KR101515590B1 - Mobile Terminal and Method for Selecting Handover Using the Same - Google Patents

Abstract

The present invention relates to a mobile terminal and a handover selection method using the same.

The present invention provides a heterogeneous network handover policy for minimizing power consumption caused by simultaneously operating a plurality of modem interfaces installed in a mobile terminal during heterogeneous wireless network handover.

According to the present invention, an optimal wireless network is selected in consideration of signal strength, transmission quality, and communication cost according to a combination of states of a plurality of wireless interfaces, and a time when a plurality of interfaces are simultaneously used .

The present invention can be expected to perform an optimal heterogeneous network handover by classifying the wireless interfaces according to the state combination and using the differentiated handover strategy for each state combination for heterogeneous network handover.

Handover, low power, mobile terminal, wireless interface, heterogeneous network

Description

Technical Field [0001] The present invention relates to a mobile terminal and a handover selecting method using the mobile terminal.

The present invention relates to a handover method, and more particularly, to a mobile terminal for minimizing power consumption in heterogeneous network handover and a handover selection method using the same.

In a cell network such as the existing 3GPP / 3GPP2, the location information is periodically updated by the user as the user moves, thereby recording the location information of the user. When there is a request for reception, the network uses the location information to paging The connection is made.

When the user moves out of the current cell and enters a new cell, a handover occurs and the changed location information is updated in the network. Such a handover may occur during communication or even in an idle state.

Until recently, the user has performed communication using only one wireless network at a time. However, in the future, a single telecom company will operate multiple wireless networks, and handover between heterogeneous networks is becoming an important issue in order to seamlessly support communication services in various wired and wireless networks.

In the handover between heterogeneous networks, the new network does not have information on the user's location information and communication type, and it must be initialized in the new network upon handover and the terminal must support multiple wireless interfaces.

That is, when a handover to a new network is required, the current network and a wireless interface for a network to be handed over must be simultaneously operated.

The handover between these heterogeneous networks is one of the following problems to be solved.

For example, first, if a short-range air interface has two states, active and idle, four combined states are possible if there are two air interfaces. The increased number of states makes handover between heterogeneous networks more complicated.

Second, to determine handover between heterogeneous networks, the received signal strength must be maintained over a certain level, such as handover between homogeneous networks, to meet transmission quality requirements, and to satisfy bandwidth demands.

Third, a plurality of wireless interfaces must be supported to support a plurality of heterogeneous networks, and a plurality of wireless interfaces must be in operation at the same time, so that handover can be performed without interruption during handover. However, placing a plurality of wireless interfaces at the same time in operation causes a problem in that the power consumption of the terminal greatly increases.

Accordingly, such a handover between heterogeneous networks requires an integrated policy for selecting a wireless network at a point in time to determine a handover while satisfying various factors to be considered in the above-mentioned handover.

In order to solve such a problem, the present invention provides a mobile terminal for minimizing power consumption in heterogeneous network handover and a handover selection method using the same.

According to an aspect of the present invention, there is provided a handover selection method comprising the steps of: (a) accessing an information server storing information necessary for generating first handover information and a handover decision policy measured by the mobile terminal Receiving second handover information; (b) a state combination of a first wireless interface of a first wireless network supported by the mobile terminal and a second wireless interface of a second wireless network, and a state combination of at least one of the first handover information and the second handover information Setting a differentiated handover condition based on the handover condition; And (c) performing the handover by driving the first wireless interface or the second wireless interface according to the set handover condition.

A mobile terminal according to an aspect of the present invention includes first handover information measured in a mobile terminal supporting a plurality of radio interfaces and second handover information required to generate a handover decision policy received from an information server, A handover decision information generation unit for generating decision information; A handover condition determiner configured to set a handover condition differentiated based on a state combination of the plurality of radio interfaces and the handover decision information; And a handover performing unit for performing a handover by driving the wireless interface of the corresponding network when the set handover condition is checked and transitioning the wireless interface of the network used before the handover to a low power state.

According to the above-described configuration, the present invention can perform an optimal heterogeneous network handover by classifying the wireless interfaces according to the state combination for heterogeneous network handover and employing a differentiated handover strategy for each state combination Can be expected.

The present invention can select a network that best satisfies current requirements by simultaneously considering the signal strength, bandwidth, transmission quality, power consumption, etc. of each network at the time of handover.

