Interference Cancellation in Quasi-Orthogonal Wireless Systems
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Solution Overview
Problem
In wireless multiple-access communication systems, the number of terminals that can simultaneously communicate with a base station is limited by the number of available orthogonal dimensions, leading to interference and degraded performance when the number of terminals exceeds the available dimensions.
Innovation Solution
The implementation of techniques for processing packets with interference cancellation using frequency hopping and hybrid automatic repeat request (H-ARQ), where receiver spatial processing and interference estimation are used to decode and cancel interference, allowing more terminals to share time-frequency resources and improve system capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of terminals exceeds the number of available orthogonal dimensions, then more terminals can be supported simultaneously, but interference between terminals increases and degrades performance
Solution Approach 1:
The patent converts the harmful interference from correctly decoded packets into a beneficial process by estimating and subtracting this interference from the received signal. This interference cancellation technique transforms the previously harmful effect into a useful step that improves the decoding of remaining packets, allowing more terminals to communicate simultaneously without degrading overall system performance
2Productivity
If more terminals share the same time-frequency resources, then system capacity improves, but interference management complexity increases
Solution Approach 1:
The patent applies preliminary action by first identifying and decoding packets that can be successfully decoded, then using these decoded packets to pre-calculate and remove their interference contribution from the received signal before attempting to decode the remaining interfered packets. This step-by-step approach simplifies the overall interference management complexity while enabling more terminals to share resources
Data Source
AI summary
To receive packets with interference cancellation, block transmissions for the packets are received on time-frequency blocks used by these packets. Receiver spatial processing is performed on input symbols to obtain detected symbols. Each packet is demodulated and decoded based on all detected symbols obtained for all block transmissions received for the packet. For each packet that is decoded correctly, the transmission for the packet is terminated, the interference due to the packet is estimated, and the estimated interference is subtracted from the input symbols for all time-frequency blocks used by the packet. Receiver spatial processing is performed on the interference-canceled symbols to obtain new detected symbols for all time-frequency blocks used by all correctly decoded packets. Each packet decoded in error and overlapping at least partially with any correctly decoded packet may be demodulated and decoded based on all detected symbols available for that packet.