Real-time Sessions Research Articles

Performance Analysis of Ad hoc Routing Protocols for Voice Communication Support over Hybrid MANETs

Multimedia real-time session services, such as voice and videoconferencing with Quality of Service support is challenging task on Mobile Ad hoc Network (MANETS). For providing multimedia services and Voice over Internet Protocol in MANET, support for Session Initiation Protocol ( SIP) is essential .The goal of QoS provisioning is to achieve a more deterministic network behaviors, so that information carried by the network can be better delivered and network resources can be better utilized. In this paper, we have analyzed various QoS parameters on different routing protocols for the voice transmission using OPNET simulator. The performance metrics comprises of QoS parameters such as packet delivery ratio, end to end delay, packet delay variation, routing overhead, throughput and jitter.

Leveraging Dynamic Spare Capacity in Wireless Systems to Conserve Mobile Terminals' Energy

In this paper, we study several ways in which mobile terminals can backoff on their uplink transmit power in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded as the degradation in user's perceived quality of service can be negligible. The challenge, however, is developing a mechanism that achieves a good tradeoff among transmit power, idling/circuit power, and the performance customers will see. We consider systems with flow-level dynamics supporting either real-time or best effort (e.g., file transfers) sessions. The energy-optimal transmission strategy for real-time sessions is determined by solving a convex optimization. An iterative approach exhibiting superlinear convergence achieves substantial amount energy savings, e.g., more than 50% when the session blocking probability is 0.1% or less. The case of file transfers is more subtle because power backoff changes the system dynamics. We study energy-efficient transmission strategies that realize energy-delay tradeoff. The proposed mechanism achieves a 35%-75% in energy savings depending on the load and file transfer target throughput. A key insight, relative to previous work focusing on <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">static</i> scenarios, is that idling power has a significant impact on energy-efficiency, while circuit power has limited impact as the load increases.

MultiDCD+Visual, an Asynchronic Visualization System for Managing the Debate of Ideas in Remote Collaboration

Globalization of architectural practices and fragmentation of knowledge are driving contemporary design studios to work within a dislocated net of partners. Consequently, the main point for successful remote collaboration is the understanding of team dynamics. During the first stages of a design activity, team members work, discuss and communicate multiple proposals in a dynamic and unclear way. Available software for teamwork assistance is focused on real time sessions, following the approach used for Product Development. However, remote collaboration in architectural design requires a specific approach supported by asynchronic collaborative visualization tools. This paper presents the Multi-dimensional Collaborative Debate Visualizer (MultiDCD+Visual), a client-server system for managing the flow of information in geographically distributed design teams. The system constructs a multi-dimensional model of the evolution of the design activity, allowing users to intuitively understand the debate of ideas.

Proportional fair scheduling algorithm in OFDMA-based wireless systems with QoS constraints

In this work we consider the problem of downlink resource allocation for proportional fairness of long term received rates of data users and quality of service for real time sessions in an OFDMA-based wireless system. The base station allocates available power and subchannels to individual users based on long term average received rates, quality of service (QoS) based rate constraints and channel conditions. We formulate and solve a joint bandwidth and power optimization problem, solving which provides a performance improvement with respect to existing resource allocation algorithms. We propose schemes for flat as well as frequency selective fading cases. Numerical evaluation results show that the proposed method provides better QoS to voice and video sessions while providing more and fair rates to data users in comparison with existing schemes.

IMS-based interactive media system and method

An interactive media system for an IP Multimedia Subsystem (IMS) architecture includes a media resource function processor (MRFP) and a media resource function controller (MRFC). The MRFP includes media resources, such as automatic speech recognition (ASR) engines and text-to-speech (TTS) engines, and a voice browser. A caller places a call to a telephone number to reach an interactive media service, and the MRFC establishes a real-time packet media session between the media gateway and the MRFP. The voice browser queries a location server to determine the location of an interactive application associated with the called telephone number and then queries an application server corresponding to the location to obtain the interactive application as a voice extensible markup language (VXML) document. The browser interprets the VXML document and responsively invokes the media resources, via the MRFC, to provide the interactive media service to the caller.

Review of Handover Mechanisms to Support Triple Play in Mobile WiMAX

Handover (HO) mechanism is one of the critical operations in mobile WiMAX. It takes place when a mobile station (MS) moves from a serving base station (BS) to another BS. However, the HO latency in mobile WiMAX is still an issue that may affect continuity of real-time application sessions such as Voice over Internet Protocol (VoIP). This paper presents performance comparison of some HO mechanisms for real-time applications in mobile WiMAX, including HO, cross-layer HO, pre-coordination HO, passport HO mechanisms and fast intra-network and cross-layer HO (FINCH). Each one of these mechanisms reduces HO latency, especially during downlink traffic; however, they still produce insufficient HO latency during uplink traffic. Except for FINCH, they do not consider the scenario of HO between BSs that belong to different access service network-gateways (ASN-GWs) or to different connectivity service networks (CSNs); these two cases cause extra layer 3 (L3) HO latency.

