BR112016017462B1 - DISCHARGE SELECTION METHOD IN HETEROGENEOUS WIRELESS COMMUNICATION NETWORKS, AND USER EQUIPMENT - Google Patents

Abstract

DISCHARGE SELECTION METHOD IN HETEROGENEOUS WIRELESS COMMUNICATION NETWORKS. An offload selection method for a UE to select between 3GPP RAT and WLAN cell is provided. The UE receives configuration information that it applies to select WLAN or 3GPP radio access technology (RAT). The UE determines whether the UE can perform WLAN offloading by evaluating 3GPP radio access network (RAN) conditions where at least one RAN condition is related to a radio signal strength or to a radio signal quality in 3GPP RAT. The UE then determines whether at least one suitable WLAN cell exists by evaluating WLAN conditions. The UE also determines whether there is candidate traffic for WLAN offloading. Finally, the UE directs the given traffic to WLAN if the UE can perform WLAN offloading and at least one suitable WLAN cell exists. Otherwise, the UE directs the determined traffic to 3GPP RAT.

Description

CROSS REFERENCE FOR RELATED ORDERS

[01] This application claims priority under 35 U.S.C. §119 of provisional application US 61/932,825, entitled “Offload Selection”, filed January 29, 2014, the subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

[02] The disclosed embodiments relate generally to wireless network communication, and, more particularly, to the functionality for working together of cellular wireless communication and Wireless Local Area Network (WLAN, also called WiFi).

BACKGROUND

[03] To meet the rapidly growing demand in mobile data service, several network operators are developing new technologies and defining new standards for next-generation wireless networks to achieve much higher peak transmission rate. For example, peak transmission rate of 1 Gbps is required by ITU-R for IMT-Advanced systems in fourth generation (“4G”) mobile communications systems. Peak transmission rate of 1 Gbps in wireless networks can provide users with an experience similar to that in wired networks, and it is sufficient to satisfy many Internet applications currently and soon.

[04] While peak transmission rate is no longer a critical issue after the 4G era, it is likely that network capacity will be exhausted within the next few years. Not only is traffic demand growing significantly (i.e. > 50x in 5 years), but also the improvement in average cell spectral efficiency is very limited from the 3G to 4G era (i.e. < 10x). Furthermore, the available spectrum resource is also limited. Network capacity will still be exhausted very soon even if all networks are upgraded with 4G air interface. This problem actually already occurs in some areas. Therefore, capacity exhaustion is predicted to be the most critical problem.

[05] Although demand for wireless communication service continues to increase, demand for broadband access may not always require mobility support. In fact, studies have shown that only a small fraction of users demand mobile access and broadband simultaneously. Therefore, in addition to cellular networks, there are other networks capable of delivering information to mobile users, with or without mobility support. In many geographic areas, multiple radio access networks (RANs) such as E-UTRAN and WLAN are usually available. Furthermore, wireless communication devices are increasingly being equipped with multiple radio transceivers to access different radio access networks. For example, a multi-radio terminal (MRT) can simultaneously include Bluetooth, WiMAX and WiFi radio transceivers. Thus, multi-radio integration becomes more feasible today and is key to helping user terminals to exploit more available bandwidth of different radio access technologies and achieve better utilization of scarce radio spectrum resources.

[06] There is currently no specified prior art that performs offloading of traffic to WiFi for a cellular UE that takes cellular load into account, or gives the Cellular Radio Access Network the possibility to control which UEs extension traffic in a certain cell is offloaded to WiFi. Furthermore, it is currently impossible for the Cellular RAN to identify and separate particular UEs for offloading traffic to WiFi.

[07] The current technique for WiFi offloading, for example, ANDSF 3GPP assumes several levels of support for traffic offloading. All traffic from a UE, all traffic towards a certain APN or individual IP flows can be offloaded. One requirement is that even if offloading to WiFi is being done, it must be possible to maintain some traffic on Cellular, for example, critical real-time traffic, certain IMS traffic, emergency call. Another requirement is that it must be possible to do load-dependent or RAN-controlled offloading without ANDSF structure. One problem then is that offloading should preferably be done at the APN or IP flow level, but in the current 3GPP architecture the RAN is not aware of APNs or IP flows.

SUMMARY

[08] It is an objective to specify a novel UE procedure for dynamic selection of 3GPP RAT or WLAN Cell for traffic offloading, which allows considering dynamic network load and radio conditions.

