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  • 1.
    Anjum, Mahnoor
    et al.
    National University of Sciences and Technology (NUST), Pakistan.
    Khan, Muhammad Abdullah
    National University of Sciences and Technology (NUST), Pakistan.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Analysis of RSSI Fingerprinting in LoRa Networks2019In: 15th International Wireless Communications & Mobile Computing Conference, IEEE, 2019, p. 1178-1183Conference paper (Refereed)
    Abstract [en]

    Localization has gained great attention in recent years, where different technologies have been utilized to achieve high positioning accuracy. Fingerprinting is a common technique for indoor positioning using short-range radio frequency (RF) technologies such as Bluetooth Low Energy (BLE). In this paper, we investigate the suitability of LoRa (Long Range) technology to implement a positioning system using received signal strength indicator (RSSI) fingerprinting. We test in real line-of-sight (LOS) and non-LOS (NLOS) environments to determine appropriate LoRa packet specifications for an accurate RSSI-to-distance mapping function. To further improve the positioning accuracy, we consider the environmental context. Extensive experiments are conducted to examine the performance of LoRa at different spreading factors. We analyze the path loss exponent and the standard deviation of shadowing in each environment

  • 2.
    Ansari, Rafay Iqbal
    et al.
    Frederick University, Nicosia, Cyprus.
    Pervaiz, Haris
    Lancaster University, UK.
    Chrysostomou, Chrysostomos
    Frederick University, Nicosia, Cyprus.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Control-Data Separation Architecture for Dual-Band mmWave Networks: A New Dimension to Spectrum Management2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 34925-34937, article id 8663278Article in journal (Refereed)
    Abstract [en]

    The exponential growth in global mobile data traffic, especially with regards to the massive deployment of devices envisioned for the fifth generation (5G) mobile networks, has given impetus to exploring new spectrum opportunities to support the new traffic demands. The millimeter wave (mmWave) frequency band is considered as a potential candidate for alleviating the spectrum scarcity. Moreover, the concept of multi-tier networks has gained popularity, especially for dense network environments. In this article, we deviate from the conventional multi-tier networks and employ the concept of control-data separation architecture (CDSA), which comprises of a control base station (CBS) overlaying the data base station (DBS). We assume that the CBS operates on the sub-6 GHz single band, while the DBS possesses a dual-band mmWave capability, i.e., 26 GHz unlicensed band and 60 GHz licensed band. We formulate a multi-objective optimization (MOO) problem, which jointly optimizes conflicting objectives: the spectral efficiency (SE) and the energy efficiency (EE). The unique aspect of this work includes the analysis of a joint radio resource allocation algorithm based on Lagrangian Dual Decomposition (LDD) and we compare the proposed algorithm with the maximal-rate (maxRx), dynamic sub-carrier allocation (DSA) and joint power and rate adaptation (JPRA) algorithms to show the performance gains achieved by the proposed algorithm.

  • 3.
    Aslam, Muhammad Shehryar
    et al.
    National University of Sciences and Technology (NUST), Pakistan.
    Khan, Alishba
    National University of Sciences and Technology (NUST), Pakistan.
    Atif, Abeera
    National University of Sciences and Technology (NUST), Pakistan.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Qureshi, Hassaan Khaliq
    National University of Sciences and Technology (NUST), Pakistan.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Exploring Multi-Hop LoRa for Green Smart Cities2019In: IEEE Network, ISSN 0890-8044, E-ISSN 1558-156XArticle in journal (Refereed)
    Abstract [en]

    With the growing popularity of Internet-of-Things (IoT)-based smart city applications, various long-range and low-power wireless connectivity solutions are under rigorous research. LoRa is one such solution that works in the sub-GHz unlicensed spectrum and promises to provide long-range communication with minimal energy consumption. However, the conventional LoRa networks are single-hop, with the end devices connected to a central gateway through a direct link, which may be subject to large path loss and hence render low connectivity and coverage. This article motivates the use of multi-hop LoRa topologies to enable energy-efficient connectivity in smart city applications. We present a case study that experimentally evaluates and compares single-hop and multi-hop LoRa topologies in terms of range extension and energy efficiency by evaluating packet reception ratio (PRR) for various source to destination distances, spreading factors (SFs), and transmission powers. The results highlight that a multi-hop LoRa network configuration can save significant energy and enhance coverage. For instance, it is shown that to achieve a 90% PRR, a two-hop network provides 50% energy savings as compared to a single-hop network while increasing 35% coverage at a particular SF. In the end, we discuss open challenges in multi-hop LoRa deployment and optimization.

