The present invention relates to optimised transmission of one media stream in a plurality of cells served by the same base station device, the media stream transported from a radio network controller over an Iub interface to the base station device and comprising multimedia data, e.g. within an MBMS (Multimedia Broadcast/Multicast Service) of the 3GPP (Third Generation Partnership Project).
The 3GPP-standard relates to technology based on radio access networks such as the UTRAN (the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network), which is a radio access network architecture providing W-CDMA (Wideband Coding Division Multiple Access) to mobile terminals. Telecommunication systems according to the 3GPP-standard offer higher transmission bitrates, high service flexibility and multiple simultaneous connections to mobile terminals, and are capable of providing new types of services to the users. The MBMS included in the 3GPP-standard provides broadcasting/multicasting of various multimedia information to users, enabling information providers to transmit multimedia information, such as real-time audio and video, still images and text, e.g. news, sport results and weather forecasts, to several joined MBMS subscribers simultaneously.
In a telecommunication system according to the 3GPP-standard, a UE, i.e. a mobile terminal such as e.g. a cellular telephone provided with a SIM (Subscriber Identity Module)-card, communicates with a core network connected to external networks, e.g. the Internet and the PSTN (the Public Switched Telephone Network), via a UTRAN covering a geographical area divided into cells with unique identities. Each cell is served by a base station device, which in the 3GPP is referred to as a Node B, and radio coverage of a cell is provided by a base transceiver station at the serving base station (i.e. Node B) site over an Uu-interface. One Node B is normally serving more than one cell, and the Node Bs are controlled by RNCs (Radio Network Controllers), which are managing the transmission resources of the UTRAN. The Node Bs are communicating with the RNCs over an Iub-interface, the RNCs are communicating with the core network over an Iu-interface, and the communication between RNCs is performed over an Iur-interface.
In an MBMS according to 3GPP, multimedia information may be transmitted in a broadcasting mode or in a multicasting mode. In the broadcasting mode, the same media stream is broadcasted simultaneously to several users, without taking into account whether any terminal is actually receiving the media stream. In the multicasting mode, two different transmission schemes may be used, either the point-to-point (PTP) scheme, in which data is delivered to each user individually, using a dedicated traffic channel, or the PTM scheme, in which the same media stream is broadcasted on a common channel, which is received simultaneously by a plurality of selected mobile terminals. In the PTM mode, duplication of the same content on different radio bearers is avoided and transmission resources are saved, while in the PTP mode, the transmission power overhead required for transmission on a common channel is avoided.
A network architecture for providing an MBMS to several mobile terminal users, which have joined the MBMS and are located in cells served by a common Node B, comprises a BM-SC (Broadcast/Multicast-Service Center) as a source for scheduling the MBMS streams for delivery to a Serving GPRS Support Node (SGSN) using suitable transmitting means, the SGSN being configured with a Gateway GPRS Support Node (GGSN). A radio network controller, RNC, supervising the Node B receives the MBMS stream from the SGSN for transmission to the Node B over an Iub interface, and the base transceiver stations of a Node B forwards the MBMS stream over an air interface to the MBMS-joined mobile terminals located in the cells served by the Node B.
In multimedia services within MBMS of the 3GPP, MBMS Cell Groups (MBMS CGs) can be defined regarding the PTM transmission of MBMS data. An MBMS Cell Group comprises a group of cells sharing the same PDCP (Packet Data Convergence Protocol) and RLC (Radio Link Control) within an RNS (Radio Network Subsystem), and is identified by an MBMS Cell Group Identifier (MBMS CG-Id). By means of the MBMS CG-Id, all cells of the MBMS Cell Group are able to receive MBMS data transmitted according the PTM scheme. The scheduling of the MBMS data transport is performed by an MAC-layer (Media Access Control-layer) of the UMTS, and more specifically by means of the MAC-m functionality located in the MAC c/sh (common/shared). Identical MBMS data blocks transmitted over the air interface to mobile terminals located in different cells may be scheduled according to a tight scheduling scheme, i.e. scheduled to be transmitted within a limited and relatively small time period. Thereby, a mobile terminal that receives an identical data block transmitted in more than one cell will be able to use advanced combining techniques to compensate for the power loss of the radio signal during transmission. However, tight scheduling is not always possible for all the cells of an MBMS Cell Group, e.g. due to cell congestion status and scheduling limitations etc. The cells within an MBMS Cell Group that can be scheduled according to a tight scheduling scheme are hereinafter defined as a Cell Group Subset, and when an MBMS Cell Group is composed of several Cell Group Subsets, MAC-m buffering may be required. Scheduling according to a tight scheduling scheme of identical MBMS data blocks to be transmitted approximately simultaneously in cells belonging to the same Cell Group Subset is hereinafter defined as common scheduling.
