CN101801109B - Medium access control system and medium access control method in wireless packet network - Google Patents
Medium access control system and medium access control method in wireless packet networkDownload PDFInfo
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Abstract
Translated fromChinese
Description
Translated fromChinese技术领域technical field
本发明涉及无线通信网络领域，尤其涉及一种通过数据链路层和物理层协同实现的无线分组网络媒质接入控制系统和方法，用于解决无线ad hoc网络中暴露终端问题，提高通信并发度和网络容量。The present invention relates to the field of wireless communication networks, in particular to a wireless packet network medium access control system and method realized through data link layer and physical layer cooperation, which are used to solve the problem of exposed terminals in wireless ad hoc networks and improve communication concurrency and network capacity.
背景技术Background technique
随着无线通信技术的发展和无线通信应用的普及，由地位平等的无线通信设备构成的自组织无线分组网络，以及联系物理环境和计算环境的无线传感器网络得到越来越广泛的应用。这种被称作无线Ad hoc的网络中，媒质接入控制协议在很大程度上决定网络的实际性能和资源利用效率。With the development of wireless communication technology and the popularization of wireless communication applications, ad hoc wireless packet networks composed of wireless communication devices with equal status, and wireless sensor networks connecting physical and computing environments have been more and more widely used. In this so-called wireless Ad hoc network, the medium access control protocol determines the actual performance and resource utilization efficiency of the network to a large extent.
无线Ad hoc网络中，媒质接入控制层广泛使用的载波侦听(Carrier Sensing)技术受困于隐藏终端问题和暴露终端问题。已成为标准的IEEE 802.11协议中规定的分布式协同机制(DCF)，采用发送请求/发送确认(RTS/CTS)帧以及控制握手规则来解决上述问题。该方法通过引入虚拟载波侦听和网络分配向量，在一定程度上弥补了物理载波侦听的不足，可以解决隐藏终端问题。但是，这种方法未能有效解决暴露终端问题。In the wireless Ad hoc network, the widely used carrier sensing (Carrier Sensing) technology in the media access control layer suffers from the hidden terminal problem and the exposed terminal problem. The Distributed Coordination Mechanism (DCF) stipulated in the standard IEEE 802.11 protocol uses Request to Send/Confirm to Send (RTS/CTS) frames and control handshake rules to solve the above problems. By introducing virtual carrier sense and network allocation vector, this method makes up for the deficiency of physical carrier sense to a certain extent, and can solve the hidden terminal problem. However, this method fails to effectively solve the problem of exposed terminals.
如附图1所示，终端D侦听到A发出的RTS控制帧，并且可以侦听到A发送数据时的载波信号，因而受到抑制，不能向终端F发送数据。但是，D向F发送实际上并不会干扰A和B之间的会话。在此情形中，D称为会话AB的暴露终端，暴露终端引起的通信抑制称为暴露终端问题。As shown in Figure 1, terminal D detects the RTS control frame sent by A, and can detect the carrier signal when A sends data, so it is suppressed and cannot send data to terminal F. However, D sending to F does not actually interfere with the conversation between A and B. In this case, D is called the exposed terminal of session AB, and the communication suppression caused by the exposed terminal is called the exposed terminal problem.
为提高无线Ad hoc网络的吞吐率，国内外在改进RTS/CTS控制信令、提高并发通信密度，即空间复用度方面进行了许多研究。这些研究工作以802.11握手机制为基础，通过适当改变控制信令和控制机制，设法识别并允许不会造成干扰的隐藏和/或暴露终端发起并发会话。根据控制帧与并发数据帧之间干扰的处理方式，这些方法可分为三类：In order to improve the throughput rate of the wireless Ad hoc network, many studies have been carried out at home and abroad on improving the RTS/CTS control signaling and increasing the concurrent communication density, that is, the degree of spatial multiplexing. Based on the 802.11 handshake mechanism, these research works try to identify and allow hidden and/or exposed terminals that will not cause interference to initiate concurrent sessions by appropriately changing control signaling and control mechanisms. Depending on how interference between control frames and concurrent data frames is handled, these methods fall into three categories:
1.取消法，为避免控制帧干扰数据帧，在协议中去掉一些控制帧。例如，MACA协议取消了物理监听，这样直接避免产生暴露终端问题，同时接收终端不再发送接收确认帧ACK，避免了ACK对正在进行的数据接收的干扰。此类方法的主要缺点是ACK的缺失引起的上层(如TCP)的性能恶化，并不适合无线网络，并且，此类方法还会恶化隐藏终端问题。1. Cancellation method, in order to avoid control frames interfering with data frames, some control frames are removed in the protocol. For example, the MACA protocol cancels the physical monitoring, which directly avoids the problem of exposing the terminal. At the same time, the receiving terminal no longer sends the receiving confirmation frame ACK, which avoids the interference of the ACK on the ongoing data reception. The main disadvantage of this type of method is that the lack of ACK causes the performance degradation of the upper layer (such as TCP), which is not suitable for wireless networks, and this type of method will also worsen the problem of hidden terminals.
2.同步法，即设法使并发会话同时结束，这样接收终端发送ACK就不会干扰另一会话的数据接收，例如对MACA的改进协议MACA-P和CTMAC协议。同步法的最大缺点是信令握手过于复杂，并且为实现并发会话的同步，终端在发送时等待时间过长。2. Synchronization method, that is to try to end concurrent sessions at the same time, so that the receiving terminal sends ACK without interfering with the data reception of another session, such as the improved protocol MACA-P and CTMAC protocol for MACA. The biggest disadvantage of the synchronization method is that the signaling handshake is too complicated, and in order to realize the synchronization of concurrent sessions, the terminal waits for too long when sending.
