Performance enhancement for LTE and beyond systems

A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of PhilosophyWireless communication systems have undergone fast development in recent years. Based on GSM/EDGE and UMTS/HSPA, the 3rd Generation Partnership Project (3GPP) specified the Long Term Evolution (LTE) standard to cope with rapidly increasing demands, including capacity, coverage, and data rate. To achieve this goal, several key techniques have been adopted by LTE, such as Multiple-Input and Multiple-Output (MIMO), Orthogonal Frequency-Division Multiplexing (OFDM), and heterogeneous network (HetNet). However, there are some inherent drawbacks regarding these techniques. Direct conversion architecture is adopted to provide a simple, low cost transmitter solution. The problem of I/Q imbalance arises due to the imperfection of circuit components; the orthogonality of OFDM is vulnerable to carrier frequency offset (CFO) and sampling frequency offset (SFO). The doubly selective channel can also severely deteriorate the receiver performance. In addition, the deployment of Heterogeneous Network (HetNet), which permits the co-existence of macro and pico cells, incurs inter-cell interference for cell edge users. The impact of these factors then results in significant degradation in relation to system performance. This dissertation aims to investigate the key techniques which can be used to mitigate the above problems. First, I/Q imbalance for the wideband transmitter is studied and a self-IQ-demodulation based compensation scheme for frequencydependent (FD) I/Q imbalance is proposed. This combats the FD I/Q imbalance by using the internal diode of the transmitter and a specially designed test signal without any external calibration instruments or internal low-IF feedback path. The instrument test results show that the proposed scheme can enhance signal quality by 10 dB in terms of image rejection ratio (IRR). In addition to the I/Q imbalance, the system suffers from CFO, SFO and frequency-time selective channel. To mitigate this, a hybrid optimum OFDM receiver with decision feedback equalizer (DFE) to cope with the CFO, SFO and doubly selective channel. The algorithm firstly estimates the CFO and channel frequency response (CFR) in the coarse estimation, with the help of hybrid classical timing and frequency synchronization algorithms. Afterwards, a pilot-aided polynomial interpolation channel estimation, combined with a low complexity DFE scheme, based on minimum mean squared error (MMSE) criteria, is developed to alleviate the impact of the residual SFO, CFO, and Doppler effect. A subspace-based signal-to-noise ratio (SNR) estimation algorithm is proposed to estimate the SNR in the doubly selective channel. This provides prior knowledge for MMSE-DFE and automatic modulation and coding (AMC). Simulation results show that this proposed estimation algorithm significantly improves the system performance. In order to speed up algorithm verification process, an FPGA based co-simulation is developed. Inter-cell interference caused by the co-existence of macro and pico cells has a big impact on system performance. Although an almost blank subframe (ABS) is proposed to mitigate this problem, the residual control signal in the ABS still inevitably causes interference. Hence, a cell-specific reference signal (CRS) interference cancellation algorithm, utilizing the information in the ABS, is proposed. First, the timing and carrier frequency offset of the interference signal is compensated by utilizing the cross-correlation properties of the synchronization signal. Afterwards, the reference signal is generated locally and channel response is estimated by making use of channel statistics. Then, the interference signal is reconstructed based on the previous estimate of the channel, timing and carrier frequency offset. The interference is mitigated by subtracting the estimation of the interference signal and LLR puncturing. The block error rate (BLER) performance of the signal is notably improved by this algorithm, according to the simulation results of different channel scenarios. The proposed techniques provide low cost, low complexity solutions for LTE and beyond systems. The simulation and measurements show good overall system performance can be achieved

AN EFFICIENT INTERFERENCE AVOIDANCE SCHEME FOR DEVICE-TODEVICE ENABLED FIFTH GENERATION NARROWBAND INTERNET OF THINGS NETWOKS’

