CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. § 371 National Phase Entry Application from PCT/EP2017/081660, filed Dec. 6, 2017, designating the United States, and also claims the benefit of European Application No. 17382761.9, filed Nov. 10, 2017, the disclosures of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The application relates to a method for controlling at least one path in a multipath environment wherein the at least one path is used for transmitting an encrypted video stream comprising a sequence of video segments. Furthermore the corresponding path control entity is provided which controls the at least one path in the multipath environment. Additionally a computer program comprising programme code is provided and a carrier comprising the computer program.

BACKGROUND

The streaming of a video based on TCP (Transport Control Protocol) comprises different phases as shown inFIG.1. A pre-download phase2is provided and a download phase3. The former phase comprises a streaming access phase4wherein the latter phase comprises a buffering phase5which starts with the first transfer of the video and which ends when the first frame of the video is displayed. The different phases shown inFIG.1can occur during a download of a video from a provider such as YouTube. The buffering occurs when there is not enough information in the video buffer of the player so that the end user cannot visualise the video.

The video session then starts with a playout phase6where the end user is playing the video and where the video is still downloaded. In Netflix and YouTube, once the additional buffering has finished, the end-user periodically downloads some video frames to keep the buffer state over a minimum needed for still reproducing the video. These video services use TCP as transport protocol. The payload of the traffic is sent using encryption mechanisms.

Adaptive bit rate (ABR) is the most common technology used to deliver video by over-the-top (OTT) video providers using HTTP/HTTPS over TCP.

With this technology, any video can be reproduced at different resolution levels (144p, 240p, 360p, 480p, 720p, . . . ), called video representations. 144p means that the video frame has 144 lines and 244p means that each video frame has 244 lines per video frame. For the same client, higher resolution level implies better video quality reproduction so both terms (video resolution and video quality reproduction) are connected. In the following the terms video quality, video resolution, resolution of a video stream, and resolution used in a video stream are used interchangeably.

The client can decide the resolution of the video reproduction, based on client properties and network conditions.FIG.2shows an example of a web server20in which a video is stored with different possible resolutions. Moreover, while video is under reproduction on a client30, the client can change the video quality on the fly, pursuing adaptation to bandwidth fluctuations as shown by the different gray scales of the transmitted video stream.

Each video stream is fragmented into small chunks called video segments. When a client is requesting more video payload from the server one video segment is the minimum video payload that has to be downloaded. The video stream has several video frames per second and a video segment comprises video content for several seconds.

With higher resolution, the client increases the video perception so this means that the QoE is improved. QoE, according to Wikipedia is the degree of delight or annoyance of the user of an application or service. QoE has historically emerged from QoS), which attempts to objectively measure service parameters QoS measurement is most of the time not related to a customer, but to the media or network itself.

Hybrid Access technology is the way network operators offer the combined usage of fixed broadband and 3GPP access networks. InTR-348Hybrid Access Broadband Network Architecturethe architectural requirements to allow coordinated and, when needed, simultaneous use of fixed broadband access and 3GPP access networks for converged operators is specified, enabling further Fixed-Mobile Convergence (FMC) use cases.

As it is explained inTR-348Hybrid Access Broadband Network Architecture, there are several solutions that may be used to transport traffic between a HCPE (Hybrid Customer Premises Equipment) and HAG (Hybrid Access Gateway) in Hybrid Access broadband networks. The main objective is faster service turn-up for new subscribers, increased access reliability and enabling higher throughput for subscribers.

There are different options to transport traffic between the HCPE and HAG in Hybrid Access broadband networks, one of them being the L4 Multipath. The connectivity between the HCPE and the HAG is established using a Layer 4 multipath transport service, enabling L4 (layer4) flows to use multiple paths in the Hybrid Access path group simultaneously. As an example, a L4 multipath implementation using MPTCP sets up multiple TCP sub-flows over the different access networks and utilizes real time HCPE to HAG flow control. The HCPE and HAG are responsible for managing the MPTCP (Multipath TCP) paths, including establishment and tear down.

FIG.3describes how this process works. In a first step S31the capabilities of the involved entities are exchanged. In step S32the hybrid access Gateway is informed of the capabilities such as deep packet inspection (DPI) and multipath. In step S33the policy server generates the connections to the customer premises equipment (CPE) and in step S34the connections are established between the policy server and the hybrid access Gateway. In step35the DSL leg is established between the hybrid access Gateway, HAG, and the customer premises equipment.

