HK1217856B - Performance monitoring of wireless local area network (wlan) offloading in wireless cellular networks - Google Patents

Description

Performance monitoring of wireless LAN offload in wireless cellular networks

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is related to and claims priority from U.S. Provisional Patent Application No. 61/748,706, filed January 3, 2013, and the contents of which are incorporated by reference in their entirety.

Technical Field

The present invention relates to performance monitoring, and in particular to performance monitoring of traffic distribution in a wireless local area network (WLAN) in a wireless cellular network.

Background Art

The accelerated adoption of smartphones, tablets, and cloud computing has led to rapid growth in global mobile data traffic. Forecasts indicate that mobile data traffic will increase 26-fold by 2015 compared to 2010, reaching 6.3 exabytes per month. Network capacity planning through the deployment of additional base stations and the implementation of new technologies will have only a limited role in addressing this growth, as mobile data pricing tends to remain relatively stable.

One solution to this problem involves offloading data traffic from mobile wireless cellular networks, such as 3GPP Long Term Evolution (LTE) or LTE-Advanced (LTE-A) networks, to wireless local area networks (WLANs). In this scenario, wireless mobile devices, such as user equipment (UE) served by a cellular base station, such as an evolved Node B (eNB), can offload some or all of their data traffic to available WLAN access points. However, mechanisms are needed to monitor the performance of this configuration to ensure efficient and reliable operation of the system in order to achieve the goals of mobile data offload.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matter will become apparent upon proceeding with the following detailed description, and upon reference to the accompanying drawings in which like numerals describe like parts, and in which:

FIG1 illustrates a top-level system block diagram of an exemplary embodiment of the present invention;

FIG2 shows a block diagram of an exemplary embodiment of the present invention;

FIG3 shows a block diagram of another exemplary embodiment of the present invention;

FIG4 shows a block diagram of another exemplary embodiment of the present invention;

FIG5 illustrates a data structure related to an exemplary embodiment of the present invention;

FIG6 shows a data structure related to another exemplary embodiment of the present invention;

FIG7 shows a data structure related to another exemplary embodiment of the present invention;

FIG8 shows an operational flow chart of an exemplary embodiment of the present invention;

FIG9 shows an operational flow chart of another exemplary embodiment of the present invention;

FIG10 is a flowchart illustrating the operation of another exemplary embodiment of the present invention;

While the following detailed description will be given with reference to exemplary embodiments, it is apparent that many equivalents, modifications, and changes therein will be apparent to those skilled in the art.

DETAILED DESCRIPTION

The present invention generally provides an apparatus, system, and method for performance monitoring of WLAN data traffic offloading in a wireless cellular network such as an LTE or LTE-A network. In response to an increase in data traffic, a UE (e.g., a mobile cellular device) may offload data traffic from a serving cell eNB to an available WLAN access point (AP). The WLAN AP is configured to measure the number of offloaded UEs and the packet throughput from these UEs to the AP. The WLAN AP is also configured to generate an offload performance report based on these measurements and send the report to an integration reference point (IRP) manager. The WLAN AP may be further configured to provide an operational status message regarding its own status (e.g., out-of-service status or restored-service status) to the IRP manager.

The IRP manager may be configured to receive offload performance reports from WLAN APs and correlate performance measurements received from eNBs with this data to calculate system-wide data traffic offload performance and operational efficiency.

FIG1 illustrates a top-level system block diagram 100 of an exemplary embodiment of the present invention. A wireless network is shown as including cell coverage areas: Cell A 102 and Cell B 104, both served by an eNB 106. In another exemplary embodiment, eNB 106 provides coverage as two sectors: Cell A 102 and Cell B 104. Any number of WLAN APs 108 are located within or within the network area of either Cell A 102 or Cell B 104. UEs 110 are typically configured to send and receive voice and data traffic to and from eNBs 106. However, in certain instances, such as under increased traffic conditions, UEs 110 offload some or all data traffic from eNBs 106 to one or more WLAN APs 108. A network manager 112 can be configured to communicate with the WLAN APs and eNBs in the network to monitor data offload performance and ensure reliable and increased availability of system operation, as described in greater detail below.

