Uplink Mode Switching for Channel State Information
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Solution Overview
Problem
In mobile communication networks, especially in LTE and LTE-Advanced, the limited capacity of sounding reference signals (SRS) for channel sounding in uplink MIMO transmission becomes inadequate with a large number of simultaneous subscribers, hindering effective channel state information acquisition and precoding for maximizing communication throughput.
Innovation Solution
The method involves temporarily switching the uplink transmission mode between precoded and non-precoded DMRS modes, allowing non-precoded DMRS to be transmitted from each antenna for channel sounding and power control, enabling dynamic and temporal mode switching without requiring frequent SRS transmissions, thereby improving channel state information and reducing SRS load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sounding reference signals (SRS) are used for channel sounding in uplink MIMO transmission, then channel state information can be obtained, but the capacity of SRS is limited and becomes inadequate with a large number of simultaneous subscribers
Solution Approach 1:
The patent makes the demodulation reference signal (DMRS) serve dual functions: both as a reference signal for channel estimation and as a sounding signal for channel state information acquisition. By configuring the DMRS with different antenna ports and applying precoding matrices, the system eliminates the need for separate SRS transmissions, thereby increasing the effective capacity for channel sounding while maintaining measurement precision.
Solution Approach 2:
The patent merges the functions of SRS and DMRS by using the same time-frequency resources for both purposes. The DMRS is configured to carry both demodulation and channel sounding functions, combining what were previously separate signaling mechanisms into a unified approach that reduces overhead and increases capacity efficiency.
2Reliability
If precoded DMRS is transmitted to maintain cell-edge performance, then communication reliability is improved, but channel sounding capability is reduced
Solution Approach 1:
The patent introduces dynamic switching between precoded and non-precoded DMRS transmission modes based on channel conditions and service requirements. The network can flexibly configure the DMRS transmission mode, applying precoding when cell-edge performance is critical and using non-precoded mode when accurate channel state information is needed, thereby adapting to varying operational demands.
Solution Approach 2:
The patent applies different precoding strategies to different user groups and channel conditions. Cell-edge users receive precoded DMRS for enhanced reliability, while users with better channel conditions or requiring accurate channel state information receive non-precoded DMRS. This localized quality adjustment optimizes both reliability and measurement precision according to specific user needs.
3Measurement precision
If non-precoded DMRS is transmitted from each antenna for channel sounding, then channel state information quality is improved, but transmission efficiency is reduced
Solution Approach 1:
The patent applies non-precoded DMRS transmission selectively rather than universally. Non-precoded DMRS is used only when accurate channel state information is required, such as for initial channel estimation or in specific service scenarios, while precoded DMRS is used for routine transmissions to maintain efficiency. This partial application of the non-precoded mode balances measurement precision with transmission efficiency.
Data Source
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AI summary
There is provided switching of an uplink transmission mode. The switching comprises manipulating an uplink transmission method and precoding of a demodulation reference signal. The switching may also comprise utilizing control signaling in indicating to a user terminal that the mode of uplink transmission is to be switched, for example.