4-TC SRS Mapping in TDD UpPTS for Multiplex Capacity
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Solution Overview
Problem
Current TDD wireless communication systems face limitations in efficiently transmitting and receiving sounding reference signals (SRS) due to insufficient uplink resources and reduced multiplex capacity, particularly in LTE systems where the number of transmission combs (TCs) supported by SRS is limited, affecting the overall performance and resource management.
Innovation Solution
The method involves supporting up to 4 transmission combs (TCs) for SRS transmission in a Time Division Duplex (TDD) system by mapping the 4-TC SRS to the Uplink Pilot Time Slot (UpPTS) of a special subframe, allowing for efficient transmission by utilizing additional symbols and resource elements, and configuring the SRS transmission through one or two antenna ports based on specific equations for optimal periodicity and power control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of transmission combs (TCs) supported by SRS is increased to 4, then the multiplex capacity and uplink resource management efficiency are improved, but the device complexity and mapping configuration requirements increase
Solution Approach 1:
The patent segments the frequency domain resources by introducing transmission comb (TC) indexing, where 4 different TCs (TC0, TC1, TC2, TC3) are defined to represent different frequency domain patterns. This segmentation allows multiple UEs to be multiplexed in the time domain while maintaining frequency domain separation through comb indexing, thereby increasing multiplex capacity without requiring excessive resource elements.
Solution Approach 2:
The patent adds a new dimension to the SRS mapping by introducing TC information as an additional parameter alongside traditional time-domain multiplexing. By mapping SRS to UpPTS symbols while incorporating TC indexing, the system achieves four-fold frequency domain multiplexing capability, effectively adding a dimensional layer to resource allocation that increases capacity without proportionally increasing complexity.
2Productivity
If 4-TC SRS is mapped to UpPTS with multiple symbols, then the uplink resource utilization is improved, but the transmission overhead and resource management complexity increase
Solution Approach 1:
The patent makes the UpPTS symbols serve multiple functions: they carry both the traditional single-TC SRS mappings and the new 4-TC SRS mappings. By configuring UpPTS with multiple symbols, the system can universally support both legacy 2-TC SRS transmissions and enhanced 4-TC SRS transmissions, improving resource utilization without requiring separate dedicated resources for different TC configurations.
Solution Approach 2:
The patent changes the mapping parameters by introducing TC information as a configurable parameter that can be signaled to UEs. By dynamically adjusting the TC parameter along with the time-domain symbol allocation, the system can adaptively allocate resources based on actual transmission needs, reducing overhead by only activating the necessary TC configurations rather than always reserving resources for all 4 TCs.
3Measurement precision
If more transmission combs are supported, then the channel estimation accuracy and user support capacity are improved, but the signal processing complexity increases
Solution Approach 1:
The patent segments the channel estimation task by associating each transmission comb with a specific frequency domain pattern. By dividing the frequency domain into 4 distinct comb patterns (TC0-TC3), the base station can independently estimate channels for each comb, simplifying the overall estimation process compared to handling all antennas simultaneously, while still achieving accurate channel state information for MIMO operations.
Data Source
AI summary
A method for transmitting a sounding reference signal (SRS) by a user equipment (UE) in a wireless communication system supporting Time Division Duplex (TDD) includes: receiving transmission comb (TC) information indicating any one of a total of 4 TCs supported by a 4-TC SRS; mapping the 4-TC SRS to an SRS symbol of an Uplink Pilot Time Slot (UpPTS) of a TDD special subframe based on the TC information; and transmitting the 4-TC SRS through the UpPTS. In the mapping of the 4-TC SRS, the 4-TC SRS is mapped in a unit of 1 resource element (RE) per 4 REs on the SRS symbol based on a TC indicated by the TC information. The transmission of the 4-TC SRS is supported when a plurality of symbols are configured in the UpPTS.