Broadcast Scheduling Strategy Based on the Priority of Real-Time Data in a Mobile Environment

Data broadcast is an important data dissemination approach in mobile environment. On broadcast channel, scalability and efficiency of data transmission are satisfied. In a mobile environment, there exists a kind of real-time database application in which both the transactions and data can have their timing constraints and priorities of different levels. In order to meet the requirement of real-time data disseminating and retrieving, a broadcast scheduling strategy HPF-ED F (Highest Priority First with Earlier Deadline and Frequency) is proposed under the BoD (Broadcast on Demand) model. Using the strategy, data items are scheduled according to their priority the transaction imposed on them or system set for them. The strategy also considers other characteristics of data items such as deadline and popularity of data. The extensive simulation experiments have been conducted to evaluate the performance of the proposed algorithm. Results show that it can achieve excellent performance compared with existing strategies.

Weak Serializable Concurrency Control in Real-time Broadcast Environments

Given the asymmetric communication capabilities in mobile real-time environments, traditional serializability-based approaches are too restrictive, unnecessary, and impractical. The new notion of correctness called weak serializability is given. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol based on this criterion is outlined for real-time broadcast environments. The simulation results confirmed that the proposed techniques help mobile transactions to meet their deadlines and improve query response time.

Improvement Design for Distributed Real-Time Stream Processing Systems

In the era of Big Data, typical architecture of distributed real-time stream processing systems is the combination of Flume, Kafka, and Storm. As a kind of distributed message system, Kafka has the characteristics of horizontal scalability and high throughput, which is manly deployed in many areas in order to address the problem of speed mismatch between message producers and consumers. When using Kafka, we need to quickly receive data sent by producers. In addition, we need to send data to consumers quickly. Therefore, the performance of Kafka is of critical importance to the performance of the whole stream processing system. In this paper, we propose the improved design of real-time stream processing systems, and focus on improving the Kafka's data loading process.We use Kafka cat to transfer data from the source to Kafka topic directly, which can reduce the network transmission. We also utilize the memory file system to accelerate the process of data loading, which can address the bottleneck and performance problems caused by disk I/O. Extensive experiments are conducted to evaluate the performance, which show the superiority of our improved design.

Joint Algorithm of Message Fragmentation and No-Wait Scheduling for Time-Sensitive Networks

Time-sensitive networks(TSNs)support not only traditional best-effort communications but also deterministic communications,which send each packet at a deterministic time so that the data transmissions of networked control systems can be precisely scheduled to guarantee hard real-time constraints.No-wait scheduling is suitable for such TSNs and generates the schedules of deterministic communications with the minimal network resources so that all of the remaining resources can be used to improve the throughput of best-effort communications.However,due to inappropriate message fragmentation,the realtime performance of no-wait scheduling algorithms is reduced.Therefore,in this paper,joint algorithms of message fragmentation and no-wait scheduling are proposed.First,a specification for the joint problem based on optimization modulo theories is proposed so that off-the-shelf solvers can be used to find optimal solutions.Second,to improve the scalability of our algorithm,the worst-case delay of messages is analyzed,and then,based on the analysis,a heuristic algorithm is proposed to construct low-delay schedules.Finally,we conduct extensive test cases to evaluate our proposed algorithms.The evaluation results indicate that,compared to existing algorithms,the proposed joint algorithm improves schedulability by up to 50%.

Confidentiality-aware message scheduling for security-critical wireless networks

Without considering security, existing message scheduling mechanisms may expose critical messages to malicious threats like confidentiality attacks. Incorporating confidentiality improvement into message scheduling, this paper investigates the problem of scheduling aperiodc messages with time-critical and security-critical requirements. A risk-based security profit model is built to quantify the security quality of messages; and a dynamic programming based approximation algorithm is proposed to schedule aperiodic messages with guaranteed security performance. Experimental results illustrate the efficiency and effectiveness of the proposed algorithm.

