Alternative Network Deployments: Taxonomy, Characterization, Technologies, and Architectures

This document presents a taxonomy of a set of "Alternative Network Deployments" that emerged in the last decade with the aim of bringing Internet connectivity to people or providing a local communication infrastructure to serve various complementary needs and objectives. They employ architectures and topologies different from those of mainstream networks and rely on alternative governance and business models. The document also surveys the technologies deployed in these networks, and their differing architectural characteristics, including a set of definitions and shared properties. The classification considers models such as Community Networks, Wireless Internet Service Providers (WISPs), networks owned by individuals but leased out to network operators who use them as a low-cost medium to reach the underserved population, networks that provide connectivity by sharing wireless resources of the users, and rural utility cooperatives

Accelerating short transfers in 802.11 networks

The legacy bandwidth discovery phase of TCP spends an unnecessary number of RTTs for reaching the fair share of the network. In this article we introduce a simple modification at the receiver that splits the TCP ACKs in a controlled manner. This mechanism allows to fast ramp-up the TCP congestion window. Our experiments performed in a real testbed show benefits not only in the increased data throughput but also in a non-congested uplink (Acknowledgement) path in an 802.11 access

On the Selection of Scanning Parameters in IEEE 802.11 Networks

In this paper, we study the IEEE 802.11 discovery process needed for handovers and propose an adaptive scanning strategy based on application requirements. The scanning process consists in actively probing the radio channels to gather access points information. We consider a well decoupled situation in which the scanning latency, the scanning failure rate and the number of discovered access points define the scanning performance. We model these scanning metrics by analytical expressions to represent the performance trade-off, i.e., finding the largest number of access points with a minimum latency. We present a novel approach based on a multi-objective optimization approach to obtain the optimal number of channels to scan, the optimal channel sequence and its correspondent scanning timers. Finally, we compare one fixed and two adaptive scanning approaches by means of simulations. We show that our adaptive scanning strategies better manage the performance trade-off and allow different application profiles to match with specific scanning latency

An evaluation of the resource discovery in IEEE 802.11 networks

International audienceToday wireless communications are synonym of mobility and resource sharing. These characteristics, proper of spontaneous and ad-hoc networks relies heavily on a general resource discovery process. The discovery process, being an unavoidable procedure, has to be fast and reliable to mitigate the effect of network disruptions. In this article, by means of simulations and a real testbed, our contribution is twofold. First we assess the discovery process focusing on the adaptation of 802.11 timers: MinChannelTime and MaxChannelTime. Then, varying these timers, we propose and evaluate an adaptive discovery strategy from which we obtain notable improvements over a fixed timers strategy

Assisted network discovery for next generation wireless networks

International audienceIEEE 802.11 networks are the most popular option to have wireless access to the Internet. The popularity of these networks have raised a costly topology discovery and connection process, in which any device has to pass through an expensive scanning process of available Access Points. In order to improve the connection process, we propose a novel architecture for asynchronous assistance for topology discovery. We discuss the role of a Topology Manager that uses computational intelligence for generating optimal scanning sequences. Preliminary results show that this approach results in 30% to 70% improvements on AP discovery rate in chaotic deployments

Intelligent Network Discovery for Next Generation Community Wireless Networks

International audienceNowadays, IEEE 802.11 networks are the most popular option to have wireless access to the Internet and a promising technology to tackle the digital divide that accounts for 2/3 of the world population. However, the popularity of these networks have raised a complex discovery and connection process, i.e., any device has to pass through an expensive scanning process of available Access Points in crowded and chaotic deployments. The scanning process can be modelled by a set of metrics exposing a trade-off between latency and the discovery rate when searching for appropriate Wi-Fi connection. Consequently, in order to improve the connection process, we use a multi-objective optimisation approach for generating optimal scanning sequences. We propose a framework to assist the network discovery within a Community Network, and we have adapted a Cultural Algorithm as an intelligent component for calculating optimal scanning sequences. Results show that we can derive optimal scanning sequences better than standard approaches for scanning in chaotic network deployments

IEEE 802.11 scanning algorithms: cross-layer experiments

In wireless communication, the discovery of the surrounding access points is crucial to provide seamless connectivity to mobile users. In IEEE 802.11, this discovery process is performed by passive and active scanning functions. For both, timers are usually constant (within the 802.11 driver) and their configuration aects the two main scanning performance metrics, i.e., scanning latency and scanning failure. In order to manage this trade-o, we propose some adaptive scanning algorithms that are aware of the access point's signal power and congestion level using cross-layer information. As shown by experimentation in a real testbed, this allows a faster topology discovery while mostly reducing the failure rate

A Study of Urban IEEE 802.11 Hotspot Networks: Towards a Community Access Network

International audienceWith the increasing demand for faster data con- nectivity, different wireless technologies have been deployed in the last decade, creating a heterogeneous wireless environment. Such wireless diversity is mainly composed of 2G/3G/4G cellular base stations, IEEE 802.11 hotspots and Community Networks. Previous work suggests that the increasing popularity of IEEE 802.11 networks would mitigate the overloading of current operator-based cellular deployments. However, the unpredictable characteristics of IEEE 802.11 deployments and its loose coupling to cellular architectures limit its user performance in terms of throughput and mobility capacity. In this paper, we describe an evaluation study of a commercial-grade hotspot network in the city of Luxembourg, namely HOTCITY. Through a set of experiments, we provide a characterization of the hotspot network and give a set of performance indicators. Finally, we evaluate hotspot networks' potential to support cellular offloading through the integration of outdoor hotspots and private access points deployed indoors in a single Community Network