Martin Jacobsson

A cellular-centric service architecture for machine-to-machine (M2M) communications

A machine-to-machine (M2M) communications system is a large-scale network with diverse applications and a massive number of interconnected heterogeneous machines (e.g., sensors, vending machines and vehicles). Cellular wireless technologies will be a potential candidate for providing the last mile M2M connectivity. Thus, the Third Generation Partnership Project (3GPP) and IEEE 802.16p, have both specified an overall cellular M2M reference architecture. The European Telecommunications Standards Institute (ETSI), in contrast, has defined a service- oriented M2M architecture. This article reviews and compares the three architectures. As a result, the 3GPP and 802.16p M2M architectures, which are functionally equivalent, complement the ETSI one. Therefore, we propose to combine the ETSI and 3GPP architectures, yielding a cellular-centric M2M service architecture. Our proposed architecture advocates the use of M2M relay nodes as a data concentrator. The M2M relay implements a tunnel-based aggregation scheme which coalesces data from several machines destined to the same tunnel exit-point. The aggregation scheme is also employed at the M2M gateway and the cellular base station. Numerical results show a significant reduction in protocol overheads as compared to not using aggregation at the expense of packet delay. However, the delay rapidly decreases with increasing machine density.

Estimating Packet Delivery Ratio for Arbitrary Packet Sizes Over Wireless Links

Real life measurements show that on a given wireless link, the packet delivery ratio of different packet lengths varies with longer packets experiencing lower delivery ratios. In this letter, we measure this effect in detail over several different wireless links and technologies. Our results show that the current models are not entirely correct. Hence, we propose a simple modification that rectifies this behavior. Using this new model, we look at how link quality estimation methods can be enhanced to include this modification. Our study shows that the use of two different packet lengths or simple compensation can be used to achieve significantly better estimation of link quality.

ProFuN TG: A tool for programming and managing performance-aware sensor network applications

Sensor network macroprogramming methodologies such as the Abstract Task Graph hold the promise of enabling high-level sensor network application development. However, progress in this area is hampered by the scarcity of tools, and also because of insufficient focus on developing tool support for programming applications aware of performance requirements. We present ProFuN TG (Task Graph), a tool for designing sensor network applications using task graphs. ProFuN TG provides automated task mapping, sensor node firmware macrocompilation, application simulation, deployment, and runtime maintenance capabilities. It allows users to incorporate performance requirements in the applications, expressed through constraints on task-to-task dataflows. The tool includes middleware that uses an efficient flooding-based protocol to set up tasks in the network, and also enables runtime assurance by keeping track of the constraint conditions. We show that the adaptive task reallocation enabled by our approach can significantly increase application reliability while decreasing energy consumption: in a network with unreliable links, we achieve above 99.89 % task-to-task PDR while keeping the maximal radio duty cycle around 2.0 %.

Investigating interference between LoRa and IEEE 802.15.4g networks

The rapid growth of new radio technologies for Smart City/Building/Home applications means that models of cross-technology interference are needed to inform the development of higher layer protocols and applications. We systematically investigate interference interactions between LoRa and IEEE 802.15.4g networks. Our results show that LoRa can obtain high packet reception rates, even in presence of strong IEEE 802.15.4g interference. IEEE 802.15.4g is also shown to have some resilience to LoRa interference. Both effects are highly dependent on the LoRa radios spreading factor and bandwidth configuration, as well as on the channelization. The results are shown to arise from the interaction between the two radios modulation schemes. The data have implications for the design and analysis of protocols for both radio technologies.

Enabling Design of Performance-Controlled Sensor Network Applications through Task Allocation and Reallocation

Task Graph (ATaG) is a sensor network application development paradigm where the application is visually described by a graph where the nodes correspond to application-level tasks and edges correspond to data flows. We extend ATaG with the option to add non-functional requirements: constraints on end-to-end delay and packet delivery rate. Setting up these constraints at the design phase naturally leads to enabling run-time assurance at the deployment phase, when the conditions of the constraints are used as networks performance goals. We provide both run-time middleware that checks the conditions of these constraints and a central management unit that dynamically adapts the system by doing task reallocation and putting task copies on redundant nodes. Through extensive simulations we show that the system is efficient enough to enable adaptations within tens of seconds even in large networks.

Comparing wireless flooding protocols using trace-based simulations

Most wireless multi-hop networks, such as ad hoc networks and wireless sensor networks, need network-wide broadcasting, which is best done with a flooding protocol. In this article, we use packet trace information from a real test-bed network to define a simulator for flooding protocol performance studies. Five protocols are compared using the simulator. Trace-based simulations promise to have the benefits of the simulator, such as reducing required work effort and repeatability but still produce results close to the real test-bed or deployment. We propose and evaluate different approaches on how to use collected trace data and how to tune the parameters to achieve the best possible accuracy in comparison with actual test-bed measurements. We study the resulting accuracy of the model so that performance studies know with what confidence a certain conclusion can be made. Using the new trace-based model and knowing its accuracy, we compare the five flooding protocols to gain additional insights into their performance. Finally, by modifying the trace data, we study how real-world effects, such as links with in-between qualities and asymmetric links, influence the different flooding protocols.

Measuring PHY layer interactions between LoRa and IEEE 802.15.4g networks

Advances in low power wireless communication have resulted in new radio technologies that can achieve long distance communication in energy efficient ways. An emerging problem in this scenario is interference between networks that share the same medium. The fact that these networks have a long transmission range increases the possibility of interference even more. Thus the investigation of how different networks can share the medium independently in a optimal way becomes an essential requirement for the IoT vision. In this poster, we present the first step of this investigation, which is measuring how LoRa and IEEE 802.15.4g PHY layers interfere.