Tactile Internet (TI) envisions communicating haptic sensory information and kinesthetic feedback over the network and is expected to transfer human skills remotely. For mission-critical TI applications, the network latency is commonly mandated to be between 1-10 ms, due to the sensitivity of human touch, and the packet delivery ratio to be 99.99999%, failing which can lead to catastrophic outcomes. However, with humans-in-the-loop, their dexterity and adaptability to varying responses to stimuli under different network conditions, measuring the performance of a TI session only with latency and packet losses are insufficient and presents an incorrect representation of the experience of the TI application. To develop an objective measure of the quality of TI sessions, we propose a framework that models TI applications as networked control systems, including humans-in-the-loop. We derive a closed-form expression for measuring the difference between the application performance in ideal and non-ideal network conditions. Based on Weber’s law of Just Noticeable Difference, we provide a metric called TIM to estimate the impact of the network on haptic feedback. We implemented TIM on multiple applications on a TI testbed to show that our approach is feasible and TIM strongly follows real subjective measurements. Further, we propose a channel compensation spring based on TIM, to alleviate the network conditions’ negative effects. We demonstrate the efficacy of the channel compensation spring in improving the user experience. We also present implementation notes for TI application developers.

@en

We present radio-frequency (RF) information harvesting, a chan-nel sensing technique that takes advantage of the energy in the wireless medium to detect channel activity at essentially no en-ergy cost. RF information harvesting is essential for event-driven wireless sensing applications using battery-less devices that har-vest tiny amounts of energy from impromptu events, such as op-erating a switch, and then transmit the event notification to a one-hop gateway. As multiple such devices may concurrently de-tect events, coordinating access to the channel is key. RF infor-mation harvesting allows devices to break the symmetry between concurrently-transmitting devices based on the harvested energy from the ongoing transmissions. To demonstrate the benefits of RF information harvesting, we integrate it in a tailor-made ultra low-power hardware MAC protocol we call Radio Frequency-Distance Packet Queuing (RF-DiPaQ). We build a hardware/software proto-type of RF-DiPaQ and use an established Markov framework to study its performance at scale. Comparing RF-DiPaQ against sta-ple contention-based MAC protocols, we show that it outperforms pure Aloha and 1-CSMA by factors of 3.55 and 1.21 respectively in throughput, while it saturates at more than double the offered load compared to 1-CSMA. As traffic increases, the energy saving of RF-DiPaQ against CSMA protocols increases, consuming 36% less energy than np-CSMA at typical offered loads.@en

Long-range wide-area network (LoRaWAN) is an energy-efficient and inexpensive networking technology that is rapidly being adopted for many Internet-of-Things applications. In this study, we perform extensive measurements on a new LoRaWAN deployment to characterise the spatio-temporal properties of the LoRaWAN channel. Our experiments reveal that LoRaWAN frames are mostly lost due to the channel effects, which are adverse when the end-devices are mobile. The frame losses are up to 70 percent, which can be bursty for both mobile and stationary scenarios. Frame losses result in data losses since the frames are transmitted only once in the basic configuration. To reduce data losses in LoRaWAN, we design a novel coding scheme for data recovery called DaRe that works on the application layer. DaRe combines techniques from convolutional and fountain codes. By implementing DaRe, we show that 99 percent of the data can be recovered with a code rate of 1/2 when the frame loss is up to 40 percent. Compared to the repetition coding scheme, DaRe provides 21 percent higher data recovery and can save up to 42 percent of the energy consumed on a transmission for 10-byte data units. We also show that DaRe provides better resilience to bursty frame losses.

@en

This chapter discusses two possible architectures to connect the cordless kitchen appliances to the Internet. Design, advantages and disadvantages of both these architectures are covered in detail.

@en

This chapter evaluates the effects of our solution on important TCP parameters such as TCP MSS, TCP CWND, NFC BER and other NFC channel characteristics using simulations and theoretical calculations.

@en

This research focused on enabling Internet connectivity to a new generation of smart kitchen appliances that work on wireless power technology. In order to provide efficient and seamless communication with the appliances, the possibilities of utilizing the NFC channel for Internet connectivity were explored.

@en

This chapter studies the existing research and solutions in using TCP/IP on low data-rate and high delay networks like NFC. It concludes that the problem on hand, i.e., using TCP/IP on time-slotted NFC in the cordless kitchen appliances, is unique and hence new novel methods are needed in this case.

