KR20220018674A - Apparatus and method for scheduling task in lora network - Google Patents

Abstract

An apparatus and method for scheduling a task in a LoRa network are disclosed. A method for scheduling a task by a node device of a LoRa network according to an embodiment of the present invention includes the steps of classifying at least one node into one of a plurality of groups, generating a frame for each group for each group, , dividing each of the frames for each group into a plurality of slots, allocating a logical slot index to each slot, and generating a task schedule based on the logical slot index.

Description

Apparatus and method for scheduling tasks in LORA network

The present invention relates to a data transmission scheduling technique in a LoRa network.

In order to use multiple wireless sensor networks in the field of industrial monitoring and control systems, it is necessary to transmit data stably in real time. Accordingly, it is necessary to connect through a stable, low-latency, low-power, low-cost network.

Recently, LoRa (Long Range; LoRa) networks have attracted attention in the field of industrial monitoring and control systems due to their reliable wireless link provision. LoRa technology has the advantage of being able to communicate over a long distance of 10 km or more with minimal power consumption, and is attracting more attention as an infrastructure technology to support the long-distance Internet of Things.

In particular, LoRaWAN (LaRa Wide Area Network), an open network standard above the LoRa physical layer, is being used in various applications such as smart cities, smart farms, and environmental monitoring. LoRaWAN uses a star network topology consisting of one or more gateways that relay data between end devices and servers. However, due to the long transmission time due to the low speed and the random nature of data transmission, the LoRaWAN node has a high probability of data collision as the traffic increases.

Many studies are being conducted to solve this collision problem, and slot scheduling is typically used to completely eliminate data collisions. However, various methods using conventional slot scheduling are not free from various problems such as a signal suppression effect that makes data transmission inefficient, scheduling overhead, unnecessary slot waste, and bandwidth efficiency degradation.

Republic of Korea Patent Publication No. 2019-0114404 (published on October 10, 2019) International Patent Publication No. WO 2016/163623 (published on October 13, 2016) International Patent Publication No. WO 2018/158242 (published on September 7, 2018) Republic of Korea Patent No. 1913607 (Registered on October 25, 2018)

The described embodiment sets task scheduling to efficiently transmit data in real time in a high-density environment where high traffic occurs to secure stability against signal attenuation, handle suppression effect, reduce scheduling overhead, and internal and external signals The purpose is to transmit stable and reliable data through the exclusion of interference and the like.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A method for scheduling a task by a node device of a LoRa network according to an embodiment comprises the steps of classifying at least one node into one of a plurality of groups, generating a frame for each group for each group, and each group It may include dividing each of the frames into a plurality of slots, allocating a logical slot index to each slot, and generating a task schedule based on the logical slot index.

In this case, the classifying may include classifying the group by each node based on the degree of signal attenuation of the message received from the gateway.

In this case, the step of generating the frame may include providing a unique spreading factor (SF) and a separate frequency channel corresponding to each group to each group.

In this case, the step of assigning a unique spreading factor may include assigning a natural number between 7 and 12 in which the difference in the diffusivity factor between adjacent groups is 1 and the spreading factor is between 7 and 12.

In this case, the step of dividing into slots may include dividing into slots such that a ratio between the number of slots between frames of adjacent groups becomes two.

In this case, the step of allocating the logical slot index may include equally dividing the plurality of slots included in the frame into two or more sections, and sequentially allocating the logical slot index to the first slot of each of the two or more sections.

In this case, in the step of allocating the logical slot index, the equally divided two or more sections may be equally divided into two or more sections again, and the logical slot index may be allocated only to the sections in which the first slot is empty among the sections.

In this case, the generating the task schedule includes comparing the number of slots in at least one of the frames of each of the groups with the number of slots required for the task to reserve the task in at least one connected frame among the frames of each of the groups. may include

In this case, the task scheduling method by the node device of the LoRa network according to the embodiment may further include repeating the channel detection by the node when the node starts data transmission in the slot to which the logical slot index is assigned. .

A task scheduling apparatus in a LoRa network according to an embodiment includes a memory in which at least one program is recorded and a processor executing the program, the program comprising the steps of: classifying at least one node into one of a plurality of groups; Creating a frame for each group for each group, dividing each of the frames for each group into a plurality of slots, allocating a logical slot index to each slot, and performing a task schedule based on the logical slot index You can follow the steps to create it.

In this case, the classifying may include classifying the group by each node based on the degree of signal attenuation of the message received from the gateway.

In this case, the generating of the frame may include assigning a unique spreading factor and a separate frequency channel corresponding to each group to each group.

