KR20140020684A - Method and apparatus for controlling an use of a heterogeneous network, considering congestion status in a wireless communication systtem - Google Patents

Abstract

The present invention relates to a method of acquiring an additional wireless resource for transmitting data to a user in a wireless communication system such as long term evolution (LTE) using a Non-3GPP access network such as WLAN, thereby improving network performance and quality of experience by the user. In the present invention, the provided method may collect information related to the dynamically changing WLAN using a UE and may provide quick and correct status information containing a congestion status of the WLAN to the UE, thereby enhancing the experience of service quality compared with existing technologies. In addition, the present invention proposes a method that may prevent a number of UEs from moving to access a network at once and adjust the frequency of the confirmation processes to check whether access to the networks are available for traffic transmission. Furthermore, the present invention proposes a method of using an indicator capable of presenting the congestion status of the WLAN more accurately.

Description

TECHNICAL AND APPARATUS FOR CONTROLLING AN USE OF A HETEROGENEOUS NETWORK, CONSIDERING CONGESTION STATUS IN A WIRELESS COMMUNICATION SYSTTEM}

The present invention relates to a control method and apparatus for using a heterogeneous network in a wireless communication system, and more particularly to a user terminal in consideration of signal strength and congestion of an access network in a wireless communication system including a heterogeneous network. A method and apparatus are provided for selecting and using a suitable access network.

In general, mobile communication systems have been developed to provide voice services while guaranteeing user activity. However, the mobile communication system is gradually expanding not only to voice but also to data service, and now it has developed to the extent of providing high-speed data service. However, in a mobile communication system in which a service is currently provided, a lack of resources and users demand higher speed services, and therefore, a more advanced mobile communication system is required.

As a system under development in the next generation mobile communication system in response to this demand, standard works for LTE (Long Term Evolution) are underway in the 3rd Generation Partnership Project (3GPP). LTE is a technology that implements high speed packet-based communication. Various methods are discussed for this purpose. For example, there is a method of reducing the number of nodes located on a communication path by simplifying the structure of a network, and a method of approaching wireless protocols to a wireless channel as much as possible.

In such a mobile communication system, the terminal may simultaneously use a plurality of heterogeneous networks. In this case, whether a user transmits specific traffic through a mobile communication system may be determined based on various information. In consideration of the characteristics of the mobile communication system that changes rapidly with time, information to be considered when selecting an access network to transmit traffic needs to be collected and provided quickly enough to reflect the actual situation. In addition, when a large number of user traffics are simultaneously moved to one access network in a heterogeneous network, the access network may be congested, thereby degrading user experience service quality. On the other hand, if a user terminal uses one access network and searches for another access network with better conditions too often, the battery is wasted. If the user terminal performs at an excessively long interval, the user may miss the opportunity to use a good access network. Occurs. Finally, if the indicators of the congestion status of the access network are not accurate, the congestion status of each access network may be blocked by unnecessary access to the access network or by allowing a larger number of user terminals to be accessed even if they are already congested. It is necessary to define an indicator that can accurately represent.

The present invention provides an efficient control method and apparatus for use of a heterogeneous network considering a congestion state in a wireless communication system.

The present invention also provides a method and apparatus for selecting an access network most suitable for a user terminal in consideration of a congestion state of an access network (AN) in a wireless communication system including a heterogeneous network.

In a wireless communication system according to an embodiment of the present invention, a control method for using a heterogeneous network may include: instructing at least one user terminal of a status report of at least one heterogeneous network; Receiving state information for one heterogeneous network, and determining whether the user terminal traffic traffic to a heterogeneous network determined based on the state information.

In addition, the heterogeneous network use control method of a base station in a wireless communication system according to an embodiment of the present invention is a command step for instructing at least one user terminal to collect and report the status of at least one heterogeneous access network, from the heterogeneous access network Acquiring the state information of the heterogeneous access network directly or through the user terminal, if the information update for the heterogeneous access network is required to notify at least one user terminal by using a broadcast method or direct communication Characterized in that it comprises a.