  • 4.
    Basir, Rabeea
    et al.
    School of Electrical Engineering and Computer Science, National University of Sciences and Technology, Islamabad 44000, Pakistan.
    Qaisar, Saad
    School of Electrical Engineering and Computer Science, National University of Sciences and Technology, Islamabad 44000, Pakistan.
    Ali, Mudassar
    School of Electrical Engineering and Computer Science, National University of Sciences and Technology, Islamabad 44000, Pakistan.
    Aldwairi, Monther
    College of Technological Innovation, Zayed University, Abu Dhabi 144534, UAE.
    Ashraf, Muhammad Ikram
    Centre for Wireless Communication, University of Oulu, 90014 Oulu, Finland.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Fog Computing Enabling Industrial Internet of Things: State-of-the-Art and Research Challenges2019In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, no 21, article id 4807Article in journal (Refereed)
    Abstract [en]

    Industry is going through a transformation phase, enabling automation and data exchange in manufacturing technologies and processes, and this transformation is called Industry 4.0. Industrial Internet-of-Things (IIoT) applications require real-time processing, near-by storage, ultra-low latency, reliability and high data rate, all of which can be satisfied by fog computing architecture. With smart devices expected to grow exponentially, the need for an optimized fog computing architecture and protocols is crucial. Therein, efficient, intelligent and decentralized solutions are required to ensure real-time connectivity, reliability and green communication. In this paper, we provide a comprehensive review of methods and techniques in fog computing. Our focus is on fog infrastructure and protocols in the context of IIoT applications. This article has two main research areas: In the first half, we discuss the history of industrial revolution, application areas of IIoT followed by key enabling technologies that act as building blocks for industrial transformation. In the second half, we focus on fog computing, providing solutions to critical challenges and as an enabler for IIoT application domains. Finally, open research challenges are discussed to enlighten fog computing aspects in different fields and technologies.

  • 5.
    Beltramelli, Luca
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Jennehag, Ulf
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Interference Modelling in a Multi-Cell LoRa System2018In: 2018 14th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    As the market for low-power wide-area network (LPWAN) technologies expands and the number of connected devices increases, it is becoming important to investigate the performance of LPWAN candidate technologies in dense deployment scenarios. In dense deployments, where the networks usually exhibit the traits of an interference-limited system, a detailed intra- and inter-cell interference analysis of LPWANs is required. In this paper, we model and analyze the performance of uplink communication of a LoRa link in a multi-cell LoRa system. To such end, we use mathematical tools from stochastic geometry and geometric probability to model the spatial distribution of LoRa devices. The model captures the effects of the density of LoRa cells and the allocation of quasi-orthogonal spreading factors (SF) on the success probability of the LoRa transmissions. To account for practical deployment of LoRa gateways, we model the spatial distribution of the gateways with a Poisson point process (PPP) and Matèrn hard-core point process (MHC). Using our analytical formulation, we find the uplink performance in terms of success probability and potential throughput for each of the available SF in LoRa’s physical layer. Our results show that in dense multi-cell LoRa deployment with uplink traffic, the intercell interference noticeably degrades the system performance.

  • 6.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    PR-CCA MAC: A Prioritized Random CCA MAC Protocol for Mission-Critical IoT Applications2018In: 2018 IEEE International Conference on Communications (ICC), IEEE, 2018, article id 8423018Conference paper (Refereed)
    Abstract [en]

    A fundamental challenge in Mission-Critical Internetof Things (MC-IoT) is to provide reliable and timely deliveryof the unpredictable critical traffic. In this paper, we propose an efficient prioritized Medium Access Control (MAC) protocol for Wireless Sensor Networks (WSNs) in MC-IoT control applications. The proposed protocol utilizes a random Clear Channel Assessment (CCA)-based channel access mechanism to handlethe simultaneous transmissions of critical data and to reduce thecollision probability between the contending nodes, which in turn decreases the transmission latency. We develop a Discrete-Time Markov Chain (DTMC) model to evaluate the performance of the proposed protocol analytically in terms of the expected delay and throughput. The obtained results show that the proposed protocolcan enhance the performance of the WirelessHART standard by 80% and 190% in terms of latency and throughput, respectively along with better transmission reliability.

