KR20110026227A - Method for assigning ids for csma/ic - Google Patents

Abstract

PURPOSE: An ID allocation method for CSMA/IC(Carrier Sense Multiple Access /ID Countdown) is provided to give a locally unique ID to each node when using a circulation ID. CONSTITUTION: Whether a medium is an idle state or not is determined(210). If the medium is the idle state, a synchronous beacon signal is transmitted(220). If a beacon signal of a competition node is sensed(230), the sensed beacon signal is converted into an ID(240). A random ID which is larger than a converted ID is allocated as an ID(250). Whether to use an ID or not is determined. If the ID must be used, their ID is converted according to a circulation rule.

Description

ID assignment method for CSM / IC {Method for assigning IDs for CSMA / IC}

The present invention relates to an ID allocation method that can be used for a carrier sense multiple access / ID countdown (CSMA / IC) which is a collision-free wireless MAC protocol.

CSMA / CA, the most widely used wireless MAC protocol, avoids collisions by accessing the medium after all nodes have waited at random time when the medium is empty. This protocol has low performance due to frequent access conflicts when there are many nodes.

On the other hand, CSMA / IC (Carrier Sense Multiple Access / ID Countdown) is a MAC protocol without media access collision.

CSMA / IC has a unique numeric ID for each wireless node and eliminates media access collisions between nodes by generating and competing signals according to the binary form of this ID. Specifically, the overall operation of the CSMA / IC will be described with reference to the frame format of the CSMA / IC protocol.

1 illustrates a frame format of the CSMA / IC protocol.

Referring to FIG. 1, the frame format of the CSMA / IC protocol is composed of four parts whose role is very simple. Prior to the media access competition, all nodes sense the medium during the "medium sensing slot" to determine if the medium is currently idle. after that. The nodes perform a local synchronous processor by sending a "Synchronizing Beacon" signal during the "SB signal sending period". The synchronous nodes then compete for media access for a predetermined length of binary competing slots.

Specifically, during the contention period, each node senses the medium according to a schedule that transmits a beacon signal or is derived from a binary form of its unique ID. This schedule is determined according to the following rules. From the most significant bit, the bits are interpreted one bit at a time. Bit "1" is interpreted as "beacon signal transmission" and bit "0" is interpreted as "sense media". If the node detects a beacon signal in the "sense media" time slot, it stops contention. By repeating this competition process, the nodes remaining to the end become winners of the competition. Since all IDs are unique, the schedule cannot be the same. Therefore, media access collisions cannot occur in CSMA / IC. Finally, the winner of the competition sends data during the "Data sending period."

The most important advantage of CSMA / IC is conflict-free ownership. Unique IDs generate a unique beacon signal schedule, and only one winner is selected. Since collisions are a major source of wasted bandwidth, CSMA / IC greatly improves network throughput performance. CSMA / IC also solves the problem of "hidden terminal" caused by nodes in the interference range. CSMA / IC uses beacon signals to eliminate contenders. Because the beacon signal can be detected by the nodes in the interference range, the hidden terminal in the interference range is also eliminated during the contention period, thus solving the "hidden terminal" problem.

Despite these attractive points, CAMS / IC is not widely used due to two fatal drawbacks. One is that the node with the largest ID always gains media access opportunities. This unfair media access problem causes serious starvation problems. In other words, according to CSMA / IC, there is a problem that a node having a large ID always acquires a medium access opportunity so that other nodes cannot access the medium. Another problem is that assigning a unique ID is very difficult in an ad hoc network environment due to its uncertainty.

Accordingly, an object of the present invention is to use a recursive ID to solve the problems of the prior art and to provide a method for assigning a unique ID locally to each node when using a recursive ID.

According to an aspect of the present invention for achieving the above object, a method for allocating an ID in a CSMA / IC based node includes allocating its ID when accessing a medium, determining whether to use an ID, and determining an ID. If necessary, the method includes transforming its ID according to the ID rotation law.

Herein, the ID recursion law is a first law that sets the first '0' bit to '1' from the most significant bit in the ID, and a second that converts all preceding bits of the bit set to '0' to '0' bits. The law and the case where all bits are '1' include a third law that converts all to '0'.

Here, the ID assignment step includes determining whether the medium is in an idle state, transmitting a synchronous beacon signal if the medium is in an idle state, and converting the detected beacon signal into an ID if a beacon signal of a contention node is detected. And assigning a random ID larger than the converted ID as its own ID.