The present invention can minimize the unnecessary power consumption in the inter-heterogeneous handover by transferring the unused wireless interface to the low power state.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise. Also, the terms " part, "" module," " module, "and " block" refer to units that process at least one function or operation, Lt; / RTI >

In the following description of the embodiment of the present invention, it is assumed that:

A media independent handover (MIH) information server manages information necessary for establishing a policy for determining a heterogeneous network handover, and provides the information when a wireless terminal requests it .

That is, the MIH information server provides the mobile terminal with the communication cost for accessing the network, the transmission quality of the network, the network operator information, and the information related to the network security.

In order to facilitate the heterogeneous network handover policy and its implementation, the following assumptions are made based on reality.

It is assumed that the transmission / reception bandwidth is higher than that of a wireless broadband (hereinafter, referred to as "WiBro") as compared with a High Speed Downlink Packet Access (HSDPA). Therefore, WiBro is advantageous when transmitting / receiving a large amount of information.

In terms of power consumption, it is assumed that HSDPA consumes low power and WiBro is much cheaper in terms of communication cost.

The state that the wireless interface can have is one of four states as follows.

The active state is a state in which the power source is large and connected to the network, the idle state is a state in which the power is turned on but not connected to the network, and the low power is not connected to the network It operates in the low power mode and consumes the minimum power, and the state where the power is completely turned off is the off state (Off).

The following three thresholds are defined for use in determining handover between heterogeneous networks.

T _CINR is the Carrier to Interference and Noise Ratio (CINR), and the threshold CINR is maintained for a certain period of time.

T _ERR is a threshold error rate, and if the threshold error rate exceeds a certain time, it is considered that the current network is unstable and can be used for handing over to another network.

T _BC is used as a threshold BC to handover to a low power consumption HSDPA network when _BC falls below T _BC .

In fact, in order to perform heterogeneous network handover, a new network should be detected and the communication cost, power consumption, transmission quality, etc. of the new network should be considered incidentally.

(CINR), W (Cost), and W (W) are applied to the CINR, the communication cost, the power and the transmission quality Power, and W (QoS).

In the embodiment of the present invention, the handover between WiBro and HSDPA will be described. Other wireless networks (such as WLAN) may be included in the embodiment.

In order to simplify the handover policy between heterogeneous networks, the following assumptions are made based on facts.

First, only HSDPA can transition from idle to low-power state.

Second, the state of the WiBro is manually determined to be low power or off state by the mobile terminal.

Third, HSDPA is assumed to be available anytime and anywhere.

1 is a block diagram schematically illustrating an internal configuration of a mobile terminal according to an embodiment of the present invention.

A mobile terminal 100 according to an embodiment of the present invention includes a power measuring unit 110, a handover information measuring unit 120, a handover decision information generating unit 130, a memory unit 140, (150) and a handover performing unit (160).

The power measuring unit 110 measures power through a power control algorithm for power control when the mobile terminal 100 is powered on. Here, the measured power means at least one of the transmission power, the power consumption of the terminal, the amount of throughput used, and the maximum throughput.

The method of measuring the above-described measured power is not a feature of the present invention as a known technology, and thus a detailed description thereof will be omitted.

The handover information measuring unit 120 may automatically measure RSSI (Received Signal Strength Indication), Carrier to Interference Ratio (CINR), and Signal to Interference Ratio (SINR) when the mobile terminal 100 is powered on The signal quality information is measured.

In the embodiment of the present invention, RSSI, SINR, and CINR are illustrated for convenience of explanation, but the present invention is not limited thereto. The method for measuring the above-described signal quality information is generally known as a mobile communication technique used in the mobile terminal 100 and is known to those of ordinary skill in the art, and thus a description thereof will be omitted.

The handover decision information generating unit 130 receives the first handover information including the CINR of each network measured by the handover information measuring unit 120 and the power consumption of the UE measured by the power measuring unit 110.

The handover decision information generating unit 130 is connected to the MIH information server and receives the second handover information including the transmission quality of the network and the communication cost required to access the network.

The memory unit 140 stores the handover decision information including the first handover information and the second handover information of each network from the handover decision information generating unit 130. [

Herein, although the handover decision information exemplifies the CINR of each network, the power consumption of the terminal, the communication cost, and the transmission quality, various parameters such as the network type, battery remaining capacity, and bandwidth can be added.