While this is a simplified example for demonstration purposes, it should be understood that in practice any configuration of different types of eNBs, UEs, and WLAN APs may be utilized and may provide coverage extending to any number or regions, areas, or sectors. The wireless network may be compatible or capable of being compatible with Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A) based on wireless network standards, including current, previous, and future releases.

FIG2 illustrates a block diagram 200 of an exemplary embodiment of the present invention. The network manager 112 is shown as including an IRP manager 204, also known as an operations support system (OSS). An IRP manager or OSS is typically a computer system and/or software application that provides and facilitates network support functions for a network operator or carrier. These support functions include performance monitoring and fault detection. The IRP manager 204 is configured to communicate with the 3GPP eNB 106 via a 3GPP domain manager 206, which includes a 3GPP element manager 208. The 3GPP domain manager 206 is configured to provide element and domain management functions for a subnetwork, while the 3GPP element manager 208 is configured to provide a set of end-user functions for the management of a group of related types of network elements, such as the 3GPP eNB 106.

The IRP manager 204 may also be configured to communicate with the WLAN AP 108 via a WLAN domain manager 210, which includes a WLAN element manager 212. The WLAN domain manager 210 may be configured to provide element and domain management functionality for a subnetwork, while the WLAN element manager 212 may be configured to provide a set of end-user functions for the management of a set of related types of network elements, such as the WLAN AP 108.

The 3GPP domain manager 206 and the WLAN domain manager 210 may be configured to provide a Type 2 interface 220, which may be a standardized interface, to the network manager 112, and a Type 1 interface 230, which may be a proprietary interface, to the eNB 106 and the WLAN AP 108. The IRP manager 204 is configured to communicate with an IRP agent resident in the WLAN element manager 212 via the Type 2 interface 220. Any message translation required between these two types of interfaces is performed by the 3GPP domain manager 206 and the WLAN domain manager 210 (which may include an IRP agent configured at least in part for this purpose).

3 shows a block diagram 300 of another exemplary embodiment of the present invention. WLAN AP 108 is shown to include a performance measurement granularity timer 302, a performance measurement module 304, a performance report timer 310, a performance report generation module 312, and an operating state determination module 314. Performance measurement module 304 is further shown to include a packet throughput measurement module 306 and a UE counting module 308.

A performance measurement granularity timer 302 can be configured to trigger performance measurements at the WLAN AP, so that measurements are taken at intervals of a predetermined or programmable suitable duration. In response to the granularity timer 302 triggering measurements, the performance measurement module 304 measures data packet throughput, such as using module 306, and measures the number of connected UEs, such as using module 308. Packet throughput measures the total volume of data being transmitted, for example, via the media access control (MAC) or internet protocol (IP) layer, and the elapsed time per unit, thereby providing an indication of activity and load on the WLAN AP from UEs. In certain embodiments, the measured packet throughput is associated with a Quality of Service (QoS) class or a user priority class. The UE count indicates the number of UEs associated or connected to a given WLAN AP. This is useful when determining offload performance. For example, a relatively low packet throughput combined with a relatively high number of UEs indicates poor WLAN performance. As another example, during expected high traffic times (eg, rush hour), a relatively low UE count associated with a WLAN AP may indicate a problem with the WLAN AP that is causing UEs difficulty connecting.

The performance report timer 310 is configured to trigger the performance report generation module 312 to generate a performance report at intervals of a predetermined or programmable suitable duration. In response to the triggering of the report timer 310, the performance report generation module 312 generates a performance report based on the measured packet throughput and the number of UEs. The WLAN performance report can then be sent to the WLAN element manager 212 via the type 1 interface 230 and to the OSS or IRP manager 204 via the type 2 interface 220.

