KR101546198B1 - Method and Device for Controlling Power in Wireless Network - Google Patents

Abstract

Disclosed are a method and an apparatus for controlling the power capable of increasing space reuse efficiency. The disclosed power control method comprises: a step of receiving an RTS message including first transfer power information from a transmitting terminal; a step of determining a distance from the transmitting terminal using the first transfer power information, noise information, and the RTS message receiving power; a step of generating second transfer power information in accordance with the determined distance; and a step of transferring a CTS message including the second transfer power information to the transmitting terminal in accordance with the second transfer power.

Description

[0001] The present invention relates to a method and apparatus for controlling power in a wireless network,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power control method and apparatus in a wireless network, and more particularly, to a power control method and apparatus capable of improving space reuse efficiency.

The MAC (Medium Access Control) layer operation of a wireless network based on the existing IEEE 802.11 and IEEE 802.15 series standards uses a CSMA / CA (Carrier Sensing Multiple Access with Collision Avoidance) scheme. CSMA is a carrier sense multiple access technique used in the IEEE 802.15.4 standard of WLAN and IEEE 802.15.4 standard of Wireless Personal Area Network (WPAN), CSMA is a state in which there is no separate central control device, Based on the competition between the media access control method.

The nodes observe the state of the channel, and when the channel detects that the idle state is not in use for a certain time (DIFS, AIFS, etc.), the node waits for an optional backoff time Later, data transmission is attempted. If a transmission collision occurs, the node selects an arbitrary number in the interval longer than the immediately preceding backoff time, and retries transmission after waiting for the number of slots. Through this process, it is possible to prevent each node from colliding with itself in a distributed manner without a central control device.

In order to solve the hidden node problem, nodes exchange small-sized Ready-to-Send (RTS) and Clear-to-Send (CTS) frames before transmitting data frames, A pre-occupancy CA (Collision Avoidance) scheme is used. In addition, the MAC protocol based on the existing WLAN IEEE 802.11 and WPAN IEEE 802.15.4 does not allow concurrent transmission within the Carrier Sensing (CS) range to prevent transmission failure due to interference.

1 is a diagram for explaining data transmission / reception according to the above-described MAC protocol.

There are four nodes A, B, C, and D on the wireless network, as shown in FIG. Nodes included in the carrier sense range (CS range) stop the backoff process, and the data transmission range indicates a range where packets can be successfully received and decoded.

Although nodes A and B and nodes C and D are located at a distance capable of transmitting and receiving data (flow1, flow2, flow3, flow4) without interfering with each other, node C is included in the carrier sensing (CS) .

Therefore, even in the absence of inter-node interference, there is a problem that node C can not transmit / receive data to / from node B, and research for increasing space reuse efficiency is needed.

The present invention is to provide a method and apparatus for power control in a wireless network.

In particular, the present invention is to provide a power control method and apparatus capable of increasing the space reuse efficiency.

According to an embodiment of the present invention, there is provided a method of transmitting a RTS message including first transmission power information, the method comprising: transmitting, by the first transmission power, an RTS message including first transmission power information; Receiving a CTS message including second transmission power information from a receiving terminal that has received the RTS message; And transmitting data using the second transmission power information, wherein the receiving terminal determines a distance to the transmitting terminal by using the first transmission power information, the interference information, and the RTS message receiving power And generating the second transmission power information based on the distance.

According to another exemplary embodiment of the present invention, there is provided a method of transmitting an RTS message, the method comprising: receiving an RTS message including first transmission power information from a transmitting terminal; Determining a distance to the transmitting terminal using the first transmission power information, the noise information, and the RTS message reception power; Generating second transmission power information according to the determined distance; And transmitting a CTS message including the second transmission power information to the transmitting terminal according to the second transmission power. The present invention also provides a method of controlling power of a receiving terminal in a wireless network.

According to still another aspect of the present invention, there is provided a mobile station comprising: a receiver for receiving an RTS message including first transmission power information from a wireless terminal; A distance determination unit for determining a distance to the wireless terminal using the first transmission power information, the noise information, and the RTS message reception power; An information generating unit generating second transmission power information according to the determined distance; And a transmitter for transmitting a CTS message including the second transmission power information to the wireless terminal according to the second transmission power.

According to the present invention, the transmission power can be adaptively adjusted according to the distance between nodes in the wireless network, and the power consumed by the node can be reduced by transmitting / receiving data with the adjusted transmission power.

Also, according to the present invention, the number of nodes capable of data transmission / reception can be increased by reducing the carrier sensing range, the overall data throughput is increased, and the space reuse efficiency can be increased.

