Joint pairing and resource allocation for backhaul of small cells using NOMA

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Highlights

  • The main objective of this paper is to design and model a joint pairing and resource (bandwidth and power) allocation scheme for the backhaul of small cells. Bounds on the power coefficient of the near and far user are computed. The significant contributions of the proposed model are as follows:

  • We formulate the joint problem of resource allocation and pairing of backhaul of small cells. The resources considered are bandwidth and power coefficient for the near and far user. The problem takes into consideration the load of each small cell.

  • We propose a heuristic to solve the formulated problem as the problem is NP-hard. The main theme of the heuristic is based of the bound of power coefficients and exhaustive search for the small cell pairing.

  • We compare the performance of the proposed heuristic with a discretized exhaustive search strategy.

Abstract

Small cells is a promising technique to improve the spectral efficiency or quality-of-service (QoS) of a cellular network as it reduces the distance between the user and the base station (MBS). It has been proposed for indoor as well as outdoor users. For the outdoor scenario, the backhaul (the link from a small cell to the core network) of the small cell has always been a challenging issue. Different schemes have been proposed in the literature such as optical fiber, satellite and wirelessly through MBS. Wireless backhaul through MBS has gained a lot of attention in the literature and different resource allocation with orthogonal resources strategies have been proposed for it as well. Apart from orthogonal techniques, non-orthogonal multiple access (NOMA) is a multi access technique with the basic principle of sharing the same bandwidth resource between multiple users with varying power levels. Successive interference cancellation (SIC) is implemented on the receiver side to decode the data. This overall increases the spectrally efficiency of the network and make NOMA a promising candidate to be deployed on the backhaul of the small cell network. In this paper, we investigate the problem of pairing of small cells and the allocation of resources. Small cells' load information plays vital role to solve this problem. An optimization problem with an objective of maximizing the spectral efficiency (SE) of the backhaul network is formulated. The joint problem is decomposed and solved using a load-based heuristic for the backhaul of small cells. Furthermore, our performance evaluation shows that the proposed heuristic is able to achieve nearly-same spectral efficiency as that of exhaustive search with much less complexity.

Introduction

Nowadays, small cell offers more flexible deployment opportunities according to its low-cost low-power Base Stations (BSs), which have identical functionalities as macro-cell BSs but with a much smaller form factor [1], [2], [3]. Small cell refers to the coverage area provided by a low cost transmit power BS with 10–200 m radius and less than 25 meters antenna heights. Small cell can be deployed in strategic locations in order to leverage the needed infrastructure, it can be deployed either indoor or outdoor. In outdoors infrastructures, it can be installed on street such as on building sides or bus stops to provide the services to surrounding areas. On the other side, in indoors infrastructures, it can be installed in public spaces to provide the services to neighboring areas [2], [4], [5].

Backhaul network considers as the intermediate network that comprises the links between the core network and the radio access network. It starts at the cell (ex. Small cells) and ends up in the core network.

Nevertheless, with small cells in networks, it is a challenge to handle the backhaul. Different solutions have been introduced for both wired and wireless backhaul networks [2], [6]. Wireless backhaul reduces the overall deployment cost of the network in big networks as compared to wired backhaul solutions.

The multiple access mechanism can be Orthogonal Multiple Access (OMA) and Non-Orthogonal Multiple Access (NOMA). NOMA has gained great consideration for the radio access techniques design for Internet of Things (IoTs) and fifth generation (5G) wireless networks. The big picture behind NOMA is to assist multiple users that located in the same resource block, such as the same time slot or space. According to that, NOMA encourages enormous connectivity, less latency, advances the user equality and spectral efficiency, and enhances the reliability when compared to the OMA techniques where the resources are allocated orthogonally to multiple users [7], [8]. NOMA schemes advantages over the OMA schemes are as follows:

  • 1.

    NOMA shows high bandwidth efficiency which improves the network's throughput [9].

  • 2.

    NOMA assigns more power to weak users (fairness between users) which guarantee a trade-off between the fairness between users and their throughput.

  • 3.

    NOMA provides high connectivity, such as 5G system can provide services to billions of IoT devices [10].

  • 4.

    NOMA can be compatible with any existing OMA techniques since it exploits the power-domain dimension.

  • 5.

    NOMA is a flexible technique since it attractive a low-complexity design [11]. Thus, these advantages make it the best candidate for backhaul networks.

NOMA schemes are categorized in two types: the code domain multiplexing in which different users are assigned various codes which are multiplexed over the same time-frequency resources and power domain multiplexing in which various users are assigned various power coefficients based on their channel conditions to achieve a high system performance [12]. In power domain NOMA, the pairing of users and power coefficient allocation is of interest and need to be handled efficientlyto achievethe full benefits of NOMA. Channel gain based pairing has been proposed in literature. These channel gain based pairing and power coefficient algorithms should not be applied directly to the backhaul of small cells as the load of small cells will play a significant role in it as well. In [13] a load aware pairing is analyzed using a discretized exhaustive search which has a very high complexity.

