Enhanced Inter-Cell Interference Coordination Challenges in Heterogeneous Networks

3GPP LTE-Advanced has started a new study item to investigate Heterogeneous Network (HetNet) deployments as a cost effective way to deal with the unrelenting traffic demand. HetNets consist of a mix of macrocells, remote radio heads, and low-power nodes such as picocells, femtocells, and relays. Leveraging network topology, increasing the proximity between the access network and the end-users, has the potential to provide the next significant performance leap in wireless networks, improving spatial spectrum reuse and enhancing indoor coverage. Nevertheless, deployment of a large number of small cells overlaying the macrocells is not without new technical challenges. In this article, we present the concept of heterogeneous networks and also describe the major technical challenges associated with such network architecture. We focus in particular on the standardization activities within the 3GPP related to enhanced inter-cell interference coordination.Comment: 12 pages, 4 figures, 2 table

A comparative investigation on the application and performance of Femtocell against Wi-Fi networks in an indoor environment

Due to the strenuous demands on the available spectrum and bandwidth, alongside the ever increasing rate at which data traffic is growing and the poor quality of experience QoE) faced with indoor communications, in order for cellular networks to remain dominant in areas pertaining to voice and data services, cellular service providers have to reform their marketing and service delivery strategies together with their overall network rchitecture. To accomplish this leap forward in performance, cellular service operators need to employ a network topology, which makes use of a mix of macrocells and small cells, effectively evolving the network, bringing it closer to the end-­‐user. This investigation explores the use of small cell technology, specifically Femtocell technology in comparison to the already employed Wi-­‐Fi technology as a viable solution to poor indoor communications.The performance evolution is done by comparing key areas in the every day use of Internet communications. These include HTTP testing, RTP testing and VoIP testing. Results are explained and the modes of operation of both technologies are compared

Radio network management in cognitive LTE-Femtocell Systems

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.There is a strong uptake of femtocell deployment as small cell application platforms in the upcoming LTE networks. In such two-tier networks of LTEfemtocell base stations, a large portion of the assigned spectrum is used sporadically leading to underutilisation of valuable frequency resources. Novel spectrum access techniques are necessary to solve these current spectrum inefficiency problems. Therefore, spectrum management solutions should have the features to improve spectrum access in both temporal and spatial manner. Cognitive Radio (CR) with the Dynamic Spectrum Access (DSA) is considered to be the key technology in this research in order to increase the spectrum efficiency. This is an effective solution to allow a group of Secondary Users (SUs) to share the radio spectrum initially allocated to the Primary User (PUs) at no interference. The core aim of this thesis is to develop new cognitive LTE-femtocell systems that offer a 4G vision, to facilitate the radio network management in order to increase the network capacity and further improve spectrum access probabilities. In this thesis, a new spectrum management model for cognitive radio networks is considered to enable a seamless integration of multi-access technology with existing networks. This involves the design of efficient resource allocation algorithms that are able to respond to the rapid changes in the dynamic wireless environment and primary users activities. Throughout this thesis a variety of network upgraded functions are developed using application simulation scenarios. Therefore, the proposed algorithms, mechanisms, methods, and system models are not restricted in the considered networks, but rather have a wider applicability to be used in other technologies. This thesis mainly investigates three aspects of research issues relating to the efficient management of cognitive networks: First, novel spectrum resource management modules are proposed to maximise the spectrum access by rapidly detecting the available transmission opportunities. Secondly, a developed pilot power controlling algorithm is introduced to minimise the power consumption by considering mobile position and application requirements. Also, there is investigation on the impact of deploying different numbers of femtocell base stations in LTE domain to identify the optimum cell size for future networks. Finally, a novel call admission control mechanism for mobility management is proposed to support seamless handover between LTE and femtocell domains. This is performed by assigning high speed mobile users to the LTE system to avoid unnecessary handovers. The proposed solutions were examined by simulation and numerical analysis to show the strength of cognitive femtocell deployment for the required applications. The results show that the new system design based on cognitive radio configuration enable an efficient resource management in terms of spectrum allocation, adaptive pilot power control, and mobile handover. The proposed framework and algorithms offer a novel spectrum management for self organised LTE-femtocell architecture. Eventually, this research shows that certain architectures fulfilling spectrum management requirements are implementable in practice and display good performance in dynamic wireless environments which recommends the consideration of CR systems in LTE and femtocell networks

