KR20140077640A - Protocol apparatus for guard time control - Google Patents

Abstract

The present invention relates to a protocol apparatus for a guard time control. The invention relates to a protocol for controlling guard time by earning the measurement of propagation delay between adjacent time slot nodes and time synchronization in the single hop distributed TDMA environment. Therefore a frame defined to control the guard time through earning the measurement of the propagation delay between the nodes and the time synchronization, in the network environment which does not match the time synchronization therebetween and which does not measure of the propagation delay therebetween, is configured to allocate the time slot of each node according to a network admission order and to allocate the remaining time slot after the time slot of the last allocated nodes.

Description

[0001] The present invention relates to a protocol apparatus for guard time control,

The present invention relates to a protocol apparatus for guard time control, more particularly, to a protocol for controlling a guard time by acquiring propagation delay measurement and time synchronization between neighboring time slot possessing nodes in a single hop distributed TDMA environment to be.

In order to prevent or mitigate data collision due to long propagation delay between each node in the TDMA network, the time slot necessarily includes a guard time. This guard time is only a wasteful factor to prevent data collision regardless of data packet transmission. Therefore, as the guard time of each time slot becomes longer, the throughput of the entire system can be reduced. Therefore, there is a need to reduce the guard time regardless of the data transmission.

The application number CA1975-219732 relates to an invention capable of operating a network without measuring the propagation delay by setting the guard time at least twice the propagation delay.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a method and apparatus for acquiring propagation delay measurement and time synchronization between neighboring time slot possessing nodes in a single- The purpose of this protocol is to provide a controllable protocol.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

It is an object of the present invention to provide a method and apparatus for controlling a guard time through measurement of a propagation delay between each node and a guard time through acquisition of time synchronization in a network environment in which time synchronization between the nodes is not matched, Time slot is allocated to each node according to a network joining order and an extra time slot is allocated after a time slot of the last allocated node.

In addition, the transmission order of each node is determined according to the network joining order.

In addition, each node updates the time synchronization between each node by transmitting the packet reception time of the previous time slot own node, its own transmission time, and the propagation delay value with the next time slot own node in a packet, The guard time interval corresponding to the propagation delay between the time slot possessing nodes can be updated.

In addition, the propagation delay measurement between each node measures the propagation delay between the node having the previous time slot and the node having the next time slot.

Also, the guard time of the time slot of each node excluding the guard time of the time slot of the last allocated node is the guard time corresponding to the propagation delay measurement value, and the guard time of the time slot of the last allocated node is the maximum propagation delay value It is the corresponding guard time.

Also, the extra time slot is a period for joining a new node, and its length is larger than the sum of the packet length and the maximum propagation delay. The new node records the reception time after receiving the packet of the last allocated node using this interval, and transmits a request for network joining in a network joining request packet.

In addition, the last allocated node measures the propagation delay with the new node after receiving the network join request packet of the new node, and approves the network join approval of the new node in its own time slot (time slot of the last allocated node) And the propagation delay value of the new node.

As described above, according to the present invention, time synchronization between time slots of each node can be obtained and guard time can be minimized.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a view showing a frame structure according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a packet format of a frame structure and an i-th time slot according to a second embodiment of the present invention,
FIG. 3 is a diagram comparing a frame structure (k + 1) -th frame according to the joining of a new node and a frame structure (k-th frame) before joining a new node according to the second embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. In addition, the embodiment described below does not unduly limit the content of the present invention described in the claims, and the entire structure described in this embodiment is not necessarily essential as the solution means of the present invention.

<First Example >

The first embodiment of the present invention relates to an invention for acquiring time synchronization and controlling a guard time by measuring a propagation delay between nodes having adjacent time slots based on sequential transmission orders. Hereinafter, the first embodiment will be described.

( Guard time control method through propagation delay measurement and time synchronization acquisition)

The guard time control method using the propagation delay measurement and the time synchronization acquisition according to the present invention comprises an initialization mode step and a normal mode step. In the initialization mode, the propagation delay value between neighboring time slot possessing nodes is measured using the fixed time slot length. In the normal mode step, the guard time value is determined according to the propagation delay value measured in the initialization mode, The length is set adaptively. Hereinafter, a method of controlling a guard time by measuring propagation delay and acquiring time synchronization according to the present invention will be described in detail with reference to the accompanying drawings.

First, in the present invention, it is assumed that the transmission order of each node is predetermined in a single hop distributed TDMA network environment with a long propagation delay, and a network composed of a plurality of nodes is not synchronized.

In FIG. 1, it is assumed that the transmission order is in the order of node 1 -> node 3 -> node 2 -> node 4. As shown in FIG. 1, in the initial mode step (1st frame in FIG. 1), the time slots between the nodes are not synchronized with each other, and the time slot lengths are the same. In an environment where synchronization is not performed, The length of the guard time is set to the maximum round trip time.

