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.