2,625 research outputs found
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
Partially Blind Handovers for mmWave New Radio Aided by Sub-6 GHz LTE Signaling
For a base station that supports cellular communications in sub-6 GHz LTE and
millimeter (mmWave) bands, we propose a supervised machine learning algorithm
to improve the success rate in the handover between the two radio frequencies
using sub-6 GHz and mmWave prior channel measurements within a temporal window.
The main contributions of our paper are to 1) introduce partially blind
handovers, 2) employ machine learning to perform handover success predictions
from sub-6 GHz to mmWave frequencies, and 3) show that this machine learning
based algorithm combined with partially blind handovers can improve the
handover success rate in a realistic network setup of colocated cells.
Simulation results show improvement in handover success rates for our proposed
algorithm compared to standard handover algorithms.Comment: (c) 2018 IEEE. Personal use of this material is permitted. Permission
from IEEE must be obtained for all other uses, in any current or future
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this work in other work
Self-organising comprehensive handover strategy for multi-tier LTE-advanced heterogeneous networks
Long term evolution (LTE)-advanced was introduced as real fourth generation (4G) with its new features and additional functions, satisfying the growing demands of quality and network coverage for the network operators' subscribers. The term muti-tier has also been recently used with respect to the heterogeneity of the network by applying the various subnetwork cooperative systems and functionalities with self-organising capabilities. Using indoor short-range low-power cellular base stations, for example, femtocells, in cooperation with existing long-range macrocells are considered as the key technical challenge of this multi-tier configuration. Furthermore, shortage of network spectrum is a major concern for network operators which forces them to spend additional attentions to overcome the degradation in performance and quality of services in 4G HetNets. This study investigates handover between the different layers of a heterogeneous LTE-advanced system, as a critical attribute to plan the best way of interactive coordination within the network for the proposed HetNet. The proposed comprehensive handover algorithm takes multiple factors in both handover sensing and decision stages, based on signal power reception, resource availability and handover optimisation, as well as prioritisation among macro and femto stations, to obtain maximum signal quality while avoiding unnecessary handovers
Performance Comparison of Dual Connectivity and Hard Handover for LTE-5G Tight Integration in mmWave Cellular Networks
MmWave communications are expected to play a major role in the Fifth
generation of mobile networks. They offer a potential multi-gigabit throughput
and an ultra-low radio latency, but at the same time suffer from high isotropic
pathloss, and a coverage area much smaller than the one of LTE macrocells. In
order to address these issues, highly directional beamforming and a very
high-density deployment of mmWave base stations were proposed. This Thesis aims
to improve the reliability and performance of the 5G network by studying its
tight and seamless integration with the current LTE cellular network. In
particular, the LTE base stations can provide a coverage layer for 5G mobile
terminals, because they operate on microWave frequencies, which are less
sensitive to blockage and have a lower pathloss. This document is a copy of the
Master's Thesis carried out by Mr. Michele Polese under the supervision of Dr.
