WO2010100315A1

WO2010100315A1 - Perceived quality driven multimedia qos optimization

Info

Publication number: WO2010100315A1
Application number: PCT/FI2009/050184
Authority: WO
Inventors: Martin Varela; Marko Jurvansuu; Mikko Hanski; Jarmo Prokkola; Matti Airas
Original assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 2009-03-06
Filing date: 2009-03-06
Publication date: 2010-09-10

Abstract

Arrangement for optimizing the perceived quality of service (QoS) relative to a multi-mode mobile terminal device (102) and associated multimedia application running over a packet network, such as audio and/or video streaming application, comprising a network QoS measurer configured to obtain, relative to a plurality of wireless communications networks of different technology capable of supporting packet data transfer for serving the multimedia application, a number of QoS metrics indicative of the network performance of each network, a perceived QoS estimator configured to estimate the current perceived QoS for each network on the basis of the associated QoS metrics obtained indicative of the network performance and said multimedia application, and to suggest whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the multimedia application associated with the multi-mode mobile terminal according to the performed estimation, and a mobility handler for initiating a vertical handover in response to such suggestion by the perceived QoS estimator. A corresponding method is presented.

Description

PERCEIVED QUALITY DRIVEN MULTIMEDIA QOS OPTIMIZATION

FIELD OF THE INVENTION

Generally the invention pertains to communications networks. In particular, the invention concerns optimization of perceived quality (QoE, Quality of Experience) relative to multimedia applications utilized in wireless terminal devices capable of co-operating with a number of communications networks.

BACKGROUND

A shift towards extensive usage of IP protocols in all telecommunication applications is a widely recognized general trend. This is also true for voice. In the long run most voice will be delivered using IP (Internet Protocol), i.e. VoIP (Voice over IP). Network technologies such as Wi-Fi (Wireless Fidelity )/WLAN (Wireless Local Area Network), WiMAX (Worldwide Interoperability for Microwave Access), HSPA (High-Speed Packet Access) and the forthcoming LTE (Long Term Evolution) will deliver users' voice traffic over packet switched VoIP instead of traditional circuit switched technologies. When such a transition ultimately takes place, the user perceived voice quality should at least be on the same level with present circuit switched networks. If this fails, the users may find difficult to adopt VoIP based solutions, whether the usage of VoIP can provide financial savings to the user or not. On the other hand, there is another change in sight relating to mobility in IP networks. Operators are deploying several technologies in their networks (e.g. 3G and Wi-Fi) and allowing their customers to roam between network domains of different technologies. This requires IP based mobility solutions like Mobile IP, which is the IETF (Internet Engineering Task Force) and 3GPP (3^rd Generation Partnership Project) (3^rd Generation Partnership Project) standard for the purpose. In the context of mobile communications a term "vertical handover" is typically used to refer to an inter-technology handover wherein a connection is transferred from one access technology, i.e. air interface technology, to another, e.g. from Wi-Fi to 3G or vice versa. The quality as perceived by the end user should certainly be an important factor to consider, when the mobility solution makes the decision for handover.

Traditional IP mobility applications bear rather limited means to determine when a vertical handover shall be performed. Typically, these means include detecting a connection break, measuring the signal strength in wireless networks, or finding an available network which has a lower cost than the one currently in use (e.g. switching to a free WiFi access from a 3G network).

Many workplaces are now turning into wireless offices, where fixed Ethernet net- works are replaced by Wi-Fi wireless network connections. In this kind of offices, the users mainly utilize VoIP applications in their mobile phones or PDA's. With Wi-Fi networks, however, the access point (AP) congestion induced by number of other users can severely degrade voice quality.

Publication US2007/0025297 discloses an arrangement for providing a seamless vertical handover between a broadband wireless communications network and WLAN while taking QoS aspects such as minimum traffic rate or maximum latency into account via mapping the QoS requirements as formulated in the source network to a form applicable in the target network by a handover processing entity. It is gen- erally disclosed how e.g. signal strength may be applied as one criterion for initiating a handover.

Granted, various solutions for maintaining a reasonable QoS in changing network conditions such as a vertical handover between different networks exist. However, these contemporary mechanisms do not really consider the QoS that the user actually perceives, i.e. the QoE. In addition, the motivation for triggering a handover or some other corrective measure is typically based purely on network-level performance metrics like loss rate, delay, transfer rate, etc. For example, in switching from 3G to a WiFi network in which there is congestion (something that it's surprisingly hard for traditional mechanisms to detect), the quality perceived by the user might drop to unacceptable levels even though WiFi, in general, offers considerably higher data rates and the aforesaid purely "objective" and technical network level QoS parameters may indicate also in this particular case that there's nothing wrong with the achieved WiFi performance. Similar situations might arise in the opposite case, in which a handover would be necessary for maintaining an acceptable quality level, but is not performed.