  • 7.
    Grimaldi, Simone
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    An SVM-Based Method for Classification of External Interference in Industrial Wireless Sensor and Actuator Networks2017In: Journal of Sensor and Actuator Network, ISSN 2224-2708, Vol. 6, no 2, article id 9Article in journal (Refereed)
    Abstract [en]

    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

  • 8.
    Grimaldi, Simone
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Real-time Interference Identification via Supervised Learning: Embedding Coexistence Awareness in IoT Devices2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 835-850Article in journal (Refereed)
    Abstract [en]

    Energy sampling-based interference detection and identification (IDI) methods collide with the limitations of commercial off-the-shelf (COTS) IoT hardware. Moreover, long sensing times, complexity and inability to track concurrent interference strongly inhibit their applicability in most IoT deployments. Motivated by the increasing need for on-device IDI for wireless coexistence, we develop a lightweight and efficient method targeting interference identification already at the level of single interference bursts. Our method exploits real-time extraction of envelope and model-aided spectral features, specifically designed considering the physical properties of signals captured with COTS hardware. We adopt manifold supervised-learning (SL) classifiers ensuring suitable performance and complexity trade-off for IoT platforms with different computational capabilities. The proposed IDI method is capable of real-time identification of IEEE 802.11b/g/n, 802.15.4, 802.15.1 and Bluetooth Low Energy wireless standards, enabling isolation and extraction of standard-specific traffic statistics even in the case of heavy concurrent interference. We perform an experimental study in real environments with heterogeneous interference scenarios, showing 90%–97% burst identification accuracy. Meanwhile, the lightweight SL methods, running online on wireless sensor networks-COTS hardware, ensure sub-ms identification time and limited performance gap from machine-learning approaches.

  • 9.
    Guntupalli, Lakshmikanth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Farag, Hossam
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Priority-Oriented Packet Transmissions in Internet of Things: Modeling and Delay Analysis2018In: 2018 IEEE International Conference on Communications (ICC), IEEE, 2018, article id 8422699Conference paper (Refereed)
    Abstract [en]

    Priority-oriented packet transmission (PPT) has been a promising solution for transmitting time-critical packets in timely manner during emergency scenarios in Internet ofThings (IoT). In this paper, we develop two associated discrete time Markov chain (DTMC) models to analyze performance of the PPT in an IoT network. Using the proposed DTMC models, we investigate the effect of traffic prioritization interms of average packet delay for a synchronous medium access control (MAC) protocol. Furthermore, the results obtained from analytical models are validated via discrete-event simulations. Numerical results prove the accuracy of the models and reveal the behavior of priority based packet transmissions.

  • 10.
    Hassan, S. F.
    et al.
    Naional University of Sciences and Technology (NUST), Pakistan.
    Hassan, S. A.
    National University of Science and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Wireless Mediation for Multiple Equi-Priority Events in Time-Critical Industrial Applications2018In: SmartCitiesSecurity'18 Proceedings of the 1st ACM MobiHoc Workshop on Networking and Cybersecurity for Smart Cities, ACM Digital Library, 2018Conference paper (Refereed)
    Abstract [en]

    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.

  • 11.
    Hassan, Syed Fahad
    et al.
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Wireless Mediation for Multi-Hop Networks in Time Critical Industrial Applications2018In: 2018 IEEE Globecom Workshops (GC Wkshps) - Proceedings, IEEE conference proceedings, 2018, article id 8644340Conference paper (Refereed)
    Abstract [en]

    Industrial Internet-of-things (IIoT) networks have recently gained enormous attention because of the huge advantages they offer. A typical IIoT network consists of a large number of sensor and actuator devices distributed randomly in an industrial area to automate various processes, where a major goal is to collect data from all these devices and to process it centrally at an aggregator. However, for an efficient system operation, a proficient scheduling mechanism is required due to its direct association with performance parameters. Many existing techniques such as time division multiple access (TDMA), do not perform well in industrial environments due to their stringent timeliness requirements. In this paper, we propose a medium access control (MAC) layer protocol for node scheduling in  a scenario where some devices may not be in one-hop range of the aggregator and thus renders a multi-hop mechanism  inevitable. A discrete time Markov chain (DTMC) model is proposed to characterize the transmission of multi-tier nodes and the analytical expressions  of throughput and latency are derived. It has been oberved that the delay scales linearly with the number of nodes which are away not in one-hop distance of the aggregator. Numerical simulations have been performed to validate the theoretical results. 

