MIMO-OFDM 지상파 방송 시스템의 프레임 동기화 기술에 관한 연구 = A study on synchronization techniques in MIMO-OFDM terrestrial broadcasting systems

다국어 초록 (Multilingual Abstract)

Recently, world’s leading countries are changing their terrestrial broadcasting services from analog to digital and developing next generation digital broadcasting system specifications to support UHDTV (ultra-high definition television) contents and other various services. In order to maximize the transmission capacity by using the bandwidth efficiently, most wireless communication and broadcasting systems adopt OFDM (orthogonal frequency division multiplexing).
OFDM is multicarrier modulation scheme which uses a number of orthogonal subcarriers to mitigate multipath fading. It is widely used thanks to its low complexity structure allowing for simple modulation and demodulation by means of FFT (fast Fourier transform) and IFFT. However, orthogonality between subcarriers causes ICI (inter-carrier interference) with a small CFO (carrier frequency offset) which leads to a significant loss in the systems performance. Therefore, synchronization is an important issue in OFDM systems.
DVB-T2 (digital video broadcasting - second generation terrestrial) and ATSC 3.0 (advanced television systems committee 3.0) are two main digital terrestrial broadcasting systems. DVB-T2 has a special symbol, named P1, for performing initial synchronization and signaling information and ATSC 3.0 has a similar one named bootstrap. In addition, these symbol can be used for detecting DVB-T2 or ATSC 3.0 signal.
This thesis analyzes synchronization techniques and detection using these special symbols. First, this thesis deals with features, roles, and generation processes of these symbols and proposes a simple detection and synchronization technique using guard interval correlation method.
This thesis also deals with the multi-antenna problems. In multi-antenna systems, data is transmitted across different channels. Especially, in distributed-MIMO (multiple-output multiple-input) systems, multiple transmit antennas are spatially separated and therefore results in MTOs (multiple symbol timing offsets) and MCFOs (multiple carrier frequency offsets). To overcome these problems, this thesis proposes a technique using a null symbol. By inserting null symbols before preambles such as P1 symbol or bootstrap, the receiver can distinguish the signals between each transmit antennas and perform initial synchronization. This method can improve symbol timing synchronization performance by simply making a time difference at each transmit antenna.

목차 (Table of Contents)

• 제1장 서론 7
• 제2장 OFDM 통신 시스템 [1] 9
• 제2.1절 OFDM의 기본 원리 9
• 2.1.1 다중 반송파 전송 방식 9
• 2.1.2 OFDM의 변조 및 복조 12
• 2.1.3 OFDM의 보호 구간 15
• 제2.2절 OFDM 시스템에서 동기화의 필요성 16
• 2.2.1 심볼 타이밍 오프셋의 영향 16
• 2.2.2 반송파 주파수 오프셋의 영향 21
• 2.2.3 샘플링 클럭 오프셋의 영향 23
• 제３장 지상파 방송 시스템의 프레임 동기화 24
• 제3.1절 DVB-T2 시스템의 동기화 25
• 3.1.1 DVB-T2 시스템의 동기화 과정 [6] 26
• 3.1.2 P1의 역할 및 생성 과정 [5] 30
• 3.1.3 P1을 이용한 프레임 동기화 방법 37
• 제3.2절 ATSC 3.0 시스템의 동기화 44
• 3.1.1 부트스트랩의 역할 및 생성 과정 [7] 46
• 3.1.2 부트스트랩을 이용한 프레임 동기화 방법 52
• 제4장 다중 안테나 지상파 방송 시스템의 프레임 동기화 57
• 제4.1절 MIMO 시스템 57
• 4.1.1 MIMO 시스템의 채널과 신호 모델 58
• 4.1.2 MIMO 기술을 통한 성능 이득 60
• 4.1.3 MIMO 시스템에서의 동기화 문제 [22] 61
• 제4.2절 분산 다중 안테나 지상파 방송 시스템의 프레임 동기화 방법 63
• 제5장 결론 70
• 참고 문헌 71