1 is a diagram for explaining data transmission / reception according to a MAC protocol.
2 is a diagram for explaining a wireless network system according to an embodiment of the present invention.
3 is a diagram for explaining a power control method of a transmitting terminal according to an embodiment of the present invention.
4 is a diagram for explaining a power control method of a receiving terminal according to an embodiment of the present invention.
5 and 6 are views for explaining the effect of the power control method according to an embodiment of the present invention.
7 is a diagram for explaining a power control method according to a specific embodiment of the present invention.
8 is a view for explaining a power control apparatus according to a specific embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The present invention improves space reuse efficiency by adaptively adjusting transmission power according to a distance between nodes in a wireless network. 1, the node C is included in the carrier sensing range of the node B and can not transmit or receive data. According to the present invention, the carrier sensing range of the node B is reduced according to the distance between the node A and the node B. Therefore, the node C can transmit and receive data, and as a result, the space reuse efficiency can be increased. Also, as the efficiency of spatial reuse increases, the number of nodes capable of data transmission increases in the wireless network, so that the overall throughput can be improved.

The transmitting terminal and the receiving terminal, which will be described below, may be referred to as a power control device in terms of performing the power control according to the present invention, for example, an access point (AP), a user terminal, . Further, the hardware-oriented description referred to in the present invention can be interpreted in terms of a process.

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

2 is a diagram for explaining a wireless network system according to an embodiment of the present invention.

As shown in FIG. 2, the wireless network system according to the present invention includes a transmitting terminal 200 and a receiving terminal 210. The transmitting terminal 200 includes a first transmitting unit 201 and a first receiving unit 203 and may further include a first information generating unit 205 according to an embodiment. The receiving terminal 210 includes a second transmitting unit 211, a second receiving unit 213, a distance determining unit 215, and a second information generating unit 217.

The first transmission unit 201 transmits the RTS message including the first transmission power information at a first transmission power. The first transmission power information is information indicating the transmission power of the transmitting terminal 200 and can be generated by the first information generating unit 205. [ The transmission power of the transmitting terminal 200 may be a preset maximum power or a power adjusted from the maximum power.

The second receiving unit 213 receives the RTS message transmitted from the transmitting terminal 200. The distance determining unit 215 receives the RTS message from the transmitting terminal 200 using the first transmission power information, And the distance between the receiving terminal 210 and the receiving terminal 210 is determined.

The second information generation unit 217 generates second transmission power information according to the distance determined by the distance determination unit 215 and transmits a CTS message to the transmission terminal 200 according to the second transmission power. The CTS message includes the second transmission power information.

The transmitting terminal 200 receiving the CTS mesh through the first receiving unit 203 transmits the data at the second transmission power using the second transmission power information. Therefore, the transmission power of the transmitting terminal 200 and the receiving terminal 210 can be reduced as the distance between the transmitting terminal 200 and the receiving terminal 210 becomes shorter.

That is, the present invention can adjust transmission power adaptively according to the distance between nodes in a wireless network, and transmit / receive data with adjusted transmission power. By transmitting / receiving data according to the adjusted transmission power, power consumed by the transmitting terminal 200 and the receiving terminal 210 can be reduced, the carrier sensing range is reduced, and the number of nodes capable of data transmission / reception increases, Throughput can be increased.

Meanwhile, the distance determination unit 215 determines the distance between the transmitting terminals 200 using the noise information, and the noise information may be interference information between the nodes of the wireless network. The reception power of the RTS message measured at the receiving terminal 210 may increase due to inter-node interference, and the present invention may be applied to receiving the RTS message for accurate distance measurement between the transmitting terminal 200 and the receiving terminal 210 Distance can be measured by removing interference power from power.

3 is a diagram for explaining a power control method of a transmitting terminal according to an embodiment of the present invention. In Fig. 3, the above-described power control method of the transmitting terminal 200 is described as an embodiment.

The transmitting terminal 200 transmits the RTS message including the first transmission power information at the first transmission power (S301). Then, the transmitting terminal 100 receives the CTS message including the second transmission power information from the receiving terminal 210 that has received the RTS message (S303), and transmits the data using the second transmission power information (S305) .

The power control method according to the present invention may further include generating first transmission power information using a first minimum threshold power for carrier sensing and a second minimum threshold power for data decoding. The first minimum threshold power is the power that is the boundary of the real sensing range, and the second minimum threshold power is the power that is the boundary of the data transmission range.

