WO2009049665A1

WO2009049665A1 - Method and apparatus for use in a network

Info

Publication number: WO2009049665A1
Application number: PCT/EP2007/060978
Authority: WO
Inventors: Ákos KOVACS; István GODOR
Original assignee: Ericsson Hungary Ltd
Priority date: 2007-10-15
Filing date: 2007-10-15
Publication date: 2009-04-23

Abstract

A method is disclosed for use in a Multimedia Broadcast Multicast Service, MBMS, in which layered multimedia content is transmitted to a plurality of remote devices. A set of layers of the multimedia content to be transmitted is determined (C3) in dependence upon information received (C2) from at least some of the remote devices. Only the determined set of layers is caused to be transmitted (C4, B1, B3). The information may comprise a measure or indication of receiving capability for the multimedia content at the remote devices, for example such as a measure or indication of radio channel conditions at the remote devices.

Description

METHOD AND APPARATUS FOR USE IN A NETWORK

Technical field

The present invention relates to a method and apparatus for use in a network.

Background

Multimedia broadcast/multicast services have become widespread, even more so since mobile handheld devices have become capable of receiving multimedia content via radio networks.

However, delivering multimedia over a wireless channel to handheld devices is a highly non-trivial task. Subscribers may experience different channel quality while receiving the same content. In addition, each user wants the highest possible quality of delivered media.

Layered and scalable codecs have developed [H. Schwarz, D. Marpe, and T. Wiegand, "Combined Scalability Extension of H.264/AVC", submitted to ICIP'05] to enable the transport network to adapt the broadcast/multicast stream to changing network conditions. A layered media consists of a base and a number of enhancement layers each providing quality refinement for the ones below.

The introduction of the Multimedia Broadcast Multicast Service (MBMS) [3GPP- 23246-720-MBMS-architecture, 3GPP-22146-820-MBMS-stagel, 3GPP-25346-730-

MBMS-stage2] in the UTRA (UMTS Terrestrial Radio Access) provides techniques for optimized transmission of a MBMS bearer service such as point-to -multipoint transmission, selective combining and transmission mode selection between Point-to-

Multipoint (PTM) and Point-to -Point (PTP) bearer. MBMS logical transmission channels are defined and are mapped to physical ones. The basic logical channels are as follows: (a) MBMS point-to-multipoint Control Channel (MCCH): This logical channel is used for a PTM downlink transmission of control plane information between network and User Equipments (UE).

(b) MBMS point-to -multipoint Traffic Channel (MTCH): This logical channel is used for a PTM downlink transmission of user plane information between network and UEs.

(c) MBMS point-to-multipoint Scheduling Channel (MSCH): This logical channel is used for a PTM downlink transmission of MBMS service transmission schedule between network and UEs.

The MBMS multicast transmission optimizes the radio resources and is able to switch between PTM and PTP transmission. For example, PTP transmission in MBMS is used if PTM scheme would cost more due to the low number or low receiving capabilities of the subscribed User Equipments (UEs).

The decision about which transmission mode to be selected is based on MBMS UE Counting. The Radio Network Controller (RNC) keeps track of the UEs that are able to receive a given service. The RNC selects PTP or PTM transmission modes and decides about transmission parameters (e.g., Tx power, transport format, etc.,) based on the number of UEs interested in the given service and on the UE capabilities.

The MBMS standard describes a minimum UE capability requirement in order to allow operators to configure MBMS channels that can be common to all UEs supporting the given service.

Power control, in general, concerns controlling the transmitted power both in the downlink and the uplink direction, for different reasons. The main aim is to transmit the signal with lowest possible power level to maintain the required signal quality. The transmit power is adjusted to the level required to meet the requested QoS. Determining the transmitter power level is a very sophisticated task due to dynamic variation of the radio channel. Whatever the radio environment is, the received power should be at an acceptable level. The aim of power control is to adjust the power to a desired level without any unnecessary increase in the transmit power of the User Equipment (UE).

Power control is an essential feature of any Code Division Multiple Access (CDMA) based cellular system. The mobile stations continually change the level of the transmission power in order to avoid the domination of users closer to base station pushing out faraway users (e.g., their signals are hardly or even not intercepted by the base station). This phenomenon is called near-far affect.

