Ismet Aktas

Wireless Communication for Factory Automation: an opportunity for LTE and 5G systems

The evolution of wireless communication from 4G toward 5G is driven by application demands and business models envisioned for 2020 and beyond. This requires network support for novel use cases in addition to classical mobile broadband services. Wireless factory automation is an application area with highly demanding communication requirements. We classify these requirements and identify the opportunities for the current LTE air interface for factory automation applications. Moreover, we give an outlook on the relevant design considerations to be addressed by 5G communication systems.

Machine learning-based jamming detection for IEEE 802.11: Design and experimental evaluation

Jamming is a well-known reliability threat for mass-market wireless networks. With the rise of safety-critical applications this is likely to become a constraining issue in the future. Thus, the design of accurate jamming detection algorithms becomes important to react to ongoing jamming attacks. With respect to experimental work, jamming detection has been mainly studied for sensor networks. However, many safety-critical applications are also likely to run over 802.11-based networks where the proposed approaches do not carry over. In this paper we present a jamming detection approach for 802.11 networks. It uses metrics that are accessible through standard device drivers and performs detection via machine learning. While it allows for stand-alone operation, it also enables cooperative detection. We experimentally show that our approach achieves remarkably high detection rates in indoor and mobile outdoor scenarios even under challenging link conditions.

Ultra-reliable and low-latency communication for wireless factory automation: From LTE to 5G

Wireless factory automation has been receiving much interest in recent years due to its advantages of low cost and high flexibility over the traditional wired networks. Factory automation is also considered as one of the important use-cases of the 5th generation (5G) cellular system. In this paper, we present comprehensive system level simulation results to evaluate the performance of LTE and new 5G radio-interface design concepts in a realistic factory deployment scenario. We believe that our detailed evaluation studies bring valuable insights to show the potential of 3GPP technologies for different factory use-cases.

An Adaptive Codec Switching Scheme for SIP-Based VoIP

Contemporary Voice-Over-IP (VoIP) systems typically negotiate only one codec for the entire VoIP session life time. However, as different codecs perform differently well under certain network conditions like delay, jitter or packet loss, this can lead to a reduction of quality if those conditions change during the call. This paper makes two core contributions: First, we compare the speech quality of a set of standard VoIP codecs given different network conditions. Second, we propose an adaptive end-to-end based codec switching scheme that fully conforms to the SIP standard. Our evaluation with a real-world prototype based on Linphone shows that our codec switching scheme adapts well to changing network conditions, improving overall speech quality.

Refector: heuristic header error recovery for error-tolerant transmissions

High bit error rates reduce the performance of wireless networks. This is exacerbated by the enforcement of bit-by-bit correct transmissions and the resulting retransmission overhead. Recently, research has focused on more efficient link layer mechanisms and on tolerating payload errors. Header errors, however, still cause todays network and transport protocols to drop the erroneous packets. Instead of retransmitting such packets, we investigate a novel concept (called Refector) of heuristically repairing header bit errors. Refector accepts erroneous packets on end hosts and exploits protocol knowledge and protocol state to assign packets to their correct destination applications. It operates on layers 3 and 4, is independent of the underlying MAC and PHY, and requires no changes to hardware, firmware, and communication behavior. We evaluate the Refector concept via a prototype implementation deployed in an 802.11 network. Our results show that Refector reduces packet loss in the network by more than 25% when compared to payload-error-tolerant protocols such as UDP-Lite.

Towards a Flexible and Versatile Cross-Layer-Coordination Architecture

In wireless and mobile networking, volatile environmental conditions are a permanent challenge, resulting in a demand for cross-layer optimizations. To further increase flexibility, we believe cross-layer architectures should adapt themselves to these changing conditions, just as they adapt the network stack, devices, and applications. In this paper, we propose CRAWLER, a novel cross-layer architecture that combines three core properties: signaling between all layers and system components; extensibility and adaptability at runtime; and high usability for cross-layer developers. CRAWLER increases flexibility, as well as expediting and simplifying cross-layer development.

CRAWLER: An experimentation platform for system monitoring and cross-layer-coordination

Applications and protocols for wireless and mobile systems have to deal with volatile environmental conditions such as interference, packet loss, and mobility. Utilizing cross-layer information from other protocols and system components such as sensors can improve their performance and responsiveness. However, application and protocol developers lack a convenient way of monitoring, experimenting and specifying optimizations to evaluate their cross-layer ideas. We present CRAWLER, a novel experimentation architecture for system monitoring and cross-layer-coordination that facilitates evaluation of applications and wireless protocols. It alleviates the problem of complicated access to relevant system information by providing a unified interface for accessing application, protocol and system information. The generic design of this interface further enables a convenient and declarative way to specify and experiment how a set of cross-layer optimizations should be composed and adapted at runtime. Our evaluation demonstrates the usability of CRAWLER by experimenting, monitoring and improving TCPs congestion control algorithm.

Modeling Application Traffic

Communication networks require a deep understanding of the source of generated traffic, i.e., the application. A multitude number of applications exist that generate different types of traffic, for example web, peer-to-peer, voice, and video traffic. Within the scope of performance analysis of protocols for communication networks, modeling and generating of such traffic is essential to achieve accurate and credible results. This requires that the most relevant aspects are captured by analyzing the traffic and subsequently properly represented in the application model.

A framework for remote automation, configuration, and monitoring of real-world experiments

The evaluation of wireless and mobile communication systems in real-world testbeds can be cumbersome and tedious. Experiments require manual intervention to coordinate the execution of involved programs and to collect test results on each involved device. Moreover, the collection of test results from protocols is difficult due to operating system restrictions. In contrast, simulation offers the ability to easily log such information and automate whole experiments. Real-testbeds should offer the same flexibility and convenience to automate whole experiments and to collect test results as in simulation. In this paper, we propose a framework that effectively addresses this challenge. Moreover, with the integration of the cross-layer architecture CRAWLER, we demonstrate that we are able to automate experiments where cross-layer optimizations are involved and while experimenting we centrally monitor and log parameters across protocol layers on different devices.

Harnessing cross-layer-design

Applications and protocols for wireless and mobile systems have to deal with volatile environmental conditions such as interference, packet loss, and mobility. Utilizing cross-layer information from other protocols and system components such as sensors can improve their performance and responsiveness. However, application and protocol developers lack a convenient way of specifying, monitoring, and experimenting with optimizations to evaluate their cross-layer ideas. We present crawler, a novel experimentation architecture for system monitoring and cross-layer-coordination that facilitates evaluation of applications and wireless protocols. It alleviates the problem of complicated access to relevant system information by providing a unified interface to application, protocol and system information. The versatile design of this interface further enables a convenient and declarative way to specify and experiment with compositions of cross-layer optimizations and their adaptions at runtime. crawler also provides the necessary support to detect cross-layer conflicts, and hence prevents performance degradation when multiple optimizations are enabled across the protocol stack. We demonstrate the usability of crawler for system monitoring and cross-layer optimizations with three use cases from different areas of wireless networking.