WO2014114525A1

WO2014114525A1 - Access network selection policy

Info

Publication number: WO2014114525A1
Application number: PCT/EP2014/050581
Authority: WO
Inventors: Jari Pekka MUSTAJÄRVI
Original assignee: Nokia Siemens Networks Oy
Priority date: 2013-01-24
Filing date: 2014-01-14
Publication date: 2014-07-31

Abstract

An access network selection policy for subscriber stations of a communications network is defined. The access network selection policy includes at least one access network selection priority associated with a wireless access network. The received priority is adjusted on the basis of a load determined for the wireless network associated with the received priority. This provides dynamic adjustment of the access network selection policy without need to communicate a new policy to the UE.

Description

DESCRI PTION

TITLE

ACCESS NETWORK SELECTION POLICY FIELD

The present invention relates to an access network selection policy and more particularly to a policy of selecting a wireless access network.

BACKGROUND

Wireless Fidelity, Wi-Fi, networks are becoming an integrated part of mobile broadband. Wi-Fi is a standard feature for example on devices which consume a relatively large amount of data such as smart phones, tablets and laptops. The 3^rd Generation Partnership Project, 3GPP, is currently working on features for Release 12 specifications. The work includes a working item, WLAN network selection (WLAN NS) concerned with Wi-Fi access network selection between different radio access technologies.

Access Network Discovery and Selection Function, ANDSF, is an entity within an Evolved Packet Core, EPC, of the system architecture evolution, SAE, for 3GPP compliant mobile networks. ANDSF provides user Equipment, UE, information to support mobility between different access technology types or access networks of the same type like Wireless Local Area Network, WLAN, hotspots that are available to the UE.

The ANDSF information comprises three main groups, that is, the inter-system mobility policies (ISMP), access network discovery information (ANDI) and inter-system routing policies (ISRP). An ISRP policy further consist of flow distribution rules. An inter-system mobility policy and an inter-system routing policy flow distribution rule can contain a preference list of the access networks the UE should use to route matching Internet

Protocol, IP, traffic or all traffic, optionally restricted by validity constraints like UE location and calendar time. The flow distribution rules and ISMP policies are further referred here as ANDSF rules and ISMP and ISRP policies as ANDSF policies.

The ANDSF information is defined by the 3GPP network operators to control access network selection in order to meet various aspects such as access network congestion control, costs, network coverage and service level expectations of the subscribers, to name a few. Accordingly, the defining of the ANDSF rules is challenging due to the number of aspects to be considered. On the other hand, the defining of the ANDSF rules may be challenging due to the aspects to be considered involving a mixture of aspects from different fields, for example a mixture of aspects from a legal , technical and economical field. After the ANDSF rules and access network discovery information are defined, they are communicated to the UE that uses them for network discovery and selection between the different available wireless access networks. However, such traffic can be considered maintenance traffic which should be kept low in order to facilitate efficient use of communications resources to the actual services, such as data transfer of the UE.

BRIEF DESCRIPTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to a more detailed description that is presented later.

Various embodiments comprise method(s), apparatus(es), a computer program product(s) and a system as defined in the independent claims. Further embodiments are disclosed in the dependent claims.

According to an aspect of the invention there is provided a method comprising receiving an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one access network selection priority associated with a wireless access network, determining load information of available wireless networks, and adjusting the received priority on the basis of the load information determined for the wireless network associated with the received priority.

According to an aspect of the invention there is provided a method comprising defining an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network, determining a load bias defining an adjustment to the at least one priority of the wireless access network, and communicating the access network selection policy including the determined load bias associated with the priority of the wireless access network to at least one subscriber station.

According to another aspect of the invention there is provided an apparatus comprising at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform a method according to an aspect.

According to another aspect of the invention there is provided an apparatus comprising means configured to perform a method according to an aspect.

According to another aspect of the invention there is provided a computer program product comprising executable code that when executed, cause execution of functions of a method according to an aspect. According to another aspect of the invention there is provided a system comprising an apparatus according to an aspect arranged to communicate with subscriber stations via a plurality of wireless access networks.

Although the various aspects, embodiments and features of the invention are recited independently, it should be appreciated that all combinations of the various aspects, embodiments and features of the invention are possible and within the scope of the present invention as claimed.

Some embodiments may provide dynamic adjustment of the access network selection policy without a need to communicate a new policy to the UE. The dynamical adjustment may be facilitated even in situations, where an operator has determined the same priority to different access networks.

Further advantages will become apparent from the accompanying description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

Figure 1 illustrates an architectural view of a wireless communications system for carrying out an embodiment;

Figures 2 and 3 illustrate adjustment of an access network selection policy according to embodiments;

Figure 4 illustrates a block diagram of an apparatus according to an embodiment; Figure 5 illustrates a block diagram of user equipment according to an embodiment; and Figure 6 illustrates a block diagram of an ANDSF server according to an embodiment.

DETAILED DESCRIPTION

Example embodiments of the present invention will now be de-scribed more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Like reference numerals refer to like elements throughout.

