Open-Loop Rate Control in TDD Systems
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Solution Overview
Problem
Existing closed-loop rate control methods in wireless communication systems are resource-intensive and incur delays due to the need for pilot transmission and feedback, making them less effective when resources are limited or speed is critical.
Innovation Solution
Implementing open-loop rate control in TDD communication systems, where channel quality is estimated using asymmetric parameters to select data transmission rates without explicit feedback, leveraging reciprocal channel properties and SNR estimates to adjust transmission rates efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop rate control is used, then rate selection accuracy is improved, but system resource overhead and delay increase
Solution Approach 1:
The patent extracts the essential function of channel quality estimation by using uplink pilot signals to infer downlink channel conditions through reciprocity, eliminating the need for explicit downlink pilot transmission and feedback. This extraction approach achieves rate selection accuracy while reducing system resource overhead.
Solution Approach 2:
The patent introduces channel reciprocity as an intermediary principle that links uplink and downlink channel characteristics. By using uplink pilot measurements as an intermediary to estimate downlink channel quality, the system avoids direct downlink pilot transmission and feedback mechanisms, thereby reducing overhead while maintaining measurement accuracy.
2Measurement precision
If closed-loop rate control is used, then rate selection accuracy is improved, but transmission delay increases
Solution Approach 1:
The patent performs preliminary channel quality estimation using uplink pilot signals transmitted before data transmission. By pre-establishing channel state information through uplink pilots and utilizing reciprocity, the system eliminates the need for real-time downlink pilot transmission and feedback loops, thereby reducing transmission delay while maintaining accurate rate selection.
Solution Approach 2:
The patent extracts the time-consuming feedback mechanism from closed-loop rate control by using uplink pilot measurements to directly infer downlink channel conditions. This extraction eliminates the round-trip delay associated with downlink pilot transmission and rate feedback, achieving faster rate selection without sacrificing accuracy.
3Device complexity
If open-loop rate control is used, then system resource overhead is reduced, but rate selection accuracy may deteriorate
Solution Approach 1:
The patent implements a form of feedback through channel reciprocity, where uplink pilot signal measurements provide implicit feedback about downlink channel conditions. This feedback mechanism enables accurate rate selection without requiring explicit downlink feedback transmission, thus maintaining measurement precision while reducing system resource overhead.
Solution Approach 2:
The patent uses channel reciprocity as an intermediary to bridge the information gap between uplink and downlink channels. By measuring uplink channel quality through pilot signals and using reciprocity to infer downlink conditions, the system achieves accurate rate selection without direct downlink feedback, thereby maintaining precision while reducing overhead.
4Loss of time
If open-loop rate control is used, then transmission delay is reduced, but channel quality estimation accuracy may worsen
Solution Approach 1:
The patent employs uplink pilot signals as a feedback mechanism that provides real-time information about channel conditions. By measuring the uplink pilot response and using reciprocity to estimate downlink channel quality, the system achieves accurate channel estimation without the delay associated with downlink feedback loops, thus maintaining precision while reducing transmission delay.
Solution Approach 2:
The patent performs channel quality estimation in advance using uplink pilot signals transmitted before data transmission begins. This preliminary action leverages channel reciprocity to establish accurate downlink channel state information without requiring real-time downlink feedback, thereby achieving both fast rate selection and accurate channel quality estimation.
Data Source
AI summary
Techniques for performing open-loop rate control in a TDD communication system are described. The channel quality of a first link is estimated based on a transmission received via the first link. The channel quality of a second link is estimated based on the estimated channel quality of the first link and an asymmetric parameter. At least one rate for a data transmission via the second link is selected based on the estimated channel quality of the second link. The estimated channel quality for each link may be given by a set of SNR estimates for a set of transmission channels on that link. The asymmetric parameter may be determined based on (1) the capabilities (e.g., transmit power, receiver noise figure, and number of antennas) of the transmitting and receiving stations or (2) received SNRs for the first and second links.