Handover mechanisms in 3GPP long term evolution (LTE)

University of Technology, Sydney. Faculty of Engineering and Information Technology.The Long-Term Evolution (LTE) network is a new radio access technology (RAT) proposed by the Third Generation Partnership Project (3GPP) to provide a smooth migration towards the fourth generation (4G) network. Long Term Evolution-Advanced (LTE-A) is a major enhancement of the LTE standard proposed by the 3GPP to meet the 4G mobile communication standards. Handover is one of the key components in cellular network mobility management. Handover is a mechanism that transfers an on-going call or data session from one base station (BS) to another BS or one sector to another sector within the same BS. Hard handover has been adopted in LTE and LTE-A systems by 3GPP due to the flat IP-based architecture and the lack of a centralized controller. The use of hard handovers reduces the complexity of the handover mechanism and minimizes the handover delay. However, the hard handover approach causes call drops that may result in lost data during a session. The objective of this thesis is to provide the basis for improving handover performance in the LTE and LTE-A systems. A C++ system level simulator that can dynamically model the large and complex downlink LTE and LTE-A was developed as part of this research work followed by a proposed handover parameters optimization method. The simulation results show that the handover parameters optimization method can effectively minimize the unnecessary number of handovers while maximizing the system throughput. Under an initial assumption of an ideal mobile cellular channel (i.e. the mobile cellular channel is not subject to any impairment), this thesis proposes a new handover algorithm in the LTE system and three new Coordinated Multiple Transmission and Reception (CoMP) handover algorithms in the LTE-A system. The simulation results show that the proposed handover algorithm outperforms well-known handover algorithms in the LTE system by having less number of handovers, shorten total system delay whilst maintaining a higher total system throughput. The performance of the proposed CoMP handover algorithms are evaluated and compared with open literature CoMP handover algorithm via simulation. It is shown via simulation that the proposed CoMP handover algorithms can improve the system throughput and minimize the system delay in a saturated system scenario in the LTE-A system. A more practical LTE-A system where the mobile cellular channels are subject to impairments is considered for performance testing of selected CoMP handover algorithms. The impairments for a practical LTE-A system are assumed to be in two scenarios: outdated feedback and missing feedback. It is shown via computer simulations that the system throughput and system delay are very sensitive against outdated Channel Quality Information (CQI) feedback and missing CQI feedback. Furthermore, a handover failure caused by an inappropriate feedback increases the number of unnecessary handovers which require additional resources in the network and may significantly degrade the system performance

Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks

Soaring capacity and coverage demands dictate that future cellular networks need to soon migrate towards ultra-dense networks. However, network densification comes with a host of challenges that include compromised energy efficiency, complex interference management, cumbersome mobility management, burdensome signaling overheads and higher backhaul costs. Interestingly, most of the problems, that beleaguer network densification, stem from legacy networks' one common feature i.e., tight coupling between the control and data planes regardless of their degree of heterogeneity and cell density. Consequently, in wake of 5G, control and data planes separation architecture (SARC) has recently been conceived as a promising paradigm that has potential to address most of aforementioned challenges. In this article, we review various proposals that have been presented in literature so far to enable SARC. More specifically, we analyze how and to what degree various SARC proposals address the four main challenges in network densification namely: energy efficiency, system level capacity maximization, interference management and mobility management. We then focus on two salient features of future cellular networks that have not yet been adapted in legacy networks at wide scale and thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and device-to-device (D2D) communications. After providing necessary background on CoMP and D2D, we analyze how SARC can particularly act as a major enabler for CoMP and D2D in context of 5G. This article thus serves as both a tutorial as well as an up to date survey on SARC, CoMP and D2D. Most importantly, the article provides an extensive outlook of challenges and opportunities that lie at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201

