Journal of Computer Networks and Communications The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Analysis of MIMO Receiver Using Generalized Least Squares Method in Colored Environments Wed, 20 Aug 2014 07:28:55 +0000 The classical detection techniques for multiple-input multiple-output (MIMO) systems are usually designed with the assumption that the additive complex Gaussian noise is uncorrelated. However, for closely spaced antennas, the additive noise is correlated due to the mutual antenna coupling. This letter analyzes an improved zero-forcing (ZF) technique for MIMO channels in colored environments. The additive noise is assumed to be correlated and the Rayleigh MIMO channel is considered doubly correlated. The improved ZF detector, based on the generalized least squares estimator (GLS), takes into account the noise covariance matrix and provides an unbiased estimator of the transmitted symbol vectors. We introduce some novel bounds on the achievable sum rate, on the normalized mean square error at the receiver output, and on the outage probability. The derived expressions are compared to Monte Carlo simulations. Mohamed Lassaad Ammari and Paul Fortier Copyright © 2014 Mohamed Lassaad Ammari and Paul Fortier. All rights reserved. A Regulation-Based Security Evaluation Method for Data Link in Wireless Sensor Network Wed, 16 Jul 2014 00:00:00 +0000 This article presents a novel approach to the analysis of wireless sensor networks (WSN) security, based on the regulations intended for wireless communication devices. Starting from the analysis and classification of attacks, countermeasures, and available protocols, we present the current state on secure communication stacks for embedded systems. The regulation analysis is based on civil EN 50150 and MIL STD-188-220, both applicable to WSN communications. Afterwards, starting from a list of known WSN attacks, we use a correspondence table to match WSN attacks with countermeasures required by regulations. This approach allows us to produce a precise security evaluation and classification methodology for WSN protocols. The results show that current protocols do not present a complete coverage of security issues. While this conclusion is already known for many WSN protocols, to the best of our knowledge this is the first time a complete methodology is proposed to base this assertion. Moreover, by using the proposed methodology, we are able to precisely identify the exposed threats for each WSN protocol under analysis. Claudio S. Malavenda, F. Menichelli, and M. Olivieri Copyright © 2014 Claudio S. Malavenda et al. All rights reserved. Performance Evaluation of MBA-OLSR Routing Protocol for MANETs Tue, 15 Jul 2014 13:15:52 +0000 This paper proposes a multipath battery aware routing protocol, namely, MBA-OLSR, based on OLSRv2 and its multipath extension. The proposed approach considers the remaining battery energy of the nodes for calculating the initial cost of the multiple links between source-destination pairs. The MBA-OLSR aims to construct energy efficient routes and extend the network lifetime to avoid network failure due to battery exhaustion. The protocol performance is evaluated in different simulation scenarios of wireless mobile ad hoc networks (MANETs) environment. The simulation results demonstrate that our approach can achieve longer network lifetime and lower energy cost per packet. In addition, the results show improvement in terms of packet delivery ratio and end-to-end delay. Waheb A. Jabbar, Mahamod Ismail, and Rosdiadee Nordin Copyright © 2014 Waheb A. Jabbar et al. All rights reserved. A New Wireless VoIP Signaling Device Supporting SIP and H.323 Protocols Wed, 02 Jul 2014 06:13:28 +0000 Nowadays, VoIP is a technology with a great demand and wireless networks are increasingly deployed. Each of these has its own technology constraints. For VoIP, it is very important to take into consideration the need to provide a high quality service according to well-defined standard transmission (jitter, end-to-end delay, MOS, and packet loss). However, wireless networks (IEEE 802.11) are based on radio which undergoes a number of technical constraints to achieve theoretical transmission rates; among these constraints the number of users of the networks, the distance between the client and the access, and the amount of data transmitted point are included. In this term, a study is made by simulating wireless network in OPNET Modeler with a fairly large number of VoIPs (15 users) whose signaling is handled via a new node that was created specifically to manage the signaling tasks under SIP and H.323 in