Fast Adaptive S-ALOHA Scheme for Event-driven Machine-to-Machine Communications

Machine-to-Machine (M2M) communication is now playing a market-changing role in a wide range of business world. However, in event-driven M2M communications, a large number of devices activate within a short period of time, which in turn causes high radio congestions and severe access delay. To address this issue, we propose a Fast Adaptive S-ALOHA (FASA) scheme for M2M communication systems with bursty traffic. The statistics of consecutive idle and collision slots, rather than the observation in a single slot, are used in FASA to accelerate the tracking process of network status. Furthermore, the fast convergence property of FASA is guaranteed by using drift analysis. Simulation results demonstrate that the proposed FASA scheme achieves near-optimal performance in reducing access delay, which outperforms that of traditional additive schemes such as PB-ALOHA. Moreover, compared to multiplicative schemes, FASA shows its robustness even under heavy traffic load in addition to better delay performance.Comment: 5 pages, 3 figures, accepted to IEEE VTC2012-Fal

Integración de redes de sensores en las nuevas generaciones de sistemas de comunicaciones móviles 4G y 5G

El concepto actual de Internet de las Cosas (Internet of Things, IoT) y la tendencia hacia la utilización masiva de redes basadas en sensores plantea la duda de cómo va a ser posible transportar la información proveniente de dichas redes de una forma factible y eficiente. Una opción prometedora es la utilización de la red móvil celular existente (LTE/LTE-A). La realidad es que esta última no puede soportar una inclusión masiva de nodos sin afectar a los usuarios. Actualmente hay una gran actividad de investigación y estandarización tanto para adaptar las próximas versiones de las tecnologías actuales, como en la definición de la próxima generación de sistemas móviles, 5G, en la que resolver esta problemática resulta un punto clave. En las redes móviles actuales, la limitación viene más por un problema de saturación de los canales de señalización que de capacidad de la red. En el presente trabajo investigamos los aspectos de señalización del estándar de comunicaciones Long Term Evolution (LTE) para su posible uso conjunto con la red de sensores en versiones futuras y en la próxima generación. Creemos que una red de sensores con un gran número de nodos, que requiera poco uso de datos, puede interferir con los usuarios. Esto es debido a que pueden colapsar los canales de control y, por lo tanto, provocar un retraso general para todos los terminales de la red. Encontramos que efectivamente se produce este problema en el canal PUCCH, que es el principal canal de control del enlace ascendente. En este canal se asigna un recurso a cada terminal para peticiones de transmisión, por lo que al aumentar el número de terminales, el retraso aumenta proporcionalmente. Después de analizar diferentes investigaciones realizadas sobre la integración de sensores en LTE y comunicaciones tipo máquina, proponemos un modelo basado en una de ellas. Se trata de un modelo del canal de acceso aleatorio (RACH), donde los sensores realicen sus peticiones de transmisión en ese canal en vez de en el PUCCH. Sobre dicho modelo proponemos diversas modificaciones para mejorar el rendimiento y conseguir que no afecte a los usuarios que usen ese canal, como por ejemplo, la separación de los recursos del canal de acceso aleatorio (RACH) entre usuarios y sensores. Finalmente comprobamos que el modelo cumple con los objetivos mediante una simulación de tiempo discreto. Explicamos la estructura de la simulación detalladamente y verificamos los resultados mediante gráficas.The actual concept of Internet of Things (IoT) and the trend towards the massive use of sensor based networks bring up the question of how it will be possible to transport the information from these networks in a feasible and efficient way. A promising choice is using the current mobile cellular network (LTE/LTE-A). But the reality is that it can’t support a massive inclusion of nodes without affecting the users. There is currently a very active research and standardization for both adapting the next versions of the current technologies and defining the next generation of mobile systems, 5G, in which solve this problem is a key factor. In the existing mobile networks, the limitation is more a saturation problem of the signalling channels than network’s capacity. In this project we investigate the signalling aspects of 3GPP Long Term Evolution (LTE) for its possible use with the sensor network in future versions and next generation. We believe that a sensor network with a large number of nodes with low data traffic can interfere with the users due to saturation of the control channels, and, therefore, causing a general delay in all the terminals of the network. We found that, indeed, this problem occurred in the PUCCH channel, which is the main uplink control channel. In this channel it is assigned a resource to each terminal for transmission requests, hence when the number of terminals is increased, the delay increases on a proportional way. Afterwards, we make an overview about the different investigations realized concerning the sensors integration on LTE and machine type communications. Then, we propose a model based on one of them. It is random access channel (RACH) model, where the sensors use that channel to perform transmission requests instead of the PUCCH. We propose some modifications to improve the performance and to attain that it does not affect the users using that channel, like, for example, a division of the random access channel (RACH) resources between users and sensors. Finally, we prove, with a discrete time simulation, that the model fulfil the objectives. We explain the simulation structure in detail and we verify the results using graphics.Ingeniería de Sistemas de Comunicacione

Modelling of a Hybrid MAC Protocol for M2M Communications

Machine-to-machine (M2M) communications is one of the enabling technologies for connecting massive number of devices to the Internet of Things (IoT). M2M communications have different characteristics than human-to-human (H2H) communications. In this work, we propose a scalable, hybrid MAC protocol that will satisfy user quality-of-service (QoS) requirements. We model both periodic and nonperiodic traffic. The proposed MAC protocol organizes transmissions into superframes consisting of a number of frames. A machine is assumed to generate a one or zero packet per its period. The machines have been divided into several types according to their packet generation probabilities. The generated packets are classified into different traffic classes according to their tolerance to packet losses and served by a subframe. Further, each subframe is divided into two sub-periods one serving contention and the other reserved traffic of that traffic class. We formulated an optimization problem that minimizes frame length subject to QoS user requirements. Then, we derived packet loss probability for each class as well as total packet loss probability for the optimization. Formulation resulted in a nonlinear optimization problem, but numerical results show that an LP approximation provides a nearly optimal solution. The work also considered the proposed protocol under user mobility. The packet arrival process under user mobility has been derived. Then the performance of the protocol has been evaluated with the contention service under this arrival process. The contention service with and without packet losses have been considered. A priority queueing mechanism also has been studied for M2M communication. The results of this thesis may be useful in the design of M2M communication system