Some access networks may be more appealing for an operator of a communications network than other access networks due to different business and operational reasons. Effectively using the ANDSF, the operator can define potentially multiple access network selection rules for the UE by listing within each rule all applicable access networks and assigning an access network selection priority for each of these networks. A rule can further be subject to different validity constraints including calendar time and UE location. Each rule has a priority level. The UE selects active ANDSF rules based on the validity constraints and UE capabilities and orders them based on rule priorities. The UE may consider the higher priority rules before lower priority rules for all traffic. In a rule, higher priority access networks may be considered for network selection before lower priority networks.

In an example scenario an operator could have the following priority list within a rule: Priority 10: operator-owned-WLAN-networks

Priority 12: partner-WLAN-networks

Priority 14: 3GPP networks.

The above example scenario may only reflect to a set of wireless access networks belonging to the "operator-owned-WLAN-networks". In the policy each network would need to be identified explicitly by SSID. Also other identifiers based on HotSpot 2.0, later HS2.0, specifications may be used.

It should be appreciated that wireless access networks may be identified in various ways. Identifiers used to identify a wireless access network may include an access technology type (Wi-Fi, 3GPP, WiMAX,...) and a technology specific identifier. For WLAN, these identifiers may comprise a Service Set Identifier, SSID, and a Homogenous Extended Service Set Identifier, HESSID. Release 12 of the 3GPP specifications may introduce more identifiers based on HS2.0.

Accordingly, in the above example scenario the "operator-owned-WLAN-networks" may, instead of indicating a specific WLAN network, be used to categorize different wireless access networks into two categories: an operator and a partner networks. In the example scenario, the operator may own two WLAN networks identified by SSID 1 and SSID 2. Then the wireless access networks belonging to the "operator-owned-WLAN-networks" could be indicated by SSID_1 and SSID_2 and optionally also by HESSID_1 and

HESSID 2, in case such a value is assigned to the networks.

Various embodiments described herein provide an access network selection policy defining priorities of wireless access networks for network selection, whereby different load indicators of these access networks are used to adjust the associated access network selection priority. In an example solution, load information is used to select a WLAN network. In the solution, a penalty is added for individual WLAN network selection priorities in the ANDSF rules based on WLAN network load. Same mechanism could be used also for other access network types.

Wi-Fi Alliance Technical Committee Hotspot 2.0 Technical Task Group has published Hotspot 2.0 (Release 2) Technical Specification that together with IEEE 802.1 1 defines load indicators which can be used to provide load information in the embodiments described herein.

In an embodiment, an operator may define an access network selection policy comprising a priority penalty for network selection based on the target access network load. In this way the operator has means to assist the UE to favor less loaded networks, without additional ad-hoc signaling with the UE but still in controlled way. The policy may be defined by the operator at an operator backend and be communicated to the ANDSF to be delivered to the UE. It should be appreciated that the access network selection policy may be defined also at the ANDSF on the basis of preferences of the operator.

Considering the example scenario above with the operator's priority list, various embodiments may provide adding a penalty to the priority of an access network in the list, when a Wi-Fi channel utilization level is exceeded. The channel utilization may be 75%, for example. The penalty may be for example to add '2' to the priority value of the access network in question. Another penalty may be set for another value of channel utilization level. For example, when the channel utilization level exceeds 90%, a penalty of '10' may be added to the priority of the access network in question. If all available WLAN networks owned by the operator have channel utilization above 75%, UE is allowed to consider partner WLAN networks for an access network to be used, since the priority of the WLAN network owned by the operator is added by '2'. The partner networks could also have a load based priority penalty, for example a penalty of '3' for channel utilization of 50%. Still, the UE would be allowed to choose best network of the evaluated highest priority networks available on operator overload situations, even initially less preferred partner networks. If all available WLAN networks are penalized enough, in this example the operator owned network by '4' and the partner networks by '2', then device shall also start considering to use the 3GPP service.

Accordingly, various embodiments described herein may provide adjusting the access network selection policy at the UE on the basis of load information for wireless access networks.

Figure 1 illustrates an architectural view of a communications system 100 connecting to

UE 108 on a plurality of different wireless access technologies 102, 104, 106. The access technologies are implemented as corresponding wireless access systems that each may comprise one or more access nodes that communicate with the UE via a wireless medium, for example radio frequency band. The communications system provides the UE service through the different wireless access networks. The service may comprise for example voice calls and data transfer between the UE and another UE or a server of a service provider. Examples of communications systems comprise a Global System for Mobile

Communications (GSM) network, 3^rd generation mobile communications (3G) network, Long Term Evolution (LTE) network and LTE-advanced (LTE-A), to name a few.

An operator may manage an access network selection policy used in the UE via a server that provides the UE the policy.

An ANDSF 1 10 contains data management and control functionality necessary to provide network discovery and selection assistance data as per the operators' policy. An ANDSF server communicates with the UE over an S14 interface as defined for example in TS 3GPP 24.302. The ANDSF can deliver the access network selection policy as pull mode operation, where it is delivered upon a request from the UE, or as push mode operation, where the ANDSF initiates the transfer of the policy to the UE. In one example the push mode operation may be performed in response to a registration of the UE to a

communications network, which may happen when the UE is roaming to a visited-Public Land Mobile Network, visited-PLMN, or registering to a home-PLMN for the first time. Typically delivery of the access network selection policy takes place, when something has changed in the operating environment and the operator has an urgent need to update the policies. In one example, the change could relate for example to a Service Level

Agreement, SLA, change with the operator when a service is activated or deactivated.

