IEEE 802.15.4非信标使能模式在车联网中的性能评估

车联网是车与车之间广泛使用的网络技术,是车与车之间经济、高效的通讯渠道。IEEE 802.15.4由一层简单物理层和一层节能型介质访问控制层所组成,是当前所有通讯标准中车联网网络的最佳选择。基于此,这里选择适合车联网的IEEE 802.15.4非信标使能模式作为分析模型,将其应用于车联网中,具体包含非饱和通讯量模式和大型网络,并分别研究了IEEE 802.15.4适合车联网的非信标使能模式的性能,这对车辆积极调整广播速度,在车与车之间联网通讯中取得更高的成功具有一定的参考价值。

IEEE802.15.4a信道对UWB功率谱影响分析

研究超宽带功率谱密度,从路径损耗模型、多路径模型和小尺度衰落模型方面分析IEEE802.15.4a工作组信道模型.采用直接序列脉冲(direct-sequence pulse-amplitude modulation,DSP-PAM)超宽带(ultra-wideband,UWB)系统的信道响应,仿真分析了8种信道对2～10 GHz超宽带系统功率谱分布情况.仿真结果表明,多路径信道对UWB功率谱影响不大,脉冲UWB具有抗多路径干扰能力强的特点.

基于IEEE802.15.4a的无线测控网络协议

为满足工业现场测控任务对网络通信实时性的要求,提出一种基于IEEE802.15.4a的无线测控网络协议,其中的令牌控制子层采用令牌机制管理各站点对无线信道的访问,克服了CSMA/CA机制无序竞争的缺陷,保证数据传输的时间确定性,介绍协议栈模型、逻辑令牌环动态建立过程以及令牌故障的自恢复机制,并在硬件平台NanoNET上加以实现。实验结果表明,该协议能够在强电磁干扰环境中稳定运行,具备实时特性。

基于IEEE802.15.4a标准的工业无线网络节点设计

针对工业自动化领域对无线数据通信的需求以及国内基于切普扩频技术(CSS)的无线短程网络研究太少的现状,从实际应用角度出发,设计了一种基于IEEE802.15.4a标准的工业无线短程网络节点,给出了硬件设计电路图和软件流程图。在所设计的硬件平台基础上,采用CSMA/CA的介质访问控制策略进行组网通信测试,在强电磁干扰的环境中所设计的无线节点能够稳定运行,实时性能满足设计要求,可将该无线节点应用于实际的无线工业现场。

基于IR-UWB的高吞吐量、低延时MAC协议硬件设计

针对IEEE 802.15.4高速数据传输的应用场景,提出一种具有高吞吐量和低延时特性的定制化MAC协议。基于HRP UWB PHY对数据传输模型和吞吐量深入分析,并结合MAC协议的冲突避免载波侦听多路访问(Carrier Sense Multiple Access with Collision Avoid,CSMA-CA)和保障时隙(Guaranteed Timeslot,GTS)实时传输的特性,设计了该机制有效的管理流程。最后在Vivado中使用Verilog HDL对MAC控制器进行硬件设计和验证。仿真结果表明,与经典IEEE 802.15.4 MAC协议相比,该MAC控制器的吞吐量提高了26%,同时数据传输时延降低了17%。

Priority Based Energy Efficient MAC Protocol by Varying Data Ratefor Wireless Body Area Network

Wireless Body Area Network(WBAN)is a cutting-edge technology that is being used in healthcare applications to monitor critical events in the human body.WBAN is a collection of in-body and on-body sensors that monitor human physical parameters such as temperature,blood pressure,pulse rate,oxygen level,body motion,and so on.They sense the data and communicate it to the Body Area Network(BAN)Coordinator.The main challenge for the WBAN is energy consumption.These issues can be addressed by implementing an effective Medium Access Control(MAC)protocol that reduces energy consumption and increases network lifetime.The purpose of the study is to minimize the energy consumption and minimize the delay using IEEE 802.15.4 standard.In our proposed work,if any critical events have occurred the proposed work is to classify and prioritize the data.We gave priority to the highly critical data to get the Guarantee Tine Slots(GTS)in IEEE 802.15.4 standard superframe to achieve greater energy efficiency.The proposed MAC provides higher data rates for critical data based on the history and current condition and also provides the best reliable service to high critical data and critical data by predicting node similarity.As an outcome,we proposed a MAC protocol for Variable Data Rates(MVDR).When compared to existing MAC protocols,the MVDR performed very well with low energy intake,less interruption,and an enhanced packet-sharing ratio.

