Radio Access Technology

Next generation networks will combine various access technologies to enable users to roam freely from one access network to another which is referred as Vertical handovers. Vertical handovers mobility management in next generation all-IP networks is the key factor that determines vertical handovers (HO) performance. Mobility management is generally based on mobility protocols that perform the handovers either horizontally (within the same access network) or vertically (between different access technologies). In this context, many solutions were proposed to provide seamless vertical handovers between WLAN and WiMax networks. These solutions aimed to perform the HO with minimum QoS degradation based on either the coupling architecture method, the mobility management protocol or the handover decision process. Our solution is based on the handover decision process that will make use of the emerging WiMax technology in order to guide the vertical handover to the suitable destination netw...

In recent years the technology in the field of wireless networks has been advanced. The mobile users are demanding access to the wireless networks at anytime and anywhere. To ensure the service continuity and to maintain the promising QoS, the decision regarding handoff is to be taken appropriately. The most common criteria for handoff is received signal strength which is not sufficient in advanced networks. Thus, this paper reviews the multi-criteria based handoff decision algorithms in wireless networks. Different techniques for multi-criteria handover are also discussed.

We present a simple and robust client-server architecture for streaming synchronized multimedia presentations to mobile terminals over a low-bandwidth connection. The server is similar to a compiler, and translates high level SMIL descriptions of multimedia presentations into low level content instructions. The client resembles a virtual machine, operating on content instructions that control the multimedia presentation. The compilation process on the server is designed to reduce the buffering on the client, and hence reduce the start-up delay for the user. Since the server takes the larger burden of the total work, the client can be kept simple. Upon request, the server assembles a sequence of content instructions corresponding to a multimedia presentation, under the optimistic assumption of a minimum communication bandwidth, and streams the content instruction sequence to the client without any other feedback mechanism than flow control. If the bandwidth assumption holds, the client renders the presentation as specified; otherwise, it is able to make controlled pauses in the presentation. We also describe a specific news application based on our architecture.

In beyond 3G systems, one of the important factors is to address Radio access technology (RAT) selection and load balancing between heterogeneous networks to ensure high spectral efficiency in an era where spectral resources are at a premium. This work aims to address the feasibility of utilizing WiFi as complementary service for HSDPA, to prevent quality of service deterioration in the event of network overload in HSDPA during the busy period. The proposed RAT selection algorithm is based on the load of each system, and the results show that the outage probability can be improved by up to 45% relative to a stand-alone HSDPA system.

The convergence of heterogeneous wireless access technologies characterizes the 4G wireless networks. In such network environment the user equipped with multiple network interfaces, would want to roam between different networks without any interruption in the running applications and services, in such a way that minimize the network usage cost. This paper proposed a algorithm to decide the best network at best time moment to handoffs. The proposed algorithm make the right vertical handoff decisions by determining the suitable network at required time among available networks based on dynamic factors such as Received Signal Strength(RSS) of network and velocity of mobile station as well as static factors such as Offered bandwidth, Power Consumption and Network usage cost. The proposed algorithm not only meets the individual user needs but also improve the whole system performance by reducing the unnecessary handoffs. The proposed algorithm is successfully developed, simulated and ana...

Many researchers have discussed various topics in universal mobile telecommunication system (UMTS) networks: the process of switching from one cell to another for the subscriber and the impact of the quality of the connection during the transition process, quality of services (QoS), the quality of the uplink and downlink carrier line, the various types of code for the voice transmitted through the Internet, especially the research that discussed voice over internet protocol (VoIP) technology as voice travels from cell to cell in mobile networks, depending on the type of delivery. In this paper, a proposed scenario of a UMTS network was implemented to evaluate the multicellular VoIP movement; the proposed UMTS network was simulated using the OPNET 14.5 simulator. The calculation and analysis of the different parameters of the user while moving from one cell to another with different movement speeds considered, the best mean opinion score (MOS) value (3.19) registered for the scenario (soft handover) comparing with another type of handover (3.00).

Fourth generation mobile communication systems are characterized by heterogeneous access networks and IP-based transport technologies. Different access technologies give users great flexibility in choosing services, which can be different in QoS support, business models, and service providers. Realization of seamless handovers to the best network section while considering QoS and AAAC (Authentication, Authorization, Accounting and Charging) calls not only for seamless handover protocols, but also intelligent handover decision strategies. The contribution of this paper is the design of a handover decision strategy in mobile All-IP networks to support seamless handover scenarios. Methods have been proposed to obtain QoS and AAAC information from candidate networks with minimum signalling overhead. New handover algorithms for wireless local area networks (WLANs) are also presented and evaluated with simulation results.