3.规避法，即通过控制信令所交互的信息，仅从网络中选取不会造成相互干扰的暴露终端或隐藏终端执行并发通信，例如进取型MAC协议和包侦听多路接入/冲突避免(PSMA/CA)技术。此类方法的实质是强化了允许并发通信发生的条件，缺点是不能充分实现并发通信和空间复用。3. Evasion method, that is, by controlling the information exchanged by signaling, only select exposed terminals or hidden terminals that will not cause mutual interference from the network to perform concurrent communication, such as aggressive MAC protocol and packet snooping multiple access/collision Avoid (PSMA/CA) techniques. The essence of this type of method is to strengthen the conditions that allow concurrent communication to occur, but the disadvantage is that concurrent communication and space multiplexing cannot be fully realized.
发明内容Contents of the invention
本发明的目的在于避免上述已有技术的缺点，在现有IEEE 802.11标准的基础上，提出一种无线分组网络媒质接入控制系统和方法，通过无线通信终端中的数据链路层和物理层协同，实现帧接收过程中的预期帧检测与消除，解决暴露终端问题，提高无线通信网络的通信容量。The purpose of the present invention is to avoid the above-mentioned shortcoming of prior art, on the basis of existing IEEE 802.11 standard, propose a kind of wireless packet network medium access control system and method, through the data link layer and the physical layer in the wireless communication terminal Cooperate to realize the expected frame detection and elimination in the frame receiving process, solve the problem of exposed terminals, and improve the communication capacity of the wireless communication network.
本发明的技术方案是这样实现的：Technical scheme of the present invention is realized like this:
一、术语说明1. Terminology
MAC层：媒质接入控制层，ISO规定的网络分层结构中，链路层中负责物理媒质获取和使用的子层；MAC layer: Media access control layer, in the network hierarchical structure stipulated by ISO, the sublayer in the link layer responsible for the acquisition and use of physical media;
帧：链路层和物理层协议单元；Frame: link layer and physical layer protocol unit;
分组：与帧对应，称链路层以上层协议单元为分组；Packet: Corresponding to the frame, the protocol unit above the link layer is called a packet;
数据帧：承载用户数据业务内容的链路层协议单元；Data frame: a link layer protocol unit that carries user data service content;
控制帧：承载信令信息，用于实现控制管理等任务的MAC层协议单元；Control frame: carries signaling information and is a MAC layer protocol unit used to implement tasks such as control and management;
RTS/CTS/ACK：三种用于实现802.11无线网络媒质接入控制握手协议的控制帧，分别对应为发送请求帧、发送允许帧和接收确认帧，控制帧有固定的帧长和帧格式；RTS/CTS/ACK: Three control frames used to implement the 802.11 wireless network medium access control handshake protocol, corresponding to the send request frame, send allow frame and receive confirmation frame, respectively, and the control frame has a fixed frame length and frame format;
终端：以对等方式构成无线网络的无线设备，终端间通过无线链路互相发送或接收数据/控制帧；Terminal: a wireless device that constitutes a wireless network in a peer-to-peer manner, and the terminals send or receive data/control frames to each other through wireless links;
会话或通信：称终端间的一次数据帧收发为会话。若A向B发送数据帧，则称之为AB会话；Session or communication: A data frame transmission and reception between terminals is called a session. If A sends a data frame to B, it is called an AB session;
暴露终端：由于载波侦听，处在发送终端信号覆盖范围内的相邻终端不能发起会话。如果该相邻终端发起的会话不会干扰原有会话，则该相邻终端即成为暴露终端。暴露终端会造成不必要的并发通信损失；Exposed terminals: due to carrier sense, adjacent terminals within the signal coverage of the sending terminal cannot initiate a session. If the session initiated by the adjacent terminal does not interfere with the original session, the adjacent terminal becomes an exposed terminal. Exposing the terminal will cause unnecessary concurrent communication loss;
发送持续时间字段：在帧中，有专门的字段用以明确记录将要进行的数据帧发送所需的时间。利用该字段对应的数值和当前时刻，终端可以预期本次会话后续的帧(例如ACK)的发送时间；Send duration field: In the frame, there is a special field to clearly record the time required for the data frame to be sent. Using the value corresponding to this field and the current time, the terminal can expect the sending time of subsequent frames (such as ACK) in this session;
物理载波侦听：终端接收机根据实际接收信号功率判断信道是否繁忙称为物理载波侦听；Physical carrier sensing: The terminal receiver judges whether the channel is busy according to the actual received signal power, which is called physical carrier sensing;
虚拟载波侦听：终端从接收到的相邻终端所发出的帧中的发送持续时间字段，可判断出相邻终端在一段时间内是否正在接收(或者发送)数据，这种侦听方式称为虚拟载波侦听；虚拟载波侦听通过NAV定时器来实现信道忙闲状态管理；Virtual carrier sense: The terminal can determine whether the adjacent terminal is receiving (or sending) data within a certain period of time from the received transmission duration field in the frame sent by the adjacent terminal. This listening method is called Virtual carrier sense; virtual carrier sense implements channel busy/idle state management through NAV timer;
NAV定时器：NAV为英文网络分配向量的缩写。终端在监听到控制帧后，根据帧中的类型字段和发送持续时间字段设置发送和/或接收NAV定时器。若发送NAV定时器正在计时，表示本终端的相邻终端中有数据正在发送；接收NAV定时器正在计时，表示相邻终端中有数据正在接收；NAV timer: NAV is the abbreviation of Network Allocation Vector in English. After the terminal monitors the control frame, it sets the sending and/or receiving NAV timer according to the type field and the sending duration field in the frame. If the sending NAV timer is counting, it means that there is data being sent in the adjacent terminal of this terminal; the receiving NAV timer is counting, which means that there is data being received in the adjacent terminal;
预期帧：指终端根据先前监听到的控制帧的内容，可以提前预测出在当前时刻之后的某个特定时刻将要出现的帧；Expected frame: Refers to the terminal that can predict in advance the frame that will appear at a specific time after the current time according to the content of the previously monitored control frame;
预期帧检测：终端接收到的无线信号可看作是一个或多个发送终端发出的信号经无线信道传播之后与噪声信号的叠加，从中检测并判断预期帧是否存在的操作称为预期帧检测；Expected frame detection: The wireless signal received by the terminal can be regarded as the superposition of the signal sent by one or more sending terminals propagated through the wireless channel and the noise signal, and the operation of detecting and judging whether the expected frame exists is called expected frame detection;
预期帧消除：一旦判断出预期帧存在，接收机可以根据已知的帧内容和信道估计参数生成一个接收到的预期帧信号的副本，并将其从接收到的无线信号中减去，从而使剩余信号能被正确接收，此操作称为预期帧消除。Anticipated frame cancellation: Once the expected frame is judged to exist, the receiver can generate a copy of the received expected frame signal based on the known frame content and channel estimation parameters, and subtract it from the received wireless signal, so that The remaining signal can be received correctly, this operation is called expected frame elimination.
