30 research outputs found

    On Improving Data Rates of Users in LTE HetNets

    Get PDF
    The proliferation of smartphones and tablets has led to huge demand for data services over cellular networks. Cisco VNI mobile forecast (2014-2019) tells that although only 3.9% of mobile connections were Long Term Evolution (LTE) based they accounted for 40% of the mobile traffic and this will rise to 51% by 2019, by which the mobile data usage will grow 11 fold to over 15 Exabytes per month. Reports by Cisco and Huawei tell that 70% of the traffic is generated in indoor environments such as homes, enterprise buildings and hotspots. Hence, it is very important for mobile operators to improve coverage and capacity of indoor environments. Indoor data demand is partly met by intensifying the deployment of Macro Base Stations (MBSs/eNodeBs) in LTE cellular networks. Owing to many obstacles in the communication path between MBS and users inside the building, radio signals attenuate at a faster rate as the distance increases. Thus, Indoor User Equipments (IUEs) receive still low signal strength ( i.e., Signal-to-Noise Ratio, SNR) compared to Outdoor User Equipments (OUEs). To address this problem, one can deploy a large number of Low Power Nodes (LPNs) a.k.a. small cells (e.g., Picos and Femtos) under an umbrella MBS coverage and thereby form an LTE Heterogeneous Network (HetNet). Small cells are mainly being deployed in homes, enterprise buildings and hotspots like shopping malls and airports to improve indoor coverage and data rates. This is a win-win situation as telecom operators also benefit by reduction in their CAPEX and OPEX. Though the deployment of Femtocells improves indoor data rates, the resulting LTE HetNet may face a host of problems like co-tier and cross-tier interference (due to frequency reuse one in LTE) and frequent handovers (due to short coverage areas of Femtocells). Deployment of Femtos inside a building can lead to signal leakage at the edges/corners of the buildings. This causes cross-tier interference and degrades the performance of OUEs in High Interference Zone (HIZone) around the building area, which are connected to one of the MBSs in the LTE HetNet. Arbitrary placement of Femtos can lead to high co-channel cross-tier interference among Femtos and Macro BSs and coverage holes inside buildings. If Femtos are placed without power control, this leads to high power consumption and high inter-cell interference in large scale deployments. Our goal is to address these problems by developing efficient architecture, Femto placement and power control schemes in LTE HetNets. Random or unplanned placement of the Femtos leads to poor SNR and hence affects achievable data rates of IUEs. Hence, placement of Femtos is important for the cellular operators to perform planned deployment of minimum number of Femtos with no coverage holes and guarantee a good signal quality with no co-tier interference. Once the placement of Femtos is done optimally in enterprise environments, operators need to ensure that traffic load is evenly distributed among neighboring Femtos for improving Quality of Service (QoS) of IUEs by efficiently utilizing the network resources. In traditional cellular networks, the uplink access and downlink access of UEs are coupled to the same (Femto) cell. Suppose a Femto is fully loaded when compared to its neighboring Femtos, the traditional offloading or load balancing algorithms will try offloading some of the UEs for both their uplink and downlink access from the loaded cell to one of less loaded neighboring cells (i.e., target cell) provided that these UEs could get connected to the chosen target cell. This type of offloading is a forced handover to reduce traffic imbalance and trigger for handover is not based on better signal strength from the target cell. But, the offloaded UEs are connected for both their uplink and downlink access to the same target cell. Since UEs are most likely separated by walls and floors from their connected cells in enterprise environments, these offloaded UEs now have to transmit with higher transmit power in the uplink and thereby affects their battery lives. In order to reduce the battery drain for the offloaded UEs while maintaining their QoS, we employ the Decoupled Uplink and Downlink (DUD) access method in such a way that, the uplink of UE is connected to the closest Femto while the downlink is connected to a less loaded neighboring Femto. To maximize the utilization of the limited operating spectrum and provide higher data rate for IUEs, operators can configure Femtos in open access mode with frequency reuse one (i.e., all Femtos and MBSs operates on a same frequency) in LTE HetNets. However, this leads to high co-tier interference and cross-tier interference. Another problem in enterprise buildings having Femtos is frequent handovers, that happens when IUEs move from one room/floor to another room/floor inside the building. This leads to degradation of network performance in terms of increased signaling overhead and low throughputs. In order to reduce this kind of unnecessary handovers in enterprise buildings, Femtos should be placed