Large-scale deployments of resource-constrained embedded devices require lightweight, self-contained hardware roots of trust that avoid long-term secret storage. Physically Unclonable Functions (PUFs) enable secure key extraction from intrinsic hardware variations without storing keys in non-volatile memory (NVM). SRAM PUFs leverage existing Static Random Access Memory (SRAM), but face reliability issues due to environmental noise. Existing solutions rely on complex error correction codes with NVM-stored helper data, or extensive SRAM measurements to pre-select stable cells. Eliminating NVM storage for helper data mitigates information leakage risks and manufacturing costs, offering a crucial benefit for resource-constrained devices lacking NVM. This paper presents a novel approach for stabilizing SRAM PUFs without NVM-stored helper data, using a simple decoder and few SRAM measurements, at the cost of increased SRAM size. We generate consistent On-Demand Helper Data (ODHD) temporarily stored in volatile memory and validate our method experimentally on real hardware. ODHD exposes a flexible trade-off between enrollment consistency, regeneration reliability, and SRAM size by varying a single enrollment threshold, a degree of freedom absent in the fixed Dark Bit approach. At the threshold-free operating point, ODHD achieves a key error rate of 8.2% for a 16-bit output, more than six times lower than Dark Bit’s 51.5%, using only 6 bytes of SRAM per 16-bit output, when ≈ 500 power cycles are used at every key derivation.

We present an agile methodology based on the open source Chipyard framework used for designing and validating manufacturable and performant heterogeneous RISC-V SoCs within the constraints of 15-week semesters by classes composed primarily of undergraduate students. Chipyard integrates configurable, generator-based IP blocks and flows, including the modular VLSI flow, Hammer, developed over a decade of tapeouts in different technologies. Students iterate their custom RTL and AMS blocks through integration, verification, and place-and-route, then write full-stack applications, characterizing performance. One recent semester’s class chips in FinFET are described: COSMIC (FFT, convolution, DMA accelerators), MELLIS (sparse‑matrix, convolution, quantized transformer engines, near‑memory MAC), and SCμM‑V (low-power crystal-free transceiver, general-purpose AFE, on-chip power management, clock generation). For example, COSMIC reaches 1.25 GHz, accelerates compute 2-12× with energy savings, and runs live demos. New documentation and infrastructure, such as the new bring-up platform, Baremetal, make Chipyard even more accessible.

Accurately determining the time constant of a circuit enables IoT nodes to easily read out resistive or capacitive sensors. However, power and cost constraints lead to hardware limitations that complicate such measurements, including ADC noise, sampling clock jitter, poor voltage control over temperature and process, and a low-power microprocessor without a fast multiplier or floating point support. This work discusses estimating the time constant of a decaying exponential’s ADC samples using a simple weighted linear regression and describes the on-chip implementation of the regression on a low-cost, low-power microprocessor. Experimental results with an imperfect ADC show that time constants over more than two orders of magnitude can be accurately estimated within 5% of the nominal value with a mean standard error of about 1% of the nominal value.

In this work we propose and demonstrate a protocol for a time synchronized channel hopping mesh network for wireless transceivers that use exclusively imprecise and inaccurate on-chip oscillators. This protocol is built on an IEEE 802.15.4 physical layer radio that enables interoperability with protocols such as 6TiSCH or Thread. A calibration-bootstrapped multi-hop mesh network is demonstrated with a single crystal-enabled node acting as the root. The protocol is designed to create a multi-hop mesh while compensating noisy and drifting oscillators and timers. With a 4 s synchronization period, an experimental implementation of the network maintains, in the worst case, 1.8 ms 3σ absolute time synchronization and 820 µs 3σ hop-to-hop synchronization across four hops, under ambient environmental conditions. The resistance to environmental variation is tested by varying one node's supply voltage. With time and frequency feedback from received packets, the node maintains this synchronization with a supply variation of 2.5 mV/s, which is equivalent to a temperature variation of 10°C/min with a packet rate of 0.5 Hz.

