Precoder Selection for Non-Coherent MIMO Terminals
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Solution Overview
Problem
In massive MIMO systems, terminal devices with non-coherent transmission capabilities are limited to restricted precoder sets, which restrict transmit diversity and multiplexing gain due to their inability to combine signals from multiple antenna ports, leading to suboptimal channel sounding and data transmission efficiency.
Innovation Solution
A method that involves receiving reference signals from terminal devices using both non-coherent and coherent precoders, determining channel estimates, and selecting precoders from an expanded set that includes both types, allowing for more flexible and adaptive precoder updates to improve channel alignment and multiplexing gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If terminal devices use non-coherent precoders only, then device complexity is reduced and ease of operation is improved, but multiplexing gain and transmit diversity are limited
Solution Approach 1:
The system dynamically adapts precoder selection based on terminal device capabilities. Non-coherent terminals can operate with simple non-coherent precoders when needed, while coherent terminals can utilize the full codebook including coherent precoders for higher performance, making the system flexible and adaptive to different device types
Solution Approach 2:
The codebook is segmented into different sections: non-coherent precoders for terminals with limited capabilities and coherent precoders for terminals with full coherence capability. This segmentation allows each terminal type to use the appropriate subset, balancing complexity and performance
2Device complexity
If terminal devices are restricted to non-coherent precoder sets, then device complexity is reduced, but channel sounding quality and multiplexing gain deteriorate
Solution Approach 1:
The system changes the precoder parameters based on terminal capability indicators. When a terminal indicates non-coherent capability, the system configures it to use non-coherent precoders from the codebook. When coherent capability is indicated, the terminal can use coherent precoders, thereby changing the operational parameters to match capabilities
3Productivity
If coherent precoders are used for non-coherent terminals, then multiplexing gain is improved, but transmission reliability deteriorates due to phase inconsistencies
Solution Approach 1:
The terminal device provides feedback about its coherence capability to the network. Based on this feedback, the network configures the appropriate precoder type. This feedback mechanism ensures that coherent precoders are only used by terminals that can maintain phase consistency, thereby preserving transmission reliability while allowing multiplexing gain improvements where applicable
Data Source
AI summary
A method includes receiving (402) a plurality of reference signals (301-303) at an antenna port of a communication device (101). Each reference signal (301-303) is sent using a corresponding precoder. The precoder is selected from a first set of precoders. The method further includes determining (403) a channel estimate based on the received plurality of reference signals (301-303), and selecting (404) a precoder from a second set of precoders based on the determined channel estimate. The second set of precoders comprises at least one precoder in addition to the precoders of the first set of precoders. The method includes sending (405) an indication (304) relating to the selected precoder.