NB-IoT OFDM Signal Generation at Lower Sampling Rates
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Solution Overview
Problem
Current NB IoT systems face challenges in reducing the sampling rate while maintaining compatibility with legacy LTE, which is costly and power-consuming, especially for low-cost MTC devices, due to the need for upsampling and complex processing.
Innovation Solution
A transmitter architecture that uses non-uniform sampling and adjusts the sampling phase during cyclic prefixes, allowing for a lower sampling rate without upsampling, specifically using a 240 kHz sample rate and configuring the digital-to-analog converter to support this, thereby reducing computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If upsampling to LTE sampling rate (1.92 MHz) is performed to maintain compatibility with legacy LTE, then compatibility with legacy LTE systems is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent applies dynamic sampling phase adjustment during cyclic prefixes to enable variable sampling rates. By dynamically changing the sampling phase rather than maintaining a fixed high sampling rate, the system achieves LTE compatibility while operating at lower sampling rates (e.g., 240 kHz) during normal OFDM symbols, thus reducing device complexity while maintaining adaptability.
Solution Approach 2:
The patent changes the sampling rate parameter from the traditional fixed LTE rate (1.92 MHz) to a lower variable rate (e.g., 240 kHz) for NB-IoT operations. By adjusting this fundamental parameter and compensating through sampling phase modification during cyclic prefixes, the system reduces processing complexity while preserving compatibility with legacy LTE through maintained timing synchronization.
2Adaptability or versatility
If upsampling to LTE sampling rate (1.92 MHz) is performed to maintain compatibility with legacy LTE, then compatibility with legacy LTE systems is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic sampling rate adjustment where the system operates at a lower sampling rate (240 kHz) during data transmission and only switches to higher effective sampling during cyclic prefix periods through phase adjustment. This dynamic approach significantly reduces average power consumption compared to continuously operating at the fixed LTE sampling rate of 1.92 MHz, while still maintaining compatibility with legacy LTE systems.
Solution Approach 2:
The patent fundamentally changes the operating sampling rate parameter from 1.92 MHz to 240 kHz for NB-IoT, reducing power consumption by avoiding the energy-intensive upsampling process. Compatibility with legacy LTE is maintained through careful parameter management during cyclic prefixes, where sampling phase adjustments ensure proper timing alignment without requiring sustained high sampling rates.
3Use of energy by moving object
If non-uniform sampling with phase adjustment is used to reduce sampling rate, then power consumption and device complexity are reduced, but signal generation accuracy may deteriorate
Solution Approach 1:
The patent applies local quality by maintaining uniform high-precision sampling during OFDM symbol periods while using non-uniform sampling with phase adjustment only during cyclic prefix periods. This localized application of different sampling strategies ensures that the critical data transmission portions maintain high signal generation accuracy, while the cyclic prefixes (which are less critical for data integrity) can tolerate the simplified non-uniform sampling approach, thus reducing overall power consumption without significantly compromising signal accuracy.
Data Source
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AI summary
A method in a transmitter circuit (200) of generating an NB IoT signal is disclosed. The NB IoT signal comprises a first sequence of an integer number Nsym of OFDM symbols. The method comprises generating (100) the signal comprising the first sequence of OFDM symbols at a sampling rate lower than 1.92 MHz and adjusting (110) a sampling phase during cyclic prefixes. A corresponding transmitter circuit is also disclosed.