A novel approach for mobility management inf lte femtocells

LTE is an emerging wireless data communication technology to provide broadband ubiquitous Internet access. Femtocells are included in 3GPP since Release 8 to enhance the indoor network coverage and capacity. The main challenge of mobility management in hierarchical LTE structure is to guarantee efficient handover to or from/to/between Femtocells. This paper focuses, on different types of Handover and comparison performance between different decision algorithms. Furthermore, a speed based Handover algorithm for macro-femto scenario is proposed with simulation result

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

Αξιολόγηση ποιότητας εμπειρίας VoIP κλήσεων σε LTE δίκτυα δύο επιπέδων

Η συνεχής ανάπτυξη των δικτύων 2ης και 3ης Γενιάς συνεπάγεται την αυξανόμενη ανάγκη για υψηλότερους ρυθμούς μετάδοσης δεδομένων και βελτιωμένη ποιότητα υπηρεσιών. Το LTE-Advanced αναμένεται να ανταποκριθεί αποτελεσματικά στις εν λόγω ανάγκες με την υποστήριξη Ετερογενών Δικτύων, δηλαδή δικτύων που συμπεριλαμβάνουν κόμβους χαμηλής ισχύος όπως τα femtocells. Τα femtocells αποτελούν μια πολλά υποσχόμενη λύση για τη βελτίωση της κάλυψης του δικτύου και την παροχή υψηλών ταχυτήτων μετάδοσης δεδομένων. Παρόλα αυτά, θα υπάρξουν σημαντικές προκλήσεις όπως η διαχείριση των παρεμβολών μεταξύ γειτονικών femtocells ή μεταξύ femtocell και macrocell. Η ποιότητα ομιλίας μπορεί να υποβαθμιστεί σημαντικά από τις παρεμβολές και γι' αυτό οι πάροχοι εστιάζουν στη συνεχή βελτίωσή της. Είναι συνεπώς απαραίτητη η αξιολόγηση της ποιότητας ομιλίας που αντιπροσωπεύεται από τη μέση γνωμοβαθμολογία. Η παρούσα διπλωματική εργασία εκπονήθηκε με στόχο τη μελέτη των επιπτώσεων που έχει η ανάπτυξη των femtocells στην ποιότητα εμπειρίας των χρηστών τηλεφωνίας μέσω IP (VoIP). Διεξάγεται προσομοίωση ενός δικτύου LTE και μελετάται η συσχέτιση της εκτιμώμενης ποιότητας ομιλίας με το πλήθος, την ταχύτητα και το φορτίο των χρηστών. Επίσης, πραγματοποιείται σύγκριση μεταξύ σεναρίων με αλλά και χωρίς τη συμμετοχή femtocells. Τέλος, εξάγονται γενικά συμπεράσματα για τον αντίκτυπο που έχει η εισαγωγή femtocells στο δίκτυο στην εκτιμώμενη ποιότητα εμπειρίας.The continuous development of 2nd and 3rd Generation cellular networks implies an increasing need for higher data rates and improved service quality. The LTE-Advanced is expected to effectively address these needs by supporting Heterogeneous Networks, i.e. networks which include low power nodes such as femtocells. Femtocells are a promising solution which will improve the network coverage and will provide high-speed data rates. However, there will be major challenges such as interference management between neighboring femtocells or between femtocell and macrocell. Voice quality can be severely degraded due to interference and therefore operators focus on continuous quality improvement. Consequently it is crucial to evaluate speech quality in terms of mean opinion score. The purpose of this Master thesis is to study the impact of femtocells deployment on quality of experience of a VoIP user. We conduct an LTE network simulation and study the relationship between the estimated VoIP quality and the number of users, the speed and the traffic load. Furthermore, we develop a comparative analysis in VoIP speech quality between scenarios which do or do not include femtocells. Finally, we draw general conclusions regarding the impact of introducing femtocells on the estimated quality of experience

