Slepian Sequence Precoder for MIMO Latency Reduction
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Solution Overview
Problem
In wireless communications, especially in line of sight multiple-input multiple-output (MIMO) systems, the overhead of channel state measurements using sounding reference signals (SRS) is high, leading to increased latency and complexity in precoding for transmission, particularly when the transmitter and receiver have a large number of antennas.
Innovation Solution
The use of Slepian sequences to construct precoders for efficient signal transmission, allowing for codebook-based precoding without relying on receiver feedback, thereby reducing overhead and complexity by selecting precoders from a codebook based on the number of transmit antennas and bandwidth for spectral concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If channel state measurements using sounding reference signals (SRS) are performed for precoding, then precoding accuracy is improved, but overhead and latency increase
Solution Approach 1:
The patent pre-computes and stores precoders in a codebook based on Slepian sequences before actual transmission. This preliminary preparation eliminates the need for real-time channel state measurements during transmission, thereby reducing latency while maintaining precoding accuracy through the use of mathematically optimized sequence properties.
Solution Approach 2:
The patent uses Slepian sequences as mathematical templates or copies that capture the essential characteristics of optimal precoding without requiring actual channel measurements. These sequences serve as representative models that can be directly applied to generate precoders, avoiding the overhead of SRS-based measurements while preserving the necessary spatial information for effective transmission.
2Reliability
If channel state feedback is obtained from receiver for precoding, then precoding performance is improved, but overhead and complexity increase
Solution Approach 1:
The patent enables the transmitter to autonomously determine precoders using locally stored Slepian sequences and codebook structures without requiring receiver feedback. The transmitter self-serves by selecting appropriate precoders from the codebook based on transmission requirements, eliminating the complex feedback loop while maintaining reliable precoding performance through the inherent properties of Slepian sequences.
Solution Approach 2:
The patent extracts the essential precoding information from the complex channel state feedback requirement and encapsulates it in the Slepian sequence codebook. By taking out only the necessary mathematical structure (Slepian sequences) and storing it in advance, the system eliminates the need for continuous receiver feedback while preserving the critical spatial information needed for effective precoding.
3Productivity
If large number of antennas are used for MIMO communications, then communication capacity is improved, but overhead for channel state measurements increases
Solution Approach 1:
The patent pre-computes precoders for large-scale MIMO systems using Slepian sequences before transmission begins. This preliminary computation allows the system to handle large numbers of antennas without incurring proportional increases in measurement overhead, as the precoding information is already prepared in the codebook and can be directly applied during transmission.
Solution Approach 2:
The patent changes the approach from measuring channel states with large numbers of antennas to using fixed mathematical parameters (Slepian sequences) that are independent of antenna count. By transforming the problem from physical measurement-based to mathematically-defined parameters, the system maintains communication capacity benefits of large-scale MIMO while eliminating the linear increase in measurement overhead associated with additional antennas.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A transmitter may select a precoder from a codebook for precoding one or more signals for transmission to a receiver. The transmitter may select the precoder from the codebook based on antenna configurations at the transmitter and the receiver. The precoder may be constructed using one or more Slepian sequences. In some implementations, the Slepian sequences may be associated with a quantity of transmit antennas at the transmitter. For instance, a length of each Slepian sequence may correspond to (for example, be equal to) a quantity of transmit antennas at the transmitter. Further, the Slepian sequences may be associated with a bandwidth within which to concentrate the one or more signals. Once the transmitter selects the precoder, the transmitter may precode the one or more signals and transmit the precoded signals to the receiver.