The main factors causing the near-far problem comes from the path-loss variation of simultaneous users with different distances from the Base Station (BS), fading variation, and other signal-power variation of the users caused by the radio wave propagation.

Regarding the downlink direction, if a fixed transmission power was used by the transmitter BS, the receivers farther from the BS experience lower channel quality and capacity.

In WCDMA, power control is employed in both the uplink and the downlink. However, for streaming services, to reach an optimal per-user quality experience the downlink direction is in focus.

Summary

According to a first aspect of the present invention there is provided a method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising: determining a set of layers of the multimedia content to be transmitted in dependence upon information received from at least some of the remote devices; and causing only the determined set of layers to be transmitted. The information may comprise a measure or indication of receiving capability for the multimedia content at the remote devices.

The information may comprise a measure or indication of radio channel conditions at the remote devices.

The information may comprise an indication of which layers of the multimedia content the remote devices wish and/or are able to receive.

The information may comprise a user request.

The information may comprise a quality of service requirement.

The method may comprise determining the set of layers in dependence upon at least one property of the multimedia content, such as the number of layers within the multimedia content, and how each layer affects the overall perceived quality.

The multimedia content may be transmitted in dependence upon at least one transmission parameter, and comprising determining the at least one parameter separately for each of at least some of the layers being transmitted.

The multimedia content may be transmitted in dependence upon at least one transmission parameter, and comprising determining the at least one parameter separately for each of at least some radio frames being transmitted.

The at least one transmission parameter may comprise the transmission power to be used for the transmission.

The at least one transmission parameter may comprise the transport format to be used for the transmission. The at least one transmission parameter may comprise the coding to be used for the transmission.

The method may comprise providing to the remote devices scheduling information for each of the layers being transmitted.

The scheduling information may specify a temporal arrangement of the layers.

The method may comprise providing the scheduling information over a scheduling channel of the MBMS.

The scheduling channel may be the MBMS Scheduling Channel, MSCH.

The method may comprise providing information relating to a repetition period for the MSCH and a temporal offset from the MBMS Control Channel, MCCH, modification period using the MCCH.

The scheduling information may indicate the start of a layered service in each of a plurality of reception periods, and within each reception period a starting point for the transmission of each layer.

The method may comprise transmitting the multimedia content over a traffic channel of the MBMS.

The traffic channel may be the MBMS Traffic Channel, MTCH.

The method may comprise performing the steps at a Radio Network Controller, RNC.

The method may comprise performing the steps before setting up a Multimedia Broadcast Multicast Service session. The method may comprise performing the steps during a Multimedia Broadcast Multicast Service session.

According to a second aspect of the present invention there is provided a method for use by a device in a Multimedia Broadcast Multicast Service, MBMS, comprising sending information to a control node, the information being for use at the control node for determining a set of layers of a layered multimedia content to be transmitted to the device, and the information comprising at least one of: information relating to radio channel conditions at the device; at least one measure or indication of receiving capability for the multimedia content for the device; an indication concerning which layers of the multimedia content the device wishes and/or is able to receive; a user request; and a specified quality of service requirement.

The method may comprise sending the information using the Dedicated Control Channel, DCCH, of a UMTS Terrestrial Radio Access Network, UTRAN.

According to a third aspect of the present invention there is provided a method for use by a base station in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising receiving information from a control node specifying a set of layers of the multimedia content to be transmitted, and transmitting only the specified set of layers in dependence upon the received information.

The method may comprise receiving at least one parameter separately for each of at least some of the layers being transmitted, and transmitting the multimedia content in dependence upon at least one transmission parameter.

According to a fourth aspect of the present invention there is provided a method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising providing to the remote devices scheduling information for each of the layers being transmitted. According to a fifth aspect of the present invention there is provided a method for use in a Multimedia Broadcast Multicast Service, MBMS, for processing received layered multimedia content, comprising receiving scheduling information for each layer of the received multimedia content, and using the scheduling information to process the received multimedia content.

The method may comprise using the scheduling information to decode only selected ones of the received layers.

According to a sixth aspect of the present invention there is provided a method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising determining at least one transmission parameter separately for each of at least some of the layers being transmitted, the determination being made in dependence upon information received from at least some of the remote devices; and transmitting the multimedia content in dependence upon the at least one transmission parameter.

