Small Cells Have Big Role in Mission-Critical Communications

By Ken Rehbehn

Principal Analyst, CritComm Insights, @krehbehn

Communications is an integral element of successful public safety operations. Law enforcement, firefighting and emergency medical operations all demand high quality, reliable communications for rapid and effective mission execution. Voice communications remains the linchpin for operations thanks to the effectiveness of speech that is heard by all personnel at the same time. Speaking into a microphone on a push-to-talk system is largely hands-free, eyes-free and rapid to use. So how is this well-honed capability changing and what role will the small cell play?

While trusted voice communications remain essential, voice communications suffer from inherent limitations in the volume of information that can be transmitted. At approximately 100 words a minute over a dedicated voice channel, there are clear limits to the amount of detail that can be communicated with voice during an emergency. Supplementing mission-critical voice communications with rich data sources made possible by LTE helps round out the feature set emergency services workers required for state-of-the-art incident response.

Around the globe, governments are adding mission-critical LTE resources to the public safety communications toolkit. The old LTE data service model restricted to best-effort consumer-grade offerings is now joined with new service models featuring mission-critical voice, video and data functionality buttressed with Quality of Service (QoS), priority and preemption mechanisms. Forward-looking nations — including the US, the UK and Korea — are pressing these new mission-critical LTE services into service. The FirstNet by AT&T offer in the US is a prime example of how mobile network operators can incorporate this critical government traffic into a large-scale commercial network operation.

Though most mission-critical LTE networks will be hosted as part of a large mobile network operator’s system, the public safety dimension introduces additional requirements not typically addressed by MNO deployments. Ensuring LTE signal coverage in remote corners of building structures, including below-grade portions, means that supplemental in-building coverage becomes essential. The outdoor environment, as well, needs additional coverage in regions with low population density. While no paying subscribers may be on a remote mountaintop, a crisis can bring in many emergency responders needing coverage during the time of the incident response.

Small cells are an ideal solution for both of these public safety coverage gaps. The form factor and low transmission power offered by small cells make the units an excellent LTE signal source for in-building distributed antenna systems. Likewise, the light weight of these units means they can be readily incorporated into deployable cell sites that are transported by hand, helicopter or vehicle. Small cell products for the public safety market have already appeared. Airbus SLC, Ericsson, Huawei, Motorola Solutions, Nokia, and Parallel Wireless have all introduced deployable public safety LTE nodes. Some are traditional small cells designed for a fixed location while others are in backpack or mobile vehicle configurations.

For the next few years, public safety voice systems will remain hosted on legacy narrow-band networks that operate as analog or digitally-trunked systems. The goal, however, is that the rich multimedia capabilities of LTE can drive the convergence of the mission-critical voice to a single mobile broadband network. Moreover, while significant challenges remain ahead — most notably, finding a viable solution the difficult direct mode communication problem — LTE is the future. Getting there, however, calls for small cells playing a fundamental role in these systems that save lives and property.