Methods, User Node and Network Node in an MBMS Network

A method in a user node for reducing signalling load in a multimedia broadcast multicast services, MBMS, network, the method comprising: receiving (301) from a network node a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service; initiating (302) a connection establishment procedure, the connection establishment procedure including one or more connection establishment messages sent between the user node and the network node to set up a connection; and during the connection establishment procedure, transmitting (303) an information to the network node in one of the one or more connection establishment messages indicating that the current frequency is a frequency of interest for the user node.

TECHNICAL FIELD

The disclosure relates to multimedia broadcast multicast service networks and, more specifically, it relates to a user node and a network node allowing for a reduction of signalling load in multimedia broadcast multicast service networks as well as methods for such reduction.

BACKGROUND

Multimedia Broadcast Multicast Services (MBMS) is a point-to-multipoint interface specification for existing and upcoming 3GPP cellular networks which is designed to provide efficient delivery of broadcast and multicast services, both within a cell as well as within the core network, such as e.g. Wideband Code Division Multiplex (W-CDMA), Enhanced Data Rates for Global System Global System for Mobile Communication (GSM) Evolution (EDGE), General Packet Radio Service (GPRS), Code Division Multiple Access 2000 (CDMA2000). Evolved Multimedia Broadcast Multicast Services (eMBMS) is a corresponding specification adapted for Evolved Packet Systems, including (Evolved Universal Terrestrial Radio Access Network) (E-UTRAN) or Long Term Evolution System Architecture Evolution (LTE-SAE).

For example, on the E-UTRAN-UE (Uu) interface, the MBMS Single Frequency Network (MBSFN) transmission mode applies. This is characterized by synchronous transmission of the same signal from all cells within the MBSFN area, which enables the user equipments (UEs) to combine eMBMS transmission from multiple cells. Transmitting the same data to multiple recipients allows network resources to be shared.

One typical use case for use of any of the specifications mentioned above may be to deliver sport game video content to a large number of mobile phone users which are gathered in a sports stadium or any other location which is attracting a lot of people at the same time. MBMS or eMBMS can use the User Datagram Protocol/protocol via File delivery over Unidirectional Transport (UDP/FLUTE), HLS or DASH as a Download Delivery Method to deliver live TV content to the UEs. Also popular files, such as e.g. Android updates, YouTube clip pre-loadings, or major news events may efficiently be distributed to a large number of recipients in this way.

When broadcasting eMBMS (LTE broadcast) on one or multiple carriers in a deployment scenario with overlapping carriers the following requirements has been defined in 3GPP:

1) Network related behaviour: Support mobility procedures such that interested UE is moved to correct frequency to start MBMS service reception kept on the correct frequency to start/continue MBMS service reception service layer and network provide the UE with reception.

2) UE related behaviour: UE in IDLE mode can perform autonomous frequency prioritization. UE in CONNECTED mode informs the network about its interest (MBMS frequency) in a MBMS Interest Indication message.

As described above, the UE needs to send its MBMS interest for two reasons:

1) The UE is in CONNECTED mode and wants to acquire a MBMS service on another frequency;

2) The UE is currently camping on the MBMS frequency of interest and changed its state from IDLE mode to CONNECTED mode after having performed an RRC connection establishment procedure.

It should be noted that the UE has to send the RRC MBMS INTEREST INDICATION message after each RRC establishment since the eNB needs to be informed about the UEs MBMS interest. Without this knowledge, the eNB might perform a load-balancing action on the UE and the MBMS service would be interrupted.

All UEs that are interested in an MBMS service need to send an extra RRC MBMS INTEREST INDICATION after each RRC establishment. This causes a lot of signalling overhead. Further, every control plane signalling increases the risk of losing the connection between the UE and the network

SUMMARY

It is therefore an object of embodiments herein to provide a way of decreasing the signalling overhead in MBMS multi carrier deployment scenarios. According to some embodiments, methods in network nodes and/or user nodes are provided for reducing signalling load in a multimedia broadcast multicast services, MBMS, network.

According to a first aspect of embodiments herein, the object is achieved by a method in a user node, which receives from a network node a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service. The user node initiates a connection establishment procedure, the connection establishment procedure including one or more connection establishment messages sent between the user node and the network node to set up a connection. During the connection establishment procedure, the user node transmits an information to the network node in one of the one or more connection establishment messages indicating that the current frequency is a frequency of interest for the user node.