SUMMARY OF THE INVENTION

The objective is to at least alleviate one or more of the above defects evident in prior art solutions what comes to maintaining QoS in multimedia applications run over packet networks. The objective is generally met by an arrangement and a related method for optimizing, in particular, the perceived quality of service, i.e. the QoE, relative to a multi- mode terminal device and multimedia application run over a packet network, which are capable of deriving perceived quality metrics out of network-level QoS metrics and changing and/or modifying the used connection so as to optimize the perceived quality. The multimedia application running over a packet network incorporates, in the context of the present invention, data transfer via a communications network substantially in real-time fashion relative to the exploitation thereof, such as interactive or non-interactive (e.g. streaming) video data and/or audio data transfer, where - upon the network performance affects the QoE thereof. The optimization may be carried out by application-level and/or network-level adjustments as described more thoroughly hereinafter.

Namely, in one aspect of the present invention, an arrangement for optimizing per- ceived quality of service (QoS) relative to a multi-mode mobile terminal device and associated multimedia application running over a packet network, such as audio and/or video streaming application, comprises

-a network QoS measurer configured to obtain, relative to a plurality of wireless communications networks of different technology capable of supporting packet data transfer for serving the multimedia application, a number of QoS metrics indicative of the network performance of each network,

-a perceived QoS estimator configured to estimate the current perceived QoS for each network on the basis of the associated QoS metrics obtained indicative of the network performance and on the basis of said multimedia application, and to suggest whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the multimedia application associated with the multi-mode mobile terminal according to the performed estimation, and

-a mobility handler for initiating a vertical handover in response to such suggestion by the perceived QoS estimator.

The features of the arrangement may be included in the mobile terminal, in network infrastructure such as one or more network elements, or in both as a distributed or at least partially duplicate implementation. Notwithstanding the particular embodiment in question, the suggested solution implies certain level of communication to take place between the mobile terminal and network infrastructure(s) e.g. in a form of multimedia application (payload) data and optionally of control data between different entities of the arrangement when distributed among a plurality of physical entities. Preferably the arrangement explicitly suggests a certain other network (of another technology) in range for use instead of the current network. Alternatively, if it is deemed that the performance of the currently selected network is too poor but there are no better options available at the moment (e.g. no coverage), the arrangement may just instruct the mobility management and/or some other entity to actively search for new better performing networks, e.g. with an accelerated scanning rate.

The perceived QoS estimator is preferably application-aware in a sense that it estimates the perceived QoS partially on the basis of application knowledge and partially based on the performance information obtained from the network QoS measurer entity, optionally supplemented by further one or more data sources and related estimation logics. Based on the estimated quality, the module may then decide whether the current network is still appropriate for the application or if a vertical handover or other corrective measures are required. The application knowledge may include at least one data element selected from the group consisting of: payload type (e.g. video, audio, or both), application identification data, application type (communications, data streaming, unidirectional/bidirectional, etc.), and indication of one or more current execution parameters, i.e. settings, such as a parameter indicative of video resolution, video codec, (nominal) bit rate, (nominal) video bit rate, (nominal) audio bit rate, audio codec, error coding method, and error coding settings. Some of the application knowledge may be fixed and stored in a database, for example, whereas other knowledge may be dynamic (such as current, i.e. really achieved, bit rate information instead of nominal rate(s)) and shall be updated accordingly. Moreover, the perceived QoS estimator may include a number of logics, e.g. in a form of one or more tables and/or algorithms, to map such application knowledge and network QoS information to the perceived QoS estimate.

