We research and develop novel IoT technologies and applications. The ever-increasing importance of IoT is supported by the significant increase in the number of connected devices, the use of wireless communication for networking, advances in low-power mobile computation, machine learning and data analytics, and sensing technologies on small devices.
We focus on application domains such as smart home, medical monitoring, industrial process control and automation, environmental monitoring, smart agriculture, sustainable environment, and structural health monitoring, just to mention a few. Due to the significant impact of these applications on quality of life and sustainable development, our goal is to identify the design and development challenges of Internet of Things/Cyber-Physical Systems/Wireless Sensor Networks from the networking, data processing, and security point of views.
— Networking Technologies, Standards and Protocols, Energy Efficiency, Machine Learning, and Scheduling methods
— Security Protocols and Architectures for IoT
— Software-Defined Networking (SDN) and
Software-Defined Wireless Networks for IoT
— Edge and Fog Computing using SDN-based Resource Allocation, Virtualization, and Enhancing Machine Learning on Resource-Constraint Devices
— Design and Interfacing of
Embedded Systems, Interfacing Sensors and Actuators,
and Power Measurement
— Empirical, Simulation-based, and Theoretical Performance Evaluation of IoT Systems
Please email me at bdezfouli [at] scu [dot] edu
Communication protocols play a major role in the reliability, energy efficiency, and timeliness of IoT systems. We address these requirements by developing novel communication protocols across the communication stack.
EAPS: Edge-Assisted Predictive Sleep Scheduling for 802.11 IoT Stations
The main reasons justifying the importance of WiFi for IoT connectivity are: (1) compared to indoor cellular gateways, WiFi APs are more popular and broadly deployed, (2) compared tocellular communication, WiFi reduces deployment cost, allows for local communication, and enables usersand enterprises to enforce a higher level of control over their network, (3) compared to Bluetooth LowEnergy (BLE) (275-300 nJ/bit), WiFi provides a lower (10-100 nJ/bit) physical layer energy consumption, and (4) compared to 802.15.4, WiFi provides 100-10000x higher data rates.
The main energy efficiency mechanisms of 802.11, namely PSM and APSD, fall short when used in IoT applications. PSM increases latency and intensifies channel access contention after each beacon instance, and APSD does not inform stations about when they need to wake up to receive their downlink packets. We present a new mechanism---edge-assisted predictive sleep scheduling (EAPS)---to adjust the sleep duration of stations while they expect downlink packets.
Enhancing the Energy-Efficiency and Timeliness of IoT Communication in WiFi Networks
Increasing the number of Internet of Things (IoT) stations or regular stations escalates downlink channel access contention and queuing delay, which in turn result in higher energy consumption and longer communication delays with IoT stations. To remedy this problem, this work presents WiFi IoT access point (Wiotap), an enhanced WiFi access point (AP) that imple- ments a downlink packet scheduling mechanism. In addition to assigning higher priority to IoT traffic compared to regular traffic, the scheduling algorithm computes per-packet priorities to arbitrate the contention between the transmission of IoT packets. This algorithm employs a least-laxity first (LLF) scheme that assigns priorities based on the remaining wake-up time of the destination stations.
Empirical Study and Enhancement of Association and Long Sleep in 802.11 IoT Systems
The three essential operations performed to ensure connectivity in an 802.11 network are association, maintaining association, and periodic beacon reception. Understanding and enhancing the energy efficiency of these operations is essential for building IoT systems. Unfortunately, the overheads of these operations have not been studied considering station’s software and hardware configuration, access point configuration, and link unreliability. We show that: (i) association cost depends on multiple factors including probing, key generation, operating system, and network stack, (ii) increasing listen interval to reduce beacon reception wake-up instances may negatively impact energy efficiency, (iii) maintaining association by relying on the poll messages generated by the access point is not reliable, and (iv) key renewal aggravates the chance of disassociation.
MonFi: A Tool for High-Rate, Efficient, and Programmable Monitoring of WiFi Devices
The 802.11 standard, known as WiFi, is currently being used for a wide variety of applications. The increasing number of WiFi devices, their stringent communication requirements, and the need for higher energy-efficiency mandate the adoption of novel methods that rely on monitoring the WiFi communication stack to analyze, enhance communication efficiency, and secure these networks. In this paper, we propose MonFi, a publicly-available, open-source tool for high-rate, efficient, and programmable monitoring of the WiFi communication stack. With this tool, regular user-space applications can specify their required measurement parameters, monitoring rate, and measurement collection method as event-based, polling-based, or a hybrid of both.
