DFT-Spread OFTM Bandwidth Allocation and Interference Coordination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing DFT-S-OFDMA transmission scheme in 3G LTE leads to uplink frequency fragmentation, limiting bit rate and causing resource allocation issues, especially for users scheduled in the middle of the frequency band, and complicates inter-cell interference coordination.
Innovation Solution
A transmitter device and method that perform discrete Fourier transform, expansion, and cyclic frequency shifting of signals in the frequency domain, allowing for efficient allocation of bandwidth without fragmentation, and enabling orthogonal resource allocation across users.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DFT-S-OFDMA maps data symbols to consecutive sub-carriers, then single carrier transmission is maintained, but frequency fragmentation occurs limiting bit rate
Solution Approach 1:
The patent segments the frequency domain signal into multiple parts and applies cyclic shifts to different segments. This allows the transmitted signal to occupy non-consecutive sub-carriers while maintaining single carrier properties through the cyclic shift operation, thereby resolving the contradiction between maintaining single carrier transmission and avoiding frequency fragmentation.
Solution Approach 2:
The patent introduces a cyclic shift dimension to the frequency domain signal. By applying cyclic shifts to the DFT-transformed signal before mapping to sub-carriers, the system can allocate resources in a non-contiguous frequency spectrum while preserving the single carrier characteristics, thus increasing bit rate without sacrificing transmission quality.
2Ease of manufacture
If DFT-S-OFDMA uses localized mapping to consecutive sub-carriers, then implementation is simple, but resource allocation flexibility is reduced
Solution Approach 1:
The patent makes the resource allocation dynamic by introducing cyclic shift parameters that can be adjusted based on scheduling requirements. The cyclic shift value can be changed per user or per time interval, allowing flexible resource allocation while maintaining a relatively simple implementation based on the existing DFT-S-OFDMA framework.
3Productivity
If frequency allocations are assigned to middle of band, then resource utilization improves, but fragmentation increases
Solution Approach 1:
The patent uses cyclic shifting to create a copied version of the frequency domain signal that can be mapped to non-consecutive sub-carriers. This copying approach with cyclic shifts allows the system to allocate resources in the middle of the band without creating fragmentation, as the cyclic shift operation naturally handles the non-contiguous mapping.
Data Source
AI summary
The invention applies Discrete Fourier Transform (DFT)-spread-OFDM (Orthogonal Frequency Division Multiple Access), which is proposed for the Third Generation Partnership Program Long Term Evolution (3GPP LTE) uplink. The core of the invention is that we use a cyclic frequency shift operation over part of the bandwidth spanned by the Inverse Fast Fourier Transform (IFFT). Furthermore, the cyclic frequency shift enables efficient inter-cell interference coordination in case neighboring cells hop with the same pattern and different initial offsets. An equivalent operation may be performed in the time domain.