OsciBear is a system-on-chip (SoC) featuring a RISC-V 32-bit 5-stage in-order scalar processor, AES accelerator, BLE 1M baseband-modem, and a 2.4 GHz radio front end (RFE) transceiver. It was designed in TSMC's 28nm process with a total die area of 1 mm2during the course of a 14-week semester by 18 students - 4 Ph.D students, 6 masters students, and 8 undergraduates - enrolled in UC Berkeley's special topics course “28nm SoC for loT” in Spring 2021. Additionally, a PCB was designed with off-chip reference clocks, bring-up tooling, as well as power amplifiers, RF switch, and an antenna to complete the radio front-end. The CPU has been demonstrated to run up to 30 MHz in typical operating conditions. The BLE 1M-compliant PHY layer packet assembly and disassembly has been verified in-hardware through “loopback” testing. Adherence to BLE's PHY FM specifications has also been verified with a commercial BLE receiver. In total, the chip consumes 8.43 mW of static power.

The single-chip micro-mote (SC$\mu \text{M}$) is a$2\times 3$mm2single-chip crystal-free mote-on-chip. SC$\mu \text{M}$implements the IEEE802.15.4 and BLE standards and can communicate with off-the-shelf radios compliant to those standards. SC$\mu \text{M}$exclusively uses on-chip oscillators, including a 2.4-GHz LC oscillator to synthesize the communication frequency, and a 2-MHz RC oscillator to clock the chip rate. The challenge is that the LC oscillator drifts at 2100 ppm over a temperature range of 45 °C, far from the 40-ppm maximum drift mandated by the IEEE802.15.4 standard. While one-shot calibration is possible, any temperature change causes IEEE802.15.4 communication to fail. This article describes a continuous calibration approach for SC$\mu \text{M}$to adapt the tuning of its oscillators as the temperature changes. Experimental results show that it allows SC$\mu \text{M}$to keep communicating with an IEEE802.15.4 radio even under the extreme condition of using a hair dryer to heat up the chip at 3 °C/min. Under these conditions, the drift of the LC oscillator stays within the ±40-ppm limit over 94% of the time. Similarly, the drift of the 2-MHz RC oscillator stays within ±1000 ppm limit 99.98% of the time.

Solar-powered actuation of a 15 mN electrostatic MEMS gripper was demonstrated while wirelessly triggered by IEEE 802.15.4 RF signals. The solar-powered gripper was shown to actuate at a rate of 640 um/s. The complete system is composed of three capacitors and three chips: MEMS gripper, microprocessor/crystal-free radio, and solar cell array/high voltage buffer. Control signals for the electrostatic inchworm motors originate from the 3×2×0.3 mm3chip with an ARM Cortex-M0 microprocessor and are passed through 119 V high voltage buffers. Power for all components, including the crystal-free radio, microprocessor, and 119 V buffers, is supplied by a multi-output array of solar cells on a CMOS SOI chip under 200 mW/cm2irradiation.

The single-chip micro mote (SC$\mu \text{M}$) is a crystal-free single-chip mote that brings us one step closer to the Smart Dust vision, in particular, as it can communicate with off-the-shelf IEEE802.15.4 and Bluetooth low energy devices. However, before it can be part of such networks, the crystal-free SC$\mu \text{M}$chip needs to be able to accurately tune its communication frequency to synchronize to the network. This is a challenge since its onboard RC and LC-based resonating circuits have a drift rate that can be three orders of magnitude worse than crystal-based oscillators typically used in today’s radios. This article introduces QuickCal, a solution that allows an SC$\mu \text{M}$chip to self-calibrate against off-the-shelf devices dedicated to assisting with its calibration. We show that an SC$\mu \text{M}$chip can self-calibrate against this QuickCal Box in fewer than 3 min. We further validate that once it has self-calibrated, an SC$\mu \text{M}$chip can reliably communicate with off-the-shelf IEEE802.15.4 devices. Finally, we demonstrate a heterogeneous network—composed of an SC$\mu \text{M}$chip and an OpenMote device—implementing a full 6TiSCH Industrial IoT protocol stack, which uses time synchronization and channel hopping. This is the first time that a crystal-free radio is participating in a channel-hopping-enabled TSCH network.

Exploration and mapping is a fundamental capability of a swarm of robots: robots enter an unknown area, explore it, and collectively build a map of it. This capability is important regardless of whether the robots are crawling, flying, or swimming. Existing exploration and mapping algorithms tend to either be inefficient, or rely on having a dense swarm of robots. This paper introduces Atlas, an exploration and mapping algorithm for sparse swarms of robots, which completes a full exploration even in the extreme case of a single robot. We develop an open-source simulator and show that Atlas outperforms the state-of-the-art in terms of exploration speed and completeness of the resulting map.

