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The recently released IEEE 802.11ac standard has implemented enhancements including higher maximum transmission rate and larger maximum packet payload length. In wireless local area networks (WLANs) where the latest 802.11ac nodes and the legacy ones coexist, nevertheless, the effects of the enhancements on the data rate performance remain largely unknown. In this paper, we tackle this open problem...
A key challenge for enabling Machine-to-Machine (M2M) communications in Long Term Evolution (LTE) networks is the intolerably low access efficiency in the presence of massive access requests. To address this issue, a new analytical framework is proposed in this paper to optimize the random access performance of M2M communications in LTE networks. Both the maximum network throughput and the corresponding...
In the multi-cloud tenancy environments, Web Service offers an standard approach for discovering and using capabilities in an environment that transcends ownership domains. This brings into concern the ownership and security related to Web Service governance. Our approach for this issue involves an ESB-integrated middleware for security criteria regulation on Clouds. It uses an attribute-based security...
Multiple-Input Multiple-Output (MIMO) systems have been widely applied to underwater acoustic (UWA) communications with promising results. However, the tradeoff between diversity and multiplexing gains in MIMO systems over underwater acoustic channel is less discussed. In this paper, a quasi-orthogonal group space-time (QoGST) scheme by combining space-time coding (STC) and layered space-time (LST)...
In this work, collapse of subsea pipelines subjected to external pressure which are dented by foreign objects is investigated through numerical method. The effect of diameter-to-thickness ratio D/t and ovalization caused by denting Δom on the collapse pressure is discussed. Of particular concern is the effect of indenter's shape on the collapse pressure. The collapse behavior between pipelines dented...
In the literature, the network throughput of slotted Aloha with the capture model over fading channels has been found to be higher than e−1, the maximum network throughput of slotted Aloha with the collision model over ideal channel conditions. Such an improvement is often misinterpreted as the result of channel fading, which as we will demonstrate in this paper, indeed comes from the receiver. Specifically,...
Human body potential caused by walking on floors has been modeled by a RC equivalent circuit. Based on the measurement of the charging voltage by human body walking, the RC equivalent model has been deduced and the influence of the parameters on the human bod voltage has also been analyzed. The human body equivalent circuit corresponds with the RC network. As a consequence, an exponential function...
Due to the rapid growth of real-time applications in wireless local area networks (WLANs), quality-of-service (QoS) guarantee becomes one of the key issues for IEEE 802.11e enhanced distributed channel access (EDCA) networks. In contrast to most existing studies which only focus on providing delay guarantee to real-time flows, in this paper we study the open question of how to adaptively tune system...
Different from the classical point-to-point multiple-input- multiple-output (MIMO) system, the ergodic capacity of a distributed MIMO system depends on the large-scale fading coefficients between the user and the geographically separated base-station (BS) antennas. Due to the lack of a closed-form expression, how the average ergodic capacity scales with the number of distributed BS antennas remains...
There has been considerable theoretical and application of data envelopment analysis (DEA) directed to environmental efficiency measurement due to its capability of accounting for undesirable outputs. However, once statistical noise as well as environmental effects considered, these methods might fail to provide an appropriate estimates as the non-stochastic nature of deterministic DEA-based model...
Despite the common belief that substantial capacity gains can be achieved by employing a large number of antennas at the base-station (BS) side in cellular networks, the effect of BS antenna topology on the capacity scaling behavior is little understood. This paper presents a comparative study on the asymptotic capacity of a downlink single-user multiple-input-multiple-output (MIMO) system with multiple...
The wireless communication channel and electric interference for communication devices are simulated by the intelligent instruments. Compared with the problems of current signal analyzer versatility, complicated operation process, the error in the operation of instrument and the measuring efficiency, the wireless signal analysis system based on the idea of intelligent control with SCPI programmable...
This paper presents an asymptotic rate analysis for downlink multi-user systems with L base-station (BS) antennas either co-located or uniformly distributed within a circular cell. A representative non-orthogonal linear precoding scheme, maximum ratio transmission (MRT), is considered, based on which the effect of BS antenna layout on the intra-cell interference is characterized. The analysis reveals...
A key open question in IEEE 802.11e networks with enhanced distributed channel access (EDCA) is how to properly tune the backoff parameters to optimize the network throughput performance under a certain differentiation requirement. To tackle this problem, a new analytical model for IEEE 802.11e EDCA networks is proposed in this paper, based on which the maximum network throughput is derived as an...
In IEEE 802.11 DCF networks, a packet is discarded if the maximum number of retransmission attempts is reached. This paper studies how the retry limit affects the throughput performance of a saturated IEEE 802.11 DCF network. In particular, the network steady-state operating point is derived as an explicit function of the retry limit, based on which the saturation throughput can be further characterized...
In this paper, we propose a novel method that performs Cross Language Text Categorization (CLTC) from the perspective of Information Retrieval. We present an input document in target language in the form of a query in source language. Then we retrieve the training documents in source language and find K most relevant results. At last, we use the class labels of the K results to predict the class of...
In this paper, a unified analytical model is established to analyze the throughput performance of M-group heterogeneous IEEE 802.11 DCF networks with a distinct input rate, number of nodes and initial backoff window size in each group. Steady-state points under unsaturated, partially-saturated and fully-saturated scenarios are characterized, and the maximum throughput is derived. Explicit expressions...
Sentiment classification is an important data mining task. Previous researches tried various machine learning techniques while didn't make fully use of the difference among features. This paper proposes a novel method for improving sentiment classification by fully exploring the different contribution of features. The method consists of two parts. First, we highlight sentimental features by increasing...
Face detection has been playing an important role in more and more fields, which makes it necessary and urgent to have its architecture reconfigurable to satisfy different requirements on detection capabilities. The paper proposes a face detection architecture, which could be adjusted by the users according to the environment, the sensor resolution, the different requirements of detection accuracy...
We study the incompleteness of exponential system in Cα from a harmonic measure point of view, where Cα is the weighted Banach space consists of complex continuous functions ƒ defined on the real axis ℝ with vanishing at infinity, in the uniform norm.
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