CN108513364A - Demand based on multichannel cooperative cooperating perceives MAC protocol optimization method - Google Patents
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Abstract
Description
技术领域technical field
本发明涉及车联网通信技术领域，尤其涉及一种基于多信道协同合作的需求感知MAC协议优化方法。The present invention relates to the technical field of Internet of Vehicles communication, in particular to a demand-aware MAC protocol optimization method based on multi-channel cooperative cooperation.
背景技术Background technique
近年来关于VANET网络的研究越来越受到学术界和工业界的重视，已经与一些流行的技术如车载云计算网络的数据安全和完整性一起研究。VANET（Vehicular Ad-hocNETwork，车载自组织网络）网络是由车辆通过ad hoc网络连接而成，由路边单元（roadside unit，RSU）和车载控制单元（on board unit，OBU）组成。OBU安装在车内可视为一个移动节点，车辆的基本通信形式可分为车辆对车辆( Vehicle to Vehicle，V2V)和车辆对基础设施(Vehicle to Infrastructure，V2I)。WAVE是一种应用于VANET网络的无线通信协议，包含了IEEE802.11p和1609协议族。WAVE中定义了七个信道其中一个控制信道（CCH），六个服务信道（SCH）。IEEE 1609.4的多信道定义同步时隙的长度为100ms，其中分为CCH时隙（CCHI）和SCH时隙（SCHI）。由于VANET网络中拓扑结构动态的变化，基于竞争的MAC协议和固定控制信道时隙和服务信道时隙，MAC协议不能有效的支持时延敏感和吞吐量敏感应用。In recent years, research on VANET networks has attracted more and more attention from academia and industry, and has been studied together with some popular technologies such as data security and integrity of vehicle cloud computing networks. The VANET (Vehicular Ad-hocNETwork, Vehicular Ad Hoc Network) network is formed by vehicles connected through an ad hoc network, and consists of a roadside unit (roadside unit, RSU) and an on board unit (OBU). The OBU installed in the vehicle can be regarded as a mobile node, and the basic communication forms of vehicles can be divided into Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I). WAVE is a wireless communication protocol applied to VANET networks, including IEEE802.11p and 1609 protocol families. Seven channels are defined in WAVE, including one control channel (CCH) and six service channels (SCH). The multi-channel definition of IEEE 1609.4 has a length of 100ms for a synchronous time slot, which is divided into a CCH time slot (CCHI) and an SCH time slot (SCHI). Due to the dynamic change of topology in VANET network, MAC protocol based on contention and fixed control channel time slot and service channel time slot, MAC protocol cannot effectively support delay-sensitive and throughput-sensitive applications.
安全消息的传输为道路提供安全保障，发送频率一般为10Hz。在控制时隙CCHI中，信道传输的是安全信息，每一辆车节点在CCHI中周期性的发送安全信息。由于安全信息属于高级别的消息类型，因此会分派一个较小的竞争窗口。在密集型网络环境中，碰撞频率会因为竞争窗口太小而增加，因此道路安全不能得到保证。目前有一种基于TDMA的安全消息传输机制，该算法主要通过车辆交换时隙占用信息，来获得他们自己的安全消息传输的空闲时隙，这种方案增加了额外的信息并且与IEEE802.11p不匹配。安全信息的时隙长度由车辆的数量决定，然而在密集网络下安全数据包的碰撞并没有降低。安全数据包发送的频率发生了改变，在SCHI期间车辆节点通过在CCH信道发送额外的安全信息来增加安全数据包的可靠性。The transmission of safety messages provides safety assurance for roads, and the transmission frequency is generally 10Hz. In the control time slot CCHI, the channel transmits safety information, and each vehicle node periodically sends safety information in CCHI. Because security information is a high-level message type, a smaller contention window is allocated. In a dense network environment, the collision frequency will increase because the contention window is too small, so road safety cannot be guaranteed. Currently there is a TDMA-based safety message transmission mechanism, the algorithm mainly obtains their own free time slots for safety message transmission by exchanging time slot occupancy information between vehicles, this scheme adds additional information and does not match IEEE802.11p . The slot length of security messages is determined by the number of vehicles, however, the collision of security packets is not reduced in dense networks. The frequency of sending safety data packets has changed, and vehicle nodes increase the reliability of safety data packets by sending additional safety information on the CCH channel during SCHI.
