# NR5G-SAM: A SLAM Framework for Field Robot Applications Based on 5G New Radio
## 4 Experimental Validation  
In a previous work [16], we developed a realistic simulation testbed that includes an agricultural environment, as shown in Figure 5. We use the Robot Operating System (ROS) ([[https://www.ros.org](https://www.ros.org)]([https://www.ros.org](https://www.ros.org)), accessed on 4 March 2023) for perception and actuation of the field robot, and the Gazebo simulator ([[https://gazebosim.org](https://gazebosim.org)]([https://gazebosim.org](https://gazebosim.org)), accessed on 4 March 2023) with integrated physics engine that generates the ground truth pose and the required raw data from the robot's sensors, including the IMU and wheel odometry. The sensors are modeled with additional Gaussian noise, which is applied to the IMU and wheel odometry measurements. The simulation environment also accounts for elevation, gravity, and other physical properties, whereas the 5G NR radio propagation is generated separately. We have coupled the simulation engine with the 5G MATLAB Toolbox ([[https://www.mathworks.com/products/5g.html](https://www.mathworks.com/products/5g.html)]([https://www.mathworks.com/products/5g.html](https://www.mathworks.com/products/5g.html)), accessed on 4 March 2023) for the 5G NR configuration and signal transmission. A key fact about the rollout of 5G NR is that signal coverage determines the geometry of the gNB locations and is envisaged to be in a grid pattern in structured urban areas, with each station being approximately a kilometer apart from the distributed micro cells. In rural agricultural areas, the gNB deployment geometry may vary depending on the morphology and is envisaged to operate under macro cells. The path loss model used within our simulation is set to the UMa, with the infrastructure height set to 5 m, the environmental height set to 2 m, and being representative of a relatively flat agricultural area, similar to the Gazebo world. The height of the gNBs is set to 25 m and the height of the UE antenna is set to 1 m; it is modeled as an attachment on the robot  
Figure 5: Ground truth trajectory of the robot (depicted in yellow) in the simulated agriculture environment. centered above the base frame \(B\) with known offset. In our experiments, we assume that all stations of the cellular network are synchronized and have the ability to communicate network time information based on a common reference. Two setups have been prepared, where we leverage the 5G NR PRS signals in the FR1 and FR2 frequency ranges. We selected the n78 band with a Sub-Carrier Spacing (SCS) of 60 KHz for the sub-6 GHz (FR1) and the n257 band with SCS 240 KHz for the mmWave (FR2). In the configuration of the 5G NR signal parameters, the PRS depends on the DL-ToA scheme and we configured the carrier slots of each gNB and a carrier frequency of 3.5 GHz for FR1 and 29.5 GHz for FR2. The transmission offset was set to be every one consecutive repeated PRS signal. The modulation scheme for the Physical Downlink Shared Channel (PDSCH) is set to Quadrature Phase Shift Keying (QPSK) and the length of the codewords to be 2 bits per symbol. The cyclic prefix is set to normal, which corresponds to 14 OFDM symbols within a slot. Orthogonal frequency-division multiplexing modulation OFDM is then performed to generate the 5G NR waveforms at each gNB for transmission. The hearability problem [82] is addressed by allocating the PRS resources and PDSCH channel to the slot grid in such a way that no other gNB transmits a signal within the same slot. As a last step, they are received by the robot and extracted by the UEB (as shown in Section 3.2). The simulated robot is a Husky Unmanned Ground Vehicle (UGV) from Clearpath Robotics ([[https://clearpathrobotics.com/husky-unmanned-ground-vehicle-robot](https://clearpathrobotics.com/husky-unmanned-ground-vehicle-robot)]([https://clearpathrobotics.com/husky-unmanned-ground-vehicle-robot](https://clearpathrobotics.com/husky-unmanned-ground-vehicle-robot)), accessed on 5 March 2023).