Overlapping Downlink Transmissions Using Orthogonal LTF Symbols
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Solution Overview
Problem
Challenges arise in wireless communication networks due to increased network density leading to reduced transmit opportunities and interference between or within base station sets, making it difficult to resolve intended transmissions from unknown interference sources.
Innovation Solution
APs coordinate simultaneous transmissions to associated STAs using orthogonal long training field (LTF) symbols, pre-compensate for carrier frequency offset, and include interference information in data frames to enable effective signal path determination and interference management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If network density is increased to improve connectivity and data transfer, then more devices can be connected, but interference between base station sets increases and transmit opportunities are reduced
Solution Approach 1:
The patent segments the training field symbols into orthogonal components that can be independently processed. By dividing the training field into multiple orthogonal segments, the system can separate desired signals from interfering signals, allowing simultaneous transmissions from multiple base stations without mutual interference
Solution Approach 2:
The patent introduces orthogonal long training field (LTF) symbols as an intermediary mechanism. These special LTF symbols act as mediators that carry information about both the desired signal and the interference signal, enabling the receiving device to estimate and compensate for interference from overlapping basic service sets
2Productivity
If simultaneous transmissions are enabled to improve throughput, then data transfer efficiency increases, but it becomes difficult to resolve intended transmissions from interference sources
Solution Approach 1:
The patent applies preliminary action by pre-compensating for carrier frequency offset and pre-establishing orthogonal relationships between LTF symbols from different base stations. This preliminary configuration enables the receiving device to easily separate and resolve simultaneous transmissions without complex real-time processing
Solution Approach 2:
The patent uses orthogonal LTF symbols as distinct identifiers (analogous to color changes) that allow the receiving device to distinguish between different base station transmissions. Each base station uses uniquely orthogonal LTF sequences, making it easy to identify and separate individual signals even when they overlap in time and frequency
3Object-affected harmful factors
If orthogonal LTF symbols are used to enable simultaneous transmissions, then interference is minimized, but device complexity increases due to coordination requirements
Solution Approach 1:
The patent implements self-service by enabling each base station to independently generate and transmit orthogonal LTF symbols based on standardized rules. The receiving device automatically performs interference estimation and compensation using these orthogonal symbols, eliminating the need for complex real-time coordination between base stations while maintaining low interference levels
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.