David E. Culler

• University of California, Berkeley

Large language models (LLMs) have excelled in various applications, yet serving them at scale is challenging due to their substantial resource demands and high latency. Our real-world studies reveal that over 60% of user requests to LLMs have semantically similar counterparts, suggesting the potential for knowledge sharing among requests. However,...

There is now a significant and growing functional gap between the public Internet, whose basic architecture has remained unchanged for several decades, and a new generation of more sophisticated private networks. To address this increasing divergence of functionality and overcome the Internet's architectural stagnation, we argue for the creation of...

Can cloud computing infrastructures provide HPC-competitive performance for scientific applications broadly? Despite prolific related literature, this question remains open. Answers are crucial for designing future systems and democratizing high-performance computing. We present a multi-level approach to investigate the performance gap between HPC...

Large scale modeling and simulation problems, from nanoscale materials to universe-scale cosmology, have in the past used the massive computing resources of High-Performance Computing (HPC) systems. Over the last decade, cloud computing has gained popularity for business applications and increasingly for computationally intensive machine learning p...

Governments around the world have become increasingly frustrated with tech giants dictating public health policy. The software created by Apple and Google enables individuals to track their own potential exposure through collated exposure notifications. However, the same software prohibits location tracking, denying key information needed by public...

We present PC-RPL, a transmission power-controlled IPv6 routing protocol for low-power and lossy wireless networks (LLNs) that significantly improves the end-to-end packet delivery performance under heavy traffic, compared to the standard RPL. We show through actual design, implementation, and experiments that a multihop wireless network can achiev...

The Heating Ventilation and Air Conditioning (HVAC) system of commercial buildings traditionally runs on a fixed schedule that does not take occupancy into account despite its huge variation over space and time, thereby wasting a lot of energy in conditioning empty or partially-occupied spaces. Occupancy information is essential to eliminate wastef...

Buildings account for 32% of worldwide energy usage. A new regime of exciting new “applications” that span a distributed fabric of sensors, actuators and humans has emerged to improve building energy efficiency and operations management. These applications leverage the technological advances in embedded sensing, processing, networking and methods b...

With the increasing commoditization of computer vision, speech recognition and machine translation systems and the widespread deployment of learning-based back-end technologies such as digital advertising and intelligent infrastructures, AI (Artificial Intelligence) has moved from research labs to production. These changes have been made possible b...

As the number and heterogeneity of appliances in smart buildings increases, identifying and controlling them becomes challenging. Existing methods face various challenges when deployed in large commercial buildings. For example, voice command assistants require users to memorize many control commands. Attaching Bluetooth dongles or QR codes to appl...

Operating buildings can be challenging, especially with poor instru-mentation of the indoor environment. There are several wireless sensor platforms on the market but most are too difficult to deploy en-masse, requiring the end-user to program devices, or manage infrastructure. Many rely on smart-phones and do not work when unattended. The Hamilton...

RPL is the IPv6 routing protocol for low-power and lossy networks (LLNs), standardized by IETF in 2012 as RFC6550. Specifically, RPL is designed to be a simple and inter-operable networking protocol for resource-constrained devices in industrial, home, and urban environments, intended to support the vision of the Internet of Things (IoT) with thous...

We show that a multihop wireless network can achieve better bandwidth and routing stability when transmission power and routing topology are jointly and adaptively controlled. Our experiments show that the predominant 'fixed and uniform' transmission power strategy with 'link quality and hop distance'-based routing topology construction loses signi...

I am often asked these days, "Is IoT really as transformative as all the buzz suggests, or is it a lot of hype?" My answer is simply, "Yes." And the road to here has been a fascinating interplay of academic research accomplishments, industry advances (often with other drivers), and standardization processes (for lack of a better term). It was predi...

The design of energy-efficient commercial building Heating Ventilation and Air Conditioning (HVAC) systems has been in the forefront of energy conservation efforts over the past few decades. The HVAC systems traditionally run on a static schedule that does not take occupancy into account, wasting a lot of energy in conditioning empty or partially-o...

Sensorized commercial buildings are a rich target for building a new class of applications that improve operational and energy efficiency of building operations that take into account human activities. Such applications, however, rarely experience widespread adoption due to the lack of a common descriptive schema that would enable porting these app...

Commercial buildings have long since been a primary target for applications from a number of areas: from cyber-physical systems to building energy use to improved human interactions in built environments. While technological advances have been made in these areas, such solutions rarely experience widespread adoption due to the lack of a common desc...

