In this paper we investigate admission control and power allocation for cognitive radios in an underlay network. We consider the problem of maximizing the number of supported secondary links under their minimum QoS requirements without violating the maximum tolerable interference on primary receivers in a cellular network. An optimal solution to our problem is shown in previous works to be NP-hard. We propose an efficient distributed algorithm with reasonable complexity that provides results close to the optimum solution without requiring neither a large amount of signaling nor a wide range of

In this paper, the degrees of freedom (DoF) of the two-user single input single output (SISO) X channel are investigated. Three cases are considered for the availability of channel state information at the transmitters (CSIT); perfect, delayed, and no-CSIT. A new achievable scheme is proposed to elucidate the potency of interference creation-resurrection (IRC) when the available CSIT alternates between these three cases. For some patterns of alternating CSIT, the proposed scheme achieves 4/3 DoF, and hence, coincides with the information theoretic upper bound on the DoF of the X channel with

In this paper, a two-hop cellular relay network consisting of two source-destination pairs equipped with M antennas is considered where each source is assisted by two decode-and-forward relays operating in half-duplex mode and the relays are equipped with N antennas. The DoF of the system is investigated for both simultaneous and alternate relaying configurations. For each relay configuration, an outer bound on the degrees of freedom (DoF) is developed. A new achievable scheme is proposed that meets the upper bound on the maximum DoF for all values of M andN except for M

We consider a multiple access primary network with N transmitters. A secondary link of one transmitter and a corresponding receiver causes interference to the primary network. An achievable rate region for the primary network and the secondary link is obtained given the following mode of operation. The secondary transmitter employs rate-splitting so that the primary receiver can decode part of the secondary's signal and cancel it. The secondary receiver, on the other hand, treats primary interference as noise. Given a Gaussian channel model, we investigate the effect of rate-splitting on the

In the last decade, many Activated Sludge Model No. 3 (ASM3) extensions were proposed to adopt new concepts such as simultaneous storage and growth of heterotrophic organisms and two-step nitrification-denitrification processes. From these ASM3 model extensions, four are included in this study: ASM3 with two-step nitrification-denitrification, ASM3 for simultaneous autotrophic and heterotrophic storage-growth, ASM3 extension for two-step nitrification-denitrification, and ASM3 for simultaneous storage-growth and nitrification-denitrification. The four models are analyzed and compared to the

In this paper, a cellular relaying network consisting of two source-destination pairs, and four decode-and-forward relays operating in half-duplex mode is considered. Each source is assisted by two relays and all nodes are equipped with N antennas. In order to compensate for the loss of capacity by a factor of half due to the half-duplex mode, an alternate transmission protocol among the two relays is proposed. An outer bound on the degrees of freedom (DoF) of this system is developed. A constructive proof of achievability based on two different schemes is provided. Aligning the inter-relay

Subsequent duplication events are responsible for the evolution of the minisatellite maps. Alignment of two minisatellite maps should therefore take these duplication events into account, in addition to the well-known edit operations. All algorithms for computing an optimal alignment of two maps, including the one presented here, first deduce the costs of optimal duplication scenarios for all substrings of the given maps. Then, they incorporate the pre-computed costs in the alignment recurrence. However, all previous algorithms addressing this problem are dependent on the number of distinct

This paper introduces a dynamic model to adequately describe an Upflow Anaerobic Sludge Blanket (UASB) reactor. Some available models of a UASB reactor are discussed in order to modify their drawbacks and propose a new improved model with less complexity and more reliability. The developed model is a combination of two recent models introduced in Sweden. According to this model, a UASB rector is divided hydraulically into three compartments with integration of a kinetic model. Simulations are performed to investigate the validity of the developed model which indicates a good agreement with

This paper proposes generalized controllable strange attractors through dynamic rotation of fractional-order chaotic systems. Dynamic rotation angle enables the generation of multi-scroll and multi-wing attractors from single and double-scroll ones. The rotating systems are integrated with a generalized dynamic switched synchronization scheme. Dynamic control switches determine whether each system plays the role of master or slave. Based on dynamic scaling factors, the master can be one system or a combination of several ones with new strange attractors. The rotating fractional-order systems

This article proposes a new simple scheme for direct power control of a PWM rectifier without a switch table and voltage sensor. The selection of the switching state of the converter is based on the transition of a Petri net, using the instantaneous active and reactive power tracking errors and the angular position of the network line voltage estimated as variables of Controller input based on Petri nets. Simulation and experimental results demonstrated better performance and verified the validity of the new command with the Petri nets applied to the bridge rectifier connected to the