Zero-Tail Spread OFDM Transmitter Diversity Coding
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Solution Overview
Problem
Current 5G wireless networks face challenges in antenna array operations and space-time coding methods, particularly in efficiently transmitting data symbols across multiple antennas and subcarriers, which affects frequency and spatial diversity.
Innovation Solution
The method involves generating and conjugating data symbols, appending zeros, spreading, and modulating them across different subcarriers and antennas, using techniques like ZT-SOFDM and Alamouti space-time coding to create and transmit time-domain symbols, ensuring effective cyclic prefix management and diversity gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional space-time coding methods are used in 5G wireless networks, then frequency and spatial diversity can be achieved, but the complexity of antenna array operations increases and spectral efficiency decreases
Solution Approach 1:
The patent segments the data symbols into multiple groups and applies different processing (conjugation, time-reversal, zero-appending) to different segments. This allows diversity gains to be achieved through structured segmentation of the signal stream, reducing the operational complexity compared to conventional space-time coding while maintaining frequency and spatial diversity benefits
Solution Approach 2:
The patent performs preliminary actions by conjugating and time-reversing data symbols before spreading and modulation. By pre-processing the symbols with conjugation and time-reversal operations, the system establishes diversity properties early in the transmission chain, simplifying subsequent antenna array operations while achieving the desired frequency and spatial diversity
2Reliability
If conventional space-time coding with multiple zero insertion steps is used, then transmit diversity can be achieved, but the number of processing steps and system complexity increases
Solution Approach 1:
The patent merges the cyclic prefix function and the diversity-generating zero-insertion function into a single integrated process. By appending zeros to create both the cyclic prefix structure and the diversity patterns simultaneously, the system achieves transmit diversity without requiring separate zero-insertion steps, thereby reducing overall system complexity while maintaining full transmit diversity performance
Solution Approach 2:
The patent creates a multi-functional processing block that simultaneously performs conjugation, time-reversal, zero-appending for cyclic prefix, and diversity pattern generation. This universal processing approach achieves multiple objectives (cyclic prefix creation, transmit diversity, spectral efficiency) in a single integrated operation, reducing the number of discrete processing steps required
3Productivity
If traditional OFDM modulation is used, then data transmission can be performed, but out-of-band emissions increase
Solution Approach 1:
The patent applies local quality modification by using zero-appending to create a zero-tail structure at the end of the modulated signal. This localized zero-insertion at specific positions in the time-domain signal effectively reduces out-of-band emissions in adjacent frequency regions while maintaining the core data transmission capability, providing spectral confinement without sacrificing productivity
Data Source
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AI summary
An example technique may include controlling receiving a first block of time domain symbols and a second block of time domain symbols, converting the blocks of time domain symbols to the frequency domain to create a first pre-equalized block of frequency domain symbols and a second pre-equalized block of frequency domain symbols, respectively, applying, a linear phase shift to the frequency domain symbols to compensate for a conjugating and time-reversing of corresponding pre-spread domain symbols being performed at a transmitter before spreading of the pre-spread domain symbols, and creating a first equalized block of frequency domain symbols and a second equalized block of frequency domain symbols as a function of the first and second pre- equalized blocks of frequency domain symbols wherein at least one of the first and second pre-equalized blocks of frequency domain symbols has the linear phase shift applied.