Reference Signal Transmission with Symbol-Wise SRS Hopping
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Solution Overview
Problem
There is a need to enable SRS transmission in the same slot as a PUSCH transmission associated with a random access process, improve the reliability of channel estimates from CSI-RS and SRS transmissions, reduce resource overhead and interference associated with DMRS transmissions, and enable dynamic TDD operation by estimating and cancelling DL interference in time division duplex systems.
Innovation Solution
The solution involves dynamically configuring transmissions of channel state information reference signals, triggering channel state information reports, and multiplexing different reference signals in frequency, while adapting the density of demodulation reference signals for data or control information transmission, and supporting cross-link interference suppression in 5G communication systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SRS transmission is enabled in the same slot as PUSCH transmission associated with random access process, then link adaptation is improved, but resource overhead and interference increase
Solution Approach 1:
The patent combines SRS and PUSCH transmissions in the same slot, allowing the UE to transmit both sounding reference signals and uplink data simultaneously. This merging approach enables link adaptation for random access processes while utilizing existing uplink resources, thereby improving reliability without proportionally increasing overhead.
Solution Approach 2:
The patent enables the uplink slot to serve multiple functions simultaneously - both carrying PUSCH data transmissions and SRS for channel sounding. This multi-functionality allows the same time-frequency resources to support both data transmission and channel estimation needs, improving link adaptation while controlling resource overhead.
2Measurement precision
If density of demodulation reference signal is increased for reliable channel estimation, then channel estimate reliability is improved, but resource overhead increases
Solution Approach 1:
The patent dynamically adapts the density of demodulation reference signals based on operating scenarios, traffic conditions, and channel characteristics. Rather than using fixed high density, the system adjusts DMRS density to match actual needs, improving channel estimation reliability when required while reducing overhead in favorable conditions.
Solution Approach 2:
The patent changes the parameter of reference signal density according to different operating scenarios. By adjusting this parameter dynamically based on channel conditions, traffic type, and quality requirements, the system achieves reliable channel estimates only when necessary, thereby optimizing the trade-off between measurement precision and resource overhead.
3Reliability
If DMRS transmissions are increased for reliable data demodulation, then demodulation reliability is improved, but interference and resource overhead increase
Solution Approach 1:
The patent performs channel sounding using SRS transmissions before actual data transmission. This preliminary action provides advance channel state information that enables the gNB to optimize DMRS configuration and data scheduling, thereby achieving reliable demodulation with minimized interference and overhead by avoiding excessive DMRS transmissions.
Solution Approach 2:
The patent utilizes SRS transmissions to obtain feedback about uplink channel conditions, which the gNB uses to adaptively configure subsequent PUSCH transmissions and DMRS density. This feedback mechanism ensures demodulation reliability is achieved through informed resource allocation rather than blanket increases in reference signal overhead, thereby controlling interference.
4Adaptability or versatility
If dynamic TDD operation is enabled with different transmission directions among interfering gNBs, then system flexibility is improved, but cross-link interference increases
Solution Approach 1:
The patent converts the harmful cross-link interference into a beneficial measurement opportunity by using SRS transmissions to sound the interfering channels. The gNB uses these measurements to estimate and cancel cross-link interference from neighboring cells with different TDD configurations, thereby enabling dynamic TDD flexibility while actively managing and reducing the harmful interference effects.
Solution Approach 2:
The patent performs preliminary channel sounding using SRS to measure and characterize cross-link interference from neighboring gNBs before data transmission. By obtaining advance knowledge of interfering channel conditions, the system can pre-compensate or cancel the harmful effects, enabling flexible dynamic TDD operation while mitigating cross-link interference.
Data Source
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AI summary
A method performed by a user equipment, UE, in a communication system, the method comprising receiving, from a base station via a higher layer signaling, configuration of a sounding reference signal, SRS; receiving, from the base station, a first downlink control information, DCI, format including one or more SRS request fields, wherein the first DCI is used for transmission of group of transmission power control, TPC, commands for SRS transmission by group of UEs and transmitting, to the base station, an SRS on one or more symbols based on a cyclic shift hopping, wherein the cyclic shift hopping is applied at every symbol for the SRS.