CN106454872B - Satellite formation network channel access control method based on directional antenna - Google Patents
Satellite formation network channel access control method based on directional antenna Download PDFInfo
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- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/002—Transmission of channel access control information
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- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access, e.g. scheduled or random access
- H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
- H04W74/0808—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using carrier sensing, e.g. as in CSMA
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- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/04—Large scale networks; Deep hierarchical networks
- H04W84/06—Airborne or Satellite Networks
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- H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks
Abstract
The invention discloses a directional antenna-based satellite formation network channel access control method, and belongs to the field of wireless self-organizing network data link layer protocol method design. The method is a multiple access protocol design method which is applied to a satellite formation network and replaces an omnidirectional antenna to adopt a directional antenna, the directional antenna is adopted to monitor a wireless channel, neighbor node angle of arrival (AOA) storage is introduced through directional virtual carrier sensing (DNAV) and based on the scanning of an antenna unit, and frame format design and cluster RTS control information are adopted to realize the full directional data transmission. The method of the invention overcomes the problem of asymmetric gain in the design of a directional MAC protocol, solves the problems of deafness and hidden terminal caused by introducing a directional antenna, improves the success rate of establishing a data link by the node in the wireless self-organizing network, effectively improves the throughput of data and reduces the data access time delay, and can be better applied to various wireless self-organizing networks.
Description
Technical Field
The invention belongs to the field of wireless self-organizing network data link layer protocol design, and relates to a multiple access protocol design method which is applied to a satellite formation network and adopts a directional antenna instead of an omnidirectional antenna.
Background
The microsatellite has the characteristics of small volume, light weight, short development period, low cost, flexible launching mode and the like, and is widely applied to the fields of communication, aerospace, military investigation, military command, environment and resource detection and the like. Due to the limitations of small size and low power of a single microsatellite, the traditional omnidirectional antenna is abandoned in the selection of communication antennas, and a directional plane antenna which is small in area and easy to fix is adopted. There is an urgent need to design network communication protocols based on directional antennas.
In addition, the development of microsatellites has experienced: 1) a single moonlet works independently. 2) The satellites form a constellation and are distributed on a single-orbit or multi-orbit plane according to requirements. The constellation can improve the ground coverage range to the world, greatly shorten the revisit period and achieve the purpose that a large satellite cannot achieve. 3) Formation flight constellations. A flight path with a certain shape is formed by a plurality of small satellites, and a virtual satellite is formed in a distributed mode. Networking communication of the satellite formation plays an important role in flying the satellite formation, executing joint tasks, realizing information sharing and making joint decisions.
The Media Access Control Protocol (Media Access Control Protocol-MAC) is located in a data link layer of an Open System Interconnection-OSI (Open System Interconnection-OSI) seven-layer Protocol, and is mainly responsible for controlling and connecting a physical medium of a physical layer. The MAC protocol in the wireless Ad hoc network (Ad hoc) is responsible for controlling the wireless sensor nodes to occupy wireless network channels and transmit data. The MAC protocol in the wireless self-organizing network mainly ensures the fairness of occupying channels among nodes and improves the utilization rate of channel resource sharing. The wireless self-organizing network has the characteristics of quick topology change, limited energy and short channel resources, so the high-efficiency MAC protocol design method can effectively improve the data throughput of the wireless self-organizing network, reduce the data transmission delay, save the energy, prolong the service life of the sensor and the like.
The design method of the wireless self-organizing network MAC protocol is mostly based on the traditional omnidirectional antenna, namely when the wireless sensor nodes transmit data, all other wireless sensor nodes in the range of the transmitted signal can receive the data. The MAC protocol design method based on the traditional directional antenna has the characteristics of simple control and high link success rate. The design of the MAC protocol using omni-directional antennas is described in detail in the documents of "a surview, classification and comparative analysis of medium access control protocols for ad hoc wireless networks, ieee commun.
The directional MAC protocol of the wireless ad hoc network was originally proposed by r.choudhury et al in the literature "using directional antennas for medium access control in ad hoc networks proc.ieeemobioc' 02, ma.2002", and has gained wide attention, and its core idea is to apply the mechanisms of binary back-off, carrier sense, handshake protocol, etc. of the wireless lan 802.11 to the method of the directional MAC protocol design. The nodes in the Ad Hoc wireless network can improve the signal transmission range of the nodes in the wireless sensor network, reduce signal interference, improve spatial multiplexing, increase data throughput, reduce time delay and the like by using the directional antenna. However, the use of directional antennas causes problems with hidden terminals and deaf nodes, as shown in fig. 1. Nasipuri et al, in order to solve the above problems, propose a solution in "A MAC protocol for mobile ad hoc networks using direct antennas, in Proc. IEEE WCNC' 00, Sep.2000" in which a wireless sensor node monitors data using an omnidirectional antenna and a directional antenna transmits data. The design method of the directional MAC protocol not only needs the wireless sensor to work under the dual modes of the omnidirectional antenna and the directional antenna, improves the complexity of switching operation, but also causes the problem of asymmetric transmission gain.