In addition, the heterogeneous network use control method of a base station in a wireless communication system according to an embodiment of the present invention is a command step for instructing at least one user terminal to collect and report the status of at least one heterogeneous access network, from the heterogeneous access network An acquiring step of acquiring state information of the heterogeneous access network directly or through the user terminal; determining whether to offload traffic of some user terminals to the heterogeneous access network in consideration of the heterogeneous access network and its own state; When offloading is required to the heterogeneous access network, it is characterized in that it comprises the step of notifying at least one user terminal by using a broadcast method or direct communication.

In addition, in the wireless communication system of the present invention, an entity providing a policy for heterogeneous access network selection may determine a parameter for a time interval at which a user terminal may attempt to select a heterogeneous access network for each policy, wherein the time interval parameter is determined. It characterized in that it comprises a transmitting step of informing the at least one user terminal a policy comprising a. Also, when the user terminal receives the policy including the time interval parameter, the user terminal includes a determination step of determining whether to change the access network to which the traffic is transmitted according to the policy once for each time interval. It is done.

In addition, in the wireless communication system of the present invention, the entity for setting and providing the parameters of the user terminal is a determination step of determining a parameter for the time interval when the user terminal attempts to switch between heterogeneous access network, at least one of the time interval parameter It characterized in that it comprises a transmitting step informing the user terminal. Also, when the user terminal receives the time interval parameter, the user terminal may include determining whether to switch the access network to which traffic is to be transmitted once for each time interval.

In addition, in the wireless communication system of the present invention, the congestion information of WLANs exchanged by each entity includes a normalized contention window size. Considering all of the above, characterized in that it comprises a process of determining whether the WLAN is congested.

According to an embodiment of the present invention, the base station collects information related to a dynamically changing WLAN (WLAN) using a user terminal to provide state information including a congestion state of the WLAN to the user terminal quickly and accurately. In comparison, the user experience service quality can be improved.

In addition, according to an embodiment of the present invention, it is possible to prevent a plurality of user terminals from moving simultaneously to one access network to prevent a situation in which the access network is congested again as soon as the access network is removed from congestion.

In addition, according to an embodiment of the present invention, by adjusting the frequency of the confirmation process for the selection of the access network to transmit traffic, it is possible to prevent the situation in which the terminal wastes unnecessary battery or inefficient use of the access network.

In addition, an embodiment of the present invention may provide a traffic offloading method and apparatus considering a congestion state of an access network.

In addition, according to an embodiment of the present invention, it is possible to prevent an excessive use of the WLAN or waste of idle resources of the WLAN by more accurately calculating and using an indicator indicating the degree of congestion of the WLAN.

1 illustrates an example of using a heterogeneous access network in a mobile communication system.
2 is a diagram illustrating an example of a process of a base station collecting information of a neighbor WLAN using a user terminal according to the first embodiment of the present invention.
3 is a diagram illustrating an example of a process of measuring and collecting information of a WLAN by a user terminal according to a command of a base station according to the first embodiment of the present invention;
4 is a diagram illustrating an example of a process of collecting information associated with a WLAN using an idle user terminal according to a first embodiment of the present invention;
5 is a diagram illustrating an example of a process of delivering information associated with a collected WLAN to user terminals according to a second embodiment of the present invention.
6 illustrates an example of a process of moving traffic of a user terminal to a WLAN according to a second embodiment of the present invention.
7 is a diagram showing an example of a structure including a time interval for re-evaluation in a policy management object according to the third embodiment of the present invention.
8 is a diagram illustrating an example of a structure including a time interval in which traffic can be moved between heterogeneous networks in a NAS management object according to a third embodiment of the present invention.
9 is a diagram showing an example of a structure of element information indicating a congestion situation of a WLAN according to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Further, in describing embodiments of the present invention in detail, while the basic 3GPP (Third Generation Partnership Project) LTE system will be the main object, embodiments of the present invention may be applied to other communication / computer systems It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1 is a diagram illustrating an example of using a heterogeneous access network in a mobile communication system.

