KR101682136B1 - Apparatus, method and program for transmission power control - Google Patents

Abstract

The present invention relates to a transmission power control apparatus, and more particularly, to a transmission power control apparatus including a TPC communication unit for transmitting and receiving a packet; An RSSI controller for calculating an average received signal strength value using a received signal strength indication every time the packet is received; And a TPL controller for changing a transmission power level when the average received signal strength value deviates from a target received signal strength indication range (target received signal strength indication margin).

Description

TECHNICAL FIELD [0001] The present invention relates to a transmission power control apparatus, a transmission power control apparatus,

The present invention relates to an apparatus, a method, and a computer program for controlling transmission power, and more particularly, to a transmission power control apparatus utilizing a received signal strength value collected by a sensor used in a wireless human body sensor field, .

Although the Wireless Sensor Network (WBSN) is gradually evolving to meet the needs of the development of WSN (Wireless Sensor Network) technology, miniaturization of devices, and human needs, there are various restrictions to integrate existing WSN into WBSN technology. WBSN technology attaches sensors to people's clothing and bodies, and even transplants sensors to the skin for the purpose of improving health care and quality of life. Therefore, since the network is formed inside and outside the human body, the number of nodes and the number of nodes is relatively reduced, but the tasks of nodes are various. In terms of network topology, if the WSN is fixed, the WBSN can be more varied due to the movement of the person wearing the sensor. Therefore, factors that create a dynamically changing channel environment should also be considered. In addition, energy acquisition resources should also take into account the effects of motion.

Power technologies such as Media Access Control (MAC) and Transmission Power Control (TPC) technology are typical technologies for efficiently operating the energy of sensor devices placed inside and outside the human body. Low-power MAC technology is designed to reduce collisions, overhearing, control packet overhead, or idle listening, which are key energy-wasting factors in wireless data communications. It is a way to save money. In TPC technology, existing TPC algorithms exist as Linear, Binary, and Dynamic algorithms, which are divided according to the level changing method. Existing TPC algorithm has a lot of control energy because of the oscillation phenomenon due to the restriction of the channel environment or the frequent change frequency. In addition, there is a disadvantage in that data is consumed in a large amount because the packet is transmitted at an inappropriate level.

The background art of the present invention is disclosed in Korean Patent Laid-Open Publication No. 2009-0065620 (published on Jun. 22, 2009, an address conversion system and method using a unique identifier for interworking with an IP-based system and a WSN node).

Accordingly, the present invention provides a transmission power control apparatus including a straight line-based TPC algorithm capable of quickly finding a suitable level of data packet transmission, and a method therefor.

The present invention provides a transmission power control apparatus for analyzing a correlation between a transmission power level and a received signal strength value in various channel environments and setting an optimum transmission power level while changing a transmission power level at a minimum number of times do.

According to an aspect of the present invention, there is provided a transmission power control apparatus.

A transmission power control apparatus according to an embodiment of the present invention includes a TPC communication unit for transmitting and receiving a packet; An RSSI controller for calculating an average received signal strength value using a received signal strength indication every time the packet is received; And a TPL control unit for changing a transmission power level when the average received signal strength value is out of a target received signal strength indication range (target received signal strength indication margin).

According to another aspect of the present invention, there is provided a transmission power control method and a computer program for executing the same.

A transmission power control method and a computer program therefor according to an embodiment of the present invention include receiving a packet from a sensor device; Calculating an average received signal strength value using the received signal strength value each time the packet is received; And changing the transmit power level if the average received signal strength value is out of the range of the target received signal strength.

The present invention can reduce the unnecessary transmission power level change frequency by reducing the transmission power level suitable for the channel environment in a stage faster than existing TPC algorithms, and can eliminate the phenomenon of not being able to find the correct transmission power level and vibrate.

Thus, the present invention has the advantage of reducing the overall energy consumption and the probability of loss of data packets, rather than sending the data packets at an improper transmission power level.

1 is a diagram illustrating a transmission power control system according to an embodiment of the present invention.
2 is a view for explaining a transmission power control apparatus according to an embodiment of the present invention.
3 is a view illustrating a sensor device according to an embodiment of the present invention.
4 is a view for explaining a transmission power control method according to an embodiment of the present invention.
5 is a diagram for explaining a method of calculating a slope of a linear regression equation according to an embodiment of the present invention.
6 is a diagram illustrating a method of estimating a transmission power level according to an embodiment of the present invention.
7 is a view for explaining pseudo code of an algorithm implementing a transmission power control method according to an embodiment of the present invention.
8 is a view for explaining the relationship between the number of packets and the average TPL for various weight values according to an embodiment of the present invention.
9 is a diagram for explaining total energy consumption for various weight values according to an embodiment of the present invention.
10 is a diagram illustrating the total energy consumption for an algorithm according to an embodiment of the present invention.