order to minimize the number of nodes in the network and avoid the congestion. In this paper, two scenarios are compared; the first contains a number of VoIP users with SIP and H.323 signaling handled by the new created device; the second scenario is similar to the first except that the distance between the stations is remarkably lower. Salma Rattal, Abdelmajid Badri, and Mohammed Moughit Copyright © 2014 Salma Rattal et al. All rights reserved. Survivable Network Design and Optimization with Network Families Tue, 01 Jul 2014 09:34:42 +0000 In modeling communication networks for simulation of survivability schemes, one goal is often to implement these schemes across varying degrees of nodal connectivity to get unbiased performance results. Abstractions of real networks, simple random networks, and families of networks are the most common categories of these sample networks. This paper looks at how using the network family concept provides a solid unbiased foundation to compare different network protection models. The network family provides an advantage over random networks by requiring one solution per average nodal degree, as opposed to having to solve many, which could take a significant amount of time. Also, because the network family looks at a protection scheme across a variety of average nodal connectivities, a clearer picture of the scheme’s performance is gained compared to just running the simulation on a single network or select few networks. Brody Todd, Abiose Ibigbami, and John Doucette Copyright © 2014 Brody Todd et al. All rights reserved. Wavelength Tuning Free Transceiver Module in OLT Downstream Multicasting    Gb/s TWDM-PON System Thu, 26 Jun 2014 06:02:02 +0000 We propose a new architecture of dynamic time-wavelength division multiplexing-passive optical network (TWDM-PON) system that employs integrated all-optical packet routing (AOPR) module using  Gbps downstream signal to support 20 km fiber transmission. This module has been designed to support high speed L2 aggregation and routing in the physical layer PON system by using multicasting cross-gain modulation (XGM) to route packet from any PON port to multiple PON links. Meanwhile, the fixed wavelength optical line terminal (OLT) transmitter with wavelength tuning free features has been designed to integrate with the semiconductor optical amplifier (SOA) and passive arrayed waveguide grating (AWG). By implementing hybrid multicasting and multiplexing, the system has been able to support a PON system with full flexibility function for managing highly efficient dynamic bandwidth allocation to support the  Gb/s TWDM-PON system used to connect 4 different PON links using fixed wavelength OLT transceivers with maximum 38 dB link loss. M. S. Salleh, A. S. M. Supa’at, S. M. Idrus, S. Yaakob, and Z. M. Yusof Copyright © 2014 M. S. Salleh et al. All rights reserved. SCAR: A Coding-Aware Routing Protocol with Self-Recommendation in Static Wireless Ad Hoc Networks Wed, 25 Jun 2014 10:56:21 +0000 There have been researchers working on the design of coding-aware routing protocols to exploit the power of network coding in static wireless ad hoc networks. However, most of them have overlooked the fact that routing decisions for multiple flows need to be coordinated in order to achieve maximum throughput. A mechanism to alter prior routing decisions is mandatory for this purpose. In this paper, we propose Self-recommendation coding-aware routing (SCAR), to provide such a mechanism. With intermediate nodes sensing the arrival of new flows, they can send self-recommendations to source nodes, triggering a route-change procedure. In the route-change procedure, adjustments are applied to the route metrics so that the newly recommended route can be fairly weighed without bias. A thorough analysis of coding structures is carried out, and a series of indicators are devised to predict how much throughput benefits we can gain from the mere knowledge of the topology. The rationale behind the protocol design and the effectiveness of the indicators are further justified by a series of simulations. Results show that SCAR can exploit coding opportunities better and provide higher throughput than other coding-aware routing protocols. It is also shown that the opportunity of throughput gain is ubiquitous and it is tested on many typical topologies. Jin Wang, Cenzhe Zhu, Teck Yoong Chai, and Wai-Choong Wong Copyright © 2014 Jin Wang et al. All rights reserved. Impact of Feedback Channel Delay over Joint User Scheduling Scheme and Separated Random User Scheduling Scheme in LTE-A System with Carrier Aggregation Thu, 12 