二、本发明的无线分组网络媒质接入控制系统，包括：媒质接入控模制块、接收信号解析模块、天线、射频前端模块、模数转换器、数模转换器、MAC层帧提取模块、物理层帧形成模块、调制/编码模块和物理信道管理模块，其中：2. The wireless packet network medium access control system of the present invention includes: a medium access control module, a received signal analysis module, an antenna, a radio frequency front-end module, an analog-to-digital converter, a digital-to-analog converter, and a MAC layer frame extraction module , a physical layer frame forming module, a modulation/coding module and a physical channel management module, wherein:
所述的媒质接入控制模块，包括：The medium access control module includes:
上层协议接口，用于从上层协议中接收数据分组，将其组装成MAC层帧后发送给发送协同单元，并从接收协同单元中收取接收到的MAC层帧，提取其中的数据分组发送给上层协议；The upper layer protocol interface is used to receive data packets from the upper layer protocol, assemble them into MAC layer frames and send them to the sending coordination unit, and receive the received MAC layer frames from the receiving coordination unit, extract the data packets and send them to the upper layer protocol;
帧发送协同单元，用于根据媒质接入控制协议和其它功能单元的指令，实现MAC层帧发送时所必需的握手控制机制，控制帧发送单元在适当的时间发出适当的控制帧和数据帧，并根据发出的RTS帧内容指示预期帧检测和消除单元设置或预期帧检测；The frame sending coordination unit is used to implement the handshake control mechanism necessary for MAC layer frame sending according to the instructions of the medium access control protocol and other functional units. The control frame sending unit sends appropriate control frames and data frames at an appropriate time, And indicate the expected frame detection and elimination unit setting or expected frame detection according to the content of the sent RTS frame;
帧发送单元，用于在帧发送协同单元、帧接收协同单元的控制下发送MAC层帧给外部的物理层帧形成模块；The frame sending unit is used to send the MAC layer frame to the external physical layer frame forming module under the control of the frame sending coordination unit and the frame receiving coordination unit;
接收协同单元，用于根据媒质接入控制协议和其它功能单元的指令，实现MAC层帧发送时所必需的握手控制机制，根据接收到的帧类型确定响应帧的类型和内容后发送给帧发送单元及时发出；The receiving coordination unit is used to implement the handshake control mechanism necessary for MAC layer frame transmission according to the instructions of the medium access control protocol and other functional units, determine the type and content of the response frame according to the received frame type, and send it to the frame transmission Units are issued in a timely manner;
帧接收单元，用于从外部MAC层帧提取模块接收MAC层帧后及时提交给接收协同单元，根据接收到的帧的类型和发送持续时间字段通知信道管理单元更改接收和发送NAV定时器，并根据接收到的RTS帧和CTS帧指示预期帧检测和消除单元设置或执行预期帧检测；The frame receiving unit is used to receive the MAC layer frame from the external MAC layer frame extraction module and submit it to the receiving coordination unit in time, and notify the channel management unit to change the receiving and sending NAV timer according to the type of the received frame and the sending duration field, and instructing the expected frame detection and elimination unit to set or perform expected frame detection according to the received RTS frame and CTS frame;
信道管理单元，用于接收来自外部的射频前端模块的接收信号起始、信号功率等级等指示，以及来自帧接收单元的NAV定时器更新指令，实现信道的状态管理；The channel management unit is used to receive indications such as the start of receiving signals and signal power levels from the external RF front-end module, and the NAV timer update instructions from the frame receiving unit to realize channel state management;
退避管理单元，用于在发送不成功时执行退避，当退避定时器计时停止时通知发送协同单元再次发送相应帧；A backoff management unit, configured to perform backoff when the transmission is unsuccessful, and notify the sending coordination unit to send the corresponding frame again when the backoff timer stops;
预期帧检测与消除控制单元，用于按照发送协同单元和接收单元的指示，根据当前发送的RTS帧或者当前接收到的RTS/CTS帧预期将要出现的ACK帧的内容和到达时间，通知和控制外部的接收信号解析模块执行预期帧检测和消除，并将结果反馈给帧发送协同单元或帧接收单元。The expected frame detection and elimination control unit is used to notify and control the content and arrival time of the ACK frame expected to appear according to the currently sent RTS frame or the currently received RTS/CTS frame according to the instructions of the sending coordination unit and the receiving unit The external received signal analysis module performs expected frame detection and elimination, and feeds back the result to the frame sending coordination unit or frame receiving unit.
