• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    In the present invention, the RTS / CTS (Request-To-Send / Clear-) is used to reduce the recovery period of packet collision in the collision avoidance function carrier detection multiple access (CSMA / CA) system used for point-to-multipoint communication of wired and wireless. To-Send) provides an adaptive data flow control method by detecting hidden nodes to prevent packet collisions between data frames by hidden nodes by detecting hidden nodes. To this end, the present invention provides a communication system for transmitting and receiving data frames for each node station by point-to-multipoint communication, wherein a destination ID for a data frame received from a station visible to each node station is represented by its own ID. If it is determined that it is not the same, the destination ID and the source ID are stored in a list, and each destination ID list and the source ID list are compared to determine an ID existing only in the destination ID list as a hidden node.
    公开号:KR20030083394A
    申请号:KR1020020021906
    申请日:2002-04-22
    公开日:2003-10-30
    发明作者:박종혁
    申请人:주식회사 젤라인；
    IPC主号:
    专利说明:

    Method for controlling adaptive data stream by hidden node detection
    [7] The present invention relates to an adaptive data flow control method based on detection of a hidden node, and more particularly, to avoid collision detection, carrier detection multiple access (CSMA / CA) used for point-to-multipoint communication. Adaptive data flow by detecting hidden nodes to prevent packet collisions between data frames by hidden nodes in medium access control (MAC) systems such as Carrier Sense Multiple Access / Collision Avoidance It relates to a control method.
    [8] As is well known, RTS / CTS is a method for performing medium reservation before transmitting data frames in point-to-multipoint communication. The wireless LAN medium access control (MAC) in IEEE 802.11 Part 11 is used. And Physical Layer (PHY) specifications.
    [9] That is, the RTS / CTS is a short control frame that transmits and receives between the source station and the destination station before the actual data frame is transmitted. The RTS / CTS is used to transmit the data frame after the exchange of the RTS / CTS. It contains time information and destination / source ID.
    [10] 1 is a diagram illustrating a basic operation of an RTS / CTS as a general flow control, in which a source station to transmit a data frame preferentially transmits an RTS, and a destination station that receives the RTS transmits a CTS to transmit data thereafter. A transmission medium reservation for frame transmission is performed.
    [11] All other stations except the destination station and the source station perform the VCS (Virtual Carrier Sense) until the transmission of the subsequent data frame is terminated after receiving the RTS, and the other station that has received the CTS but has not received the RTS. In VCS, VCS is performed until the transmission of the data frame is completed.
    [12] Here, the VCS means waiting until the transmission of the data frame is completed.
    [13] Meanwhile, in the RTS / CTS, it can be used to prevent packet collision between frames generated by a hidden node. As shown in FIG. 2, a node is assumed to be a hidden node that is invisible to each other. Since the data frame transmitted from A to Node B is not visible at Node C, Node C side recognizes the current channel status as an idle state.
    [14] At this time, if a data frame is transmitted from Node C to Node B or Node D, packet collision occurs, and Node B cannot receive normal frame. Therefore, in order to solve this hidden node problem, RTS / CTS Can be used.
    [15] That is, FIG. 3 is a diagram illustrating a state in which data collision by a hidden node is prevented. Node A transmits an RTS before transmitting a data frame, and node B transmits a CTS in response. Since Node C also receives the CTS transmitted by Node B, it performs VCS.
    [16] As described above, in all stations where the source station or the destination station is visible, VCS may be performed until the corresponding data frame is terminated to prevent packet collision by the hidden node, and the packet generated by the existing contention. Since collision occurs between RTSs having a short frame length, the recovery period of packet collision is reduced.
    [17] However, since these RTS / CTS specifies that IEEE 802.11 manually selects whether to use RTS / CTS for each station, RTS / CTS may be used all the time or not, or may be used only for frames longer than a certain length. This decision is made manually, and if all stations use RTS / CTS without knowing whether there is a hidden node, fast collision estimation can reduce the recovery time of packet collisions. If you decide to use RTS / CTS of all stations in the same state without detection of node, the network efficiency is greatly reduced and the RTS / CTS is used manually. There is a problem that it is difficult to determine.
    [18] Accordingly, the present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to provide a recovery period of packet collision in a collision detection multiple access (CSMA / CA) system with collision avoidance function used for point-to-multipoint communication in wired and wireless communication. Adaptation by detecting hidden nodes to prevent packet collisions between data frames by hidden nodes by detecting hidden nodes using RTS / CTS (Request-To-Send / Clear-To-Send) Type data flow control method.
    [1] 1 is a view for explaining the basic operation of the RTS / CTS as a general flow control;
    [2] 2 is a diagram illustrating a state in which data collision occurs at another node by a hidden node;
    [3] 3 is a diagram illustrating a state in which data collision by a hidden node is prevented;
    [4] 4 is a view for explaining a detection state of a hidden node in the master / slave structure according to a preferred embodiment of the present invention,
    [5] 5 is a view for explaining a hidden node detection state under the LAN communication structure according to an embodiment of the present invention;
    [6] 6 is a flowchart illustrating an operation of an adaptive data flow control method by detecting a hidden node according to the present invention.
