Journal of Computer Networks and Communications http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . 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 http://www.hindawi.com/journals/jcnc/2014/154983/ 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 http://www.hindawi.com/journals/jcnc/2014/526231/ 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 http://www.hindawi.com/journals/jcnc/2014/795489/ 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 http://www.hindawi.com/journals/jcnc/2013/723913/ 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 http://www.hindawi.com/journals/jcnc/2013/453893/ 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 http://www.hindawi.com/journals/jcnc/2013/953797/ 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 http://www.hindawi.com/journals/jcnc/2013/154953/ 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 http://www.hindawi.com/journals/jcnc/2013/185138/ 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 http://www.hindawi.com/journals/jcnc/2013/645174/ 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 http://www.hindawi.com/journals/jcnc/2013/962643/ 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 http://www.hindawi.com/journals/jcnc/2013/405858/ 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 http://www.hindawi.com/journals/jcnc/2013/578241/ 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 http://www.hindawi.com/journals/jcnc/2013/312376/ 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 http://www.hindawi.com/journals/jcnc/2013/497157/ 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 http://www.hindawi.com/journals/jcnc/2013/752363/ 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 http://www.hindawi.com/journals/jcnc/2013/597461/ 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 http://www.hindawi.com/journals/jcnc/2013/412491/ 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 http://www.hindawi.com/journals/jcnc/2013/351435/ 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 http://www.hindawi.com/journals/jcnc/2013/176217/ 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 connections to 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 http://www.hindawi.com/journals/jcnc/2013/134760/ 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 http://www.hindawi.com/journals/jcnc/2013/165146/ 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 http://www.hindawi.com/journals/jcnc/2013/528750/ Sergio Saponara, Agusti Solanas, Gildas Avoine, and Bruno Neri Copyright © 2013 Sergio Saponara et al. All rights reserved. Operating Protocol and Networking Issues of a Telemedicine Platform Integrating from Wireless Home Sensors to the Hospital Information System Wed, 13 Mar 2013 18:07:10 +0000 http://www.hindawi.com/journals/jcnc/2013/781620/ Chronic heart failure (CHF) is among the major causes of hospitalization for elderly citizens. Its considerable impact on patient quality of life, the resources congestion, and the related costs can be efficiently mitigated using remote wireless biosensors networks placed at patient home, able to communicate in secure way over the public Internet with the cardiology departmental Hospital Information System (HIS). In this way, physicians can monitor the situation of several patients at distance and quickly realize and act alterations in vital parameters. In this scenario, the Health@Home (H@H) platform is conceived. The pool of Bluetooth sensors enables patients to daily collect vital signs at home in noninvasive fashion. A home gateway receives and processes all signals before sending them to a server node in charge of interfacing with the usual HIS. The novel concept of operating protocol (OP) represents a list of actions, remotely configurable, that the domestic network has to follow (required measurements, transmissions, comparisons with personalized thresholds, etc.). The first medical tests on 30 patients (1 month) allowed to verify the model, both from the patient and the medical perspective. The main evaluation metrics were usability, flexibility, and reliability of the communication from sensors to HIS. Massimiliano Donati, Tony Bacchillone, Luca Fanucci, Sergio Saponara, and Filippo Costalli Copyright © 2013 Massimiliano Donati et al. All rights reserved. Robust On-Demand Multipath Routing with Dynamic Path Upgrade for Delay-Sensitive Data over Ad Hoc Networks Wed, 13 Mar 2013 10:44:20 +0000 http://www.hindawi.com/journals/jcnc/2013/791097/ Node mobility in mobile ad hoc networks (MANETs) causes frequent route breakages and intermittent link stability. In this paper, we introduce a robust routing scheme, known as ad hoc on-demand multipath distance vector with dynamic path update (AOMDV-DPU), for delay-sensitive data transmission over MANET. The proposed scheme improves the AOMDV scheme by incorporating the following features: (i) a routing metric based on the combination of minimum hops and received signal strength indicator (RSSI) for discovery of reliable routes; (ii) a local path update mechanism which strengthens the route, reduces the route breakage frequency, and increases the route longevity; (iii) a keep alive mechanism for secondary route maintenance which enables smooth switching between routes and reduces the route discovery frequency; (iv) a packet salvaging scheme to improve packet delivery in the event of a route breakage; and (v) low HELLO packet overhead. The simulations are carried out in ns-2 for varying node speeds, number of sources, and traffic load conditions. Our AOMDV-DPU scheme achieves significantly higher throughput, lower delay, routing overhead, and route discovery frequency and latency compared to AOMDV. For H.264 compressed video traffic, AOMDV-DPU scheme achieves 3 dB or higher PSNR gain over AOMDV at both low and high node speeds. Sunil Kumar, Siddharth Khimsara, Kashyap Kambhatla, Kalyani Girivanesh, John D. Matyjas, and Michael Medley Copyright © 2013 Sunil Kumar et al. All rights reserved. Energy-Efficient Wireless Communications with Future Networks and Diverse Devices Mon, 04 Mar 2013 10:38:36 +0000 http://www.hindawi.com/journals/jcnc/2013/897029/ Runhua Chen, Lingjia Liu, Krishna Sayana, and Hongxiang Li Copyright © 2013 Runhua Chen et al. All rights reserved. Untangling RFID Privacy Models Mon, 11 Feb 2013 09:47:28 +0000 http://www.hindawi.com/journals/jcnc/2013/710275/ The rise of wireless applications based on RFID has brought up major concerns on privacy. Indeed nowadays, when such an application is deployed, informed customers yearn for guarantees that their privacy will not be threatened. One formal way to perform this task is to assess the privacy level of the RFID application