In this article, we investigate a joint problem of backhaul pairing and resource allocation (power and bandwidth) for the downlink of a backhauls of small cells. The power coefficient bounds of the near and far small cells are computed. The main contributions of this work are mentioned as follows:

  • We formulate the joint problem of resource allocation and pairing of backhaul of small cells. The resources considered are bandwidth and power coefficient for the near and far user. The problem takes into consideration the load of each small cell.

  • A heuristic to solve the formulated problem as the problem is NP-hard has been proposed. The main theme of the heuristic is based of the bound of power coefficients and exhaustive search for the small cell pairing.

  • The performance of the proposed heuristic with a discretized exhaustive search strategy has been compared to show the proposed system feasibility.

The proposed system results show the performance of the heuristic is comparable to exhaustive search in terms of spectral efficiency but with much less complexity.

The rest of the paper is organized as follows. Section 2 layouts this study's related works. Section 3 introduces the system model and formulates the problem. Section 4 proposes a heuristic to solve the problem. Experimental and result analysis are presented in Section 5. Finally, we present the conclusion in Section 6.

Section snippets

Related work

Providing continuous and dependable communication for future networks in our never-stop evolving cities is not an easy task [14], [15]. Various works have been proposed to acquire the full potential of NOMA for small cell schemes. The authors in [16] investigated the wireless backhauls’ downlink performance that consists of multi-tier small cells. In [16], the authors adopted NOMA to various types of small cells such as the microcells. A NOMA hierarchical power allocation procedure has been

System model and problem formulation

In this section, we will discuss the system model considered for resource allocation and pairing of backhaul of small cells and state the problem formulation for this. All the variables are defined and the assumptions are stated.

We consider a two-tier network with one macrocell basestation (MBS) and a total of M small cells placed in the coverage of MBS as shown in Fig. 1. The set of small cells is represented as S={sii,1iM}. For each small cells we have two link, the access link and the

Power and bandwidth allocation and Backhaul pairing of small cells

In this section, we present a heuristic to solve the joint allocation and pairing problem. we took a decomposition approach to solve the problem. The problem is decomposed in the following two parts:

  • Part I: Power and bandwidth allocation for a selected pair based on bounds.

  • Part II: Selection of pairs of small cells using exhaustive search.

Performance evaluation

Performance evaluation is one of the critical components to verify the paired small cells functioning under various parameters. In this section, performance of above mentioned pairing schemes for backhaul of small cells is evaluated. Important parameters used for evaluating the performance are tabulated in Table 2. We compared the performance of the proposed heuristic to an exhaustive search strategy [13].

Conclusion and future work

We proposed a heuristic for a joint backhaul pairing and resource allocation for a backhaul of a small cell network. The proposed heuristic took a decomposition approach to solve the problem sequentially. We compared the performance of the heuristic with an exhaustive search algotrithm. The results demonstrate that the computational complexity of heuristic approach algorithm is less when compared with the exhaustive search algorithm. Moreover, both approaches are also comparable in terms of

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgement

This research was funded by the Higher Education Commission (HEC) Pakistan, under grant No. HEC NRPU8549/Federal/NRPU/R&D/HEC/2017.

H. Faizan Saeed[email protected] H. Faizan Saeed received the B.Eng. degree in electrical engineering from Govt. College University Faisalabad, Pakistan and the M.Eng. degree in electrical engineering from Institute of Space Technology, Pakistan in 2014 and 2019 respectively. Currently, he is with Institute of Space Technology working as a Graduate Research Assistant in the WiSP LAB. His research interests include signal processing for wireless communications and 5G Radio Access Technologies.

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  • Cited by (0)

    H. Faizan Saeed[email protected] H. Faizan Saeed received the B.Eng. degree in electrical engineering from Govt. College University Faisalabad, Pakistan and the M.Eng. degree in electrical engineering from Institute of Space Technology, Pakistan in 2014 and 2019 respectively. Currently, he is with Institute of Space Technology working as a Graduate Research Assistant in the WiSP LAB. His research interests include signal processing for wireless communications and 5G Radio Access Technologies.

    Sobia Jangsher [email protected] Sobia Jangsher received her B.E. degree in electronics engineering and M.S. in communication system engineering from National University of Science and Technology (NUST), Pakistan and PhD in Wireless Communication from The University of Hong Kong, Hong Kong. She did her M.S. thesis on “Adaptive transmission of video over MIMO channels” under the supervision of Dr. Syed Ali Khayam and PhD thesis on “Resource Allocation in Moving Small Cell Network” under the supervision of Prof. Victor O.K Li. She is currently working as an Assistant Professor in Institute of Space Technology, Islamabad, Pakistan. Her research mainly focuses on resource allocation in future wireless communication systems.