While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and similarities. 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, the singular phrases used in the present specification and claims should be interpreted generally to mean " one or more " unless otherwise stated.

1 is a diagram illustrating a transmission power control system according to an embodiment of the present invention.

In the body sensor network environment, various channel states can be configured according to the position of the sensor device, the position of the transmission power control device, the motion of the subject, and the location. Hereinafter, a system for changing the transmission power level of a packet by the transmission power control apparatus and the sensor apparatus in various channel states will be described.

Referring to FIG. 1, a transmit power control system 100 may include a data acquisition device 110, a gateway node 120, a transmit power control device 130, and a sensor device 140.

The transmission power control system 100 uses TPC (Transmission Power Control) technology in a human body sensor network to save energy by controlling transmission power when a sensor device sends a data packet to a transmission power control device. Here, the TPC technique dynamically adjusts the transmission power level (TPL) to the current channel state to maintain a proper RSSI (Received Signal Strength Indication). Basically, if the TPL of the transmitting node is high, the RSSI value of the receiving node is high, and if the TPL of the transmitting node is low, the RSSI value is also low. However, this relationship can be changed by the channel state of the dynamically changing human sensor network environment. For example, even if a packet is transmitted from the transmitting node to the same TPL, the RSSI value is high in the receiving node if the channel status is improved, but the RSSI value may be low in the receiving node if the channel status is deteriorated. Therefore, it is very important to find a proper TPL considering energy efficiency in various dynamically changing wireless human sensor network channel environment in TPC technology.

The data collection device 110 may issue a command command to the gateway node 120 according to a user's instruction. The data collecting apparatus 110 may be a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP) slate PCs, tablet PCs, ultrabooks, and the like.

The gateway node 120 may receive a command command from the data collecting apparatus 110 and transmit the received command command to the transmission power control apparatus 130. Generally, the gateway node 120 is closely connected to the transmission power control device 130 to interwork with the wireless sensor network and the Internet. 1, the gateway node 120 and the transmission power controller 130 are described as being separated from each other, but they can be used together.

The transmission power control device 130 sets the current power level, the timer, and the first log data through the received command command. The transmission power control device 130 transmits data to the sensor device 140 in accordance with the set timer.

The sensor device 140 may measure the received signal strength value of the received data and store the second log data in the data collection device 110. [ When the gateway node 120 requests the sensor device 140 to log the log data through the log extraction command (for example, Get Log), the sensor device 140 sends the log data to the gateway node 120 to the data collection device 110 The stored measurement values can be transmitted.

2 is a view for explaining a transmission power control apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the transmission power control apparatus 200 includes a TPC communication unit 210, an RSSI control unit 220, and a TPL control unit 230.

The TPC communication unit 210 receives the packet transmitted from the sensor device.

The RSSI control unit 220 extracts a received signal strength value immediately when a packet is received.

The RSSI controller 220 calculates an average received signal strength value using the extracted received signal strength value. If the current received signal strength value is within the target received signal strength range, the deviation of the received signal strength value can not be overcome. If the channel condition is unstable, the control packet is excessively generated. Lt; / RTI >

The calculation method is as follows.

[Equation 1]

The average received signal strength value can be obtained by multiplying the weight value of the current received signal strength value by (1-weighted) the average received signal strength value. The weights are shown in Table 1 below.

The weighted average received signal strength value is used to determine whether or not the received signal strength value is included in the target received signal strength range. Therefore, the deviation of the received signal strength value can be overcome. At this time, the target received signal strength means a range of values in which the transmission power level does not need to be changed within a range in which a predetermined value is increased or decreased from the target received signal strength value.

If the average received signal strength value is included in the target received signal range, the TPL controller 230 transmits the packet at the same level as the previously transmitted transmission power. However, if the average received signal strength value is not included in the target received signal range, the packet is transmitted at a new transmission power level using a predetermined slope value. The method of predicting the transmission power level will be described in detail with reference to FIG.

3 is a view illustrating a sensor device according to an embodiment of the present invention.

Referring to FIG. 3, the sensor device 300 includes a sensor communication unit 310 and a sensor TPL control unit 320.

The sensor communication unit 310 can transmit the packet at the set transmission power level.

The sensor TPL control unit 320 can notify the transmission power control unit of the new transmission power level and change the setting to the new transmission power level.

4 is a view for explaining a power control method according to an embodiment of the present invention.

Referring to FIG. 4, in step S400, the sensor device transmits a data packet at a set current transmission power level. At this time, the current transmission power level can be transmitted as a maximum value to prevent the loss of the data packet in order to grasp the current channel state.

In step S410, the transmission power controller 130 extracts the received signal strength value in real time every time a packet is received.

