KR102057899B1 - Apparatus for data transmission and reception by adaptively selecting a network in a mobile station supporting heterogeneous network communication systems - Google Patents

Abstract

According to an embodiment of the present invention, in a method for transmitting and receiving data in a terminal supporting different types of networks, at least one of state information of the terminal, at least one network state information for each network, and size information of data to be transmitted and received Obtaining at least one candidate network that can be used to transmit and receive the data using at least one of the obtaining, at least one of the terminal state information and the network state information, and data for each network combination possible in the determined candidate network. Calculating a cost function for transmission and reception, selecting a network combination having a minimum cost function value among the calculated cost function values for each network combination, and performing data transmission / reception using the selected network combination To include, other than the above embodiment Are other embodiments are possible.

Description

Method and apparatus for adaptively selecting a network and transmitting and receiving data in a user terminal supporting a heterogeneous network communication system

The present invention relates to a method and apparatus for transmitting and receiving data by selecting a network in a user terminal using a heterogeneous network.

Recently, a user terminal supports both a cellular communication network and a wireless LAN network to receive a communication service. Representative examples of the cellular communication network include WCDMA, Long Term Evolution (LTE), WiBro, and the like, and Wi-Fi is a representative example of the WLAN network.

Meanwhile, with the advent of smart phones and high-speed data communication such as LTE, the user terminal transmits and receives high capacity data, while the user of the user terminal provides data service using, for example, any network between LTE and WiFI. You will choose whether to receive it. In general, data service using a cellular communication system such as LTE is additionally charged when the data usage exceeds the data capacity corresponding to the user's subscription plan, but in the case of WiFi, it is generally possible to receive data service without charging. to be.

Meanwhile, although the data transmission / reception rate through the WCDMA system, which is a third generation mobile communication system, has been generally slower than the data transmission / reception rate through WiFi, the data transmission / reception rate in the recent LTE or LTE-A is faster than the data transmission / reception rate using Wifi. Therefore, when WCDMA and Wifi are supported at the same time, users generally use Wifi service, but when LTE or LTE-A and Wifi are simultaneously supported, the user generally selects the cost and data rate.

On the other hand, WiFi is generally known to consume less energy than LTE. However, when WiFi is turned off and the data is transmitted more efficiently, the access point for the WiFi (Access Point: AP) is unconditionally turned on. ), Additional energy is consumed until data can be transmitted, so energy consumption may be less if the data is transmitted over LTE without using WiFi.

When both WiFi and LTE can be used If WiFi and LTE are simultaneously used to distribute traffic from a network perspective, this does not take into account the user's preference or the situation of the terminal. In addition, in order for a user to use only one network or WiFi and LTE simultaneously, a criterion for this selection is required, but the user cannot determine the operation state of the user terminal and the change state of the network that change momentarily.

Therefore, there is a need to adaptively select an efficient network for data transmission and reception in a user terminal supporting heterogeneous communication networks such as a cellular mobile communication system and a WLAN communication system.

An embodiment of the present invention provides a method and apparatus for selecting an optimal network for transmitting data by reflecting an operation state of a terminal and a state of a network in a user terminal supporting heterogeneous networks.

An embodiment of the present invention provides a method and apparatus for setting a weight for transmission time, power consumption, and transmission cost in a user terminal supporting heterogeneous networks, and selecting an optimal network for transmitting data according to the set weight.

An embodiment of the present invention provides a method and apparatus for determining a cost function for selecting a network by reflecting a weight set in a user terminal supporting heterogeneous networks and for selecting a network having a minimum value of the cost function.

An embodiment of the present invention provides a method and apparatus for setting a data transmission rate of a network in order to select an optimal network by reflecting the state of the network in a user terminal supporting heterogeneous networks.

An embodiment of the present invention provides a method and apparatus for selecting a new optimal network by selecting a network for data transmission in a user terminal supporting heterogeneous networks and starting data transmission after reflecting the remaining transmission data size and network status. do.

In a method for transmitting and receiving data in a terminal supporting different types of networks provided by an embodiment of the present invention, at least one of state information of the terminal, at least one network state information for each network, and size information of data to be transmitted and received is obtained. Determining at least one candidate network that can be used for data transmission and reception using at least one of the terminal state information and the network state information, and transmitting and receiving data for each network combination possible in the determined candidate network. Calculating a cost function for a; selecting a network combination having a minimum cost function value among the calculated cost function for each network combination; and performing a data transmission / reception using the selected network combination Include.

A terminal device for transmitting and receiving data by supporting different types of networks provided by an embodiment of the present invention includes a terminal information collecting unit collecting state information of a terminal and collecting network information collecting at least one network state information for each network. Determine at least one candidate network that can be used for data transmission and reception by using a unit, an application analysis unit for analyzing size information of data to be transmitted and received, state information of the terminal, and network state information. A control unit for calculating a cost function for data transmission / reception for each possible network combination in the determined candidate network, and selecting a network combination having a minimum cost function value among the calculated cost function for each network combination, and using the selected network combination Send and receive the data Transmission includes parts performing.

Briefly describing the effects of the various embodiments of the present invention are as follows.

In an embodiment of the present invention, in order to select a network for data transmission in a user terminal supporting a heterogeneous communication network, a weight is given to each item by weighting transmission time, energy consumption, and transmission cost in consideration of the transmission preference of the user. It is possible to select an optimal transport network in which priority is reflected.

On the other hand, when selecting a transmission network, the state information of the user terminal, the state information of the network, the size of data to be transmitted, etc. are taken into consideration so that the optimal network can be adaptively selected according to the changing situation, thereby greatly improving the transmission efficiency. You can.

1 is a view illustrating a device configuration of a user terminal according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating detailed items for setting weights and detailed items of a network state through a user interface 110 of a user terminal according to an embodiment of the present invention.
FIG. 3 is a diagram for explaining possible forms of a normalization cost function according to the size of LTE partial data among sizes of total transmission data and an example of selecting an optimal network according to an embodiment of the present invention;
4 is a diagram illustrating a method in a user terminal according to an embodiment of the present invention;
5 (a), 5 (b) and 5 (c) show the relative gains of transmission time, energy consumption and paid data costs according to the ratio of energy already used up to now according to the embodiment of the present invention. Drawings to explain each,
6 (a), 6 (b), and 6 (c) illustrate the transmission time, energy consumption, and paid data cost according to the ratio Bu of the used data to the present allowable data amount according to the embodiment of the present invention. A diagram illustrating each of the relative gains,
7 (a), 7 (b), and 7 (c) are relative gains of transmission time, energy consumption, and pay data cost according to the change in the weight value α with respect to the transmission time according to an embodiment of the present invention. To illustrate each,
8 (a), 8 (b), and 8 (c) illustrate relative gains of transmission time, energy consumption, and pay data cost according to a change in the weight value β for power saving according to an embodiment of the present invention. To illustrate each,
9 (a), 9 (b), and 9 (c) illustrate relative gains of transmission time, energy consumption, and paid data cost according to a change in the weighting value γ for cost saving according to an embodiment of the present invention. To explain each.

Various embodiments of the present invention are described in detail below. It is to be understood that the various embodiments of the invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

Meanwhile, the terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In addition, the terms "comprise" or "having" in the present invention are intended to indicate that there exists a feature, number, step, operation, component, part, or a combination thereof described in the specification, and one or more other It is to be understood that the present invention does not exclude in advance the possibility of the presence or the addition of features or numbers, 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. Terms such as those defined in the commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and are not construed in ideal or excessively formal meanings unless expressly defined in the present invention. Should not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Terms and abbreviations used in the present specification will be described.

The term "data transmission" means that a user terminal transmits or receives various data having a predetermined size such as video, audio, text, and image with an arbitrary data server in order to receive a data service. That is, unless explicitly stated otherwise, in the present invention, "data transmission" is a concept that includes both the user terminal transmits data to the server, and the server transmits data to the user terminal. In addition, in terms of a user terminal, "data transmission" may be used interchangeably with the same meaning "data transmission and reception".

The "LTE communication system" may be used as a representative example of the "cellular communication system", but this description is not intended to limit the present invention to the LTE communication system alone. That is, in the present invention, the LTE system and the cellular communication system may be used interchangeably in the same meaning. In addition, although "WiFi communication system" may be used as an example representing "Wireless LAN communication system", this description is not intended to limit the present invention to only the WiFi communication system. That is, in the present invention, the WiFi system and the WLAN communication system may be used interchangeably in the same meaning.

An “active network” is a network that can receive an identifier of the network from the network when the corresponding network is active and any terminal is located in the coverage of the network and the terminal turns on the network device. Means.

The term "candidate network" means a network that can be used for a combination of networks when selecting an optimal combination of networks proposed by the present invention. The active network is generally included in the candidate network, but may not be included in the candidate network among active networks, or may be included in the candidate network among non-active networks.

"Used network" or "used network", or "selected network", "selected network" are all optimal networks selected for data transmission according to the method proposed by the present invention. Means a combination, and the terms may be used interchangeably in the present specification.

"Combination of networks" means that one network is selected or more than one network is selected. For example, the possible combinations of networks in Networks A, B, and C are <Network A>, <Network B>, <Network C>, <Network A, B>, <Network B, C>, <Network A, C >, <Network A, B, C>.

In the present specification, "transmission time" and "transmission rate" may be used interchangeably in the same concept. In addition, "energy", "power" "battery" can be used interchangeably with the same concept. In addition, “paid data cost” and “data transfer cost” may be used interchangeably with the same concept.

