Financial analysis considering distress prediction models of telecommunications companies listed in Athens Stock Exchange: Hellenic Telecommunications Organization, Forthnet, Hellas Online

Within over a decade of liberalisation of the Greek telecommunications market and given the current adverse conditions caused by the economic crisis, a limited number of companies managed to survive and relatively stabilise their market position. On one hand, this paper constitutes a comprehensive financial analysis of the Greek telecommunications companies that are currently listed in the Athens Stock Exchange. The respective companies are: Hellenic Telecommunications Organization (OTE), Forthnet, and Hellas Online (HOL). These companies' financial data over the past five years, from 2008 to 2012, are analysed using universally accepted methods. On the other hand, this work presents a relatively original approach of analysing companies' survivability, by combining the four widely accepted distress prediction models of Altman, Springate, Ohlson, and Zmijewski. In this manner, criticism on the credibility and applicability of this model on the specific field is also provided

The effect of group mobility on the efficacy of routing in next generation mobile networks

© 2016 IEEE.A key challenge in next generation mobile networks is ensuring effective routing that efficiently adapts to the special characteristics of the various mobility schemes. The purpose of this paper is to study and illustrate how group mobility affects the network performance of a wireless ad hoc network depending on the type of movement, in a space with or without obstacles. In the scope of this paper, we created a simulator of a MANET that uses AODV routing protocol, while the entities of the network move according to the chosen group mobility model. Despite the fact that the routing protocol supports mobility in general, the results greatly vary depending on the specific mobility scenario. The strong connection between mobility properties and network performance is revealed

QAP: A QoS supportive adaptive polling protocol for wireless LANs

A QoS supportive adaptive polling (QAP) protocol for wireless LANs is introduced. QAP operates under an infrastructure wireless LAN, where an access point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, QAP takes into account packet priorities, so it supports QoS by means of the Highest Priority First packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a single node to dominate the medium permanently. QAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance. © 2005 Elsevier B.V. All rights reserved

SQAP: A simple QoS supportive adaptive polling protocol for wireless LANs

A Simple QoS supportive Adaptive Polling (SQAP) protocol for wireless LANs is introduced. SQAP operates under an infrastructure wireless LAN, where an Access Point (AP) polls the wireless nodes in order to grant them permission to transmit. The polled node sends data directly to the destination node. We consider bursty traffic conditions, under which the protocol operates efficiently. The polling scheme is based on an adaptive algorithm according to which it is most likely that an active node is polled. Also, SQAP takes into account packet priorities, so it supports QoS by means of the Highest Priority First packet buffer discipline and the priority distinctive polling scheme. Lastly, the protocol combines efficiency and fairness, since it prohibits a singe node to dominate the medium permanently. SQAP is compared to the efficient learning automata-based polling (LEAP) protocol, and is shown to have superior performance. © 2005 Elsevier B.V. All rights reserved

HIPERSIM: A Sense Range Distinctive Simulation Environment for HiperLAN Systems

This paper presents the simulator “HIPERSIM” which was developed and used to examine the behavior of HIPERLAN (Type 1). HIPERSIM simulates the HIPERLAN network under various conditions, assuming that the communication range and the sense range (signal detection range) of a node are different. In a wireless LAN, like HIPERLAN, the medium access protocol, the hidden nodes, the packet forwarding and the power saving mechanism are important issues that significantly affect the overall performance. The intention is to provide a HIPERLAN specialized tool (HIPERSIM) which can simulate most of the features of this WLAN protocol, in order to examine the performance of HIPER-LAN. The main focus is to simulate the channel access mechanism accurately, so as to examine the effectiveness of the EY-NPMA protocol, and underline its advantages and the elements that need improvement. Also, in HIPERSIM, there is emphasis on the “hidden nodes” issue. More specifically, we distinguish between the communication range and the signal detection range of a node, since this is a characteristic of the wireless nature and it affects the network operation. The simulation results show that EY-NPMA is effective and suitable for WLANs. Probably there could be some improvement in order to avert the collisions close to the receiver. © 2003, SAGE Publications. All rights reserved

Technology-Enhanced Peer Review: Benefits and Implications of Providing Multiple Reviews