Interworked WiMAX-3G cellular data networks: An architecture for mobility management and performance evaluation

This paper proposes an architecture for interworking heterogeneous all-IP networks with an in-depth analysis of its performance. The novelty of this framework is that it freely enables any 3G cellular technology, such as the Universal Mobile Telecommunications System (UMTS) or the CDMA 2000 system, to interwork with a given broadband wireless access (BWA) system, such as the Worldwide interoperability for microwave access (WiMAX) network or the wireless local area network (WLAN) via a common signaling plane. As a universal coupling mediator for real-time session negotiation and management between these dissimilar networks, the IP multimedia subsystem (IMS) has been exploited. The analytical evaluation investigates the behavior of handoff delay, transient packet loss, jitter, and signaling cost during a vertical handoff for the given framework. Finally, an OPNET based simulation platform has been introduced for the verification of the analytical model and results.

Handover Control Method Using Resource Reservation in Mobile Multimedia Networks

When handover events occur during the transmission of multimedia traffic, efficient handover control procedures and radio resource allocation are necessary to maintain the same QoS of transmitted multimedia traffic because the QoS may be degraded by additional delay and information loss. In this paper we propose a new handover control method for the next generation mobile multimedia networks, in which the handover setup process is done in advance of a handover request by predicting the handover cell from mobile terminal's current position. The handover procedures for real-time sessions are performed based on the handover cell information and the resource reservation condition. The radio resources in the estimated adjacent cells should be reserved and allocated to guarantee the continuity of the real-time sessions. We conduct a simulation model that is focused on the handover failure rate and packet loss rate. The simulation results show that our proposed method provides better performance than the previous methods.

Enhancement of Handoff Speed by Improving Mobility of Data Packets

Mobility and Quality of Service(QoS) plays a vital role in the Wireless networks based on the IEEE 802.11 protocol family.When mobile systems move across heterogeneous networks, ongoing real time sessions are affected not only by handoff delay but also by jitter. With respect to this scenario, we describe the features to enhance mobility by reducing the handoff latency along with reduced packet loss across the heterogeneous networks such as WLAN and UMTS by comparing the predicted rss (received signal strength) against two thresholds calculated by the mobile terminal (MT) to make handoff decision. The packet losses can be reduced by having jitter buffer with some extra delay added. Handoff speed can be improved by having pre-handoff notification using CoA (Care of Address) maintained in each router and hence the binding updates to home agent and correspondent node are performed once Previous Access Router knows a mobile node's new CoA. By this during handoff only the node movement happens hence reducing handoff latency.

An analytical evaluation of mobility management in integrated WLAN-UMTS networks

Ensuring uninterrupted service continuity for handoff calls in an all-IP inter-networked heterogeneous environment requires successful session management among participating access networks. As such, a mobility-aware novel interworking architecture is presented in this article that facilitates session management including session establishment and seamless session handoff across different networks. This framework conveniently enables any 3G cellular technology such as the Universal Mobile Telecommunications System (UMTS) to interwork with a given Broadband Wireless Access (BWA) technology such as the Worldwide Interoperability for Microwave Access (WiMAX) network or the Wireless Local Area Network (WLAN) under a common signaling platform. This framework exploits the IP Multimedia Subsystem (IMS) as a universal coupling mediator for real-time session negotiation and management. Next, a Queuing Theory based analytical model for evaluating the performance of vertical handoff management between these interworked 3rd Generation (3G) cellular networks and the WLANs is presented. The analysis includes vertical handoff performance measures such as delay, transient packet loss, jitter, and signaling overhead/cost. The latter part of this paper presents some results from OPNET based simulations for the verification of the analytical model and results.

Interworking of WLAN-UMTS networks: an IMS-based platform for session mobility

In this article a framework for interworking between a WLAN and the UMTS is presented. The uniqueness of this architecture is that the IP multimedia subsystem proposed by the 3GPP has been used as an arbitrator for network coupling and real-time session management. Apart from the advantage of a cellular network user being able to enjoy higher levels of bandwidth over a WLAN, IMS also provides a common platform for unified session control, as well as higher levels of terminal and service mobility over a heterogeneous networking environment. The article concludes by presenting the potential of this model for service continuity during and after vertical handoff with simulation results for validation.