As used herein, the term “average data rate” refers to an average data rate during a time interval in which data is transmitted using a corresponding network or a combination of networks, and unless otherwise stated, “data rate” or “average rate” or “rate”. May be abbreviated or used interchangeably.

In this specification, "user terminal" and "mobile terminal" may be abbreviated as "terminal" or may be used interchangeably.

Prior to the detailed description of the embodiments of the present invention, the basic concepts of the various embodiments of the present invention will be briefly described.

Embodiments of the invention relate to a method for a user terminal to select an optimal network combination for data transmission from among possible combinations of at least one or more candidate networks. For example, to select an optimal network for transmitting and receiving data at a user terminal such as a smartphone using a cellular communication network such as Long Term Evolution (LTE) or WiBro and a wireless LAN such as WiFi. A method and apparatus are disclosed.

To this end, embodiments of the present invention weight the data transmission time, power consumption of the user terminal, and data transmission cost, and normalize costs for transmission time, power consumption, and transmission costs in consideration of each weight. Calculate the function and choose the best network for data transfer with a combination of networks where the entire normalized cost function is minimal. In this case, the state information of the user terminal, the state information of the network, the size of data to be transmitted, etc. may be considered to calculate the normalized cost function.

In addition, when the power of the network device is off, the dynamic host configuration protocol (DHCP) and routing ( routing Consider the additional time delay and power required for network connectivity such as routing. In addition, an additional promotion time delay, promotion power, and tail power consumed before and after data transmission by each network device in a sleep mode may be considered. For reference, the promotion time delay and promotion power refer to a time delay and power consumption for the corresponding network device of the user terminal to be activated in the sleep mode, and the tail power refers to the time until the return to the sleep mode after data transmission is completed. Says power.

Meanwhile, even when the network conditions are the same and weight values for transmission time, power consumption, and transmission cost are the same, an optimal network combination may vary according to the size of transmission data. This is because the cost function of data transmission time, power consumption, and paid data usage can be expressed as a function of data size. In this case, when the size of the data to be transmitted is input, the network status and the weight value of each item are reflected, and the data is continuously transmitted using the network currently connected to the user terminal or by using a combination of new networks. You can choose whether to transfer the data.

Meanwhile, in the step of selecting a network for data transmission before the start of data transmission, an estimated value of the average data rate is estimated for each possible combination of candidate networks, and a network is selected by calculating a cost function using the estimated value. However, after the actual data is transmitted using the selected network, the actual average rate may be different from the expected value of the average rate used in the network selection step. Therefore, after the actual data is transmitted in consideration of these differences, if the average rate considered in calculating the cost function of the currently selected network increases the total cost function value by more than a predetermined range, the new network combination is considered in consideration of the actual average rate. You can also select.

Hereinafter, a cellular communication network and a wireless LAN communication network as heterogeneous communication networks will be described as embodiments. Also, an LTE network is illustrated as a cellular communication network and a WiFi network is illustrated as a wireless LAN communication network. However, embodiments of the present invention reveal that heterogeneous communication networks are not limited to these and can be applied regardless of the number and type of heterogeneous communication networks.

Hereinafter, embodiments of the present invention will be described in detail.

1 is a view illustrating a device configuration of a user terminal according to an embodiment of the present invention.

The terminal information collecting unit 105 monitors the state information of the current user terminal and collects it. The state information of the user terminal refers to information related to whether the current user terminal is configured and used, mobility of the terminal, or operation of the terminal. In more detail, the state information of the user terminal includes “battery level information” of the current user terminal, “monthly data total amount information” according to a plan subscribed to by the user terminal, and “paid data usage information” up to now, and the information includes the control unit. And to the user interface 110. Meanwhile, the monitoring of the state information of the terminal information collecting unit 105 may be performed periodically according to a predetermined cycle, or may be performed by the occurrence of a specific event such as an update request of the controller 125 or a change in the usage environment of the user terminal.

In addition, the state information of the user terminal includes the "mobility information of the user terminal" including the moving speed, the moving range, etc. of the terminal when the user terminal is moving, "display-related information" related to the user terminal display device, the user terminal It further includes "user terminal operation information" on whether it is currently operating. This information is transmitted to the controller 125.

The “mobility information of the user terminal” may be obtained using a signal strength of a network currently connected to the user terminal, an accelerometer, a gravity meter, or a global positioning system (GPS). The “display related information” may include information about whether the display device is on / off and information on brightness of the display in the on state. In addition, the “user terminal operation information” may be determined based on whether a specific application other than a background application is running or whether CPU usage is equal to or greater than a predetermined threshold.

The state information of the user terminal may be used for the operation of the controller 125 and may be used as initial values of values displayed on the user interface 110.

For example, when the state information of the terminal is used in the user interface 110, the user interface 110 may be used as an initial value of an energy use allowance and a pay data allowance using at least one of the received state information of the terminal. I can display it. This will be further explained in FIG. 2 described below.

The network information collecting unit 115 analyzes and collects network state information and transmits it to the controller 125 or the user interface 110. The network state information collection may be performed periodically according to a predetermined period, or may be performed by the occurrence of a specific event such as a request of the controller 125 or an environment change of the network. The network state information includes "active network information" and "average data rate" for each active network. The "active network information" and the "average data rate" will be described later.

The user interface 110 includes a network status display unit 109 and a weight setting unit 107.

The network status display unit 109 displays network status information necessary for the user to set weights for each item of transmission speed, power consumption, and transmission cost. Specifically, the type of the candidate network, the current operating state of the network, the estimated transmission time of the data to be transmitted, the estimated battery consumption when the data is transmitted, and the amount of paid data used up to now are displayed. In this case, the displayed items may be displayed based on the network state information transmitted from the network information collecting unit 115 or the state information of the terminal delivered from the terminal information collecting unit 105.

The weight setting unit 107 allows the user to set weights for each of data transmission speed (transmission time), power consumption (power saving), and transmission cost (cost saving). The weight may be set to a default value or may be set for each item by the user.

The detailed items of the weight setting unit 107 are displayed to the user through the user interface 110 to allow the user to set the weight for the detailed items. The weight thus set is transmitted to the controller 125.

FIG. 2 is a diagram illustrating that detailed items for weight setting and detailed items of network status are displayed through the user interface 110 of the user terminal.

The network status display unit 109 displays the type of the current candidate network, the current operating state of the network, and detailed items related to data transmission in the network. The information is based on the network state information transmitted from the network information collecting unit 115 or the terminal information collecting unit 115.

 Specifically, the LTE 211 and the WiFi 212 are displayed as candidate networks, and the LTE 211 and the WiFi 212 are currently being used while the LTE is turned on, and the WiFi is in use.

In addition, the detailed items include transmission time 213, battery consumption 215, and paid network usage 217. The transmission time 221 item may display a value related to a transmission time such as an estimated transmission time of all data and / or a remaining transmission time during the current data transmission, and may be updated in real time as data is transmitted and received. .

In addition, the minimum transmission rate requirement 214 may be displayed in relation to the transmission time 221 item. The minimum transmission rate requirement 214 initial value may be set to a minimum value of the data rates of candidate networks, the user being larger than the set initial value, and smaller than the sum of the data rates of the candidate networks (LTE and WiFi in FIG. 2). Can be set within the range of values. The minimum transfer rate requirement amount 214 set by the user is transmitted to the controller 125.

The battery consumption 215 item may display a value related to the power of the user terminal when transmitting and receiving data using a corresponding network, such as an estimated battery consumption when the entire data is transmitted / received, battery consumption so far, and the like. In addition, when the display screen of the user terminal on (on) and off (off) may be displayed separately for each. For example, when the display is on, the battery consumption by the display can be expressed as the product of the average power value of the display and the expected transmission time value, which is added to the expected battery consumption by the data transfer. Can be.

An energy usage allowance 216 item may be displayed in relation to the battery consumption 215, and an initial value thereof may be set as a current battery remaining amount and set by a user within a range smaller than the initial value. The energy use allowance 216 value set by the user is transmitted to the controller 125.

 The paid network usage (217) column shows values related to paid data usage when data is transmitted using the network, such as the expected paid data usage and / or the paid data usage to date. Can be.

The paid data allowance 218 may be displayed in relation to the paid network usage 217, and if the user terminal subscribes to the data service with the data flat rate plan, the remaining amount of data currently available among the monthly quota of the subscription data and / Alternatively, the monthly quota of subscription data divided by the number of days in the month (typically, 30 days) may be displayed, such as the current amount of available data compared to the available paid data per day, which can be increased or decreased by the user. do. The paid data allowance amount 218 set by the user is transmitted to the controller 125.

In the detailed items of the weight setting unit 107, a weight setting bar for each of the transmission rate weight 231, the power saving weight 232, and the cost saving weight 223 is displayed. A weight desired by the user may be set for each item using the weight setting bar. At this time, the weight of each item may be selected as a value between “high” and “low” or “not considered”, and “low” has a value of 1 and “high” is, for example, 10 It has a value of, and the closer to "high", the larger the weight value. On the other hand, if you choose "not considered", the weight value of the item becomes 0 and the item is excluded from the cost function calculation and is not considered for network selection.

1, the application analyzer 120 analyzes the type of the application 135 related to the data to be transmitted and the operation state of the corresponding application 135 to analyze the size of the data to be transmitted and the size of the data to be transmitted. The information is transmitted to the controller 125. The size of the data to be transmitted analyzes the size of the entire data to be transmitted or the data size to be transmitted during the transmission session or the size per file of the data to be transmitted to the control unit 125.

