KR101086266B1 - A hierarchical medium access control method for point-to-multipoint communication - Google Patents

Abstract

The present invention relates to a hierarchical medium access control method for point-to-multipoint communication. Hierarchical media access control (HMAC) provides a repeatable repeater function and a multi-master function where multiple master stations can coexist.

The present invention is characterized in that all stations in the network form a plurality of layers in a tree structure. Each station dynamically determines its Hierarchy Level in advance to determine which stations can communicate with it first. In such a network, repeaters can be easily installed anywhere as needed, eliminating distance constraints. In addition, multiple master stations coexist through Group ID and provide a multi-master function, which allows each to configure its own logical network.

Description

A hierarchical medium access control method for point-to-multipoint communication

1 is a diagram for explaining a tree structure of hierarchical media access control (HMAC) according to the present invention;

2 is a view showing an example of a frame header (Frame Header) that can be used to implement the present invention,

3 is a view for explaining broadcast frame transmission in hierarchical media access control (HMAC),

4 is a diagram illustrating the application of hierarchical media access control (HMAC) to power line communication in an apartment according to a preferred embodiment of the present invention.

The present invention relates to a hierarchical medium access control method for point-to-multipoint communication, and more particularly to distance in wired / wireless point-to-point communication based on collision avoidance function carrier sensing multiple access (CSMA / CA). The present invention relates to a hierarchical media access control method for point-to-multipoint communication that provides a repeater function that can remove restrictions on a network and a multi-master function that can coexist with multiple master stations. .

In general, when there is no predetermined target topology such as power line communication, a media access control method that can satisfy various types of topologies is required.

In addition, a repeater and a multi-master function are needed to overcome this limitation when distance is limited due to poor channel environment.

Accordingly, there are two technical problems to be achieved by the present invention, a repeater function and a multi-master function. These two functions solve the distance constraints and are essential for medium access control (MAC), which can be applied to all topologies.

Multi-Master issues mean that multiple master stations coexist in a single physical network. Each master forms a logical network with a number of slave stations subordinate to it. Thus, multi-master issues mean the coexistence of multiple logical networks. If the slave is invisible to the master due to poor channel conditions or long distances and the number of slaves exceeds the capacity of the master, the multi-master feature allows the installation of another master on the same physical network.

Repeater issue means that if there are only a few slaves at a relatively far distance from the master, the repeater is located in the middle of the master and the slave to retransmit the frames sent and received between the master and the slave. The repeater function also solves the distance constraint.

Accordingly, the present invention has been made to achieve the above technical problem, and the point-to-multi can be operated efficiently without any distance limitation in all kinds of topologies regardless of the network topology by the repeater function and the multi-master function. Its purpose is to provide a hierarchical media access control method for point communication.

According to a preferred embodiment of the present invention for achieving the above object, a hierarchical medium access control method for point-to-multipoint communication is based on a hierarchical level.

In addition, the present invention is characterized in that the relationship between stations is defined as parent / child / sibling on a hierarchy and allows only communication between the parent and the child.

In addition, in the present invention, a type of station is defined as a master, a slave, and a repeater, and a unique station ID is assigned to each station to form a tree structure network. It is another feature to do.

In addition, the present invention is characterized in that the repeater can be a parent of the slave, thereby providing a repeater function without being restricted by the distance between the master and the slave.

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

 In the hierarchical media access control (HMAC) proposed in the present invention, each station has its own hierarchical level and all communication can only occur between two adjacent hierarchy levels.

In hierarchical media access control (HMAC), all stations are divided into Master, Slave, or Repeater.

The master is an access point to a backbone network, and the slave is a customer premise equipment (CPE) that has broadband access through the master.

The repeater is responsible for retransmitting incoming frames to the active device, which can be installed as needed between the master and the slave. Here, the master and repeater must always be powered on, unlike slaves, so the always-on concept applies.

1 is a diagram illustrating a tree structure of hierarchical media access control (HMAC). As shown in the figure, each station is represented by a station type and a preset station ID.

All stations coexist in a single physical network and are assumed to share the same medium. The line drawn between stations represents the communication link and the length of the line represents the channel situation rather than the physical distance between the two stations.

Here, each station is defined by the relationship with other stations and the type of station. The relationship between the stations is represented by parent / child / sibling.

For example, R1 is a parent of R3 and S19 and S20 are children of R3. Further, S15 and S16 are defined by sibling of R3. The three station types, master, slave, and repeater, are the same device that sends and receives frames by the same medium access control (MAC).

These three stations may be classified according to the presence or absence of a parent or child. The master has only children and the slave only has parents, while the repeater has both parents and children.

In hierarchical media access control (HMAC) all communication takes place only between the parent and the child. This is the most basic rule of hierarchical media access control (HMAC). Direct communication cannot occur between siblings.

Upstream communication is simply a matter of a child sending a frame to his or her parent unconditionally. The repeater retransmits the frame received from its child back to its parent.

In contrast, in downstream communication, the parent must distinguish to which child to send each frame. To this end, all parents have a routing table. The routing table is a mapping table of a source / destination address and a preset station ID included in a frame.