In this case, the step of assigning a unique spreading factor may include assigning a natural number between 7 and 12 in which the difference in the diffusivity factor between adjacent groups is 1 and the spreading factor is between 7 and 12.

In this case, the step of dividing into slots may include dividing into slots such that a ratio between the number of slots between frames of adjacent groups becomes two.

In this case, the step of allocating the logical slot index may include equally dividing the plurality of slots included in the frame into two or more sections, and sequentially allocating the logical slot index to the first slot of each of the two or more sections.

In this case, in the step of allocating the logical slot index, the equally divided two or more sections may be equally divided into two or more sections again, and the logical slot index may be allocated only to the sections in which the first slot is empty among the sections.

In this case, the generating the task schedule includes comparing the number of slots in at least one of the frames of each of the groups with the number of slots required for the task to reserve the task in at least one connected frame among the frames of each of the groups. may include

In the LoRa network according to the embodiment, the task scheduling apparatus may further perform the step of repeating the channel detection by the node when data transmission of the node starts in the slot to which the logical slot index is allocated.

A method for scheduling a task by a node device of a LoRa network according to an embodiment includes: classifying at least one node into one of a plurality of groups based on a signal attenuation degree of a message received by each node from a gateway; Generating a frame for each group for each group, dividing each of the frames for each group into a plurality of slots so that a ratio between the number of slots between frames of adjacent groups becomes 2, and allocating a logical slot index to each slot and generating a task schedule based on the logical slot index, wherein the generating of the task schedule comprises comparing the number of slots in at least one of the frames of each of the groups with the number of slots required for the task. The method may include reserving a task in at least one connected frame among each of the frames.

In this case, the step of allocating the logical slot index includes equally dividing the plurality of slots included in the frame into two or more sections, sequentially allocating the logical slot index to the first slot of each of the two or more sections, and equal division The method may include equally dividing each of the two or more sections into two or more sections, and allocating the logical slot index to only the sections in which the first slot is empty among the sections.

According to an embodiment, task scheduling is set to efficiently transmit data in real time in a high-density environment where high traffic occurs to secure stability for signal attenuation, handle suppression effect, reduce scheduling overhead, and It excludes external signal interference, which enables stable and reliable data transmission in LoRa networks.

1 is a schematic configuration diagram of a LoRa network according to an embodiment.
2 is a flowchart illustrating a task scheduling method for data transmission in a LoRa network according to an embodiment.
3 is a diagram illustrating a frame structure using a diffusion factor (SF) according to an embodiment.
4 is a diagram illustrating a frame slot structure for each group according to an embodiment.
5 is a diagram illustrating a review of validity according to the allocation of logical slot indexes according to an embodiment.
6 is a flowchart for describing in detail a step of allocating a logical slot index according to an embodiment.
7 is an exemplary diagram of allocating a logical slot index according to an embodiment.
8 is a diagram illustrating a task scheduling step according to a logical slot index according to an embodiment.
9 is a diagram for explaining a Multiple Listen-Before-Talk (MLBT) mechanism for detecting channel activity according to an embodiment.
10 is a diagram illustrating a configuration of a computer system according to an embodiment.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and those of ordinary skill in the art to which the present invention pertains. It is provided to fully inform the person of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Although "first" or "second" is used to describe various elements, these elements are not limited by the above terms. Such terms may only be used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

The terminology used herein is for the purpose of describing the embodiment and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” or “comprising” implies that the stated component or step does not exclude the presence or addition of one or more other components or steps.

Unless otherwise defined, all terms used herein may be interpreted with meanings commonly understood by those of ordinary skill in the art to which the present invention pertains. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless specifically defined explicitly.

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

1 is a schematic configuration diagram of a LoRa network according to an embodiment.

Referring to FIG. 1, a LoRa network is a star topology 10-1 directly connected between one gateway 12 and each end device 14, hereinafter referred to as a 'node'). 10-2, 10-3).

These LoRa networks can demodulate very low-strength signals using CSS (Chirp Spread Spectrum) technology, which enables long-distance communication. In addition, long-distance communication is possible even with low power.

Here, the network server (Network Server, 20, referred to as 'server') is connected to the gateway 12 through the backbone network 5 and manages the connected nodes 14 . The gateway 12 may receive multiple packets simultaneously on different channels. At this time, the server 20 performs protocol security and management functions with the node 14 .

In addition, the nodes 14 receive available resource information and scheduling rules from the server 20 .

