Bart Jooris

The w-iLab.t Testbed

In this paper, the W-iLab.t wireless testbed is presented. The testbed consists of nearly 200 sensor nodes and an equal amount of WiFi nodes, which are installed across three floors of an office building. The testbed supports wireless sensor experiments, WiFi based mesh and ad hoc experiments, and mixed sensor/WiFi experiments. It is explained how changes in the environment of the sensor nodes can be emulated and how experiments with heterogeneous wireless nodes are enabled. Additional features of the testbed are listed and lessons learned are presented that will help researchers to construct their own testbed infrastructure or add functionality to an existing testbed. Finally, it is argued that deep analysis of unexpected testbed behavior is key to understanding the dynamics of wireless network deployments.

Federating Wired and Wireless Test Facilities through Emulab and OMF: The iLab.t Use Case

The IBBT iLab.t technology centre provides computing hardware, software tools and measurement equipment to support researchers and developers in building their ICT solutions, and in measuring the performance of these solutions. Among other things, the iLab.t hosts several generic Emulab-based wired test environments called the Virtual Walls, and two wireless test environments which are grouped under the name w-iLab.t. Until very recently, these wired and wireless test facilities each had their own history: they were deployed and maintained by a different group of people, were operated using different tools, and each had their own community of experimenters. This paper provides insight on the origin and evolution of the Virtual Wall and w-iLab.t facilities. It explains how these facilities were federated, by using the best parts of both the OMF and Emulab frameworks. It discusses the benefits of our local federation as well as our future federation plans.

Design and implementation of a generic energy-harvesting framework applied to the evaluation of a large-scale electronic shelf-labeling wireless sensor network

Most wireless sensor networks (WSNs) consist of battery-powered nodes and are limited to hundreds of nodes. Battery replacement is a very costly operation and a key factor in limiting successful large-scale deployments. The recent advances in both energy harvesters and low-power communication systems hold promise for deploying large-scale wireless green-powered sensor networks (WGSNs). This will enable new applications and will eliminate environmentally unfriendly battery disposal. This paper explores the use of energy harvesters to scavenge power for nodes in a WSN. The design and implementation of a generic energy-harvesting framework, suited for a WSN simulator as well as a real-life testbed, are proposed. These frameworks are used to evaluate whether a carrier sense multiple access with collision avoidance scheme is sufficiently reliable for use in emerging large-scale energy harvesting electronic shelf label (EHESL) systems (i.e., 12000 labels in a star topology). Both the simulator and testbed experiments yielded an average success rate up to 92%, with an arrival rate of 40 transceive cycles per second. We have demonstrated that our generic energy-harvesting framework is useful for WGSN research because the simulator allowed us to verify the achieved results on the real-life testbed and vice versa.

TAISC: A cross-platform MAC protocol compiler and execution engine

Abstract MAC protocols significantly impact wireless performance metrics such as throughput, energy consumption and reliability. Although the choice of the optimal MAC protocol depends on time-varying criteria such as the current application requirements and the current environmental conditions, MAC protocols cannot be upgraded after deployment since their implementations are typically written in low level, hardware specific code which is hard to reuse on other hardware platforms. To remedy this shortcoming, this paper introduces TAISC, Time Annotated Instruction Set Computer, a framework for hardware independent MAC protocol development and management. The solution presented in this paper allows describing MAC protocols in a platform independent language, followed by a straightforward compilation step, yielding dedicated binary code, optimized for specific radio chips. The compiled code is as efficient in terms of memory footprint as custom-written protocols for specific devices. To enable time-critical operation, the TAISC compiler adds exact time annotations to every instruction of the optimized binary code. As a result, the TAISC approach can be used for energy-efficient cross-platform MAC protocol design, while achieving up to 97% of the theoretical throughput at an overhead of only 20 µs per instruction.