[09] In one embodiment, an offload selection method for a UE to select between 3GPP RAT and WLAN cell is provided. The UE receives configuration information that it applies to select WLAN or 3GPP radio access technology (RAT). The UE determines whether the UE can perform WLAN offloading by evaluating 3GPP radio access network (RAN) conditions where at least one RAN condition is related to a radio signal strength or to a radio signal quality in 3GPP RAT. The UE then determines whether at least one suitable WLAN cell exists by evaluating WLAN conditions. The UE also determines whether there is candidate traffic for WLAN offloading. Finally, the UE directs the given traffic to WLAN if the UE can perform WLAN offloading and at least one suitable WLAN cell exists. Otherwise, the UE directs the determined traffic to 3GPP RAT.

[10] In one embodiment, the configuration information comprises at least one of a first threshold indicating a first 3GPP RAN condition, a second threshold indicating a second 3GPP RAN condition, a third threshold of a randomly generated number, a fourth threshold indicating a first WLAN condition, a fifth threshold indicating a second WLAN condition, a sixth threshold indicating a WLAN load, and a seventh threshold indicating a minimum estimated throughput. The configuration information further comprises at least one of a first predefined time period indicating a minimum time in which the UE remains as a candidate for WLAN offload, a second predefined time period indicating a minimum time in which the UE remains as a non- candidate for WLAN offloading, a third predefined time for determining whether a WLAN cell is suitable when the UE has a high or medium speed, and a fourth predefined time indicating a minimum time that a WLAN cell remains suitable.

[11] Other modalities and advantages are described in the detailed description below. This summary is not intended to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[12] The attached drawings, where like numbers indicate like components, illustrate embodiments of the invention.

[13] Figure 1 illustrates a mobile communication network with download selection according to a new aspect.

[14] Figure 2 illustrates a simplified block diagram of a UE that executes embodiments of the invention.

[15] Figure 3 illustrates a WiFi download selection procedure according to a novel aspect.

[16] Figure 4 illustrates a process of determining whether a UE can perform WiFi offloading.

[17] Figure 5 illustrates a process of determining whether a suitable WiFi cell exists.

[18] Figure 6 illustrates one embodiment of a process for determining what traffic can be offloaded to WiFi.

[19] Figure 7 illustrates another embodiment of a process for determining what traffic can be offloaded to WiFi.

[20] Figure 8 illustrates how UE receives download configuration information through different methods.

[21] Figure 9 illustrates a variant of the invention in a realistic architectural context for 3GPP.

[22] Figure 10 is a flowchart of a discharge selection method according to a novel aspect. DETAILED DESCRIPTION

[23] Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the attached drawings.

[24] Figure 1 illustrates a mobile communication network 100 with download selection according to a novel aspect. A radio access network (RAN) is part of a mobile telecommunications system implementing radio access technology. In many geographic areas, multiple radio access networks are usually available for the UE user equipment 101 to access the information source 110 (e.g., the Internet) and obtain mobile data service. Examples of different types of radio access networks are the GSM radio access network, UTRA or E-UTRA cellular access network, WiMAX system, and the Wireless Local Area Network (WLAN, also called WiFi). If multiple RANs support the same air interface, then the total access network is a homogeneous network. On the other hand, if multiple RANs support different air interfaces (e.g., cellular and WLAN), then the total access network is a heterogeneous network. From the UE point of view, it does not matter through which access network the desired information is delivered, as long as the data service is maintained at high speed and high quality.

[25] The mobile communication network 100 comprises a radio access network RAN 111 and an evolved packet core network 112. The RAN 111 comprises an E-UTRAN including the eNB 102 and a WLAN including a WiFi access point 103, and each RAN provides radio access to user equipment UE 101 via radio access technology (RAT) and different air interfaces. The evolved packet backbone network 112 comprises a mobility management entity (MME) 106, a server communication port (SGW) 107, and a packet data network (PDN GW) communication port 108. evolved packets 112 and E-UTRAN together are also referred to as a public land mobile network (PLMN). From the perspective of the UE 101, it is equipped with both a cellular transceiver and a WLAN/WiFi transceiver, and is capable of accessing the Internet 110 via cellular access or WLAN access.