The handover condition determination unit 150 sets a handover condition differentiated based on a combination of states of a plurality of radio interfaces and handover decision information.

When the handover condition is satisfied, the handover performing unit 160 performs a handover by driving the wireless interface of the corresponding network and transmits the handover request to the wireless interface To a low power state.

2 is a diagram illustrating a handover policy when a WiBro interface according to an embodiment of the present invention is idle and the HSDPA interface is in an idle state or a low power state.

The handover policy shown in FIG. 2 can be connected to a WiBro network (first wireless network) or an HSDPA network (second wireless network) at the request of the mobile terminal 100.

In order to connect to the WiBro network, one of two conditions (A1 (200) and A3 (220)) must be satisfied. To connect to the HSDPA network, A2 condition (210) may be satisfied.

The A1 condition 200 is a case of handover to a WiBro network when the mobile terminal 100 requests a large bandwidth to transmit a large amount of data (CINR> bandwidth threshold> HSDPA maximum bandwidth while maintaining a threshold CINR condition for a predetermined time) .

As assumed above, the mobile terminal 100 requests a large bandwidth for high capacity data transmission because HSDPA is always available, and handover to a WiBro network when a WiBro network is detected at the same time.

Since the handover performing unit 160 connects to the WiBro network for the first time, the handover performing unit 160 accesses the WiBro network through a normal handover process (location update, ranging, etc.) of the WiBro terminal.

Here, a location information update, a ranging, a handover initialization process, a PDP context (packet data protocol context) session setup, and the like are generally known as a series of processes performed at the time of handover, .

Then, when the HSDPA interface is in the idle state, the handover performing unit 160 transitions the HSDPA interface state to low power as needed to reduce power consumption.

A3 condition 220 is a case in which the mobile terminal 100 requests a low communication cost and performs handover to a WiBro network when a WiBro network is detected (CINR> threshold CINR condition is maintained for a predetermined time, Occation).

As assumed above, since the communication cost of the current WiBro is lower than that of the HSDPA in the mobile terminal 100 per unit bit, it is advantageous to select the WiBro network when two networks are available at the same time.

The handover performing unit 160 connects to the WiBro network and transitions the HSDPA interface to the low power state through the normal handover process as in the A1 condition 200 described above.

The A2 condition 210 performs the connection to the HSDPA network when power consumption is a critical issue (bandwidth requirement> HSDPA maximum bandwidth, priority to power consumption).

As described above, the mobile terminal 100 connects to the HSDPA network when the HSDPA does not require a large bandwidth because it consumes low power when transmitting and receiving data compared to the WiBro.

When the HSDPA interface is in the low power state, the handover performing unit 160 transitions to the idle state and transitions to the active state after a normal handover process (location information update, PDP context activation). The mobile terminal 100 may transition the state of the WiBro interface to the low power state.

3 is a diagram illustrating a handover policy when a WiBro interface according to an embodiment of the present invention is in an idle state and an HSDPA interface is in an active state.

The B1 condition 300 indicates a condition for performing a handover when a WiBro network is found while the mobile terminal 100 is performing communication via the HSDPA connection.

In order to actually perform a handover to the WiBro network, the following factors should be considered.

First, the signal intensity of the WiBro should be maintained for a certain time longer than T _CINR .

Second, when the mobile terminal 100 requests high transmission quality, it is advantageous to perform handover to the WiBro network.

Third, the network type of the communication partner should be considered. For example, when the mobile terminal 100 wishes to perform handover to a WiBro network, it is necessary to confirm whether the network type of the communication partner is a WiBro network. If the other terminal is connected to the HSDPA network rather than the WiBro network, it may not be advantageous to perform a handover from the HSDPA network to the WiBro network.

Fourth, it is necessary to consider the remaining battery capacity of the terminal. If the remaining battery capacity of the mobile terminal 100 is not large, handover to the WiBro network may increase the power consumption rate and shorten the available communication time of the terminal. In this case, it is advantageous to maintain an efficient HSDPA network in terms of power consumption.

When the handover to the WiBro network is determined in consideration of the above four conditions, the handover performing unit 160 performs handover to the WiBro network through a normal handover process, and the HSDPA interface is idle or low- Transitioning to a low power state for consumption.

4 is a diagram illustrating a handover policy when the WiBro interface is active and the HSDPA interface is in the idle state or the low power state according to the embodiment of the present invention.

