Uplink Precoding via Downlink Channel Estimation in OFDMA Systems
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Solution Overview
Problem
In OFDMA mobile communication systems, the limited number of uplink pilot signals degrades the performance and throughput of uplink channel estimation, as increasing their number reduces data signal transmission.
Innovation Solution
A method and apparatus where a mobile station estimates a downlink channel state, determines a precoding matrix, and precodes the uplink signal using this information to improve uplink channel estimation and increase system throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of uplink pilot signals is increased to improve channel estimation accuracy, then measurement precision is improved, but productivity decreases due to reduced data signal transmission
Solution Approach 1:
The patent applies the copying principle by using the downlink channel estimation results as a copy or reference for uplink channel estimation. Since the downlink channel matrix can be accurately estimated using multiple pilot signals, this estimation is copied to represent the uplink channel characteristics, allowing accurate uplink channel estimation without increasing uplink pilot signal overhead.
Solution Approach 2:
The patent uses precoding matrix information as an intermediary to transfer channel state information from downlink to uplink. The downlink channel estimation results are processed through precoding matrix determination to create an intermediary representation that captures uplink channel characteristics, enabling accurate estimation without direct uplink pilot signals.
2Measurement precision
If precoding is applied to improve uplink channel estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing downlink channel estimation and precoding matrix determination in advance before uplink data transmission. The mobile station prepares the precoding matrix based on downlink channel conditions beforehand, so that when uplink transmission occurs, the channel estimation is already optimized without requiring complex real-time processing during uplink transmission.
Data Source
AI summary
Disclosed is a method for transmitting an uplink signal by a mobile station in a mobile communication system using an OFDMA scheme. The method includes estimating a downlink channel status by using a signal received from a base station; determining a precoding matrix by using the estimated downlink channel status; and transmitting a signal obtained by multiplying an uplink signal to be transmitted by the precoding matrix to the base station.