Abhishek Kumar

• Kumar, Abhishek; Vidal, José Ramón; Martinez-Bauset, Jorge & Li, Frank Yong (2025). Hashing and DQN Enabled Semi-Contention-Free Small Data Transmission in NOMA IoT Networks. IEEE Global Communications Conference (GLOBECOM). ISSN 2334-0983. s. 3274–3279. doi: https:/ieeexplore.ieee.org/document/11432641. Fulltekst i vitenarkiv Vis sammendrag

  Small data transmission (SDT) is a novel technique that allows IoT devices to transmit their payload data without a pre-allocated radio resource. However, unresolvable SDT collisions occur due to the unpredictability of IoT traffic. In this paper, we propose a semi-contention-free transmission scheme that combines dedicated time-slot allocation through hashing and random access with access control through a dueling deep Q-network. Focusing on uplink IoT traffic for SDT in a NOMA-enabled network with two clusters of devices, we implement the proposed scheme and demonstrate its effectiveness and performance with respect to throughput, latency, and energy consumption through extensive simulations.

• Kumar, Abhishek; Vidal, Jose Ramon; Martinez-Bauset, Jorge & Li, Frank Yong (2025). Semi-Contention-Free Access in IoT NOMA Networks: A Reinforcement Learning Framework. IEEE Transactions on Communications. ISSN 0090-6778. 73(12), s. 14413–14429. doi: 10.1109/TCOMM.2025.3615678. Fulltekst i vitenarkiv Vis sammendrag

  The unprecedented surge of massive Internet of things (mIoT) traffic in beyond fifth generation (B5G) communication systems calls for transformative approaches for multiple access and data transmission. While classical model-based tools have been proven to be powerful and precise, an imminent trend for resource management in B5G networks is promoting solutions towards data-driven design. Considering an IoT network with devices spread in clusters covered by a base station, we present in this paper a novel model-free multiple access and data transmission framework empowered by reinforcement learning, designed for power-domain non-orthogonal multiple access networks to facilitate uplink traffic of small data packets. The framework supports two access modes referred to as contention-based and semi-contention-free, with its core component being a policy gradient algorithm executed at the base station. The base station performs access control and optimal radio resource allocation by periodically broadcasting two control parameters to each cluster of devices that considerably reduce data detection failures with a minimum computation requirement on devices. Numerical results, in terms of system and cluster throughput, throughput fairness, access delay, and energy consumption, demonstrate the efficiency and scalability of the framework as network size and traffic load vary.

• Kumar, Abhishek; Martinez-Bauset, Jorge; Li, Frank Yong; Florea, Carmen & Dobre, Octavia A. (2023). Understanding Inter- and Intra-Cluster Concurrent Transmissions for IoT Uplink Traffic in MIMO-NOMA Networks: A DTMC Analysis. IEEE Internet of Things Journal. ISSN 2327-4662. 11(8), s. 14328–14343. doi: 10.1109/JIOT.2023.3341613. Fulltekst i vitenarkiv
• Kumar, Abhishek; Li, Frank Yong & Martinez-Bauset, Jorge (2023). Performance Evaluation of Cluster-based Concurrent Uplink Transmissions in MIMO-NOMA Networks, 2023 IEEE International Conference on Communications (ICC): Mobile and Wireless Networks Symposium. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781538674628. s. 1042–1047. doi: 10.1109/ICC45041.2023.10279821. Fulltekst i vitenarkiv Vis sammendrag

  To obtain benefits for non-orthogonal multiple access (NOMA) based concurrent transmissions for uplink Internet of things (IoT) traffic in multi-antenna enabled networks, device clustering has been a challenging task. Most previous studies focused on grouping devices into clusters that are served by different beams in multiple input multiple output (MIMO)-NOMA networks. In this paper, we perform an exploratory study on the impact of both intra- and inter-cluster interference on the performance of uplink concurrent transmissions considering that multiple clusters are served by a single beam. For performance assessment, we define two metrics, cluster throughput and transmission latency, and evaluate network performance with various network configurations. The study provides insight on how to configure device clusters and perform access control in order to maximize performance and improve fairness. As devices closer to the base station experience less path attenuation, we introduce distinct access control mechanisms to improve transmissions fairness for concurrent transmissions from difference clusters.