Referring to FIG. 1, as shown, the radio access network 110 of an LTE mobile communication system includes a next-generation base station (evolved Node B, EUTRAN, hereinafter referred to as base station, eNB, or Node B) (not shown) and control plane. It includes a Mobility Management Entity (MME) (not shown) in charge and a Serving-Gate (S-GW) 120 in charge of a user plane. The user equipment (hereinafter referred to as UE) 100 refers to an ENB and a serving gateway (S-GW) 120, and a PDN (Packet Data Network) gateway (P-GW) (PDN-Gateway) 130. Connect to external network via The S-GW 120 operates as a reference point unchanged in terms of network during handover of the UE 100. That is, even if the UE 100 moves between a plurality of eNBs, the S-GW 120 does not change. The P-GW 130 assigns an IP address to the UE 100, adapts to the QoS level of the service, and performs flow-based charging.

The eNB corresponds to an existing Node B of the UMTS system. The eNB is connected to the UE 100 through a wireless channel and performs a more complicated role than the existing Node B. In FIG. 1, it is assumed that the eNB is included in a 3GPP Access 110 block.

In the LTE system, all user traffic including real-time services such as Voice over IP (VoIP) through the Internet protocol is serviced through a shared channel, so a device for collecting and scheduling situation information of UEs is required. Is in charge.

In addition, in FIG. 1, the S-GW 120 is a device for providing a data bearer, and generates or removes a data bearer under the control of the MME. The MME is a device that is in charge of various control functions. One MME may be connected to a plurality of base stations. The Policy Control and Charging Rules Function (PCRF) 140 controls the policies related to Quality of Service (QoS) and billing.

As in the example of FIG. 1, the mobile communication system is not only a 3GPP access network (or a first wireless network, hereinafter also used interchangeably) such as LTE, but also a Non-3GPP access network 150 (or WLAN, WiMAX, CDMA2000) (or Or a second wireless network, which will be used interchangeably hereinafter).

The UE 100 may transmit and receive data by accessing the P-GW 130 through the Non-3GPP access network 150. In this case, a separate ePDG (enhanced packet) for security or QoS mapping is performed. Data Gateway) 150 may be used, and in this case, Non-3GPP Access Network 150 is referred to as an Untrusted Non-3GPP Access Network. The ePDG 150 authenticates between the terminal and the ePDG 150 and creates a tunnel in order to make the untrusted access network having a security problem reliable. And through this, the UE that can be trusted the Non-3GPP access network 150 is connected to the P-GW 130 via the ePDG (150).

Meanwhile, when the 3GPP access network and the Non-3GPP access network 150 are available for the UE to access and transmit data to the mobile communication system, there must be information and a selection policy necessary for selecting an access network, which is previously known to the UE. It may be set or may be provided to the terminal from a separate server such as an access network discovery service function (ANDSF) (not shown).

An embodiment of the present invention will first be described a method in which a base station can obtain status information of a non-3GPP access network such as a WLAN (hereinafter, for convenience of description, the WLAN will be described as an example). The state information of the access network collected according to the present embodiment may be used to assist a user in determining a traffic movement according to another embodiment of the present invention, and specific operations thereof will be described below.

2 is a diagram illustrating a process in which a base station measures a state of a WLAN using a UE and collects a result according to the first embodiment of the present invention.

In step 204, the base station 202 transmits an RRCConnectionReconfiguration message to the UE 200 to set a measurement for WLANs in the vicinity, and the message is a message of a WLAN to be measured. Information is transmitted including at least one measurement target wireless LAN information (measObjectWLAN), the measObjectWLAN is a frequency or channel number of the WLAN, an identifier of the WLAN (Homogenous Extended Service Set ID), SSID (Service Set ID), BSSID At least one of (Basic Service Set ID) is included. In step 205, the UE, having received the message, stores the measObjectWLANs inserted in the message and collects information on WLANs corresponding to each of the measObjectWLANs using the stored information. If only the frequency or channel information is included in the measObjectWLAN, the UE moves to the corresponding frequency or channel and includes at least one of information (HESSID, SSID, BSSID, signal strength, BSS (Basic Service Set) load information) of the existing WLAN AP. Collect one). The BSS load information includes at least one of the number of STAs (corresponding to the UE) belonging to the WLAN, channel utilization, available admission capacity, and normalized contention window size. This is information.