We also propose methods to ensure deterministic sampling rate regardless of the processor load caused by other processes including packet switching. In terms of sampling rate and processing efficiency, we show that MonFi outperforms the Linux tools used to monitor the communication stack.
Implementation and Analysis of QUIC for MQTT
Transport and security protocols are essential to ensure reliable and secure communication between two parties. For IoT applications, these protocols must be lightweight, since IoT devices are usually resource constrained. Unfortunately, the existing transport and security protocols – namely TCP/TLS and UDP/DTLS – fall short in terms of connection overhead, latency, and connection migration when used in IoT applications. In this paper, after studying the root causes of these shortcomings, we show how utilizing QUIC in IoT scenarios results in a higher performance. Based on these observations, and given the popularity of MQTT as an IoT application layer protocol, we integrate MQTT with QUIC. By presenting the main APIs and functions developed, we explain how connection establishment and message exchange functionalities work. We evaluate the performance of MQTTw/QUIC versus MQTTw/TCP using wired, wireless, and long-distance testbeds.
CentriFi: A Centralized Wireless Access Point Management Platform
With the ubiquity of wireless end-devices, more strain is placed on standard network deployment architectures. Mesh networks have started to rise in popularity in order to meet the needs of modern wireless networks. However, the exis- tent solutions for deploying and centrally configuring mesh networks leave much to be desired, as most are either too expensive or too cumbersome. This paper showcases a solution to this problem, CentriFi—an open source platform, built to run on OpenWrt access points, providing a quick and easy way to set up and configure mesh networks in a central location using the 802.11s standard. CentriFi provides a web-based front-end for configuring the most crucial settings. Further, the system allows for greater expandability by providing a platform in which other configuration feature can be added by the open-source community in the future.
REWIMO: A Real-Time and Reliable Low-Power Wireless Mobile Network
Industrial applications and cyber-physical systems rely on real-time wireless networks to deliver data in a timely and reliable manner. However, existing solutions provide these guarantees only for stationary nodes. We present REWIMO, a solution for real-time and reliable communications in mobile networks. REWIMO has a two-tier architecture composed of (i) infrastructure nodes and (ii) mobile nodes that associate with infrastructure nodes as they move. REWIMO employs an on-join bandwidth reservation ap- proach and benefits from a set of techniques to efficiently reserve bandwidth for each mobile node at the time of its admission and over its potential communication paths. To ensure association of mobile nodes with infrastructure nodes over high-quality links, REWIMO uses the two-phase scheduling technique to coordinate neighbor discovery with data transmission. To mitigate the overhead of handling network dynamics, REWIMO employs an additive scheduling algorithm, which is capable of additive bandwidth reservation without modifying existing schedules. Compared to the algorithms used by static real-time wireless networks, the techniques and the algorithms employed by REWIMO result in a significant increase in real-time capacity, enhanced reliability, and considerably faster handling of network dynamics.
With the rise of the Internet of Things (IoT), edge and fog computing has emerged to help traditional cloud computing in meeting scalability demands. Edge and Fog computing makes it possible to fulfill real-time requirements of applications by bringing more processing, storage, and control power geographically closer to end devices.
The Fog Development Kit: A Platform for the Development and Management of Fog Systems
Since fog computing is a relatively new field, there is no standard platform for research and development in a realistic environment, and this dramatically inhibits innovation and development of fog-based applications. We propose the fog development kit (FDK). By providing high-level interfaces for allocating computing and networking resources, the FDK abstracts the complexities of fog computing from developers and enables the rapid devel- opment of fog systems. In addition to supporting application development on a physical deployment, the FDK supports the use of emulation tools (e.g., GNS3 and Mininet) to create realistic environments, allowing fog application prototypes to be built with zero additional costs and enabling seamless portability to a physical infrastructure. Using a physical testbed and various kinds of applications running on it, we verify the operation and study the performance of the FDK. Specifically, we demonstrate that resource allocations are appropriately enforced and guaranteed, even amidst extreme network congestion. We also present simulation-based scalability analysis of the FDK versus the number of switches, the number of end devices, and the number of fog devices.