According to a seventh aspect of the present invention there is provided an apparatus for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising: means for determining a set of layers of the multimedia content to be transmitted in dependence upon information received from at least some of the remote devices; and means for causing only the determined set of layers to be transmitted.

According to an eighth aspect of the present invention there is provided an apparatus for use by a device in a Multimedia Broadcast Multicast Service, MBMS, comprising means for sending information to a control node, the information being for use at the control node for determining a set of layers of a layered multimedia content to be transmitted to the device, and the information comprising at least one of: information relating to radio channel conditions at the device; at least one measure or indication of receiving capability for the multimedia content for the device; an indication concerning which layers of the multimedia content the device wishes and/or is able to receive; a user request; and a specified quality of service requirement.

According to a ninth aspect of the present invention there is provided an apparatus for use in or as a base station in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for receiving information from a control node specifying a set of layers of the multimedia content to be transmitted, and means for transmitting only the specified set of layers in dependence upon the received information.

According to a tenth aspect of the present invention there is provided an apparatus for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for providing to the remote devices scheduling information for each of the layers being transmitted.

According to an eleventh aspect of the present invention there is provided an apparatus for use in a Multimedia Broadcast Multicast Service, MBMS, for processing received layered multimedia content, comprising means for receiving scheduling information for each layer of the received multimedia content, and means for using the scheduling information to process the received multimedia content.

According to a twelfth aspect of the present invention there is provided an apparatus for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for determining at least one transmission parameter separately for each of at least some of the layers being transmitted, the determination being made in dependence upon information received from at least some of the remote devices; and means for transmitting the multimedia content in dependence upon the at least one transmission parameter.

According to a thirteenth aspect of the present invention there is provided a program for controlling an apparatus to perform a method according to any of the first to sixth aspects of the present invention or which, when loaded into an apparatus, causes the apparatus to become an apparatus according to any of the seventh to twelfth aspects of the present invention. The program may be carried on a carrier medium. The carrier medium may be a storage medium. The carrier medium may be a transmission medium.

According to a fourteenth aspect of the present invention there is provided an apparatus programmed by a program according to the third aspect of the present invention.

According to a fifteenth aspect of the present invention there is provided a storage medium containing a program according to the third aspect of the present invention.

Brief description of the drawings

Figure 1 schematically illustrates a system model for optimized layered media transmission according to an embodiment of the present invention;

Figure 2 is a schematic illustration of the use of scheduling information in an embodiment of the present invention;

Figure 3 is a schematic flowchart for illustrating method steps performed in an embodiment of the present invention;

Figure 4 is a schematic block diagram illustrating apparatus embodying the present invention;

Figure 5 shows another representation of a UE embodying the present invention; and

Figure 6 shows another representation of a RNC and RBS embodying the present invention.

Detailed description As mentioned above, based on UE Capability information and Counting, as currently defined in MBMS, the RNC is able to switch between Point-to-Multipoint (PTM) and Point-to -Point (PTP) transmission types. The selection depends on which type of transmission costs less for the Radio Access Network (RAN).

Roughly, as a rule of thumb, if less than seven UEs are to receive a service, PTP transmission is used. Also PTP is applied if, although a number of receivers are counted for a selected service, their UE capabilities do not allow PTM transmission. The reason why the switching is necessary is that PTM transmission is worth using if several UEs are able to receive the service, so it is worth applying higher level of transmission power in the cells.

The transmission power (Tx power) and other transmission parameters (e.g., coding rate) have to be set to the worst-case cell-edge user. However, the applicant has appreciated that this dimensioning can be resource wasting since the transmission parameters cannot be adjusted to the actual channel quality of the receiving UEs. In other words, it is not possible to adjust the quality of the transmitted media stream according to the channel conditions of the receiving UEs.

That is, for example, higher quality media components would need to be transmitted only if there are UEs with sufficiently good channel conditions to receive it. If there are no such UEs, the given media component does not need to be transmitted, and instead the corresponding radio resources can be used for other purposes, e.g., for unicast traffic. Thereby a better utilization of radio resources can be achieved.