现有技术中大多都是固定时隙的MAC协议，这种方法虽在一定程度上提高了链路吞吐量和降低了时延，但由于VANET网络中拓扑结构动态的变化，基于竞争的MAC协议和固定控制信道时隙和服务信道时隙，事实上在SCHI期间，一些车辆节点可能没有在监听CCH的安全信息。所以固定比例的安全消息传输时隙不适用于车辆数量变化的情况，不能有效的支持时延敏感和吞吐量敏感应用。在这种情况下，设计一个有效的MAC协议来提高VANETS网络的可靠性和降低信道时延是非常重要的。Most of the existing technologies are MAC protocols with fixed time slots. Although this method improves the link throughput and reduces the delay to a certain extent, due to the dynamic change of the topology structure in the VANET network, the contention-based MAC protocol and fixed control channel slots and service channel slots, in fact during SCHI, some vehicle nodes may not be listening to the safety information of CCH. Therefore, the fixed ratio of safety message transmission time slots is not suitable for the situation where the number of vehicles changes, and cannot effectively support delay-sensitive and throughput-sensitive applications. In this case, it is very important to design an effective MAC protocol to improve the reliability of VANETS network and reduce the channel delay.
发明内容Contents of the invention
本发明的主要目的在于解决现有技术中存在的的题，提供一种基于多信道协同合作的需求感知MAC协议优化方法，具体技术方案如下：The main purpose of the present invention is to solve the problems existing in the prior art, and to provide a demand-aware MAC protocol optimization method based on multi-channel cooperative cooperation. The specific technical scheme is as follows:
一种基于多信道协同合作的需求感知MAC协议优化方法，所述方法应用于车辆自组织网络中，所述车辆自组织网络包括RSU和在对应RSU信号覆盖范围内的车辆，其特征在于，所述方法包括步骤：A demand-aware MAC protocol optimization method based on multi-channel collaborative cooperation, the method is applied in a vehicle ad hoc network, the vehicle ad hoc network includes RSUs and vehicles within the corresponding RSU signal coverage, characterized in that the Said method comprises steps:
S1：RSU根据当前覆盖范围的车辆数量，RSU根据车辆数量初始化MAC帧的时隙，并且在DA时隙向所有车辆发送一个查询数据包；S1: According to the number of vehicles in the current coverage area, the RSU initializes the time slot of the MAC frame according to the number of vehicles, and sends a query data packet to all vehicles in the DA time slot;
S2：若有新车辆进入RSU的覆盖范围，每一个新进车辆在DA时隙给RSU发送报道信号，RSU根据接收到的报道信号动态维护覆盖范围内的车辆总数信息；S2: If a new vehicle enters the coverage area of the RSU, each new vehicle sends a report signal to the RSU in the DA time slot, and the RSU dynamically maintains the total number of vehicles in the coverage area according to the received report signal;
S3：RSU根据每个车辆给RSU反馈回的RES信号准备与当前时隙同步的下一个LI包，发送至RSU覆盖范围内的所有车辆；S3: RSU prepares the next LI packet synchronized with the current time slot according to the RES signal fed back by each vehicle to the RSU, and sends it to all vehicles within the coverage of the RSU;
S4：所有RSU覆盖范围内的车辆根据LI包中包含的信息通过多信道进行无碰撞的数据传输操作。S4: All vehicles within the coverage area of the RSU perform collision-free data transmission operations through multiple channels according to the information contained in the LI package.