Jun 2014 08:37:02 +0000 In Long Term Evolution-Advanced (LTE-A), the signal quality in a wireless channel is estimated based on the channel quality measurements. The measurement results are used to select suitable modulation and coding scheme for each transmission, feedback, and processing delay, which can cause a mismatch between channel quality information (CQI) and current channel state at the base station. However, prospect delays in the reception of such CQI may lead to a system performance degradation. This study analyzes the impact of CQI feedback delay on joint user scheduling (JUS) scheme and separated random user scheduling (SRUS) scheme in LTE-A system over carrier aggregation. The analysis will be compared with the system having delayed channel and perfect knowledge at different deployment scenario. We will study the throughput performance of both scheduling schemes with different deployment scenario, and then recommend the suitable deployment scenario to keep the desired QoS for a specific number of users. Results show that, in main beam directed at sector boundaries and diverse coverage, JUS scheme performs better than SRUS, which can justify the intensive use of user equipment power and extra control signaling overhead. Ahmed A. Ali, Rosdiadee Nordin, Mahamod Ismail, and Huda Abdullah Copyright © 2014 Ahmed A. Ali et al. All rights reserved. On the Performance of the Current MANET Routing Protocols for VoIP, HTTP, and FTP Applications Mon, 17 Feb 2014 11:51:53 +0000 The recent advances of ensemble mobile environment of smart devices with embedded sensors have enabled the MANET to play a key role in the smart cities as well as WSN and WMN. However, these smart devices are still limited in terms of energy, processor, and memory. Moreover, the efficient routing for reliable network connectivity at anytime, anywhere, and about everything is still a challenge in multihop wireless networks. This paper evaluates the QoS and energy efficiency of three active routing protocols: (i) OLSRv2, a successor to OLSR, (ii) DYMO, a successor to both DSR and AODV, and (iii) MP-OLSR multipath extension to OLSRv2. In contrast to the related previous works which focused only on CBR traffic without considering the influence of specific traffic types on the performance of routing protocols, this work focused on this area from a different perspective. It evaluates the performance of three internet-based traffic types that can be used in the smart city applications: VoIP, HTTP, and FTP using different simulation models. The impact of the network density, load traffic, and nodes mobility on the considered protocols was evaluated by considering particular performance metrics for each traffic application. Based on the results, the study concludes by presenting useful recommendations for future work. Waheb A. Jabbar, Mahamod Ismail, and Rosdiadee Nordin Copyright © 2014 Waheb A. Jabbar et al. All rights reserved. Exploratory Analysis of a GGSN’s PDP Context Signaling Load Thu, 13 Feb 2014 14:05:13 +0000 This paper takes an exploratory look on control plane signaling in a mobile cellular core network. In contrast to most contributions in this field, our focus does not lie on the wireless or user-oriented parts of the network, but on signaling in the core network. In an investigation of core network data we take a look at statistics related to GTP tunnels and their signaling. Based on the results thereof we propose a definition of load at the GGSN and create an initial load queuing model. We find signs of user devices putting burden on the core network through their behavior. Florian Metzger, Albert Rafetseder, Peter Romirer-Maierhofer, and Kurt Tutschku Copyright © 2014 Florian Metzger et al. All rights reserved. Impact of Loss Synchronization on Reliable High Speed Networks: A Model Based Simulation Sun, 19 Jan 2014 14:05:19 +0000 Contemporary nature of network evolution demands for simulation models which are flexible, scalable, and easily implementable. In this paper, we propose a fluid based model for performance analysis of reliable high speed networks. In particular, this paper aims to study the dynamic relationship between congestion control algorithms and queue management schemes, in order to develop a better understanding of the causal linkages between the two. We propose a loss synchronization module which is user configurable. We validate our model through simulations under controlled settings. Also, we present a performance analysis to provide insights into two important issues concerning 10 Gbps high speed networks: (i) impact of bottleneck buffer size on the