@en

It is a huge challenge to run IoT devices/sensors powered solely through ambient harvested energy. Since the harvested energy is less and is stochastic in nature, it is extremely challenging to achieve low latency and high reliability. To this end, we propose a distributed, energy-management module called ReNEW, using Constructive Interference (CI) to achieve our target of increased reliability, especially in the low harvesting regimes. We choose CI-based protocols to leverage low latency guarantees. Specifically, we propose a Markov-Decision model to maximize the energy utility in the infinite horizon by allocating energy optimally using a threshold-optimal policy. Since an energy scheduler is insufficient we propose distributed techniques to conserve energy on redundant nodes in the network, and dynamically activate them based on feedback. We implement ReNEW on Indriya and FlockLab testbeds for real-world scenarios in a network of 20 source nodes out of the 30 nodes. ReNEW collects data periodically with 2.5 times higher packet reception compared to LWB when the harvested energy is as low as 50μ J/s for 100B packets every 30s with a saving of 25% higher residual energy. In a nutshell, by integrating ReNEW with CI based protocols, we enable guaranteed latency and increased reliability in battery-less devices/networks.

@en

The next frontier for immersive applications is enabling sentience over the Internet. Tactile Internet (TI) envisages transporting skills by providing ultra-low-latency (ULL) communications for transporting touch senses. In this work, we focus our study on the first/last mile communication, where the future generation WiFi-7 is pitched as the front-runner for ULL applications. We discuss a few candidate features of WiFi-7 and highlight its major pitfalls with respect to ULL communication. Further, through a specific implementation of WiFi-7 (vanilla WiFi-7) in our custom simulator, we demonstrate the impact of one of the pitfalls - the standard practice of using jitter buffer in conjunction with frame aggregation - on TI communication. To circumvent this, we propose the Non-Buffered Scheme (NoBuS) - a simple MAC layer enhancement for enabling TI applications over WiFi-7. NoBuS trades off packet loss for latency, enabling swift synchronization between the master and controlled domains. Our findings reveal that employing NoBuS yields a significant improvement in RMSE of TI signals. Further, we show that the worst case WiFi latency with NoBuS is 3.72 ms - an order of magnitude lower than vanilla WiFi-7 even under highly congested network conditions.

@en

This chapter gives an introduction to the Cordless Kitchen concept, benefits and use cases. It throws light on the benefits of connecting cordless kitchen to the Internet and highlights the challenges involved in enabling Internet connectivity. A few possible solutions are also proposed.

@en

This chapter discusses the comprehensive experimental evaluation of the Bridge Architecture by analyzing its performance based on latency, throughput, packet retransmissions, NFC bandwidth utilization, etc. for different NFC bit rates and data sizes. It also provides some recommendations for implementing this architecture.

@en

This book focuses on enabling internet connectivity to cordless kitchen appliances. It introduces the Ki Cordless Kitchen standard, describes the possible architectures to enable internet connectivity and dives deep into addressing the networking challenges.

Today many kitchen appliances are being connected to the internet to facilitate “smart cooking”. The Wireless Power Consortium is working on the Ki Cordless Kitchen standard to make wirelessly powered cordless appliances a reality. In Ki, the cordless appliances are powered by inductive power sources integrated into the kitchen countertops. The cordless appliance and the power transmitter exchange data using a time-slotted NFC channel.

The book describes architectures and solutions using lightweight TCP/IP stacks to optimise and seamlessly adapt TCP to the time-slotted, low data rate NFC channel, and thereby enable a truly IoT-based cooking experience for cordless kitchens.@en

This chapter explains the Bridge Architecture for internet connectivity in detail. It describes the experimental setup used to study the architecture, discusses the two main challenges that this architecture presents and proposes solutions.

