Open Topics

Vol. 73, n° 05-06, May-June 2018
Content available on Springerlink


An iterative heuristic approach for channel and power allocation in wireless networks

Giovanna Garcia1, Hermes I. D. Monego1, Marcelo E. Pellenz 2, Richard D. Souza 3, Anelise Munaretto 1, Mauro S. P. Fonseca1
1 Federal University of Technology-Paraná (UTFPR), Curitiba, Brazil
2 Pontifical Catholic University of Paraná (PUCPR), Curitiba, Brazil
3 Federal University of Santa Catarina (UFSC), Florianópolis, Brazil

Abstract A large number of access points (APs) may be required to provide network coverage in a given environment. However, a non-optimized deployment of these APs can reduce the network performance significantly due to the excessive interference. The optimization of the channel and transmit power is an efficient method to reduce the interference and therefore guarantee a minimally acceptable performance. In this paper, we propose a heuristic algorithm to find a proper channel and transmit power configuration for all APs within a network. The algorithm evaluates the network, using theoretical models, and employs several techniques to optimize the channel and the transmit power to increase the network performance. We also estimate the complexity of the proposed algorithm comparing it with an exhaustive search approach. The results show that the proposed algorithm can arrive at a solution very close to the optimal with a much reduced computational complexity.

Keywords Wireless local area networks – Power allocation – Channel allocation – Heuristic Interference

Video conference in the fog: an economical approach based on enterprise desktop grid

Roman Sorokin1, Jean-Louis Rougier2
1 ALE International, Colombes, France
2 Télécom ParisTech, Paris, France

Abstract There exist two classical and well-understood approaches to video-processing tasks (such as mixing or trans-coding) for videoconferencing. The first one is using a centralized multipoint control unit (MCU), hardware- or software-based, deployed on-premises or in the cloud. In the second approach, the video-processing tasks are directly handled in endpoints (i.e., equipment such as PCs, laptops, and tablets that are involved in the video session). Performance is then restricted by device characteristics, especially in the case of mobile devices. In this paper, we propose a third alternative approach. It has been shown that there exist significant computational resources in user equipment deployed in enterprises, which are under-utilized most of the time. In this paper, we propose a system, which distributes real-time video-processing tasks on these available resources. A dedicated multi-attribute decision-making (MADM) method is designed in order to take into account the variety of attributes impacting Quality of Experience. We enumerate a comprehensive list of events, which may cause distribution or redistribution of video-processing activities and provide simple algorithms to tackle all these cases. We then test the MADM algorithm by means of simulations in order to study the impact of the main critical parameters.

Keywords Video conferencing – Enterprise desktop grid – Multi-attribute decision-making – MCU – SFU – CPU

Efficient and viable intersection-based routing in VANETs on top of a virtualization layer

José Víctor Saiáns-Vázquez1, Martín López-Nores1, Yolanda Blanco-Fernández1, Esteban Fernando Ordóñez-Morales2, Jack Fernando Bravo-Torres2, José Juan Pazos-Arias1
1 AtlantTIC Research Center for Information and Communication Technologies, Department of Telematics Engineering, University of Vigo, Vigo, Spain
2 Universidad Politécnica Salesiana, Cuenca, Ecuador

Abstract Recent vehicular ad hoc network routing protocols have relied on geographic forwarding and careful selection of road segments as ways to reduce the impact of individual vehicle movements. This paper shows how a virtualization layer and a new protocol running on top of it —called VNIBR, intersection-based routing on virtual nodes—can achieve better performance than state-of-the-art approaches, enabling an efficient and computationally feasible combination of topological and geographical routing. We prove by means of network simulations that this proposal consistently ensures moderate overhead, good packet delivery ratios, and low end-to-end delays, whereas the other protocols exhibit weaknesses due to flooding processes that scale poorly, proactive routing burdens or costly location services. We also present the results of graphics processing unit profiling used to assess the computational feasibility of the different schemes in the context of a real on-board computer, which reveals new advantages about scalability and impact of computational shortages on the routing performance.