Image classification on IoT edge devices: profiling and modeling
With the advent of powerful, low-cost IoT systems, processing data closer to where the data originates, known as edge computing, has become an increasingly viable option. In addition to lowering the cost of networking infrastructures, edge computing reduces edge-cloud delay, which is essential for mission-critical applications.
We show the feasibility and study the performance of image classification using IoT devices. Specifically, we explore the relationships between various factors of image classification algorithms that may affect energy consumption, such as dataset size, image resolution, algorithm type, algorithm phase, and device hardware. In order to provide a means of predicting the energy consumption of an edge device performing image classification, we investigate the usage of three machine learning algorithms using the data generated from our experiments. The performance as well as the trade-offs for using linear regression, Gaussian process, and random forests are discussed and validated.
Profiling and Improving the Duty-Cycling Performance of Linux-based IoT Devices
Minimizing the energy consumption of Linux-based devices is an essential step towards their wide deployment in various IoT scenarios. Energy saving methods such as duty-cycling aim to address this constraint by limiting the amount of time the device is powered on. We study and improve the amount of time a Linux-based IoT device is powered on to accomplish its tasks. We analyze the processes of system boot up and shutdown on two platforms, the Raspberry Pi 3 and Raspberry Pi Zero Wireless, and enhance duty-cycling performance by identifying and disabling time-consuming or unnecessary units initialized in the userspace. We also study whether SD card speed and SD card capacity utilization aect boot up duration and energy consumption. In addition, we propose Pallex, a parallel execution framework built on top of the systemd init system to run a user application concurrently with userspace initialization. We validate the performance impact of Pallex when applied to var- ious IoT application scenarios: (i) capturing an image, (ii) capturing and encrypting an image, (iii) capturing and classifying an image using the the k-nearest neigh- bor algorithm, and (iv) capturing images and sending them to a cloud server.
EdgeAP: Enabling Edge Computing on Wireless Access Points
With the rise of the Internet of Things (IoT) leading to an explosion in the number of internet-connected devices, the current cloud computing paradigm is approaching its limits. Moving data back and forth between its origin and a far-away data center leads to issues regarding privacy, latency, and energy consumption. Edge computing, which instead processes data as close to its origin as possible, o↵ers a promising solution to the pitfalls of cloud computing.
Our proof-of-concept edge computing platform, EdgeAP, is a programmable platform for the delivery of applica- tions on wireless access points. Use cases of the platform will be demonstrated via an example application. Addition- ally, the viability of edge computing on wireless access points will be thoroughly evaluated.
Despite the significant increase of IoT devices, they show vulnerabilities to diverse security and privacy attacks, such as Distributed Denial of Service attacks (DDoS), energy-oriented DDoS attacks (E-DDoS), harvesting and forging data, blackmail/extortion, bitcoin mining, stalking, or robbery. The reasons are multi-fold. First, because of competition and revenue gain, many manufactures disregard the security aspects of IoT devices, which demands resources and skills—adding to the cost. Second, consumers are usually not well educated about the potential security issues caused by arbitrarily adding IoT devices into their home networks, not to mention the importance of keeping their IoT devices’ security features up-to-date. Third, smart home devices usually share a WiFi Access Point (AP) for Internet access and local interconnection.
A Quantitative Study of DDoS and E-DDoS Attacks on WiFi Smart Home Devices
We quantify the impact of Distributed Denial of Service (DDoS) and energy-oriented DDoS attacks (E-DDoS) on WiFi smart home devices and explores the underlying reasons from the perspective of attacker, victim device, and access point (AP). Compared to the existing work, which primarily focus on DDoS attacks launched by compromised IoT devices against servers, our work focuses on the connectivity and energy consumption of IoT devices when under attack.
Our key findings are three-fold. First, the minimum DDoS attack rate causing service disruptions varies significantly among different IoT smart home devices, and buffer overflow within the victim device is validated as critical. Second, the group key updating process of WiFi, may facilitate DDoS attacks by causing faster victim disconnections. Third, a higher E-DDoS attack rate sent by the attacker may not necessarily lead to a victim’s higher energy consumption. Our study reveals the communication protocols, attack rates, payload sizes, and victim devices’ ports state as the vital factors to determine the energy consumption of victim devices. These findings facilitate a thorough understanding of IoT devices’ potential vulnerabilities within a smart home environment and pave solid foundations for future studies on defense solutions.
