Precoded Narrowband Transmissions for DC Offset Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LTE systems face performance degradation due to DC offset interference in narrowband transmissions for Machine-Type Communication (MTC) devices, which can be exacerbated by nulling DC subcarriers, affecting system throughput and demodulation performance.
Innovation Solution
Implementing precoding techniques for narrowband transmissions, such as DFT spreading, to spread DC interference across all subcarriers, reducing the need for nulling DC subcarriers and minimizing interference impact, while ensuring compatibility with legacy UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If DC subcarriers are nulled to reduce DC offset interference, then DC interference is reduced, but system throughput and demodulation performance deteriorate
Solution Approach 1:
The patent converts the harmful DC offset interference into a beneficial spreading effect by applying precoding. The DC subcarrier interference is spread across multiple subcarriers through the precoding matrix, transforming concentrated harmful interference into distributed, manageable interference that can be handled by the receiver's channel estimation and equalization processes, thereby maintaining system throughput while reducing peak interference impact.
Solution Approach 2:
The patent changes the parameter of DC subcarrier handling from binary nulling to continuous precoding transformation. Instead of simply setting DC subcarriers to zero (nulling), the system applies a precoding matrix that transforms the DC subcarrier values into a distributed pattern across multiple subcarriers, changing the interference characteristic from concentrated to distributed while maintaining the same total power, thus improving demodulation performance.
2Object-affected harmful factors
If DC subcarriers are nulled to reduce DC offset interference, then DC interference is reduced, but demodulation performance deteriorates
Solution Approach 1:
The patent converts the harmful DC offset interference into a beneficial spreading effect by applying precoding. The DC subcarrier interference is spread across multiple subcarriers through the precoding matrix, transforming concentrated harmful interference into distributed, manageable interference that can be handled by the receiver's channel estimation and equalization processes, thereby maintaining system throughput while maintaining demodulation performance.
Solution Approach 2:
The precoding matrix acts as an intermediary transformation layer between the transmitted signal and the received signal. Instead of directly nulling DC subcarriers, the precoding matrix transforms the signal in a way that distributes the DC interference, and the receiver uses channel estimation and equalization as intermediary processes to compensate for the transformed interference, thereby preserving demodulation performance.
3Object-affected harmful factors
If precoding is applied to spread DC interference, then interference impact is reduced, but device complexity increases
Solution Approach 1:
The precoding matrix serves multiple functions simultaneously: it performs the traditional role of beamforming and spatial filtering while also distributing DC offset interference across subcarriers. This multi-functionality means that the same processing structure handles both signal optimization and interference mitigation, reducing the need for separate dedicated interference cancellation mechanisms and thereby limiting the increase in device complexity.
Solution Approach 2:
The precoding operation is performed in advance at the transmitter before signal transmission, preliminarily distributing the DC interference across multiple subcarriers. This preliminary action simplifies the receiver's task, as the interference distribution pattern is already established, allowing the receiver to use standard channel estimation and equalization procedures without requiring complex real-time interference cancellation algorithms.
4Use of energy by moving object
If narrowband transmissions are implemented for MTC devices, then power consumption is reduced, but DC offset interference increases
Solution Approach 1:
The patent applies precoding to convert the harmful concentrated DC offset interference into a beneficial distributed interference pattern. By spreading the DC interference across multiple subcarriers through the precoding matrix, the system maintains the power-efficient narrowband transmission for MTC devices while transforming the interference characteristic to be more manageable and less impactful on demodulation performance.
Solution Approach 2:
The patent changes the spatial distribution parameter of DC interference from concentrated (affecting only the DC subcarrier) to distributed (affecting multiple subcarriers). This parameter change is achieved through precoding transformation, which redistributes the interference energy while maintaining the narrowband transmission structure that provides power savings for MTC devices.
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
Embodiments of an Evolved Node B (eNB) for reducing direct current (DC) interference are disclosed herein. The eNB can include transceiver circuitry to receive a first waveform designated for a first User Equipment (UE) type and receive a second waveform designated for a second UE type. Additionally, the eNB can include a processing circuitry to precode the first waveform to reduce DC interference for the first UE type. Subsequently, the transceiver circuitry of the eNB can be further configured to send, using a single system bandwidth signal having a DC carrier frequency, the precoded first waveform and the second waveform to the first UE type and the second UE type.