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Dr. Alessandro Raschella
Liverpool John Moores University
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Representative Publications
View All Publications20 October 2021 in Wireless Networks
Journal Article
As we enter a new era of next-generation wireless systems represented by Fifth Generation (5G) New Radio (NR) technology, it is essential to grasp the recent progress in their standardization and development. This article offers a concise survey of the 5G NR system design that aims at introducing its features according to the relevant Third Generation Partnership (3GPP) specifications. Our focus is set on the flexibility of 5G NR, which refers to its capability to support novel services and technologies, such as enhanced Mobile Broadband (eMBB) and Internet of Things (IoT) for massive Machine Type Communications (mMTC) while satisfying the underlying quality requirements. The key enablers of the 5G NR operation are scalable numerology, ultra-lean and beam-centric design, support for low latency, spectrum extension, and forward compatibility. This work summarizes these important features by studying the overall 5G architecture and the user-/control-plane protocol stacks specified by 3GPP. Furthermore, the impact of scalable numerology on system performance is discussed. Finally, we also consider open challenges and future research directions.
3 March 2017 in IEEE Transactions on Network and Service Management
Journal Article
ARAlessandro Raschella
Alessandro RaschellaFBFaycal Bouhafs
Faycal Bouhafs
MSMirghiasaldin Seyedebrahimi
Mirghiasaldin Seyedebrahimi
MMMichael Mackay
Michael Mackay
QSQi Shi
Qi Shi
This paper addresses the problem of access point (AP) selection in large Wi-Fi networks. Unlike current solutions that rely on received signal strength to determine the best AP that could serve a wireless user's request, we propose a novel framework that considers the quality of service (QoS) requirements of the user's data flow. The proposed framework relies on a function reflecting the suitability of a Wi-Fi AP to satisfy the QoS requirements of the data flow. The framework takes advantage of the flexibility and centralised nature of software defined networking (SDN). A performance comparison of this algorithm developed through an SDN-based simulator shows significant achievements against other state-of-the-art solutions in terms of provided QoS and improved wireless network capacity.
15 March 2019 in IEEE Transactions on Mobile Computing
Journal Article
FBFaycal Bouhafs
Faycal BouhafsMSMirghiasaldin Seyedebrahimi
Mirghiasaldin SeyedebrahimiARAlessandro Raschella
Alessandro RaschellaMMMichael Mackay
Michael MackayQSQi Shi
Qi ShiCurrent interference management solutions for dense IEEE 802.11 Wireless Local Area Networks (WLANs) rely on locally measuring the cumulative interference at the Acess Point (AP) in charge of adjusting the spectrum resources to its clients. These solutions often result in coarse-grained spectrum allocation that often leaves many wireless users unsatisfied and increases the spectrum congestion problem instead of easing it. In this paper we present a centralised interference management algorithm that treats the network-wide interference impact of each channel individually and allows the controller to adjust the radio resource of each AP while it is utilised. This coordinated allocation takes into account the Quality of Service (QoS) requirements of downlink flows while minimising its effect on neighbouring APs. Therefore, this paper proposes a novel approach for quantifying the interference impact of each employed channel and jointly addressing the user-side quality requirements and the network-side interference management. The algorithm is tailored for operator-agnostic Software-Defined Networking (SDN)-based Radio Resource Management (RRM) in dense Wireless Fidelity (Wi-Fi) networks and adopts a fine-grained per-flow approach. Simulation results show that our algorithm outperforms existing solutions in terms of reducing the overall interference, increasing the capacity of the wireless channel and improving the users' satisfaction.
