Base station, user equipment and methods for sending and receiving a multicast beam in a telecommunications network.

TECHNICAL FIELD

The present invention generally relates to the field of telecommunications network technology. Particularly, the present invention relates to a base station for sending a multicast beam to a group of user equipment in a telecommunications network, and to a user equipment, UE, for receiving a multicast beam from a base station in a telecommunications network. Further, the invention relates to a method, in a base station, for sending a multicast beam to a group of user equipment in a telecommunications network, and a method, in a user equipment, for receiving a multicast beam from a base station in a telecommunications network. Further, the invention relates to a base station in a telecommunications network.

BACKGROUND

Multicasting is used in a lot of use cases in which communication involves the transmission of the same data to a group of users (e.g. infotainment or multimedia streaming, distribution of software updates). Instead of sharing the available resources between multiple unicast links, we can send the data to the group of users simultaneously on the same resource, using a single multicast link. Furthermore, base stations will be equipped with multiple antennas. In this case, multicasting can be combined with beamforming. Multicast beamforming is mainly addressed under theoretical perspective in the literature, in particular based on mathematical approaches. Those approaches are often developed under the implicit assumption of perfect available channel information, and the proposed solutions disadvantageously depend on computationally expensive, iterative algorithms and overhead due to channel information reporting from all user equipment. Current data multicasting standards, in particular evolved Multimedia Broadcast Multicast Service (eMBMS) or Single- Cell Point-To-Multipoint (SC-PTM) do not exploit multicast beamforming as directional transmission towards a group of users. Multicast Beamforming relies on channel information, which is fed back from the user equipment UE to the base station BS. Based on the observed signal at the UE, user equipment usually returns its feedback in an explicit or implicit way. Explicit feedback means feeding back the full or partial channel information from a receiver to a transmitter. Explicit feedback has the disadvantage of needing large amount of feedback resources, especially for "massive MIMO" channels with many antennas. The disadvantage of explicit full channel information, in particular channel state information, feedback is the required large bandwidth for the feedback channel between user equipment and base station.

Implicit means the user equipment feeds back the index of a recommended precoder (PMI), chosen from a known codebook. Implicit channel information feedback, in particular CSI feedback, is not suitable for forming a multicast beam to a group of user equipment, since the multicast beam depends on more than one channel information feedback. The assumption of a user equipment-specific precoder to be selected is not valid. Instead, explicit channel information is needed for creating the multicast beam.

The current LTE architecture for multicast such as SC-PTM or eMBMS comprises a high number of nodes involved to enable multicast for ultra-reliable low latency services (uRLLC) among vehicles in a close proximity. This complex signalling architecture disadvantageously increases the latency of transmissions. Therefore the current LTE multicast technology is not suitable for the upcoming uRLLC multicast services.

Finally, the new 5G technology will be used in parallel to the existing 4G- or LTE-technology, in particular within the bandwidth of an LTE component carrier. Using this same bandwidth will disadvantageously increase the problem of interference.

SUMMARY

Having recognized the above-mentioned disadvantages and problems, the present invention aims to improve the state of the art, in particular of V2x multicast technology over Uu interface. In particular, an object of the present invention is to provide a base station, a user equipment and methods for further improving signal-to-noise-ratio SNR, for reducing interference and for advantageously exploiting the multicast beamforming.

The above-mentioned object is achieved by the features of the independent claims. Further embodiments of the invention are apparent from the dependent claims, the description and the figures.

According to a first aspect, the invention relates to a base station for sending a multicast beam to a group of user equipment in a telecommunications network, wherein the base station comprises an antenna array, and wherein the base station is configured to send multiple reference beams, wherein each of the multiple reference beam is associated with an index, receive, from a group of user equipment, channel information associated with a subset of the sent reference beams, and send the multicast beam a group of user equipment based on received channel information.

Thereby, using the reporting of received channel information, in particular explicit channel information, has the advantage that the reporting scheme does not make any assumption on a user specific transmitting or receiving strategy. The received channel information can advantageously be used in a flexible and efficient way for multicast beamforming by using a fixed DFT (direct Fourier transformation) grid of beams, which is not adjusted to individual users. The reference signals of the reference beams are not user equipment-specific, they are beam-specific. Therefore the received channel information is useable for all user equipment. Further, this allows the usage of a large number of user equipment. According to a first implementation of the base station according to the first aspect, the base station is configured to send received channel information to a further base station.