The next generation of wireless communications will be based on a heterogeneous infrastructure consisting different wireless and wired access systems where users will enjoy fast and seamless mobility and "anytime -anywhere" access to applications with least interruption and disruption of wireless connectivity .In this context, a strong need has been emerged to integrate WLAN with 3G mobile networks and design a hybrid architecture capable to suffice the needs of users with ubiquitous data services and seamless roaming .This paper addresses this need by introducing a vertical handoff algorithm for integrated UMTS-WLAN which uses signal strength as well as predefined threshold value to predict where and when the handover should occur, thus optimizing user throughput and network performance.

Transmission Control Protocol (TCP) is the vastly researched, used and implemented transport protocol from the bouquet of standardized protocols we have. Since its first introduction, TCP has experienced tremendous revolutions specifically regarding the way it should control congestion . Many TCP flavors exist, one can control its sending rate according to link bandwidth estimation like in the Westwood variant , while another tunes its congestion window (cwnd) based on the round-trip time (RTT) evaluation such as TCP Vegas , just to name few examples. However, all of these TCP versions assume a bulk transfer of data and thus they are optimized upon this type of traffic. On the other hand, Air Traffic Management (ATM) data traffic has other characteristics than file transfer. Messages generated from aeronautical services are triggered by events in the aeronautical environment. Further, these messages have bursty inter-arrival times, which can go up to several minutes, relatively small size mostly in the order of few hundreds of bytes and a maximum delay (a maximum of few seconds) that they have to be delivered within. As can be realized, a TCP source may experience some inactive periods due to the burstiness of the traffic. However, in , it is recommended that to control and avoid congestion, TCP should use slow start mechanism when restarting a transmission after a ratherly long idle period. The NEWSKY project recommends to design a transport protocol for avionics which is based on the User Datagram Protocol (UDP) but with reliability measures. Taking these suggestions into account, the Reliable User Datagram Protocol (RUDP) ) is an interesting option. However, it has features from TCP, which are not desirable for the ATM context, like connection initiation and shutdown, congestion control and byte streaming mechanism, which according to the authors of (NEWSKY, 2009) and (Muhammad & Berioli, 2010) reduce the performance of a transport protocol when transferring small files. Therefore, RUDP could be a highly qualified candidate to transport aeronautical traffic in case it is carefully re-designed and adjusted to consider the properties of an ATM traffic over highly asymmetrical links. Furthermore, in the context of checking the validity of TCP to transfer messages of ATM services, questions related to the performance of the protocol will be addressed. For example, the relation between the cwnd of TCP, aeronautical messages and congestion control. The Seamless Aeronautical Networking through integration of Data links, Radios and Antennas (SANDRA) (SANDRA, 2011) concept consists of the integration of complex and disparate communication media into a lean and coherent architecture. SANDRA as a project 4 www.intechopen.com 2 Future Aeronautical Communications is divided into several sub projects (SPs). This work belongs to the one dealing with seamless networking specifically for the transport layer protocols and performance task. Transport layer protocols should be assessed with respect to their suitability for aeronautical communication and their impact on the system availability and reliability. Finally, an optimization for these protocols in order to be used in avionics context should be provided. The work in this chapter is organized as follows. In the next Section, an overview about the aeronautical services is presented. In Section 3, the system architecture design in which the protocol will be operating is discussed. Section 4 explains some properties and illustrates few drawbacks of using TCP in avionics from theoretical and technical perspectives. The RUDP is further investigated in Section 5 where adjustment recommendations are given. In Section 6, detailed analysis of the ATM traffic pattern is shown and suggestions on system design are provided. Finally, a conclusion is drawn in Section 7.

Maintaining permanent availability and high quality connection to desired networks are amongst the essential concerns of heterogeneous networks considering user criteria. In this direction, suggesting solutions to decrease the processing delay and the number of extra vertical handovers of the SAW and TOPSIS through proposed techniques are the main purpose of this paper.

Handoff in Vehicular Adhoc Networks (VANET) is a process in which one vehicle disconnected from one network and join to another network. In VANET, handover is a big challenge for a vehicle due to high mobility and the process of handover occurs frequently. This mobility of a vehicle creates a lot of issues. Many solutions have been proposed to resolve these problems and some of them became standardized like MIPv6, HMIPv6, PMIPv6, and NEMO BS. In this research, we have addressed issues that lie in such network, when a vehicle performs the handover procedure. The challenges that a vehicle faces in handover procedure have been discussed and compared. Also, a methodology Cluster Based Handoff using Backup node (CBHBCK) is proposed to achieve the continuity in the network named as cluster based handoff using backup node, in which a backup node that is responsible for handoff is introduced. Using this backup node overhead on cluster head and disconnectivity during handoff procedure will be reduced. At the end, results are compared with the NEMO and Cluster Based technology by simulation using NS2 simulator. Simulation result proves that the proposed technique has better ability to achieve the continuity in communication during handoff procedure.