In the current MBMS solution, channel quality information cannot be taken into account when selecting MBMS transmission modes, the transmission parameters have to be set such that even the UE with the worst channel condition can receive the transmission.

Current PTM transmission scheme does not utilize any properties of the media and thereby they cannot optimize the quality of the media stream and the use of radio resources in accordance with the changing channel conditions of the UEs. An embodiment of the present invention proposes a method by which layered (or scalable) multimedia can be multicast in 3 G MBMS, thereby providing support for the adaptation of multimedia flows using the delivery technologies and access networks made available by 3 G MBMS. An aim is to improve the per-user perceived quality and at the same time utilize the radio interface resources efficiently by taking into account the radio channel conditions of the receiving UEs when deciding which components of the media stream to transmit and/or what transmission parameters to use (e.g., Tx power, coding, etc.,).

Use is made in an embodiment of present invention of the MBMS Scheduling Channel (MSCH), MBMS Control Channel (MCCH) and UE (User Equipment) channel quality reports for optimal and power-saving delivery of the corresponding layers of the media.

An optimization algorithm, for example deployed in the Radio Network Controller (RNC), computes the optimal set of transmitted layers based on some input information in order to reach the subscribed recipients. The input information consists of the particular properties of the media (there are existing solutions to signal such information, see for example Takacs, F. Kalleitner, "Multimedia Transport Optimization through Forward Information Signalling", PCT/EP2005/009387, WO 2007/025560, August 2005), the channel quality reports from the UEs and the users' own requests and capability for the required media stream and quality.

A system model for optimized Layered Media Transmission (LMT) according to an embodiment of the present invention is illustrated schematically in Figure 1.

A process embodying the present invention is summarized in the following steps; these steps will be described in further detail below:

1. The layer information on the media {Signalled Characteristics) to be transmitted is made available in the RNC. This information helps the RNC to identify the corresponding layers to be forwarded. 2. To enable the system for optimal layer transmission right from the start of the service session, the UEs may send initial channel quality measurement reports to the RNC. For such initial channel quality reports the MBMS counting can be used such that the counting mechanism should be extended to be able to carry the quality reports uplink to the RNC.

3. The 3 G RAN (RNC) network (periodically) collects information on channel quality of the UEs.

4. The RNC, based on the given inputs: (i) computes the set of layers that is optimal to be distributed according to the current UE capabilities and channel conditions (this can be a subset of the whole number of layers); and (ii) signals the Radio Base Station (RBS) the appropriate transmission parameters (e.g., coding parameters, Tx power) levels that should be applied for the layers in the selected set.

The receiving capability of the users depends, for example, on: (i) display constraints of the handheld devices; (ii) subscription limitations set by the service provider; and the optimization itself is based on the periodical channel quality measurement reports. The latter can be obtained by path loss measurements, similar to what the UE does during handover (e.g., Common Reference Signal Power Measurement) or optionally by utilizing power control information, if available. Also, the MBMS Counting procedure can be utilized to measure the initial channel conditions of the UEs before the MBMS service session starts.

The MBMS logical channels are involved in an embodiment of the present invention as follows:

• MBMS Traffic Channel (MTCH): This multicast logical channel transmits the set of layers selected by the optimization algorithm. • MBMS Scheduling Channel (MSCH): The scheduling (timing) information is transmitted through the MSCH channel. The UE may discontinuously and periodically receive data on MTCH based on scheduling information indicated by the MTCH scheduling information. The MSCH should therefore indicate the offset of the starting point of the transmission of a layer corresponds to a media service.

• MBMS Control Channel (MCCH): The MSCH repetition period and the offset from the MCCH modification period are indicated on the MCCH logical channel.

The optimized layer transmission is controlled by the MSCH. The MSCH indicates the start of the layered service in each reception period. Also, within each reception period the starting point of the transmission of each layer is indicated as well. The transmit power (Tx power) for each corresponding layer may be different according to current receiving capabilities of the UEs. The determination of the transmit power is the due of the optimization process. The appropriate level of the transmit power for each layer is signalled by the RNC to the Radio Base Station (RBS). Figure 2 illustrates how the MSCH channel hints to the receivers and the RBS on layered multicast information. A user capability update message is received during the other service's timeslot. This message indicates that in further transmission periods none of the users will need layer #3, and this explains why, in Figure 2, layer #3 is not indicated in the following layered transmission period.

