Pilot Frequency Sequence Generation for Phase Tracking
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Solution Overview
Problem
Existing methods for generating pilot frequencies in Wi-Fi communication systems struggle with accurate phase tracking, particularly in high-order modulation scenarios like 1024QAM, leading to inefficiencies in carrier frequency offset estimation and channel estimation.
Innovation Solution
A method and apparatus for generating a pilot frequency sequence that involves generating a data pilot frequency and a multi-stream data pilot frequency sequence, multiplying it by an orthogonal code, and sending it to the receiving end, where it is used to estimate phase rotation and compensate for channel variations across multiple streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the same pilot frequency is inserted for multi-stream TS to compensate phase rotation, then phase rotation compensation is enabled, but stream identification capability is lost leading to reduced estimation accuracy
Solution Approach 1:
The patent segments the pilot frequency sequence by multiplying different streams' pilot frequencies with different orthogonal codes (e.g., Walsh-Hadamard codes). This segmentation allows each stream to have a distinct pilot signature while maintaining the ability to compensate for phase rotation, thereby resolving the contradiction between phase compensation and stream identification.
Solution Approach 2:
The patent introduces orthogonal codes as an intermediary mechanism between the pilot frequency and the multi-stream signals. These orthogonal codes enable the receiving end to separate and identify different streams while still allowing phase rotation compensation to be performed on the combined signal, thus mediating between the two conflicting requirements.
2Productivity
If high-order modulation (1024QAM) is used to improve spectral efficiency, then data transmission rate increases, but phase rotation estimation accuracy deteriorates
Solution Approach 1:
The patent applies preliminary phase rotation compensation using pilot frequencies before the actual data demodulation process. By compensating for phase rotation in advance using the orthogonal-coded pilot sequences, the system prepares the signal for high-order modulation demodulation, thereby maintaining estimation accuracy even when using 1024QAM.
3Measurement precision
If orthogonal codes are removed to obtain channel estimation of multiple streams, then stream-specific channel estimation is achieved, but frequency error effects accumulate leading to reduced accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the receiving end first compensates for phase rotation using the orthogonal-coded pilot frequencies, then removes the orthogonal codes to obtain stream-specific channel estimates. This feedback loop ensures that frequency errors are corrected before stream separation, maintaining both accuracy and reliability.
Data Source
AI summary
Disclosed in the present invention are a method and an apparatus for generating a pilot frequency sequence. The method comprises: generating a data pilot frequency by a data pilot frequency generator of a transmitting end, and generating a multi-stream data pilot frequency sequence by a multi-stream data pilot frequency sequence mapper of the transmitting end; generating an orthogonal code by an orthogonal code generator of the transmitting end, and generating an extracted orthogonal code word by a column loop extractor of the transmitting end; obtaining, by the transmitting end, a data pilot frequency sending value by multiplying the multi-stream data pilot frequency sequence of each symbol by the corresponding orthogonal code word; and sending the data pilot frequency sending value to a receiving end. The present invention effectively improves the accuracy of phase tracking obtained at the receiving end, and thus, high-order modulation can be effectively dealt with.