Le travail réalisé s’inscrit dans le contexte du développement des observatoires câblés de fond de mer. Il s’agit de dimensionner des dispositifs de capteurs sous-marins opto-alimentés, afin de développer des systèmes d’observation plus flexibles Dans ce contexte, nous avons proposé et testé une extension tout-optique qui permet la transmission conjointe de la puissance et des données sur une fibre optique unique. Ce dispositif nécessite la transmission de fortes puissances optiques pour recueillir une puissance électrique suffisante pour alimenter un capteur. La présence de forte puissance optique engendre la manifestation de phénomènes optiques dont les effets et leur interaction doivent être étudiés Nous souhaitons étendre cette étude à l'opto-alimentation de capteurs dans de nouvelles configurations (multicapteurs, réseau de capteurs). Ceci nous amène à compléter notre étude expérimentale en prenant en compte ces nouvelles configurations de réseaux opto-alimentés. Les résult...

Existing terminal oriented handover mechanisms capable of meeting the strict delay bounds of real time applications such as VoIP do not consider the QoS of candidate handover networks. In this paper ECHO -a QoS based handover solution for VoIP-is proposed. ECHO is endpoint centric and does not require any network support; it leverages the SCTP transport protocol. ECHO incorporates network metrics that directly affect VoIP quality into the handover decision process. A dynamic variant of the ITU-T E-Model is used to calculate how the network metrics map to a user perceived voice quality metric known as the MOS. The MOS value is then used to make handover decisions between each of the available access networks. The results show that the addition of the QoS capabilities significantly improves the handover decisions that are made.

Abstract. Fixed to mobile convergence is a very promising field due to the success in recent years of mobile devices such as smart phones and PDAs. A wide variety of wireless technologies ranging from Bluetooth, Wi-Fi, Wimax, to GPRS, UMTS and its later releases, allow ubiquitous connectivity. Roaming between different access technologies will be an important area of activity. As a result of the heterogeneity of radio access technologies, there is a growing trend to use IP as underlying protocol. Analysing the behaviour of IP based ...

In this paper we extend the base station (BS) assignment problem to incorporate backhaul related constraints into the assignment decision. This is motivated by the fact that the deployment of more spectral efficient radio access technologies are currently imposing stringent bandwidth requirements at cell sites, and there is a growing concern that backhaul network can become a new network bottleneck in certain deployment scenarios. Unlike existing assignment approaches, we propose a BS assignment algorithm envisioned as a suitable technique capable to cope, at some extent, with possible backhaul congestion situations in OFDMA-based systems. Simulation results demonstrate that the proposed algorithm can provide the same system capacity with less backhaul resources so that, under backhaul bottleneck situations, a better overall network performance is effectively achieved.

The network selection is a decisional process aimed at determining the Radio Access Network (RAN) that a Mobile Node (MN) has to use and represents the core-function of the Vertical Handover procedure. In this paper, the authors propose a new algorithm for the network selection, called Dynamic-Technique for Order of Preference by Similarity to Ideal Solution (D-TOPSIS) that is a new formulation of the TOPSIS algorithm aimed at performing the same selection but requiring a minor number of operations and consequently reducing the time necessary to perform the selection. The main contribution of this work is the evaluation of the D-TOPSIS performance in a scenario where are available simultaneously a satellite network and Wi-Fi and WiMAX networks. The proposed approach is compared with other network selection methods found in the literature in two different cases: i) pedestrian, with a MN speed equal to 3 [m/s] and ii) vehicular, with a MN speed equal to 10 [m/s]. The numerical results show that D-TOPSIS assures a good performance as well as a limited execution time in both cases.

5G slicing has become a key technology in 5G and beyond (B5G) for realizing IMT 2020 services, including enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC). These advancements necessitate the support of advanced technologies and optimal solutions to satisfy the network requirements of IMT-2020 services. This study evaluated enhancements through network slicing, focusing on access and diversity technologies. Specifically, it examines the application of access and diversity technologies, such as orthogonal multiple access (OMA), non-orthogonal multiple access (NOMA), maximal ratio combiner (MRC), frequency diversity, spatial diversity, and other types of diversity. These technologies are tailored to various service combinations to optimize the 5G performance, including throughput, latency, capacity, and energy efficiency. Network slicing is a significant concept that allows the virtual division of a single physical infrastructure into several logical networks. Network slicing is commonly achieved using orthogonal access technology, specifically OMA. This approach ensures that separate services are assigned non-interfering resources. As the user population expands, OMA-based slicing may not always be the most effective approach, and employing a non-orthogonal strategy could potentially yield superior performance. In this paper, the classification of 5G slicing methods is comprehensively explained such that the correlations among slicing, access technologies, and diversity are well defined and identified according to the characteristics of each service. A systematic literature review was conducted to provide guidelines for the design of 5G network models. INDEX TERMS 5G, B5G, enhanced mobile broadband (eMBB), frequency diversity, massive machine type communication (mMTC), network slicing, non-orthogonal multiple-access (NOMA), orthogonal multipleaccess (OMA), spatial diversity, ultra-reliable low latency (URLLC).

