Open Topics

Vol. 70, n° 11-12, November-December 2015
Content available on Springerlink

Improving web experience on DVB-RCS2 links

Nicolas Kuhn1,2,3, Olivier Mehani3, Huyen-Chi Bui2, Emmanuel Lochin2, Jérôme Lacan2, José Radzik2, Roksana Boreli3
1 Télécom Bretagne, IRISA, Rennes, France
2 ISAE, Toulouse, France
3 National ICT Australia

Abstract The specifications of digital video broadcasting—return channel via satellite (DVB-RCS2) state that the satellite gateway could introduce both random and dedicated access methods to distribute the capacity among the different home users. Before starting an engineering process to design an algorithm allowing to combine both methods, it seems necessary to assess the performance of each. This paper compares random and dedicated access methods by measuring their impact on the performance of transmission control protocol (TCP) sessions when the home users exploit the DVB-RCS2 link for regular use (e.g., web browsing or email transmission). In this paper, we detail the implementation of an NS-2 module emulating physical channel access (PCA). This module fills a gap in terms of random and deterministic access methods and allows to model various satellite channel access strategies. Based on NS-2 simulations using realistic system parameters of the DVB-RCS2 link, we demonstrate that, compared to dedicated access methods, which generally result in higher levels of transmitted data, random access methods enable faster transmission for short flows. We propose to combine random and dedicated access methods, with the selection of a specific method dependent on the dynamic load of the network and the sequence number of the TCP segments.

Keywords Access methods – NS-2 – DVB – DVB-RCS2 – TCP

Standardization of cognitive radio networking: a comprehensive survey

Ahmed Khattab1, Magdy A. Bayoumi2
1 Cairo Unversity, Giza, Egypt
2 University of Louisiana at Lafayette, USA

Abstract Cognitive radio networking has recently presented itself as a key technology to alleviate the severe spectrum underutilization and provide a solution for spectrum scarcity. Cognitive radio networks (CRNs) are foreseen as the future wireless information and communications technologies (ICT) that exploit dynamic spectrum access (DSA) strategies to provide wireless connectivity. The enabling component of CRNs and DSA is the cognitive radio (CR). A CR is a wireless device that senses the surrounding radio environment and opportunistically accesses the unutilized spectrum bands based on the activities of the surrounding primary licensed networks. In this paper, we provide a comprehensive survey of the recent and ongoing standardization activities of the different ICT standardization bodies related to CRN and DSA systems. Unlike existing literature, our comprehensive study covers the standardization efforts of the different involved standardization bodies all over the globe. We classify such standards into TV white space standards and coexistence standards. We also discuss the standards developed to incorporate CRN and DSA concepts to existing wireless technologies.

Keywords Cognitive radio – Cognitive radio networks – Software-defined radio – Dynamic spectrum access – Standardization

Theoretical expression of link performance in OFDM cellular networks with MIMO compared to simulation and measurements

Mohamed Kadhem Karray1, Miodrag Jovanovic1, Bartłomiej Błaszczyszyn2
1 Orange Labs, Issy-les-Moulineaux, France
2 INRIA, Paris, France

Abstract The objective of this paper is to establish a theoretical expression of the link performance in the downlink of a multiple input multiple output (MIMO) cellular network and compare it to the real Long-Term Evolution (LTE ) performance. In order to account for the interference, we prove that the worst additive noise process in the MIMO context is the white Gaussian one. Based on this theoretical result, we build an analytic expression of the link performance in LTE cellular networks with MIMO. We study also the minimum mean square error (MMSE) scheme currently implemented in the field, as well as its improvement MMSE-SIC (successive interference cancellation) known to achieve the MIMO capacity. Comparison to simulation results as well as to measurements in the field shows that the theoretical expression predicts well practical link performance of LTE cellular networks. This theoretical expression of link performance is the basis of a global analytic approach to the evaluation of the quality of service perceived by the users in the long run of their arrivals and departures.

Keywords Multiple input multiple output – Wireless cellular networks – Code division multiple access – Orthogonal frequency-division multiplexing

Improving precision of mobile positioning in highway environments

Predrag Pejović, Mirjana Simić
University of Belgrade, Serbia,

Abstract A new method for mobile station positioning applying circular lateration data is proposed. The method is intended for application in close to singular cases, typical in highway environments, to reduce the positioning error. The method is non-iterative and avoids reduction of the original system of equations to linear, being based on processing intersections of circles, instead. In this manner, inconsistencies of the positioning result with the input data are reduced. Implementation of the new algorithm requires modifications in software only. Performance of the method is shown to be statistically better in comparison to the method that reduces the equation system to linear even in general case.