[26] The UE 101 is connected to the public land mobile network (PLMN) and maintains a communication association with the MME Mobility Management Entity 106. The UE 101 may be provisionally housing in the 3GPP Cell 104 in RRC_Idle mode or the UE 101 may be connected to 3GPP Cell 104 in RRC_Connected mode. There may also be cases where the UE 101 is connected to the Radio Access Network RAN 111 by more than one cell. In this exemplary figure, a 3GPP Long Term Evolution (LTE) and 3GPP Enhanced Packet Core (EPS) network is illustrated. Another applicable scenario is a 3GPP Universal Mobile Telephony System (UMTS) network. The UE 101, furthermore, is receiving signals from, or communicating with, at least one WiFi Access Point 103 via at least one WiFi cell 105. In this document, the WLAN/WiFi cell notation 105 is used, meaning the communication link or potential communication link that is established between the UE 101 and the WLAN/WiFi Access Point 103. Operator WiFi Access can be integrated into the 3GPP Core Network in various modes. The example shows the possibility where WiFi connections and 3GPP connections are using the same PDN communication port 108, which makes it possible to maintain IP address while moving between Cellular access 104 and WLAN access 105, which is also referred to as a “non-stop discharge”.

[27] In a first, the cellular radio module and the WiFi radio module of the UE 101 cooperate with each other to provide integrated cellular and WiFi access in both E-UTRAN and WLAN to improve transmission efficiency and network utilization. bandwidth. A novel UE procedure for dynamic selection of Cellular access or WiFi access for traffic offloading is proposed, which allows considering dynamic network load and radio conditions, addressing the limitations of current technique.

[28] Figure 2 illustrates a simplified block diagram of a UE 201 that executes certain embodiments of the present invention. The UE 201 comprises memory 202 containing programming codes and data 204, a processor 203, a 3GPP transceiver 205 coupled to antenna 206, and a WiFi transceiver 206 coupled to antenna 207. In the transmission direction, the transceiver converts bandwidth signals base, received from the processor for RF signals and sends them to the antenna. Similarly, in the receive direction, the processor processes the baseband signals received from the transceiver and calls different functional modules to be configured to perform various features and functions supported by the UE 201.

[29] The UE 201 further comprises functional modules including the measurement module 211, the traffic control module 212, the 3GPP control module 213, the WiFi control module 214 and the traffic offload control module 215. The Different modules are functional modules that can be implemented in software, firmware, hardware or any combination thereof. The function modules, when executed by processors 203 (via program codes 204 contained in memory 202), work in conjunction with each other to execute embodiments of the present invention. For example, the measurement module 211 performs measurements on received radio signals, for both 3GPP and WiFi radio access technologies. The traffic control module 212 determines which traffic is a candidate for offloading, the 3GPP control module 213 evaluates 3GPP RAN conditions, the WiFi control module 214 evaluates cell WiFi suitability, and the traffic offload module 215 receives network offload configuration and determines whether, when, and how to perform WiFi offload accordingly.

[30] Figure 3 illustrates a WiFi download selection procedure for a UE according to a novel aspect. In the example of Figure 3, the UE first receives a configuration in step 301, with at least one dynamic parameter such as, for example, a parameter that allows an eNB to regulate to which extent UEs in a cell are offloaded to WiFi. A novel configuration can be received at any point in step 301. Furthermore, a dynamic part of the procedure is activated regularly in step 310. It is then checked whether the UE can perform WiFi offloading, for example, whether the UE can perform WiFi offloading in step 311. It is then checked whether at least one suitable WiFi Cell exists in step 312. The conditions performed in steps 311 and 312 can be checked in any order. This means that conditions can also be checked at the same time, that is, they can be merged into one big condition. In case any of the conditions in step 311 or step 312 result in NO, then traffic should not be offloaded to WiFi, i.e. if offloading is in progress then it should be stopped at step 321.

[31] Otherwise, if both conditions in step 311 and 312 result in YES, then the UE needs to determine what traffic can be offloaded to WiFi in step 313. This may depend on the capability of the UE. Some UEs may only be able to offload all traffic or no traffic. Other UEs, for example, may have the ability to offload via APN. Furthermore, the UE can perform offload selection dependent on actual traffic. For example, if there are no or very small data volumes that can be currently downloaded to WiFi, then download to WiFi in step 320 may not be done even if the conditions in steps 311 and 312 have YES as results. Finally, in step 314, the determined traffic is offloaded to WiFi. It should be noted that in a realistic implementation there would be more steps than those shown in the figure such as, for example, a step to select a WiFi Cell in case there are several cells appropriate.

