Sounding Reference Signal Arrangement for LTE Uplink
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Solution Overview
Problem
Current UMTS LTE systems face challenges in maximizing cyclic shift separation between SRS resources and ensuring efficient SRS transmission, particularly near the cell edge, which affects channel quality indication measurement accuracy and resource allocation, leading to errors in modulation and coding scheme selection.
Innovation Solution
The proposed solution involves an SRS arrangement that calculates actual cyclic shift values and uses an efficient signaling scheme based on existing DM RS signals, supporting maximum cyclic shift separation and code-tree-based bandwidth assignment, while preventing SRS transmission from puncturing the PUCCH region, using a minimum SRS bandwidth of 4 RBs to enhance user throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SRS transmission bandwidth is increased to improve channel estimation accuracy, then measurement precision is improved, but the SRS may puncture the PUCCH region causing transmission conflicts
Solution Approach 1:
The SRS transmission bandwidth is segmented and restricted to specific resource blocks that do not overlap with the PUCCH region. The network configures the SRS to transmit only in allowed resource blocks, effectively dividing the available spectrum into SRS-only regions and PUCCH regions to avoid puncturing conflicts while maintaining adequate bandwidth for channel estimation.
2Reliability
If cyclic shift separation is maximized to improve SRS resource differentiation, then reliability is improved, but device complexity increases due to additional signaling requirements
Solution Approach 1:
The cyclic shift values are locally optimized for each SRS resource configuration to maximize separation between adjacent resources. Instead of using a uniform cyclic shift scheme across all resources, the patent applies specific cyclic shift offsets tailored to each resource's position and configuration, achieving maximum differentiation where needed while keeping the signaling overhead manageable through efficient representation.
3Object-affected harmful factors
If SRS bandwidth is reduced to avoid PUCCH puncturing, then harmful factors are reduced, but channel estimation accuracy deteriorates
Solution Approach 1:
The patent compensates for reduced SRS bandwidth in the frequency domain by utilizing the time domain dimension more effectively. Multiple SRS transmissions are scheduled across different time slots with varying cyclic shifts, allowing the system to accumulate channel estimation information over time and frequency, thereby maintaining estimation accuracy even with narrower instantaneous bandwidth.
Data Source
AI summary
A method, apparatus, and computer program embodied on a computer-readable medium to create an uplink message to be transmitted to a base station, the created uplink message comprises a sounding reference signal based on accessed data. An uplink scheduling grant signal is received via downlink, from the base station, in response to the transmission of the uplink message. An uplink data transmission is transmitted to the base station responsive to the received uplink scheduling grant signal.