According to the transmission order, the node 1 transmits a packet including its transmission time information (t _{s , 1} ) to each node through broadcasting in the first time slot. At this time, the transmission time information of the node 1 means the time when the node 1 transmits the packet. The packet in the initialization mode step includes its own transmission time information and reception time information of the packet received from the previous time slot possessing node, and the length of the packet is regarded as the same. In accordance with the packet transmission of the node 1, the node 2 to the node 4 receive the packet from the node 1 and at the same time, regard it as the start of the frame and adjust their own local clock. Therefore, as shown in FIG. 1, the node 2 to the node 4 are set to the local clock at the packet reception time from the node 1. In addition, the nodes 2 to 4 record the time at which the packet is received from the node 1. That is, node 2 records t _{r , 1,3} , node 3 records t _{r , 1, 2} , and node 4 records t _{r , 1,4} . Where the first subscript is the time slot that transmitted the packet and the second subscript is the time slot that received the packet.

The second transmission order, node 3, transmits packets in the second time slot. In this case, the transmitted packet is different from the contents of the packet sent by node 1, which is the first transmission order. That is, node 1 is transmitted in the first time slot, and therefore, since there is no time for transmitting the packet from the previous time slot possessing node, only the transmission time information of its own is transmitted in the packet. However, the packet transmitted in the time slot other than the first time slot is included in the packet in transmission because the time information of the packet received from the previous time slot own node is recorded. Therefore, the packet transmitted by the node 3 includes its own transmission time information (t _{s , 2} ) and the time information (t _{r , 1,2} ) of the packet received by the previous time slot proprietary node 1.

The packet transmitted from node 3 is transmitted to node 1 through broadcasting. Node 1 records reception time information (t _{r , 2,1} ) of the packet transmitted from node 3. Therefore, the propagation delay value between node 1 and node 3 is

. &Lt; / RTI &gt;

Next, according to the transmission order, node 2 transmits a packet to each node in the third time slot. Since the node 2 records the reception time information (t _{r , 2, 3} ) of the packet transmitted from the node 3, the transmitted packet is transmitted from the node 2's transmission time information (t _{s , 3} ) (T _{r , 2, 3} ) of the received packet, and node 2 contains the received time information Transmits via broadcasting. At this time, the node 3 receiving the packet from the node 2 records the reception time information (t _{r , 3, 2} ) received from the node 2. Therefore, the propagation delay value between node 3 and node 2 is represented by node 3

. &Lt; / RTI &gt;

The node 4 transmits the packet in the next transmission sequence, and the propagation delay value between the node 2 and the node 4 by the concept as described above is transmitted to the node 2

. &Lt; / RTI &gt;

The propagation delay value between the nodes having the adjacent time slots described above can be generalized by the following equation (1).

In this case, p _{i , i + 1} is the propagation delay from the i th time slot owning node to the i + 1 th time slot owning node, and t _{r , i, i + 1} is the propagation delay from the i th time slot owning node i is the time at which the i + 1th time slot owning node starts receiving, t _{s , i} is the time at which the ith time slot owning node starts transmitting packets, t _{s , i + 1} is the i + 1 th time slot owning node The time when the packet began to be transmitted

According to Equation (1), propagation delay values between nodes having adjacent time slots are calculated in the initialization mode. However, in the initialization mode, only the node 1 can know the propagation delay value between the node 1 and the node 3. In the normal mode step, which will be described later, the propagation delay value calculated in the initialization mode is included in the packet, 3, the guard time can be substantially reduced compared to the initial mode step. Hereinafter, the normal mode step will be described.

In the normal mode step (2nd frame in FIG. 1), node 1 transmits a packet first according to the transmission order. As shown in FIG. 1, the packet transmitted by the node 1 includes its own transmission time information (t _{s , 1} ), the propagation delay value (p _{1 , 2} ) calculated at the initialization mode step, (t _{r , 4,1} ). The packet reception time information of the node 4 is transmitted to the node 4 so that the propagation delay value between the node 4 and the node 1 is calculated by the node 4 according to Equation (1).

On the other hand, it can be seen that the node 3 that has transmitted the propagation delay value (p _{1 , 2} ) can calculate its own transmission time by the following Equation ( ₂ ) and the guard time is reduced compared to the time slot in the initial mode step . This is because the guard time corresponding to the propagation delay between the node 1 and the node 3 is considered according to Equation 2 although the maximum round trip time is set as the guard time in the initialization mode. In addition, the node 3 records the reception time information of the packet from the node 1. The recording of the reception time information in the normal mode step is the same as in the initialization mode step described above. Therefore, even in the normal mode stage, it is possible to continuously update the propagation delay value between neighboring time slot possessing nodes (node 1).

Here, i is an i-th time slot, and T _{s , i} is expressed by the following equation (3).

