Collision Classification MAC Protocol for Underwater Acoustic Communication Networks Using Directional Antennas

Traditional underwater acoustic communication networks(UACNs)generally use omnidirectional transmission technology that causes a large number of data-packet collisions,thus resulting in low network throughput and high end-to-end delays.Compared with omnidirectional transmission technology,directional technology only sends and receives data packets in a specified direction.This can significantly reduce the probability of collisions and improve network performance.However,it also causes a deafness problem,which occurs when the sending node sends a data packet to the receiving node but the receiving node is unable to reply to the sender,because its antenna beam is closed.To resolve this issue,this study proposes a collision classification media access control(CC-MAC)protocol for UACNs.With this protocol,the underwater acoustic channel is divided into two subchannels,and the nodes transmit corresponding data types on them.The sending node can estimate the current status of the receiving node(i.e.,no collision,normal collision,deafness)according to the type of the data packet received and the sub-channel it arrived on,and it can choose correct options to improve network efficiency.Finally,we verify the performance of CC-MAC via simulations,showing that the protocol achieved higher network throughput and lower end-toend delays.

Multi-Point Communication System Based on CAN Bus

The paper introduced CAN （Controller Area Network） bus and CAN2.0 standard, the design of hardware frame-work multi-point communication based on CAN bus, and the software design method. At the same time, the system normal communication function and stability were shown in the experiment.

Simulation and Field Testing of Multiple Vehicles Collision Avoidance Algorithms

A global planning algorithm for intelligent vehicles is designed based on the A* algorithm, which provides intelligent vehicles with a global path towards their destinations. A distributed real-time multiple vehicle collision avoidance(MVCA)algorithm is proposed by extending the reciprocal n-body collision avoidance method. MVCA enables the intelligent vehicles to choose their destinations and control inputs independently,without needing to negotiate with each other or with the coordinator. Compared to the centralized trajectory-planning algorithm, MVCA reduces computation costs and greatly improves the robustness of the system. Because the destination of each intelligent vehicle can be regarded as private, which can be protected by MVCA, at the same time MVCA can provide a real-time trajectory planning for intelligent vehicles. Therefore,MVCA can better improve the safety of intelligent vehicles. The simulation was conducted in MATLAB, including crossroads scene simulation and circular exchange position simulation. The results show that MVCA behaves safely and reliably. The effects of latency and packet loss on MVCA are also statistically investigated through theoretically formulating broadcasting process based on one-dimensional Markov chain. The results uncover that the tolerant delay should not exceed the half of deciding cycle of trajectory planning, and shortening the sending interval could alleviate the negative effects caused by the packet loss to an extent. The cases of short delay(< 100100 ms) and low packet loss(< 5%) can bring little influence to those trajectory planning algorithms that only depend on V2 V to sense the context, but the unpredictable collision may occur if the delay and packet loss are further worsened. The MVCA was also tested by a real intelligent vehicle, the test results prove the operability of MVCA.

Investigation on full distribution CNC system based on SERCOS bus

A full distribution CNC system based on SERCOS bus is studied in accordance with the limitations of traditional PC-based motion card. The conventional PC-based motion control card is dispersed into several autonomous intelligent servo-control units with the function of servo driver. The autonomous intelligent servocontrol units realize the loop control of position, velocity and current. Interpolation computation is completed in PC and the computational results are transferred to every autonomous intelligent servo-control unit by high speed SERCOS bus. Software or hardware synchronization technology is used to ensure all servomotors are successive and synchronously running. The communication and synchronization technology of SERCOS are also researched and the autonomous intelligent servo-control card is developed byself. Finally, the experiment of circle contour process on a prototype system proves the feasibility.

Windows and Fieldbus Based Software Computer Numerical Control System

Computer numerical control(CNC)system is the base of modern digital and intelligent manufacturing technolo- gy.And opened its architecture and constituted based on PC and Windows operating system(OS)is the main trend of CNC sys- tem.However,even if the highest system priority is used in user mode,real-time capability of Windows(2000,NT,XP)for applications is not guaranteed.By using a device driver,which is running in kernel mode,the real time performance of Windows can be enhanced greatly.The acknowledgment performance of Windows to peripheral interrupts was evaluated.Harmonized with an intelligent real-time serial communication bus(RTSB),strict real-time performance can be achieved in Windows platform. An opened architecture software CNC system which is hardware independence is proposed based on PC and RTSB.A numerical control real time kernel(NCRTK),which is implemented as a device driver on Windows,is used to perform the NC tasks.Tasks are divided into real-time and non real-time.Real-time task is running in kernel mode and non real-time task is running in user mode.Data are exchanged between kernel and user mode by DMA and Windows Messages.

