HE WLAN Preamble Extra Tones for Lower OFDM PAPR
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Solution Overview
Problem
High Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems degrades signal-to-quantization noise ratio and power amplifier efficiency, particularly in the preamble of High Efficiency (HE) WLAN transmissions, which affects throughput and power consumption in wireless networks.
Innovation Solution
The method involves generating and transmitting High Efficiency (HE) Physical Layer Protocol Data Units (PPDU) with specific sequences of extra tones in the Legacy Signal (L-SIG) and Repeated L-SIG fields, using BPSK constellation values of -1, -1, -1, and +1 in subcarriers -28, -27, 27, and 28, to reduce PAPR, thereby optimizing channel estimation and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional OFDM preamble transmission is used in HE WLAN, then the transmission structure is simple, but the PAPR is high which degrades signal quality and power amplifier efficiency
Solution Approach 1:
The patent changes the parameter values of extra tones in the L-SIG and RL-SIG fields by assigning specific BPSK constellation values (-1, -1, -1, +1) to subcarriers -28, -27, 27, and 28. This parameter optimization reduces the PAPR of the preamble without changing the overall transmission structure, thereby maintaining simplicity while improving signal quality and power amplifier efficiency
2Ease of manufacture
If conventional OFDM preamble transmission is used in HE WLAN, then the implementation is straightforward, but the power amplifier efficiency is degraded due to high PAPR
Solution Approach 1:
The patent optimizes the power amplifier efficiency by changing the constellation values of extra tones in the preamble. By setting specific BPSK values for subcarriers -28, -27, 27, and 28 in both L-SIG and RL-SIG fields, the PAPR is reduced, allowing the power amplifier to operate more efficiently and reducing energy loss without complicating the implementation
3Ease of operation
If conventional OFDM preamble transmission is used in HE WLAN, then the system is easy to operate, but the throughput is limited due to degraded signal-to-quantization noise ratio
Solution Approach 1:
The patent improves throughput by optimizing the signal-to-quantization noise ratio through parameter changes in the extra tones. By assigning specific BPSK constellation values to subcarriers -28, -27, 27, and 28, the PAPR reduction leads to better signal quality and higher effective throughput, while the system remains easy to operate as the changes are transparent to the operational interface
Data Source
AI summary
A wireless device generates a High Efficiency (HE) Physical layer Protocol Data Units (PPDU) including a non-High Throughput Signal (L-SIG) field and transmits the HE PPDU. Transmitting the HE PDDU includes transmitting a set of extra tones with the L-SIG field. The set of extra tones include a sequence of values, and first, second, third, and fourth values of the sequence of values respectively correspond to BPSK constellation values of −1, −1, −1, and +1. The set of extra tones may include −28th, −27th, 27th, and 28th subcarriers, relative to a center (zero) subcarrier, of a 20 MHz bandwidth of the HE PPDU, and may be used to transmit the first, second, third, and fourth values of the sequence of values, respectively. Another wireless device may receive the HE PPDU, and may use the set of extra tones to estimate a channel.