Therefore, the method does not fundamentally solve the problems of hidden terminals and deaf nodes caused by adopting the directional antenna. In the current research on the MAC protocol of the directional antenna of the wireless self-organizing network, a simple and efficient design method for transmitting data by adopting a fully directional antenna does not exist.
Disclosure of Invention
In order to overcome the problems of gain asymmetry caused by semi-directional data transmission and complex dual-mode operation switching design in the existing wireless self-organizing network directional MAC protocol design method, the invention provides a satellite formation network channel access control method based on a directional antenna, which is a fully directional multiple access control protocol.
In order to achieve the purpose, the invention adopts the following technical scheme:
a satellite formation network channel access control method based on a directional antenna is characterized in that a node in a wireless self-organizing network is provided with the directional antenna, the directional antenna is adopted to monitor a wireless channel, and full directional data transmission is realized through directional virtual carrier sensing (DNAV) based on scanning of an antenna unit.
Furthermore, the directional antenna is an adaptive array antenna or a plurality of directional plane antennas arranged in sequence, the directional antenna unit comprises a plurality of antenna sectors, the beam angle of each antenna sector is the same, and all the antenna sectors cover 360 degrees; wherein wireless sensor nodes in the network obey a poisson distribution.
Further, the method also employs neighbor node angle of arrival (AOA) storage.
Further, the directional virtual carrier sensing (DNAV) specifically is that nodes in the wireless ad hoc network store DNAV information in each antenna sector, record whether other nodes transmit data in the current sector, and the nodes update DNAV data from the received directional RTS and directional CTS information.
Further, the neighbor node angle of arrival (AOA) stores information that each node successfully receives, and stores the direction of the neighbor node in the current node antenna unit sector; when a node sends data to a neighbor node, firstly searching whether the direction of an antenna unit sector of the neighbor node is cached, and if the cache exists, trying to send RTS handshake control information to establish connection in the direction of the cached antenna unit sector preferentially.
Further, the method also adopts frame format design to extend directional RTS frame to D on the basis of 802.11RTS control framethReceiving node address information; when the wireless sensor node has cache data to send, first extracting front D in FIFOthCachingAdding address information into a directional RTS frame by using a destination address ID of a data packet, and then sending the directional RTS frame by using cluster RTS control information to establish a wireless link; if the AOA direction information of the destination node of the cached data is stored, the AOA direction information is preferentially sent towards the antenna sector of the destination node of the cached data.
Further, the scanning of the antenna unit specifically includes: all wireless sensor nodes continuously switch antenna sectors in sequence; the wireless sensor node can capture the directional RTS from the neighbor node while sending the directional RTS, and the operation of the wireless sensor node in each sector comprises two stages of channel monitoring and data sending; wherein the wireless sensor node switches antenna sectors in a clockwise or counterclockwise order.
Further, the operation of the wireless sensor node in each sector is specifically as follows:
(1) listening channel phase of wireless sensor node
The monitoring time of the wireless sensor node comprises two parts, namely monitoring time in a fixed period and monitoring time in a random period; when the passive node switches to a new antenna sector, it randomly selects an integer from the window as the initial value (LC) of the listening counter; if the source node detects that the channel is idle, reducing the value of LC by 1 through a minimum time slot; if the channel is detected to be occupied, the LC count is frozen until the channel is free for a minimum interframe space (DIFS), then the channel continues to be monitored, and the listening count is decremented;
if the source node receives a directional RTS frame sent by other nodes in the process of counting down by the LC, the source node firstly detects whether the RTS frame contains the MAC address of the source node; if yes, replying a directional CTS signal in the antenna sector, locking the antenna sector, waiting for receiving a data packet, then replying an ACK signal to indicate that the data packet is successfully received, if replying the directional RTS, the source node does not receive the data packet, namely waiting for the data frame to be overtime, the source node continues to detect the idle of the channel, and decrements LC counting; if the directional RTS frame does not contain the MAC address of the source node, the source node acquires the channel occupation time parameter from the directional RTS frame, then sets the directional NAV time interruption of the antenna sector, stops other activities, waits for the arrival of the directional NAV time interruption, then continues to detect the idle channel, and decrements LC count;
(2) data transmission phase of wireless sensor
When the monitoring count LC of the source node reaches zero, the source node enters a data packet sending state from a monitoring state; if the source node has a plurality of data frames to be sent, the source node firstly generates and sends a directional RTS frame, and then sets Timeout interrupt waiting for receiving a directional CTS reply; if the source node receives a directional CTS reply before the Timeout time is interrupted, a link is established, then a directional RTS frame is transmitted, after the transmission of the directional RTS frame is completed, the source node waits for replying an ACK signal, when the ACK signal is successfully received, one frame of data is successfully transmitted, the source node regenerates the directional RTS frame and judges that one antenna unit is selected to continuously execute a mechanism for monitoring a channel and transmitting data; if the directional CTS reply is not received, namely the time of the directional CTS which is waited to reply by the wireless sensor node is overtime, the node is switched to the next antenna unit according to a certain sequence, and the channel monitoring and the link process established by sending the directional RTS are repeated.