If the identifier corresponding to the WLAN corresponding to the measObjectWLAN, that is, HESSID, SSID, and BSSID is included, the WLAN detects whether the WLAN having the corresponding identifier exists and collects the state (signal strength and BSS load information) together with the presence or absence of the WLAN. In step 208, the UE 200 transmits a probe request message, and in step 210, the UE 200 sends a probe response message from the WLAN AP 206. It may be performed by receiving, or may be performed by the UE 200 receiving a Beacon message transmitted by the WLAN AP 206. The Probe Response message or the Beacon message includes at least one of WLAN information, that is, HESSID, BSSID, SSID, and BSS load. In addition, in operation 212, the UE 200 may also measure signal strength using a message received from the WLAN AP 206. When the information on the WLANs is collected, the UE 200 transmits the measurement result (measResultsWLAN) for at least one WLAN to the base station 202 in the measurement report message in step 214. The measResultWLAN includes at least one of frequency or channel number, HESSID, SSID, BSSID, BSS load, signal strength, and user location for the measured WLAN. In step 216, the base station 202 stores the new WLAN information if it is reported from the UE 200, and updates the existing information when the existing information is changed. Similarly, it is also possible for the WLAN AP 206 to report the information about the WLAN directly to the base station 202, where the information included in the report message is the same as the UE 200 reports, The only difference is that it can only contain information from the WLAN.

3 is a diagram illustrating an operation of a UE for measuring and collecting information related to a WLAN according to a first embodiment of the present invention.

Referring to FIG. 3, in step 302, the UE receives the measurement target WLAN information (measObjectWLAN) from the base station, and in step 304, the set of WLANs to be included in the measurement target is determined using these measObjectWLANs. In step 308, the UE selects one measObjectWLAN from the target set of the WLAN and performs a measurement process using information included in the selected measObjectWLAN in step 310. The method of collecting information about WLANs is the same as the operations of steps 206, 208, 210, and 212 described with reference to FIG. 2.

In step 312, if the WLAN AP includes the BSS load element in the beacon or probe response message, the UE proceeds to step 316 to store the measurement result and excludes the measObjectWLAN from the target set. If the WLAN AP does not include the BSS load element in the beacon or probe response message in step 312, the UE directly measures BSS load information in step 314. The object to be measured is at least one of the ratio of time used to transmit the actual packet during a certain time (Channel Utilization), the number of STAs (Stations) using the WLAN, or the size of the contention window (Normalized Contention Window) ). In step 318, if the measurement of the corresponding measObjectWLAN is completed, the same process is repeated with respect to the remaining measObjectWLAN, and when the measurement is completed, the measurement process is terminated.

An embodiment of the present invention will now be described a method for an LTE system to collect information related to a neighbor WLAN by using a UE that enters an idle mode because there is no data transmission and reception. When the UE is idle, no communication with the base station is performed until data transmission and reception occurs. In this case, unlike the connection state, the base station cannot determine the location of the terminal at the cell level. Therefore, it is useful to report the information measured in the idle state in relation to the position of the terminal when the measurement is performed.

4 is a diagram illustrating a process of collecting and reporting information on a WLAN by using an idle UE according to a first embodiment of the present invention.

Referring to FIG. 4, in step 406, the base station 404 may set the at least one UE 402 to collect WLAN information in an idle state, which is a WLAN frequency or channel number, HESSID in a logged measurement configuration message. At least one or more of the SSID and the BSSID is transmitted. The UE, which has received this information, performs measurement and information collection on the WLAN when it is idle in step 408. Since the operation of the specific terminal performed in step 408 is similar to that shown in FIG. 3, description thereof is omitted. After the RRC connection establishment operation is performed between the terminal and the base station, and in step 410, when the UE is in the connected state, the measured UE reports the measurement result for the WLAN including measurement WLAN indication information (logMeasAvailableWLAN indication) in the RRC message. Inform the base station that there is a presence. In step 412, the base station receiving the notification sends a request to the UE to report the collected information from the UE. Upon receiving the report request from the base station, the UE inserts measurement information on the WLAN into a log measurement report (LogMeasReport) in a UE information response (UEInformationResponse) message in step 414 and transmits the WLAN frequency or channel number, At least one of the HESSID, the SSID, the BSSID, the BSS load, and the user location is included. In step 416, the base station stores the new WLAN information if it is reported from the UE, and updates the existing information when the existing information is changed. In addition, in step 420, the base station reports the measured information including the ID of the UE reporting the measurement information to the trace server (418), if necessary. The trace server is a network entity that collects and stores the overall state of an operator network. When the UE reports the information collected according to the above process to the base station, the base station reports it back to the trace server. Through this process, the trace server can collect the state of the entire provider network.