We present the results of a latency-bounded, high-reliability conveyor belt control system for a cart containing a self-localizing wireless sensor node. The node is equipped with an ARM Cortex-M3 microprocessor, 802.15.4 transceiver, 9axis inertial measurement unit (IMU), and an infrared-sensitive photodiode which allows the wireless node to localize itself using a high-precision localization system for small, resource-constrained, low-cost wireless sensor nodes known as “lighthouse” localization. The cart moves across the conveyor belt, and upon reaching a specified position sends a wireless signal to a set of receiving nodes attached to the conveyor belt’s motor to reverse direction. Using an extended Kalman filter (EKF) running on-board the cart’s wireless sensor node to estimate the position and velocity of the cart, we are able to achieve 3ms response latency, equivalent to the response latency of industrial photoelectric sensors used in a related implementation. We also show the lighthouse system used in this implementation has no outlier measurements outside the $\pm 1 mm$ error range when stationed 3 meters away from the conveyor belt. This, in addition to use of the EKF, enables high-reliability control with strong occlusion tolerance. We show the wireless sensor node is able to continue estimating its position along the conveyor belt when occluded from the lighthouse base station with a median standard deviation reported by the EKF of 0.875mm after 10 cm of occlusion compared to a median 0.109mm standard deviation of the position estimate when not occluded.

Robot design is often a slow and difficult process requiring the iterative construction and testing of prototypes, with the goal of sequentially optimizing the design. For most robots, this process is further complicated by the need, when validating the capabilities of the hardware to solve the desired task, to already have an appropriate controller, which is in turn designed and tuned for the specific hardware. In this paper, we propose a novel approach, HPC-BBO, to efficiently and automatically design hardware configurations, and evaluate them by also automatically tuning the corresponding controller. HPC-BBO is based on a hierarchical Bayesian optimization process which iteratively optimizes morphology configurations (based on the performance of the previous designs during the controller learning process) and subsequently learns the corresponding controllers (exploiting the knowledge collected from optimizing for previous morphologies). Moreover, HPC-BBO can select a “batch” of multiple morphology designs at once, thus parallelizing hardware validation and reducing the number of time-consuming production cycles. We validate HPC-BBO on the design of the morphology and controller for a simulated 6-legged microrobot. Experimental results show that HPC-BBO outperforms multiple competitive baselines, and yields a 360% reduction in production cycles over standard Bayesian optimization, thus reducing the hypothetical manufacturing time of our microrobot from 21 to 4 months.

The Internet-of-Things (IoT) promises one trillion wireless sensors in the next 10 to 15 years. To enable this scale, we present the experimental results on the time-keeping ability of crystal-free radios to lower the cost of the wireless sensors. We propose a network referenced frequency lock loop and demonstrate a one sigma mean frequency accuracy of 47 p/min, post calibration. We also extend this concept to calibrate the on-chip RF local oscillator by exploiting the network time synchronization for frequency calibration. This timing accuracy is sufficient to create a scalable wireless mesh network up to 10 hops deep with a 1 ms guard time interval. The impact of time synchronization on the average power consumption of the wireless sensor node is negligible and especially true for environments with mobility and high data traffic. We envision these emerging microsystems to be embedded into everyday objects and discuss the tradeoff of mobility with the average power consumption.

The convergence of operational and information technologies in the industry requires a new generation of IP-compliant communication protocols that can meet the industrial performance requirements while facilitating the integration with novel web-based supervisory control and data acquisition (SCADA) systems. For more than a decade, the industry has relied on time-slotted channel hopping (TSCH) communication technology to meet these performance requirements through standards such as WirelessHART and ISA100.11a. TSCH-based networks have proven to yield over 99.999% end-to-end reliability, supporting flow isolation and QoS management while ensuring over a decade of battery lifetime. However, these technologies were designed to address the factory use cases of a decade ago, not considering IP compliance or standardized network management and resource orchestration as a must. The Internet Engineering Task Force (IETF) and the 6TiSCH working group (WG) have been actively working on this challenge by designing protocols to bridge the performance of industrial solutions with IP-compliant networks. The effort has resulted in 6TiSCH, a set of specifications that define the IPv6 control plane to manage and orchestrate a TSCH network. 6TiSCH provides the missing elements for zero-configuration TSCH network bootstrap, efficient network access authentication, and distributed and modular scheduling mechanisms. As a cross-layer effort, 6TiSCH leverages and integrates other IETF specifications and the WG has also driven the definition of novel specifications in other IETF WGs. An ultimate goal of this effort is the definition of a fully functional architecture where a combination of IETF protocols enables the envisioned convergence on top of the IEEE industrial standard. This paper introduces the work done by the 6TiSCH WG at IETF, evaluates the performance of the reference implementation, and discusses the 6TiSCH software ecosystem.