[32] Figure 4 illustrates a process of determining whether a UE can perform WiFi offloading. Figure 4 shows an example of how the UE can determine whether it can perform WiFi offloading, that is, as a candidate for WiFi offloading. In this model For example, two states or two situations are modeled, in which the UE can perform WiFi offloading (state 401) or that the UE cannot perform WiFi offloading (state 402). One possible way, to enable RAN control, is to use UE measurements of signal strength or 3GPP radio signal quality and compare the measured values to a threshold value that is configured by the RAN. In one embodiment, transition 410 would be activated by signal strength or signal quality received by the UE from the 3GPP RAN < a first threshold. The benefit of such an approach is that UEs in poor 3GPP radio conditions consuming large amount of radio resources are discharged before UEs in good radio conditions consuming less resources. If the threshold is configurable, then the 3GPP RAN can change the threshold when its load changes, and thus adapt WiFi offloading to its load. In another embodiment, transition 411 would be activated by the signal strength or signal quality received by the UE from the 3GPP RAN > a second threshold. The second threshold can be formed by the first threshold + a hysteresis value.

[33] In order to prevent too rapid transition between these two states or situations, several measures can be taken. The UE may be forced to remain in state 401 for at least a minimum time such as, for example, a first predefined period of time. This can be modeled as state transition 412 being active for this minimum time once it has entered state 401. Similarly, the UE can be forced to remain in state 402 for at least a minimum time such as e.g. , a second predefined period of time. This can be modeled as state transition 413 being active for this minimum time once it has entered state 402. In a specific embodiment, prevention of ping-pong between the two states can be supported through particular measurement filtering. for signal strength or signal quality received from the 3GPP network, which allows filtered measurements to change more slowly. For example, the current Layer 3 filtering approach in 3GPP can be used. In another example, the concept of a timed activation can be used, in which a measured quantity is considered to be above or below a threshold only after the UE has remained above or below the threshold for a certain period of timed activation.

[34] In one embodiment of Figure 4, state transition 410 or 411 would be activated by a stochastic function where a random number is extracted and compared to a configured threshold such as, for example, a third threshold. If the number is greater or less than the third threshold, then state transition 410 or 411 is activated. It should be noted that in this application, for simplicity, the process of determining whether the UE can perform WiFi offloading in general is described separately from the process of discovering a suitable WiFi Cell. In a real implementation, however, these two processes can be fused, and other conditions can be considered when determining whether a UE can perform WiFi offloading.

[35] In a specific embodiment, a UE considers itself to be moving at high or medium speed across the cellular network, but discovers a WiFi cell that is consistently suitable. In such a condition, the UE considers itself as a candidate for WiFi offloading and can perform WiFi offloading. The benefit of such an approach is that UEs in vehicles with WiFi in vehicles would always consider themselves as candidates for WiFi offloading. A possibility to determine speed of UE is to use the current 3GPP mobility state estimation (MSE) function, based on cell change count. One possibility to determine whether a WiFi cell is consistently suitable is to apply a timing condition, i.e. if the cell remains suitable for a certain period of time such as, for example, a third predefined period of time, then it is considered that the adequacy is consistent.

[36] In another embodiment based on Figure 4, the UE would consider itself as a candidate for WiFi offloading as soon as the serving cell becomes unavailable for use, for example, through Access Class Blocking or other bandwidth limitations. traffic. The benefit of this is that the UE can then use WiFi without cellular.

[37] Figure 5 illustrates a process of determining whether a suitable WiFi cell exists. Figure 5 shows an example of how a UE can determine whether a detected WiFi Cell is suitable or not. In this example model, two states or two situations are modeled that the WiFi cell is suitable (state 501) or that the WiFi cell is not suitable (state 502). In this document, the word suitable has a composite meaning, considering multiple aspects when determining suitability. A basic criteria for a WiFi cell to be suitable is that the signal strength or WiFi radio signal quality needs to be good enough. Transition 510 can thus be activated by signal strength or WiFi signal quality > a fourth threshold. Typically the inverse transition 511 may then be activated by a condition in which signal strength or WiFi signal quality < a fifth threshold, where the fifth threshold may be the fourth threshold + a hysteresis value. The benefit of a hysteresis value would be to prevent rapid ping-pong between these states or situations.

