Reference Signal Precoder Rank Reduction for Channel State Acquisition
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Solution Overview
Problem
The increasing number of antenna ports in wireless communication systems leads to a significant increase in the overhead required for transmitting reference signals, counteracting the gain in channel capacity and making it expensive in terms of time and radio resources.
Innovation Solution
A method that defines a first set of precoders for the number of antenna ports and derives a second set with a reduced rank, allowing for efficient transmission of reference signals by associating non-zero energy with each antenna port, thereby reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of antenna ports is increased to improve channel capacity, then the channel capacity increases through spatial multiplexing, but the overhead for transmitting reference signals increases linearly
Solution Approach 1:
The patent segments the channel state information acquisition process into two stages: first acquiring coarse-granularity CSI using a reduced number of precoders, then refining specific directions if needed. This segmentation allows the system to maintain high channel capacity with large antenna ports while reducing reference signal overhead by not transmitting all possible beam directions with fine granularity.
Solution Approach 2:
The patent changes the granularity parameter of channel state information acquisition. Instead of using fine granularity for all antenna ports, the system dynamically adjusts the granularity level - using coarse granularity when channel conditions permit and fine granularity only when necessary. This parameter change reduces the number of reference signals needed while maintaining adequate channel capacity.
2Loss of information
If beam sweeping is performed with a large number of antenna ports to measure the entire radio channel, then complete channel state information is obtained, but the time and radio resource overhead increases significantly
Solution Approach 1:
The patent applies partial action by acquiring channel state information at a reduced granularity level rather than measuring every possible beam direction with fine precision. The system determines that complete fine-granularity measurement is excessive for many scenarios, and partial measurement at coarse granularity suffices to capture the essential channel characteristics, thereby reducing time overhead while maintaining adequate information quality.
3Measurement precision
If reference signals are transmitted for each antenna port to ensure accurate channel measurement, then measurement precision is improved, but the radio resource overhead increases
Solution Approach 1:
The patent applies local quality by differentiating the measurement precision required for different spatial directions or channel conditions. Instead of uniformly applying fine-granularity measurement across all antenna ports, the system identifies regions or directions where high precision is necessary and applies coarse granularity elsewhere. This localized approach maintains measurement precision where critical while reducing overall radio resource consumption.
Data Source
AI summary
A technique for transmitting reference signals (RS), from a first station using a transmit antenna (400) with a number of antenna ports to a second station for determining channel state information (CSI), of a radio channel between the first station and the second station is described. As to a method aspect of the technique, a first set of precoders (502) is defined for the number of antenna ports. Based on the first set, a second set of precoders (702) is derived for the number of antenna ports. A second rank of the second set of precoders (502) is different from a first rank of the first set of precoders (702). The second rank of the second set is less than the number of antenna ports (402). Each of the antenna ports is associated with non-zero energy by at least one of the precoders (702) of the second set. The RS are transmitted using each of the precoders (702) of the second set.