The construction of Low Earth Orbit satellite constellations has recently spurred tremendous attention from both academia and industry. 5G and 6G standards have specified the LEO satellite network as a key component of the mobile network. However, due to the satellites' fast traveling speed, ground terminals usually experience frequent and high-latency handover, which significantly deteriorates the performance of latencysensitive applications. To address this challenge, we propose a parallel handover mechanism for the mobile satellite network which can considerably reduce the handover latency. The main idea is to use plan-based handovers instead of measurementbased handovers to avoid interactions between the access and core networks, hence eliminating the significant time overhead in the traditional handover procedure. Specifically, we introduce a novel network function named Satellite Synchronized Function (SSF), which is designed for being compliant with the standard 5G core network. Moreover, we propose a machine learning model for signal strength prediction, coupled with an efficient handover scheduling algorithm. We have conducted extensive experiments and results demonstrate that our proposed handover scheme can considerably reduce the handover latency by 21× compared to the standard NTN handover scheme and two other existing handover schemes, along with significant improvements in network stability and user-level performance.

The construction of Low Earth Orbit (LEO) satellite constellations has recently spurred tremendous attention from academia and industry. 5G and 6G standards have specified LEO satellite network as a key component of 5G and 6G networks. However, ground terminals experience frequent, high-latency handover incurred by satellites’ fast travelling speed, which deteriorates the performance of latency-sensitive applications. To address this challenge, we propose a novel handover flowchart for mobile satellite networks, which can considerably reduce the handover latency. The innovation behind this scheme is to mitigate the interaction between the access and core networks that occupy the majority of time overhead by leveraging the predictable travelling trajectory and spatial distribution inherent in mobile satellite networks. Specifically, we design a fine-grained synchronized algorithm to address the synchronization problem due to the lack of control signalling delivery between the access and core networks. Moreover, we minimize the computational complexity of the core network using information such as the satellite access strategy and unique spatial distribution, which is caused by frequent prediction operations. We have built a prototype for a mobile satellite network using modified Open5GS and UERANSIM, which is driven by actual LEO satellite constellations such as Starlink and Kuiper. We have conducted extensive experiments, and the results demonstrate that our proposed handover scheme can considerably reduce the handover latency compared to the 3GPP Non-terrestrial Networks (NTN) and two other existing handover schemes.

To improve the accuracy of implant placement in Total Hip Replacement (THR) surgeries, this paper proposes a computer-aided visual system for THR which is composed of a customized acetabular cup, a multi-sensor femoral head trial and a computer for data processing and display. The customized trial is of the same size as the real prosthesis. An image sensor, a gyroscope and an e-compass (including an accelerometer and a magnetometer) are adopted in the femoral head trial. Reference patterns are designed and printed on the internal surface of the cup, whose images are taken by the image sensor for estimation of relative pose and position between the femoral head trial and the acetabulum cup. Two methods of pose estimation are adopted in this system: one based on images and the other based on motion data from gyroscope and e-compass. The efficient perspective-n-point (EPNP) algorithm is used in the image-based pose estimation and achieves a rotation relative error of less than 8% and a translation relative error of less than 10%. The complementary algorithm is adopted in the motion-based pose estimation to smooth the results. Experimental results verified the proposed system.

This paper presents a wirelessly monitoring system for Total Hip Replacement (THR) surgery. This system aims to measure and display the attitude and position of femoral head of prosthetic implant during the surgery. The system consists of two parts: the Sensors Array Measuring System (SAMS) and the display part. The SAMS is composed of a sensors array, signal conditioning circuits, a low power Micro Control Unit (MCU), and a low-power transceiver. The SAMS is designed to measure the contact distribution of the sensors array (which is on the surface of the femoral head) between the surface of the femoral head and the acetabulum of the prosthesis. The data is transmitted wirelessly by a low power transceiver. The display part demonstrates the contact distribution and the attitude of the prothesis in-vivo in 3-D images. The two parts of the system communicate with each other on a RF link at the band of 400MHz. The signal conditioning circuits have been designed and fabricated in 0.18μm CMOS process. The tested results show that the resolution of the signal conditioning circuits is 60.1μVpp (1.35g) with ±100mVpp input and the chip can operate under 1.2V to 3.6V voltage supply for single battery application with 116-160μA power current consumption. The system has been validated by experimental results.