L-Comb Subcarrier Modulation for Transient Error Mitigation
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Solution Overview
Problem
Wireless communication systems face issues with transient power, phase, and frequency changes during signal transmission, leading to errors and reduced throughput due to overlapping transient periods with code block transmissions in LTE and NR systems, particularly affecting OFDM symbols and Hybrid Automatic Repeat Request (HARQ) feedback.
Innovation Solution
The method involves generating and transmitting signals using L-combs with subcarriers separated by L−1 subcarriers, allowing for partial or repeated transmission during transient periods, enabling the receiver to process reliable symbol contents by modulating only every L-th subcarrier, thus protecting code blocks from transient errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time-first mapping is used to distribute code blocks across multiple OFDM symbols, then robustness to time-localized impairments is improved, but latency increases due to encoding delays
Solution Approach 1:
The patent segments the code block into multiple code block groups (CBGs) that can be mapped to different OFDM symbols. This allows selective transmission and acknowledgment of individual CBGs, reducing the impact of transient errors on the entire transport block while maintaining efficient resource utilization.
Solution Approach 2:
The patent introduces a transient indication field in the downlink control information (DCI) that dynamically indicates whether a transient condition is detected. Based on this indication, the receiver can adjust its decoding strategy, requesting retransmission only for affected CBGs rather than the entire transport block, thus reducing latency while maintaining reliability.
2Loss of time
If frequency-first mapping is used to confine code blocks to single OFDM symbols, then latency is reduced, but robustness to time-localized impairments deteriorates
Solution Approach 1:
By dividing the transport block into multiple code block groups that can be independently mapped to different OFDM symbols, the system achieves frequency-first mapping benefits (lower latency) while maintaining robustness through selective distribution of CBGs across symbols when transients are detected.
Solution Approach 2:
The transmitter preliminarily detects transient conditions and sets the transient indication field in advance before transmitting the PDSCH. This allows the receiver to prepare appropriate decoding strategies beforehand, reducing the impact of transients on latency-sensitive transmissions.
3Productivity
If power amplifiers rapidly change power levels to reduce transient time, then productivity is improved, but transmission reliability deteriorates due to power and phase instability
Solution Approach 1:
The patent implements feedback through the transient indication field sent from transmitter to receiver. When rapid power changes cause transients, the transmitter detects this and signals the receiver, which then requests selective retransmission of affected CBGs, allowing the system to maintain high transmission speeds while compensating for instability through targeted error correction.
Solution Approach 2:
The system dynamically changes the transmission parameters by using different modulation and coding schemes for different CBGs based on transient conditions. Affected CBGs can use more robust modulation schemes while unaffected CBGs maintain higher-order modulation, optimizing the trade-off between transmission speed and reliability.
4Adaptability or versatility
If frequency-hopping is performed to improve adaptability, then versatility is improved, but transient time increases due to filter switching and power adjustments
Solution Approach 1:
The patent segments the frequency-hopping transmission into multiple CBGs that can be independently handled. When frequency-hopping transients occur, only the affected CBGs are identified and requested for retransmission, rather than requiring retransmission of the entire transport block, thus reducing the effective transient time impact.
Solution Approach 2:
The system applies partial retransmission action by requesting retransmission only for the subset of CBGs affected by frequency-hopping transients, rather than performing excessive full-block retransmission. This partial action approach reduces latency while maintaining the adaptability benefits of frequency-hopping.
Data Source
AI summary
Techniques for mitigating transient overlap times between wireless signals are presented. For instance, an example method performed by a transmitting device is presented that includes generating a signal comprising data to be transmitted to a receiving device during a symbol by modulating the data on L-K L-combs. In an aspect, each L-comb has an associated group of subcarriers that are separated from one another by L-1 subcarriers. In addition, in some instances, the method can include the transmitting device transmitting the generated signal to the receiving device (106) during at least a portion of the symbol. Corresponding devices and computer/processor-executable instructions are also described.