    [19] In order to achieve the above object, according to the present invention, in a communication system for transmitting and receiving data frames for each node station by point-to-multipoint communication, for each data station received from the station visible to itself at each node station If it is determined that the destination ID is not the same as its ID, storing the destination ID and the source ID in the list, comparing each destination ID list and the source ID list, and determining an ID existing only in the destination ID list as the hidden node. It provides an adaptive data flow control method by detecting a hidden node, characterized in that consisting of.
    [20] Hereinafter, the present invention configured as described above will be described in detail with reference to the accompanying drawings.
    [21] That is, in the present invention, since every frame transmitted in point-to-multipoint communication includes a destination ID and a source ID, the hidden node can be independently detected for each station by using the destination ID and the source ID. .
    [22] All stations are able to receive all frames transmitted by the station visible to them. When all stations receive a frame, they check the destination ID of the frame and determine whether it is a frame sent to them, and then process accordingly. If it is confirmed that the received frame is not transmitted to itself, it is possible to determine whether there is a hidden node by storing and comparing the destination ID and the source ID of the frame in a list, respectively.
    [23] Meanwhile, referring to the drawing of FIG. 2, if the node B transmits a data frame to the node C, the frame A may also receive the node A. Therefore, the node A stores the node C in the destination ID list. Node B is stored in the source ID list. Here, if there is an ARQ (Automatic Repeat reQuest) mechanism and successful transmission and reception of data, Node C transmits an acknowledgment (ACK) frame in response to the received data frame, and if Node A and Node C are visible to each other, Similarly, A receives the ACK frame, stores Node B in the destination ID list, and stores Node C in the source ID list.
    [24] In this case, since node A has the same destination ID list and source ID list as B and C, it can be seen that there are no hidden nodes. If node A and node C are hidden nodes, node A Since ACK does not receive the ACK frame transmitted from Node C, the destination ID list and the source ID list are not updated, and each list is not identical. Through this, the node A can recognize that there is a hidden node, and the hidden node can know that the hidden node exists in the destination ID list and not in the source ID list.
    [25] As described above, in the present invention, the detection of the hidden node is performed by comparing the stored destination ID list with the source ID list, and when the ID stored in the destination ID list is not present in the source ID list, the hidden node having the corresponding ID is hidden. In this case, the adaptive RTS / CTS by hidden node detection allows only the station that detects the hidden node to use the RTS / CTS individually.
    [26] 4 is a view for explaining the detection state of the hidden node in the master / slave structure in accordance with a preferred embodiment of the present invention.
    [27] As shown in FIG. 4, when all slave nodes are visible to the master node, there is no hidden node for the master node, so there is no need to use RTS / CTS in the master node.
    [28] On the other hand, when the first slave node and the fourth slave node are hidden nodes, the destination ID list and the source ID list of the first slave node are updated as shown in Table 1 below.
    [29] Frame transmissionDestination ID ListSource ID list Master ⇒ Second Slave20 Second Slave ⇒ Master02 3rd Slave ⇒ Master-3 Master ⇒ Third Slave3- 4th Slave ⇒ MasterFrame not detected MASTER ⇒ 4th Slave4- Fifth Slave ⇒ Master-5 MASTER ⇒ Fifth Slave5-
    [30] Here, in Table 1, it can be seen that the hidden node detected by the first slave node is a fourth slave node stored in the destination ID list but not in the source ID list, and the first slave node in the same manner in the fourth slave node. It can be seen that is a hidden node. In the destination ID list and the source ID list of the second, third, and fifth slave nodes, all other stations are visible, and thus the same.
    [31] In the figure, since the frames transmitted and received by the master node and the second slave node can be received by the first slave node, the IDs of # 0 and # 2 are stored in the destination ID list and the source ID list identically, and the master node When the third slave node communicates with the third slave node, only the ID of # 3 is stored because the ID of # 0 is already stored in the destination ID list and the source ID list.
    [32] Since the frame transmitted by the fourth slave node to the master node is not visible to the first slave node, the ID of # 4 is stored only in the destination ID list by the frame transmitted by the master node to the fourth slave node.
    [33] Next, FIG. 5 is a diagram for explaining a hidden node detection state under a LAN communication structure according to a preferred embodiment of the present invention.
    [34] As shown in FIG. 5, under the LAN communication structure, the first node and the fourth node detect the hidden node because the destination ID list and the source ID list are not identical to each other, and detect the hidden node. In this case, since the first, second, third, and fourth nodes are completely separated from each other, only the IDs of # 5, # 6, and # 7 are stored in the destination ID list and the source ID list, and RTS / CTS will not be used. That is, as illustrated in FIG. 5, only the first node and the fourth node can use the RTS / CTS.