An ANDSF 1 10 server located in the home PLMN of a UE may be referred to as the Home-ANDSF (H ANDSF) for this UE, whereas an ANDSF element located in the visited PLMN of a UE may be referred to as the Visited-ANDSF (V ANDSF) for this UE. Unless otherwise specified, the term ANDSF is used to refer to both an H ANDSF and a V ANDSF. More details on the ANDSF framework can be found in 3GPP TS 23.402 V1 1 .5.0 (2012-12) and 3GPP TS 24.302 V1 1 .5.0 (2012-12). Details about the ANDSF functionality and its interaction with the UE are provided in the above 3GPP TS 23.402 clause 4.8.2.1 .

The information exchanged between UE and ANDSF server is provided in 3GPP TS 24.312.

The ANDSF may connect to wireless access networks 102, 104, 106 that communicate with the UE. The wireless access networks may provide internet connectivity to the UE, whereby the UE and the ANDSF can communicate over an Internet Protocol connection via the wireless access network serving the UE. An access network selection policy to be followed by the UE may be communicated by the ANDSF to the UE over the IP connection between the UE and the ANDSF. Accordingly, the information of access network selection and/or discovery may be delivered to the UE via the wireless access network that connects the UE to the operator's communications network. The delivery of data and signaling within each wireless access network may be performed using the means well known to a skilled person and they do not need to be described herein any further.

Figures 2 and 3 illustrate adjustment of an access network selection policy according to embodiments. The access network selection policy may be used in the communications system of Figure 1 . The access network selection policy may be adjusted by UE subscribed to a communications network, for example to the communications network of Figure 1 . An ANDSF server may deployed to the communications network to cater for delivery of the access network policy to be followed by the UE according to the ANDSF framework described in the 3GPP TS 23.402 and the TS 24.302. The policy defined by the operator may be communicated to the ANDSF for delivery to the UE. Delivery of the access network selection policy may be performed as operator settings conventionally using push mode or pull mode delivery.

In the embodiments, an operator may define an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one rule with an access network selection priority associated with a wireless access network. The access network selection policy of the operator may be stored to the ANDSF. If specific networks for example are high cost networks for the operator, the operator may plan the penalties and access network selection priority values so that high cost networks will be used only during extreme congestion. Also some subscriber classes may have access network selection priority values more close to each other and thereby even small penalty would elevate those high cost networks and providing better end user service. An example scenario of an access network selection policy is described above with penalties. Further examples of an access network selection policy are provided below.

In the process of Figure 2, the access network selection rule within a policy is adjusted on the basis of load information obtained of a wireless access network. The process of Figure 3 illustrates adjusting the access network selection rule on the basis of the load information, when a load bias is associated with a threshold for a load in a wireless access network.

The access network rule adjustment may start 202, when the UE is registered to the communications network. The communications network may be a home network of the UE or a visited network of the UE. The home network may comprise a PLM-N that the UE is permanently registered to at subscription. The visited network may comprise a PLMN that the UE is temporarily registered to, for example when the UE is roaming.

In 204 an access network selection policy is received by the UE. The access network selection policy may be received from the ANDSF server. It should be appreciated that the access network selection policy may be also preconfigured in the UE, whereby it may be stored into a memory. Then, the receiving may also comprise receiving the access network selection policy at a processor to be processed.

The access network selection policy may be received by a pull mode operation of the UE or by a push mode operation from the ANDSF server. In the pull mode, the UE can initiate communication with any wireless access network that provides IP connectivity. In one example, the wireless access network may be performed at home via Wi-Fi deployed there. Accordingly, the used wireless access network does not have to be operator network. For push mode operation the UE must be accessible for ANDSF server. ANDSF could alert UE with special SMS. UE could also maintain an IP connection with ANDSF to allow the ANDSF server push data to the UE when needed. After the UE has received the access network selection policy it may start selecting a wireless access network according to the access network selection policy. The selection process may include monitoring nearby wireless access networks, for example available WLANs. The UE may receive load information indicating loads of one or more available wireless access networks. This information may be received as part of the monitoring of nearby wireless access networks, where signaling from the nearby networks may be received. The load information may be used to determine adjustments to the access network selection policy defined by the operator. The available wireless access networks may comprise wireless access networks from which the UE may receive signaling, for example a common broadcast channel or a beacon. To receive the signaling, the UE may be located in the coverage area of the wireless access network. The signaling may comprise one or more from a group comprising a utilization level of a wireless channel and a number of terminals served by an access node of a wireless access network. This information may be available from beacons transmitted by an access point conforming to WLAN according to IEEE Std 802.1 1™-2007 (Revision of IEEE Std 802.1 1 -1999 ), where beacons are described in Section 7.2.3.1 . or the earlier IEEE 802.1 1 e version of the standard.