optimally with handover constraints. Hence, we obtain the optimal coordinates from the OptHO model by adding handover constraints to the Minimize Number of Femtos (MinNF) model which guarantees threshold Signal-to-Interference plus Noise Ratio (SINR) of -2 dB for all IUEs inside the building. Such optimized deployment of Femtos reduces the number of handovers while guaranteeing good SINR to all IUEs. In LTE HetNets, even though planned deployment of Femtos in open access mode boosts the IUEs performance, the power leakage from indoor Femtos create interferix ence to the OUEs in the HIZone in the buildings surrounding areas. We propose an efficient placement and power control SON (Self organizing Network) algorithm which optimally places Femtos and dynamically adjusts the transmit power of Femtos based on the occupancy of Macro connected OUEs in the HIZone. To do this, we use the same MinNF model to place the Femtos optimally and solve Optimal Femto Power (OptFP) allocation problem (Mixed Integer Linear Programming (MILP)) which guarantees threshold SINR of -4 dB for IUEs with the Macro users SINR degradation as lesser than 2 dB. In the OptFP model, Femto’s transmit power is tuned dynamically according to the occupancy of OUEs in the HIZone. But the presence of even a single OUE in the HIZone decreases SINR of numerous IUEs, which is not fair to IUEs. In order to address this issue, we propose two solutions a) On improving SINR in LTE HetNets with D2D relays and b) A novel resource allocation and power control mechanism for Hybrid Access Femtos in LTE HetNets, which we describe in the following two paragraphs. To guarantee certain minimum SINR and fairness to both IUEs and OUEs in HIZone, we consider a system model by applying the concept of Device-to-Device (D2D) communication wherein free/idle IUEs connected to Femto act like UE-relays (i.e., UE-like BS, forwarding downlink data plane traffic for some of the HIZone users connected to MBS). We formulate a Mixed-Integer Linear Programming (MILP) optimization model which efficiently establishes D2D pairs between free/idle celledge IUEs and HIZone users by guaranteeing certain SINRT h for both IUEs and HIZone users. As D2D MILP model takes more computation time, it is not usable in real-world scenarios for establishing D2D pairs on the fly. Hence, we propose a two-step D2D heuristic algorithm for establishing D2D pairs. In above works, we assume that Femtos are configured in open access mode. But Hybrid Access Femtocells (HAFs) are favored by the operators because they ensure the paid Subscribed Group (SG) users certain QoS and then try to maximize the system capacity by serving near-by Non Subscribed Group (NSG) users in a best-effort manner. To reap in the benefits of HAFs, the operators need to employ effective resource sharing and scheduling mechanisms to contain co-tier and cross-tier interference arising out of reuse one in the HetNet system. Towards this, we address various challenges in terms of deployment and operation of HAFs in indoor environments. We propose an Optimal Placement of hybrid access Femtos (OPF) model which ensures a certain SINRT h inside the building and a certain SINRT h in the HIZone of the building. Unlike in previous optimization models, in this model, users in HIZone are connected to HAF s deployed inside the building. Also we propose a decentralized Dynamic Bandwidth Allocation (BWA) mechanism which divides the available HAF bandwidth between the two sets of user groups: SG and NSG. In order to mitigate co-tier and cross-tier interference, we then propose a dynamic Optimal Power Control (OPC) mechanism which adjusts the transmit powers of HAFs whenever the users in the HIZone cannot be served by the HAFs. In such a case, HIZone users connect to an MBS instead. Since the OPC problem is hard to solve in polynomial time, we also present a Sub-Optimal Power Control (SOPC) mechanism. To maintain fair resource allocation between SG and NSG users, we propose an Enhanced Priority (EP) scheduling mechanism which employs two schedulers which are based on the Proportional Fair (PF) and the Priority Set (PS) scheduling mechanisms. In above works, placement of Femtos is optimized to reduce co-channel co-tier interference among neighboring Femtos and transmit power of Femtos is optimized to reduce cross-tier interference between MBSs and Femtos. But, for arbitrary deployed Femtos, Inter Cell Interference Coordination (ICIC) techniques could be employed to address co-tier interference problem among Femtos which are connected with each other over X2 interface. Hence, in this work, we propose an ICIC technique, Variable Radius (VR) algorithm which dynamically increases or decreases the cell edge/non-cell edge regions of Femtos and efficiently allocates radio resources among cell edge/non-cell edge regions of Femtos so that the interference between neighboring Femtos can be avoided. We implement the proposed VR algorithm on top of PF scheduler in NS-3 simulator and find that it significantly improves average network throughput when compared to existing techniques in the literature

    Techno-economical Analysis of Indoor Enterprise Solutions