Real-time Audio &Video Transmission System Based on Visible Light Communication

With the increasing popularity of solid sate lighting devices, Visible Light Communication (VLC) is globally recognized as an advanced and promising technology to realize short-range, high speed as well as large capacity wireless data transmission. In this paper, we propose a prototype of real-time audio and video broadcast system using inexpensive commercially available light emitting diode (LED) lamps. Experimental results show that real-time high quality audio and video with the maximum distance of 3 m can be achieved through proper layout of LED sources and improvement of concentration effects. Lighting model within room environment is designed and simulated which indicates close relationship between layout of light sources and distribution of illuminance.

Scheduling transactions in mobile distributed real-time database systems

A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load （think time is ls） the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.

IPC Mechanisms in Satellite Real-Time Microkernel Operating System

One of the most important features of modem minor satellites is to realize autonomous moving. The perfomance of the satellite autonomous computer operating system acting as the control center is of utrnost importance. The recent trend in operating system development is adopting microkernel architecture that holds such advantages as microminiaturization, modularity, portability and extendibility. IPC is the key of microkernel design. Message-based IPC mechanism is generally used in existing microkernel Operating system. It is of consistency, safety and reliability.However, it can not provide efficient support for real-time applications in satellite systems and it only applies to loose coupling multi-processor architecture. In this paper, an improvement solution for existing message-based IPC is proposed at first to obtain real-time performance. Then a new IPC mechanism is designed. It particulary applies to shared memory tight coupling multi-processor architecture.

A Robust Emergency Messages Routing Scheme for Urban VANETs

Vehicular ad-hoc networks(VANETs)play an essential role in enhancing transport infrastructure by making vehicles intelligent and proficient in preventing traffic fatalities.Direction-based greedy protocols pick the next route vehicle for transmitting emergency messages(EMs)depending upon the present location of adjacent vehicles towards sink vehicles by using an optimal uni-directional road traffic approach.Nevertheless,such protocols suffer performance degradation by ignoring the moving directions of vehicles in bi-directional road traffic where topological changes happen continuously.Due to the high number of vehicles,it is essential to broadcast EMs to all vehicles to prevent traffic delays and collisions.A cluster-based EM transmitting technique is proposed in this paper.For urban VANETs,this paper pioneers the clustering of bi-directional road traffic for robust and efficient routing of EMs.In this regard,this paper introduces a routing protocol,namely,the bi-directional urban routing protocol(BURP).In addition to the paths and relative locations of vehicles,BURP takes account of the distance parameter by using the Hamming distance function to determine the direction ofmotion of vehicles and communicates EMs through the cluster head(CH).Amodified k-medoids algorithm is presented for the clustering of bi-directional road traffic.A median method is presented for selecting CH to ensure the longrunning of a cluster.Simulation results show that BURP provides enhanced throughput,a maximized packet delivery ratio,low energy consumption,and network delay relative to eminent routing protocols.

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.

利用MQTT通信实现图像广播功能

图像广播功能不仅可以降低项目建设成本,而且能够提高图像采集设备的利用效率。为有效解除应用程序耦合及简化代码复杂度,本文提出一种基于MQTT通信的图像广播功能的方案。该系统采用EMQX软件搭建MQTT服务端,使用paho-mqtt客户端库创建客户端应用程序,并采用BASE64对图像进行编解码。测试结果表明,该图像广播系统基本达到了设计要求。

基于消息触发的音频智能分播系统设计与实现

随着广播频率逐步从本地化向跨地域与互联网化传播方式转变,应改变节目制作和播出方式,除满足不同渠道用户的收听需求,还需要针对不同地域和不同渠道制作差异化的节目与广告,并通过智能分播的方式进行播发。基于此,设计基于消息触发机制的音频智能分播系统,并分析详细的设计流程,为定制化服务应用提供参考。