Radio over Fiber technology (RoF), an integration of wireless and optical systems is a promising solution for increasing the capacity and mobility of the access network cost effectively. RoF has the potentiality to the backbone of the wireless access network and it has gained significant momentum in the last decade as a potential last-mile access scheme. This paper gives the brief introduction of radio over fiber technology used in communication system. In these paper quality parameters, optical transport schemes for wireless signals, advantages and limitations of the RoF technology are discussed. Some transmission techniques for generating and transporting radio signal over fiber are also explained in this review paper.

Emerging Vehicle-to-Everything (V2X) applications such as Advanced Driver Assistance Systems (ADAS) and Connected and Autonomous Driving (CAD) requires an excessive amount of data by vehicular sensors, collected, processed, and exchanged in real-time. A heterogeneous wireless network is envisioned where multiple Radio Access Technologies (RATs) can coexist to cater for these and other future applications. The primary challenge in such systems is the Radio Resource Management (RRM) strategy and the RAT selection algorithm. In this article, a Hybrid Vehicular Network (HVN) architecture and protocol stack is proposed, which combines Dedicated Short-Range Communication (DSRC) technology-enabled ad hoc network and infrastructure-based Cellular V2X (C-V2X) technologies. To this end, we address the design and performance evaluation of a distributed RRM entity that manages and coordinates Radio Resources (RR) in both RATs. Central to distributed RRM are adaptive RAT selection and Vertical Handover (VHO) algorithms supported by two procedures. (1) Measurement of Quality of Service (QoS) parameters and associated criteria to select the suitable RAT according to the network conditions. (2) Dynamic communication management (DCM) via implementing RR-QoS negotiation. The simulation results show the effectiveness of the proposed architecture and protocol suite under various parameter settings and performance metrics such as the number of VHOs, packet delivery ratio, and throughput, and latency. INDEX TERMS C-V2X, DSRC, hybrid vehicular networks, IEEE 802.11p, LTE, RAT selection, vertical handover (VHO).

Nowadays, with the abundance of diverse air interfaces in the same operating area, advanced Radio Resource Management (RRM) is vital to take advantage of the available system resources. In such a scenario, a mobile user will be able to connect concurrently to different wireless access networks. In this paper, we consider the downlink of a hybrid network with two broadband Radio Access Technologies (RAT): WiMAX [1] and WiFi . Two approaches are proposed to load balance the traffic of every user between the two available RATs: an individual approach where mobile users selfishly strive to improve their performance and a global approach where resource allocation is made in a way to satisfy all mobile users. We devise for the individual approach a fully distributed resource management scheme portrayed as a non-cooperative game. We characterize the Nash equilibriums of the proposed RRM game and put forward a decentralized algorithm based on replicator dynamics to achieve those equilibriums. In the global approach, resources are assigned by the system in order to enhance global performances. For the two approaches, we show that after convergence, each user is connected to a single RAT which avoids costly traffic splitting between available RATs.

This article proposes criteria and mechanisms that achieve seamless inter-working between the multiradio access technologies that will compose the fourth-generation (4G) wireless mobile environment. We address the problem of incorporating system interoperability in order to provide the user with seamless mobility across different radio access technologies; namely we focus on inter-working UMTS-High Speed Downlink Packet Access (HSDPA) and WLAN networks, as these two networks are believed to be major components of the 4G wireless network. Interoperability results in providing the user with a rich range of services across a wide range of propagation environment and mobility conditions, using a single terminal. Specifically, the article aims at defining the criteria and mechanisms for interoperability between the two networks. Our approach considers the use of Cost functions to monitor the essential parameters at the system level in order to trigger an interoperability procedure. Initial user assignment and inter-system handover are considered the incidents that initiate the interoperability algorithm execution. The overall objective of this work is to assess the performance of our developed interoperability platform and to optimize system performance by guarantying a minimum QoS requirement and maximizing network capacity.

The proliferation of wireless broadband usage over the last decade has led to the development and deployment of multiple broadband wireless radio access technologies (RATs) such as EVDO, WiMAX, HSPA and LTE. To support the ever-increasing wireless traffic demand, researchers have worked on the concept of an integrated heterogeneous wireless environment that encompasses several of these RATs which makes the resource allocation process more efficient by assigning each user in the system to the best RAT/RATs. In this paper, for such an integrated heterogeneous wireless system, we show the possible gains in spectral efficiency at the cost of increased energy consumption for an unbalanced heterogeneous wireless network deployment scenario. In prior work, based on the assumption that all cellular operators under study were equally well-provisioned, we showed an increase in spectral efficiency of up to 75%. In the research presented in this paper, we assume the coverage of each operator might differ significantly in a given area. With this 'unbalanced' scenario, we show that an ideal, centralized allocation strategy provides an almost linear tradeoff between gain in spectral efficiency (554%) and worst-case increase in energy consumption (615%) for users supporting elastic traffic.