    Get PDF

    Context-based Resource Management and Slicing for SDN-enabled 5G Smart, Connected Environments

    Get PDF
    Τα συστήματα κινητής επικοινωνίας πέμπτης γενιάς (5G) τα οποία αναμένονται τα αμέσως επόμενα χρόνια, θα αντιμετωπίσουν πρωτοφανείς απαιτήσεις όσον αφορά τον όγκο και το ρυθμό μεταδόσης δεδομένων, τις καθυστερήσεις του δικτύου, καθώς και τον αριθμό των συνδεδεμένων συσκευών. Τα μελλοντικά δικτυακά οικοσυστήματα θα περιλαμβάνουν μια πληθώρα τεχνολογιών ασύρματης επικοινωνίας (είτε τεχνολογιών 3GPP, είτε μη-3GPP) όπως το Wi-Fi, το 3G, το 4G ή LTE, το Bluetooth, κτλ. Τα σενάρια ανάπτυξης του 5G προβλέπουν έναν πολυεπίπεδο συνδυασμό μακρο- και μικρο-κυψελών, όπου πολυλειτουργικές συσκευές –οι οποίες μπορούν να υποστηρίξουν ποικιλία διαφορετικών εφαρμογών και υπηρεσιών- εξυπηρετούνται από διαφορετικές τεχνολογίες. Οι περιορισμοί που υπήρξαν στα παλιότερα συστήματα κινητών επικοινωνιών πρέπει να εξαλειφθούν, ανοίγοντας το δρόμο για ένα νέο κύμα υπηρεσιών και συνολική εμπειρία χρήστη. Ως εκ τούτου, η διαχείριση των ασύρματων πόρων μέσω της χαρτογράφησης και διανομής τους στις κινητές συσκευές, μέσω της πλέον κατάλληλης τεχνολογίας πρόσβασης, η οποία εξυπηρετεί τις ανάγκες των συγκεκριμένων υπηρεσιών/εφαρμογών αποκτά πρωταρχική σημασία. Οι κύριοι μηχανισμοί διαχείρισης πόρων δικτύου πρόσβασης δηλαδή η επιλογή κυψέλης (cell selection/reselection), η παράδοση υπηρεσίας από τη μία κυψέλη στην άλλη (handover), καθώς και ο έλεγχος εισαγωγής κλήσεων/υπηρεσιών (call/service admission control), είναι αυτοί που τελικώς θα μπορέσουν να προσφέρουν στους χρήστες εξαιρετικά υψηλή ποιότητα υπηρεσιών (Quality of Service - QoS) και εμπειρίας (Quality of Experience - QoE) προς τις πολύ απαιτητικές περιπτώσεις χρήσης του 5G. Αυτό θα γίνει εφικτό μέσω της βελτιστοποίησης του συσχετισμού-χαρτογράφησης μεταξύ των διαφορετικών (τελικών) κινητών συσκευών και των συνυπαρχόντων ασύρματων δικτύων πρόσβασης. Επιπλέον της οπτικής του χρήστη, οι Πάροχοι Δικτύων Κινητής θα είναι σε θέση να εκμεταλλευτούν τη μέγιστη αποδοτικότητα και χρήση των –ήδη δυσεύρετων- ασύρματων πόρων. Ευφυείς βελτιστοποιήσεις και αποδοτικές λύσεις όσον αφορά το κόστος και την κατανάλωση ενέργειας πρέπει επίσης να εισαχθούν στα δίκτυα 5ης γενιάς με σκοπό να προάγουν ένα συνεκτικό, στοχευμένο στο χρήστη και πολυδιάστατο οικοσύστημα πληροφοριών. Η παρούσα διατριβή αυτή εστιάζει στη Διαχείριση Ασύρματων Δικτυακών Πόρων (ΔΑΔΠ - RRM) από την οπτική των κύριων διαδικασιών που σχετίζονται με την επιλογή ασύρματης τεχνολογίας πρόσβασης και στρώματος κυψέλης (μικρο-, μάκρο κυψέλη, κτλ.), δηλαδή η επιλογή κυψέλης, η παράδοση υπηρεσίας και ο έλεγχος εισαγωγής κλήσεων/υπηρεσιών. Έπειτα, η διατριβή προχωρά ένα βήμα παραπέρα, με σκοπό να συνδέσει τη ΔΑΔΠ με μία από τις πιο πρόσφατες προσεγγίσεις διαχείρισης δικτυακών πόρων, δηλαδή τον «τεμαχισμό δικτύου» (network slicing), όπως αυτή εισάγεται σε περιβάλλοντα που χρησιμοποιούν τη μέθοδος της Δικτύωσης Βασισμένης στο Λογισμικό (Software Defined Networking), η οποία δημιουργεί μικρότερα, εικονικά τμήματα του δικτύου, προσαρμοσμένα και βελτιστοποιημένα για συκεκριμένες υπηρεσίες και αντίστοιχες απαιτήσεις. Σαν πρώτο βήμα, πραγματοποιήθηκε μια ολοκληρωμένη ανάλυση για τις υπάρχουσες λύσεις – όπως αυτές προδιαγράφονται στα πρότυπα της 3GPP, στη βιβλιογραφία, καθώς και τις σχετικές πατέντες-. Η διατριβή αυτή αρχικά εντοπίζει τους δεσμούς μεταξύ των προσπαθειών της ερευνητικής κοινότητας, των υλοποιήσεων της βιομηχανίας, καθώς και των δράσεων προτυποποίησης, σε μια προσπάθεια να επισημανθούν ρεαλιστικές λύσεις εφαρμογής, να προσδιοριστούν οι κύριοι στόχοι, τα πλεονεκτήματα, αλλά και οι ελλείψεις αυτών των προσπαθειών. Όπως θα δειχθεί, οι υπάρχουσες λύσεις προσπαθούν να εξισορροπήσουν σε ένα σημείο μεταξύ της βέλτιστης λύσης και μιας απλής υλοποίησης. Έτσι, οι λύσεις που έχουν προταθεί είτε είναι απλοποιημένες σε τέτοιο βαθμό που απομακρύνονται από μια ρεαλιστική πρόταση, και επιτυγχάνουν υπο-βέλτιστες λύσεις ή από την άλλη παρέχουν πολύ σημαντικές βελτιώσεις, αλλά η πολυπλοκότητά τους και η επιβάρυνση που επιβάλλουν στο δίκτυο (όσον αφορά για παράδειγμα κόστος σηματοδοσίας, ή επεξεργαστικής ισχύος) τις καθιστούν ελκυστικές για μια πραγματική ανάπτυξη. Προς αυτή την κατεύθυνση, η παρούσα διατριβή εισαγωγή ένα σύνολο μηχανισμών επίγνωσης πλαισίου για τη διαχείριση δικτυακών πόρων, που αποτελείται από τρεις επιμέρους μηχανισμούς με διακριτό ρόλο: Δύο από τους μηχανισμούς χρησιμοποιούν πληροφορία πλαισίου με σκοπό τη βελτίωση τη διαχείριση πόρων και και τη χαρτογράφηση μεταξύ ροών δεδομένων κινητών συσκευών και κυψέλης/τεχνολογίας δικτύου. Ο τρίτος μηχανισμός δρα με έναν ενισχυτικό ρόλο στους δύο προηγούμενους, μέσω μιας προ-επεξεργασίας που πραγματοποιεί πάνω σε πληροφορία πλαισίου, με σκοπό τον περιορισμό του κόστους της επιπλέον σηματοδοσίας που απαιτείται για την μεταφορά της πληροφορίας πλαισίου μεταξύ των διαφόρων ενδιαφερόμενων δικτυακών οντοτήτων. Εκτός από τους τρεις μηχανισμούς αυτούς, πραγματοποιήθηκαν εκτενείς μελέτες σε σχέση με αρχιτεκτονικά ζητήματα και πτυχές, στο πλαίσιο της επικείμενης αρχιτεκτονικής δικτύου 5G και χαρτογράφηση των προτεινόμενων μηχανισμών στα συστατικά στοιχεία του δικτύου 