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Wi-Fi devices are popular because of low cost and easy deployment, which lead to high density of WLANs in urban areas. Due to high density, WLANs suffer performance degradation unless networks interfering with each other can allocate wireless resource reasonably. Hence, our goal is to minimize the interference caused by high density of WLANs and in turn it helps improve throughput. In this paper,...
We present optimization algorithms for source and relay power allocations for a multicarrier three-node relay system with direct link. We show that there is a benefit to the system capacity by allowing the source power to be split in both phases in a two-phase relay scheme. While the source power allocation problem is convex, the relay power allocation problem is not. But in both cases, we present...
In an Orthogonal Frequency Division Multiple Access (OFDMA) system, cumulative distribution function (CDF) based scheduling can be applied to prioritize users. In such a wideband multiuser system, it is essential to reduce the typically very large feedback requirement. Herein, we consider a system in which several adjacent highly correlated subcarriers are grouped into a resource block. Then, the...
In this paper, we apply results from multi-user information theory to study the limits of information capacity and collision resolution for SAW RFID tags. In particular, we derive bounds on the achievable data rate per tag as a function of fundamental parameters such as tag time-bandwidth product, tag signal-to-noise ratio (SNR), and number of tags in the environment. We also discuss the implications...
Due to the frequency reuse, LTE-A is interference limited system, the small rates can only been obtained by cell-edge users. Cooperative communication through using relays is an efficient approach to resolve this problem. In this paper, We proposed a dynamic relay placement scheme to maximize either the total cell capacity or the total cell-edge user capacity in a LTE-A network under co-channel interference...
For asynchronous transmission, the scheme with fountain codes is more attractive. In multi-relay system, each relay encodes with fountain codes and transmits encoded packets independently. A practical family of Raptor codes is proposed, which combines flexible pre-code with short-length LT codes. Simulation results show that the transmission scheme with our proposed fountain codes can achieve better...
A novel radar target recognition method using high-resolution range profile (HRRP), called as optimal transformation (OT), is proposed in this paper. The aim of this approach is to increase the distance between the different classes, and reduce the distance between the same class. Firstly, OT enhances the between-class difference by increasing the distance between clustering centers. Then, OT reduces...
In this paper we develop a framework for distributed power control in a wireless network where femto and macro cells co-exist and interfere with each other. In order to ensure a minimum QoS, femto and macro access points have the challenging and realistic objective of minimizing their users' SINR (Signal to Interference and Noise Ratio) outage. Furthermore, due to mobility and interference, an accurate...
Topology structure for UAWSN has to be of general characters of WSN not only, but also consider the limited communication range and cell energy, the effect of single damaged cell to the whole network and so on. This paper analyzes the energy efficiency for UAWSN theoretically and then presents the simulation results for square and triangle topology structures with different network scale. All these...
Small cell networks promise to boost the capacity and provide good QoS (Quality of Service) to cell edge users. However they pose serious challenges, especially in the case of high speed unidirectional (e.g., users traveling on highways or in metros) users, in the form of frequent handovers. The extent of the handover losses depend greatly upon the speed of the user and it is shown previously that...
Cognitive Radio is a promising concept that offers solution to spectral crowding problem by introducing opportunistic usage of the unoccupied licensed frequency bands. Improving the network capacity and reliability of the communication has been recently studied and this through the introduction of cooperative technology in the CR networks. Furthermore, OFDM system is considered to be a good candidate...
In this paper, we propose an effective user association rule for resolving the unbalanced loading problem in multi-cell cellular networks. We first derive an improved user throughput estimation formula for the proportional fair (PF) scheduling algorithm under the Rayleigh fading environment. Our simple and accurate throughput estimation can be regarded as an extended version of the conventional scheme...
In this paper, we propose distribution based binary discriminative features and a novel feature enhancement process for automatic modulation classification. The new features exploit the signal distribution mismatch between two modulations. Signal distributions on I-Q segments, amplitude and phase, are considered to produce a comprehensive feature set for improved robustness. Logistic regression is...
Cooperative Communication is a wireless communication scheme, which gains signal transmission diversity through user cooperation. In cooperative communications, the existing relaying strategies include amplify-and-forward (AF) and decode-and-forward (DF). Moreover, cooperative communications through opportunistic relay selection and nonorthogonal signal transmission can further improve the system...
This article first give the concept of the scale space, and construct the relationship between the heat conduction equation and the Gaussian scale space, which lead to the partial differential equations. Then the article introduces linear diffusion equation, nonlinear isotropic diffusion and the nonlinear an isotropic diffusion. After analyze the connection between nonlinear filters and an isotropic...
Currently Underwater Acoustic Sensor Network (UASN) is playing a vital role in exploration and monitoring operations in underwater environments that are difficult to reach. Underwater communication mainly relies on acoustic waves, which limits the performance of UASN due to its limited bandwidth, large propagation delays, and high path loss. In this paper, we present a comprehensive mathematical model...
In this paper, a procedure for the design of time-interleaved variable center-frequency sigma-delta modulator is developed and presented. The proposed sigma-delta modulators will be suitable for high performance data conversion in Global Navigation Satellite Systems applications. By the application of this method, different orders of a generalized multi-path topology that can operate at any arbitrary...
We investigate the sensitivity of Compute-and-Forward (C&F) to channel estimation errors. More specifically, a general formula for the computation rate region of a C&F relay, suffering from imperfect channel estimation, is derived, which is then tightly approximated for Gaussian distributed channel estimation errors. Furthermore, a closed-form expression for the distribution of the C&F...
In this paper, we consider the problem of distributed power control for multiple access channels when energy-efficiency has to be optimized. In contrast with related works, the presence of a queue at each transmitter is accounted for and globally efficient solutions are sought. To this end, a repeated game model is exploited and shown to lead to solutions which are distributed in the sense of the...
Brightness contrast detection of indefinite form objects on a clutter background in grayscale images is considered. Variant procedures of adaptive thresholding are offered. Performance analysis based on statistical modeling is fulfilled and comparison results are presented.
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