Insights on Significant Implication on Research Approach for Enhancing 5G Network System

With the exponential growth of mobile users, there is a massive growth of data as well as novel services to support such data management. However, the existing 4G network is absolutely not meant for catering up such higher demands of bandwidth utilization as well as servicing massive users with similar Quality of service. Such problems are claimed to be effectively addressed by the adoption of 5G networking system. Although the characteristics of 5G networking are theoretically sound, still it is under the roof of the research. Therefore, this paper presents a discussion about the conventional approach as well as an approach using cognitive radio network towards addressing the frequently identified problems of energy, resource allocation, and spectral efficiency. The study collects the existing, recent researches in the domain of 5G communications from various publications. Different from existing review work, the paper also contributes towards identifying the core research findings as well as a significant research gap towards improving the communication in the 5G network system

Potentzia domeinuko NOMA 5G sareetarako eta haratago

Tesis inglés 268 p. -- Tesis euskera 274 p.During the last decade, the amount of data carried over wireless networks has grown exponentially. Several reasons have led to this situation, but the most influential ones are the massive deployment of devices connected to the network and the constant evolution in the services offered. In this context, 5G targets the correct implementation of every application integrated into the use cases. Nevertheless, the biggest challenge to make ITU-R defined cases (eMBB, URLLC and mMTC) a reality is the improvement in spectral efficiency. Therefore, in this thesis, a combination of two mechanisms is proposed to improve spectral efficiency: Non-Orthogonal Multiple Access (NOMA) techniques and Radio Resource Management (RRM) schemes. Specifically, NOMA transmits simultaneously several layered data flows so that the whole bandwidth is used throughout the entire time to deliver more than one service simultaneously. Then, RRM schemes provide efficient management and distribution of radio resources among network users. Although NOMA techniques and RRM schemes can be very advantageous in all use cases, this thesis focuses on making contributions in eMBB and URLLC environments and proposing solutions to communications that are expected to be relevant in 6G

A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future

A High Altitude Platform Station (HAPS) is a network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks. In this article, we provide a vision and framework for the HAPS networks of the future supported by a comprehensive and state-of-the-art literature review. We highlight the unrealized potential of HAPS systems and elaborate on their unique ability to serve metropolitan areas. The latest advancements and promising technologies in the HAPS energy and payload systems are discussed. The integration of the emerging Reconfigurable Smart Surface (RSS) technology in the communications payload of HAPS systems for providing a cost-effective deployment is proposed. A detailed overview of the radio resource management in HAPS systems is presented along with synergistic physical layer techniques, including Faster-Than-Nyquist (FTN) signaling. Numerous aspects of handoff management in HAPS systems are described. The notable contributions of Artificial Intelligence (AI) in HAPS, including machine learning in the design, topology management, handoff, and resource allocation aspects are emphasized. The extensive overview of the literature we provide is crucial for substantiating our vision that depicts the expected deployment opportunities and challenges in the next 10 years (next-generation networks), as well as in the subsequent 10 years (next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial

Characterisation and performance analysis of random linear network coding for reliable and secure communication

