KR20160106964A - Communication control method in wireless communication system - Google Patents

Abstract

The present invention relates to a communication control method capable of acquiring spatial reuse effects by applying a beam forming technology to CSMA/CA. According to an embodiment, the communication control method of the wireless communication system comprises the steps of: setting a directional network allocation vector (D-NAV), if a request to send (RTS) control frame and a clear to send (CTS) control frame are received from adjacent nodes; determining the probability of interference with the adjacent nodes by using the RTS control frame and CTS control frame, when the D-NAV is completed to set; and releasing the D-NAV setting and trying media access to a target node, when the probability of interference is determined to be low.

Description

Technical Field [0001] The present invention relates to a communication control method in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control method in a wireless communication system using a CSMA / CA scheme, and more particularly, to a communication control scheme in which a space reuse effect can be obtained by applying a beam- ≪ / RTI >

Recently, due to the spread of smart devices and the increase of multimedia services, the traffic of mobile service has been increasing, and the capacity of communication system has been required to increase. Accordingly, various methods for increasing the capacity of a communication system have been studied. One of them is beamforming.

Unlike an omni antenna in which a radio wave is radiated in all directions, beamforming radiates radio waves in a specific direction, thereby increasing the signal strength at the receiving end while reducing interference to other adjacent nodes, It is possible to obtain an effect of increasing the distance of distraction. To implement such beamforming, a directional antenna is required. As the directional antenna, a smart antenna having a plurality of antennas arranged in an array shape is used.

However, such an array antenna is mainly used in a base station because it is difficult to apply to a mobile terminal due to its large volume and high power consumption. Recently, a SPA (Switched Parasitic Antenna) or an ESPAR (Electronically Steerable Passive Array Radiator) antenna has been proposed as a directional antenna for application to a mobile terminal.

Meanwhile, a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method is widely used as a medium access control protocol that can operate in a simple and distributed manner in a wireless communication system. In this method, a node that is to transmit data firstly checks whether a medium is currently used or not through channel sensing, and then waits if it is used. If it is empty, it performs random back-off ) To gain access to the media. In the CSMA / CA scheme, since the access to the medium is determined through channel sensing, it is difficult to apply the beamforming scheme. In other words, in the existing CSMA / CA, it is assumed that the transmitting node transmits the radio wave in all directions (omni).

FIG. 1 is a diagram showing an RTS (Request To Send) / CTS (Clear To Send) according to a forward transmission / reception scheme, FIG. 2 is a diagram illustrating a transmission of an RTS / CTS according to a beamforming transmission / to be.

When two nodes (a transmitting node and a receiving node) perform a forward-direction transmitting and receiving operation, adjacent nodes existing in a constant coverage of radio waves, as shown in FIG. 1, recognize that the medium is currently used through channel sensing, The medium is not accessed. Thus, communication between two nodes can be performed without interference of other nodes.

However, if beamforming is applied to the transmission and reception operations between the two nodes to transmit and receive a radio wave only in a specific direction, it is impossible for other nodes in the radio coverage to judge whether the current medium is in use or empty through channel sensing. As a result, as shown in FIG. 2, there is a possibility that another node approaches and interferes with the medium during transmission / reception operations between the two nodes.

Therefore, in order to apply the beam forming method to the CSMA / CA protocol, a method for overcoming the above problems is needed.

The present invention provides a new communication control method that can obtain a spatial reuse effect by applying a beamforming scheme to a CSMA / CA scheme.

A communication control method of a wireless communication system according to an exemplary embodiment of the present invention includes receiving a Request To Send (RTS) control frame and a CTS (Clear To Send) control frame from neighboring nodes and receiving a Directional Network Allocation Vector (D-NAV) Determining whether interference with the neighboring nodes is possible using the RTS control frame and the CTS control frame when the D-NAV is set; And attempting to access the medium for the target node.

The communication control method of a wireless communication system according to another embodiment of the present invention includes the steps of transmitting an RTS control frame to a target node through omni transmission and receiving a CTS from the target node in response to the RTS, And transmitting data to the target node in a forming manner.

The technical problems of the present invention are not limited to the above-mentioned technical problems, and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

The present invention can achieve a spatial reuse effect by applying a beamforming scheme to the CSMA / CA scheme.

