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— We present a new initial ranging method for OFDMA systems such as IEEE 802.16-2004. First, a new orthogonal ranging signal design is proposed by which an efficient, low-complexity multiuser ranging signal detection is developed. Based on the ranging signal detector results, power estimation for the detected ranging subscriber stations is performed. Then,(More)
—We address joint estimation of frequency offsets and channel responses in OFDMA uplink. A cyclically equal-spaced, equal-energy interleaved pilot preamble is proposed by which two iterative estimators are developed. In the first estimator, we develop a modified SAGE (space alternating generalized expectation-maximization) method by incorporating multiuser(More)
In this paper, we obtain a global exact controllability result for a class of multidi-mensional semilinear hyperbolic equations with a superlinear nonlinearity and variable coefficients. For this purpose, we establish an observability estimate for the linear hyperbolic equation with an unbounded potential, in which the crucial observability constant is(More)
— We address initial ranging process in OFDMA systems such as IEEE 802.16a. The proposed ranging method includes three main tasks – timing estimation, multiuser ranging code detection, and power estimation. All tasks are performed based on a bank of correlators corresponding to ranging codes. The timing estimation scheme is based on the peak of correlator(More)
—This paper presents a set of innovative algorithms and a system, named LogMaster, for mining correlations of events that have multiple attributions, i.e., node ID, application ID, event type, and event severity, in logs of large-scale cloud and HPC systems. Different from traditional transactional data, e.g., supermarket purchases, system logs have their(More)
— In data-pilot-multiplexed OFDM schemes, data-interference to pilot tones causes degradation in frequency offset and channel estimation. This paper derives the best data-pilot-multiplexed scheme in terms of minimizing data-interference on pilot tones. This design gives a correlated data insertion scheme (CD) (data on the left and right adjacent tones of(More)
— The existing synchronization and channel estimation methods utilizing the IEEE 802.16a OFDMA uplink preamble structure are associated with very high complexity. This paper proposes a TDMA-type preamble structure and the corresponding synchronization and channel estimation methods for OFDMA uplink. The proposed approach decouples multiuser synchronization(More)