In one embodiment the perceived QoS estimator particularly includes a PSQA (Pseudo-Subjective Quality Assessment) entity configured to quantify the quality of e.g. a video or an audio sequence as perceived by the user and received through an IP network. The PSQA is advantageously capable of providing accurately and efficiently computed evaluation of the perceived quality. In this context "accuracy" ad- vantageously means that the PSQA gives quality values close to those than can be obtained from a panel of true human observers, under a controlled subjective testing experiment, following an appropriate norm (which depends on the type of sequence or application). In another, either supplementary or alternative, embodiment the arrangement further comprises a predictor entity co-operating with the network QoS and/or perceived QoS estimation entity, as a functionally connected entity or integrated therewith, and configured to temporally monitor the network QoS and/or perceived QoS relative to each network so that an estimate of network QoS and/or perceived QoS may be given with regard to certain location, time and/or application on the basis of such monitoring. In case the predictor estimates only network QoS, the perceived QoS may be, substantially in real-time, calculated by the perceived QoS estimator on the basis of the network QoS and application knowledge. The accuracy of monitoring and the resulting estimate may be location-wise, i.e. spatially, network-specific or e.g. access point (/base station) -specific within each (access) network having a plurality of technically homogeneous access points. In the latter, higher resolution case the predictor may still additionally provide an aggregate estimate for each network of certain technology as a whole. The QoS estimates may relate to the present moment of providing the estimate or a certain future time instant or time period. The temporal resolution of the predictor may be fixed or adaptive, e.g. minute, hour, or other time period-based.

In a further, either supplementary or alternative, embodiment the arrangement further comprises an application adjuster co-operating with the perceived QoS estimation entity, as a functionally connected entity or integrated therewith, and provided with information on the adjustability of the multimedia application and related aspects such as current and/or the available parameter (value) range for parame- ters/settings like video resolution, video codec, video bit rate, audio bit rate, audio codec, error coding method, loss concealment algorithm, dejittering buffer length, and/or error coding settings. The application adjuster is configured to determine and suggest how to modify one or more application-related settings in order to optimize the perceived QoS as determined by the perceived QoS estimator. Information on currently available network resources, such as obtainable bit rate, as indicated by the network QoS or some other entity may be utilized in the process so that the difference between a theoretical parameter value range for a parameter and the range really available in current network conditions can be recognized, whereupon the adjustments can be done within the truly practicable range, this range possibly being equivalent to or at least one sub-range of the whole nominal range. The adjuster may include a number of logics to map a change of an application parameter to a change in the perceived QoS. At least one API (Application Programming Interface) may be provided for the application and optionally related entities in order to con- trol the settings thereof and/or for providing information on the current settings, for instance. The adjuster may then control the settings of the application and/or related entities (e.g. channel coder) via the API(s). Alternatively, the application may be QoS or QoE aware and include at least portion of the application adjuster logic for adjusting the settings internally.

Yet in a further embodiment the arrangement utilizes the perceived QoS estimator for obtaining an estimate of the QoS such that primarily the application settings are to be modified by the application adjuster and optionally a vertical handover may be subsequently performed provided that even the modified application settings do not alone and/or permanently provide the necessary level of perceived QoS for the application according to one or more criteria. The effect of modifying the application setting may be estimated or verified based on trying them in practice. In case a vertical handover is needed, the application settings may be left unaltered or they may be adjusted based on the expected and/or actual QoE performance of the new network, for example.

Still in a further embodiment the QoS metrics, i.e. characterizing elements, may include at least one network performance indicator selected from the group consisting of: transfer rate, maximum transfer rate, minimum transfer rate, average transfer rate, error rate, minimum error rate, maximum error rate, average error rate, signal to interference ratio, signal to noise ratio, noise power, noise level, packet loss rate, loss patterns, packet reordering, retransmission rate, number of users, transmission level, reception level, transmission delay, one-way latency, round-trip latency vari- ance (jitter), and error distribution. The network QoS measurer may be configured to obtain such information on the basis of locally performed calculations in view of monitored data transfer events and/or on the basis of already available corresponding indicators determined by some other entities of the device including the overall arrangement of the present invention, such as a mobile terminal. Additionally or al- ternatively, the network QoS measurer may obtain the information by receiving it from external entities (e.g. a mobile terminal may receive QoS indicators or data for determining those from a network element such as a server/router/switch, or vice versa).

Considering any embodiment, the obtained network QoS metrics are advantageously up-to-date, i.e. fresh enough to properly reflect the current situation. Most preferably at least some of the network QoS metrics are obtained substantially in real-time. Naturally the accuracy of the perceived QoE estimates is partially dependent on the accuracy of obtained network QoS metrics.

According to one embodiment the arrangement is also configured to obtain informa- tion relative to the performance of networks the coverage of which does not yet extend to the particular mobile terminal in question. Such information may still be used proactively for shortening response times in view of scenarios wherein the coverage is finally entered by the terminal and/or otherwise, for example. The information may be obtained via intermediate entities such as other network(s).

In practice the above functionalities provided by any of the network QoS measurer, perceived QoS estimator, mobility handler, and application adjuster entities may, depending on the particular embodiment, be implemented as a number of mutually communicating parallel entities or e.g. a as centralized solution with a main control- ler entity and a number of sub-entities handling various specific sub-tasks tasks on behalf of the main controller entity.