Based on the above, the current specifications of the MSCH can be extended so that it is able to indicate the beginning of the transmitted layers within the service.

The reception method of UEs subscribed for a media service in an embodiment of the present invention is as follows: (1) A UE starts to listen to the MTCH at the given time instance that is indicated by the MCCH. The MCCH explicitly indicates the beginning of the transmission of the subscribed service.

(2) The UE receives all layers but decodes only certain of those according to its receiving capability. For example, suppose that there are five layers in the media, and two users are available for the service. The first reports that he can receive two layers and the second user also reports that he can receive two layers out of the three. However, the first user has a limitation because of his service subscription (through a Service Level Agreement or SLA with the content provider) that he can only receive a movie at a quality that is provided for by the first layer. In this case, the first user receives two layers but decodes only the first. It is possible that, due to channel capacity restrictions, only a (contiguous in decoding importance) subset of the media layers could be transmitted. The decodable data should contain neighbouring layers in the layered hierarchy of the media stream. The start position of each received layer is hinted by the MSCH logical channel. This information helps the receiver to identify the decodable sections in the data stream.

The system can benefit from the Layered Multicast Transmission (LMT) because Error Protection (EP) can be applied for more important parts of the media. For example, an important part can be the base layer (B). That is, the (i) duplication of the protected layer or (ii) data of other applicable error correction schemes can be transmitted parallel to the basic data. This way, Unequal Error Protection (UEP) can be applied for the transmitted media.

Operation of an embodiment of the present invention is summarised as follows:

• The UE sends measurement reports on the experienced radio environment. The RNC configures the frequency of the measurement reports. • For the UE measurement reports, an uplink feedback channel is used. In the case of UTRAN, this channel could be the Dedicated Control Channel (DCCH). This requires the UE to either be in CELL DCH or in CELL F ACH states.

• Before the start of the MBMS service, the RNC can signal to the RBS the configuration of the transmission parameters for each layer of the entire media. This may include the Tx power and the transport formats (or transport format sets) for each layer of the entire media. Alternatively, it would be possible to select the Tx power on a per radio frame basis and signal this information within each radio frame sent from the RNC. The transport format may also be selected on a frame-by- frame basis by the RNC using the available transport format selection mechanisms in UTRAN.

If there are any additional reception parameters related to the different media layers that the UE should know in order to be able to receive and decode the data correctly (e.g., the set of transport formats to be used for each respective layer, etc.,) then these parameters can be configured in the UE during the available MBMS bearer setup procedure.

• Before the start of the service the UEs may report their initial channel experience through channel measurement reports. This initial information can be signalled via the MBMS counting mechanism.

• During the service the following network entities operate as described: o RNC: based on the path loss measurement reports from UEs it computes the optional (sub)set of layers to be sent. Also the RNC signals the offsets (hints) of the participating layers (via the MSCH). o RBS: based on the MSCH hints the RBS transmits the corresponding layers with the pre-configured Tx power and the transport format. Optionally, the RNC may indicate for each radio frame the Tx power that the RBS should use when sending the particular frame over the radio interface. The RNC may also change the transport format depending on the media layer that is transmitted, using the available transport format selection mechanism in UTRAN. o UE: periodically sends path loss measurement reports to the RNC with pre-configurable interval. The UE receives as many layers as it can and decodes according to the signalled transport formats of the corresponding layers.

Resources can be saved in the UE if through a downlink control channel the RNC can hint the UE which layers it should receive and try to decode and which it should not. During the transmission of those layers which are not available for a UE, the UE can go to power saving mode.

The method steps as described above are illustrated schematically in the flowchart of Figure 3. Illustrated steps Al to A3 are performed by the UE, illustrated steps Bl to B3 are performed by the RBS, and illustrated steps Cl to C5 are performed by the RNC.

In step Cl, the RNC receives the layered multimedia content for broadcasting to the various UEs including that depicted in Figure 3. In step Al, the UE sends information relating to radio channel conditions at the UE to the RNC, which is received at the RNC in step C2. Step Al is performed at predetermined intervals, or whenever or however often is necessary to maintain sufficiently up-to-date information at the RNC.