Further, before the source node receives the directional CTS reply transmission directional RTS frame in step (3), the source node firstly locks the antenna sector, secondly extracts the MAC address information and the destination address information of the receiving node from the received directional CTS frame, and updates the cache AOA antenna sector information of the receiving node; if the destination address information corresponds to the MAC address of the destination address information, then searching a cache data packet corresponding to the MAC address of the receiving node in a data cache FIFO, extracting the cache data packet, and sending a directional RTS frame on an antenna sector; if the destination address information does not correspond to the MAC address of the antenna sector, other nodes exist on the antenna sector to transmit and receive data, and the directional CTS frame is discarded without processing.
Further, the source node is a node when a wireless sensor node has a generated data packet or cached sensor acquisition data to wait for transmission.
Has the advantages that: compared with the prior art, the beneficial effects of the invention comprise the following aspects: the satellite formation network channel access control method based on the directional antenna provided by the invention adopts full directional transmission data, overcomes the problem of asymmetric gain in directional MAC protocol design, and solves the problem of hidden terminals by introducing a directional virtual carrier sense (DNAV) technology; on the basis, the method of the invention also scans all directional antenna units periodically based on the antenna units, solves the problem of deafness nodes caused by introducing directional antennas, and realizes the full coverage of three-dimensional space signals by combining a monitoring channel and a data sending mechanism of the nodes in a single antenna sector.
Furthermore, the method introduces a neighbor node wave arrival angle (AoA) storage mechanism, and when the node sends data To the neighbor node, the node tries To send RTS (ready To Send) handshake control information in the direction To establish connection preferentially by searching whether To cache the antenna direction of the neighbor node or not if the antenna direction information exists, thereby improving the success rate of establishing a data link by the node in the wireless self-organizing network.
Furthermore, the method of the invention adopts frame format design to improve the directional RTS frame on the basis of 802.11RTS control frame, increases a plurality of receiving node addresses, and adopts cluster-sent directional RTS control information which means that actually transmitting an improved directional RTS frame structure is equivalent to transmitting a plurality of traditional RTS handshaking signals simultaneously, thereby improving the success rate of establishing a data link by the nodes in the wireless self-organizing network.
Further, the directional MAC protocol of the present invention reduces the possibility of signal collisions by handshaking signals multiple times. Compared with the MAC of the traditional wireless self-organizing network, the method can effectively improve the throughput of data and reduce the data access delay.
Furthermore, the wireless sensor node randomly selects the monitoring time count from the window, so that the problem of synchronization of node antenna rotation in the wireless self-organizing network is solved.
Furthermore, the directional MAC protocol does not need a large amount of complex calculation, the algorithm is simple, and the wireless sensor nodes work in a distributed, fully directional and asynchronous transmission mode, so that the scheme mechanism is simple to deploy.
Drawings
FIG. 1 directed MAC protocol deafness node problem;
FIG. 2 is a directional antenna model of the present invention;
FIG. 3 is a diagram of a directional MAC protocol contention neighbor node of the present invention;
fig. 4 is a schematic diagram of an antenna unit scanning, switching and transmitting mechanism according to the present invention.
Detailed Description
A satellite formation network channel access control method based on a directional antenna is characterized in that a node in a wireless self-organizing network is provided with the directional antenna, the directional antenna is adopted to monitor a wireless channel, and full directional data transmission is realized through directional virtual carrier sensing (DNAV) based on scanning of an antenna unit.
