Device-to-device communications in 5G — known as the lateral link — promise to offer new flexibility and functionality, but their potential range is expected to pale in comparison to the direct mode displays of land mobile radio (LMR) used by public safety responders today, according to National Institute of Standards and Technology research (NISTR). NIST).
The 5G New Radio (NR) side link is expected to support device-to-device communications at a maximum distance of 981.8 meters — less Slightly more than 5/8 of a mile – in an “ideal” outdoor scenario with line-of-sight, based on simulation research (graph in the photo above). More realistic scenarios in the research refer to a device-to-machine range of 644.9 meters (705.3 yards) for a pedestrian user and 582.0 meters (636.5 yards) for an in-vehicle user.
These projected baseline numbers indicate that the 5G NR lateral link will provide band-like functionality for Proximity Services (ProSe) in LTE. ProSe has been largely abandoned as a technology, with Samsung developing the only commercially available ProSe device Support a range of “half a mile maybe”, According to a Samsung official.
Liu noted that the 5G NR sidelink provides several options that can be used to extend device-to-device range, such as increasing the number of transmissions to ensure signal reception. She said the technology can increase range by up to 70%, but also increase latency and reduce data throughput to levels that could render many applications unusable for a first responder.
Liu said during a recorded presentation of the recent PSCR 2022 Broadband Stakeholder Meeting.
“Our results also show that increased scope comes with cost, and careful design is required to balance scale with other service requirements.”
One way to increase the range of device-to-device communications without degrading performance, Liu said, is to take advantage of High Power User Equipment (HPUE), which can transmit the signal at 1.25 watts — more than six times the normal 0.2 watt rate of handheld devices. cellular device. With HPUE operating on the 14 700MHz band spectrum licensed to FirstNet, the device-to-device bandwidth is increased by more than 50%, resulting in an “ideal” scenario providing a range of 1,554.4 metres, or approximately one mile.
But even this HPUE represents a significant reduction in range when compared to the device-to-device communications supported by LMRs, which can use 3 watts to 5 watts of power to send signals. In addition to the additional power, the LMR often operates on a spectrum that provides better signal propagation, and the LMR often has an external antenna, as opposed to the internal antennas found on most LTE devices.
Meanwhile, Liu said the expected 5G side-link range is significantly reduced in scenarios where the devices are not outdoors with a clear line of sight between them, according to unique simulation research.
“As far as we know, our simulator is the first 5G lateral link level simulator that has been developed,” Liu said. “We are in the process of documenting it and plan to release it for public use.”
In outdoor non-line-of-sight (NLOS) scenarios, device-to-device range is expected to be 389.0 meters (425.4 yards) for pedestrian users, while the same scenario would result in device-to-device range of 354.1 meters (387.2 yards) for in-vehicle users, According to simulation research.
Indoors, the maximum expected range is 304.4 meters (332.9 yards), but this assumes a line-of-sight (LOS) scenario, Liu said. Obstacles such as walls will reduce the performance of the internal device of the device, but their exact amount depends on a number of factors, including the materials used in the structure.
The most difficult scenario that the emulator designed was device-to-device communications where one user is outside and the other inside. In this outside-to-inside (O2I) scenario, the range is expected to be 139.0 meters (152.0 yards) among pedestrian users and 126.6 meters (138.5 yards) between users in vehicles.
Several industry sources assert that such limitations in device-to-device communications over LTE or 5G are a major factor in the reluctance of major public safety agencies to move mission-critical voice communications from LMR to wireless broadband solutions. After all, first responders often need to communicate when commercial cellular services are unavailable, because the system is down or because they are operating outside of terrestrial network coverage.
However, with coverage extension technologies such as HPUE and “bring the network with you” deployable solutions—from pelican case form factors to Compact Rapid Deployable (CRD) assets that agencies can own—some are questioning how frequently first responders need connections from device to device in the future.
Another potential factor that could influence this discussion is the development of companies like Lynk Global and AST SpaceMobile, which plan to provide connectivity from a LEO-supported “LTE tower in space” with satellites directly to unmodified smart devices outside the carrier’s ground coverage. . Both companies expect to provide a global service by 2025.