In one example, load information is available from a WLAN access network via BSSLoad information element in the beacon. The used load indicator could be the Wi-Fi channel utilization value in the BSSLoad information with values ranging from 0 to 255 and indicating channel utilization from 0% to 100%. It could also incorporate associated UE count information also included into the BSSLoad information. It could be either channel utilization value or associated UE count or combination of the two.

In 206, 308, 310 load information is used to adjust the access network selection policy. When the load information indicates a high load of a wireless access network, the policy is adjusted to decrease a likelihood of selecting the wireless access network. The likelihood is decreased with increasing load. This may be implemented by load thresholds with corresponding penalties, referred herein as load biases.

Accordingly, the load information may be used to determine a load bias to be applied to the access network selection rules in the policies. In this way the policy may be biased 310 on the basis of the observed load. The ANDSF information may include one or more load biases each associated with a threshold for a load of a wireless access network. Then, the bias may be determined as the bias associated with the highest threshold that the load information exceeds.

When load information of available wireless access networks is received at the UE, the access network selection policy may be applied by steps of a process that may start 302, where an access network selection policy is defined by an operator introducing a load bias to the access network selection priority. The policy may be stored in UE or in an ANDSF, where it is delivered to the UE.

In 304 a load bias for the access network selection policy is determined. The load bias facilitates updating of the access network policy on the basis of load information received from available wireless access networks. The load bias may concern all wireless access networks or it may be specified to apply to a specific wireless access network. The load bias may be associated with a threshold for applying the load bias, which may be obtained together with the load bias. In one example, the load bias may be defined to apply to different levels. The levels may be defined on the basis of an operator, ISRP rule, ISMP rule and/or an access network defined by a rule. The load bias may also be specific to a defined access network or defined access network technology type. When multiple load biases apply to a wireless access network, the one to be applied may be determined as the closest bias for the specific access network. Preferably, the load bias is defined at operator level or

ISRP/ISMP level for easy management.

The load bias may be received 304 within the ANDSF information together with a threshold associated with the load bias. In this way, the policy is ready to be applied when received. It should be appreciated that an existing policy may be updated with one or more load biases which may be associated with corresponding thresholds. The existing policy may be located at UE in which case the UE may receive the update via a pull mode or push mode operation from the ANDSF. When the existing policy is at the ANDSF, the operator may send an update to the ANDSF to update the policy with the load biases and associated thresholds. The update may be performed to the UE in next ANDSF session either via a pull mode operation or push mode operation. An update may include for example a management object as described in the below examples.

A threshold may comprise a minimum access network load level required to adjust the access network selection policy with the load bias associated with the threshold. The threshold may have a range 0 to 100, for example. The threshold may comprise a value scaled to the range. For a WLAN conforming to the IEEE 802.1 1 , the threshold may be compared with load of the WLAN access network received in a BSSLoad channel utilization level when broadcasted in beacons. The BSSLoad channel utilization level may have range from 0 to 255. The comparison between the BSSLoad channel utilization level and the threshold may include scaling, where the BSSLoad channel utilization level may be scaled to the range of the threshold.

The threshold may also comprise a definite indicator like minimum number of associated UE in a wireless access network, for example a WLAN access point. This information may be available from the said BSSLoad information. Then, different load biases, i.e. penalties, could be defined on the basis of the number of UE associated in the WLAn access point.

For example, a penalty for 10 associated UE could be lower than a penalty for 20 UE. Accordingly, a threshold my comprise either UE count or channel load or a combination of the two. Also other criteria may be defined that can be converted to a penalty.

When a load of a wireless access network exceeds 308 a threshold associated with the determined 304 load bias, the load bias is used to adjust 206, 310 the access network selection policy for the wireless access network. In the example of the WLAN conforming to the IEEE 802.1 1 above, adjustment may be provided by a load bias applied to the WLAN when a BSSLoad channel utilization level broadcasted in beacons exceeds the threshold. In case the load does not exceed the threshold, the access network selection policy may be applied at the UE without adjustment and the process ends in 312, where the UE may use the existing access network selection policy for accessing the

communications network and receive services according to his subscription. In an embodiment the access network selection policy may be received in a management object, MO. An example of the MO is described in 3GPP TS 24.312 V1 1 .5.0 (2012-12) that is compatible with Open Mobile Alliance Device Management specifications version 1 .2 and upwards. In another example of the MO, Wi-Fi Alliance Technical Committee Hotspot 2.0 Technical Task Group has published Hotspot 2.0 (Release 2) Technical Specification. Similarly to ANDSF it also provides access network selection rules to the device adhering to HS 2.0 model. Each service provider (3GPP or non-3GPP) can publish own network selection policies to the HS 2.0 devices.

In the following an example of a MO is described, where the MO comprises an extended markup language, XML, document. Then one or more ISMP access network selection policies may be arranged in an XML document by a root node < >/Policy/< >/ where <X> represents an arbitrary intermediate node name. An IRSP policy may be arranged as a node below the root node to < >/ISRP/< >/ and an ISMP policy may be arranged as a node below the root node to < >/ISMP/< >/. ISRP flow distribution rules may be further organized to the <X>/ISRP/<X>/ForFlowBased/<X>,

<X>/ISRP/<X>/ForServiceBased/<X> or <X>/ISRP/<X>/ForNonSeamlessOffload/<X> nodes. Every ISRP and ISRP node is owned by a PLMN and indicated via a PLMN leaf in the node.