FIG. 5 is a diagram illustrating a method for notifying at least one UE of information related to a WLAN using information collected by a base station according to a second embodiment of the present invention.

Referring to FIG. 5, in step 508 and 510, the base station 504 may collect information on the WLAN using the measurement method using the UE of the previous embodiment, or may collect information on the WLAN using another method. . In step 512, the base station 504 may transmit WLAN discovery information including WLAN-related information to a plurality of UEs in a cell through broadcast, or to one UE at a time using RRC signaling. have. The WLAN discovery information transmitted to the UE includes at least one of WLAN frequency or channel number, HESSID, SSID, BSSID, BSS load, location of WLAN AP, and validity timer. The WLAN discovery information is included in one of a System Information Block (SIB) when transmitted through a broadcast, and included in one of RRC messages transmitted to a UE by a base station when transmitted through RRC signaling. If the WLAN discovery information includes a timer (validity timer), the UE determines that the received information is valid until the end of the timer (validity timer). In step 514, when the UE having received the message including the WLAN discovery information stores the information and determines whether to move the IP flow, the UE (Access Network Discovery and Selection, which is a server performing a traffic movement / distribution function) Function), or when using a policy stored in the terminal).

On the other hand, traffic transfer / distribution between heterogeneous networks is generally determined by a policy delivered from the policy server such as ANDSF to the UE. This ANDSF-based mechanism has the following disadvantages.

First, policy delivery through ANDSF is based on IP communication between ANDSF and UE, and a secure connection must be created for ANDSF to deliver policy to UE. Considering this point, collecting the state information of the rapidly changing access network and delivering it to the UE by reflecting it in the policy is a factor to reduce the adaptability to the access network. Therefore, an embodiment of the present invention proposes a method in which a base station already having a secure connection with a UE can accurately and quickly instruct a command for using a WLAN.

6 is a diagram illustrating a process of a base station moving traffic to a WLAN by a base station according to a second embodiment of the present invention.

Referring to FIG. 6, in step 608, the base station 604 sets up a measurement for the UE 602 and receives a report on the measurement. In step 610, the base station determines to move traffic to the WLAN in consideration of measurement information reported from the UE, its state, and the QCI (QoS Class Identifier) of the bearer of the UE. At this time, the re-evaluation timer used to later determine whether the UE that will use the WLAN continues to use the WLAN may be set to have different values between the UEs. In step 612, the base station transmits a mobility command message to the UE, and transmits a WLAN frequency or channel number, HESSID, SSID, BSSID, EPS bearer ID list, re-evaluation timer, and return condition for the traffic to be transferred to the WLAN. Include at least one. Here, the return condition is a condition for the UE to stop using the WLAN and to use the 3GPP access network again, and the values related to the BSS load, that is, station count, channel utilization, and contention window A threshold may be included for a content window size. When the UE receives a Mobliity Command message for WLAN movement, if there is a policy previously received from ANDSF, it takes precedence over the policy. In step 614, if the UE decides to use the WLAN, the UE starts transmitting traffic through the WLAN to the bearer included in the bearer ID list. If the re-evaluation timer expires in step 616, the UE resets the re-evaluation timer and measures whether the state of the access network has changed. In step 618, the UE compares the return condition with the measured return condition. send.