5G -όπως αυτά εισήχθησαν στα τελευταίο κείμενα προτυποποίησης της 3GPP-. Η πρώτη κύρια συμβολή της παρούσας διατριβής είναι το COmpAsS, ένας μηχανισμός επιλογής Τεχνολογίας Ασύρματης Πρόσβασης πολλαπλών κριτηρίων, με γνώμονα το περιβάλλον, το κύριο μέρος του οποίου λειτουργεί στην πλευρά του Εξοπλισμού Χρήστη (UE), ελαχιστοποιώντας με αυτό τον τρόπο τις επιβαρύνσεις σηματοδότησης στη διεπαφή αέρα και το φορτίο υπολογισμού στους σταθμούς βάσης. Ο μηχανισμός COmpAsS εκτελεί παρακολούθηση σε πραγματικό χρόνο, υιοθετώντας την Ασαφή Λογική (Fuzzy Logic -FL) ως μία από τις βασικές προσεγγίσεις αντίληψης και ανάλυσης της κατάστασης του δικτύου. Σε συνδυασμό με ένα σύνολο προκαθορισμένων κανόνων, υπολογίζει μια λίστα με τις καταλληλότερες διαθέσιμες επιλογές πρόσβασης δικτύου, για κάθε μία από τις ροές δεδομένων/υπηρεσίας που είναι ενεργές εκείνη τη στιγμή. Τα πλεονεκτήματα του COmpAsS παρουσιάζονται μέσω μιας εκτεταμένης σειράς σεναρίων προσομοίωσης, ως μέρος των περιπτώσεων χρήσης εξαιρετικά πυκνών δικτύων (UDN) 5G. Τα αποτελέσματα αποδεικνύουν τον τρόπο με τον οποίο ο προτεινόμενος μηχανισμός βελτιστοποιεί τους βασικούς δείκτες επιδόσεων (Key Performance Indicators - KPIs), όταν αντιπαρατίθεται σε έναν από τους καθιερωμένους LTE αλγορίθμους. Η δεύτερη σημαντική συμβολή της παρούσας διατριβής είναι η Μηχανή Εξόρυξης Πλαισίου και Δημιουργίας Προφίλ (Context Extraction and Profiling Engine – CEPE), ένας μηχανισμός διαχείρισης πόρων, ο οποίος αναλύει συμπεριφορικά πρότυπα των χρηστών/κινητών συσκευών, εξάγει ουσιώδη γνώση και δημιουργεί αντίστοιχα προφίλ/πρότυπα συμπεριφοράς, με σκοπό να τα χρησιμοποιήσει για βέλτιστο προγραμματισμό πόρων, καθώς επίσης και για την μελλοντική πρόβλεψη απαιτήσεων πόρων. Το CEPE συλλέγει πληροφορίες σχετικά με τους χρήστες, τις υπηρεσίες, τις κινητές συσκευές, καθώς και τις συνθήκες δικτύου, και μέσω επεξεργασίας -χωρίς σύνδεση, ετεροχρονισμένα- αποκτά ένα μοντέλο γνώσης, το οποίο στη συνέχεια χρησιμοποιείται για τη βελτιστοποίηση των κύριων μηχανισμών ΔΑΔΠ (RRM). Το προαναφερθέν μοντέλο γνώσης μεταφράζεται έπειτα σε προφίλ χρηστών/κινητών συσκευών, τα οποία εφαρμόζονται ως είσοδος κατά τις διαδικασίες ΔΑΔΠ. Η βιωσιμότητα και η εγκυρότητα του CEPE επιδεικνύεται μέσω εκτεταμένων σεναρίων προσομοίωσης. Η τρίτη σημαντική συμβολή είναι το CIP (Context Information Preprocessor), ένας μηχανισμός προεπεξεργασίας πληροφοριών πλαισίου, με στόχο τον εντοπισμό και την απόρριψη περιττών δεδομένων κατά τη σηματοδοσία πριν από την εξαγωγή της γνώσης. Το CIP θα μπορούσε να θεωρηθεί ως αναπόσπαστο μέρος των προαναφερθέντων σχημάτων σχεδίασης, δηλαδή των COmpAsS και CEPE. Ο προτεινόμενος μηχανισμός περιλαμβάνει τη συγκέντρωση και συμπίεση πληροφοριών πλαισίου σχετικά με το δίκτυο ανά μοναδικό αναγνωριστικό κινητής συσκευής/χρήστη, -όπως η διεθνής ταυτότητα συνδρομητή κινητού (IMSI)-, καθώς και τεχνικές που σχετίζονται με την αναγνώριση και την απόρριψη δεδομένων πλαισίου που δε συμβάλλουν στην βελτίωση ή διόρθωση του πρόφιλ χρήστη, πριν από οποιαδήποτε μετάδοση προς το CEPE (ή άλλο μηχανισμό ΔΑΔΠ). Οι βελτιώσεις και τα κέρδη του CIP στη διαδικασία της σηματοδοσίας απεικονίζονται μέσω λεπτομερούς αναλυτικής προσέγγισης, η οποία καθορίζεται από τις καθιερωμένες απαιτήσεις περί χρήσης 5G. Ως τελική σημαντική συμβολή αυτής της διατριβής, διεξάγεται μια εκτεταμένη ανάλυση όσον αφορά τη διασύνδεση των CEPE-COmpAsS, στο πλαίσιο της επικείμενης αρχιτεκτονικής δικτύου 5G και της χαρτογράφησης αυτών με τα τελευταία συστατικά στοιχεία του δικτύου 5G –όπως αυτά παρουσιάστηκαν στις τελευταίες δημοσιεύσεις προτυποποίησης της 3GPP -. Το έργο σε αυτή την ενότητα δείχνει πώς μπορεί να παρουσιαστεί το προτεινόμενο πλαίσιο ως μέρος των συνιστωσών του δικτύου 5G και των λειτουργιών που εισάγονται σε περιβάλλοντα με δυνατότητα SDN, όπως η προσέγγιση του «Τεμαχισμού Δικτύου», ο Μηχανισμός Ανάλυσης Δικτυακών Δεδομένων (Network Data Analytics Function – NWDAF), η λειτουργία επιλογής βέλτιστου τεμαχίου δικτύου (Network Slice Selection Function) - προς περαιτέρω βελτιστοποίηση της διανομής και της διαχείρισης των διαθέσιμων πόρων δικτύου μεταξύ των συσκευών-, καθώς και το ATSSS – Access Traffic Steering, Switching and Splitting, μια οντότητα υπεύθυνη για τη διαχείριση των ροών δεδομένων των UE –με δυνατότητες επαναδρομολόγησης, διαχωρισμού και σύνδεσης της κάθε ροής με την αντίστοιχη βέλτιστη, διαθέσιμη τεχνολογία πρόσβασης. Δύο συμπληρωματικές μελέτες περιλαμβάνονται –τέλος- σε αυτή τη διατριβή: μια αρχική ανάλυση των πολιτικών μηχανικής κυκλοφορίας (Traffic Engineering) που βασίζονται σε προφίλ χρηστών που προκύπτουν από το CEPE, καθώς και μία περίπτωση χρήσης 5G που σχετίζεται με τον τομέα του Διαδικτύου των Πραγμάτων - και πιο συγκεκριμένα την «Καλλιέργεια Ακριβείας» (Precision Farming), με σκοπό να δοθεί έμφαση σε ρητές απαιτήσεις των περιπτώσεων χρήσης 5G, όπως η επικοινωνία τύπου μηχανής κρίσιμης σημασίας (Mission-Critical Machine Type Communication).The fifth-generation (5G) mobile communication systems, which are expected to emerge in the forthcoming years, will address unprecedented demands in terms of system capacity, service latency and number of connected devices. Future 5G network ecosystems will comprise