As an emerging technique, unmanned aerial vehicle (UAV) aided multi-access edge computing (MEC) network has been improving the performance of the communication network. The novel architecture is beneficial for coverage, flexibility, and reliability. However, reducing network latency is a critical issue. In this paper, we design a UAV-aided network with a millimeter wave (mmWave) backhaul to achieve the multi-access edge computing. The routing problem is formulated and solved first to obtain the optimal routes through the ad hoc link for all users. Then, we formulate the joint trajectory design and resource allocation problem, which is a mixed-integer nonconvex programming, to minimize the network latency. Furthermore, we design a novel iterative algorithm framework to handle this challenging problem. In the outer loop, the proposed problem is separated into the primal problems and master problems by adopting generalized benders decomposition (GBD). In the inner loop, we design the algorithm to solve the continuous nonconvex primal problem by combining the alternating direction method of multipliers (ADMM), Dinkelbach algorithm, and successive convex approximation (SCA) algorithm. The simulation results demonstrate that our proposed algorithm framework is effective and feasible.

The performance of seismic exploration instruments directly affects the quality of acquired seismic data as well as the efficiency of seismic survey operation. Consequently, they play a pivotal role in oil/gas and mineral resource exploration. Compared with traditional cabled seismic acquisition systems, nodal seismic acquisition systems have the advantages of light weight, small size, low capital and operational cost, reduced health safety and environment risk and strong adaptability to complex terrain environment. Therefore, they have been widely used in seismic exploration and have shown a trend of accelerated development. The major manufacturers have carried out research and development of nodal instruments, and various types of nodal seismographs have appeared. Based on the investigation of influential nodal seismographs, we summarize the research status of nodal seismographs. Based on different wireless monitoring capabilities and data harvesting modes, we classify the nodal seismographs into a shoot-blind system, semi-blind system, real-time system and enhanced real-time system. We discuss structural principles and key technologies of the four types of nodal seismographs, analyze their characteristics and predict their future development directions. Focusing on node data quality monitoring, we discuss the application of communication technologies, such as Bluetooth, Wi-Fi, ZigBee, Long Term Evolution, and satellites in nodal seismographs in detail. Furthermore, we analyze and evaluate three main networking architectures including planar multi-hop networks, hierarchical cluster networks and hybrid networks, and sum up the research progress of wireless routing algorithms and large-scale seismic data real-time harvesting methods. Finally, the latest applications of nodal seismographs in energy and mineral resource exploration, geological environment monitoring, urban subsurface space survey and novel seismic technologies are covered. As research on the application of micro-electro-mechanical systems technology, cloud computing, 5G, Internet of Things, edge computing, machine learning and robotics in nodal systems deepens, the performance of nodal seismographs will be greatly promoted.

A new doubly balanced drain-pumped topology for CMOS passive mixer design is proposed in this paper. In the efforts to improve the conversion loss of passive balanced mixers, the CMOS drain-pumped topology is employed. In addition, the doubly balanced architecture with the advantages of good port-to- port isolations has been combined with the CMOS drain mixer de- sign. For the broad bandwidth and the flatness of the conversion loss, a wideband matching technique using a broadband Marchand balun network is analyzed and successfully implemented in the mixer design. This mixer is fabricated in standard 90-nm CMOS technology. According to experiment results, the mixer has a measured conversion loss of 7.5 ± 1.5 dB from 33 to 58 GHz. Based on the double-balanced architecture, the local oscillator (LO)-to-RF and LO-to-IF isolations are better than 42.7 and 51.5 dB, respectively. The mixer consumes zero dc power with a compact size of 0.55 × 0.52 mm². To the best of our knowledge, this paper presents the first CMOS drain mixer using doubly balanced topology.

Large numbers of seismic channels and high-density energy-efficient acquisition systems are the development trend of seismic instruments and have attracted high R&D interests in recent years. The combination of remote sensing and wireless sensor network technology provides superior observation capabilities for high-density seismic exploration. However, large-scale and multi-node acquisition methods place higher requirements on time synchronization performance. Seismic data with poor time synchronization will cause considerable errors in the interpretation of seismic data and even have no practical significance. Thus, the strict time synchronization performance is the prerequisite and basis for the application of cable-less storage seismograph in high-density seismic array applications. The existing time synchronization methods have high power consumption and poor time synchronization accuracy, which is not suitable for the long-time task. In addition, these methods are affected by the number of nodes and the distance. This paper presents an energy-efficient time-sharing indexed interpolation intercept method for the seismic data synchronization. The time synchronization method uses the high-precision TCXO as the main clock and records GPS time in the SD card at intervals to achieve the high-precision time-stamp for the seismic data. Then the seismic data is intercepted intermittently based on precise time stamps, which achieves the strict seismic data synchronization. Performance analysis shows that the time synchronization accuracy of the proposed method is 0.6 μs and saves 73% energy of the time-sync periods compared to the common GPS timing method. The field measurement results indicate that the time synchronization accuracy is not associated with the working time and the distance between nodes so that the proposed synchronization method is suitable for the high-density seismic survey.

A rectangular array of seismic nodes is called a 3D seismic sensors array which is suitable for geographic routing. However, when certain seismic nodes have no location information, using detours or other methods to detect the path will increase latency and power consumption of geographic routing. It is challenging to maintain the high performance of geographic routing in practical 3D exploration networks. This letter proposes a greedy flee in the direction routing algorithm (GFDR). According to the feature that the intersection of the connection set of nodes is not empty, GFDR can drive the packet continuously forward in a specified direction without location information when the packet records the node ID of the path. Simulation results show that as the size of the area without location information (AWLI) increases, GFDR can keep the delivery ratio above 98%, while maintaining an approximately constant packet delay without increasing the number of packet-forwarding hops. A real seismic system experiment running GFDR algorithm confirms the simulation results and demonstrates the effectiveness of GFDR.