Furthermore, the directional antenna is an adaptive array antenna or a plurality of directional plane antennas arranged in sequence, the directional antenna unit comprises a plurality of antenna sectors, the beam angle of each antenna sector is the same, and all the antenna sectors cover 360 degrees; wherein wireless sensor nodes in the network obey a poisson distribution.
Further, the method also employs neighbor node angle of arrival (AOA) storage.
Further, the directional virtual carrier sensing (DNAV) specifically is that nodes in the wireless ad hoc network store DNAV information in each antenna sector, record whether other nodes transmit data in the current sector, and the nodes update DNAV data from the received directional RTS and directional CTS information.
Further, the neighbor node angle of arrival (AOA) stores information that each node successfully receives, and stores the direction of the neighbor node in the current node antenna unit sector; when a node sends data to a neighbor node, firstly searching whether the direction of an antenna unit sector of the neighbor node is cached, and if the cache exists, trying to send RTS handshake control information to establish connection in the direction of the cached antenna unit sector preferentially.
Further, the method also adopts frame format design to extend directional RTS frame to D on the basis of 802.11RTS control framethReceiving node address information; when the wireless sensor node has cache data to send, first extracting front D in FIFOthCaching a destination address ID of the data packet, adding address information into a directional RTS frame, and then sending the directional RTS frame by adopting cluster RTS control information to establish a wireless link; if the AOA direction information of the destination node of the cached data is stored, the AOA direction information is preferentially sent towards the antenna sector of the destination node of the cached data.
Further, the scanning of the antenna unit specifically includes: all wireless sensor nodes switch antenna sectors continuously in sequence; the wireless sensor node can capture the directional RTS from the neighbor node while sending the directional RTS, and the operation of the wireless sensor node in each sector comprises two stages of channel monitoring and data sending; wherein the wireless sensor node switches antenna sectors in a clockwise or counterclockwise order.
Further, the operation of the wireless sensor node in each sector is specifically as follows:
(1) listening channel phase of wireless sensor node
The monitoring time of the wireless sensor node comprises two parts, namely monitoring time in a fixed period and monitoring time in a random period; when the source node switches to a new antenna sector, it randomly selects an integer from the window as the initial value (LC) of the listening counter; if the source node detects that the channel is idle, reducing the value of LC by 1 through a minimum time slot; if the channel is detected to be occupied, the LC count is frozen until the channel is free for a minimum interframe space (DIFS), then the channel continues to be monitored, and the listening count is decremented;
if the source node receives a directional RTS frame sent by other nodes in the process of counting down by the LC, the source node firstly detects whether the RTS frame contains the MAC address of the source node; if yes, replying a directional CTS signal in the antenna sector, locking the antenna sector, waiting for receiving a data packet, then replying an ACK signal to indicate that the data packet is successfully received, if replying the directional RTS, the source node does not receive the data packet, namely waiting for the data frame to be overtime, the source node continues to detect the idle of the channel, and decrements LC counting; if the directional RTS frame does not contain the MAC address of the source node, the source node acquires the channel occupation time parameter from the directional RTS frame, then sets the directional NAV time interruption of the antenna sector, stops other activities, waits for the arrival of the directional NAV time interruption, then continues to detect the idle channel, and decrements LC count;
(2) data transmission phase of wireless sensor
When the monitoring count LC of the source node reaches zero, the node enters a data packet sending state from a monitoring state; if the source node has a plurality of data frames to be sent, the source node firstly generates and sends a directional RTS frame, and then sets Timeout interrupt waiting for receiving a directional CTS reply; if the source node receives a directional CTS reply before the Timeout time is interrupted, a link is established, then a directional RTS frame is transmitted, after the transmission of the directional RTS frame is completed, the source node waits for replying an ACK signal, when the ACK signal is successfully received, one frame of data is successfully transmitted, the source node regenerates the directional RTS frame and judges that one antenna unit is selected to continuously execute a mechanism for monitoring a channel and transmitting data; if the directional CTS reply is not received, namely the time of the directional CTS which is waited to reply by the wireless sensor node is overtime, the node is switched to the next antenna unit according to a certain sequence, and the channel monitoring and the link process established by sending the directional RTS are repeated.
Further, in the step (3), the source node receives the directional CTS reply, the source node firstly locks the antenna sector, secondly extracts the MAC address information and the destination address information of the receiving node from the received directional CTS frame, and updates the cache AOA antenna sector information of the receiving node; if the destination address information corresponds to the MAC address of the destination address information, then searching a cache data packet corresponding to the MAC address of the receiving node in a data cache FIFO, extracting the cache data packet, and sending a directional RTS frame on an antenna sector; if the destination address information does not correspond to the MAC address of the antenna sector, other nodes exist on the antenna sector to transmit and receive data, and the directional CTS frame is discarded without processing.
