Five Alarms: Assessing the Vulnerability of US Cellular Communication Infrastructure to Wildfires Scott Anderson Carol Barford Paul Barford [email protected] [email protected] [email protected] University of Wisconsin—Madison University of Wisconsin—Madison University of Wisconsin—Madison ABSTRACT KEYWORDS Natural disasters can wreak havoc on Internet infrastructure. Cellular infrastructure risk, Climate change, Wildfires, Geo- Short term impacts include impediments to first responders graphic Information System; Physical Internet Infrastructure and long term impacts include requirements to repair or 1 INTRODUCTION replace damaged physical components. In this paper, we Assuring robust service availability in communication sys- present an analysis of the vulnerability of cellular communi- tems is a complex task. It requires, among other things, a cation infrastructure in the US to one type of natural disaster broad and thorough understanding of a wide range of threats – wildfires. Three data sets are the basis for our study: histor- including threats to physical infrastructure e.g., buildings ical wildfire records, wildfire risk projections, and cellular that house equipment, fiber conduits, overhead wiring, and infrastructure deployment. We utilize the geographic fea- cellular antennas and towers. Understanding the nature of tures in each data set to assess the spatial overlap between such threats, including probability, scope and potential im- historical wildfires and cellular infrastructure and to analyze pact, enables providers to take appropriate steps to mitigate current vulnerability. We find wide variability in the num- risks. ber of cell transceivers that were within wildfire perimeters Natural disasters and weather-related phenomena are clear over the past 18 years. In a focused analysis of the California and present dangers to deployed communication infrastruc- wildfires of 2019, we find that the primary risk to cellular ture. Examples of events that have had wide-ranging impact communication is power outage rather than cellular equip- on communications include hurricanes [14], earthquakes ment damage. Our analysis of future risk based on wildfire [13], floods and thunderstorms27 [ ]. A distinguishing feature hazard potential identifies California, Florida and Texas as of these threats is that they can damage or destroy physical the three states with the largest number of cell transceivers communication infrastructure resulting in potentially sig- at risk. Importantly, we find that many of the areas at high nificant downtime and significant costs to repair. Another risk are quite close to urban population centers, thus outages feature of these threats is that while they may not directly im- could have serious impacts on a large number of cell users. pact communication infrastructure, they can damage critical We believe that our study has important implications for infrastructure in close proximity (e.g., power transmission governmental communication assurance efforts and for risk systems), which can lead to communication outages. planning by cell infrastructure owners and service providers. In this paper, we assess the risks of one particular natural disaster threat to a critical aspect of today’s communication CCS CONCEPTS infrastructure. Specifically, we assess how wildfires pose risks • Networks ! Physical links; Mobile networks. to cellular communication infrastructure in the continental US. Over the past several years, wildfires have made head- lines by wreaking havoc in different parts of the world – in particular eastern Australia and the western US. Unfor- tunately, the probability for future large-scale wildfires is Permission to make digital or hard copies of all or part of this work for exacerbated by climate change [22]. We focus on cellular personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear infrastructure due to its intrinsic importance in day-to-day this notice and the full citation on the first page. Copyrights for components life and due to the fact that cell transceivers and towers, of this work owned by others than ACM must be honored. Abstracting with unlike other elements of Internet infrastructure, are above credit is permitted. To copy otherwise, or republish, to post on servers or to ground and thus potentially at risk of damage by wildfires. redistribute to lists, requires prior specific permission and/or a fee. Request Our work is further motivated by the fact that planning and permissions from [email protected]. emergency response for wildfire effects on communication IMC ’20, October 27–29, 2020, Virtual Event, USA © 2020 Association for Computing Machinery. infrastructure is not well understood [25]. ACM ISBN 978-1-4503-8138-3/20/10...$15.00 There are several key challenges in wildfire risk assess- https://doi.org/10.1145/3419394.3423663 ment for cellular infrastructure. First, cellular infrastructure in the US is vast and highly diverse, and cellular service due to wildfires is an equally important risk consideration. providers do not typically publish details on their infras- This work raises no ethical concerns. tructures. Second, as discussed in Section 2.1, wildfires are a 2 RISK ASSESSMENT complex phenomenon that include unpredictable elements In this section, we provide an overview of the general aspects such as ignition. Third, some predicted future climates have of wildfires and how they pose a threat to communication in- no analog among present day climates, which makes future frastructure. We describe the data sets and methods we use to wildfires difficult to predict. Any risk analysis must address assess wildfire risk to cellular communication infrastructure. these challenges and generate results that provide detailed, actionable guidance whenever possible. 2.1 Overview of Wildfires We address these challenges in this first-of-its-kind study by applying geospatial analysis to three data sets. The first Wildfires are fires, either naturally ignited or resulting from is the crowd-sourced database provided by OpenCelliD [7] human activity, that burn wild vegetation. They most often that includes locations of over 5M cellular transceivers in occur in unpopulated or sparsely populated areas and are a the US. The second is the historical wildfire record in the common occurrence in many areas of the world, including US. [5] This data set provides details on wildfires that have the western and southeastern US. Many ecosystems depend occurred over the past 18 years including dates and perimeter on periodic wildfires to maintain stability of various plant locations. The third is the Wildfire Hazard Potential (WHP) and animal species. Wildfires depend on a source of igni- [15] data set which identifies potential locations and probable tion and fuel. The ignition source is most commonly either occurrence of wildfire in the US in the near future. In addition, lightning strikes or human activity including sparks from we consider models of wildfire potential that include the power transmission lines, embers flying away from camp- projected impact of climate change through the year 2080. fires, or sparks from metal objects. Fuel is mainly in theform We utilize the geographic features in each data set to assess of dead vegetation or dry living vegetation. Most wildfires the overlap between wildfires and cellular infrastructure and are quickly contained, either by naturally burning the lim- to project future vulnerability. ited available fuel in the immediate area or through actions Our analysis of the historical correspondence between by first responders. wildfires and cellular infrastructure shows wide temporal Despite these efforts, a small number of wildfires escape variability in the number of cell transceivers that were within initial containment and can burn through tens or even hun- wildfire perimeters during the past 18 years. In a focused dreds of thousands of acres of wildlands. This occurs when analysis of the California wildfires of 2019, we find that over weather conditions work against firefighters: winds blow 800 cell sites were down during the peak of the fires and burning embers to new fuel sources, dry fuel is readily avail- that the primary cause of disruption was power outage rather able, or shifting winds quickly change the fire’s spread. Al- than tower damage. While power can generally be restored though these large fires can have devastating effects onthe in a matter of days, longer term effects were due to tower ecosystem or even human health through smoke traveling repair and rolling blackouts to limit the fires’ impact. to populated areas, most often they do not directly affect Our analysis of future risk based on WHP indicates that critical infrastructure, which is concentrated in more urban over 430,800 cell transceivers are within moderate to very areas. high risk areas for wildfires. The aggregate populations of Society takes many preventive measures to limit the im- the areas served by these transceivers is over 85 million pact of wildfires on infrastructure, including forest vegeta- indicating that the potential impact on users is significant. tion management, fire breaks, and fire watches. Additionally, We find that California, Florida, and Texas are the three there are often limits to human activity in fire-prone regions states with the largest number of cell transceivers at risk. during certain weather conditions and, infrequently, even We that