According to a second aspect of embodiments herein, the object is achieved by a method in a network node, which broadcasts to one or more user node(s) a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service. The network node further establishes a connection procedure with a user node, the connection establishment procedure including one or more connection establishment messages sent between the user node and the network node to set up a connection. During the connection establishment procedure, the network node receives an information from the user node in one of the one or more connection establishment messages indicating that the current frequency is a frequency of interest for the user node.

According to a third aspect of embodiments herein, the object is achieved by a user node, which includes a receiver adapted to receive from a network node a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service. The user node further includes a processing unit adapted to initiate a connection establishment procedure, the connection establishment procedure including one or more connection establishment messages sent between the user node and the network node to set up a connection. A transmitter in the user node is adapted, during the connection establishment procedure, to transmit an information to the network node in one of the one or more connection establishment messages indicating that the current frequency is a frequency of interest for the user node.

According to a fourth aspect of embodiments herein, the object is achieved by a network node, which includes a transmitter adapted to broadcast to one or more user node(s) a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service. The network node further includes a processing unit adapted to establish a connection procedure with a user node, the connection establishment procedure including one or more connection establishment messages sent between the user node and the network node to set up a connection. The network node also includes a receiver adapted, during the connection establishment procedure, to receive an information from the user node in one of the one or more connection establishment messages indicating that the current frequency is a frequency of interest for the user node.

Thanks to the provision of a specific information element (IE) or information bit in the RRC establishment procedure indicating that a current frequency is a frequency of MBMS interest, the RRC signalling load in MBMS multi carrier deployment scenarios is significantly reduced. This will also lead to fewer dropped UEs and saved battery consumption in the UE. Although the example described and discussed herein mainly concerns overlapping carriers in a multi carrier scenario, embodiments of the present invention could also be used in a single carrier scenario.

DETAILED DESCRIPTION

FIG. 1depicts a wireless radio network in which embodiments herein may be implemented. The wireless radio network is a wireless communication network such as a LTE network. The wireless communication network includes a Radio Access Network (RAN), such as E-UTRAN. The RAN comprises at least one network node, such as a Radio Base Station (RBS), which in the LTE system is called eNode B (eNB)15a,15band15c. The eNBs are connected over an interface such as the S1-interface17to at least one server gateway and mobility management entity node (S-GW/MME)10aand10b. The S-GW/MME node handles control signalling for instance for mobility, and is connected to external networks (not shown inFIG. 1) such as the Public Switched Telephone Network (PSTN) or the Integrated Services Digital Network (ISDN), and/or a connectionless external network as the Internet.

The RAN provides communication and control for a plurality of user nodes or user equipments (UE)18(only one shown inFIG. 1) and each eNB15a-15cis serving at least one cell19through and in which the UEs18are moving. The eNBs15a-15care communicating with each other over a communication interface16, such as X2. The UEs each uses downlink (DL) channels12and uplink (UL) channels13to communicate with at least one eNB over a radio or air interface.

According to one embodiment of the present invention, the communication system is herein described as a LTE system. The skilled person, however, realizes that the inventive method and arrangement work very well on other communications systems as well, such as GSM and WCDMA. The user equipments may be mobile stations such as mobile telephones (“cellular” telephones), tablets, and laptops with mobile termination and thus can be, for example, portable, pocket, hand-held, computer-included or car-mounted mobile devices which communicate voice and/or data with the RAN. The user equipment may also be a telemetry node, or any type of node communicating in a radio network system.

The wireless communication network covers a geographical area which is divided into cell areas19, wherein each cell area being served by a base station15, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, Base Transceiver Station (BTS), or AP (Access Point), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro NodeB, home NodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.

As stated above in the background section, Multimedia Broadcast Multicast Services (MBMS) is a point-to-multipoint interface specification for existing and upcoming 3GPP cellular networks which is designed to provide efficient delivery of broadcast and multicast services, such as to deliver sport game video content to a large number of mobile phone users or to deliver live TV contents etc.

3GPP has requested the following functionality for MBMS:

1) When entering RRC Connected Mode, the UE indicates the MBMS Interest by sending the RRC MBMS INTEREST INDICATION message

2) The eNB shall support the MBMS Service Acquisition by notifying all UEs about the availability of specific MBMS service areas per carrier in a system information block (SIB), such as SIB15;

3) the eNB shall react upon the UE's indicated MBMS Service preferences by means of Inter-Frequency HO.; and

4) This eNB shall also ensure MBMS Service continuity by preventing Inter-Frequency HO due to Load balancing.

The MBMSInterestIndication message is used to inform E-UTRAN that the UE is receiving/interested to receive or no longer receiving/interested to receive MBMS via an MRB.