Wireless sensor networks for factory automation and control will require strict latency and reliability requirements on the order of 1 millisecond end-to-end latency and 10-9total packet error rate. Current wireless sensor networks can achieve up to nine nines (10-9total packet error rate) of reliability, but without tight latency bounds. In order to meet these requirements, wireless sensor networks will require effective modes of network diversity that are also compatible with low-latency time scales. We evaluated the efficacy of time, space, and frequency diversity in cooperative IEEE 802.15.4 wireless networks. We demonstrated a wireless sensor network topology that achieved 99.99999% of reliability bounded by a worst case end - to-end latency of 3 milliseconds.

In the spring of 2017, the UC Berkeley department of EECS introduced an innovative new course: "28nm SoC for IoT." This course went far beyond schematic-level design typical of circuits education and resulted in a chip going out for manufacturing. Ten students with no prior IC experience, nine undergraduate and one graduate, designed and laid out an SoC in ST 28nm FD-SOI CMOS including a 2.4GHz transceiver, baseband filtering, ADC, Bluetooth MAC, a RISC-V CPU, and internal power regulation. The transceiver, baseband, ADC, and power regulation were successfully fabricated. This paper discusses the instructors' experiences and results with this course.

Ring oscillators have area and power advantages over LC tanks, but conventional wisdom is that rings must be locked to a high-Q external reference to be useful in RF communications. In this paper we explore performance of a 2.4GHz receiver incorporating only a free-running ring as a local oscillator. Using a simple technique to compensate for frequency error, we find that a minimum-size ring fabricated in 65nm CMOS and consuming only 105μW is able to demodulate 75% of received 802.15.4 packets and, if the FSK tone deviation is doubled from 802.15.4 spec, packet receive rate exceeds 99.8%.

We describe opportunities and challenges with wireless robotic materials. Robotic materials are multi-functional composites that tightly integrate sensing, actuation, computation and communication to create smart composites that can sense their environment and change their physical properties in an arbitrary programmable manner. Computation and communication in such materials are based on miniature, possibly wireless, devices that are scattered in the material and interface with sensors and actuators inside the material. Whereas routing and processing of information within the material build upon results from the field of sensor networks, robotic materials are pushing the limits of sensor networks in both size (down to the order of microns) and numbers of devices (up to the order of millions). In order to solve the algorithmic and systems challenges of such an approach, which will involve not only computer scientists, but also roboticists, chemists and material scientists, the community requires a common platform --- much like the "Mote" that bootstrapped the widespread adoption of the field of sensor networks --- that is small, provides ample of computation, is equipped with basic networking functionalities, and preferably can be powered wirelessly.

6TiSCH is a technology being standardized at the IETF which brings determinism to low-power wireless communication. In a 6TiSCH network, all communication is orchestrated by a communication schedule. This paper explores the applicability of this new technology to control systems. In particular, we apply it to the inverted pendulum, a canonical control system in which a cart moves along a track to keep a pendulum — which naturally falls over — upright. This paper presents the first characterization and implementation of a closed-loop wireless feedback control network using completely standards-compliant IEEE802.15.4 TSCH technology. First, we implement a control loop in OpenWSN and experimentally evaluate the performance of the network by varying the radio duty cycle, number of hops, and introducing controlled external interference. We show that 100% reliability can be achieved while maintaining latencies well below the critical delay of the system. Second, we use the network on an inverted pendulum system and show that angular deviations from the upright position do not exceed 3 degrees, even in a multi-hop setup. Finally, we discuss the results in detail, and advocate for a co-design of the controller and the networking system.

