DMRS Automatic Gain Control for Low-Power MIMO Equalization
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Solution Overview
Problem
In wireless communication systems, particularly in MIMO receivers, low signal power levels lead to inaccurate intermediate results, causing performance degradation due to hardware constraints and limitations in word lengths, which is exacerbated in advanced technologies like 5G, where strict latency and performance requirements are challenging to meet.
Innovation Solution
Implementing digital domain automatic gain control (AGC) specifically for the DMRS symbol within a subframe, allowing accurate scaling and gain adjustment only for the reference signal, thereby improving channel estimation and equalization without increasing latency or hardware costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital domain automatic gain control is applied to the entire received signal, then signal power level accuracy is improved, but latency increases and hardware complexity increases
Solution Approach 1:
The received signal is segmented into reference signal portions and data signal portions. AGC is applied selectively only to the reference signal portions, not the entire received signal. This segmentation allows gain control to be performed on a smaller subset of the signal, reducing processing latency while maintaining accuracy for channel estimation purposes.
Solution Approach 2:
Different quality levels of processing are applied to different parts of the signal. High-quality gain control is applied locally to reference signal portions where precision is critical for channel estimation, while data signal portions use the estimated channel response without additional gain control processing. This local quality approach optimizes the balance between accuracy and processing speed.
2Measurement precision
If digital domain automatic gain control is applied to the entire received signal, then signal power level accuracy is improved, but device complexity increases
Solution Approach 1:
The signal processing is divided into distinct segments: reference signal processing and data signal processing. The AGC function is implemented only in the reference signal processing path, reducing the overall hardware complexity compared to applying AGC to the entire signal chain. This segmentation allows reuse of the channel estimation results for data processing without duplicating the gain control hardware.
Solution Approach 2:
The reference signal processing block serves multiple functions: it performs gain control, channel estimation, and provides the channel response for data signal equalization. By making this block multi-functional, the patent avoids needing separate dedicated hardware for each function, thereby reducing overall device complexity while maintaining measurement precision.
3Reliability
If word lengths are increased to meet performance requirements for low signal power, then receiver performance is improved, but hardware costs increase
Solution Approach 1:
The patent changes the parameter of signal power level through selective AGC application to reference signals. By adjusting the gain of reference signals to an optimal level before channel estimation, the system ensures that channel estimates are accurate even when the original received signal power is low. This allows the use of standard word lengths in subsequent processing without sacrificing reliability, thereby avoiding increased hardware costs.
Data Source
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AI summary
When processing a signal received wirelessly a gain is applied to a reference signal and the wireless channel over which a received signal passed is estimated using the reference signal with the applied gain. Equalization values obtained from the estimating are adjusted to remove effects of the applied gain. Those adjusted equalization values are then used to equalize at least a data portion of the received signal. The results are stored in a computer readable memory, such as a buffer of a decoder also within the same receiver. Embodiments describe the received signal can be a subframe in which the reference signal is a DMRS or similar that occupies an entire symbol position thereof, as well as a single symbol in which the reference signal is a pilot sequence or pilot samples and the data portion is also within that same single symbol.