Spectrum Management via Precoding Codeword Index
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Solution Overview
Problem
In cognitive radio systems, especially in LTE networks sharing spectrum with other systems like TV channels, traditional filtering methods lead to significant out-of-band emission due to discontinuous frequency bands, causing demodulation errors as the receiving terminals are unaware of pre-filtering operations performed by transmitting terminals.
Innovation Solution
A spectrum management method that involves calculating and broadcasting a precoding codeword index based on a predefined codebook, allowing both transmitting and receiving terminals to use a precoding vector for modulating and demodulating data, thereby synchronizing pre-filtering operations and reducing out-of-band emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional filtering methods are used to suppress out-of-band emission from discontinuous frequency bands, then out-of-band emission is reduced, but the receiving terminal cannot correctly demodulate the data because it is unaware of the pre-filtering operation
Solution Approach 1:
The transmitting terminal feeds back the filtering parameters (precoding codeword index) to the receiving terminal through the control channel, enabling the receiving terminal to replicate the same filtering operation and correctly demodulate the data, thus resolving the contradiction between suppressing out-of-band emission and maintaining demodulation accuracy
Solution Approach 2:
The transmitting terminal performs pre-filtering (precoding) on the baseband signal before modulation, and the receiving terminal performs the corresponding inverse filtering operation before demodulation, ensuring that both terminals are synchronized in their signal processing operations
2Adaptability or versatility
If the LTE system uses only standard frequency bands (5MHz, 10MHz, 15MHz), then compatibility with existing standards is maintained, but the frequency band cannot be made full use of when sharing with other systems
Solution Approach 1:
The system dynamically adjusts the frequency band configuration based on real-time spectrum sensing results and allocated bandwidth requirements, allowing flexible allocation of discontinuous frequency bands while maintaining compatibility with LTE standards through dynamic TDD reconfiguration
Solution Approach 2:
The system applies different frequency band configurations to different time slots and spatial locations, allowing LTE to share spectrum with other systems (e.g., TV channels, GSM) in specific bands while maintaining standard compliance in other bands
Data Source
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AI summary
A data modulation method, a data demodulation method, and a method, an apparatus and a system for managing spectrum are disclosed, including: obtaining a target frequency band allocated to a transmitting terminal; calculating a precoding codeword index of spectrum shaping according to a codebook corresponding to a current radio scene and the target frequency band, where the codeword index corresponds to a return-to-zero subcarrier sequence, and the return-to-zero subcarrier sequence serves to calculate a precoding vector for modulating data; and sending the precoding codeword index out through broadcast.