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TCP communication has the feature that decreases the throughput over a virtual private WAN between global offices, which has larger delay and causes packet loss at higher frequency than LAN. This paper proposes a high-speed original TCP applied for a virtual private WAN: RADIC-TCP (RTT — And — Discard — Independent Congestion control TCP). RADIC-TCP comprises of following three features: the bandwidth...
Spectrum handover becomes one of the hot topics of Cognitive Radio recently. Spectrum handover happens when the primary users and secondary users collide on the same spectrum hole, and the secondary users need to switch to other spectrum holes to continue the communication. Therefore, the reliability of spectrum Q-learning handover, which is reflected by the quality of service of secondary users and...
As currently specified by 3GPP for UMTS, MBMS services are provided within a cell, either by P-t-P or by P-t-M transmission mode, but not both at the same time. Our previous work highlighted the inefficiencies that can occur with this approach and proposed the “Dual Transmission mode cell” (that allows both transmission modes to coexist within the same cell) to address them. This approach, compared...
In optical networks, physical topology design is critically important, and key underlying parameters to be considered are cost, power consumption, and resilience. Optimization of these parameters is a difficult problem to solve. In this paper, we present a new heuristic algorithm that successfully minimizes the cost and power consumption of an optical network without compromising its resilience. The...
Detailed passive analysis of TCP sender behaviour requires accurate identification of congestion events. Previous tools that attempt to provide such information do not incorporate the behaviour of recent operating systems and TCP features and are therefore of little use to researchers analysing contemporary TCP traffic. In this paper, we present a new tool for identifying and classifying TCP congestion...
Wireless sensor and actuator networks (WSANs) have been studied for about ten years now. However, a gap between research and real applications and implementations remains. The lack of an integrated solution, capable of providing the reliability levels of monitoring and actuation required by critical applications, have postponed the replacement and extension of the existing inflexible and expensive...
Motivated by the cellular model paradigm, this paper develops a distributed on-line algorithm for determining the values of the control parameters (in this case, the buffer sizes) that optimize some predefined performance metrics of interest (e.g. average queue length, average loss probability). Stochastic Fluid Model (SFM) framework is adopted to model the queuing systems. Using this framework, we...
A modular method was suggested before to recover a band limited signal from the sample and hold and linearly interpolated (or, in general, an nth-order-hold) version of the regular samples. In this paper a novel approach for compensating the distortion of any interpolation based on modular method has been proposed. In this method the performance of the modular method is optimized by adding only some...
Cognitive Radio (CR) systems are a promising solution to the spectrum scarcity problem. However, accurate modeling of spectrum utilization is essential to obtain a better quantitative understanding of important concepts of CR systems. Compact mathematical formulations that describe the realistic spectrum usage would improve the recent theoretical work to a large extent. The data generated from such...
Wireless cooperative communication through link adaptation with untrusted relay assignment is considered. Using sharp channel codes in different transmission modes, reliability for destination and security in the presence of untrusted relays are provided through rate and power allocation. Scenarios with single available relay and opportunistic relaying in the presence of multiple relays are investigated...
In this paper we study a wavelength division multiplexing multi-ring metropolitan area network architecture with a separate control wavelength and a finite number of access nodes. Each access node is equipped with a fixed tuned transmitter and a fixed tuned receiver for control information exchange. Also, each access node has a tunable transmitter to exploit all data wavelengths while it uses a set...
Use of multi-homing has became important in order to provide customers with better communication experience. This has been made possible with widespread use of mobile and wireless technology and its capacity to support many network interfaces simultaneously. Connection-oriented transport layer protocols ensure in-order delivery of data during transmission. However multipath transfers cause out-of-order...
Inter-domain QoS routing is a very challenging problem area. This problem combines the complexity of QoS routing, with the limitations of inter-domain routing, such as domain heterogeneity and information confidentiality. The pre-computation offers a very promising solution for addressing this problem. Although the pre-computation scheme has been investigated in several previous studies for a single...
In this paper, we address the problem of allocating users to radio resources (i.e. subcarriers) in the downlink of an OFDMA system. In particular, we consider a multi-format resource allocation problem (MF-RAP) in which the link adaptation adjusts the spectral efficiency for each user-subcarrier pair, i.e. for each radio link, in order to minimize the total transmission power while fulfilling a rate...
This paper focuses on the uplink transmission in a cellular system in which the channels in two neighboring cells are modeled as two mutually interfering multiple access channels (2-IMAC). The base stations (BSs) are equipped with multiple antennas while each user has only one antenna and K users are active in each cell. By increasing the number of users, it is shown in [1] that for single-antenna...
Orthogonal frequency division multiplexing (OFDM) is one of the widely used multiplexing techniques in wireless communications and especially cognitive radio networks. One of the key challenges of this technique is its high peak to average power ratio (PAPR) of the transmitted signal. This paper, introduces a new approach to PAPR reduction of OFDM signals using harmony search algorithm (HSA) based...
Wireless sensor network (WSN) motes are resource constrained devices. Especially, bandwidth and energy are scarce resources. Therefore, lots of effort is put into the optimization of low-power networking protocols. While network control overhead is an issue for many to most of such protocols, we present an approach that is virtually overhead-free. We introduce the implementation of an autonomous network...
In this paper, we propose a distributed rate and power allocation algorithm for real time traffic by using second order statistics of the channel. Our method minimizes the average delay of transmission over the fading channel. We assume that each sub carrier relies on its own buffer, and a constant arrival rate from higher layer application arrives at input buffers of each sub-carrier. This constant...
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