In another aspect of the present invention, a method for optimizing the perceived quality of service (QoS) relative to a multi-mode terminal device and associated multimedia application run over a packet network, comprises

-obtaining, relative to a plurality of wireless communications networks of different technology capable of supporting packet data transfer for serving the multimedia application, a number of QoS metrics indicative of the network performance of each network,

-estimating the current perceived QoS for each network in the light of the associated QoS metrics obtained indicative of the network performance and in the light of said multimedia application,

-suggesting whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the multimedia application associated with the multi-mode mobile terminal according to the performed estimation, and

- initiating a vertical handover to another network, when suggested.

The utility of the present invention arises from a plurality of issues. The solution may provide optimization substantially in real-time fashion in contrast to many prior solutions requiring off-line calculations and comparisons between payload signals and/or reference signals from a plurality of sources. Instead, QoE assessment of the present invention is preferably done parametrically, which allows predicting QoE based on network performance indicators and application parameters. This enables probing a number of candidate networks at any given instant prior to actually performing the handover. The resulting optimization is based on user perceived quality, which is, from the standpoint of user experience, more important criterion than mere technical network-level quality applied by many prior art arrangements. The optimization methods of altering the application settings, i.e. internal functional parame- ters thereof, and/or performing a vertical handover, may be performed rapidly and efficiently after recognizing the problem with the current scenario. The computational requirements set by the solution are relatively light, which enables implementing it in many cases purely via software, and acquisition of new, possibly pricey hardware can be omitted. The provided solution is itself thus transparent in view of the user as only the positive outcome of executed optimization is advantageously visible and/or audible through the utilization of the multimedia application itself.

The expression "multi-mode mobile terminal" refers herein to any portable comput- ing device that is enabled to access at least two wireless networks of different technology, such as Wi-Fi (access) network and a cellular (access) network. E.g. different smartphones or PDA's (Personal Digital Assistant) supplied with wireless transceivers may support a plurality of different network interfaces.

The expression "a wireless communications network" refers herein to a network of one or more base stations, or "access points" in the terminology typically used in connection with Wi-Fi, of certain technology for providing network access to mobile terminals. For example, such a wireless network may be wireless a local area network (WLAN) (like an IEEE 802.1 Ix network), a wireless personal area network (WPAN), a wireless metropolitan area network (WMAN), or a wireless wide area network (WWAN) such as a cellular or even satellite network. The heterogeneous wireless communications networks between which a vertical handover may take place may belong to the same or different (administrative) domain, which results in macro- and micro-mobility mm (mobility management) scenarios, respectively. The handovers may generally be of hard or soft type.

The expression "data transfer" and derivatives thereof may refer herein to transmitting or receiving data, or both, depending on the viewpoint naturally present in con- nection with each instance of the term. From the standpoint of the sender, transfer is substantially about transmitting data, whereas from the standpoint of the recipient, the transfer includes mostly receiving data, although in both cases the communication may also be bidirectional. For example, a recipient may send acknowledge- ments to the sender that receives those while, between, or after sending the data. Data transfer may imply copying data or moving data, i.e. the sent data may remain at the sending party after communication thereof or it may be deleted after the transmission.

The terms "Wi-Fi" and WLAN are used interchangeably.

The expression "a number of refers herein to any positive integer starting from one (1), e.g. one, two, or three.

The expression "a plurality of refers herein to any positive integer starting from two (2), e.g. two, three, or four.

In an embodiment of the present invention a mobile terminal is communicating with a WLAN network and the arrangement of the present invention is applied in assess- ing the perceived QoS, i.e. QoE, relative to the used multimedia application and the network performance metrics of the WLAN. The multimedia application may include transferring coded speech or video, for example. Probing is actuated towards one or more other networks such that when the perceived quality obtained with the WLAN network drops below an acceptable, predetermined level, a vertical hand- over to a better-performing network is initiated. Further features of adjusting application-level parameters in addition to or instead of a handover, and/or predicting the QoS and/or QoE of one or more networks (and/or more specific (access) locations) based on historical data are optionally applied. Various other alternatives, modifications, and supplementary features of the basic scenario are presented as well.

Various embodiments of the present invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF THE RELATED DRAWINGS

Next the invention is described in more detail with reference to the appended drawings in which Fig. 1 depicts the concept and various features of the present invention in general. Fig. 2 is block diagram of an embodiment of the arrangement according to the present invention.