Thereby, the further base station advantageously uses the received channel information to match its multicast beam to the group of user equipment. Instead of matching of the multicast beam, this forwarded channel information can also be used by the base station for prioritizing the uRLLC service by avoiding the interference to the user equipment connected to the base station. According to a second implementation of the base station according to the first aspect, the base station and the further base station are part of a single frequency network, and wherein the base station is further configured to send received channel information and data to the further base station. Thereby, the base station and the further base station are advantageously enabled for collaboratively or simultaneously sending of multicast data using beams to the user equipment in the telecommunications network coverage area of the base stations.

According to a third implementation of the base station according to the first aspect, the base station is further configured to receive, from a group of user equipment, further channel information associated with a subset of further reference beams, and send the multicast beam to a group of user equipment based on received channel information and received further channel information. Thereby, the sending of further channel information has the advantage that the base station can send this further channel information comprising information regarding the interfering reference signals of the further reference beams to the further base station for adjusting the further base station's beam. According to a fourth implementation of the base station according to the first aspect, the base station is further configured to send received channel information to a further base station for adjusting a signal sent by the further base station.

Thereby, the forwarding of the received channel information can be advantageously used for reducing interference between transmitted beams of the base stations in the telecommunications network. Consequently, there is the advantage of a better SINR for the user equipment, in particular for the group of user equipment, and hence a more reliable transmission.

According to a fifth implementation of the base station according to the first aspect, the channel information comprises phase information, amplitude information and the index of the reference beam.

Thereby, the received channel information does not comprise channel information related to a user-specific transmission strategy. The channel information is advantageously useable for a group of user equipment, particularly useable to each user equipment of a group.

Particularly, phase information comprises relative phase shifts among the reference beams belonging to the same base station, measured with regards to a certain reference phase.

According to a sixth implementation of the base station according to the first aspect, the base station is further configured to send the multicast beam based on computing antenna weights w _n of the antenna array, wherein the computation of the antenna weights w _n is based on a transformation algorithm associated with the subset of the sent reference beams, forming the multicast beam based on the computed antenna weights w _n of the antenna array. Thereby, the base station advantageously adapts the multicast beam for improving the signal quality for each user equipment of a multicast group.

According to a second aspect, the invention relates to a method, in a base station, for sending a multicast beam to a group of user equipment in a telecommunications network, the method comprises the steps of sending multiple reference beams, wherein each of the multiple reference beams is associated with an index, receiving, from a group of user equipment, channel information associated with a subset of the sent reference beams, and sending the multicast beam to a group of user equipment based on received channel information. Thereby, using the reporting of received channel information has the advantage that the reporting scheme does not make any assumption on a user specific transmitting or receiving strategy. The received channel information can advantageously be used in a more flexible and more efficient way for multicast beamforming by using a fixed DFT (direct Fourier transformation) grid of beams, which is not adjusted to individual users. The reference signals of the reference beams are not user equipment-specific, they are beam-specific. Therefore the received channel information is useable for all user equipment. Further, this allows the usage of a large number of user equipment.

According to a first implementation of the method according to the second aspect, the method further comprises the step of sending received channel information to a further base station.

Thereby, the further base station advantageously uses the received channel information to match its multicast beam to the group of user equipment.

Alternatively, this forwarded channel information is used by the base station for prioritizing the uRLLC service by avoiding the interference to the user equipment connected to the base station.

According to a second implementation of the method according to the second aspect, the base station and the further base station are part of a single frequency network and the method further comprises the step of sending received channel information and data to the further base station.

Thereby, the base station and the further base station are advantageously enabled for collaboratively or simultaneously sending of multicast beams to the user equipment in the telecommunications network coverage area of the base stations.

According to a third implementation of the method according to the second aspect, the method further comprises the steps of receiving, from a group of user equipment, further channel information associated with a subset of further reference beams, and sending the multicast beam to a group of user equipment based on received channel information and received further channel information. Thereby, the sending of further channel information has the advantage that the base station can send this further channel information comprising information regarding the interfering further reference beams to the further base station for adjusting the further base station's beam.

According to a fourth implementation of the method according to the second aspect, the method further comprises the step of sending received channel information to a further base station for adjusting a signal sent by the further base station. Thereby, the forwarding of the received channel information can be advantageously used for reducing interference between transmitted beams of the base stations in the telecommunications network. Further, there is the advantage that there is a better SINR for the user equipment, in particular user equipment of the group, and hence a more reliable transmission.

According to a fifth implementation of the method according to the second aspect the channel information comprises phase information, amplitude information and the index of the reference beam. Thereby, the received channel information does not comprise channel information related to a user-specific transmission strategy. The channel information is advantageously useable for a group of user equipment, particularly useable to each user equipment of a group.

Particularly, phase information comprises relative phase shifts among the reference beams belonging to the same base station, measured with regards to a certain reference phase.

