Communication methods have become more complex and feature-filled over time, but the terminology used to describe them has remained strikingly the same. For years, we have spoken about communications networks, or “nets”; one of our most common means of information exchange is the worldwide “Web.” As we move deeper into the 21st century, these descriptors are joined by the word “mesh,” a term poised to become increasingly familiar to public safety personnel.
Let’s consider how mesh networks are already transforming public safety communications and what the future holds for this new technology.
Fixed Mesh
The term “mesh” can describe several related, yet distinctly different technologies. The first, commonly referred to as a fixed mesh system, uses a series of wireless hotspots spread throughout the coverage area to establish public safety access. Much like Internet cafà‚‚s that provide portals to enable data exchange, these dedicated points deliver the means and method to communicate with municipal computers.
Fixed-mesh networks generally rely on permanently mounted devices that act as access points to the network. Typical user devices include laptops with cards that allow communication with the network or mobile data terminals (MDT).
One common application of fixed mesh is the immediate download of information from the field by users into Records Management Systems (RMS). For example, users can update fire inspection information in real time directly into the Computer Aided Dispatch (CAD). This can be critical to firefighter safety in cases where serious violations or changes in hazardous materials storage are discovered. In the past, it may have taken days to bring these records online; now, they are ready to access for the next alarm.
Using mesh technology and grant funding, local government officials in Providence, R.I., established a way for first responders to immediately retrieve critical information, including floor plans. After conducting a cost-benefits analysis, public utility poles were selected as the mounting points for wireless routers, which enable on-the-street access for users. In addition, the system is designed so that if one device ceases to function, another nearby unit picks up the load, a feature commonly called “self-healing,” which provides a built-in backup. Obviously, such redundancy is critical to public safety applications.
The Los Angeles Police Department recently announced it will implement a mesh network designed to improve security at a local housing project. A series of cameras located throughout the property can be wirelessly accessed by laptops in patrol cars, allowing officers to remotely monitor activity. The city plans to expand this capacity to its fire departments units as well, allowing firefighters to receive real-time video during response. In 2006, Detroit used a similar system to augment Superbowl security. Cameras were positioned to protect the stadium perimeter and other sensitive locations.
Coverage of a defined area, as in the above examples, is often referred to as a “canopy,” and acts as a wireless umbrella of sorts. Both Los Angeles and Detroit used 4.9-GHz devices to deliver a broadband path for video. The Federal Communications Commission (FCC) made these frequencies available for dedicated public-safety use in 2002 with such applications in mind. Five years later, this decision is bearing fruit. Complementary technology is also available in other portions of the spectrum; however, frequencies outside the 4.9-GHz range do not require licensure, and are therefore viewed as less secure and potentially more congested-factors that concern the fire, rescue and law enforcement communities.
Providence, on the other hand, chose 2.4-GHz devices with technology that reduced interference, enhanced security and allowed access from moving, rather than stationary, vehicles.
Mobile Mesh
Mobile mesh networks differ in architecture from most conventional systems in that all devices do not require direct access to the main data source, but can connect to each other and essentially piggy-back to any other point in the network.
Traditional radio requires some direct communications pathway from the base to the apparatus, even if that communication is relayed through a dedicated repeater. Most information systems also feature some fixed connection between the host and the client. A CAD server located at the 911 center typically uses telephone lines or fiber to route information to terminals and rip-and-run printers located in fire stations. In these common scenarios, dozens of devices may access information simultaneously, but each works independently.
In a mobile mesh network, every user potentially bears the load, so no expansive (and expensive) infrastructure is required. While relatively new to emergency services, mesh technology has already undergone several generations of design improvements.
One of the more promising private-sector uses of mesh is bringing the Internet to remote areas here and abroad. Properly equipped computers can continuously expand access by relaying information to one another through wireless intercommunication. It’s precisely this capability-the seamless addition of diverse users over a broad geographic area-that makes this technology a promising option for the fire service.
Interoperability may well be the most overused buzzword of the decade; however, the ability to talk to other first responders is a real and serious need. This focus on cooperation was reinforced by the federal government in 2006.
During the past year, agencies were required to complete National Incident Management System (NIMS) training to be eligible for a share of the $1.67 billion worth of grants available in 2007. However, based on the current distribution formula, a significant amount of this funding is slated for a limited number of urban areas, or to activities other than improving communications. Therefore, agencies continue to search for new and cost-effective means of sharing critical information. Here, mobile mesh offers potential.