进一步的，还包括步骤，判断每个所述车辆是否需要进行信息发送，若所述车辆有信息需要发送，则根据所述RSU和RES信号对车辆进行时隙分配，且若RSU没有对车辆进行时隙预留，则将车辆放置下一时隙中；若所述车辆无信息发送，则每个所述车辆维持原所述RSU分配的时隙进行通信。Further, it also includes the step of judging whether each of the vehicles needs to send information, if the vehicles have information to send, then allocate time slots to the vehicles according to the RSU and RES signals, and if the RSU does not send information to the vehicles If the time slot is reserved, the vehicle is placed in the next time slot; if the vehicle has no information to send, each vehicle maintains the original time slot allocated by the RSU for communication.
进一步的，进入所述RSU信号覆盖范围内的所述新进车辆需要获得所述RSU执行的认证，以保证可以获得安全信息的传输机会。Further, the new vehicle entering the coverage area of the RSU signal needs to obtain the authentication performed by the RSU, so as to ensure that the transmission opportunity of safety information can be obtained.
进一步的，所述二分图以及加权二分图中顶点集之间每条边表示权重，所述时隙包括CRP时隙和SCHI时隙，所述车辆先进入CRP时隙，后进入SCHI时隙。Further, each edge between the vertex sets in the bipartite graph and the weighted bipartite graph represents a weight, and the time slot includes a CRP time slot and a SCHI time slot, and the vehicle first enters the CRP time slot and then enters the SCHI time slot.
进一步的，所述RSU根据所述车辆的数量动态进行时隙分配和调整。Further, the RSU dynamically allocates and adjusts time slots according to the number of vehicles.
本发明基于基于多信道协同合作的需求感知MAC协议优化方法，首先通过RSU统计其覆盖范围内的车辆数，并广播安全询问数据包，RSU根据车辆反馈的信息给车辆动态的划分时隙，以实现数据无碰撞传输的概率；同时，在新车辆进入到RSU的覆盖范围内时，新进入的车辆需要获得RSU执行的认证，以获得安全信息的传输机会；与现有技术相比，本发明通过RSU来广播安全信息，在SCHI时隙发送DA询问数据包来收集RSU覆盖范围内的车辆信息，同时有安全消息要发送或接收的车辆通过预约CCH时隙并且在SCHI时隙通过多信道预留机制实现了无碰撞的非安全数据传输；本发明采用动态的调整时隙来设置恰当的时隙值，适用于车辆自组织网络环境中；本发明降低了碰撞的概率和安全数据包时延，提高了信道的吞吐量，实现了信道的无碰撞传输。The present invention is based on a demand-aware MAC protocol optimization method based on multi-channel cooperative cooperation. First, the number of vehicles within its coverage is counted by the RSU, and a safety inquiry data packet is broadcast. The RSU dynamically divides time slots for the vehicle according to the information fed back by the vehicle. Realize the probability of data transmission without collision; at the same time, when a new vehicle enters the coverage area of the RSU, the newly entered vehicle needs to obtain the authentication performed by the RSU to obtain the transmission opportunity of safety information; compared with the prior art, the present invention The safety information is broadcast through the RSU, and the DA inquiry data packet is sent in the SCHI time slot to collect the vehicle information within the RSU coverage. The retention mechanism realizes non-collision-free data transmission; the present invention uses dynamic adjustment time slots to set appropriate time slot values, and is suitable for vehicle ad hoc network environments; the present invention reduces the probability of collision and the time delay of safe data packets , which improves the throughput of the channel and realizes the collision-free transmission of the channel.
附图说明Description of drawings
图1为本发明所述方法的流程示意图；Fig. 1 is a schematic flow sheet of the method of the present invention;
图2~图4为本发明所述方法中车辆的报道及询问过程示意；Fig. 2～Fig. 4 is the report of vehicle in the method for the present invention and inquiry process schematic diagram;
图5为本发明所述方法中DA-MAC时隙模型示意。FIG. 5 is a schematic diagram of a DA-MAC time slot model in the method of the present invention.
