No. 1 (2018)
Published:
2018-03-30
ARTICLES FROM THIS ISSUE
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Call-level Analysis of a Two-Link Multirate Loss Model based on a Convolution Algorithm
Abstract
We consider a two-link system that accommodates Poisson arriving calls from different service-classes and propose a multirate teletraffic loss model for its analysis. Each link has two thresholds, which refer to the number of inservice calls in the link. The lowest threshold, named support threshold, defines up to which point the link can support calls offloaded from the other link. The highest threshold, named offloading threshold, defines the point where the link starts offloading calls to the other link. The adopted bandwidth sharing policy is the complete sharing policy, in which a call can be accepted in a link if there exist enough available bandwidth units. The model does not have a product form solution for the steady state probabilities. However, we propose approximate formulas, based on a convolution algorithm, for the calculation of call blocking probabilities. The accuracy of the formulas is verified through simulation and found to be quite satisfactory.
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Rearrangeability of 2×2 W-S-W Elastic Switching Fabrics with Two Connection Rates
Abstract
The rearreangeable conditions for the 2×2 threestage switching fabric of a W-S-W architecture for elastic optical switches are considered in this paper. Analogies between the switching fabric considered and the three-stage Clos network are shown. On the other hand, differences are also shown, which presented the modifications required in the control algorithm used in rearrangeable networks. The rearrangeable conditions and the control algorithm are presented and proved. Operation of the proposed control algorithm is shown based on a few examples. The required number of frequency slot units in interstage links of rearrangeable switching fabrics is much lower than in the strict-sense non-blocking switching fabrics characterized by the same parameters.
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Defragmentation in W-S-W Elastic Optical Networks
Abstract
In most cases defragmentation occurs, in elastic optical networks, in the links between the network’s nodes. In this article, defragmentation in an elastic optical network’s node is investigated. The W-S-W switching architecture has been used as a node. A short description of a purpose-built simulator is introduced. Several methods of defragmentation which are implemented in this simulator are described as well.
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SMM Clos-Network Switches under SD Algorithm
Abstract
This paper is devoted to evaluating the performance of Space-Memory-Memory (SMM) Clos-network switches under a packet dispatching scheme employing static connection patterns, referred to as Static Dispatching (SD). The control algorithm with static connection patterns can be easily implemented in the SMM fabric due to bufferless switches in the first stage. Stability is one of the very important performance factors of packet switching nodes. In general, a switch is stable for a particular arrival process if the expected length of the packet queues does not increase without limitation. To prove the stability of the SMM Clos-network switches considered under the SD packet dispatching scheme the discrete Markov chain model of the switch is used and Foster’s criteria to extend Lyapunov’s second (direct) method of stability investigation of discrete time stochastic systems are used. The results of simulation experiments, in terms of average cell delay and packet queue lengths, are shown as well.
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Ganging of Resources via Fuzzy Manhattan Distance Similarity with Priority Task Scheduling in Cloud Computing
Abstract
This paper proposes a fuzzy Manhattan distancebased similarity for gang formation of resources (FMDSGR) method with priority task scheduling in cloud computing. The proposed work decides which processor is to execute the current task in order to achieve efficient resource utilization and effective task scheduling. FMDSGR groups the resources into gangs which rely upon the similarity of resource characteristics in order to use the resources effectively. Then, the tasks are scheduled based on the priority in the gang of processors using gang-based priority scheduling (GPS). This reduces mainly the cost of deciding which processor is to execute the current task. Performance has been evaluated in terms of makespan, scheduling length ratio, speedup, efficiency and load balancing. CloudSim simulator is the toolkit used for simulation and for demonstrating experimental results in cloud computing environments.
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Observation of WiMAX Radio Parameters to Enhance Spectrum Utilization in Mixed Environment
Abstract
It is believed that 5G networks will provide 1000 times more capacity than current solutions. One of the keys to achieve that goal is not only the utilization of additional radio bands, but also and foremost, the dynamic and efficient spectrum sharing. To successfully implement it such feature statistical observation and analysis of currently operational legacy systems are required. Comprehensive data on the signal parameters will allow then to determine and tune the approach to simultaneous bandwidth usage by existing and new systems. Therefore, to define and introduce the problem this paper presents a conceptual analysis of IEEE 802.16e based WiMAX network operating in the 3.6–3.8 GHz band on the eve of spectrum sharing introduction.