performance of 10 Gbps high speed network and (ii) impact of level of loss synchronization on link utilization-fairness tradeoffs. The practical impact of the proposed work is to provide design guidelines along with a powerful simulation tool to protocol designers and network developers. Suman Kumar, Lin Xue, and Seung-Jong Park Copyright © 2014 Suman Kumar et al. All rights reserved. Efficient Cluster Head Selection Algorithm for MANET Tue, 24 Dec 2013 19:26:32 +0000 In mobile ad hoc network (MANET) cluster head selection is considered a gigantic challenge. In wireless sensor network LEACH protocol can be used to select cluster head on the bases of energy, but it is still a dispute in mobil ad hoc networks and especially when nodes are itinerant. In this paper we proposed an efficient cluster head selection algorithm (ECHSA), for selection of the cluster head efficiently in Mobile ad hoc networks. We evaluate our proposed algorithm through simulation in OMNet++ as well as on test bed; we experience the result according to our assumption. For further evaluation we also compare our proposed protocol with several other protocols like LEACH-C and consequences show perfection. Khalid Hussain, Abdul Hanan Abdullah, Saleem Iqbal, Khalid M. Awan, and Faraz Ahsan Copyright © 2013 Khalid Hussain et al. All rights reserved. Survey of Green Radio Communications Networks: Techniques and Recent Advances Sun, 22 Dec 2013 11:03:50 +0000 Energy efficiency in cellular networks has received significant attention from both academia and industry because of the importance of reducing the operational expenditures and maintaining the profitability of cellular networks, in addition to making these networks “greener.” Because the base station is the primary energy consumer in the network, efforts have been made to study base station energy consumption and to find ways to improve energy efficiency. In this paper, we present a brief review of the techniques that have been used recently to improve energy efficiency, such as energy-efficient power amplifier techniques, time-domain techniques, cell switching, management of the physical layer through multiple-input multiple-output (MIMO) management, heterogeneous network architectures based on Micro-Pico-Femtocells, cell zooming, and relay techniques. In addition, this paper discusses the advantages and disadvantages of each technique to contribute to a better understanding of each of the techniques and thereby offer clear insights to researchers about how to choose the best ways to reduce energy consumption in future green radio networks. Mohammed H. Alsharif, Rosdiadee Nordin, and Mahamod Ismail Copyright © 2013 Mohammed H. Alsharif et al. All rights reserved. Analytical Performance Evaluation of Different Switch Solutions Thu, 12 Dec 2013 14:04:33 +0000 The virtualization of the network access layer has opened new doors in how we perceive networks. With this virtualization of the network, it is possible to transform a regular PC with several network interface cards into a switch. PC-based switches are becoming an alternative to off-the-shelf switches, since they are cheaper. For this reason, it is important to evaluate the performance of PC-based switches. In this paper, we present a performance evaluation of two PC-based switches, using Open vSwitch and LiSA, and compare their performance with an off-the-shelf Cisco switch. The RTT, throughput, and fairness for UDP are measured for both Ethernet and Fast Ethernet technologies. From this research, we can conclude that the Cisco switch presents the best performance, and both PC-based switches have similar performance. Between Open vSwitch and LiSA, Open vSwitch represents a better choice since it has more features and is currently actively developed. Francisco Sans and Eric Gamess Copyright © 2013 Francisco Sans and Eric Gamess. All rights reserved. Power-Aware Routing and Network Design with Bundled Links: Solutions and Analysis Sun, 10 Nov 2013 13:27:14 +0000 The paper deeply analyzes a novel network-wide power management problem, called Power-Aware Routing and Network Design with Bundled Links (PARND-BL), which is able to take into account both the relationship between the power consumption and the traffic throughput of the nodes and to power off both the chassis and even the single Physical Interface Card (PIC) composing each link. The solutions of the PARND-BL model have been analyzed by taking into account different aspects associated with the actual applicability in real network scenarios: (i) the time for obtaining the solution, (ii) the deployed network topology and the resulting