Υποστήριξη Ποιότητας Υπηρεσίας (QoS) και Ποιότητας Εμπειρίας (QoE) σε δίκτυα LTE-A

Ο τομέας των τηλεπικοινωνιών έχει εξελιχθεί ραγδαία τα τελευταία χρόνια. Η εισαγωγή πολυμεσικών και απαιτητικών υπηρεσιών καθώς και η ραγδαία αύξηση των χρηστών απαιτούν καλύτερη και εγγυημένη ποιότητα υπηρεσίας (Quality of Service, (QoS)). Ενώ για τη συνεχή παρακολούθηση του δικτύου και των υπηρεσιών που παρέχονται, οι τηλεπικοινωνιακοί πάροχοι δύναται να εκτιμήσουν την εμπειρία που αντιλαμβάνεται ο τελικός χρήστης (Quality of Experience, (QoE)). Πρόσφατα, η 3GPP (3rd Generation Partnership Project) ανέπτυξε το δίκτυο LTE-A (Long Term Evolution-Advanced) με στόχο την επίτευξη επιδόσεων επιπέδου 4G, όπως αυτές ορίζονται από την ITU-R στο IMT-Advanced. Το LTE-A παρέχει υψηλές ταχύτητες, μέγιστο εύρος ζώνης, αυξημένη χωρητικότητα και απόδοση σε σύγκριση με τα υφιστάμενα δίκτυα, ενώ η υποστήριξη QoS και QoE στα δίκτυα αυτά είναι μια ανοιχτή πρόκληση. Στα πλαίσια της διπλωματικής αυτής μελετώνται τρόποι υποστήριξης QoS και QoE σε δίκτυα LTE-A. Αρχικά, γίνεται μια σύντομη ιστορική αναδρομή στα τηλεπικοινωνιακά συστήματα και στη συνέχεια αναφορά στην αρχιτεκτονική του δικτύου LTE-A. Σε ότι αφορά την υποστήριξη QoS, ο κομβικός ρόλος της λειτουργίας Policy control and charging rules function (PCRF) του δικτύου κορμού του LTE-A μελετάται αναλυτικά. Για την εκτίμηση και παροχή υψηλής QoE στο LTE-A όλες οι απαραίτητες πληροφορίες που σχετίζονται άμεσα ή έμμεσα με την QoE διαχειρίζονται σε ένα κεντρικό σημείο του δικτύου, το οποίο συλλέγει δείκτες επιδόσεων και δίνει εντολές διαχείρισης με βάση την QoE.The telecommunication sector has grown rapidly in recent years. The introduction of multimedia and demanding services and the rapid growth of users require better and guaranteed QoS (Quality of Service, (QoS)) while continuously monitoring the network and services provided by telecommunications providers may assess the experience perceived by the end-users (Quality of Experience, (QoE). Recently the 3GPP (3rd Generation Partnership Project) developed the LTE-A (Long Term Evolution-Advanced) network to achieve 4G requirements as defined by ITU-R in IMT-Advanced. LTE-A aims at providing high speeds, wide bandwidth usage and increased capacity and performance compared to existing networks, while the support of QoS and QoE in such networks is an open challenge. This thesis studies ways to support QoS and QoE network in LTE-A networks. First, a brief historical review of telecommunications systems is provided leading to the description of the LTE-A network. Considering the QoS, the key role of the operating Policy control and charging rules function (PCRF) backbone network of LTE-A is studied in detail. To assess and delivery high QoE in LTE-A all the necessary information related directly or indirectly to the QoE managed at a central point in the network, which collects performance indicators and gives commands for QoE-based management