The implementation itself is access network agnostic, therefore no changes at either the fixed broadband or the 3GPP access networks are necessary.

The HCPE and HAG terminate the end user layer 4 sessions before transporting the data over the Hybrid Access paths, effectively executing a proxy function for the end user sessions.

There are several steering policies proposed:Route all user traffic through one leg (e.g. Fixed) and only when overload route it through the other leg/s (e.g. 3GPP access)Route the traffic for one service (e.g. Netflix) through one leg (e.g. Fixed) and only when overload route it through the other leg/s (e.g. 3GPP access)Route all user traffic through all legs (carrier aggregation Use Case, i.e. to increase the bandwidth)Route the traffic for one service (e.g. Netflix) through all legs (carrier aggregation Use Case, i.e. to increase the bandwidth)Block the traffic for one leg (e.g. to prioritize the other leg/s)Throttle (bandwidth limitation) the traffic for one leg (e.g. to prioritize the other leg/s)Select the best leg based on link behavior and characteristics (e.g. RTT, Packet loss).

In the multipath environment policies are applied taking into account how much congestion exists in each of the path or a priority of each path, e.g. which is the cheaper path for the user.

In the above discussed hybrid scenario it is furthermore possible that the path is opened as soon as it is available. This can mean that both paths, the DSL and LTE path are opened at the beginning. However there may exist scenarios where both paths are not needed at the same time for transmitting a video to a user.

Accordingly a need exists to improve the selection of a path in a multipath environment for transmitting encrypted video streams.

SUMMARY

This need is met by the features of the independent claims. In the dependent claims further embodiments are disclosed.

According to a first aspect a method for controlling at least one path in a multipath environment is provided by a path control entity, wherein the at least one path is used for transmitting an encrypted video stream comprising a sequence of video segments. According to one step, a resolution used in the video stream is estimated based on the video segments. Furthermore, it is determined that the resolution used in the video stream has changed during the transmission. When it is determined that the resolution used in the video stream has changed, an adaptation of a number of the at least one path used for transmitting the video stream in the multipath configuration is initiated based on the determined change of the resolution.

In an encrypted video the resolution of the media stream can be estimated based on the video segments of the media stream, e.g. based on the size of the video segments. When the resolution changes, this can mean that the resolution is increased or that the resolution is decreased. When the resolution decreases it can mean that the Quality of experience for the user also decreases. In order to guarantee the same quality at the user, it may be necessary to open a further path in the multipath environment to be able to provide the same amount of data to the end user so that the quality of experience remains substantially the same. When the resolution increases it may be deduced that one of the path in the multipath environment may not be needed any more. With the invention it is possible to react to a change of the resolution by adapting the at least one path that is used for transmitting a video stream in the multipath environment.

Preferably the size of the reduce segments is determined and the change of the size can initiate the adaptation of the transmission path in the multipath environment. Initiating the change of the at least one path can mean that a further path is opened or one of the existing path is closed or can mean that another entity such as a policy controller is contacted in order to indicate that the at least one path should be adapted.

Furthermore the corresponding path control entity configured to control the at least one path in the multipath environment is provided. The path control entity comprises a memory and at least one processing unit, wherein the memory contains instructions executable by the at least one processing unit. The path control unit is operative to estimate a resolution used in the media stream based on the video segments. Furthermore the path adapting entity is operative to determine that the resolution used in the media stream has changed during the transmission and when the path adapting entity determines that the resolution used in the encrypted video stream has changed an adaptation of the number of the at least one path used for transmitting the video in the multipath configuration is initiated based on the determined change of the resolution.

Furthermore our a computer program comprising programme code to be executed by the at least one processing unit of the path control entity is provided wherein execution of the program code causes the at least one processing unit to execute a method as discussed above or as discussed in more detail below.

Additionally a carrier comprising the computer program is provided wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

Alternatively a path control entity is provided configured to control the at least one path in the multipath environment wherein the path control entity comprises a first module configured to estimate the resolution used individual stream based on the video segments. The path control entity can furthermore comprise a second module configured to determine that the resolution individual stream is changed during the transmission and configured to initiate an adaptation of the number of the least one path used for the transmission when it is determined that the resolution used in the media stream has changed.

It is to be understood that the features mentioned above and features yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the present invention. Features of the above-mentioned aspects and embodiments may be combined with each other in other embodiments unless explicitly mentioned otherwise.

