The emergence of the Internet of Things (IoT) makes real-time monitoring possible. The Information-Centric Networking (ICN) standard presents an effective way to rapidly access data by enabling in-network caching, so we propose a hybrid data transmission system for information-centric IoT and aim to leverage ICN to achieve energy-efficient and rapid access to data for monitoring. The system learns forwarding information on caching providers and leverages the user registration mechanism to rapidly inform users of emergency information in a unicast way. Meanwhile, users exploit forwarding information on caching providers to share data from optimal caching providers simultaneously. The system is analyzed and evaluated to verify its advances.

为了降低IEEE 802.15.4MAC层数据帧丢包率,在分析丢包率的原因基础上,提出了一种基于Markov链的信道竞争机制模型.通过对网络发送、退避和信道检测状态的稳态概率进行数学推导,研究了信道碰撞和数据帧的丢包率分析式,研究了参数数据包到达速率、节点数量、误码率、后退指数、后退等待次数对碰撞概率和丢包率的影响.实验结果表明,与节点无休眠态的IEEE 802.15.4网络相比,节点丢包率平均降低了23.7％,模型较好地描述了提出的MAC层信道访问机制,合理的网络参数设置能够优化数据帧丢包率,研究结果对无线传感网的应用提供了可靠传输优化参考.

为了提高802.15.4网络吞吐量性能,设计了一种改进的节点状态转换过程,提出了一种考虑隐藏终端问题和重传的节点接入信道模型,并对模型进行分析计算.基于计算结果和信道状态模型分析,对考虑隐藏终端问题的数据碰撞概率、丢包率和网络吞吐量进行推导.最后研究了数据包到达率、退避指数和隐藏终端对网络吞吐量性能的影响.实验表明,模型较好地描述了节点接入信道过程,能够对网络吞吐量进行精准的动态分析.实验结果表明,与无重传机制的802.15.4网络相比,网络吞吐量增加了83.9％左右.与部分条件休眠的方法比较,网络吞吐量平均增加了13.3％,提出的模型能够有效提升网络吞吐量性能.

This paper proposes a hierarchical addressing scheme for 6LoWPAN WSN and aims to reduce the addressing cost and latency. The proposed scheme includes the address initialization and address maintenance algorithms. When the network starts, the address initialization algorithm is performed. Through the address initialization process, each node can be configured with a globally unique address without duplication address detection. The address maintenance algorithm is made up of the address configuration sub-algorithm and the address reclamation sub-algorithm. After the address initialization process ends, a new node performs the address configuration sub-algorithm to obtain a globally unique address from a neighbor. The address reclamation sub-algorithm is performed to reclaim the released addresses for reuse so that there is enough address resources available for assignment. Finally, the proposed scheme is evaluated, and the results show that this scheme effectively reduces the addressing delay and cost.

This paper proposes a routing scheme for connecting urban vehicular networks to the IPv6-based internet. In this scheme, the architecture based on vehicular domains is proposed to reduce the routing delay and packet loss. Based on this architecture, the intra-VD and inter-VD routing algorithms are proposed. In the intra-VD routing algorithm, a vehicle achieves the communications with the IPv6-based internet via the nearest access point, so the routing delay and packet loss are lowered. When a vehicle moves within one vehicular domain, its care-of address keeps unchanged. As a result, the extra routing delay and packet loss caused by the routing establishment due to the care-of address change are avoided. In the inter-VD routing algorithm, a vehicle can receive the data destined for the old and new care-of addresses from one access point, so the packet loss caused by the routing reestablishment due to the care-of address change is reduced. This scheme is quantitatively evaluated. Compared to the existing routing approach, our solution reduces the routing delay and packet loss by nearly 60 and 53%, respectively.

针对基于隐藏终端的802.15.4网络数据丢包问题,提出了一种时隙CSMA/CA算法的数学模型.基于模型推导建立数据丢包概率的数学模型,并研究隐藏终端对数据丢包现象的影响.然后研究不同网络参数如隐藏终端数、 λ、N、minBE和NB对数据丢包的影响.实验表明:通过合理的参数配置能够改善网络丢包问题,且相对于不考虑隐藏终端的情形,隐藏终端导致的丢包问题更加严重(高出25.2%).实验结果说明提出的算法模型较好的描述了802.15.4网络实际运行特征.

