Critical Machine-to-Machine Communcations

For a couple years, there is more and more interest in low-latency, ultra-reliable wireless networks. This interest is triggered by new, anticipated application domains of such networks, most importantly in the areas of industrial automation, car-to-x communications, as well as new consumer electronics gadgets like virtual reality glasses. If we require latencies in the range of 1 ms or below, from a theoretical as well as from a practical perspective many new research questions arrise. Over the last five years, I have been working in this area, focusing on aspects such as cooperative schemes for low-latency systems, corresponding MAC protocols, verification and validation of low-latency protocol stacks as well as experimental prototyping of corresponding systems. Among others, this activity has lead to the design and experimental prototyping of the EchoRing system.

Currently, I am focusing most on:

  • Theoretical modeling of low-latency systems via finite block-length capacity models
  • Wireless /wired low-latency communication paths with in-network processing
  • Centralized network architectures for sub-millisecond ultra-reliable wireless networking
  • Abstractions of control systems for cross-layer optimization in low-latency systems

Resource Allocation for Wireless (Cellular) Networks

Since I started research in wireless networking, I have been interested in resource allocation problems. Over the last ten years, I have been working on subcarrier assignment in cellular and wireless local area networks, reduction of associated signaling overhead from dynamic scheduling, spectrum sharing of secondary systems in cognitive radio networks, as well as user association and load balancing for local area networks.

Currently, I am focusing on two topics with respect to resource allocation:

  • Interference coordination schemes for 4G networks
  • Resource allocation schemes for dense outdoor deployments of 5G networks.

Stochastic Network Calculus

Link-layer performance evaluation of wireless systems is typically best done if it considers also queuing effects. There are several ways how to do this, among which network calculus is a fairly powerful one (but arguably also a quite involved one). Over the last ten years, stochastic network calculus has been developed where the cumulative arrival and service processes of a queuing system are captured for example by the moment-generating function or by the Mellin transform. Today, we are in a good position to extend these results to specific service processes encountered in wireless systems. Apart from this, a second approach to this modeling is associated to the effective service capacity model.

Currently, I am most interested in stochastic network calculus models for:

  • Interference-limited communication systems
  • Wireless communication under the finite block-length regime
  • Secrecy channels

Parallel Wireless Network Simulations

Network simulation is still one of the most intensely used methods for performance evaluation of communication systems and networks. Especially in the case of wireless systems, we are witnessing a constantly increasing complexity with respect to the lower layers, that needs to be taken into account for accurate evaluation results. However, simulation cores of well-known engines typically come only with a limited capability to parallelize corresponding simulation models. This triggered me to look into various new methods for speeding up (wireless) network simulation, among them we considered simulation architectures like HORIZON, distributed HORIZON or most recently PSimLa which is a modeling approach (coupled with a simulation engine) to exploit data independencies of a simulation model.