所述的接收信号解析模块，包括：The receiving signal analysis module includes:
数字信号缓存器，用于接收并缓存经模数转换之后的数字中频信号，并按照不同需求分别提供给预期帧检测单元、预期帧消除单元和解调/解码单元使用；The digital signal buffer is used to receive and buffer the digital intermediate frequency signal after analog-to-digital conversion, and provide it to the expected frame detection unit, the expected frame elimination unit and the demodulation/decoding unit according to different requirements;
预期帧检测单元，用于根据外部媒质接入控制模块的指令，从接收到的数字信号序列中检测出特定的预期帧，并将结果返回给外部媒质接入控制模块；The expected frame detection unit is used to detect a specific expected frame from the received digital signal sequence according to the instruction of the external medium access control module, and return the result to the external medium access control module;
预期帧消除单元，用于根据外部媒质接入控制模块或者预期帧消除模块的指令，从接收到的数字信号序列中消除相应的预期帧信号，并将消除预期帧后的信号发送给解调/解码单元；The expected frame elimination unit is used to eliminate the corresponding expected frame signal from the received digital signal sequence according to the instruction of the external medium access control module or the expected frame elimination module, and send the signal after the expected frame is eliminated to the demodulator/ decoding unit;
解调/解码单元，用于接收来自数字信号缓存器或者预期帧消除单元的数字中频信号，对其进行解调/解码操作，从中获得数字基带信号并发送给外部的MAC层帧提取模块。The demodulation/decoding unit is used to receive the digital intermediate frequency signal from the digital signal buffer or the expected frame elimination unit, perform demodulation/decoding operation on it, obtain the digital baseband signal from it and send it to the external MAC layer frame extraction module.
三、本发明的无线分组网络媒质接入控制方法，包括如下步骤：Three, the wireless packet network medium access control method of the present invention, comprises the following steps:
(1)在终端有数据帧需要发送时，根据当前是否有被载波监听抑制确定数据帧的发送，如果该终端没有被抑制，或者被抑制但是属于暴露终端抑制，则发送RTS，并等待接收终端响应CTS；否则，执行退避，直至终端发出RTS；(1) When the terminal has a data frame to send, it determines the transmission of the data frame according to whether it is currently suppressed by carrier sense. If the terminal is not suppressed, or is suppressed but belongs to exposed terminal suppression, send RTS and wait for the receiving terminal Respond to CTS; otherwise, perform backoff until the terminal sends RTS;
(2)接收终端收到RTS后，如果没有被抑制，则响应CTS并等待接收数据帧；否则不响应；(2) After the receiving terminal receives the RTS, if it is not suppressed, it responds to the CTS and waits to receive the data frame; otherwise, it does not respond;
(3)相邻终端根据监听到的帧的类型和发送持续时间字段，分别设置接收和发送NAV定时器，以确定自己属于何种状态；(3) Adjacent terminals respectively set receiving and sending NAV timers according to the type of the monitored frame and the sending duration field, so as to determine which state they belong to;
(4)若终端根据刚发送出或者接收到的帧的类型、地址和持续时间字段能够完整准确预期出将来某时刻将出现一个ACK帧，则设置在预期ACK帧出现的时刻，执行预期帧检测和消除，否则不需要设置预期帧；(4) If the terminal can completely and accurately predict that an ACK frame will appear at a certain time in the future based on the type, address, and duration field of the frame just sent or received, then set the time when the expected ACK frame appears to perform expected frame detection and eliminate, otherwise no expected frame needs to be set;
(5)终端在接收到无线信号后，若所接收到的信号与提前设置的预期帧时间重叠，则根据预期的帧起始时间、帧前导序列和帧定界序列、以及帧内容字段，采用序列相关法进行预期帧的检测，根据预期帧检测获得的精确时间和信道参数估计，产生一个预期帧经信道传输后的接收信号副本，将该预期帧副本从接收信号中消除，并对消除预期帧之后的信号进行解调解码和帧提取；(5) After the terminal receives the wireless signal, if the received signal overlaps with the expected frame time set in advance, according to the expected frame start time, frame preamble sequence, frame delimitation sequence, and frame content field, use The sequence correlation method detects the expected frame. According to the accurate time and channel parameter estimation obtained by the expected frame detection, a copy of the received signal after the expected frame is transmitted through the channel is generated, and the expected frame copy is eliminated from the received signal, and the expected frame is eliminated. The signal after the frame is demodulated, decoded and frame extracted;
(6)发送终端接收到CTS，握手成功，设置预期ACK帧接收，并发出数据帧，等待接收ACK；(6) The sending terminal receives the CTS, the handshake is successful, the expected ACK frame is set to receive, and the data frame is sent, waiting to receive the ACK;
(7)接收终端成功接收到数据帧后，发出ACK帧确认，否则接收失败；(7) After the receiving terminal successfully receives the data frame, it sends an ACK frame for confirmation, otherwise the reception fails;
(8)发送终端成功接收到ACK帧，数据发送成功；否则发送失败，返回步骤(1)。(8) The sending terminal successfully receives the ACK frame, and the data is sent successfully; otherwise, the sending fails and returns to step (1).