In the prior art, identical MBMS data blocks to be transmitted in cells belonging to the same Cell Group Subset and within a limited, small time period, such as 1 TTI (Transmission Time Interval), are copied in the RNC into one separate FACH data frame (Forward Access Channel data frame) for each cell served by the Node B. The RNC sends each separate FACH data frame over the Iub interface, resulting in the transmission of several identical MBMS data blocks over the Iub interface to the same Node B, i.e. a “parallel” Iub transport. After receiving the FACH data frame for each cell, the Node B will create a separate MBMS data stream for each cell and transmit on a forward access channel (FACH) for reception by MBMS-joined mobile terminals located in the cells. The transmission over the Iub interface between the RNC and the Node Bs is performed according to the PTP mode, i.e. the multimedia service data is transmitted individually between the RNC and the Node Bs, which leads to a transmission of identical multimedia content in a plurality of data frames over the Iub interface, and to an inefficient use of transport resources.
Thus, the prior art involves several drawbacks, such as e.g. an inefficient use of available Iub transport resources and a relative offset between the cells in the timing to the TTIs in the transmission of identical multimedia service data streams from a radio network controller into a plurality of cells served by the same base station device and scheduled according to a tight scheduling scheme.
It is an object of the present invention to achieve an improved utilization of available Iub transport resources and a small relative offset between the cells in the timing to the TTIs, providing an improved transmission of identical multimedia service streams approximately simultaneously from a radio network controller over the Iub interface to mobile terminals located in a plurality of cells served by the same base station device, facilitating use of advanced combining techniques, such as e.g. soft-combining. More specifically, an object of the invention is to provide an optimised transmission of identical MBMS data blocks of the 3GPP approximately simultaneously from a radio network controller (RNC) over the Iub interface to a plurality of cells of a Cell Group Subset served by the same Node B.
These and other objects are achieved by the method in a radio network controller, by the corresponding method in a base station device, by the radio network controller and by the base station device according to the attached claims. The independent claim of a method in a radio network controller relates to a method performed in a transmitting node in a common Iub transport and the independent claim of a method in a base station device relates to a method performed in the corresponding receiving node in said common Iub transport. The independent claim of a radio network controller relates to a transmitting node in a common Iub transport and the independent claim of a base station device relates to the corresponding receiving node in a common Iub transport.
The claims relate to a method in a radio network controller (RNC) within a radio access network for transmitting common multimedia service data blocks over an Iub interface between the radio network controller and a base station device serving a plurality of cells in which multimedia service joined mobile terminals are located. A common Iub transport is transmitting said common multimedia service data blocks, comprising the steps of storing the common multimedia data blocks in one single data frame, and transmitting said single data frame over the Iub interface to the base station device, which is configured to duplicate said common multimedia data blocks into separate multimedia service data streams for each of said plurality of cells.
The claims also relates to a method in a base station device within a radio access network for transmitting common multimedia service data blocks received over an Iub interface from a radio network controller (RNC), said base station device serving a plurality of cells in which multimedia service joined mobile terminals are located. A common Iub transport is transmitting said common multimedia data blocks, comprising the steps of receiving a single data frame from the radio network controller, the data frame comprising said common multimedia data blocks, storing said common multimedia data block, and duplicating said common multimedia data blocks into separate multimedia service data streams for transmission in each of said plurality of cells.
The claims further relates to a radio network controller (RNC) in a radio access network, arranged to communicate over an Iub interface with a base station device serving a plurality of cells. The radio network controller comprises means for transmitting common multimedia service data blocks to multimedia service joined mobile terminals located in said cells, said means adapting said common multimedia service data blocks into one single data frame and transporting said single data frame over the Iub interface to a base station device for duplication and transmission in each of said cells.
The claims also relates to a base station device serving a plurality of cells in a radio access network, and arranged to communicate over an Iub interface with a radio network controller (RNC). The base station device comprises means for receiving multimedia service data blocks from said radio network controller and for transmitting a multimedia service data stream to multimedia service joined mobile terminals located in said cells. Said means are arranged to receive a single data frame comprising common multimedia service blocks transferred over the Iub interface and to create separate multimedia service data streams comprising said common multimedia service blocks for transmission in each of said cells.
The transmission of said common multimedia service blocks may be scheduled according to common scheduling.
Said single data frame transporting said common multimedia service data blocks over the Iub interface may be a multimedia service data frame, which is transmitted over the Iub interface in connection with a non-multimedia service FACH data frame provided with an indicator for said multimedia service data frame.
Alternatively, said single data frame transporting said common multimedia service data blocks over the Iub interface may be an extended FACH data frame.
Said radio access network may be a UTRAN (Universal Mobile Telecommunications Terrestrial Radio Access Network), said multimedia service may be a Multimedia Broadcasting/Multicasting Service (MBMS) according to the 3GPP standard and said base station device may be a Node B of the 3GPP.
Other features and further advantages of the invention will be apparent from the following description and figures, as well as from the attached claims.