To enable a prosperous Internet of Things (IoT), devices and services must be extensible and adapt to changes in the environment or user interaction patterns. These requirements manifest as a set of design principles for each of the layers in an IoT ecosystem, from hardware to cloud services. This paper gives concrete guidelines learned from implem...

Carpooling has been long deemed a promising approach to better utilizing existing transportation infrastructure. However, there are several reasons carpooling is still not the preferred mode of commute in the United States: first, complex human factors, including time constraints and not having right incentive structures, discourage the sharing of...

In Building Automation Systems contextual information about sensors is frequently missing or hard-coded in the control code. Retrieving this data is time consuming and error-prone, but necessary to write any type of control application. Automating metadata acquisition is a new and active area of research. Methods to infer metadata from sensor label...

Commercial buildings account for a large amount of delivered energy in the U.S., nearly 42% of which is consumed in buildings with digital control systems {EIA}. These buildings are a ripe venue to deploy novel applications because of (a) access to sensors and actuators that are used in their digital control systems, (b) deployed wireless sensor ne...

We present XBOS, an eXtensible Building Operating System for integrated management of previously isolated building subsystems. The key contribution of XBOS is the Building Profile, a canonical, executable description of a building and its subsystems that changes with a building and evolves control processes and applications accordingly. The design...

Personal Comfort Systems (PCS) are capable of maintaining occupant comfort in buildings despite large deviations from recommended "comfortable" temperatures. We present a novel digital controller for a well-studied (previously analog) PCS, allowing it to report real-time telemetry and respond to programmatic actuation requests. This enables the est...

Commercial buildings consume nearly 19\% of delivered energy in the U.S, nearly half (42%) of which is consumed in buildings with digital control systems comprised of wired sensor networks. These sensors have scant metadata, and are represented by ``tags'' which are obscure, building-specific and not machine parseable. We develop a human-in-the-loo...

The introduction and deployment of cheap, high precision, high-sample-rate next-generation synchrophasors en masse in both the transmission and distribution tier — while invaluable for event diagnosis, situational awareness and capacity planning — poses a problem for existing methods of phasor data analysis and storage. Addressing this, we present...

Syntax-guided synthesis searches for an implementation of a given specification by exploring large spaces of candidate programs. Sketches reduce these search spaces, making synthesis more tractable, by predefining the structure of the desired implementation. Typically, this structure is obtained through human insight---this paper introduces a metho...

Rust, a new systems programming language, provides compile-time memory safety checks to help eliminate runtime bugs that manifest from improper memory management. This feature is advantageous for operating system development, and especially for embedded OS development, where recovery and debugging are particularly challenging. However, embedded pla...

Information technology can increase energy efficiency by improving the control of energy-using devices and systems. Awareness of this potential is not new—ideas for applications of information technology for energy efficiency have been promoted for more than 20 years. But much of the potential gain from the application of information technology has...

Many indoor localization algorithms have been proposed to enable location-based applications in indoor environments. However, these systems are monolithic and not component-based. We present BearLoc, a distributed modular framework for indoor localization systems that provides (1) natural development abstractions for sensor, algorithm, and applicat...

For the last fifteen years, research explored the hardware, software, sensing, communication abstractions, languages, and protocols that could make networks of small, embedded devices-motes-sample and report data for long periods of time unattended. Today, the application and technological landscapes have shifted, introducing new requirements and n...

In this demonstration, we present a novel system of building control and simulation focused on the integration of the physical and virtual worlds. Actuations and schedules can be manifested either in a physical space or in a virtualization of that space, allowing for more natural interactions with simulations and easier transferring of schedules an...

Sensor network research has facilitated advancements in various domains, such as industrial monitoring, environmental sensing, etc., and research challenges have shifted from creating infrastructure to utilizing it. Extracting meaningful information from sensor data, or control applications using the data, depends on the metadata available to inter...

Extracting meaningful information from a building's sensor data, or writing control applications using the data, depends on the metadata available to interpret it, whether provided by novel networks or legacy instrumentation. Commercial buildings comprise large sensor networks, but have limited, obscure 'tags' that are often meaningful only to the...

We present nesC, a programming language for networked embedded systems that represent a new design space for application developers. An example of a networked embedded system is a sensor network, which consists of (potentially) thousands of tiny, lowpower "motes," each of which execute concurrent, reactive programs that must operate with severe mem...

Building power proportional High Performance Computing (HPC) clusters comprising of servers which are not power-proportional is a well-studied problem, and has the potential to provide large energy savings. However, a large emphasis on maintaining cluster uptime disincentivizes system administrators from deploying prior research techniques that int...

This paper describes a research project to develop a network of high-precision phasor measurement units, termed micro-synchrophasors or μPMUs, and explore the applications of μPMU data for electric power distribution systems.

