OFDM Symbol Interleaving Addresses for DVB-T2 8K Error Correction
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Solution Overview
Problem
Existing OFDM systems, such as DVB-T and DVB-H, face challenges in error correction due to correlated fading in terrestrial broadcast channels, which can be mitigated by effectively interleaving data symbols across sub-carrier signals, but current interleaving schemes are not optimal, especially for the 8K mode of DVB-T2.
Innovation Solution
A data processing apparatus with an address generator using a linear feedback shift register and permutation circuit generates addresses to interleave and de-interleave data symbols, employing an odd interleaving process and cycling through different permutation codes to reduce the likelihood of successive data bits being mapped to the same sub-carrier, thereby improving error correction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data symbols are mapped sequentially onto sub-carrier signals without interleaving, then the mapping process is simple and fast, but error correction performance deteriorates due to correlated fading affecting successive symbols
Solution Approach 1:
The patent applies dynamics by making the interleaving pattern variable through different permutation codes (first and second permutation codes) that can be selected based on system conditions. The address generator dynamically changes the interleaving pattern by selecting between different permutation codes, allowing the system to adapt to varying channel conditions while maintaining effective error correction performance.
Solution Approach 2:
The patent segments the interleaving process into distinct components: a linear feedback shift register for generating base addresses, permutation circuits for reordering addresses according to different permutation codes, and an offset generator for adding offsets to addresses. This segmentation allows each component to be optimized independently while working together to achieve effective symbol separation.
2Reliability
If a fixed permutation code is used for address generation, then the address generator is simpler to implement, but successive data bits may be mapped to the same sub-carrier reducing interleaving effectiveness
Solution Approach 1:
The patent implements dynamics by switching between different permutation codes (first permutation code and second permutation code) based on system conditions such as OFDM symbol type or channel state. This dynamic selection ensures that successive data bits are effectively separated across different sub-carriers, preventing the mapping of adjacent bits to the same sub-carrier while managing permutation code complexity through structured selection criteria.
Solution Approach 2:
The patent changes the permutation code parameter dynamically by selecting between different permutation codes. This parameter change allows the system to adapt the interleaving pattern to different transmission conditions, ensuring optimal separation of data symbols while maintaining manageable complexity through a finite set of predefined permutation codes.
3Adaptability or versatility
If the same interleaving pattern is used for all OFDM symbols, then the processing is more consistent and simpler, but the system cannot adapt to varying channel conditions in terrestrial broadcast
Solution Approach 1:
The patent applies dynamics by enabling the address generator to switch between different permutation codes based on channel conditions or symbol type. This dynamic adaptation allows the interleaving pattern to vary across different OFDM symbols, providing versatility in handling diverse terrestrial broadcast channel conditions while maintaining manageable complexity through a structured approach to code selection.
Solution Approach 2:
The patent changes the permutation code parameter adaptively to match varying channel conditions. By selecting from multiple predefined permutation codes, the system achieves adaptability to different terrestrial broadcast scenarios without requiring complex real-time optimization, balancing versatility with implementation feasibility.
Data Source
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AI summary
A data processing apparatus maps symbols received from a predetermined number of sub-carrier signals of Orthogonal Frequency Division Multiplexed (OFDM) symbols into an output symbol stream, the data symbols being divided into first sets of data symbols received from first OFDM symbols and second sets of data symbols received from second OFDM symbols. The data processor includes an interleaver memory which reads-in the predetermined number of data symbols for mapping onto the OFDM sub-carrier signals. The interleaver memory reads-out the data symbols on to the OFDM sub-carriers to effect the mapping, the read-out being in a different order than the read-in, the order being determined from a set of addresses, with the effect that the data symbols are interleaved on to the sub-carrier signals. The set of addresses are generated from an address generator which comprises a linear feedback shift register and a permutation circuit. The linear feedback shift register has twelve register stages with a generator polynomial for the linear feedback shift register of Riʹ11=Ri-1ʹ0⊕Ri-1ʹ1⊕Ri-1ʹ4⊕Ri-1ʹ6, and the permutation code forms, with an additional bit, a thirteen bit address. The address generator includes an offset generator operable to add an offset to the formed thirteen bit address, and the data processing apparatus is operable to de-interleave the first and second sets of data symbols into the output data stream in accordance with an odd interleaving process, thereby providing an improvement in interleaving the data symbols for an 8K operating mode of an OFDM modulated system such as a Digital Video Broadcasting (DVB) standard such as DVB-Terrestrial2 (DVB-T2). This is because there is a reduced likelihood that successive data bits which are close in order in an input data stream are mapped onto the same sub-carrier of an OFDM symbol.