TDD Uplink Spatial Pre-coding via Channel Reciprocity
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Solution Overview
Problem
Current uplink spatial transmission methods in MIMO systems do not utilize spatial channel state information effectively, limiting the achievable channel capacity in time division duplex (TDD) systems.
Innovation Solution
A method and system where a terminal measures downlink spatial channel state information, estimates uplink spatial channel state information using channel reciprocity, and selects an uplink spatial pre-coding matrix to maximize channel capacity, enabling spatial pre-coding and optimal resource allocation for uplink transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional open-loop transmitting methods (transmit diversity, antenna selection, spatial multiplexing) are used, then the terminal can transmit uplink data, but the maximal channel capacity cannot be achieved because spatial channel state information is not measured
Solution Approach 1:
The terminal measures the downlink spatial channel state information in advance using common reference symbols before uplink data transmission. This preliminary measurement enables the terminal to obtain uplink spatial channel state information through channel reciprocity, allowing optimal spatial pre-coding to be selected before transmission, thereby achieving maximal channel capacity.
Solution Approach 2:
The system implements channel state information feedback by measuring downlink channel characteristics and using channel reciprocity to infer uplink channel state. This feedback mechanism enables the terminal to adapt its spatial pre-coding strategy based on actual channel conditions, transforming the open-loop system into a closed-loop system that can achieve optimal performance.
2Productivity
If multi-antenna spatial multiplexing is used, then the theoretical channel capacity increases, but in practice the terminal only maps data streams directly onto antennas without measuring spatial channel state information, thus not achieving maximal capacity
Solution Approach 1:
The terminal uses the downlink common reference symbols transmitted by the base station to measure the downlink spatial channel state information itself. By utilizing channel reciprocity in TDD systems, the terminal can derive uplink channel state information without requiring additional dedicated reference symbols or complex feedback mechanisms from the base station, thus achieving self-service channel estimation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the achievement of maximal channel capacity by optimizing uplink spatial transmission through informed pre-coding and resource allocation, surpassing the limitations of traditional open-loop technologies.
Implementation Method 1
measuring downlink spatial channel state information based on the public reference symbols, and estimating uplink spatial channel state information based on the measured downlink spatial channel state information
Data Source
AI summary
A method for uplink transmission based on a time division duplex (TDD) system is provided. In the method, a terminal measures downlink channel state information, estimates the state information of the uplink spatial channel using the channel reciprocity of the TDD system, and selects an uplink spatial pre-coding matrix using the state information of the uplink spatial channel based on a certain criterion, the terminal executes spatial pre-coding using the selected pre-coding matrix, and transmits the data stream to a base station via terminal transmit antennae. A terminal, a base station and a system which are based on the method are also provided. The invention uses the reciprocity of the TDD system channel fully to achieve the maximal channel capacity, thereby optimizes the uplink spatial-transmission.