Here, the ID assignment step may include determining whether the medium is in an idle state, transmitting a synchronous beacon signal if the medium is in an idle state, and if not detecting a beacon signal of a contention node, a random ID greater than zero. It assigns to its ID.

Here, the ID assignment step includes determining whether the medium is in an idle state, transmitting a synchronous beacon signal if the medium is in an idle state, and converting the detected beacon signal into an ID if a beacon signal of a contention node is detected. And if the converted ID is the largest ID among the available IDs, determine whether the number of attempts to allocate ID exceeds a threshold value, and if so, the intercept bit that allows the node to be a winner in the media access competition. And assigning a random ID to its own ID.

Here, the determining of whether to use the ID includes determining whether there is data to be transmitted.

According to another aspect of the present invention, a method for allocating an ID in a CSMA / IC based node includes determining whether a medium is in an idle state, transmitting a sync beacon signal if the medium is in an idle state, and beacon of a contention node. Converting the detected beacon signal to an ID if the signal is detected and assigning a random ID larger than the converted ID as its own ID; and if not detecting the beacon signal of the contention node, random ID greater than 0 Assigning by ID.

According to another aspect of the present invention, a method for allocating an ID in a CSMA / IC based node includes determining whether a medium is in an idle state, transmitting a sync beacon signal if the medium is in an idle state, Converting the detected beacon signal to an ID if a beacon signal is detected; and if the converted ID is the largest ID among the available IDs, determining whether the number of attempts to assign an ID exceeds a threshold and accessing the medium if the node is exceeded. Setting the intercept bit to 1 to enable the winner in the competition, and assigning a random ID to its own ID.

Here, if the ID allocation method does not detect the beacon signal of the contention node, the method further comprises the step of assigning a random ID greater than zero as its own ID.

Here, the ID allocation method further includes the step of allocating a random ID larger than the converted ID as its own ID if the converted ID is not the largest ID among the available IDs.

The present invention as described above is composed of a scheme for assigning a unique ID in the circular ID system and ID system. The recursive ID system provides a fair access to media access by having IDs recur in every media access competition. The unique ID granting technique improves network efficiency by assigning IDs by judging by the nodes themselves without exchanging ID information between nodes based on the characteristics of CSMA / IC that the largest ID always wins the media access competition.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to describing the present invention, an ID screen effect in the CSMA / IC will be described.

2 is a diagram for explaining an ID screen effect in CSMA / IC.

Nodes that detect the beacon signals of other nodes in CSMA / IC give up competition. Therefore, only the winner can fully perform the beacon schedule. For example, in FIG. 2, the ID of node A 10 is "0110", the ID of node B 20 is "1001", and the ID of node C 30 is "1010", and nodes A, B and C Are combined with each other. In FIG. 2, only the beacon schedule of “1010” is completely performed. In the first contention slot, node A910 abandons contention due to the beacon signals of node B 20 and node C 30. Node B 20 then abandons the competition in the third contention slot. As shown in FIG. 2, other beacon schedules are completely blocked by the winner's beacon schedule. The beacons of node A 10 in the second contention slot and the beacons of node B 20 in the fourth contention slot are blocked. This phenomenon is called "ID Screeen Effect." This ID screen effect provides the fact that none of the neighbors has an ID greater than the observed ID. That is, if a node assigns an ID greater than the detected ID, then that ID is certain to be unique in the local area. The present invention utilizes this ID screen effect.

3 is a diagram illustrating an ID allocation method according to an embodiment of the present invention.

Referring to FIG. 3, the node determines whether the medium is in an idle state in step 210. In more detail, a node intending to participate in a medium access competition waits until the medium is in an idle state so as not to interfere with transmission of other nodes. When the medium is idle, the node may wait for additional time for a certain duration to determine if the medium is actually idle.

The node then sends a synch beacon to synchronize the contention starting point in step 220. After synchronization, the node detects the beacons of the competing nodes during the predetermined " Binary competing slots " If the node does not detect any beacon signals during the binary race slot period, the node proceeds to step 260 and assigns a random random ID greater than zero as its ID. That is, all neighbors are idle or their neighbors' IDs are zero. However, if the node detects the beacon signal, the process proceeds to step 240 and converts the detected beacon signal into an ID. That is, the node obtains an ID from the detected beacon signal. The detected beacon signal due to the "ID screen effect" is the winner's beacon signal. Therefore, the ID obtained from the beacon signal becomes the largest ID among the neighbors.

After converting the beacon signal to an ID, the node assigns as its ID an arbitrary random ID greater than the ID obtained from the beacon signal in step 250.