topology provided by the solution, (iii) the power behavior of the network elements, (iv) the traffic load, (v) the QoS requirement, and (vi) the number of paths to route each traffic demand. Among the most interesting and novel results, our analysis shows that the strategy of minimizing the number of powered-on network elements through the traffic consolidation does not always produce power savings, and the solution of this kind of problems, in some cases, can lead to spliting a single traffic demand into a high number of paths. Rosario G. Garroppo, Stefano Giordano, Gianfranco Nencioni, and Maria Grazia Scutellà Copyright © 2013 Rosario G. Garroppo et al. All rights reserved. Recent Advances in Wireless Indoor Localization Techniques and System Sun, 22 Sep 2013 14:37:39 +0000 The advances in localization based technologies and the increasing importance of ubiquitous computing and context-dependent information have led to a growing business interest in location-based applications and services. Today, most application requirements are locating or real-time tracking of physical belongings inside buildings accurately; thus, the demand for indoor localization services has become a key prerequisite in some markets. Moreover, indoor localization technologies address the inadequacy of global positioning system inside a closed environment, like buildings. Based on this, though, this paper aims to provide the reader with a review of the recent advances in wireless indoor localization techniques and system to deliver a better understanding of state-of-the-art technologies and motivate new research efforts in this promising field. For this purpose, existing wireless localization position system and location estimation schemes are reviewed, as we also compare the related techniques and systems along with a conclusion and future trends. Zahid Farid, Rosdiadee Nordin, and Mahamod Ismail Copyright © 2013 Zahid Farid et al. All rights reserved. Improving QoS and QoE for Mobile Communications Wed, 11 Sep 2013 09:39:17 +0000 Pedro Merino, Maria G. Martini, Raimund Schatz, Lea Skorin-Kapov, and Martin Varela Copyright © 2013 Pedro Merino et al. All rights reserved. Dynamic Subchannel Assignment-Based Cross-Layer MAC and Network Protocol for Multihop Ad Hoc Networks Sat, 31 Aug 2013 12:18:03 +0000 The paper presents a dynamic subchannel assignment algorithm based on orthogonal frequency division multiple access technology operating in the time division duplexing and a new cross-layer design based on a proposed routing protocol jointed with the MAC protocol. The proposed dynamic sub-channel assignment algorithm provides a new interference avoidance mechanism which solves several drawbacks of existing radio resource allocation techniques in wireless networks using OFDMA/TDD, such as the hidden node and exposed node problems, mobility, and cochannels interference in frequency (CCI). Besides, in wireless networks, when a route is established, the radio resource allocation problems may decrease the end to end performance proportionally with the length of each route. The contention at MAC layer may cause the routing protocol at network layer to respond by finding new routes and routing table updates. The proposed routing protocol is jointed with the MAC protocol based on dynamic sub-channel assignment to ensure that the quality of service in multihop ad hoc networks is significantly improved. Khanh Nguyen Quang, Van Duc Nguyen, and Hyunseung Choo Copyright © 2013 Khanh Nguyen Quang et al. All rights reserved. Obtaining More Realistic Cross-Layer QoS Measurements: A VoIP over LTE Use Case Mon, 19 Aug 2013 08:05:32 +0000 We introduce a real-time experimentation testbed in this paper which enables more realistic analysis of quality of service (QoS) in LTE networks. This testbed is envisioned for the improvement of QoS and quality of experience (QoE) through the experimentation with real devices, services, and radio configurations. Radio configurations suggested in the literature typically arise from simulations; the testbed provides a real and controlled testing environment where such configurations can be validated. The added value of this testbed goes a long way not only in the provision of more realistic results but also in the provision of QoS and QoE cross-layer measurements through the correlation of information collected at different layers: from service and IP levels to radio and protocol parameters. Analyzing the interlayer dependencies will allow us to identify optimal settings for the radio access network and service parameters. This information can be used to suggest new