The operational state determination module 314 is configured to determine the operational state of the WLAN AP 108. The operational state includes an out-of-service state and a restored-service state. An out-of-service state relates to a failed or "faulty" state of the WLAN AP. In some embodiments, the operational state includes a "test" state to indicate that the WLAN AP is in test mode and is not currently transmitting packets. This "test" state is a temporary state. The operational state determination module 314 sends a WLAN notification or message to the WLAN element manager 212 via the type 1 interface 230, and then to the OSS or IRP manager 204 via the type 2 interface 220. In some embodiments, the WLAN notification may be combined with a WLAN performance report and sent as one or more data elements or counters associated with a management information base (MIB) message.

4 shows a block diagram 400 of another exemplary embodiment of the present invention. The IRP manager (or OSS) 204 is shown to include a WLAN performance report receiver module 402, an eNB performance measurement data receiver module 404, a WLAN operation status tracking module 406, a performance correlation module 408, and an offload performance calculation module 410.

WLAN performance report receiver module 402 may be configured to receive WLAN performance reports generated by one or more of the aforementioned WLAN APs. eNB performance measurement data receiver module 404 may be configured to receive performance measurement data from one or more eNBs 106. The eNB measurement data may provide information collected by the eNB regarding the amount of data traffic received or transmitted from a UE served by the eNB at any given time. The WLAN measurement data may provide information collected by the WLAN AP regarding the amount of data traffic transmitted or received from a UE served by the WLAN AP. Performance correlation module 408 may be configured to correlate the WLAN performance data from module 402 with the eNB performance data from module 404 to determine the amount of data traffic offloaded from the eNB to one or more WLAN APs that overlap within a cell served by the eNB at any given time.

The WLAN operational status tracking module 406 may be configured to receive operational status notifications from the WLAN APs 108 and track their status, for example, whether they are in service (out of service or restored).

The WLAN operational status can be provided along with the performance-related data from module 408 to an offload performance calculation module 410, which is configured to calculate the data traffic offload performance for the WLAN APs within the range of the network manager 112. For example, if the performance measurements provided by the eNB show an increase in the throughput of data packets offloaded to the WLAN AP, then there is a relatively good indication that the overlay WLAN AP is performing as expected. Similarly, if the operational status of the WLAN AP remains in an interrupted state for a period exceeding an acceptable threshold, then another type of problem is indicated and corrective action (e.g., maintenance) is called for.

In certain embodiments, the performance information is received from the WLAN AP and eNB as one or more data elements or counters associated with a Management Information Base (MIB) message.

5 through 7 illustrate data structures and/or message fields, such as in MIB messages, that may be compatible or capable of being compatible with 3GPP LTE and/or LTE-A based wireless network standards and/or IEEE 802.11 wireless standards, including existing, previous, and future releases.

FIG5 illustrates a data structure 500 associated with one embodiment of the present invention. The WLAN element manager 212 is configured to receive a MIB message, including a Dot11QoS counter entry (Dot11QoSCountersEntry) 502 providing a Dot11QoS Transmitted FrameCount 504 and a Dot11QoS MPDU Received Count 506. These data elements or counters 504, 506 are configured to indicate the data packet offload throughput associated with the WLAN AP. In some embodiments, the data throughput is associated with a QoS class or a user priority class. The WLAN element manager 212 is configured to convert the Dot11QoS Transmitted FrameCount 504 and the Dot11QoS MPDU Received Count 506 into a format acceptable to the IRP manager 204 and transmit them to the IRP manager 204.

FIG6 illustrates a data structure 600 associated with another exemplary embodiment of the present invention. The WLAN element manager 212 is configured to receive a MIB message including a Dot11QoSCountersEntry 602 providing a dot11 associated station count (dot11AssociatedStationCount) 604. This data element or counter 604 is configured to indicate the number of UEs connected to the WLAN AP for data traffic offload. The WLAN element manager 212 is configured to convert the dot11AssociatedStationCount counter 604 into a format acceptable to the IRP manager 204 and transmit it to the IRP manager 204.