RLC-SAP: AM

MBMSInterestIndication field descriptionsmbms-FreqListList of MBMS frequencies which the UE is receiving or interested toreceive.mbms-PriorityIndicates whether the UE prioritises MBMS reception above unicastreception. The field is present (i.e. value true), if the UE prioritisesreception of all listed MBMS frequencies above reception of any of theunicast bearers. Otherwise the field is absent.

The MBMS assistance information is a combination of service layer information and information from the RAN. The user service description (USD) in the service layer provides information about availability of the MBMS service which is identified by a temporary mobile group identity (TMGI).

FIG. 2shows an example of a USD20for a specific TMGI, which in this example is TMGI120. As can be seen inFIG. 2, the USD20includes MBMS service area identities (SAIs), MBMS frequency, and session start and end time.

A system information block (SIB), which is a new SIB called herein SIB15is broadcasted by the RAN. In SIB15, all cells provide MBMS SAIs for the current frequency and also for neighboring frequencies where MBMS is provided.

Thus, based on the USD and SIB15, the UE knows when its MBMS service is provided and on which frequency.

When the UE is in IDLE state it has the possibility to change frequency itself. When the UE is interested in a MBMS service, such as a live TV event, and changes its state from IDLE mode to CONNECTED mode (to for example look for any new e-mails) it necessarily needs to inform the eNB about its interest in the frequency it currently is camping on. Without this knowledge, the eNB might perform a load-balancing action and interrupt the service. The UE thereafter initiates a connection establishment procedure. As discussed above in the background section, according to prior art the UE needs to send a separate RRC MBMS Interest Indication message after each RRC connection establishment procedure. According to embodiments of the present invention, the RRC establishment procedure is enhanced with a new one-bit information or a new information element, e.g. the MBMSInterestIndication-r11-IEs, that gives the UE the possibility to indicate that the current frequency on which the UE is camping, is a frequency of MBMS interest. That is, the new one-bit information or the new information element is sent on an already sent message during the connection establishment procedure. Thus, the RRC signaling load in MBMS scenarios will be reduced, since no separate RRC MBMS Interest Indication message is sent.

Example embodiments of the user node18for reducing a signalling load in a MBMS network, will now be described with reference to a flowchart depicted inFIG. 3.

The method comprises the following actions, which actions may be taken in any suitable order.

The user node18receives from a network node15a broadcasted system information block, such as SIB15, with information about at least one MBMS service including a service area identifier supported by a current frequency for said service.

For example, in the system information block, all cells provide MBMS SAIs for the current frequency and also for neighboring frequencies where the MBMS service is provided.

According to some embodiments, the system information block is a system information block called SIB15.

The user node initiates a connection establishment procedure, the connection establishment procedure including one or more connection establishment messages sent between the user node18and the network node15to set up a connection.

For example, the user node18is in IDLE mode and wants to change its state to CONNECTED mode to be able to check for new e-mails or the like.

During the connection establishment procedure, the user node transmits an information to the network node15in one of the one or more connection establishment messages502;504;510(shown inFIG. 5) indicating that the current frequency is a frequency of interest for the user node18.

According to some embodiments, the one or more connection establishment messages is one of the following as shown inFIG. 5: a RRC Connection Request message502; a RRC Connection Setup Complete message504; or a RRC Connection Reconfiguration Complete message510.

According to some embodiments, the information is a one bit information.

According to some embodiments, the information is an information element (IE).

Optionally, the user node18also receives the MBMS service of interest.

Example embodiments of the network node15for reducing a signalling load in a MBMS network, will now be described with reference to a flowchart depicted inFIG. 4.

The method comprises the following actions, which actions may be taken in any suitable order.

The network node15, broadcasts to one or more user nodes18system information block with information about at least one MBMS service including a service area identifier supported by a current frequency for said service.

For example, in the system information block, all cells provide MBMS SAIs for the current frequency and also for neighboring frequencies where the MBMS service is provided.

According to some embodiments, the system information block is a system information block called SIB15.

The network node establishes a connection procedure with a user node18, the connection establishment procedure including one or more connection establishment messages sent between the user node18and the network node15to set up a connection.

For example, the user node initiates the connection establishment procedure when it is in IDLE mode and wants to change its state to CONNECTED mode to be able to check for new e-mails or the like.

During the connection establishment procedure, the network node receives an information from the user node18in one of the one or more connection establishment messages502;504;510(shown inFIG. 5) indicating that the current frequency is a frequency of interest for the user node18. Thus, the network node has the knowledge that this particular user node is interested in this specific frequency and will not perform a load balancing action and move the user node to a different frequency.