In an example of a MO, where a load bias associated to a threshold are both included in an access network selection policy, the load bias and threshold may be implemented as a load penalty node attached to access network selection policy in an XML document. Accordingly, the load penalty node includes load bias and threshold leaves. The threshold may be expressed in the XML document LoadPenalty/<X>/Threshold and the load bias may be expressed in the XML document as LoadPenalty/<X>/LoadBias. Alternatively, load penalty values could be presented with single leaf node LoadPenalty where the different threshold/load bias values could be encoded as single comma separated list of <Threshold>:<Load Bias> values. The LoadPenalty node could be placed into the ANDSF MO as separate operator specific node into the ANDSF root MO level <X> and the same load penalties would affect all operator policies. Operator might also restrict the load penalty scope by placing it under specific policy node like <X>/Policy/<X>/ and

<X>/ISRP/<X>/ where it would apply only policies and rules under the policy node. An operator might further restrict the load penalty scope by placing it under specific ISRP pocily rule node like <X>/ISRP/<X>/ForFlowBased/<X>,

<X>/ISRP/<X>/ForServiceBased/<X> and <X>/ISRP/<X>/ForNonSeamlessOffload/<X> nodes. Finally if the load penalty would be applied only to specific access network then It could be defined for such an access network directly into the access network selection rule like <X>/ISMP/<X>/PrioritizedAccess/<X>.

In an embodiment an access network selection policy may define priorities of wireless access networks, whereby the load bias adjusts 206, 310 the priorities of the wireless access networks. The adjustment may be determined by adding the load bias to the priorities. When the load bias is specific to a wireless access network, only the priority of the specific wireless access network is adjusted.

In an embodiment an access network selection policy may include a plurality of load biases and corresponding thresholds, whereby the load bias corresponding to the highest threshold for the load being exceeded in a wireless access network, is used to adjust 206, 310 the policy, for example a priorities of wireless access networks. It should be appreciated that a wireless access network may have a specific configuration of one or more load biases and associated thresholds, whereby the adjustment 206, 310 of the priority may be specific to each wireless access network defined in the policy.

After the load information is used to adjust the access network selection policy, the process ends 208, 312. The UE may then use the adjusted policy for accessing the communications network and thereby receive services according to his subscription.

It should be appreciated that priority of a wireless access network in an access network selection policy may be a relative priority value that provides priority of the access network compared to at least one other access network. The priority of the other access network may be fixed and stored in the UE, for example.

A priority of a wireless access network may be indicated by a numeric value, for example, by values between 0 and 255, where a smaller value indicates a higher priority as is performed in the ANDSF framework and in the Wi-Fi Alliance HS 2.0. It should be appreciated that depending on implementation, the indication may also be reversed, such that a higher value indicates a higher priority.

An adjustment 206, 310 of the priority value may cause an overflow of the priority value, i.e. the value range is exceeded, the overflow may be determined and the interpreted as a priority value. In case of the overflow, the numerical range of the priority value may be extended to calculate the adjusted priority value correctly and in this way enable comparing priorities that are adjusted beyond the original range. In one example, the priority values use only a part of the values 0-255, where values 0-250 may be reserved for the priority values and values 251 to 255 may be reserved for other purposes. Then an adjustment of the priority value between 0 and 250 may fall within the range 251 -255.

However, as explained above, the interpretation of the adjusted value is still maintained as a priority value.

In an embodiment the access network selection policy includes a plurality of priorities of a plurality of wireless access networks from a group comprising a wireless local area network and a cellular access network. The wireless access networks may comprise one or more from an LTE, an LTE-A, a WiMAX and a WLAN access network for example. The different access networks may be identified from PLMN identifiers that are communicated on a control channel, for example in a WLAN beacon.

In an embodiment the access network selection policy includes identifiers of WLAN access networks. A WLAN conforming to the IEEE 802.1 1 standard may be identified for example by a Service Set Identifier, SSID, or a combination of a Homogenous Extended Service Set Identifier, HESSID, and SSID. A HESS (homogeneous extended service set) defines the physical infrastructure having a common configuration and common

Distribution system connectivity. The SSID defines a logical network operating on the physical infrastructure; there may be multiple SSIDs configured on a single HESS. Further examples of identifiers to identify suitable target networks include information that can be retrieved with Access Network Query Protocol, ANQP, in HS2.0 compliant networks. Like consortium Organization Identifier in the IEEE 802.1 1 - 2012 Section 8.4.1 .31 , Rel12 ANDSF might introduce a few of them.