In step S420, the transmission power controller 130 calculates an average received signal strength value using the extracted received signal strength value. At this time, a moving average can be used as a method of calculating the average received signal strength value.

In step S430, the transmission power controller 130 determines whether the average received signal strength value is included in the range of the target received signal strength. If yes, the process goes back to step S400 to send and receive packets again.

If not included in step S420, the transmission power controller 130 predicts a new transmission power level using a predetermined slope value in step S440.

In step S450, the transmission power control apparatus 130 transmits the packet with a new transmission power level.

5 is a diagram for explaining a method of calculating a slope of a linear regression equation according to an embodiment of the present invention.

Referring to FIG. 5, a graph showing an average received signal intensity value according to a transmission power level in various channel environments can be seen. Each legend shows the location of the sensor device, the location of the experiment, and the movement of the user, which are factors that determine the channel status. In addition, a straight line representing each channel state means an average value of the received signal strength values measured through experiments. In the graph shown in FIG. 6, a slope of a simple linear function that minimizes a difference from each straight line can be derived, and this slope becomes a linear linear regression equation. Since the slope of the straight line converges to a specific slope even if the distance is changed, it can be a proper slope value reflecting the rapidly changing wireless body sensor network environment.

6 is a diagram illustrating a method of estimating a transmission power level according to an embodiment of the present invention.

Referring to FIG. 6, a straight line equation can be obtained using a preset slope value representing a wireless human body sensor network environment, and a new transmission power level can be predicted therefrom. Specifically, when it is determined that the average received signal strength value calculated by the transmission power control apparatus is out of the target received signal strength range, a new transmission power level can be obtained using the graph shown in FIG. 6 and Equation (2).

FIG. 6 is a graph illustrating a relationship between a transmission power level and a received signal strength value according to a predetermined slope value representative of a wireless human body sensor network environment using an actual received signal strength value from a current transmission power level, . Here, the predetermined slope value becomes the slope of the linear regression equation. The method of obtaining the slope of the linear regression equation is as shown in FIG.

[Equation 2]

Equation 2 can obtain a new transmission power level by substituting the average received signal strength value, the slope of the linear regression equation s, and the current transmission power level.

7 is a view for explaining pseudo code of an algorithm implementing a power control method according to an embodiment of the present invention.

Referring to FIG. 7, each time a sensor apparatus transmits a data packet and the transmission power control apparatus receives the data packet, the sensor apparatus measures a current received signal strength value, and calculates a weighted average received signal strength value. When the new transmit power level is found out of the range of the target received signal strength, the y intercept is a value obtained by excluding the value obtained by multiplying the slope by the current transmit power by the average received signal strength value. The new transmission power level of the packet to be transmitted next becomes a value obtained by dividing the value obtained by subtracting the y intercept from the target received signal strength value by the slope of the straight line. The algorithm terminates the process after transferring the data packet by a preset cycle.

8 is a view for explaining the relationship between the number of packets and the average TPL for various weight values according to an embodiment of the present invention.

Referring to FIG. 8, the number of control packets generated according to the weight setting and the average TPL can be known. The x-axis represents the weight value, the y-axis on the left represents the number of control packets, and the y-axis on the right represents the mean TPL value.

The smaller the weight value, the larger the weight of the average received signal strength value and the smaller the weight of the current received signal strength value. Therefore, the number of control packets is the smallest at 0.03125 because it responds more slowly to channel changes and reduces the number of control packets. If the number of control packets is small, the energy consumption of sending and receiving control packets is reduced, resulting in a reduction in total energy consumption. However, the mean TPL is lowest at 11.62 when the weight is 0.125 than 0.03125. If the number of control packets is small, even if a data packet is transmitted at an improper transmission power level, the channel change is recognized slowly and the transmission power level is changed slowly. As a result, it can be seen that the energy required for data packet transmission and reception increases, which may adversely affect the total energy consumption.

9 is a diagram for explaining total energy consumption for various weight values according to an embodiment of the present invention.

In the WBSN environment, the total energy consumption of nodes deployed when communicating over a wireless link is the sum of dataTX, controlRX, dataRX, and controlTX. At this time, dataTX is the amount of energy consumed by the sensor device when the data packet is transmitted to the transmission power control device and contorlRX is the control packet when receiving the control packet from the transmission power control device. And dataRX and controlTX represent the amount of energy consumed by the transmission power control apparatus when transmitting the control packet to the sensor apparatus, respectively, when receiving the data packet from the sensor apparatus. The formula for calculating energy consumption for each packet is as follows.

