Wireless Resource Allocation via Grouped Pilot Sequences
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Solution Overview
Problem
Conventional Massive Multiple-Input Multiple-Output (MIMO) systems face limitations in scheduling a large number of users due to pilot contamination, which degrades performance and restricts spectral efficiency, especially in Time-Division Duplex (TDD) mode, where the number of scheduled users is limited by the coherence time and bandwidth.
Innovation Solution
The system groups users into multiple groups and allocates overlapping time-frequency resources for data sequences within each group, while ensuring orthogonal pilot sequences within each group to avoid contamination, allowing for the reuse of pilot sequences across groups and efficient utilization of resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If orthogonal pilot symbols are transmitted for each UE to enable channel estimation, then channel estimation accuracy is improved, but the number of scheduled UEs is limited due to pilot sequence overhead
Solution Approach 1:
The system segments UEs into multiple groups and allocates different orthogonal pilot sequences to each group. This segmentation allows the total number of scheduled UEs to exceed the number of available orthogonal pilot sequences by reusing pilot sequences across groups, while maintaining orthogonality within each group to ensure accurate channel estimation.
Solution Approach 2:
The patent introduces a new dimension of resource allocation by using group-specific cyclic shifts and group-specific orthogonal cover codes (OCC) in addition to the traditional pilot sequence allocation. This multi-dimensional approach allows pilot sequence reuse across groups while maintaining orthogonality within groups, thereby increasing the number of schedulable UEs without compromising channel estimation accuracy.
2Productivity
If pilot sequences are reused to schedule more UEs, then the number of scheduled UEs is increased, but pilot contamination occurs causing performance degradation
Solution Approach 1:
By dividing UEs into multiple groups with group-specific pilot configurations (different cyclic shifts and OCC), the system enables pilot sequence reuse across groups while preventing pilot contamination within groups. This segmentation strategy increases the number of schedulable UEs without degrading performance due to pilot contamination.
Solution Approach 2:
The patent applies local quality by ensuring that orthogonality is maintained locally within each UE group through group-specific pilot configurations, while allowing global pilot sequence reuse across different groups. This local orthogonality prevents pilot contamination while enabling increased user scheduling capacity.
3Device complexity
If conventional TDD resource allocation is used, then implementation simplicity is maintained, but spectral efficiency is limited to 50% due to non-overlapping pilot and data resources
Solution Approach 1:
The patent merges the pilot resource allocation and data resource allocation in the time-frequency domain by allowing overlapping resources for different UE groups. This merging enables more efficient utilization of available resources and achieves up to 60% spectral efficiency improvement compared to conventional non-overlapping allocation, while maintaining relatively simple implementation through group-based resource allocation.
Data Source
AI summary
An apparatus and method for allocating time-frequency resource, comprising: allocating a first group-specific data time-frequency resource to data sequences associated to UEs comprised in a first UE group of the plurality of UE groups; and allocating a second group-specific data time-frequency data resource to data sequences associated to UEs comprised in a second UE group of the plurality of UE groups; wherein the first and the second group-specific data time-frequency resources at least partly overlap in time domain.