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

An Innovative RAN Architecture for Emerging Heterogeneous Networks: The Road to the 5G Era

The global demand for mobile-broadband data services has experienced phenomenal growth over the last few years, driven by the rapid proliferation of smart devices such as smartphones and tablets. This growth is expected to continue unabated as mobile data traffic is predicted to grow anywhere from 20 to 50 times over the next 5 years. Exacerbating the problem is that such unprecedented surge in smartphones usage, which is characterized by frequent short on/off connections and mobility, generates heavy signaling traffic load in the network signaling storms . This consumes a disproportion amount of network resources, compromising network throughput and efficiency, and in extreme cases can cause the Third-Generation (3G) or 4G (long-term evolution (LTE) and LTE-Advanced (LTE-A)) cellular networks to crash. As the conventional approaches of improving the spectral efficiency and/or allocation additional spectrum are fast approaching their theoretical limits, there is a growing consensus that current 3G and 4G (LTE/LTE-A) cellular radio access technologies (RATs) won\u27t be able to meet the anticipated growth in mobile traffic demand. To address these challenges, the wireless industry and standardization bodies have initiated a roadmap for transition from 4G to 5G cellular technology with a key objective to increase capacity by 1000Ã? by 2020 . Even though the technology hasn\u27t been invented yet, the hype around 5G networks has begun to bubble. The emerging consensus is that 5G is not a single technology, but rather a synergistic collection of interworking technical innovations and solutions that collectively address the challenge of traffic growth. The core emerging ingredients that are widely considered the key enabling technologies to realize the envisioned 5G era, listed in the order of importance, are: 1) Heterogeneous networks (HetNets); 2) flexible backhauling; 3) efficient traffic offload techniques; and 4) Self Organizing Networks (SONs). The anticipated solutions delivered by efficient interworking/ integration of these enabling technologies are not simply about throwing more resources and /or spectrum at the challenge. The envisioned solution, however, requires radically different cellular RAN and mobile core architectures that efficiently and cost-effectively deploy and manage radio resources as well as offload mobile traffic from the overloaded core network. The main objective of this thesis is to address the key techno-economics challenges facing the transition from current Fourth-Generation (4G) cellular technology to the 5G era in the context of proposing a novel high-risk revolutionary direction to the design and implementation of the envisioned 5G cellular networks. The ultimate goal is to explore the potential and viability of cost-effectively implementing the 1000x capacity challenge while continuing to provide adequate mobile broadband experience to users. Specifically, this work proposes and devises a novel PON-based HetNet mobile backhaul RAN architecture that: 1) holistically addresses the key techno-economics hurdles facing the implementation of the envisioned 5G cellular technology, specifically, the backhauling and signaling challenges; and 2) enables, for the first time to the best of our knowledge, the support of efficient ground-breaking mobile data and signaling offload techniques, which significantly enhance the performance of both the HetNet-based RAN and LTE-A\u27s core network (Evolved Packet Core (EPC) per 3GPP standard), ensure that core network equipment is used more productively, and moderate the evolving 5G\u27s signaling growth and optimize its impact. To address the backhauling challenge, we propose a cost-effective fiber-based small cell backhaul infrastructure, which leverages existing fibered and powered facilities associated with a PON-based fiber-to-the-Node/Home (FTTN/FTTH)) residential access network. Due to the sharing of existing valuable fiber assets, the proposed PON-based backhaul architecture, in which the small cells are collocated with existing FTTN remote terminals (optical network units (ONUs)), is much more economical than conventional point-to-point (PTP) fiber backhaul designs. A fully distributed ring-based EPON architecture is utilized here as the fiber-based HetNet backhaul. The techno-economics merits of utilizing the proposed PON-based FTTx access HetNet RAN architecture versus that of traditional 4G LTE-A\u27s RAN will be thoroughly examined and quantified. Specifically, we quantify the techno-economics merits of the proposed PON-based HetNet backhaul by comparing its performance versus that of a conventional fiber-based PTP backhaul architecture as a benchmark. It is shown that the purposely selected ring-based PON architecture along with the supporting distributed control plane enable the proposed PON-based FTTx RAN architecture to support several key salient networking features that collectively significantly enhance the overall performance of both the HetNet-based RAN and 4G LTE-A\u27s core (EPC) compared to that of the typical fiber-based PTP backhaul architecture in terms of handoff capability, signaling overhead, overall network throughput and latency, and QoS support. It will also been shown that the proposed HetNet-based RAN architecture is not only capable of providing the typical macro-cell offloading gain (RAN gain) but also can provide ground-breaking EPC offloading gain. The simulation results indicate that the overall capacity of the proposed HetNet scales with the number of deployed small cells, thanks to LTE-A\u27s advanced interference management techniques. For example, if there are 10 deployed outdoor small cells for every macrocell in the network, then the overall capacity will be approximately 10-11x capacity gain over a macro-only network. To reach the 1000x capacity goal, numerous small cells including 3G, 4G, and WiFi (femtos, picos, metros, relays, remote radio heads, distributed antenna systems) need to be deployed indoors and outdoors, at all possible venues (residences and enterprises)

