NB-IoT OFDM Signal Generation With CP Phase Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solutions for Narrowband IoT (NB IoT) systems face challenges in reducing sampling rates while maintaining compatibility with legacy LTE systems, leading to increased processing costs and power consumption, especially in low-cost Machine-Type Communication (MTC) devices.
Innovation Solution
A transmitter architecture that adjusts the sampling phase during cyclic prefixes to generate signals at a lower sampling rate, using a digital-to-analog converter with non-uniform sampling, allowing for reduced sampling rates without the need for upsampling to higher clock frequencies, and utilizing a 240 kHz sample rate to satisfy the Nyquist sampling theorem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lower sampling rate is used to reduce processing complexity and power consumption, then power consumption and processing complexity are reduced, but compatibility with legacy LTE systems and signal generation accuracy deteriorate
Solution Approach 1:
The patent changes the sampling rate parameter from the conventional 1.92 MHz to a lower rate (e.g., 480 kHz or 240 kHz) while adjusting the cyclic prefix duration parameter accordingly. This parameter transformation allows the system to operate at lower power consumption while maintaining signal integrity and LTE compatibility through mathematical resampling techniques during the cyclic prefix generation process.
2Ease of manufacture
If a lower sampling rate is used to reduce device cost, then device cost is reduced, but signal generation accuracy and processing quality worsen
Solution Approach 1:
The patent transforms the sampling rate parameter to a lower value that is still sufficient for NB-IoT bandwidth requirements, and adjusts the cyclic prefix duration parameter to compensate. This allows the use of lower-cost components while maintaining signal generation accuracy through the modified parameter relationship and resampling techniques applied during cyclic prefix insertion.
3Duration of action of moving object
If the sampling rate is reduced to extend battery life, then battery life is extended, but processing complexity and signal fidelity deteriorate
Solution Approach 1:
The patent reduces the sampling rate parameter to extend battery life by lowering the clock frequency requirements, while simultaneously adjusting the cyclic prefix duration parameter to maintain proper signal timing relationships. The resampling technique applied during cyclic prefix generation maintains signal fidelity without requiring high-speed processing, thus reducing overall processing complexity.
4Use of energy by moving object
If a lower sampling rate is used, then power consumption and device cost are reduced, but the ability to maintain LTE timing structure and avoid interference worsens
Solution Approach 1:
The patent transforms the sampling rate parameter to a lower value while adjusting the cyclic prefix duration parameter to maintain the LTE timing structure. By modifying these parameters in a coordinated manner and applying resampling techniques during cyclic prefix generation, the system maintains proper orthogonality and timing relationships with LTE signals, preventing interference while operating at lower power consumption.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method in a transmitter circuit (200) of generating a signal comprising a first sequence of OFDM symbols, which are to be transmitted within a frequency sub band of a second sequence of OFDM symbols is disclosed. A first CP of the second sequence of OFDM symbols has a first duration, and a second CP of the second sequence of OFDM symbols has a second duration. In order to generate both the first and the second cyclic prefix with an integer number of equidistant samples, a first sampling rate is required. The method comprises generating (100) the signal comprising the first sequence of OFDM symbols at a second sampling rate, lower than the first sampling rate, and adjusting (110) a sampling phase during CPs.