Michael Methfessel

Vertical optimization of data transmission for mobile wireless terminals

A major problem for TCP connections over wireless links is that errors introduced by the wireless channel interfere with the TCP protocol, leading to reduced data rates and power wastage. Based on accurate simulations for the TCP and IEEE 802.11 MAC protocols, we discuss recipes to optimize transmission. It is argued that the best approach is to restrict modifications to the mobile device. While this requires separate solutions for the uplink and downlink, the results of optimization are then available when roaming into any WLAN obeying the relevant MAC protocol. Simulation results show that the combination of specific strategies with a vertical interaction between the protocol layers can lead to the required improvements, giving a promising approach to enhance the performance of wireless mobile terminals.

Bluetooth Scatternet Tree Formation for Wireless Sensor Networks

A method for information exchange between Bluetooth nodes, the method comprising the Bluetooth nodes, without establishing a new Bluetooth connection in accordance with a Bluetooth standard, repeatedly requesting, receiving and accumulating state information from different neighbor nodes in their respective neighborhood of Bluetooth nodes by means of inquiry and extended inquiry response messages, the state information provided in response to a request comprising a tree identifier indicative of a tree, to which the respective neighbor node currently belongs, a depth information element indicative of a depth of the respective neighbor node in the respective tree and a descendant information element indicative of a number of descendants managed by the respective neighbor node.

Fault-tolerant ASIC Design for High System Dependability

Fault-tolerant devices are becoming more and more important in safety-critical applications. In addition, because of further decreased geometries, integrated circuits are becoming more susceptible to induced interference. This paper presents new methods and design concepts to make application specific integrated circuit (ASIC) devices fault-tolerant to effects generated in the harsh automotive environment, especially to single event effects (SEEs). We describe how to mitigate single event effects which can immediately affect the function of electronic components. ASICs provided with this technique will increase the reliability and dependability while simultaneously maintaining the full real-time behaviour of the system.

ParSec: A PSSS approach to industrial radio with very low and very flexible cycle timing

Industry 4.0 is a subject of current relevance which targets detailed information acquisition from industrial production processes. Wireless communication to ease this acquisition process is highly interesting but suffers today from problems of low reliability, high latency and small flexibility. ParSec addresses these subjects by investigating an innovative, CDMA based approach with very low latency of <; 50 μs, flexible resource block scheduling and BER of ≤ 10-9. While the latency figure is completely based on the assumption that a minimum of 3 symbol durations are needed the BER comes from the requirement specification. Two forms of FEC are used to achieve this requested figure. The radio will be used in the frequency range from 5,725 to 5,875 GHz and work without listen before talk. A rapid prototype has been built to conduct channel measurements and prove the promised properties of the PSSS255 approach. The project is conducted in the framework of other “Industrial Radio” oriented projects supported by the German federal ministry of education and research (BMBF).

Real-Life Deployment of Bluetooth Scatternets for Wireless Sensor Networks

Bluetooth scatternets are constructed from overlapping piconets, allowing any number of nodes to be connected into a multi-hop wireless network. Although the topic has been researched for 15 years, no deployments of self-organized scatternets have been published. Recently we have presented the SFX algorithm, which was implemented on commercial Bluetooth nodes and is an extension of SHAPER from 2003. Here measurements are presented for scatternet trees for a laboratory network of 24 nodes and for deployment in a photovoltaic power plant with 39 nodes. The results demonstrate the effectiveness of the SFX algorithm, which is evidently the only actually implemented scatternet contruction procedure which is distributed and does not assume full node-to-node visibility.

Shielding TCP from Wireless Link Errors: Retransmission Effort and Fragmentation

A known problem for TCP connections over wireless links is that errors in the wireless channel interfere with the TCP protocol even for minor packet loss. In the first part of this paper we evaluate how the data rate reduction depends on the channel delay. For comparatively short delays in the order of 100 ms, the decrease of the throughout is noticeable but not dramatic. This indicates that the problem is not severe if the communication partners are located in the same WLAN or interact over a fast Internet connection. A significant throughput reduction arises in the case of a large network delay. Simulation results for the uplink transmission are presented as part of an overall strategy in which all improvements are made by optimizing the mobile end device only, an approach which allows performance improvements without any protocol modifications.

An encryption-enabled network protocol accelerator

Even in light-weight wireless computing applications, processing of network-protocols becomes more and more computation- and energy-hungry, with increasing data rated and the need for security operations. To cope with such requirements and as alternative to heavyweight computation systems we propose an embedded system that is build for fast network-processing while supporting acceleration of state-of-the-art symmetric (AES) and asymmetric (ECC) cryptographic operations. We demonstrate how to build a dedicated TCP accelerating system based on a profiling analysis. We also discuss optimized implementations of the AES and ECC cryptographic protocols while considering the trade-off between software and hardware. Compared to an initial software-only implementation our final system accelerates the protocol handling by a factor of three, while the cryptographic operations are improved by two orders of magnitude. Our system which was manufactured in 0.25µm CMOS technology needs about 55 mW for a data rate of 40 MBit/sec.