Networking Solutions for Integrated Heterogeneous Wireless Ecosystem

As wireless communications technology is steadily evolving to improve the offered connectivity levels, additional research on emerging network architectures is becoming timely to understand the applicability of both traditional and novel networking solutions. This chapter concentrates on the utilization of cloud computing techniques to construct feasible system prototypes and demonstrators within the rapidly maturing heterogeneous wireless ecosystem. Our first solution facilitates cooperative radio resource management in heterogeneous networks. The second solution enables assisted direct connectivity between proximate users. The contents of the chapter outline our corresponding research and development efforts as well as summarize the major experiences and lessons learned

Mode selection in device-to-device communications

Device-to-Device (D2D) communication refers to a technology that enables devices to communicate directly with each other, without sending data to the base station and the core network. This technology has the potential to improve system performance, enhance the user experience, increase spectral efficiency, reduce the terminal transmitting power, reduce the burden of the cellular network, and expand cellular applications. In D2D communication UEs are enabled to select among different Transmission Modes (TM)s which are defined based on the frequency resource sharing. Dedicated mode where the D2D communication is direct and data is transmitted through the D2D link by the orthogonal frequency resources to the cellular users so there is not any interference. Reuse mode where data is transmitted through the D2D link by reusing the same frequency resources that are considered for a cellular user or another D2D link so reused mode causes interference at receivers however, the system spectrum efficiency and user access rate may be increased. Cellular mode where the D2D communication is relayed via eNB and it is treated as cellular users. In this work, we aim to reach the optimal mode selection policy, and we use the Markov Decision Process (MDP) method with the objective of maximizing the total expected reward per connection. We present and analyse optimal mode selection policy for several scenarios with different rewards and cost for cellular, dedicated and reused mode. In our study of mode selection issues in D2D enabled network we propose an algorithm for the case when the cellular UE moves in the network. We use QoS parameters, mobility parameters and Analytic Hierarchy Process (AHP) method to define new mobility based mode selection algorithm. To evaluate our proposed algorithm, we considered SNR and delay

Μελέτη και προσομοίωση αλγοριθμικών διαδικασιών για επικοινωνίες συσκευής-προς-συσκευή σε δίκτυα 4ης γενιάς

Στην παρούσα εργασία, το πρώτο κεφάλαιο παρουσιάζει μία επισκόπηση του LTE-A εστιάζοντας στην αρχιτεκτονική του συστήματος και των πρωτοκόλλων που χρησιμοποιεί. Στο δεύτερο κεφάλαιο γίνεται μία εισαγωγή στις επικοινωνίες συσκευής-προς-συσκευή και επικεντρώνεται στην παρουσίαση των σημαντικότερων προκλήσεων που αφορούν την πραγματοποίηση και την ενσωμάτωση τους στο σύστημα LTE-A. Στο τρίτο κεφάλαιο παρουσιάζονται οι αλγόριθμοι που έχουν σχεδιαστεί για την επίλυση αυτών των προκλήσεων και αφορούν το δίκτυο LTE-A. Στο τέταρτο κεφάλαιο περιγράφονται οι βασικές οντότητες που έχουν υλοποιηθεί στο περιβάλλον omnet++, γίνεται μία εισαγωγή του SimuLTE και παριστάνονται τα αποτελέσματα των προσομοιώσεων ενός απλού αλγορίθμου επιλογής λειτουργίας. Τέλος το πέμπτο κεφάλαιο παρέχει συμπεράσματα και προτάσεις για περαιτέρω έρευνα στο μέλλον.In this thesis, the first chapter presents an overview of LTE-A focusing on the architecture of the system and the protocols it uses. The second chapter introduces device-to-device communications and focuses on presenting the most important challenges that D2D communications' integration into the LTE-A system has. Algorithms designed to solve these challenges are presented in the third chapter. The fourth chapter describes the basic entities that have been implemented into the omnet ++ environment. It also introduces SimuLTE and presents the results of simulations of a simple mode selection algorithm. Finally, the fifth chapter provides conclusions and suggestions for further research in the future