Application of the DQCA protocol to the optimization of wireless communications systems in cellular environments

This final career thesis (Master thesis) is a contribution on the enhancement of wireless communications, specifically WLAN multi-cell systems based on the IEEE 802.11 standard. The objectives were to propose and study different Cross-Layer AP selection mechanisms that include single, dual and multiple metric based criteria using PHY-MAC interactions. These mechanisms are designed in order to improve system efficiency through the increase of the utilization of the available transmission resources. The key idea of these mechanisms is to make use of certain PHY and MAC parameters, other than the traditional RSSI measurements, in order to optimize the association to the best AP, specially focusing on the innovative use of MAC level state metrics. In this regard, of special interest is the inclusion of MAC level AP traffic load estimations within these association decisions. All the proposals are based on the use of a high-performance MAC protocol called DQCA (Distributed Queueing Collision Avoidance), which is specially fitted to include the proposed techniques. Computer simulations have been carried out to evaluate and quantify the benefits of the proposed mechanisms and techniques in representative scenarios. Moreover, a completely new handoff procedure has been designed for the DQCA muti-cell operation. This handoff process allows implementing each of the proposed AP selection mechanisms. Furthermore, the interaction between a Cross-Layer scheduling technique at the MAC level and two proposed AP selection mechanisms has also been studied. The performance of these techniques has also been assessed by means of computer simulations. The analysis of the obtained results show that the proposed mechanisms perform differently under the considered scenarios. However, the main conclusion that can be drawn is that AP selection mechanisms that are based on joint multiple metrics considerations (SNR, AP load, delay, etc.) perform significantly better than those that use only single or dual metric based mechanisms. After the study, we can conclude that the proposed techniques and mechanisms provide significant efficiency enhancements for DQCA-based WLAN multi-cell systems so that all of them may be taken into account in future wireless networks

Cross-layer design and optimization of medium access control protocols for wlans

This thesis provides a contribution to the field of Medium Access Control (MAC) layer protocol design for wireless networks by proposing and evaluating mechanisms that enhance different aspects of the network performance. These enhancements are achieved through the exchange of information between different layers of the traditional protocol stack, a concept known as Cross-Layer (CL) design. The main thesis contributions are divided into two parts. The first part of the thesis introduces a novel MAC layer protocol named Distributed Queuing Collision Avoidance (DQCA). DQCA behaves as a reservation scheme that ensures collision-free data transmissions at the majority of the time and switches automatically to an Aloha-like random access mechanism when the traffic load is low. DQCA can be enriched by more advanced scheduling algorithms based on a CL dialogue between the MAC and other protocol layers, to provide higher throughput and Quality of Service (QoS) guarantees. The second part of the thesis explores a different challenge in MAC layer design, related to the ability of multiple antenna systems to offer point-to-multipoint communications. Some modifications to the recently approved IEEE 802.11n standard are proposed in order to handle simultaneous multiuser downlink transmissions. A number of multiuser MAC schemes that handle channel access and scheduling issues and provide mechanisms for feedback acquisition have been presented and evaluated. The obtained performance enhancements have been demonstrated with the help of both theoretical analysis and simulation obtained results

General Model for Infrastructure Multi-channel Wireless LANs

In this paper we develop an integrated model for request mechanism and data transmission in multi-channel wireless local area networks. We calculated the performance parameters for single and multi-channel wireless networks when the channel is noisy. The proposed model is general it can be applied to different wireless networks such as IEEE802.11x, IEEE802.16, CDMA operated networks and Hiperlan\2.Comment: 11 Pages, IJCN

Application of the DQCA protocol to the optimization of wireless communications systems in cellular environments

This final career thesis (Master thesis) is a contribution on the enhancement of wireless communications, specifically WLAN multi-cell systems based on the IEEE 802.11 standard. The objectives were to propose and study different Cross-Layer AP selection mechanisms that include single, dual and multiple metric based criteria using PHY-MAC interactions. These mechanisms are designed in order to improve system efficiency through the increase of the utilization of the available transmission resources. The key idea of these mechanisms is to make use of certain PHY and MAC parameters, other than the traditional RSSI measurements, in order to optimize the association to the best AP, specially focusing on the innovative use of MAC level state metrics. In this regard, of special interest is the inclusion of MAC level AP traffic load estimations within these association decisions. All the proposals are based on the use of a high-performance MAC protocol called DQCA (Distributed Queueing Collision Avoidance), which is specially fitted to include the proposed techniques. Computer simulations have been carried out to evaluate and quantify the benefits of the proposed mechanisms and techniques in representative scenarios. Moreover, a completely new handoff procedure has been designed for the DQCA muti-cell operation. This handoff process allows implementing each of the proposed AP selection mechanisms. Furthermore, the interaction between a Cross-Layer scheduling technique at the MAC level and two proposed AP selection mechanisms has also been studied. The performance of these techniques has also been assessed by means of computer simulations. The analysis of the obtained results show that the proposed mechanisms perform differently under the considered scenarios. However, the main conclusion that can be drawn is that AP selection mechanisms that are based on joint multiple metrics considerations (SNR, AP load, delay, etc.) perform significantly better than those that use only single or dual metric based mechanisms. After the study, we can conclude that the proposed techniques and mechanisms provide significant efficiency enhancements for DQCA-based WLAN multi-cell systems so that all of them may be taken into account in future wireless networks

Análisis de técnicas de acceso al medio avanzadas basadas en colas distribuidas y mecanismos Cross-Layer para sistemas de comunicaciones inalámbricas