That is, according to the present invention, the nodes 14 do not perform scheduling by receiving scheduling information (eg, scheduling MAP) predetermined from the Gateway (GW) as in the conventional slot scheduling scheme, but in FIGS. 2 to 9 . Task scheduling is performed in the LoRa network according to a scheduling rule defined according to an embodiment to be described later with reference to . Accordingly, each node can know its own scheduled slot with minimal information transfer, thereby reducing scheduling overhead. Also, the nodes 14 have one task as an active entity for communication with the gateway 12 . In this case, the task periodically transmits at least one packet to the server 20 through the gateway 12 . Then, the server 20 may send a control message to the nodes 14 through the gateway 12 .

2 is a flowchart illustrating a task scheduling method for data transmission in a LoRa network according to an embodiment.

Referring to FIG. 2 , in the method for scheduling a task for data transmission in a LoRa network according to an embodiment of the present invention, classifying each node into one of two or more groups ( S110 ), generating a frame for each group (S120), dividing each group frame into a plurality of slots (S130), allocating a logical slot index to each slot (S140), and generating a task schedule based on the logical slot index (S150) ) may be included.

At this time, in the step of classifying each node into one of two or more groups (S110), each of the nodes 14 is based on the received signal strength information between the gateway 12 and the node 14, two or more groups can be classified into one of these groups.

For example, when classified into two groups, it may be classified into a group of nodes having a low attenuation signal and a group of nodes having a high signal attenuation.

As such, as the nodes 14 are classified into different groups according to the degree of signal attenuation, the problem of data loss can be solved. That is, if each of the nodes 14 determines a group based on the signal attenuation of the message received from the gateway 12, the problem of data loss due to signal attenuation can be significantly alleviated. In particular, setting different channels to different groups completely avoids the data loss problem.

Meanwhile, in the step of generating the frame for each group ( S120 ), the frame may be generated based on the degree of signal attenuation that is a criterion for group classification.

For example, when classified into two groups, by classifying into a group of nodes having a low attenuation signal and a group of nodes having a high attenuation signal, a frame consisting of a group of nodes having a low attenuation signal and a high attenuation signal A branch can create a frame consisting of a group of nodes.

On the other hand, the LoRa network may allow different Spreading Factors (SF) between 7 and 12 in order to control the trade-off between the data rate and the transmission range. The higher the spreading factor, the lower the data rate, but the longer the transmission range. The use of different spreading factors makes it possible to overcome the signal attenuation of nodes due to distance and obstacles in LoRa networks. Star topology is possible, and time synchronization of LoRa networks is very easy by using different spreading factors.

Therefore, it is possible to give each group a different unique diffusion factor.

Specifically, a low spreading factor may be given to a group of nodes having a low attenuation signal, and a high spreading factor may be given to a group of nodes having a high attenuation signal. That is, to better overcome the high signal attenuation, a higher spreading factor is used.

Here, the intrinsic diffusion factor has a difference of 1 between the groups, and as described above, the diffusion factor can be assigned as a natural number between 7 and 12. That is, an adjacent diffusion factor between 7 and 12 may be used.

For example, if the groups are classified into three groups based on the attenuation signal, if the spreading factor used for the group of nodes with the highest attenuation signal is 9, it is used for the group of nodes with the attenuation signal of the next magnitude. The spreading factor used is 8, and the spreading factor used for the group of nodes with the next lowest attenuation signal may be 7.

Also, according to an embodiment, the channels provided to each group may be the same. That is, since the present invention can use orthogonality between time, frequency, and spreading factor (SF), simultaneous transmission and reception are possible because different unique spreading factors are assigned to each group even at the same time (slot) and frequency.

This is different from having to set both time and frequency differently in a conventional cellular system.

However, in this case, in the case of the same time, the same frequency, and different SFs, if they are received with similar signal strengths, simultaneous reception is possible.

However, in the case of the same time, the same frequency, and different SFs, only a large signal can be received if the strength of one signal is greater than the other signal by a certain size or more. This is called the suppression effect.

Accordingly, according to another embodiment, the channels provided to each group may be different. In this way, different channels may be assigned to each group to avoid a signal suppression effect.

For example, if the channels used for the group of nodes having the low attenuation signal are ch1 to 3, the channels used for the group of nodes having the high attenuation signal may be ch4 to 7.

3 is a diagram illustrating a frame structure using a diffusion factor (SF) according to an embodiment.

은 확산인자

가 사용되며, 낮은 신호 감쇠를 갖는 노드를 포함하는

로 이루어진다. 또한, 다른 하나의 프레임

은 확산인자

가 사용되며, 높은 신호 감쇠를 갖는 노드로 이루어지는

로 이루어진다. 3, any one frame

is a diffusion factor

is used, including nodes with low signal attenuation

is made of Also, one frame

is a diffusion factor

is used and consists of nodes with high signal attenuation

is made of

Here, each frame has a frame period, and each frame period may be composed of a downlink period (DL period) and an uplink period (UL period).