a plethora of 3GPP and non-3GGP Radio Access Technologies (RATs), such as Wi-Fi, 3G, 4G or LTE, Bluetooth, etc. Deployment scenarios envision a multi-layer combination of macro, micro and femto cells where multi-mode end devices, supporting diverse applications, are served by different technologies. Limitations previously posed by legacy generation systems need to be eliminated, paving the way to a new wave of services and overall experience for the user. As a result, the management of radio resources via mapping the end devices to the most appropriate access network becomes of paramount importance; the primary Radio Resource Management (RRM) mechanisms, i.e. cell selection/reselection, handover and call admission control will be able to offer extremely high Quality of Service (QoS) and Experience (QoE) to the users, towards the very demanding 5G use case requirements; this will be realised via an optimal association between the diverse end devices and the coexisting available access networks. Besides the user’s perspective, the Mobile Network Operators (MNOs) will be able to take advantage of the maximum efficiency and utilization over the –already scarce- wireless resources. Intelligent optimizations, as well as cost and energy efficient solutions need to be introduced in 5G networks in order to promote a consistent, user-centred and all-dimensional information ecosystem. This thesis focuses on the radio resource management (RRM) from the perspective of the primary RAT and cell layer selection processes (i.e., cell (re)selection, handover, admission control); afterwards, it goes one step beyond, in order to link the RRM with one of the latest RRM optimization approaches, i.e. the Network Slicing, as introduced in Software Defined Networking (SDN)-enabled environments, which creates smaller, virtual “portions” of the network, adapted and optimized for specific services/requirements. As a first step, a comprehensive analysis for the existing solutions -as these are specified in 3GPP standards, research papers, and patents has taken place. This thesis initially identifies the links between the research community efforts, the industry implementations, as well as the standardization efforts, in an attempt to highlight realistic solution implementations, identify the main goals, advantages and shortcomings of these efforts. As will be shown, existing solutions attempt to balance between implementation simplicity and solution optimality. Thus, solutions are either simple to implement but achieve sub-optimal solutions or provide significant improvements but their complexity and the burden placed on the network components renders them unattractive for a real-life deployment. Towards this end, this thesis introduces a context-based radio resource management (RRM) framework, comprised of three distinct mechanisms: Two out of the three mechanisms exploit contextual information with the aim of optimising the resource management and UE-RAT mapping, while the third mechanism acts with an augmenting role to the former two, by pre-processing the contextual information required by such, context-based mechanisms and –thus- by limiting the signalling cost required for communicating this contextual information among network entities. In addition to the three mechanisms, comprehensive analysis has taken place in relation to architectural aspects, in the context of the forthcoming 5G network architecture and by mapping them with the latest 5G network components –as these were introduced in the latest 3GPP work-. The first major contribution of this thesis is COmpAsS, a context-aware, multi-criteria RAT selection mechanism, the main part of which operates on the User Equipment (UE) side, minimizing signalling overhead over the air interface and computation load on the base stations. COmpAsS mechanism performs real-time monitoring and adopts Fuzzy Logic (FL) as one the core logic modules, responsible for the perception of the network situation and, in combination with a set of pre-defined rules, calculates a list of the most suitable available access network options. The merits of COmpAsS are showcased via an extensive series of simulation scenarios, as part of 5G ultra dense networks (UDN) use cases. The results prove how the proposed mechanism optimises Key Performance Indicators (KPIs), when juxtaposed to a well-established LTE handover algorithm. The second major contribution of the current thesis the Context Extraction and Profiling Engine (CEPE), a resource management framework, which analyzes user behavioral patterns, extracts meaningful knowledge and performs user profiling in order to apply it for optimal resource planning, as well as prediction of resource requirements. CEPE collects information about users, services, terminals and network conditions and –based on offline processing– derives a knowledge model, which is subsequently used for the optimization of the primary RRM mechanisms. Then, the extracted context information is translated into user profiles and is finally applied as input for enhanced cell (re)selection, handover or admission control. The viability and validity of CEPE is demonstrated via an