Cooperative Radio Transmission Dithering Against Destructive Interference
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Solution Overview
Problem
Cooperative communication between non-collocated radio transmitters is challenging due to the difficulty in achieving coordination, leading to stable destructive interference patterns that hinder reliable communication, especially in mobile ad-hoc networks where rapid coordination is impractical.
Innovation Solution
Introducing a method that dithers the transmitted signal parameters such as amplitude, frequency, phase, and symbol timing to induce time variation in the composite signal SNR, using forward error correction (FEC) and interleaving to provide diversity against destructive interference, without requiring coordination between transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple non-collocated transmitters send the same signal to a common receiver, then communication range and robustness are improved, but stable destructive interference patterns occur that reduce communication reliability
Solution Approach 1:
The patent applies dynamics by making the transmitted signal parameters time-varying through dithering. Each transmitter modulates its signal with a unique time-varying phase and frequency dither sequence, causing the composite signal at the receiver to exhibit time-varying constructive and destructive interference patterns rather than stable destructive patterns. This temporal variation allows the receiver to average out the interference effects over time, improving communication reliability.
Solution Approach 2:
The patent changes the parameters of the transmitted signals by introducing controlled dithering in phase and frequency domains. Each transmitter applies a unique dither sequence that continuously varies the phase and frequency of its transmitted signal. This parameter modulation transforms the static interference pattern into a dynamic one, enabling the receiver to recover the transmitted information despite the presence of multiple transmitters.
2Reliability
If coordination mechanisms are implemented between non-collocated transmitters, then signal alignment and communication reliability are improved, but system complexity and coordination overhead increase significantly
Solution Approach 1:
The patent implements self-service by enabling each transmitter to autonomously generate and apply its own unique dither sequence without requiring coordination with other transmitters. Each transmitter independently modulates its signal with a predetermined dither pattern, and the receiver independently processes the composite signal to recover the transmitted information. This eliminates the need for complex inter-transmitter coordination mechanisms while maintaining communication reliability.
Solution Approach 2:
The patent applies preliminary action by pre-establishing unique dither sequences at each transmitter before communication begins. These dither patterns are predetermined and stored locally, allowing transmitters to immediately begin coordinated transmission without real-time negotiation or synchronization. The receiver is also pre-configured to understand the dithering scheme, enabling direct signal recovery without coordination overhead.
3Ease of operation
If transmitters operate completely autonomously without coordination, then system simplicity and ease of deployment are improved, but stable destructive interference patterns reduce communication reliability
Solution Approach 1:
The patent enables each transmitter to serve itself by independently generating and applying unique dither sequences to its transmitted signal. This self-service approach maintains system simplicity and ease of deployment while improving reliability, as each transmitter operates autonomously without requiring coordination with others. The dithering inherently prevents stable destructive interference patterns.
Solution Approach 2:
The patent introduces dynamics into the autonomous transmission by applying time-varying dither sequences to each transmitter's signal. This temporal variation transforms static destructive interference patterns into dynamic patterns that average out over time, improving communication reliability while maintaining system simplicity. The receiver processes these dynamic signals using corresponding dither sequences to recover the transmitted information.
Data Source
AI summary
A method and system are provided in a wireless communications system comprising a plurality of nodes (users) working cooperatively. The system provides cooperative diversity by allowing nodes to actively share their antennas and other resources to obtain spatial diversity. The nodes receive the same message (information data) from a common source. Each node enhances the reliability of the message with a modern forward error correction (FEC) code, converts the FEC encoded message into an ensemble of symbols, divides the ensemble of symbols into packets, modulates, dithers and transmits the packets to a receiving node. The dithering process is performed by varying the signal amplitude, phase, frequency and/or symbol timing of the modulated packets. A unique dither pattern is assigned to each node. The receiving node captures a composite signal comprising the transmitted packets of all or most of the transmitting nodes in the cooperative communications system. Because the transmitted packets are dithered independently in phase and/or amplitude, spatial diversity is transformed into temporal diversity.