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In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are i...
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In wireless networks without nodes equipped with multiple antennas, cooperative Multiple Input Multiple Output (MIMO) transmissions may be used to harness diversity gains. In general, diversity gains are larger if more nodes are involved in the transmission. However, a transmission policy that maximizes the diversity gain or throughput need not maximize the stability region, since queues at the nodes may grow while waiting for a sufficient number of nodes to become available. To address this issue, this paper develops a mechanism for maximizing the throughput while reducing the energy consumption and maintaining queue stability. We develop a sufficient condition that ensures the throughput optimality of a stable transmission policy and then use it to design a distributed, dynamic threshold based Medium Access Control (MAC) protocol for cooperative MIMO transmissions. The MAC protocol requires only limited local information for its operation. Simulation results are provided to evaluate the performance of the proposed protocol and compare it against regular point-to-point and existing cooperative MIMO MAC protocols. The results show that the proposed scheme can provide considerable gains in the throughput and energy savings compared to cooperative MIMO based on fixed number of cooperating nodes.
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Understanding and optimizing the energy consumption of wireless devices is critical to maximize the network lifetime and to provide guidelines for the design of new protocols and interfaces. In this work, we first provide an accur...
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Understanding and optimizing the energy consumption of wireless devices is critical to maximize the network lifetime and to provide guidelines for the design of new protocols and interfaces. In this work, we first provide an accurate analysis of the energy performance of an IEEE 802.11 WLAN, and then we derive the configuration to optimize it. We further analyze the impact of the energy configuration of the stations on the throughput performance, and we discuss under which circumstances throughput and energy efficiency can be both jointly maximized and where they constitute different challenges. Our findings are that, although an energy-optimized configuration typically yields gains in terms of throughput as compared against the default configuration, it conies with a reduction in performance as compared against the maximum-bandwidth configuration, a reduction that depends on the energy parameters of the wireless interface.
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This paper presents a new cognitive radio network (CRN) framework with radio frequency (RF) energy harvesting, namely, RF-powered cognitive radio networks (RF-CRNs), wherein multiple secondary users (SUs) harvest energy from the R...
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This paper presents a new cognitive radio network (CRN) framework with radio frequency (RF) energy harvesting, namely, RF-powered cognitive radio networks (RF-CRNs), wherein multiple secondary users (SUs) harvest energy from the RF signals of primary users (PUs) all the time except when transmitting data in the allocated time, namely, the "harvesting-transmission-harvesting" mode. In this way, the energy harvested by each SU can be maximized until the next data transmission. Also, the total energy consumed by the SUs must be less than or equal to the total harvested energy (the energy causality constraint), while the transmit power of SUs must be restricted to protect the PUs from interference (collision constraint). Finally, under the satisfaction of quality of service of SUs (throughput constraint), our goal is to determine the optimal transmitting time and power allocation that maximize the achievable throughput in the RF-CRNs. We achieved the optimal result by transforming the optimization problem into a convex optimization problem and then applying Lagrange multiplier methods. Extensive performance evaluations showed the efficiency of the proposed algorithm.
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This paper presents a prediction model based on historical data to achieve optimal values of pipelining, concurrency and parallelism (PCP) in GridFTP data transfers in Cloud systems. Setting the correct values for these three para...
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This paper presents a prediction model based on historical data to achieve optimal values of pipelining, concurrency and parallelism (PCP) in GridFTP data transfers in Cloud systems. Setting the correct values for these three parameters is crucial in achieving high throughput in end-to-end data movement. However, predicting and setting the optimal values for these parameters is a challenging task, especially in shared and non-predictive network conditions. Several factors can affect the optimal values for these parameters such as the background network traffic, available bandwidth, Round-Trip Time (RTT), TCP buffer size, and file size. Existing models either fail to provide accurate predictions or come with very high prediction overheads. The author shows that new model based on historical data can achieve high accuracy with low overhead.
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In this paper we examine the aggregate throughput of the uplink of a circuit switched CDMA data transmission system using a combination of theoretical and simulation techniques. The theoretical analysis determines the transmitter ...
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In this paper we examine the aggregate throughput of the uplink of a circuit switched CDMA data transmission system using a combination of theoretical and simulation techniques. The theoretical analysis determines the transmitter power levels and the number of active terminals that jointly maximize the throughput via standard optimization methods. We find that the terminal with the lowest path gain should transmit at maximum power and that all other terminals should aim for a common received power level that is higher than the received power from the terminal with lowest path gain. In addition we show that the system should admit the number of terminals that results in a target signal-to-interference-plus-noise ratio that depends on the processing gain and the noise power. A numerical example suggests that power control designed to achieve equal received power for all terminals results in aggregate throughput nearly as high as that obtained with optimum power control. This finding greatly simplifies the engineering problem from a network manager's viewpoint.