extensive set of simulation scenarios. The third major contribution is CIP, a Context Information Pre-processing scheme, aiming to identify and discard redundant or unnecessary data during network signalling and before knowledge extraction. CIP could be considered as an integral part of the afore described profiling schemes, i.e. COmpAsS and CEPE. The module comprises aggregating and compressing mobile network-related context information per unique identifier, such as the end device’s International Mobile Subscriber Identity (IMSI), as well as techniques related to identifying and discarding user profile-redundant or unnecessary context data, before any transmission to CEPE. CIP gains are illustrated via a detailed analytical approach, guided by well-established 5G use case requirements. As a final major contribution of this thesis, a comprehensive analysis takes place with regard to the CEPE-COmpAsS interworking, in the context of the forthcoming 5G network architecture and by mapping them with the latest 5G network components –as these were introduced in the latest 3GPP work-. The work in this section shows how the proposed framework can be instantiated as part of the 5G network components and functions introduced in SDN-enabled environments, such as the Network Slicing approach, the Network Data Analytics and the Network Slice Selection Functions, towards further optimising the distribution and management of the available infrastructure and network resources among the UEs, as well as the Access Traffic Steering, Switching and Splitting (ATSSS), responsible for managing the UE data flows and mapping each single UE flow with the optimal available access technology.. Two supplementary studies are finally included in this dissertation: a preliminary analysis on traffic engineering policies based on user profiling realised by CEPE, as well as a 5G use case related to the Internet of Things domain -and more specifically, Precision Farming-, aiming to highlight explicit requirements such as mission-critical machine type communication

    On three use cases of multi-connectivity paradigm in emerging wireless networks

    Get PDF
    As envisioned by global network operators, the increasing trend of data traffic demand is expected to continue with exponential growth in the coming years. To cope with this rapid increase, significant efforts from the research community, industry and even regulators have been focused towards improving two main aspects of the wireless spectrum: (i) spectrum capacity and (ii) spectral efficiency. Concerning the spectrum capacity enhancement, the multi-connectivity paradigm has been seen to be fundamentally important to solve the capacity problem in the next generation networks. Multi-connectivity is a feature that allows wireless devices to establish and maintain multiple simultaneous connections across homogeneous or heterogeneous technologies. In this thesis, we focus on identifying the core issues in applying the multi-connectivity paradigm for different use cases and propose novel solutions to address them. Specifically, this thesis studies three use cases of the multi-connectivity paradigm. First, we study the uplink/downlink decoupling problem in 4G networks. More specifically, we focus on the user association problem in the decoupling context, which is considered challenging due to the conflicting objectives of different entities (e.g., mobile users and base stations) in the system. We use a combination of matching theory and stochastic geometry to reconcile competing objectives between users in the uplink/downlink directions and also from the perspective of base stations. Second, we tackle the spectrum aggregation problem for wireless backhauling links in unlicensed opportunistic shared spectrum bands, specifically, TV White Space (TVWS) spectrum. In relation to this, we present a DIY mobile network deployment model to accelerate the roll-out of high-end mobile services in rural and developing regions. As part of this model, we highlight the importance of low-cost and high-capacity backhaul infrastructure for which TVWS spectrum can be exploited. Building on that, we conduct a thorough analytical study to identify the characteristics of TVWS in rural areas. Our study sheds light on the nature of TVWS spectrum fragmentation for the backhauling use case, which in turn poses requirements for the design of spectrum aggregation systems for TVWS backhaul. Motivated by these findings, we design and implement WhiteHaul, a flexible platform for spectrum aggregation in TVWS. Three challenges have been tackled in this work. First, TVWS spectrum is fragmented in that the spectrum is available in non-contiguous manner. To fully utilize the available spectrum, multiple radios should be enabled to work simultaneously. However, all the radios have to share only a single antenna. The key challenge is to design a system architecture that is capable of achieving different aggregation configurations while avoiding the interference. Second, the heterogeneous nature of the available spectrum (i.e., in terms of bandwidth and link characteristics) requires a design of efficient traffic