• Kumar, Abhishek; Li, Frank Yong & Martinez-Bauset, Jorge (2022). Revealing the Benefits of Rate-Splitting Multiple Access for Uplink IoT Traffic. IEEE Global Communications Conference (GLOBECOM). ISSN 2334-0983. doi: 10.1109/GLOBECOM48099.2022.10000752. Fulltekst i vitenarkiv Vis sammendrag

  To address the challenges faced by non-orthogonal multiple access (NOMA) for multiple access in beyond fifth gen-eration (B5G) networks, rate-splitting multiple access (RSMA) has newly emerged as a promising approach. In addition to achieving high data rates, RSMA may be used for massive machine-type communication (mMTC)/massive Internet of things (mIoT) applications as well. Although RSMA addresses the user coupling and scheduling overhead problems met by NOMA, it is not clear whether and how RSMA can be applied to uplink mMTC/mIoT traffic. In this study, we explore the applicability of RSMA for uplink traffic and investigate whether there is any benefit to employ RSMA and if yes how this benefit can be achieved. To this end, we propose a novel uplink RSMA scheme with two constituent components, known as inter-device decoding and intra -device decoding, respectively. Through user pairing for inter-device decoding and power allocation for intra-device decoding, we reveal under which circumstances RSMA can bring benefits for uplink traffic.

• Kumar, Abhishek & Dash, Soumya P. (2022). Optimal Multi-Level Amplitude-Shift Keying Modulation for a Reliable Channel Magnitude Detection-Based Receive Diversity Powerline Communication System. IEEE Transactions on Green Communications and Networking (ITGCN). 6(4), s. 2168–2178. doi: 10.1109/TGCN.2022.3172786. Fulltekst i vitenarkiv Vis sammendrag

  The implementation of a coherent powerline communication (PLC) receiver increases its hardware complexity and energy consumption, which can be tackled by a non-coherent receiver. However, this reduces the reliability of the PLC systems. To meet this trade-off, a novel energy-efficient receiver structure is proposed in this study that exploits the knowledge of the channel magnitude of a receive diversity PLC system. The transmitter employs multi-level amplitude-shift keying (ASK) modulation for data transmission via the PLC channels subjected to Rayleigh multipath phenomenon and corrupted by additive Nakagami-m background noise, which would lead to a superior performance as compared to other modulation schemes owing to the channel magnitude-based proposed receiver. Utilizing the receiver structure, closed-form expression for symbol error probability (SEP) and its asymptotic expression at a high average signal-to-noise ratio (SNR) are derived using a characteristic function approach. Furthermore, to achieve the simultaneous design of an energy-efficient modulation scheme and a reliable PLC system, optimal ASK signaling levels are obtained with a constraint on the total available energy at the transmitter end. The analytical relation of the derived optimal multi-level ASK constellation with the traditional ASK constellation is obtained at high SNR values. The proposed channel magnitude-based receiver is found to achieve full diversity order and numerical results presented provide various insights towards the design of the energy-efficient PLC system.

• Afshar, Mehran; Patel, Hitendra R.H.; Jain, Ankit; Kumar, Abhishek; Patel, Prashant & James, Nicholas D. [Vis alle 7 forfattere av denne artikkelen] (2019). Chronic tyrosine kinase inhibitor (TKI) use in metastatic renal cell carcinoma (mRCC): can this lead to the adverse effect of hypogonadism? Expert Review of Anticancer Therapy. ISSN 1473-7140. 19(6), s. 529–532. doi: 10.1080/14737140.2019.1609355. Fulltekst i vitenarkiv
• Ananthanarayanan, Divya; Wong, Johnson; Ho, Jian Wei; Kumar, Abhishek; Lee, Rainer & Haug, Halvard [Vis alle 7 forfattere av denne artikkelen] (2018). Evaluation of diffused phosphorus emitters using Griddler-PC1D, Proceedings of 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7) 2018. IEEE (Institute of Electrical and Electronics Engineers). ISSN 9781538685297. s. 2651–2654. doi: 10.1109/pvsc.2018.8547617. Fulltekst i vitenarkiv
• Kumar, Abhishek; Priyadarshi, Anish; Shukla, Sudhanshu; Manjappa, Manukumara; Haur, Lew Jia & Mhaisalkar, Subodh G. [Vis alle 7 forfattere av denne artikkelen] (2018). Ultrafast THz photophysics of solvent engineered triple-cation halide perovskites. Journal of Applied Physics. ISSN 0021-8979. 124:215106(21), s. 1–5. doi: 10.1063/1.5051561. Fulltekst i vitenarkiv