cross-layer optimizations to further improve quality of experience of mobile subscribers. As a use case, we examine VoIP service over LTE, which is currently an open issue. F. Javier Rivas, Almudena Díaz, and Pedro Merino Copyright © 2013 F. Javier Rivas et al. All rights reserved. Synthesized Cluster Head Selection and Routing for Two Tier Wireless Sensor Network Sun, 21 Jul 2013 10:14:51 +0000 Large scale sensor networks can be efficiently managed by dividing them into several clusters. With the help of cluster heads, each cluster communicates using some routing schedule. It is essential to rotate the role of cluster heads in a cluster to distribute energy consumption if we do not have dedicated high energy cluster heads. Usually routing and cluster head selection for such networks have been separately solved. If cluster heads are selected with the consideration of routing and routing schedule is prepared with the consideration of selected cluster heads, it can help each other. We have proposed an integrated approach of cluster head selection and routing in two tier wireless sensor network (WSN) using Genetic Algorithm based cluster head selection with A-Star algorithm based routing method to extend life of WSN. This approach can lead to significant improvements in the network lifetime over other techniques. Keyur Rana and Mukesh Zaveri Copyright © 2013 Keyur Rana and Mukesh Zaveri. All rights reserved. Peer-to-Peer Multicasting Inspired by Huffman Coding Thu, 30 May 2013 08:59:57 +0000 Stringent QoS requirements of video streaming are not addressed by the delay characteristics of highly dynamic peer-to-peer (P2P) networks. To solve this problem, a novel locality-aware method for choosing optimal neighbors in live streaming multicast P2P overlays is presented in this paper. To create the appropriate multicast tree topology, a round-trip-time (RTT) value is used as a parameter distinguishing peers capabilities. The multicast tree construction is based on the Huffman source coding algorithm. First, a centrally managed version is presented, and then an effective use of a distributed paradigm is shown. Performance evaluation results prove that the proposed approach considerably improves the overlay efficiency from the viewpoint of end-users and content providers. Moreover, the proposed technique ensures a high level of resilience against gateway-link failures and adaptively reorganizes the overlay topology in case of dynamic, transient network fluctuations. Bartosz Polaczyk, Piotr Chołda, and Andrzej Jajszczyk Copyright © 2013 Bartosz Polaczyk et al. All rights reserved. Optimized Quality of Service for Real-Time Wireless Sensor Networks Using a Partitioning Multipath Routing Approach Thu, 16 May 2013 16:01:13 +0000 Multimedia sensor networks for real-time applications have strict constraints on delay, packet loss, and energy consumption requirements. For example, video streaming in a disaster-management scenario requires careful handling to ensure that the end-to-end delay is within the acceptable range and the video is received properly without any distortion. The failure to transmit a video stream effectively occurs for many reasons, including sensor function limitations, excessive power consumption, and a lack of routing reliability. We propose a novel mathematical model for quality of service (QoS) route determination that enables a sensor to determine the optimal path for minimising resource use while satisfying the required QoS constraints. The proposed mathematical model uses the Lagrangian relaxation mixed integer programming technique to define critical parameters and appropriate objective functions for controlling the adaptive QoS constrained route discovery process. Performance trade-offs between QoS requirements and energy efficiency were simulated using the LINGO mathematical programming language. The proposed approach significantly improves the network lifetime, while reducing energy consumption and decreasing average end-to-end delays within the sensor network via optimised resource sharing in intermediate nodes compared with existing routing algorithms. Mohammed Zaki Hasan and Tat-Chee Wan Copyright © 2013 Mohammed Zaki Hasan and Tat-Chee Wan. All rights reserved. Optimizing TCP Performance in Multi-AP Residential Broadband Connections via Minislot Access Tue, 23 Apr 2013 16:59:03 +0000 The high bandwidth demand of Internet applications has recently driven the need of increasing the residential download speed. A practical solution to the problem is to aggregate the bandwidth of 802.11 access points (APs) backhauls in range. Since 802.11 devices