At this time, in the downlink period (DL period), the DL message is transmitted by the server 20, and in the uplink period (UL period), data transmission is performed by the node (14).

Referring back to FIG. 2 , in the step of dividing each group frame into a plurality of slots ( S130 ), data may be transmitted several times within one frame period.

In this case, the slot is a scheduling unit having a size large enough to transmit one data packet. Further, a group of one or more adjacent slots is called a section, and when a section is divided into two smaller parts of the same size, each divided part is also called a section.

In this case, the number of slots in the frame may have a predetermined ratio between groups of nodes. For example, when there are two node groups, the number of slots may be divided into slots such that a ratio between the number of slots in the first frame and the number of slots in the second frame becomes 2. For example, when a frame including a group consisting of nodes having high signal attenuation is divided into 8 slots, a frame including a group consisting of nodes having low signal attenuation may be divided into 16 slots.

4 is a diagram illustrating a frame slot structure for each group according to an embodiment.

프레임에 사용되고 있으며, m-k 개의 채널들은

프레임에 사용되고 있다. 여기에서,

을 사용하는 패킷 ToA(Time on Air)는

를 사용하는 패킷 ToA의 2 배인 경우,

이

개의 슬롯으로 분할되면,

은

개의 슬롯으로 분할될 수 있다. 4, k channels are

used for the frame, mk channels are

used in the frame. From here,

Packet Time on Air (ToA) using

For twice the packet ToA using

this

When divided into slots,

silver

It can be divided into slots.

는 다음의 <수학식 1>과 같이 산출될 수 있다. The total number of slots shown in FIG. 4

can be calculated as in the following <Equation 1>.

는 288일 수 있다.In <Equation 1>, for example, if m is 6, k is 3, and N is 6, the total number of slots

may be 288.

In this case, it is assumed that q is 7, the length of one UL slot is 100 ms, the length of one DL slot is 200 ms, and all nodes 14 transmit one packet every 6.6 s frame period. , 288 nodes 14 may transmit a packet to gateway 12 during the frame period.

Referring back to FIG. 2 , in the step of allocating a logical slot index to each slot ( S140 ), n logical slot indexes are sequentially assigned to the n slots. At this time, the reason for allocating the logical slot index is to prevent a case in which the deadline is not met when the slots are sequentially filled from the beginning, and according to the embodiment, the slots are filled in by mixing them in a logical order. .

인 태스크가

슬롯을 순차적으로 선택하는 경우, 프레임 내 각 슬롯에 논리 슬롯 인덱스를 할당하여

슬롯의 프레임이 주어진다. 이에, 주기 P 마다 서버에 하나의 데이터 패킷을 전송할 수 있다.Specifically, the period P is

in task

When slots are selected sequentially, a logical slot index is assigned to each slot in the frame.

The frame of the slot is given. Accordingly, one data packet may be transmitted to the server every period P.

인 태스크가 두 슬롯을 선택할 경우에 주기 P마다 적어도 하나의 데이터 패킷을 전송할 수 있게 된다.For example, two sequential logical slot indices are assigned to two slots so that they do not belong to the same part of the two parts of an equally divided frame, and the period P

When the in-task selects two slots, at least one data packet can be transmitted every period P.

This can be defined as follows.

<Definition 1>

이며,

프레임의 균등 분할 섹션의 하나에 속하는 슬롯에 인덱스가 할당되면, i에서 i+j-1까지의 순차적인 인덱스 j는 정상적(sound)이다.Given an index i,

is,

If an index is assigned to a slot belonging to one of the equally divided sections of the frame, the sequential index j from i to i+j-1 is sound.

<Definition 2>

에서

,

에서 j까지 인덱스가 정상적이면, i에서 j까지의 순차적인 인덱스 j는 실현가능(feasible)이다.Condition (1) a sequential index j-1 from 1 to j-1 is feasible, condition (2)

at

,

If the index from to j is normal, then the sequential index j from i to j is feasible.

논리 슬롯 인덱스의 정상성을 보장하여 회귀 형식에서 순차적인 논리 슬롯 인덱스의 실현가능성을 정의하며, 회귀적으로

이 정상적이다. 그러나, 이것이

이 정상적임을 보장하지 않으므로, 조건 (1)이 요구된다.Definition 2 states that condition (2) is reversed from j

We define the feasibility of sequential logical slot indexes in the regression form by ensuring the stationaryness of the logical slot indexes, and regressively

This is normal. However, this

Since this is not guaranteed to be normal, condition (1) is required.