As described above, the transmitting terminal 200 can transmit data at a preset maximum power or transmit data from the maximum power to a modified power. The transmitting terminal 200 can transmit the RTS message according to the above-described minimum threshold power Lt; / RTI >

)를 결정할 수 있다. 즉, 제1전송 파워는 제1최소 임계 파워에 비례하며, 제2최소 임계 파워에 반비례할 수 있다.The transmitting terminal 200 transmits the first transmission power (< RTI ID = 0.0 >

Can be determined. That is, the first transmission power is proportional to the first minimum-threshold power and may be inversely proportional to the second minimum-threshold power.

는 제1최소 임계 파워를 나타내며,

는 제2최소 임계 파워를 나타내며, 송신 단말(200)에 정의되어 있거나 실험적으로 결정될 수 있다. 그리고

는 기 설정된 최대 송신 파워를 나타내며,

는 SINR(Signal to Interference plus Noise Ratio)을 나타낸다.here,

Lt; / RTI > represents the first minimum-threshold power,

Represents the second minimum threshold power, and may be defined in the transmitting terminal 200 or may be determined experimentally. And

Indicates a predetermined maximum transmission power,

Indicates a Signal to Interference plus Noise Ratio (SINR).

가

보다 크다. 따라서, 송신 단말(200)은 최초 RTS 메시지를 전송하면서 보다 적은 전송 파워로 데이터를 전송할 수 있다.As shown in Figure 1, the carrier sensing range is wider than the data transmission range,

end

Lt; / RTI > Accordingly, the transmitting terminal 200 can transmit data with a lower transmission power while transmitting the initial RTS message.

The transmitting terminal 200 can retransmit the RTS message with a predetermined maximum transmission power when it transmits the RTS message with the transmission power according to Equation (1) and does not receive the CTS message from another node.

4 is a diagram for explaining a power control method of a receiving terminal according to an embodiment of the present invention. In FIG. 4, the power control method of the above-described receiving terminal 210 is described as an embodiment.

The receiving terminal 210 receives the RTS message including the first transmission power information from the transmitting terminal 200 (S401). Then, a distance between the transmitting terminal 200 and the receiving terminal 210 is determined using the first transmission power information, the noise information, and the RTS message receiving power (S403). Herein, the noise information includes interference information between nodes of the wireless network, and in one embodiment, the interference information may be a maximum interference intensity value between nodes of the wireless network.

또는

)를 판단할 수 있다.The receiving terminal 210 calculates the distance (< EMI ID = 2.0 >

or

).

은 RTS 메시지 수신 파워, 즉 수신 단말(110)에서 측정된 RTS 메시지에 대한 RSS(Received signal strength) 값이며,

는 제1전송 파워와 간섭 정보가 포함된 값이다. 그리고

은 송신(수신) 안테나의 이득을 의미하고,

은 송신(수신) 안테나의 height를 의미한다.

는 wavelength,

은 system loss, 그리고

를 의미한다. 각각의 파라미터는 송신 단말(200)에서 제공되거나 수신 단말(210)에서 기 정의된 값, 또는 측정된 값일 수 있다.here,

(Received Signal Strength) value of the RTS message reception power, i.e., the RTS message measured at the receiving terminal 110,

Is a value including first transmission power and interference information. And

(Gain) of the transmitting (receiving) antenna,

Is the height of the transmitting (receiving) antenna.

Is a wavelength,

System loss, and

. Each parameter may be provided at the transmitting terminal 200 or may be a predefined value at the receiving terminal 210, or a measured value.

)를 결정할 수 있다.The receiving terminal 210 generates second transmission power information according to the determined distance (S405). The receiving terminal 210 may determine the second transmission power to be in inverse proportion to the determined distance. Specifically, the receiving terminal 210 calculates the second transmission power (i.e.,

Can be determined.

는 최대 간섭 세기 값이며,

및

각각은 하기 [수학식 4] 및 [수학식 5]와 같이 나타낼 수 있다.here,

Is the maximum interference intensity value,

And

Can be expressed by the following equations (4) and (5), respectively.

The receiving terminal 210 transmits the CTS message including the second transmission power information to the transmitting terminal 200 according to the second transmission power (S407). The transmitting terminal 200 transmits data at a second transmission power using the second transmission power information and the receiving terminal 210 receives data transmitted according to the second transmission power from the transmitting terminal 200. [ The receiving terminal 210 may transmit the ACK message to the transmitting terminal 200 after receiving the data of the transmitting terminal 200.

5 and 6 are views for explaining the effect of the power control method according to an embodiment of the present invention.

5 and 6 are diagrams showing total average throughput and transmission energy efficiency of a transmitting node in a wireless network including N nodes located at random and transmitting / receiving node pairs at a constant bit rate to be. 5 and 6 are experimental results using parameters in Table 1. In the graphs of FIGS. 5 and 6, the horizontal axis represents the number of node pairs transmitting and receiving data.

