2015. 4rd Issue
Full issue (22 MB)
H. Charaf and S. Imre
Special Issue on Advanced Wireless and Mobile Technologies and Services, Part II.
PAPERS OF THE SPECIAL ISSUE
D. Szabó, A. Csoma, P. Megyesi, A. Gulyás, and F. H.P. Fitzek Network Coding as a Software
Network Coding (NC) shows great potential in various communication scenarios through changing the packet forwarding principles of current networks. It can improve not only throughput, latency, reliability and security but also alleviates the need of coordination in many cases. However, it is still controversial due to widespread misunderstandings on how to exploit the advantages of it. The aim of the paper is to facilitate the usage of NC by (i) explaining how it can improve the performance of the network (regardless the existence of any butterfly in the network), (ii) showing how Software Defined Networking (SDN) can resolve the crucial problems of deployment and orchestration of NC elements, and (iii) providing a prototype architecture with measurement results on the performance of our network coding capable software router implementation compared by fountain codes.
Á. Milánkovich, G. Ill, K. Lendvai, S. Imre and S. Szabó
Increasing energy efficiency in WSNs using wakeup signal length optimization combined with payload aggregation and FEC
Energy efficiency in wireless sensor networks is a vital question. There are several possibilities to achieve longer battery life in such devices. We investigated delay-tolerant wireless sensor networks with battery-operated nodes and use dataaggregation to lower the size of transmitted data overhead caused by packet headers. In this paper a mathematical formula is presented to calculate the optimal wakeup signal (a special radio signal) length, which minimizes the energy consumed for waking up nodes in sleep mode. The demonstrated results and graphs are based on the investigation of an existing system. The contribution of this paper is a general method to improve the energy efficiency of wireless sensor networks by using the optimal length of the wakeup signal in case of different amounts of aggregated packet payloads and Forward Error Correction (FEC) schemes. The results presented can be applied to arbitrary packet-based wireless protocols and radio modules supporting wakeup signal listening.
PAPERS FROM OPEN CALL
T. Cseh and T. Berceli
Modeling and Simulation of Mode Filtered Radio over Multimode Fiber Links
In this paper mode filtered radio over multimode fiber systems are analyzed by simulations. Several mode filters are investigated such as mandrel wrap, air gap mode filter and single mode fiber patchcord. The multimode fibers and the mode filters are modeled, these models are implemented into VPI Transmission Maker and frequency responses are analyzed. According to the frequency responses, EVM analyses are also carried out, and the most advantageous mode filter is selected. All of these mode filters can reduce the effect of the modal dispersion however, their effect is different and their insertion loss is different too. The single mode fiber patchcord is the best choice when modal dispersion is the dominant effect. Mandrel and air gap filter provided better results if the noise is significant.
N. Al-Qadami and A. Koucheryavy
Fault-Tolerance Algorithm in Wireless Sensor Networks
In wireless sensor networks that rely on clustering hierarchical structure for routing and information exchange, some nodes are essential and have a pivotal role in the clustering process and data routing. Consequently, any failures of these important nodes may cause paralysis of the network and effect on the quality of services and the reliability of the network. In this paper, we proposed a fault tolerant routing TEEN (FT-TEEN) algorithm which is a modified version of the well-known TEEN protocol; FT-TEEN proposes vital solutions to some shortcomings of the pure TEEN. It provides fault detection, recovery process, reliability and quality of service. The simulation results showed a significant reliability in the amount of receiving data by the cluster heads and the base station compared to the amount of data in the reference TEEN protocol. The developed algorithm can be used in the ground fragments flying ubiquitous sensor networks.
A. Csoma, A. Gulyás and L. Toka
On Measuring the Geographic Diversity of Internet Routes
Route diversity in networks is elemental for establishing reliable, high-capacity connections with appropriate security between endpoints. As for the Internet, route diversity has already been studied at both Autonomous System- and routerlevel topologies by means of graph theoretical disjoint paths. In this paper we complement these approaches by proposing a method for measuring the diversity of Internet paths in a geographical sense. By leveraging the recent developments in IP geolocation we show how to map the paths discovered by traceroute into geographically equivalent classes. This allows us to identify the geographical footprints of the major transmission paths between end-hosts, and building on our observations, we propose a quantitative measure for geographical diversity of Internet routes between any two hosts.
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