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Performance of Hybrid Sensing Method in Environment with Noise Uncertainty
Abstract
The paper presents a novel hybrid spectrum sensing method used in cognitive radio and presents a hybrid detector (HD) which improves the sensing performance. The proposed HD takes advantage of the energy detection (ED) principle and a method based on Covariance Absolute Value (CAV), as well as on Cyclic Autocorrelation Function (CAF). The paper shows the limitations of using ED, resulting from the uncertainty of spectral density of noise power estimation, known as the SNR wall. The paper describes a system model and presents simulation results for the OFDM signal of a WiMAX-based communications system. The simulation results refer to an ideal environment with well-known parameters, and to an environment with uncertain spectral density of noise power estimation.
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Performance Analysis of SPSK with Dual Polarized Transmit Antennas over Rayleigh Fading Channel
Abstract
In this paper, the Space Polarization Shift Keying (SPSK) system, which is an extended version of Space Shift Keying (SSK) and includes both space and polarization dimensions with dual polarized antennas, is studied. The capacity and error probability analysis of SPSK for different polarization configurations are dealt with over the Rayleigh fading channel with a rich scattering environment. The analysis conducted shows that the SPSK with a dual polarized antenna (DP) offers better results than SPSK with a single orthogonal polarized antenna SPSK(SP), under non-LOS conditions. SPSK(DP) outperforms SSK by 4.2 dB over the correlated Rayleigh fading channel at 3 bits/s/Hz.
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Outage Performance of Bidirectional Full-Duplex Amplify-and-Forward Relay Network with Transmit Antenna Selection and Maximal Ratio Combining
Abstract
In this paper, a bidirectional full-duplex amplifyand-forward (AF) relay network with multiple antennas at source nodes is proposed. Assuming that the channel state information is known at the source nodes, transmit antenna selection and maximal ratio combining (MRC) are employed when source nodes transmit information to the relay node and receive information from the relay node respectively, in order to improve the overall signal-to-interference plus noise ratio (SINR). Analytical expressions are derived for tight upper bound SINR at the relay node and source nodes upon reception. Further, closed form expressions are also derived for end-to-end outage probability of the proposed bidirectional full-duplex AF relay network in the Nakagami-m fading channel environment. Although self-interference at the relay node limits the performance of the full-duplex network, the outage performance of the proposed network is better than that of conventional bidirectional full-duplex and half-duplex AF relay networks, due to the selection diversity gain in TAS and diversity and array gain in MRC.
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Miniaturized Spectacles Shaped Tapered Slotted Patch Antenna for UWB Applications
Abstract
A compact planner patch ultra-wideband (UWB) antenna is presented in this paper. The antenna configuration consists of a spectacles-shaped patch and a slotted ground plane. Different parameters are investigated for improving the antenna’s properties and for achieving the preferred UWB band (3.1–10.6 GHz). The experimental and simulated results demonstrate that the proposed antenna acquires an operating bandwidth of 117% (3–11.5 GHz) with a stable omnidirectional radiation pattern, about 89% of average radiation efficiency and 4.2 dBi of average gain with the maximum of 5.7 dBi at 10.2 GHz.
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Protocols for Wireless Sensor Networks: A Survey
Abstract
This paper presents a survey on the MAC and network layer of Wireless Sensor Networks. Performance requirements of the MAC layer are explored. MAC layer protocols for battery-powered networks and energy harvestingbased networks are discussed and compared. A detailed discussion on design constraints and classification of routing protocols is presented. Several routing protocols are compared in terms of such parameters as: energy consumption, scalability, network lifetime and mobility. Problems that require future research are presented. The cross-layer approach for WSNs is also surveyed.
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Underwater Acoustic Sensor Node Scheduling using an Evolutionary Memetic Algorithm
Abstract
Underwater Acoustic Sensor Networks (UWASNs) play an important role in monitoring the aqueous environment which has created a lot of interest for researchers and scientists. Utilization of underwater acoustic sensor node (UASN) scheduling for transmission remains, due to the limited acoustic bandwidth available, a challenge in such an environment. One of the methods to overcome this problem is to efficiently schedule UASN data using time division multiple access (TDMA) protocols the parallel transmissions, simultaneously avoiding interference. The paper shows how to optimize the utilization of acoustic sensor node bandwidth by maximizing the possible node transmissions in the TDMA frame and also by minimizing the node’s turnaround wait time for its subsequent transmissions by using an evolutionary memetic algorithm (MA). The simulation of MA-TDMA proves that as the size of the network increases, every node in UWASN transmits with an average minimal turnaround transmission time. It also proves that as the TDMA cycle repeats, the overall network throughput gets maximized by increasing the possible node transmissions in the MA-TDMA frame.