具体实施方式Detailed ways
为了使本技术领域的人员更好地理解本发明方案，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述。显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例，附图中给出了本发明的较佳实施例。本发明可以以许多不同的形式来实现，并不限于本文所描述的实施例，相反地，提供这些实施例的目的是使对本发明的公开内容的理解更加透彻全面。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments, and the preferred embodiments of the present invention are shown in the accompanying drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein, on the contrary, these embodiments are provided for the purpose of making the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.
参阅图1，在本发明实施例中，提供了一种基于多信道协同合作的需求感知MAC协议优化方法，所述方法应用于车辆自组织网络中，车辆自组织网络包括RSU和在对应RSU信号覆盖范围内的车辆，在RSU覆盖范围内的每一车辆视为一个车辆节点；具体通过RSUs来广播安全询问数据包，通过提前预约控制时隙，实现车辆节点紧急信息的发送，基于安全数据的需求量动态划分时隙，促使每一个节点都能通过RSU的动态调度，按序广播安全信息；具体方法步骤如下：Referring to FIG. 1 , in an embodiment of the present invention, a demand-aware MAC protocol optimization method based on multi-channel cooperative cooperation is provided, and the method is applied in a vehicle ad hoc network, and the vehicle ad hoc network includes an RSU and a corresponding RSU signal For vehicles within the coverage area, each vehicle within the coverage area of the RSU is regarded as a vehicle node; specifically, the RSUs are used to broadcast safety inquiry data packets, and the emergency information of the vehicle nodes is sent by pre-reserving the control time slot. The demand dynamically divides time slots, so that each node can broadcast security information in sequence through the dynamic scheduling of RSU; the specific method steps are as follows:
S1：RSU根据当前覆盖范围的车辆数量，RSU根据车辆数量初始化MAC帧的时隙，并且在DA时隙向所有车辆发送一个查询数据包；S1: According to the number of vehicles in the current coverage area, the RSU initializes the time slot of the MAC frame according to the number of vehicles, and sends a query data packet to all vehicles in the DA time slot;
具体的，本发明中的方法通过公式nnew=V·D·TSI来计算当前RSU信号覆盖范围内的车辆数，其中，公式中V，D和TSI分别表示车速、车辆密度和同步时隙的长度。Specifically, the method in the present invention calculates the number of vehicles within the coverage of the current RSU signal through the formula n new = V D T SI , wherein, V, D and T SI in the formula represent vehicle speed, vehicle density and synchronization time respectively The length of the gap.
S2：若有新车辆进入RSU的覆盖范围，每一个新进车辆在DA时隙给RSU发送报道信号，RSU根据接收到的报道信号动态维护覆盖范围内的车辆总数信息；以及S3：RSU根据每个车辆给RSU反馈回的RES信号准备与当前时隙同步的下一个LI包，发送至RSU覆盖范围内的所有车辆；S2: If a new vehicle enters the coverage area of the RSU, each new vehicle sends a report signal to the RSU in the DA time slot, and the RSU dynamically maintains the total number of vehicles in the coverage area according to the received report signal; and S3: RSU according to each The RES signal fed back by a vehicle to the RSU prepares the next LI packet synchronized with the current time slot, and sends it to all vehicles within the coverage of the RSU;
