Extended Range PPDU Configuration for Wide Bandwidth WLANs
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Solution Overview
Problem
Current wireless local area networks (WLANs) face challenges in maintaining reliable data transmission over extended ranges due to low received signal levels, particularly with wideband transmissions, where receivers struggle to detect and decode physical layer protocol data units (PPDUs), especially in IEEE 802.11 standards like Wi-Fi 7 and future Wi-Fi 8 standards.
Innovation Solution
The implementation of an extended range (ER) PPDU configuration that includes pre-ER and ER modulated fields, with enhanced training fields and signal fields, such as ER-STF, ER-LTF, and ER-SIG, to support packet acquisition and channel estimation at low signal strength, and the use of a universal signal field (U-SIG) to indicate ER mode, allowing for improved decoding and channel estimation across wider channel bandwidths like 40/80/160 MHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wideband transmissions are used to increase data rate, then throughput is improved, but receiver ability to detect and decode preamble deteriorates due to lower received signal levels
Solution Approach 1:
The PPDU is segmented into multiple parts with different modulation schemes. The initial portion uses robust modulation (e.g., BPSK) that can be detected at low signal levels, while subsequent portions use higher-order modulation (e.g., 64-QAM) to achieve high throughput. This segmentation allows the receiver to first reliably detect the preamble using robust modulation, then decode the data using high-rate modulation.
Solution Approach 2:
Different portions of the PPDU are assigned different local qualities in terms of modulation robustness. The preamble and signaling fields use high-robustness modulation suitable for extended range, while the data payload uses high-throughput modulation. This local quality differentiation ensures that critical detection functions work reliably even when overall signal levels are low.
2Length of moving object
If extended range transmission is used to increase coverage, then transmission distance is improved, but signal strength at receiver deteriorates
Solution Approach 1:
The modulation parameters are changed based on the transmission distance and signal conditions. For extended range transmissions, the system switches to more robust modulation schemes (changing the modulation parameter) that can tolerate lower received signal strengths. This parameter change allows reliable communication at extended ranges without requiring excessive transmit power.
3Reliability
If robust modulation is used to improve detection at low signal levels, then detection reliability is improved, but data throughput deteriorates
Solution Approach 1:
The transmission is divided into segments with different modulation schemes. The initial segment uses robust modulation for reliable detection, while subsequent segments use high-throughput modulation for efficient data transfer. This segmentation resolves the contradiction by applying different modulation strategies to different parts of the transmission based on their functional requirements.
Solution Approach 2:
The modulation scheme is made dynamic rather than static. The system can adaptively switch between robust and high-throughput modulation depending on the received signal conditions and the portion of the PPDU being transmitted. This dynamic approach allows the system to optimize both detection reliability and data throughput in different transmission phases.
Data Source
AI summary
A physical layer protocol data unit (PPDU) may include legacy preamble fields followed by a universal signal field (U-SIG). For an extended range (ER) transmission, the U-SIG is encoded to indicate via a bit whether the PPDU is an ER PPDU or a non-ER PPDU. When the U-SIG is encoded to indicate that the PPDU is an ER PPDU, the PPDU may include ER preamble fields following the U-SIG and an ER data field following the ER preamble fields. The ER preamble fields may comprise pre-ER modulated fields followed by ER modulated fields. The pre-ER modulate fields may comprise an ER short training field (ER-STF) followed by an ER long training field (ER-LTF) followed by an ER signal field (ER-SIG). The ER modulated fields may comprise at least the ER data field.