In this paper, we model energy use in commercial buildings using empirical data captured through sMAP, a campus building data portal at UC Berkeley. We conduct at-scale experiments in a newly constructed building on campus. By modulating the supply duct static pressure (SDSP) for the main supply air duct, we induce a response on the main supply fan...

Most large, commercial buildings contain thousands of sensors that are manually deployed and managed. These sensors are used by software and firmware processes to analyze and control building operations. Many such processes rely on sensor placement information in order to perform correctly. However, as buildings evolve and building subsystems grow...

The system is environment monitoring service based on Wireless Sensor Networks (WSN). Users can know temperature, humidity, light, and CO2 level in real time. Excessive electricity consumption by lighting in the office can be saved and the quality of the office environment can become better by controlling lighting and CO2 level.

We develop a flexible and responsive electrical load in the form of domestic refrigerators augmented with a thermal storage system, a wireless sensor network for monitoring and actuation, and a controller that enables response to external controls. Using this, we investigate the potential of such loads for two applications: price-responsive demand...

Electricity grids are transforming as renewables proliferate, yet operational concerns due to fluctuations in renewables sources could limit the ultimate potential for high penetrations of renewables. In this paper, we compare three electricity grids - California, Germany, and Ontario - studying the effects of relative cost of solar and wind genera...

There has been a recent industrial effort to develop multi-resource hierarchical schedulers. However, the existing implementations have some shortcomings in that they might leave resources unallocated or starve certain jobs. This is because the multi-resource setting introduces new challenges for hierarchical scheduling policies. We provide an algo...

Data centers can lower costs significantly by provisioning expensive electrical equipment (such as UPS, diesel generators, and cooling capacity) for the actual peak power consumption rather than server nameplate power ratings. However, it is possible that this under-provisioned power level is exceeded due to software behaviors on rare occasions and...

There is enormous potential for building-focused applications to improve operation and sustainability, both for classical uses like modeling or fault detection as well as innovative ones like occupant-driven control or grid-aware energy management. We show that a building application stack - that addresses shortcomings of existing antiquated archit...

Mapping sidewalks in urban environments is key in the creation of pedestrian-friendly, sustainable cities. Currently, urban planners are hindered by a lack of information available in a format suitable for the large-scale analysis of sidewalk design. To demonstrate the impact that information technology could have in this area, we leverage techniqu...

A typical large building contains thousands of sensors, monitoring the HVAC system, lighting, and other operational sub-systems. With the increased push for operational efficiency, operators are relying more on historical data processing to uncover opportunities for energy-savings. However, they are overwhelmed with the deluge of data and seek more...

Commercial buildings are attractive targets for introducing innovative cyber-physical control systems, because they are already highly instrumented distributed systems which consume large quantities of energy. However, they are not currently programmable in a meaningful sense because each building is constructed with vertically integrated, closed s...

We develop a vignette of an information-rich energy network with flexible and responsive electrical loads in the form of a domestic refrigerator augmented with a thermal storage system and a supply-following controller that responds to the availability of fluctuating renewable sources. We fully characterize our prototype thermal storage-enhanced re...

Through accurate and dynamic occupancy detection, building actuation systems can fine tune the targets of their actions to better fit the patterns of usage in modern buildings. We outline a method for achieving this through existing wireless infrastructure and present a demonstration of its viability in a corporate environment.

In this paper we present a system called the Energy Lens -- a system that provides deeper, real-time visibility of plug-load energy consumption in buildings. Our initial work focuses on plug-load power metering, display, and real-time aggregation, presented to the user through a mobile phone. We discuss the three main, non-trivial challenges that m...

Many commercial buildings have digital controls and extensive sensor networks that can be used to develop novel applications for saving energy, detecting faults, improving comfort, etc. However, buildings are custom designed, leading to differences in functionality, connectivity, controls and operation. As a result today's building applications are...

In the US buildings consume 70% of electricity, but the sector exhibits little innovation for reducing its consumption. Efficiency is not yet evaluated to the same standard as comfort and reliability, but with better user input, control policy, and awareness of the building's state, energy consumption can be intelligently reduced. It is argued that...

Micro-solar power system design is challenging because it must address long-term system behavior under highly variable solar energy conditions and consider a large space of design options. Several micro-solar power systems and models have been made, validating particular points in the whole design space. We provide a general architecture of micro-s...

Heating, ventilation, and air-conditioning (HVAC) systems use a large amount of energy, and so they are an interesting area for efficiency improvements. The focus here is on the use of semiparametric regression to identify models, which are amenable to analysis and control system design, of HVAC systems. This paper briefly describes two testbeds th...