On the other hand, the application 135 may inform the controller 125 of the size information of the data to be transmitted. When an event for data transmission and reception between the terminal and the server occurs, when the data is transmitted from the terminal to the server, the application 135 of the terminal may inform the data size information. When the server transmits data to the terminal, the server may transmit the terminal application ( 135, the application may inform the controller 125 of the data size information.

The controller 125 receives the state information of the user terminal from the terminal information collecting unit 105, receives the weight values from the weight setting unit 107, and activates the "active network information" and the active from the network information collecting unit 115. Network status information including the “average data rate” for each network is received, and the size of data to be transmitted is transmitted from the application analyzer 120 or the application 135.

The controller 125 determines the "candidate network" using the state information of the network and / or the state information of the terminal. In particular, the candidate network may be determined using “active network information” of the network state information and “terminal mobility information” or “terminal operation information” of the terminal state information.

For example, it is possible to know whether a WiFi network or an LTE base station exists in an area adjacent to a terminal by using “active network information” among network state information. Therefore, it is common to determine a network included in active network information as a candidate network.

However, some of the active networks may not be included in the candidate network, and a network other than the active network may also be a candidate network. Such a case may occur especially when considering mobility information of a terminal while determining whether a WiFi network is a candidate network.

 For example, it is assumed that the terminal is located within the coverage of the LTE base station A and the WiFi AP B coverage. In addition, since the coverage of the LTE base station is generally much larger than that of the WiFi AP, several WiFi APs may exist within the coverage of the base station A, so that the WiFi AP C exists in the coverage of the base station A, and the AP C is Although it is in an area adjacent to AP B, the terminal has previously communicated with AP C, so it is assumed that the location of AP C is known, but is not currently located in the coverage of C.

Under these assumptions, if both the LTE device and the WiFi device of the terminal are in the current position, when the network information collection unit 115 collects network state information, the base station A and the WiFi AP B becomes an active network. On the other hand, since the terminal is not located in the coverage of WiFi AP C, WiFi AP C will not be included in the active network.

In this case, the terminal may know its location based on the base station A or the WiFi AP B as described above. On the other hand, if the terminal is currently moving and the moving speed of the terminal is very large and the strength of the received signal from the WiFi AP B is weakening, the terminal will be out of coverage of the WiFi AP B after some time. Therefore, the terminal may not transmit or receive data with the WiFi AP B. Therefore, in this case, the WiFi AP B, which is the active network, may not be determined as the candidate network. That is, the candidate network may be determined using the received signal strength in the active network and the mobility information of the terminal.

On the other hand, if the terminal is in the direction of coverage of the WiFi AP C, the terminal will enter into the coverage of the WiFi AP C. Therefore, in this case, the terminal may determine the WiFi AP C that is not included in the active network as the candidate network. That is, a network not included in the active network information may be determined as the candidate network using the mobility information of the terminal and the location information of the terminal.

In summary, it is common for a terminal to determine a candidate network using network state information, in particular, active network information in a normal case, but in a special situation such as a terminal moving, state information of the terminal, in particular, mobility information of the terminal. The candidate network may be determined using location information of the terminal and received signal strength of the active network.

On the other hand, it is determined from the "user terminal operation information" whether the user terminal is currently performing an application or other operation requiring transmission and reception of user data, and if the terminal is operating, the candidate network is determined and the terminal is not operating. If not, then determining the candidate network is pointless, so we no longer decide on the candidate network.

In addition, the controller 125 calculates a normalized cost function for possible combinations of candidate networks using the information received from the respective functional blocks. That is, when only LTE is used, when only WiFi is used, a normalization cost function is calculated for each of the LTE networks and WiFi simultaneously. In this case, the control unit 125 may use the energy use allowance and the paid data allowance value as the normalization factor of the energy cost and the pay data cost when calculating the normalization cost function. The method of calculating the normalized cost function will be described in detail later.

Meanwhile, the controller 125 selects a network or a combination of networks for which the calculated normalized cost function is minimized, and activates the corresponding network device when the network device of the terminal corresponding to the selected network is inactive. Thereafter, the information on the selected network is transmitted to the transmitter 130.

The transmission unit 130 receives the selected network information from the control unit 125, and if the selected network is a single network, establishes a communication connection with a server for an arbitrary communication service by using a single stream for data transmission, and transmits the data. send. On the other hand, when two or more networks are selected at the same time, after establishing a connection with a server using a multi-stream constituting a stream for each network, the data transmitted from the application 135 for data transmission is divided or transmitted, or received from the server. The divided data is transmitted to the corresponding application 135.

Hereinafter, the "active network information" and the "(average) data transmission rate" described in the network information collecting unit 115 will be described in detail.

The “active network” may receive an identifier of the network from the corresponding network when the corresponding network is activated and any terminal is located within the coverage of the corresponding network and the terminal turns on the corresponding network device. Means a network, and “active network information” means information about the active network. “Active network information” may include “active network identifier”, “on / off state information” of a network device in a user terminal for connecting to the network, and the network device is in an on state and corresponding When connected to the network may include "connection mode information" indicating the connection state of the terminal. However, since "active network information" must include the "active network identifier", "active network information" can be used as the same meaning as "active network identifier" unless otherwise stated. Specifically, an example of "active network information" is described below.

For example, if the LTE base station A is active, the LTE device in the current terminal is on, connected to the LTE base station A, and currently connected to the "sleep mode", the "active network information" is the "LTE network A Contains information such as "active status", "LTE device on", "LTE network connection", and "sleep mode". Similarly, if the WiFi AP B is active, the WiFi device in the terminal is currently on and connected to the WiFi AP B, the "active network information" is "WiFi AP B-active state", "WiFi device on", Includes information such as “WiFi Network Connection” and “Sleep Mode”.

If the LTE base station A is active and the current LTE device is on but not connected to the LTE base station A, the "active network information" is "LTE base station A- active state", "LTE device on", "LTE network not connected" Information ”. Similarly, if the current WiFi AP B is active and the WiFi device is on but not connected to the WiFi network, the “Active Network Information” will be “WiFi AP B-Active”, “WiFi Device On”, “WiFi Network Unconnected ”information.

If the LTE base station A is in an active state and the LTE device in the terminal is in an off state, the active network information may include information such as “LTE base station A-active state” and “LTE off”. Similarly, if the WiFi AP B is in the active state and the WiFi device in the terminal is in the off state, the active network information may include information such as “WiFi AP B-active state” and “WiFi off”.

Hereinafter, a method of determining an average transmission rate in the network information collecting unit 125 will be described.

In relation to the “average rate” for possible combinations of candidate networks, the network information collector 115 may determine the data rate as described below.

In the embodiment of the present invention, since there is no data actually transmitted in the step of selecting an optimal network before data transmission, the “actual data transmission rate” transmitted through the actual network is not known. Therefore, data rates for combinations of candidate networks must be predicted or estimated.

In an embodiment of the present invention, when a terminal transmits and receives data, the terminal may make a data rate through each network at a corresponding location, and when the terminal transmits and receives data at the same location again, the data rate may be used again.

The following describes a method in which the terminal pre-databases the data rate.

First, when the terminal is currently connected to the first network, the location information of the user terminal can be known based on the first network, and the average transmission rate while transmitting and receiving data through the first network at the current location of the terminal is measured.

In addition, the average transmission rate during transmission and reception of data through the second network is measured by connecting to the second network at the location of the user terminal based on the first network. As such, the location of the user terminal based on the first network, the average transmission rate in the first network, and the average transmission rate of the second network may be mapped and stored.

After storing the location of the user terminal and the average transmission rate for each network, when the user terminal sends and receives data through the first network or the second network at the corresponding location, the stored average transmission rate is estimated by the average transmission rate of each network. Can be used as a value.

In the same way, the location information of the user terminal based on the second network, the average transmission rate of the second network and the average transmission rate of the first network are mapped and stored, and then the user terminal is again located in the corresponding location based on the second network. When is in the average transmission rate of the stored first network and / or the average transmission rate of the second network may be used as an estimated value of the average transmission rate per network (combination).

 For example, the above description is as follows.

When the user terminal is connected to the current LTE network, the location of the current user terminal is determined based on a signal received from the current LTE base station. For example, the current location of the user terminal may be represented in the following format by using a cell ID (CID) of a currently connected base station and signal strength from a base station, a CID of a neighboring base station, and signal strength information from a neighboring base station. have.

(CID # 1: [-80, -75 dBm], CID # 2: [-100, -95 dBm])

CID # 1: [-80, -75 dBm] indicates the current base station identifier and signal strength of the signal received from the current base station, and CID # 2: [-100, -95 dBm] indicates the neighbor base station's identifier and neighbor Indicates the signal strength of the signal received from the base station.

The user terminal measures an average data rate of data transmitted and received with the LTE base station connected from the current location. On the other hand, the average data rate may be measured for each predetermined time interval.

In this way, while the terminal is transmitting and receiving data through the LTE base station, when the terminal is connected to the first AP by turning on the WiFi (ON) occurs, the average transmission rate through the first AP is measured. Thereafter, the user terminal corresponds to an average transmission rate through the corresponding LTE base station according to the location information of the terminal based on the LTE network, a basic service set identifier (BSSID) of the first AP and the first AP, the first AP and the BSSID. Map the average rate through and store in the terminal.

Even if the location of the terminal based on the LTE network is the same, if the terminal is connected to WiFi through a second AP different from the first AP, the average transmission rate through the second AP may be stored. That is, in the case of WiFi, the average transmission rate can be stored for each AP. For reference, the BSSID refers to a network ID for identifying a basic service set (BSS) in IEEE 802.11.

