Aamir Mahmood

An SVM-Based Method for Classification of External Interference in Industrial Wireless Sensor and Actuator Networks

In recent years, the adoption of industrial wireless sensor and actuator networks (IWSANs) has greatly increased. However, the time-critical performance of IWSANs is considerably affected by external sources of interference. In particular, when an IEEE 802.11 network is coexisting in the same environment, a significant drop in communication reliability is observed. This, in turn, represents one of the main challenges for a wide-scale adoption of IWSAN. Interference classification through spectrum sensing is a possible step towards interference mitigation, but the long sampling window required by many of the approaches in the literature undermines their run-time applicability in time-slotted channel hopping (TSCH)-based IWSAN. Aiming at minimizing both the sensing time and the memory footprint of the collected samples, a centralized interference classifier based on support vector machines (SVMs) is introduced in this article. The proposed mechanism, tested with sample traces collected in industrial scenarios, enables the classification of interference from IEEE 802.11 networks and microwave ovens, while ensuring high classification accuracy with a sensing duration below 300 ms. In addition, the obtained results show that the fast classification together with a contained sampling frequency ensure the suitability of the method for TSCH-based IWSAN.

Packet Error Rate Analysis of Uncoded Schemes in Block-Fading Channels Using Extreme Value Theory

We present a generic approximation of the packet error rate (PER) function of uncoded schemes in the additive white Gaussian noise channel using extreme value theory (EVT). The PER function can assume both the exponential and the Gaussian

Wireless Mediation of Multiple Equi-Priority Events in Time-Critical Industrial Applications

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Advanced Communication Solutions for Reliable Wireless Sensor Systems

-function bit error rate forms. The EVT approach leads us to a best closed-form approximation, in terms of accuracy and computational efficiency, of the average PER in block-fading channels. The numerical analysis shows that the approximation holds tight for any value of signal-to-noise ratio (SNR) and packet length whereas the earlier studies approximate the average PER only at asymptotic SNRs and packet lengths.

Cross-layer optimization of wireless links under reliability and energy constraints

Wireless technologies are nowadays being considered for implementation in industrial automation. However due to strict reliability and timeliness requirements of time-critical applications, there are many open research challenges for the merger of wireless technologies with the industrial systems. Although many medium access and control (MAC) protocols are proposed in recent years, a coherent effort on both the physical (PHY) and MAC layers is needed. In this paper, we propose a protocol termed as multiple equi-priority MAC (MEP-MAC) which combines the functions of MAC and PHY layers: the MAC layer ensures a deterministic behavior of the system by assigning priorities to the nodes, while non-orthogonal multiple access (NOMA) at PHY layer enables multiple nodes of equal priorities to simultaneously gain the channel access and transmit data to the gateway. We adapt a discrete-time Markov chain (DTMC) model to handle multiple nodes of equal priorities and perform the analytical analysis of the proposed protocol. The results show that the proposed protocol can provide up to 70% and 40% improvement in terms of system throughput and latency respectively as compared to a system that does not leverage NOMA at PHY layer.

Over-the-Air Time Synchronization for URLLC: Requirements, Challenges and Possible Enablers

State-of-the-art Wireless Sensor Network (WSN) technology enables design and implementation of novel, intriguing applications that can be used to address numerous industrial, environmental, societal and economical challenges and thus, the importance and potential of WSNs are constantly growing. Wireless sensor nodes constituting a WSN consist of a sensor interface, microcontroller, memory and battery units together with a radio module. Hence, wireless sensor nodes are able to carry out distributed sensing and data processing, and to share the collected data using radio communications. In the beginning the development of wireless sensors was driven by military applications but the introduction of civilian wireless sensor systems has greatly diversified application domain which has further boosted research efforts in the field of wireless sensor networks. Present state of the evolution of wireless sensor nodes allows utilization of smart sensors to enhance the performance and robustness of WSNs.