In an example, an access network selection policy comprises two or more load biases, each of which is associated with a threshold for load of a wireless access network. In this example, the threshold comprises a threshold for the channel utilization level. A higher of the thresholds for the load is '80%' and the lower is '60%'. The load bias to be applied to the access network selection policy, when the higher load is exceeded is Ί Ο', and the load bias to be applied to the policy, when the lower threshold is exceeded is '5'. It should be appreciated that in this example and also in the described embodiments, when a threshold for a load of a wireless access network is not exceeded, there policy need not be adjusted. A MO according to the example may have following nodes for operator level load penalty definition applying to all operator ANDSF policies:

<X>/LoadPenalties/<X>/PLMN=<PLMN>

<X>/LoadPenalties/<X>/LoadPenalty=80:10,60:5

Or

<X>/LoadPenalties/<X>/PLMN=<PLMN>

<X>/LoadPenalties/<X>/LoadPenalty/<1 >/Threshold=80

<X>/LoadPenalties/<X>/LoadPenalty/<1 >/LoadBias=10

<X>/LoadPenalties/<X>/LoadPenalty/<2>/Threshold=60

<X>/LoadPenalties/<X>/LoadPenalty/<2>/LoadBias=5

Another MO according to the example may have the following nodes for ISMP specific policy:

<X>/Policy/<X>/LoadPenalty=80:10,60:5

Or

<X>/Policy/<X>/LoadPenalty/<1 >/Threshold=80

<X>/Policy/<X>/LoadPenalty/<1 >/LoadBias=10

<X>/Policy/<X>/LoadPenalty/<2>/Threshold=60

<X>/Policy/<X>/LoadPenalty/<2>/LoadBias=5

In another example an access network selection policy may comprise a definition of an adjustment to be applied to the policy for a specific wireless access network and a condition for applying the adjustment. Accordingly, the adjustment may comprise a load bias and a threshold associated with the load bias. One or more load biases may be defined in the policy per each wireless access network. A MO having different load biases for different access networks may be as follows: <X>/Policy/<X>/LoadPenalty=80:10,60:5

Or

<X>/Policy/<X>/LoadPenalty/<1 >/Threshold=80

<X>/Policy/<X>/LoadPenalty/<1 >/LoadBias=10

<X>/Policy/<X>/LoadPenalty/<2>/Threshold=60

<X>/Policy/<X>/LoadPenalty/<2>/LoadBias=5

<X>/Policy/<X>/PrioritizedAccess/<1 >/LoadPenalty=80:10,60:5

<X>/Policy/<X>/PrioritizedAccess/<2>/LoadPenalty=60:10

Or

<X>/Policy/<X>/PrioritizedAccess/<1 >/LoadPenalty/<1 >/Threshold=80

<X>/Policy/<X>/PrioritizedAcess/<1 >/LoadPenalty/<1 >/LoadBias=10

<X>/Policy/<X>/PrioritizedAccess/<1 >/LoadPenalty/<2>/Threshold=60

<X>/Policy/<X>/PrioritizedAccess/<1 >/LoadPenalty/<2>/LoadBias=5

<X>/Policy/<X>/PrioritizedAccess/<2>/LoadPenalty/<1 >/Threshold=60

<X>/Policy/<X>/PrioritizedAccess/<2>/LoadPenalty/<1 >/LoadBias=10

In the above MO, the WLAN access network 1 has a plurality of load biases and another WLAN access network 2 has a single load bias.

In one example, where a load bias associated to a threshold are both included in an access network selection policy, the load bias and threshold may be implemented as a load penalty node attached to access network selection policy in an XML document, the load bias may be defined to apply to different levels. Then the XML document may comprise a new leaf in the LoadPenalty indicating applicable access technologies. A new leaf node 'Technologies' may be defined into the LoadPenalty/<X> node listing access technology types applicable for this penalty value. The access technology types may be indicated by a bitmask or similar - one bit for each technology, for example. For a given access network UE would consider only penalty values which include the access technology of the network considered.

The load biases used in various embodiments, may be defined by an operator of a communications network. When load biases are be defined as operator level applying to all operator ANDSF policies, adjustment of an access network selection policy of an operator may be performed in a simple manner since the priorities need not to be changed. Adjustment of the access network selection policy is further facilitated such that it can be adjusted without a new policy from the communications network, since the adaptation of the policy may be performed based on the load information at the UE. In this way the maintenance traffic may be kept at acceptable level in the communications network, while the access network selection may be controlled according to the operator's business reasons and have control when less preferred networks can be selected by the device due to load constraints.

It should be appreciated that it is also possible for UE and an ANDSF to receive an update including information of load biases and corresponding thresholds. This update may then be used to update an existing access network selection policy in UE or in an ANDSF server.

Figures 4, 5 and 6 illustrate block diagrams of an apparatus 400, 500, 600 according to an embodiment. The apparatus of Figure 4 may be used as a reference configuration for implementing the block diagram of UE illustrated in Figure 5 and the block diagram of an ANDSF server illustrated in Figure 6. Although the apparatuses have been depicted as single entities, different modules and memory may be implemented in one or more physical or logical entities. The apparatus may be a terminal suitable for operating as a termination point for telecommunication sessions.

