Null Data Packet Tone Subsets for WLAN Feedback
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Solution Overview
Problem
Existing uplink orthogonal frequency-division multiple access (UL-OFDMA) schemes in wireless local area networks (WLANs) are inefficient for transmitting small amounts of feedback information due to their complexity and the small amount of data being transmitted, particularly when using High Efficiency Long Training Fields (HELTFs) and payload OFDM symbols.
Innovation Solution
A null data packet (NDP) transmission scheme is introduced that divides a set of tones into subsets to transmit information bits, using different values to indicate zero or one, and employs various modulation techniques such as on-off keying and differential binary phase-shift keying to efficiently convey feedback information without the need for UL-OFDMA payload symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If UL-OFDMA schemes with HELTFs and payload OFDM symbols are used for feedback transmission, then information can be transmitted, but the encoding and modulation complexity increases significantly
Solution Approach 1:
The feedback information is segmented into individual bits, where each bit is transmitted using a simple tone assignment (present/absent or high/low frequency) rather than complex modulation. This segmentation allows each bit to be transmitted independently with minimal encoding overhead, resolving the contradiction between information transmission and complexity.
Solution Approach 2:
The patent uses simple, disposable tone assignments for each feedback bit without requiring complex modulation schemes. Each tone assignment is a lightweight, standalone transmission method that can be quickly implemented and discarded, avoiding the need for sophisticated encoding and modulation infrastructure.
2Loss of information
If UL-OFDMA schemes with HELTFs and payload OFDM symbols are used, then feedback information can be transmitted, but the transmission efficiency decreases for small amounts of data
Solution Approach 1:
The patent applies partial action by transmitting only the essential feedback bits using minimal tone assignments, rather than using full OFDMA resource allocation. This partial approach eliminates unnecessary overhead and improves efficiency for small amounts of feedback data while still achieving complete information transmission.
Solution Approach 2:
By segmenting feedback information into individual bits transmitted through simple tone assignments, the patent avoids the overhead of complete OFDMA frame structures. This segmentation enables efficient transmission of small data amounts by matching the transmission resources exactly to the information requirements.
3Device complexity
If simple tone assignment is used for feedback transmission, then complexity is reduced, but robustness to spurious signals and interference decreases
Solution Approach 1:
The patent incorporates feedback mechanisms where the access point receives the tone assignments and determines feedback bits by comparing against expected patterns. This feedback loop enables error detection and correction, enhancing robustness while maintaining simple transmission schemes. The system can identify and correct errors caused by spurious signals through this feedback process.
Solution Approach 2:
The patent uses predetermined tone assignments and comparison-based detection to cushion against potential errors from spurious signals. By having expected patterns established beforehand and comparing received signals against these patterns, the system prepares in advance for potential interference, maintaining reliability without increasing transmission complexity.
Data Source
AI summary
Embodiments described herein provide a method for null data packet transmission. An information symbol is obtained for transmission in a null data packet. A set of tones for transmitting the information symbol is obtained and divided into a first subset of tones and a second subset of tones. A first value is transmitted over the first subset of tones and a second value is transmitted over the second subset of tones to indicate a feedback information bit of zero from the information symbol. A third value is transmitted over the first subset of tones and a fourth value is transmitted over the second subset of tones to indicate a feedback information bit of one from the information symbol.