BusTechn

Introduced the characteristics of series communicat io n I 2C bus and basic communication protocol, and introduced the application of the bus I 2C according to the image sensor OV7610.The computer correspondence s tyle can be divided the parallel correspondence and the series correspondence. T he rate of series correspondence is rapid, and the property of real time is exce llent. Because the number of ports which it takes is great, it is not proper to miniaturize. Whereas the rate of series correspondence is low, but when the corr espondence of data is not great, it is simpleconvenient and agile to dispose t he circuit. Commonly series correspondence divide synchronization correspondence and asynchronies correspondence. The standard of interface RC232 is series asyn chronies correspondence. Recently the standard of bus I 2C is adopted widely in the micro-electronics correspondence realm, it is a special form of synchr onization correspondence. I 2C bus is a two-cabledouble-direction series co rrespondence bus. The address of the machine is set in hardware, and software pe rform the search of the address instead of hardware. So it reduce the number of the corresponding cable, moreover it predigest the design of the hardware. It resolve many interface problems in design of numeric circuit. More and more se miconductor manufacturer accept the standard. Its characteristics can be listed as followed. In text, the image sensor OV7610 is introduced as the example the bus I 2C appl ication.

Steady-State Analysis of the Distributed Queueing Algorithm in a Single-Channel M2M Network

The Distributed Queuing (DQ) algorithm is predicted as one of the solutions to the issues currently found in IoT networks over the use of Aloha based algorithms. Since recently, the algorithm has been of interest to many IoT researchers as a replacement of those Aloha variants for channel access. However, previous works analyzed and evaluated the DQ algorithm without any consideration of the stability of its queues, assuming it is stable for any given number of nodes in the network. In this paper, we define the DQ stability condition in a single-channel M2M environment considering a traffic model of periodic and urgent frames from each node in the network. Besides, a steady-state evaluation of the algorithm’s performance metrics is also presented. In general, the DQ algorithm, when it is stable, was observed not to efficiently use the contention slots for the collision resolution. In a single-channel environment, the DQ algorithm is found to outperform the Aloha based algorithms only in an idle-to-saturation scenario.

An On-Line Scheduler over Hard Real-Time Communication System

By thorough research on the prominent periodic and aperiodic scheduling algorithms,anon-line hard real-time scheduler is presented,which is applicable to the scheduling of packets over a link.This scheduler,based on both Rate Monotonic,pinwheel scheduling algorithm Sr and Polling Serverscheduling algorithms,can rapidly judge the schedulability and then automatically generate a bus tablefor the scheduling algorithm to schedule the packets as the periodic packets.The implementation of thescheduler is simple and easy to use,and it is effective for the utilization of bus link.The orderly executionof the bus table can not only guarantee the performance of the hard real time but also avoid the blockageand interruption of the message transmission.So the scheduler perfectly meets the demand of hard real-time communication system on the field bus domain.

Marketing Development and Recognition of DFH-4 Series Bus Satellites

In this paper,we examine the interrelation between innovation and commercial marketing using the DFH-4 series bus satellite as an example which customers are familiar with.Strategies in evolving satellite buses and key subsystem technologies without compromising on advanced innovations,favorable heritage and thorough verification are also discussed.Market development experiences with the DFH-4 series bus satellite are summarized and market recognition is reflected from the space insurance perspective.

A Fairness-Enhanced Intelligent MAC Scheme Using Q-Learning-Based Bidirectional Backoff for Distributed Vehicular Communication Networks

With the increasing attention to front-edge vehicular communication applications,distributed resource allocation is beneficial to the direct communications between vehicle nodes.However,in highly dynamic distributed vehicular networks,quality of service(QoS)of the systems would degrade dramatically because of serious packet collisions in the absence of sufficient link knowledge.Focusing on the fairness optimization,a Q-learning-based collision avoidance(QCA)scheme,which is characterized by an ingenious bidirectional backoff reward model RQCA corresponding to arbitrary backoff stage transitions,has been proposed in an intelligent distributed media access control protocol.In QCA,an intelligent bidirectional backoff agent based on the Markov decision process model can actively motivate each vehicle agent to update itself toward an optimal backoff sub-intervel BSIopt through either positive or negative bidirectional transition individually,resulting in the distinct fair communication with a proper balance of the resource allocation.According to the reinforcement learning theory,the problem of goodness evaluation on the backoff stage self-selection policy is equal to the problem of maximizing Q function of the vehicle in the current environment.The final decision on BSI_(opt) related to an optimal contention window range was solved through maximizing the Q value or Q_(max).The ε-greedy algorithm was used to keep a reasonable convergence of the Q_(max) solution.For the fairness evaluation of QCA,four kinds of dynamic impacts on the vehicular networks were investigated:mobility,density,payload size,and data rate with a network simulator NS2.Consequently,QCA can achieve fair communication efficiently and robustly,with advantages of superior Jain’s fairness index,relatively high packet delivery ratio,and low time delay.