As broadband data further blends with cellular voice, mobile devices will become the dominant portals to the connected world. However current design practices still involve building independent networks that each make their own resource decisions. To move beyond 4G, wireless networks will need to cooperate to provide better performing and more robust wireless services. In this paper, we present a 'cleanslate' approach to wireless networking. The approach requires the following assumptions to hold: 1)Incentives are in place motivating independent, autonomous wireless systems (AWSs) to cooperate with each other to provide users with universal broadband wireless coverage; 2)In any given geographic area, a handset might have access to many independent, autonomous wireless networks; 3)Mobile nodes will support a small number of adaptive radios that are capable of operating in a number of supported communication modes and over a range of spectrum. With these liberating assumptions, we present an architecture for a heterogeneous wireless system that moves beyond 4G systems. We present preliminary results from a MATLABbased simulation designed to demonstrate the essence of the ideas. We identify the key research challenges that must be addressed to move the idea from a concept to a viable network system.

The Quality for Service Protocol draft-aranda-dispatch-q4s-02.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

In beyond 3G systems, one of the important factors is to address Radio access technology (RAT) selection and load balancing between heterogeneous networks to ensure high spectral efficiency in an era where spectral resources are at a premium. This work aims to address the feasibility of utilizing WiFi as complementary service for HSDPA, to prevent quality of service deterioration in the event of network overload in HSDPA during the busy period. The proposed RAT selection algorithm is based on the load of each system, and the results show that the outage probability can be improved by up to 45% relative to a stand-alone HSDPA system.

This paper introduces a new paging technique to track and wake up a mobile node (MN) attached to an access point (AP) in a wireless LAN network after a session initiation protocol (SIP) INVITE message is initiated by a caller. A tracking agent (TA) keeps track of the mobiles' handoffs between the APs. A paging agent (PA) triggers the TA to page the mobile when a SIP INVITE is received for one of its users. The context transfer feature of our paging protocol allows the paging messages to deliver the station context in order to enable faster session reestablishment. The AP then does onlink paging in a wireless link. SIP extensions are needed to trigger the PA to start paging MNs to notify their dormant status using an extended SIP REGISTER method. Tracking protocol is analyzed to compare soft-and hard-state approaches for state inconsistency ratio, message rate, and the overall cost. The simulation model we developed enables us to evaluate the traffic introduced by the tracking protocol and the cache (state) size. Paging protocol is analyzed for CPU processing times and the transmission delays in the SIP session setup with paging. Simulation of the paging with context transfer is used to show the gains in reauthentication. Index Terms-Context transfer, fluid flow and random walk mobility model, onlink paging, paging agent (PA), session initiation protocol (SIP), tracking agent (TA).

In recent years, the need for broadband wireless access, is directly associated with the demand for multimedia services (e.g. video streaming, videoconference or even high speed web browsing), especially inside hot-spot areas. The evolution of "third-generation" (3G) systems seems a very promising answer to the users' demands for enhanced service provision. However the successful deployment of 3G systems is frequently debated these days. Furthermore, the beyond 3G systems or the so called "fourth generation" (4G) systems (i.e. multiple different radio access technologies, collaborating with each other, providing both diverse access alternatives and QoS improvement) attract the interest of both network and service providers. Taking into consideration the above described trends in the area of wireless network systems, the IP-enabled DVB-T (the terrestrial specification of the Digital Video Broadcasting family) networks are considered as an appealing network access alternative. Along this direction, this paper presents the most important points; as far as concerns network planning and performance evaluation, arise from the IP-enabled DVB-T networks utilization, inside beyond 3G systems.

This paper presents a study addressed to evaluate the variation in perceived QoS experienced by a user running multimedia applications in a heterogeneous wireless network. To perform this evaluation, a real-time testbed emulating an all-IP B3G network that includes UMTS Terrestrial Radio Access Network (UTRAN), GSM/EDGE Radio Access Network (GERAN), and Wireless Local Area Network (WLAN); and the corresponding common core network (CN) based on DiffServ technology and Multiprotocol Label Switching (MPLS) has been used. Results for videostreaming and video conference applications when running under interruptions due to a vertical handover (VHO) are included in this paper, pointing out the variations in behaviour of different applications.

The coexistence of 3G cellular networks with wireless local area networks (WLAN) has been a topic of great interest to the experts in recent years. Heterogeneous networks can complement each other in terms of data rate and coverage area. WLAN provides a high bandwidth data service over a small area while the 3G cellular network provides a higher mobility with lower bandwidth data service. When a mobile node switches between networks, vertical handoff (VHO) that ensures an uninterrupted data service becomes important. During VHO the conventional TCP scheme suffers packet reordering and premature timeout which causes severe throughput degradation. In this paper we propose a Sender based Freeze-TCP (SFTCP) scheme for seamless vertical handoff. SFTCP stops transmitting packets before the disconnection occurs in a way inspired by Freeze-TCP, then it probes link bandwidth after the reconnection to enable the full use of the newly available bandwidth. Instead of using
conventional mechanism of freezing we propose a new technique where the mobile sender controls the freezing behavior. Through this approach we can have an immediate recovery upon reconnection as well as a significantly improved window adjustment to the newly available network conditions. Simulation results show that our proposed scheme can achieve faster recovery and improved throughput.