Performance of handover in long term evolution

Tässä diplomityössä tutkitaan LTE:n (Long Term Evolution) yhteydellisen tilan solunvaihdon vaikutusta tiedostonsiirtoon, suoratoistoon, sekä internetpuheluihin. Analyysi perustuu Soneran tuotantoverkossa suoritettuihin mittauksiin, joissa tutkittiin viivettä, datakatkosta ja hävinnyttä datamäärää. Solunvaihdon vaikutusta puheluihin tutkitaan laadullisella käyttäjätutkimuksella. Työssä esitetään ensin kirjallisuuskatsaus LTE:stä. Katsaus pohjautuu järjestelmän spesifikaatioihin, laitevalmistajien julkaisuihin, sekä tieteellisiin tutkimuksiin. Eniten huomiota kiinnitetään liikkuvuuden hallintaan. Solunvaihtoprosessi käsitellään signalointitasolla. Tämän jälkeen esitetään mittaustulokset ja niiden analyysi. Lopuksi esitetään johtopäätökset, sekä ehdotetaan mahdollisia kohteita jatkotutkimukselle. Mittaustulokset osoittavat, että tavallisella solunvaihdolla ei ole vaikutusta palveluiden suorituskykyyn. Dataa ei häviä solunvaihdon aikana. 95%:ssa tapauksista päätelaite on kokonaan verkosta irti kytkettynä alle 50 ms, ja käyttäjän kokema datakatko on alle 75 ms. Näin ollen käyttäjä ei koe laadun heikentymistä, elleivät radio-olosuhteet sitä aiheuta. Käyttäjätutkimuksen tulokset osoittavat, että tavallinen solunvaihto ei aiheuta laadullista häiriötä loppukäyttäjälle. Keskusverkon avustaman solunvaihdon huomattiin hävittävän dataa. Tämä ei ole spesifikaatioiden mukaista. Datan häviäminen aiheutti TCP:n (Transmission Control Protocol) uudelleenlähetyksiä, joista 26% johtui uudelleenlähetysajastimen laukeamisesta. Käyttäjätutkimuksen mukaan kyseinen solunvaihto aiheuttaa lyhyen häiriön puheluun. Häiriö on kuitenkin laadultaan vähäinen.This thesis studies the effect of intra-system handover in Long Term Evolution to the performance of popular services and protocols. Protocols examined include file transfer using Transmission Control Protocol (TCP), streaming, and internet phone calls. The analysis is based on measurements conducted in a live production network in Helsinki. The measurements include delay, data pause and data loss. Additionally, the effects of handover to voice quality are studied with a qualitative user survey. The thesis first presents a literature review of Long Term Evolution based on the system specifications, white papers and scientific studies. Most detail is given to mobility management. The handover process is studied at the level of signalling messages. Measurement results and their analysis are then discussed. Finally, conclusions and opportunities for further study are given. The measurement results show that the normal handover has minimal effect on the service performance. No data is lost because of the handover. In 95% of the cases the device is disconnected from the network for under 50 ms, and the data pause experienced is less than 75 ms. Thus, the end user will not experience any disturbance other than that resulting from low radio conditions. The results of the voice call user survey confirm that the normal handover is not audible to the end user. The core network assisted handover was found to lose data during handover, not according to the specifications. This caused TCP retransmissions, of which 26% were triggered because of a retransmission timeout. The user survey established that this type of handover is also audible to the user, but the overall quality impairment is not significant

Self-organising network management for heterogeneous LTE-advanced networks

This thesis was submitted for the award of Doctor of Philosophy and awarded by Brunel University LondonSince 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network

Handover between LTE and 3G Radio Access Technologies: Test measurement challenges and field environment test planning