FIG7 illustrates a data structure 700 associated with another exemplary embodiment of the present invention. The WLAN element manager 212 is configured to receive a MIB message including an interface table (ifTable) 702. The interface table further includes an interface entry (ifEntry) 704 that provides an operational status indicator (ifOperStatus) 706 for the WLAN AP. This data element 706 is configured to indicate an operational status of "up," "down," or "test." The "up" state indicates that the WLAN AP is operational (or operationally recovered from a previous condition) and is ready to transmit data packets. The "down" state indicates that the WLAN AP is experiencing some type of service interruption and is not ready to transmit data packets. This may be a temporary condition or require corrective action. The "test" state indicates that the WLAN AP is in test mode and is not ready to transmit data packets. Other suitable conditions may also be indicated as needed. The WLAN element manager 212 is configured to convert the ifOperStatus 706 into a format acceptable to the IRP manager 204 and transmit it to the IRP manager 204.

FIG8 illustrates a flow chart of operations 800 of an exemplary embodiment of the present invention. In operation 810, the WLAN AP waits for the performance measurement (PM) granularity timer to expire. In operation 820, the WLAN AP stores packet throughput measurements in a PM data log. The throughput information is associated with QoS or user priority categories. In operation 830, the number of UEs associated with the WLAN AP is stored in the PM data log. In operation 840, if the PM report timer expires, the PM data log is sent to the OSS in operation 850. The process repeats for the WLAN AP in operation 810.

In operation 860, the OSS correlates the received WLAN PM data with the additional PM data received from the eNB. In operation 870, the OSS calculates WLAN offload performance based on the correlation.

FIG9 illustrates a flowchart of operations 900 according to another exemplary embodiment of the present invention. At operation 910, a determination is made as to whether WLAN service has been interrupted. At operation 920, if service has been interrupted, an out-of-service or "failure" notification is sent from the WLAN AP to the OSS. At operation 930, a determination is made as to whether WLAN service has been restored. At operation 940, if service has been restored, a restoration-of-service notification is sent from the WLAN AP to the OSS. The process at operation 910 is repeated for the WLAN AP. At operation 950, the OSS receives the out-of-service notification, and at operation 960, the OSS receives the restoration-of-service notification.

FIG10 illustrates a flow chart of operations 1000 of another exemplary embodiment of the present invention. At operation 1010, a WLAN performance report is received from a WLAN AP. At operation 1020, performance measurement data is received from an eNB. At operation 1030, the WLAN AP performance measurement data provided in the WLAN performance report is correlated with the eNB performance measurement data. At operation 1040, data traffic offload performance is calculated based on the performance correlation between the WLAN AP and the eNB.

The embodiments of the methods described herein can be executed in a system including one or more storage media, which can store instructions that implement the above methods when executed by one or more processors, either individually or in combination. Here, the processor may include, for example, a system CPU (e.g., a core processor) and/or a programmable circuit. Therefore, it is expected that the operations according to the methods described herein can be distributed to multiple physical devices, such as processing structures at different physical locations. Similarly, it is expected that the method operations can be performed individually or in combination, as understood by those skilled in the art. Therefore, it is not necessary that each step of the flow chart is performed, and the present invention is clearly intended to enable sub-combinations of such operations, as understood by those skilled in the art.

Storage media may include any form of tangible medium, for example, any type of disk, including a floppy disk, an optical disk, a compact disc read-only memory (CD-ROM), a compact disc read-write (CD-RW), a digital versatile disc (DVD), and a magneto-optical disk; semiconductor devices such as read-only memory (ROM), random access memory (RAM) such as dynamic and static RAM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, a magnetic or optical card, or any type of medium suitable for storing electronic instructions.

The term "circuit" used in the embodiments includes, for example, hardware circuits, programmable circuits, state machine circuits, and/or firmware storing instructions executed by programmable circuits, either alone or in combination. An APP (application program) may be embodied as code or instructions executed on a programmable circuit, such as a host processor or other programmable circuit. A module used in any embodiment may be embodied as a circuit. The circuit may be embodied as an integrated circuit, such as an integrated circuit chip.