Referring now to the apparatus of Figure 4. The apparatus 400 comprises an interfacing unit 402, a central processing unit (CPU) 408, and a memory 410, that are all being electrically interconnected. The interfacing unit comprises an input 404 and an output unit 406 that provide, respectively, the input and output interfaces to the apparatus. The input and output units may be configured or arranged to send and receive data and/or messages according to one or more protocols used in the above-mentioned

communication standards. The memory may comprise one or more applications that are executable by the CPU.

The CPU may comprise a set of registers, an arithmetic logic unit, and a control unit. The control unit is controlled by a 7sequence of program instructions transferred to the CPU from the memory. The control unit may contain a number of microinstructions for basic operations. The implementation of micro-instructions may vary, depending on the CPU design. The program instructions may be coded by a programming language, which may be a high-level programming language, such as C, Java, etc., or a low-level programming language, such as a machine language, or an assembler. The electronic digital computer may also have an operating system, which may provide system services to a computer program written with the program instructions. The memory may be a volatile or a nonvolatile memory, for example EEPROM, ROM, PROM, RAM, DRAM, SRAM, firmware, programmable logic, etc.

An embodiment provides a computer program embodied on a distribution medium, comprising program instructions which, when loaded into an electronic apparatus, cause the CPU to perform according to an embodiment of the present invention.

The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

Referring now to Figure 5 illustrating a block diagram of user equipment according to an embodiment. A communications element 504 may provide reception of an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one access network selection priority associated with a wireless access network. In one example the communications element may provide an S14 interface to an ANDSF, as described in Figure 1 . An adjustment element 502 may adjust the received access network selection priority on the basis of a load determined for the wireless network associated with the received priority. The load may be determined on the basis of load information determined of available wireless access networks by the communications element 504, for example by measurements. The communications element may comprise a subscriber identity module for unique identification of UE to a communications network, for example the communications network of Figure 1 . The communications element may further include a transmitter to communicate with a wireless access network selected on the basis of the access network selection policy. The communications element and adjustment element may be connected by an electrical connection provided by a communications bus or a via a memory. The access network selection policy may be communicated from the communications element to the adjustment element. Once adjusted, the policy may be sent back to the communications element.

Figure 6 illustrates a block diagram of an ANDSF server according to an embodiment. A load bias determiner 602 may define an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network. The access network selection policy may be determined including a load bias that defines an adjustment to the at least one priority of the wireless access network. A communications element 604 may be provided to receive an access network policy to be followed by subscribers from an operator of a communications network for example as illustrated in Figure 1 . Alternatively or in addition, a load bias may be received from the operator which may be used to update an access network selection policy already stored at the ANDSF. The access network selection policy including the determined load bias associated with the priority of the wireless access network to at least one subscriber station may be transmitted to one or more subscribers by the communications unit 604. The access network selection policy may be communicated for example using a pull mode or push mode operation. The communications element and load bias determined may be connected by an electrical connection provided by a communications bus or a via a memory. The access network selection policy may be tansmitted to the UE, for example over the S14 interface.

The apparatuses 400, 500 and 600 may also be implemented as one or more integrated circuits, such as application-specific integrated circuits ASIC. Other hardware

embodiments are also feasible, such as a circuit built of separate logic components. A hybrid of these different implementations is also feasible. The communications elements of Figures 5 and 6 may be provided by the interfacing unit 402 of Figure 4.

In an embodiment the input unit may provide circuitry for obtaining data, signalling, signalling messages and/or transmissions to the apparatus. The obtaining may comprise receiving radio frequency signals from an antenna, for example. In another example the obtaining may comprise receiving baseband signals from an RF unit or a wired

communications interface, e.g. an Ethernet interface. Accordingly, data, signalling, signalling messages and transmissions in embodiments of the present disclosure may be provided as RF signals or baseband signals.

In an embodiment the output unit may provide circuitry for transmitting data, signalling, signalling messages and/or transmissions from the apparatus. The transmitting may comprise transmitting radio frequency signals from an antenna, for example. In another example the transmitting may comprise transmitting baseband signals to an RF unit or a wired communications interface, e.g. an Ethernet interface. Accordingly, data, signalling, signalling messages and transmissions in embodiments of the present disclosure may be provided as RF signals or baseband signals.

In an embodiment the interfacing unit of Figure 4 provides communications of access network selection policy between UE and a server of a communications network, for example an ANDSF server.

The techniques described herein may be implemented by various means so that an apparatus such as UE, subscriber station, a server or corresponding component, or an apparatus implementing one or more functions described with an embodiment comprises not only prior art means, but also means for receiving an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network, determining load information of available wireless access networks, and adjusting the received priority on the basis of a load determined for the wireless network associated with the received priority.

Another apparatus such as UE, subscriber station, a server or corresponding component, or an apparatus implementing one or more functions described with an embodiment comprises not only prior art means, but also means for defining an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network, determining a load bias defining an adjustment to the at least one priority of the wireless access network, and communicating the access network selection policy including the determined load bias associated with the priority of the wireless access network to at least one subscriber station.