[38] In a complementary embodiment, a WiFi cell can be considered suitable or not suitable based on its load or congestion level. For example, transition 511 may be activated if the WiFi cell indicates a certain load parameter to the UE and the load parameter is above a certain threshold such as, for example, a sixth threshold, or the WiFi cell signals with an indication of congestion for the UE. On the other hand, if the condition ceases, then this may activate the 510 transition.

[39] In a further complementary embodiment, a WiFi cell may be considered suitable or not suitable based on estimated throughput. For example, transition 511 may be activated if the estimated throughput for the WiFi cell is below a certain threshold such as, for example, a seventh threshold. If the condition ceases, this may trigger transition 510. It should be noted that this throughput estimate may be based on actual measured throughput. It is not easy to propose a definition of throughput that would produce comparable results. Probably the best type of throughput estimate is based on the throughput that would be seen during a burst of data.

[40] In another embodiment, the UE would choose to offload to WiFi if the estimated throughput for the WiFi Cell was better than the estimated throughput for the 3GPP cell. This condition can be modeled in several ways. In an example, the WiFi Cell is suitable if the estimated throughput of the WiFi cell is greater than the estimated throughput of the serving 3GPP cell(s).

[41] It should be noted that a UE would also apply other conditions when determining whether a WiFi Cell is suitable, for example, whether the UE is permitted access to this WiFi Cell.

[42] To avoid rapid ping-pong between states, in particular for conditions unrelated to radio signal strength or quality, minimum times may be applied. For example, after state 501 has been entered, transition 512 is introduced for a certain time such as, for example, a fourth predefined period of time, preventing a transition 511 during this time. Similarly, after state 502 has been entered, transition 513 is introduced for a certain time such as, for example, a fifth predefined period of time, preventing a transition 510 during this time. The fourth and fifth time period may be the same.

[43] Figure 6 illustrates one embodiment of a process of determining what traffic can be offloaded to WiFi. In the embodiment of Figure 6, an example signaling sequence is shown for determining what traffic can be offloaded to WiFi. In step 600, the UE 601 establishes an RRC connection with the eNB 602 via RRC connection configuration. In step 610, the UE 601 sends a NAS uplink message to the MME 603. In step 611, the UE 601 receives a NAS downlink message from the MME 603. Finally, in step 612, the UE 601 stores the information and uses the information received later when determining what traffic to offload to WiFi.

[44] In this example, information regarding what traffic can be offloaded is provided via the NAS protocol by MME or SGSN. The benefit of providing such information via the MME or SGSN directly, although the RAN has better control of dynamic offloading, is that the MME or SGSN is aware of concepts such as APN and IP flows, and aware of the requirements of each traffic flow. whereas the RAN is not. If the MME or SGSN is also aware of the UE's capability, it can provide information to the UE that the UE can use as is, that is, which APNs can be offloaded over WiFi, or which IP flows can be offloaded over WiFi in the step 612. In the case where the UE does not have the capacity to handle individual IP flows, we can assume that it must treat all IP flows for a certain APN in the same way, and if a flow is downloaded all flows for this APN must be downloaded at 612. In one example, the NAS downlink message at step 611 from MME 603 may include an EPS Session Management Message, ACCEPT DEFAULT EPS CARRIER CONTEXT ENABLED; an EPS Session Management Message, REQUEST DEDICATED EPS CARRIER CONTEXT ENABLED; an EPS Session Management Message, REQUEST CARRIER RESOURCE MODIFICATION; or an EPS Session Management Information Element, aggregated description of traffic flow.

[45] Figure 7 illustrates another embodiment of a process of determining what traffic can be offloaded to WiFi. In the embodiment of Figure 7, offload information is provided to the UE 701 via RRC signaling by the eNB 702. In step 700, the UE 701 establishes an RRC connection with the eNB 702 via RRC connection configuration. In step 710, the eNB 702 and the MME 703 perform carrier configuration via S1-AP. Since the RAN is not aware of the APN, a simpler way to signal to the UE may be to indicate exactly which carrier(s) are candidates for offloading to the UE in step 711. The UE 701 may then handle all carriers of a certain APN in the same way, that is, if a carrier for a certain APN is indicated as a candidate for offloading WiFi traffic, then in step 712, the UE 701 treats all traffic of the certain APN as a candidate for offload WiFi.

