Qualcomm’s 5G vision is to intelligently connect virtually everything around us, enabling new applications for a wide range of devices, services, and deployments. Sidelink, or device-to-device connectivity, is an important piece of this vision, particularly for public safety and other safety-critical communications.
Sidelink is a direct device-to-device and device-to-network topology standardized by 3GPP, that supports direct communications between two or more devices even when cellular network coverage is absent. It expands cellular system coverage and introduces much-needed public safety capabilities.
Last week at the IWCE 2023 conference, we explained how 5G can make cities safer, smarter, and more efficient, and explained what 5G sidelink brings to the table for push-to-talk (PTT) and other device-to-device communications use cases. Let’s walk through some of the key points we made at the event, showing how our technologies are solving critical communications issues for public safety personnel.
5G sidelink significantly improves today’s PTT solutions
Removing communication silos and achieving economy of scale
5G sidelink allows first responders to communicate directly to one another in all locations — especially areas cellular network coverage is unavailable — including in sub-basements, within concrete-reinforced walls, and in remote wildfire zones (see Figure 1). Since sidelink does not require a centralized network controller used in traditional cellular networks, it’s available even when wide-area network coverage is unavailable or temporarily overloaded during times of extreme demand. As a globally standardized technology, 5G sidelink brings inter-vendor, cross-network interoperability, which can enable personnel from disparate public safety agencies to directly communicate with one another over the air. Leveraging the mature mobile ecosystem also can provide economy of scale benefits, resulting in reduced equipment costs.
Extending wide-area network coverage
Another key benefit of 5G sidelink is its ability to expand wide-area network coverage by supporting a multi-hop mesh device network architecture (see Figure 2). Even when a first responder is out of coverage (e.g., in a sub-basement), that first responder can still communicate with the command center via an intervening 5G sidelink-capable radio. The sidelink channel extends wide-area network coverage beyond the traditional boundary, and devices in coverage can act as a network relay to/from the wide-area network.
For instance, a first responder with a sidelink-enabled device fighting a wildfire in a remote area can still communicate to the on-site command center located on a nearby fire truck. This is enabled through multi-hop connections using other sidelink-enabled devices that are sufficiently close to one another and the command center. The sidelink device could vary from a PTT radio to a wearable device capable of monitoring and sharing a first responder’s vital-sign data (e.g., heart and breathing rates) and environmental data (e.g., air quality) with nearby colleagues, as well as the command center.
We have showcased that sidelink device relays can support dynamic routing based on channel conditions and provide timing sources to out-of-coverage (e.g., indoor) devices that do not have access to the satellite navigation system. Furthermore, this communication can take place without much battery drain as the distance to the “next hop” can be short, allowing mobile devices to conserve precious battery resources.
These multiple configurations make sidelink a crucial communications capability for first responders. Whether fighting a wildfire in a remote area or office building, or responding to a robbery or hostage situation in a building sub-basement, sidelink can provide first responders with reliable, low-latency communications in areas where land mobile radio and cellular coverage are not available.
Delivering new services beyond voice
While a 5G sidelink-enabled device can support important services such as PTT voice communications, its mobile broadband heritage also brings new opportunities to support additional services such as live video broadcasting, precise positioning, and in the near future, radio frequency (RF) sensing — technology that uses radio signals and their reflections to capture the surrounding details — to enhance situational awareness for first responders at the scene of an emergency. Since 5G sidelink is designed to seamlessly coexist with wide-area mobile networks, its quality of service (QoS) can be ensured by coordinating prioritized access to public safety services over secondary services like mobile broadband, even when they use the same spectrum band.
Spectrum readiness in 4.9 GHz in the United States
In the United States, the 4.9 GHz band (4940-4990 MHz) is allocated for public safety uses. The Federal Communications Commission (FCC) recently released a Report and Order and Further Notice of Proposed Rulemaking outlining a new approach to managing this spectrum.
This new approach solidifies the 4.9 GHz band's primary status as public safety spectrum, ensuring it remains available to first responders during emergencies. At the same time, the FCC recognizes the need for secondary, non-public safety use cases. Permitting commercial applications on a secondary basis will help reduce device costs for all users and enable valuable low-power device-to-device connections for countless new applications, including local sharing of media and walkie-talkie applications.
What’s next?
5G sidelink offers tremendous potential (see Figure 3) for improved public safety services and critical communications. Its direct device-to-device communication capabilities, range extension, and interoperability benefits can significantly enhance emergency response efforts and enable new use cases. With the FCC's recent decision to allow public safety licensees to more intensively use the 4.9 GHz spectrum band, the potential for 5G sidelink in public safety and broader commercial use cases is becoming more tangible. 5G sidelink holds the promise of further enhancing public safety operations and enabling new applications. As a result, stakeholders across the public safety community and wireless industry should work together to realize the full potential of 5G sidelink and bring its benefits to the public at large.