The clock is synchronized only by the node 3 and the node 1 due to the transmission time of the node 3, which is the second time slot possessing node calculated by Equation (2).

Here, T _{s, i} is the length of the i-th time slot, T _P is the packet length, T _{G, i} is the guard time length of the i-th time slot, T _MS is the length of the mini slot. There are a plurality of minislots in a time slot.

At this time, T _{G , i} is defined by the following Equation 4, and assuming that e _max = 0 in FIG. 1, the propagation delay value is equal to the guard time value.

Here, e _max is an additional time for correcting the maximum error that may occur from time synchronization and propagation delay measurement. In general, e _max can be measured by an experiment when developing a communication terminal.

Next, the node 3, which is the transmission order, transmits its own transmission time information (t _{s , 2} ) to the packet, the propagation delay value (p _{2 , 3} ) between the node 3 and the node 2 calculated at the initialization mode _, And transmits one reception time information (t _{r , 2,1} ).

If the transmission time information of the packet transmitted in the normal mode and the packet reception time information of the previous time slot own node are used, the propagation delay value can be continuously updated even in the normal mode, do. In addition, the propagation delay value between neighboring time slot possessing nodes is transmitted, so that its own transmission time is calculated and clock synchronization is established with the neighboring time slot owned node.

1, node 3 is synchronized with node 1 at t _{s , 2} , node 3 and node 2 are synchronized at t _{s , 3} , and node 2 and node 4 are synchronized at t _{s , &lt; / RTI & gt ; 4} .

The node 2 and the node 4, which are the next transmission order, sequentially transmit the packet with the same concept as the node 3 described above, and a description thereof will be omitted.

In the normal mode step, the propagation delay time calculated in the initialization mode step can be used to calculate its transmission time according to Equation (2), so that the synchronization between the time slots of each node can be performed and the guard time can be reduced. In addition, it is possible to continuously update the propagation delay value between adjacent nodes by recording and transmitting its own transmission time information and reception time information.

The above-mentioned equation or formula can be implemented by the calculation means of each node, and the calculation means can be embodied by a digital logic circuit and an analog logic circuit which are a microprocessor and peripheral circuits thereof.

Also, the above-described transmission order can be calculated by a coordinator located on the ground controlling each node, and can be transmitted to each node through broadcasting. If necessary, any one of a plurality of nodes connected to the network can be a coordinator It can also play a role. Each of the nodes described above may be an aircraft such as a moving object, such as a fighter aircraft, which is moving in the air where a long propagation delay should be considered.

<2nd Example >

In the second embodiment of the present invention, a network join procedure is added based on the contents of the first embodiment described above, and a frame structure and a MAC protocol for supporting the network join procedure are proposed. The difference from the first embodiment is that in the second embodiment, since each node performs propagation delay measurement and time synchronization acquisition at network joining, it operates in the normal mode without distinguishing between the initial mode and the normal mode described in the first embodiment .

Therefore, the first embodiment proposes a scheduling method for guard time control, and the second embodiment proposes a frame structure and a MAC protocol. Hereinafter, a MAC protocol description and a procedure for joining a new node according to a second embodiment of the present invention will be described with reference to FIG. 2 and FIG.

( MAC  protocol)

As shown in FIG. 2, the length of one frame is expressed by Equation (5) below. At this time, it is assumed that each frame owns one or more time slots, and each time slot possesses one or more minislots. It is also assumed that each time slot is made up of a packet (data area, T _{P , i} ) and a guard time (T _{G , i} ).

Where, T _f is the frame length, M is the number of mini-slots, _MS T is the length of the mini slot.

On the other hand, the length (T _f ) of each frame is a fixed length in which a certain length is determined on the environment in which it is used, for example, in the case of military communication, a military tactical network.

As shown in FIG. 2, one frame is allocated m time slots for each node, and an extra time slot (Remain) is assigned to the last time slot. In this case, the order of the time slots for each node is determined in advance according to the order of transmission (for example, according to the network join order) of each node, so that the time slot of each node can be sequentially determined according to the transmission order. For example, assume that the transmission order is node 1 -> node 2 -> node 3 -> node 4 (assuming that a total of four nodes are connected to the network in this case, and are sequentially subscribed to the network) The time slot is occupied by node 1, the second time slot by node 2, the third time slot by node 3, and the fourth time slot by node 4. The lengths of the respective time slots may differ from each other depending on the propagation delay value between adjacent nodes calculated in the above-described first embodiment.

On the other hand, the extra time slot occupying the last time slot of the frame has a length of (Remain) T _R. That is, the length of the surplus excluding the time slot occupied by the node joining the current network in a fixed-length frame is T _R. This extra timeslot is a redundant timeslot for joining a new network in the network as described below. Assuming that there are four nodes joined in the initial network, the length of T _R will gradually decrease as new nodes join the network. In addition, the number of nodes newly joined by a frame having a fixed length will be limited.