However, the ID obtained from the beacon signal may be the largest ID in the ID pool, so that the node must reassign the ID in the next contention slot. Also, if almost all IDs are in use, the node may not be able to wait a long time or assign an ID.

In order to solve this problem, the second embodiment of the present invention uses the "Intercept bit.

4 is a diagram illustrating an ID allocation method according to a second embodiment of the present invention. Steps 310 to 330 of FIG. 4 are similar to steps 210 to 230 of FIG. 3, and thus, descriptions related to FIG. 3 will be referred to.

Referring to FIG. 4, in step 310, the node determines whether the medium is in an idle state. The node waits until the medium is in the idle state and then transmits a synch beacon to synchronize the contention starting point in step 320. After synchronization, the node detects the beacons of the contention nodes during a predetermined " Binary competing slots " interval at step 330.

If the node does not detect any beacon signals during the binary contention slot period, the node proceeds to step 370 to assign its ID. In this case, the node may assign any random ID greater than zero as its ID.

If the node detects the beacon signal during the binary contention slot period, the process proceeds to step 340 and converts the detected beacon signal into an ID. That is, the node obtains an ID from the detected beacon signal. The detected beacon signal due to the "ID screen effect" is the winner's beacon signal. Therefore, the ID obtained from the beacon signal becomes the largest ID among the neighbors.

The node then proceeds to step 350 to determine if the converted ID is the largest of the available IDs. If the converted ID is not the largest ID among the available IDs, the node proceeds to step 370 to assign its ID. In this case, the node assigns as its ID an arbitrary random ID that is greater than the ID obtained from the beacon signal.

If the converted ID is the largest ID among the available IDs, the node proceeds to step 360 to determine whether the number of ID allocation attempts exceeds a threshold. If the number of ID allocation attempts exceeds the threshold, the node proceeds to step 380 and sets the intercept bit to 1. The intercept bit allows the node to be the winner in the media access competition.

Although not shown in Fig. 4, the node assigns a random ID. In this case, if one of the neighbor nodes detects its ID, the node releases its ID. If the intercept bit is set to 1, it can be used regardless of whether the assigned ID is occupied by another node.

In other words, the node sets the intercept bit to 1 if the ID assignment fails even though the node attempts to assign its ID multiple times and attempts to assign the ID multiple times.

Accordingly, the node participates in a media access competition by intercept bits and randomly assigned IDs. Because the "intercept bit" is located before the ID part, the node can be a winner, and all other neighbor nodes sense the beacon signal.

5 shows the format of a "binary contention slot" according to the second embodiment of the present invention.

Referring to FIG. 5, since the intercept bit is located in the first contention slot in the format of the binary contention interval, if the intercept bit is set to 1, the node is the winner in the medium access contention.

On the other hand, after the ID assignment process according to the present invention, a newly entering node competes with its neighboring nodes using a rotated ID. All nodes cycle their IDs in every race, so a newly entering node must also be gentle with its assigned ID to avoid ID collisions. The law of ID rotation according to the present invention is described below.

6 is a view showing an ID allocation method according to a third embodiment of the present invention. In FIG. 6, steps 410 to 460 are the same as steps 210 to 260 of FIG. 3 and related descriptions, and thus a detailed description thereof will be omitted.

Referring to FIG. 6, the node determines whether the medium is in an idle state in step 410. If the medium is not idle, then the node sends a synch beacon to synchronize the contention starting point in step 420. After synchronization, the node detects the beacons of the contention nodes during a predetermined " Binary competing slots " interval in step 430. If the node does not detect any beacon signals during the binary contention slot period, the node proceeds to step 440 and assigns a random random ID greater than zero as its ID. If the node detects the beacon signal, the process proceeds to step 450 and converts the detected beacon signal into an ID. That is, the node obtains an ID from the detected beacon signal. After converting the beacon signal to an ID, the node assigns as its ID an arbitrary random ID greater than the ID obtained from the beacon signal in step 460.

The node then determines in step 470 whether to use the ID. The node participated in a media access competition using the assigned ID. The node may or may not be a winner in the media access competition. The node may transmit data to the medium if it wins the media access competition. Even if a node has won the media access competition and sent data to the medium, there may be more data to transmit. The node should use the ID if there is more data to send.

Also, a node cannot transmit data unless it is a winner in a media access competition. As a result, a node must use an ID to transmit data if it is not a winner in a media access competition.

Accordingly, the node determines whether to use the ID in step 470. If an ID is to be used, the node converts its ID in step 480 according to the ID rotation law according to the present invention. It demonstrates concretely below.

