Alessandro Raschellà

SINR-Based Transport Channel Selection for MBMS Applications

Multimedia broadcast multicast services (MBMS), introduced by Third Generation Partnership Project (3GPP) in universal mobile telecommunications system (UMTS) release 6 specification, have the aim to support downlink streaming and game services to groups of users. MBMS can supply users with resources in two different modalities: point-to-point (PtP) and point-to-multipoint (PtM). The power consumed by the network is an important topic to discuss when considering the presence of MBMS services. The UMTS system is, in fact, interference- limited; thus, the power available to Node B is limited and it must be enough to serve any user under its coverage. Therefore, the choice of the most efficient transport channel in terms of power consumption is a key aspect for the MBMS, since a wrong transport channel selection for the transmission of the MBMS data could adversely affect the overall capacity of the system. In this paper we search for the most efficient transport channel to convey MBMS data, by comparing the performance of the high speed downlink shared channel (HS-DSCH), the dedicated channel (DCH), and the forward access channel (FACH), for given transmission power levels and cell coverage size.

Implementation of Cognitive Radio Networks to evaluate spectrum management strategies in real-time

This paper illustrates a Universal Software Radio Peripheral (USRP)-based real-time testbed that is able to evaluate different spectrum management solutions that exploit the Cognitive Radio (CR) paradigm. The main objective of this testbed is to provide an accurate and realistic platform by which the performance of innovative spectrum management solutions for a wide set of scenarios and use cases in the context of Opportunistic Networks (ONs) and Cognitive Radio Networks (CRNs) can be entirely validated and assessed before their implementation in real systems. Real-time platforms are essential to carry out significant studies and to accurately assess the performance of innovative solutions before their implementation in the real world. This work provides a comprehensive description of the testbed, highlighting many interesting implementation details and illustrating its applicability for different studies that rely on the CR paradigm. Then, a particular application in a realistic Digital Home (DH) scenario is also illustrated, which allows demonstrating the effectiveness of the real-time testbed and assessing its practicality in terms of user-perceived end-to-end Quality of Experience (QoE) in a realistic environment.

A Belief-Based Decision-Making Framework for Spectrum Selection in Cognitive Radio Networks

This paper presents a comprehensive cognitive management framework for spectrum selection in cognitive radio (CR) networks. The framework uses a belief vector concept as a means to predict the interference affecting the different spectrum blocks (SBs) and relies on a smart analysis of the scenario dynamicity to properly determine an adequate observation strategy to balance the tradeoff between achievable performance and measurement requirements. In this respect, the paper shows that the interference dynamics in a given SB can be properly characterized through the second highest eigenvalue of the interference state transition matrix. Therefore, this indicator is retained in the proposed framework as a relevant parameter to drive the selection of both the observation strategy and spectrum selection decision-making criterion. This paper evaluates the proposed framework to illustrate the capability to properly choose among a set of possible observation strategies under different scenario conditions. Furthermore, a comparison against other state-of-the-art solutions is presented.

On the optimization of power assignment to support multicast applications in HAP-based systems

The goal of this research work is to investigate how efficient High Altitude Platforms (HAPs) can be in supporting Multimedia Broadcast/Multicast Service (MBMS) in scenarios in which the terrestrial coverage is not available. Specifically, we propose to implement an effective Radio Resources Management (RRM) policy into the HAP Radio Network Controller (H-RNC), whose main aim is to increase the overall system capacity. The proposed technique achieves its goal by dynamically selecting the most efficient multicast transport channel in terms of power consumption, chosen amongst Dedicated Channel (DCH), Forward Access Channel (FACH), and High Speed Downlink Shared Channel (HS-DSCH). Advantages deriving from the joint use of channels belonging to different categories are exploited. Results achieved when using the proposed RRM are quite manifest and witnesses to the necessity of providing such a feature when deploying integrated HAP/Terrestrial platforms supporting MBMS services.