In this thesis, we develop theoretical frameworks to characterize the performance of Random Linear Network Coding (RLNC), and propose novel communication schemes for the achievement of both reliability and security in wireless networks. In particular, (i) we present an analytical model to evaluate the performance of practical RLNC schemes suitable for low-complexity receivers, prioritized (i.e., layered) coding and multi-hop communications, (ii) investigate the performance of RLNC in relay assisted networks and propose a new cross-layer RLNC-aided cooperative scheme for reliable communication, (iii) characterize the secrecy feature of RLNC and propose a new physical-application layer security technique for the purpose of achieving security and reliability in multi-hope communications. At first, we investigate random block matrices and derive mathematical expressions for the enumeration of full-rank matrices that contain blocks of random entries arranged in a diagonal, lower-triangular or tri-diagonal structure. The derived expressions are then used to model the probability that a receiver will successfully decode a source message or layers of a service, when RLNC based on non-overlapping, expanding or sliding generations is employed. Moreover, the design parameters of these schemes allow to adjust the desired decoding performance. Next, we evaluate the performance of Random Linear Network Coded Cooperation (RLNCC) in relay assisted networks, and propose a cross-layer cooperative scheme which combines the emerging Non-Orthogonal Multiple Access (NOMA) technique and RLNCC. In this regard, we first consider the multiple-access relay channel in a setting where two source nodes transmit packets to a destination node, both directly and via a relay node. Secondly, we consider a multi-source multi-relay network, in which relay nodes employ RLNC on source packets and generate coded packets. For each network, we build our analysis on fundamental probability expressions for random matrices over finite fields and we derive theoretical expressions of the probability that the destination node will successfully decode the source packets. Finally, we consider a multi-relay network comprising of two groups of source nodes, where each group transmits packets to its own designated destination node over single-hop links and via a cluster of relay nodes shared by both groups. In an effort to boost reliability without sacrificing throughput, a scheme is proposed whereby packets at the relay nodes are combined using two methods; packets delivered by different groups are mixed using non-orthogonal multiple access principles, while packets originating from the same group are mixed using RLNC. An analytical framework that characterizes the performance of the proposed scheme is developed, and benchmarked against a counterpart scheme that is based on orthogonal multiple access. Finally, we quantify and characterize the intrinsic security feature of RLNC and design a joint physical-application layer security technique. For this purpose, we first consider a network comprising a transmitter, which employs RLNC to encode a message, a legitimate receiver, and a passive eavesdropper. Closed-form analytical expressions are derived to evaluate the intercept probability of RLNC, and a resource allocation model is presented to further minimize the intercept probability. Afterward, we propose a joint RLNC and opportunistic relaying scheme in a multi relay network to transmit confi- dential data to a destination in the presence of an eavesdropper. Four relay selection protocols are studied covering a range of network capabilities, such as the availability of the eavesdropper’s channel state information or the possibility to pair the selected relay with a jammer node that intentionally generates interference. For each case, expressions of the probability that a coded packet will not be decoded by a receiver, which can be either the destination or the eavesdropper, are derived. Based on those expressions, a framework is developed that characterizes the probability of the eavesdropper intercepting a sufficient number of coded packets and partially or fully decoding the confidential data. We observe that the field size over which RLNC is performed at the application layer as well as the adopted modulation and coding scheme at the physical layer can be modified to fine-tune the trade-off between security and reliability

Stochastic Geometry-Based Analysis of Cache-Enabled Hybrid Satellite-Aerial-Terrestrial Networks With Non-Orthogonal Multiple Access

Due to the emergence of non-terrestrial platformswith extensive coverage, flexible deployment, and reconfigurablecharacteristics, the hybrid satellite-aerial-terrestrial networks(HSATNs) can accommodate a great variety of wireless accessservices in different applications. To effectively reduce the trans-mission latency and facilitate the frequent update of files withimproved spectrum efficiency, we investigate the performanceof cache-enabled HSATN, where the user retrieves the requiredcontent files from the cache-enabled aerial relay or the satellitewith the non-orthogonal multiple access (NOMA) scheme. If therequired content files of the user are cached in the aerial relay,the cache-enabled relay would serve directly. Otherwise, the userwould retrieve the content file from the satellite system, where thesatellite system seeks opportunities for proactive content pushingto the relay during the user content delivery phase. Specifically,taking into account the uncertainty of the number and locationof aerial relays, along with the channel fading of terrestrialusers, the outage probability and hit probability of the considerednetwork are, respectively, derived based on stochastic geometry.Numerical results unveil the effectiveness of the cache-enabledHSATN with the NOMA scheme and proclaim the influence ofkey factors on the system performance. The realistic, tractable,and expandable framework, as well as associated methodology,provide both useful guidance and a solid foundation for evolvednetworks with advanced configurations in the performance ofcache-enabled HSATN