本文選題：交通信息物理融合系統(tǒng) + 車載無線自組網(wǎng)��； 參考：《西北工業(yè)大學(xué)》2015年博士論文

【摘要】：道路交通事故一直以來是全球性最重要的公共安全問題之一，給人類社會(huì)帶來了巨大的生命和財(cái)產(chǎn)損失。為了避免交通事故的發(fā)生，在過去三十多年中，各大汽車研究機(jī)構(gòu)都在積極研發(fā)車輛主動(dòng)式安全應(yīng)用，以提高行車安全。由于傳統(tǒng)交通系統(tǒng)的計(jì)算過程和物理環(huán)境之間缺乏廣泛的互連互通，大多數(shù)主動(dòng)安全技術(shù)還是基于單一車輛實(shí)現(xiàn)，使得交通系統(tǒng)安全控制未達(dá)到充分的整體協(xié)調(diào)優(yōu)化。而信息物理融合系統(tǒng)（Cyber PhysicalSystem, CPS）概念的出現(xiàn)，為上述問題開辟了新的解決途徑。交通信息物理融合系統(tǒng)（Transportation Cyber Physical System, T-CPS）是CPS在交通領(lǐng)域的應(yīng)用，通過將傳感、計(jì)算、控制和通信等技術(shù)，有效集成運(yùn)用于交通運(yùn)行管理系統(tǒng)，形成信息化、智能化、人性化的新型交通運(yùn)輸系統(tǒng)。 為了達(dá)到交通信息系統(tǒng)和交通物理系統(tǒng)的深度融合，需要一種適用于道路環(huán)境下的通信技術(shù)來實(shí)現(xiàn)兩者的廣泛互連互通。在這種需求背景下，車載無線自組網(wǎng)（VehicularAd Hoc Network, VANET）應(yīng)運(yùn)而生。通過車與車（Vehicle-to-Vehicle, V2V）和車與路邊基礎(chǔ)設(shè)施（Vehicle-2-Infrastructure, V2I）兩種通信方式，使得駕駛者可以及時(shí)獲取視野范圍外的潛在威脅信息并作出預(yù)判。研究表明，車載無線自組網(wǎng)能夠提供比傳統(tǒng)安全技術(shù)更為全面和有效的安全保障。因此，各國政府、研究機(jī)構(gòu)和汽車廠商都開始致力于研究基于車載無線自組網(wǎng)的車輛主動(dòng)式安全通信（Vehicle Safety Communication, VSC）技術(shù)。 由于車輛主動(dòng)式安全應(yīng)用對(duì)于通信性能的要求較高，因此，現(xiàn)有協(xié)議是否能夠滿足此類應(yīng)用的實(shí)時(shí)性和穩(wěn)定性需求，是協(xié)議設(shè)計(jì)和參數(shù)制定的關(guān)鍵問題。本文采用數(shù)理分析模型的方法，建立了基于IEEE802.11p的車載無線自組網(wǎng)在典型行車環(huán)境下的協(xié)議模型，并提出了協(xié)議實(shí)時(shí)性與穩(wěn)定性分析方法。結(jié)合模型分析結(jié)果，進(jìn)一步討論與協(xié)議兼容的優(yōu)化方案，設(shè)計(jì)了車輛主動(dòng)式安全通信環(huán)境下自適應(yīng)速率控制協(xié)議以提高通信的穩(wěn)定性。本文的主要貢獻(xiàn)如下： 第一，本文結(jié)合車輛主動(dòng)式安全通信的特點(diǎn)，考慮高速公路環(huán)境下車輛分布、信道衰落等影響，運(yùn)用數(shù)學(xué)模型分析的方法，建立了車輛主動(dòng)式安全通信網(wǎng)絡(luò)綜合模型。與大多數(shù)無線通信網(wǎng)絡(luò)模型僅僅只對(duì)通信環(huán)節(jié)中單一層級(jí)進(jìn)行建模不同，本文研究的模型涵蓋了環(huán)境模型、信道模型、IEEE802.11p協(xié)議的物理層模型以及MAC層模型，并詳細(xì)刻畫了隱藏節(jié)點(diǎn)、虛擬沖突、非飽和網(wǎng)絡(luò)狀態(tài)等問題，更接近真實(shí)的通信環(huán)境。該模型是目前車輛主動(dòng)式安全通信環(huán)境下較為有效的綜合模型，對(duì)于深層次理解協(xié)議存在的問題、分析網(wǎng)絡(luò)各項(xiàng)性能指標(biāo)和協(xié)議改進(jìn)與優(yōu)化提供了很好的研究基礎(chǔ)； 第二，提出了車輛主動(dòng)式安全通信實(shí)時(shí)性與穩(wěn)定性分析方法�？紤]到通信節(jié)點(diǎn)緩存能力限制，本文研究了有限隊(duì)列長(zhǎng)度下的協(xié)議性能指標(biāo)。建立M/G/1/K隊(duì)列模型，分析了標(biāo)準(zhǔn)IEEE802.11p協(xié)議在典型行車環(huán)境下的平均延時(shí)，并采用區(qū)域劃分的分析方法估算了平均丟包率。仿真結(jié)果證明，本文提出的實(shí)時(shí)性與穩(wěn)定性分析模型的理論值與仿真值基本一致，平均計(jì)算誤差小于5%，具有較高的準(zhǔn)確性。進(jìn)而采用該模型詳細(xì)分析了各種外部因素、系統(tǒng)參數(shù)對(duì)于通信實(shí)時(shí)性與穩(wěn)定性的影響。