5 is a diagram illustrating a review of validity according to the allocation of logical slot indexes according to an embodiment of the present invention.

에 속하고, 각 논리 슬롯 인덱스가

균등 분할 섹션의 하나에 속하기 때문에, 세 개의 논리 슬롯 인덱스 (1, 2, 3)이 정상적(sound)이다.5, according to definition 1, j (=3) is

belongs to, and each logical slot index is

Since it belongs to one of the equally divided sections, three logical slot indexes (1, 2, 3) are sound.

Also, according to definition 2, (1, 2) is feasible when j=2, and (2, 3) is regressively normal when j=3 so that (3) and (2, 3) are normal . However, in the case of the logical slot index (1, 2, 3, 4), (1, 2, 3) is not feasible, and (2, 3) is not feasible because (2, 3) is not normal.

The order of allocation of logical slot indexes follows Definition 2. Specifically, the condition (1) can be guaranteed by repeating the “regressive steadiness satisfaction” given in condition (2) with the entire frame whenever a new logical slot index is allocated.

In order to realize condition (2) when allocating a new index j, the whole section is divided into two small sections, and then the section with the smaller maximum index is selected after generating the (j-1, j) normal. If you do this process one more time with the selected section, (j-3, j-2, j-1, j) is normal. We can ensure regression steadiness by continuing this process until we find an unindexed section or the entire frame is fully indexed.

개의 슬롯들로 분할된 경우에 적용되고, 도 7은 하나의 프레임이

의 슬롯들로 분할된 경우의 슬롯 인덱스 할당을 예시한 도면이다. 6 is a flowchart for explaining in detail a step of allocating a logical slot index according to an embodiment, and FIG. 7 is an exemplary diagram of a step of allocating a logical slot index according to the embodiment. At this time, FIG. 6 shows that one frame is

It is applied to the case where it is divided into slots, and FIG. 7 shows that one frame is

A diagram exemplifying slot index allocation in the case of partitioning into slots of .

를 '1'로, 분할 횟수

를 '0'으로 초기화한다(S210). 6, the node 14 is a logical slot index (Logical Slot Index)

is '1', the number of divisions

is initialized to '0' (S210).

개의 섹션들이 되도록 균등 분할한다(S220). 이때, 분할된

개의 섹션들의 순번인

을 '1'로 초기화한다. Then, node 14 sends the frame

The sections are equally divided into n sections (S220). At this time, divided

the sequence number of the sections

is initialized to '1'.

이 '0'이므로,

이 되어 프레임이 1개의 섹션으로 균등 분할하는 것으로, 실질적으로 분할하지 않는다. At this time, at first

Since this is '0',

This means that the frame is equally divided into one section, and is not substantially divided.

번째 분할된 섹션들 중에서

번째 섹션에 해당하는

을 선택 섹션(

)으로 한다(S230). Then, node 14

Among the second divided sections

corresponding to the second section

Select the section (

) to (S230).

은

이 된다. At this time, initially, as shown in FIG.

silver

becomes this

의 논리 슬롯 인덱스 할당 여부를 판단한다(S240). Node 14 is

It is determined whether to allocate a logical slot index of (S240).

가 논리 슬롯 인덱스가 할당되지 않았을 경우, 즉, index-free일 경우, 노드(14)는

에 포함된 슬롯에 논리 슬롯 인덱스

를 할당한다(S250). 이때,

의 첫 번째 슬롯에 논리 슬롯 인덱스를 할당할 수 있다.As a result of judgment of S240,

When a logical slot index is not assigned, that is, when index-free, node 14 is

logical slot index to the slot contained in

is assigned (S250). At this time,

A logical slot index can be assigned to the first slot of .

가

이므로,

의 첫번째 슬롯에

가 '1'을 할당되게 된다. At this time, referring to FIG. 7, at first

go

Because of,

in the first slot of

will be assigned '1'.

을 '1'만큼 증가시킨다(S260). Then, node 14

is increased by '1' (S260).

개의 섹션들의 순번인

가

인지를 판단한다(S270). 즉, 분할된 섹션들에 대해 모두 논리 슬롯 인덱스가 할당되었는지를 판단하기 위한 것이다. Then, the node 14 is partitioned

the sequence number of the sections

go

It is determined whether it is recognized (S270). That is, it is for determining whether logical slot indexes are allocated to all the divided sections.