4 illustrates conditions for the MS 100 to be handed over to the HSDPA network while the MS is currently connected to the WiBro network.

The C1 condition 400 is a case where the mobile terminal 100 is out of the WiBro network and the signal strength is weak or the error rate is larger than T _ERR , so that handover to the HSDPA network is performed.

The C2 condition 410 is a case where the current data rate can not be continuously satisfied with the current battery state of the mobile terminal 100 (BC < T _BC ). Therefore, if handover to the HSDPA network is not performed by the mobile terminal 100, the available time of the UE significantly decreases.

C3 condition 420 is a case where a terminal delay time or jitter (E2E Delay or Jitter> transmission quality) occurs higher than that required by the current WiBro network in transmission quality.

As described above, the handover performing unit 160 determines that the handover performed by the handover performing unit 160 is satisfied when any one of the C1 condition 400, the C2 condition 410, and the C3 condition 420 is satisfied (HSDPA is available anytime and anywhere) , When the HSDPA interface is in the low power state, it transitions to the idle state and transitions to the active state via the normal handover process (HSDPA location update, PDP context activation, etc.), and transitions the WiBro interface to the idle state.

FIG. 5 is a diagram illustrating a state combination of a WiBro interface and an HSDPA interface according to an embodiment of the present invention in a finite state machine (FSM) according to a handover policy.

A finite state machine consists of three states.

The three states are (WiBro: Idle, HSDPA: Idle (Low-Power)), (WiBro: Idle, HSDPA: Active), WiBro: Active and HSDPA: Idle (Low-Power).

Mobile terminal 100 (WiBro: Idle, HSDPA: Idle (Low-Power)) state in the A2 condition 210 or satisfies (WiBro: Active, HSDPA: Idle (Low-Power)) from the state C1 (400 ), The C2 410 or the C3 condition 420 is satisfied (WiBro: Idle, HSDPA: Active) .

The mobile terminal 100 determines whether the condition A1 (200) or A2 (210) is satisfied (WiBro: Idle, HSDPA: Active) (WiBro: Active, HSDPA: Idle (Low-Power)) .

Finally, the mobile terminal 100 transitions to a WiBro or HSDPA state (WiBro: Idle, HSDPA: Idle (Low-Power)) state.

FIG. 6 is a diagram illustrating a condition for performing a handover between a WiBro and a HSDPA according to an exemplary embodiment of the present invention using a weight function. Referring to FIG.

The handover condition determination unit 150 determines a network to which handover is to be performed by applying weights to the four elements affecting the handover using the sum of the weights.

Here, the four factors affecting the handover are CINR, COST, POWER, and QoS. The weights for these are defined as W _CINR , W _COST , W _POWER , and W _QoS , respectively.

The handover decision function using the weight is defined as follows.

Fn = W _CINR * CINRn + W _COST * COSTn + W _POWER * POWERn + W _QoS * QoSn

Where n is the type of network (WiBro, HSDPA). For example, CINRn is the CINR of network type n. Therefore, as shown in FIG. 6, F _WiBro F _HSDPA , handover to WiBro is performed. FIG. 6 shows handover policies between WiBro and HSDPA using a weight function.

The embodiments of the present invention described above are not implemented only by the apparatus and / or method, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

1 is a block diagram schematically illustrating an internal configuration of a mobile terminal according to an embodiment of the present invention.

2 is a diagram illustrating a handover policy when a WiBro interface according to an embodiment of the present invention is idle and the HSDPA interface is in an idle state or a low power state.

3 is a diagram illustrating a handover policy when a WiBro interface according to an embodiment of the present invention is in an idle state and an HSDPA interface is in an active state.

4 is a diagram illustrating a handover policy when the WiBro interface is active and the HSDPA interface is in the idle state or the low power state according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a state combination of a WiBro interface and an HSDPA interface according to an embodiment of the present invention in a finite state machine (FSM) according to a handover policy.

FIG. 6 is a diagram illustrating a condition for performing a handover between a WiBro and a HSDPA according to an exemplary embodiment of the present invention using a weight function. Referring to FIG.

