OFDM Symbol Interleaving With Offset Addressing for DVB-T2
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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 onto sub-carrier signals, but current interleaving schemes are not optimal, especially for the 1K operating mode of DVB-T2.
Innovation Solution
A data processing apparatus that includes an interleaver memory and an address generator with a linear feedback shift register and permutation circuit, which generates pseudo-random addresses to interleave data symbols onto OFDM sub-carriers, with an additional offset to prevent successive data bits from being mapped to the same sub-carrier, and uses an odd interleaving process to improve 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 changes the mapping parameters by introducing an offset value that varies between different OFDM symbols. This offset is added to the sub-carrier index, causing successive data symbols to be mapped to different sub-carriers even without complex interleaving. This parameter change effectively breaks the correlation caused by fading while keeping the mapping process simple.
2Reliability
If a symbol interleaver with interleaver memory and address generator is used to separate encoded symbols onto different sub-carriers, then error correction coding performance improves, but device complexity and memory requirements increase
Solution Approach 1:
The patent extracts the essential interleaving function by removing the need for large interleaver memory and complex address generators. Instead, it uses a simple offset addition mechanism that achieves the same goal of separating successive symbols onto different sub-carriers without requiring the full interleaving infrastructure.
Solution Approach 2:
The patent changes the mapping parameters by introducing an offset value that varies between different OFDM symbols. This offset is added to the sub-carrier index, causing successive data symbols to be mapped to different sub-carriers even without complex interleving. This parameter change effectively breaks the correlation caused by fading while keeping the mapping process simple.
3Productivity
If successive data bits are mapped to the same sub-carrier, then the mapping process is efficient and simple, but the integrity of data communication deteriorates when fading affects that sub-carrier
Solution Approach 1:
The patent changes the mapping parameters by introducing an offset value that varies between different OFDM symbols. This offset is added to the sub-carrier index, causing successive data symbols to be mapped to different sub-carriers even without complex interleving. This parameter change effectively breaks the correlation caused by fading while keeping the mapping process simple.
Data Source
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AI summary
A data processing apparatus maps input symbols to be communicated onto a predetermined number of sub-carrier signals of an Orthogonal Frequency Division Multiplexed (OFDM) symbol. 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 nine register stages and the permutation code forms, with an additional bit, a ten bit address. The address generator includes an offset generator operable to add an offset to the formed ten bit address, thereby providing an improvement in interleaving the data symbols for a 1K 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.