MIMO Artificial Signals for Capacity and Secrecy
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Solution Overview
Problem
MIMO transmission systems face capacity reduction and secrecy issues due to mismatches between pre-determined precoder/combiner matrices and actual channel matrices, allowing eavesdroppers to intercept signals easily.
Innovation Solution
The system generates artificial signals through convex optimization to minimize errors between information signals and received signals, using estimated channel coefficients to select precoding/combining matrix pairs and limit power, thereby increasing channel capacity and secrecy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pre-determined precoder/combiner matrices from a codebook are used, then device complexity is reduced and ease of operation is improved, but channel capacity is reduced and communication secrecy is compromised
Solution Approach 1:
The patent performs preliminary channel decomposition to obtain singular values and vectors, then uses these to generate artificial signals that are tailored to the specific channel characteristics. This preliminary action enables the system to compensate for the limitations of codebook-based precoding by adapting the transmitted signal to the actual channel, thereby maintaining high capacity while using fixed precoder matrices.
Solution Approach 2:
The patent changes the parameters of the transmitted signal by generating artificial signals based on channel singular values and vectors. Instead of transmitting raw data symbols, the system transforms the signal parameters to match the channel characteristics, which compensates for the quantization error introduced by codebook-based precoding and maintains channel capacity.
2Device complexity
If pre-determined precoder/combiner matrices from a codebook are used, then device complexity is reduced, but communication secrecy is compromised
Solution Approach 1:
The patent changes the signal parameters by generating artificial signals that are unique to each channel realization. This transformation ensures that even if an eavesdropper intercepts the transmission, the signal appears as random noise without knowledge of the channel characteristics, thereby maintaining secrecy while using simple codebook-based precoders.
Solution Approach 2:
The patent converts the limitation of using fixed codebook matrices into a security feature. By generating artificial signals that are tailored to the legitimate receiver's channel, the system ensures that the transmission is optimized for the intended recipient while appearing as unintelligible noise to any eavesdropper, thus converting the potential harm of fixed matrices into a benefit for communication secrecy.
3Loss of information
If artificial signals are generated through convex optimization, then channel capacity and secrecy are improved, but computational complexity increases
Solution Approach 1:
The patent performs preliminary channel decomposition to obtain singular values and vectors before signal transmission. This preliminary action separates the computationally intensive task into two parts: an offline decomposition phase and an online signal generation phase. The decomposition results are stored and reused, reducing the real-time computational burden while maintaining the ability to generate optimal artificial signals.
Data Source
AI summary
A system and method for increasing the capacity of a Multiple-Input Multiple-Output (MIMO) system at desired user's locations and reducing the capacity at locations, other than that of the desired user, while also providing secrecy. Knowing the channel coefficient between each transmitter and receiver antenna pair at the transmitter, the method of the present invention calculates the artificial signal that minimizes the Euclidean distance between the desired and received data symbols if the precoding/combining matrix pair from the set that has the minimum Euclidean distance to the singular value decomposition (SVD) of the channel matrix is used for transmission and reception. The artificial signal may be fed to the precoder, instead of the actual desired data symbols, or may be transmitted directly to reduce computational complexity, power consumption and processing delay if the hardware configuration allows.