Evaluación y optimización del consumo de recursos en VoWIFI

La tecnología de voz sobre protocolo de internet o VoIP ha sufrido un gran desarrollo durante los últimos años y por ello se ha convertido en un objeto de estudio; especialmente en las cuestiones relacionadas con la calidad de servicio ofrecida. Originalmente los teléfonos empleados eran dispositivos cableados, pero debido al desarrollo de las tecnologías inalámbricas, la voz sobre IP en redes inalámbricas ha tomado un peso importante. La utilización de un medio inalámbrico implica una serie de restricciones derivadas del empleo de un medio físico común y saturado, y de terminales con baterías. El objetivo de este documento es el desarrollo de un estudio de los mecanismos de calidad de servicio y ahorro de energía empleados en redes inalámbricas y la realización de pruebas que permitan valorar el funcionamiento de los mismos.VoIP technology has experimented a great development during the last years and as a result it has become an object of study; especially on issues related to quality of service. Originally, telephones were wired devices, but due to the development of wireless technologies, voice over IP over wireless networks has taken an important weight. The use of a wireless medium involves a number of restrictions arising from the use of a common and saturated physical medium, and non-wired terminals. The purpose of this paper is the development of a study of the mechanisms of quality of service and power saving used in wireless networks, and to test this mechanisms.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

Design and Analysis of Medium Access Control Protocols for Broadband Wireless Networks

The next-generation wireless networks are expected to integrate diverse network architectures and various wireless access technologies to provide a robust solution for ubiquitous broadband wireless access, such as wireless local area networks (WLANs), Ultra-Wideband (UWB), and millimeter-wave (mmWave) based wireless personal area networks (WPANs), etc. To enhance the spectral efficiency and link reliability, smart antenna systems have been proposed as a promising candidate for future broadband access networks. To effectively exploit the increased capabilities of the emerging wireless networks, the different network characteristics and the underlying physical layer features need to be considered in the medium access control (MAC) design, which plays a critical role in providing efficient and fair resource sharing among multiple users. In this thesis, we comprehensively investigate the MAC design in both single- and multi-hop broadband wireless networks, with and without infrastructure support. We first develop mathematical models to identify the performance bottlenecks and constraints in the design and operation of existing MAC. We then use a cross-layer approach to mitigate the identified bottleneck problems. Finally, by evaluating the performance of the proposed protocols with analytical models and extensive simulations, we determine the optimal protocol parameters to maximize the network performance. In specific, a generic analytical framework is developed for capacity study of an IEEE 802.11 WLAN in support of non-persistent asymmetric traffic flows. The analysis can be applied for effective admission control to guarantee the quality of service (QoS) performance of multimedia applications. As the access point (AP) becomes the bottleneck in an infrastructure based WLAN, we explore the multiple-input multiple-output (MIMO) capability in the future IEEE 802.11n WLANs and propose a MIMO-aware multi-user (MU) MAC. By exploiting the multi-user degree of freedom in a MIMO system to allow the AP to communicate with multiple users in the downlink simultaneously, the proposed MU MAC can minimize the AP-bottleneck effect and significantly improve the network capacity. Other enhanced MAC mechanisms, e.g., frame aggregation and bidirectional transmissions, are also studied. Furthermore, different from a narrowband system where simultaneous transmissions by nearby neighbors collide with each other, wideband system can support multiple concurrent transmissions if the multi-user interference can be properly managed. Taking advantage of the salient features of UWB and mmWave communications, we propose an exclusive region (ER) based MAC protocol to exploit the spatial multiplexing gain of centralized UWB and mmWave based wireless networks. Moreover, instead of studying the asymptotic capacity bounds of arbitrary networks which may be too loose to be useful in realistic networks, we derive the expected capacity or transport capacity of UWB and mmWave based networks with random topology. The analysis reveals the main factors affecting the network (transport) capacity, and how to determine the best protocol parameters to maximize the network capacity. In addition, due to limited transmission range, multi-hop relay is necessary to extend the communication coverage of UWB networks. A simple, scalable, and distributed UWB MAC protocol is crucial for efficiently utilizing the large bandwidth of UWB channels and enabling numerous new applications cost-effectively. To address this issue, we further design a distributed asynchronous ER based MAC for multi-hop UWB networks and derive the optimal ER size towards the maximum network throughput. The proposed MAC can significantly improve both network throughput and fairness performance, while the throughput and fairness are usually treated as a tradeoff in other MAC protocols

Consumo de 802.11e UAPSD en conversaciones VoIP

La tecnología VoIP es la más usada en la actualidad para ofrecer servicio de telefonía tanto en entornos empresariales como residenciales, con el fin de unificar y homogeneizar las redes. Por otro lado, las tecnologías de interconexión inalámbricas son cada vez más usadas, ya que ofrecen facilidades y comodidades a los usuarios de los dispositivos. Teniendo en cuenta lo mencionado anteriormente, cobra importancia del ahorro energético de los dispositivos para dotar a estos de mayor autonomía. En este proyecto se pretende estudiar y realizar un balance entre el la calidad de servicio de comunicaciones usando la tecnología VoIP y el ahorro energético de los dispositivos usando 802.11e UAPSD. Como resultado del estudio realizado, se puede ver la importante mejora de la calidad de las llamadas y el notable ahorro de energía que supone el uso del mecanismo UAPSD.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

A VOICE PRIORITY QUEUE (VPQ) SCHEDULER FOR VOIP OVER WLANs

The Voice over Internet Protocol (VoIP) application has observed the fastest growth in the world of telecommunication. The Wireless Local Area Network (WLAN) is the most assuring of technologies among the wireless networks, which has facilitated high-rate voice services at low cost and good flexibility. In a voice conversation, each client works as a sender and as a receiver depending on the direction of traffic flow over the network. A VoIP application requires a higher throughput, less packet loss and a higher fairness index over the network. The packets of VoIP streaming may experience drops because of the competition among the different kinds of traffic flow over the network. A VoIP application is also sensitive to delay and requires the voice packets to arrive on time from the sender to the receiver side without any delay over WLANs. The scheduling system model for VoIP traffic is still an unresolved problem. A new traffic scheduler is necessary to offer higher throughput and a higher fairness index for a VoIP application. The objectives of this thesis are to propose a new scheduler and algorithms that support the VoIP application and to evaluate, validate and verify the newly proposed scheduler and algorithms with the existing scheduling algorithms over WLANs through simulation and experimental environment. We proposed a new Voice Priority Queue (VPQ) scheduling system model and algorithms to solve scheduling issues. VPQ system model is implemented in three stages. The first stage of the model is to ensure efficiency by producing a higher throughput and fairness for VoIP packets. The second stage will be designed for bursty Virtual-VoIP Flow (Virtual-VF) while the third stage is a Switch Movement (SM) technique. Furthermore, we compared the VPQ scheduler with other well known schedulers and algorithms. We observed in our simulation and experimental environment that the VPQ provides better results for the VoIP over WLANs