OFDM Modulator Combining Numerologies via Integer Block Ratios
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Solution Overview
Problem
Current OFDM-modulation and demodulation systems face challenges in supporting multiple numerologies with different block lengths, which limits their ability to efficiently manage mixed service use cases and maintain compatibility with legacy LTE devices in 5G networks, leading to suboptimal bandwidth utilization and performance.
Innovation Solution
The proposed OFDM-modulator and demodulator systems utilize a scheme where the second block length multiplied by an integer factor equals the first block length, allowing for the combination of modulation/demodulation systems with different FFT/IFFT lengths on a fixed subcarrier grid, while maintaining orthogonality and supporting multiple numerologies, enabling compatibility with LTE devices and increased bandwidth utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If different OFDM numerologies with different block lengths are supported in 5G networks, then service diversity and quality of service classes are improved, but system complexity and difficulty of managing mixed numerologies increase
Solution Approach 1:
The patent segments the OFDM system into multiple numerology configurations, each with distinct block lengths (e.g., 2048, 1024, 512 samples) and subcarrier spacings. Each numerology can be independently configured for different service types (eMBB, mMTC, URLLC), allowing the system to handle diverse service requirements while maintaining manageable complexity through modular numerology definitions.
Solution Approach 2:
The patent creates a universal OFDM framework that can accommodate multiple numerologies within a single system. The base station and user equipment are designed to support multiple numerology configurations simultaneously, enabling one system to perform multiple service functions (enhanced mobile broadband, massive machine type communication, ultra-reliable low latency communication) without requiring separate dedicated systems for each service type.
2Productivity
If multiple FFT/IFFT lengths are combined on a fixed subcarrier grid, then bandwidth utilization and scheduling flexibility are improved, but maintaining orthogonality and synchronization becomes more difficult
Solution Approach 1:
The patent changes key OFDM parameters (block length, subcarrier spacing, cyclic prefix length) to define different numerologies while maintaining their mathematical relationships. By carefully selecting parameter sets where shorter block lengths are integer divisors of longer block lengths (e.g., 512 divides 1024 divides 2048), the system maintains orthogonality across different numerologies on the same subcarrier grid, enabling flexible bandwidth utilization without sacrificing reliability.
3Adaptability or versatility
If LTE legacy devices and 5G devices operate in the same radio cell, then migration and backward compatibility are improved, but device complexity and resource management become more challenging
Solution Approach 1:
The patent introduces a numerology indicator as an intermediary mechanism that enables seamless coexistence of LTE and 5G devices. The base station transmits numerology indicators to user equipment, allowing devices to identify and adapt to the appropriate numerology configuration for their capabilities. LTE legacy devices can operate with standard LTE numerologies while 5G devices utilize extended numerology options, with the numerology indicator serving as the mediator that manages resource allocation and prevents interference between the two device types.
4Loss of time
If shorter OFDM symbols are used, then latency and response time are improved, but synchronization and frequency offset management become more challenging
Solution Approach 1:
The patent applies preliminary synchronization actions by transmitting synchronization signals and reference signals at predetermined positions within the OFDM structure, even before data transmission begins. For shorter block lengths, the system pre-configures appropriate cyclic prefix lengths and synchronization signal positions to facilitate rapid timing and frequency synchronization. This preliminary action enables devices to quickly acquire synchronization information, reducing overall latency while managing the increased synchronization challenges of shorter symbols.
Data Source
Figure 1a~1b
Figure 1c
Figure 1d
AI summary
It is proposed an OFDM-modulator (1000) for operating in a radio device (BS; UE) of a cellular radio communications network (RCN), wherein the OFDM-modulator (1000) is configured to determine a joined sample stream (g0, ..., gA-1) in dependence on a first and second egress sample stream (d0, ..., dA-1, e0, ..., eB-1) for up-converting the joined sample stream (g0, ..., gA-1) to a carrier frequency higher than respective subcarrier frequencies.