OFDM Signal Generation With CP Phase Adjustment at Lower Sampling Rates
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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, allowing for a lower sampling rate than the traditional 1.92 MHz, using a digital-to-analog converter with non-uniform sampling and a control unit to manage the sampling phase, enabling efficient signal generation with reduced computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the traditional sampling rate of 1.92 MHz is used to generate both cyclic prefixes with integer number of samples, then compatibility with legacy LTE systems is maintained, but processing costs and power consumption increase
Solution Approach 1:
The patent changes the sampling rate parameter from the traditional 1.92 MHz to a lower rate, and introduces non-uniform sampling intervals during cyclic prefixes. This parameter change allows NB IoT to operate at reduced sampling rates while maintaining compatibility with LTE through controlled phase adjustments during the cyclic prefix period
Solution Approach 2:
The patent implements dynamic sampling phase adjustment during cyclic prefixes. The sampling phase is modified temporarily during the cyclic prefix duration to ensure proper signal alignment, then returns to normal operation. This dynamic adjustment allows lower sampling rates while maintaining compatibility
2Reliability
If upsampling is performed to maintain compatibility with legacy LTE systems, then signal quality is preserved, but processing complexity and cost increase
Solution Approach 1:
The patent applies preliminary phase adjustment during the cyclic prefix period before the main data transmission. By pre-adjusting the sampling phase during the cyclic prefix, the system avoids the need for complex real-time upsampling operations during data transmission, reducing overall processing complexity
Solution Approach 2:
The patent segments the signal transmission into distinct phases: a cyclic prefix phase with non-uniform sampling and phase adjustment, and a main data phase with uniform sampling. This segmentation allows different sampling strategies for different parts of the signal, reducing overall processing requirements
Data Source
AI summary
A method in a transmitter circuit 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 cyclic prefix (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 the signal comprising the first sequence of OFDM symbols at a second sampling rate, lower than the first sampling rate, and adjusting a sampling phase during CPs.