Digital Broadcasting Transmitter Mobile Service Encoding
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Solution Overview
Problem
The Vestigial Sideband (VSB) transmission mode used in digital broadcasting in North America and Korea is prone to performance deterioration in poor channel environments, especially with mobile receivers, due to limited resistance to channel changes and noise.
Innovation Solution
A digital broadcasting system that enhances receiving performance by performing additional encoding on mobile service data, multiplexing it with main service data, and inserting known data sequences for channel equalization, using a service multiplexer and transmitter with a channel equalizer that includes a frequency domain converter, CIR estimator, and distortion compensator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VSB transmission mode is used for digital broadcasting, then the system is simple and compatible with existing standards, but receiving performance deteriorates in poor channel environments and mobile conditions
Solution Approach 1:
The patent applies preliminary action by inserting known data sequences (pilot signals) before actual data transmission. These pilot signals are used in advance to estimate channel characteristics and perform equalization, preparing the receiving system to compensate for anticipated channel distortions and noise, thereby improving reliability in mobile and poor channel environments
Solution Approach 2:
The patent changes transmission parameters by implementing additional encoding schemes and modifying the data structure to include known sequences. The transmitting system adjusts encoding rates and inserts training sequences with specific properties (known amplitude and phase) to enable the receiver to adapt to channel conditions, transforming the system to achieve better noise and channel change resistance
2Reliability
If additional encoding is performed on mobile service data, then resistance to channel changes and noise is enhanced, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the transmission into distinct segments: pilot signal segments with known data and data segments with actual information. The encoding process is segmented into channel estimation phase and data transmission phase, allowing the receiver to process pilot signals separately for channel characterization, then use this information to decode data segments, reducing overall system complexity while maintaining reliability
Solution Approach 2:
The patent introduces an intermediary element - the known data sequence (pilot signal) - that mediates between the transmitter and receiver. This pilot signal serves as a reference that carries no information but enables channel estimation and equalization, simplifying the decoding process by providing a basis for compensation without requiring complex real-time adaptive algorithms
3Reliability
If known data sequences are inserted in data areas, then channel equalization and receiving performance are improved, but transmission efficiency decreases
Solution Approach 1:
The patent applies partial action by inserting known data sequences only in specific portions of the transmission frame rather than throughout the entire data stream. The pilot signals are placed at strategic locations (e.g., beginning of frames or at intervals) sufficient for channel estimation and equalization, avoiding excessive insertion that would unnecessarily reduce transmission efficiency while still achieving the required receiving performance
Solution Approach 2:
The known data sequences serve multiple functions: they enable channel estimation, provide reference for equalization, assist in synchronization, and facilitate timing recovery. This multi-functionality means that a single insertion of pilot signals achieves several objectives simultaneously, reducing the overall overhead compared to using separate signals for each function and thereby minimizing the impact on transmission efficiency
Data Source
AI summary
A digital broadcast transmitter includes: a first encoder configured to Forward Error Correction (FEC) encode broadcast service data to add parity data, thereby generating an FEC frame, and divide the FEC frame into a plurality of groups, each of the plurality of groups having a same size; a second encoder configured to encode transmission parameter data; an interleaver configured to interleave data of the plurality of groups; and a transmitting unit configured to transmit the interleaved data and the encoded transmission parameter data, wherein the transmission parameter data include information for identifying a number of the parity data.