Fig. 3a illustrates an embodiment of the present invention at a first time instant. Fig. 3b illustrates the above embodiment at a second, subsequent time instant.

Fig. 4 illustrates a flow diagram of an embodiment of a method according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 discloses, by way of example only, a sketch of the concept of the present invention, wherein heterogeneous wireless communications networks A 104 and B 106 have at least partially overlapping coverage and at least a functional connection to network C 108 whereto a server 110 providing the real-time service to a mobile terminal 102 is also connected. Instead of a server, the real-time service may also be arranged relative to another terminal device or some other entity reachable through the networks 104, 106 from the standpoint of the terminal 102.

Generally, mobility management (mm) can be implemented on different layers of the applied system for layered communications. In view of the ordinarily used OSI (Open Systems Interconnection) model, e.g. the existing network layer (L3), link layer (L2) and cross-layer (L3 + L2) mm solutions may be applied in addition to various higher level (transport, application, etc.) solutions. For example, Unlicensed Mobile Access ('UMA' or 3GPP Generic Access Network), Mobile IP, SIP and/or IEEE 802.21 could be considered for the purpose. Thereby, in one embodiment of the invention one of the networks 104, 106, such as network A 104, could be a cellular network and the other e.g. a WLAN network, whereupon Mobile IP (e.g. Mobile IPv4 or Mobile IPv6), an extension to the TCP/IP suite, could be exploited for mobility management between a cellular network and a WLAN network, for in- stance. A person skilled in the art will appreciate the fact that as the core of the present invention relates more to the subjective performance analysis of the consumed service and related triggering of the vertical handover and/or adjusting the application settings than to the internals of the actual handover and mobility management mechanism, the selection of the mm method may be done use case-specifically by a skilled person according to his/her preferences and other implementation requirements or guidelines. An embodiment of the multi-mode mobile terminal 102 comprises at least one processor 120 such as one or more microprocessors, micro-controllers, DSP's (digital signal processor), programmable logic chips, etc. The processor 120 may comprise a plurality of co-operating processors or sub-processors. The processor 120 is config- ured to execute the code stored in a memory 126, which may imply processing instructions and data relative to the QoE-based vertical handover control functionality 128 of the present invention and optionally other functionalities such as OS related functionalities, I/O-related functionalities, and other applications. The memory 126 may be divided between one or more physical memory chips or other memory ele- ments. The memory 126 may further refer to and include other storage media such as a preferably detachable memory card, a floppy disc, a CD-ROM, or a fixed storage medium such as a hard drive. The memory 126 may be non-volatile, e.g. ROM, and/or volatile, e.g. RAM, by nature. The UI (user interface) 122 may comprise a display, or a connector to an external display or data projector, and key- board/keypad or other applicable control input means (e.g. touch screen or voice control input, or separate keys/buttons/knobs) configured so as to provide the user of the device 102 with practicable data visualization and device control means.

In addition, the multi-mode device 102 comprises a network interface part such as two or more wireless transceivers 124, or "network adapters", complying with a predetermined wireless technology such as GSM, UMTS, WLAN, Bluetooth, Wi- max, etc, for communication with other devices such as terminal devices, peripheral devices and/or network infrastructure(s). It is clear to a skilled person that the device 102 may in practice comprise numerous further functional and/or structural elements for providing various beneficial communication, processing, or other features, whereupon this disclosure is not to be construed as limiting the presence of potential additional elements in any manner.

As mentioned above, the functionality of the suggested arrangement may be imple- mented as a software application that is executed by the processor 120 and stored in memory 126. This computer software (product) may be thus provided on a carrier medium such as a memory card, memory stick, an optical disc (e.g. CD-ROM or DVD), or some other memory carrier. The software may also be distributed over a communications network. The instructions required for implementing the applica- tion may be stored in the carrier medium as executable or in some other, e.g. compressed, format, such that the software may be transported via the carrier medium to a target device and installed therein, e.g. in the hard disk thereof, or executed directly from the carrier medium in the target device by loading the related Iy from the carrier medium in the target device by loading the related instructions to the memory 126 of the target device not until execution, for instance.

Likewise, the functionality of the suggested arrangement may be provided via a network element, a combination of multiple network elements, or via a combination of a mobile terminal and one or more network elements. For example, the server arrangement 110, of one or more at least functionally connected servers or other network entities, being naturally provided with at least one network adapter 134, may further comprise at least one processor 130, a memory 136 and QoE-based vertical handover control functionality 138 of the present invention. The entity 110 may be thus configured to provide instructions to and/or obtaining data from the mobile terminal 102 for implementing at least its part of the aforesaid vertical handover control functionality. In a shared model, multiple elements like a plurality of server entities, or a mobile terminal 102 and one or more server 110 entities, may arrange a portion of the overall QoE logic required. Yet, the server 110 may comprise a UI for administration purposes (not shown).