本发明通过所述的媒质接入控制模块和接收信号解析模块，增加了预期帧检测和消除功能，使终端设备成为暴露终端时，也能够发出RTS帧和数据帧；本发明采用预期帧检测，使终端在受到干扰的情况下也能够正确接收到预期的ACK帧；本发明采用预期帧消除，可将产生干扰的预期ACK帧从接收信号中消除，使剩余信号可以被正确接收。本发明与现有三类支持并发通信的媒质接入控制方法相比，不仅能增加无线网络通信并发度和网络容量，而且可避免这些方法所引起的上层协议性能恶化、发送等待时间过长、协议过于复杂、不能充分实现空间复用以及不兼容802.11标准的缺点。The present invention adds the expected frame detection and elimination functions through the medium access control module and the received signal analysis module, so that when the terminal equipment becomes an exposed terminal, it can also send RTS frames and data frames; the present invention adopts the expected frame detection, The terminal can correctly receive the expected ACK frame even when it is interfered; the present invention adopts the expected frame elimination, which can eliminate the expected ACK frame that causes interference from the received signal, so that the remaining signal can be received correctly. Compared with the existing three types of media access control methods that support concurrent communication, the present invention can not only increase the concurrency of wireless network communication and network capacity, but also avoid the performance deterioration of the upper layer protocol caused by these methods, the long waiting time for sending, and the protocol It is too complex, cannot fully realize spatial multiplexing, and is not compatible with the 802.11 standard.
附图说明Description of drawings
图1为无线网络中的隐藏和暴露终端示意图；Figure 1 is a schematic diagram of hidden and exposed terminals in a wireless network;
图2为本发明的系统结构框图；Fig. 2 is a system structure block diagram of the present invention;
图3为本发明系统中的媒质接入控制模块结构示意图；Fig. 3 is a schematic structural diagram of a medium access control module in the system of the present invention;
图4为本发明系统中的接收信号解析模块结构示意图；Fig. 4 is a schematic structural diagram of a received signal analysis module in the system of the present invention;
图5为本发明媒质接入控制总流程图；Fig. 5 is the overall flowchart of medium access control of the present invention;
图6为本发明媒质接入控制中根据RTS和CTS预期ACK帧示意图；6 is a schematic diagram of an expected ACK frame according to RTS and CTS in the medium access control of the present invention;
图7为本发明的预期帧检测子流程图；Fig. 7 is the expected frame detection subflow chart of the present invention;
图8为本发明的预期帧消除子流程图。Fig. 8 is a sub-flow chart of the anticipation frame elimination in the present invention.
具体实施方式Detailed ways
为使本发明目的、技术方案以及优点更加清楚明白，以下参照附图并举实施例，对本发明进行进一步的详细说明。In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and examples.
参照图2，本发明无线终端系统包括：媒质接入控制模块10、接收信号解析模块20、模数转换器30、MAC层帧提取模块40、物理层帧形成模块50、调制/编码模块60、数模转换器70、射频前端模块80、物理层信道管理模块90和天线。其中：Referring to Fig. 2, the wireless terminal system of the present invention includes: a medium
媒质接入控制模块10、物理层帧形成模块50、调制/编码模块60、数模转换器70与射频前端模块80依次单向连接，构成数据发送通道；射频前端模块80、模数转换器30、接收信号解析模块20、MAC层帧提取模块40与媒质接入控制模块10依次单向连接，构成数据接收通道。射频前端模块80与物理信道管理模块90双向连接传递控制与通知消息；物理信道管理模块90与媒质接入控制模块10单向连接，向该媒质接入控制模块通知信道状态；媒质接入控制模块10与接收信号解析模块20双向连接，传递接收信号解析所需的控制指令和相关信息；射频前端模块80与天线双向连接接收和发送无线信号。The medium
当媒质接入控制模块10发送数据帧时，首先将上层数据分组组装成MAC层帧发给物理层帧形成模块50，在该物理层帧形成模块中添加物理层传输所需字段，包括前导序列和帧定位序列，构成物理层帧；然后将物理层帧传递给调制/编码模块60；调制/编码模块60执行编码、扩频和调制功能，将物理层帧转变为适合在无线信道中传输的中频数字信号，并传给数模转换器70转换为中频模拟信号；数模转换器70在物理信道管理模块90的配合下，将该信号传给射频前端模块80，经过变频、滤波和放大操作后转变为射频无线信号；最后将射频无线信号通过天线发出。When the medium
当射频前端模块80接收到来自天线的微弱无线高频信号，经过放大、滤波和变频之后，转变为无线中频信号，传送给模数转换器30，将该无线中频信号转换为中频数字信号；同时，射频前端模块80将检测到的无线射频信号的起止时间和功率大小信息通知给物理信道管理模块90；该物理信道管理模块将起止时间和功率大小信息转变为物理载波侦听消息，并传达给媒质接入控制模块10；经模数转换之后的中频数字信号由模数转换器30传递给接收信号解析模块20；接收信号解析模块20在媒质接入控制模块10的控制下对中频数字信号进行预期帧检测、预期帧消除与解调/解码，并将必要的中间结果通知给媒质接入控制模块10；经接收信号解析模块20解调解码后的信号发送给MAC层帧提取模块40，从中提取出MAC层数据帧或控制帧，提交给媒质接入控制模块10。When the radio frequency front-end module 80 receives the weak wireless high-frequency signal from the antenna, after amplification, filtering and frequency conversion, it is converted into a wireless intermediate frequency signal and sent to the analog-to-digital converter 30 to convert the wireless intermediate frequency signal into an intermediate frequency digital signal; , the RF front-end module 80 notifies the physical channel management module 90 of the detected start and end time and power information of the radio frequency signal; the physical channel management module converts the start and end time and the power information into a physical carrier sense message and communicates it to Media access control module 10; The intermediate frequency digital signal after the analog-to-digital conversion is delivered to the receiving signal analysis module 20 by the analog-to-digital converter 30; The receiving signal analysis module 20 carries out the intermediate frequency digital signal under the control of the medium access control module 10 Expected frame detection, expected frame elimination and demodulation/decoding, and the necessary intermediate results are notified to the medium access control module 10; the signal after demodulation and decoding by the received signal analysis module 20 is sent to the MAC layer frame extraction module 40, from which The MAC layer data frame or control frame is extracted and submitted to the medium access control module 10 .
