Multi-User Wireless Channel Pre-Equalization for Pilot Contamination
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Solution Overview
Problem
In wireless communications networks, especially in multi-user transmission scenarios, channel estimation is hindered by pilot signal contamination due to channel dispersion, making it difficult to separate and decode signals effectively, particularly in Non-Orthogonal Multiple Access (NOMA) systems.
Innovation Solution
The method involves determining phase and amplitude differences between Resource Elements (REs) in Physical Resource Blocks (PRBs) to pre-equalize channels, aligning phases and amplitudes to mitigate pilot signal contamination and enhance channel estimation, allowing for better separation of channel estimates and data in multi-user transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-user transmissions use pilot signals for channel estimation, then channel information can be obtained, but pilot signal contamination occurs due to channel dispersion which impairs orthogonality of Orthogonal Cover Codes
Solution Approach 1:
The patent applies preliminary action by performing pre-equalization of the channel before transmission. The transmitting node determines phase and amplitude differences between Resource Elements in advance, then pre-equalizes the channel by aligning phases and amplitudes of Resource Elements in a second set based on differences from a first set. This preliminary channel conditioning prevents pilot signal contamination from degrading orthogonality, allowing accurate channel estimation without the harmful effects that would otherwise occur during multi-user transmissions.
2Measurement precision
If channel pre-equalization is performed to align phases and amplitudes, then channel estimation is improved, but additional processing complexity is introduced
Solution Approach 1:
The patent applies local quality by performing pre-equalization operations locally on specific Resource Elements within Physical Resource Blocks rather than globally across the entire transmission. The transmitting node selects a first set of contiguous Resource Elements in a first PRB and a second set of contiguous Resource Elements in a second PRB, determining phase and amplitude differences only for these local groups. This localized approach improves channel estimation where needed while minimizing additional processing complexity compared to global pre-equalization of all Resource Elements.
Data Source
AI summary
A method performed by a node in a wireless communications network for improving multi-user transmissions in the wireless communications network is provided. The node determines channel estimates based on demodulation reference signals, or a data symbol in at least one Physical Resource Block, PRB, of the latest received subframe. Then, the node determines a phase difference and an amplitude difference between Resource Elements, REs, in a first set of contiguous REs in the at least one PRB of the latest received subframe based on the obtained channel estimates. The node then pre-equalizes at least one channel within at least one PRB of a transmission subframe by aligning the phase and amplitude of REs in a second set of contiguous REs therein based on the determined phase and amplitude differences. A node for improving multi-user transmissions in the wireless communications network is also provided.