KR101620956B1 - Method of scheduling for multicasting - Google Patents

Abstract

Disclosed is a method of scheduling a multicast transmission performed by a central controller included in a wireless LAN system. The method includes: (a) a step in which the central controller receives positional information on each of a plurality of nodes from a plurality of access points (APs) which has a plurality of accessible sectors; (b) a step of allocating each of the nodes to each of the sectors of the APs; (c) a step of determining the number of the nodes allocated to each of the sectors; and (d) a step of selecting, with a time slot as the unit, a transmission sector based on the calculated number of the nodes.

Description

[0001] METHOD OF SCHEDULING FOR MULTICASTING [0002]

The present invention relates to a multicast transmission scheduling method, and more particularly, to a multicast transmission scheduling method for efficiently performing multicast transmission in a wireless LAN system including a central controller.

2. Description of the Related Art [0002] Recently, as users of wireless networks have increased in number and types of wireless devices have diversified, many dense network environments including a plurality of access points (APs) and a plurality of nodes have appeared. At this time, when a plurality of APs exist in a limited network area, overlapping areas where APs are adjacent to each other and transmission ranges overlap are generated. When multicast transmission is performed to a plurality of nodes using a plurality of APs in such a dense network, collision may occur when data is received at the same time when nodes are located in the overlapping area of the AP. Therefore, scheduling considering multicast transmission in a dense network is essential.

In order to more effectively manage multiple APs in a dense environment, a central controller-based virtualized Wi-Fi network system can be applied. In such a system, one central controller manages several APs. A typical example of a centralized controller-based virtualization Wi-Fi network system is Cloud MAC technology. Cloud MAC technology consists of one central controller and a plurality of thin-APs. The central controller collects information of all APs in the network and manages the transmission of each AP. Because the thin-AP has only the transmission function and is managed by the central controller, it is possible to implement a wireless LAN system with a complex structure at a low cost. In this virtualized Wi-Fi network system, the central controller can manage or control all the APs in the network in consideration of the network conditions, thereby improving the overall network efficiency.

In the current 60 GHz band mmWave network, standardization of IEEE 802.11 ad, a standard technology supporting fast transmission speed, has been completed. In a mmWave network using a 60 GHz band, directional antennas are used for data transmission since signal attenuation due to distance is significant. Unlike conventional isotropic antennas, directional antennas can transmit data only in a desired direction. In addition, the IEEE 802.11ad standard supports a multiplexing rate, and the distance that can be transmitted can be adjusted according to a transmission rate (MCS value). Therefore, it is possible to minimize the interference with adjacent APs according to the network conditions and transmit them.

However, when multicast transmission is performed when there are a plurality of APs operating in a distributed manner in a network using directional antennas, redundant transmission and data collision may occur unnecessarily. On the other hand, more efficient multicast transmission is possible if multiple APs use a virtualized Wi-Fi network system controlled by a central controller. Also, scheduling the transmission order considering the characteristics of the directional antenna can prevent the collision and reduce the total transmission time.

Currently, many efficient multicast transmission schemes for one AP are proposed, but researches considering multiplexing rates in a dense network in which a plurality of APs are present have not been proposed. Therefore, it is necessary to study multicast transmission method in virtual Wi-Fi network system using directional antenna considering multi-rate environment.

Korean Patent Publication No. 10-2013-0036986 Korean Patent Publication No. 10-2007-0022096

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multicast transmission scheduling method for efficiently performing multicast transmission in a wireless LAN system supporting multiple transmission rates.

A multicast transmission scheduling method according to an exemplary embodiment of the present invention is a multicast transmission scheduling method performed by a central controller included in a wireless local area network (LAN) system, the method comprising the steps of: (a) (B) assigning each of the plurality of nodes to each sector of each of the plurality of APs; (c) assigning the number of nodes allocated per sector And (d) selecting a transmission sector based on the number of nodes calculated, on a time slot basis.

According to the multicast transmission scheduling method according to the embodiment of the present invention, an efficient multicast transmission can be performed to nodes in a virtual WLAN system by combining a directional antenna and a virtual WLAN system.

In addition, according to the multicast transmission scheduling method, it is possible to prevent duplicated transmission due to multicasting by each AP under a network environment composed of a plurality of APs.

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

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more fully understand the drawings recited in the detailed description of the present invention, a detailed description of each drawing is provided.
1 shows a wireless LAN system according to an embodiment of the present invention.
2 is a diagram for explaining sectors and transmission speed of the AP shown in FIG.
Figure 3 is an exemplary block diagram of a central controller.
4 is a flowchart illustrating a scheduling method by the central controller shown in FIG.