For example, R3 stores the real addresses (ex. MAC addresses) of S19 and S20 in the routing table, and R1 stores the addresses of S15, S16, S19, and S20 in the routing table, so that frames falling from the upper level are stored. You can send it to the appropriate child.

Hierarchical Media Access Control (HMAC) may support both broadband access and home networking at the same time using a routing table owned by the parent. Home networking is possible by intercommunication via parent.

For example, when S15 and S16 of FIG. 1 are located in the same home and communicate with each other, their parent R1 checks the destination using a routing table and transmits the received frame to the master instead of transmitting the received frame to the master. Resend.

For intercommunication through the parent, all parents can determine the destination by checking the routing table for the address of the frame received from the child. Thus, intercommunication between two slaves is equally possible if they have different parents.

2 is a diagram illustrating an example of a frame header that can be used to implement the present invention. It is assumed that the presented frame header is always included in the frame and can be decoded by all stations. The 4-byte frame header may have the following fields.

『A) FT (Frame Type) : Indicates the type of frame. This field may indicate the structure, transmission mode, broadcast frame, etc. of the corresponding frame.

b) Hierarchy Level (HL) : Hierarchy level of a transmitting source station.

c) GID (Group ID) : This field enables the multimaster function.

d) DID (Destination ID) : indicates the station ID of the destination station. The station ID is a unique ID assigned to each station. The station ID of the master is always 0, while the station ID of the repeater may be from 1 to 7. The station IDs of the slaves are from 8 to 63.

e) SID (Source ID) : indicates the station ID of the source station.

f) Frame Symbol Length (FSL) : Number of symbols in the frame.

g) CRC (Cyclic Redundancy Check) 』

3 illustrates a method in which broadcast frames are transmitted in hierarchical media access control (HMAC). A broadcast frame refers to a frame that all stations in the network should receive.

A child without a slave needs to send only its own parent when sending a broadcast frame. However, the master and repeater send broadcast frames in a transmission mode that can be decoded by all stations for both their parent or child to receive.

The most basic rule of broadcast frame transmission is to retransmit all broadcast frames received by the master and repeater. Receiving the frame transmitted by the other station by retransmission of another station can be solved by including the last broadcast transmitter station ID (Last Broadcast Transmitter ID or LBT ID) in each frame.

3 (a) shows that S13 transmits a broadcast frame. In this case, since S13 is a slave, simply transmit the corresponding broadcast frame only to R3. When R3 receives this frame, it changes its LBT ID to 13 and retransmits it to a transmission mode that all stations can decode.

This is shown in Figure 3 (b). In this case, the broadcast frame retransmitted by R3 may be received by R1, S13, and S14. S13 discards the frame received through the LBT ID because it knows that it has transmitted it. R1 changes the LBT ID of the received broadcast frame to 3 and retransmits it.

Every station has its own hierarchical level. The hierarchical level of the master is always zero, while all slaves and repeaters determine their hierarchical level in the channel scanning procedure performed after the initial power-up. The hierarchy level can then change fluidly.

Determining the hierarchy level means determining the parent. Channel scanning is the process of quickly adapting to changing channel conditions over time and finding a better parent. This means finding the most efficient route in the hierarchy of hierarchical media access control (HMAC). Channel scanning is performed by the slave and the repeater only if:

`` As soon as the power is turned on.

   경우 The error occurs continuously in the frame received from its parent.

   계층 The hierarchy level of your parent has changed.

   적 으로 periodically. 』

As described above, all stations are assigned a unique unique station ID. In the case of using the frame header shown in FIG. 2, there are a total of eight stations, which can be parents of slaves, with a master and seven repeaters.

There are a total of seven stations that can be parents of repeaters, the master and six other repeaters. The station starts a channel scanning by transmitting a short control frame called a channel scanning request frame or a CSR frame.

The CSR frame is transmitted in turn to all parent candidates. The parent candidate capable of receiving the CSR frame transmits a pseudo random training sequence in response to the request so that the station transmitting the CSR frame performs downstream channel estimation.                     

Here, the station transmitting the CSR frame determines its parent by referring to the calculated downstream channel signal-to-noise ratio (SNR) and the hierarchical level specified in the training sequence. Once a parent is determined that provides the most efficient route among the parent candidates, it is also natural to determine its Hierarchy Level.

In hierarchical media access control (HMAC), the multi-master function is provided through a unique group ID (GID) assigned to each station, such as a station ID. The stations look at the group ID specified in the frame header and decide whether or not to perform a virtual carrier sense.

Each group ID represents one logical network. When using the frame header shown in FIG. 2, the GID field is 3-bit, which means that a total of eight logical networks can coexist.

Each logical network consists of one master, up to seven repeaters, and up to 56 slaves, so the multi-master function allows up to eight masters, 56 repeaters, and 448 slaves to be a single physical network. to coexist in a network).

4 is a diagram showing the application of hierarchical media access control (HMAC) to power line communication in an apartment according to a preferred embodiment of the present invention.