Figure 2 illustrates a functional block diagram in accordance with one embodiment of the present invention comprising a network QoS measurer 202, perceived QoS estimator 204, mobility handler 206, optional application adjuster 208, and optional predictor 210 functionally incorporating a history analyzer. The arrangement entity of the present invention 201 co-operates (shown via the broken lines) with the multimedia application(s) 212 and network interfaces 124, 134 so as to obtain information on them and providing control instructions in response, for example. The illus- trated entities covered by a dotted rectangle may be implemented as software 128, 138 executed by a processor 120, 130 and stored in a memory 126, 136 either in a mobile terminal 102, at least one network entity such as a server 110, or in a combination of both.

In one embodiment the perceived QoS estimator 204 comprises a PSQA or some other predetermined QoE analysis -capable entity. Preferably the entity may work substantially in real time, if necessary. Preferably the entity is enabled for both oneway (e.g. streaming flows) and two-way (e.g. interactive communications) estimation of data flows. Yet, advantageously the entity is capable of handing a plurality of payload types such as audio and video sequences. For example, the PSQA may be applied with VoIP, IP telephony, video-conferences, streaming, both real-time (TV flows) and batch (VoD), etc. As depicted in figure 5, the PSQA module 502 comprises an input API 504, an optional extension API 506, a number of application- and/or application-type-specific data sets 508, a statistical estimator 510 and an output API 512. The input API 504 provides a means to feed relevant network QoS as measured by either the applica- tion or the network QoS measurer, and application configuration data to the PSQA module. The application- and/or application-type-specific data sets provide a means for the PSQA statistical estimator 510 to map the data gathered via the input API 504 to subjective QoS perception (i.e. QoE) for the application or application-type in question. The optional PSQA extension API 506 provides a means for extending the functionality of the PSQA module to new applications if required. The statistical estimation module is usually implemented as a Random Neural Network, but can be eventually substituted by other estimator types such as Artificial Neural Networks, Bayesian filters, or any other statistical or analytic method capable of reliably mapping the data collected via the input API 504 to the subjective perception of the QoS. The output API 512 feeds other modules in the arrangement, such as the application adjuster and the mobility handler as needed. The functionality implemented by the PSQA module might conceivably be implemented with other adequate parametric or signal-based quality estimators (e.g. ITU E-Model or ITU P.563, respectively), although the performance of the arrangement would likely considerably suffer in this case.

In another embodiment the application adjuster 208 is used, on the basis of QoE estimate derived from the network QoS metrics and current application settings, to determine how to adjust the application and/or related settings so as to improve the QoE. For example, let's consider a scenario wherein the mobile terminal is connected to a WLAN (say, 802.1 In with retransmits disabled to minimize delay) and it is configured to execute a VoIP application. However, interference in the WLAN creates bursty losses, which is indicated by the network metrics. As a corrective measure, the adjuster 208 may be configured to modifying the FEC (Forward Error Correction) scheme such that the spacing between FEC data is increased.

If both the aforementioned embodiments were to be combined, a likely policy would be to attempt to maintain quality via application level settings, and if this is not enough to obtain good quality, then proceed with a handover to a different (ac- cess) network. This could, of course, be done in a single step, and the handover could also create a need for using different application level parameters (e.g. switch from a wideband codec to AMR (Adaptive Multi-Rate) when moving from WLAN to 3G). Concerning the embodiment of predictive handover and the predictor entity 210, one underlying thesis is that in most cases the users do not continually roam among new, unknown networks, but mostly use the same networks (e.g. within their com- pany premises, etc.). Furthermore, usage patterns in many, if not most, networks are fairly static (for instance, network load evolution during weekdays is surprisingly regular in many cases), and problems in some cases are static too (e.g. areas with spotty coverage, or consistently crowded). Therefore, it makes sense to create a mapping of quality for the different networks, locations, times, and/or applications in such a way that if a network provides consistently bad quality (at certain locations and certain times) according to predetermined criteria (e.g. temporal and quantitative), it can be avoided preemptively, and thus drops in the perceived quality are avoided. The predictor may temporally monitor network level QoS and/or application-level perceived QoS (e.g. in co-operation with perceived QoS estimator 204).