Claims (12)

A handover selection method for performing a handover when a mobile terminal simultaneously supporting a plurality of radio interfaces simultaneously detects heterogeneous radio networks, (a) receiving second handover information by accessing an information server storing information required for generating a first handover information and a handover decision policy measured by the mobile terminal; (b) a state combination of a first wireless interface of a first wireless network supported by the mobile terminal and a second wireless interface of a second wireless network, and a state combination of at least one of the first handover information and the second handover information Setting a differentiated handover condition based on the handover condition; And (c) performing a handover by driving the first wireless interface or the second wireless interface according to the set handover condition, Wherein the state combination in the step (b) is configured based on an operation state of the first wireless interface and the second wireless interface, The operation state is one of an idle state (Idle) or a low power state (Low-Power) and an active state (Active) The handover selection method comprising the steps of: The method according to claim 1, In the step (b) (b1) when the first wireless interface is idle and the second wireless interface is idle or low-power, (b2) the first wireless interface is in an idle state, the second wireless interface is in an active state, (b3) the first wireless interface is active and the second wireless interface comprises an idle state or a low-power state, Wherein the step (b1), the step (b2), and the step (b3) are performed. 3. The method of claim 2, In the step (b1) Wherein the mobile station maintains a state in which the signal quality information in the first wireless network is greater than a predetermined threshold signal quality information for a predetermined time, and when the bandwidth requirement of the mobile station is greater than a maximum available bandwidth of the second wireless network, To the first wireless network, and transitioning the state of the second wireless access interface controlling the second wireless network to a low power state / RTI &gt; 3. The method of claim 2, If it is assumed in the step (b1) that the second wireless network consumes a lower power than the first wireless network, When the bandwidth requirement of the mobile station is smaller than the maximum available bandwidth of the second wireless network and prioritizes power consumption, driving the second wireless interface to perform connection to the second wireless network / RTI &gt; 3. The method of claim 2, If it is assumed that the first wireless network is less expensive than the second wireless network in step (b1) If the state of the signal quality information in the first wireless network is greater than a predetermined threshold signal quality information for a predetermined time and gives priority to the communication cost, the first wireless interface is driven to connect to the first wireless network And transitioning the state of the second air interface to a low power state / RTI &gt; 3. The method of claim 2, In the step (b2) The first wireless network is detected by maintaining a state in which the signal quality information in the first wireless network is greater than a predetermined threshold signal quality information for a predetermined period of time. The first wireless network is detected and the remaining network capacity of the mobile terminal, Determining a handover to the first wireless network considering at least one of transmission quality of the first wireless network / RTI &gt; 3. The method of claim 2, In the step (b3) Wherein the first wireless network maintains a state in which the signal quality information in the first wireless network is smaller than a predetermined threshold signal quality information for a predetermined time and drives the second wireless interface to perform connection to the second wireless network, Transitioning the state of the interface to the idle state / RTI &gt; 3. The method of claim 2, In the step (b3) When the remaining battery capacity of the mobile terminal is less than a predetermined threshold battery capacity and the second wireless network satisfies the communication bandwidth request of the mobile terminal, the second wireless interface is driven to connect to the second wireless network , Transitioning the state of the first air interface to an idle state / RTI &gt; 3. The method of claim 2, In the step (b3) If the second wireless network satisfies the current transmission quality requirement while maintaining a state in which the inter-terminal delay time or jitter of the mobile terminal is greater than a predetermined transmission quality requirement for a predetermined time, Performing a connection to the second wireless network, and transitioning the state of the first wireless interface to an idle state / RTI &gt; A handover decision information generating step of generating handover decision information including first handover information measured in a mobile terminal supporting a plurality of radio interfaces and second handover information required to generate a handover decision policy received from the information server, Generating unit; A handover condition determiner configured to set a handover condition differentiated based on a state combination of the plurality of radio interfaces and the handover decision information; And And a handover performing unit for performing a handover by driving the wireless interface of the network when the set handover condition is satisfied and transitioning the wireless interface of the network used before the handover to a low power state, Wherein said state combination is configured based on an operation state of said plurality of wireless interfaces, The operation state is one of an idle state (Idle) or a low power state (Low-Power) and an active state (Active) The mobile terminal comprising: 11. The method of claim 10, Wherein the handover decision information is at least one of a transmission quality of a network, a communication cost required to access a network, a power consumption of the mobile station, and signal quality information of the mobile station. 12. The method of claim 11, Wherein the handover condition determiner sets the handover condition using a value obtained by multiplying the transmission quality, the communication cost, the power consumption, and the signal quality information by predetermined weights, respectively.

Images