Narrowband Internet of Things (NB-IoT) is a low-power wide-area (LPWA) technology built on long-term evolution (LTE) functionalities and standardized by the 3rd-Generation Partnership Project (3GPP). Due to its support for massive machine-type communication (mMTC) and different IoT use cases with rigorous standards in terms of connection, energy efficiency, reachability, reliability, and latency, NB-IoT has attracted the research community. However, as the capacity needs for various IoT use cases expand, the LTE evolved packet core (EPC) system's numerous functionalities may become overburdened and suboptimal. Several research efforts are currently in progress to address these challenges. As a result, an overview of these efforts with a specific focus on the optimized architecture of the LTE EPC functionalities, the 5G architectural design for NB-IoT integration, the enabling technologies necessary for 5G NB-IoT, 5G new radio (NR) coexistence with NB-IoT, and feasible architectural deployment schemes of NB-IoT with cellular networks is discussed. This thesis also presents cloud-assisted relay with backscatter communication as part of a detailed study of the technical performance attributes and channel communication characteristics from the physical (PHY) and medium access control (MAC) layers of the NB-IoT, with a focus on 5G. The numerous drawbacks that come with simulating these systems are explored. The enabling market for NB-IoT, the benefits for a few use cases, and the potential critical challenges associated with their deployment are all highlighted. Fortunately, the cyclic prefix orthogonal frequency division multiplexing (CPOFDM) based waveform by 3GPP NR for improved mobile broadband (eMBB) services does not prohibit the use of other waveforms in other services, such as the NB-IoT service for mMTC. As a result, the coexistence of 5G NR and NB-IoT must be manageably orthogonal (or quasi-orthogonal) to minimize mutual interference that limits the form of freedom in the waveform's overall design. As a result, 5G coexistence with NB-IoT will introduce a new interference challenge, distinct from that of the legacy network, even though the NR's coexistence with NB-IoT is believed to improve network capacity and expand the coverage of the user data rate, as well as improves robust communication through frequency reuse. Interference challenges may make channel estimation difficult for NB-IoT devices, limiting the user performance and spectral efficiency. Various existing interference mitigation solutions either add to the network's overhead, computational complexity and delay or are hampered by low data rate and coverage. These algorithms are unsuitable for an NB-IoT network owing to the low-complexity nature. As a result, a D2D communication based interference-control technique becomes an effective strategy for addressing this problem. This thesis used D2D communication to decrease the network bottleneck in dense 5G NBIoT networks prone to interference. For D2D-enabled 5G NB-IoT systems, the thesis presents an interference-avoidance resource allocation that considers the less favourable cell edge NUEs. To simplify the algorithm's computing complexity and reduce interference power, the system divides the optimization problem into three sub-problems. First, in an orthogonal deployment technique using channel state information (CSI), the channel gain factor is leveraged by selecting a probable reuse channel with higher QoS control. Second, a bisection search approach is used to find the best power control that maximizes the network sum rate, and third, the Hungarian algorithm is used to build a maximum bipartite matching strategy to choose the optimal pairing pattern between the sets of NUEs and the D2D pairs. The proposed approach improves the D2D sum rate and overall network SINR of the 5G NB-IoT system, according to the numerical data. The maximum power constraint of the D2D pair, D2D's location, Pico-base station (PBS) cell radius, number of potential reuse channels, and cluster distance impact the D2D pair's performance. The simulation results achieve 28.35%, 31.33%, and 39% SINR performance higher than the ARSAD, DCORA, and RRA algorithms when the number of NUEs is twice the number of D2D pairs, and 2.52%, 14.80%, and 39.89% SINR performance higher than the ARSAD, RRA, and DCORA when the number of NUEs and D2D pairs are equal. As a result, a D2D sum rate increase of 9.23%, 11.26%, and 13.92% higher than the ARSAD, DCORA, and RRA when the NUE’s number is twice the number of D2D pairs, and a D2D’s sum rate increase of 1.18%, 4.64% and 15.93% higher than the ARSAD, RRA and DCORA respectively, with an equal number of NUEs and D2D pairs is achieved. The results demonstrate the efficacy of the proposed scheme. The thesis also addressed the problem where the cell-edge NUE's QoS is critical to challenges such as long-distance transmission, delays, low bandwidth utilization, and high system overhead that affect 5G NB-IoT network performance. In this case, most cell-edge NUEs boost their transmit power to maximize network throughput. Integrating cooperating D2D relaying technique into 5G NB-IoT heterogeneous network (HetNet) uplink spectrum sharing increases the system's spectral efficiency and interference power, further degrading the network. Using a max-max SINR (Max-SINR) approach, this thesis proposed an interference-aware D2D relaying strategy for 5G NB-IoT QoS improvement for a cell-edge NUE to achieve optimum system performance. The Lagrangian-dual technique is used to optimize the transmit power of the cell-edge NUE to the relay based on the average interference power constraint, while the relay to the NB-IoT base station (NBS) employs a fixed transmit power. To choose an optimal D2D relay node, the channel-to-interference plus noise ratio (CINR) of all available D2D relays is used to maximize the minimum cell-edge NUE's data rate while ensuring the cellular NUEs' QoS requirements are satisfied. Best harmonic mean, best-worst, half-duplex relay selection, and a D2D communication scheme were among the other relaying selection strategies studied. The simulation results reveal that the Max-SINR selection scheme outperforms all other selection schemes due to the high channel gain between the two communication devices except for the D2D communication scheme. The proposed algorithm achieves 21.27% SINR performance, which is nearly identical to the half-duplex scheme, but outperforms the best-worst and harmonic selection techniques by 81.27% and 40.29%, respectively. As a result, as the number of D2D relays increases, the capacity increases by 14.10% and 47.19%, respectively, over harmonic and half-duplex techniques. Finally, the thesis presents future research works on interference control in addition with the open research directions on PHY and MAC properties and a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis presented in Chapter 2 to encourage further study on 5G NB-IoT

