MIMO CSI-RS Allocation for Overhead Reduction
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Solution Overview
Problem
In multiple antenna communication systems, especially in LTE and LTE-Advanced systems, there is a lack of efficient methods for allocating and transmitting reference signals, particularly for channel measurement, which leads to increased transmission overhead and reduced channel estimation performance when supporting multiple transmit antennas.
Innovation Solution
A method is proposed where Channel State Information-Reference Signals (CSI-RS) are allocated and transmitted using two resource blocks with an interval of 8 frequency resource elements, and data signals are allocated to redundant frequency resource elements, allowing CSI-RS of each antenna to be transmitted on different frequency resource elements with varying numbers of elements in each resource block, and CSI-RS are intermittently transmitted with specific periods to reduce overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference signals are transmitted for each transmit antenna in MIMO systems, then channel measurement capability is improved, but transmission overhead increases
Solution Approach 1:
The patent segments the reference signal transmission by dividing it into cell-specific reference signals (CRS) and channel state information reference signals (CSI-RS) with different functions. CRS provides basic channel estimation while CSI-RS is specifically optimized for channel quality measurement, allowing the system to obtain accurate channel measurements without requiring excessive reference signal resources for each antenna
Solution Approach 2:
The patent implements periodic transmission of CSI-RS with configurable periods (e.g., every 5, 10, 20 subframes). This periodic action reduces transmission overhead by not continuously transmitting reference signals for all antennas, while still maintaining adequate channel measurement capability through timely periodic updates
2Loss of information
If reference signals are transmitted across the entire broadband, then channel information acquisition is improved, but resource consumption increases
Solution Approach 1:
The patent applies local quality by making the reference signal density and allocation adaptive to local channel conditions. In frequency-selective fading regions, reference signals are allocated more densely to ensure accurate channel estimation, while in flat fading regions, sparser allocation suffices. This localized optimization reduces overall resource consumption while maintaining channel information acquisition capability
Solution Approach 2:
The patent transitions from purely frequency-domain reference signal allocation to joint time-frequency resource allocation. By introducing time dimension (different subframes, slots) alongside frequency resources, the system can acquire channel information more efficiently through temporal diversity, reducing the need for excessive frequency resources
3Measurement precision
If more frequency resource elements are allocated to CSI-RS, then channel estimation performance is improved, but data transmission capacity is reduced
Solution Approach 1:
The patent changes parameters such as CSI-RS density (e.g., 1/12, 1/6, 1/3 of resource elements), allocation patterns, and periodicity to optimize the balance between channel estimation performance and data capacity. By adjusting these parameters based on channel conditions and service requirements, the system achieves adequate channel estimation without excessively sacrificing data transmission capacity
Solution Approach 2:
The patent applies partial action by allocating reference signals only where necessary for channel estimation rather than uniformly across all resources. The system uses just enough reference signal resources to achieve required channel estimation accuracy, avoiding excessive allocation that would unnecessarily reduce data capacity
Data Source
AI summary
Disclosed is a method for allocating a reference signal, in a method for transmitting a Channel State Information-Reference Signal (CSI-RS) for measuring a transmission channel according to each antenna and a data signal in a broadband wireless communication system based on a multiple input multiple output (MIMO) scheme through a plurality of antennas.