Keywords Vehicular ad hoc networks – Virtualization – Intersection-based routing – On-board computational viability

Outage probability of macrodiversity reception in the presence of Gamma long-term fading, Rayleigh short-term fading and Rician co-channel interference

Dragana Krstić1, Suad Suljović1, Dejan Milić1, Stefan Panić2, Mihajlo Stefanović1
1 Faculty of Electronic Engineering, University of Niš, Niš, Serbia
Faculty of Natural Sciences, University of Pristina, Kosovska Mitrovica, Serbia

Abstract Macrodiversity (MACD) system with MACD selection combining (SC) receiver and two microdiversity (MICD) selection receivers in the presence of Gamma long-term fading, Rayleigh short-term fading, and co-channel interference affected to Rician short-term fading is studied in this article. The closed-form expressions for probability density function (PDF) and cumulative distribution function (CDF) of the ratio of Rayleigh random variable and Rician random variable are presented, and probability density function and cumulative distribution function of MICD SC receiver output signal to interference ratio are derived. These results are used for evaluation of the outage probability (P out) of considered MACD system, and the influence of Rician factor and Gamma long-term fading severity parameter on the outage probability is analyzed.

Keywords Gamma long-term fading – Rayleigh short-term fading – Rician co-channel interference – Cumulative distribution function (CDF) – Probability density function (PDF) – Outage probability (Pout)

Secure communication via an energy-harvesting untrusted relay with imperfect CSI

Van Phu Tuan1, Hyung Yun Kong1
1 Department of Electrical Engineering, University of Ulsan, Ulsan, South Korea

Abstract This paper studies the secure communication of an energy-harvesting system in which a source communicates with a destination via an amplify-and-forward (AF) untrusted relay. The relay uses the power-splitting policy to harvest energy from wireless signals. The source is equipped with multiple antennas and uses transmit antenna selection (TAS) and maximum ratio transmission (MRT) to enhance the harvested energy at the relay; for performance comparison, random antenna selection (RAS) is examined. The relay and destination are single-antenna nodes. To create a positive secrecy capacity, destination-assisted jamming is deployed. Because the use of multiple antennas can cause the imperfect channel state information (CSI), the channel between the source and the relay is examined in two cases: perfect CSI and imperfect CSI. To evaluate the secrecy performance, analytical expressions for the secrecy outage probability (SOP) and the average secrecy capacity (ASC) for the TAS, MRT, and RAS schemes are derived. Moreover, a high-power approximation for the SOP is presented. The accuracy of the analytical results is verified by Monte Carlo simulations. The results show the benefit of using multiple antennas in improving the secrecy performance. Specifically, MRT performs better than TAS, and both of them outperform RAS. Moreover, the results provide valuable insight into the effects of various system parameters, such as the channel correlation coefficient, energy-harvesting efficiency, secrecy rate threshold, power-splitting ratio, transmit powers, and locations of the relay, on the secrecy performance.

Keywords Energy harvesting – Power-splitting architecture – Untrusted relay – Amplify-and-forward – Imperfect CSI – Physical layer security

A dynamic harmony search-based fuzzy clustering protocol for energy-efficient wireless sensor networks

Osama Moh’d Alia1
Department of Computer Science, Faculty of Computers and Information Technology, University of Tabuk, Tabuk, Saudi Arabia

Abstract In the development of cluster-based energy-efficient protocols for wireless sensor networks (WSNs), a particularly challenging problem is the dynamic organization of sensors into a wireless communication network and the routing of sensed information from the field sensors to a remote base station (BS) in a manner that prolongs the lifetime of WSNs. This paper presents a new energy-efficient clustering protocol for WSNs, which can minimize total network energy dissipation while maximizing network lifetime. The protocol is divided into two parts. The first deals with constructing an infrastructure for the given WSN. A newly developed algorithm, based on a harmony search (HS), automatically determines the optimal number of clusters and allocates sensors into these clusters. This algorithm also eliminates the need to set the number of clusters a priori. The second part is concerned with the process of sending sensed data from nodes to their cluster head and then to the BS. A decentralized fuzzy clustering algorithm is proposed, where the selection of cluster heads in each round is locally made in each cluster during the network lifetime. Simulation results demonstrate that the proposed protocol can achieve an optimal number of clusters, prolong the network lifetime and increase the data delivery at the BS, when compared to other well-known clustering-based routing protocols.

Keywords Wireless sensor networks – Energy-efficient routing protocols – Harmony search algorithm – Fuzzy clustering

Cost estimation of a fixed network deployment over an urban territory

Catherine Gloaguen1, Elie Cali1
1 Orange SA, Orange Labs Networks, Châtillon, France

Abstract This paper presents a methodology for fast and reliable cost estimation of fixed access network deployment on any urban area. It is based on theoretical results presented in former papers for distances and attenuation results, adding the most important part of cost estimation. In particular it is showed that good estimations can be obtained in a very short time. The territory to be deployed, the network architecture and the scenarios are defined by the user via two user-friendly prototypes. The first one helps defining the limit of the city and computes mathematical parameters representing its street system. The second one computes global information on the network deployment on this territory, namely the probability distributions of distances and attenuation from a node of the network to the final customer, and an evaluation of the deployment cost, once given an architecture and engineering rules. The results were compared on two real French urban territories (in Tours and Rouen) to those given by an optimization tool currently used by Orange.