A key aspect of Beyond 3G heterogeneous wireless systems is the definition of Joint Radio Resource Management techniques capable to efficiently manage the radio resources from different Radio Access Technologies physically coexisting. This work proposes a set of JRRM techniques based on linear programming optimization tools that simultaneously assign to each user the adequate radio access technology and number of

The advent of software-defined radio products and recent advances in cognitive radio research will facilitate the preservation or even improvement of user perception in volatile radio conditions while optimizing the use of network resources. Based on cognition techniques, the autonomic communication paradigm attempts to pave the way towards self-governed systems that will alleviate the shortcomings of present remotely managed user devices. This article identifies the challenges for such cognitive reconfigurable systems and introduces CORPS, a new end-to-end architecture that unifies software and cognitive radio themes enriched by selfware capabilities. The manuscript discusses the adopted network-agnostic protocolindependent modeling approach, which is in line with best common practices in the industry, and presents the system architecture in terms of functional specification and UML modeling. Next, the CORPS functional architecture is mapped to the evolved-UMTS system under development in 3GPP. Finally, the paper proposes and evaluates CREST, a novel signaling protocol for improving the quality of service of existing bearers in a post-3G network through radio-access-technology switching and coordinated dynamic spectrum access.

The Autonomic Communications concept emerges as one of the most promising solutions for future heterogeneous systems networking. This notion implies the introduction of advanced mechanisms for autonomic decision making and self-configuration. To this end, this paper proposes an integrated framework that facilitates autonomic features to capture the needs for RAT selection and device reconfiguration in a Composite Radio Environment. Specifically, a game theoretical approach targeted to the definition of appropriate policies for distributed equipment elements is presented. Thus, the user terminals are able to exploit context information in order to i) identify an optimum trade-off for (multiple) Radio Access Technology (RAT) selection and ii) adapt the protocol stack and respective protocol functionality using a proposed component based framework for transparent protocol component replacement. Simulation and performance results finally show that the proposed mechanisms lead to efficient resource management, minimizing the complexity on the network and terminal side as well as keeping the required signaling overhead as low as possible.

The advent of software-defined radio products and recent advances in cognitive radio research will facilitate the preservation or even improvement of user perception in volatile radio conditions while optimizing the use of network resources. Based on cognition techniques, the autonomic communication paradigm attempts to pave the way towards self-governed systems that will alleviate the shortcomings of present remotely managed user devices. This article identifies the challenges for such cognitive reconfigurable systems and introduces CORPS, a new end-to-end architecture that unifies software and cognitive radio themes enriched by self-ware capabilities. The manuscript discusses the adopted network-agnostic protocol-independent modeling approach, which is in line with best common practices in the industry, and presents the system architecture in terms of functional specification and UML modeling. Next, the CORPS functional architecture is mapped to the evolved-UMTS system under devel...

The emergence of multi-Radio Access Technology (RAT) networks has revolutionized mobile communications by integrating various network technologies to enhance connectivity, coverage, and overall user experience. This paper explores the critical issue of call drops and accessibility challenges within multi-RAT networks, focusing on how the integration of multiple RATs such as 2G, 3G, 4G, and 5G can impact network performance and user satisfaction. Call drops and accessibility issues remain significant challenges in mobile network operations, affecting user experience and network reliability. In multi-RAT environments, where multiple network technologies coexist to provide seamless connectivity, these issues can become more complex. Call drops, characterized by abrupt disconnections during ongoing calls, and accessibility issues, which include difficulties in establishing connections, are influenced by various factors such as network handover processes, signal strength, interference, and coverage gaps. Multi-RAT networks aim to provide a seamless user experience by leveraging the strengths of different RATs. For instance, 2G and 3G technologies offer wide coverage and are beneficial in areas with limited 4G or 5G coverage, while 4G and 5G technologies provide high-speed data and advanced features. However, the integration of these diverse technologies introduces challenges related to interoperability, handover management, and network optimization. The integration of multiple RATs in modern networks presents both opportunities and challenges. While multi-RAT networks enhance connectivity and provide improved user experiences, call drops and accessibility issues remain critical concerns. Addressing these challenges requires a combination of advanced handover mechanisms, optimized network planning, and effective interference and traffic management strategies. By implementing these solutions, network operators can enhance the reliability and performance of multi-RAT networks, ultimately improving user satisfaction and network efficiency.

