Nested OFDMA Slot Structure for High-Speed Channel Estimation
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Solution Overview
Problem
High-speed mobile users in wireless cellular communication networks experience link-level performance degradations due to the inability of existing slot structures to effectively cope with fast channel changes, particularly in high-Doppler environments, leading to throughput reductions and reliability issues with reference signal transmission.
Innovation Solution
The proposed solution involves a slot structure where reference signals are piggy-backed with data transmission in fractional payload symbols, maintaining the single-carrier property and avoiding throughput degradation, by partitioning symbols into data-bearing and reference signal components with specific cyclic prefix configurations, allowing for efficient channel estimation and data demodulation even at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference signals are transmitted separately in dedicated symbols, then channel estimation reliability is improved, but throughput is degraded due to rate-matching issues and resource overhead
Solution Approach 1:
The patent combines reference signals with data transmission by multiplexing them in the same time-frequency resources. Specifically, reference signals are embedded within data symbols using code division multiplexing or frequency division multiplexing, allowing simultaneous transmission of both reference signals and data without separate dedicated symbols, thereby maintaining throughput while enabling channel estimation
Solution Approach 2:
The patent makes data symbols serve dual purposes: carrying user data and embedding reference signals for channel estimation. By allowing data symbols to function both as payload carriers and reference signal carriers, the system eliminates the need for separate reference signal resources, thus avoiding throughput degradation while maintaining channel estimation capability
2Device complexity
If existing slot structures are used for high-speed UEs, then device complexity is maintained, but link reliability deteriorates due to inability to cope with fast channel changes
Solution Approach 1:
The patent introduces dynamic reference signal embedding within data symbols, allowing the reference signal positions and patterns to adapt to varying channel conditions and UE speeds. This dynamic approach enables the slot structure to respond to fast channel changes in high-Doppler environments without requiring completely new slot formats, thus maintaining reasonable complexity while improving link reliability
Solution Approach 2:
The patent changes the parameters of existing slot structures by embedding reference signals within data symbols at specific positions and using specific mapping patterns. These parameter changes allow the system to handle fast channel changes by providing more frequent channel estimation opportunities without fundamentally redesigning the slot structure, thereby maintaining complexity while improving reliability
3Productivity
If reference signals are piggy-backed with data in fractional payload symbols, then throughput is maintained, but measurement precision of channel estimation may be compromised
Solution Approach 1:
The patent segments the piggy-backed reference signals into multiple orthogonal codes or frequency resources within the fractional payload symbols. By dividing the reference signal transmission across multiple orthogonal dimensions, the system maintains sufficient signal energy and estimation precision while embedding them within data-bearing symbols, thus preserving both throughput and measurement precision
Solution Approach 2:
The patent uses orthogonal codes or frequency resources as intermediaries to separate the reference signal from data in the piggy-backed transmission. These intermediary resources allow the reference signal to be embedded within data symbols while maintaining distinguishability and estimation accuracy, thus preserving measurement precision while maintaining throughput
Data Source
AI summary
A transmission of information within a wireless cellular network may include a first and second group of samples. A first group of samples is created comprising at least a first and a last subgroup, wherein the last subgroup is same as the first subgroup. A second group of samples created. A transformed set of samples produced by jointly transforming the created first and second group with a discrete Fourier transform (DFT). The transformed set of samples is expanded to produce an expanded set, and the expanded set is transformed with an inverse discrete Fourier transform (IDFT) to produce an OFDM symbol with a fractional payload. The first group of samples is a reference signal (RS), which is known to the receiver before the transmission occurs, while the second group of samples is information data.