分析結(jié)果表明標(biāo)準(zhǔn)IEEE802.11p協(xié)議可以很好的滿足車輛主動(dòng)式安全通信實(shí)時(shí)性需求，但不能達(dá)到其對(duì)穩(wěn)定性的要求； 第三，設(shè)計(jì)和實(shí)現(xiàn)了適合車載環(huán)境下主動(dòng)安全應(yīng)用的自適應(yīng)通信協(xié)議VSCRA。目前，尚無針對(duì)單跳廣播的自適應(yīng)速率控制協(xié)議相關(guān)研究，本文率先提出了適用于單跳廣播的自適應(yīng)速率控制跨層協(xié)議框架。該優(yōu)化協(xié)議解決了車輛主動(dòng)式安全通信環(huán)境下自適應(yīng)速率控制的兩個(gè)重要問題：第一，在單跳廣播通信缺乏反饋信息的條件下，發(fā)送節(jié)點(diǎn)如何在本地進(jìn)行信道狀態(tài)估計(jì)；第二，在車流密度較大的環(huán)境中，節(jié)點(diǎn)間相互干擾造成的丟包嚴(yán)重，如何區(qū)分信道衰落丟包和信道干擾丟包造成的影響，并選擇最優(yōu)傳輸速率。針對(duì)這兩個(gè)問題，本文分別提出了基于信道對(duì)稱性理論的本地丟包估計(jì)方法和基于節(jié)點(diǎn)間相對(duì)距離的信道衰落丟包估計(jì)，并設(shè)計(jì)了基于自組織模糊神經(jīng)網(wǎng)絡(luò)的自適應(yīng)速率選擇算法。仿真結(jié)果證明，優(yōu)化協(xié)議能夠在車流密度變化的環(huán)境中大大提高通信穩(wěn)定性； 第四，基于實(shí)際的DSRC車載無線通信單元搭建了實(shí)驗(yàn)平臺(tái)，驗(yàn)證基于節(jié)點(diǎn)相對(duì)距離的信道衰落丟包估計(jì)。實(shí)驗(yàn)結(jié)果表明，，相同距離下的丟包率偏移值均小于4%，變化比較平穩(wěn)，說明相對(duì)距離能夠很好的估算大尺度信道衰落造成的丟包。同時(shí)，本文基于NS2設(shè)計(jì)了VSCRA仿真平臺(tái)，進(jìn)行大規(guī)模仿真，主要驗(yàn)證不同行車環(huán)境下，所提出理論模型和優(yōu)化協(xié)議的正確性和有效性。仿真結(jié)果表明VSCRA較之固定速率傳輸模式3Mbps，6Mbps和12Mbps，其丟包率平均降低了34.16%，43.07%和60.76%。 綜上所述，本文的工作采用建立模型的方式分析了車載無線自組網(wǎng)在車輛主動(dòng)式安全通信中的缺陷，并基于理論分析提出了有效的協(xié)議優(yōu)化方案。論文的研究有助于車載環(huán)境下標(biāo)準(zhǔn)協(xié)議的制定與性能改善。
[Abstract]:Road traffic accident has always been one of the most important public safety problems in the world, which has brought great loss of life and property to human society. In order to avoid the occurrence of traffic accidents, in order to avoid the occurrence of traffic accidents, in the past thirty years, various automobile research institutions have actively developed vehicle active safety applications in order to improve traffic safety. There is a lack of extensive interconnection and intercommunication between the computing process of the traffic system and the physical environment. Most active safety technologies are based on a single vehicle, which makes the safety control of the traffic system not fully integrated and optimized. The emergence of the concept of Cyber PhysicalSystem (CPS) has opened up a new problem for the above problems. The transportation information physical fusion system (Transportation Cyber Physical System, T-CPS) is the application of CPS in the traffic field. Through the technology of sensing, computing, control and communication, it is effectively integrated into the traffic operation management system to form a new type of transportation system with information, intelligence and humanization.