Therefore, the present invention provides an apparatus, method, system and computer readable memory for performance monitoring of WLAN data traffic offload in a wireless cellular network.The following examples relate to further embodiments.

According to one aspect, a WLAN AP is provided. The WLAN AP may include a performance measurement module that measures the number of user equipment (UE) connected to the WLAN AP for data traffic offload and further measures packet throughput from the UE to the WLAN AP. The WLAN AP of this example may also include a measurement granularity timer that triggers the performance measurement module to perform measurements. The WLAN AP of this example may also include a performance report generation module that generates a WLAN report based on the measurements provided by the performance measurement module. The WLAN AP of this example may also include a performance report timer that triggers the performance report generation module to generate the WLAN report.

Another exemplary WLAN AP includes the aforementioned components, and the measured packet throughput is associated with a quality of service (QoS) class or a user priority class.

Another exemplary WLAN AP includes the aforementioned components and further includes an operation status determination module that determines whether the WLAN AP is in an out-of-service state or a restored-service state and further generates a service status notification.

Another exemplary WLAN AP includes the aforementioned components, and the WLAN report is provided to an integrated reference point (IRP) manager.

Another exemplary WLAN AP includes the aforementioned components, and the service status notification is provided to the IRP manager.

Another exemplary WLAN AP includes the aforementioned components, and the WLAN AP communicates with the IRP manager through the IRP agent of the WLAN element manager to provide a standardized interface to the IRP manager.

Another exemplary WLAN AP includes the aforementioned components, and the IRP agent converts the packet throughput and the number of connected UEs into a format compatible with a standardized interface and an IRP manager.

Another exemplary WLAN AP includes the aforementioned components, and the WLAN report and the service status notification are incorporated into one or more data elements associated with a Management Information Base (MIB) message.

According to another aspect of the present invention, a method is provided. The method may include waiting for a performance measurement granularity timer to expire. The example method may also include measuring the number of UEs connected to the WLAN AP for data traffic offload. The example method may also include measuring packet throughput from the UE to the WLAN AP. The example method may also include storing the measured number of UEs and packet throughput in a performance data log. The example method may also include sending the performance data log to an IRP manager in response to the report timer expiring.

Another exemplary method includes the foregoing operations, and the measuring packet throughput is associated with a quality of service (QoS) class or a user priority class.

Another exemplary method includes the foregoing operations and further includes determining whether the WLAN AP is in an out-of-service state or a restored-service state, and generating a service status notification.

Another exemplary method includes the foregoing operations, and the service status notification is sent to the IRP manager.

Another exemplary method includes the foregoing operations and further includes providing, by an IRP agent of a WLAN element manager, a standardized interface to the IRP manager for transmission to the IRP manager.

Another exemplary method includes the foregoing operations and further includes incorporating the performance data log and service status notification into one or more data elements associated with a Management Information Base (MIB) message.

According to another aspect of the present invention, an IRP manager is provided. The IRP manager may include a WLAN performance report receiving module configured to receive a WLAN performance report from a WLAN AP. The IRP manager of this example may also include an evolved Node B (eNB) performance measurement data receiving module configured to receive performance measurement data from an eNB. The IRP manager of this example may also include a performance correlation module configured to correlate WLAN AP performance measurement data provided in the WLAN performance report with eNB performance measurement data. The IRP manager of this example may also include an offload performance calculation module configured to calculate data traffic offload performance based on the correlation between the WLAN AP and the eNB.

Another exemplary IRP manager includes the aforementioned components and further includes a WLAN AP operation status tracking module that receives WLAN notifications and provides WLAN AP operation status updates based on the notifications to the offload performance calculation module, wherein the calculated data traffic offload performance is further based on the provided WLAN AP operation status.

