962 research outputs found
An Efficient Data-aided Synchronization in L-DACS1 for Aeronautical Communications
L-band Digital Aeronautical Communication System type-1 (L-DACS1) is an
emerging standard that aims at enhancing air traffic management (ATM) by
transitioning the traditional analog aeronautical communication systems to the
superior and highly efficient digital domain. L-DACS1 employs modern and
efficient orthogonal frequency division multiplexing (OFDM) modulation
technique to achieve more efficient and higher data rate in comparison to the
existing aeronautical communication systems. However, the performance of OFDM
systems is very sensitive to synchronization errors. L-DACS1 transmission is in
the L-band aeronautical channels that suffer from large interference and large
Doppler shifts, which makes the synchronization for L-DACS more challenging.
This paper proposes a novel computationally efficient synchronization method
for L-DACS1 systems that offers robust performance. Through simulation, the
proposed method is shown to provide accurate symbol timing offset (STO)
estimation as well as fractional carrier frequency offset (CFO) estimation in a
range of aeronautical channels. In particular, it can yield excellent
synchronization performance in the face of a large carrier frequency offset.Comment: In the proceeding of International Conference on Data Mining,
Communications and Information Technology (DMCIT
Blind block synchronization algorithms in cyclic prefix systems
In orthogonal frequency division multiplexing
(OFDM) systems, symbol synchronization is a critical step for
successful data transmission. While this task is done in most
current systems by using training symbols, a few studies have
been dedicated to solving the problem blindly, that is, where
training symbols are not available. Blind symbol synchronization
problem is especially important in many blind channel estimation
algorithms in the literature which assume that OFDM symbol
synchronization is perfect. In this paper, a broader version of the
blind symbol synchronization problem is studied, namely, blind
block synchronization in cyclic-prefix (CP) systems. The proposed
algorithm for this broader problem covers the blind symbol
synchronization problem in OFDM systems. Unlike previously
reported algorithms which are based on obtaining sufficient
statistics of received samples, the proposed algorithm is capable
of identifying the correct block boundaries using much less
received data in absence of noise. Simulation results of the
proposed algorithm not only verify the declared property but also
demonstrate improvement in accuracy of symbol synchronization
over previously reported algorithms in presence of noise
Blind symbol synchronization based on cyclic prefix for OFDM systems
In this paper, a blind symbol synchronization algorithm is presented for orthogonal frequency-division multiplexing (OFDM) systems, and a new timing function based on the redundancy of the cyclic prefix (CP) is introduced. It proves that the maximum of this function necessarily points to the correct timing offset, irrespective of channel conditions when the signal-to-noise ratio is high. Using the timing function, the timing offset is estimated through a searching algorithm. Channel power profile and channel length information are unnecessary. Simulation results show that the proposed algorithm is robust and outperforms the existing CP-based algorithms, particularly in frequency-selective fading channels. © 2008 IEEE.published_or_final_versio
New Blind Block Synchronization for Transceivers Using Redundant Precoders
This paper studies the blind block synchronization problem in block transmission systems using linear redundant precoders (LRP). Two commonly used LRP systems, namely, zero padding (ZP) and cyclic prefix (CP) systems, are considered in this paper. In particular, the block synchronization problem in CP systems is a broader version of timing synchronization problem in the popular orthogonal frequency division multiplexing (OFDM) systems. The proposed algorithms exploit the rank deficiency property of the matrix composed of received blocks when the block synchronization is perfect and use a parameter called repetition index which can be chosen as any positive integer. Theoretical results suggest advantages in blind block synchronization performances when using a large repetition index. Furthermore, unlike previously reported algorithms, which require a large amount of received data, the proposed methods, with properly chosen repetition indices, guarantee correct block synchronization in absence of noise using only two received blocks in ZP systems and three in CP systems. Computer simulations are conducted to evaluate the performances of the proposed algorithms and compare them with previously reported algorithms. Simulation results not only verify the capability of the proposed algorithms to work with limited received data but also show significant improvements in the block synchronization error rate performance of the proposed algorithms over previously reported algorithms
MIMO signal processing in offset-QAM based filter bank multicarrier systems
Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.Peer ReviewedPostprint (author's final draft
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
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