The same applies to the reverse case. That is, if the network to which the current terminal is connected is WiFi and the LTE device is turned off, the channel number, BSSID and received signal strength of the first AP to which the user terminal is currently connected, and the channel number, BSSID and signal strength of the neighboring second AP are used. The location information of the current terminal can be known. Then, when data is transmitted and received through the LTE network at the corresponding location, the CID and the average data rate of the corresponding LTE base station is measured and mapped to the location information of the WiFi-based terminal and stored. The location of the terminal and the average data rate for each network are continuously updated within the range allowed by the memory of the terminal.

As described above, if the average transmission rate for each network is stored in advance based on the location of the user terminal, the network information collecting unit 115 may determine the average transmission rate as follows.

First, the average transmission rate of unconnected networks is determined when only one network is currently connected and no other network is connected.

If an average transmission rate in another network mapped to location information based on the network to which the terminal is connected is stored, the average transmission rate in the other network may be determined as the average transmission rate in the stored other network. In the above example, if the average data rate information in the WiFi network corresponding to the LTE-based location information is stored while connected to the LTE network and not connected to the WiFi, the network information collecting unit 115 may store the The maximum or minimum value of the average transmission rate information of the WiFi network, or a specific value or a stored average value between the maximum and minimum values may be determined as the average transmission rate of the WiFi network.

Secondly, when the terminal is connected to the network, the terminal determines the average transmission rate in the connected network.

One way is to monitor the state of the network over a period of time to determine the average rate of transmission of the network, which may be more accurate than using a stored database. For example, the average transmission rate in the desired network may be determined using at least one of signal strength from the LTE base station or signal strength from the AP, channel state, network load information, and air time information. Specifically, in case of LTE, a reference signal transmitted periodically by the base station can be received to know the average signal strength from the base station, and the load information of the network can be known from the system information. The average transmission rate in the network can be estimated. In the case of WiFi, signal strength and channel information can be known through beacon information periodically transmitted from the AP, and the average transmission rate can be estimated.

Alternatively, if the network device was in use within a predetermined time interval T before the current time point, and the position change of the terminal estimated from the received signal strength from the base station or the AP is within a predetermined threshold, the T time. The average transmission rate can be determined as the average transmission rate of the corresponding network.

Another way is to use the average rate already stored in the user terminal as described above. That is, if the location information of the terminal estimated from the signal strength received from the LTE base station or the WiFi AP and the average transmission rate for the past time interval corresponding to the current time interval are already stored, the average transmission rate for this past time interval Is determined as an average rate expected value corresponding to the current time interval.

In addition, as a result of combining the average rates determined in the above-described three schemes may be determined as the average rate of the network. For example, the above-described three kinds of arithmetic averages may be used, or arithmetic averages given predetermined weights to the respective result values may be used.

On the other hand, the average transmission rate is determined before the data transmission by the above-described method, and since the actual data transmission is performed after the optimal network is selected based on this, the actual average transmission rate can be calculated.

Therefore, when a network is selected and data is being transmitted using the selected network, the network state collecting unit 115 periodically monitors the data rate for each network in use, obtains an average rate, and delivers the average rate to the controller 125. . If a predetermined network selection update request occurs or the update cycle arrives, the controller 125 uses this value to obtain a new normalized cost function.

In the meantime, although the data rate is determined by the “average” data rate, the “momentary” data rate may be considered if necessary instead of the “average” data rate.

Hereinafter, operations of the controller 125 will be described in detail.

First, the normalization cost function for data transmission proposed in the embodiment of the present invention will be described.

The controller 125 transmits the weight value received from the weight setting unit 107, the terminal state information received from the terminal information collecting unit 105, the network state information received from the network information collecting unit, and the application analyzing unit 120. When using only LTE for data transmission using the data transfer amount per received transmission session (LTE-only), using only WiFi (WiFi-only), and simultaneously using LTE and WiFi (LTE + WiFi) Calculate the value of the normalized cost function by adding the normalized values of the transmission time cost, energy consumption cost, and paid data cost for each possible combination of the two.

Hereinafter, a method of calculating the normalized cost function will be described.

When the total size of data to be transmitted is B _tr , and the size of data to be separately transmitted using LTE and WiFi is B ^c _tr and B ^w _tr , B _tr = B ^c _tr + B ^w _tr is established. The total normalized cost function of is expressed by Equation 1.

Equation 1 consists of the sum of three normalized cost functions, the first item being a normalization cost function for transmission time (speed), and the second item being a normalization cost function related to energy (battery) consumption. The third item is the normalization cost function associated with the paid data cost.

The normalized cost function for each item is determined by (weighted X normalization factor X itemized cost model). For example, in the transmission time normalization cost function, which is the first item in Equation 1, α is a weight value of transmission time, n _e is a normalization factor, and a max operation item is a cost model of transmission time. The cost model of the transmission time models the transmission time of the data. That is, in the modeling of the transmission time, a larger value of the transmission time of the data transmitted through the LTE and the transmission time of the data transmitted through the WiFi becomes the transmission time of the entire transmission data. Time is formulated. The second item, the cost model of energy consumption, is also modeled after estimating energy consumption, and the cost model of paid data cost is also modeled by estimating paid data cost.

In Equation 1, α, β, γ, and n _t , n _e , n _c will be described first.

α, β, and γ denote weight values for transmission time, power saving, and cost saving, respectively.

n _t , n _e , and n _c are normalization factors for normalizing transmission time cost, energy consumption cost, and pay network use cost, respectively. The value of these normalization factors is set to the inverse of the maximum allowable value for each item.

As to the transmission time, the value obtained by dividing the transmission data size by the minimum transmission rate or the minimum transmission rate requirement set by the user becomes the maximum allowable value in the transmission time, and thus the inverse of this value can be set to n _t .

As for the energy (battery) consumption amount, since the current battery remaining amount or the energy use allowance set by the user becomes the maximum allowable value in the energy consumption amount, the inverse of this value can be made n _e .

Regarding paid data usage, the amount of data remaining after subtracting paid data from one month's fixed data or the amount of fixed data for one month divided by the number of days in the month (typically 30 days) is converted into one day's data volume. Since the remaining amount of data per day minus the data used up to that day, or the paid data allowance set by the user becomes the maximum allowable network usage allowable at the time of the current data transmission, the inverse of these values can be set as n _c .

The relationship between the normalization factor and the cost model of the item is as follows.

For example, if the current battery has 100 percent remaining and 100 is set to the maximum energy consumption cost, then the normalization factor n _e for the energy consumption cost is 1/100 of the inverse. Therefore, in a typical situation, multiplying the normalization factor by the value of the item's cost model does not exceed the maximum.

However, if the value obtained by multiplying the normalization factors and the cost model of the item exceeds 1, it means that the estimated cost value of the item exceeds the maximum allowable cost of the item. This means that the cost of the item is excessively high, and if a combination of networks having such a cost function value is selected, the overall transmission cost becomes very high and inefficient. Therefore, such a combination of networks needs to be excluded when selecting a network for data transmission. The following scheme can be used to exclude this.

That is, if the value obtained by multiplying the normalization factor and the cost model exceeds a predetermined value (“1” in the above example), the resultant value is a penalty greater than the predetermined value (for example, 10). By multiplying the value, the cost function of that item is further increased so that the value of the total normalized cost function containing the item is much larger than the normalized cost function value of the combination of other networks. This makes the normalization cost function of the combination of networks that contain that item very large, preventing the combination of networks from being selected as the optimal network combination. For example, when the value of the energy consumption model E _tr becomes so large that n _e · E _tr ≧ 1, the value of n _e · E _tr is replaced with O _e >> 1 (eg, 10). The same method can be applied to the transmission time and the paid data usage. In this case, each substituted value is denoted by O _t , O _c . Similarly, without considering the normalization factor, if the value of the cost model of a particular item exceeds the value of the maximum allowable cost for that item, the network containing that item may not be selected.

Hereinafter, the cost model for each item will be described in Equation 1 above.

First, in Equation 1, a factor related to the transmission time (speed), which is the first item, and modeling of the transmission time using the same will be described.

B ^c _tr : size of data transmitted through LTE (LTE partial data),

r _c : LTE average transmission rate (LTE average transmission rate),

B ^w _tr : Size of data transmitted via WiFi (WiFi partial data),

r _w : average transfer rate of WiFi,

t ^c _sw : Delay time (LTE connection delay time) until the LTE device is turned off and on and is connected to the LTE base station to allow the actual data transmission, and is set to 0 if the corresponding LTE device is on.

t ^w _sw : Delay (WiFi connection delay time) until the WiFi device is turned off, turned on, turned on, connected to the AP, and the actual data can be transmitted, and is set to 0 if the WiFi device is on.

t ^c _oh : Promotion time delay overhead for the LTE device to transition to active state, which starts data transmission from sleep mode state, and a constant value when data transmission is performed in sleep mode state Item added as.

t ^w _oh : Promotional time delay overhead for the WiFi device to transition to active state, which initiates data transfer from sleep mode, constant value when data transfer is performed in sleep mode Item added as.

The total transmission time is LTE transmission time (T ^c _tr (B ^c _tr, r _c , t ^c _sw , t ^c _oh )) and WiFi transmission time (T ^w _tr (B ^w _tr, r _w , t ^w _sw , t ^w) _oh )) can be modeled as the maximum value.

For reference, in Equation 1, the values of the average transmission rates (r _c and r _w ) for each network use the average transmission rates in the corresponding network in the step of selecting a network before the actual data is transmitted.