  • 12.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Ashraf, Ikram
    University of Oulo and Ericsson Research, Finland.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Torsner, Johan
    Ericsson Research, Finland.
    Over-the-Air Time Synchronization for URLLC: Requirements, Challenges and Possible Enablers2018In: Proceedings of the International Symposium on Wireless Communication Systems, IEEE, 2018, article id 8491188Conference paper (Refereed)
    Abstract [en]

    Ultra-reliable and low-latency communications (URLLC) is an emerging feature in 5G and beyond wireless systems, which is introduced to support stringent latency and reliability requirements of mission-critical industrial applications. In many potential applications, multiple sensors/actuators collaborate and require isochronous operation with strict and bounded jitter, e.g., 1µs. To this end, network time synchronization becomes crucial for real-time and isochronous communication between a controller and the sensors/actuators. In this paper, we look at different applications in factory automation and smart grids to reveal the requirements of device-level time synchronization and the challenges in extending the high-granularity timing information to the devices. Also, we identify the potential over-the-air synchronization mechanisms in 5G radio interface, and discuss the needed enhancements to meet the jitter constraints of time-sensitive URLLC applications.

  • 13.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Renewal-theoretic Packet Collision Modeling under Long-tailed Heterogenous Traffic2017In: 28th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC'17), Montreal, Canada, Oct. 2017., IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Internet-of-things (IoT), with the vision of billions of connected devices, is bringing a massively heterogeneouscharacter to wireless connectivity in unlicensed bands. The heterogeneity in medium access parameters, transmit power and activity levels among the coexisting networks leads to detrimental cross-technology interference.The stochastic traffic distributions, shaped under CSMA/CA rules, of an interfering network and channel fading makes it challenging to model and analyze the performanceof an interfered network. In this paper, to study the temporal interaction between the traffic distributions of two coexisting networks, we develop a renewal-theoretic packet collision model and derive a generic collision-time distribution (CTD) function of an interfered system. The CTD function holds for any busy- and idle-time distributions of the coexisting traffic. As the earlier studies suggesta long-tailed idle-time statistics in real environments, the developed model only requires the Laplace transform of long-tailed distributions to find the CTD. Furthermore,we present a packet error rate (PER) model under the proposed CTD and multipath fading of the interfering signals. Using this model, a computationally efficient PERapproximation for interference-limited case is developed to analyze the performance of an interfered link.

  • 14.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Hossain, M. M. Aftab
    KTH Royal Institute of Technology, Sweden.
    Cavdar, Cicek
    KTH Royal Institute of Technology, Sweden.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Energy-Reliability Aware Link Optimization for Battery-Powered IoT Devices with Non-Ideal Power Amplifiers2019In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 6, no 3, p. 5058-5067, article id 8625460Article in journal (Refereed)
    Abstract [en]

    In this paper, we study cross-layer optimization of low-power wireless links for reliability-aware applications while considering both the constraints and the non-ideal characteristics of the hardware in Internet-of-things (IoT) devices. Specifically, we define an energy consumption (EC) model that captures the energy cost—of transceiver circuitry, power amplifier, packet error statistics, packet overhead, etc.—in delivering a useful data bit. We derive the EC models for an ideal and two realistic non-linear power amplifier models. To incorporate packet error statistics, we develop a simple, in the form of elementary functions, and accurate closed-form packet error rate (PER) approximation in Rayleigh block-fading. Using the EC models, we derive energy optimal yet reliability and hardware compliant conditions for limiting unconstrained optimal signal-to-noise ratio (SNR), and payload size. Together with these conditions, we develop a semi-analytic algorithm for resource-constrained IoT devices to jointly optimize parameters on physical (modulation size, SNR) and medium access control (payload size and the number of retransmissions) layers in relation to link distance. Our results show that despite reliability constraints, the common notion—higher-order M-ary modulations (MQAM) are energy optimal for short-range communication—prevails, and can provide up to 180% lifetime extension as compared to often used OQPSK modulation in IoT devices. However, the reliability constraints reduce both their range and the energy efficiency, while non-ideal traditional PA reduces the range further by 50% and diminishes the energy gains unless a better PA is used.