가

일 경우,

가

인지를 판단하고(S280),

가

가 아닐 경우

를 '1' 증가시킨다(S290).As a result of the judgment of S270,

go

In case,

go

Determining recognition (S280),

go

if not

is increased by '1' (S290).

에 논리 슬롯 인덱스가 할당된 후에는 프레임에 포함된 슬롯들 중 하나에만 논리 슬롯 인덱스가 할당되므로,

를 '1' 증가시키게 된다. For example, referring to Figure 7,

After the logical slot index is assigned to , only one of the slots included in the frame is assigned the logical slot index,

is increased by '1'.

After that, the node 14 starts again from S220.

가 '1' 증가하였으므로, 프레임을

개의 섹션들로 균등 분할한다. in other words,

is incremented by '1', so the frame

equally divided into sections.

이 첫 번째 네 개 슬롯의 섹션

및 두 번째 네 개 슬롯의 섹션

로 분할된다. For example, referring to Figure 7,

Sections of these first four slots

and section of the second four slots

is divided into

Then, the node 14 performs S230 to S250 for each of the divided sections.

가 논리 슬롯 인덱스가 할당되었을 경우, 즉, index-free가 아닐 경우, 노드(14)는 S270으로 진행한다. On the other hand, the judgment result of S240,

When a logical slot index is assigned, that is, when it is not index-free, the node 14 proceeds to S270.

는 첫 번째 슬롯에 이미 논리 슬롯 인덱스가 할당되어 있으므로, 논리 슬롯 인덱스 할당 과정을 건너뛰게 된다. For example, referring to Figure 7,

Since the logical slot index is already assigned to the first slot, the logical slot index assignment process is skipped.

가

가 아닐 경우, 노드(14)는

을 '1' 증가시키고(S270), S230으로 다시 진행한다. On the other hand, as a result of the judgment of S270,

go

If not, node 14 is

is increased by '1' (S270), and the process proceeds again to S230.

에는 논리 슬롯 인덱스가 할당되어 있지 않으므로,

의 첫 번째 슬롯에

, 즉,'2'를 할당한다. For example, referring to Figure 7,

has no logical slot index assigned to it, so

in the first slot of

, that is, '2' is assigned.

Then, the node 14 sequentially performs steps S260 to S290, and then proceeds to S220 again.

이 섹션들의 순서대로 넘버링되는 것이 아니라,

이 균등 분할되어

및

이 되고,

가 균등 분할되어

및

가 된다. For example, referring to FIG. 7, the frame is again divided into four sections in S220,

Rather than numbering these sections in order,

is equally divided

and

become this,

is equally divided

and

becomes

일 수 있고, 논리 인덱스 '4'가 할당된 이후(AFTER THE 4^th round)에서는 마지막 섹션은

가 될 수 있다. At this time, as shown in FIG. 7 , before the logical index '4' is assigned (AFTER THE ^3rd round), the last section is

may be, and after logical index '4' is assigned ( ^AFTER THE 4th round), the last section is

can be

Thereafter, the logical index slot allocation is completed as shown in FIG. 7 by repeatedly performing steps S230 to S300 described above.

In this case, in allocating the logical slot index, a logical slot index may be allocated to each slot except for the physical slot index. That is, an assigned logical slot index is allocated to each slot except for an essentially existing physical slot index.

번 반복함에 있어. 두 개의 분할된 섹션 각각에 대해

비교는 최대 슬롯 인덱스를 찾게 한다.Also, split

in repetition. for each of the two divided sections

The comparison allows to find the maximum slot index.

은 다음의 <수학식 2>와 같이 표현할 수 있다.Meanwhile, the time complexity function of the logical slot indexing (LSI) algorithm shown in FIG. 6 .

can be expressed as the following <Equation 2>.

This LSI algorithm is executed only once when the size of the frame is redefined.

Next, referring back to FIG. 2 , in the step of generating the task schedule based on the logical slot index ( S150 ), the node 14 generates the task schedule by allowing the task to sequentially select the required number of slots.

At this time, when the task transmits data in each allocated slot, a task schedule is created to satisfy the data transmission period. Each task must transmit at least one data packet to the server 20 for each data transmission period, and since the task may have a transmission period shorter than the frame length, data may be transmitted several times within one frame period.

In this case, by comparing the number of slots of at least one of the first and second frames with the number of slots required for the task, the task may be reserved in the connected frame of at least one of the first and second frames.

슬롯을 순차적으로 선택하여 간단히 태스크를 스케줄링 할 수 있다. 여기에서, 태스크

는 주기

마다 하나의 패킷을 전송하며,

이다.For example, given k connected frames, starting from the logical slot index,

You can schedule tasks simply by selecting slots sequentially. Here, task

is the cycle

Each packet is sent

to be.