Further, the source node is a node when a wireless sensor node has a generated data packet or cached sensor acquisition data to wait for transmission.
The invention mainly completes the design work of a wireless self-organizing network directional MAC protocol (FDD-MAC), and the mechanism related to the whole protocol comprises the following steps: neighbor node angle of arrival (AOA) storage and orientation virtual carrier sensing (DNAV) mechanism, antenna unit based scanning mechanism, frame format design, and clustering rts (ready To send) control information.
One, angle of arrival (AOA) storage and directed virtual carrier sensing (DNAV) mechanism
The FDD-MAC protocol uses a directional virtual carrier sensing (DNAV) technique to solve the hidden terminal problem. Nodes in the wireless ad hoc network store DNAV information in each antenna sector and record whether other nodes transmit data in the current sector. The node updates DNAV data from the received directional RTS and directional CTS information. Meanwhile, the FDD-MAC protocol adopts a neighbor node AOA information caching mechanism to improve the probability of establishing a link by the node. And each node stores the direction of the neighbor node in the antenna unit sector of the node from the successfully received information. When a node sends data to a neighbor node, whether the antenna direction of the neighbor node is cached or not is firstly searched, if the antenna direction information is stored, RTS (ReadyTo Send) handshake control information is preferably sent in the direction to establish connection.
Scanning mechanism based on antenna unit
The FDD-MAC protocol solves the deafness problem due to the introduction of directional antennas by introducing an antenna sector scanning mechanism. All wireless sensor nodes switch antenna sectors continuously in a clockwise (or counterclockwise) direction to simulate an omni-directional antenna to transmit data. In order to ensure that the wireless sensor node can receive the directional RTS when sending the directional RTS and can also capture the directional RTS from the neighbor node, the operation of the wireless sensor node in each sector comprises two phases of channel monitoring and data sending. When a wireless sensor node switches to a new antenna sector, regardless of whether there are buffered data frames to be sent, the node first listens to the channel for a period of time to allow for a buffered data frame to be sent from itAnd the other neighbor nodes hear the directional RTS control information. The listening time of a node comprises two parts, namely a fixed period of listening time and a random period of listening time. When the wireless sensor node switches to a new antenna sector, it randomly moves from the window Wmin，Wmax]Selects an integer as the initial value (LC Listening Counter) of the Listening Counter. If the wireless sensor node detects that the channel is idle, the value of LC is reduced by 1 through a minimum time slot. If the channel detects occupancy, the LC count is frozen until the channel is free for a minimum interframe space (DIFS), and then the channel continues to be monitored, decrementing the listen count. The wireless sensor node monitors W at leastminAnd each time slot (called a constant listening period), each node has an opportunity to listen to control and data information sent by other nodes. In addition, the wireless sensor nodes randomly select the monitoring time count from the window, so that the problem of synchronization of node antenna rotation in the wireless self-organizing network is solved.
When the wireless sensor node successfully receives the directional RTS sent by other sensor nodes in the antenna sector, if the wireless sensor node contains the address information ID of the wireless sensor node, the wireless sensor node immediately updates the AOA cache information, then replies a directional CTS, locks the antenna sector in the direction and waits for a data frame. And after receiving the data frame, continuously replying the ACK signal. When the monitoring count LC of the wireless sensor node in one antenna sector reaches zero, the node enters a data packet sending state from a monitoring state. If the wireless sensor node has a plurality of data frames to be sent, the wireless sensor node firstly generates and sends an improved directional RTS frame. If a directed CTS reply is received, the link is established and a data frame will then be transmitted. After the data frame transmission is completed, the sensor node waits for an ACK signal to be replied. When the ACK signal is successfully received, a frame of data is successfully transmitted. The node will regenerate a directional RTS and decide to select one antenna element to continue the mechanism to listen to the channel and transmit data. If no directional CTS reply is received, i.e., the wireless sensor node waits for the directional CTS timeout to reply, the node will switch to the next antenna unit. By switching the antenna sector clockwise or counterclockwise, a channel monitoring and sending stage is executed, and the FDD-MAC ensures that the wireless sensor node has a chance to monitor the directional RTS information sent by other nodes, and can also successfully establish connection and send data to the neighbor nodes.
