Frequency Domain Scheduling in TDD Systems Using Non-Precoded Reference Symbols
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Solution Overview
Problem
Frequency domain scheduling is unable to be performed when a channel sounding method is employed to obtain a pre-coding matrix in time division duplex (TDD) communication systems, leading to performance losses in both frequency domain scheduling and linear spatial domain pre-coding/beam-forming.
Innovation Solution
A method where a user terminal transmits a non pre-coded reference symbol to a base station, allowing the base station to obtain a channel impulse response matrix and calculate a linear spatial domain pre-coding matrix for each downlink physical resource block, enabling the determination of a channel quality indicator for frequency domain scheduling while performing linear spatial domain pre-coding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel sounding method is employed to obtain pre-coding matrix, then linear spatial domain pre-coding performance is improved, but frequency domain scheduling becomes unable to be performed
Solution Approach 1:
The patent segments the reference signal into two distinct parts: a non-precoded reference symbol for channel sounding and a precoded reference symbol for data demodulation. This segmentation allows the base station to separately obtain channel impulse response (for pre-coding) and channel quality indicator (for frequency domain scheduling), thereby resolving the contradiction between maintaining pre-coding performance and enabling frequency domain scheduling.
2Measurement precision
If feedback-based manner is employed to obtain pre-coding matrix, then pre-coding/beam-forming information accuracy is improved, but system complexity and feedback overhead increase
Solution Approach 1:
The patent extracts only the necessary channel quality information (CQI) from the channel state feedback process. Instead of requiring full channel state feedback, the system extracts CQI based on channel impulse response and pre-coding matrix, which is then used for frequency domain scheduling. This extraction approach maintains pre-coding accuracy while significantly reducing feedback overhead and system complexity.
3Use of energy by moving object
If user terminal estimates equivalent channel response matrix, then reference symbol cost is reduced, but channel quality indicator calculation becomes unavailable
Solution Approach 1:
The patent introduces an intermediary approach where the base station acts as the mediator to calculate the channel quality indicator. Instead of requiring the user terminal to calculate CQI (which would require additional reference symbols and processing), the base station calculates CQI using the channel impulse response and pre-coding matrix obtained from the non-precoded reference symbol. This intermediary calculation method preserves energy while maintaining channel quality information availability.
Data Source
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AI summary
A method and system for achieving frequency domain scheduling in a time division duplex system is disclosed, the method comprising: a first device transmits a non pre-coded reference symbol to a second device; from the reference symbol, the second device obtains a channel impulse response matrix experienced by the reference symbol transmitted from the first device, and according to the channel impulse response matrix, obtains linear spatial domain pre-coding matrix of candidate physical resource blocks used in transmitting data to the first device; from the channel impulse response matrix and the linear spatial domain pre-coding matrix, the second device obtains the channel quality indication of the candidate physical resource blocks; and performs the frequency domain scheduling according to the channel quality indication. The use of the method not only solves the problem in the prior art that the frequency domain scheduling is unable to be performed when a channel sounding method is employed, but also the contradiction in the use of the frequency domain scheduling and the linear spatial domain pre-coding. A communication system is also disclosed.