슬롯의 연결된 프레임이

에 대응하는 유휴 슬롯(idle slot)이 있는 경우, 태스크

를 예약할 수 있다. 여기에서, 시작하는 논리 슬롯 인덱스는

에 할당된 마지막 논리 슬롯 인덱스에 1을 더한 값이 된다.Specifically,

The connected frame of the slot

If there is an idle slot corresponding to

can be reserved. Here, the starting logical slot index is

It becomes a value by adding 1 to the last logical slot index allocated to .

8 is a diagram illustrating a task scheduling step according to a logical slot index according to an embodiment.

Referring to FIG. 8 , there are two connected frames of N=3.

에 할당되어 있다. 다음 태스크

는 논리 슬롯 인덱스 5, 6을 가지고,

는 논리 슬롯 인덱스를 7에서 10으로 가지게 된다.Logical slot indexes 1, 2, 3, 4 are already in some task list

is assigned to Next task

has logical slot indexes 5 and 6,

has logical slot indexes from 7 to 10.

Accordingly, if the total number of slots required for the task set does not exceed the number of slots defined in k frames, the task set can be reserved with k concatenated frames. Accordingly, the task set can be reserved only when the following <Equation 3> is satisfied.

In <Equation 3>, the numerator represents the total number of slots required for n tasks in the task set, and the denominator represents the total number of slots available in k connected frames. Thus, if the numerator is less than or equal to the denominator, all operations can get the required slot.

Also, although not shown in the drawing, when the node starts data transmission in the slot to which the logical slot index is allocated, the channel detection by the node may be repeated. A so-called MLBT (Multiple Listen-Before-Talk) mechanism can be used.

The Multiple Listen-Before-Talk (MLBT) mechanism is a response to the problem that a node may temporarily experience external interference, and the node immediately abandons data transmission when it detects that the channel is in use. If the task gives up data transmission immediately by detecting that the channel is in use within the assigned slot, it will be too costly, which is solved by detecting the channel multiple times within the slot.

9 is a diagram for explaining a Multiple Listen-Before-Talk (MLBT) mechanism for detecting channel activity according to an embodiment.

)을 수행할 수 있도록 하는 MLBT(Multiple Listen-Before-Talk) 메커니즘을 적용한다.Referring to Figure 9, the node is a channel activity detection (CAD) m (

), apply the MLBT (Multiple Listen-Before-Talk) mechanism.

으로 표시된 이중 슬롯의 길이로 확장된다. 노드의 채널 활동 감지(CAD)에 따른 CAD 간격(interval)은 다음의 <수학식 4>와 같다.the length of the slot

is extended to the length of the double slot indicated by . The CAD interval according to the node's channel activity detection (CAD) is as shown in Equation 4 below.

Through this MLBT (Multiple Listen-Before-Talk) mechanism, it is possible to detect a channel multiple times within one slot to handle external interference.

10 is a diagram illustrating a configuration of a computer system according to an embodiment.

The apparatus for scheduling a task for data transmission in a LoRa network according to an embodiment may be implemented in the computer system 1000 such as a computer-readable recording medium.

Computer system 1000 may include one or more processors 1010 , memory 1030 , user interface input device 1040 , user interface output device 1050 , and storage 1060 that communicate with each other via bus 1020 . can In addition, computer system 1000 may further include a network interface 1070 coupled to network 1080 . The processor 1010 may be a central processing unit or a semiconductor device that executes programs or processing instructions stored in the memory 1030 or the storage 1060 . The memory 1030 and the storage 1060 may be storage media including at least one of a volatile medium, a non-volatile medium, a removable medium, a non-removable medium, a communication medium, and an information delivery medium. For example, the memory 1030 may include a ROM 1031 or a RAM 1032 .

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can practice the present invention in other specific forms without changing its technical spirit or essential features. You will understand that there is Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

10-1, 10-2, 10-3: Star topology 12: Gateway
14: Node 20: Server

Claims (20)