More precisely, the various means comprise means for implementing functionality of a corresponding apparatus described with an embodiment and it may comprise separate means for each separate function, or means may be configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or combinations thereof. For a firmware or software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in any suitable, processor/computer-readable data storage medium(s) or memory unit(s) or article(s) of manufacture and executed by one or more processors/computers. The data storage medium or the memory unit may be implemented within the processor/computer or external to the processor/computer, in which case it can be communicatively coupled to the processor/computer via various means as is known in the art.

The steps/points, and related functions described above in Figure 2 and 3 are in no absolute chronological order, and some of the steps/points may be performed

simultaneously or in an order differing from the given one. Other functions can also be executed between the steps/points or within the steps/points and other signaling messages sent between the illustrated messages. Some of the steps/points or part of the steps/points can also be left out or replaced by a corresponding step/point or part of the step/point.

The present invention is applicable to UE, subscriber station and a server or

corresponding component that define access network selection policies or use them to select an access network. All words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the described embodiments.

For example, an apparatus according to an embodiment may be implemented in hardware (one or more apparatuses), firmware (one or more apparatuses), software (one or more modules), or combinations thereof. For a firmware or software, implementation can be through modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in any suitable, processor/computer- readable data storage medium(s) or memory unit(s) or article(s) of manufacture and executed by one or more processors/computers. The data storage medium or the memory unit may be implemented within the processor/computer or external to the

processor/computer, in which case it can be communicatively coupled to the

processor/computer via various means as is known in the art.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its

embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1 . A method comprising:

receiving an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one access network selection priority associated with a wireless access network;

determining load information of available wireless access networks; and

adjusting the received access network selection priority on the basis of the load information determined for the wireless network associated with the received priority.

2. A method according to claim 1 , comprising:

establishing a connection to the communications network via one of the available wireless access networks on the basis of the adjusted access network selection priorities.

3. A method according to any one of claims 1 or 2, wherein a connection is established to the communications network via a wireless access network having a highest access network selection priority of the priorities after adjustment.

4. A method according to any one of the preceding claims, wherein the access network selection policy comprises a load bias; and a priority of a wireless access network is adjusted by the load bias, when a threshold for a load of the wireless access network is exceeded.

5. A method according to any one of the preceding claims, wherein a received priority of a wireless access network is associated with a load bias for the wireless access network, and the received priority of the wireless access network is adjusted, when the load information exceeds a threshold.

6. A method comprising:

defining an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network;

determining a load bias defining an adjustment to the at least one priority of the wireless access network; and communicating the access network selection policy including the determined load bias associated with the priority of the wireless access network to at least one subscriber station.

7. A method according to any one of the preceding claims, wherein the access network selection policy comprises a threshold for a load of a wireless access network, whereby the load bias defines the adjustment to the priority of the wireless access network, when the load of the wireless access network exceeds the threshold for the load.

8. A method according to any one of the preceding claims, wherein the load information comprises a load of a wireless access network determined by one or more from a group comprising: a utilization level of a wireless channel and a number of terminals served by an access node of a wireless access network.

9. A method according to any one of the preceding claims, wherein a priority of a wireless access network is associated with a plurality of load biases with different thresholds for a load of a wireless access network, whereby the received priority is adjusted by the load bias corresponding to the highest threshold for the load being exceeded in the wireless access network.

10. A method according to any one of the preceding claims, wherein a priority of a wireless access network is associated with a plurality of load biases and the priority is decreased, when the load of the wireless access network is high.

1 1 . A method according to any one of the preceding claims, wherein the access network selection policy comprises priorities of a plurality of wireless access networks from a group comprising a wireless local area network and a cellular access network.

12. An apparatus comprising means configured to perform a method according to any one of claims 1 -5 or any one of claims 7 to 1 1 .

13. An apparatus according to claim 12, wherein the means comprise an adjustment element connected to a communications element, wherein the communications element is arranged to receive an access network selection policy for subscriber stations of a communications network and determine load information of available wireless access networks; and the adjustment element is arranged to adjust the received access network selection priority on the basis of the load information determined for the wireless network associated with the received priority

14. An apparatus according to claim 12 or 13, wherein the apparatus comprises subscriber station.

15. An apparatus comprising means configured to perform a method according to any one of claims 6 to 1 1 .

16. An apparatus according to claim 15, wherein the means comprise a load bias determiner connected to a communications element, wherein,

the load bias determiner is arranged to determine an access network selection policy for subscriber stations of a communications network, said access network selection policy including at least one priority associated with a wireless access network, and a load bias that defines an adjustment to the at least one priority of the wireless access network; and the communications element is arranged to communicate the determined access network selection policy including the determined load bias associated with the priority of the wireless access network to at least one subscriber station.

17. An apparatus according to claim 12 or 15, wherein the apparatus comprises a server, for example an Access Network Discovery and Selection Function server.

18. A computer program product comprising executable code that when executed, execution of functions of a method according to any one of claims 1 to 5 or 7 to 1 1 .

19. A computer program product comprising executable code that when executed, cause execution of functions of a method according to any one of claims 6 to 1 1 .

20. A communications system comprising an apparatus according to any one of claim 12, 13 or 14 arranged to communicate with an apparatus according to any one of claims 15, 16 and 17 via a plurality of wireless access networks.