Radio-over-fibre for ultra-small 5G cells

The need of a wireless network with a very low latency, a high bandwidth, and a high cellular density is paramount for serving futuristic applications. For this purpose, we design a very dense wireless network, consisting of radio cells of less than 10 m2. To serve these small cells, a backbone network implemented over a radio-over-fibre (RoF) based architecture can be an ideal solution. In this paper we propose different RoF architectures that are varying in architectural complexity, flexibility, supported user densities (depending on the sharing ratio of the optical transceivers between cells) and the number of users per cell. We indicate their main challenges and propose some specific scenarios where they can be applied. Not only there are architectural challenges to design the RoF network to bring a high capacity to every small cell, but also a medium access control (MAC) protocol is needed to confirm the quality of service (QoS) bounds of a low latency, seamless handovers, and a high throughput. We differentiate between two approaches to design such a MAC protocol, either distributed or centralized mechanisms.

Real-time wide-band spectrum sensing for cognitive radio

Cognitive radio has received considerable amount of attention as a promising technique to provide dynamic spectrum allocation. Wide-band spectrum sensing is the corner stone for cognitive radio to be functional. Most existing commercial sensing solutions lack either the required flexibility or speed. Software-defined radio (SDR) on the other hand offers very high flexibility and therefore becomes a common platform for CR implementation. Among various SDR platforms, the universal software-defined radio peripheral (USRP) gained broad popularity. This paper presents a real-time wide-band-capable spectrum sensing solution based on USRP. The concept of energy detection and the methodology for wide-band sensing are explained. Finally, the performance of the proposed sensing solution is verified and compared with another popular commercial sensing solution, Airmagnet.

Access network controlled fast handoff for streaming multimedia in WLAN

The focus of the research presented in this paper was to develop a novel way to support voice over IP (VoIP) and streaming video applications on mobile devices over a 802.11 access network Fast handoff in a wireless local area network (WLAN) environment has been the research topic of many previous studies, the majority of which described ways to optimize the three main 802.11 handoff phases -scanning, authentication, and reassociation. In this paper however we propose a fast handoff scheme that skips all mentioned phases. Instead, the handoff is controlled and prepared by the access network and is triggered by sending a hop request message to the mobile station (STA). At the STA the three phases are reduced to a single frequency change phase. The proposed solution extends the standard 802.11 scheme; if the extension is not available at the access network or the STA, the devices will fall back on the standard handoff procedure. Because the access network fully controls the handoff process and actively invokes the frequency change on the STA, we can guarantee a minimal duration of the time the STA stays disconnected.

The IBBT w-iLab.t: A Large-Scale Generic Experimentation Facility for Heterogeneous Wireless Networks

The w-iLab.t is a large-scale generic wireless experimentation facility. Over 260 wireless nodes are installed at two different locations. Every single wireless node is equipped with multiple wireless technologies, namely IEEE 802.15.4, Wi-Fi a/b/g(/n), and on some devices also Bluetooth. Additionally, w-iLab.t provides access to software defined radio platforms and also uses them to characterize the wireless environment during an experiment. The w-iLab.t flexibility and its tools enable experimenters to design and schedule a wide range of wireless experiments, and to collect and process results in a user-friendly way.

Exploiting programmable architectures for WiFi/ZigBee inter-technology cooperation

The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions.In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software-defined radio (SDR) platforms, in which every function is programmed from scratch, our programmable architectures are based on a clear decoupling between elementary commands (hard-coded into the devices) and programmable protocol logic (injected into the devices) according to which the commands execution is scheduled.Our contribution is two-fold: first, we designed and implemented a cross-technology time division multiple access (TDMA) scheme devised to provide a global synchronization signal and allocate alternating channel intervals to WiFi and ZigBee programmable nodes; second, we used the OMF control framework to define an interference detection and adaptation strategy that in principle could work in independent and autonomous networks. Experimental results prove the benefits of the envisioned solution.

Cross-technology wireless experimentation: Improving 802.11 and 802.15.4e coexistence

In this demo we demonstrate the functionalities of a novel experimentation framework, called WiSHFUL, that facilitates the prototyping and experimental validation of innovative solutions for heterogeneous wireless networks, including cross-technology coordination mechanisms. The framework supports a clean separation between the definition of the logic for optimizing the behaviors of wireless devices and the underlying device capabilities, by means of a unifying platform-independent control interface and programming model. The use of the framework is demonstrated through two representative use cases, where medium access is coordinated between IEEE-802.11 and IEEE-802.15.4 networks.