@en

Long Range Wide Area Network (LoRaWAN) covers the needs of energy-constrained IoT-devices for operational longevity and extended communication range in a best-effort fashion. However, Lo- RaWAN’s minimalist design cannot handle the traffic from dense deployments with more than a few hundred devices connected to a single gateway, since each LoRa-device transmits data-packets without any information regarding the availability of the medium. In this paper, we try to improve the scalability of LoRaWAN by manifolds, serving thousands of devices per gateway. We present a novel protocol called p persistent-Channel Activity Recognition Multiple Access (p-CARMA) that exploits LoRaWAN’s Channel Activity Detection (CAD) as a crude mechanism to assess if the channel is free. Due to CAD’s imperfections (it only scans for preambles, not for any channel activity) p-CARMA operates probabilistically with each device deciding on a p value based upon local estimation. At the beginning of operation, this estimate is derived from pure local information, that is without involvement of the gateway, and devices automatically adapt to changes in the environment. Then, the adaptation of p-value is assisted by critical information on the cumulative device-delays, multicasted by the gateway at regular, large timespans. To evaluate the performance of p-CARMA, we implemented it in ns-3 based upon a detailed characterization of LoRaWAN’s CAD mechanism involving an extensive set of real-world experiments. We compared p-CARMA to vanilla LoRaWAN as well as a variant using the theoretically optimal p = 1=N (N being the total number of devices). The simulation results show that p-CARMA achieves from three-fold, up to a twenty-fold higher Packet Reception Ratio than LoRaWAN while handling thousands of devices. Further, its adaptivity outperforms the fixed p-value by a factor of 5.25 when scaling up. Moreover, p-CARMA does so while consuming 37.31%-58.17% less energy on average per device compared to vanilla LoRaWAN. @en

High accuracy and device-free indoor localization is still a holy grail to enable smart environments. With the growing privacy concerns and regulations, it is necessary to develop methods and systems that can be low-power, device-free as well as privacy-aware. While IR-based solutions fit the bill, they require many modules to be installed in the area of interest for higher accuracy, or proper planning during installation, or they may not work if the background has multiple heat-emitting objects, etc. In this paper, we propose a custom-built miniature device called LOCI that uses IR sensing. One unit of LOCI can provide three-dimensional localization at best. LOCI uses only a thermopile and a PIR sensor built within a 5x5x2 cm³ module. Since IR-based sensing is used, LOCI consumes around 80 mW. LOCI uses analog waveform from the PIR sensor with the gain of the PIR sensor dynamically controlled through software in real-time to simulate spatial diversity. LOCI proposes low-complexity techniques with sensor fusion to eliminate the noise in the background, which has not been handled in previous works even with sophisticated signal processing techniques. Since LOCI uses raw data from the thermopile, the computations are power-efficient. We present the complete design of LOCI and the proposed methodology to estimate height and location. LOCI achieves accuracies of sub-22 cm with a confidence of 0.5 and sub-35 cm with a confidence of 0.8. The best-case location accuracy is 12.5 cm. The accuracy of height estimation is within 8 cm in majority cases. LOCI can easily be extended to recognize activities.

@en

The next frontier in communications is teleoperation - manipulation and control of remote environments. Compared to conventional networked applications, teleoperation poses widely different requirements, ultra-low latency (ULL) being the primary one. Teleoperation, along with a host of other applications requiring ULL communication, is termed as Tactile Internet (TI). A significant redesign of conventional networking techniques is necessary to realize TI applications. Further, these advancements can be evaluated only when meaningful performance metrics are available. However, existing TI performance metrics fall severely short of comprehensively characterizing TI performance. In this paper, we take the first step towards bridging this gap. To this end, we propose a method that captures the fine-grained performance of TI in terms of delay and precision. We take Dynamic Time Warping (DTW) as the basis of our work and identify whether it is sufficient in characterizing TI systems. We refine DTW by developing a framework called Effective Time- and Value-Offset (ETVO) that extracts fine-grained time and value offsets between input and output signals of TI. Using ETVO, we present two quantitative metrics for TI - Effective Delay-Derivative (EDD) and Effective Root Mean Square Error. Through rigorous experiments conducted on a realistic TI setup, we demonstrate the potential of the proposed metrics to precisely characterize TI interactions.

@en

Global Positioning System is a widely adopted localization technique. With the increasing demand for small satellites, the need for a low-power GPS for satellites is also increasing. To enable many state-of-the-art applications, the exact position of the satellites is necessary. However, building low-power GPS receivers which operate in low earth orbit pose significant challenges. This is mainly due to the high speed (∼7.8 km/s) of small satellites. While duty-cycling the receiver is a possible solution, the high relative Doppler shift between the GPS satellites and the small satellite contributes to the increase in Time To First Fix (TTFF), thus increasing the energy consumption. Further, if the GPS receiver is tumbling along with the small satellite on which it is mounted, longer TTFF may lead to no GPS fix due to disorientation of the receiver antenna. In this paper, we elucidate the design of a low-cost, low-power GPS receiver for small satellite applications. We also propose an energy optimization algorithm called F³to improve the TTFF which is the main contributor to the energy consumption during cold start. With simulations and in-orbit evaluation from a launched nanosatellite with our μGPS and high-end GPS simulators, we show that up to 96.16% of energy savings (consuming only ∼ 1/25th energy compared to the state of the art) can be achieved using our algorithm without compromising much (∼10 m) on the navigation accuracy. The TTFF achieved is at most 33 s.

