Zero-Forcing Precoding in Massive MIMO Systems
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Solution Overview
Problem
In massive MIMO systems, conventional per sub-band precoding leads to increased multi-user interference due to mismatches between calculated and actual channel conditions, making it difficult to achieve accurate downlink channel estimation, especially as the number of antennas grows, while also increasing signaling overhead.
Innovation Solution
Implementing zero-forcing precoding on each subcarrier and transmitting downlink control signaling with effective channel mean value information from the base station to user equipment, allowing demodulation based on this information without relying on reference signals, thereby reducing precoding granularity and signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If per sub-band precoding is used, then reference signals can be inserted to facilitate DL effective channel estimation, but additional multiuser interference occurs due to mismatch between precoding matrix and actual channel on each subcarrier
Solution Approach 1:
The patent segments the frequency band into multiple sub-bands and applies different precoding matrices to each sub-band. This allows the system to adapt to channel variations across frequency while maintaining manageable complexity. The base station determines multiple precoding matrices corresponding to different sub-bands and notifies the terminal of the appropriate matrix to use for channel estimation.
Solution Approach 2:
The patent changes the precoding parameters by selecting different precoding matrices for different sub-bands based on channel conditions. The base station determines which precoding matrix to use for each sub-band and notifies the terminal through downlink control information, allowing adaptive optimization of channel estimation accuracy while controlling multiuser interference.
2Productivity
If antenna number increases in massive MIMO system, then system capacity improves, but per sub-band precoding advantage shrinks and disadvantage expands
Solution Approach 1:
The patent divides the frequency spectrum into multiple sub-bands and applies separate precoding matrices to each sub-band. This segmentation approach allows massive MIMO systems to handle the increased complexity from more antennas by processing different frequency portions independently, thereby maintaining system capacity while reducing multiuser interference through sub-band specific optimization.
Solution Approach 2:
The patent dynamically adjusts precoding parameters by selecting appropriate precoding matrices for each sub-band based on channel state information. This parameter adaptation enables the system to exploit the large number of antennas for capacity enhancement while mitigating interference through frequency-selective precoding optimization.
3Measurement precision
If precoding granularity is reduced in frequency, then channel estimation accuracy improves, but reference signal overhead increases
Solution Approach 1:
The patent makes the downlink control information serve multiple functions: it not only schedules data transmission but also conveys precoding matrix information necessary for channel estimation. By embedding precoding matrix indicators in the control signaling, the system enables accurate channel estimation without requiring separate reference signals for each sub-band, thus reducing overall overhead while maintaining fine precoding granularity.
Solution Approach 2:
The terminal uses the precoding matrix information received in downlink control information to perform its own channel estimation autonomously. This self-service approach eliminates the need for additional dedicated reference signals from the network, allowing fine-grained precoding to be implemented without proportionally increasing reference signal overhead.
Data Source
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AI summary
An objective of the application is to provide a method and apparatus for obtaining downlink data in a massive MIMO system. Specifically, the base station transmits a downlink control signaling indicating downlink channel estimation information to a user equipment, wherein the downlink control signaling comprises corresponding effective channel mean value information; performs zero-forcing precoding to a to-be-transmitted signal on each subcarrier of a transmission sub-band; transmits the zero-forcing precoded signal to the user equipment. Compared with the prior art, the base station in the present application can perform zero-forcing precoding to signals on each subcarrier and transmitting a DL control signaling indicating downlink channel estimation information to a user equipment, such that the user equipment can perform demodulation based on an effective channel mean value information in the DL control signaling but does not rely on the DL reference signal, thereby achieving reduction of precoding granularity and signaling overheads, system performance also be enhanced greatly.