Overlapping Downlink Frames With Orthogonal LTF Coordination
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Solution Overview
Problem
In wireless communication networks, simultaneous transmissions from multiple access points (APs) to associated stations (STAs) often result in interference due to unknown and uncoordinated signal paths, making it challenging to resolve intended transmissions from overlapping basic service sets (BSSs.
Innovation Solution
APs coordinate transmission of simultaneous messages with orthogonal long training field (LTF) symbols, including synchronized guard intervals and modulation schemes, allowing STAs to determine interference characteristics and adjust transmission parameters for effective signal reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple APs transmit simultaneously to increase network density and throughput, then productivity is improved, but interference between transmissions increases causing reliability to deteriorate
Solution Approach 1:
The patent segments the transmission signal into distinct components with different properties. Specifically, it divides the LTF symbols into different types (first LTF symbols and second LTF symbols) that are transmitted simultaneously from different APs but can be distinguished at the receiver through their orthogonal characteristics
Solution Approach 2:
The patent changes the orthogonality parameter of the LTF symbols to enable simultaneous transmissions. By ensuring that LTF symbols from different APs are orthogonal to each other while maintaining intra-AP consistency, the system allows multiple transmissions on the same frequency band while enabling the STA to separate and process signals from different APs independently
2Device complexity
If APs transmit without coordination to reduce complexity, then device complexity is reduced, but interference resolution becomes difficult requiring advanced signal processing
Solution Approach 1:
The patent applies preliminary action by pre-configuring the LTF symbols with specific orthogonality properties before transmission. The first and second LTF symbols are designed to be orthogonal to each other in advance, and this orthogonality relationship is maintained across multiple transmissions. This preliminary structuring of the signal enables the STA to easily identify and separate interfering signals without requiring complex real-time coordination or advanced interference resolution algorithms
Data Source
AI summary
Spatial reuse is provided. A device can identify first symbols orthogonal to second symbols, responsive to a receipt of an indication, from a second device, of a transmission of a second message including the second symbols. The device can transmit a first message including the first symbols, simultaneously with the transmission of the second message.