A use scenario for this could be as follows: The user of the mobile terminal is a factory manager that does several daily rounds on the premises, and uses VoIP often during these rounds. Over time, quality patterns emerge, such that it is visible that if the user is connected to WLAN B (see e.g. figure 1) between noon and 2pm, there's a high chance of having bad VoIP quality which results in a handover to network A such as a 3G or other cellular network when the quality deteriorates. The system can learn these patterns, and react accordingly in order to avoid even short periods of lower quality. Thus, network B is to be avoided between noon and 2pm (at least if the user is using VoIP). A quality data history bank may be constructed from net- work QoS data (-metrics), location data (if available), time data, and QoE data. Once the history is stable, it can be used as a source for triggering adaptations, both application (e.g. setting adjustments) and network level, proactively before the QoE levels are affected.

Alternatively or additionally, the history data may be used for shortening response times in connection with application and/or network-level optimization. For instance, when detected a problematic daily period for certain network's QoE performance, upon entering associated time window in real-time, the QoE optimization measures may be configured to be triggered more rapidly, i.e. based on shorter pe- riod of deteriorated performance, than during time windows carrying no such historical burden. Thus the embodiment may be cleverly combined with any of the preceding embodiments. Figs 3a and 3b illustrate temporally an embodiment of the present invention and a use scenario thereof. A skilled reader will immediately recognize that the embodiment is congruent with the afore-explained embodiments and may be combined or merged with them mutatis mutandis. The arrows illustrate data transfer. Optional elements are visualized using broken lines. To visualize how the different entities might conceptually reside relative to network, application, and user levels, corresponding layers have been shown in the figure. Fig. 3a illustrates the situation of the depicted scenario at a first time instant. Currently the mobile terminal in question is connected to ("current choice") network A 314 as controlled by the mobility, e.g. IP mobility (shown), entity 306 while the other networks 316, 318 are only probed as to the performance thereof. Use of different words "monitoring" and "probing" relative to the current network and other networks, respectively, highlights the fact that more and/or more detailed monitoring data may be obtainable (not necessarily though) relative to the current network.

The optional predictor entity 310 is deliberately located in the figure between the network QoS measurer 302 and QoE estimator 304, and network and application layers, respectively, to imply that the history data may be collected and analyzed either on network or application level, or using both resolution levels, when feasible. The optional application adjuster 308 is shown as linked and next to the QoE estimator 304 as it shall be aware of the application level aspects such as applications settings anyway.

Fig. 3b illustrates the above embodiment at a second, subsequent time instant. The performance offered by network A 314 has been deemed as sub-optimal, and a vertical handover has taken place to network B 316 to raise the QoE back to an acceptable level.

Fig. 4 is a flow diagram of an embodiment of a method according to the present in- vention. Optional blocks are highlighted with a dotted border line. At start-up 402, initial actions enabling the execution of the further method steps are performed, i.e. a mobile device and/or other device(s) for hosting the arrangement are obtained and configured. At 404 the arrangement obtains, relative to a plurality of wireless communications networks of different technology and including the network(s) whereto the terminal is currently connected, a number of QoS metrics indicative of the network performance of each network, said metrics preferably substantially indicating the current (real-time) performance of each network or at least the latest available performance information. At 406 the arrangement estimates the current perceived QoS, i.e. QoE, for each such network in the light of associated QoS metrics obtained and application knowledge. The arrangement further ponders, at 408, whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the executed multimedia application. In response, the arrangement optionally controls 410 adjusting the application-level settings and/or initiates a vertical handover 412 when necessary prior to the end of method execution at 414. Dotted loop-back arrow illustrates the potentially continuous, re- peatable nature of the suggested method. The predictor 416 may be used for providing history-based QoE and/or network QoS estimates for omitting a badly perform- ing network from the pool of applicable networks and/or for changing (e.g. quickening and/or lowering some quality-related threshold) the response of the arrangement towards it as deliberated hereinbefore, for instance.

The scope of the invention can be found in the following claims. Notwithstanding the various embodiments described hereinbefore in detail, a person skilled in the art will appreciate the fact that different modifications may be introduced to the explicitly disclosed solutions without diverging from the fulcrum of the present invention as set forth in this text and defined by the independent claims.