In another embodiment of the present invention, a process of preventing a large number of UEs from simultaneously moving to an access network to prevent congestion as soon as the access network is removed from congestion and confirming whether an access network to which traffic is available is available. We'll describe how to control the frequency of data loss to avoid unnecessary battery waste and inefficient use of access networks. If the first problem situation is more specifically described, for example, if the WLAN enters a congestion state and cannot accept additional UEs, then the congestion is resolved and notified, a large number of UEs aware of this use the WLAN at the same time. You can try. In this case, as soon as the WLAN is removed from the congestion situation, the WLAN will be congested again. The second problem situation is that if the UE tries to receive information about nearby WLANs too often to check whether the WLAN is available, the battery consumption will be high, and conversely, if the UE tries to check whether the WLAN is available too much Running at longer intervals increases the unused time even when the WLAN is available.

In order to solve this problem, the following two methods will be described with reference to FIGS. 7 and 8.

FIG. 7 illustrates an example of a structure including a time interval for re-evaluation in a policy management object according to the third embodiment of the present invention, and FIG. 8 illustrates a NAS management object according to the third embodiment of the present invention. Shows an example of a structure including a time interval in which traffic movement between heterogeneous networks is possible.

The first method is applicable when using a policy for heterogeneous network selection (using Policy or ISRP Management Object, 702).

Referring to FIG. 7, the policy transmitted from the ANDSF to the terminal or stored in advance by the terminal is set to have additional information called an evaluation interval in addition to existing information such as RulePriority, Roaming, PLMN, etc. (704). If the UE has the policy, the process of selecting an access network to transmit traffic according to the policy is limited to be performed only once per Evaluation Interval. That is, if the UE has performed the process of evaluating and selecting the access network to transmit traffic according to the policy, the next evaluation according to the policy is possible only after the evaluation interval. Here, Evaluation Interval is set separately for each policy.

Referring to FIG. 8, a second method is to configure an Intersystem Mobility Interval 804 on a UE using a Non-Access Stratum (NAS) Management Object (802). That is, when a UE receives a NAS Management Object and applies an Intersystem Mobility Interval accordingly, an attempt by the UE to move traffic to another access network using only one access network can be performed only once for that interval. . If the UE has performed the process of selecting an access network to transmit traffic according to the policy or the command of the base station, the next traffic movement attempt according to the policy or command is possible only after the Intersystem Mobility Interval. In this case, only one Intersystem Mobility Interval is maintained in the UE.

Lastly, according to an embodiment of the present invention, a method of more accurately calculating and using an indicator indicating the degree of congestion of a WLAN will be described so as to prevent an excessive use of the WLAN or a waste of idle resources of the WLAN.

9 is a diagram illustrating the format of an information element including indicators indicating a congestion degree of a WLAN according to a fourth embodiment of the present invention.

This information element may be delivered to the UE by the WLAN AP by inserting it into a Probe Response or Beacon message, and part of the information element may be used when the UE reports the state of the WLAN to the base station or informs the UEs of the state of the base station's WLAN. Can be.

Referring to FIG. 9, the station count 906 represents the number of STAs (UEs) associated with the WLAN AP, and the channel utilization 908 represents the ratio of time used for actual data transmission among time periods between two consecutive beacons. The value representing. The Available Admission Capacity 910 is a value indicating how much the WLAN can accept usage requests from UEs, and the Normalized Contention Window 912 is an indicator indicating the degree of contention required to transmit data packets within the WLAN. The larger this value is, the higher the probability of collision for packet transmission is, indicating that the WLAN is congested. The Normalized Contention Window 912 should be calculated using a statistical method to reflect the overall situation of the WLAN.

If the UE or the base station receives both the STA number 906 and the Channel Utilization 908 information, the two information should be considered simultaneously when determining whether the WLAN having the corresponding information is congested. This is because Channel Utilization can be 100% even when only one UE uses the entire resource due to the characteristics of the WLAN. In this case, WLAN is not congested, so the number of STAs and Channel Utilization must be considered at the same time. Meanwhile, the normalized contention window 912 is an index indicating a congestion state of the entire WLAN and may be independently considered and used when determining whether the WLAN is congested.

Claims (1)

In the control method for the use of heterogeneous networks in a wireless communication system,
Instructing at least one user terminal of at least one heterogeneous network status report;
Receiving state information on the at least one heterogeneous network from the at least one user terminal; And
And determining whether to move traffic of the user terminal to a heterogeneous network determined based on the state information.

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