It is to be understood that the specific structural or functional description of embodiments of the present invention disclosed herein is for illustrative purposes only and is not intended to limit the scope of the inventive concept But may be embodied in many different forms and is not limited to the embodiments set forth herein.

The embodiments according to the concept of the present invention can make various changes and can take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It should be understood, however, that it is not intended to limit the embodiments according to the concepts of the present invention to the particular forms disclosed, but includes all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example, without departing from the scope of the right according to the concept of the present invention, the first element may be referred to as a second element, The component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Other expressions that describe the relationship between components, such as "between" and "between" or "neighboring to" and "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having" and the like are used to specify that there are features, numbers, steps, operations, elements, parts or combinations thereof described herein, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations 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 to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning of the context in the relevant art and, unless explicitly defined herein, are to be interpreted as ideal or overly formal Do not.

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

1 illustrates a wireless local area network (WLAN) system according to an embodiment of the present invention. Referring to FIG. 1, the WLAN system 10 may be a central controller based virtual Wi-Fi network system. The wireless LAN system 10 includes a central controller 100, a plurality of APs AP1 to AP3, and a plurality of nodes.

The central controller 100 can communicate with each of the plurality of APs AP1 to AP3 through the wired / wireless communication network and can control the operation of each of the plurality of APs AP1 to AP3.

A plurality of APs AP1 to AP3 constitute a wireless LAN system 10 and can provide a wireless LAN environment to the plurality of nodes. Each of the plurality of APs AP1 to AP3 has a directional antenna and can transmit data to the plurality of nodes or receive data from the plurality of nodes using the same wireless channel on the wireless LAN. For example, a plurality of APs AP1 to AP3 can communicate with the plurality of nodes using the same frequency band of radio, and transmit multicasting data to the plurality of nodes using the same channel of the same frequency band can do. At this time, each of the plurality of APs AP1 to P3 may be a thin-AP.

The plurality of nodes may be wirelessly connected to at least one AP among the plurality of APs AP1 to AP3 to receive or transmit data. Each of the plurality of nodes may be a personal computer (PC), a tablet PC, a notebook, a net-book, an e-reader, a personal digital assistant (PDA) player, an MP3 player, or an MP4 player, or may be implemented as a handheld device such as a mobile phone or a smart phone.

2 is a diagram for explaining sectors and transmission speed of the AP shown in FIG. 2, only two APs (AP1 and AP2) are shown for convenience of explanation.

,

,

,

,

, 및

를 가지고, AP2는 액세스 가능한 복수의 섹터들인

,

,

,

,

, 및

을 가진다.Referring to FIGS. 1 and 2, AP1 and AP2 having a directional antenna have a plurality of sectors that can be accessed. Here, it is assumed that the number of sectors accessible to AP1 and AP2 is six. That is, the AP1 is a plurality of accessible sectors

,

,

,

,

, And

AP2 is a plurality of accessible sectors

,

,

,

,

, And

.

Also, AP1 and AP2 can support multiple transmission rates. That is, AP1 and AP2 can support multiple transmission rates by using the phenomenon that the signal is attenuated according to the transmission distance. For example, it is assumed that AP1 and AP2 can support three transmission speeds.

AP1 may transmit or receive data within a first transmission distance 11 at a first transmission rate and may transmit or receive data within a second transmission distance 12 at a second transmission rate, Data can be transmitted or received within the third transmission distance 13 at a transmission rate. Similarly, AP2 may transmit or receive data within a first transmission distance 21 at a first transmission rate and may transmit or receive data within a second transmission distance 22 at a second transmission rate, And may transmit or receive data within the third transmission distance 23 at a third transmission rate. The number of transmission speeds and transmission distances supported by AP1 and AP2 may be two or more, but it is assumed herein that three transmission speeds and three transmission distances are supported for convenience of description.

에는 n₁, n₂, n₃, 및 n₄가 위치하고, AP2의

에는 n₃, n₅, 및 n₆가 위치한다. 또한, n₁은 AP1의 제3 전송 거리(13) 내에 위치하고, n₂, n₃, 및 n₄는 AP1의 제2 전송 거리(12) 내에 위치하며, n₃은 AP2의 제1 전송 거리(21) 내에 위치하며, n₆은 AP2의 제3 전송 거리(23) 내에 위치하며, n₅는 AP2의 제2 전송 거리(22) 내에 위치한다.At this time, each of the plurality of nodes n ₁ to n ₆ may be located as shown in FIG. That is,

N ₁ , n ₂ , n ₃ , and n ₄ are located in the AP 2,

N ₃ , n ₅ , and n ₆ are located. In addition, n ₁ is located within the third transmission distance 13 of AP ₁ , n ₂ , n ₃ , and n ₄ are located within the second transmission distance 12 of AP 1, n ₃ is the first transmission distance of AP 2 located within 21) and, n ₆ is located within a third transmission distance 23 of AP2, n ₅ is located in a second transmission distance 22 of AP2.

