Differential STBC Decoding Without CSI for Passive Terminals
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Solution Overview
Problem
Conventional orthogonal space time block code (OSTBC) coding codebooks, including Alamouti codes, are designed for active radio frequency communication and require channel state information (CSI) between all transmit and receive antennas, which is not feasible for passive terminals like backscatter communication due to power and hardware limitations.
Innovation Solution
A decoding method that utilizes a differential space time block code (DSTBC) combined with a new space time block code (NSTBC) codebook, allowing decoding without requiring CSI, reducing hardware complexity and error detection probability by optimizing the codebook for backscatter communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OSTBC coding codebooks are used, then full diversity gain and full rate are achieved, but decoder complexity increases and CSI knowledge is required
Solution Approach 1:
The patent changes the encoding parameters by introducing a differential encoding approach where the encoding coefficient vector is updated incrementally based on previous symbols. Instead of requiring full CSI knowledge for each transmission, the system uses parameter updates (encoding coefficient vectors) that can be tracked differentially, reducing the information burden on the decoder while maintaining diversity gain through the structured codebook design.
2Reliability
If conventional OSTBC coding codebooks are used, then full diversity gain is achieved, but implementation complexity in passive terminals increases
Solution Approach 1:
The differential encoding scheme enables the system to serve itself by using previously transmitted encoding coefficient vectors as reference points for current encoding. This self-referential approach eliminates the need for external CSI feedback mechanisms, making the system particularly suitable for passive terminals that cannot actively measure or report channel conditions. The encoding process becomes more manufacturable as it relies on stored historical data rather than complex real-time channel estimation infrastructure.
3Device complexity
If DSTBC encoding mode with NSTBC codebook is used, then system implementation complexity is reduced, but decoding requires differential decoding process
Solution Approach 1:
The patent performs preliminary encoding by pre-calculating and storing encoding coefficient vectors in the codebook before transmission. The differential encoding process prepares the signal in advance by incorporating reference to previous symbols during the encoding phase itself, rather than requiring complex post-reception processing. This preliminary action simplifies the overall system implementation while the decoding operation, though differential, follows a straightforward reconstruction process using the stored codebook and received signals.
Data Source
AI summary
A decoding method, a device, and a readable storage medium. The method includes: determining, by a decoder, an encoding coefficient vector based on a received signal and an NSTBC codebook; and decoding, by the decoder, original encoded input symbols in a current symbol period based on the encoding coefficient vector, a differential space time block code DSTBC encoding mode, and the NSTBC codebook.