In current vehicular content-centric networks, contents are usually acquired in the broadcast way. Moreover, it is hard for a requester to acquire contents from a remote provider because the global routing is not supported. Taking these issues into account, this paper proposes an IPv6-based unban vehicular content-centric networking frame. In this frame, the architecture based on road segments is proposed, and based on this architecture a requester can obtain contents in the unicast way instead of in the broadcast way. Moreover, the content address structure is proposed, and via a content address a requester can acquire contents from a remote provider. Finally, the performance of the proposed frame is evaluated, and the data results show that this frame effectively improves the contents acquisition success rate and reduces the contents acquisition cost and latency.

In wireless networks, the handover in the network layer (L3) is usually initiated after the handover in the link layer (L2) is complete, so the total handover delay is equal to the sum of the L2 handover delay and the L3 handover delay. In order to reduce the total handover delay, this paper studies the correlations between the L2 messages and L3 ones, and proposes a cross-layering handover scheme. The main idea behind this scheme is to effectively combine the related messages in L2 and L3 and achieve the L3 handover with the L2 messages in order to minimize the effect of the L3 handover delay on the total handover delay. The performance of this scheme is evaluated, and the results show that this scheme effectively reduces the total handover delay.

In order to improve the data transmission reliability in Media Access Control (MAC) layer for 802.15.4 network,this paper proposes a Markov chain model of node working process based on unsaturated state,and the derivation calculation is carried out for the steady-state probability of the node status.The two factors affecting the transmission reliability in MAC layer are researched:the failure of node access channel and the limit of maximum retransmission times,and the analytical formula of reliability performance is derived.The influence of the parameters including minBE,NB and λ and two factors on the reliability is analyzed,and the effects of the two kinds of factors on the reliability performance are compared.Experimental results show that compared with the node working model without sleep mechanism,the proposed model can greatly reduce channel conflict,and improve network reliability.

In wireless sensor network with a long-thin and tree-based topology, sensor nodes might fail to be configured with an address due to the lack of the address space and the routes along a tree might not be optimal. In order to overcome these deficiencies, this paper proposes an addressing-based routing optimization scheme for IPv6 over low-power wireless personal area network in vehicular scenarios AROV. In AROV, the architecture based on super nodes is proposed. Via one addressing process, all nodes included in one super node can be configured with an address. Because a super node covers sensor nodes in a multi-hop scope, it effectively avoids the addressing failure. Moreover, a super node makes use of its neighbor super nodes to calculate an optimal path, so the routing latency is reduced. AROV is evaluated, and the data results show that AROV effectively shortens the routing latency.

In order to decrease the frame packet lost rate in 802 . 15 . 4 network , this paper analyzed the packet lost rate based on the retransmission mechanism , proposed the mathematical model for the working process of network node in MAC layer , and derived the steady-state probability of the main state . Afterwards , this paper carried out the mathematical analysis for the retransmission probability and the packet lost rate . Finally , the effect of MAC layer parameters minBE , NB and network environment parameter λ、N、BER on the retransmission probability and the packet loss rate was compared through the experimental analysis . Experimental re-sults show that the node packet loss rate is reduced by 88 . 9%, compared with the data transmission performance without retrans-mission mechanism . And the model could accurately reflect the node data transmission characteristics . Furthermore , equilibrium pa-rameter deployment could effectively improve the data transmission success rate , and theoretical research could provide the reference for 802 . 15 . 4 network standard .

基于Z-Stack协议栈,以CC2530射频收发芯片和DHT22数字温湿度传感器为核心,采用ZigBee无线通信技术设计实现了无线温湿度采集监测系统,并在IAR环境下采用上位机软件以GUI的方式在终端直观地显示温湿度变化情况.主要阐述了系统结构设计、温湿度数据采集流程和图形化界面监测实现.实验表明,该系统实现温湿度数据的采集不但实时有效、可扩展性良好,而且具有极高的可靠性和卓越的稳定性.

Aiming at the optimization problems of the data packet average service time of 802.15.4 MAC layer,this paper proposed a conversion mechanism of node state based on super frame structure,and analyzed the definition of the data packet average service time.After that,it derived the steady-state probability of the main state and the formula of the data packet aver-age service time by establishing the model of Markov chain on the state of the node.At last,this paper researched the influ-ence of the protocol parameters such as NB,BE,SO to the data packet service time of the steady-state probability.The research results show that,the data packet average service time is reduced by 2.3%,compared with other dormant node models.The model describes the working characteristics of 802.15.4 network nodes very well.The balanced configuration of protocol pa-rameters can improve the packet transmission performance.And the model can provide the reference for raising the real-time performance of the network.