[46] Figure 8 illustrates how the UE can handle broadcast and dedication configurations. First, it is assumed that a configuration for WiFi offloading would be consistently applicable regardless of whether the UE is in RRC Idle Mode or RRC Connected Mode in 3GPP. Second, it is assumed that in order for load balancing to be dynamic and adapt to load situations, parts of the configuration can change quickly. The benefit of using broadcast configuration is that parameters that are dependent on 3GPP RAN load can change and be communicated consistently to all UEs in a cell regardless of their 3GPP state, for example, if the load on 3GPP RAT is passed Suddenly it may be desired to activate UEs to stop WiFi offloading and instead go to connected mode in 3GPP RAT. A primary benefit of using dedicated configuration is that 3GPP RAN can identify particular UEs that are good candidates for WiFi offloading, or that are good candidates for being maintained in 3GPP RAT, for example, based on service history, or based on usage. of Radio Resource. Through dedicated configuration, such UEs can be given particular configuration to make them more or less likely as a candidate for WiFi offloading. With this benefit in mind, it is proposed that a dedicated configuration like this should be kept valid also after the UE switch to RRC Idle Mode, and that it must have higher priority than the broadcast configuration to the extent that they overlap. Thus, it also needs to be clear when such a dedicated configuration is no longer valid, and when broadcast configuration should be used instead of dedicated. For simplicity, it is proposed that a timer can be used, so that the start value can be provided along with the dedicated configuration. The timer starts when the dedicated configuration is received and when the timer expires the dedicated configuration is discarded, see also step 850.

[47] Generally speaking, the exemplary signaling sequence begins with a UE 801 in RRC Idle Mode (step 810). The UE then receives its first configuration for WiFi offloading via broadcast signaling in step 811, and subsequently initiates the offload selection process in step 812 to determine whether it can perform WiFi offload as a candidate for WiFi offload, and whether there are suitable WiFi cells. The UE later goes to RRC Connected Mode in step 822 after performing an RRC connection setup in step 821. The UE further performs the WiFi offload selection process in step 823 similar to that in RRC Idle Mode, using parameters received through of broadcast signaling in step 811. We assume that the RAN needs to know whether or not the UE is capable of receiving dedicated offload configuration, see step 824. If the UE is capable, the RAN can then provide a dedicated configuration to the UE in step 831. The UE then uses a received start value and starts a discard timer for the dedicated WiFi offload configuration received in step 831. The UE additionally replaces its stored broadcast parameters with parameters received in the dedicated configuration and executes the process discharge selection process in step 832 using these parameters. After the UE is released to RRC Idle Mode in step 842 after performing an RRC Connection Release in step 841, the UE still performs offload selection in step 843 using the dedicated parameters. At a certain point in time, the dedicated configuration discard timer expires and the dedicated configuration is discarded in step 850. Then the UE instead applies configuration parameters provided via broadcast signaling again in step 851, and executes discharge selection in step 852.

[48] It can be generally assumed that a new dedicated configuration overwrites an old configuration. There is a general problem that if a UE connects to a 3GPP cell after idle mode, the 3GPP cell cannot know which WiFi offload configuration the UE is currently using. Therefore, if the 3GPP RAN provides a new dedicated configuration it may be distinctly different from the first dedicated configuration, causing a ping-pong situation. For example, a first eNB providing a dedicated configuration to offload WiFi because of heavy load, and in a second eNB there is no load because all traffic is already offloaded. As a result, the second eNB reverts to another configuration that induces the UE to switch from heavy traffic back to 3GPP and so on. If RAN nodes are well synchronized by implementation and OAM (operation, administration and maintenance), then there is little risk of such ping-pong behavior. However, if they are not well synchronized, then there may well be a ping pong problem.

[49] In one embodiment, a UE is performing WiFi offloading and is then connecting to a 3GPP cell. The UE informs the RAN that WiFi offloading is in progress. The RAN can then consider this information, typically to avoid making dedicated reconfigurations to activate offloading, as offloading is already in progress. In an alternative or complementary embodiment, a UE already has a dedicated configuration that was received in a previous cell. The UE is performing discharge selection, and then the UE goes to connected mode. The UE then provides information regarding its dedicated offload configuration to the RAN. The simplest type of information is exactly a Boolean information that a dedicated configuration exists. A more sophisticated variant may include having the UE report the configuration details and/or its current WiFi offload configuration discard timer value.

