5G-Based Remote Driving: Facilitating Free Movement of RTGC in Ports

A rubber tire gantry crane (RTGC) is an important vertical transport tool

for container ports, implementing the turnover of containers in the yards. Currently, the driving of RTGC has evolved from on-site control in a narrow cabin hanging under RTGC to remote control in a spacious central operating room, which greatly improves the working conditions of the drivers (Fig. 1). However, remote driving brings a great challenge to network deployment. The network not only needs to meet the requirements of high-bandwidth and real-time transmission of multiple HD videos, extremely low latency and ultra-high reliability of control commands, but also the requirement for RTGC to move at a rate of 15 km/h.

In addition, unlike a rail mounted gantry crane (RMGC) travelling on a fixed railway, RTGC does not run in a full straight line, and more importantly, RTGC needs to be transferred between different container areas and yards, so the wired connection based on fiber can't be adopted.

At present, a typical solution in the industry is to use the WiFi network based on a waveguide, that is, the WiFi signal is transmitted along the tube of waveguide fastened to the ground, and the WiFi signal leaks out through the gaps of the tube. This method avoids direct connection of cables, however, due to the weak leakage signal, RTGC must travel along and close to the tube, which limits its range of movement. In addition, the WiFi waveguide solution still has the following problems. First, the transmission distance of a waveguide is normally less than 50 meters, and during travelling, RTGC needs to switch between different waveguides, which may cause interruption of signal transmission. Second, when the signals of several RTGCs are transmitted in the same waveguide, the service quality may be degraded because of the conflict mechanism of WiFi channels. Third, when a RTGC needs to be transferred between different container areas and yards, the tube of waveguide cannot cross a road, and in this case, remote driving cannot be implemented.

For its large uplink bandwidth, low latency, high reliability, network slice isolation, and precise SLA guarantee, 5G has attracted the attention of port owners and has been widely adopted in port scenarios. However, for the remote driving of RTGC in the port, the 5G network still faces the following challenges: the large uplink bandwidth caused by the backhaul of multiple HD videos, the low network latency and high reliability required by the two-way transmitting and receiving of control commands, and the concurrent services caused by the remote control of multiple RTGCs at the same time. ZTE's port-oriented 5G remote driving solution now is at the forefront of the industry and has overcome the above difficulties by introducing key technologies and solutions such as SuperMIMO, SuperCell, I-frame collision elimination, frame replication and elimination for reliability (FRER), and local traffic offload function (TOF) based on NodeEngine, a base station with embedded computing engine.

The real-time backhaul of HD videos of RTGC remote control requires a network with large uplink bandwidth capability. Generally, there are two to four RTGCs deployed in a 400-meter container area, and each RTGC has four to six HD video cameras for video backhaul. Therefore, there are totally 24-channel HD videos at the same time. Considering the probability of I-frame collision, the maximum uplink instantaneous rate can reach over 250 Mbps. Taking the bandwidth of 100M in the 3.5G band of ITU as an example, an uplink bandwidth of 180–200 Mbps can be provided in practical applications, which cannot fully meet the transmission requirement. ZTE's SuperMIMO can eliminate cell boundaries through the multiple-input multiple-output antenna technology and improve spectrum resource utilization through the space division multiplexing technology. The maximum cell capacity can be increased by four times, effectively meeting the requirement for large uplink bandwidth for HD video backhaul of RTGC.

The transmission of remote control commands for RTGC requires a network with very low latency and very high reliability. Generally, the bidirectional transmission delay of control commands is required to be less than 20 ms, and the reliability is required to be above 99.99%. This is a challenge for conventional 5G coverage. Especially when a RTGC travels at the edge of a cell or frequently switches between multiple cells, the signal quality may be degraded, which may increase the transmission time and retransmission times of control commands significantly, and the quality of service may be affected in a severe case. The SuperCell technology provided by ZTE can eliminate inter-cell interference, expand cell coverage, reduce cell handover times, and greatly meet the low latency and high reliability requirements of control commands by combining multiple adjacent cells into a logical cell.

Moreover, ZTE's unique NodeEngine, self-developed function software, and industrial grade edge gateway can enhance the 5G capability for RTGC remote driving. For example, the I frame collision cancellation technology is used for video optimization. By optimizing video encoding and decoding algorithms on the edge gateway, the periodic I-frame design can be cancelled. Alternatively, an AI application can be deployed on NodeEngine to identify the cameras with I-frame collisions and provide suggestions on adjusting the I-frame period, so as to greatly reduce the instantaneous impact of video on network bandwidth. For control commands, the FRER technology is used to realize the function of dual-

transmission and optimal-receiving, which means that the same signal is sent to NodeEngine through two different frequencies on the edge gateway, and the FRER software selects the optimal receiving signal. This greatly reduces the risk of dependence on the signal quality from a single frequency. At the same time, the FRER function based on different frequencies also avoids the problem of simultaneous cell handover on different frequencies in the overlapped coverage area, and solves the pain points of RTGC remote driving when crossing a road between different container areas in the yard. In addition, the local traffic offload function of NodeEngine can quickly offload RTGC remote driving traffic from the base station side to the local campus, avoiding the traffic passing through the core network UPF, thereby reducing the network latency to less than 10 ms. The local traffic offload function of NodeEngine and the traffic offload function of the core network UPF can inter-backup to increase the robustness of the network.

ZTE's 5G-based remote driving solution is being trialed and verified in some ports in China. This technology can be used not only for remote driving of RTGC, but also for remote driving of RMGC, quayside container crane (QC) and intelligent guided vehicle (IGV) in the ports. In addition, as a universal remote control technology, the 5G-based remote driving solution can also be widely used for remote control of electric traveling crane in steel and metallurgy, as well as remote driving of unmanned mining trunk in mines. This solution has a wide application prospect.