参照图3，本发明所述媒质接入控制模块包括：上层协议接口101、发送协同单元102、帧发送单元103、接收协同单元104、帧接收单元105、信道管理单元106、退避管理单元107和预期帧检测与消除控制单元108。其中上层协议接口101单向连接到发送协同单元102，发送协同单元102单向连接到帧发送单元103，103单向连接到模块外部的物理层帧形成模块50，形成来自上层协议的数据帧的发送通道。帧接收单元105与外部MAC层帧提取模块40单向连接，并单向连接到接收协同单元104，该接收协同单元单向连接到上层协议接口101，构成去往上层协议的数据帧接收通道。接收协同单元104与帧发送单元103单向连接，根据接收到的帧类型通知103发出相应的控制帧。退避管理单元107单向连接到发送协同单元102和信道管理单元106，根据退避算法执行退避以及更改信道状态管理信息。帧接收单元105单向连接到信道管理单元106，根据接收到的帧中发送持续时长字段和类型设置106中的相应NAV定时器。信道管理单元106同时与外部的物理信道管理模块90单向连接，接收来自该物理信道管理模块的物理载波侦听结果。预期帧检测与消除控制单元108与物理信道管理模块90单向连接，接收来自该物理信道管理模块的接收信号起止时间、信号强度和信道估计参数消息；同时预期帧检测与消除控制单元108分别与接收信号解析模块20、发送协同单元102和帧接收单元105双向连接，控制接收信号解析模块执行检测与消除并接收执行的结果，接收来自发送协同单元和帧接收单元的预期帧检测与消除请求，并将执行结果返回给发送协同单元和帧接收单元。Referring to Fig. 3, the medium access control module of the present invention includes: an upper
参照图4，本发明所述接收信号解析模块包括：数字信号缓存201、预期帧检测单元202、预期帧消除单元203和解调/解码单元204，其中数字信号缓存器201与外部模数转换模块30单向连接，接收并缓存经转换之后的数字中频信号；同时数字信号缓存器分别与预期帧检测单元202、预期帧消除单元203和解调/解码单元204单向连接，传送需要进行检测或消除的数字信号给预期帧检测单元和预期帧消除单元，传送可直接进行解调/解码的数字中频信号给解调/解码单元。解调/解码单元204与预期帧消除单元203之间单向连接，接收经预期帧消除之后的数字中频信号；解调/解码之后的数据发给外部MAC层帧提取模块40，用于提取完整的MAC层帧；同时，解调/解码单元204与预期帧消除单元203双向连接，该解调/解码单元204与媒质接入控制模块10中的预期帧检测与消除控制单元108单向连接，均用以辅助实现预期帧消除。预期帧检测单元202与外部媒质接入控制模块10中的预期检测与消除控制单元108双向连接，接收预期帧检测请求并能够返回检测结果和相关信息；预期帧消除单元203与预期帧检测单元202之间双向连接，用于在直接检测不成功时先进行预期帧消除再进行检测；预期帧消除单元203同时与外部媒质接入控制模块10中的预期检测与消除控制单元108单向连接，接受来自108的预期帧消除请求。Referring to Fig. 4, the received signal analysis module of the present invention includes:
参照图5，本发明的无线分组网络媒质接入控制方法实现方法，包括如下步骤：With reference to Fig. 5, the implementation method of the wireless packet network medium access control method of the present invention comprises the following steps:
步骤1，终端收到来自上层的数据分组，将其组装成MAC层数据帧，并根据其目的地址，数据长度等产生相应的RTS帧准备发送。
步骤2，发送终端判断自身当前是否被物理载波侦听和虚拟载波侦听抑制，若终端物理和虚拟载波侦听结果均显示信道闲，或者虽然物理载波侦听为忙但是虚拟载波侦听发现该终端属于暴露终端，则执行步骤3；否则，执行退避，直至终端发出RTS。Step 2: The transmitting terminal judges whether it is currently suppressed by physical carrier sensing and virtual carrier sensing. If the terminal is an exposed terminal, perform step 3; otherwise, perform backoff until the terminal sends an RTS.
步骤3，发送终端发出RTS，并等待接收来自目的终端的CTS。Step 3, the sending terminal sends out the RTS, and waits to receive the CTS from the destination terminal.
步骤4，接收终端收到RTS后，如果根据载波侦听判断可以接收，则响应CTS并等待接收数据帧；否则不响应。Step 4: After receiving the RTS, the receiving terminal responds to the CTS and waits to receive the data frame if it can be received according to the carrier sense judgment; otherwise, it does not respond.