It is often highly valuable for organizations to have their data analyzed by external agents. However, any program that computes on potentially sensitive data risks leaking information through its output. Differential privacy provides a theoretical framework for processing data while protecting the privacy of individual records in a dataset. Unfort...

A flurry of recent work has examined the interaction between system design and power optimization, with the promise of energy savings. We find that the power consumed by current commodity hardware can be well-approximated by a model with two components: a large always-present constant power and a linear power-performance tradeoff. As a result, many...

We present insights obtained from conducting a year-long, 455 meter deployment of wireless plug-load electric meters in a large commercial building. We develop a stratified sampling methodology for surveying the energy use of Miscellaneous Electric Loads (MELs) in commercial buildings, and apply it to our study building. Over the deployment period,...

Experimentally comparing the energy usage and comfort characteristics of different controllers in heating, ventilation, and air-conditioning (HVAC) systems is difficult because variations in weather and occupancy conditions preclude the possibility of establishing equivalent experimental conditions across the order of hours, days, and weeks. This p...

Improving the energy-efficiency of heating, ventilation, and air-conditioning (HVAC) systems has the potential to realize large economic and societal benefits. This paper concerns the system identification of a hybrid system model of a building-wide HVAC system and its subsequent control using a hybrid system formulation of learning-based model pre...

Buildings are some of the largest energy consumers in the world and yet occupants are regularly dissatisfied with the interior environment in large part due to thermal discomfort [7]. Studies show that given personal control over their environment, occupants are comfortable in a much larger range of ambient temperatures [2]. We present a personaliz...

Cyber-Physical Systems (CPS) are characterized as complex distributed systems exhibiting substantial uncertainty due to interactions with the physical world. Today's electric grids are often described as CPS because a portfolio of distributed supplies must be dispatched in real-time to match uncontrolled, uncertain demand while adhering to constrai...

Heating, ventilation, and air conditioning (HVAC) systems are an important target for efficiency improvements through new equipment and retrofitting because of their large energy footprint. One type of equipment that is common in homes and some offices is an electrical, single-stage heat pump air conditioner (AC). To study this setup, we have built...

Interoperability is key to widespread adoption of sensor network technology, but interoperable systems have traditionally been difficult to develop and test. We demonstrate an interoperable system development and performance diagnosis environment in which different systems, different software, and different hardware can be simulated in a single net...

Interoperability is essential for the commercial adoption of wireless sensor networks. However, existing sensor network architectures have been developed in isolation and thus interoperability has not been a concern. Recently, IP has been proposed as a solution to the interoperability problem of low-power and lossy networks (LLNs), considering its...

Miscellaneous and electronic loads (MELs) consume about 30% of the electricity used in U.S. commercial buildings, but our understanding of their energy use lags the traditional end-uses. A key component of reducing energy use is understanding how devices are used, but few studies have collected field data on the long-term energy used by a large sam...

We report on an experimental case study of personalized lighting controls built on top of an infrastructure designed to enable rapid development of applications in commercial buildings. Our personalized lighting controls (PLC) use an existing standard commercial building lighting automation system and require no new hardware to deploy. PLC presents...

Many applications, ranging from wireless healthcare to energy metering on the smart grid, have emerged from a decade of research in wireless sensor networks. However, the lack of an IP-based network architecture precluded sensor networks from interoperating with the Internet, limiting their real-world impact. Given this disconnect, the IETF charter...

We describe an approach for how to design an essentially more scalable, flexible and resilient electric power infrastructure – one that encourages efficient use, integrates local generation, and manages demand through omnipresent awareness of energy availability and use over time. We are inspired by how the Internet has revolutionized communication...

The variable and intermittent nature of many renewable energy sources makes integrating them into the electric grid challenging and limits their penetration. The current grid requires expensive, largescale energy storage and peaker plants to match such supplies to conventional loads. We present an alternative solution, in which supply-following loa...

With deeply embedded wireless sensors, a new tier of the Internet is emerging that will extend into the physical world. These wireless sensor nodes are expected to vastly outnumber conventional computer hosts as we see them today, but their strict resource constraints are unlike other technologies already common to the Internet. As wireless sensor...

Faced with an uncertain path forward to renewables portfolio standard (RPS) goals and the high cost of energy storage, we believe that deep demand side management must be a central strategy to achieve widespread penetration of renewable energy sources. We examine the variability of wind as a source of renewable, non-dispatchable energy and the load...

Existing routing protocols for sensor networks ei- ther exclusively focus on collection-based traffic, or optimize for point-to-point traffic in a homogeneous network. As these networks become more general, a mix of these workloads in a heterogeneous setting is expected, while still abiding by the resource constraints of low- power and lossy networ...