Frame format design and clustering RTS (ready To Send) control information
The wireless sensor node transmits rts (ready To send) and cts (clear To send) control signals by using a directional antenna, and listens To a wireless channel by using the directional antenna, which results in a reduced probability of establishing a link for the wireless sensor node. In order to solve the problem, the invention carries out certain modification on the basis of the 802.11RTS control frame so as to improve the success rate of establishing the link.
(A) Data frame structure design
Table 1 existing 802.11MAC frame format
The Frame Control part records the attribute of the 802.11MAC of the conventional omni-directional antenna, the Duration/ID (life cycle) is mainly used in the virtual carrier sensing mechanism, the addresses 1-4 (Address) respectively indicate the addresses of the transceiving nodes, the Sequence Control field (Sequence Control field) is used to reassemble the Frame fragment and discard the repeated Frame, the Frame Body stores the effective data payload part of the user, and the FCS (Frame check Sequence) enables the workstation to check the integrity of the received Frame.
On the basis of the original data frame format, the invention adds a plurality of receiving address information in the frame structure:
(A-1) firstly, addresses 1-4 (addresses) on the basis of the original addresses are fully utilized to respectively represent the addresses of the transmitting and receiving nodes, and the addresses are expanded to DthAddress information of each receiving node.
Table 2 improved 802.11MAC frame format-directional RTS frame
(B) Cluster-sent RTS (Ready To Send) control information
In the design of the FDD-MAC protocol, a wireless sensor node first sends a directional RTS and a directional CTS for establishing a wireless link between a source node and a destination node. In a conventional wireless ad hoc network, data packets waiting for transmission inside nodes are buffered in a memory in a first-in first-out (FIFO) manner. However, in the MAC protocol with a fully directional antenna, the source node may first scan the antenna unit, find a target node buffering the first frame data packet in the FIFO storage area, and establish a link by sending a directional RTS and a directional CTS. While scanning the antenna elements for the destination node of the first frame, it is possible to point to other destination nodes for the data packets buffered in the FIFO. Therefore, the FDD-MAC protocol increases the address of the destination node to be received by expanding the conventional RTS control packet structure, and improves the success rate of establishing a link.
When the wireless sensor node has cache data to send, first extracting front D in FIFOthAnd buffering the destination address ID of the data packet, adding address information into a directional RTS frame, and then sending a directional RTS to establish a wireless link. Cluster-sent directional RTS control information actually refers to the transmission of an improved directional RTS frame structure, which is equivalent to the simultaneous transmission of multiple conventional RTS handshake signals. In addition, the FDD-MAC protocol divides the data frames in the buffer queue into two priority levels. If the AOA direction information of the destination node caching the data packet is stored, the AOA direction information is preferentially sent by an antenna sector facing the destination node, so that the probability that the directional RTS control information faces the receiving node can be improved, and the probability of wireless connection is further improved.
The process according to the invention is further elucidated with reference to the figures and examples.
Examples
(A) Initialization phase of environment and node.
The invention is mainly applied to the mobile wireless self-organizing network, and the nodes in the network are randomly distributed in the transmission range of 100m × 100 m. The maximum radiation radius of each node is R, the node radiation distance R is larger than 200m, namely the radiation distance of a single node can cover the whole wireless self-organizing network. All nodes are equipped with directional antennas as shown in fig. 2, which may be adaptive array antennas or a plurality of directional surface antennas arranged in sequence. The directional antenna unit comprises M antenna sectors, each antenna sector having the same beam angle, all antenna sectors covering 360 degrees. Nodes in a wireless ad hoc network transmit or receive data using one antenna sector at a time. The operating mode and typical configuration of the system are set according to the ieee802.ll specification, the node data transmission rate is set to 2Mbps, the Time length of SIFS is defined as 10 μ s, DIFS is defined as 50 μ s, and the Slot interval (Slot Time) is defined as 20 μ s. The wireless sensor nodes in the network obey Poisson distribution, a data source is generated, the length of the data source is 1024 bytes, and one of the MAC addresses of the wireless self-organizing network nodes is randomly selected from the addresses of the receiving nodes.
(B) Source node S data transmission phase
(B-1) if the wireless sensor node has the generated data packet (or the cached sensor acquisition data) to wait for sending, the node is called a source node. The source node first detects whether the packet length L in the buffer FIFO is greater than D. And if the L is larger than the D, the source node extracts the destination address IDs of the previous D cache data packets and adds the address information into the directional RTS frame. If the number L of the cache data packets is smaller than D, only the first (L +1) th addresses of the directional RTS frame are filled, and the last (L +2) th-Dth addresses are null and assigned with zero. The finally generated directional RTS control information is shown in table 3.
