Showing papers presented at "IFIP Wireless Days in 2019"

A Case for Good Defaults: Pitfalls in VANET Physical Layer Simulations

Abstract: Network simulations are often the first choice to design, test, and evaluate novel applications and protocols for vehicular networks. Aiming for higher realism, simulators become increasingly complex, relying on detailed simulation models that are developed by different communities. With this trend, it also becomes difficult to understand all models in detail and researchers might lack the expert knowledge to parameterize such models properly. In this paper, we identify suboptimal default parameter values for physical layer effects in common simulation frameworks and show how they can negatively impact the results. We also review papers that use said simulation models and highlight that this is not simply a theoretical issue: We found that the majority of the papers simply copy these default parameter values or do not mention physical layer parameters at all. Both cases are clearly problematic. We thus argue that we should focus on reasonable default parameter values just as much as on the functional correctness of simulation models.

Performance Evaluation of Channel Access Methods for Dedicated IoT Networks

Abstract: Networking technologies dedicated for the Internet of Things are different from the classical mobile networks in terms of architecture and applications. This new type of network is facing several challenges to satisfy specific user requirements. Sharing the communication medium between (hundreds of) thousands of connected nodes and one base station is one of these main requirements, hence the necessity to imagine new solutions, or to adapt existing ones, for medium access control. In this paper, we start by comparing two classical medium access control protocols, CSMA/CA and Aloha, in the context of Internet of Things dedicated networks. We continue by evaluating a specific adaptation of Aloha, already used in low-power wide area networks, where no acknowledgement messages are transmitted in the network. Finally, we apply the same concept to CSMA/CA, showing that this can bring a number of benefits. The results we obtain after a thorough simulation study show that the choice of the best protocol depends on many parameters (number of connected objects, traffic arrival rate, allowed retransmission number), as well as on the metric of interest (e.g. packet reception probability or energy consumption).