[Equation 3]

TPL 0 One 2 3 4 5 6 7 Transmission current 6.9 7.1 7.4 7.6 7.9 8.2 8.4 8.7 Output power -20 -18 -15 -12 -10 -8 -7 -6 TPL 8 9 10 11 12 13 14 15 Transmission current 8.9 9.4 9.6 9.7 10.2 10.4 11.8 12.8 Output power -5 -4 -3 -2 -One 0 One 2 TPL 16 17 18 19 20 21 22 Transmission current 13.8 14.8 15.8 16.8 20.0 22.1 26.7 Output power 4 5 6 7 8 9 10

In Equation 3, V denotes a power supply voltage,

Represents the energy consumption when transmitted with the corresponding power. S denotes the packet size, and the data packet and the control packet are 36 and 22 bytes, respectively. C denotes the channel capacity.

When a data packet is transmitted at a too high level, energy consumption is too high. Conversely, when transmitting at a low power without consideration of a channel environment, the energy consumption is small, but the probability of loss is high. Therefore, it is very important to find an optimal transmission power level in a fast step and to transmit the data packet to the corresponding level in terms of energy saving, and it can be seen that the present invention is effective in terms of total energy consumption.

Referring to FIG. 9, the total energy consumption according to the weight setting is shown. The x-axis of the graph represents the weight value, and the y-axis represents the energy consumption. It can be confirmed that the energy consumption is the smallest since the difference in the number of control packets is small and the energy required for the transmission power control device to transmit the data packet is reduced. The factors considered in determining the representative weight value are the number of control packets, average TPL, and total energy consumption. 8 and 9, it can be seen that the difference in the number of control packets is insignificant except for the case where the weight is 0.5. Therefore, the data packet is transmitted to the most appropriate TPL on average, and the weight with the lowest total energy consumption is 0.125.

10 is a diagram illustrating the total energy consumption for an algorithm according to an embodiment of the present invention.

Referring to FIG. 10, when each algorithm is executed in the same scenario, the total energy consumption is shown. The x-axis of the graph is the TPC algorithm and the y-axis is the total energy consumption.

According to the present invention, energy consumption is reduced in all elements of controlTX, dataRX, controlRX, and dataTX constituting the total energy consumption. Saving energy by reducing the number of control packets and saving control energy by switching to a more appropriate TPL in a faster phase, resulting in a total energy consumption of 523.48mJ, a minimum of 119%, a maximum of 145% The energy efficiency is improved up to a certain level.

The apparatus and method according to embodiments of the present invention 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.

Program instructions to be recorded on a computer-readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software arts. 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; Includes hardware devices specifically configured to store and execute program instructions such as magneto-optical media and ROM, RAM, flash memory, and the like. The above-mentioned medium may also be a transmission medium such as a light or metal wire, wave guide, etc., including a carrier wave for transmitting a signal designating a program command, a data structure 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 devices described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

The embodiments of the present invention have been described above. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

110: Data collecting device
120: Gateway node
130: Transmission power control device
140: Sensor device

Claims (11)

A transmission power control apparatus for controlling transmission power in a wireless human body sensor network,
A TPC communication unit for transmitting and receiving a packet to and from a sensor disposed inside and outside the human body;
An RSSI controller for calculating an average received signal strength value using a received signal strength indicator (RSSI) every time the packet is received; And
And a TPL controller for changing a transmission power level when the average received signal strength value deviates from a target received signal strength indication range (Target Received Signal Strength Indication Margin)
The TPL control unit
The modified transmission power level is calculated by Equation (2) below,
[Equation 2]

Here, nextTPL is the changed transmission power level, average RSSI is the average received signal strength, s is the slope of the linear regression equation, and currentTPL is the current transmission power level,
Wherein the slope of the linear regression equation is calculated in advance based on an average received signal intensity value received from a sensor disposed in and out of the human body in accordance with a transmission power level in a plurality of channel environments in a wireless human body sensor network. .
The method according to claim 1,
And the RSSI controller extracts the received signal strength value each time the packet is received.
delete delete delete A transmission power control method for controlling transmission power in a wireless human body sensor network,
Receiving a packet from a sensor device disposed inside or outside a human body;
Calculating an average received signal strength value using the received signal strength value each time the packet is received; And
And changing the transmit power level if the average received signal strength value is out of the range of the target received signal strength,
The transmission power level to be changed is calculated by Equation (2) below,
[Equation 2]

Here, nextTPL is the changed transmission power level, average RSSI is the average received signal strength, s is the slope of the linear regression equation, and currentTPL is the current transmission power level,
Wherein the slope of the linear regression equation is calculated in advance based on an average received signal strength value received from a sensor device disposed in and out of the human body in accordance with a transmission power level in a plurality of channel environments in a wireless human body sensor network. Way.
The method according to claim 6,
And extracting the received signal strength value each time the packet is received.
delete delete delete A computer program stored in a computer-readable recording medium for executing the transmission power control method of claim 6 or 7.

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