Paolo Di Francesco

Dynamic spectrum scheduling for carrier aggregation: A game theoretic approach

In this paper, we investigate the performance of the dynamic allocation of resources between separate cellular networks. We propose a Dynamic Internetworking Carrier Aggregation (DI-CA) framework which involves every network operator releasing some of its exclusive, but excess, spectrum to another network operator for a limited time. We derive the basic condition for which DI-CA can improve the performance for all the operators and then propose a distributed scheduling framework that uses coalition formation with uncertainty, in which each independent operator can decide whether or not DI-CA can improve its performance without having information regarding channel conditions or load experienced by other operators. We propose a distributed Bayesian coalition formation algorithm to approach a neighborhood of the Bayesian Nash equilibrium.

A Split MAC Approach for SDR Platforms

Implementation of carrier sensing-based medium access control (MAC) protocols on inexpensive reconfigurable radio platforms has proven challenging due to long and unpredictable delays associated with both signal processing on a general purpose processor (GPP) and the interface between the radio frequency (RF) front end and the GPP. This paper describes the development and implementation of a split-functionality architecture for a contention-based carrier sensing MAC, in which some of the functions reside on an field-programmable gate array (FPGA) and others reside in the GPP. We provide an FPGA-based implementation of a carrier sensing block and develop two versions of a carrier sense multiple access (CSMA) MAC protocol based upon this block. We experimentally test the performance of the resulting protocols in a multihop environment in terms of end-to-end throughput and required frame retransmissions. We cross-validate these results with a network simulator with modules modified to reflect the mean and variance of delays measured in components of the real software-defined radio system.

Mobile network sharing between operators: a demand trace-driven study

Network sharing is often hailed as a promising and cost-effective way to tackle the ever-increasing load of cellular networks. However, its actual effectiveness strongly depends on the correlation between the networks being joined -- intuitively, there is no benefit in joining two networks with exactly the same load and exactly the same deployment. In this paper, we analyse the deployment and traffic traces of two Irish operators to (i) study their correlation in space and time, and (ii) assess the potential benefit brought by network sharing. Through our analysis, we are able to show that network sharing is remarkably effective in making the load more regular over space, improving the operations and performance of cellular networks.

Multi-hop MAC implementations for affordable SDR hardware

This paper presents the implementation and experimental evaluation of a MAC protocol designed to overcome some of the limitations of affordable and widely-deployed software defined radio hardware. We propose a modified Aloha-based MAC protocol with implicit acknowledgements to mitigate the impact of intra-flow collisions in multi-hop wireless communications. We experimentally observe a significant improvement in throughput and delay through simple modifications to the MAC protocol, tailoring it to the timing constraints of the USRP1.

Coexistence through adaptive sensing and Markov chains

The goal of this paper is to construct a dynamic Secondary User (SU) link that can successfully coexist with a Primary User (PU).

Enhancing the performance of random access MAC protocols for low-cost SDRs

Software Defined Radio (SDR) is a technology which facilitates experimentation and the practical realization of novel wireless communication systems. Especially low-cost SDRs, however, experience high communication delays due to the connection between the radio hardware and the host computer. This delay hinders the implementation of Medium Access Control (MAC) protocols. In Carrier Sense Multiple Access (CSMA) based protocols, especially the Clear Channel Assessment (CCA) as well as the subsequent channel access phase are subject to strict temporal constraints. In this paper, we present two strategies that address both issues and aim to enhance the performance and efficiency of CSMA protocols implemented on low-cost SDRs. The first approach employs a dedicated spectrum sensing engine as a CCA agent for the SDR. The second strategy optimizes the frame transmission path inside the SDR. Experimental results indicate that both strategies have a positive impact on reducing the slot time parameter of the CSMA MAC.

Assembling and Using a Cellular Dataset for Mobile Network Analysis and Planning

In a world of open data and large-scale measurements, it is often feasible to obtain a real-world trace to fit to ones research problem. Feasible, however, does not imply simple. Taking next-generation cellular network planning as a case study, in this paper we describe a large-scale dataset, combining topology, traffic demand from call detail records, and demographic information throughout a whole country. We investigate how these aspects interact, revealing effects that are normally not captured by smaller-scale or synthetic datasets. In addition to making the resulting dataset available for download, we discuss how our experience can be generalized to other scenarios and case studies, i.e., how everyone can construct a similar dataset from publicly available information.

Sensitivity Analysis on Service-Driven Network Planning

Service providers are expected to play an increasingly central role in the mobile market and their relationship with the traditional mobile network operators (MNOs) is starting to change. The dilemma faced by over-the-top service-providers (OTTs) is now whether to enter into a service level agreement with the MNOs (in the same spirit of mobile virtual network operator agreements) or to invest in deploying their own network infrastructure to serve their demand. The purpose of this paper is to study the factors shaping the agreements between OTTs and MNOs and how these factors impact network planning decisions. To this end, we build a synthetic model of cellular network deployment that explores how traditional mobile operators and OTTs compete in deploying new infrastructure. Using our model in conjunction with real-world data, we find that service-driven networks are heavily influenced by regulatory decisions, and that cost structures and demand characteristics play non-marginal roles in the definition of service-driven networks.