UE Grouping and Pilot Sequence Reuse in Wireless Networks
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Solution Overview
Problem
Current wireless communication networks face limitations in scheduling multiple User Equipment (UEs) due to the limited number of orthogonal pilot sequences, leading to pilot contamination and reduced network throughput, especially in massive MIMO environments where intense pilot signaling is required.
Innovation Solution
A network node is configured to group UEs into different UE groups, assigning mutually orthogonal pilot sequences and resource-offsets to each group, allowing pilot sequence reuse and reducing interference, thereby enabling more UEs to be scheduled for uplink transmission and enhancing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of orthogonal pilot sequences is increased to schedule more UEs, then the number of schedulable UEs increases, but the spectral efficiency decreases due to increased pilot overhead
Solution Approach 1:
The patent segments UEs into different groups (first UE group and second UE group) and assigns different cyclic shifts of the same pilot sequence to each group. This segmentation allows pilot sequence reuse across groups while maintaining orthogonality within groups, thereby increasing the number of schedulable UEs without proportionally increasing pilot overhead.
Solution Approach 2:
The patent makes a single pilot sequence serve multiple functions by using it for multiple UE groups through different cyclic shifts. The same base pilot sequence is reused across different UE groups, allowing one pilot sequence to identify multiple UEs when combined with group-specific cyclic shifts, thus reducing the total number of unique pilot sequences needed.
2Quantity of substance
If pilot sequences are reused to increase the number of schedulable UEs, then more UEs can be scheduled, but pilot contamination occurs reducing channel estimation accuracy
Solution Approach 1:
The patent applies different cyclic shifts of the same pilot sequence to different UE groups, creating local orthogonality within each group while allowing global reuse across groups. This local quality differentiation ensures that channel estimation remains accurate within each group while enabling pilot reuse across groups to schedule more UEs.
Solution Approach 2:
The patent changes the parameter of cyclic shift applied to the pilot sequence based on the UE group assignment. By varying the cyclic shift parameter across different UE groups, the system enables pilot sequence reuse while maintaining distinguishability and avoiding pilot contamination, thus preserving channel estimation accuracy.
3Measurement precision
If the number of pilot sequences is increased to avoid pilot contamination, then channel estimation accuracy improves, but the spectral efficiency decreases due to increased overhead
Solution Approach 1:
The patent creates copies of the same pilot sequence with different cyclic shifts for different UE groups. Instead of using entirely different pilot sequences, the system copies a base pilot sequence and applies cyclic shift transformations, thereby maintaining channel estimation accuracy through orthogonality while reducing the total number of unique pilot sequences required.
4Productivity
If resource allocation is optimized to schedule more UEs, then the aggregate throughput increases, but the complexity of resource management increases
Solution Approach 1:
The patent segments UEs into groups and assigns resource offsets to each group, simplifying resource management by creating a structured allocation pattern. This segmentation approach allows the system to manage resources for many UEs through systematic group-based allocation rather than individualized complex management, thereby increasing aggregate throughput while controlling complexity.
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
Network node (210) and method (800) in a network node (210), comprising: grouping (801) a plurality of UEs (220-1, 220-2, 220-3, 220-4) into at least a first UE group (260) and a second UE group (270); assigning (802) a mutually orthogonal pilot sequence to each UE (220-1, 220-2) comprised in the first UE group (260); assigning (803) a mutually orthogonal pilot sequence to each UE (220-3, 220-4) comprised in the second UE group (270); assigning (804) a resource-offset to the UEs (220-1, 220-2, 220-3, 220-4) comprised in each UE group (260, 270), by which each UE (220-1, 220-2, 220-3, 220-4) is allowed to start its transmission sub-frame in its Transmission Time Interval, TTI; and transmitting (805) the assigned (802, 803) pilot sequences and the assigned (804) resource-offset to UEs (220-1, 220-2, 220-3, 220-4).