By Andy Dachs
Tait Communications
When your frontline staff encounters trouble, knowing their location and status in real time could be the difference between life and death.
The pressure is on every public safety and utility organization to know exactly where workers and assets are deployed at all times. The drivers for location data are not only health and safety. Location services can also help streamline workflows and improve organizational efficiency.
Thanks to Smartphones; GPS modules and applications like Google Maps™ are now standard features of life. It raises the question: why has this technology not transferred completely into the professional mobile radio market? What is different about the workplace and why do so many PMR systems under-deliver in these location services?
The answer is complex but it’s possible to find some common causes. Foremost is the fact that while consumer technology provides high resolution information about the location of a single device, enterprise applications monitor the location of large fleets of users. Secondly, the information is needed back at a control centre, not just at the user device, which requires a communications channel. That channel is constrained by availability, data rates and cost. The third major difference is the sensitivity of the information. Real time location information about public service personnel has to be protected. Together, these requirements translate into large volumes of time-critical data flowing through encrypted radio networks.
To get an understanding of how these factors interact we can group location-based applications for enterprise into three categories, each with its own requirements on location data accuracy and immediacy:
- Situational awareness applications: These are large scale moving maps, providing a low resolution view of the current location of people and vehicles. They often include the ability to zoom in, or select an individual to learn more about their status. Situational awareness requires moderate location data accuracy and immediacy.
- Safety applications: These provide real time, high resolution tracking of specific vehicles or people when they are in dangerous situations. Accuracy and immediacy are paramount.
- Post-event logging and analysis applications: These are non-real-time applications that require access to a moderately accurate, time stamped archive of location and event data.
If we dig deeper into the requirements of accuracy and immediacy, we find that even their definitions will vary between organizations. For most organizations location data only really becomes useful when it is associated with an event such as the door of a vehicle opening or a crew arriving at a situation. The number of event types and their required precision (in time and location) can only be established with a deep knowledge of their operational significance. Failure to fully understand organizational requirements can lead to systems that fail to employ bandwidth efficiently.
Whatever the organization’s requirements, location data is carried over the network from the radio to the command centre as a stream of short messages and there is an important trade-off to be made between business as usual and emergency requirements. It is clear that constantly capturing location data at maximum accuracy and immediacy would require an un-necessarily large and expensive system. Conversely, failure to provide enough capacity for the worst case situations can lead to network failures at the worst possible moment.
Although designing a robust network with capacity for location based data is challenging, it can be mastered. The key is making sensible trade-offs to reduce the amount of data gathered while still meeting the organizational objectives, and to design for stable and predictable behaviour under over-load conditions.
Examples of the trade-offs that can reduce data traffic are to only send updates when the location is no longer as was predicted by a proven model, or when a significant event occurs, such as a vehicle’s bucket arm being raised. The level of operational predictability will vary between organizations. For a linesman inspecting lines, or for a security patrol following a known route, location can be highly predictable and any variance from the expected location can be a useful trigger for a location and status update.
Designing for robust network support of location services requires that worst case scenarios are taken into account and mechanisms are put in place to deal with them when they occur. Emergency responses mean large teams are deployed simultaneously. This can cause location data overload within a geographic area. It is important to recognise that these events do occur and to plan for them. One solution is to make several different location service profiles available for activation under different scenarios. A level of automatic load-shedding may also be appropriate to keep voice services intact throughout any event. The deployment of a high quality network management system, providing full control of network usage, is an import step in the right direction.
In summary, communications systems are being developed to deliver accurate location information while leaving priority services such as voice intact. Sharing a radio link, particularly a narrowband one, between multiple streams of voice and data does demand trade-offs. Making the right trade-offs requires a deep understanding of the organizational needs as well as of the communication technology carrying the data. Tait continues to work with customers to find optimized solutions to this complex challenge.