As described above, the present invention is a type of medium access control (MAC) based on a carrier detection multiple access (CSMA / CA) with a collision avoidance function composed of a master and a slave. In a network constituted by a master or an access point, there are multiple slaves and the master has point-to-multipoint communication with these slaves. In other words, the master can communicate 1: 1 with all slaves, while the slave cannot communicate directly with other stations except the master. As such, a medium access control (MAC) scheme consisting of a master and a slave is useful for broadband access.

Stations using collision avoidance carrier detection multiple access (CSMA / CA) always observe the presence of frames transmitted by other stations on the channel through physical carrier sense. When transmission of a frame is detected, the collision between the frames is minimized by waiting for a period during which the frame is transmitted through a virtual carrier sense. If there is a frame to be transmitted, a backoff procedure minimizes collisions between frames and enables efficient point-to-multipoint communication.

The medium access control (MAC) method based on the existing carrier detection multiple access (CSMA / CA) with collision avoidance function is limited to distance because it assumes that the master and the slave are always visible to each other. The present invention enables communication between invisible stations through a medium access control (MAC) with the concept of hierarchy. It also allows multiple masters to coexist on a single physical network.

In the above, the present invention is illustrated by illustrating specific embodiments, but the present invention is not limited to the above embodiments. Those skilled in the art can easily make various changes and modifications to the present invention, and it should be noted that such variations or modifications are included within the scope of the present invention as long as the features of the present invention are used.

As described above, the hierarchical media access control (HMAC) proposed in the present invention has an advantage that it can be applied to any topology without limiting distance through the repeater function and the multi-master function. Channel scanning maximizes communication efficiency within the network. In addition, the repeater proposed in the present invention can be easily installed anywhere as needed.

Claims (9)

Observing whether each station has a frame transmitted by another station on a channel through a physical carrier sense; When each station detects transmission of a frame transmitted by the other station, waiting for a period during which the detected frame is transmitted through a virtual carrier sense; And Each station transmitting a frame to be transmitted through a backoff procedure when there is a frame to be transmitted; Each station is a master station that is an access point to a backbone network, a slave station that is a customer premise equipment (CPE) that performs broadband access through the master station, and the master station and the Any one of repeater stations installed between slave stations to retransmit received frames, Each station has its own Hierarchy Level, Each station is determined by parent, child, and sibling according to the relationship with other stations, The master station becomes a parent of the repeater station and the slave station, The slave station becomes a child of the master station and the repeater station, The repeater station becomes a child station of the master station and another repeater station and becomes a parent of the slave station and another repeater station, The master station has only the child, The repeater station has both the parent and the child, The slave station has only the parent, The sibling refers to two or more stations having the same parent and the hierarchical level; The transmission of frames between the stations is made only between the parent and the child, Transmitting the frame to be transmitted, The child transmitting the frame to the parent to the parent; And And the parent is one of the steps of transmitting the frame to be transmitted to the child, hierarchical media access control method for point-to-multipoint communication. The method according to claim 1, The transmission of frames between stations, which are made only between the parent and the child, An upstream transmission for transmitting the frame from the higher to the lower hierarchical level, and a downstream transmission for transmitting the frame from the lower to the higher hierarchical level; The parent has a routing table that is a mapping table of source and destination addresses and preset station IDs contained in a frame. After transmitting the frame to be transmitted, If the child receiving the frame to be transmitted is the repeater station, the repeater station further comprises transmitting a portion of the frame received through the routing table to any one of the children of the repeater station. A hierarchical media access control method for multi-point communication. The method according to claim 2, After transmitting to any one of the children of the repeater station, Confirming a destination of a frame received by the parent that has received the frame transmitted by the child using the routing table; And The parent receiving the frame transmitted by the child further comprises retransmitting a specific portion of the received frame to the other child if the destination is another child of the parent. A hierarchical media access control method. delete The method according to claim 1, The frame transmitted by the child or parent, Is a broadcast frame that contains a Last Broadcast Transmitter (LBT) ID and is decipherable by all stations, Transmitting the frame to be transmitted, A station receiving the broadcast frame; When the station is one of a master station and a repeater station, the station receiving the broadcast frame modifies the last broadcast transmission station ID to the station that sent the broadcast frame; And And retransmitting, by the station receiving the broadcast frame, the broadcast frame including the modified last broadcast transmission station ID. The method according to claim 5, The station receiving the retransmitted broadcast frame is either a master station or a repeater station, After retransmitting the broadcast frame, If the last broadcast transmitting station ID included in the retransmitted broadcast frame is the same as the ID of the station receiving the retransmitted broadcast frame, the station receiving the retransmitted broadcast frame further discards the retransmitted broadcast frame. And a hierarchical medium access control method for point-to-multipoint communication. delete delete The method according to claim 1, Each station stores a unique Group ID (GID), The frame transmitted by the other station includes a group ID of the station transmitting the frame. Wherein each station waits for a period during which the detected frame is transmitted through the virtual carrier detection when the group ID included in the detected frame is different from the group ID stored in each station. Hierarchical Media Access Control Method for Networks.

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