Past interoperability concerns focused largely on voice communications; both 800-MHz trunking and devices specifically designed to “patch” disparate radios together were considered solutions. Although trunking provides a reliable and robust tool for a wide range of needs, its cost makes it hardly the best choice for occasional users. So-called “black box” solutions that provide short-term relief are better designed for these temporary situations, but typically require direct connection to one radio from every service on scene to operate. Out of necessity, there is a practical limit to the number of frequencies that can be patched.
With mobile mesh, interoperability is accomplished through the use of compatible air cards that provide access to the network. As users are added, they become another node that communicates with other users online. Unlike conventional radio systems, whereby channel loading can be a serious concern, increasing the number of users on a mobile mesh network can actually be a good thing because it adds more distributed relay points. What separates mobile mesh from fixed mesh? Access to the main network is often provided by a temporary device, such as a repeater or a Web portal located in a command vehicle.
Packet-Hop, a company specializing in mobile mesh applications, has demonstrated effective distances of 3,400 feet between users using mobile mesh. While this is considerably less than all but the lowest power radio applications, it applies to the distance between the next closest unit, not to a fixed point. In essence, not needing to rely on a fixed infrastructure allows mobile mesh coverage to extend over a wide area.
Benefits of Mesh
Since mesh networks use broadband technology, they can provide a number of options not normally found in conventional systems, and they can do it quickly. In fact, speed is one of Providence’s reasons for choosing a mesh solution. The city’s former means of wireless data access was extremely slow. A helpful comparison: dial-up Internet access as opposed to use of a cable modem. You can get to the Web by either method, but data certainly moves more quickly using the latter.
Included in this data are several applications of interest to fire and rescue services. We have already mentioned the potential to route real-time video from fixed locations to first responders, but mobile mesh networks allow video mobility as well. Field units can send video to the incident commander (IC) from anywhere on the fireground, whether it is a feed from all four sides of a major structure fire, or from selected sectors of a search and rescue operation.
Options like white-boarding allow feedback from command regarding management of the emergency. Maps and diagrams can be marked up and electronically distributed, in essence providing written orders in the field. Since global positioning system (GPS) tracking can also be enabled, mesh units also support an on-the-fly means of automatic personnel location (APL) to accurately track deployed resources. In fact, mesh can also support tracking that doesn’t rely on obtaining a GPS signal, a significant advantage when tracking personnel inside hardened structures or anywhere else satellites may not be reached.
If connectivity is available (through access to a wireless router, satellite link or open-air network), mesh networks can also provide Internet access. Although the Internet is not a dedicated public safety tool, there’s a wealth of information online that can be used to manage emergencies, including Web-based Emergency Operations Center (EOC) programs, local property records and mapping applications. In fact, some communities like Plano, Texas, are rolling out solutions that provide both secure public safety access as well as Wi-Fi hotspots for the public.
Deploy & Expand
Mesh systems are designed to augment, rather than replace more conventional means of communication. Their strong suits are data and video. Since they use fairly efficient technology, including products originally developed for the broader wireless Internet market, it would appear that the current allocation of frequencies in the 4.9-GHz spectrum will support public safety needs for some time to come. And, because the frequency assignments are in a contiguous section of spectrum, channel reassignment such as that currently underway in the 800-MHz band should not be required.
It is, however, this design that bestows upon mesh networks their greatest value: the ability to quickly deploy and expand. According to Shawn Welsh, manager of Business Development for Motorola’s Mesh Networking Product Group, mesh networks are a “low-site solution” versus the “high-site solutions” normally associated with large and costly fixed hilltop applications. Not only does this translate into reduced investment, but it also increases survivability. Welsh notes, “In the wake of any large natural disaster, you are going to see damage to the traditional infrastructure. Mesh gives you the ability to operate when nothing else is left.”
Time Will Tell
Despite the promise mesh technology provides, there’s little field-tested evidence of its ability. Frequencies allocated for fixed systems have been available for less than a decade, and there are no large-scale mobile systems on which to base our conclusions. Although tests have shown tremendous prospect of mesh networks, public safety users tend to be understandably conservative when choosing technology.
Mesh technology addresses several issues of current concern in communications, such as redundancy and secure access. But it will certainly not replace two-way radio systems as a means of communication anytime soon. However, as a tool for delivering a mixed bag of data quickly at a competitive price, it has the potential for “meshing” well with the needs of the fire and rescue services.