In this regard, a method of determining an average transmission rate for each network has been described above with respect to the network information collecting unit 115. On the other hand, after the network is selected, while the actual data is being transmitted using the selected network, the average value of the actual data rate from the start of transmission to the present time is used while monitoring the transmission rate of the transmitting network. In this case, the transmission time cost may be reduced by adjusting the amount of partial data for each network transmitted through each network according to the actual average transmission rate.

For example, it was chosen to estimate the average data rate at the network selection stage and to use LTE and WiFi simultaneously as the optimal network, and then the average data rate of each network was different from the average data rate applied at the network selection stage during data transmission. If not, the cost function of the selected network may increase. In this case, you may need to select a new network. However, before selecting a new network, if the total cost function is reduced by adjusting the amount of data transmitted via LTE and the amount of data transmitted via WiFi, considering the average transmission rate of each network, if the total cost function is reduced, You may not need to select a network.

On the other hand, if there is an unused network among LTE or WiFi among factors related to the cost model related to the transmission time, the transmission time value of the unused network becomes 0, and the cost model of the transmission time is related to the network used Only variables will be modeled.

Factors related to energy (battery) consumption, which is the second item in Equation 1, are as follows, and total energy consumption may be modeled as E _tr using the following factors.

B ^c _tr : size of data transmitted through LTE (LTE partial data),

r _c : LTE average transmission rate (LTE average transmission rate),

B ^w _tr : Size of data transmitted via WiFi (WiFi partial data),

r _w : average transfer rate of WiFi,

e ^c _sw : The energy consumption (LTE switch on energy) until the LTE device is turned on and receives an IP address through dynamic IP address allocation (DHCP), etc., and the actual data transmission is possible. At run time, if the LTE device is on, it is 0. If it is off, it has a constant value until it is connected to the LTE network.

e ^w _sw : Energy consumption (WiFi switch-on energy) until the WiFi device is turned off and receives an IP address through dynamic IP address assignment (DHCP), etc. If the WiFi device is on when it is executed, it is 0, and if it is off, it has a constant value until it is connected to the WiFi network.

e ^c _oh : Promotional energy for the LTE device to become active in starting data transmission in sleep mode and tail energy until returning to sleep mode after data transmission is completed. It is the sum of (LTE energy overhead), and is added to a constant value when data transmission is performed in the sleep mode.

e ^w _oh : Promotional energy for the WiFi device to become active when data transfer is initiated from sleep mode and tail energy until returning to sleep mode after data transfer is complete. It is the sum of (WiFi energy overhead), and is added to a constant value when data transmission is performed in the sleep mode.

In addition, the cost model for energy consumption may include an energy value consumed by the screen display of the user terminal. For reference, the energy consumption value of the display is a value obtained by multiplying an average value of power consumption of the display by an expected transmission time of the entire data.

On the other hand, if there is an unused network among the factors related to the energy consumption cost model among LTE or WiFi, the energy consumption value of the unused network becomes 0, and the energy consumption cost model is applied to the network used. Only relevant variables will be modeled.

In the following Equation 1, the third item, the pay data usage factor, is as follows. The pay data usage cost may be modeled as C _tr using the following factors.

B ^c _tr : Data size transmitted via LTE (LTE partial data)

B ^w _tr : Size of data transmitted via WiFi (WiFi partial data)

However, in general, since there is no additional charge for the transmission of WiFi data, the B ^w _tr = 0, and thus the fee for using the paid data will be a function of the LTE partial data B ^c _tr only. In addition, if you use only the WiFi network without using the LTE network, the paid data usage cost will be zero.

Hereinafter, based on Equation 1, a process of expressing a normalization cost function as a function of the size of data to be transmitted for each possible combination of candidate networks will be described.

Suppose that at least one of the weight of the energy consumption and the weight of the paid data usage is not zero, and the weight value of the transmission time is also not zero. In this case, the weight value of the transmission time and the remaining items must also be taken into consideration, so it is common to use both networks rather than to use either WiFi or LTE. However, in order to use both WiFi and LTE networks, the following conditions must be satisfied.

The minimum condition for using the {LTE + WiFi} network at the same time is that the network with a longer connection delay time, which is the time until the network device can start transmitting data, has a shorter connection delay time during the connection delay time. This is when the amount of data that can be transmitted over the network is smaller than the total amount of data to be transmitted. If not, it is not meaningful to transmit data using two networks at the same time, since the entire data transmission can be terminated through the network with the shorter connection delay before the transmission starts in the network with a long connection delay. Because.

For example, assume that the connection delay time of LTE is 1 second, the connection delay time of WiFi is 0.5 second, and the size of data to be transmitted is 1000 bytes. If the data that can be transmitted through WiFi for 1 second is 1100 bytes, all data cannot be transmitted during the LTE connection delay time (1 second), so it is meaningful to use two networks, WiFi and LTE. On the other hand, if the data to be transmitted is 800 bytes, since all of the 800 bytes of data can be transmitted through WiFi during the connection delay time (1 second) of LTE, there is no meaning of transmitting data using both LTE and WiFi simultaneously.

The minimum condition for the relationship between the size of data to be transmitted and the transmission delay time for simultaneously using the two networks as described above may be represented by Equation 2 below.

On the other hand, the <Equation 1> size (B ^w _tr) of the transmitted data to WiFi in, to indicates the size of the transmitted data to the size of the entire transmission data (B _tr) and LTE (B ^c _tr) <Equation 3>.

In addition, if both LTE and WiFi are used at the same time, and the average transmission rates in the two networks are given, the total transmission time will be minimum when the time for transmitting the partial data transmitted to the LTE and WiFi is the same. The transmission time of the LTE partial data and the WiFi partial data is expressed by Equation 4 below. Equation 4 is expressed as a condition under which the values of two operands in the max operator are equal in the transmission time cost function, which is the first item in Equation 1 above.

Therefore, when LTE and WiFi are used at the same time, the total transmission time is minimum when the LTE partial data size satisfies the conditional equation of Equation 4.

Meanwhile, Equation 3 is substituted into Equation 4, and a solution of the LTE partial data B ^c _tr is obtained from Equation 4. If the solution is a value of LTE partial data that minimizes the transmission time when using LTE and WiFi simultaneously, and is represented by B ^{c *} _tr as a symbol, the value is represented by Equation 5.

On the other hand, the Wifi partial data (B ^{w *} _tr ) of which the transmission time is minimized using Equation 5 is expressed by Equation 6 below.

Hereinafter, a process of expressing a normalization cost function for possible combinations of candidate networks as a function of the size of data to be transmitted using Equations 1 to 6 will be described.

If the candidate networks are LTE and WiFi, the possible network combinations using them are (1) LTE network (LTE-only), (2) WiFi network (WiFi-only), and (3) LTE network + WiFi network (LTE + WiFi). . Therefore, for each of the three combinations, the normalized cost function can be obtained using Equation 1. Meanwhile, if values of parameters other than the size of data to be transmitted (B _tr ) are given among the parameters of each normalization cost function, each normalization cost function may be expressed as a linear function of the size (B _tr ) of data to be transmitted. .

Equation (7) below represents the normalized cost function (F ^c _tr ) for LTE-only as a linear function of the data size (B _tr ) to be transmitted. In Equation 1, B ^c _tr = B _tr , B Substitute ^w _tr = 0, t ^w _sw = 0, t ^w _oh = 0, e ^w _sw = 0, e ^w _oh = 0, and summarize them with respect to B _tr .

g _c and h _c are the values corresponding to the slope and y-intercept of the first linear graph of B _tr in Equation 1 in the LTE-only network.

Equation (8) below represents the normalized cost function (F ^w _tr ) for WiFi-only as a linear function of the data size (B _tr ) to be transmitted. In Equation 1, B ^c _tr = 0 and B Substitute ^w _tr = B _tr , t ^c _sw = 0, t ^c _oh = 0, e ^c _sw = 0, e ^c _oh = 0, and summarize them with respect to B _tr .

g _w and h _w are the values corresponding to the slope and y-intercept of the first linear graph for B _tr in Equation 1 in the WiFi-only network.

Equation (9) is expressed as a linear function of the data size (B _tr ) to be transmitted to the normalized cost function (F ^cw _tr ) for LTE + WiFi, when using the LTE + WiFi in Equation (1) at the same time Substitute the size value B ^c _tr = B ^{c *} _tr of the LTE partial data with the minimum transmission time and substitute the size value B ^w _tr = B _tr -B ^{c *} _tr of WiFi partial data from Equation (6). after, B ^{c *} _tr again summarizes about <equation 6> _tr B was substituted by the following formula for the data size B _tr transferred from.

g _cw and h _cw are the values corresponding to the slope and y-intercept when expressing Equation 1 in the linear linear graph of B _tr in the LTE + WiFi network, and are represented by the factors in the parentheses.

As shown in Equations 7 to 9, the normalized cost function in each network is linear with respect to the size (B _tr ) of data to be transmitted when given values of all parameters except the size of data to be transmitted. Can be represented by a function. Therefore, given the size of data to be transmitted, the value of each of the three cost functions can be obtained.

The contents described in Equations 1 to 9 are summarized as follows.

That is, first, a normalization cost function according to Equation 1 is obtained, and the parameters given according to Equation (1) LTE-only, (2) WiFi-only, and (3) LTE + WiFi in Equation 1 Given these values, the normalization cost function for each of the three networks is given by Equations 7, 8, and 9, with the size of the data to be transmitted as a variable.