In step C3, the RNC determines a set of layers of the multimedia content to be transmitted in dependence upon the latest information received in step C2 from the various remote devices including that depicted in Figure 3, the information relating to radio channel conditions at the remote devices. The RNC also determines in step C3 a set of transmission parameters, possibly on a per-layer basis, and/or on a frame-by- frame basis, to be used by the RBS when transmitting the multimedia content to the UEs. The set of transmission parameters may comprise one or more of: the transmission power to be used for the transmission; the transport format to be used for the transmission; and the coding to be used for the transmission. The set of layers and set of transmission parameters determined in step C3 are together described in Figure 3 as "layer control information".

In step C4 the RNC sends the layer control information to the RBS, which is received by the RBS in step Bl. In step C5 the RNC sends the multimedia content to the RBS, which is received by the RBS in step B2. In step B3 the RBS transmits the multimedia content to the UEs, including that depicted in Figure 3, based on the received layer control information and using the MSCH and MTCH as described previously herein.

In step A2 the UE receives the multimedia content over the MTCH, and in step A3 the UE uses the scheduling information contained in the MSCH to process the multimedia content.

Apparatus for performing each of the above-described method steps of Figure 3 is illustrated schematically in Figure 4. Each of the apparatus portions in Figure 4 has the function of performing a corresponding one of the method steps of Figure 3, where an apparatus portion arranged to perform a method step is identified by adding a zero to the identifying reference. For example, apparatus portion AlO of Figure 4 is part of the UE and is for performing the step Al of Figure 3, portion C40 is for performing step C4, and so on.

Figure 5 shows another representation of a UE embodying the present invention. As indicated previously, the quality of media displayed at the UE is affected by subscription limitations, and the component that prevents reception of a higher quality than agreed in the SLA is the Subscription Limiter 2. The Register of Device Capability 6 stores the media quality limitations derived from the UE characteristics (for example, display size, etc.). The Measurer Component of Channel Quality 4 sends periodical Channel Quality Reports to the RNC; as described previously, these reports help the RNC to adjust the number of transmitted layers to the actual request of UEs and channel conditions. The optimised set of layers are transmitted via the MTCH channel to the UE. The offset of each layer where the UEs should start the reception of media content is indicated by the MSCH channel. From these two MBMS channels, the Receiver of Media Layers 10 passes the media content to the Decoder 8, and the output of the Decoder 8 is displayed on the Display 12.

Figure 6 shows another representation of a RNC and RBS embodying the present invention. The RNC receives periodical Channel Quality Measurement Reports from the UEs as described previously, and these are received at the Transmission Optimizer 16 of the RNC. Based on the received reports and the Signalled Characteristics (Media Information) that is stored in the Storage of Signalled Characteristics 18 of the RNC, the Transmission Optimizer 16 generates the actual Transmission Parameters for the media. The Transmission Parameters are signalled to the RBS. Furthermore, the Layer-starting Indicator 20 of the RNC places indication points to the MSCH to signal the RBS and the UE where the transmitted layers start on the MTCH within the layered media service.

The RBS reads the layer-starting points from the MSCH and the Transmission Parameter Defϊner 14 sets the appropriate transmission parameters (for example, coding, transmission power, etc.) for each transmitted layer on the MTCH.

In the above-described embodiments it is the RNC that decides on which layers to transmit, based on channel quality reports (or the like) received from the various UEs.

Rather than merely sending channel quality reports (or the like), it is also possible that at least one (possibly all) of the UEs are provided with the capability of deciding for themselves what layers they are capable of, or wish to, receive and display to the user.

Such UEs would be able to "convert" its display constraints and subscription limitations (e.g. through a SLA with the content provider concerning the maximum quality the UE is allowed to receive) to a set of layers (the maximum number of layers the UE can receive), and this information would be notified to the RNC. This would save even more bandwidth in the RAN. However, for this to operate, the layer information about the media should be known in advance of the media transmission itself. That is, the layer information should be known not only by the RNC but also by the UE. An embodiment of the present invention offers one or more of the following advantages:

• The proposed solution provides optimal user-perceived quality in a broadcast system.

• The quality is adjusted to the receiving capabilities of the end-users.