Here, the first transmission distances 11 and 21 are denoted by m ₀ , the second transmission distances 12 and 22 are denoted by m ₁ , the third transmission distances 13 and 23 are denoted by m ₂ , The locations of the receiving nodes are summarized in Table 1 below.

Node Sector of AP1 Area (transmission distance) Sector of AP2 Area (transmission distance) n ₁ S _(1,6) m ₂ - - n ₂ S _(1,6) m ₁ - - n ₃ S _(1,6) m ₁ S _(2,2) m ₀ n ₄ S _(1,6) m ₁ - - n ₅ - - S _(2,2) m ₁ n ₆ - - S _(2,2) m ₂

Table 1 shows that n ₃ can be accessed by AP1 and AP2.

Figure 3 is an exemplary block diagram of a central controller. 1 and 3, the central controller 100 includes a communication unit 110, a memory 120, a control unit 130, and a system bus / control bus 140.

Referring to the respective blocks of the central controller 100, the communication unit 110 can transmit and receive data with a plurality of APs by wire or wirelessly. The communication unit 110 receives the data indicating the state information including the location information of the node as a packet, and transmits data of multicasting control information for controlling multicasting of data in a plurality of APs as packets to a plurality of APs do. The communication unit 110 may transmit the data of the status information, which is controlled and received by the control unit 130, to the control unit 130 or may receive the data of the multicasting control information from the control unit 130 and transmit the data by wire or wirelessly. According to an embodiment, the communication unit 110 may include a communication IC configured to transmit and receive data packets of a wired LAN or a wireless LAN according to a designated communication protocol.

Memory 120 includes volatile memory and / or non-volatile memory. The memory 120 may store a program for determining the transmission order of transmission sectors per time slot and / or generating multicasting control information, various tables generated or managed by the program, state information received from the AP, and the like.

The control unit 130 may be implemented by one or a plurality of processors, a CPU, or the like. The control unit 130 is configured to process the information or the request received through the communication unit 110 by using the program stored in the memory 120. [ In particular, the control unit 130 receives status information from a plurality of APs via the communication unit 110, determines a sector corresponding to a node accessible from a plurality of APs using the received status information, Sector is used to calculate the transmission order for each sector of a plurality of APs. Also, the controller 130 may generate multicasting control information based on the calculated transmission order, and may transmit data of the multicasting control information to a plurality of APs via the communication unit 110. [

The system bus / control bus 140 is a bus capable of transmitting and receiving data and control signals between the components in the central controller 100. The system bus / control bus 140 is comprised of, for example, a parallel bus, a serial bus, a general purpose input / output (GPIO), or a combination thereof.

4 is a flowchart illustrating a scheduling method by the central controller shown in FIG.

In the wireless LAN system 10, the selection of the sector and the transmission rate of the AP to be multicast-transmitted on a time slot-by-time slot basis is determined by the central controller 100. The selection and order of sectors for each AP is determined by the central controller 100 using time slots, overlapping nodes in sectors, number of nodes in a sector, and the like.

First, the central controller 100 receives position information of nodes connected to each of a plurality of APs controlled by the central controller 100 (S110). The location information of the nodes may be received from each of the plurality of APs AP1 and AP2. That is, the central controller 100 receives the location information of the nodes located within the transmission range of the AP 1 from the AP 1 and receives the location information of the reception nodes located within the transmission range of the AP 2 from the AP 2. At this time, the central controller 100 may further receive position information of each of the plurality of APs AP1 and AP2. According to the embodiment, the location information of each of the plurality of APs AP1 and AP2 may be stored in the central controller 100 in advance.

When two APs are included in the wireless LAN system 10 and the nodes are located as shown in FIG. 2, the location information of the nodes received from each of the plurality of APs is summarized in Table 1 above.

The central controller 100, which receives the position information of the plurality of nodes included in the wireless LAN system 10, allocates each of the plurality of nodes to each sector (S130). At this time, one node can be assigned to one sector. This makes it possible to avoid the problem of data being duplicated and the collision between sectors.

