Flexible SRS Sequence Design for LTE Bandwidth Adaptation
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Solution Overview
Problem
Current SRS arrangements in LTE are inflexible in frequency, limiting bandwidth flexibility and multiplexing capabilities, which affects channel estimation accuracy and overhead in CoMP scenarios, and are not backward compatible with existing standard releases.
Innovation Solution
Defining a new SRS sequence over the maximum bandwidth of interest with cyclic shifts applied across the sequence, allowing for flexible allocation of narrower frequency parts for UEs, enabling orthogonality irrespective of PRB allocations and supporting multiple SRS bandwidth options, including less than 4 PRBs, while maintaining compatibility with existing systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current SRS arrangements in LTE are used, then backward compatibility with existing standard releases is maintained, but bandwidth flexibility and multiplexing capabilities are limited
Solution Approach 1:
The patent applies dynamics by making the SRS sequence generation flexible and configurable. The base sequence length, cyclic shift values, and frequency comb selections can be dynamically adjusted based on bandwidth requirements while maintaining compatibility with existing LTE standards. This allows the system to adapt to different bandwidth scenarios without requiring complete system redesign.
Solution Approach 2:
The patent changes key parameters including base sequence length (Xmax), cyclic shift values (alpha), and frequency comb selections to achieve different bandwidth configurations. By modifying these parameters, the system can support various SRS bandwidth options including less than 4 PRBs while maintaining backward compatibility through controlled parameter selection.
2Measurement precision
If current SRS arrangements in LTE are used, then existing system structure is maintained, but channel estimation accuracy at cell edges deteriorates
Solution Approach 1:
The patent applies local quality by optimizing SRS sequences specifically for cell-edge scenarios. Different base sequences and cyclic shifts are selected based on local channel conditions, allowing improved channel estimation accuracy at cell edges while maintaining standard compliance. The frequency comb selection is also optimized locally to match specific deployment scenarios.
Solution Approach 2:
The patent performs preliminary actions by pre-configuring multiple base sequences and cyclic shift values that are optimized for different channel conditions. The system prepares multiple SRS sequence options in advance, allowing the network to select the most appropriate sequence for cell-edge users before transmission, thereby improving estimation accuracy without increasing real-time complexity.
3Productivity
If flexible bandwidth allocation is implemented, then multiplexing capacity is improved, but compatibility with existing standard releases is compromised
Solution Approach 1:
The patent achieves universality by designing an SRS sequence generation method that can serve multiple functions across different LTE releases and bandwidth configurations. The same base sequence generation framework supports both legacy configurations and new flexible bandwidth allocations, allowing a single system to maintain compatibility while enabling advanced multiplexing capabilities.
Solution Approach 2:
The patent applies segmentation by dividing the SRS resource configuration into separate controllable parameters (base sequence length, cyclic shift, frequency comb). This segmentation allows independent optimization of each parameter for multiplexing capacity while maintaining overall compatibility with existing standards through controlled parameter selection and configuration.
Data Source
AI summary
A method includes determining a base sequence, cyclic shift, and UE-specific portion of a frequency comb, applying the cyclic shift to the base sequence to create a shifted sequence, and selecting a portion of the shifted sequence as a user equipment-specific SRS. The selected portion of the shifted sequence corresponds to the portion of the frequency comb. A second method includes assigning a cyclic shift and a UE-specific portion of a frequency comb to a UE, where the cyclic shift is for use by the UE to apply the cyclic shift to the determined base sequence to create a shifted sequence. The portion of the frequency comb is for the UE to select a portion of the shifted sequence for SRS. The method includes transmitting indications of the base sequence, the cyclic shift, and the portion of the frequency comb. Auxiliary DMRS may be provided using SRS resources.