OFDM Symbol Interleaving for Variable Sub-Carrier Modes
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Solution Overview
Problem
Existing OFDM systems face challenges in efficiently adapting to varying numbers of sub-carriers per symbol, leading to increased memory requirements and complexity, which hinders flexible data communication in applications like DVB-T/H and cable communications.
Innovation Solution
A symbol interleaver that dynamically adjusts its operation based on whether the read or write addresses are valid for the current or previous OFDM symbol, using a single memory size equal to the maximum number of sub-carriers, allowing for flexible mapping of input data symbols onto varying sub-carrier signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single interleaver memory is used for both even and odd OFDM symbols, then memory cost is reduced, but it becomes difficult to handle varying sub-carrier numbers between symbols
Solution Approach 1:
The patent implements dynamic control of read/write address generation based on the OFDM symbol type (even/odd) and the actual number of sub-carriers. The controller dynamically selects between different address generation modes: for even symbols it uses addresses generated by the address generator circuit, while for odd symbols it uses sequential addresses. This dynamic adaptation allows a single memory to efficiently handle varying sub-carrier configurations without requiring separate memory structures for each symbol type.
2Adaptability or versatility
If separate interleaver memories are provided for even and odd OFDM symbols, then handling of varying sub-carrier numbers becomes easier, but memory requirements and system complexity increase
Solution Approach 1:
The patent merges the interleaving functionality for even and odd OFDM symbols into a single interleaver memory structure. By implementing mode-dependent address generation control within one memory, the system achieves the adaptability of separate memories while reducing the total memory quantity and system complexity. The single memory is flexibly configured through controller logic that adapts address generation based on symbol type and sub-carrier count.
3Adaptability or versatility
If the number of sub-carriers per OFDM symbol is made variable, then data communication flexibility is improved, but memory management complexity increases
Solution Approach 1:
The patent changes the operational parameters of the interleaver based on the OFDM symbol type and sub-carrier configuration. For even symbols, it uses one set of addressing parameters generated by the address generator circuit, while for odd symbols, it switches to sequential addressing parameters. This parameter switching mechanism allows the system to adapt to variable sub-carrier numbers without requiring complex memory management logic, as the complexity is confined to simple address generation mode selection.
Data Source
AI summary
A data processing apparatus to map input data symbols to be communicated onto sub-carrier signals of Orthogonal Frequency Division Multiplexed (OFDM) symbols. The number of sub-carrier signals available from each of the OFDM symbols being variable between OFDM symbols and the input data symbols include first sets of data symbols and second sets of input data symbols. The data processing apparatus includes a controller, an address generator, and an interleaver memory. The controller is configured, when operating in accordance with an even interleaving process to read out a first set of the input data symbols from the interleaver memory on to the sub-carrier signals of an even OFDM symbol using read addresses generated by the address generator, and to write in a second set of the input data symbols into the interleaver memory using the addresses generated by the address generator.