76 research outputs found
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
A novel uplink multiple access scheme based on TDS-FDMA
This contribution proposes a novel time-domain synchronous frequency division multiple access (TDS-FDMA) scheme to support multi-user uplink application. A unified frame structure for both single-carrier and multi-carrier transmissions and the corresponding low-complexity receiver design are derived. Compared with standard cyclic prefix based orthogonal frequency division multiple access systems, the proposed TDSFDMA scheme improves the spectral efficiency by about 5% to 10% as well as imposes a similarly low computational complexity, while obtaining a slightly better bit error rate performance over Rayleigh fading channels
CAPACITY ESTIMATION FOR WIRELESS SPREAD-SPECTRUM ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING (SS-OFDM)
OFDM is a modulation and multiple access technique that has been a centre of
attention in these recent years. Since its development for military application in the
1960s, technical implementations of OFDM have appeared in digital audio
broadcasting, asymmetric digital subscriber lines (ADSL), high speed definition
television terrestrial broadcasting, and other systems. Because of its capabilities,
OFDM becomes a potential candidate as a multiple access technique for beyond 3G
mobile technology. This project presents a studyon OFDM performance for wireless
mobile environment. Spread-spectrum is employed in combination withOFDM. This
project paper presents a simulation of spread-spectrum OFDM using MATLAB and
capacity estimation of the simulated environment in wireless channel. The results of
the simulation are then compared with the theoretical capacity values of available 3G
systems
Classical and Bayesian Linear Data Estimators for Unique Word OFDM
Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel
OFDM signaling concept, where the guard interval is built of a deterministic
sequence - the so-called unique word - instead of the conventional random
cyclic prefix. In contrast to previous attempts with deterministic sequences in
the guard interval the addressed UW-OFDM signaling approach introduces
correlations between the subcarrier symbols, which can be exploited by the
receiver in order to improve the bit error ratio performance. In this paper we
develop several linear data estimators specifically designed for UW-OFDM, some
based on classical and some based on Bayesian estimation theory. Furthermore,
we derive complexity optimized versions of these estimators, and we study their
individual complex multiplication count in detail. Finally, we evaluate the
estimators' performance for the additive white Gaussian noise channel as well
as for selected indoor multipath channel scenarios.Comment: Preprint, 13 page
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