Brief Description of the Drawings Fig. 1 is a diagram illustrating transmission of an RTS / CTS according to a forward transmission / reception scheme;
FIG. 2 is a diagram illustrating transmission of an RTS / CTS according to a beamforming transmission / reception scheme; FIG.
3 illustrates a wireless network scenario in accordance with one embodiment of the present invention.
FIG. 4 is a diagram showing RTS / CTS timing diagrams of the transmission / reception nodes STA1 and AP1 in FIG. 3. FIG.
5 is a diagram showing RTS / CTS timing diagrams of nodes STA3 and AP2 adjacent to the transmission / reception nodes STA1 and AP1 in FIG.
6 is a flowchart for explaining operations of neighbor nodes STA2 and STA3 adjacent to the transmitting and receiving nodes;

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. Also, unless otherwise defined, 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 should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be interpreted in an ideal or overly formal sense unless explicitly defined in the present application Do not.

The present invention is a method for applying beamforming to a system operating in the CSMA / CA protocol and obtaining a space reuse effect. First, the following is assumed.

1) All nodes (STA and AP) are equipped with a directional antenna capable of beamforming.

2) Every station (STA) knows the DOA (Direction of Arrival) of a neighboring access point (AP) by a periodically measured beacon. At this time, any conventional method of measuring the DOA may be used, and therefore the following description does not show how to measure the DOA by any method.

3) In this embodiment, only the method of exchanging RTS / CTS control frames among the methods of transmitting / receiving data by CSMA / CA method is considered. That is, the method of exchanging only Data / Ack is not considered.

FIG. 3 is a diagram illustrating a wireless network scenario according to an embodiment of the present invention. FIG. 4 is a diagram illustrating RTS / CTS timing diagrams of the transmission / reception nodes STA1 and AP1 in FIG. CTS timing diagram of the nodes STA3 and AP2 adjacent to the transmission / reception nodes STA1 and AP1 of FIG.

Transceiver nodes (STA1, AP1) to exchange data first exchange RTS control frames and CTS control frames as shown in FIG. For example, when the station STA1 transmits an RTS to the access point AP1 after the DIFS, the access point AP1 transmits a CTS (short interframe space) after the RTS is received in response to the RTS, To the station STA1. At this time, the station STA1 and the access point AP1 transmit the RTS and CTS according to the forward direction transmission / reception method as in the prior art.

The RTS and the CTS are also received at the adjacent nodes (STA2, STA3) existing within the radio wave arrival range.

6 is a flowchart for explaining operations of the transmission / reception nodes STA1 and AP1 and neighboring nodes STA2 and STA3 adjacent to each other.

The neighboring nodes STA2 and STA3 set a Directional Network Allocation Vector (D-NAV) when RTS and CTS between the STA1 and the AP1 are received (step 610).

Conventionally, when neighboring nodes receive RTS and CTS, they set up a Network Allocation Vector (NAV), and did not attempt to access the medium during a period in which NAV is set. However, when the RTS and the CTS are received, the neighbor nodes STA2 and STA3 according to the present embodiment perform the following operations in the interval in which the D-NAV is set after setting the D-NAV.

The nodes STA2 and STA3 that have set the D-NAV first compare the received signal strength (received power) of the RTS and the CTS with a predetermined threshold to check whether the received signal strength is below a threshold value (step 620).

This is because the neighboring nodes STA2 and STA3 use the signal strengths of the RTS and the CTS to check whether the neighboring nodes STA2 and STA3 are farther apart from the nodes STA1 and AP1 that transmit / receive the RTS / CTS.

For example, in FIG. 3, the station STA2 maintains the D-NAV setting and does not attempt to access the medium during this period since it exists near the station STA1 and the access point AP1 that transmit and receive RTS and CTS 690).

That is, the station STA2 is in an idle state.

In step 620, if the strength of the signal is below the threshold value (or smaller than the threshold value), the corresponding node STA3 confirms whether the target node to transmit / receive is matched with the transmission / reception node of the RTS / CTS (step 630) .

For example, the station STA3 uses a source address (SA) and a destination address (DA) of the received RTS / CTS to determine whether a source address or a destination address is an address of a target node ≪ / RTI >

At this time, if the target node to which the station STA3 wants to transmit / receive data is the access point AP1, the station STA3 maintains the D-NAV setting and does not attempt to access the medium during this interval (step 690).

That is, the station STA3 is in an idle state.

However, if the target node to which the station STA3 wants to transmit / receive data is the access point AP2, since the station STA3 receives the CTS transmitted from the access point AP1 as shown in FIG. 4, Sensing is performed (step 640).

As a result of the channel sensing, if the channel is busy, the station STA3 maintains the D-NAV setting and does not attempt to access the medium during this interval (step 690).

That is, the station STA3 is in an idle state.

If channel sensing results in a channel idle state, the station STA3 cancels the preset D-NAV setting (step 660).

Next, the station STA3 transmits a D-RTS to the access point AP2 using a beamforming scheme as shown in FIG. 5 after a random back-off procedure defined in the CSMA / CA protocol, And receives the CTS transmitted by the access point AP2 (step 670).

