OFDM Preamble Configuration for Antenna Gain and Efficiency
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Solution Overview
Problem
In radio communication systems using OFDM, narrow frequency bands assigned to each user result in suboptimal antenna combined gain due to insufficient preamble symbols, leading to degraded transmission efficiency when more preamble symbols are added in the time axis direction.
Innovation Solution
A radio communication device and method that dynamically adjust the symbol string configuration based on receiving state, increasing preamble symbols in the frequency axis direction for better gain when SNR is high and in the time axis direction when SNR is low, to maintain desired antenna combined gain while minimizing data symbol transmission efficiency degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more preamble symbols are arranged in the time axis direction to obtain antenna combined gain close to theoretical value, then antenna combined gain is improved, but transmission efficiency of data symbols is degraded
Solution Approach 1:
The patent applies dynamics by making the symbol string configuration changeable based on receiving conditions. The base station dynamically selects between first and second symbol string configurations according to the receiving state of uplink radio signals, allowing the system to adapt between prioritizing antenna combined gain (when receiving state is poor) and transmission efficiency (when receiving state is good).
Solution Approach 2:
The patent changes parameters by varying the arrangement of preamble symbols and data symbols in the symbol string. Specifically, it adjusts the number of preamble symbols in the frequency axis direction and their arrangement pattern based on receiving state, thereby changing the effective bandwidth and gain characteristics without permanently sacrificing data transmission capacity.
2Quantity of substance
If narrow frequency band is assigned to each user to enable multiple users to communicate simultaneously, then system capacity is improved, but antenna combined gain is degraded due to insufficient preamble symbols
Solution Approach 1:
The patent applies dimensionality change by arranging preamble symbols not only in the time axis direction but also in the frequency axis direction. By distributing preamble symbols across multiple subcarriers (frequency dimension), the system obtains antenna combined gain even when the total frequency band per user is narrow, thus supporting multiple users while maintaining gain performance.
Solution Approach 2:
The system dynamically adjusts the symbol string configuration to change the effective bandwidth utilization. When receiving state is poor, it uses configurations that spread preamble symbols across more subcarriers, effectively increasing the bandwidth used for gain calculation without permanently allocating more frequency resources.
Data Source
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AI summary
A radio base station 100 judges a receiving state of a radio signal in conformity with the orthogonal frequency division multiplexing scheme, and changes a symbol string configuration of a symbol string defined by a size in a frequency axis direction and in a time axis direction, on the basis of the judged receiving state.