As more and more physical information becomes available, a critical problem is enabling the simple and efficient exchange of this data. We present our design for a simple RESTful web service called the Simple Measuring and Actuation Profile (sMAP) which allows instruments and other producers of physical information to directly publish their data. I...

Buildings account for a large portion of the world's total delivered energy consumption. With smartphones becoming increasingly ubiquitous and sensor networks growing more mature, buildings can provide personal-ized and context-aware services to an occupant while minimizing energy consumption. This paper proposes the architecture of a Human-Buildin...

AC power meters require both voltage and current to be sampled concurrently to obtain real, reactive, and apparent power. Typically, the two measurements are taken in close physical proximity and fed into a single power metering de-vice. In this paper, we explore the viability of decoupling the voltage and current channels, and placing them in phys...

Energy consumption is a major and costly problem in data centers. A large fraction of this energy goes to powering idle machines that are not doing any useful work. We identify two causes of this inefficiency: low server utilization and a lack of power-proportionality. To address this problem we present a design for an power-proportional cluster co...

Energy consumption is a major and costly problem in data centers. A large fraction of this energy goes to powering idle machines that are not doing any useful work. We identify two causes of this inefficiency: low server utilization and a lack of power-proportionality. To address this problem we present a design for an power-proportional cluster co...

Office buildings contain large sensor network de-ployments to monitor and maintain their internal envi-ronment. They also consume a significant amount of en-ergy. This paper proposes the use of the use of horizon-tal layering, rather than the current vertical-solution ap-proach, to expose the building data plane and enable in-teroporable software s...

We present the architecture, specification, and implementations of a simple monitoring and action profile (sMAP), optimized for sensors, meters, and actuators in building environments. Our architecture is built on HTTP/REST and uses JSON as the object format for interoperability. We implement sMAP on a variety of resource monitors and actuators ins...

We study the utility of dynamic frequency agility in real-world wireless sensor networks. Many view such agility as essential to obtaining adequate reliability in industrial environments. We quantify the actual utility by identifying the two facets of connectivity graphs that yield potential benefits called Multichannel Links (MCLs) and Multichanne...

Summary form only given. In distribution and embedded systems, data compression is often used to reduce the size of flash RAM and transmission data, while a rapid decompression speed enables faster rebooting of the compressed program code. We have developed a new data compression algorithm with a high decompression speed and a good compression rate...

We describe the design, deployment, and experience with a wireless sensor network for high-fidelity monitoring of electrical usage in buildings. A network of 38 mote-class AC meters, 6 light sensors, and 1 vibration sensor is used to determine and audit the energy envelope of an active labo- ratory. Classic WSN issues of coverage, aggregation, sam-...

The system and network architecture for static sensor- nets is largely solved today with many stable commer- cial solutions now available and standardization efforts underway at the IEEE, IETF, ISA, and within many in- dustry groups. As a result, many researchers have be- gun to explore new domains like mobile sensor networks, or mobiscopes, since...

We present the architecture, design, and preliminary evaluation of ACme, a wireless sensor and actuator net- work for monitoring AC energy usage and controlling AC devices in a large and diverse building environment. The ACme system consists of three tiers: the ACme node which provides a metering and control interface to a single outlet, a network...

The United States electricity grid faces significant problems resulting from fundamental design principles that limit its ability to handle the key energy challenges of the 21^st century. We propose an innovative electric power architecture, rooted in lessons learned from the Internet and microgrids, which addresses these problems while i...

A home where every major appliance can be monitored for energy consumption and individually controlled wirelessly has long been a dream of gadgeteers and the green-conscious alike. Research has shown that real-time, per-appliance electricity usage feedback can induce behavior changes that lead to 10% to 20% reduction in usage [2]. We present ACME:...

As the number of wireless devices increase, the frequency spectrum becomes further congested. Deployments of wireless devices in harsh radio environments (i.e. an industrial plant) also motivates the study of alternate communication protocols that offer enough diversity to overcome interference. This work explores the use of frequency diversity to...

A decade ago as wireless sensor network research took off many researchers in the field denounced the use of IP as inadequate and in contradiction to the needs of wireless sensor networking. Since then the field has matured, standard links have emerged, and IP has evolved. In this paper, we present the design of a complete IPv6-based network archit...

We present a building block approach to hardware platform design based on a decade of collective experience in this area, arriving at an architecture in which general-purpose modules that require expertise to design and incorporate commonly- used functionality are integrated with application-specic carriers that satisfy the unique sensing, power su...