According to some embodiments, the one or more connection establishment messages is one of the following as shown inFIG. 5: a RRC Connection Request message502; a RRC Connection Setup Complete message504; or a RRC Connection Reconfiguration Complete message510.

According to some embodiments, the information is a one bit information.

According to some embodiments, the information is an information element (IE).

Optionally, the network node15transmits the MBMS service to the user node18.

FIG. 5is a signalling diagram showing an exemplary signalling between the user node, such as the UE18, and the network node, such as an eNB15. The exemplary signalling diagram shows a connection establishment procedure according to embodiments of the present invention. A connection establishment procedure between a UE18and an eNB15is, however, not limited to the signalling as shown inFIG. 5but may have more signalling which has been omitted from the shown diagram.

In501, the eNB15, broadcasts to one or more UEs18system information block with information about at least one MBMS service including a service area identifier supported by a current frequency for said service. This is broadcasted on SIB15as discussed above.

The UE18initiates the connection establishment procedure by sending a RRC Connection Request message502to the eNB15. Optionally, an information indicating that the current frequency is a frequency of interest for the UE18is sent with this message502as a one-bit information to the eNB15.

The eNB15sends a RRC Connection Setup message502back to the UE18, whereby the UE18send a RRC Connection Setup Complete message504. Optionally, the information indicating that the current frequency is a frequency of interest for the UE18is sent with this message504as a one-bit information or an information element to the eNB15.

The eNB sends an Initial UE message505to the MME10and receives an Initial Context Setup message506back from the MME10, which for example informs the eNB about the UE capabilities.

The eNB15sends a Security mode Command message507to the UE18and receives a Security mode Command Complete message508back.

Thereafter, the eNB15sends a RRC Reconfiguration Request message509to the UE18. The UE18sends a RRC Reconfiguration Complete message510to the eNB18and, optionally, includes the information indicating that the current frequency is a frequency of interest for the UE18in this message510as a one-bit information or an information element.

Finally, the eNB15sends an Initial Context Setup Complete message511to the MME10when the connection establishment procedure is terminated.

FIG. 6is a block diagram showing a user node, such as a user equipment18, and a network node15, such as eNB. The shown network node and user node being used for reducing signalling load in a multimedia broadcast multicast services, MBMS, network.

The network node15comprises a radio transmitter62and a receiver61. The network node further includes a processing unit63. The transmitter62is adapted to broadcast to one or more user node(s)18a system information block with information about at least one MBMS service supported by a current frequency for said service. The processing unit63is adapted to establish a connection procedure with a user node18, the connection establishment procedure including one or more connection establishment messages sent between the user node18and the network node15to set up a connection. The receiver61is adapted, during the connection establishment procedure, to receive an information from the user node18in one of the one or more connection establishment messages502;504;510(shown inFIG. 5) indicating that the current frequency is a frequency of interest for the user node18.

The user node18comprises a radio transmitter66and a receiver67. The user node18further includes a processing unit68. The receiver67is adapted to receive from a network node15a broadcasted system information block with information about at least one MBMS service supported by a current frequency for said service. The processing unit68is adapted to initiate a connection establishment procedure, the connection establishment procedure including one or more connection establishment messages sent between the user node18and the network node15to set up a connection. The transmitter66is adapted, during the connection establishment procedure, to transmit an information to the network node15in one of the one or more connection establishment messages502;504;510(shown inFIG. 5) indicating that the current frequency is a frequency of interest for the user node18.

It will be appreciated that at least some of the procedures described above are carried out repetitively as necessary to respond to the time-varying characteristics of the channel between the transmitter and the receiver. To facilitate understanding, many aspects of the invention are described in terms of sequences of actions to be performed by, for example, elements of a programmable computer system. It will be recognized that the various actions could be performed by specialized circuits (e.g. discrete logic gates interconnected to perform a specialized function or application-specific integrated circuits), by program instructions executed by one or more processors, or a combination of both.

Moreover, the invention can additionally be considered to be embodied entirely within any form of computer-readable storage medium having stored therein an appropriate set of instructions for use by or in connection with an instruction-execution system, apparatus or device, such as computer-based system, processor-containing system, or other system that can fetch instructions from a medium and execute the instructions. As used here, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction-execution system, apparatus or device. The computer-readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium include an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read only memory (ROM), an erasable programmable read only memory (EPROM or Flash memory), an optical fibre, and a portable compact disc read only memory (CD-ROM).

When using the words “comprise”, “comprising”, “including” or “includes” they shall be interpreted as non-limiting, i.e. meaning “consist at least of”.