A method for scheduling a task by a node device in a LoRa network, the method comprising:
classifying at least one node into one of a plurality of groups;
generating a frame for each group for each of the groups;
dividing each of the frames for each group into a plurality of slots;
allocating a logical slot index to each slot; and
A method for scheduling a task in a LoRa network, comprising: generating a task schedule based on a logical slot index. The method of claim 1, wherein the classifying comprises:
A method for scheduling tasks in a LoRa network, comprising: each node classifying a group based on a degree of signal attenuation of a message received from a gateway. The method of claim 1, wherein generating a frame comprises:
A method for scheduling a task in a LoRa network, comprising the step of assigning a unique spreading factor and a separate frequency channel corresponding to each group to each group. The method of claim 3, wherein the step of imparting a unique spreading factor comprises:
A method for scheduling a task in a LoRa network, comprising the step of giving a difference in a spreading factor between adjacent groups of 1 and a spreading factor as a natural number between 7 and 12. The method of claim 1, wherein the dividing into slots comprises:
A method for scheduling a task in a LoRa network, comprising: dividing into slots such that a ratio between the number of slots between frames of adjacent groups becomes two. The method of claim 1, wherein allocating a logical slot index comprises:
A method of scheduling a task in a LoRa network by equally dividing a plurality of slots included in a frame into two or more sections, and sequentially assigning a logical slot index to a first slot of each of the two or more sections. The method of claim 6, wherein allocating a logical slot index comprises:
A method for scheduling a task in a LoRa network, in which each of two or more equally divided sections is equally divided into two or more sections again, and a logical slot index is assigned only to sections in which the first slot is empty among the sections. The method of claim 1, wherein generating the task schedule comprises:
A method for scheduling a task in a LoRa network, comprising: comparing a number of slots in at least one of the frames of each of the groups with a number of slots required for the task to reserve the task in at least one concatenated frame of the frames in each of the groups. The method of claim 1,
When the node ends data transmission in the slot to which the logical slot index is assigned, repeating the channel detection by the node. a memory in which at least one program is recorded; and
including a processor executing a program;
program,
classifying at least one node into one of a plurality of groups;
generating a frame for each group for each of the groups;
dividing each of the frames for each group into a plurality of slots;
allocating a logical slot index to each slot; and
A task scheduling device in a LoRa network, which performs the step of generating a task schedule based on a logical slot index. The method of claim 10, wherein the classifying comprises:
A task scheduling apparatus in a LoRa network, comprising: each node classifying a group based on a degree of signal attenuation of a message received from a gateway. The method of claim 10, wherein generating a frame comprises:
A task scheduling apparatus in a LoRa network, comprising the step of assigning a unique spreading factor and a separate frequency channel corresponding to each group to each group. 13. The method of claim 12, wherein the step of imparting a unique spreading factor comprises:
A method for scheduling a task in a LoRa network, comprising: giving a difference in a spreading factor between adjacent groups of 1 and a spreading factor as a natural number between 7 and 12. The method of claim 10, wherein the dividing into slots comprises:
A task scheduling apparatus in a LoRa network, comprising the step of dividing into slots such that a ratio between the number of slots between frames of adjacent groups becomes two. 11. The method of claim 10, wherein allocating a logical slot index comprises:
A task scheduling apparatus in a LoRa network that equally divides a plurality of slots included in a frame into two or more sections, and sequentially allocates a logical slot index to a first slot of each of the two or more sections. The method of claim 15, wherein allocating a logical slot index comprises:
A task scheduling apparatus in a LoRa network, in which each of two or more equally divided sections is equally divided into two or more sections again, and a logical slot index assigns only sections in which the first slot is empty among the sections. 11. The method of claim 10, wherein generating the task schedule comprises:
and comparing the number of slots in at least one of the frames of each of the groups with the number of slots required for the task to reserve the task in at least one concatenated frame of the frames in each of the groups. 11. The method of claim 10,
The apparatus for scheduling a task in a LoRa network, further comprising: repeating the channel detection by the node when the node starts data transmission in the slot to which the logical slot index is assigned. A method for scheduling a task by a node device in a LoRa network, the method comprising:
classifying at least one node into one of a plurality of groups based on a signal attenuation degree of a message received by each node from the gateway;
generating a frame for each group for each of the groups;
dividing each of the frames for each group into a plurality of slots such that a ratio between the number of slots between frames of adjacent groups becomes 2;
allocating a logical slot index to each slot; and
generating a task schedule based on the logical slot index;
The steps to create a task schedule are:
A method for scheduling a task in a LoRa network, comprising: comparing a number of slots in at least one of frames in each of the groups with a number of slots required for the task to reserve a task in at least one connected frame among frames in each of the groups. The method of claim 1, wherein allocating a logical slot index comprises:
equally dividing a plurality of slots included in a frame into two or more sections, and sequentially allocating a logical slot index to a first slot of each of the two or more sections; and
A method for scheduling a task in a LoRa network, comprising: equally dividing two or more equally divided sections into two or more sections again, and allocating, by a logical slot index, only sections in which a first slot is empty among the sections.

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