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In this paper we present a mathematical technique for determining the optimum transmission rate and power in wireless system that have multi-carriers for OFDM modulation in downlink transmission. The throughput is defined as the n...
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In this paper we present a mathematical technique for determining the optimum transmission rate and power in wireless system that have multi-carriers for OFDM modulation in downlink transmission. The throughput is defined as the number of bits per second correctly received. Trade-offs between the throughput and the operation range are observed, and equations are derived for the optimal choice of the design variables. The transmitter has a fixed amount of maximum power level to send data. Our goal is the Development of a method of adaptation of power transmission which maximizes the throughput of the systems that have multi-carrier for OFDM modulation in a downlink transmission.
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The use of existing network devices as relays has a potential to improve the overall network performance. In this work, we consider a two-hop wireless relay setting, where the channels between the source and relay nodes to the des...
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The use of existing network devices as relays has a potential to improve the overall network performance. In this work, we consider a two-hop wireless relay setting, where the channels between the source and relay nodes to the destination node are time varying. The relay nodes are able to overhear the transmissions of the source node which may have a weak connection to the destination, and they help the source node by forwarding its messages to the destination on its behalf, whenever this is needed. We develop a distributed scheme for relay selection and channel access that is suitable for time-varying channels, and prove that this scheme is throughput optimal. We obtain the achievable rate region of our proposed scheme analytically for a relay network with a single source and a single relay node. Meanwhile, for a more general network with more than one relay nodes, we perform Monte Carlo simulations to obtain the achievable rate region. In both cases, we demonstrate that the achievable rate region attained with our distributed scheme is the same as the one attained with centralized optimal scheme.
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Multi-hop wireless mesh network (WMN) is considered to be an economical technique for last-mile broadband Internet access (Tang et al., 2006). Fueled by the rapid development of the Internet of Things, it is increasing important t...
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Multi-hop wireless mesh network (WMN) is considered to be an economical technique for last-mile broadband Internet access (Tang et al., 2006). Fueled by the rapid development of the Internet of Things, it is increasing important to provide robust and high-quality urban wireless mesh networks (WMNs) for public service. However, WMNs encounter frequent link failures during their lifetime in practical use as a consequence of large-scale wireless interference, block buildings, etc., which deeply influences the performance of the network. These failures should be recovered in time or prevented with foresight. Tremendous labor and management cost should also be avoided. In this paper, we focus on an interesting phenomenon called "loop effect" in urban WMNs which may cause frequent link failures. A scheme named anti-loop network reconfiguration system (ALRS) for link recovery in municipal WMNs with QoS requirement is proposed and analyzed. ALRS takes the historical information into consideration to achieve maximum throughput, interference avoidance and self-reconfiguration with no requirement on mesh node antennas. Our evaluation results show that ALRS outperforms all the existing techniques in improving network throughput and reducing the occurrence probability of continuous link failure.
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It is well-known that the power-of-dchoices routing algorithm maximizes throughput and is heavy-traffic optimal in load balancing systems with homogeneous servers. However, if the servers are heterogeneous, throughput optimality d...
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It is well-known that the power-of-dchoices routing algorithm maximizes throughput and is heavy-traffic optimal in load balancing systems with homogeneous servers. However, if the servers are heterogeneous, throughput optimality does not hold in general. We find necessary and sufficient conditions for throughput optimality of power-of-dchoices when the servers are heterogeneous, and we prove that almost the same conditions are sufficient to show heavy-traffic optimality. Additionally, we generalize the sufficient condition for throughput optimality to a larger class of routing policies. (C) 2021 Elsevier B.V. All rights reserved.
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The MAC layer of the 802.11 standard, based on the CSMA/CA mechanism, specifies a set of parameters to control the aggressiveness of stations when trying to access the channel. However, these parameters are statically set independ...
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The MAC layer of the 802.11 standard, based on the CSMA/CA mechanism, specifies a set of parameters to control the aggressiveness of stations when trying to access the channel. However, these parameters are statically set independently of the conditions of the WLAN (e.g. the number of contending stations), leading to poor performance for most scenarios. To overcome this limitation previous work proposes to adapt the value of one of those parameters, namely the CW, based on an estimation of the conditions of the WLAN. However, these approaches suffer from two major drawbacks: i) they require extending the capabilities of standard devices or ii) are based on heuristics. In this paper we propose a control theoretic approach to adapt the CW to the conditions of the WLAN, based on an analytical model of its operation, that is fully compliant with the 802.11e standard. We use a Proportional Integrator controller in order to drive the WLAN to its optimal point of operation and perform a theoretic analysis to determine its configuration. We show by means of an exhaustive performance evaluation that our algorithm maximizes the total throughput of the WLAN and substantially outperforms previous standard-compliant proposals.
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