    [35] In the present invention made as described above, regardless of the hidden node detection, it is possible to use adaptively even when the channel situation becomes the idle (Idle). Since it means that the reference time point is lost, all stations can randomly transmit frames without contention. In this case, the probability of packet collision is expressed as a function of the total number of stations and the probability that there is a frame to be transmitted for each station.When RTS / CTS is used only when the channel situation becomes idle, the collision recovery period is increased when packet collision occurs. Can be reduced.
    [36] Next, an operation of determining whether to use RTS / CTS by hidden node detection in the present invention made as described above will be described in detail with reference to the flowchart of FIG. 6.
    [37] First, after resetting the destination ID list and the source ID list and turning off the RTS / CTS (step S10), a state of waiting for reception of a data frame is entered (step S11).
    [38] In that state, the specific node judges whether the reset period of each ID list has passed (step S12).
    [39] If it is determined that the reset period of the destination ID list and the source ID list has not elapsed, it is determined whether or not a data frame is received from a predetermined node (step S13).
    [40] As a result of the determination, if it is determined that the data frame is received from the predetermined node, the specific node determines whether the destination ID is the same as its ID (step S14).
    [41] As a result of the determination, if it is determined that the destination ID for the data frame received from the predetermined node is not the same as its ID, the destination ID and the source ID are stored in each ID list, but the destination ID is the same as its ID. If so, the process returns to the step S1 and enters the reception standby state of the data frame.
    [42] On the other hand, while the destination ID and the source ID are stored in each ID list, the specific node determines whether the destination ID list and the source ID list are the same (step S16).
    [43] As a result of the determination, if it is determined that the destination ID list and the source ID list are the same, it is determined that the hidden node does not exist, the RTS / CTS is turned off, and the process proceeds to step S11 again to enter the reception standby state of the data frame. .
    [44] That is, in most communications, the data frame and the ACK frame are related to each other by transmitting and receiving, so that when there is no hidden node, the destination ID list and the source ID list become identical within a short time.
    [45] However, if it is determined that the destination ID list and the source ID list are not the same according to the determination result of step S16, it is determined that the hidden node is detected, and the node having an ID not present in the source ID list among the IDs present in the destination ID list is determined. The station is defined as a hidden node, and the RTS / CTS is turned on (step S18).
    [46] On the other hand, each node prevents aging of the destination ID list and the source ID list, and periodically resets the destination ID list and the source ID list periodically after a certain time in order to keep adapting to the rapidly changing network conditions. When the station determined to be the hidden node is inactive, the station is deleted from the destination ID list.
    [47] It is a matter of course that the present invention having the above-described embodiments can be variously modified and implemented without departing from the technical spirit of the present invention without departing from the embodiments.
    [48] As described above, according to the present invention, only the station that detects the hidden node can use the RTS / CTS, thereby minimizing the efficiency reduction of the network and efficiently preventing packet collision by the hidden node, In point-to-multipoint communication, RTS / CTS can be adaptively applied regardless of the network situation, and it is operated independently by station, so there is no need to manage it centrally and between stations for detecting hidden nodes. The effect is that there is no need to exchange separate information.
    [49] In addition, even if a hidden node exists, the destination ID list and the source ID list can be initialized periodically. Therefore, when the hidden node does not communicate with other stations, it stops using the RTS / CTS to improve its efficiency. Will have the effect of maximizing.
    权利要求:
    Claims (4)
    [1" claim-type="Currently amended] A communication system for transmitting and receiving data frames for each node station by point-to-multipoint communication,
    If it is determined that the destination ID for the data frame received from the station visible to each node station is not the same as its ID, the destination ID and source ID are stored in the list, and each destination ID list is compared with the source ID list. And determining an ID existing only in the destination ID list as a hidden node.
    [2" claim-type="Currently amended] The method of claim 1, wherein the step further comprises: periodically resetting the destination ID list and the source ID list at the same time.
    [3" claim-type="Currently amended] The method of claim 1, wherein the step is configured to use RTS / CTS individually for each node station when the hidden node is detected.
    [4" claim-type="Currently amended] [4] The adaptive data flow according to the detection of a hidden node according to claim 3, wherein in the step, if a channel state before transmitting a frame is in an idle state, RTS / CTS is individually used for each station. Control method.
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    同族专利:
    公开号 | 公开日
    KR100887406B1|2009-03-06|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2002-04-22|Application filed by 주식회사 젤라인
    2002-04-22|Priority to KR1020020021906A
    2003-10-30|Publication of KR20030083394A
    2009-03-06|Application granted
    2009-03-06|Publication of KR100887406B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1020020021906A|KR100887406B1|2002-04-22|2002-04-22|Method for adaptive data communication by hidden node detection|
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