Evaluation of High-speed Train Communication Handover Models Based on DEA

Broadband communications for high speed train is becoming a main trend in high mobility communications. The main bottleneck of this communication network is handover, since the handover occurs so frequently and the delays are so long that broadband real-time communication cannot apply. Various handover models have been developed and studied recently. However, no comprehensive evaluation method for these models is employed. To this end, we borrow Data Envelopment Analysis (DEA) method to evaluate six typical handover system models. Handover models that to be evaluated are introduced. A brief presentation of DEA and its characters is provided. A specific procedure of the evaluation is proposed. Then the results of the evaluation are obtained by running the DEA. Finally, we give our comments and conclusions to all the handover models. We hope our work will supply a gap in the system evaluation area.Comment: 5 pages, accepted for publication, The IEEE 79th Vehicular Technology Conference (VTC 2014 Spring), May, 201

Algoritmos de transferência de redes LTE em meios de transporte massivo

Handover in LTE occurs when a device moves from the cell coverage serving it towards another; a process where the user established session must not be interrupted due to this cell change. Handovers in LTE are classified as hard ones, since the link with the serving cell is interrupted before establishing the new link with the target cell. This entails a larger failure risk and, consequently, a potential deterioration in the quality of service. This article presents a review of the handover algorithms in LTE, focusing on the ones oriented to massive means of transport. We show how the new algorithms offer a larger success in handovers, increasing the networkdata rate. This indicates that factors such as speed, position, and direction should be included in the algorithms to improve the handover in means of transport. We also present the algorithms focused on mobile relays such as an important study field for future research works.El traspaso en LTE se presenta cuando un equipo pasa de la cobertura de una celda a la de otra, un proceso en el que se debe asegurar que el usuario no vea interrumpida su sesión, como efecto de ese cambio de celda. Los traspasos en LTE son del tipo duro, en ellos, el enlace con la celda servidora se interrumpe antes de establecer el nuevo enlace con la celda destino, lo que conlleva a un mayor riesgo de falla y con ello a un probable deterioro de la calidad del servicio al usuario. Este artículo revisa algoritmos de traspaso LTE, enfocándose en aquellos orientados a medios de trasporte masivo. Muestra cómo los nuevos algoritmos ofrecen una tasa mayor de traspasos exitosos y con ello una mejor tasa de transferencia de datos; evidencia que factores como la velocidad, la posición y la dirección deben ser incluidos en los algoritmos dirigidos a mejorar el traspaso en medios de transporte; y presenta a los algoritmos enfocados en relays móviles, como un importante campo de estudio para futuras investigaciones.A transferência em LTE ocorre quando um dispositivo passa da cobertura de uma célula para outra, um processo no qual deve ser assegurado que o usuário não veja sua sessão interrompida, como resultado dessa mudança de célula. As transferências em LTE são do tipo duro, nelas, o link com a célula do servidor é interrompido antes de se estabelecer o novo link com a célula alvo, o que leva a um maior risco de falha e, portanto, a uma provável deterioração da qualidade do serviço ao usuário. Este artigo revisa os algoritmos de transferência LTE, com foco naqueles orientados a meios de transporte massivo. Mostra como os novos algoritmos oferecem uma taxa maior de transferências bem-sucedidas e, com isso, uma melhor taxa de transferência de dados; evidencia de que fatores como a velocidade, a posição e a direção devem ser incluídos nos algoritmos que visam melhorar a transferência nos meios de transporte; e apresenta os algoritmos focados em relés móveis, como um importante campo de estudo para futuras pesquisas

A Moving Direction and Historical Information Assisted Fast Handover in LTE-A

Handover is one of the critical features in mobility management of Long Term Evolution Advanced (LTE-A) wireless systems. It allows the User Equipment (UE) to roam between LTE-A wireless networks. LTE-A is purely on hard handover, which may cause loss data if the handover is not fast. In this paper, an advanced technique proposed which combined between the current UE moving direction and its history information. Our proposed tracks the UE positions to discover its direction. When the UE is being near to handover area the UE starts searching in its history to return back the target cell. If the UE trajectory does not exist in its history then the UE and its serving cell start searching for target cell through using cosine function in order to select target cell.  Our proposed technique is expected to increase the throughput, reduce the packet delay and loss, and reduce the frequent handovers