RIS Channel Estimation with Two-Stage Signals to Reduce Overhead
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Solution Overview
Problem
The estimation of RIS channels in wireless communication networks involves high overheads due to the large number of unit cells in reconfigurable intelligent surfaces, necessitating excessive reference signals.
Innovation Solution
A method involving two rounds of reference signal transmission, where T1 reference signals are sent in the first round and T2 in the second, with T1 and T2 being less than the total unit cells, reducing overall signal overheads while ensuring accurate channel estimation through a first codebook determined based on the angular domain path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the quantity of reference signals is increased to estimate the RIS channel accurately, then the channel estimation accuracy is improved, but the reference signal overhead increases significantly
Solution Approach 1:
The patent segments the channel estimation process into two distinct rounds: a first round for estimating the RIS channel using T1 reference signals, and a second round for estimating the cascaded channel using T2 reference signals. This segmentation allows each round to focus on specific estimation tasks, reducing the total number of reference signals needed compared to a single comprehensive estimation approach.
Solution Approach 2:
The patent applies partial action by using T1 reference signals (where T1 < M) in the first round to estimate the RIS channel, and T2 reference signals (where T2 < M) in the second round to estimate the cascaded channel. This partial estimation approach, combined with the codebook mechanism, achieves accurate channel estimation without requiring T >= M reference signals, thereby reducing overhead.
2Area of stationary object
If the number of unit cells in RIS is increased to expand coverage, then the network coverage is improved, but the reference signal overhead increases
Solution Approach 1:
The patent changes the parameter of reference signal quantity from being equal to or greater than the number of unit cells (M) to being less than M (specifically T1 < M and T2 < M). This parameter change is enabled by the codebook mechanism that allows efficient channel estimation with fewer reference signals, thus maintaining large RIS coverage while reducing overhead.
3Quantity of substance
If a codebook is introduced to reduce reference signal overhead, then the signal overhead is reduced, but the system complexity increases
Solution Approach 1:
The codebook acts as an intermediary mechanism between the reference signals and the channel estimation process. It provides a structured set of pre-defined signal patterns that enable efficient estimation of both the RIS channel and cascaded channel. The codebook mediates the relationship between the number of reference signals and the estimation accuracy, allowing reduced overhead while maintaining performance.
Data Source
AI summary
A terminal device sends T1 reference signals, where the T1 reference signals are reflected to a network device through a reconfigurable intelligent surface (RIS), T1 is a positive integer less than M, and M is a quantity of unit cells included in the RIS. The terminal device receives first information from the network device, where the first information indicates a value of T2, and T2 is a positive integer less than M. The terminal device sends T2 reference signals, where the T2 reference signals are reflected to the network device through the RIS, the T2 reference signals are used to estimate a cascaded channel, and the cascaded channel includes a channel between the network device and the RIS and a channel between the RIS and the terminal device.