  • 15.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Hossain, M. M. Aftab
    KTH Royal Institute of Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Cross-Layer Optimization of Wireless Links under Reliability and Energy Constraints2018In: IEEE Wireless Communications and Networking Conference, WCNC, New York: IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    The vision of connecting billions of battery operated devices to be used for diverse emerging applications calls for a wireless communication system that can support stringent reliability and latency requirements. Both reliability and energy efficiency are critical for many of these applications that involve communication with short packets which undermine the coding gain achievable from large packets. In this paper, we study a cross-layer approach to optimize the performance of low-power wireless links. At first, we derive a simple and accurate packet error rate (PER) expression for uncoded schemes in block fading channels based on a new proposition that shows that the waterfall threshold in the PER upper bound in Nakagami-m fading channels is tightly approximated by the m-th moment of an asymptotic distribution of PER in AWGN channel. The proposed PER approximation establishes an explicit connection between the physical and link layers parameters, and the packet error rate. We exploit this connection for cross-layer design and optimization of communication links. To this end, we propose a semi-analytic framework to jointly optimize signal-to-noise ratio (SNR) and modulation order at physical layer, and the packet length and number of retransmissions at link layer with respect to distance under the prescribed delay and reliability constraints.

  • 16.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Jäntti, Riku
    Aalto University, School of Science and Technology, Department of Communications and Networking, Finland .
    Packet Error Rate Analysis of Uncoded Schemes in Block-Fading Channels using Extreme Value Theory2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 1, p. 208-211, article id 7583696Article in journal (Refereed)
    Abstract [en]

    We present a generic approximation of the packet error rate (PER) function of uncoded schemes in the AWGN channel using extreme value theory (EVT). The PER function can assume both the exponential and the Gaussian Q-function bit error rate (BER) 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 SNR and packet length whereas the earlier studies approximate the average PER only at asymptotic SNRs and packet lengths.

  • 17.
    Mahmood, Aamir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sisinni, Emiliano
    University of Brescia, Italy.
    Guntupalli, Lakshmikanth
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Rondón, Raúl
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Hassan, Syed Ali
    National University of Science and Technology (NUST), Pakistan.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Scalability Analysis of a LoRa Network under Imperfect Orthogonality2019In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 15, no 3, p. 1425-1436Article in journal (Refereed)
    Abstract [en]

    Low-power wide-area network (LPWAN) technologies are gaining momentum for internet-of-things (IoT) applications since they promise wide coverage to a massive number of battery-operated devices using grant-free medium access. LoRaWAN, with its physical (PHY) layer design and regulatory efforts, has emerged as the widely adopted LPWAN solution. By using chirp spread spectrum modulation with qausi-orthogonal spreading factors (SFs), LoRa PHY offers coverage to wide-area applications while supporting high-density of devices. However, thus far its scalability performance has been inadequately modeled and the effect of interference resulting from the imperfect orthogonality of the SFs has not been considered. In this paper, we present an analytical model of a single-cell LoRa system that accounts for the impact of interference among transmissions over the same SF (co-SF) as well as different SFs (inter-SF). By modeling the interference field as Poisson point process under duty-cycled ALOHA, we derive the signal-to-interference ratio (SIR) distributions for several interference conditions. Results show that, for a duty cycle as low as 0.33%, the network performance under co-SF interference alone is considerably optimistic as the inclusion of inter-SF interference unveils a further drop in the success probability and the coverage probability of approximately 10% and 15%, respectively for 1500 devices in a LoRa channel. Finally, we illustrate how our analysis can characterize the critical device density with respect to cell size for a given reliability target.

