Demo Abstract: Applications on theSignpost Platform for City-Scale Sensing

Joshua AdkinsUniversity of California, Berkeley

Branden GhenaUniversity of California, Berkeley

Neal JacksonUniversity of California, Berkeley

Pat PannutoUniversity of California, Berkeley

Samuel RohrerUniversity of Michigan

Bradford CampbellUniversity of Virginia

Prabal DuttaUniversity of California, Berkeley

ABSTRACTCity-scale sensing holds the promise of enabling deeper insightinto how our urban environments function. Applications such asobserving air quality and measuring traffic flows can have powerfulimpacts, allowing city planners and citizen scientists alike to under-stand and improve their world. However, the path from conceivingapplications to implementing them is fraught with difficulty. A suc-cessful city-scale deployment requires physical installation, powermanagement, and communications—all challenging tasks standingbetween a good idea and a realized one.

The Signpost platform, presented at IPSN 2018, has been createdto address these challenges. Signpost enables easy deployment byrelying on harvested, solar energy and wireless networking ratherthan their wired counterparts. To further lower the bar to deployingapplications, the platform provides the key resources necessary tosupport its pluggable sensor modules in their distributed sensingtasks. In this demo, we present the Signpost hardware and sev-eral applications running on a deployment of Signposts on UCBerkeley’s campus, including distributed, energy-adaptive trafficmonitoring and fine grained weather reporting. Additionally weshow the cloud infrastructure supporting the Signpost deployment,specifically the ability to push new applications and parametersdown to existing sensors, with the goal of demonstrating that theexisting deployment can serve as a future testbed.

1 SIGNPOST PLATFORMThe Signpost platform, presented at IPSN 2018 [1], is designed toenable fined-grained, city-scale sensing by embracing deployabilityand providing the key services necessary for generic sensing tasks.The use of solar energy-harvesting and wireless networking allowSignposts to be placed throughout a city using a simple, two-boltattachment mechanism. Sensor modules, which plug into any ofthe five generic sensing slots, are provided with power and canaccess networking, storage, time, location or local Linux processingthrough a standard software API. As shown in Figure 3, the librarywhich provides access to these resources supports common embed-ded computing platforms such as Arduino, Mbed, or Tock, and caneasily be ported to support other software environments.

For questions email adkins@berkeley.eduSoftware and hardware is open source at github.com/lab11/signpost

IPSN ’18, April 11–13, 2018, Porto, Portugal

Figure 1: Left: A deployed Signpost. Right: Desktop devel-opment kit. The Signpost can be easily installed on sign poststhroughout a city. It provides power to its pluggable sensor mod-ules through solar energy harvesting and makes other servicesavailable through a standard software API. The desktop develop-ment kit emulates a Signpost, allowing for easy development ofnew sensor modules and city-scale sensing applications.

While the combination of multiple sensor modules and con-strained resources creates problems with service availability, theSignpost platform includes mechanisms for measuring resourceusage and isolating sensor modules that use over their fair shareof available resources. Additionally, API calls are provided to helpsensor modules adapt to the varying amounts of harvested energy.

1.1 Development PlatformTo facilitate the bring-up of modules before deployment, we intro-duce a “desktop” development version of Signpost that enables theemulation of constrained resources and provides more traditionaldebugging aides. The desktop version is designed to represent theconditions experienced by modules on a deployed Signpost, suchas limited energy and network bandwidth budgets.

1.2 Cloud InfrastructureIn addition to local resources, the Signpost API also provides astandard way of interfacing with deployed sensor modules from thecloud. The API exposes a generic pub/sub interface, and users cansubscribe to sensor module topics (if they have proper permissions)for further data storage and processing. The internals of this API

To the extent possible under law, the authors have waived all copyright and related or neighboring rights to this work. This work is published from the United States.

IPSN ’18, April 11–13, 2018, Porto, Portugal Adkins, Campbell, Ghena, Jackson, Pannuto, Rohrer, and Dutta

ElectricalIsolation

SharedData Bus Power

Figure 2: Signpost software architecture. Sensor modules onthe Signpost platform are provided with power, networking, stor-age, time, location, and local Linux processing. These services areavailable through a standard software API over a shared (I2C) databus. Currently the API supports Arduino, Mbed and Tock program-ming environments. Signpost includes mechanisms to measureresource utilization and electrically isolate sensor modules usingover their fair share of platform resources.

automatically select the best networking interface based on currentconnectivity and power constraints.

Application installation and updates are also enabled by thisAPI, and Signpost uses its on board storage and dedicated controlmodule to ensure reliability during the update process. We believethese considerations will allow the Signpost platform to enable afuture city-scale sensing testbed.

2 DEMOIn addition to showing several running Signposts and desktop de-velopment modules, we will demonstrate a deployment of 20 Sign-posts on UC Berkeley’s campus. These Signposts will be runningseveral applications including traffic flow monitoring using theaudio-volume sensor and periodic weather reporting based on theenvironmental sensor. Further, we will show how these applicationscan be distributed across the deployment and how they can adaptto save energy with little compromise on sensing ability.

We will also show the features of the cloud infrastructure, focus-ing on how a user of the system would update a Signpost with newapplications and collect data from published sensor streams.

Figure 3: Signpost Signpost Deployment Locations. The cur-rent (darker green) and proposed (lighter orange) deployment loca-tions for the Signpost platform on UC Berkeley’s campus. We willuse these signposts to demonstrate several applications includingenergy-adaptive traffic flow monitoring and individual weatherreporting.

3 ACKNOWLEDGMENTSThis work was supported in part by the CONIX Research Center,one of six centers in JUMP, a Semiconductor Research Corporation(SRC) program sponsored by DARPA, and in part by Terraswarm,an SRC program sponsored by MARCO and DARPA. Additionally,this material is based upon work supported by the National ScienceFoundation Graduate Research Fellowship Program under grantnumbers DGE-1256260 and DGE-1106400, NSF/Intel CPS Securityunder grant 1505684, and generous gifts from Intel.

We would also like to thank our anonymous reviewers for theirinsightful feedback, our shepherd Neal Patwari, and the many col-laborators that helped make this work possible. Specifically AmitLevy and the Tock development team for their support in usingan under-development operating system, Anthony Rowe, CraigHesling, and Artur Balanuta for LoRaWAN gateway hardware andsupport, William Huang for designing the environmental sensingmodule, Yifan Hao for designing the radar module, Theo Miller forporting the software library to Arduino, Justin Hsieh for work onthe communication protocol, Ken Lutz for helping with deploymentlogistics, and Noah Klugman for help with Signpost assembly.

REFERENCES[1] Joshua Adkins, Branden Ghena, Neal Jackson, Pat Pannuto, Samuel Rohrer, Brad-

ford Campbell, and Prabal Dutta. 2018. The Signpost Platform for City-ScaleSensing. In The 17th ACM/IEEE Conference on Information Processing in SensorNetworks (IPSN’18).

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