    Moayad Aloqaily received the M.Sc. degree in electrical and computer engineering from Concordia University, Montreal, QC, Canada, in 2012, and the Ph.D. degree in electrical and computer engineering from the University of Ottawa, Ottawa, ON, in 2016. He was an instructor in the Systems and Computer Engineering Department at Carleton University, Ottawa, Canada, 2017. He is working with Gnowit Inc. as a Senior Researcher and Data Scientist since 2016. He is also the managing director of xAnalytics Inc., Ottawa, ON, Canada, 2019. Currently, he is with the Faculty of Engineering, Al Ain University, United Arab Emirates. His current research interests include the applications of AI and ML, Connected and Autonomous Vehicles, Blockchain Solutions, and Sustainable Energy and Data Management. He has chaired and co-chaired many IEEE conferences and workshops including BCCA2020, AdHocNets2020, PEDISWESA-ISCC2020, ITCVT-NOMS2020, E2NIoT-IWCMC2020, ICCN-INFOCOM19, AICSSA19, and BAT-FMEC19-20. He has served as a guest editor in many journals including IEEE Wireless Communications Magazine, IEEE Network, International Journal of Machine Learning and Cybernetics, Elsevier IPM Journal, Springer JONS, Springer Cluster Computer, Internet Technology Letters, Transaction on Telecommunications Technologies, Security and Privacy, and IEEE Access. He is an Associate Editor with Cluster Computing, Security and Privacy, and IEEE Access. He is an IEEE member and a Professional Engineer Ontario (P.Eng.)..

    Hassaan Khaliq Qureshi [email protected] Hassaan Khaliq Qureshi received the M.Sc. degree (Hons.) in electrical engineering from the Blekinge Institute of Technology, Sweden, in 2006, and the Ph.D. degree in electrical engineering from the City, University of London, U.K., in 2011. He completed his European Union's (EU) Erasmus Mundus Postdoctoral Fellowship from Frederick University, Cyprus. He remained as a Research Assistant with the Technical University of Dresden and worked on European Union OPERA Project. His main research interests include wireless networks, blockchains, the Internet of Things (IoTs), network intrusion detection systems, and energy provisioning issues for infrastructure-less networks. He was also a recipient of EU Erasmus Mundus Staff Research Mobility under STRONG TIES Program. He is currently working as an Associate Professor with NUST, Pakistan. He serves as a TPC member of IEEE ICOIN and a Reviewer for various IEEE conferences, including GLOBECOM, ICC, ISCC, IWCMC, CCNC, TENCON, and DCOSS. He also serves as a Reviewer for the IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, the IEEE COMMUNICATION LETTERS, the IEEE WIRELESS COMMUNICATIONS LETTERS, the IEEE Communications Magazine, the IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, IEEE ACCESS, the IEEE INTERNET OF THINGS (IoT), Elsevier Computer Networks, Springer's Wireless Personal Communications (WPC), Wireless Networks (WINET), the International Journal of Distributed Sensor Networks, China Communications Journal, and the Proceedings of the Pakistan Academy of Sciences.

    Jalal Ben Othman [email protected] JALEL BEN-OTHMAN received the B.Sc. and M.Sc. degrees in computer science from the University of Pierre et Marie Curie, Paris, France, in 1992 and 1994, respectively, and the Ph.D. degree from the University of Versailles, France, in 1998. He was appointed as the IEEE COMSOC Distinguished Lecturer, from 2015 to 2018. He has been a Full Professor with the University of Paris 13, since 2011. He is also a member of the L2S Laboratory, Centrale Supélec. He is currently the IEEE VTS Distinguished Lecturer, where he did several tours all around the world. His research interests include the area of wireless ad hoc and sensor networks, VANETs, the IoT, performance evaluation, and security in wireless networks in general. He has been a member of the IEEE Technical Services Board, since 2016. He was a recipient of the IEEE COMSOC Communication Software Technical Committee Recognition Award, in 2016, and the IEEE Computer Society Meritorious Service Award, in 2016. He is a Golden Core Member of the IEEE Computer Society, the AHSN Exceptional Service and Contribution Award, in 2018, and the VEHCOM Fabio Neri Award, in 2018. He is currently in steering committee of the IEEE TRANSACTION ON MOBILE COMPUTING (IEEE TMC), an Editorial Board Member of several journals the IEEE NETWORKS, the IEEE COMMUNICATIONS LETTERS, the Journal of Communications and Networks (JCN), the International Journal of Computer Systems (IJCS), the Security and Privacy Journal (SPY), and the IEEE SENSORS JOURNAL. He has also served as a TPC Co-Chair for the IEEE Globecom and ICC conferences and other conferences, such as WCNC, IWCMC, VTC, ComComAp, ICNC, WCSP, Q2SWinet, P2MNET, and WLN. He was the Chair of the IEEE Ad Hoc and Sensor Networks Technical Committee, from 2016 to 2018. He was previously the Vice Chair and Secretary for this committee.

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