distribution algorithm that takes into account these factors. Third, TVWS is unlicensed opportunistic shared spectrum. Thus, the coordination mechanism between the two nodes of backhauling link is essential to enable seamless channel switching. Third, we study the integration of multiple radio access technologies (RATs) in the context of 4G/5G networks. More specifically, we study the potential gain of enabling the Multi-RAT integration at the Packet Data Convergence Protocol (PDCP) layer compared with doing it at the transport layer. In this work, we consider ultra-reliable low-latency communication (URLLC) as one of the motivating services. This work tackles the different challenges that arise from enabling the Multi-RAT integration at the PDCP layer, including, packet reordering and traffic scheduling

    Performance and power optimizations in chip multiprocessors for throughput-aware computation

    Get PDF
    The so-called "power (or power density) wall" has caused core frequency (and single-thread performance) to slow down, giving rise to the era of multi-core/multi-thread processors. For example, the IBM POWER4 processor, released in 2001, incorporated two single-thread cores into the same chip. In 2010, IBM released the POWER7 processor with eight 4-thread cores in the same chip, for a total capacity of 32 execution contexts. The ever increasing number of cores and threads gives rise to new opportunities and challenges for software and hardware architects. At software level, applications can benefit from the abundant number of execution contexts to boost throughput. But this challenges programmers to create highly-parallel applications and operating systems capable of scheduling them correctly. At hardware level, the increasing core and thread count puts pressure on the memory interface, because memory bandwidth grows at a slower pace ---phenomenon known as the "bandwidth (or memory) wall". In addition to memory bandwidth issues, chip power consumption rises due to manufacturers' difficulty to lower operating voltages sufficiently every processor generation. This thesis presents innovations to improve bandwidth and power consumption in chip multiprocessors (CMPs) for throughput-aware computation: a bandwidth-optimized last-level cache (LLC), a bandwidth-optimized vector register file, and a power/performance-aware thread placement heuristic. In contrast to state-of-the-art LLC designs, our organization avoids data replication and, hence, does not require keeping data coherent. Instead, the address space is statically distributed all over the LLC (in a fine-grained interleaving fashion). The absence of data replication increases the cache effective capacity, which results in better hit rates and higher bandwidth compared to a coherent LLC. We use double buffering to hide the extra access latency due to the lack of data replication. The proposed vector register file is composed of thousands of registers and organized as an aggregation of banks. We leverage such organization to attach small special-function "local computation elements" (LCEs) to each bank. This approach ---referred to as the "processor-in-regfile" (PIR) strategy--- overcomes the limited number of register file ports. Because each LCE is a SIMD computation element and all of them can proceed concurrently, the PIR strategy constitutes a highly-parallel super-wide-SIMD device (ideal for throughput-aware computation). Finally, we present a heuristic to reduce chip power consumption by dynamically placing software (application) threads across hardware (physical) threads. The heuristic gathers chip-level power and performance information at runtime to infer characteristics of the applications being executed. For example, if an application's threads share data, the heuristic may decide to place them in fewer cores to favor inter-thread data sharing and communication. In such case, the number of active cores decreases, which is a good opportunity to switch off the unused cores to save power. It is increasingly harder to find bulletproof (micro-)architectural solutions for the bandwidth and power scalability limitations in CMPs. Consequently, we think that architects should attack those problems from different flanks simultaneously, with complementary innovations. This thesis contributes with a battery of solutions to alleviate those problems in the context of throughput-aware computation: 1) proposing a bandwidth-optimized LLC; 2) proposing a bandwidth-optimized register file organization; and 3) proposing a simple technique to improve power-performance efficiency.El excesivo consumo de potencia de los procesadores actuales ha desacelerado el incremento en la frecuencia operativa de los mismos para dar lugar a la era de los procesadores con múltiples núcleos y múltiples hilos de ejecución. Por ejemplo, el procesador POWER7 de IBM, lanzado al mercado en 2010, incorpora ocho núcleos en el mismo chip, con cuatro hilos de ejecución por núcleo. Esto da lugar a nuevas oportunidades y desafíos para los arquitectos de software y hardware. A nivel de software, las aplicaciones pueden beneficiarse del abundante número de núcleos e hilos de ejecución