In mobile communications, simultaneous transmissions of several devices may lead to interference causing some transmissions to fail and sent information to be lost. Due to the ever-increasing density of mobile devices and base stations, managing interference becomes more and more important.
Some technologies try to avoid interference completely by using reserved channels for each communication. The mature GSM is a typical example for this approach. Today’s WLANs reserve a “transmission floor” around a communicating pair of devices to avoid interference as far as possible and employ retransmission protocols in case packets are nevertheless lost. In other technologies, interference will basically be allowed but then be mitigated at the receiver with help of modern signal processing techniques and multiple antenna systems.
The performance of all these techniques is influenced by the dynamic behavior of interference. “Immediate retransmission of unreceived data makes no sense if interference persists over time,” explains Christian Bettstetter, and continues: “A transmission is more likely to succeed under changed interference conditions.”
The Klagenfurt group made an original contribution to wireless communications that greatly enhances our understanding of interference.
A project team led by Bettstetter aims at gaining a deep understanding of interference dynamics over time and space and to rigorously analyze its impact on system performance. A key challenge is to express the correlation of interference in terms of mathematical equations. Postdoctoral researcher Udo Schilcher explains: “Accurate mathematical models form the basis for good research in this field. A branch of mathematics called stochastic geometry apparently suits our needs very well.”
Using expressions for interference correlation, the team intends to advance interference mitigation techniques and test them in a real-world setup with programmable mobile devices. The scientists’ ultimate goal, however, is to predict interference into the future. “Being successful in such prediction could revolutionize the way wireless networks are designed,” Schilcher adds.
This basic research was awarded a funding contract from the Austrian Science Fund FWF and has been performed in the project “Dynamics of Interference in Wireless Networks” since 2012. The team collaborates with Stavros Toumpis (Athens) and Martin Haenggi (Notre Dame).
U. Schilcher, S. Toumpis, M. Haenggi, A. Crismani, G. Brandner, and C. Bettstetter. Interference functionals in Poisson networks. IEEE Transactions on Information Theory, 2016.
A. Crismani, S. Toumpis, U. Schilcher, G. Brandner, and C. Bettstetter. Cooperative relaying under spatially and temporally correlated interference. IEEE Transactions on Vehicular Technology, 2015.
U. Schilcher, C. Bettstetter, and G. Brandner. Temporal correlation of interference in wireless networks with Rayleigh block fading. IEEE Transactions on Mobile Computing, 2012.