)과 AP2의

에 중복 위치하여 AP1 또는 AP2로부터 액세스가 가능하다. 따라서, n₃은

또는

에 할당될 수 있다. 이와는 다르게, n₃은 중첩되는 섹터들(

와

) 중 노드가 가장 많이 분포된

에 할당될 수도 있다. 즉,

에는 전송 범위가 중첩되지 않는 3 개의 노드(n₁,n₂, 및 n₄)가 위치하고 있고,

에는 전송 범위가 중첩되지 않는 2 개의 노드(n₅와 n₆)가 위치하고 있므로, n₃은 분포된 노드의 개수가 많은

에 할당될 수 있다.There are various methods for allocating nodes accessible from two or more APs to one sector. For example, a node accessible from the two or more APs may be assigned to a sector of the selected AP by selecting any one of two or more accessible APs. According to an embodiment, a node accessible from the two or more APs may be assigned to a sector in which nodes are most distributed among overlapping sectors. That is, in the case of n ₃ ,

) And AP2

And access from AP1 or AP2 is possible. Therefore, n ₃ is

or

Lt; / RTI > Alternatively, n ₃ may be the number of overlapping sectors (

Wow

) Is the most distributed node

Lt; / RTI > In other words,

There are three and located nodes that do not overlap the transmission range (n _1, n _2, and n _4),

(N ₅ and n ₆ ) in which the transmission range is not overlapped, n ₃ is the number of distributed nodes

Lt; / RTI >

에는 4개의 노드(n₁, n₂, n₃, 및 n₄)가 할당되고,

에는 2 개의 노드(n₅과 n₆)가 할당된다.The central controller 100 determines the number of nodes allocated to each sector and the maximum transmission rate (S150). For example, as to the number of nodes allocated to each sector determined by the central controller 100,

Four nodes n ₁ , n ₂ , n ₃ , and n ₄ are allocated,

Two nodes n ₅ and n ₆ are allocated.

에 할당된 노드들(n₁, n₂, n₃, 및 n₄)을 대상으로 AP1이 멀티캐스팅 전송을 수행하기 위해서는, AP1으로부터 가장 멀리 위치한 n₃에게 전송 가능한 최대 전송 속도로 멀티캐스팅을 수행하여야 한다. n₃은 AP1의 제2 전송 거리(12) 내에 위치하고 있으므로, 제2 전송 거리(12)에 대응하는 제2 전송 속도(MCS1)가 최대 전송 속도로 결정될 수 있다. 결국, AP1이

에서 제2 전송 속도로 멀티캐스팅을 수행할 경우,

에 할당된 모든 노드들(n₁, n₂, n₃, 및 n₄)에게 성공적으로 멀티캐스팅을 수행할 수 있다. 본 발명에서 전송 속도의 결정은 전송 거리에 대응하는 MCS(modulation and coding scheme)값을 결정함으로써 결정될 수 있다.In addition, the central controller 100 can determine the maximum transmission rate that can be transmitted based on the position information of the allocated node. The maximum transmission rate is determined based on the node located farthest from the AP among the nodes allocated to each sector. for example,

Of the node assigned to the (n _1, n _2, n _3, and n ₄₎ of the AP1 performs multicasting in order to perform the multicast transmission, the maximum transmission rate can be transmitted to n ₃ furthest located from AP1 target shall. n ₃ is so located in the second transmission range 12 of the AP1, the second transfer rate (MCS1) corresponding to the second transmission range (12) can be determined at the maximum transfer rate. Finally,

When multicasting is performed at a second transmission rate,

(N ₁ , n ₂ , n ₃ , and n ₄ ) assigned to the node N ₁ . In the present invention, the determination of the transmission rate can be determined by determining a modulation and coding scheme (MCS) value corresponding to the transmission distance.

에 할당된 노드들(n₅과 n₆)을 대상으로 AP2가 멀티캐스트 전송을 수행하기 위해서는, AP2로부터 가장 멀리 위치한 n₅에게 전송 가능한 최대 전송 속도로 멀티캐스팅을 수행하여야 한다. n₅는 AP2의 제2 전송 거리(22) 내에 위치하고 있으므로, 제2 전송 거리(22)에 대응하는 제2 전송 속도(MCS1)가 최대 전송 속도로 결정될 수 있다.Likewise,

In order for the AP 2 to perform the multicast transmission on the nodes (n ₅ and n ₆ ) allocated to the AP 2, the multicasting must be performed at the maximum transmission rate that can be transmitted to the n ₅ located farthest from the AP 2. Since n ₅ is located within the second transmission distance 22 of AP2, the second transmission rate MCS1 corresponding to the second transmission distance 22 can be determined as the maximum transmission rate.

