Low Bandwidth PHY OFDM Tone Spacing for Extended Range
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Solution Overview
Problem
Current wireless local area networks (WLANs) operating in sub-1 GHz frequencies face challenges in efficiently utilizing low bandwidth modes for extended range communications, as existing protocols do not effectively adapt to varying spectrum availability and data rate requirements.
Innovation Solution
The implementation of a method that generates data units with reduced bandwidth and data rate by utilizing a lower clock rate and specific OFDM symbol configurations, including tone spacing and constellation symbol mapping, to support both normal and low bandwidth modes within the same communication protocol, allowing for extended range and improved receiver sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If normal bandwidth OFDM modes are used, then data throughput is maintained, but communication range is limited and receiver sensitivity is reduced
Solution Approach 1:
The system dynamically adapts OFDM parameters including tone spacing, cyclic prefix length, and subcarrier allocation based on channel conditions and bandwidth availability. This allows the system to switch between normal and extended range modes, optimizing receiver sensitivity when bandwidth is constrained while maintaining normal data throughput when full bandwidth is available.
Solution Approach 2:
The patent modifies key OFDM parameters to enable extended range operation: increasing tone spacing between subcarriers, extending cyclic prefix length to accommodate larger delay spreads, and adjusting subcarrier allocation patterns. These parameter changes improve receiver sensitivity and communication range while maintaining protocol compatibility.
2Length of moving object
If bandwidth is reduced for extended range communication, then communication range is extended, but data rate decreases
Solution Approach 1:
The available bandwidth is segmented into multiple subcarriers with flexible allocation. In extended range mode, the system activates only a subset of subcarriers with increased spacing, effectively segmenting the frequency resource to extend range while maintaining reasonable data rates through selective subcarrier utilization.
Solution Approach 2:
The system uses partial bandwidth activation where only necessary portions of the spectrum are utilized for transmission. This partial action approach extends communication range by concentrating power into fewer, more widely spaced subcarriers, accepting reduced data rate as a trade-off for improved range coverage.
3Reliability
If tone spacing is increased for low bandwidth mode, then bandwidth efficiency is reduced, but receiver sensitivity in constrained spectra is improved
Solution Approach 1:
The system changes the tone spacing parameter from standard OFDM values to larger spacings suitable for low bandwidth modes. This parameter adjustment improves receiver sensitivity by reducing interference between subcarriers in constrained spectral environments, while the system compensates for reduced bandwidth efficiency through adaptive modulation and coding schemes.
Data Source
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AI summary
A method includes generating first and second data units corresponding to first and second PHY modes, respectively. Generating the first data unit includes FEC encoding first information bits, mapping the FEC-encoded bits to first constellation symbols, and generating first OFDM symbols to include the first constellation symbols. The first OFDM symbols utilize a first tone spacing, and include a first number of non-zero tones collectively spanning a first bandwidth. Generating the second data unit includes FEC encoding second information bits, block encoding the FEC-encoded bits, mapping the block-encoded bits to second constellation symbols, and generating second OFDM symbols to include the second constellation symbols. The second OFDM symbols utilize the first tone spacing, and include a second number of non-zero tones collectively spanning a second bandwidth less than the first bandwidth. The second number of non-zero tones is less than the first number of non-zero tones.