Transmitter Differential Block Coding OFDM Subcarrier Mapping
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Solution Overview
Problem
Differential space-time block coding in orthogonal frequency division multiplexing results in a decrease in transmission rate due to the presence of start symbols that carry no information, especially as the number of subcarriers and antennas increases.
Innovation Solution
A transmitter configuration that employs differential block coding in both the frequency and time directions, allowing for the allocation of symbols such that only two symbols per subcarrier or OFDM symbol carry no information, thereby reducing the number of symbols without information and enhancing transmission rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential space-time block coding is applied to OFDM, then transmission diversity is achieved, but the transmission rate decreases due to informationless start symbols
Solution Approach 1:
The patent applies differential block coding in both frequency and time dimensions. By performing differential coding across multiple dimensions (frequency through subcarriers and time through OFDM symbols), the system reduces the number of informationless start symbols while maintaining transmission diversity. This multi-dimensional approach allows information to be carried more efficiently without sacrificing the diversity gain from space-time block coding.
2Quantity of substance
If the number of subcarriers and antennas is increased, then transmission capacity is improved, but the number of informationless symbols increases proportionally
Solution Approach 1:
The patent segments the differential coding process into multiple independent blocks across different frequency and time resources. By dividing the transmission into segmented blocks that can be independently coded, the system reduces the overhead of informationless start symbols. Each segment can carry information more efficiently, and the overall transmission capacity increases without a proportional increase in informationless symbols.
Solution Approach 2:
The patent extends differential coding into both frequency and time dimensions simultaneously. This multi-dimensional coding approach allows the system to maintain a constant or reduced number of informationless symbols even as the number of subcarriers and antennas increases, thereby improving transmission capacity without proportionally increasing information loss.
3Loss of information
If differential block coding is performed in both frequency and time directions, then the number of informationless symbols is reduced, but the coding complexity increases
Solution Approach 1:
The patent divides the differential coding operation into segmented blocks across frequency and time. This segmentation allows the complex multi-dimensional coding to be broken down into manageable, independent processing units. The segmented approach reduces coding complexity by enabling parallel processing and avoiding the need for complex inter-dependencies across the entire transmission block.
Solution Approach 2:
The patent applies differential block coding selectively in frequency and time directions rather than uniformly across all dimensions. This partial application approach reduces the overall coding complexity while still achieving the benefit of reduced informationless symbols in the most critical dimensions, balancing performance improvement with computational feasibility.
Data Source
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AI summary
A transmitter (100) includes: a first mapping unit (2) to allocate modulation symbols to orthogonal frequency division multiplexing subcarriers; a first differential block coding unit (3) to perform differential block coding on a part of the modulation symbols allocated; a second differential block coding unit (4) to perform, by using output of the first differential block coding unit as a start symbol, differential block coding on a remaining modulation symbol excluding the part of the modulation symbols subjected to differential block coding by the first differential block coding unit; and a second mapping unit (5) to convert output of the second differential block coding unit into a transmit signal that is transmitted from a plurality of antennas.