  • 18.
    Nikonowicz, Jakub
    et al.
    Poznań University of Technology, Poland.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sisinni, Emiliano
    University of Brescia, Italy.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Noise Power Estimators in ISM Radio Environments: Performance Comparison and Enhancement Using a Novel Samples Separation Technique2019In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 68, no 1, p. 105-115Article in journal (Refereed)
    Abstract [en]

    Noise power estimation is central to efficient radio resource allocation in modern wireless communication systems. In the literature, there exist many noise power estimation methods that can be classified based on underlying theoretical principle; the most common are spectral averaging, eigenvalues of sample covariance matrix, information theory, and statistical signal analysis. However, how these estimation methods compare against each other in terms of accuracy, stability, and complexity is not well studied, and the focus instead remains on the enhancement of individual methods. In this paper, we adopt a common simulation methodology to perform a detailed performance evaluation of the prominent estimation techniques. The basis of our comparison is the signal-to-noise ratio estimation in the simulated industrial, scientific and medical band transmission, while the reference noise signal is acquired from an industrial production plant using a software-defined radio platform, USRP-2932. In addition, we analyze the impact of different techniques for noise-samples' separation on the estimation process. As a response to defects in the existing techniques, we propose a novel noise-samples' separation algorithm based on the adaptation of rank-order filtering. Our analysis shows that the proposed solution, apart from its low complexity, has a very good root-mean-squared error of 0.5 dB and smaller than 0.1-dB resolution, thus  achieving a performance comparable with the methods exploiting information theory concepts.

  • 19.
    Rondón, Raúl
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Grimaldi, Simone
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Understanding the Performance of Bluetooth Mesh: Reliability, Delayand Scalability AnalysisManuscript (preprint) (Other academic)
  • 20.
    Shehzad, Muhammad Karam
    et al.
    National University of Sciences and Technology (NUST), Pakistan.
    Hassan, Syed Ali
    National University of Sciences and Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    On the Association of Small Cell Base Stations with UAVs using Unsupervised Learning2019In: IEEE 89th Vehicular Technology Conference, VTC2019-Spring, Institute of Electrical and Electronics Engineers (IEEE), 2019, article id 8746456Conference paper (Refereed)
    Abstract [en]

    Small cell networks (SCNs) offer a cost-effective coverage solution to wireless applications demanding high data rates. However in SCNs, a challenging problem is the proper management of backhaul links to small cell base stations(SCBSs). To make a good backhaul link, perfect line-of-sight (LoS) communication between the SCBSs and the core network plays a vital role. In this study, we use the idea of employing unmanned aerial vehicles (UAVs) to provide connectivity betweenSCBSs and the core network. We focus on the association of SCBSs with UAVs by considering multiple communication-related factors including data rate limit and available bandwidth resources of the backhaul. In particular, we address the optimum placement of UAVs to serve a maximum number of SCBSswhile considering available resources using the unsupervised k-means algorithm. Numerical results show that the proposed approach outperforms the conventional approach in terms of associatedSCBSs, bandwidth consumption, available link utilization, and sum-rate maximization.

  • 21.
    Zeb, Shah
    et al.
    National University of Sciences & Technology (NUST), Pakistan.
    Abbas, Qamar
    National University of Sciences & Technology (NUST), Pakistan.
    Hassan, Syed Ali
    National University of Sciences & Technology (NUST), Pakistan.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mumtaz, Rafia
    National University of Sciences & Technology (NUST), Pakistan.
    Zaidi, S. M. Hassan
    National University of Sciences & Technology (NUST), Pakistan.
    Zaidi, Syed Ali Raza
    The University of Leeds, Leeds, UK.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    NOMA Enhanced Backscatter Communication for Green IoT Networks2019In: 16th International Symposium on Wireless Communication Systems (ISWCS), VDE Verlag GmbH, 2019Conference paper (Refereed)
    Abstract [en]

    Backscatter communication has recently emerged as a promising technology to enable passive sensing-based Internet-of-things (IoT) applications. In a backscatter communication network, uplink transmissions of multiple nodes are usually multiplexed in time- or frequency-domain to avoid collisions, yet it is desirable to improve the uplink capacity further. In this paper, we study a wireless-powered backscatter communication system, where the sensors use a hybrid channel access scheme by combining time division multiplexing access(TDMA) with power-domain non-orthogonal multiple access(PD-NOMA) to enhance the system performance in terms of outage probability and throughput. Our analysis shows that the proposed PD-NOMA increases both the spectrum efficiency and the throughput of the system.

1 - 21 of 21
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