy for first protocol devices is improved, but compatibility with second protocol devices deteriorates
Solution Approach 1:
Different portions of the data unit have different CRC characteristics tailored to their intended recipients. The preamble portion uses a CRC generation scheme compatible with second protocol devices, while the data portion or specific fields within it use a CRC scheme optimized for first protocol devices. This local differentiation allows each device type to verify its relevant data with the appropriate error detection method.
Data Source
Figure 1
Figure 2A~2B
Figure 3~5
AI summary
In a method for generating a data unit conforming to a first communication protocol, a first field and a second field to be included in a preamble of the data unit are generated. The first field includes a first set of one or more information bits that indicate a duration of the data unit and is formatted such that the first field allows a receiver device that conforms to a second communication protocol to determine the duration of the data unit. The second field includes a second set of one or more information bits that indicate to a receiver device that conforms to the first communication protocol that the data unit conforms to the first communication protocol. The first field and the second field are modulated using a modulation scheme specified for a field corresponding to the first field and the second field, respectively, by the second communication protocol.