Claims

1. An arrangement (201) for optimizing the perceived quality of service relative to a multi-mode mobile terminal device and associated multimedia application run- ning over a packet network, such as audio and/or video streaming application, comprising

-a network QoS (Quality of Service) measurer (202, 302) configured to obtain, relative to a plurality of wireless communications networks of different technology ca- pable of supporting packet data transfer for serving the multimedia application, a number of QoS metrics indicative of the network performance of each network,

-a perceived QoS estimator (204, 304) configured to estimate the current perceived QoS for each network on the basis of the associated QoS metrics obtained indicative of the network performance and on the basis of said multimedia application, and to suggest whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the multimedia application associated with the multi-mode mobile terminal according to the performed estimation, and

-a mobility handler (206, 306) for initiating a vertical handover in response to such suggestion by the perceived QoS estimator.

2. The arrangement of claim 1, wherein said perceived QoS estimator is substantially parametric.

3. The arrangement of any preceding claim, further comprising a predictor (210, 310) configured to monitor QoS in relation to one or more networks over time, and to estimate on the basis of gathered past QoS information current or future QoS of said one or more networks.

4. The arrangement of claim 3, wherein at least one QoS estimate for a network obtained by the temporal monitoring is provided with a spatial resolution of one or more base stations or other access points instead of the whole network.

5. The arrangement of claim 3 or 4, wherein an obtained estimate includes a network QoS estimate.

6. The arrangement of any of claims 3-5, wherein an obtained estimate includes a perceived QoS estimate taking the user experience and the particular multimedia application into account.

7. The arrangement of any preceding claim, further comprising an application adjuster (208, 308) configured to determine how to adjust application-related settings to optimize the perceived QoS.

8. The arrangement of claim 7, configured to optimize the perceived QoS primar- ily using the application adjuster and then by conducting a vertical handover provided that adjusting the application-related settings does not provide perceived quality high enough according to one or more criteria.

9. The arrangement of any preceding claim, wherein the perceived QoS estimator includes a PSQA (Pseudo-Subjective Quality Assessment) entity (502).

10. The arrangement of any preceding claim, wherein said number of network QoS metrics include at least one element selected from the group consisting of: transfer rate, maximum transfer rate, minimum transfer rate, average transfer rate, error rate, minimum error rate, maximum error rate, average error rate, signal to interference ratio, signal to noise ratio, noise power, noise level, packet loss rate, loss pattern, packet reordering, retransmission rate, number of users, transmission level, reception level, transmission delay, one-way latency, round-trip latency variance, and error distribution.

11. The arrangement of any preceding claim, wherein the perceived QoS estimator utilizes, in order to provide the estimate of perceived QoS relative to a certain network and the particular multimedia application, application-specific knowledge including at least one element selected from the group consisting of: payload type, application identification data, application type, video resolution, video codec, nominal video bit rate, nominal audio bit rate, current video bit rate, current audio bit rate, current bit rate, nominal bit rate, audio codec, error coding method, and error coding settings.

12. A mobile terminal (102) comprising the arrangement of any preceding claim.

13. A network entity comprising one or more network elements and the arrangement of any of claims 1-11.

14. A system comprising a mobile terminal and a at least one network element, further comprising the arrangement of any of claims 1-11, wherein the mobile terminal comprises at least one entity of said network QoS measurer, perceived QoS estimator, and mobility handler of the arrangement, and the at least one network element comprises at least the remaining entities.

15. A method for optimizing the perceived quality of service relative to a multi- mode terminal device and associated multimedia application run over a packet network, comprising

-obtaining (404), relative to a plurality of wireless communications networks of different technology capable of supporting packet data transfer for serving the multimedia application, a number of QoS (Quality of Service) metrics indicative of the network performance of each network,

-estimating (406) the current perceived QoS for each network in the light of the associated QoS metrics obtained indicative of the network performance and on the basis of said multimedia application,

-suggesting (408) whether to stay with the current network or switch into another network providing a higher level of perceived QoS for the multimedia application associated with the multi-mode mobile terminal according to the performed estimation, and

- initiating a vertical handover (412) to said another network, when suggested.

16. The method of claim 15, further comprising monitoring the QoS in relation to one or more networks over time, and estimating on the basis of gathered past QoS information current or future QoS of said one or more networks (416).

17. The method of any of claims 14-15, further comprising determining adjustments (410) to the application-related settings to optimize the perceived QoS.

18. The method of any of claims 14-16, wherein PSQA (Pseudo-Subjective Qual- ity Assessment) is utilized for estimating the current perceived QoS.

19. A computer program, comprising code means adapted, when run on a computer such as the mobile terminal of claim 12 or network entity of claim 13, to execute the method steps of any of claims 15-18.

20. A carrier medium comprising the computer program of claim 19.