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Tailoring Pairwise Non-Orthogonal Multiple Access to the Requirements of Critical Cyber-Physical Systems
Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. (Data Communication)ORCID iD: 0000-0001-8109-1685
2021 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Within the context of Industry 4.0, many devices have become more intelligent and connected, leading to challenges on how to meet the stringent requirements on latency and reliability in networks of critical cyber-physical systems. In particular, timely channel access and high reliability are of essence to guarantee real-time deadlines. To this end, time-division multiple-access (TDMA) schemes are often used in industrial applications to get contention-free access to the channel. Using pairwise non-orthogonal multiple access (NOMA) on top of such an existing TDMA scheme has recently emerged as a promising solution. With pairwise NOMA, two nodes are served simultaneously using the same time-frequency resources but with different power levels. To separate the signals, successive interference cancellation is used at the receiver. In addition, by adjusting the power allocation, pairwise NOMA can easily switch to TDMA by assigning zero power to one user, if and when needed. Due to this flexibility, pairwise NOMA can be integrated into existing wireless networks and schedulers with improved performance as a result. In particular, if pairwise NOMA could be tailored to the requirements of systems of collaborating cyber-physical systems, it would be possible to enhance performance in terms of latency and reliability, while still providing timely channel access to critical users using TDMA. This is the scope of the thesis work.

In order to evaluate the communication reliability for each user in the system as well as for the overall system, the individual outage probability (IOP) and the overall outage probability (OOP) are of essence, but have so far not been available for pairwise NOMA used on top of TDMA. In this thesis work, closed-form expressions for the IOP and the OOP of both uplink and downlink NOMA are derived – also in the presence of a mobile smart jammer. Using these performance metrics, insightful guidelines on the impact of some key parameters on the communication reliability such as power allocation, decoding order, node placements and so on are provided. It should be noted that the conclusions on node placement can be used for smart user pairing, but also for placement of access points (AP) or even mobile APs, using a UAV. Moreover, by formulating a non-cooperative game between a malicious smart mobile jammer and a friendly mobile AP serving two friendly sensor nodes simultaneously, Nash equilibrium points are obtained to reduce power consumption for the AP, while satisfying the communication reliability requirements. Using the derived expressions for OOP and IOP to select proper settings for pairwise NOMA, it is shown that NOMA can be tailored to ensure user fairness, provide timely channel access and high reliability, which is useful for enhancing performance of critical cyber-physical systems even in the presence of jamming.

Place, publisher, year, edition, pages
Västerås: Mälardalen university , 2021.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 314
National Category
Engineering and Technology Computer Systems
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-56282ISBN: 978-91-7485-531-9 (print)OAI: oai:DiVA.org:mdh-56282DiVA, id: diva2:1605580
Presentation
2021-11-26, Delta (and virtually), Mälardalens högskola, Västerås, 09:30 (English)
Opponent
Supervisors
Available from: 2021-10-26 Created: 2021-10-25 Last updated: 2021-11-05Bibliographically approved
List of papers
1. Reliability and Fairness for CANT Communication Based on Non-Orthogonal Multiple Access
Open this publication in new window or tab >>Reliability and Fairness for CANT Communication Based on Non-Orthogonal Multiple Access
2019 (English)In: 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS), IEEE , 2019Conference paper, Published paper (Refereed)
Abstract [en]

Recently, communication using unmanned aerial vehicles (LAVO as relay nodes has been considered beneficial for a number of applications. Moreover, nomorthogonM multiple access (NONIA) with users being assigned different signal passer levels while sharing the same tune-frequency domain has been found effective to enhance spectrum utilization and provide predictable access to the channel. Thus, in this paper we consider an UAV communication system with NOMA and propose a solution to find the optimal values for the user's power allocation coefficients (PA(s) needed to achieve the required levels of communication reliability. We present a closed-form expression for the PAC of each user and also propose an algori for finding the optimal altitude of the UAV required to satisfy the fairness condition for all users. Finally, we provide numerical mutinies and compare the results tar three types of communication environments.

