Analysis and Performance Comparison of DVB-T and DTMB Systems for Terrestrial Digital TV

Orthogonal frequency-division multiplexing (OFDM) is the most popular transmission technology in digital terrestrial broadcasting (DTTB), adopted by many DTTB standards. In this paper, the bit error rate (BER) performance of two DTTB systems, namely cyclic prefix OFDM (CP-OFDM) based DVB-T and time domain synchronous OFDM (TDS-OFDM) based DTMB, is evaluated in different channel conditions. Spectrum utilization and power efficiency are also discussed to demonstrate the transmission overhead of both systems. Simulation results show that the performances of the two systems are much close. Given the same ratio of guard interval (GI), the DVB-T outperforms DTMB in terms of signal to noise ratio (SNR) in Gaussian and Ricean channels, while DTMB behaves better performance in Rayleigh channel in higher code rates and higher orders of constellation thanks to its efficient channel coding and interleaving scheme

An Adaptive Feedback Interference Cancellation Algorithm for Digital On-channel Repeaters in DTTB Networks

Abstract-In this paper, a variable step-size block normalized least mean square (VSSBNLMS) algorithm is derived to cancel the feedback interference in a Digital On-Channel Repeater (DOCR) for the Digital Terrestrial Television Broadcasting (DTTB) networks. By dividing the input signal into blocks with the same length and updating the tap weights once per every block, the computational complexity can be decreased effectively. Furthermore, variable step-size is applied to increase the convergence speed. Compared with the NLMS and BLMS algorithm, VSSBNLMS algorithm achieves rapid convergence and the computational complexity is reduced compared to the NLMS algorithm. Results from numerical examples illustrate these advantages. Keywords-variable step-size block normalized LMS (VSSBNLMS) algorithm, Digital Terrestrial Television Broadcasting (DTTB), digital on-channel repeater (DOCR), feedback interference canceller (FIC

A Novel Data-Aided Channel Estimation with Reduced Complexity for TDS-OFDM Systems

In contrast to the classical cyclic prefix (CP)-OFDM, the time domain synchronous (TDS)-OFDM employs a known pseudo noise (PN) sequence as guard interval (GI). Conventional channel estimation methods for TDS-OFDM are based on the exploitation of the PN sequence and consequently suffer from intersymbol interference (ISI). This paper proposes a novel dataaided channel estimation method which combines the channel estimates obtained from the PN sequence and, most importantly, additional channel estimates extracted from OFDM data symbols. Data-aided channel estimation is carried out using the rebuilt OFDM data symbols as virtual training sequences. In contrast to the classical turbo channel estimation, interleaving and decoding functions are not included in the feedback loop when rebuilding OFDM data symbols thereby reducing the complexity. Several improved techniques are proposed to refine the data-aided channel estimates, namely one-dimensional (1-D)/two-dimensional (2-D) moving average and Wiener filtering. Finally, the MMSE criteria is used to obtain the best combination results and an iterative process is proposed to progressively refine the estimation. Both MSE and BER simulations using specifications of the DTMB system are carried out to prove the effectiveness of the proposed algorithm even in very harsh channel conditions such as in the single frequency network (SFN) case