在本发明中，新进入RSU覆盖范围的车辆为了获得安全信息的传输机会，它们必须获得RSU执行的认证，具体过程可参阅图2、图3和图4；如图2所示为SCHI时隙，在实施例中，一帧包含一个询问时隙和随后时隙，RSU会估计刚刚进入覆盖范围内车辆的数量，当帧的时隙数量等于刚刚进来的车数时为最优解，RSU决定初始帧的大小，并且在询问时隙期间发送一个查询数据包，当车辆接收到查询数据包时，它们会随机的在SMP时期选择一个时隙来传输安全数据包，然后DA过后会分派同样数量的时隙；刚刚进入覆盖范围内的车辆会在DA时隙给当前的RSU发送一个报道信号以便RSU动态的维护覆盖范围内车辆总数的信息；RSU收集被覆盖车辆的信息，并且为下一同步时隙准备LI包，参阅图3所示的报道过程：在SCHI结束之后，RSU在下一个同步时隙的LIBP时隙广播LI包，并在SMP有序的传输安全数据；因为LI包包含了安全数据的传输顺序，车辆接收到LI包可以决定自己的传输时隙，SMP的长度要与发送安全数据包的数量相等。In the present invention, in order to obtain the transmission opportunity of safety information, the vehicles that newly enter the coverage area of RSU must obtain the authentication that RSU performs, and the specific process can refer to Fig. 2, Fig. 3 and Fig. 4; as shown in Fig. 2, it is the SCHI time slot , in an embodiment, a frame includes an inquiry time slot and subsequent time slots, RSU will estimate the number of vehicles that have just entered the coverage area, when the number of time slots in the frame is equal to the number of vehicles that have just come in, it is the optimal solution, RSU decides The size of the initial frame, and send a query packet during the query slot, when the vehicle receives the query packet, they will randomly select a slot in the SMP period to transmit the security packet, and then the same amount will be dispatched after DA time slot; the vehicle that has just entered the coverage area will send a report signal to the current RSU in the DA time slot so that the RSU can dynamically maintain the information of the total number of vehicles in the coverage area; Time slot preparation LI packet, refer to the reporting process shown in Figure 3: After the SCHI ends, the RSU broadcasts the LI packet in the LIBP time slot of the next synchronous time slot, and transmits the security data in an orderly manner in the SMP; because the LI packet contains the security The sequence of data transmission, the vehicle can determine its own transmission time slot after receiving the LI packet, and the length of the SMP should be equal to the number of sent security data packets.
S4：所有RSU覆盖范围内的车辆根据LI包中包含的信息通过多信道进行无碰撞的数据传输操作。S4: All vehicles within the coverage area of the RSU perform collision-free data transmission operations through multiple channels according to the information contained in the LI package.
在本发明实施例中，LIBP之后进入SMP时期，此时，分配好了时隙的车辆将会按照RSU发送的LI包信息进行有序的广播车辆安全信息；具体的，车辆节点在CRP时隙通过竞争预留SCHs来传输数据，并通过三次握手机制：请求（REQ）、响应（RES）和RSU协调数据包（RC）来完成；在有数据要发送的节点会向目的节点先发一个REQ数据包，如果目的节点成功接收到REQ信号，就会回复一个RES数据包。RSU监听到这些数据包就会广播RC数据包来告诉其覆盖范围内的所有车辆预留成功，所有的节点就会维护已经预留的SCH信道信息；竞争的节点发送REQ数据包，选择SCH信道其中包含了已经预留信道的信息；节点选择一个最不拥挤的SCHs，如果SCHs都没有被占用，节点就会随机选择，这个过程将会在CRP时隙内进行。In the embodiment of the present invention, after LIBP enters the SMP period, at this time, the vehicles that have allocated time slots will broadcast vehicle safety information in an orderly manner according to the LI packet information sent by the RSU; Data is transmitted by competing to reserve SCHs, and it is completed through a three-way handshake mechanism: request (REQ), response (RES) and RSU coordination packet (RC); the node that has data to send will first send a REQ to the destination node Data packet, if the destination node successfully receives the REQ signal, it will reply with a RES data packet. When RSU listens to these data packets, it will broadcast RC data packets to tell all vehicles within its coverage that the reservation is successful, and all nodes will maintain the reserved SCH channel information; competing nodes send REQ data packets to select SCH channels It contains the information of the reserved channel; the node selects the least congested SCHs, if none of the SCHs are occupied, the node will choose randomly, and this process will be carried out in the CRP time slot.
