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Along with the increase of signal's bandwidth, large number of tapped delay lines (TDL) will be needed in the TDL-based beamformers to retain the desired signal to interference pulse noise ratio (SINR), which slows down the convergence and increases computational load. To solve the problem, a new broadband beamformer based on the generalized sidelobe canceller (GSC) beamformer is designed. Only one...
Under bad condition, GPS (Globe Positioning System) signals are too weak to be received, so High-sensitivity GPS positioning under any conditions is the problem that should be addressed at present. For the weak signals tracking, the nonlinear Kalman filter algorithm instead of the traditional methods used by standard PLL (Phase Locked Loop) and DLL (Delay Locked Loop). Simulation results confirmed...
Power control strategy that guarantees users' quality-of-service (QoS) in a power-efficient manner is a critical yet challenging issue in distributed wireless networks. In this paper, we investigate the problem by considering the energy consumption and QoS provisioning simultaneously, where the QoS requirement is specified by the target signal-to- interference-plus-noise ratio (SINR). The problem...
Dynamic Spectrum Access provides novel solutions to improve spectral efficiency. Wireless Service Providers (WSPs) are allowed to transmit data over their exclusive licensed bands and multiple available unlicensed bands. The critical challenge is how to allocate power rationally to prevent severe interference between coexistent users. We formulate the problem as a Users Coexistence Game (UCG) and...
This paper presents a structured optimization framework for reducing the computational complexity of LDPC decoders. Subject to specified performance constraints and adaptive to environment conditions, the proposed framework leverages the adjustable performance-complexity tradeoffs of the decoder to deliver satisfying performance with minimum computational complexity. More specifically, two constraint...
Gradient adaptive step size adaptive filters have been widely used to adapt different biomedical application environments and obtain useful life signals from serious ambient noise and interferences. In order to further improve the signal-to-noise ratio (SNR) of the life signals, this paper presents a class of signed-gradient adaptive step size least mean square (LMS) adaptive filters. The proposed...
In this paper, we derive a novel probability density function (PDF)-based expression for various performance criteria with L-branch maximal-ratio combining over independent and not necessarily identical Weibull fading channels. Approximating the output SNR by a simple H-distribution, useful closed formulas for cumulative distribution function, moment generating function, outage probability, amount...
The convergence behavior of capacity of ergodic channels is of great importance for the performance analysis of communication systems. This paper presents a fundamental study on the convergence rate of capacity of ergodic channels on the basis of large deviation theory. It can be revealed that both the probability that the information capacity differs from the ergodic capacity by more than δ(δ >...
In this paper, we propose an equalization algorithm which greatly reduces the convergence problems and the steady-state error rate of the conventional constant modulus algorithm (CMA). The algorithm introduces a buffer and multiple step-size decision layers to the existing variable step size modified constant modulus algorithm (VSS-MCMA). The buffer is employed to combat the convergence issue while...
Speech enhancement has been proposed to reduce noise in noisy speech. However, it is difficult to reduce the transient noise with a narrow band component which is associated with a natural oscillation of the object. In order to solve the problem, we have proposed the speech enhancement based on a linear predictor with 4th order cumulant adaptive algorithm. However, the divergence of the proposed adaptive...
The stability and performance of the normalized subband adaptive filter (NSAF) algorithm is influenced by the regularization parameter. However, in various noise environments, the regularization parameter is difficult to be determined. The basic idea of this paper is to eliminate the effects of the noise in filter estimation. Simulation results show the proposed method has valid results in various...
In this paper we examine convergence properties of massive MIMO systems with the aim of determining the number of antennas required for massive MIMO gains. We consider three characteristics of a channel matrix and study their asymptotic behaviour. Furthermore, we derive ZF SNR and MF SINR for a scenario of unequal receive powers. In our results we include the effects of spatial correlation. We show...
In this work, we develop a multi-objective optimization framework for reducing network wide energy consumption through base station (BS) sleep mode (SLM) in an OFDMA based cellular systems. While putting BSs in SLM, we take into account the effects such as coverage and overlap. After putting BSs in SLM, in order to ensure sufficient coverage, overlap (for hand-overs), and to achieve maximum network...
In this paper, we propose a novel distributed optimization method for dynamic user association in a downlink Heterogeneous cellular network (Hetnet). We aim at maximizing the utilization of the base stations (BSs) in such a network by jointly considering the effect of the channel gains and load balancing of different BSs. Specifically, we first formulate the user association as a combinatorial optimization...
Accurate channel estimation is essential for broadband wireless communications. Adaptive sparse channel estimation schemes based on normalized least mean square (NLMS) have been proposed to exploit channel sparsity for improved performance. However, their performance bound as derived in this paper indicates that the invariable step size (ISS) usually used for iteration in these schemes would lead...
For a connected network, consensus based algorithms guarantee that local estimates are iteratively shared and refined among neighbors to reach the same weighted average on all nodes. Parameter estimation for linear models are common problems where average consensus are routinely adopted to mimic a centralized approach without the need of any fusion center. Convergence speed, accuracy and the amount...
Device-to-device (D2D) communications as an underlay to cellular networks can not only increase the system capacity and energy efficiency, but it can also enable national security and public safety (NSPS) services. A key requirement is to provide access to cellular services when the network is available and maintain local communication in the (partial) absence of the infrastructure. In this paper...
We study a system where a base station (BS) with an antenna array serves multiple users. Each user has a single antenna. Due to practical limitations, each antenna of the BS has an individual power constraint. Assume that only long-term channel state information (CSI) is available. The objective is to minimize the downlink transmission power under the users' signal-to-interference-plus-noise ratio...
Recent technological advances in electronics, sensors, and communications devices have facilitated the proliferation of Unmanned Aircraft System (UAS)-aided applications. However, the UAS-aided communications networks are yet to receive sufficient research endeavor. In this paper, we address one of the most important research challenges pertaining to UAS-aided networks comprising adaptive modulation-capable...
Time of fight (TOF) PET reconstruction provides statistically improved images and converges fast. However, the convergence rates of large and small regions are often different due to the measured counts for those regions are different. In particular, signal to noise ratio (SNR) for a small region is lower than that of a large region. This results in problems that can degrade the image quality during...
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