OFDM Convolutional Interleaving for Decodable FEC Frame Starts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Convolutional interleaving in OFDM systems for television broadcast systems poses challenges, particularly when a receiver powers on or changes channels, as it may not be able to decode the first forward error correction encoded frame of a new service frame due to latency issues, leading to incomplete recovery of symbols.
Innovation Solution
A transmitter and receiver system that calculates a displacement value to determine the minimum displacement of the first encoded data cell of a forward error correction frame from the start of the service frame, ensuring that only fully transmissible frames are decoded, and includes signaling data to indicate the start of decodable frames, allowing the receiver to ignore incomplete frames and await the next error correction encoded frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If convolutional interleaving is used in OFDM systems, then memory size is reduced compared to block interleaving, but receivers cannot decode the first FEC frame of a new service frame due to latency issues
Solution Approach 1:
The transmitter calculates the displacement value in advance and includes it in signaling data before transmission. This allows the receiver to know beforehand which FEC frames are complete and decodable, preventing wasted processing on incomplete frames and ensuring reliable decoding of the first FEC frame after service frame switching.
Solution Approach 2:
The transmitter provides feedback information (signaling data including displacement value and first FEC frame indication) to the receiver about the interleaved stream structure. This feedback enables the receiver to correctly identify and decode complete FEC frames without needing to buffer excessive data, resolving the contradiction between memory efficiency and decoding reliability.
2Loss of information
If the receiver processes all FEC frames in a service frame, then data recovery is maximized, but energy is wasted on processing incomplete frames that cannot be decoded
Solution Approach 1:
The receiver extracts and processes only the complete, decodable FEC frames identified by the signaling data, discarding incomplete frames. This selective processing approach maximizes data recovery from valid frames while avoiding unnecessary energy consumption on frames that cannot be decoded, directly resolving the contradiction between information recovery and energy usage.
3Reliability
If the receiver waits for complete FEC frames for decoding, then decoding accuracy is improved, but latency increases
Solution Approach 1:
The transmitter performs preliminary calculation of displacement values and identifies complete FEC frames before transmission. This advance preparation allows the receiver to immediately identify and decode complete frames without waiting or buffering, achieving both high decoding accuracy and low latency by eliminating unnecessary waiting time.
Data Source
AI summary
A transmitter transmits data using Orthogonal Frequency Division, OFDM, symbols. The transmitter comprising a forward error correction encoder configured to encode the data to form forward error correction encoded frames of encoded data cells, a service frame builder configured to form a service frame for transmission comprising a plurality of forward error correction encoded frames, a convolutional interleaves comprising a plurality of delay portions and configured to convolutionally interleave the data cells of the service frames, a modulation symbol mapper configured to map the interleaved and encoded data cells of the service frames onto modulation cells, and a modulator configured to modulate the sub-carriers of one or more OFDM symbols with the modulation cells.