步骤5，与接收和发送终端相邻的终端，根据监听到的帧的类型和发送持续时间字段，设置或者更新接收NAV定时器或发送NAV定时器。Step 5: The terminals adjacent to the receiving and sending terminals set or update the receiving NAV timer or the sending NAV timer according to the detected frame type and the sending duration field.
步骤6，若终端根据已知的刚发送出或者接收到的帧的类型、地址和持续时间字段能够完整准确预期出将来某时刻将出现一个ACK帧，则设置在预期ACK帧出现的时刻，执行预期帧检测和消除，否则不需要设置预期帧；Step 6: If the terminal can fully and accurately predict that an ACK frame will appear at a certain time in the future based on the known type, address, and duration field of the frame just sent or received, then set it at the time when the expected ACK frame appears, and execute Expected frame detection and elimination, otherwise no need to set expected frame;
参照图6，其中根据已知帧获得预期ACK帧出现时间和帧内容的具体情况分为如下三种情况：With reference to Fig. 6, wherein according to known frame, obtain the specific situation of expected ACK frame appearance time and frame content and be divided into following three kinds of situations:
第一种情况是：如果终端刚发出或者接收到RTS帧，则预期ACK帧的目的地址为RTS帧的源地址；预期ACK帧的出现时间：T＝t+D-tsfs-tACK，其中t为当前时间，DRTS为RTS帧中的发送持续时间，tsfs为最短帧间隔，tACK为ACK帧传送所需时间；The first case is: if the terminal has just sent or received an RTS frame, the destination address of the expected ACK frame is the source address of the RTS frame; the time of appearance of the expected ACK frame: T=t+Dtsfs -tACK , where t is At the current time, DRTS is the transmission duration in the RTS frame, tsfs is the shortest frame interval, and tACK is the time required for ACK frame transmission;
第二种情况是：如果终端接收到的帧为CTS，则预期ACK帧的目的地址即为CTS帧的目的地址；预期ACK帧的出现时间：T＝t+D-tsfs-tACK，其中t为当前时间，DCTS为CTS帧中的发送持续时间，tsfs为最短帧间隔，tACK为ACK帧传送所需时间；The second case is: if the frame received by the terminal is a CTS, the destination address of the expected ACK frame is the destination address of the CTS frame; the time of appearance of the expected ACK frame: T=t+Dtsfs -tACK , where t is At the current time, DCTS is the transmission duration in the CTS frame, tsfs is the shortest frame interval, and tACK is the time required for ACK frame transmission;
第三种情况是：如果终端接收到的帧是其他类型的帧，不进行预期帧设置；The third case is: if the frame received by the terminal is another type of frame, no expected frame setting is performed;
在以上第一种和第二种情况中，预期ACK帧中的帧控制字为已知固定格式，发送持续时间字段为0，帧校验序列根据帧控制字、发送持续时间和目的地址字段的内容重新计算。In the above first and second cases, the frame control word in the expected ACK frame is a known fixed format, the transmission duration field is 0, and the frame check sequence is based on the frame control word, transmission duration and destination address fields. The content is recalculated.
步骤7，终端在接收到无线信号后，若所接收到的信号与提前设置的预期帧时间重叠，则根据预期的帧起始时间、帧前导序列和帧定界序列，以及帧内容字段，采用序列相关法进行预期帧的检测。Step 7: After receiving the wireless signal, if the received signal overlaps with the expected frame time set in advance, according to the expected frame start time, frame preamble sequence, frame delimiting sequence, and frame content field, use The detection of the expected frame is performed by the sequence correlation method.
参照图7，本步骤的具体实现如下：Referring to Figure 7, the specific implementation of this step is as follows:
7.1，预期帧检测单元接收经数字化后的中频无线信号，以及预置的预期帧起始时刻和帧格式内容信息；7.1. The expected frame detection unit receives the digitized intermediate frequency wireless signal, as well as the preset expected frame start time and frame format content information;
7.2，在预期帧起始时刻附近，用已知的帧前导序列与接收信号进行滑动相乘运算，在预期帧起始位置附近，若滑动相乘的积明显大于此位置之前和此位置之后的乘积，则认为出现显著相关峰值，执行步骤7.3；否则认为不存在预期帧，检测失败，返回预期帧检测失败消息；7.2, near the expected frame start time, use the known frame preamble sequence and the received signal to perform sliding multiplication operation, near the expected frame start position, if the product of sliding multiplication is significantly greater than the position before and after this position product, it is considered that there is a significant correlation peak, and step 7.3 is performed; otherwise, it is considered that there is no expected frame, the detection fails, and the expected frame detection failure message is returned;
7.3，从相关峰指示的确切位置开始，按照信道估计的参数对完整预期帧进行滑动相乘计算，若从此位置开始的滑动相乘积远大于此位置之前和此位置之后的乘积，则认为预期帧检测成功，返回预期帧检测成功消息，由检测获得的帧确切起始位置和信道参数估计等信息给预期帧检测与消除控制单元；否则执行步骤7.4；7.3. Starting from the exact position indicated by the correlation peak, perform a sliding multiplication calculation on the complete expected frame according to the parameters of the channel estimation. If the product of the sliding phase starting from this position is much greater than the product before and after this position, the expected frame is considered The detection is successful, and the expected frame detection success message is returned, and information such as the exact starting position of the frame obtained by the detection and channel parameter estimation are given to the expected frame detection and elimination control unit; otherwise, step 7.4 is performed;
7.4，发送前导序列相关峰确切位置、信道和发送机参数估计、预期帧格式内容给预期帧消除单元请求尝试消除；7.4. Send the exact position of the correlation peak of the preamble sequence, the channel and transmitter parameter estimates, and the content of the expected frame format to the expected frame elimination unit to request to try to eliminate;
7.5，若预期帧消除成功，则预期检测成功，返回预期帧检测成功消息、前导序列相关峰确切位置和信道参数估计信息给预期帧检测与消除控制单元；否则，预期帧检测失败，返回预期帧检测失败消息。7.5, if the expected frame is eliminated successfully, the expected detection is successful, and the expected frame detection success message, the exact position of the preamble sequence correlation peak and the channel parameter estimation information are returned to the expected frame detection and elimination control unit; otherwise, the expected frame detection fails, and the expected frame is returned Detection failure message.
