Local Wireless Networks
Fraunhofer Institute for Communication Systems ESK
- © Fraunhofer ESK
The utility of wireless networks has long since moved beyond the telephone and computer and into a wide range of new applications. Concrete examples are networked vehicle environments (Car-to-X Communication) and networked industrial applications such as machine-to-machine (M2M). In many cases, standard technologies cannot be directly deployed. For example, unreliable connectivity is one factor that keeps potential users from utilizing wireless technologies. On the other side of the coin, wireless networks feature characteristics such as flexibility and device mobility that make applications like Car-to-X and industrial sensor networks possible in the first place. This aspect, plus the potential cost savings that result from the reduced installation effort, make wireless systems an attractive alternative.
Wireless data transmission is subject to special physical constraints. In contrast to wired transmission technologies, wireless networks possess specific characteristics such as transmission loss, sensitivity to external emissions and multipath propagation that can cause interference. The environment, whether outdoor or indoor, determines the characteristics of the channel. When designing transmitter and receiver systems and the implementation of the protocol stacks, engineers have to take these characteristics into account.
Cognitive radio in local networks
The growth in wireless traffic necessitates more efficient utilization of the frequency spectrum. At the same time, transmissions must be made more robust by preventing collisions and interference from occurring. Fraunhofer ESK relies on cognitive radio technology to carry out research in this area. Spectrum sensing and channel prediction methods were also evaluated and implemented. Researchers utilize software defined radio (SDR) technology as the underlying platform. This research has yielded several important developments including a wireless test and measurement station for analyzing and monitoring the wireless spectrum, as well as a software component library for cognitive radio.
Wireless sensor actuator networks
In the area of sensor networks, Fraunhofer ESK focuses on reliability, energy-efficiency and realtime-capability. Using its own modular sensor network stack, the institute developed a protocol stack designed especially for applications that require a high level of energy efficiency. An additional highlight of this work is an energy-optimized MAC protocol that works in the 868 MHz and 2.4 GHz ranges. Furthermore, research into robust and scalable routing protocols, as well as sensor network middleware solutions, will be carried out.
The 5.9 GHz band is reserved for safety relevant applications in Car-to-X Communication, which is carried out in 10 MHz wide channels. Even during heavy traffic periods, the fast and reliable transmission and forwarding of safety-critical information from other networked vehicles is essential. For this reason, Fraunhofer ESK evaluates reliable and realtime-capable communication methods suitable for cooperative traffic safety applications. This includes analyzing heterogeneous wireless transmission technologies, reliable routing protocols, multihop and multichannel communication and mechanisms for controlling distributed congestion. To accelerate the development and testing of these methods, Fraunhofer ESK implemented its own Car-to-X Framework that contains the protocol stack, in addition to the basic services.