OFDM Channel Bandwidth Identification via Cross-Correlation
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Solution Overview
Problem
Traditional methods for determining the channel bandwidth and channel offset of received orthogonal frequency division multiplexing (OFDM) signals are vulnerable to frequency selectivity and are performed before channel equalization, leading to suboptimal performance.
Innovation Solution
A receiver apparatus and method that utilize a Bandwidth identification module, including a 40 MHz channel offset identification and validation module, to accurately determine channel bandwidth and offset after channel equalization, using cross-correlation and energy computation to identify specific channel offset modes, such as CH_OFF_40 or CH_OFF_80, without requiring extensive hardware components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If channel bandwidth and offset identification is performed before channel equalization, then the identification process can be completed earlier in the signal processing chain, but the performance is highly vulnerable to frequency selectivity and suboptimal
Solution Approach 1:
The patent applies preliminary action by performing channel equalization before bandwidth and offset identification. The receiver first equalizes the received OFDM signal to compensate for channel effects, then performs the identification algorithms on the equalized signal. This reverses the traditional order to improve reliability while maintaining efficiency.
2Ease of manufacture
If traditional frequency offset estimation algorithms are used, then the implementation is straightforward, but the performance is highly vulnerable to frequency selectivity of the channel
Solution Approach 1:
The patent performs channel equalization as a preliminary step before applying the frequency offset estimation algorithm. This equalization compensates for the frequency selectivity effects of the channel, making the subsequent offset estimation more accurate and reliable while maintaining algorithmic simplicity.
3Measurement precision
If extensive hardware components are used for accurate bandwidth identification, then the identification accuracy improves, but the hardware requirements and device complexity increase
Solution Approach 1:
The patent uses signal field copies at different frequency offsets to identify channel bandwidth and offset. By analyzing the correlation between these copied signal fields, the receiver can accurately determine channel parameters using simple correlation operations rather than complex hardware components.
Solution Approach 2:
The patent changes the frequency offset parameter of signal field copies to create multiple versions of the signal at different offsets. By analyzing these parameter-varied copies through correlation and energy computation, accurate bandwidth identification is achieved without increasing hardware complexity.
4Productivity
If channel bonding technique is used to utilize full spectrum, then the data rate increases, but the number of channel offset modes increases making identification more complex
Solution Approach 1:
The patent uses signal field copies at different frequency offsets to identify channel bandwidth and offset. By analyzing the correlation between these copied signal fields, the receiver can accurately determine channel parameters using simple correlation operations rather than complex hardware components.
Solution Approach 2:
The patent employs a validation mechanism where identified channel offset modes are verified through correlation threshold checks. This feedback-based validation ensures accurate identification among multiple offset modes while maintaining systematic and manageable complexity.
Data Source
AI summary
Methods, apparatuses and systems for identifying a channel bandwidth and channel offset of an orthogonal frequency division multiplexing (OFDM) signal. The OFDM signal is received by a receiver apparatus that may be tuned to RF bandwidth of 20 MHz, 40 MHz or 80 MHz. The method utilized by the apparatus includes identifying the location of the primary channel and subsequently determining a sequence of equalized frequency domain sub-symbols of the signal field in the lower and the upper frequency band. Further, a cross-correlation between the sequence of equalized frequency domain sub-symbols is computed along with the computing energy of the sequence of equalized frequency domain sub-symbols. Finally, the cross-correlation and the computed energy are compared for identifying the channel offset and the channel bandwidth.