para aumentar el rendimiento. Pero esto obliga a los programadores a crear aplicaciones altamente paralelas y sistemas operativos capaces de planificar correctamente la ejecución de las mismas. A nivel de hardware, el creciente número de núcleos e hilos de ejecución ejerce presión sobre la interfaz de memoria, ya que el ancho de banda de memoria crece a un ritmo más lento. Además de los problemas de ancho de banda de memoria, el consumo de energía del chip se eleva debido a la dificultad de los fabricantes para reducir suficientemente los voltajes de operación entre generaciones de procesadores. Esta tesis presenta innovaciones para mejorar el ancho de banda y consumo de energía en procesadores multinúcleo en el ámbito de la computación orientada a rendimiento ("throughput-aware computation"): una memoria caché de último nivel ("last-level cache" o LLC) optimizada para ancho de banda, un banco de registros vectorial optimizado para ancho de banda, y una heurística para planificar la ejecución de aplicaciones paralelas orientada a mejorar la eficiencia del consumo de potencia y desempeño. En contraste con los diseños de LLC de última generación, nuestra organización evita la duplicación de datos y, por tanto, no requiere de técnicas de coherencia. El espacio de direcciones de memoria se distribuye estáticamente en la LLC con un entrelazado de grano fino. La ausencia de replicación de datos aumenta la capacidad efectiva de la memoria caché, lo que se traduce en mejores tasas de acierto y mayor ancho de banda en comparación con una LLC coherente. Utilizamos la técnica de "doble buffering" para ocultar la latencia adicional necesaria para acceder a datos remotos. El banco de registros vectorial propuesto se compone de miles de registros y se organiza como una agregación de bancos. Incorporamos a cada banco una pequeña unidad de cómputo de propósito especial ("local computation element" o LCE). Este enfoque ---que llamamos "computación en banco de registros"--- permite superar el número limitado de puertos en el banco de registros. Debido a que cada LCE es una unidad de cómputo con soporte SIMD ("single instruction, multiple data") y todas ellas pueden proceder de forma concurrente, la estrategia de "computación en banco de registros" constituye un dispositivo SIMD altamente paralelo. Por último, presentamos una heurística para planificar la ejecución de aplicaciones paralelas orientada a reducir el consumo de energía del chip, colocando dinámicamente los hilos de ejecución a nivel de software entre los hilos de ejecución a nivel de hardware. La heurística obtiene, en tiempo de ejecución, información de consumo de potencia y desempeño del chip para inferir las características de las aplicaciones. Por ejemplo, si los hilos de ejecución a nivel de software comparten datos significativamente, la heurística puede decidir colocarlos en un menor número de núcleos para favorecer el intercambio de datos entre ellos. En tal caso, los núcleos no utilizados se pueden apagar para ahorrar energía. Cada vez es más difícil encontrar soluciones de arquitectura "a prueba de balas" para resolver las limitaciones de escalabilidad de los procesadores actuales. En consecuencia, creemos que los arquitectos deben atacar dichos problemas desde diferentes flancos simultáneamente, con innovaciones complementarias

    On-demand offloading collaboration framework based on LTE network virtualisation

    Get PDF
    Recently, there has been a significant increase in data traffic on mobile networks, due to the growth in the numbers of users and the average data volume per user. In a context of traffic surge and reduced revenues, operators face the challenge of finding costless solutions to increase capacity and coverage. Such a solution should necessarily rule out any physical expansion, and mainly conceive real-time strategies to utilise the spectrum more efficiently, such as network offload and Long-term Evolution (LTE) network virtualisation. Virtualisation is playing a significant role in shaping the way of networking now and in future, since it is being devised as one of the available technologies heading towards the upcoming 5G mobile broadband. Now, the successful utilisation of such innovative techniques relies critically on an efficient call admission control (CAC) algorithm. In this work, framework is proposed to manage the operation of a system in which CAC, virtualisation and Local break out (LBO) strategies are collaboratively implemented to avoid congestion in a mobile network, while simultaneously guaranteeing that measures of quality of service (QoS) are kept above desired thresholds. In order to evaluate the proposed framework, two simulation stages were carried out. In the first stage, MATLAB was used to run a numerical example, with the purpose of verifying the mathematical model of the proposed framework in air interface level. The second stage involved of using open source applications such as, Emulated Virtual Environment (EVE) and Wireshark, for emulating the traffic in the network for different scenarios inside the core network. The results confirm the effectiveness of the proposed framework
    corecore