FDD Channel Sounding via Uplink Signals in Downlink Band
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Solution Overview
Problem
Frequency division duplex (FDD) systems face challenges in obtaining precise channel state information due to high overhead and feedback delay, especially in large-scale multiple-input multiple-output (MIMO) systems, where pilot overhead increases significantly, limiting the accuracy of downlink channel sounding.
Innovation Solution
A method and system for downlink channel sounding in FDD systems that reserve a configurable uplink sounding window in the downlink frequency band, allowing user equipment to send sounding signals, leveraging channel reciprocity to obtain complete channel state information, while managing interference through dynamic scheduling and beamforming techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional uplink sounding methods are used in FDD systems, then channel state information can be obtained, but pilot overhead increases significantly and feedback delay occurs
Solution Approach 1:
The patent inverts the traditional sounding direction by enabling downlink channel sounding through uplink transmissions. Instead of the base station transmitting sounding signals in the uplink, user equipment transmits sounding signals in the downlink frequency band, allowing the base station to estimate downlink channel state information from these uplink transmissions, thereby reducing pilot overhead while maintaining accuracy
Solution Approach 2:
The patent makes the uplink sounding window configurable and reusable for multiple purposes. The same time window in the downlink frequency band can be used for channel sounding, interference measurement, and other wireless communications functions, increasing resource utilization efficiency and reducing dedicated pilot overhead
2Measurement precision
If traditional channel feedback schemes are used in FDD systems, then downlink channel information can be obtained, but feedback delay increases
Solution Approach 1:
The patent performs downlink channel sounding in advance by having user equipment transmit sounding signals during configured uplink sounding windows. The base station obtains downlink channel state information before actual downlink data transmission, enabling proactive channel knowledge acquisition and reducing feedback delay for time-sensitive applications
Solution Approach 2:
The system enables user equipment to actively participate in channel sounding by transmitting sounding signals in the downlink frequency band. This self-service approach allows the user equipment to provide its own channel measurement data, reducing the need for extensive base station-initiated feedback mechanisms and minimizing feedback delay
3Quantity of substance
If uplink sounding window is reserved in downlink frequency band, then pilot overhead is reduced, but interference management becomes more complex
Solution Approach 1:
The patent implements dynamic scheduling of uplink sounding windows, where the time resources for sounding can be flexibly allocated and adjusted based on traffic conditions, channel state, and interference levels. This dynamic approach allows the system to optimize the balance between sounding accuracy and interference management, reducing overall system complexity compared to static configurations
Solution Approach 2:
The patent applies different scheduling and resource allocation strategies for different user equipment and channel conditions. By tailoring the uplink sounding window configuration and interference management techniques to specific local conditions, the system reduces overall complexity while maintaining effective interference management where needed
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 reduces pilot overhead, enhances channel state information accuracy, and mitigates interference, enabling more efficient downlink channel estimation and precoding, particularly in large-scale MIMO systems.
Implementation Method 1
allowing user equipment to send sounding signals, leveraging channel reciprocity to obtain complete channel state information
Data Source
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AI summary
System and method embodiments are provided for channel sounding in a frequency division duplex (FDD) system. The embodiments enable a transmission point (TP) to determine channel information about a downlink channel from an uplink channel sounding signal received on the downlink channel frequency band during a time window reserved for uplink channel sounding on the downlink channel frequency band. In an embodiment, a method in a controller includes determining with the controller a schedule for an uplink sounding window in a downlink frequency band, wherein the uplink sounding window comprises a transmission window in at least a partial downlink frequency band that is reserved for uplink channel sounding, instructing a TP to signal the schedule to at least one wireless device in a coverage area of the TP, receiving a channel sounding signal in the downlink frequency band, and obtaining downlink channel state information from the channel sounding signal.