In order to achieve the depth fusion of traffic information system and traffic physical system, a communication technology suitable for the road environment is needed to realize the wide interconnection and intercommunication between the two. In this context, the VehicularAd Hoc Network (VANET) has come into being. Through the vehicle and vehicle (Vehicle-to-Vehicle, V2V) and the road and road Vehicle-2-Infrastructure (V2I) is the two communication mode that enables the driver to obtain the potential threat information outside the field of vision and make a prejudgement. The research shows that the vehicle wireless ad hoc network can provide more comprehensive and effective security than the traditional security technology. Therefore, governments, research institutions and automobile factories are provided. Businesses are working on Vehicle Safety Communication (VSC) technology based on vehicular ad hoc networks.
Due to the high requirement of vehicle active safety application for communication performance, it is the key problem for the design of protocol and the formulation of parameters whether the existing protocols can meet the real-time and stability requirements of such applications. In this paper, a vehicle based vehicle wireless ad hoc network based on IEEE802.11p is established by means of mathematical analysis model. Based on the protocol model in the environment, the method of protocol real-time and stability analysis is proposed. Combined with the result of the model analysis, the optimization scheme compatible with the protocol is discussed, and the adaptive rate control protocol is designed to improve the stability of the communication in the vehicle active security communication environment. The main contributions of this paper are as follows:
First, considering the characteristics of vehicle active safety communication, considering the influence of vehicle distribution and channel fading under the environment of the expressway, the integrated model of vehicle active safety communication network is established by mathematical model analysis. And most of the wireless communication network models only model the single level of the communication link. In the same way, this model covers the environment model, channel model, the physical layer model of IEEE802.11p protocol and the MAC layer model, and depicts the hidden nodes, the virtual conflict, the unsaturated network state and so on, which is closer to the real communication environment. This model is a more effective comprehensive model in the current vehicle active security communication environment. It provides a good foundation for further understanding of the problems in the deeper understanding of the protocol, analyzing the performance indicators and improving and optimizing the protocols.
Second, the real time and stability analysis method of vehicle active safety communication is proposed. Considering the limitation of the communication node caching capability, this paper studies the performance index of the protocol under the finite queue length. The M/G/1/K queue model is set up, the average delay of the standard IEEE802.11p protocol under the typical driving environment is analyzed, and the regional partition is used. The analysis method estimates the average packet loss rate. The simulation results show that the theoretical value of the real time and stability analysis model is basically consistent with the simulation value. The average calculation error is less than 5% and has a high accuracy. Then the model is used to analyze the various external factors in detail, and the system parameters have a shadow on the real-time and stability of communication. The analysis results show that the standard IEEE802.11p protocol can meet the real-time requirement of vehicle active safety communication, but it can not meet the requirement of stability.
Third, the adaptive communication protocol VSCRA. suitable for active safety application in vehicle environment is designed and implemented. There is no related research on adaptive rate control protocol for single hop broadcasting. This paper first proposes an adaptive rate control cross layer protocol frame for single hop broadcasting. The optimization protocol solves the vehicle active security. Two important problems of adaptive rate control in communication environment: first, under the condition of lack of feedback information for single hop broadcast communication, how to estimate the channel state of the transmission node locally; second, in the environment with large traffic density, the loss of packet caused by mutual interference between nodes is serious, and how to distinguish the channel fading packet loss and channel dry. In this paper, the local packet loss estimation method based on the theory of channel symmetry and the channel fading estimation based on relative distance between nodes are proposed, and the adaptive rate selection algorithm based on self organizing fuzzy neural network is designed for these two problems. The simulation results are proved to be proved by the simulation results. Obviously, the optimization protocol can greatly improve the communication stability in the environment of changing vehicle density.
Fourth, based on the actual DSRC vehicle wireless communication unit, an experimental platform is built to verify the channel fading loss estimation based on the relative distance of the nodes. The experimental results show that the loss rate of the packet loss rate under the same distance is less than 4%, and the change is relatively stable, which shows that the relative distance can be used to estimate the packet loss caused by the large scale channel fading. Based on NS2, this paper designs a VSCRA simulation platform for large-scale simulation, which mainly validating the correctness and effectiveness of the proposed theoretical model and optimization protocol under different driving environments. The simulation results show that the packet loss rate of VSCRA is reduced by 34.16%, 43.07% and 60.76%., compared with the fixed rate transmission mode 3Mbps, 6Mbps and 12Mbps.
To sum up, this paper analyzes the defects of vehicle wireless ad hoc network in vehicle active security communication by establishing model, and proposes an effective protocol optimization scheme based on theoretical analysis. The research of this paper is helpful to the formulation and performance improvement of the standard protocol under the vehicle environment.

【學(xué)位授予單位】：西北工業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：U495

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本文編號(hào)：1886900