ABSTRACT This study analyses the impact of self and peer feedback in technology-enhanced peer review settings. The impact of receiving peer comments (“receiver” perspective) is compared to that of reaching own insights by reviewing others’ work (“giver” perspective). In this study, 38 sophomore students were randomly assigned in two conditions and engaged in peer review activity facilitated by a web-based learning environment asking them to provide multiple reviews. In the Peer Reviewed (PR) condition students both reviewed peer work and received peer comments for their own work. By contrast, in the Self Reviewed (SR) condition students provided peer reviews, but did not receive any. Instead, they were asked to perform self reviewing, before proceeding to any revisions of their work. Result showed that the two groups were comparable in all aspects, suggesting that the lack of getting peer reviews can be efficiently alleviated by other type of scaffolds such as a scripted self review process. Overall, the study provides evidence that the review “giver” perspective (as opposed to the typical “receiver” perspective) is a vital option and has noteworthy implications for the design of technological systems that aim to flexibly support more efficient peer review schemes

A new approach to the, design of MAC Protocols for wireless LANs: Combining QoS guarantee with power saving

An alternative WLAN protocol which could be adapted in the HCF access scheme defined by IEEE 802.11e, in place of the HCCA mechanism, is introduced. LEPOAC-QG (Low Energy Priority Oriented Adaptive Control with QoS Guarantee) is a centralized access mechanism that supports low energy consumption, guarantees QoS for all types of multimedia network applications, enhances the parameterized traffic with priorities, and supports time division access. It instantly negotiates the quality levels of the traffic streams trying to support multiple streams with best possible quality. LEPOAC-QG, compared with HCCA, exhibits generally superior performance

The impact of mobility patterns on the efficiency of data forwarding in MANETs

One of the most challenging requirements in cutting-edge Mobile Ad hoc Networks is the need for adaptive and efficient routing. Networks capable of adapting their behavior based on current conditions are often characterized as self-organizing networks, which are lately considered very promising for future applications. This work examines the impact of the different mobility properties on the performance of self-organizing networks. For that purpose, a simulator was developed to model different mobility patterns and study the way they affect the effectiveness of the well-known AODV routing protocol. Particularly, this paper focuses on the effect of the different mobility schemes on network topology and consequently to the overall network performance. The results reveal the tight correlations between node mobility characteristics and network metrics

Connectivity and coverage in machine-type communications

Machine-type communication (MTC) provides a potential playground for deploying machine-to-machine (M2M), IP-enabled 'things' and wireless sensor networks (WSNs) that support modern, added-value services and applications. 4G/5G technology can facilitate the connectivity and the coverage of the MTC entities and elements by providing M2M-enabled gateways and base stations for carrying traffic streams to/from the backbone network. For example, the latest releases of long-term evolution (LTE) such as LTE-Advanced (LTE-A) are being transformed to support the migration of M2M devices. MTC-oriented technical definitions and requirements are defined to support the emerging M2M proliferation. ETSI describes three types of MTC access methods, namely a) the direct access, b) the gateway access and c) the coordinator access. This work is focused on studying coverage aspects when a gateway access takes place. A deployment planar field is considered where a number of M2M devices are randomly deployed, e.g., a hospital where body sensor networks form a M2M infrastructure. An analytical framework is devised that computes the average number of connected M2M devices when a M2C gateway is randomly placed for supporting connectivity access to the M2M devices. The introduced analytical framework is verified by simulation and numerical results

Connectivity and coverage in machine-type communications

Machine-type communication (MTC) provides a potential playground for deploying machine-to-machine (M2M), IP-enabled 'things' and wireless sensor networks (WSNs) that support modern, added-value services and applications. 4G/5G technology can facilitate the connectivity and the coverage of the MTC entities and elements by providing M2M-enabled gateways and base stations for carrying traffic streams to/from the backbone network. For example, the latest releases of long-term evolution (LTE) such as LTE-Advanced (LTE-A) are being transformed to support the migration of M2M devices. MTC-oriented technical definitions and requirements are defined to support the emerging M2M proliferation. ETSI describes three types of MTC access methods, namely a) the direct access, b) the gateway access and c) the coordinator access. This work is focused on studying coverage aspects when a gateway access takes place. A deployment planar field is considered where a number of M2M devices are randomly deployed, e.g., a hospital where body sensor networks form a M2M infrastructure. An analytical framework is devised that computes the average number of connected M2M devices when a M2C gateway is randomly placed for supporting connectivity access to the M2M devices. The introduced analytical framework is verified by simulation and numerical results