A Comprehensive Empirical Analysis of TLS Handshake and Record Layer on IoT Platforms
The Transport Layer Security (TLS) protocol has been considered as a promising approach to secure Internet of Things (IoT) applications. The different cipher suites offered by the TLS protocol play an essential role in determining communication security level. Each cipher suite encompasses a set of cryptographic algorithms, which can vary in terms of their resource consumption and significantly influence the lifetime of IoT devices.
We present a comprehensive study of the widely used cryptographic algorithms by annotating their source codes and running empirical measurements on two state-of-the-art, low- power wireless IoT platforms. Specifically, we present fine-grained resource consumption of the building blocks of the handshake and record layer algorithms and formulate tree structures that present various possible combinations of ciphers as well as individual func- tions. Depending on the parameters, a path is selected and traversed to calculate the corresponding resource impact. Our studies enable IoT developers to change cipher suite parameters and immediately observe the resource costs.
Design and development of low-power, reliable sensing systems requires application-oriented hardware design, tailored communication protocols, accurate power measurement, accurate sensor calibration, extensive performance evaluations.
EMPIOT: An energy measurement platform for wireless IoT devices
Profiling and minimizing the energy consumption of resource-constrained devices is an essential step towards employing IoT in various application domains. Due to the large size and high cost of commercial energy measurement platforms, alternative solutions have been proposed by the research community. However, the three main shortcomings of existing tools are complexity, limited measurement range, and low accuracy. Specifically, these tools are not suitable for the energy measurement of new IoT devices such as those supporting the 802.11 technology. We propose EMPIOT, an accurate, low-cost, easy to build, and flexible, power measurement platform. We present the hardware and software components of this platform and study the effect of various design parameters on accuracy and overhead. In particular, we analyze the effects of driver, bus speed, input voltage, and buffering mechanism on sampling rate, measurement accuracy and processing demand. These extensive experimental studies enable us to configure the system in order to achieve its highest performance. We also propose a novel calibration technique and report the calibration parameters under various settings. Using five different IoT devices performing four types of workloads, we evaluate the performance of EMPIOT against the ground truth obtained from a high-accuracy industrial-grade power measurement tool.
Flomosys: A Flood Monitoring System
Every year, there are significant and preventable financial losses, not to mention the safety hazards caused by floods. To warn people ahead of time, we can deploy low-power wireless sensor nodes to send readings across any terrain to a cloud platform, which can perform pattern analysis, prediction, and alert forwarding to anyone’s cellular device. In this paper, we propose Flomosys, a low-cost, low-power, secure, scalable, reliable, and extensible IoT system for monitoring creek and river water levels. Although there are multiple competing solutions to help mitigate this problem, Flomosys fills a niche not covered by existing solutions. Flomosys can be built inexpensively with off-the-shelf components and scales across vast territories at a low cost per sensor node. We present the design and implementation of this system as well as real-world test results.
Excalibur: An Accurate, Scalable, and Low-Cost Calibration Tool for Sensing Devices
Calibration of an analog-to-digital converter is an essential step to compensate for static errors and ensure accurate digital output. In addition, ad-hoc deployments and operations require fault-tolerant IoT devices capable of adapting to unpredictable environments. In this paper, we present the design and implementation of Excalibur – a low-cost, accurate, and scalable calibration tool. Excalibur is a programmable platform, which provides linear current output and rational function voltage output with a dynamic range. The basic idea is to use a set of digital switches to connect with a parallel resistor network and program the digital switches to change the total resistance of the circuit. The total resistance and output frequency of Excalibur is controlled by a program communicating through the GPIO and I2C interfaces. The software provides two salient features to improve accuracy and reliability: time synchronization and self-calibration. Furthermore, Excalibur is equipped with a temperature sensor to measure the temperature before calibration, and a current sensor which enables current calibration without using a digital multimeter. We present the mathematical model and a solution to compensate for thermal and wire resistance effects and validate scalability by incorporating the concept of the Fibonacci sequence. Our extensive experimental studies show that Excalibur can significantly improve measurement accuracy.
We thank the following companies/organizations for funding/equipment donation to our lab