Dariush Abbasi-Moghadam

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With the one-bit time reversal ultra wideband (OTR-UWB) transceiver, the data symbols are encoded using the reversed order of the channel phase. The major factor limiting SISO OTR capacity and performance is intersymbol interference (ISI). As the data rate goes up, the ISI becomes more severe and it degrades system performance and capacity. In this article,(More)
Vector quantization (VQ) is a lossy compression technique that mainly includes three stages: codebook generation, encoding and decoding. The efficiency of VQ extremely depends on the achieved codebook quality. The most commonly used method for VQ codebook generation, is the Linde-Buzo-Gray (LBG) algorithm. High sensitivity to initial codebook, is mentioned(More)
An ultra wideband (UWB) communications system that applies time reversal to transmit the desired signal is investigated. Exact expressions for the firstand second-order moments, cross-correlation, intersymbol interference metric, and correlation coefficient of time reversal (TR) UWB equivalent channel are derived in terms of the physical channel parameters(More)
In this paper, secure channel coding schemes based on turbo codes are suggested for time reversal ultra wideband (TR-UWB) systems. Turbo code has the capability of error correction near Shannon’s limit. Adding security to turbo code is an attractive idea since it could reduce the overall processing cost of providing secure coded data and enjoys the(More)
In this paper; dynamical resource allocation scheme is proposed to improve throughput and fairness in the modern broadband wireless systems such as IEEE 802.16 Worldwide Interoperability for Microwave Access. To assign the subcarriers to users, dynamic fractional frequency reuse is used. In dynamic fractional frequency reuse, each cell is partitioned into(More)
Non-coherent receivers, such as energy detectors (ED), are the simplest and the most practical alternatives to coherent receivers for low-rate and low-complexity applications in ultra-wideband (UWB) systems. However, these advantages are achieved at the expense of non-negligible performance degradation. One solution to improve the performance is to make use(More)