セルラーシステムにおける周波数利用とエネルギー利用効率改善に関する研究

早大学位記番号:新7583早稲田大

D13.3 Overall assessment of selected techniques on energy- and bandwidth-efficient communications

Deliverable D13.3 del projecte europeu NEWCOM#The report presents the outcome of the Joint Research Activities (JRA) of WP1.3 in the last year of the Newcom# project. The activities focus on the investigation of bandwidth and energy efficient techniques for current and emerging wireless systems. The JRAs are categorized in three Tasks: (i) the first deals with techniques for power efficiency and minimization at the transceiver and network level; (ii) the second deals with the handling of interference by appropriate low interference transmission techniques; (iii) the third is concentrated on Radio Resource Management (RRM) and Interference Management (IM) in selected scenarios, including HetNets and multi-tier networks.Peer ReviewedPostprint (published version

Stochastic geometric analysis of energy efficiency in two-tier heterogeneous networks

The exponential growth in the number of users of cellular mobile networks (and their requirements) has created a massive challenge for network operators to cope with demands for coverage and data rates. Among the possible solutions for the ever increasing user needs, the deployment of Heterogeneous Networks (HetNets) constitutes both a practical and an economical solution. Moreover, while the typical approach for network operators has been to consider the coverage and data rates as design parameters in a network, a major concern for next generation networks is the efficiency in the power usage of the network. Therefore, in recent years the energy efficiency parameter has gathered a great deal of attention in the design of next generation networks. In the context of HetNets, while the densification of the network in terms of the number of base stations deployed can potentially increase the coverage and boost the data rates, it can also lead to a huge power consumption as the energy used escalates with the number of base stations deployed. To this end, the purpose of this thesis is to investigate the energy efficiency performance of different deployment strategies in a HetNet consisting of macro- and femtocells. We make use of well established tools from stochastic geometry to model the different strategies, as it provides a theoretical framework from which the scalability of the network in terms of the design parameters can be taken into account. Those strategies consisted first, on the analysis of the effect of using multiple antennas and diversity schemes on both, the throughput and the energy efficiency of the network. The optimum diversity schemes and antenna configurations were found for an optimal energy efficiency while keeping constraints on the quality of Service of both tiers. Then, the effect of the vertical antenna tilt was analyzed for both, a traditional macrocell only network and a two-tier network. The optimum antenna tilt in terms of energy efficiency was found while keeping constraints on the Quality of Service required. Finally, an energy efficient deployment of femtocells was proposed where the smart positioning of femtocells derived into improvements of coverage probability, effective throughput and energy efficiency of the network. The proposed model also improved in general the performance of the cell edge user which in turn resulted in a more balanced network in terms of the overall performance

Implementation of New Multiple Access Technique Encoder for 5G Wireless Telecomunication Networks