Another exemplary IRP manager includes the aforementioned components, and further includes that the WLAN AP performance measurement data includes a number of UEs connected to the WLAN AP and a packet throughput from the UEs to the WLAN AP.

Another exemplary IRP manager includes the aforementioned components, and further includes wherein the packet throughput is associated with a quality of service (QoS) class or a user priority class.

Another exemplary IRP manager includes the aforementioned components, and further includes that the WLAN AP operation state is an out-of-service state or a restored-service state.

Another exemplary IRP manager includes the aforementioned components, and further includes incorporating the WLAN AP performance measurement data and the WLAN AP operational status notification into one or more data elements associated with a MIB message.

According to another aspect, a method is provided. The method includes receiving a WLAN performance report from one or more WLAN APs. This example method may also include receiving performance measurement data from an eNB. This example method may also include correlating the WLAN AP performance measurement data provided in the WLAN performance report with the eNB performance measurement data. This example method may also include calculating data traffic offload performance based on performance correlation between the WLAN APs and the eNB.

Another exemplary method includes the foregoing operations, and one or more of the WLAN APs overlaps an eNB coverage area.

Another exemplary method includes the foregoing operations and further includes receiving a WLAN notification from the WLAN AP and tracking an operational status update of the WLAN AP based on the notification, wherein the calculated data traffic offload performance is further based on the tracked WLAN AP operational status.

Another exemplary method includes the foregoing operations, and the WLAN AP performance measurement data includes a number of UEs connected to the WLAN AP and a packet throughput from the UEs to the WLAN AP.

Another exemplary method includes the foregoing operations, and the packet throughput is associated with a quality of service (QoS) class or a user priority class.

Another exemplary method includes the aforementioned operations, and the WLAN AP operation state is an out-of-service state or a restored-service state.

Another exemplary method includes the foregoing operations and further includes incorporating the WLAN AP performance measurement data and the WLAN AP operational status notification into one or more data elements associated with a Management Information Base (MIB) message.

According to another aspect, a system is provided. The system includes means for waiting for a performance test granularity timer to expire. This example system may also include means for measuring the number of UEs connected to a WLAN AP for data traffic offload. This example system may also include means for measuring packet throughput from the UEs to the WLAN AP. This example system may also include means for storing the measured number of UEs and packet throughput in a performance data log. This example system may also include means for sending the performance data log to an IRP manager in response to the expiration of the report timer.

Another exemplary system includes the aforementioned components, and the measured packet throughput is associated with a QoS class or a user priority class.

Another exemplary system includes the aforementioned components and further includes means for determining whether the WLAN AP is in an out-of-service state or a restored-service state and generating a service status notification.

Another exemplary system includes the aforementioned components, and the service status notification is sent to an IRP manager.

Another exemplary system includes the aforementioned components and further includes means for providing a standardized interface to an IRP manager via an IRP agent of a WLAN element manager for transmission to the IRP manager.

Another exemplary system includes the aforementioned components and further comprises means for incorporating the performance data log and service status notification into one or more data elements associated with a MIB message.

According to another aspect, a system is provided. The system includes means for receiving WLAN performance reports from one or more WLAN APs. This example apparatus may also include means for receiving performance measurement data from an eNB. This example system may also include means for correlating the WLAN AP performance measurement data provided in the WLAN performance report with the eNB performance measurement data. This example system may also include means for calculating data traffic offload performance based on performance correlation between the WLAN APs and the eNB.

Another exemplary system includes the aforementioned components, and one or more WLAN APs overlap in an eNB coverage area.

Another exemplary system includes the aforementioned components and further includes a device for receiving a WLAN notification from a WLAN AP and a device for tracking an operating status update of the WLAN AP based on the notification, wherein the calculated data traffic offload performance is further based on the tracking WLAN AP operating status.

Another exemplary system includes the aforementioned components, and the WLAN AP performance measurement data includes the number of UEs connected to the WLAN AP and a packet throughput from the UEs to the WLAN AP.

