Performance Evaluation of VoIP in Mobile WiMAX; Simulation and Emulation studies

Worldwide Interoperability for Microwave Access (WiMAX) is an acronym for IEEE 802.16 family which is a leading contemporary broadband wireless Access (BWA) technology. IEEE 802.16e is intended for mobile WiMAX, which supports vehicular mobility with the stringent quality of service (QoS) parameters for various data traffics. Voice over IP (VoIP) provides low cost, modern telephony which can become a better alternative for classical telephony; however there are some issues need to be addressed prior to the deployment of any new technology. Significance of simulation study results can be verified and assessed by emulation testbed results. It is expected that both the results should match closely with each other. This paper makes an effort to study the performance evaluation of VoIP for a mobile user and how the QoS parameters vary for different speeds. The simulation and emulation of a mobile WiMAX system using EXata 2.0.1 are performed. The effectiveness of the comparison of results is discussed

Novel Method of Improving Quality of Service for Voice over Internet Protocol Traffic in Mobile Ad Hoc Networks

In recent years, the application of Mobile Ad-hoc Network (MANET) with Voice over Internet Protocol (VoIP) has been increased.  However, the level of Quality of Service (QoS) for VoIP traffic in MANET, while there is no infrastructure, will reduce when dealing with a large number of calls. In this type of dynamic environment, the developing of a new infrastructure becomes more costly and time-consuming. In this paper, we proposed an efficient method, called the Quality of Service-Nearest Neighbor (QoS-NN), to improve the QoS level for VoIP in order to manage the huge number of calls over MANET network. We utilized the Ad-hoc On-demand Distance Vector (AODV) protocol as the underlying routing protocol to implement our proposed method. We evaluated the proposed QoS-NN method using Network Simulator version 2 (NS2). The performance of the proposed QoS-NN method was compared with Lexicographic order method. The comparison was evaluated in terms of R-factor, end-to-end delay, packet loss ratio, and packet delivery ratio performance metrics. In addition, the proposed method evaluated under different network parameters such as VoIP CODECs, node mobility speed, number of calls and number of nodes. The comparison results indicate that the proposed QoS-NN outperform the Lexicographic order method

IMPROVING QoS OF VoWLAN VIA CROSS-LAYER BASED ADAPTIVE APPROACH

Voice over Internet Protocol (VoIP) is a technology that allows the transmission of voice packets over Internet Protocol (IP). Recently, the integration of VoIP and Wireless Local Area Network (WLAN), and known as Voice over WLAN (VoWLAN), has become popular driven by the mobility requirements ofusers, as well as by factor of its tangible cost effectiveness. However, WLAN network architecture was primarily designed to support the transmission of data, and not for voice traffic, which makes it lack ofproviding the stringent Quality ofService (QoS) for VoIP applications. On the other hand, WLAN operates based on IEEE 802.11 standards that support Link Adaptive (LA) technique. However, LA leads to having a network with multi-rate transmissions that causes network bandwidth variation, which hence degrades the voice quality. Therefore, it is important to develop an algorithm that would be able to overcome the negative effect of the multi-rate issue on VoIP quality. Hence, the main goal ofthis research work is to develop an agent that utilizes IP protocols by applying a Cross-Layering approach to eliminate the above-mentioned negative effect. This could be expected from the interaction between Medium Access Control (MAC) layer and Application layer, where the proposed agent adapts the voice packet size at the Application layer according to the change of MAC transmission data rate to avoid network congestion from happening. The agent also monitors the quality of conversations from the periodically generated Real Time Control Protocol (RTCP) reports. If voice quality degradation is detected, then the agent performs further rate adaptation to improve the quality. The agent performance has been evaluated by carrying out an extensive series ofsimulation using OPNET Modeler. The obtained results of different performance parameters are presented, comparing the performance ofVoWLAN that used the proposed agent to that ofthe standard network without agent. The results ofall measured quality parameters hav

Improving R-Score Of Voip Streams Over Wimax

In this paper, we exploit the flexible features in the medium access control (MAC) layer of WiMax for construction and transmission of MAC protocol data units (MPDU) for supporting multiple VoIP streams over a WiMax link. Quality of VoIP calls, usually given by R-score, is studied with respect to delay and loss of packets. We observe that loss is more sensitive than delay, hence we trade delay for loss. We propose a combination of techniques that exploit the flexibility of the WiMax MAC layer to strike a balance between loss and delay. These techniques are forward error correction, automatic repeat request, MPDU aggregation, and minislot allocation. Simulation experiments are conducted to test the performance of the proposed mechanisms. We assume a three-state Markovian channel model and study the performance with and without retransmissions. We show that the feedback-based technique coupled with retransmissions, aggregation, and variable length MPDUs are effective and increases the R-score by about 40%. © 2006 IEEE

