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Load balancing in data centers have been a common practice in the last couple of decades. This has been done statically in traditional networks with little or no feedback information from the underlying network state. With the current large cloud data centers and continuous changing traffic patterns, the drive for more interactive and dynamic solution to reduce the latency and improve the network...
In Software Defined Networks (SDN), each flow table entry is dedicated to an individual flow and has an idle timeout value associated with it. Due to limited flow table and controller processing resources, SDN suffers from scalability problem especially when dealing with a large number of flows. As Instant Messaging (IM) applications usually generate too many different flows and idle timeout has effect...
Network management system (NMS) is important to ensure security and efficiency of network. Traditional NMS usually adopts SNMP as management protocol and has achieved great success. However, with emerging of various services, traditional network exposes shortcomings. Software-Defined Network (SDN) is a new paradigm which separates the control plane from the forwarding plane as opposed to the distributed...
The SDN architecture decouples the control plane and data plane, and multiple controllers are adopted to solve the scalability and reliability problem in SDN. However, most of the researches are focused on the control architecture and ignore the controller placement problem. Moreover, the mapping between the switches and controllers are static in current proposals, which will lead to the load unbalance...
This paper proposes an architecture of layered control plane of OpenFlow networks managed by multiple controllers. Considering the logical network partitioning to decide administrative domains of controllers, this paper focuses on the relationship between the network partitioning and the amount of global network information shared among controllers. Then, this paper handles the issue as a mathematical...
SDN is a novel network architecture that separates the control plane from the data plane. It usually utilizes a centralized controller to manage all the switches in the network. With the expanding of network scale, both the complexity of computing routes and the amount of messages exchanged between controller and switches are increasing sharply. The limited performance of a single controller will...
New strategies based on cognitive radio are being discussed to make a more efficient use of the HF band. Multiple users transmit in this band with a worldwide coverage but having multiple collisions with other HF stations. The use of the Upper Confidence Bound (UCB) algorithm is proposed in this work to provide them with a dynamic spectrum access mitigating mutual interference. Based on reinforcement...
Future mobile communication networks will require enhanced network efficiency and reduced system overhead due to their user density and high data rate demanding applications of the mobile devices. Research on Blind Interference Alignment (BIA) and Topological Interference Management (TIM) has shown that optimal Degrees of Freedom (DoF) can be achieved, in the absence of Channel State Information (CSI)...
Interference due to multi-channel CR hidden terminals and edge PU receivers at link level has direct impact on performance of CR-MAC protocol. State-of-the-art research in CR-MAC propose sequential, cluster-CCC coverage for In-band and global CCC coverage for out-of-band spectrum to avoid primary (PU) and secondary (CR) hidden terminals. But, imperfect node synchronization due to per hop and group...
This paper investigates a joint spectrum scheduling and power allocation problem in Cognitive Radio (CR) network composed of several secondary (SU) and primary users (PU). The objective is to minimize the overall SU system power consumption (over several orthogonal frequency bands) under minimum Quality of Service (QoS) constraints, maximum peak and average interference to the PUs constraints. The...
This paper proposes a new analytical model for the performance of a p persistent slotted Aloha medium access protocol in a Cognitive Radio Network (CRN) composed by a single Primary user (PU) and several Secondary users (SUs) with Poisson traffic. SUs run a synchronized sensing-access operation cycle, and when they have a packet to transmit and the channel is sensed free, they access to the data slots...
Cognitive radio is regarded as the most promising technology for driving the future development of next-generation wireless networks, increasing spectrum efficiency by dynamic spectrum access. Allowing white spaces to be used in a deregulated manner exposes the radio spectrum to anomalous usage, which in turn may intentionally or unintentionally cause interference to primary users (PUs) as well as...
This work proposes the use of a unitary modulation scheme to enhance physical layer secrecy in multi-antenna wireless systems. The proposed scheme takes advantage of having only channel state information at the transmitter (CSIT) but not at the receiver and the eavesdropper. With CSIT, the transmitter can first take the LQ or singular value decomposition of the channel matrix and then replace its...
This paper investigates the joint robust beamforming and artificial noise design in two-user interference networks, where one of the two pairs is wiretapped by an external eavesdropper, and only imperfect eavesdropper's channel state information (ECSI) is available for the two pairs. Under individual transmission power constraint, our goal is to maximize the worst-case achievable secrecy rate of the...
This paper considers the problem of key generation with a helper, which might be subjected to Byzantine attacks. If the helper is not under attack, it will follow the key generation protocol. However, if the helper is under attack, it will modify the messages to mislead the key generation parties. We propose a scheme that can benefit from the helper, if the helper is not under attack, and can detect...
In this work we study the reliability and secrecy performance achievable by practical low-density parity-check (LDPC) codes over the Gaussian wiretap channel. While several works have already addressed this problem in asymptotic conditions, i.e., under the hypothesis of codewords of infinite length, only a few approaches exist for the finite length regime. We propose an approach to measure the performance...
This work examines the properties of code sequences for the degraded scalar Gaussian broadcast channel with confidential messages (BCC) in terms of the behavior of the mutual information and minimum mean-square error (MMSE) functions for all signal-to-noise ratios (SNRs). More specifically, the work focuses on both completely secure code sequences, meaning that the transmitted message to the stronger...
We address the physical layer security question of whether a multiple antenna receiver can enhance the secrecy rate of the multiple-input multiple-output wiretap channel by transmitting artificial noise from some of its antennas to jam a multiple antenna eavesdropper. To answer this question we use a QoS-MMSE approach to formulate a global constrained optimisation problem that is efficiently solved...
In this paper, we study the multiple-input multiple-output (MIMO) wiretap channel performing simultaneous wireless information and power transfer (SWIPT), where there are a multiple-antenna base station (BS), a multiple-antenna information decoding (ID) user, and a multiple-antenna energy harvesting (EH) user. The messages intended to the ID user need to be kept confidential to the EH user. The channels...
Increasing the spectral efficiency was always the motivation behind the evolution of wireless communication systems. Also, due to the widespread usage of wireless systems, securing the transmitted data rises as a main concern nowadays. Hereby, we introduce a scheme that increases the capacity of wireless systems by transmitting multiple independent data streams, while using the space domain as a source...
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