Hereinafter, a process of selecting a combination of networks for data transmission by using the normalization cost function of Equation 1 will be described.

The situation in which the terminal selects a network to transmit data may be as follows.

First, when the terminal is transmitting data through an arbitrary network, the terminal changes to another network instead of the network currently transmitting data. The second case is when the data transmission is completed through any network of the terminal, but the data transmission event occurs again while the connection with the corresponding network is maintained. Third, the terminal selects a network for data transmission in a state in which the terminal is not currently connected to any network.

The first case is when a change is made from the current network to another network. Therefore, additional time, energy, etc. required for network change should be considered in the cost function. That is, the change needs to be made only when the gain of transmitting data using the new network is greater than the effort required to change from the currently selected network to the new network. In consideration of this point, the embodiment of the present invention considers a normalization cost function of Equation 1 and a predetermined margin (m) value. Specifically, when the value of the normalized cost function in the new network plus a predetermined margin value is smaller than the value of the normalized cost function in the current network, the new network is changed. The margin m value may be determined at a predetermined rate relative to the normalized cost function value in the current network. For example, if the normalization cost value of the current network is 20 and m is set at a ratio of 0.1 to 20, then m = 2. If the normalization cost value of the new network is 17, the normalization cost function value (17) + margin value (2) of the new network is smaller than the normalization cost function value (20) of the current network. On the other hand, if the normalization cost function value of the new network is 19, the margin value 2 plus 21 is 21, which is larger than the current network normalization cost function value 20, so there is no benefit to changing the network. Therefore, the current network is used continuously to transmit data. Meanwhile, the margin m may be set at a predetermined ratio with respect to the normalized cost function value of the new network.

However, one more thing may be considered before selecting a new network from the current network. That is, the average transmission rate for each network applied when calculating the normalization cost function of the current network may be different from the actual current average transmission rate. This difference can increase the current network actual normalization cost function. In this case, you may need to select a new network. However, before selecting a new network, if the total cost function is reduced by adjusting the amount of data transmitted via LTE and the amount of data transmitted via WiFi, considering the average transmission rate of each network, if the total cost function is reduced, You may not need to select a network.

Meanwhile, the second case also sets up the network in the same manner as the first case described above. That is, if there is a network to which the terminal is currently connected, it is the easiest option to transmit data using the current network. Therefore, as described in the first case, the new network may be changed in consideration of the margin value m.

In the third case, since there is no network to which the terminal is currently connected, the network may be selected by setting the margin value m to zero.

In summary, in all three cases, the margin value is taken into consideration in order to select a network. However, if there is no current network, a margin value of 0 may be used to select a network to transmit data.

In the following description, a case where the current network is changed to WiFi-only or LTE + WiFi when the current network is LTE-only will be described.

First, when the current network is LTE-only, the condition for changing to WiFi-only is between the normalized cost function values in each network according to Equations (7), (8) and (9). It is time to satisfy Equation 10 below.

F ^c _tr : LTE-only normalized cost function,

F ^w _tr : normalization cost function of WiFi-only,

F ^cw _tr : normalization cost function of LTE + WiFi,

m: predetermined margin value.

On the other hand, by substituting <Equation 7>, <Equation 8>, and <Equation 9> into the normalized cost function values of Equation 10, and arranging the result data size (B _tr ) , Can be expressed as in Equation 11, which indicates a condition for changing from LTE-only to WiFi-only.

g _c , g _w , g _cw , h _c , h _w , h _cw are as described in Equation 7, Equation 8 and Equation 9,

The m _w represents a margin for changing from the current LTE network to the WiFi network.

For reference, in Equation 11, (a), (b), (d), and (e) are expressed as conditions for a range of data size (B _tr ) to be transmitted, and (c) and (f) are g _{Since w} = g _cw or g _w = g _c , the size of data to be transmitted (B _tr ) in the inequality is erased, and the condition at that time is expressed by the relation between h _c , h _w , h _cw and m _w . .

Next, when the current network is LTE-only, the conditions for changing to LTE + WiFi,

It is when the following Equation 12 is satisfied between the normalized cost function values in each network according to Equations 7, 8, and 9.

<Equation 12> In addition to the data size (B _tr ) to be transmitted in a manner similar to the <Equation 11> can be expressed as shown in Equation 13 below, changing from LTE-only to LTE + WiFi The conditions for

Similar to Equation 11, in Formula 13, (g), (h), (j), and (k) are expressed as conditions for a range of data size B _{tr to be} transmitted, and (c ), (f) is a condition when g _w = g _cw or g _w = g _c , so the data size (B _tr ) to be transmitted in the inequality is erased, and the conditions at that time are h _c , h _w , h _cw and It is expressed as relation between m _cw .

In the same manner as described above, it is possible to obtain a condition for changing to a new network even if the current network is WiFi-only or LTE + WiFi. Detailed description thereof will be omitted.

FIG. 3 is a diagram for explaining possible forms of a normalization cost function according to the size of LTE partial data among sizes of total transmission data and an example of selecting an optimal network according to an embodiment of the present invention.

(A), (b) and (c) in FIG. 3, black circular dots and black diamond dots are in the order of (WiFi-only), (LTE + WiFi), (LTE- only) represents the normalized cost function value when the network is selected.

(a) shows that the normalized cost function value 401 in the case of selecting a WiFi-only network in consideration of the WiFi margin (m _w ) becomes the minimum value compared with other points, and the LTE data size at this time is 0 do. This is shown at 302.

(b) shows that the normalized cost function value 403 when selecting an LTE + WiFi network in consideration of LTE + WiFi margin (m _cw ) is the minimum value compared to other points, and the LTE data size at this time is the total transmission. The value of Equation 5 is obtained for the data size B _tr . This is shown at 304.

(c) shows that the normalized cost function value 305 when the LTE-only network is selected in consideration of the LTE margin (m _c ) becomes the minimum value compared to the other points, and the LTE data size is B _tr . . This is shown at reference numeral 306.

Hereinafter, an application example of an embodiment of the present invention will be described in a case where the transmission environment is changed while the control unit 125 selects an optimal network and data is transmitted using the selected network.

First, a case in which the above-described weight value or normalization factor is changed during data transmission will be described.

If any of the values of α, β, γ, n _t , n _e , n _c changes during the data transmission, the changed values are transferred to the control unit 125, and the control unit 125 collects the terminal information. Obtain the updated information of the state information of the terminal and / or the state information of the network from the 105 and / or the network information collecting unit 115. On the other hand, if any one of the values of α, β, γ, n _t , n _e , n _c is changed when the data is not being transmitted, the changed values are reflected in the next data transmission session. The per-normalized cost function value is newly calculated, and the most optimal network is selected using this.

Next, a description will be given of a difference between the average transmission rate applied when calculating the cost function value of the corresponding network and the actual average transmission rate of the corresponding network during data transmission.

 As described above, when the network is selected and data is transmitted using the average rate transmitted from the network information collecting unit 115, the data rate during actual data transmission is different from the average rate used at the time of network selection. Will occur. However, the normalization cost function is a function of the average transfer rate for each network. The actual normalization cost function taking into account the data transfer rate when data is actually transmitted differs from the normalization cost function considering the average transfer rate when selecting a network.

If the difference is not large, the optimal network will not change because the margin for network change is set in the normalization cost function used in the network selection step. However, the difference may be larger so that the normalization cost function for the other network combination is smaller than the normalization cost function of the selected network combination. Therefore, in order to prepare for such a case, even while the actual data is transmitted after the network is selected, the network information collecting unit 115 updates the actual average transmission rate for each network every predetermined update period Tu and delivers it to the controller 125. .

The controller 125 receives the state information and the network state information of the terminal for each update period Tu to determine the candidate network, and when there is a change in the candidate network, newly calculates and calculates a normalization cost function for the combination of candidate networks. It is possible to reselect the optimal network according to the normalized cost function.

If there is no change to the candidate network, the average transmission rate during transmission is monitored to maintain the currently selected network if the average transmission rate to date is decreasing the normalized cost function. On the other hand, when the currently applied average rate increases the normalized cost function, the normalized cost function is recalculated for the combinations of candidate networks in consideration of the actual average rate.

The number of times when the recalculated normalized cost function value is greater than the value of {normalized cost function value calculated by applying the average rate estimate estimated at the initial network selection step + the margin in the network combination} ( N) is counted every update period Tu. When the N value becomes larger than the N _max value, which is a preset threshold, the normalized cost function value is recalculated for each network combination for the data size of the remaining data except for the data transmitted up to now.

If the result of the calculation is that the normalized cost function value including the margin is smaller than the normalized cost function value in the network currently used in other network combinations except for the network used for the current transmission, the network combination is used to transmit the remaining data. You can choose a new network combination.

However, as mentioned above, even if the average transmission rate of the actual network changes according to the change of transmission environment during data transmission, if the normalized cost function value in the current network can be reduced by adjusting the proportion of partial data transmitted per network accordingly. In this case, the new network does not need to be selected again as described above.

4 is a diagram illustrating a method in a user terminal according to an embodiment of the present invention.

When an event for data transmission, such as a data transmission request, occurs in step 401, in step 303, state information of the terminal is obtained. This is performed by the terminal information collecting unit 105 of the user terminal.

The state information of the user terminal refers to information related to the setting and use of the current user terminal. Specifically, the state information of the user terminal includes "battery remaining amount information" of the current user terminal, "monthly data total amount information" according to the rate plan subscribed to the user terminal, "paid data usage information" up to now. In addition, the state information of the user terminal may include "mobility information of the user terminal" when the user terminal is moving, "display related information" related to the user terminal display device, and "user terminal operation information regarding whether the user terminal is currently operating." Includes more. The “mobility information of the user terminal” may be obtained using a signal strength of a network currently connected to the user terminal, an accelerometer, a gravity meter, or a global positioning system (GPS).

