Pilot Signal Assignment via UE Clustering
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Solution Overview
Problem
In dense wireless networks, pilot contamination occurs due to the limited number of orthogonal pilot signals, leading to interference and degradation of channel estimation accuracy and overall system performance, as multiple terminals share the same pilots across cells without coordination.
Innovation Solution
A pilot signal assignment scheme that clusters user equipment (UEs) based on their spatial signatures, assigning distinct orthogonal or semi-orthogonal pilots to spatially similar UEs, allowing for the reuse of pilot signals while minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If orthogonal pilot signals are used to avoid interference during channel estimation, then channel estimation accuracy is improved, but the number of supported wireless terminals is limited due to the limited number of available orthogonal pilots
Solution Approach 1:
The patent segments the network into multiple cells and further segments terminals within each cell into different groups. Each group is assigned orthogonal pilot signals, allowing multiple groups across different cells to reuse the same pilot sequences. This segmentation enables the system to support more terminals than the number of available orthogonal pilots by creating a hierarchical structure where orthogonality is maintained within groups while reuse is permitted between groups in different cells.
Solution Approach 2:
The patent introduces a new dimension of differentiation beyond just the pilot signal sequence itself. By incorporating cell-specific parameters and group identifiers into the pilot assignment strategy, the system creates additional degrees of freedom. Terminals are differentiated not only by their pilot sequences but also by their cell identity and group membership, effectively adding dimensional separation that allows pilot reuse while maintaining distinguishability for channel estimation.
2Quantity of substance
If the same pilot signals are reused across multiple cells to serve more terminals, then the number of supported wireless terminals increases, but pilot contamination occurs leading to interference and degradation of channel estimation accuracy
Solution Approach 1:
The patent segments terminals into distinct groups within each cell and assigns specific orthogonal pilot sequences to each group. This segmentation ensures that while pilot sequences may be reused across different cells, the actual channel estimation for each terminal remains uncontaminated because terminals using the same pilot are grouped together and processed with cell-specific and group-specific parameters that differentiate their channels.
Solution Approach 2:
The patent applies local quality by making pilot assignment cell-specific and group-specific rather than uniform across the entire network. Each cell and group combination has its own pilot assignment strategy, allowing local optimization of channel estimation accuracy while enabling global pilot reuse. The cell-specific parameters and group identifiers ensure that local channel estimation remains accurate even when pilots are reused in other cells.
3Quantity of substance
If a large number of wireless terminals share the same pilots across cells, then network density increases, but severe interference results in degradation of channel estimation accuracy and overall system performance
Solution Approach 1:
The patent segments the dense network into multiple cells and further segments terminals within each cell into organized groups. This dual-level segmentation allows the system to accommodate high network density by efficiently organizing terminals, while maintaining reliability through cell-specific and group-specific pilot assignment strategies that prevent interference even when pilots are reused across cells.
Solution Approach 2:
The patent performs preliminary action by pre-organizing terminals into groups and pre-assigning pilot sequences before channel estimation and data transmission. This preliminary grouping and assignment, based on cell identity and terminal characteristics, ensures that when high-density terminals share pilots across cells, their channels are already differentiated through the group and cell parameters, preventing interference and maintaining system performance.
Data Source
AI summary
The disclosure provides methods, a base station and network nodes relating to the assignment of pilot signals to wireless devices. One aspect provides a method including obtaining grouping information grouping one or more of the plurality of wireless devices together based at least in part on clustering information corresponding to each of the plurality of wireless devices and according to one or more clustering criterion, assigning at least one pilot signal to the one or more wireless devices based on the grouping information and transmitting the at least one pilot signal.