The present invention will now be described in more detail and with reference to the embodiments and to the drawings, of which:
The terms and expressions used in the description and in the claims are intended to have the meaning normally used by a person skilled in the art, and the following abbreviations will be used:
3GPP: Third Generation Partnership Protocol
UTRAN: UMTS Radio Access Network
UMTS: Universal Mobile Telecommunications
MBMS: Multimedia Broadcast/Multicast Service
RNC: Radio Network Controller
BTS: Base Transceiver Station
RRC: Radio Resource Control
RNS: Radio Network Subsystem
RLC: Radio Link Control
PDCP: Packet Data Convergence Protocol
CG: Cell Group
FACH: Forward Access Channel
SGSN: Serving GPRS Support Node
CFN: Connection Frame Number
RAN: Radio Access Network
URA: UTRAN Registration Area
PTP: Point To Point
PTM: Point To Multipoint
MCCH: MBMS Control Channel
MAC: Media Access Control
GPRS: General Packet Radio Service
PDU: Protocol Data Unit
In the prior art regarding transmission of identical MBMS data block in cells of a Cell Group Subset served by the same Node B, the transmission scheduled according to a tight scheduling scheme, i.e. transmission to be performed approximately simultaneously, the RNC copies and sends the MBMS data block over the Iub interface in one separate FACH data frame for each cell. Consequently, several identical MBMS data blocks will be transmitted in separate data frames within a small time interval to the same Node B over the Iub interface, i.e. “parallel” Iub transport of MBMS data blocks, which introduces a timing offset in the TTIs between the cells.
According to this invention, an improved Iub transport is achieved by a common transport over the Iub interface of identical MBMS data blocks to be transmitted within a relatively small time interval in a plurality of cells belonging to the same Cell Group Subset, served by the same Node B. The present solution involves a common Iub transport of a MBMS data block from an RNC to the Node B, in the case of tight scheduling of identical MBMS data in cells belonging to the same Cell Group Subset and served by the same Node B. Scheduling according to a tight scheduling scheme of identical MBMS data blocks to be transmitted approximately simultaneously in cells belonging to the same Cell Group Subset is hereinafter defined as common scheduling. The common MBMS data blocks are packed into one single data frame, which is transported over the Iub interface and received by the Node B. The Node B duplicates the common MBMS data blocks and creates a plurality of separate data streams, each comprising the common MBMS data blocks, for transmission on a forward access channel (FACH) in the cells of the Cell Group Subset in which MBMS-joined mobile terminals are located.
In the “parallel” Iub transport illustrated in
The common Iub transport procedure according to this invention may be implemented by means of two different schemes. In a first embodiment, the common Iub transport is implemented according to a scheme introducing an MBMS data frame to be transmitted over the Iub interface in connection with the transmission of a standard non-MBMS FACH data frame. In a second embodiment, the common Iub transport is implemented according to a scheme introducing an extended FACH data frame for transport of common MBMS data.
The first embodiment of the invention introduces an MBMS data frame for transmission of common MBMS data over the Iub interface between an RNC and a Node B, where the MBMS data is to be transmitted approximately simultaneously in more than one cell of a Cell Group Subset served by the Node B. A layout of an MBMS data frame according to the invention is illustrated in
A non-MBMS FACH data frame is transmitted in connection with the MBMS data frame according to this embodiment of the invention, i.e. the non-NBNS FACH data frame is transmitted approximately simultaneously with the MBMS data frame. A prior art FACH data frame structure, such as an R99bis-FACH data frame, is shown in
A layout of a non-MBMS FACH data frame according to this invention is illustrated in
When the Node B receives an MBMS data frame transmitted from the RNC over the Iub interface, it will store the payload therein, i.e. the MBMS data block, and check the header information for each cell. Thereafter, the Node B will create a FACH data stream, including the MBMS data blocks, for each cell in which the MBMS data shall be forwarded to MBMS joined mobile terminal. Potential additional headers and other data are added to the FACH data stream, which is transmitted on a FACH at the time indicated in the CFN field in the MBMS data frame. After transmitting FACH data streams, including the common MBMS data block, to all the cells indicated in the MBMS data frame, the Node B will delete the stored MBMS data blocks.
The second embodiment of the invention implements the common Iub transport from an RNC to a Node B by means of an updated, extended FACH data frame, and a layout of the extended FACH data frame according to this invention is illustrated in
When an extended FACH data frame transmitted over the Iub interface is received by the Node B, the Node B will create separate FACH data streams to be transmitted in each cell of the cells. The Node B will append the correct MAC-m to the corresponding MBMS data blocks and transmit these blocks and non-MBMS data blocks simultaneously by transmitting individual FACH data streams in each cell over an air interface, to be received by MBMS-joined mobile terminals located in the cells.
By employing the common Iub transport of identical MBMS data according to this invention a more efficient use of the Iub transporting resources and a “tighter” scheduling is accomplished if more than one cell served by one Node B shall receive identical and common MBMS data approximately simultaneously, thereby facilitating use of advanced combining techniques when a mobile terminal receives identical data blocks from more than one BTS, i.e. transmitted in more than one cell.
The invention has been described with reference to specific exemplary embodiments and figures only to illustrate the inventive concept, and the invention is not limited to the disclosed embodiments. Instead, the invention is intended to cover various modification within the scope of the appended claims.
Number | Date | Country | Kind |
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0401211-8 | May 2004 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE05/00573 | 4/20/2005 | WO | 3/5/2007 |