If a node has gained access in a media access competition, it may have had the largest ID among neighboring nodes, including itself. In this case, if a node keeps its ID continuously, it is difficult for other nodes to gain access in the media access competition. Therefore, in this case, it is preferable that the node converts its ID into a low value ID.

Alternatively, if a node failed to obtain access rights in a media access competition, the node may have a smaller ID among neighboring nodes, including itself. In this case, if a node keeps its ID continuously, it is difficult to obtain access rights in the media access competition. Therefore, in this case, it is preferable that the node converts its ID into a high value ID.

In view of the above circumstances, the present invention converts the ID every time the node accesses a media access race cycle, that is, every medium access race cycle. At this time, the ID is converted according to the following rules.

1. In the binary ID, set the first '0' bit from the most significant bit to '1'.

2. Convert all the preceding bits of the bit set to '0' to '0' bit.

3. If all bits are '1', all are converted to '0'.

Accordingly, if the binary form of the ID is " 11001 ", it becomes " 00101 " according to the ID rotation law. Because the third bit is the first "0" bit, the first and second bits are set to '0' and the third bit is set to '1'.

7 is a diagram illustrating an example ID cycle according to the present invention. The nodes convert their IDs in the order as shown in FIG. 7 after participating in every media access competition.

As such, by utilizing the circular ID in the CSMA / IC network, all nodes have an equal access to media and have an effect of increasing the efficiency of the network by assigning IDs without exchanging messages.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

1 illustrates a frame format of the CSMA / IC protocol.

2 is a diagram for explaining an ID screen effect in CSMA / IC.

3 is a diagram illustrating an ID allocation method according to an embodiment of the present invention.

4 is a diagram illustrating an ID allocation method according to a second embodiment of the present invention.

5 shows the format of a "binary contention slot" according to the second embodiment of the present invention.

6 is a view showing an ID allocation method according to a third embodiment of the present invention.

7 is a diagram illustrating an example ID cycle according to the present invention.

Claims (10)

In the method for allocating ID in CSMA / IC based node, Assigning its ID when accessing the medium, Determining whether an ID should be used, If it is necessary to use an ID, comprising the step of converting its own ID according to the ID rotation law. The method of claim 1, The ID recursion law is a first law that sets the first '0' bit to '1' from the most significant bit in the ID, a second law that converts all the preceding bits of the bit set to '0' to '0' bits, and all of them. And a third law of converting all bits to '0' when the bit is '1'. The method of claim 1, The ID assignment step Determining whether the medium is in an idle state, Transmitting a sync beacon signal if the medium is idle; And converting the detected beacon signal into an ID if the beacon signal of the contention node is detected and assigning a random ID larger than the converted ID as its ID. The method of claim 1, The ID assignment step Determining whether the medium is in an idle state, Transmitting a sync beacon signal if the medium is idle; And if the beacon signal of the contention node is not detected, allocating a random ID greater than zero as its own ID. The method of claim 1, The ID assignment step Determining whether the medium is in an idle state, Transmitting a sync beacon signal if the medium is idle; Converting the detected beacon signal into an ID when detecting a beacon signal of a contention node; If the converted ID is the largest of the available IDs, determining whether the number of attempts to allocate the ID exceeds a threshold value, and if so, setting the intercept bit to 1 to allow the node to be a winner in a media access race. Wow, And assigning a random ID as its own ID. The method of claim 1, Determining whether to use the ID is And determining whether there is data to be transmitted. In the method for allocating ID in CSMA / IC based node, Determining whether the medium is in an idle state, Transmitting a sync beacon signal if the medium is idle; Converting the detected beacon signal into an ID when the beacon signal of the contention node is detected and assigning a random ID larger than the converted ID as its ID; And if the beacon signal of the contention node is not detected, allocating a random ID greater than zero as its own ID. In the method for allocating ID in CSMA / IC based node, Determining whether the medium is in an idle state, Transmitting a sync beacon signal if the medium is idle; Converting the detected beacon signal into an ID when detecting a beacon signal of a contention node; If the converted ID is the largest ID among the available IDs, determining whether the number of attempts to allocate the ID exceeds a threshold value and, if exceeded, setting the intercept bit to 1 to allow the node to be a winner in the media access competition; , And assigning a random ID as its own ID. The method of claim 8, And if the beacon signal of the contention node is not detected, assigning a random ID greater than 0 as its own ID. The method of claim 8, And if the converted ID is not the largest ID among usable IDs, assigning a random ID larger than the converted ID as its ID.

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