En este proyecto se partirá de los resultados previos realizados sobre el rendimientos de protocolos de la familia DQ* como DQCA o DQMAN para sistemas de comunicaciones inalámbricas. Estos protocolos se basan en colas distribuidas y permiten incluir de forma sencilla mecanismos Cross-Layer que mejoran sustancialmente las comunicaciones en términos de throughput, retardo y jitter de los paquetes. Se pretende analizar a partir de simulaciones el rendimiento de algunas mejoras propuestas recientemente sobre los protocolos, así como su comportamiento en entornos multicelulares (con múltiples AP o nodos móviles).El uso de las redes inalámbricas 802.11 está en continua expansión en la actualidad. Este hecho provoca que cada vez se requiera un mayor control para garantizar una cierta calidad de servicio (QoS) en diferentes aplicaciones, especialmente las que trabajan en tiempo real. Un primer objetivo de este trabajo ha sido estudiar el comportamiento de un sistema WLAN haciendo uso de la variación MS de un protocolo MAC de alta eficiencia llamado DQCA (Distributed Queueing Collision Avoidance), dando soporte a cuatro clases de servicio, diferenciando y priorizando cada servicio. Este escenario ha requerido realizar la adaptación del funcionamiento del protocolo para dar soporte a la situación multi-servicio. Otro objetivo era poder estudiar el sistema haciendo uso de la capa física del estándar 802.11g partiendo de la base de los estudios ya realizados a partir de la capa física de 802.11b. Una vez realizado el primer paso y obtenido un sistema DQCA multiservicio (MS systems) con cuatro clases de servicios de diferente prioridad, se han propuesto y estudiado dos técnicas basadas en el diseño Cross-Layer, con el fin de mejorar la eficiencia y el aprovechamiento de los recursos disponibles en redes WLAN. La idea fundamental del diseño Croos- Layer consiste en permitir un intercambio de información entre las capas del modelo OSI que forman el sistema de comunicaciones. En el presente trabajo se han propuesto técnicas Cross-Layer que utilizan la información proveniente de la capa física en la capa MAC, adaptando las transmisiones según el estado del canal radio. El estudio del rendimiento de las diferentes técnicas se han llevado a cabo con simulaciones por ordenador, que han permitido evaluar y cuantificar las mejoras que las técnicas propuestas ofrecen en distintos escenarios significativos. El análisis de los resultados obtenidos ha permitido concluir que las técnicas propuestas ofrecen mejoras significativas en los distintos escenarios de trabajo considerados, especialmente en términos de throughput y retardo medio. Sus principales virtudes son la sencillez de implementación y los buenos resultados que ofrecen en cuanto al aprovechamiento de los recursos del sistema. Tras el estudio realizado concluimos que las técnicas propuestas permiten mejorar la eficiencia de sistemas WLAN de forma significativa y por tanto se trata de propuestas interesantes a tener en cuenta en el diseño de futuras redes inalámbricas

A New MAC Approach in Wireless Body Sensor Networks for Health Care

Postprint (published version

LPDQ: a self-scheduled TDMA MAC protocol for one-hop dynamic lowpower wireless networks

Current Medium Access Control (MAC) protocols for data collection scenarios with a large number of nodes that generate bursty traffic are based on Low-Power Listening (LPL) for network synchronization and Frame Slotted ALOHA (FSA) as the channel access mechanism. However, FSA has an efficiency bounded to 36.8% due to contention effects, which reduces packet throughput and increases energy consumption. In this paper, we target such scenarios by presenting Low-Power Distributed Queuing (LPDQ), a highly efficient and low-power MAC protocol. LPDQ is able to self-schedule data transmissions, acting as a FSA MAC under light traffic and seamlessly converging to a Time Division Multiple Access (TDMA) MAC under congestion. The paper presents the design principles and the implementation details of LPDQ using low-power commercial radio transceivers. Experiments demonstrate an efficiency close to 99% that is independent of the number of nodes and is fair in terms of resource allocation.Peer ReviewedPostprint (author’s final draft

Towards Massive Machine Type Communications in Ultra-Dense Cellular IoT Networks: Current Issues and Machine Learning-Assisted Solutions

The ever-increasing number of resource-constrained Machine-Type Communication (MTC) devices is leading to the critical challenge of fulfilling diverse communication requirements in dynamic and ultra-dense wireless environments. Among different application scenarios that the upcoming 5G and beyond cellular networks are expected to support, such as eMBB, mMTC and URLLC, mMTC brings the unique technical challenge of supporting a huge number of MTC devices, which is the main focus of this paper. The related challenges include QoS provisioning, handling highly dynamic and sporadic MTC traffic, huge signalling overhead and Radio Access Network (RAN) congestion. In this regard, this paper aims to identify and analyze the involved technical issues, to review recent advances, to highlight potential solutions and to propose new research directions. First, starting with an overview of mMTC features and QoS provisioning issues, we present the key enablers for mMTC in cellular networks. Along with the highlights on the inefficiency of the legacy Random Access (RA) procedure in the mMTC scenario, we then present the key features and channel access mechanisms in the emerging cellular IoT standards, namely, LTE-M and NB-IoT. Subsequently, we present a framework for the performance analysis of transmission scheduling with the QoS support along with the issues involved in short data packet transmission. Next, we provide a detailed overview of the existing and emerging solutions towards addressing RAN congestion problem, and then identify potential advantages, challenges and use cases for the applications of emerging Machine Learning (ML) techniques in ultra-dense cellular networks. Out of several ML techniques, we focus on the application of low-complexity Q-learning approach in the mMTC scenarios. Finally, we discuss some open research challenges and promising future research directions.Comment: 37 pages, 8 figures, 7 tables, submitted for a possible future publication in IEEE Communications Surveys and Tutorial