Collision Avoidance Strategy Supported by LTE-V-Based Vehicle Automation and Communication Systems for Car Following

We analyzed and improved a collision avoidance strategy, which was supported by Long Term EvolutionVehicle(LTE-V)-based Vehicle-to-Vehicle(V2 V) communication, for automated vehicles. This work was completed in two steps. In the first step, we analyzed the probability distribution of message transmission time, which was conditional on transmission distance and vehicle density. Our analysis revealed that transmission time exhibited a near-linear increase with distance and density. We also quantified the trade-off between high/low resource reselection probabilities to improve the setting of media access parameters. In the second step, we studied the required safety distance in accordance with the response time, i.e., the transmission time, derived on the basis of a novel concept of Responsibility-Sensitive Safety(RSS). We improved the strategy by considering the uncertainty of response time and its dependence on vehicle distance and density. We performed theoretical analysis and numerical testing to illustrate the effectiveness of the improved robust RSS strategy. Our results enhance the practicability of building driverless highways with special lanes reserved for the exclusive use of LTE-V vehicles.

ASIC Design of High-Speed Low-Power HDLC Controller

Combined with the engineering requirement, a high-speed low-power ASIC design of HDLC controller based on RS-485 bus is given in this paper. On principle of Top-Down design, this ASIC design uses multi-techniques to reduce its die area and dynamic power, and overcomes some problems appeared frequently in application systems of the RS-485 circuits formed by the Standard Interface Chips. This design also improves the system reliability and reduces the system area.

Design of Distributed Temperature Measurement System for Switchgear

This paper develops a novel distributed temperature measurement system based on DSP and DS18B20 digital thermometer. The real-time temperature of each node in the switchgear is obtained by several DS18B20s which are connected on the 1-wire bus together. RS-485 master-slave communication protocol is used to centralize monitoring temperatures of several switchgear cabinets. The system also has the function of temperature alarm. The operation of simulation experiment has showed that the system is able to complete monitoring real-time temperatures in high voltage switchgear.

Design and evaluation of V2X communication system for vehicle and pedestrian safety

As the vehicles gain the extensive popularity and increasing demand, traffic accident is one of the most serious problems faced by modem transportation system. Hereinto, crashes between cars and pedestrians cause plenty of injuries and even death. Diverting attention from walking to smartphones is one of the main reasons for pedestrians getting injured by vehicles. However, the traditional measures protecting pedestrians from the vehicles heavily rely on the sound warning method, which do not capable for pedestrians focusing on the smartphones. As the smartphones become ubiquitous and intelligent, they have the capacity to provide alert for the pedestrians with the help of vehicle-to-pedestrian （V2P） communication. In this paper, an efficient vehicle-to-X （V2X） communication system is designed for the vehicle and pedestrian communication to guarantee the safety of people. It achieves the IEEE 802.11p and the WiFi protocols meanwhile on the on-board unit （OBU） designed for vehicles. Extensive evaluation shows that the OBU can provide the reliable communication for vehicle-to-vehicle （V2V） and V2P in terms of packet delivery rate and average delay. Furthermore, two safety applications have been developed to protect the safety of vehicles and pedestrians based on the data transferred from the OBU. The first application is designed to show the driving information and provide the collision forewaming alert on the tablet within the vehicle. The second application is developed for the smartphone to provide forewarning alert information to the smartphone-distracted vulnerable pedestrians. Smartphone states are appreciable to provide the adaptive alert modes. Experimental results show that these applications are capable of alerting the intersection accidents, and the pedestrians can get the adaptive alerts according to smartphone usage contexts.

IEC 61850 as Backbone for Smart PAC Systems

This paper discusses a working definition of smartness in protection,automation and control systems(PACS)in substations.A summary is given about the standard IEC 61850 features that support smartness,i.e.,the data model,the multiple communication services,and the system configuration description language(SCL).With help of known examples of application functions for control,supervision,and protection,the building of smart systems out of the modules of IEC 61850 is demonstrated.From the possible architectures,the standardized redundancy is explained.The process bus is exploited in detail since it is seen by users as the core of a smart substation.In this context,attention is given also to the time synchronization in theµs range over the communication network,a rather new part of the standard.In the last part,all features are summarized and it is concluded that IEC 61850 may really be named the backbone for smart PAC systems.

Distributed and Decentralized Control Architectures for Converter-Interfaced Microgrids

This paper gives a summary on recently available technologies for decentralized and distributed control of microgrids.They can be classified into two general categories:1)power line communication based architectures and 2)multi-agent based architectures.The essential control methods and information sharing algorithms applied in these architectures are reviewed and examined in a hierarchical manner,in order to point out benefits they will bring to future microgrid applications.The paper is concluded with a summary on existing methods and a discussion on future development trends.