are usually single radio, the communication to APs on different radio channels requires a time-division multiple access (TDMA) policy at the client station. With an in-depth experimental analysis and a customized 802.11 driver, in this paper, we show that the usage of multi-AP TDMA policy may cause degradation of the TCP throughput and an underutilization of the AP backhauls. We then introduce a simple analytical model that accurately predicts the TCP round-trip time (RTT) with a multi-AP TDMA policy and propose a resource allocation algorithm to reduce the observed TCP RTT with a very low computational cost. Our proposed scheme runs locally at the client station and improves the aggregate throughput up to 1.5 times compared to state-of-the-art allocations. We finally show that the throughput achieved by our algorithm is very close to the theoretical upper bound in key simulation scenarios. Domenico Giustiniano, Eduard Goma, Alberto Lopez Toledo, and George Athanasiou Copyright © 2013 Domenico Giustiniano et al. All rights reserved. Efficient Heuristic Based on Clustering Approach for OLSR Thu, 18 Apr 2013 14:12:31 +0000 Due to the dynamic nature of mobile ad hoc network (MANET), the quality of service (QoS) requires several improvements. The present papercomeswithin the framework of research to optimize QoS in MANET. In this paper, we propose a novel version of OLSR based on the clustering approach which is inspired from Lin and Chu heuristic and adapted to beimplemented inOLSR. We studied its stability and we compared its performances to those of standard OLSR. The metrics we used in evaluating network performances were average end-to-end delay, control routing overhead, and packet delivery ratio. Experimental results show that our alternative significantly reduces the traffic reserved to monitoring the network, which positively influences other performances such as throughput, delay, and loss. Ali Choukri, Ahmed Habbani, and Mohamed El Koutbi Copyright © 2013 Ali Choukri et al. All rights reserved. Dealing with Energy-QoE Trade-Offs in Mobile Video Mon, 15 Apr 2013 11:23:06 +0000 Scalable video coding allows an efficient provision of video services at different quality levels with different energy demands. According to the specific type of service and network scenario, end users and/or operators may decide to choose among different energy versus quality combinations. In order to deal with the resulting trade-off, in this paper we analyze the number of video layers that are worth to be received taking into account the energy constraints. A single-objective optimization is proposed based on dynamically selecting the number of layers, which is able to minimize the energy consumption with the constraint of a minimal quality threshold to be reached. However, this approach cannot reflect the fact that the same increment of energy consumption may result in different increments of visual quality. Thus, a multiobjective optimization is proposed and a utility function is defined in order to weight the energy consumption and the visual quality criteria. Finally, since the optimization solving mechanism is computationally expensive to be implemented in mobile devices, a heuristic algorithm is proposed. This way, significant energy consumption reduction will be achieved while keeping reasonable quality levels. Fidel Liberal, Ianire Taboada, and Jose-Oscar Fajardo Copyright © 2013 Fidel Liberal et al. All rights reserved. Estimation of Modelling Parameters for H.263-Quantized Video Traces Wed, 03 Apr 2013 11:25:43 +0000 We propose methods for selecting the modelling parameters of H.263-quantized video traffic under two different encoding scenarios. For videos encoded with a constant quantization step (unconstrained), we conclude that a two-parameter power relation holds between the exhibited video bit rate and the quantizer value and that the autocorrelation decay rate remains constant for all cases. On the basis of these results, we propose a generic method for estimating the modelling parameters of unconstrained traffic by means of measuring the statistics of the single “raw” video trace. For rate-controlled video (constrained), we propose an approximate method based on the adjustment of the “shape” parameter of the counterpart—with respect to rate—unconstrained video trace. The convergence of the constructed models is assessed via q-q plots and queuing simulations. On the assumption that the popular MPEG-4 encoders like XVID, DIVX usually employ identical H.263 quantization and rate control schemes, it is expected that the results of this paper also hold for the