工业IEEE802.15.4a标准无线网络性能测试设计与实现

基于IEEE 802.15.4a标准的短距离无线传输技术在工业中得到了广泛的应用,然而,针对IEEE802.15.4a协议工业无线网络的性能测试研究较少,评判工业无线控制系统是否符合工业场合的应用缺乏精确的描述;为评价基于IEEE 802.15.4a标准的工业无线网络的性能,搭建了基于该标准的无线网络测试平台,基于ARM处理器开发了工业无线网络性能测试装置,给出了测试装置的软硬件设计,通过测试获得工业无线网络控制系统的丢包率、吞吐率、协议转换时间等性能指标,测试结果表明该装置能够有效地实现对基于该标准的无线网络进行性能测试,为改善和优化工业无线网络的应用、保证系统的稳定运行提供了有力的依据。

基于TSCH的工业无线网络流量自适应传输调度机制研究

当今LLN网络设备要满足低功耗要求的同时必须支持多种业务数据的传输,所以需要一种动态调度算法提高网络的可靠性。虽然基于IEEE 802.15.4标准的时隙信道跳变(TSCH)技术可以满足LLN的需求,然而现有的TSCH调度算法缺少灵活性。为了解决这一问题,本文提出了基于TSCH的流量感知自适应调度改进算法(Enhanced Adaptive Transmission Scheduling Mechanism,EATSM)。本文通过自相似性采样方法采集各链路流量信息,在准确获取各个邻居链路流量之后进行按权按序为每个邻居链路分配时隙数量与位置,保证传输可靠性的同时又能做到调度灵活性。通过理论分析与实验数据对比,本文提出的EATSM调度算法设计相比较于主流自适应调度算法,数据包投递率为99.57%,提高了0.26个百分点,节点运行占空比为0.34%,减少了0.88个百分点。

基于IEEE 802.15.3a的超宽带信道模型仿真

对于超宽带(UWB)无线通信技术来说,无线信道的特征直接决定了能否实现高速数据传输、低功耗、低复杂度的无线通信系统。基于多径传播、路径损耗、信道响应等参数,对IEEE 802.15.3a UWB技术的信道模型进行建模,并将RS编码和BPSK调制技术与UWB无线信道模型相结合,对4种环境下的传播情况进行仿真研究。结果表明,信道仿真的结论与实测数据结论一致性较好,所建模型能够准确反映和评估UWB无线通信的信道特征。

基于IEEE802.15.4a的工业无线网络嗅探器

针对基于IEEE802.15.4a的工业无线传感器监控网络嗅探器的研究和实现,从分析嗅探器原理,介绍了IEEE802.15.4a协议,详细描述了嗅探器的系统结构及设计中对数据包的捕获和过滤过程。给出了针对4种不同过滤设置条件所对应的类定义,可根据用户要求对指定类型、特定站点或设定时间段及包含热点关键字的数据进行捕获过滤,动态显示网络的实时状况。经过试验,本嗅探器完全达到了设计要求,实现了对无线传感器网络的主动侦听监控。

基于IEEE802.15.4a信道的高性能脉冲超宽带系统

随着通信技术的不断进步,超宽带技术作为一种新型无线通信方式,较传统无线通信方式具备许多技术上的优势,在许多应用领域如航空、医疗、军事以及消费类电子产品中都有着广阔的应用前景和特有的应用价值。文中在对脉冲超宽带系统的信源、信道、接收机进行理论分析的基础上,研究了一种具有高性能的脉冲超宽带系统并对该系统进行了建模和仿真。根据仿真实验结果分析得出该系统的各项性能要远远优于其他脉冲超宽带系统。

Throughput Analysis of the IEEE 802.11 Distributed Coordination Function Considering Erroneous Channel and Capture Effects