Approaches to resource reservation for migrating real-time sessions in future mobile wireless networks

This paper presents two novel frameworks for session admission control and resource reservation in the context of next generation mobile and cellular networks. We also devised a special scheme that avoids per-user reservation signaling overhead in order to meet scalability requirements needed for next generation multi-access networks. The first proposal, Distributed Call Admission Control with Aggregate Resource Reservation (VR), uses mobility prediction based on mobile positioning system location information and takes into account the expected bandwidth to be used by calls handing off to and from neighboring cells within a configurable estimation time window. In conjunction, a novel concept called virtual reservation has been devised to prevent per-user reservation. Our second proposal, Local Call Admission Control and Time Series-based Resource Reservation, takes into account the expected bandwidth to be used by calls handed off from neighboring cells based only on local information stored into the current cell a user is seeking admission to. To this end, we suggest the use of two time series-based models for predicting handoff load: the Trigg and Leach (TL), which is an adaptive exponential smoothing technique, and Autoregressive Integrated Moving Average (ARIMA) that uses the Box and Jenkins methodology. It is worth to emphasize that the use of bandwidth prediction based on ARIMA technique still exist for wireless networks. The novelty of our approach is to build an adaptive framework based on ARIMA technique that takes into account the measured handoff dropping probability in order to tuning the prediction time window size so increasing the prediction accuracy. The proposed schemes are compared through simulations with the fixed guard channel (GC) and other optimized dynamic reservation-based proposals present in the literature. The results show that our schemes outperform many others and that the simpler local proposal based on TL can grant nearly similar levels of handoff dropping probability as compared to those from more the complex distributed approach.

IDENTIFICATION AND MANAGEMENT OF SESSIONS GENERATED BY INSTANT MESSAGING AND PEER-TO-PEER SYSTEMS

Sessions generated by Instant Messaging and Peer-to-Peer systems (IM/P2Ps) not only consume considerable bandwidth and computing resources but also dramatically change the characteristics of data flows affecting both the operation and performance of networks. Most IM/P2Ps have known security loopholes and vulnerabilities making them an ideal platform for the dissemination of viruses, worms, and other malware. The lack of access control and weak authentication on shared resources further exacerbates the situation. Should IM/P2Ps be deployed in production environments, performance of conventional applications may significantly deteriorate and enterprise data may be contaminated. It is therefore imperative to identify, monitor and finally manage IM/P2P traffic. Unfortunately, this task cannot be easily attained as IM/P2Ps resort to advanced techniques to hide their traces including multiple channels to deliver services, port hopping, message encapsulation and encryption. In this paper, we propose an extensible framework that not only helps to identify and classify IM/P2P-generated sessions in real time but also assists in the manipulation of such traffic. Consisting of four modules namely, session manager, traffic assembler, IM/P2P dissector, and traffic arbitrator, our proposed framework uses multiple techniques to improve its traffic classification accuracy and performance. Through fine-tuned splay and interval trees that help organize IM/P2P sessions and packets in data streams, we accomplish stateful inspection, traffic re-assembly, data stream correlation, and application layer analysis that combined will boost the framework's identification precision. More importantly, we introduce IM/P2Ps "plug-and-play" protocol analyzers that inspect data streams according to their syntax and semantics; these analyzers render our framework easily extensible. Identified IM/P2P sessions can be shaped, blocked, or disconnected, and corresponding traffic can be stored for forensic analysis and threat evaluation. Experiments with our prototype show high IM/P2Ps detection accuracy rates under diverse settings and excellent overall performance in both controlled and real-world environments.

Improvement of Graduate School Education Using High Definition Video Course Material

AbstractA case study was carried out to improve the efficiency and the quality of graduate school level education which was carried out simultaneously in two separate campuses in our university. The high definition video (HDV) technique and real-time session type distance education technique were combined with the traditional teaching method of using slide type and text-based teaching materials. The selections of the bitrate and the data compression parameters in the video format conversion process were keys for producing high quality video records of lectures accessible from student’s home PC. The students could have a feeling of realistic atmosphere of lectures from the HDV contents. The students were not forced to use the course materials but the contents themselves attracted their interests. Questionnaire survey was carried out to obtain detailed information how the students used the course material. The effect of the course materials was estimated from assignments which were given to the students at the end of the semester. It was found that more than 70% of the students used the course materials on their own initiative and the average mark of the assignment was improved by 8 points out of 100 marks.

Managing Resources and Quality of Service in Heterogeneous Wireless Systems Exploiting Opportunism

We propose a novel class of opportunistic scheduling disciplines to handle mixes of real-time and best-effort traffic at a wireless access point. The objective is to support probabilistic service rate guarantees to real-time sessions while still achieving opportunistic throughput gains across users and traffic types. We are able to show a ldquotightrdquo stochastic lower bound on the service a real-time session would receive assuming that the users possibly heterogeneous capacity variations are known or estimated, and are fast fading across slots. Such bounds are critical to enabling predictable quality of service and thus the development of complementary resource management and admission control strategies. Idealized simulation results show that the scheme can achieve 80%-90% of the maximum system throughput capacity while satisfying the quality of service (QoS) requirements for real-time traffic, and that the degradation in system throughput is slow in the number of real-time users, i.e., inter- and intra-class opportunism are being properly exploited. We note however, that there is a tradeoff between strictness of QoS requirements and the overall system throughput one can achieve. Thus if QoS requirements on real-time traffic are very tight, one would need to simply give priority to real-time traffic, and in the process lose the throughput gains of opportunism.