5 and 6, a power control method according to the present invention is represented by DTPC (Distributed Power Control). The power control method includes DCF (Distributed Coordination Function), MTP (Minimum Transmission Power), OTP ) And the MCA (Minimum Cease Area) protocol. The MTP protocol is a protocol for transmitting an RTS message and a CTS message at maximum power and transmitting data and ACK messages at a minimum power capable of data decoding. The OTP protocol is a protocol that transmits RTS and CTS messages with maximum power, and transmits data and ACK messages with minimum power where interference occurs. The MCA protocol is a protocol that transmits RTS messages at maximum power and transmits RTS messages, data, and ACK messages with the minimum power at which interference occurs.

As shown in FIG. 5, it can be seen that the overall average throughput of the power control method according to the present invention is higher than other protocols. Also, as shown in FIG. 6, in the power control method according to the present invention, it can be seen that more data can be transmitted with the same power as compared with other protocols.

PHY  variable

0.2818 W

1.0 (1.0)

1.5 (1.5) m

1.0

0.33 m

10 dB

(

) W MAC  variable Payload length 1000 bytes PHY (MAC) Header 24 (28) bytes RTS (CTS) 20 (14) bytes + PHY Header ACK 14 bytes + PHY Header Basic (Data) rate 1 Mbps Slot Time 20

SIFS (DIFS) 10 (50)

7 is a diagram for explaining a power control method according to a specific embodiment of the present invention.

)는 캐리어 센싱을 위한 최소 임계 파워 및 데이터 디코딩을 위한 최소 임계 파워를 이용하여 결정된 전송 파워이다.Referring to FIG. 7, if the transmitting terminal succeeds in occupying the channel according to the CSMA / CA protocol, it transmits the RTS message including the first transmission power information with the first transmission power. Here, the first transmission power (

Is the transmit power determined using the minimum threshold power for carrier sensing and the minimum threshold power for data decoding.

)로 재전송한다.If the transmitting terminal fails to receive the CTS message from the receiving terminal and the retransmission of the RTS message is allowed, the RTS message including the predetermined maximum transmission power information is transmitted at the maximum transmission power

).

If the transmitting terminal succeeds in receiving the CTS message from the receiving terminal, the transmitting terminal can transmit the data using the second transmission power information included in the CTS message.

)를 계산하고, 계산된 거리를 이용하여 제2전송 파워(

)를 계산한다. 그리고 수신 단말은 제2전송 파워 정보를 포함하는 CTS 메시지를 송신 단말로 전송하며, 송신 단말로부터 데이터가 수신될 경우 ACK 메시지를 송신 단말로 전송한다. ACK 메시지에도 제2전송 파워 정보가 포함될 수 있다.
The receiving terminal receives the RTS message and determines the distance from the transmitting terminal

), And calculates the second transmission power (

). The receiving terminal transmits a CTS message including the second transmission power information to the transmitting terminal, and transmits an ACK message to the transmitting terminal when data is received from the transmitting terminal. The second transmission power information may also be included in the ACK message.

8 is a view for explaining a power control apparatus according to a specific embodiment of the present invention.

8, the power control apparatus according to the present invention includes an input interface 810, a received message type determination unit 820, a setting unit 830, a controller 840, and an output interface 850. The setting unit 830 includes a distance calculation setting unit 831, a power calculation setting unit 833, an interference calculation setting unit 835, and a message type setting unit 837.

The input interface 801 receives a message from the node, and the received message type determination unit 803 determines the type of the received message using the message type field of the received message. The distance calculation setting unit 831 calculates the distance to the node by using the information included in the received message and the interference information between the nodes calculated by the interference calculation setting unit 835. The power calculation setting unit 833 calculates the transmission power using the calculated distance. The message type setting unit 837 determines the type of a message to be transmitted according to the received message.

The control unit 840 controls the components of the power control device and allows information and messages generated in the setting unit 830 to be transmitted through the output interface 850.

The above-described technical features may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (10)

A method of controlling power of a transmitting terminal in a wireless network,
Generating first transmission power information using a first minimum-threshold power for carrier sensing and a second minimum-threshold power for data decoding;
Transmitting an RTS message including the first transmission power information at the first transmission power;
Receiving a CTS message including second transmission power information from a receiving terminal that has received the RTS message; And
Transmitting data using the second transmission power information
≪ / RTI >
delete The method according to claim 1,
The first transmission power
The second minimum-threshold power being proportional to the first minimum-threshold power,
Power control method.
The method according to claim 1,
The transmission power of the CTS message is
And is determined according to the second transmission power information
Power control method.
delete delete delete delete delete delete

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