Despite recent growth in the field of wearable devices, persistent collection of data with clear biomedical relevance remains elusive. The majority of products focus on short-term personal fitness metrics instead of long-term biomedical monitoring. The ideal wearable platform for researchers would include flexibility to test different biometric sensors. We present an open-source, modifiable, and user-reconfigurable wearable sensor system capable of enabling biomedical investigations not feasible with currently-available devices. Our armband device has been configured to measure skin temperature, light, and activity across days to detect internal circadian rhythms. Instability of circadian rhythms is linked to risk of many diseases, including mental illness such as depression, and has predictive power for personal affective state, yet its clinical use is slow in adoption in part because of the difficulty in acquiring relevant data. We provide evidence that such measurements are attainable at high resolution, low cost, and with minimal subject burden. Our device was tested with a variety of other sensors, and results indicate that daily circadian stability and hourly ultradian rhythms in core body temperature and hormone concentrations can be predicted from armband data. Future devices will be self-powered and perform automatic data collection to improve data continuity.

Thousands of industrial gas leaks occur every year, with many leading to injuries, deaths, equipment damage, and a disastrous environmental effect. There have been many attempts at solving this problem, but with limited success. This paper proposes a wireless gas leak detection and localization solution. With a monitoring network of 20 wireless devices covering 200 m2, 60 propane releases are performed. The detection and localization algorithms proposed here are applied to the collected concentration data, and the methodology is evaluated. A detection rate of 91% is achieved, with seven false alarms recorded over 3 days, and an average detection delay of 108 s. The localization results show an accuracy of 5 m. Recommendations for future explosive gas sensor design are then presented.

Industrial low-power wireless mesh networks are shifting towards time-synchronized medium access control (MAC) protocols which are able to yield over 99.9% end-to-end reliability and radio duty cycles well below 1%. In these networks, motes use time slots to communicate, and neighbor motes maintain their clocks' alignment, typically within 1 ms. Temperature, supply voltage, and fabrication differences cause the motes' clocks to drift with respect to one another. Neighbor motes need to re-synchronize periodically through pairwise communication. This period is typically determined a priori, based on the worst case drift. In this paper, we propose a novel technique which measures and models the relative clock drift between neighbor motes, thereby reducing the effective drift rate. Instead of resynchronizing at a preset rate, neighbor motes resynchronize only when needed. This reduces the minimum achievable duty cycle of an idle network by a factor of 10, which in turn lowers the mote power consumption and extends the network lifetime. This Adaptive Synchronization is implemented as part of IEEE802.15.4e in the OpenWSN protocol stack and is validated through extensive experimentation.

This paper presents a Microelectromechanical systems (MEMS) solution to rotary valve position monitoring. With a device holding commercial off-the-shelf inertial sensors, we develop a sensing algorithm encompassing self-calibration, and noise and drift removal. Our repeatable results show an accuracy of ±5° for part-turn valves and ±10% of a turn for multi-turn models. Our small energy-efficient wireless solution is a cheap and reliable replacement for products on the market.

In this work, we present the results of a study on the detrimental effects of sinkhole attacks on Wireless Sensor Networks (WSNs) which employ the Routing Protocol for LLNs (Low-power and Lossy Networks). A sinkhole is a compromised node which attempts to capture traffic with the intent to drop messages, thus degrading the end-to-end delivery performance, that is, reducing the number of messages successfully delivered to their destination. The mechanism by which the sinkhole captures traffic is by advertising an attractive route to its neighbors. We evaluate two countermeasures addressing the sinkhole problem: a parent fail-over and a rank authentication technique. We show via simulation that while each technique, applied alone, does not work all that well, the combination of the two techniques significantly improves the performance of a network under attack. We also demonstrate that, with the defenses described, increasing the density of the network can combat a penetration of sinkholes nodes, without needing to identify the sinkholes.

This paper presents one possible approach to Signalized Left Turn Assist at intersections. A sensing platform is designed to detect the presence of cars by measuring the deflection of the magnetic field when driving by. This platform is tested experimentally under different conditions. A threshold detection algorithm is designed to determine whether a car is passing in front of the sensor. The algorithm is first run off-board using a set of previously collected magnetometer measurements, before being implemented and run on-board the platform. We show how this detection algorithm performs better as the sensor is placed close to the traffic flow and we discuss how such sensors can be networked together to form a smart intersection.

