9:30, SPCOM-P7.1
EQUALIZATION AND BLOCK-SYNCHRONIZATION FOR OFDM SIGNALS
S. PRAKRIYA
In this paper, blind algorithms based on a deterministic framework are proposed for equalization of finite-memory Linear Time Invariant (LTI) channels carrying OFDM signals. Unlike algorithms proposed to date, the channel memory is not restricted to be smaller than the cyclic prefix. It is shown that equalizers termed "Synchronizer-equalizers" can be estimated that always result in block-synchronized output, thus making separate block synchronization unnecessary. These algorithms are based on a deterministic framework, and require short data records. Performance of the proposed algorithms is analyzed by computer simulations.

9:30, SPCOM-P7.2
PERFORMANCE ANALYSIS OF BLIND CARRIER FREQUENCY OFFSET AND SYMBOL TIMING DELAY ESTIMATORS IN FLAT-FADING CHANNELS
E. SERPEDIN, P. LOUBATON, P. CIBLAT, Y. WANG
By exploiting the received signal's second-order cyclostationary statistics, blind algorithms have been recently proposed for joint estimation of the frequency offset and the symbol timing delay of a linearly modulated waveform transmitted through a flat-fading channel. The goal of this paper is to establish and analyze the asymptotic (large sample) performance of the Gini-Giannakis and Ghogho-Swami-Durrani estimators as a function of the pulse shape bandwidth and the oversampling factor. It is shown that the performance of these estimators improves as the pulse shape bandwidth increases, and the best performance is obtained by selecting small values for the oversampling factor.

9:30, SPCOM-P7.3
DIGITAL TIMING SYNCHRONIZATION WITH JITTER REDUCTION TECHNIQUE FOR CAP-BASED VDSL SYSTEM
Y. SONG, K. LEE, B. KIM
This paper describes a digital timing synchronization method for the CAP-based VDSL system. An adaptive loop filter with digitally controlled loop gain is proposed for jitter performance improvement. The proposed loop filter allows both fast locking and low steady state jitter. A digital spectral line method is used for robust timing extraction. Simulation results show that RMS timing jitter is less than 0.4% of the symbol period even for the worst case channel and synchronization is established within 400 symbol periods. The VDSL system is implemented in a 0.6um CMOS technology, and tested. The measured peak-to-peak timing jitter is about 0.1% of the symbol period, which makes the VDSL system receive data up to 52Mbps over the telephone wire.

9:30, SPCOM-P7.4
NEW FRAME SYNCHRONIZATION TECHNIQUE FOR OFDM/OFDMA AND MC-CDMA SYSTEMS
C. LEE, M. DARNELL
In the context of orthogonal frequency division multiplexing (OFDM), most papers define OFDM symbol synchronization as frame synchronization. In this paper, a frame is defined as a block of several OFDM symbols in the time dimension. The main contribution of this work is to propose a novel, low-complexity, frame synchronization method for multi-carrier systems that does not require any transmission overhead; this increases the channel capacity, power and bandwidth efficiency. Also, it enables a flexible multiple-access scheme to be implemented in OFDM, whereby each user can have different frame size. The proposed frame synchronization method is compared with a conventional method using a preamble. Power compensation and frame averaging techniques are proposed to improve the performance of the frame synchronizer. The performance of the proposed frame synchronizer is evaluated over a Rayleigh fading channel for orthogonal frequency division multiple-access (OFDMA) and multi-carrier code- division multiple-access (MC-CDMA) systems.

9:30, SPCOM-P7.5
ROBUST ITERATIVE SYNCHRONIZATION ALGORITHM USING CALABRO WOLF PERFECT ARRAYS
E. DEL RE, L. RONGA, M. BARTOLOZZI
Next generation wireless communication systems are characterized by high bit-rate services. UMTS systems, already subject to standardization process, require a strict synchronization also for the uplink (mobile-to-base) channel. The operation is not trivial due to the fact that during the acquisition process, non synchronous users can impact on the ongoing transmissions reducing the overall systems efficiency. The following proposal describes a different approach to the synchronization problem which is based on a dedicated channel, shared by more users with a OFDM-CDMA transmission technique. The paper focuses on the adaptative algorithm used by the base station to track the users into the synchronization dedicated channel. The results obtained by computer simulations explore the dependence of the performances from the many parameters involved.

9:30, SPCOM-P7.6
COARSE FREQUENCY ESTIMATION IN OFDM PACKET ORIENTED SYSTEMS
P. MARTI-PUIG, J. SALA-ALVAREZ
In this paper we derive a fast blind coarse frequency offset estimator for OFDM systems in frequency selective channels. The estimator takes advantage of the strong structure of the OFDM signal. In packet-oriented systems, using the method of Schmild and Cox for timing and fine frequency offset estimation, it is possible to obtain very accurate synchronization using only one known OFDM symbol transmitted at the beginning of the burst. In systems using a continuous stream of data this estimator can solve the ambiguity of multiples of the subcarrier spacing that produces a fine estimator based on cyclic extensions.

9:30, SPCOM-P7.7
CHANNEL-INDEPENDENT NON-DATA AIDED SYNCHRONIZATION OF GENERALIZED MULTIUSER OFDM
M. POMPILI, S. BARBAROSSA, G. GIANNAKIS
We develop and analyze timing and carrier frequency offset synchronization algorithms for generalized asynchronous and quasi-synchronous orthogonal frequency division multiple access systems using null subcarriers and subcarrier hopping. We derive an approximate analytic expression for the variance of the frequency offset estimators as a function of the number of active users and the SNR and show that the performance of our algorithms is asymptotically independent of the channel zero locations for quasi- synchronous systems. Finally, we validate our theoretical expressions with simulations.

9:30, SPCOM-P7.8
FOURTH ORDER NON-DATA-AIDED SYNCHRONIZATION
X. VILLARES, G. VAZQUEZ-GRAU, J. RIBA-SAGARRA