I would like to thank my adviser, Dr. Fernando J. Velez, for all the knowledge and guidance he provided during this journey. I also want to thank several friends that helped me with the work that will be presented in the following pages and highlight that this work would not be possible without their help. First of all I would like to thank the engineer Rui Paulo for the support, friendship, and for his help with the work involving the LTE-Sim, for the knowledge he shared and for the codes he provided that made it possible to perform most of the simulations done with LTE-Sim. To Bruno Cruz for his friendship during all my time in Portugal and for the help he provided with the code he developed that were key to the results that will be shown in this thesis. To my great Brazilian friend Rooderson Andrade, who not only helped me with the knowledge about MIMO but also supported me in all moments. To Marisa Lourenço, my college at the Instituto de Telecomunicações who helped a lot with the work performed with Matalab.To Emanuel Teixeira for his support in several aspects of this work, specially with the work involving Matlab. To Emanuel Mahina, another college from the Instituto de Telecomunicações whose friendship and insights were of paramount importance. To all the teachers I had during this Master course and that guided me through the different areas of knowledge that contributed to this work. Finally, I would like to thank the Instituto de Telecomunicações for the opportunity, and for the scholarship supported by National Founding from FCT through CONQUEST (CMU/ECE/030/2017), for the support provided via National Founding from FCT through the UID/EEA/50008/2013, and as well as for the equipment provided by ORCIP (CENTRO-01-0145-FEDER-022-141) and for the support from COST CA 15104.

This paper investigated the energy utilisation of edge IoT mobile devices on the 3G and 4G networks, specifically focusing on the impact of the distance from the base station and user-friendly applications. Measurements were taken, and data was collected on a live network during active and passive sessions using enabling software on the test device. The study found that energy consumption varies based on distance, service type, and network usage. With IoT-matched software applications, the Umudigi A9 Pro device showed increased power consumption as distance from the base station increased and as a function of the network utilised. The study also examined video streaming, voice calls, and video playback services, focusing on their energy profiles. The analysis of both real-time and non-real-time services was carried out. Real-time services exhibited an average maximum power consumption of 243.2mW, while non-realtime usage averaged 209.1mW. The internal energy utilisation levels ranged from 370.1mW to 446.9mW for online idle radio operations and from 322.5mW to 458.3mW for offline idle radio operations, varying from the cell centre to the cell edge within a base station sector. It was shown that real-time applications on edge mobile user equipment (UEs) are more energy-intensive than other applications. Their energy requirements increased as these nodes moved towards the cell edge of the network coverage area, possibly due to Signal-to-Interference-plus-Noise Ratio (SINR) limitations. Real-time services require more energy than non-real-time services and understanding the relationship between signal strength and test device energy requirements about the service deployed can serve as an advisory tool for energy management.

Background: Due to the rising prevalence of smart devices and the need for dependable, high-speed internet connections, it is imperative to enhance existing network infrastructures. The fundamental framework of mobile telephony, referred to as RAN (Radio Access Network), needs help fulfilling these requirements due to its restricted capacity and concerns over scalability. Objective: The purpose of this research is to investigate the capabilities of 5G technology in addressing these restrictions, with a specific focus on integration techniques, advantages, and obstacles. Methodology: The study used a mixed-method approach to assess the efficacy and feasibility of incorporating 5G-RAN. This is achieved by integrating quantitative data from pilot studies with qualitative literature analysis. Results: The findings suggest that using 5G technology results in substantial improvements in data transfer rates, reduced latency, enhanced network reliability, scalability, and lowered latency. However, several obstacles have been identified, including the significant costs

Carrier aggregation (CA) is a technology introduced by the Long-Term Evolution-Advanced (LTE-A) system to increase user throughput by combining a selected number of component carriers (CCs). Its integration with heterogeneous networks enables the mobile user equipment to take advantage of increased throughput and radio coverage of various access technologies. However, due to the mobility of user equipment, these innovations have increased the likelihood of handoff scenarios, resulting in a high outage probability and low throughput. Handover is a crucial part of mobility management since it enables users to move from one cell to another while maintaining connections. However, no single access technique can provide seamless communication without interruption or delay. As a result, creating a suitable handover decision algorithm is necessary for ensuring high-quality service continuity and dependable user equipment access to the network at all times. An Adaptive Real-Time Spectrum Sel...

Une architecture de réseau d'accès optique multiplexé en longueur d'onde (WDM-PON) utilisant des émetteurs achromatiques à base de lasers Fabry-Perot verrouillés en longueur d'onde par injection optique est proposée. Une source multi-longueur d'onde composée d'un seul laser à modes bloqués à bâtonnets quantiques est utilisée pour verrouiller les lasers Fabry-Perot. La transmission bidirectionnelle de 8 canaux sur 20 km de fibre dans une telle architecture a été réalisée à 2,5 Gb/s par canal et un bilan optique total de 23 dB a été obtenu.