Reducing the time the radio is on in wireless devices results in lower power consumption, so sending the same data in fewer bytes can greatly extend the lifetime of a network. In this paper, we explore the use of protocol-agnostic packet compression, a technique orthogonal to current explicit compaction techniques. Because it functions as a transparent layer inside a communication stack and makes no assumption about the specific protocols used, it is generic enough to be used on multiple technologies. Compression is performed by identifying patterns in recent packets and replacing those patterns with bit flags in the transmitted packet. We present the results of compressing actual packet traces collected from several commercial networks using this algorithm and discuss the resource trade-offs of the algorithm. Results indicate compression ratios between 40% and 80%, yielding predicted energy savings of 30-70% in a typical time- synchronized network.

Having a wake-up receiver constantly listening is often seen as a replacement for running a duty- cycled medium access control protocol on a commercial low-power radio chip. Wake-up receivers do offer a better latency while consuming negligible power. Recent wake-up receivers show an impressively low power consumption of 52μW, but at the cost of a sensitivity of -72dBm, 20-30dB higher than the sensitivity of a commercial radio chip. This difference in sensitivity causes the wake-up receiver to have a much smaller communication range than the commercially available low power radio. In practice, this translates into requiring a denser deployment, or having to add an external power amplifier. This paper discusses the applicability of wake-up receivers in low-power wireless multihop networks. We show how, at available sensitivity levels, a wake-up receiver helps reducing the power consumption, but also requires a dramatically higher design or deployment cost.

Wireless communication between a pair of nodes can suffer from self interference arising from multipath propagation reflecting off obstacles in the environment. In the event of a deep fade, caused by destructive interference, no signal power is seen at the receiver, and so communication fails. Multipath fading can be overcome by shifting the location of one node, or by switching the communication carrier frequency. The effects of such actions can be characterized by the coherence length (L) and coherence bandwidth (B), respectively, given as the amount of shift necessary to transition from a deep fade to a region of average signal strength. Experimental results for a representative 2.4GHz wireless link indicate L = 5.5cm and B can vary from 5MHz at long ranges up to 15MHz for short links. For wireless sensor networks (WSNs), typically operating under the IEEE802.15.4 standard, multipath effects are therefore best handled by a channel hopping scheme in which successive communication attempts are widely spread across available carrier frequencies.

The electronics packages for many robot control systems have very similar requirements, yet are often redesigned for each custom application. To reduce wasted time and effort, the project presented in this paper (the Wireless Autonomous Robot Platform with Inertial Navigation and Guidance, WARP-WING) is intended to create a complete and easily customizable general purpose control system for miniature robotic systems, in particular micro air vehicles. In its default configuration, hardware designs, firmware, and software are all available to deliver an out-of-the-box robot control solution comprising 6 degree-of-freedom inertial sensors, a microprocessor, and wireless communication, along with general purpose input/output pins, serial ports, and control outputs for interfacing to additional sensors and actuators. The entire project is open source and a process is in place to enable modification of any component, allowing for easy adaptation to any need. WARPWING is already in use in a number of labs, with each research group contributing its expertise to enhance the platform and make such modifications available to others as well.

Reducing the number of transmitted bytes in a wireless sensor network reduces the time the radio is on, resulting in a significant increase in battery lifetime. Toward this end we have developed a compression technique that is independent of the protocols used in the network, acts as a transparent layer, and consumes minimal computing resources. Patterns in recent packets are identified and replaced in the transmitted packet by bit flags. This algorithm was tested on packet traces collected from commercial wireless sensor networks for 40-80% compression, yielding comparable energy savings in a time-synchronized network.

The 25 papers in this special issue focus on simple wireless sensor networking solutions.

IETF ROLL has recently proposed gradient routing as a fundamental building block for data collection in Wireless Sensor Networks. This paper seconds this choice by presenting an implementation of gradient routing on current hardware, and by showing experimentally that gradient routing is robust against topological changes. To stress its self-healing quality, we design and implement a complete communication stack in which neighbor tables are built in a purely reactive fashion. We quantify the resulting topological changes, and show how gradient routing elegantly handles these dynamics. This paper presents, to the best of our knowledge, the first experimental study on gradient routing as advocated by IETF ROLL.