Marco Mezzavilla and Prof. Michele Zorzi. It will propose an LTE-5G tight
integration architecture, based on mobile terminals' dual connectivity to LTE
and 5G radio access networks, and will evaluate which are the new network
procedures that will be needed to support it. Moreover, this new architecture
will be implemented in the ns-3 simulator, and a thorough simulation campaign
will be conducted in order to evaluate its performance, with respect to the
baseline of handover between LTE and 5G.Comment: Master's Thesis carried out by Mr. Michele Polese under the
supervision of Dr. Marco Mezzavilla and Prof. Michele Zorz
Memory-full context-aware predictive mobility management in dual connectivity 5G networks
Network densification with small cell deployment is being considered as one of the dominant themes in the fifth generation (5G) cellular system. Despite the capacity gains, such deployment scenarios raise several challenges from mobility management perspective. The small cell size, which implies a small cell residence time, will increase the handover (HO) rate dramatically. Consequently, the HO latency will become a critical consideration in the 5G era. The latter requires an intelligent, fast and light-weight HO procedure with minimal signalling overhead. In this direction, we propose a memory-full context-aware HO scheme with mobility prediction to achieve the aforementioned objectives. We consider a dual connectivity radio access network architecture with logical separation between control and data planes because it offers relaxed constraints in implementing the predictive approaches. The proposed scheme predicts future HO events along with the expected HO time by combining radio frequency performance to physical proximity along with the user context in terms of speed, direction and HO history. To minimise the processing and the storage requirements whilst improving the prediction performance, a user-specific prediction triggering threshold is proposed. The prediction outcome is utilised to perform advance HO signalling whilst suspending the periodic transmission of measurement reports. Analytical and simulation results show that the proposed scheme provides promising gains over the conventional approach
Integration of Carrier Aggregation and Dual Connectivity for the ns-3 mmWave Module
Thanks to the wide availability of bandwidth, the millimeter wave (mmWave)
frequencies will provide very high data rates to mobile users in next
generation 5G cellular networks. However, mmWave links suffer from high
isotropic pathloss and blockage from common materials, and are subject to an
intermittent channel quality. Therefore, protocols and solutions at different
layers in the cellular network and the TCP/IP protocol stack have been proposed
and studied. A valuable tool for the end-to-end performance analysis of mmWave
cellular networks is the ns-3 mmWave module, which already models in detail the
channel, Physical (PHY) and Medium Access Control (MAC) layers, and extends the
Long Term Evolution (LTE) stack for the higher layers. In this paper we present
an implementation for the ns-3 mmWave module of multi connectivity techniques
for 3GPP New Radio (NR) at mmWave frequencies, namely Carrier Aggregation (CA)
and Dual Connectivity (DC), and discuss how they can be integrated to increase
the functionalities offered by the ns-3 mmWave module.Comment: 9 pages, 7 figures, submitted to the Workshop on ns-3 (WNS3) 201
A survey of self organisation in future cellular networks
This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks
SAI: safety application identifier algorithm at MAC layer for vehicular safety message dissemination over LTE VANET networks
Vehicular safety applications have much significance in preventing road accidents and fatalities. Among others, cellular networks have been under investigation for the procurement of these applications subject to stringent requirements for latency, transmission parameters, and successful delivery of messages. Earlier contributions have studied utilization of Long-Term Evolution (LTE) under single cell, Friis radio, or simplified higher layer. In this paper, we study the utilization of LTE under multicell and multipath fading environment and introduce the use of adaptive awareness range. Then, we propose an algorithm that uses the concept of quality of service (QoS) class identifiers (QCIs) along with dynamic adaptive awareness range. Furthermore, we investigate the impact of background traffic on the proposed algorithm. Finally, we utilize medium access control (MAC) layer elements in order to fulfill vehicular application requirements through extensive system-level simulations. The results show that, by using an awareness range of up to 250 m, the LTE system is capable of fulfilling the safety application requirements for up to 10 beacons/s with 150 vehicles in an area of 2 × 2 km2. The urban vehicular radio environment has a significant impact and decreases the probability for end-to-end delay to be ≤100 ms from 93%–97% to 76%–78% compared to the Friis radio environment. The proposed algorithm reduces the amount of vehicular application traffic from 21 Mbps to 13 Mbps, while improving the probability of end-to-end delay being ≤100 ms by 20%. Lastly, use of MAC layer control elements brings the processing of messages towards the edge of network increasing capacity of the system by about 50%
Energy efficiency in heterogeneous wireless access networks
In this article, we bring forward the important aspect of energy savings in wireless access networks. We specifically focus on the energy saving opportunities in the recently evolving heterogeneous networks (HetNets), both Single- RAT and Multi-RAT. Issues such as sleep/wakeup cycles and interference management are discussed for co-channel Single-RAT HetNets. In addition to that, a simulation based study for LTE macro-femto HetNets is presented, indicating the need for dynamic energy efficient resource management schemes. Multi-RAT HetNets also come with challenges such as network integration, combined resource management and network selection. Along with a discussion on these challenges, we also investigate the performance of the conventional WLAN-first network selection mechanism in terms of energy efficiency (EE) and suggest that EE can be improved by the application of intelligent call admission control policies
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