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The evolution of cellular networks from its first generation (1G) to its fourth generation (4G) was driven by the demand of user-centric downlink capacity also technically called Mobile Broad-Band (MBB). With its fifth generation (5G), Machine Type Communication (MTC) has been added into the target use cases and the upcoming generation of cellular networks is expected to support them. However, such support requires improvements in the existing technologies in terms of latency, reliability, energy efficiency, data rate, scalability, and capacity.
Originally, MTC was designed for low-bandwidth high-latency applications such as, environmental sensing, smart dustbin, etc. Nowadays there is an additional demand around applications with low-latency requirements. Among other well-known challenges for recent cellular networks such as data rate energy efficiency, reliability etc., latency is also not suitable for mission-critical applications such as real-time control of machines, autonomous driving, tactile Internet etc. Therefore, in the currently deployed cellular networks, there is a necessity to reduce the latency and increase the reliability offered by the networks to support use cases such as, cooperative autonomous driving or factory automation, that are grouped under the denomination Ultra-Reliable Low-Latency Communication (URLLC).
This thesis is primarily concerned with the latency into the Universal Terrestrial Radio Access Network (UTRAN) of cellular networks. The overall work is divided into five parts. The first part presents the state of the art for cellular networks. The second part contains a detailed overview of URLLC use cases and the requirements that must be fulfilled by the cellular networks to support them. The work in this thesis is done as part of a collaboration project between IRIMAS lab in Université de Haute-Alsace, France and Institute for Reliable Embedded Systems and Communication Electronics (ivESK) in Offenburg University of Applied Sciences, Germany. The selected use cases of URLLC are part of the research interests of both partner institutes. The third part presents a detailed study and evaluation of user- and control-plane latency mechanisms in current generation of cellular networks. The evaluation and analysis of these latencies, performed with the open-source ns-3 simulator, were conducted by exploring a broad range of parameters that include among others, traffic models, channel access parameters, realistic propagation models, and a broad set of cellular network protocol stack parameters. These simulations were performed with low-power, low-cost, and wide-range devices, commonly called IoT devices, and standardized for cellular networks. These devices use either LTE-M or Narrowband-IoT (NB-IoT) technologies that are designed for connected things. They differ mainly by the provided bandwidth and other additional characteristics such as coding scheme, device complexity, and so on.
The fourth part of this thesis shows a study, an implementation, and an evaluation of latency reduction techniques that target the different layers of the currently used Long Term Evolution (LTE) network protocol stack. These techniques based on Transmission Time Interval (TTI) reduction and Semi-Persistent Scheduling (SPS) methods are implemented into the ns-3 simulator and are evaluated through realistic simulations performed for a variety of low-latency use cases focused on industry automation and vehicular networking. For testing the proposed latency reduction techniques in cellular networks, since ns-3 does not support NB-IoT in its current release, an NB-IoT extension for LTE module was developed. This makes it possible to explore deployment limitations and issues.
In the last part of this thesis, a flexible deployment framework called Hybrid Scheduling and Flexible TTI for the proposed latency reduction techniques is presented, implemented and evaluated through realistic simulations. With help of the simulation evaluation, it is shown that the improved LTE network proposed and implemented in the simulator can support low-latency applications with low cost, higher range, and narrow bandwidth devices. The work in this thesis points out the potential improvement techniques, their deployment issues and paves the way towards the support for URLLC applications with upcoming cellular networks.
The status quo of PROFINET, a commonly used industrial Ethernet standard, provides no inherent security in its communication protocols. In this thesis an approach for protecting real-time PROFINET RTC messages against spoofing, tampering and optionally information disclosure is specified and implemented into a real-world prototype setup. Therefor authenticated encryption is used, which relies on symmetric cipher schemes. In addition a procedure to update the used symmetric encryption key in a bumpless manner, e.g. without interrupting the real-time communication, is introduced and realized.
The concept for protecting the PROFINET RTC messages was developed in collaboration with a task group within the security working group of PROFINET International. The author of this thesis has also been part of that task group. This thesis contributes by proofing the practicability of the concept in a real-world prototype setup, which consists of three FPGA-based development boards that communicate with each other to showcase bumpless key updates.
To enable a bumpless key update without disturbing the deterministic real-time traffic by dedicated messages, the key update annunciation and status is embedded into the header. By provisioning two key slots, of which only one is in used, while the other is being prepared, a well-synchronized coordinated switch between the receiver and the sender performs the key update.
The developed prototype setup allows to test the concept and builds the foundation for further research and implementation activities, e.g. the impact of cryptographic operations onto the processing time.
Die Vision vom "Internet der Dinge" prägt seit Jahren Forschung und Entwicklung, wenn es um smarte Technologien und die Vernetzung von Geräten geht. In der Zukunft wird die reale Welt zunehmend mit dem Internet verknüpft, wodurch zahlreiche Gegenstände (Dinge) des normalen Alltags dazu befähigt werden, zu interagieren und sowohl online als auch autark zu kommunizieren. Viele Branchen wie Medizin, Automobilbau, Energieversorgung und Unterhaltungselektronik sind gleichermaßen betroffen, wodurch trotz Risiken auch neues wirtschaftliches Potential entsteht. Im Bereich "Connected Home" sind bereits Lösungen vorhanden, mittels intelligenter Vernetzung von Haushaltsgeräten und Sensoren, die Lebensqualität in den eigenen vier Wänden zu erhöhen. Diese Arbeit beschäftigt sich mit dem Thread Protokoll; einer neuen Technologie zur Integration mehrerer Kommunikationsschnittstellen innerhalb eines Netzwerks. Darüber hinaus wird die Implementierung auf Netzwerkebene (Network Layer) vorgestellt, sowie aufbereitete Informationen bezüglich verwendeter Technologien dargestellt.