步骤8，根据预期帧检测获得的精确时间和信道参数估计，产生一个预期帧经信道传输后的接收信号副本，将该预期帧副本从接收信号中消除，并对消除预期帧之后的信号进行解调解码和帧提取。Step 8, according to the accurate time and channel parameter estimation obtained by the detection of the expected frame, generate a copy of the received signal after the expected frame is transmitted through the channel, eliminate the copy of the expected frame from the received signal, and decompose the signal after the expected frame is eliminated Modulation decoding and frame extraction.
参照图8，本步骤的具体实现如下：Referring to Figure 8, the specific implementation of this step is as follows:
8.1，预期帧消除单元接收必要信息，包括预期帧消除请求、需要从中消除预期帧的无线数字信号、预期帧确切起始位置、预期帧格式内容、信道估计参数和发送机估计参数；8.1. The expected frame elimination unit receives necessary information, including the expected frame elimination request, the wireless digital signal from which the expected frame needs to be eliminated, the exact starting position of the expected frame, the content of the expected frame format, channel estimation parameters and transmitter estimation parameters;
8.2，根据预期帧的格式内容和802.11标准中规定的物理层帧结构，添加前导序列和帧定位序列，组装出完整的物理层帧；8.2, according to the format and content of the expected frame and the physical layer frame structure specified in the 802.11 standard, add a preamble sequence and a frame alignment sequence to assemble a complete physical layer frame;
8.3，根据802.11标准中对物理层规定的调制编码方法，对物理层帧进行逐比特编码和调制，获得经编码和调制之后的数字信号序列；8.3, according to the modulation and coding method specified for the physical layer in the 802.11 standard, perform bit-by-bit coding and modulation on the physical layer frame to obtain the coded and modulated digital signal sequence;
8.4，根据信道和发送机估计参数，增加对调制和编码后的数字信号的频率、相位和幅度的畸变，所得到的数字信号序列即为经信道传输之后的预期帧信号副本；8.4. According to the estimated parameters of the channel and transmitter, increase the frequency, phase and amplitude distortion of the modulated and encoded digital signal, and the obtained digital signal sequence is the expected frame signal copy after channel transmission;
8.5，从需要进行预期帧消除的数字信号中，从前导序列相关峰出现的确切位置开始，减去生成的预期帧信号副本，并将所余信号提交给解调解码单元；8.5. From the digital signal that needs to be eliminated by the expected frame, subtract the generated copy of the expected frame signal from the exact position where the correlation peak of the preamble sequence appears, and submit the remaining signal to the demodulation and decoding unit;
8.6，解调解码单元对剩余信号进行解调和解码，并将解调和解码之后的比特序列提交给MAC层帧提取模块；8.6. The demodulation and decoding unit demodulates and decodes the remaining signal, and submits the demodulated and decoded bit sequence to the MAC layer frame extraction module;
8.7，MAC层帧提取模块对接收到的比特序列进行MAC层帧定界，并使用802.11标准中规定的校验多项式对该帧进行循环冗余校验，如果得到的校验和与帧中的一致，则预期帧消除成功，将获得的MAC层帧提交给媒质接入控制模块；否则执行步骤8.8；8.7. The MAC layer frame extraction module performs MAC layer frame delimitation on the received bit sequence, and uses the check polynomial specified in the 802.11 standard to perform a cyclic redundancy check on the frame. If the obtained checksum is the same as that in the frame Consistent, then the expected frame is eliminated successfully, and the obtained MAC layer frame is submitted to the media access control module; otherwise, step 8.8 is performed;
8.8，选择是否重新尝试，若重试次数未超过上限，则调整信道和发送机估计参数，生成新的预期帧信号副本，执行步骤8.5；否则，返回消除失败消息，预期帧消除终止。8.8. Choose whether to retry. If the number of retries does not exceed the upper limit, adjust the channel and transmitter estimation parameters to generate a new copy of the expected frame signal, and perform step 8.5; otherwise, return an elimination failure message, and the expected frame elimination is terminated.
步骤9，发送终端接收到CTS，握手成功，设置预期ACK帧接收，并发出数据帧，等待接收ACK；否则执行退避后重新执行步骤1。Step 9, the sending terminal receives the CTS, the handshake is successful, sets the expected ACK frame reception, sends out the data frame, and waits to receive the ACK; otherwise, execute
步骤10，接收终端成功接收到数据帧后，发出ACK帧确认，否则接收失败。Step 10: After successfully receiving the data frame, the receiving terminal sends an ACK frame for confirmation, otherwise the reception fails.
步骤11，发送终端成功接收到ACK帧，数据发送成功；否则发送失败，执行退避后返回步骤1。In step 11, the sending terminal successfully receives the ACK frame, and the data is sent successfully; otherwise, the sending fails, and returns to step 1 after performing backoff.
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