This paper presents a performance study of the distributed coordination function （DCF） of 802.11 networks considering erroneous channel and capture effects under non-saturated traffic conditions employing a basic access method.The aggregate throughput of a practical wireless local area network （WLAN） strongly depends on the channel conditions.In a real radio environment,the received signal power at the access point from a station is subjected to deterministic path loss,shadowing,and fast multipath fading.The binary exponential backoff （BEB） mechanism of IEEE 802.11 DCF severely suffers from more channel idle time under high bit error rate （BER）.To alleviate the low performance of IEEE 802.11 DCF,a new mechanism is introduced,which greatly outperforms the existing methods under a high BER.A multidimensional Markov chain model is used to characterize the behavior of DCF in order to account both non-ideal channel conditions and capture effects.

Influence of Error-prone Channel on the Performance of IEEE 802.11 WLAN Utilizing RTS/CTS Handshaking

A comprehensive study was presented for WLAN 802.11b using error-prone channel. It was theoretically and numerically evaluated the performance of three different network sizes with the bit rates that available in 802.11b protocol. Results show that throughput does not change with the size of the network for wide range of bit error rates (BERs) and the channel bit rates play a significant role in the main characteristics of the network. A comprehensive explanation has given for the phenomenon of the packet delay suppression at relatively high level of BERs in view of the size of the networks and the BERs. The effect length of the transmitting packets is also investigated.

Influence of the Limited Retransmission on the Performance of WLANs Using Error-Prone Channel

In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have been done either under assumption of idealistic channel condition or with unlimited retransmitting number. This paper is devoted to investigate influence of limited retransmissions and error level in the utilizing channel on the network throughput, probability of packet dropping and time to drop a packet. The results show that for networks using basic access mechanism the throughput is suppressed with increasing amount of errors in the transmitting channel over all the range of the retry limit. It is also quite sensitive to the size of the network. On the other side, the networks using four-way handshaking mechanism has a good immunity against the error over the available range of retry limits. Also the throughput is unchangeable with size of the network over the range of retransmission limits. However, the throughput does not change with retry limits when it exceeds the maximum number of the backoff stage in both DCF’s mechanisms. In both mechanisms the probability of dropping a packet is a decreasing function with number of retransmissions and the time to drop a packet in the queue of a station is a strong function to the number of retry limit, size of the network, the utilizing medium access mechanism and amount of errors in the channel.

GRAPH COLORING BASED CHANNEL ASSIGNMENT FRAMEWORK FOR RURAL WIRELESS MESH NETWORKS

IEEE 802.11 based wireless mesh networks with directional antennas are expected to be a new promising technology and an economic approach for providing wireless broadband services in rural areas.In this paper,we discuss interference models and address how they can affect the design of channel assignment in rural mesh networks.We present a new channel assignment framework based on graph coloring for rural wireless mesh networks.The goal of the framework is to allow synchronously transmitting or receiving data from multiple neighbor links at the same time,and continuously doing full-duplex data transfer on every link,creating an efficient rural mesh network without interference.Channel assignment is shown to be NP-hard.We frame this channel allocation problem in terms of Adjacent Vertex Distinguishing Edge Coloring(AVDEC).Detailed assignment results on grid topology are presented and discussed.Furthermore,we design an algorithm.Finally,we evaluate the performance of the proposed algorithm through extensive simulations and show the algorithm is effective to the regular grid topologies,and the number of colors used by the algorithm is upper bounded by+1.Hence the algorithm guarantees that the number of channels available in standards such as IEEE802.11a is sufficient to have a valid AVDEC for many grid topologies.We also evaluate the proposed algorithm for arbitrary graphs.The algorithm provides a lower upper bound on the minimum number of channels to the AVDEC index channel assignment problem.

