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A wireless network with unsaturated traffic and N classes of users sharing a channel under random access is analyzed here. Necessary and sufficient conditions for the network stability are derived, along with simple closed formulas for the stationary packet transmission success probabilities and mean packet delays for all classes under stability conditions. We also show, through simple and elegant expressions, that the channel sharing mechanism in the investigated scenario can be seen as a process of partitioning a well-defined quantity into portions, each portion assigned to each user class, the size of which determined by system parameters and performance metrics of that user class. Using the derived expressions, optimization problems are then formulated and solved to minimize the mean packet delay and to maximize the channel throughput per unit of area. These results indicate that the proposed analysis is capable of assessing the trade-off involved in radio-resource management when different classes of users are considered.

Internet of Things (IoT) is pushing the Internet to the next level, bringing the number of connected devices to an unprecedented amount, creating new services and improving old services like the metering system. The advanced meter infrastructure (AMI) measures, collects and analyzes the distribution and consumption of utilities such as water, electricity, and gas, which are of vital importance for the implementation of smart cities. In this paper, we employ LoRa, which is a low power wide area network technology (LPWAN), for the communication of meter devices and network server, and we study the coexistence of two kinds of messages: regular and alarm events. Our focus is on the analysis of the alarm events, which can be characterized by emergency situations and require ultra-reliability. We investigated the feasibility of the alarms for a smart metering scenario through simulation campaigns and a mathematical model. By assigning a different spreading factor (SF) to the device depending on whether the event is regular or alarm, we assessed the system performance. We evaluate the availability, reliability, and quantity of alarms that satisfy the restricted requirements of alarms events and do not compromise the performance of regular events. The best performance for regular events at SF-7 was obtained when alarm events are allocated to SF-8, whereas the other combinations are affected for a stronger interference.

This paper analyzes the feasibility of the coexistence of telemetry and alarm messages employing Long-Range Wide-Area Network (LoRaWAN) technology in industrial environments. The regular telemetry messages come from periodic measurements from the majority of sensors while the alarm messages come from sensors whose transmissions are triggered by rarer (random) events that require highly reliable communication. To reach such a strict requirement, we propose here strategies of allocation of spreading factor, by treating alarm and regular (telemetry) messages differently. The potential of such allocation strategies has also been investigated under retransmission and diversity of gateways. Both indoor industrial plant and open-field scenarios are investigated. We compare the proposed solution with a benchmark scenario&mdash, where no alarm is considered&mdash, by using system level simulation. Our results show that it is possible to achieve high reliability with reasonably low delay for the alarm messages without significantly affecting the performance of the regular links.

Machine-to-Machine communication (M2M) or machine type communication (MTC) is the form of communication in which devices communicate with each other and with servers on the Internet without human intervention, defining the new concept known as Internet of Things (IoT). The machine type communication generates a lot of new services and, with them, big problems and challenges that must be addressed. A major challenge is to define the behavior of a new traffic generated by the devices, that is the goal of this work. We propose a traffic model for the uplink traffic, which is composed of deterministic and stochastic parts, and perform a study of throughput, delay and packet loss for this uplink traffic in a central node of the wireless sensor network.