[50] Figure 9 illustrates a variant of the present invention in a realistic architectural context for 3GPP. The functionality for performing offload selection in the UE 900 is divided between two layers, i.e., a lower layer, the Access Stratum 901 and a higher layer, the Non-Access Stratum 902. In this embodiment, the Access Stratum 901 is the configuration receiver that controls the offload selection in step 913. Based on the configuration, measurements and indications the Access Stratum 901 determines whether the UE can perform WiFi offload in step 911, and determines whether there are any suitable WiFi Cells in step 912 The result of processing in the Access Layer is indicated for the highest layer 902 in step 914. In this case it is indicated that WiFi offloading should be done, and a list of suitable WiFi cells is also indicated. It may also be indicated that WiFi downloading should not be done. The non-access stratum 902 would do the additional logical processing necessary to make the final offload decision in step 922, e.g., when taking into account the determination of what traffic should be offloaded, taking into account additional conditions 923 outside of this invention, such as settings and user, or conditions imposed by other traffic steering functionality on the UE, such as ANDSF (access network detection and selection function). Non-access stratum 902 would also activate and control final WiFi cell selection in step 921, in accordance with WiFi standards, based on the list of WiFi cells indicated by Access Stratum 901, and by calling the WiFi transceiver in step 924. When final offload decision in step 922 and WiFi selection in step 921 are made, traffic can be directed accordingly in step 925.

[51] It should be noted that a UE that performs WiFi offloading transfers part or all of its traffic to WiFi in such a way that data from the transferred traffic is transmitted and/or received on WiFi. On the other hand, a UE that does not perform WiFi offloading receives and transmits all its traffic on 3GPP Radio Access Technology. The methods described in this document for starting and stopping WiFi offloading are complementary to other methods in a UE and on a network for starting and stopping use of WiFi to load traffic.

[52] Figure 10 is a flowchart of a discharge selection method according to a novel aspect. In step 1001, a UE receives configuration information that it applies to select WLAN or 3GPP radio access technology (RAT). In step 1002, the UE determines whether the UE can perform WLAN offloading (e.g., whether the UE is a candidate for offloading) by evaluating 3GPP radio access network (RAN) conditions where at least one RAN condition is related to a radio signal strength or radio signal quality in 3GPP RAT. In step 1003, the UE determines whether there is at least one suitable WLAN cell by evaluating WLAN conditions. In step 1004, the UE determines whether candidate traffic for WLAN offload exists. In step 1005, the UE directs the determined traffic to WLAN if the UE can perform WLAN offloading and if there is at least one suitable WLAN cell, otherwise it directs the traffic to 3GPP RAT.

[53] Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Therefore, various modifications, adaptations and combinations of various features of the described embodiments can be practiced without diverging from the scope of the invention as set out in the claims.

Claims (21)