Mobility Management for VoIP on Heterogeneous Networks: Evaluation of Adaptive Schemes

The introduction of the IP multimedia subsystem on 3G cellular networks and the integration with other widely deployed wireless networks based on the IEEE 802.11 protocol family require support for both mobility and quality of service. When mobile systems move across heterogeneous networks, ongoing real-time sessions are affected not only by handoff delay but also by different packet delay and bit rate. In this paper, we propose a cross-layer mechanism that takes into account mobility at different layers of the network stack in order to yield better quality for VoIP, videoconferencing, and other real-time applications. We describe our cross-layer architecture, adaptation techniques, a prototype implementation, and experimental results.

A novel scheme for mobility management in heterogeneous wireless networks

In this paper, we present a mobility management scheme for real-time multimedia sessions over heterogeneous wireless networks. Most approaches in the current literature use Mobile IP (MIP) or Session Initiation Protocol (SIP) to maintain real-time sessions during mobility. In this paper, we analyze MIP and SIP in terms of the mobility rate, packet loss and packet overheads in the user plane and propose a mechanism by which the network can choose the optimum protocol for mobility management. We perform the analysis for constant bit rate (CBR) as well as for variable bit rate (VBR) traffic. We show that for CBR traffic, the proposed mechanism leads to 12---35% improvement in the system capacity, while for VBR traffic, capacity improvements ranging from about 35---50% can be obtained. Our proposed approach and the analysis are applicable to handovers between different IP domains both in homogeneous as well as in heterogeneous wireless networks.

Making SIP Make Cents

The Session Initiation Protocol (SIP) is used to set up realtime sessions in IP-based networks. These sessions might be for audio, video, or IM communications, or they might be used to relay presence information. SIP service providers are mainly focused on providing a service that copies that provided by the PSTN (public switched telephone network) or the PLMN (public land mobile network) to the Internet-based environment.

Optimization of Mobile IPv6-Based Handovers to Support VoIP Services in Wireless Heterogeneous Networks

The support of voice over Internet Protocol (VoIP) services in next-generation wireless systems requires the coupling of mobility with quality of service. The mobile node can experience disruptions or even intermittent disconnections of an ongoing real-time session due to handovers. The duration of such interruptions is called disruption time or handover delay and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good-quality VoIP services. In this paper, the focus is on the network layer mobility, specifically on mobile Internet Protocols (MIPs), since they are natural candidates for providing mobility at layer 3. Using analytical models, the authors evaluate MIPv4, MIPv6, fast MIPv6 (FMIPv6), and hierarchical MIPv6 (HMIPv6) and compare their performances in terms of handover delay for VoIP services. To optimize the handover delay, the authors propose to use the adaptive retransmission timer described in this paper. The results obtained using the adaptive timer technique show that for a 3% frame error rate and a 128-kb/s channel, the handoff delay is about 0.075 s (predictive) and 0.051 s (reactive) for FMIPv6. It is around 0.047 s [intra-mobile anchor point (MAP)] and 1.47 s (inter-MAP) for HMIPv6, around 1 s for MIPv6, and 0.26 s for MIPv4

Leakage-resilient security architecture for mobile IPv6 in wireless overlay networks

The coupling of mobility and quality-of-service with security is a challenge that should be addressed in future wireless overlay systems. The mobility of a node can disrupt or even intermittently disconnect an ongoing real-time session because a secure handover must be performed to ensure continuous connectivity. The duration of the such interruptions is called disruption time or handover delay and can heavily affect the user satisfaction. The handover procedure needs to protect its integrity and confidentiality-otherwise, the packets may be rerouted to a malicious node and the legitimate handover may not be performed. The security procedure to ensure this should not lengthen significantly the handover delay to provide good quality real-time services. In this paper, we focus on the network-layer mobility, specifically, on Mobile Internet protocol version 6 (MIPv6) since it is the natural candidate for providing such mobility in future systems. To solve the problem of on-path attackers and prevent leakage of secrets, we propose a security architecture for MIPv6 based on leakage resilient-authenticated key establishment (LR-AKE) protocol and its cooperation with public key infrastructure. The proposed architecture prevents against on-path attackers which was not addressed in the specifications of MIPv6, and also provides robustness against leakage of secret values. Using analytical models, we evaluate MIPv6 handover delay for real-time services. We identify the crucial factors affecting the handover delay among transmission delays of MIPv6, security and LR-AKE messages, queueing delays and en/decryption delays.