TABLE 3 Directional RTS frame generated
Wherein, the Address1 is set as the Address of the node, Address2-DthSet as the address of the receiving node, the Seq-Ctrl records the sequence number of the current data frame.
(B-2) the source node prepares to send a directional RTS frame. When the directional RTS frame is completed, the source node polls and detects the Address2-D in the generated directional RTS framethAn address. And if the AOA antenna Sector information corresponding to the MAC address of the receiving node is cached, updating the antenna Sector Ante _ Sector selected to be sent, and exiting the polling. If the address information is detected to be empty, or the receiving address (D +1)thAnd after the detection is finished, the Ante _ Sector is not updated, and then the Ante _ Sector randomly selects one antenna Sector M.
(B-3) the source node switches the antenna Sector to Ante _ Sector, and before the antenna Sector sends a directional RTS frame, the source node firstly switches from a monitoring window Wmin，Wmax]Selects an integer as the initial value of the snoop counter (LC ListeningCounter). The source node first listens to the channel for a free minimum inter frame space (DIFS), and thereafter if the channel continues to be free, the LC count value is decremented by 1 through a minimum time slot. If the channel detection is busy (other nodes in the antenna sector transmit data) in the above process, the source node freezes the LC count until detecting the channel idle minimum interframe space (DIFS), then continues to monitor the channel idle, and decrements the LC count.
If the node receives a directional RTS frame sent by other nodes in the process of counting down the LC, the source node firstly detects whether the RTS frame contains the MAC address of the source node. If yes, a directional CTS signal is replied in the antenna sector, the antenna sector is locked, a data packet is waited to be received, and then an ACK signal is replied to indicate that the data packet is successfully received. If the directional RTS is replied, the node does not receive the data packet, namely the node waits for the data frame to be overtime, the source node continues to detect the idle channel and decrements the LC count. If the directional RTS frame does not contain the MAC address of the source node, the source node acquires the channel occupation time parameter from the directional RTS frame, then sets the directional NAV time interrupt of the antenna sector, stops other activities, waits for the arrival of the directional NAV time interrupt, then continues to detect the channel idleness, and decrements the LC count.
(B-3) when the listening count LC of the source node decreases to zero, the source node starts sending a directional RTS frame on the antenna sector and then sets a Timeout interrupt to wait for receiving a directional CTS reply.
(C) Waiting to receive a directed CTS reply
(C-1) if the source node receives the CTS signal returned by the receiving node before the Timeout time interruption arrives, the node locks the antenna sector. And secondly, extracting the MAC address information and the destination address information of the receiving node from the received directional CTS frame, and updating the cached AOA antenna sector information of the receiving node. If the destination address information is corresponding to the MAC address of the destination address information, then a cache data packet corresponding to the MAC address of the receiving node is searched in the data cache FIFO, extracted and a data frame is sent on an antenna sector.
And (C-2) if the destination address information does not correspond to the MAC address of the antenna sector, other nodes exist on the antenna sector to transmit and receive data. The directional CTS frame is discarded and not processed. This problem is mainly due to the fact that the receiving node may compete for collisions with multiple neighboring nodes, resulting in multiple data packets being received on the antenna sector of the source node, as shown in fig. 3. If the Timeout is interrupted and no directional CTS reply is received, referring to fig. 4, the antenna sector is switched in a clockwise (or counterclockwise) direction, and the above channel monitoring and directional RTS establishment link process is repeated.
Claims (6)
1. A satellite formation network channel access control method based on directional antennas is characterized in that: the nodes in the wireless self-organizing network are provided with directional antennas, the directional antennas are adopted to monitor wireless channels, and full directional data transmission is realized through directional virtual carrier sensing (DNAV) based on the scanning of antenna units; storing by adopting a neighboring node wave arrival angle AOA, wherein each node stores the direction of the neighboring node in the current node antenna unit sector from the successfully received information; when a node sends data to a neighbor node every time, firstly searching whether the direction of an antenna unit sector of the neighbor node is cached or not, and if the cache exists, preferentially trying to send RTS handshake control information in the direction of the cached antenna unit sector to establish connection;
the directional antenna is an adaptive array antenna or a plurality of directional plane antennas which are arranged in sequence, the directional antenna unit comprises a plurality of antenna sectors, the wave beam angle of each antenna sector is the same, and all the antenna sectors cover 360 degrees; wherein wireless sensor nodes in the network obey a poisson distribution;
extension of directional RTS frame to D on the basis of 802.11RTS control frame by adopting frame format designthReceiving node address information; when the wireless sensor node has cache data to send, first extracting front D in FIFOthCaching a destination address ID of the data packet, adding address information into a directional RTS frame, and then sending the directional RTS frame by adopting cluster RTS control information to establish a wireless link; if the AOA direction information of the destination node of the cached data is stored, the AOA direction information is preferentially sent towards the antenna sector of the destination node of the cached data.