In operation 405, network state information is obtained for each of the networks. This operation is performed by the network information collecting unit 115 of the user terminal. The network state information includes "active network information" and "average data rate" for each network. Since the active network information and the average transmission rate have been described above, a detailed description thereof will be omitted.

In step 407, the candidate network is determined using the state information of the network and / or the state information of the terminal. In particular, the candidate network may be determined using “active network information” of the network state information and “terminal mobility information” or “terminal operation information” of the terminal state information. This has been described in detail with reference to FIG. 1, and a description thereof will be omitted.

In step 409, each weight value for transmission time, power saving, and cost saving is obtained. The weight value may be obtained by a user's input through the user interface 110 described with reference to FIG. 2, using a value set as a default value, or a weight value set at a previous data transmission.

In step 411, the size of the transmission data is analyzed. This is performed by the application analyzer 120 or the application 135 of the user terminal.

In step 413, the controller 125 calculates a normalized cost function value for each combination of candidate networks. This has been described below in Equation 1, and thus detailed description thereof will be omitted.

In step 415, the optimal network combination is selected according to the calculated cost function. It is usually desirable to select a network combination where the cost function value is minimal. However, as described above, if there is a currently connected network as described above, the margin value is considered when changing from the current network to a new network.

In step 417, data is transmitted using the selected network combination during the preset network update period Tu. Since the control unit 125 of FIG. 1 has been described above with respect to the update period, a detailed description thereof will be omitted.

Hereinafter, a simulation result according to an embodiment of the present invention will be described.

The simulation method compares the case of applying the optimal network selection method according to the average data rate of each network, the battery of the terminal, the subscription data usage, and the size of the transmitted data, and the case of using the previous method and continuing the network according to the existing method. Through this, the relative gain for each item of transmission time, energy consumption, and paid data usage was verified.

For reference, the relative gain means that the optimal network is adaptive when the transmission time, energy consumption, and paid data usage is 1 when the network selection of LTE-only or WiFi-only or LTE + WiFi is continuously maintained from the beginning to the end of the simulation. If it is selected, it indicates how many times the additional gain can be obtained. If the value is larger than 0, it indicates that there is a gain in that ratio, and if it is smaller than 0, it indicates the damage in that ratio. To find the average relative gain for various data sizes, the size of the data has a certain probability distribution (ie, log-normal distribution) within the range of [100 kB, 3 GB] so that the relative gain for the data of various sizes The average value of is shown.

5 (a), 5 (b) and 5 (c) show the relative gains of transmission time, energy consumption and paid data costs according to the ratio of energy already used up to now according to the embodiment of the present invention. It is a figure explaining each.

5 (a), 5 (b) and 5 (c), when the total energy of a fully charged battery is 1, the x axis represents the ratio of energy (Eu) that has been used so far, and the Y axis represents the energy. As the ratio increases, that is, the distribution of the relative energy consumption gain (Nomalized gain) as the remaining battery power decreases.

Reference number 501 is adapted during data transmission in case of using only LTE network (C-only) from the start of data transmission to the completion of transmission when the ratio (Bu) of paid data already used so far is 0.1 of the allowable data allowance. It shows the relative gain of selecting and using the network.

Reference numeral 502 denotes a relative gain when the data is adaptively selected during data transmission in the case of Bu = 0.5, in contrast to the case of using only the WiFi network (W-only) from the start of data transmission to the completion of transmission. .

Reference number 503 represents the relative gain of adaptively selecting and using data during data transmission in the case of Bu = 0.9, when using LTE network and WiFi simultaneously (LTE + WiFi) from the beginning of data transmission to the completion of transmission. Indicates.

Reference number 504 is adapted during data transmission in case of using only LTE network (C-only) from start of data transmission to completion of transmission when the ratio (Bu) of paid data already used so far is 0.1 of the allowable data allowance. It shows the relative gain of selecting and using the network. Reference numeral 505 denotes a relative gain when the data is adaptively selected during data transmission in the case of Bu = 0.5, in contrast to the case of using only the WiFi network (W-only) from the start of data transmission to the completion of transmission. . Reference number 506 represents the relative gain of adaptively selecting and using data during data transmission, in contrast to the case of using LTE network and WiFi simultaneously (LTE + WiFi) from the start of data transmission to the completion of transmission when Bu = 0.9. Indicates.

Reference number 507 is adapted during data transmission in case of using only LTE network (C-only) from the start of data transmission to the completion of transmission when the ratio (Bu) of paid data already used so far is 0.1 of the allowable data allowance. It shows the relative gain of selecting and using the network. Reference numeral 508 denotes a relative gain of data transmission when Bu = 0.5, when the network is adaptively selected and used during data transmission, in contrast to the case of using only a WiFi network (W-only) from the start of data transmission to the completion of transmission. . Reference number 509 represents the relative gain of adaptively selecting and using data during data transmission in the case of Bu = 0.9, when using LTE network and WiFi simultaneously (LTE + WiFi) from start of data transmission to completion of transmission. Indicates.

The above description of the reference numerals also applies to FIGS. 5 (b) and 5 (c).

The results of FIGS. 5A, 5B, and 5C are as follows.

As battery usage increases (i.e., toward the right side on the x-axis), we can see that the energy gain in Figure 5 (b) increases as the weight for energy consumption increases (the graph curves are upwards), and accordingly It can be seen that the pay data cost benefit of 5 (c) is reduced (graph curves are downward oriented). And most of the graphs show values above 0 on the Y-axis, which means that the adaptive selection of the transport network selects only one of LTE-only or WiFi-only or LTE + WiFi from the start to the end of the transmission. That means there is overall gain than sending it.

However, among the transmission time gain graphs of FIG. 5 (a), reference number 509 represents a gain when the network is adaptively selected in comparison with the case where only LTE + WiFi is transmitted and the graph curve is less than zero. It has a value, which means that the adaptive network selection has lost data transmission time using only LTE + WiFi. However, since the energy gain of FIG. 5 (b) (reference number 509 of FIG. 5 (b)) and the paid data cost gain of FIG. 5 (c) (reference number 509 of FIG. 5 (c)) are generated, the loss is compensated for. It is a result.

6 (a), 6 (b), and 6 (c) illustrate the transmission time, energy consumption, and paid data cost according to the ratio Bu of the used data to the present allowable data amount according to the embodiment of the present invention. It is a figure explaining a relative gain, respectively.

Description of the reference numerals in each drawing is as described in FIG.

6 (a), 6 (b) and 6 (c), the pay data cost gain of FIG. 6 (c) increases because the weight of the pay data cost increases as the pay data usage increases. As a trade-off therewith, the transmission time gain of FIG. 6 (a) and the energy consumption gain of FIG. 6 (b) are reduced.

7 (a), 7 (b), and 7 (c) are relative gains of transmission time, energy consumption, and pay data cost according to the change in the weight value α with respect to the transmission time according to an embodiment of the present invention. It is a figure explaining each.

Reference numeral 701 denotes Bu = 0.5, and when Eu = 0.5, data is prepared according to the method proposed in the embodiment of the present invention in preparation for using only the LTE network (C-only) from the start of data transmission to the completion of transmission. It shows the relative gain when adaptively selecting and using a network during transmission.

Reference numeral 702 denotes Bu = 0.5, and when Eu = 0.5, data is prepared according to the scheme proposed in the embodiment of the present invention in preparation for using only a WiFi network (W-only) from the start of data transmission to completion of transmission. It shows the relative gain when adaptively selecting and using a network during transmission.

Reference numeral 703 denotes Bu = 0.5, and when Eu = 0.5, the scheme proposed in the embodiment of the present invention is prepared in case of simultaneously using the LTE network and WiFi from the start of data transmission to the completion of the transmission (LTE + WiFi). Shows the relative gain of adaptive network selection during data transmission.

Referring to FIGS. 7 (a), 7 (b) and 7 (c), as the value of α increases, the transmission time cost gain of FIG. 7 (a) rapidly increases and becomes saturated over a certain value. . Further, according to the value of α, the energy consumption cost gain of FIG. 7 (b) tends to be similar to the transmission time cost gain of FIG. 7 (a), and the paid data cost of FIG. 7 (c) is opposite. Able to know.

8 (a), 8 (b), and 8 (c) illustrate relative gains of transmission time, energy consumption, and pay data cost according to a change in the weight value β for power saving according to an embodiment of the present invention. It is a figure explaining each.

Even in this case, as the β value increases, an energy gain occurs in FIG. 8 (b), but the gain is saturated above a predetermined value. Also, it can be seen that the transmission time cost gain of FIG. 8 (a) tends to be similar to the energy gain of FIG. 8 (b) and the pay data cost of FIG.

9 (a), 9 (b), and 9 (c) illustrate relative gains of transmission time, energy consumption, and paid data cost according to a change in the weighting value γ for cost saving according to an embodiment of the present invention. It is a figure explaining each.

Also in this case, as the value of γ increases, a gain in pay data cost occurs in FIG. 9 (c). Here, although the gain of the paid data cost is not saturated, it can be seen that the gain increase rate decreases as the γ value increases. In addition, it can be seen that the transmission time cost gain of FIG. 9 (a) and the energy gain of FIG. 9 (b) tend to be opposite to those of FIG. 9 (c) according to the value of γ.