Quality of Service Oriented Access Point Selection Framework for Large Wi-Fi Networks

This paper addresses the problem of access point (AP) selection in large Wi-Fi networks. Unlike current solutions that rely on received signal strength to determine the best AP that could serve a wireless user’s request, we propose a novel framework that considers the quality of service (QoS) requirements of the user’s data flow. The proposed framework relies on a function reflecting the suitability of a Wi-Fi AP to satisfy the QoS requirements of the data flow. The framework takes advantage of the flexibility and centralised nature of software defined networking (SDN). A performance comparison of this algorithm developed through an SDN-based simulator shows significant achievements against other state-of-the-art solutions in terms of provided QoS and improved wireless network capacity.

On the impact of the observation strategy in a POMDP-based framework for spectrum selection

Dynamic Spectrum Access, based on the Cognitive Radio (CR) paradigm, is a promising solution to improve the currently inefficient spectrum utilization. In this respect, this paper deals with the spectrum selection problem when a number of radio links has to be established in a CR network. A novel strategy based on a Partially Observable Markov Decision Process (POMDP) is proposed combining partial observations of the interference state together with a statistical characterization of the interference dynamics. In this context, the use of an efficient observation strategy is a key element to account for the trade-off between achieved performance and measurement requirements. For that purpose, the aim of the paper is to propose and evaluate different observation policies for the POMDP-based spectrum selection framework. Results show that the proposed framework is able to achieve very similar performance than a strategy operating under full knowledge of the interference state requiring much less associated signaling.

A testbed platform to demonstrate spectrum selection in opportunistic networks

This paper presents a testbed platform to demonstrate and validate spectrum opportunity identification and spectrum selection functionalities in Opportunistic Networks (ONs). The hardware component of the testbed is based on reconfigurable devices able to transmit and receive data at different operating frequencies, which are dynamically configured. The software component has been developed to perform the creation and maintenance of ON radio links, including spectrum opportunity identification and selection decision making as well as all the necessary signaling to support the ON operation. Results presented in the paper validate the implementation conducted at the laboratory and illustrate the reconfigurability capabilities of the ON links under different conditions.

High Altitude Platforms: Radio Resource Management Policy for MBMS Applications

In this work we are interested in investigating how the High Altitude Platform (HAP) can efficiently support Multimedia Broadcast/Multicast Service (MBMS) in a scenarios wherein the terrestrial network is not available. To this aim, we propose to implement an efficient policy of Radio Resources Management (RRM) into the HAP Radio Network Controller (H-RNC). The proposed technique allows to improve the overall system capacity by selecting the most efficient multicast transport channel in terms of power consumption and by defining the switching thresholds between point-to-point and point-to-multipoint connections.

Device-to-Device Communications over 5G Systems: Standardization, Challenges and Open Issues

This chapter deals with a comprehensive analysis of the challenges behind the introduction of Device-to-Device (D2D) communications in the context of 5th Generation (5G) communications. In fact, although D2D communications have emerged as an efficient solution for local traffic between mobile User Equipments (UEs) in proximity in cellular environments, has recently also attracted attention as a key enabling technology for 5G wireless networks. In details, this chapter addresses an overview of the current standardization, its integration in the cellular system architecture, future challenges and open issues. This chapter also provides a performance analysis, which illustrates the important achievements in terms of data rate in a scenario where the proximity communications between devices in an LTE-A system has been introduced for multicast downloading services.

A centralised Wi-Fi management framework for D2D communications in dense Wi-Fi networks

In Wi-Fi networks, Device-to-Device (D2D) communications aim to improve the efficiency of the network by supporting direct communication between users in close proximity. However, in a congested Wi-Fi network, establishing D2D connections through a locally managed self-organising approach will intensify the congestion and reduce the scalability of the solution. Therefore, a centralised management approach must be involved in orchestrating those actions to guarantee the sufficiency of D2D communications. In this paper, we propose a novel management framework for D2D communications in dense Wi-Fi networks. The proposed framework employs a Software-Defined Networking (SDN) based centralised controller in synergy with a novel Access Point (AP) channel assignment process. This framework is designed to proactively establish and manage D2D connections in Wi-Fi networks considering the available radio resources and the effect of the subsequent interference. Thus, improving the overall performance of the network and providing users with higher data rate. Through simulation, we validate the effectiveness of the proposed framework and demonstrate how D2D deployment considerably improves the Wi-Fi network efficiency especially when the data rate requirements are high. Furthermore, we show that our proposed framework achieves better performance than the widely deployed Least Congested Channel selection strategy (LCC).