Place, publisher, year, edition, pages
IEEE, 2019
Series
IEEE International Conference on Communications Workshops, ISSN 2164-7038
National Category
Telecommunications Communication Systems Signal Processing
Identifiers
urn:nbn:se:mdh:diva-45313 (URN)000484917800207 ()978-1-7281-2373-8 (ISBN)
Conference
IEEE International Conference on Communications (ICC), MAY 20-24, 2019, Shanghai, PEOPLES R CHINA
Available from: 2019-09-26 Created: 2019-09-26 Last updated: 2024-05-03Bibliographically approved
2. Defeating Jamming Using Outage Performance Aware Joint Power Allocation and Access Point Placement in Uplink Pairwise NOMA
Open this publication in new window or tab >>Defeating Jamming Using Outage Performance Aware Joint Power Allocation and Access Point Placement in Uplink Pairwise NOMA
2021 (English)In: IEEE Open Journal of the Communications Society, E-ISSN 2644-125X, Vol. 2, p. 1957-1979Article in journal (Refereed) Published
Abstract [en]

In this paper, an uplink pairwise Non-Orthogonal Multiple Access (NOMA) scenario using a mobile access point (AP) or an unmanned aerial vehicle in the presence of a jamming attack is considered. To mitigate the influence of the jamming attack, a joint power allocation and AP placement design is proposed. Accordingly, closed-form expressions of the overall outage probability (OOP) and the individual outage probability (TOP) considering imperfect channel state information for each of the source nodes the AP serves, are derived over Nakagami-m fading channels using dynamic decoding order and fixed pairwise power allocation. We conduct an investigation of the effect of different parameters such as power allocation, source node placements, AP placement, target rates, and jammer location on the OOP and the IOP performance. By adapting the power allocation and the AP placement to the jamming attack, the communication reliability can be increased significantly compared to neglecting the presence of the jammer or treating the jammer as noise. Since the malicious jammer and the AP have conflicting interests in terms of communication reliability, we formulate a non-cooperative game for the two players considering their positions and the power allocation of the NOMA nodes as their strategies and the OOP as utility function. We propose using hybrid simulated annealing - greedy algorithms to address the joint power allocation and AP placement problem for the cases of both a fixed and a mobile jammer. Finally, the Nash equilibrium points are obtained and then the UAV goes directly to this position and keeps staying there to save power consumption.

National Category
Telecommunications
Identifiers
urn:nbn:se:mdh:diva-55890 (URN)10.1109/OJCOMS.2021.3103540 (DOI)000692134000002 ()2-s2.0-85127267538 (Scopus ID)
Available from: 2021-09-16 Created: 2021-09-16 Last updated: 2024-01-23Bibliographically approved
3. Outage Performance of Pairwise NOMA Allowing a Dynamic Decoding Order and Optimal Pairs of Power Levels
Open this publication in new window or tab >>Outage Performance of Pairwise NOMA Allowing a Dynamic Decoding Order and Optimal Pairs of Power Levels
2020 (English)In: IEEE Open Journal of the Communications Society, E-ISSN 2644-125X, Vol. 1, p. 1886-1906Article in journal (Refereed) Published
Abstract [en]

In this article, we evaluate the overall outage probability (OOP) of pairwise Non-orthogonal Multiple Access (NOMA) for both uplink and downlink. We also propose a dynamic decoding order (DDO) together with a fixed pairwise power allocation (FPPA) scheme, in which the optimal decoding order is decided based on the instantaneous channel gains, and thereafter, a pair of power levels is assigned in accordance with the selected decoding order. Exact closed-form expressions of the OOPs for both uplink and downlink pairwise NOMA considering all proposed decoding orders over Nakagami- m fading are derived. Further, we find the optimal fixed power levels for different power allocation strategies so that the OOPs are minimized. Moreover, we investigate the influence of the distances between the source nodes and the access point (AP), the target transfer rates and the path-loss exponents on the OOPs for all cases of decoding orders. In addition, we benchmark our proposed DDO against other decoding orders in terms of the OOP. The results show that assigning optimal fixed power levels which takes the instantaneous decoding order into account not only improves the communication reliability, but also reduces the complexity and computational load at the AP.

Place, publisher, year, edition, pages
Sweden: IEEE OJCOMS, 2020
Keywords
Overall outage probability, pairwise NOMA, dynamic decoding order, optimal power allocation, uplink/downlink NOMA
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-53953 (URN)10.1109/OJCOMS.2020.3039536 (DOI)000723372400126 ()2-s2.0-85119495170 (Scopus ID)
Projects
Future factories in the CloudFORA - Fog Computing for Robotics and Industrial Automation
Available from: 2021-04-22 Created: 2021-04-22 Last updated: 2023-09-06Bibliographically approved

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