LTE (Long Term Evolution) on neljännen sukupolven matkapuhelinverkkoteknologia, joka tarjoaa paremman suorituskyvyn verrattuna perinteisiin matkapuhelinverkkoihin. Tehostettu ilmarajapinta sekä litteä, "puhdas-IP" -pakettidatalle optimoitu verkko-arkkitehtuuri tarjoavat parempia siirtonopeuksia ja lyhyempiä siirtoviiveitä käyttäjille, sekä operaattoreille kustannustehokasta toimintaa. Ensimmäisten kaupallisten LTE-verkkojen käyttöönotto perustuu todennäköisesti paikallisverkkoihin suurissa kaupungeissa. Suunnitteltuna tavoitteena on kuitenkin tarjota maailmanlaajuinen mobiilipalvelu, jonka avulla tilaajat saavat mistä vain ja milloin vain yhteyden sekä operaattorin, että Internetin tarjoamiin palveluihin, ja että yhteys myös pysyy päällä, kun käyttäjät ovat liikkeellä. Saumattoman palvelun tarjoamiseksi, solunvaihto LTE:n ja perinteisten radio-teknologioiden kuten GSM:n ja UMTS:n välillä on välttämätön ominaisuus. Tämän työn tutkimusaihe on aktiivinen solunvaihto LTE:n ja 3G matkapuhelinverkkojen, mikä on tärkeä toiminnallisuus operaattoreille, jotka pyrkivät tarjoamaan kattavaa mobiilipalvelua. Täytettääkseen tietyt palvelun laatua koskevat vaatimukset, tämän toiminnallisuuden täytyy käydä läpi kehitysprosessi, joka sisältää perusteellisen toiminnallisuus-, suorituskyky-sekä viankorjaustestaamisen. Tässä työssä esitellään testaussuunnitelma, sekä työkalut ja menetelmät testien suorittamiseen. Verkon suorituskykyä kuvaavat mittarit, kuten solunvaihdon onnistumisprosentti, yhteyden katkeamisprosentti, tiedonsiirtonopeus ja solunvaihdon viive esitellään yksityiskohtaisesti. Luotettavien tuloksien saamiseksi mittaukset suoritetaan kenttätesteinä, jotta radio-olosuhteet ovat realistisia. Oikeiden työkalujen avulla, kuten ilmarajapintaa analysoiva XCAL-ohjelmisto, voidaan tuottaa tuloksia, jotka vastaavat operaattorien tekemiä testauksia kaupallisissa LTE-verkoissa.LTE (Long Term Evolution) is a fourth generation cellular network technology that provides improved performance compared to legacy cellular systems. LTE introduces an enhanced air interface as well as a flat, "all-IP" packet data optimized network architecture that provides higher user data rates, reduced latencies and cost efficient operations. The rollout of initial commercial LTE networks is likely based on service hot spots in major cities. The design goal is however to provide a universal mobile service that allows the subscribers to connect to both operator and Internet services anywhere anytime and stay connected as the users are on the move. To provide seamless service, mobility towards widespread legacy radio access technologies such as GSM and UMTS is required. The research topic of this thesis is handover from LTE to 3G cellular networks, which is a high priority item to the operators that seek to provide an all-round service. To satisfy certain quality of service requirements this feature needs to go through a development process that consists of thorough functionality, performance and fault correction testing This thesis introduces a plan for test execution and introduces the tools and procedures required to perform inter radio access technology handover tests. The metrics that indicate the network performance, namely Key Performance Indicators (KPIs), i.e. handover success rate, call drop rate, throughput and handover delay are introduced in detail. In order to provide reliable results, the plan is to perform the measurements in a field environment with realistic radio conditions. With the proper tools such as XCAL for air interface performance analysis, the field tests should provide results that are comparable to tests performed by the operators in live commercial LTE networks

Will SDN be part of 5G?

For many, this is no longer a valid question and the case is considered settled with SDN/NFV (Software Defined Networking/Network Function Virtualization) providing the inevitable innovation enablers solving many outstanding management issues regarding 5G. However, given the monumental task of softwarization of radio access network (RAN) while 5G is just around the corner and some companies have started unveiling their 5G equipment already, the concern is very realistic that we may only see some point solutions involving SDN technology instead of a fully SDN-enabled RAN. This survey paper identifies all important obstacles in the way and looks at the state of the art of the relevant solutions. This survey is different from the previous surveys on SDN-based RAN as it focuses on the salient problems and discusses solutions proposed within and outside SDN literature. Our main focus is on fronthaul, backward compatibility, supposedly disruptive nature of SDN deployment, business cases and monetization of SDN related upgrades, latency of general purpose processors (GPP), and additional security vulnerabilities, softwarization brings along to the RAN. We have also provided a summary of the architectural developments in SDN-based RAN landscape as not all work can be covered under the focused issues. This paper provides a comprehensive survey on the state of the art of SDN-based RAN and clearly points out the gaps in the technology.Comment: 33 pages, 10 figure