@en

The constructive interference (CI) phenomenon has been exploited by a number of protocols for providing energy-efficient, low-latency, and reliable data collection and dissemination services in wireless sensor networks. These protocols consider CI to provide highly reliable packet delivery. This has attracted attention to understand the working of CI; however, the existing works present inconsistent views. Furthermore, these works do not study in the real-world settings where the physical conditions of deployment and unreliable wireless channels also impact the performance of CI. Therefore, we study the phenomenon of CI, considering a receiver's viewpoint and analyze the parameters that affect CI. We validate our arguments with results from extensive and rigorous experimentation in real-world settings. This paper presents comprehensive insights into the CI phenomenon. With the understanding, we develop the destructive interference-based power adaptation (DIPA), an energy-efficient and distributed algorithm, that adapts transmission power to improve the performance of CI. Since CI-based protocols cannot have an explicit acknowledgment packet, we make use of destructive interference on a designated byte to provide a feedback. We leverage this feedback to adapt transmission powers. We compared CI with and without DIPA in two real-life testbeds. On one testbed, we achieve around 25% lower packet losses while using only half of its transmission power for 64-B packets. On the other testbed, we achieve 25% lower packet losses while consuming only 47% of its transmission power for 128-B packets. Existing CI-based protocols can easily incorporate DIPA into them to achieve lower packet losses and higher energy efficiencies.

@en

Two nanosatellites recently launched into space had issues with respect to its stabilization, power and orientation. The signals were intermittent, and amateur radio enthusiasts around the globe were requested to observe the satellites so as to get their health information. As decoding the received signals required proprietary hardware (that could not be sent to everyone), amateur radio receivers recorded the signal using Software Defined Radios (SDRs) and sub-sampled the carrier signals to make it easy to share. The captured signals, modulated using binary Frequency Shift Keying (FSK), included noise and more importantly the frequency shifts due to Doppler, caused by the speed of the satellites (of about 7.8 km/s), thus making decoding a major challenge even for the designated proprietary receivers (failed in some cases). As the existing FSK methods did not work effectively, we were motivated by this challenge to design an effective FSK decoder that works in the presence of Doppler and noise. In this paper, we propose Teager Energy Decoder (TED) based on Teager Energy Operator to decode such Doppler and noise influenced sub-sampled data. TED does not need any Doppler correction mechanisms and can dynamically adapt to the changing frequency shifts. We evaluate TED using simulation as well as from the signals from those two satellites. We show that TED performs better than COTS transceivers and available GNU-radio-based solutions using SDRs. TED is low-complexity algorithm, O(N²), and has been prototyped on a low-power microcontroller. TED can be easily adopted on satellites to decode signals for space Internet of Things applications.

@en

Electronic Freight Security (EFS) systems are being increasingly deployed to reliably monitor the cargo in real-time and prevent theft in air cargo. As the existing technologies fall short in achieving these goals due to cost of deployment and/or higher latencies, we propose to exploit the existing infrastructure of power lines when the aircraft is on the tarmac. We propose an architecture that extends power line communications with Bluetooth Low Energy (BLE) devices that are embedded on the cargo. We show that BLE mesh can extend the range by interfacing with PLC modems to achieve an IoT solution for continuous monitoring and tracking. In order to evaluate this, we also propose a novel software-defined radio based testbed that can be used to evaluate various scenarios. The novelty of our testbed includes BLE mesh network that supports high reliability and low latency communication and support for emulation of electrical loads to inject impulse noise into the powerline network. We then measure end-to-end latencies and packet delivery ratios in realistic settings for the smart cargo monitoring solution. Our results indicate that our hybrid network offers a worst case latency of 24.85ms for a 570 m distance between warehouse and cargo monitoring station.

@en