RRH Subset Selection for Mobile-Rate Adaptive Downlink MIMO
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Solution Overview
Problem
Existing LTE cellular technologies with remote radio heads (RRHs) do not fully optimize downlink spectral efficiency in multi-input multi-output (MIMO) systems, particularly in scenarios with geographically distributed antennas.
Innovation Solution
A base station selects a subset of geographically separated antennas for user equipment based on motion rate, precodes data streams, and transmits them using a hybrid signaling approach that combines semi-static and dynamic methods to manage RRH subsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If remote radio heads are distributed over a wide area to extend cell coverage, then coverage area is improved, but downlink spectral efficiency deteriorates due to lack of optimization for geographically distributed antennas
Solution Approach 1:
The patent segments the downlink transmission by dividing remote radio heads into different groups based on their geographic locations. Each group serves specific user equipment, allowing optimized precoding and resource allocation for each segment. This segmentation enables the system to maintain high spectral efficiency while covering a wide area by treating different geographic regions as separate transmission units.
Solution Approach 2:
The patent applies local quality by configuring downlink transmissions differently for different geographic locations. Each remote radio head group uses location-specific precoding matrices and resource allocations tailored to the local channel conditions and user equipment distribution. This allows the system to optimize spectral efficiency for each local area while maintaining overall wide coverage.
2Measurement precision
If codebook-based feedback is used for FDD MIMO systems, then precoding accuracy is improved, but signaling overhead and complexity increase
Solution Approach 1:
The patent implements partial codebook-based feedback by using it only for certain remote radio head groups or under specific channel conditions, rather than applying it universally. For other groups or conditions, simplified precoding methods are used. This partial application maintains sufficient precoding accuracy where needed while reducing overall signaling overhead and system complexity.
Solution Approach 2:
The patent changes the codebook parameters and feedback granularity based on the geographic distribution of remote radio heads and the channel conditions. Instead of using a fixed comprehensive codebook, the system adapts the codebook size and structure to match the specific deployment scenario, reducing signaling overhead while maintaining necessary precoding accuracy for geographically distributed antennas.
Data Source
AI summary
A base station selects a subset of at least one geographically separated antenna for a user equipment based on a rate of motion of the user equipment. The base station forms at least one layer of data stream including modulated symbols, precodes the at least one layer of data stream into one or more data streams via a linear transformation, and transmits the one or more data streams to the user equipment via the selected subset of at least one geographically separated antenna. In some examples, the base station semi-statically selects the subset of at least one geographically separated antenna for the user equipment in response to the rate of motion less than a predetermined amount; otherwise, dynamically selects the subset of at least one geographically separated antenna for the user equipment.