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• Kumar, Abhishek; Martinez-Bauset, Jorge & Li, Frank Yong (2024). Dynamic Medium Access in Clustered NOMA IoT Networks based on Reinforcement Learning. IEEE (Institute of Electrical and Electronics Engineers). ISBN 9798350362244. doi: 10.1109/PIMRC59610.2024.10817308. Fulltekst i vitenarkiv

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• Kumar, Abhishek (2026). Enabling Uplink Medium Access and Transmission in IoT Networks using Rate-Splitting, Clustered MIMO-NOMA, Markov Modeling, and Reinforcement Learning. Universitetet i Agder. ISSN 9788284273204. Fulltekst i vitenarkiv Vis sammendrag

  Den eksplosive populariteten til tingenes internett (IoT) presenterer nye utfordringer for å designe effektive mekanismer for medieaksess, samt dataoverføring av opplinktrafikk (dvs. datatrafikk som blir sendt fra IoT enheter mot en basestasjon) i neste generasjons mobile og trådløse nettverk. Denne avhandlingen leverer en omfattende studie av avanserte medieaksess- og dataoverføringsstrategier for opplinktrafikk, med vekt på klyngebasert ikke-ortogonal multippelaksess (NOMA), samt analytisk modellering og modellfrie tilnærminger. Arbeidet begynner med å skissere multippeltilgangsstrategier for IoT-opplink – inkludert rate-splitting multiple aksess (RSMA) som en alternativ tilnærming – før det går videre til kjernebidragene som fokuserer på klyngede multippel-inputmultippel- output (MIMO)-NOMA-nettverk. Gjennom grundig ytelsesevaluering kvantifiserer avhandlingen virkningen av enhetsklynging, tilgangsordninger og samtidige overføringer på flere parametere, inkludert gjennomstrømning, forsinkelse og energiforbruk. En betydelig del av avhandlingen er viet til utviklingen av analytiske modeller ved bruk av diskret-tids Markov-kjede (DTMC). Dette muliggjør en dyptgående forståelse av interferens innen og mellom klynger på overføringskollisjon og datadeteksjon, tilgangsforsinkelse og ressursallokering under realistiske, feilutsatte kanalforhold for suksessiv interferenskansellering (SIC)-basert datadeteksjon. Dette arbeidet gir innsikt i utformingen av mer adaptive og robuste aksessprotokoller. Bygget på disse grunnlagene utforsker avhandlingen forsterkningslærings (RL)- drevet tilgangskontroll og dataoverføring, som gir basestasjoner (BS) mulighet til dynamisk optimalisere tilgangssannsynligheter og radioressursallokering i sanntid. Den RL-aktiverte tilnærmingen forenkles til semi-konfliktfrie protokoller for NOMAbasert opplink massiv IoT (mIoT)-trafikk, hvor maskinlæring (ML) fremstår som et kraftig verktøy for å utnytte effektiv konfliktløsning og optimal radioressursallokering i nettverk med høy tetthet under ulike trafikkbelastningsforhold. I den siste delen foreslås avanserte mekanismer som kombinerer hashing og dypt Q-nettverk (DQN) for skalerbar, lav-latens, semi-konfliktfri smådataoverføring, og utforsker en annen løsning for dataoverføring i realistiske mIoT-scenarier. Gjennom dyptgående analyser og omfattende simuleringer viser denne avhandlingen at integreringen av klynging og NOMA, optimal radioressursallokering og intelligent tilgangskontroll gir betydelige gevinster i gjennomstrømning, forsinkelse og rettferdighet sammenlignet med konvensjonelle mekanismer. Rammeverket og skjemaene som er utviklet i denne avhandlingen fremmer de nyeste teknikkene innenfor temaet medieaksess og dataoverføring for mIoT og gir innsiktsfulle innspill for neste generasjons IoT-nettverksdesign.

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