Meanwhile, in setting the α, β, and γ values, a meaningful range (for example, [1, 10], appropriate values) may be set with reference to the results of FIGS. 6, 7, and 8 above. When the user sets the weight values based on the value, the user may be recommended to the user as a weight by the user terminal setting or may be used as a default value of the system.

So far, embodiments of the present invention have been described in detail.

According to embodiments of the present invention, when using different networks for data transmission, considering the status information of the user terminal, network status information, the size of the data to be transmitted, the transmission time, energy (battery) consumption during data transmission By weighting the data transmission cost, an optimal network for data transmission can be selected.

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. On the other hand, in the present specification and drawings have been described with respect to preferred embodiments of the present invention, although specific terms are used, it is merely used in a general sense to easily explain the technical details of the present invention and to help the understanding of the invention, It is not intended to limit the scope of the invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

105: terminal information collection unit
107: weight setting unit
109: network status display
110: user interface
115: network information collection unit
120: application analysis unit
125: control unit
130: transmission unit
135: application
301: Cost function value when selecting a WiFi-only network in consideration of WiFi margin (m _w )
302: LTE data size at 401 is 0
303: Normalized cost function value when LTE + WiFi network is selected in consideration of LTE + WiFi margin (m _cw )
304: LTE data size at 403 is the total transmission data size (value of Equation 6).
305: Normalized cost function value when LTE-only network is selected in consideration of LTE margin (m _c )
LTE data size (B _tr ) at 306: 405
501: If the ratio (Bu) of the paid data already used so far is 0.1 of the allowable data allowance, adaptively during data transmission in preparation for using the LTE network only (C-only) from the start of data transmission to the completion of the transmission Relative Benefits of Selecting and Using Networks
502: Data transmission in case of Bu = 0.5 Relative gain in case of adaptively selecting and using data during data transmission in case of using only WiFi network from start of data transmission to completion of transmission (W-only)
503: When Bu = 0.9, relative gain when adaptively selecting and using a network during data transmission, compared to when using LTE network and WiFi simultaneously from start of data transmission to completion of transmission (LTE + WiFi)
504: If the ratio (Bu) of the paid data already used so far is 0.1 of the allowable data allowance, adaptively during data transmission in preparation for using the LTE network only (C-only) from the start of data transmission to the completion of the transmission Relative Benefits of Selecting and Using Networks
505: When Bu = 0.5, data transmission Relative gain when adaptively selecting and using the network during data transmission in case of using only the WiFi network (W-only) from start of data transmission to completion of transmission
506: When Bu = 0.9, relative gain when adaptively selecting and using a network during data transmission in case of using LTE network and WiFi simultaneously (LTE + WiFi) from start of data transmission to completion of transmission
507: If the ratio (Bu) of the paid data already used so far is 0.1 of the allowable data allowance, adaptively during data transmission in preparation for using the LTE network only (C-only) from the start of data transmission to the completion of transmission (C-only). Relative Benefits of Selecting and Using Networks
508: When Bu = 0.5, data transmission Relative gains when adaptively selecting and using data during data transmission in case of using only WiFi network from start of data transmission to completion of transmission (W-only)
509: Relative gains when adaptively selecting and using a network during data transmission in case of using LTE network and WiFi simultaneously (LTE + WiFi) from the start of data transmission to the completion of transmission
701: When Bu = 0.5 and Eu = 0.5, in case of using only the LTE network (C-only) from the start of data transmission to the completion of transmission (C-only), adaptively during data transmission according to the scheme proposed in the present invention. Relative Benefits of Selecting and Using Networks
702: When Bu = 0.5 and Eu = 0.5, in case of using only a WiFi network (W-only) from start of data transmission to completion of transmission, adaptively during data transmission according to the scheme proposed in the present invention. Relative Benefits of Selecting and Using Networks
703: When Bu = 0.5 and Eu = 0.5, in case of using LTE network and WiFi simultaneously (LTE + WiFi) from the start of data transmission to the completion of transmission, during data transmission according to the method proposed in the present invention Relative Benefits of Adaptive Network Selection

Claims (36)

In the method of transmitting and receiving data in a wireless communication system,
Obtaining at least one of terminal state information, at least one network state information for each network, and size information of data to be transmitted and received;
Determining at least one candidate network that can be used for data transmission and reception using at least one of the state information of the terminal and the network state information;
Determining a cost function for each possible network combination in the determined candidate network;
Selecting a network combination having a minimum cost function value among the determined cost function for each network combination; And
Transmitting and receiving data including the step of performing data transmission and reception using the selected network combination,
The cost function includes itemized cost functions of a transmission time cost function, an energy consumption cost function, and a paid data cost function,
Each of the cost function of each item is determined by a product of a cost model of each item, a normalization factor of each item, and a weight of each item,
The energy consumption cost function is determined using an average transmission rate for each candidate network constituting the network combination, the size of the partial data which is transmission data for each candidate network, and an additional factor.
The additional factor includes at least one of switch on energy for each candidate network and energy overhead for each candidate network,
The switch on energy means the energy consumption until the terminal is turned on from the off state to the actual data transmission,
The energy overhead is a sum of a first energy for becoming active when the terminal starts data transmission in a sleep mode and a second energy until returning to the sleep mode after data transmission is completed. Method for transmitting and receiving data, characterized in that.
The method of claim 1, wherein the selecting of the network combination comprises:
If there is a network combination currently connected to the terminal, and the data transmission and reception is performed through the currently connected network combination,
Reducing the cost function of the currently connected network combination by adjusting a data transfer amount in the at least one network according to an actual transmission rate in at least one network constituting the currently connected network combination; And
Selecting the currently connected network combination, wherein the cost function is reduced.
The method of claim 1, wherein the selecting of the network combination comprises:
When there is a network combination currently connected to the terminal, when a value obtained by adding a margin value to a cost function value of the network combination having the minimum cost function is smaller than the cost function value of the currently connected network combination. And selecting a network having the least cost function value.
delete The method of claim 1, wherein the normalization factor for each item is
A method of transmitting and receiving data that is set by the inverse of the maximum allowable value for each item.
The method of claim 5, wherein when the multiplication of the item normalization factor and the item cost model exceeds 1, the normalization factor is replaced with a penalty value larger than the original value.
The method of claim 1, wherein the cost model for the transmission time,
Data modeled by at least one of the average transmission rate for each candidate network constituting the network combination, the size of the partial data which is transmission data for each candidate network, the connection delay time for the candidate network, the promotion time delay overhead for the candidate network. How to send and receive.
The method of claim 7, wherein the average transmission rate for each candidate network,
And transmitting / receiving data determined using a database stored in advance for each candidate network.
The method of claim 7, wherein the average transmission rate for each candidate network,
And transmitting and receiving data determined by an actual transmission rate in the at least one network when there is a network combination currently connected to the terminal and the data transmission and reception is performed through the currently connected network combination.
delete The method of claim 1, wherein the cost model for the paid data,
And transmitting / receiving data modeled by the size of partial data which is transmission data for each candidate network constituting the network combination.
The method of claim 1, wherein the cost function is
And transmitting and receiving data expressed as a function of the size of the data.
The method of claim 1, wherein the network state information,
At least one active network information and transmission rate information for each active network;
And the active network is a network in which the corresponding network is in an active state and the terminal is located within the coverage of the corresponding network so that the terminal can obtain a network identifier from the corresponding network.
The method of claim 13, wherein the active network information,
At least one of an " active network identifier &quot;," on / off state information " of a network device in the terminal for connection with the active network, and " connection mode information " indicating a connection state of the terminal. Method of transmitting and receiving data comprising.
The method of claim 13, wherein the determining of the candidate network comprises:
And determining the active network as the candidate network.
The method of claim 13, wherein the state information of the terminal,
Method for transmitting and receiving data, characterized in that it comprises the mobility information of the terminal.
The method of claim 16, wherein the determining of the candidate network comprises:
And determining the candidate network by using received signal strength of the at least one active network and mobility information of the terminal.
The method of claim 16, wherein the determining of the candidate network comprises:
And determining a network that is not included in the active network information as the candidate network using the mobility information of the terminal and the location information of the terminal.
In the terminal for transmitting and receiving data in a wireless communication system,
Transmission unit for transmitting and receiving data; And
A control unit for controlling the transmission unit,
The control unit,
Obtaining at least one of terminal state information, at least one network state information for each network, and size information of data to be transmitted and received;
Determining at least one candidate network that can be used for data transmission and reception using at least one of the state information of the terminal and the network state information;
Determine a cost function for each possible network combination in the determined candidate network,
Selecting a network combination having a minimum cost function value among the determined cost function for each network combination,
Transmitting and receiving data using the selected network combination, transmitting and receiving data,
The cost function includes itemized cost functions of a transmission time cost function, an energy consumption cost function, and a paid data cost function,
Each of the cost function of each item is determined by a product of a cost model of each item, a normalization factor of each item, and a weight of each item,
The energy consumption cost function is determined using an average transmission rate for each candidate network constituting the network combination, the size of partial data which is transmission data for each candidate network, and additional factors.
The additional factor includes at least one of switch on energy for each candidate network and energy overhead for each candidate network,
The switch on energy means the energy consumption until the terminal is turned on from the off state to the actual data transmission,
The energy overhead is a sum of a first energy for becoming active when the terminal starts data transmission in a sleep mode and a second energy until returning to the sleep mode after data transmission is completed. Terminal for transmitting and receiving data characterized in that.
20. The terminal of claim 19, which performs the method of any one of claims 2, 3, 5-9, 11-11. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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