Hereinafter, a method of selecting a sector and a transmission rate for each time slot will be described.

을 제1 시간 슬롯에서 전송할 섹터로 선택한다. 이때, 전송 속도는 앞서 결정된

의 최대 전송 속도일 수 있다.The central controller 100 selects a sector having the largest number of nodes for each time slot as a transmission sector (S210). An example, the central controller 100 includes a total of four nodes (n _1, n _2, n _3, and n ₄₎ is assigned

As a sector to be transmitted in the first time slot. At this time,

Lt; / RTI >

)와 동시에 전송 가능한 섹터가 모두 선택되었는지 여부를 결정한다(S230). The central controller 100 determines which of the sectors (< RTI ID = 0.0 >

(Step S230). In step S230, it is determined whether or not all of the sectors that can be transmitted are selected.

)와 동시에 전송 가능한 섹터들 중에서 노드가 가장 많이 할당된 섹터(

)를 전송 섹터로 선택한다. 이때,

의 전송 속도는 앞서 결정된

의 최대 전송 속도일 수 있다.If all of the sectors that can be simultaneously transmitted are not selected in step S230, the central controller 100 repeats step 210. [ Thus, the central controller 100 may select the selected sector

) Of the sectors that can be transmitted at the same time

) As a transmission sector. At this time,

Lt; RTI ID = 0.0 >

Lt; / RTI >

The central controller 100 performs step 230 again, and if all the transmittable sectors are selected at the same time, the step 250 is performed. Of course, if there are other APs except for AP1 and AP2, and a node is assigned to the other AP, then there may be other sectors that can transmit at the same time.

The central controller 100 determines in step S250 whether the sectors to which the node is allocated, i.e., all transmittable sectors are selected. If all transmittable sectors, that is, all sectors to which a node is allocated, are selected by the central controller 100, the scheduling by the central controller 100 is completed.

If it is determined in step S250 that all transmittable sectors are not selected, the central controller 100 increments the time slot by a unit time slot, for example, one time slot (S270). In addition, the central controller 100 selects a sector to be transmitted and a transmission rate in a second time slot, which is an increased time slot.

Table 2 below shows transmission tables generated by summarizing transmission sectors and transmission speed determined through the scheduling method.

The first transmission sector The first transmission rate The second transmission sector Second transmission rate The first time slot S _(1,6) m ₁ S _(2,2) m ₁ The second time slot - - - -

Referring to Table 2, it is assumed that the wireless LAN system 10 includes only two APs. Therefore, it can be seen that the number of sectors that can be simultaneously transmitted in each time slot is two. Also, multicast transmission is possible to all nodes included in the WLAN system 10 through multicast transmission in the first time slot, so that it can be seen that there is no AP allocated in the second time slot.

The central controller 100 can control a plurality of APs included in the WLAN system 10 according to a schedule generated by the multicast transmission scheduling method. Accordingly, the plurality of APs can perform multicast transmission according to the schedule under the control of the central controller 100. [

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: Wireless LAN system
100: Central controller
110:
120: Memory
130:
140: System bus / control bus

Claims (8)

A multicast transmission scheduling method performed by a central controller included in a wireless local area network (WLAN) system,
(a) receiving, by the central controller, location information of each of a plurality of nodes from a plurality of access points (APs) having a plurality of sectors each of which can be accessed;
(b) allocating each of the plurality of nodes for each sector of the plurality of APs;
(c) determining the number of nodes allocated for each sector; And
(d) selecting a transmission sector based on the number of nodes calculated, on a time slot basis,
Wherein the step (b) allocates a node simultaneously accessible from the sectors of adjacent APs to one of the sectors of the neighboring APs,
A multicast transmission scheduling method. The method of claim 1, wherein step (c)
(c-1) selecting a sector to which the most nodes are allocated as the transmission sector; And
(c-2) repeatedly performing the step (c-1) on the sectors simultaneously transmittable. The method according to claim 1,
The multicast transmission scheduling method includes:
(e) repeating step (d) after increasing the time slot by a unit time slot until all the sectors to which the node is assigned are selected. The method according to claim 1,
Wherein each of the plurality of APs is a thin-AP that includes a directional antenna. The method according to claim 1,
Wherein the step (b) further comprises determining a transmission rate that can be transmitted on a sector-by-sector basis. 6. The method of claim 5,
Wherein the transmission rate is a maximum transmission rate that can be transmitted to a node having the highest transmission distance among nodes allocated to a sector. delete The method according to claim 1,
Wherein any one of the sectors is a sector having the largest number of accessible nodes.

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