LTE-3G Inter-Operability Study

In this thesis the author have studied and measured how LTE Release 8 interworks with previous legacy 3G networks in real environmental conditions. At present, LTE technology is deployed based on service hotspots that cover small geographical areas. It is expected that full scale deployment of LTE network will take a considerable time, which also means the mobile users have to primarily depend on legacy 3G and 2G networks for years to come. Therefore, it is important to study the interworking mechanisms between LTE and legacy networks in order to provide seamless mobility and uninterrupted user services in primarily available LTE hotspots. In order to perform this study, field measurements have been carried out in DNA commercial network in outdoor and indoor environments. Initially, cell selection and reselection criteria for inter-RAT mobility in idle condition is mathematically checked and verified. Then, channel conditions are studied and analyzed based on radio parameters like RSRP, RSCP, RSRQ, Ec/No, SNR and CQI when inter-RAT handover is performed. After that, an inter-RAT handover test from LTE towards 3G is studied with the help of signalling message. Next, the impact of inter-RAT handover on KPIs like MAC DL throughput, handover success rate, RTT, handover latency and user plane delay are studied and analyzed. Finally, performance of inter-RAT handover in outdoor and indoor measurement environment is compared based on KPI measurements. From this study, it is found that inter-RAT mobility from LTE towards 3G network is working in both idle and connected modes with 100 percent handover success rate, however, the user experienced network latency around 4 seconds in average. The user experienced degradation in throughput because of decreasing link quality. The user data service interruption is roughly for 3-4 seconds and the RTT value for 32 bytes of data is observed to be around 300 ms in average during handover. It is also found that the impact of inter-RAT handover in indoor environment is higher than outdoor environment based on KPIs results

Optimizing handover performance in LTE networks containing relays

The purpose of relays in Long Term Evolution (LTE) networks is to provide coverage extension and higher bitrates for cell edge users. Similar to any other new nodes in the network, relays bring new challenges. One of these challenges concerns mobility. More specifically, back and forth data transmission between the Donor Evolved NodeB (DeNB) and the Relay (RN) during the handover can occur. For the services that are sensitive to packet loss, receiving all the packets at the destination is crucial. In cellular networks when the User Equipment (UE) detaches from the old cell and attaches to the new cell, it faces a short disruption. In the disruption time when the UE is not connected to anywhere, packets can be easily lost. To avoid the consequences of these packet losses, the data forwarding concept was developed and the lost packets in handover were identified and forwarded to the destination. The forwarded packets would be transmitted to the UE as it becomes attached to the new cell. In the networks using the relays all the packets should still transfer via the DeNB. If the UE is connected to the RN and is handed over to a new cell, the unacknowledged packets between the RN and the UE which are still in the RN buffer should be transmitted back to the DeNB and onwards to the target afterwards. Furthermore, the ongoing packets in S1 interface are transmitted through the old path until the path switch occurs. This data transfer from the DeNB to the RN and again back to the DeNB increases the latency and occupies the resources in the Un interface. In this thesis work the problem of back and forth forwarding is studied. Different solutions to overcome this challenge are proposed and simulations are performed to evaluate the proposals. The evaluated approaches showed up to considerable performance enhancement compared to the previous solutions

LTE Handover performance evaluation based on power budget handover algorithm

LTE (Long Term Evolution) is a fourth generation cellular network technology that provides improved performance related to data rate, coverage and capacity compared to legacy cellular systems. In this context, one of the main goals of LTE is to provide fast and seamless handover from one cell to another to meet a strict delay requirement while simultaneously keeping network management simple. Hence, the decision to trigger a handover is a crucial component in the design process of handover, since the success and the efficiency, to a large extent, depends on the accuracy and timeliness of the decision. The design of an efficient and successful handover requires a careful selection of HO parameters and the optimal setting of these. The LTE standard supports two parameters to trigger the handover and select the target cell: hysteresis margin and Time-to-Trigger (TTT) The research topic of this thesis which is “LTE Handover Performance Evaluation Based on Power Budget Handover Algorithm”, focuses on different combinations or settings of HOM and TTT values to evaluate the handover performance based on Reference Signal Received Power (RSRP) measurement within certain deployment scenarios, such as different UE speeds, system loads and cell sizes. The Power Budget Handover Algorithm (PBHA) picks the best hysteresis and time-to-trigger combinations to evaluate the system performance in terms of number of handovers, signal-to-interference plus noise ratio (SINR), throughput, delay and packet lost for UE's which are about to perform the handover