Keywords Circular lateration – Least squares methods – Location based services – Mobile communication – Position measurement – Positioning

Data collection model for energy-efficient wireless sensor networks

Nidhi Gautam1, Sanjeev Sofat2, Renu Vig3
1 U.I.A.M.S., Panjab University, Chandigarh, India
2 PEC University of Technology, Chandigarh, India
3 U.I.E.T., Panjab University, Chandigarh, India

Abstract To deal with real life scenarios for wireless sensor networks with uneven contours, connectivity issues, and dropping packets, heterogeneous sensors became the vital factor to enhance its capability in terms of energy efficiency and end-to-end packet delay. In recent times, end-to-end packet delay has a significant role in wireless sensor networks along with energy efficiency and network lifetime. In the present situation, the information delayed is information lost, and hence, end-to-end packet delay is playing an important role in wireless sensor networks. To address the issue of end-to-end packet delay in wireless sensor network, a mobile cluster-head data collection model for heterogeneous wireless sensor networks has been evaluated. In this paper, the mobile cluster-head data collection model has been evaluated for two different scenarios. This paper also illustrates the velocity of the cluster-head node with which it should move to reduce the end-to-end packet delay. The mobile cluster-head data collection mobility model has been evaluated for end-to-end packet delay on the basis of data send rate, network size, sensor node density, and cluster-head node density. For verification and validation, extensive simulations have been conducted which validates that the efficient mobility pattern of the mobile cluster-head nodes can lower end-to-end packet delay of wireless sensor networks.

Keywords Mobile cluster-head – Mobile data collector – Average end-to-end packet delay – Data-delivery ratio – Energy consumed

Bit error rate analysis of chaotic cognitive radio system over slow fading channels

Lin Zhang1, Huaiyin Lu1, Zhiqiang Wu2, Ming Jiang1
1 Sun Yat-sen University, Guangzhou, Guangdong, China
2 Wright State University, Dayton, USA

Abstract In this paper, we analyze the bit error rate (BER) performance of a chaotic cognitive radio (CCR) system, which enjoys benefits of high security provided by a chaotic communication system and high flexibility in non-contiguous spectrum access offered by an overlay cognitive radio (CR) system. In the proposed CCR system, the chaotic sequence is generated in the frequency domain instead of in the time domain, hence enabling non-contiguous spectrum access. We hereby derive the bit error rate expressions of CCR systems over additive white Gaussian noise (AWGN) channel and slow flat Rayleigh, Rician, and Nakagami fading channels. Specifically, we use the probability distribution of the chaotic map to evaluate the energy distribution of the transmitted signals over the identified non-continuous subcarrier bands, and then apply the definite integral representation of Q-function to calculate the bit error rate. The results from theoretical analysis and numerical simulations are compared, demonstrating an excellent agreement between the two approaches.

Keywords Bit error rate Frequency domain based chaos Cognitive radio Orthogonal frequency division multiplexing

A DTN-based architecture for public transport networks

Ioannis Komnios, Eirini Kalogeiton
Democritus University of Thrace, Xanthi, Greece

Abstract Delay/disruption-tolerant networking has been exploited in a variety of communication scenarios to provide basic delay-tolerant Internet services. In this paper, we propose a delay/disruption-tolerant networking (DTN)-based architecture for dense urban environments that exploits the existing infrastructure of public transport networks to provide Internet services through applications that can withstand certain delays without significantly affecting user experience. To achieve data delivery within the delay tolerance threshold that each user defines, we couple the proposed architecture with the enhanced connectivity plan routing protocol (CARPOOL+) that includes smart mechanisms for route calculation. In particular, the proposed architecture exploits both scheduled and opportunistic contact opportunities and mitigates the impact of typical delays caused by traffic, road accidents, etc. Our simulation results show that the proposed architecture achieves high delivery ratio with low latency, even when significant delays occur. We also compare CARPOOL+ with the most well-known DTN routing solutions and show that CARPOOL+ achieves the highest delivery ratio with the lowest overhead.

Keywords Delay-tolerant networking – DTN routing – Message ferries – Connectivity plan – Internet access