As shown in FIG. 2, the i-th time slot includes a packet T _{P , i,} which is a data area, and a guard time T _{G, i} . In this case, the length of the i-th time slot is expressed by Equation (6).

Here, _{S T, i} is the length of the i-th time slots, S _i is the number of mini-slots, _MS T is the length of the mini slot.

On the other hand, in the packet, the Src_ID field, which is the MAC address value of each node, is located in the first slot. Next, m (the number of nodes joined to the current network), i (i th time slot), S _i (the number of minislots of the i th time slot), T _R (the length of the Remain section) Field is located. Next, t _{s , i} (transmission time of the ith time slot own node), t _{r , i-1, i} (i-th time slot owning node to calculate the propagation delay value between neighboring _{i- I,} and _{i , i + 1} calculated by t _{s , i} and t _{r , i-1, i} . Finally, REQ_ID and RES for joining the new node are located. The REQ_ID is a MAC address value of a new node that is not subscribed to the current network when it wants to join the network. RES indicates whether or not the node owning the mth time slot accepts the network join when there is a network join request of the new node. For example, if the subscription request of a new node is allowed, the MAC address value of the new node may be written to the RES, and may be set to "0x00 " As an example of the case in which the network is not allowed to join, all the nodes that are already accepted in the frame having the fixed length are subscribed.

On the other hand, a new node not joining the network requests a join using the Remain interval and the REQ_ID field upon receiving the packet of the node having the mth time slot.

The time slots allocated to each node may have different time slot lengths by the above described p _{i , i + 1} . However, the time slot length of the node having the last time slot (m in FIG. 2) here has a length corresponding to the maximum propagation delay value of the network. Because there is a Remain interval after the m-th time slot, if the m-th time slot does not have a length corresponding to the maximum propagation delay value, when a new node that wishes to join the network utilizes the Remain interval, Data collision may occur.

As shown in FIG. 3, when a new node that wishes to join the network requests a request (REQ) in the k-th frame and the node having the m-th time slot approves it, It can be seen that the Remain interval of the frame can be reduced by the slot length. Also, the guard time of the new node has a length corresponding to the maximum propagation delay value. And owned by k m-th time slot is the m-th time slots by the _{t s, i, t r,} i-1, i, p i, i + 1 in the second frame has a length of a guard time corresponding to the maximum propagation delay value And a guard time length corresponding to the propagation delay value of the node and the newly joined node.

In the above example, the Remain interval is fixed to the interval except for the time slot length of each node (in this case, the fixed length refers to the first fixed length and it is natural that the Remain interval decreases with the addition of the new node). However, the Remain interval can be used more efficiently by allocating the length for the join request of the new node and the approval of the last node.

(New node join procedure)

As shown in FIG. 2 and FIG. 3, a new node that is not currently subscribed to the network requests a network join request (REQ) as soon as the packet of the mth time slot possessing node is received using the Remain interval in the kth frame. At this time, the join request uses the REQ_ID (its own MAC address value) field as shown in FIG.

The mth time slot owning node that received the network join request transmits the approval or disapproval of the joining of the new node using the Remain interval. At this time, the grant and denial of the new node use the RES field shown in FIG.

If acknowledgment is made, a new node in the (k + 1) th frame is allocated after the m th time slot.

In the above-described second embodiment, it is assumed that the transmission order of each node is determined according to the network joining order. However, if there is a joining of a new node, the transmission order may be newly changed for efficient use of the time slot. Also, the number of nodes joined to the current network can be known by joining a new node, and each node can sufficiently calculate the remain interval.

Although the present invention has been described with reference to the embodiment thereof, the present invention is not limited thereto, and various modifications and applications are possible. In other words, those skilled in the art can easily understand that many variations are possible without departing from the gist of the present invention.

Claims (5)

In the network environment where the time synchronization between the nodes is not matched and the propagation delay between each node is not measured, the frame defined to control the guard time through measurement of propagation delay between each node and acquisition of time synchronization, And allocates an extra time slot after the time slot of the last allocated node.
The method according to claim 1,
The propagation delay measurement value between each node,
Wherein the propagation delay between the node having the previous time slot and the node having the next time slot is measured.
3. The method of claim 2,
Wherein a guard time of a time slot of each node except a guard time of a time slot of the last allocated node is a guard time corresponding to the propagation delay measurement value,
The guard time of the time slot of the last allocated node,
And a guard time corresponding to a maximum propagation delay value.
The method according to claim 1,
The extra timeslot is a period for joining a new node,
Wherein the new node sends a request for network join to the extra time slot after receiving the packet of the last assigned node.
5. The method of claim 4,
After the last assigned node receives the network join request,
And transmits the approval of network join approval of the new node using the extra timeslot.

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