中波广播技术在应急广播领域的应用研究

概述应急广播、中波广播技术,重点分析中波广播技术在应急广播中应用的优势,深入探讨中波应急广播的具体应用,推动中波广播技术与应急广播的深度融合应用。

基于北斗短报文的应急广播系统设计与应用

本文结合2022年云南省怒江傈僳族自治州实施的基于北斗短报文传输系统的应急广播项目,概括性地阐述了该系统的技术特性和主要功能。文章论证了北斗短报文技术在应急广播体系建设中,可作为地面无线、有线及直播卫星等传统链路的有效补充。同时,客观地分析了其技术局限性和应用场景的约束,并对未来相关技术广泛应用的前景进行了探讨。

应急广播系统通用类行业标准解读

本文主要从术语定义、系统架构、功能要求、性能要求、接口格式要求等方面对《应急广播系统总体技术规范》等应急广播系统通用类行业标准的修订情况进行了说明。

基于ZeroMQ的聚变数据实时发布系统研究

针对等离子体核聚变放电实验中传统数据获取方式的滞后性,设计并实现一套实时数据发布系统,旨在提升实验数据的即时性,支持实验过程中的即时决策与调整。采用分布式架构,通过分布式的诊断数据收集模块实时采集实验数据,并利用高效的通信协议将数据快速传输至中央服务器。服务器根据客户端需求,将处理后的数据实时推送到客户端,实现数据的实时共享与可视化。性能测试结果表明,该系统能实现等离子体核聚变放电实验数据的实时发布,数据传输延迟低于60 s,且兼容Windows、Android等主流操作系统,确保研究人员可随时随地访问实时数据。该实时数据发布系统显著提高了核聚变实验的数据时效性,增强了实验操作的灵活性和安全性,对推动核聚变科学的发展具有重要意义。

IP MULTICAST GROUP MANAGEMENT FOR BROADCAST LANS DISTRIBUTION

Problems of the current IGMP mechanism were identified, such as unnecessary periodic probing of hosts and leave latency, which wastes bandwidth and cause more traffic and overhead. Alternative mechanism that preserve the IP multicast model but employ join/leave messages to track local group membership for broadcast LANs (shared medium LANs) was proposed in this paper. We describe the implementation requirements of the new mechanism and compare it to existing one, demonstrating that join/leave approach is uniformly superior for the environment of broadcast LANs.

P2P Model Based on Isolated Broadcast Domains

Resource location is the most important issue for Peer-to-Peer (P2P) system and flooding is the fundamental mechanism for unstructured P2P systems. Redundant messages will exponential growth with flooding scope increasing which severely influences the scalability of the system. In this paper, a new P2P model based on isolated broadcast domains is given to reduce the amount of redundant messages by limiting the radius of messages transmitted. Analysis and experiments show that this model can guarantee coverage of nodes and significantly reduce the amount of redundant messages generated.

Cryptanalysis of quantum broadcast communication and authentication protocol with a one-time pad

Chang et al.[Chin.Phys.623 010305（2014）]have proposed a quantum broadcast communication and authentication protocol.However,we find that an intercept-resend attack can be preformed successfully by a potential eavesdropper,who will be able to destroy the authentication function.Afterwards,he or she can acquire the secret transmitted message or even modify it while escaping detection,by implementing an efficient man-in-the-middle attack.Furthermore,we show a simple scheme to defend this attack,that is,applying non-reusable identity strings.

ADS-B中基于格的分层无证书消息可恢复认证方案

广播式自动相关监视(ADS-B)作为新一代空中交通管制的关键技术,已部署在全球大部分空域。已有的ADS-B消息认证方案主要利用传统的公钥密码系统来保证数据安全,计算负担较重且无法抵御量子攻击。首次将基于格的密码体制用于ADS-B通信安全,提出一种同时支持消息可恢复和批量验证的分层无证书消息认证方案。ADS-B机载设备不需要管理证书,也无密钥托管问题。ADS-B消息不需要与签名一起传输,可以在验证阶段进行恢复。利用拒绝采样和无陷门技术,该方案仅需执行计算复杂度较低的线性运算即可实现消息认证。在随机预言机模型和小整数解问题假设下,该方案是可证安全的。性能评价实验结果表明,在同等的比特安全级别下,该方案相比相关工作在节省计算开销方面有显著的提升,对于计算资源受限的航空电子设备十分适用。