At this time, the CTS is transmitted in all directions.

In this embodiment, the D-RTS is for indicating that the RTS is transmitted in a non-forward direction beamforming scheme. The D-RTS / CTS according to this embodiment may be defined as a new frame distinguished from the conventional RTS / CTS or may be distinguished by marking a specific bit of the conventional RTS / CTS.

Thereafter, the station STA3 and the access point AP2 perform data / Ack transmission / reception using beamforming (680).

While the STA3 performs the operations of steps 640 to 680, the station STA1 and the access point AP1 perform Data / Ack transmission / reception as shown in FIG. At this time, Data / Ack transmission / reception between the station STA1 and the access point AP1 is performed using a beam forming method.

That is, when the station STA1 and the access point AP1 perform data / ack transmission / reception using the beam forming method, when the station STA3 performs channel sensing in step 640, the station STA1 and the access point AP1 The data to be transmitted or received is not sensed.

In the above-described embodiment, when the transmitting / receiving nodes STA1 and AP1 exchange data, the neighboring nodes STA3 and AP3 can exchange data while reusing the space. However, if there is no possibility of interference with neighboring nodes, the station and the access point can transmit RTS / CTS in all directions and Data / Ack in a beamforming manner like the transmitting / receiving nodes STA1 and AP1. That is, in the wireless communication system according to the present embodiment, the station and the access point basically transmit the RTS / CTS in all directions, and when the RTS / CTS is received from the neighboring nodes, the operation for space reuse is performed as described above .

The embodiment of the present invention described above can be performed in the computing system as shown in FIG.

7, a computing system 1000 includes at least one processor 1100, a memory 1300, a user interface input device 1400, a user interface output device 1500, (1600), and a network interface (1700).

The processor 1100 may be a central processing unit (CPU) or a memory device 1300 and / or a semiconductor device that performs processing for instructions stored in the storage 1600. Memory 1300 and storage 1600 may include various types of volatile or non-volatile storage media. For example, the memory 1300 may include a ROM (Read Only Memory) and a RAM (Random Access Memory).

Thus, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by processor 1100, or in a combination of the two. The software module may reside in a storage medium (i.e., memory 1300 and / or storage 1600) such as a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, You may. An exemplary storage medium is coupled to the processor 1100, which can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integral to the processor 1100. [ The processor and the storage medium may reside within an application specific integrated circuit (ASIC). The ASIC may reside within the user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

1000: Computing System
1100: Processor
1200: bus
1300: Memory
1310: ROM
1320: RAM
1400: User interface input device
1500: User interface output device
1600: Storage
1700: Network interface

Claims (12)

Setting a D-NAV (Directional Network Allocation Vector) when a RTS (Request To Send) control frame and a CTS (Clear To Send) control frame are received from neighboring nodes;
Determining whether interference with the neighboring nodes is possible using the RTS control frame and the CTS control frame when the D-NAV is set; And
And if it is determined that there is no possibility of interference, releasing the D-NAV setting and trying to access the medium for the target node. 2. The method of claim 1, wherein determining interference potential comprises:
Determining whether the node is a predetermined distance from the neighboring nodes; And
And determining whether the target node matches the neighboring nodes when the target node is located at a predetermined distance from the target node. 3. The method of claim 2,
The step of determining whether or not the predetermined distance is apart
And determines whether the signal strength of the RTS control frame and the CTS control frame is less than a preset threshold value. The method of claim 3,
Wherein if the signal strength of the RTS control frame and the CTS control frame is greater than a predetermined threshold value, the D-NAV setting is maintained and the medium access is not attempted. 3. The method of claim 2,
Wherein the step of determining whether the target node and the neighboring nodes match
And comparing the source address and the destination address of the RTS control frame and the CTS frame with the address of the target node. 6. The method of claim 5,
Wherein the D-NAV setting is maintained and the medium access is not attempted when the target node and the neighboring node coincide with each other. The method of claim 1, wherein the D-NAV setting cancellation
And checking the channel state to release the channel state if the channel state is in an idle state. 8. The method of claim 7, wherein identifying the channel condition comprises:
Wherein the CTS control frame is received and channel sensing is performed after a predetermined period of time. 8. The method of claim 7,
Wherein when the channel status is busy, the D-NAV setting is maintained and the medium access is not attempted. 2. The method of claim 1, wherein the attempting to access the medium for the target node comprises:
And transmitting the RTS control frame to the target node using a beamforming method. 11. The method of claim 10,
And transmitting data to the target node in a beamforming manner when a CTS is received from the target node in response to the RTS. Transmitting an RTS control frame to a target node through omni transmission; And
And transmitting data to the target node in a beamforming manner when a CTS is received from the target node in response to the RTS.

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