Quality of Service optimisation framework for Next Generation Networks

Within recent years, the concept of Next Generation Networks (NGN) has become widely accepted within the telecommunication area, in parallel with the migration of telecommunication networks from traditional circuit-switched technologies such as ISDN (Integrated Services Digital Network) towards packet-switched NGN. In this context, SIP (Session Initiation Protocol), originally developed for Internet use only, has emerged as the major signalling protocol for multimedia sessions in IP (Internet Protocol) based NGN. One of the traditional limitations of IP when faced with the challenges of real-time communications is the lack of quality support at the network layer. In line with NGN specification work, international standardisation bodies have defined a sophisticated QoS (Quality of Service) architecture for NGN, controlling IP transport resources and conventional IP QoS mechanisms through centralised higher layer network elements via cross-layer signalling. Being able to centrally control QoS conditions for any media session in NGN without the imperative of a cross-layer approach would result in a feasible and less complex NGN architecture. Especially the demand for additional network elements would be decreased, resulting in the reduction of system and operational costs in both, service and transport infrastructure. This thesis proposes a novel framework for QoS optimisation for media sessions in SIP-based NGN without the need for cross-layer signalling. One key contribution of the framework is the approach to identify and logically group media sessions that encounter similar QoS conditions, which is performed by applying pattern recognition and clustering techniques. Based on this novel methodology, the framework provides functions and mechanisms for comprehensive resource-saving QoS estimation, adaptation of QoS conditions, and support of Call Admission Control. The framework can be integrated with any arbitrary SIP-IP-based real-time communication infrastructure, since it does not require access to any particular QoS control or monitoring functionalities provided within the IP transport network. The proposed framework concept has been deployed and validated in a prototypical simulation environment. Simulation results show MOS (Mean Opinion Score) improvement rates between 53 and 66 percent without any active control of transport network resources. Overall, the proposed framework comes as an effective concept for central controlled QoS optimisation in NGN without the need for cross-layer signalling. As such, by either being run stand-alone or combined with conventional QoS control mechanisms, the framework provides a comprehensive basis for both the reduction of complexity and mitigation of issues coming along with QoS provision in NGN

Suporte de mobilidade em redes WIMAX

O desenvolvimento crescente da Internet, com novos serviços e aplicações que requerem elevadas exigências a nível de qualidade de serviço, como por exemplo, o VoIP e IPTV, a crescente necessidade de um utilizador estar sempre contactável em qualquer sítio e a qualquer momento, torna necessária a integração actual da Internet com as redes móveis da próxima geração. A tecnologia IEEE 802.16 surge como uma tecnologia de banda larga sem fios que pode ter um papel fundamental num ambiente de próxima geração. Devido aos seus baixos custos de instalação e à possibilidade de chegar facilmente a zonas rurais ou a zonas de difícil acesso, torna-se um sério candidato para suprir as necessidades dos utilizadores. A necessidade de mobilidade pelo utilizador, para aceder a diversos serviços em diferentes sítios ou ser identificado remotamente para a posterior recepção de informação também é um desejo futuro. O protocolo IEEE 802.21 surge como um meio que providencia a optimização de handover entre diferentes tecnologias de acesso, quer sejam elas WiFi, WiMAX, 3GGP ou 3GPP2, no sentido de proporcionar ao utilizador a utilização de diferentes serviços de uma forma transparente à tecnologia de acesso, quando em situações de mobilidade. Esta dissertação apresenta a arquitectura desenvolvida para proporcionar a correcta avaliação da atribuição de QoS e mobilidade transparente, num ambiente real de próxima geração. Serão também efectuados testes com o equipamento WiMAX disponível, no sentido de mostrar o seu correcto comportamento na atribuição de QoS fim-a-fim em cenários ponto-a-ponto e ponto-a-multiponto com serviços com características de tempo real. A integração do software da primeira fase do projecto WEIRD e o seu correcto comportamento em ambientes de atribuição de QoS também vai ser estudado. A implementação dos diferentes módulos, em especial a implementação da unidade central da arquitectura de IEEE 802.21 (MIHF), vai ser descrita, no sentido de avaliar o desempenho do WiMAX e do protocolo IEEE 802.21 numa rede real no âmbito da segunda fase do projecto WEIRD. Os resultados obtidos demonstram que a arquitectura desenvolvida consegue fornecer QoS fim-a-fim com suporte de mobilidade entre redes heterogéneas. ABSTRACT: The growing development of the Internet, with new services and applications that require a high level of quality of service, such as, VoIP and IPTV, the increasing need for a user to be always reachable anywhere and at anytime, motivates the integration of current Internet with the next generation of mobile networks. The IEEE 802.16 technology emerges as a technology for broadband wireless access that may have a key role in a next generation environment. Due to its low costs of installation and its ability to easily reach rural areas or areas with difficult access, it becomes a serious candidate to supply the needs of users. The mobility’s necessity by the user, to access to several services in different locations or be identified remotely for subsequent receipt of information, is also a future desire. The IEEE 802.21 protocol provides the optimization of handover between heterogeneous networks, such as WiFi, WiMAX, 3GGP or 3GPP2, to offer the user different services in a transparent manner to his access technology, when in situations of mobility. This Thesis presents the architecture developed to provide the correct integration of QoS and seamless mobility, in a real next generation environment. It will also present tests carries out with the available WiMAX equipment, to show its correct behaviour in the allocation of end-to-end QoS in point-to-point and point-to-multipoint scenarios with real-time services. The integration of software from the first phase of the WEIRD project and its correct behaviour in environments of QoS allocation will also be studied. The implementation of the various modules, in particular the implementation of the central unit of IEEE 802.21 architecture (MIHF), will be described, to evaluate the performance of WiMAX and IEEE 802.21 protocol in a real network provided by the second phase of the WEIRD project. The obtained results show that the developed architecture is able to provide end-toend QoS with seamless mobility support over heterogeneous networks