MPEG-4 part 2 family. A. Drigas and S. Kouremenos Copyright © 2013 A. Drigas and S. Kouremenos. All rights reserved. Angry Apps: The Impact of Network Timer Selection on Power Consumption, Signalling Load, and Web QoE Wed, 03 Apr 2013 08:35:29 +0000 The popularity of smartphones and mobile applications has experienced a considerable growth during the recent years, and this growth is expected to continue in the future. Since smartphones have only very limited energy resources, battery efficiency is one of the determining factors for a good user experience. Therefore, some smartphones tear down connectionsto the mobile network soon after a completed data transmission to reduce the power consumption of their transmission unit. However, frequent connection reestablishments caused by apps which send or receive small amounts of data often lead to a heavy signalling load within the mobile network. One of the major contributions of this paper is the investigation of the resulting tradeoff between energy consumption at the smartphone and the generated signalling traffic in the mobile network. We explain that this tradeoff can be controlled by the connection release timeout and study the impact of this parameter for a number of popular apps that cover a wide range of traffic characteristics in terms of bandwidth requirements and resulting signalling traffic. Finally, we study the impact of the timer settings on Quality of Experience (QoE) for web traffic. This is an important aspect since connection establishments not only lead to signalling traffic but also increase the load time of web pages. Christian Schwartz, Tobias Hoßfeld, Frank Lehrieder, and Phuoc Tran-Gia Copyright © 2013 Christian Schwartz et al. All rights reserved. A Retroactive-Burst Framework for Automated Intrusion Response System Tue, 26 Mar 2013 11:55:36 +0000 The aim of this paper is to present an adaptive and cost-sensitive model to prevent security intrusions. In most automated intrusion response systems, response selection is performed locally based on current threat without using the knowledge of attacks history. Another challenge is that a group of responses are applied without any feedback mechanism to measure the response effect. We address these problems through retroactive-burst execution of responses and a Response Coordinator (RC) mechanism, the main contributions of this work. The retroactive-burst execution consists of several burst executions of responses with, at the end of each burst, a mechanism for measuring the effectiveness of the applied responses by the risk assessment component. The appropriate combination of responses must be considered for each burst execution to mitigate the progress of the attack without necessarily running the next round of responses, because of the impact on legitimate users. In the proposed model, there is a multilevel response mechanism. To indicate which level is appropriate to apply based on the retroactive-burst execution, we get help from a Response Coordinator mechanism. The applied responses can improve the health of Applications, Kernel, Local Services, Network Services, and Physical Status. Based on these indexes, the RC gives a general overview of an attacker’s goal in a distributed environment. Alireza Shameli-Sendi, Julien Desfossez, Michel Dagenais, and Masoume Jabbarifar Copyright © 2013 Alireza Shameli-Sendi et al. All rights reserved. Survey and Challenges of QoE Management Issues in Wireless Networks Sat, 23 Mar 2013 15:00:32 +0000 With the move towards converged all-IP wireless network environments, managing end-user Quality of Experience (QoE) poses a challenging task, aimed at meeting high user expectations and requirements regarding reliable and cost-effective communication, access to any service, anytime and anywhere, and across multiple operator domains. In this paper, we give a survey of state-of-the-art research activities addressing the field of QoE management, focusing in particular on the domain of wireless networks and addressing three management aspects: QoE modeling, monitoring and measurement, and adaptation and optimization. Furthermore, we identify and discuss the key aspects and challenges that need to be considered when conducting research in this area. Sabina Baraković and Lea Skorin-Kapov Copyright © 2013 Sabina Baraković and Lea Skorin-Kapov. All rights reserved. Privacy and Security in Wireless Sensor Networks: Protocols, Algorithms, and Efficient Architectures Sun, 17 Mar 2013 08:08:58 +0000 Sergio Saponara, Agusti Solanas, Gildas Avoine, and Bruno Neri Copyright © 2013 Sergio Saponara et al. All rights reserved.