RÉSUMÉ Les exigences de la connectivité mobile massive de différents appareils et de diverses applications déterminent les besoins des prochaines générations de technologies mobiles (5G) afin de surmonter les demandes futures. L'expansion significative de la connectivité et de la densité du trafic caractérisent les besoins de la cinquième génération de réseaux mobiles. Par conséquent, pour la 5G, il est nécessaire d'avoir une densité de connectivité beaucoup plus élevée et une plus grande portée de mobilité, un débit beaucoup plus élevé et une latence beaucoup plus faible. En raison de l'exigence d'une connectivité massive, de nombreuses nouvelles technologies doivent être améliorées: le codage des canaux, la technique d'accès multiple, la modulation et la diversité, etc. Par conséquent, compte tenu de l'environnement 5G, surcoût de signalisation et de la latence devrait être pris en compte [1]. En outre, l'application de la virtualisation des accès sans fil (WAV) devrait également être considérée et, par conséquent, il est également nécessaire de concevoir la plate-forme matérielle prenant en charge les nouvelles normes pour la mise en œuvre des émetteurs-récepteurs virtuels. L'une des nouvelles technologies possibles pour la 5G est l'accès multiple pour améliorer le débit. Par conséquent, au lieu d'OFDMA utilisé dans la norme LTE (4G), l'application d'une nouvelle technique d'accès multiple appelée Sparse Code Multiple Access (SCMA) est investiguée dans cette dissertation. SCMA est une nouvelle technique d'accès multiple non orthogonale du domaine fréquentiel proposée pour améliorer l'efficacité spectrale de l'accès radio sans fil [2]. L'encodage SCMA est l'un des algorithmes les plus simples dans les techniques d'accès multiple qui offre l'opportunité d'expérimenter des méthodes génériques de mise en oeuvre. En outre, la nouvelle méthode d'accès multiple est supposée fournir un débit plus élevé. Le choix du codage SCMA avec moins de complexité pourrait être une approche appropriée. La cible fixée pour cette recherche était d'atteindre un débit d’encodage de plus de 1 Gbps pour le codeur SCMA. Les implémentations de codage SCMA ont été effectuées à la fois en logiciel et en matériel pour permettre de les comparer. Les implémentations logicielles ont été développées avec le langage de programmation C. Parmi plusieurs conceptions, la performance a été améliorée en utilisant différentes méthodes pour augmenter le parallélisme, diminuer la complexité de calcul et par conséquent le temps de traitement.----------ABSTRACT The demands of massive mobile connectivity of different devices and diverse applications at the same time set requirments for next generations of mobile technology (5G). The significant expansion of connectivity and traffic density characterize the requirements of fifth generation mobile. Therefore, in 5G, there is a need to have much higher connectivity density, higher mobility ranges, much higher throughput, and much lower latency. In pursuance of the requirement of massive connectivity, numerous technologies must be improved: channel coding, multiple access technique, modulation and diversity, etc. For instance, with 5G, the cost of signaling overhead and latency should be taken into account [1]. Besides, applying wireless access virtualization (WAV) should be considered and there is also a need to have effective implementations supporting novel virtual transceiver. One of the possible new technologies for 5G is exploiting multiple access techniques to improve throughput. Therefore, instead of OFDMA in LTE (4G), applying a new multiple access technique called Sparse Code Multiple Access (SCMA) is an approach considered in this dissertation. SCMA is a new frequency domain non-orthogonal multiple access technique proposed to improve spectral efficiency of wireless radio access [2]. SCMA encoding is one of the simplest multiple access technique that offers an opportunity to experiment generic implementation methods. In addition, the new multiple access method is supposed to provide higher throughput, thus choosing SCMA encoding with less complexity could be an appropriate approach. The target with SCMA was to achieve an encoding throughput of more that 1Gbps. SCMA encoding implementations were done both in software and hardware to allow comparing them. The software implementations were developed with the C programing language. Among several designs, the performance was improved by using different methods to increase parallelism, decrease the computational complexity and consequently the processing time. The best achieved results with software implementations offer a 3.59 Gbps throughput, which is 3.5 times more that the target. For hardware implementation, high level synthesis was experimented. In order to do that, the C based functions and testbenches which were developed for software implementations, were used as inputs to Vivado HLS

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin