User-Specific Pilot Signal Placement for Channel Estimation
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Solution Overview
Problem
In wireless communication systems using OFDM technology, particularly in LTE-A systems, the precision of channel estimation is affected due to the placement of pilot signals, leading to suboptimal data demodulation performance, especially in non-compatible carriers where pilot signals are placed at the last two OFDM symbols, limiting the accuracy of channel interpolation.
Innovation Solution
A method and device for sending pilot signals are introduced, where user-specific pilot signals are distributed across the initial and subsequent OFDM symbols within resource blocks in the symbol-subcarrier plane, allowing for improved channel estimation without occupying existing pilot signal locations, thus enhancing channel interpolation precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pilot signals are placed at the last two OFDM symbols in non-compatible carriers, then resource allocation is simplified, but channel estimation precision deteriorates
Solution Approach 1:
The patent divides the resource block into two parts: the first part contains cell-specific reference signals (CRS) for backward compatibility, while the second part contains user-specific reference signals (URS) for improved channel estimation. This segmentation allows different pilot signal types to serve different functions without interfering with each other, resolving the contradiction between resource allocation simplicity and channel estimation precision.
Solution Approach 2:
The patent applies different pilot signal patterns to different regions of the resource block. The first part uses CRS with a specific pattern optimized for cell-wide coverage, while the second part uses URS with a pattern optimized for user-specific channel estimation. This local differentiation allows each region to have the quality characteristics needed for its specific function.
2Measurement precision
If user-specific pilot signals are added in non-compatible carriers, then channel estimation precision is improved, but resource block complexity increases
Solution Approach 1:
The resource block is segmented into two distinct parts with clearly defined functions: the first part for CRS and the second part for URS. This segmentation reduces complexity by providing a clear structure that is easier to implement and manage compared to a fully mixed or uniformly complex design.
Solution Approach 2:
Instead of adding complexity throughout the entire resource block, the patent inverts the approach by concentrating user-specific pilot signals in a dedicated second part, while keeping the first part simple and compatible with existing LTE structures. This inversion minimizes the overall complexity increase while achieving the desired precision improvement.
3Reliability
If PDSCH starts from the (n+1)th OFDM symbol in compatible carriers, then control channel transmission is ensured, but data transmission efficiency decreases
Solution Approach 1:
The patent segments the resource block so that the first part maintains the traditional CRS structure for reliable control channel transmission, while the second part is optimized for efficient data transmission with user-specific pilot signals. This segmentation allows both reliability and efficiency to coexist by giving each function its optimized space.
Solution Approach 2:
The patent performs preliminary channel estimation using the user-specific reference signals in the second part before data demodulation. This preliminary action enables more accurate and efficient data transmission in the PDSCH, as the channel conditions are already characterized by the time the data arrives, improving overall productivity without compromising control channel reliability.
Data Source
AI summary
Embodiments of the disclosure disclose a method and device for sending a pilot signal. The method includes: generating a sub-frame carrying user-specific pilot signals, wherein the sub-frame includes one or more resource blocks, the resource block includes a plurality of resource elements in a symbol-subcarrier plane, locations of the resource elements in the symbol-subcarrier plane are determined by an OFDM symbol and subcarrier, a first part of the user-specific pilots signal are carried by the resource elements of the initial one or more OFDM symbols in the resource block, and a second part of the user-specific pilot signals are carried by resource elements of other OFDM symbols in the resource block; and sending the sub-frame carrying the user-specific pilot signals. The methods and devices are capable of improving the precision of channel estimation.