Network-Load Aware Adaptive Channel Access Control for WLAN

Wireless local area network (WLAN) brings us a low cost and high bandwidth experience and thus plays a critically important role in current/future networks to support high-rate transmissions. To better provide quality-of-service (QoS) for WLAN users, we in this paper propose an improved scheme called “A-EDCA”(adaptive EDCA), based on enhanced distributed channel access (EDCA) of IEEE 802.11e under the infrastructure mode. Our proposed scheme aims at efficiently adapting the transmission over WLAN to the time-varying network conditions and mitigating the competition ability unfairness between access point (AP) and non-AP stations (STAs). Specifically, all non-AP STAs adaptive-ly modify the contention window based on the network condition. Moreover, AP skips the backoff phase by setting its backoff counter as zero when non-AP STA completes transmission successfully to relieve the unfairness. At last, simulation results demonstrate the effectiveness of the proposed approach.

Error Resilient IPTV for an IEEE 802.16e Channel

Data-partitioning of IPTV video streams is a way of providing graceful quality degradation in a form that will work in good and difficult wireless channel conditions, as experienced by mobile devices. This paper’s proposal is to combine redundant slice protection along with an adaptive channel coding scheme that is also proposed in the paper. Adaptive channel coding is achieved by retransmission when necessary of additional redundant data to reconstruct corrupted packets. In the proposal, outright packet loss is provided for by a form of redundant slice protection. The paper finds that it is preferable: not to simply protect only the highest priority packets;that a moderate quantization level should be employed;and that video quality is differentiated by content type. It is important also to configure the partitioning correctly to remove inter-partition dependencies when possible.

An Adaptive Management Strategy of CQI Channel Allocation in IEEE 802.16 Systems

IEEE 802.16 systems adopt a "semi-dynamic" allocation mechanism of channel quality indicator (CQI) channels.However,low utilization ratio of CQI channels reduces the spectrum efficiency.So we propose an adaptive management strategy of CQI channels based on an analysis model named "toy brick model" to improve the efficiency.The simulation results validate the improvement.

基于权值构建数据导频的V2V信道估计算法

针对IEEE 802.11p协议中导频数量不足无法准确跟踪车联网信道快速变化的问题,本文提出了一种基于时频域相关性构建数据导频、加权平滑重构判决策略的信道估计算法。该算法在不改变IEEE 802.11p协议标准导频结构的前提下,有效利用频域相邻子载波间以及时域相邻正交频分复用符号间的强相关性构建数据导频,引入权值因子对前后时刻信道估计值动态时域更新,结合频域平均重构数据导频构建算法的判决策略。仿真结果表明:在3种不同车-车(vehicle-to-vehicle,V2V)通信场景下,本文提出的算法在误码率和均方根误差方面优于时频平均、数据导频构建等算法。

Accurate Phase Detection for ZigBee Using Artificial Neural Network

The IEEE802.15.4 standard has been widely used in modern industry due to its several benefits for stability,scalability,and enhancement of wireless mesh networking.This standard uses a physical layer of binary phase-shift keying(BPSK)modulation and can be operated with two frequency bands,868 and 915 MHz.The frequency noise could interfere with the BPSK signal,which causes distortion to the signal before its arrival at receiver.Therefore,filtering the BPSK signal from noise is essential to ensure carrying the signal from the sen-der to the receiver with less error.Therefore,removing signal noise in the BPSK signal is necessary to mitigate its negative sequences and increase its capability in industrial wireless sensor networks.Moreover,researchers have reported a posi-tive impact of utilizing the Kalmen filter in detecting the modulated signal at the receiver side in different communication systems,including ZigBee.Mean-while,artificial neural network(ANN)and machine learning(ML)models outper-formed results for predicting signals for detection and classification purposes.This paper develops a neural network predictive detection method to enhance the performance of BPSK modulation.First,a simulation-based model is used to generate the modulated signal of BPSK in the IEEE802.15.4 wireless personal area network(WPAN)standard.Then,Gaussian noise was injected into the BPSK simulation model.To reduce the noise of BPSK phase signals,a recurrent neural networks(RNN)model is implemented and integrated at the receiver side to esti-mate the BPSK’s phase signal.We evaluated our predictive-detection RNN model using mean square error(MSE),correlation coefficient,recall,and F1-score metrics.The result shows that our predictive-detection method is superior to the existing model due to the low MSE and correlation coefficient(R-value)metric for different signal-to-noise(SNR)values.In addition,our RNN-based model scored 98.71%and 96.34%based on recall and F1-score,respectively.