The use of variable data rate can reduce network latency and average power consumption, and automatic rate selection is critical for improving scalability and minimizing network overhead. In the IEEE 802.15.4 standard the SNR can be inferred through the radio reported link quality or received signal strength, and an extension to the standard leads to highly dynamic and accurate rate selection. Using data from an experimental study of 44 IEEE 802.15.4 nodes in an industrial mesh network, SNR is extracted to show sufficient margin exists for higher data rate communication. A variable rate signaling scheme with automatic rate selection is proposed to provide links at the standard 250 kb/s as well as 500 kb/s, 1000 kb/s and 2000 kb/s with a minimum of hardware changes. Using the experimental data to generate a model of the real world system, total network energy is compared using legacy and variable rate signaling showing over 40% savings.

This paper addresses estimating the distance between wireless nodes using a two-way ranging technique that approaches the Cramer-Rao Lower Bound (CRB) on ranging accuracy in a white noise environment. Standard two-way ranging methods do not achieve this bound because sampling artifacts limit resolution through range binning, so multiple measurements are combined to improve performance. Code modulus synchronization is presented as an alternative that approaches the CRB. The analytical results presented in this article are confirmed by implementing the technique on a prototype wireless system and measuring the performance in the presence of noise.

This paper presents the design and initial results for an autonomous jumping microrobot. At the millimeter size scale, jumping can offer numerous advantages for efficient locomotion, including dealing with obstacles and potentially even latching onto other larger mobile hosts. Robot design is divided into four primary areas: energy storage, actuation, power, and control. Like its biological inspiration, the flea, a jumping microrobot requires an energy storage system to store energy and release it quickly to jump. Silicone micro rubber bands have been fabricated and assembled into the microrobot for this task. To stretch these micro rubber bands, electrostatic inchworm motors are chosen as actuators due to their high forces, long throw, and low input power requirements. Finally, solar cells and a microcontroller have been chosen to power and control the microrobot. A small-scale version of this system has been prototyped with the solar cells and a simple 4-bit microcontroller driving an inchworm motor. Separately, an inchworm motor has been demonstrated pulling and storing 4.9 nJ of energy in a micro rubber band. Finally, initial tests with a probe-loaded robot prototype have demonstrated a microrobot which can potentially jump 1.2 cm straight up.

Wireless sensor nodes are autonomous devices incorporating sensing, power, computation, and communication into one system. Applications for large scale networks of these nodes are presented in the context of their impact on the hardware design. The demand for low unit cost and multiyear lifetimes, combined with progress in CMOS and MEMS processing, are driving development of SoC solutions for sensor nodes at the cubic centimeter scale with a minimum number of off-chip components. Here, the feasibility of a complete, cubic millimeter scale, single-chip sensor node is explored by examining practical limits on process integration and energetic cost of short-range RF communication. Autonomous cubic millimeter nodes appear within reach, but process complexity and substantial sacrifices in performance involved with a true single-chip solution establish a tradeoff between integration and assembly.

An evaluation methodology is presented for the performance of reporting node self-selection in wireless sensor networks. Five cost metrics are proposed along with several methods for self-selection that involve little or no collaboration with other nodes. These costs are used to evaluate how efficiently the various algorithms allow for node self-selection as simulated on different field complexities. Analysis of different methods over 100 test fields sampled by 2000 nodes indicates that there is no single method that is superior in all respects. Trade-offs in latency and overall energy consumption are revealed to be highly dependent on the selection method and the field complexity.

With the MEMS revolution in full swing, microsensors are now following manufacturing curves that are at least related to Moore's Law. Combined with the push for low power communication and computation coming from the handheld community, this enables an exciting new field of low-cost, high-performance wireless sensor networks. This talk will address some of the practical and physical limits associated with miniaturization of wireless sensor networks.

The CotsBots are inexpensive and modular mobile robots built entirely from commercial off-the-shelf components. These robots provide a convenient platform on which to investigate algorithms, cooperation, and distributed sensing in large (> 50) robot networks. Each robot is small (13 cm /spl times/ 6.5 cm base) and costs under $200. Each is equipped with on-board processing, radio communication, and a base platform for mobility. Software is written using TinyOS, an open-source, event-driven operating system for large-scale distributed sensor and actuator networks. TinyOS also provides a modular software environment where implementation details many be abstracted away from the robot application developer. A simple robot diffusion algorithm has been outlined to demonstrate the ease of using CotsBots for large-scale systems.