1 March 2017
Conference Paper
MSM. Seyedebrahimi
M. SeyedebrahimiFBFaycal Bouhafs
Faycal BouhafsARAlessandro Raschella
Alessandro RaschellaMMMichael Mackay
Michael MackayQSQi Shi
Qi ShiIn spite of the enormous popularity of Wi-Fi-enabled devices, the utilisation of Wi-Fi radio resources (e.g. RF spectrum and transmission power levels) at Access Points (APs) is degraded in current decentralised Radio Resource Management (RRM) schemes. Most state of the art centralised control solutions apply configurations in which the network-wide impacts of the involved parameters and their mutual relationships are ignored. In this paper, we propose an algorithm for jointly adjusting the transmission power levels and optimising the RF channel assignment of APs by taking into account the flows' required qualities while minimising their interference impact throughout the network. The proposed solution is tailored for an operator-agnostic and Software Defined Wireless Networking (SDWN)-based centralised RRM in dense Wi-Fi networks. Our extensive simulation results validate the performance improvements of the proposed algorithm compared to the main state of the art alternative by showing more than 25% higher spectrum efficiency, satisfying the users' demands and further mitigating the network-wide interference through flow-based and quality-oriented power level adjustment.
Journal Article
With the widespread deployment of 5G gaining pace, there is increasing interest in deploying this technology beyond traditional Mobile Network Operators (MNO) into private and community scenarios. These deployments leverage the flexibility of 5G itself to support private networks that sit alongside or even on top of existing public 5G. By utilizing a range of virtualisation and slicing techniques in the 5G Core (5GC) and heterogeneous Radio Access Networks (RAN) at the edge, a wide variety of use cases can be supported by 5G. However, these non-typical deployments may experience different performance characteristics as they adapt to their specific scenario. In this paper we present the results of our work to model and predict the performance of millimeter wave (mmWave) backhaul links that were deployed as part of the Liverpool 5G network. Based on the properties of the 802.11ad protocol and the physical characteristics of the environment, we simulate how each link will perform with different signal-to-noise ratio (SNR) and Packet Error Rate (PER) values and verify them against real-world deployed links. Our results show good convergence between simulated and real results and provide a solid foundation for further network planning and optimization.
29 December 2021 in International Journal of Wireless Information Networks
Journal Article
OAOmar Aldhaibani
Omar AldhaibaniARAlessandro Raschella
Alessandro RaschellaGMGhulam Mohi-Ud-Din
Ghulam Mohi-Ud-DinMMMichael Mackay
Michael MackayThis paper proposes an algorithm that enhances horizontal handover (HO) in dense wireless local area networks (WLANs), which is implemented in a software-defined wireless networking (SDWN)-based architecture. The algorithm considers the concept of user prioritisation, classifying the WLAN stations (STAs) into two categories representing high and low priorities respectively, and always attempts to guarantee the best quality of experience (QoE) to the high priority users. The architecture that implements the algorithm leverages the flexibility, programmability, and centralised nature of SDWN to efficiently manage the HO process. Moreover, the paper presents a performance evaluation campaign that demonstrates significant achievements against a state-of-the-art solution in terms of the provided QoE, throughput and delay. Finally, we discuss the importance of considering user prioritisation in a HO algorithm for dense WLANs.
About Me
Dr. Alessandro Raschella joined the School of Computer Science and Mathematics of LJMU as a Research Fellow in August 2015, as a lecturer in Networking and a member of the PROTECT Research Centre in August 2019, and as a senior lecturer in Computing and Networking in August 2022. He received BSc and MSc degrees in Telecommunications Engineering from the University Mediterranea of Reggio Calabria (UNIRC), Italy, in 2004 and 2007, respectively, and a PhD degree in Wireless Communications from the Universitat Politècnica de Catalunya (UPC), Barcelona, Spain, in 2015. His research interests include wireless network optimization, dynamic spectrum access in cognitive radio networks, Software-Defined Networking, the Internet of Things (IoT), Wi-Fi networks, 5G and beyond, and heterogeneous networks. He has been a co-investigator as part of the Wi-5 research project funded by the Horizon 2020 (H2020) Framework Programme of the European Union and the projects Liverpool 5G and 5G Create funded by the Sensor City consortium of Liverpool. He has also been involved in the SALICE project funded by the Italian Ministry of University and Research (MIUR) and the OneFIT project funded by the Seventh Framework Programme (FP7) of the European Union. He has served as a Technical Program Committees (TPCs) member at several IEEE conferences, including IEEE ICC, WCNC, GLOBECOM, ISCC, and VTC, and as a reviewer for IEEE and non-IEEE conferences and peer-reviewed journals.