Keywords Access network – Stochastic geometry – Cost analysis – Network planning – Urban street network – Fibre-to-the-home (FTTH)

Secure multiuser MISO communication systems with limited feedback link

Berna Özbek1, Özgecan Özdoğan Şenol1, Güneş Karabulut Kurt2
Department of Electrical and Electronics Engineering, Izmir Institute of Technology, Izmir, Turkey
2 Department of Electronics and Communication Engineering, Istanbul Technical University, Istanbul, Turkey

Abstract Physical layer security is one of the promising techniques for the security of next-generation wireless systems. In this paper, we analyze the impact of the limited feedback link on the secrecy capacity for a system which includes a base station with multiple antennas, a single legitimate user selected from multiple active ones and multiple eavesdroppers. We propose to design a limited feedback link by reducing the feedback load and quantizing the channel state information (CSI) of legitimate users to establish a secure communication system. The feedback load is decreased with a self discrimination criterion at the legitimate users’ side while keeping the secrecy capacity constant. The best legitimate user is selected based on the quantized CSI through a limited feedback link. We also analyze the impact of CSI of eavesdroppers, which information may or may not be available at transmitter. In practical cases where eavesdroppers are passive and their location is not known by the transmitter, an artificial noise is used to disrupt their reception. When the CSI of eavesdroppers is known, the generalized singular value decomposition is applied. We illustrate the performance results of the proposed limited feedback link through the availability of CSI of eavesdroppers at the transmitter.

Keywords Physical layer security – Reduced feedback link – Quantized feedback – Multiple antennas

Joint sensing time and power allocation in cognitive networks with amplify-and-forward cooperation

Shunling Ruan1, Chengshi Zhao2, Song Jiang1, Kyungsup Kwak3
1 Xi’an University of Architecture and Technology, Xi’an, China
2 Huawei Technologies Co., Ltd., Shenzhen, China
Telecommunication Engineering Lab, Graduate School of IT and Telecommunications, Inha University, Incheon, Republic of Korea

Abstract Cognitive radio is a novel approach to cope with spectrum scarcity, in which either a network or a wireless node changes its transmission or reception parameters to communicate efficiently. However, it is difficult to avoid the interference between licensed and unlicensed users in various scenarios. This paper analyzes the jointly optimized allocation of sensing time and power for a two-user, amplify-and-forward (AF) cognitive network developed by maximizing the average aggregate throughput of its secondary network. In particular, this paper discusses diverse cooperation ratios for different scenarios and a unique cooperation ratio in spite of scenario changes. The observations of experiment results indicate that the sensing duration is within a strict interval. The results show that the optimized sensing time is 14.111 ms and the aggregate throughput equals to 1.1451 bps/Hz which are tractable by sequential optimization. This result indicates that by adopting the fixed cooperation ratios, the achievable throughput of the system is decreased. The system innovatively creates multiple independent fading channels to achieve technological diversity among partners.

Keywords Cognitive radio – Spectrum sensing – Power allocation – Amplify-and-forward relaying – Cooperative communications – Optimization

High-performance software implementations of SCAN decoder for polar codes

Bertrand Le Gal1, Camille Leroux1, Christophe Jego1
1 IMS Laboratory, UMR CNRS 5218, Bordeaux-INP, Talence, France

Abstract This paper presents the first optimized software implementation of a SCAN decoder for Polar codes. Unlike SC and SC-List decoding algorithms, the SCAN decoding algorithm provides soft outputs (useful for, e.g., parallel concatenated decoders Zhang et al. IEEE Trans Commun 64(2):456–466 2016). Despite the strong data dependencies in the SCAN decoding, two highly parallel software implementations are devised for x86 processor target. Different parallelization strategies, algorithmic improvements, and source code optimizations were applied in order to enhance the throughput of the decoders. The impact of the parallelization approach, the code rate, and the code length on the throughput and the latency is investigated. Extensive experimentations demonstrate that the proposed software polar decoder can exceed 600 Mb/s on a single core and reaches multi-Gb/s when using four cores simultaneously. These decoders can then achieve real-time performance required in many applications such as software defined radio or cloud-RAN systems where network physical layer is implemented in software.

Keywords Polar codes – SCAN decoding – Soft-inputs and Soft-outputs – SIMD – Multi-core – x86 processor