Femto Cell Subframe Design for OFDMA Data Rate
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Solution Overview
Problem
Current mobile communication systems face inefficiencies in downlink transmission due to the use of the same frame format for both macro and femto cells, leading to reduced resource utilization and performance degradation caused by different radio channel environments and mobility conditions.
Innovation Solution
A downlink transmission method and apparatus that optimize the frame format for femto cells by using a second type of subframe with short and long symbols, differing from the macro cell subframe in frequency, to improve data rate and resource allocation, while maintaining compatibility with LTE/LTE-A systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the same frame format is used for both macro and femto cells, then system compatibility is maintained, but resource utilization efficiency and data rate in femto cells deteriorate due to unnecessary cyclic prefix overhead
Solution Approach 1:
The patent segments the frame structure into different types (first type for macro cells with long cyclic prefix, second type for femto cells with short cyclic prefix) based on the specific needs of each cell type. This segmentation allows femto cells to use a shortened frame format that reduces cyclic prefix overhead while maintaining compatibility with the overall LTE/LTE-A system through proper scheduling and signaling.
2Productivity
If a shortened frame format is used for femto cells, then resource utilization efficiency improves, but robustness to delay spread may worsen
Solution Approach 1:
The patent applies local quality by tailoring the cyclic prefix length to the specific propagation conditions of femto cells. Since femto cells typically have shorter transmission distances and less severe delay spread compared to macro cells, the invention uses a shortened cyclic prefix format specifically for femto cells, optimizing resource utilization for each local environment rather than applying a uniform format system-wide.
3Productivity
If different frame formats are used for macro and femto cells, then performance is optimized for each cell type, but system complexity increases
Solution Approach 1:
The patent implements dynamics by enabling flexible switching between different frame formats (first type with long cyclic prefix, second type with short cyclic prefix) based on real-time scheduling decisions. The base station dynamically selects which format to use for each femto cell transmission, and this information is signaled to user equipment through downlink control information, allowing the system to adapt to varying channel conditions and traffic requirements without requiring complex permanent configurations.
Data Source
AI summary
A downlink transmission/reception apparatus and a method are provided for improving a data rate in a mobile communication based on Orthogonal Frequency Division Multiple Access (OFDMA). The downlink transmission method of a base station in a mobile communication system including at least one femto cell deployed in a macro cell includes generating signals to be mapped to at least one short symbol and a plurality of long symbols in a second type of subframe for the femto cell which differs from a first type of subframe for the macro cell in frequency, the first and second types of subframes being identical with each other in the time domain, and transmitting the at least one short symbol and the plurality of long symbols at predetermined positions in the second type of subframe.