1. Method, characterized by the fact that it comprises: receiving configuration information (301) by a user equipment (UE), the configuration information applies to select wireless local area network (WLAN) or Access Technology via Radio (RAT) 3GPP; determining (311) whether the UE can perform WLAN offloading by evaluating 3GPP Radio Access Network (RAN) conditions where at least one RAN condition is related to a radio signal strength or radio signal quality in 3GPP RAT; determining (312) whether at least one suitable WLAN cell exists by evaluating WLAN conditions; receiving additional conditions from a Mobility Management Entity (MME) via Non-Access Stratum (NAS) signaling in response to an uplink NAS message sent to the MME; determining (313) whether candidate traffic exists for WLAN offloading based on the additional conditions; and directing (314) the determined candidate traffic to WLAN if the UE can perform WLAN offloading and if at least one suitable WLAN cell exists, otherwise directing (321) the determined traffic to 3GPP RAT. 2. Method according to claim 1, characterized by the fact that the UE determines (311) that the UE can perform WLAN offloading if the radio signal strength or radio signal quality measured in 3GPP RAT is below a first threshold, and in which configuration information is received via Access Stratum signaling. 3. The method of claim 2, wherein the UE remains a candidate for WLAN offloading for at least a first predefined period of time after determining that the UE can perform WLAN offloading. 4. Method according to claim 1, characterized by the fact that the UE determines (311) that the UE cannot perform WLAN offloading if the signal strength or signal quality measured in 3GPP RAT is above a second threshold . 5. The method of claim 4, wherein the UE remains a non-candidate for WLAN offloading for at least a second predefined period of time after determining that the UE cannot perform WLAN offloading. 6. The method of claim 1, wherein the signal strength or signal quality measured in the 3GPP RAT is subject to filtering that is specific to determining whether the UE can perform WLAN offloading. 7. The method of claim 1, wherein the UE determines (311) that the UE can perform WLAN offloading if a randomly selected number is below or above a third threshold. 8. Method according to claim 1, characterized by the fact that the UE determines (311) that the UE can perform WLAN offloading if the UE has a high or medium speed and a specific WLAN cell has remained adequate during a third period of time. 9. The method of claim 1, wherein the UE determines (312) that a WLAN cell is suitable if a measured WLAN signal strength or signal quality is above a fourth threshold. 10. The method of claim 1, wherein the UE determines (312) that a WLAN cell is not suitable if a measured WLAN signal strength or signal quality is below a fifth threshold. 11. The method of claim 1, wherein the UE determines (312) that a WLAN cell is suitable if a load indicator received from the WLAN cell is below a sixth threshold. 12. The method of claim 1, wherein the UE determines (312) that a WLAN cell is suitable if an estimated throughput in a WLAN cell is better than an estimated throughput in a 3GPP cell server. 13. The method of claim 1, wherein the UE determines (312) that a WLAN cell is not suitable if an estimated throughput in the WLAN cell is worse than a seventh threshold. 14. The method of claim 1, wherein determining whether a WLAN cell is suitable involves using a time filter based on a predefined fourth time period. 15. The method of claim 1, wherein the UE determines (313) which traffic is a candidate for WLAN offload based on a NAS configuration of a mobility management entity (MME) that indicates that APN or which EPS bearers or which IP streams are candidates for WLAN offloading, wherein the NAS configuration includes an EPS session management message to activate or modify a dedicated EPS bearer context. 16. The method of claim 1, wherein the configuration information comprises at least one of a first threshold indicating a first 3GPP RAN condition, a second threshold indicating a second 3GPP RAN condition, a fourth threshold indicating a first WLAN condition, a fifth threshold indicating a second WLAN condition, a sixth threshold indicating a WLAN load, a first predefined time period indicating a minimum time that the UE remains as a candidate for WLAN offloading, and a second predefined time period indicating a minimum time that the UE remains as a non-candidate for WLAN offloading. 17. The method of claim 1, wherein the configuration information further comprises at least one of a third threshold of a randomly generated number, a seventh threshold indicating a minimum estimated throughput, a third predefined time to determine whether a WLAN cell is suitable when the UE has a high or medium speed, and a fourth predefined time indicating a minimum time that a WLAN cell remains suitable. 18. Method according to claim 1, characterized by the fact that the UE receives (301) configuration information from broadcast signaling or through dedicated signaling. 19. The method of claim 18, wherein the UE applies the dedicated configuration for a validity time during which the dedicated configuration is valid. 20. Method, according to claim 18, characterized by the fact that the UE applies the dedicated configuration also after being released to RRC Idle Mode. 21. User equipment (UE), characterized in that it comprises: a receiver that receives (301) configuration information, the configuration information to apply to select wireless local area network (WLAN) or Radio Access Technology (RAT) 3GPP; a 3GPP control module that determines (311) whether the UE can perform WLAN offloading by evaluating 3GPP radio access network (RAN) conditions where at least one RAN condition is related to a radio signal strength or signal quality. radio in RAT 3GPP; a WLAN control module that determines (312) whether there is at least one suitable WLAN cell by evaluating WLAN conditions; a traffic control module that receives additional conditions from a Mobility Management Entity (MME) via Non-Access Stratum (NAS) signaling in response to an uplink NAS message sent to the MME and determines (313) whether there is candidate traffic for WLAN offloading; and a WLAN offload module that directs (314) the determined candidate traffic to WLAN if the UE can perform WLAN offload and if at least one suitable WLAN cell exists, otherwise directs (321) the determined traffic to 3GPP RAT.