Sounding Reference Signal Frequency Hopping Pattern
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Solution Overview
Problem
In UMTS LTE networks, the accuracy of channel quality indication (CQI) measurement is degraded due to restrictions on UE transmission power, leading to errors in optimum resource unit assignment and modulation and coding scheme selection, especially for user equipment located near the cell edge, affecting user throughput and channel-aware scheduling.
Innovation Solution
A frequency hopping pattern for the sounding reference signal (SRS) is implemented using a tree assignment for frequency allocation, supporting multiple frequency band branches per layer and providing consecutive SRS signals on widely separated frequency allocations to enhance CQI measurement accuracy and prevent SRS from puncturing critical regions like PUCCH and PUSCH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SRS is transmitted with wide bandwidth to enable channel aware scheduling, then the channel quality indication measurement accuracy is improved, but the UE transmission power is exceeded especially for cell edge users
Solution Approach 1:
The patent divides the wide bandwidth SRS transmission into multiple narrower bandwidth segments transmitted at different frequency positions. Instead of transmitting one wide bandwidth SRS that exceeds power limits, the system transmits multiple narrow bandwidth SRS signals at different frequency locations, allowing cell edge users to maintain adequate transmission power while still achieving wideband channel quality assessment through multiple measurements.
Solution Approach 2:
The patent introduces frequency hopping as an additional dimension to the SRS transmission. By hopping between multiple frequency positions, the system achieves wideband channel sounding without requiring a single wide bandwidth transmission. This transforms the problem from a single high-power wideband transmission to multiple lower-power narrowband transmissions across different frequency dimensions.
2Measurement precision
If frequency hopping is implemented for SRS to improve CQI measurement accuracy, then the channel awareness is improved, but the signaling burden increases
Solution Approach 1:
The patent implements dynamic frequency hopping where the SRS frequency position changes over time according to a predefined hopping pattern. This dynamic approach allows the system to explore multiple frequency positions without requiring complex signaling for each position, as the hopping pattern is determined by simple parameters (starting frequency, hopping distance, hopping period) that can be configured with minimal signaling overhead.
3Productivity
If the SRS frequency allocation is densely packed to maximize resource utilization, then the spectral efficiency is improved, but the SRS may puncture critical regions like PUCCH and PUSCH
Solution Approach 1:
The patent applies different frequency allocation strategies for different regions of the spectrum. Critical regions like PUCCH and PUSCH are identified and protected from SRS transmissions, while non-critical regions are utilized for SRS hopping. This local differentiation allows the system to maintain high spectral efficiency in available regions while avoiding interference with critical control channels.
Data Source
AI summary
A method, an apparatus, and a computer program that includes forming frequency hopping position of the sounding reference signal is based on a hopping pattern. The hopping pattern of the sounding reference signal is configured to utilize a tree assignment for a frequency allocation of the sounding reference signal and to support at least one frequency band branch per layer. The hopping pattern of the sounding reference signal is also configured to provide consecutive sounding reference signals on widely separated frequency allocations.