with a model. However, if the chosen model does not reflect the assumptions and requirements of the analyzed application, it may misevaluate its privacy level. Therefore, selecting the most appropriate model among all the existing ones is not an easy task. This paper investigates the eight most well-known RFID privacy models and thoroughly examines their advantages and drawbacks in three steps. Firstly, five RFID authentication protocols are analyzed with these models. This discloses a main worry: although these protocols intuitively ensure different privacy levels, no model is able to accurately distinguish them. Secondly, these models are grouped according to their features (e.g., tag corruption ability). This classification reveals the most appropriate candidate model(s) to be used for a privacy analysis when one of these features is especially required. Furthermore, it points out that none of the models are comprehensive. Hence, some combinations of features may not match any model. Finally, the privacy properties of the eight models are compared in order to provide an overall view of their relations. This part highlights that no model globally outclasses the other ones. Considering the required properties of an application, the thorough study provided in this paper aims to assist system designers to choose the best suited model. Iwen Coisel and Tania Martin Copyright © 2013 Iwen Coisel and Tania Martin. All rights reserved. ECOPS: Energy-Efficient Collaborative Opportunistic Positioning for Heterogeneous Mobile Devices Tue, 29 Jan 2013 11:38:29 +0000 http://www.hindawi.com/journals/jcnc/2013/136213/ The fast growing popularity of smartphones and tablets enables us to use various intelligent mobile applications. As many of those applications require position information, smart mobile devices provide positioning methods such as Global Positioning System (GPS), WiFi-based positioning system (WPS), or Cell-ID-based positioning service. However, those positioning methods have different characteristics of energy-efficiency, accuracy, and service availability. In this paper, we present an Energy-Efficient Collaborative and Opportunistic Positioning System (ECOPS) for heterogeneous mobile devices. ECOPS facilitates a collaborative environment where many mobile devices can opportunistically receive position information over energy-efficient and prevalent WiFi, broadcasted from a few other devices in the communication range. The position-broadcasting devices in ECOPS have sufficient battery power and up-to-date location information obtained from accurate but energy-inefficient GPS. A position receiver in ECOPS estimates its location using a combination of methods including received signal strength indicators and 2D trilateration. Our field experiments show that ECOPS significantly reduces the total energy consumption of devices while achieving an acceptable level of location accuracy. ECOPS can be especially useful for unique resource scarce, infrastructureless, and mission critical scenarios such as battlefields, border patrol, mountaineering expeditions, and disaster area assistance. Kaustubh Dhondge, Hyungbae Park, Baek-Young Choi, and Sejun Song Copyright © 2013 Kaustubh Dhondge et al. All rights reserved. Equalizer's Use Limitation for Complexity Reduction in a Green Radio Receiver Sun, 27 Jan 2013 08:16:22 +0000 http://www.hindawi.com/journals/jcnc/2013/794202/ This work is about reducing energy consumption in the receiver chain by limiting the use of the equalizer. It is to make the radio receiver aware of its environment and able to take decision to turn on or off the equalizer according to its necessity or not. When the equalizer is off, the computational complexity is reduced and the rate of reduction depends on the percentage of time during which this component is disabled. In order to achieve this scenario of adapting the use of the equalizer, we need to develop a decision-making technique that provides the receiver with the capacities of awareness and adaptability to the state of its environment. For this, we improve a technique based on a statistical modeling of the environment by defining two metrics as channel quality indicators to evaluate the effect of the intersymbol interferences and the channel fading. The statistical modeling technique allows to take into account the impact of the uncertainties of the estimated metrics on the decision making. Salma Bourbia, Daniel Le Guennec, Jacques Palicot, Khaled Grati, and Adel Ghazel Copyright © 2013 Salma Bourbia et al. All rights reserved. Miscellaneous Service Delivery to Modern Mobile Devices Mon, 21 Jan 2013 10:50:38 +0000 http://www.hindawi.com/journals/jcnc/2013/302502/ Ondrej Krejcar, Peter Brida, and Stavros Kotsopoulos Copyright © 2013 Ondrej Krejcar et al. All rights reserved. Stability Properties of Network Diversity Multiple Access with Multiple-Antenna Reception and Imperfect Collision Multiplicity Estimation Sun, 20 Jan 2013 14:35:10 +0000 http://www.hindawi.com/journals/jcnc/2013/984956/ In NDMA (network diversity multiple access), protocol-controlled retransmissions are used to create a virtual MIMO (multiple-input multiple-output) system, where collisions can be resolved via source separation. By using this retransmission diversity approach for collision resolution, NDMA is the family of random access protocols with the highest potential throughput. However, several issues remain open today in the modeling and design of this type of protocol, particularly in terms of dynamic stable performance and backlog delay. This paper attempts to partially fill this gap by proposing a Markov model for the study of the dynamic-stable performance of a symmetrical and non-blind NDMA protocol assisted by a multiple-antenna receiver. The model is useful in the study of stability aspects in terms of the backlog-user distribution and average backlog delay. It also allows for the investigation of the different states of the system and the transition probabilities between them. Unlike previous works, the proposed approach considers the imperfect estimation of the collision multiplicity, which is a crucial process to the performance of NDMA. The results suggest that NDMA improves not only the throughput performance over previous solutions, but also the average number of backlogged users, the average backlog delay and, in general, the stability of random access protocols. It is also shown that when multiuser detection conditions degrade, ALOHA-type backlog retransmission becomes relevant to the stable operation of NDMA. Ramiro Samano-Robles and Atilio Gameiro Copyright © 2013 Ramiro Samano-Robles and Atilio Gameiro. All rights reserved.