2. The directional antenna based channel access control method for the satellite formation network, according to claim 1, characterized in that: the method specifically includes that nodes in the wireless ad hoc network store DNAV information in each antenna sector, whether other nodes in the current sector transmit data is recorded, and the nodes update the DNAV data from received directional RTS frames and directional CTS information.
3. The directional antenna based channel access control method for the satellite formation network, according to claim 1, characterized in that: the scanning of the antenna unit is specifically: all wireless sensor nodes continuously switch antenna sectors in sequence; the wireless sensor node can capture a directional RTS frame from a neighbor node while sending the directional RTS frame, and the operation of the wireless sensor node in each sector comprises two stages of monitoring a channel and sending data; wherein the wireless sensor node switching order is clockwise or counterclockwise.
4. The directional antenna based channel access control method for the satellite formation network, according to claim 1, characterized in that: the operation of the wireless sensor node in each sector is specifically as follows:
(1) listening channel phase of wireless sensor node
The monitoring time of the wireless sensor node comprises two parts, namely monitoring time in a fixed period and monitoring time in a random period; when the source node switches to a new antenna sector, it randomly selects an integer from the window as the initial value (LC) of the listening counter; if the source node detects that the channel is idle, reducing the value of LC by 1 through a minimum time slot; if the channel is detected to be occupied, the LC count is frozen until the channel is free for a minimum interframe space (DIFS), then the channel continues to be monitored, and the listening count is decremented;
if the source node receives a directional RTS frame sent by other nodes in the process of counting down by the LC, the source node firstly detects whether the RTS frame contains the MAC address of the source node; if yes, replying a directional CTS signal in the antenna sector, locking the antenna sector, waiting for receiving a data packet, then replying an ACK signal to indicate that the data packet is successfully received, if replying the directional RTS, the source node does not receive the data packet, namely waiting for the data frame to be overtime, the source node continues to detect the idle of the channel, and decrements LC counting; if the directional RTS frame does not contain the MAC address of the source node, the source node acquires the channel occupation time parameter from the directional RTS frame, then sets the directional NAV time interruption of the antenna sector, stops other activities, waits for the arrival of the directional NAV time interruption, then continues to detect the idle channel, and decrements LC count;
(2) data transmission phase of wireless sensor
When the monitoring count LC of the source node reaches zero, the source node enters a data packet sending state from a monitoring state; if the source node has a plurality of data frames to be sent, the source node firstly generates and sends a directional RTS frame, and then sets Timeout interrupt waiting for receiving a directional CTS reply; if the source node receives a directional CTS reply before the Timeout time interruption arrives, a link is established, then a directional RTS frame is transmitted, after the transmission of the directional RTS frame is completed, the source node waits for replying an ACK signal, when the ACK signal is successfully received, one frame of data is successfully transmitted, the source node regenerates the directional RTS frame and judges that the next antenna unit is selected to continuously execute a mechanism for monitoring a channel and transmitting data; if the directional CTS reply is not received, namely the time of the directional CTS which is waited to reply by the wireless sensor node is overtime, the node is switched to the next antenna unit according to a certain sequence, and the channel monitoring and the link process established by sending the directional RTS are repeated.
5. The directional-antenna-based channel access control method for the satellite formation network, according to claim 4, is characterized in that: before the source node receives the directional CTS reply transmission directional RTS frame in the step (2), the source node firstly locks an antenna sector, secondly extracts the MAC address information and the destination address information of the receiving node from the received directional CTS frame, and updates the cache AOA antenna sector information of the receiving node; if the destination address information corresponds to the MAC address of the destination address information, then searching a cache data packet corresponding to the MAC address of the receiving node in a data cache FIFO, extracting the cache data packet, and sending a directional RTS frame on an antenna sector; if the destination address information does not correspond to the MAC address of the antenna sector, other nodes exist on the antenna sector to transmit and receive data, and the directional CTS frame is discarded without processing.
6. The directional-antenna-based channel access control method for the satellite formation network, according to claim 4, is characterized in that: the source node is a node when a wireless sensor node has a generated data packet or cached sensor acquisition data to wait for sending.
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| CN107979872B (en) * | 2017-11-10 | 2021-06-01 | 西安电子科技大学 | Multi-frequency time division multiple access system and method based on directional antenna |
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