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The accuracy of prior Signal to Noise Ratio (SNR) estimation directly affects the performance of single-channel speech enhancement de-noising algorithm. In the single-channel enhancement algorithms based on short-time amplitude spectrum estimation, the gain is usually described as function about priori and posteriori SNR. The decision-directed (DD) method is widely applied in prior SNR estimation...
In order to improve the power efficiency and extend the lifetime of the two-way amplify-and-forward (AF) relaying system, this paper proposes a distributed relay selection scheme based on relay power conservation. The closed-form solution of the the optimal power allocation based on total power minimization under the signal-to-noise ratio (SNR) constraints is derived, and the relay which requires...
Two different two-way amplify-and-forward (AF) wireless relay systems with transmit power constraints at the relay(s) are studied: 1) one- relay system with multiple N antennas between two sources, and 2) multiple N-relay system with one antenna per relay between two sources. The iterative and explicit relay amplifying matrices (or vectors) with perfect cancelation of self- interference under channel...
This paper addresses optimum nondiagonal and diagonal amplifying relay matrices for the amplify- and-forward (AF) wireless relay networks. Single- input multiple-output (SIMO) nondistributed and distributed relaying system strategies with the relay power constraint are applied, based on the signal-to-noise ratio (SNR) criterion. By adopting the optimum amplifying relay matrices derived, the SNRs at...
This paper presents optimum relay amplifying matrices (or vectors) using the minimum mean square error (MMSE), maximum signal-to-noise ratio (SNR), zero-forcing (ZF), and matched-filter (MF) criteria for an amplify-and-forward (AF) wireless distributed relay network with a one-source-one-destination pair and iV-relay under the global power constraint (GPC) at the relays in a channel uncertainty (CU)...
This paper proposes amplify-and-forward (AF) relay strategies for two-way wireless distributed relay networks consisting of two sources with a single antenna per source and multiple N relays with a single antenna per relay. The objective of this paper is to determine optimal relay amplifying matrices (or vectors) under global and local power constraints at the relays based on the minimum mean square...
This paper proposes a cooperative wireless relay network consisting of a one-source-one-destination node pair and N relay nodes in three wireless communication environments, i.e., jamming, node geometry, and channel uncertainty. The main objective of this paper is to analytically derive the optimal cooperative amplify-and-forward (AF) wireless relay matrix under three conditions with the relay power...
In this paper, we investigate the performance of cooperative decode-and-forward (DF) multiple-input multiple-output (MIMO) relaying system with orthogonal space-time block code (OSTBC) transmissions over correlated Nakagami-m fading channels. For maximal ratio combining (MRC) receiver at the destination, we provide the compact closed-form expressions for cumulative distribution function (CDF) and...
Spectrum sensing is the premise of cognitive radio, which determines the communication quality of the total system. For the cognitive nodes far away from the primary user, the probability of correct detecting drops clearly because of the great fading, no matter they spend more time sensing. Cooperation between relay nodes can enlarge the valid transmit distance and improve the quality of communication...
The time domain maximum likelihood (ML) Doppler spread estimation for OFDM systems provides an accurate estimation performance; however, it results in a much higher computation cost. We propose a low-complexity ML Doppler estimator based on a well-designed preamble sequence along with a suboptimal ML (SML) method to reduce the computational complexity of the optimal ML scheme. Because of the proposed...
Orthogonal frequency-division multiplexing (OFDM) technology with the DCT encoding, orthogonal coding can make the transmitted video data extended to sub-channel of the each group, and this can improve the capability of the well-narrowband jamming system. Experimental results show that, the coding method can not only make good use of the transmission of the video data, but it also has very clear-Narrowband...
In order to detect a weak signal under the condition of intensive noise, the signal and additive white noise were used as input of a bistable stochastic resonance (SR) system. The noise intensity and the system parameters were adjusted adaptively with particle swarm optimization (PSO) algorithm by examining the SR effect on output signal-to-noise ratio (SNR). An improved numerical solution for a bistable...
In order to detect a weak periodic signal under the condition of intensive noise, the weak signal including strong background noise and adscititious multiplicative noise were used as input of a monostable stochastic resonance (SR) system. The adscititious noise intensity and the system parameter were adjusted adaptively with genetic algorithm by examining the SR effect on output signal-to-noise ratio...
To investigate the blind symbol rate estimation of any linear base-band digital modulation scheme with square root raised cosine filter, an algorithm based on cyclic correlation and Haar wavelet transform estimator is proposed. First we use FFT to estimate the bandwidth roughly. Then we set the sampling frequency and range scale of wavelet transform according to bandwidth. Using the signals filtered...
Generally, the code excited linear predictive (CELP) coding is known as one of the best algorithms for bit rate between 4 kbps and 16 kbps. Recently, the algebraic CELP (ACELP) algorithm has been widely adopted in standard speech coders such as G.729 and Adaptive multi rate (AMR) and AMR Wide Band (AMR-WB).In order to improve the speech quality based on CELP algorithm, harmonic Pitch pre-emphasis...
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