• The proposed solution offers a method that enables the 3G MBMS system to save more power for layered media multicast and better utilize the radio resources. • The proposed solution has great impact on current standards and services such as Mobile TV.

• The deployment and integration of the proposed methods are relatively easy.

It will be appreciated that operation of one or more of the above-described components can be controlled by a program operating on the device or apparatus. Such an operating program can be stored on a computer-readable medium, or could, for example, be embodied in a signal such as a downloadable data signal provided from an Internet website. The appended claims are to be interpreted as covering an operating program by itself, or as a record on a carrier, or as a signal, or in any other form.

It will also be appreciated by the person of skill in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined by the appended claims. It will also be appreciated that, where it is stated that a message or signal is sent to a remote node, it is not to be implied that the message or signal is sent directly to the remote node; it can be that the message or signal is eventually received at the remote node via another node or nodes.

Although the method and apparatus has been described above in relation to MBMS, it will be appreciated that the invention can be applied to other similar types of architecture. For example, the invention can be applied to any unidirectional point-to- multipoint service in which data is transmitted from a single source entity to a group of users in a specific area; all group members in the area may receive the same data over a common radio channel, and during transmission resources in the core- and radio network are shared.

Claims

1. A method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising: determining a set of layers of the multimedia content to be transmitted in dependence upon information received from at least some of the remote devices; and causing only the determined set of layers to be transmitted.

2. A method as claimed in claim 1, wherein the information comprises a measure or indication of receiving capability for the multimedia content at the remote devices.

3. A method as claimed in claim 1 or 2, wherein the information comprises a measure or indication of radio channel conditions at the remote devices.

4. A method as claimed in claim 1, 2 or 3, wherein the information comprises an indication of which layers of the multimedia content the remote devices wish and/or are able to receive.

5. A method as claimed in any preceding claim, comprising determining the set of layers in dependence upon at least one property of the multimedia content.

6. A method as claimed in any preceding claim, wherein the information comprises at least one of: a user request; and a specified quality of service requirement.

7. A method as claimed in any preceding claim, wherein the multimedia content is transmitted in dependence upon at least one transmission parameter, and comprising determining the at least one parameter separately for each of at least some of the layers being transmitted.

8. A method as claimed in any preceding claim, wherein the multimedia content is transmitted in dependence upon at least one transmission parameter, and comprising determining the at least one parameter separately for each of at least some radio frames being transmitted.

9. A method as claimed in claim 7 or 8, wherein the at least one transmission parameter comprises the transmission power to be used for the transmission.

10. A method as claimed in claim 7, 8 or 9, wherein the at least one transmission parameter comprises the transport format to be used for the transmission.

11. A method as claimed in any one of claims 7 to 10, wherein the at least one transmission parameter comprises the coding to be used for the transmission.

12. A method as claimed in any preceding claim, comprising providing to the remote devices scheduling information for each of the layers being transmitted.

13. A method as claimed in claim 12, wherein the scheduling information specifies a temporal arrangement of the layers.

14. A method as claimed in claim 12 or 13, comprising providing the scheduling information over a scheduling channel of the MBMS.

15. A method as claimed in claim 14, wherein the scheduling channel is the MBMS Scheduling Channel, MSCH.

16. A method as claimed in claim 15, comprising providing information relating to a repetition period for the MSCH and a temporal offset from the MBMS Control Channel, MCCH, modification period using the MCCH.

17. A method as claimed in any one of claims 12 to 16, wherein the scheduling information indicates the start of a layered service in each of a plurality of reception periods, and within each reception period a starting point for the transmission of each layer.

18. A method as claimed in any preceding claim, comprising transmitting the multimedia content over a traffic channel of the MBMS.

19. A method as claimed in claim 18, wherein the traffic channel is the MBMS Traffic Channel, MTCH.

20. A method as claimed in any preceding claim, comprising performing the steps at a Radio Network Controller, RNC.

21. A method as claimed in any preceding claim, comprising performing the steps before setting up a Multimedia Broadcast Multicast Service session.

22. A method as claimed in any preceding claim, comprising performing the steps during a Multimedia Broadcast Multicast Service session.