A method for estimating unknown node positions in a sensor network based exclusively on connectivity-induced constraints is described. Known peer-to-peer communication in the network is modeled as a set of geometric constraints on the node positions. The global solution of a feasibility problem for these constraints yields estimates for the unknown positions of the nodes in the network. Providing that the constraints are tight enough, simulation illustrates that this estimate becomes close to the actual node positions. Additionally, a method for placing rectangular bounds around the possible positions for all unknown nodes in the network is given. The area of the bounding rectangles decreases as additional or tighter constraints are included in the problem. Specific models are suggested and simulated for isotropic and directional communication, representative of broadcast-based and optical transmission respectively, though the methods presented are not limited to these simple cases.

No abstract available.

Article Next century challenges: mobile networking for "Smart Dust" Share on Authors: J. M. Kahn Department of Electrical Engineering and Computer Sciences, University of California, Berkeley Department of Electrical Engineering and Computer Sciences, University of California, BerkeleyView Profile , R. H. Katz Department of Electrical Engineering and Computer Sciences, University of California, Berkeley Department of Electrical Engineering and Computer Sciences, University of California, BerkeleyView Profile , K. S. J. Pister Department of Electrical Engineering and Computer Sciences, University of California, Berkeley Department of Electrical Engineering and Computer Sciences, University of California, BerkeleyView Profile Authors Info & Claims MobiCom '99: Proceedings of the 5th annual ACM/IEEE international conference on Mobile computing and networkingAugust 1999 Pages 271–278https://doi.org/10.1145/313451.313558Online:01 August 1999Publication History 972citation5,666DownloadsMetricsTotal Citations972Total Downloads5,666Last 12 Months122Last 6 weeks18 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Low power wireless sensor networks provide a new monitoring and control capability for civil and military applications in transportation, manufacturing, biomedical, environmental management, and safety and security systems. Wireless microsensor network nodes, operating at average and peak power levels constrained by compact power sources, offer a range of important challenges for low power methods. This paper reports advances in low power systems spanning network design, through power management, low power mixed signal circuits, and highly integrated RF network interfaces. Particular attention is focused on methods for low power RF receiver systems.

A design of a high-force-output large-deflection parallel-plate electrostatically actuated microgripper is described. This design uses polysilicon as a structural material and may be fabricated using an IC-based surface machining process. This paper shows that by using a position feedback controller, the microgripper can be stabilized in theory, which is supported by computer simulations. Preliminary data from fabricated micro-grippers also supports the mathematical model for the open loop system, although the pull-in voltages (50 V to 100 V for gaps of 80 to 100 /spl mu/m/sup 2/) are generally lower than predicted ones, probably due to the inherent instability of the electrostatic system. Further experiments are in progress to evaluate the open-loop system and the closed-loop system.>

The authors present a technique to analyze the forces and dynamics of a class of mechanical systems, called fingerlike systems, which may be viewed as an extension of simple robots to include networks for force/displacement generation and transmission. Fingerlike mechanical system can be described using a graph-theoretic approach to force and displacement generation and transmission. Branches consist of actuators, cables, springs, and other building blocks. Upon specification of the connectivity graph and branch behaviors, a symbolic mathematics program can generate the affine maps from actuator control variables to mechanical system torques and forces. This process systematizes and simplifies the determination of biological and robotic mechanical dynamics.>

A set of primitive operations that forms the core of a robot system description and control language is presented. The actions of the individual primitives are derived from the mathematical structure of the equations of motion for constrained mechanical systems. The recursive nature of the primitives allows composite robots to be constructed from more elementary daughter robots. A few pertinent results of classical mechanics are reviewed, the functionality of the primitive operation is described, and several different hierarchical strategies for the description and control of a two-fingered hand holding a box are presented.>

A methodology is developed for describing of hierarchical control of robot systems in a manner which is faithful to the underlying mechanics, structured enough to be used as an interpreted language, and sufficiently flexible to encompass a wide variety of systems. A consistent set of primitive operations which form the core of a robot system description and control language is presented. This language, motivated by the hierarchical organization of neuromuscular systems, is capable of describing a large class of robot systems under a variety of single-level and distributed control schemes.>