차세대 T-DMB 시스템의 부가서비스 제공을 위한 계층적 전송방식에 대한 연구

Abstract

The quality of traditional analog radio broadcasting systems has significantly deteriorated in recent years, due to serious electromagnetic pollution in urban areas, especially in mobile environments. Among the new broadcasting systems, Digital Audio Broadcasting (DAB), which is based on the Eureka-147 standard, provides CD-quality audio broadcasting services for fixed, portable and mobile applications, and has been recognized as a promising solution. Recently, the DAB system was announced as the official transmission specification of the Digital Multimedia Broadcasting (DMB) system in Korea.

The DMB system has a 1.7Mbps throughput, which is sufficient for multimedia broadcasting services as well as CD-quality digital audio services. However, the throughput is reduced to 1.152Mbps when we take into account the overhead such as bits needed for synchronization, error correction and multiplex configuration information. Therefore, multimedia broadcasting services have a low throughput.

Recently, there is a need to upgrade the conventional T-DMB system, in order to provide additional services and a higher throughput for multimedia broadcasting services.

In this thesis, we propose a structure for an advanced T-DMB (AT-DMB) system, which is based on Eureka-147, with UEP coding methods and hierarchical 16QAM/64QAM modulation, to provide additional services while maintaining the BER performance. A hierarchical modulation scheme, strong channel code and unequal error protection (UEP) are applied to the conventional T-DMB system, in order to enhance the conventional T-DMB system and provide additional mobile user services. Furthermore, this thesis proposes a non-uniform 16QAM/64QAM modulation scheme combined with various bit splitting methods and coding methods such as iterative codes.

The conventional T-DMB system based on Eureka-147 has the approved serial concatenated coding scheme. This thesis also applies the serial concatenated coding scheme as an HP(High priority) stream coding scheme, in order to provide a continuous conventional T-DMB service to subscribers.

The performance gap between HP and LP(Low priority) streams is very large. This means that the performance of the HP and LP streams involves trade-offs, when applying the same coding method. If the performance of the LP stream is poor, there is no point in providing the LP stream to subscribers. Therefore, this thesis focuses on reducing the performance gap between the HP and LP streams. This is why this thesis applies iterative codes to the LP stream. Among iterative codes, double binary turbo codes and LDPC (low density parity check) codes are good candidates for the AT-DMB system, because they approach the Shannon limit performance and involve a simple puncturing device and a flexible block size/coding rate combination.

The proposed AT-DMB system model with the UEP coding method, hierarchical modulation and bit splitting method provides a means of achieving high performance, multimedia broadcasting via the conventional T-DMB system.