Ultra Dense Network (UDN) is the extreme densification of heterogeneous Radio Access Technology (RAT) that is deployed closely in coordinated or uncoordinated manner. The densification of RAT forms an overlapping zone of signal coverage leading to the frequent service handovers among the RAT, thus degrading overall system performance. The current RAT selection approach is biased towards network-centric criteria pertaining to signal strength. However, the paradigm shift from network-centric to user-centric approach necessitates a multi-criteria selection process, with methodology relating to both network and user preferences in the context of future generation networks. Hence, an effective selection approach is required to avoid unnecessary handovers in RAT. The main aim of this study is to propose the Context-aware Multiattribute decision making for RAT (CMRAT) selection for investigating the need to choose a new RAT and further determine the best amongst the available methods. The ...

Ultra Dense Network (UDN) is the extreme densification of heterogeneous Radio Access Technology (RAT) that is deployed closely in coordinated or uncoordinated manner. The densification of RAT forms an overlapping zone of signal coverage leading to the frequent service handovers among the RAT, thus degrading overall system performance. The current RAT selection approach is biased towards network-centric criteria pertaining to signal strength. However, the paradigm shift from network-centric to user-centric approach necessitates a multi-criteria selection process, with methodology relating to both network and user preferences in the context of future generation networks. Hence, an effective selection approach is required to avoid unnecessary handovers in RAT. The main aim of this study is to propose the Context-aware Multiattribute decision making for RAT (CMRAT) selection for investigating the need to choose a new RAT and further determine the best amongst the available methods. The CMRAT consists of two mechanisms, namely the Context-aware Analytical Hierarchy Process (CAHP) and Context-aware Technique for Order Preference by Similarity to an Ideal Solution (CTOPSIS). The CAHP mechanism measures the need to switch from the current RAT, while CTOPSIS aids in decision making to choose the best target RAT. A series of experimental studies were conducted to validate the effectiveness of CMRAT for achieving improved system performance. The investigation utilises shopping mall and urban dense network scenarios to evaluate the performance of RAT selection through simulation. The findings demonstrated that the CMRAT approach reduces delay and the number of handovers leading to an improvement of throughput and packet delivery ratio when compared to that of the commonly used A2A4-RSRQ approach. The CMRAT approach is effective in the RAT selection within UDN environment, thus supporting heterogeneous RAT deployment in future 5G networks. With context-aware selection, the user-centric feature is also emphasized.

The increase will of ubiquitous access of the users to the requested services points towards the integration of heterogeneous networks. In this sense, a user shall be able to access its services through different access technologies, such as WLAN, Wimax, UMTS and DVB technologies, from the same or different network operators, and to seamless move between different networks with active communications. In this paper we propose a mobility architecture able to support this users' ubiquitous access and seamless movement, while ...

Internet of Vehicles (IoV) is a network of vehicles communicating with each other by exchanging road traffic information via radio access technologies. Two potential technologies of V2X that have gained attention over the past years are DSRC and cellular networks such as 4G LTE and 5G. DSRC is suitable for low latency communications, however provides a shorter coverage range whereas, 4G LTE offers a wide coverage range but has high transmission time intervals. In contrast, 5G offers higher data rates, low latencies but prone to blockages. Single technology might not fully accommodate the requirements of vehicular communications. Hence, it is required to interwork with more than one radio access network to satisfy the requirements of safety vehicular applications. One issue identified when working with multiple radio access networks is the selection of the most appropriate network for vertical handover. Usually, in the previous works, the network is selected directly or will be connected to the available network due to which the handover had to take place frequently resulting in unnecessary handovers. Hence, in the existing state-of-the-art, the need for handover is not validated. In this paper, we have proposed a dynamic Q-learning algorithm to validate the need for handover, and then, appropriate selection of network would take place by using a fuzzy convolutional neural network. Besides, a modified jellyfish optimization algorithm is proposed to select the shortest paths by forming V2V pairs that take into account channel metrics, vehicle metrics, and vehicle performance metrics. The proposed algorithms are then evaluated using OMNET++ and compared with the existing state-of-the-art concerning mean handover, HO failure, throughput, delay, and packet loss as the performance metrics.

Je tiens à remercier Monsieur Jean LE BIHAN pour son soutien scientifique et pour la confiance qu'il a pu m'accorder. Je remercie particulièrement Monsieur André PÉRENNOU pour sa direction avisée et la rigueur scientifique apportée lors de cette thèse. Je tiens également à remercier Madame Véronique QUINTARD et Monsieur Mikael GUÉGAN, pour m'avoir encadré avec Monsieur André PÉRENNOU. Cette équipe m'a dirigé, soutenu et motivé pendant l'ensemble de la thèse. Je leur suis reconnaissant pour les nombreuses discussions fructueuses lors des réunions de travail et leur disponibilité tout au long de la thèse. Je remercie Monsieur Pascal BESNARD, Professeur des Universités à l'ENSSAT à Lannion, qui m'a fait l'honneur de présider le jury de cette thèse. J'exprime également ma sincère gratitude à Monsieur Bernard ORSAL, professeur