HT-STF Sequence Generation for IEEE 802.11n Buffer Optimization
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Solution Overview
Problem
Existing methods for generating High-Throughput Short Training Field (HT-STF) sequences in IEEE 802.11n WLAN systems require significant buffer size and complex arithmetic operations to support all four bandwidth configurations, as they need to store multiple sets of time-domain sequences.
Innovation Solution
The method involves storing only one set of time-domain HT-STF sequences, either for the lower or upper 20 MHz of 40 MHz bandwidth configuration, and deriving the other three sets through simple calculations, reducing the ROM requirement and buffer size needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If all four sets of time-domain HT-STF sequences are stored in ROM to support all bandwidth configurations, then all bandwidth configurations can be transmitted, but the buffer size becomes significant and large
Solution Approach 1:
The patent applies universality by enabling a single stored time-domain sequence to serve multiple bandwidth configurations (20 MHz, 40 MHz, lower 20 MHz of 40 MHz, and upper 20 MHz of 40 MHz). Through frequency-shifting operations and selective usage, one universal sequence can be adapted to generate the required sequences for all four bandwidth configurations, eliminating the need to store four separate sequences.
Solution Approach 2:
The patent employs parameter changes by modifying the frequency domain characteristics of the stored time-domain sequence through frequency-shifting operations. By changing the frequency offset and applying appropriate scaling factors, the same time-domain sequence can be transformed to match the requirements of different bandwidth configurations, thereby reducing memory requirements while maintaining full configurational support.
2Measurement precision
If over-sampling is implemented at transmitter to improve signal quality, then signal accuracy is improved, but the required buffer size is further multiplied
Solution Approach 1:
The patent applies preliminary action by performing frequency-shifting and scaling operations on the stored time-domain sequence before transmission. These preprocessing operations prepare the sequence for over-sampling and multiple bandwidth configurations in advance, ensuring that the oversampled signals maintain high accuracy without requiring proportionally larger buffer sizes. The frequency-domain manipulation is done once on the base sequence rather than on each oversampled version.
3Adaptability or versatility
If four sets of time-domain HT-STF sequences are stored in ROM, then all bandwidth configurations are supported, but complex arithmetic operations are required to generate the sequences
Solution Approach 1:
The patent simplifies arithmetic operations by using frequency-shifting and scaling parameter changes instead of generating sequences from scratch for each bandwidth configuration. The frequency-shift operation and multiplication by scaling factors are computationally simpler than performing full inverse Fast Fourier Transform operations for each configuration, thereby reducing device complexity while maintaining support for all four bandwidth configurations.
Data Source
AI summary
The present invention discloses a generating method for short training field in IEEE 802.11n communication systems, mainly comprising the steps of: storing only a first set of time-domain HT-STF sequences in the memory; and deriving a second set of the time-domain HT-STF sequences from the first set of the time-domain HT-STF sequences. The first set of time-domain HT-STF sequences is the time-domain HT-STF sequences either for lower 20 MHz of 40 MHz BW or upper 20 MHz of 40 MHz BW. According to the invention, it is shown that only one set of time-domain HT-STF sequence needs to be stored in the memory. The other three sets of time-domain HT-STF sequence can be generated easily from simple calculation. Therefore, the saving in buffer size to implement all four configurations is significant.