在SCHI时隙，已经预留成功的节点会调到SCHs发送数据包，因为每个节点都准确有序的占用SCH，所以车辆节点传输数据是有序的；结合图5，SCH1数据传输预留的是节点4向节点5发送数据，之后是节点5到节点4的数据传输。SCH2信道首先预留的是V2-V3，之后是V3-RSU。SCHI结束之后开始新的同步时隙。我们假设在图1中节点1到节点6成功预约了时隙。因此车辆在SMP时隙有序广播它们的安全数据包，其中一些车辆由于走出RSU覆盖范围，不能传输安全数据。RSU通过监听这些节点的所有时隙，如果节点1时隙不停的处于空闲，RSU就会判断出节点1已经移出其覆盖范围并在下一个LI数据包将其除外。In the SCHI time slot, the nodes that have been successfully reserved will transfer to the SCHs to send data packets, because each node occupies the SCH accurately and orderly, so the data transmission of the vehicle nodes is orderly; combined with Figure 5, SCH1 data transmission reservation What is the transmission of data from node 4 to node 5, followed by the data transmission from node 5 to node 4. The SCH2 channel is first reserved for V2-V3, followed by V3-RSU. A new synchronization time slot starts after the end of SCHI. We assume that nodes 1 to 6 have successfully reserved time slots in Figure 1 . Therefore vehicles broadcast their security data packets sequentially in SMP time slots, and some of them cannot transmit security data due to going out of RSU coverage. RSU monitors all time slots of these nodes. If the time slot of node 1 is constantly idle, RSU will judge that node 1 has moved out of its coverage and exclude it in the next LI data packet.
本发明基于多信协同合作的需求感知MAC协议优化方法，首先通过RSU统计其覆盖范围内的车辆数，并广播安全询问数据包，RSU根据车辆反馈的信息给车辆动态的划分时隙，以实现数据无碰撞传输的概率；同时，在新车辆进入到RSU的覆盖范围内时，新进入的车辆需要获得RSU执行的认证，以获得安全信息的传输机会；与现有技术相比，本发明通过RSU来广播安全信息，在SCHI时隙发送DA询问数据包来收集RSU覆盖范围内的车辆信息，同时有安全消息要发送或接收的车辆通过预约CCH时隙并且在SCHI时隙通过多信道预留机制实现了无碰撞的非安全数据传输；本发明采用动态的调整时隙来设置恰当的时隙值，适用于车辆自组织网络环境中；本发明降低了碰撞的概率和安全数据包时延，提高了信道的吞吐量，实现了信道的无碰撞传输。The present invention is based on multi-signal collaborative cooperation demand-aware MAC protocol optimization method. Firstly, the RSU counts the number of vehicles within its coverage area, and broadcasts safety inquiry data packets. The RSU dynamically divides time slots for vehicles according to the information fed back by the vehicles to realize The probability of data transmission without collision; at the same time, when a new vehicle enters the coverage area of the RSU, the newly entered vehicle needs to obtain the authentication performed by the RSU to obtain the transmission opportunity of safety information; compared with the prior art, the present invention passes RSU broadcasts safety information, and sends DA inquiry data packets in SCHI time slots to collect vehicle information within the coverage of RSU. At the same time, vehicles with safety messages to send or receive reserve CCH time slots and reserve through multi-channel in SCHI time slots The mechanism realizes the non-safe data transmission without collision; the present invention adopts the dynamic adjustment time slot to set the appropriate time slot value, and is applicable to the vehicle ad hoc network environment; the present invention reduces the probability of collision and the time delay of safe data packets, The throughput of the channel is improved, and the collision-free transmission of the channel is realized.
以上仅为本发明的较佳实施例，但并不限制本发明的专利范围，尽管参照前述实施例对本发明进行了详细的说明，对于本领域的技术人员来而言，其依然可以对前述各具体实施方式所记载的技术方案进行修改，或者对其中部分技术特征进行等效替换。凡是利用本发明说明书及附图内容所做的等效结构，直接或间接运用在其他相关的技术领域，均同理在本发明专利保护范围之内。The above are only preferred embodiments of the present invention, but do not limit the scope of patents of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it can still understand the foregoing aspects The technical solutions described in the specific embodiments are modified, or some of the technical features are equivalently replaced. All equivalent structures made by utilizing the contents of the specification and drawings of the present invention and directly or indirectly used in other related technical fields are also within the protection scope of the patent of the present invention.
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