23. A method for use by a device in a Multimedia Broadcast Multicast Service, MBMS, comprising sending information to a control node, the information being for use at the control node for determining a set of layers of a layered multimedia content to be transmitted to the device, and the information comprising at least one of: information relating to radio channel conditions at the device; at least one measure or indication of receiving capability for the multimedia content for the device; an indication concerning which layers of the multimedia content the device wishes and/or is able to receive; a user request; and a specified quality of service requirement.

24. A method as claimed in claim 23, comprising sending the information using the Dedicated Control Channel, DCCH, of a UMTS Terrestrial Radio Access Network, UTRAN.

25. A method for use by a base station in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising receiving information from a control node specifying a set of layers of the multimedia content to be transmitted, and transmitting only the specified set of layers in dependence upon the received information.

26. A method as claimed in claim 25, comprising receiving at least one parameter separately for each of at least some of the layers being transmitted, and transmitting the multimedia content in dependence upon at least one transmission parameter.

27. A method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising providing to the remote devices scheduling information for each of the layers being transmitted.

28. A method for use in a Multimedia Broadcast Multicast Service, MBMS, for processing received layered multimedia content, comprising receiving scheduling information for each layer of the received multimedia content, and using the scheduling information to process the received multimedia content.

29. A method as claimed in claim 28, comprising using the scheduling information to decode only selected ones of the received layers.

30. A method for use in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising determining at least one transmission parameter separately for each of at least some of the layers being transmitted, the determination being made in dependence upon information received from at least some of the remote devices; and arranging for the transmission of the multimedia content in dependence upon the at least one transmission parameter.

31. An apparatus for use in or as a radio network controller in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising: means for determining a set of layers of the multimedia content to be transmitted in dependence upon information received from at least some of the remote devices; and means for causing only the determined set of layers to be transmitted.

32. An apparatus for use in or as a user equipment device in a Multimedia Broadcast Multicast Service, MBMS, comprising means for sending information to a control node, the information being for use at the control node for determining a set of layers of a layered multimedia content to be transmitted to the device, and the information comprising at least one of: information relating to radio channel conditions at the device; at least one measure or indication of receiving capability for the multimedia content for the device; an indication concerning which layers of the multimedia content the device wishes and/or is able to receive; a user request; and a specified quality of service requirement.

33. An apparatus for use in or as a radio base station in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for receiving information from a control node specifying a set of layers of the multimedia content to be transmitted, and means for transmitting only the specified set of layers in dependence upon the received information.

34. An apparatus for use in or as a radio base station or a radio network controller in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for providing to the remote devices scheduling information for each of the layers being transmitted.

35. An apparatus for use in or as a user equipment in a Multimedia Broadcast Multicast Service, MBMS, for processing received layered multimedia content, comprising means for receiving scheduling information for each layer of the received multimedia content, and means for using the scheduling information to process the received multimedia content.

36. An apparatus as claimed in claim 34 or 35, wherein the scheduling information specifies a temporal arrangement of the layers.

37. An apparatus as claimed in claim 34, 35 or 36, wherein the scheduling information is provided over the MBMS Scheduling Channel, MSCH.

38. An apparatus as claimed in any one of claims 34 to 37 wherein the scheduling information indicates the start of a layered service in each of a plurality of reception periods, and within each reception period a starting point for the transmission of each layer.

39. An apparatus for use in or as a radio base station or a radio network controller in a Multimedia Broadcast Multicast Service, MBMS, for transmitting layered multimedia content to a plurality of remote devices, comprising means for determining at least one transmission parameter separately for each of at least some of the layers being transmitted, the determination being made in dependence upon information received from at least some of the remote devices; and means for arranging for the transmission of the multimedia content in dependence upon the at least one transmission parameter.

40. A program for controlling an apparatus to perform a method as claimed in any one of claims 1 to 29.

41. A program which, when loaded into an apparatus, causes the apparatus to become an apparatus as claimed in any one of claims 31 to 39.

42. A program as claimed in claim 40 or 41, carried on a carrier medium.

43. A program as claimed in claim 42, wherein the carrier medium is a storage medium.

44. A program as claimed in claim 42, wherein the carrier medium is a transmission medium.

45. An apparatus programmed by a program as claimed in any one of claims 40 to 44.

46. A storage medium containing a program as claimed in any one of claims 40 to 43.