针对IEEE 802.15.4 WSNs数据传输可靠性优化问题,提出了一种基于单跳通信的信道竞争算法模型。基于模型的数学推导,研究了MAC层数据包传输可靠性的影响因素,然后建立了可靠性性能指标的数学分析式;最后研究了协议参数minBE、NB和N对可靠性的影响,并分析了参数配置对信道接入失败和重传次数的影响。研究表明,相对于无休眠态的信道竞争算法,在网络规模较大时可靠性提高了94.5%,提出的算法模型能够有效改善数据传送的可靠性性能。

This paper proposes a distributed IPv6 address configuration scheme for hybrid MANETs. In the scheme, the architecture for hybrid MANETs is proposed and it achieves the communication between MANETs and the IPv6 Internet. Based on the proposed architecture, a distributed and stateful address configuration algorithm is proposed. In the algorithm, a new node obtains a unique address from a neighbor gateway/allocator without DAD. Since allocators are distributed across MANETs, multiple new nodes can perform the address configuration simultaneously. As a result, the bottleneck in the centralized address configuration is effectively avoided, and the address configuration cost and delay are reduced. The paper also proposes the network merging/splitting algorithm in order to ensure the address uniqueness. Finally, the performance of the proposed scheme is analyzed, and the data results show that the proposed scheme effectively reduces the address configuration cost and shortens the address configuration delay.

针对《汇编语言与微机原理》课程教学效果欠佳的问题,通过构建研究性课程,基于课程知识体系和学生兴趣,合理选择研究性教学内容,不断改进教学方法、注重理论联系实际,构建仿真实践平台和设计仿真案例.通过加强实践能力的培养,激发学生的学习兴趣等措施,以期提高课程教学效果和学生的创新能力,为社会培养具有较强动手能力和创新精神的微机应用型人才.

Due to long latency and considerable packet loss, stateful and stateless address configuration standards cannot efficiently work in vehicular networks, so this paper proposes an IPv6 address configuration scheme for vehicular networks based on location information. This scheme combines a stateless address configuration mechanism with a stateful one. In the stateless algorithm, duplicate address detection is performed within a road domain instead of a network. A random ID is introduced to reduce the address conflict rate, so the address configuration cost and delay are reduced. In the stateful algorithm, a vehicle acquires a unique address from a neighbor vehicle without recording the address allocation states, so the address configuration task is distributed around all vehicles and the distributed address configuration is achieved. This paper evaluates the performance of this scheme, and the data results show that this scheme reduces the addressing costs and delays.

To reduce the delay of channel contention at the Medium Access Control(MAC) layer for IEEE 802.15.4 networks,a channel contention mechanism for nodes,with unsaturated load is designed.A mathematical model is built and a derivation is carried on to obtain the steady-state probability of the main state.According to the result of the model,the formula of channel access delay is derived based on the modeling of channel state conversion process.The impact of protocol parameters such as λ,NB and minBE on the performance of node access delay is researched,and it is compared with the delay performance of the saturated load network.Analysis results show that the new model can describe and evaluate the mechanism of channel contention access very well,and the competition optimization mechanism can reduce effectively the deterioration degree of channel.Moreover,settings of protocol parameters can improve the performance of channel contention delay.

针对C语言课程教学效果欠佳的现状,提出基于OBE教育理念的C语言课程教学方案.以最终学习目标为出发点进行反向课程设计,主要从教学内容、教学策略、拓展实践、考核方式等方面进行C语言课程教学模式研究和改革.在C语言课程教学中实施基于成果导向教育的教学模式,能够使学生清晰的了解学习本课程后会达到的学习成果和能力,从而激发学生的自主学习兴趣,有效的提高C语言课程的教学质量、教学水平和学生的学习成效.

To optimize the performance of media access control( MAC) protocol for ZigBee network,a mechanism based on saturated traffic for channel competitive access is proposed. This paper establishes a Markov chain model for the process of node state transition. The numerical analysis of throughput and node average power consumption based on the mechanism is carried out. The impact of protocol parameters such as NB and aminBE on the performance of conflict probability,throughput and node average power consumption is researched. The results show that this model can describe the mechanism of channel competitive access well and that the reasonable settings for parameters can improve the performance of the MAC protocol.