Another exemplary system includes the aforementioned components, and the packet throughput is related to a QoS class or a user priority class.

Another exemplary system includes the aforementioned components, and the WLAN AP operation state is an out-of-service state or a restored-service state.

Another exemplary system includes the aforementioned components and further includes means for incorporating WLAN AP performance measurement data and WLAN AP operational status notifications into one or more data elements associated with a MIB message.

According to another aspect, at least one computer-readable storage medium is provided having instructions stored thereon that, when executed by a processor, cause the processor to perform the operations of any of the above-described example methods.

According to another aspect, an apparatus is provided, comprising means for performing any of the above exemplary methods.

The terms and expressions used herein are used as terms of description, not limitation, and are not intended to exclude any equivalents of the features (or portions thereof) shown and described herein when such terms and expressions are used, and it should be recognized that various modifications are possible within the scope of the claims. Accordingly, the claims are intended to cover all equivalent alternatives. Different features, aspects, and embodiments have been described herein. As will be appreciated by those skilled in the art, combinations of these features, aspects, and embodiments with one another, as well as variations and improvements, are acceptable. Therefore, the present invention should be considered to include such combinations, variations, and improvements.

Claims (15)

1. A wireless local area network (WLAN) access point (AP), comprising: a performance measurement module configured to measure, in response to a measurement granularity timer expiring, the number of user equipments (UEs) connected to the WLAN AP for data traffic offload for a first duration, and further measure a packet throughput from the UEs to the WLAN AP via a media access control layer or an internet protocol layer; the measurement granularity timer, which triggers the performance measurement module to perform the measurement, wherein the measurement granularity timer is configured to time out based on a predetermined interval; a performance report generation module that generates a WLAN report based on the measurements provided from the performance measurement module; and A performance report timer triggers the performance report generation module to generate the WLAN report. 2 . The WLAN AP of claim 1 , wherein the measured packet throughput is related to a Quality of Service (QoS) category or a user priority category. 3 . The WLAN AP of claim 1 , further comprising an operation status determination module that determines whether the WLAN AP is in an out-of-service state or a restored-service state, and further generates a service status notification. 4. The WLAN AP of claim 1, wherein the WLAN report is provided to an integrated reference point (IRP) manager. The WLAN AP of claim 3 , wherein the service status notification is provided to an IRP manager. 6. The WLAN AP according to claim 4 or 5, wherein the WLAN AP communicates with the IRP manager through an IRP agent of a WLAN element manager to provide a standardized interface to the IRP manager. 7 . The WLAN AP of claim 6 , wherein the IRP agent converts the packet throughput and the number of connected UEs into a format compatible with the standardized interface and the IRP manager. 8. The WLAN AP of claim 1, wherein the WLAN report and service status notification are incorporated into one or more data elements associated with a Management Information Base (MIB) message. 9. A method for monitoring performance of wireless local area network offload in a wireless cellular network, comprising: Waiting for the performance measurement granularity timer to time out; Measuring the number of UEs connected to the WLAN AP for data traffic offload; measuring a packet throughput from the UE to the WLAN AP through a media access control layer or an internet protocol layer; storing the measured number of UEs and packet throughput in a performance data log; and In response to the report timer expiring, sending the performance data log to the IRP manager. 10. The method of claim 9, wherein the measured packet throughput is related to a Quality of Service (QoS) class or a user priority class. 11. The method of claim 9, further comprising determining whether the WLAN AP is in an out-of-service state or a restored-service state, and generating a service status notification. 12. The method of claim 11, wherein the service status notification is sent to the IRP manager. 13. The method of claim 9, further comprising providing, by an IRP agent of a WLAN element manager, a standardized interface to the IRP manager for transmission to the IRP manager. 14. The method of claim 9, further comprising: incorporating the performance data log and service status notification into one or more data elements associated with a Management Information Base (MIB) message. 15. A system for monitoring performance of wireless local area network offload in a wireless cellular network, comprising an apparatus for executing the method according to any one of claims 9 to 14.