According to a sixth implementation of the method according to the second aspect, before the method step of sending the multicast beam, the method further comprises the steps of computing antenna weights w _n of the antenna array, wherein the computation of the antenna weights w _n is based on a transformation algorithm associated with the subset of the sent reference beams, and forming the multicast beam based on the computed antenna weights w _n of the antenna array. Thereby, the base station advantageously adapts the multicast beam for improving the receive beam or signal quality for each user equipment of a multicast group.

According to a third aspect, the invention relates to a user equipment for receiving a multicast beam from a base station in a telecommunications network, the user equipment is configured to receive, from the base station, multiple reference beams, wherein each of the multiple reference beams is associated with an index, determine conditions of a channel associated with each of the received reference beams, select a subset of the received reference beams, send, to the base station, channel information associated with the subset of the received reference beams.

Thereby, the reporting of channel information from the user equipment to the base station has the advantage that the reporting scheme does not make any assumption on a user specific transmitting or receiving strategy. The channel information can advantageously be used in a more flexible and more efficient way for multicast beamforming by using a fixed DFT (direct Fourier transformation) grid of beams, which is not adjusted to individual users. The reference signals of the reference beams are not user equipment-specific, they are beam- specific. Therefore the channel information is useable for all user equipment. Further, this allows the usage of a large number of user equipment.

According to a first implementation of the user equipment according to the third aspect, the user equipment is further configured to select the subset of the received reference beams by determining if the received reference beam's power level is above a pre-set power level threshold.

Thereby, the advantage of this selecting is that only those contributions of the received reference beams relevant for the group of user equipment is sent to the base station. Further, the selection of the subset of the received reference beams advantageously reduces the required feedback resources. According to a second implementation of the user equipment according to the third aspect, the channel information comprises phase information, amplitude information and the index of the reference beam. Thereby, the sent channel information comprising information for all other user equipment of the same group is advantageously useable for the base station.

Preferably, phase information comprises relative phase shifts among the reference beams belonging to the same base station, measured with regards to an arbitrary reference phase. According to a third implementation of the user equipment according to the third aspect, the user equipment is further configured to receive, from a further base station, multiple further reference beams, wherein each of the multiple further reference beams is associated with an index, determine conditions of a channel associated with each of the received further reference beams, select a subset of the received further reference beams, send, to the base station, further channel information associated with the subset of the received further reference beams.

Thereby, the user equipment advantageously will improve the receive quality of the multicast beam based on the reducing of interference reduction.

According to a fourth aspect, the invention relates to a method, in a user equipment, for receiving a multicast beam from a base station in a telecommunications network, the method comprises the following steps receive, from the base station, multiple reference beams, wherein each of the multiple reference beams is associated with an index, determine conditions of a channel associated with each of the received reference beams, select a subset of the received reference beams, send, to the base station, channel information associated with the subset of the received reference beams.

Thereby, the reporting of channel information from the user equipment to the base station has the advantage that the reporting scheme does not make any assumption on a user specific transmitting or receiving strategy. The channel information can advantageously be used in a more flexible and more efficient way for multicast beamforming by using a fixed DFT (direct Fourier transformation) grid of beams, which is not adjusted to individual users. The reference signals of the reference beams are not user equipment-specific, they are beam-specific. Therefore the channel information is useable for all user equipment. Further, this allows the usage of a large number of user equipment.

According to a first implementation of the method according to the fourth aspect, the method further comprises the step of selecting the subset of the received reference beams by determining if the received reference beam's power level is above a pre-set power level threshold.

Thereby, the advantage of this selecting is that only those contributions of the received reference beams relevant for the group of user equipment, in particular the group of user equipment, is sent to the base station. Further, the selection of the subset of the received reference beams advantageously reduces the required feedback resources.

According to a second implementation of the method according to the fourth aspect, the channel information comprises phase information, amplitude information and the index of the reference beam. Thereby, the sent channel information comprising information for all other user equipment of the same group is advantageously useable for the base station.

Preferably, phase information comprises relative phase shifts among the reference beams belonging to the same base station, measured with regards to an arbitrary reference phase. According to a third implementation of the method according to the fourth aspect, the method comprises the further steps of receiving, from a further base station, multiple further reference beams, each of the multiple further reference beams is associated with an index, determining conditions of a channel associated with each of the received further reference beams, selecting a subset of the received further reference beams, and sending, to the base station, further channel information associated with the subset of the received further reference beams. Thereby, the user equipment advantageously will improve its receive quality based on the reducing of interference reduction.

According to a fifth aspect, the invention relates to a base station in a telecommunications network, the base station is configured to receive channel information from a base station according to the first implementation of the base station according to the first aspect.

Thereby, the base station advantageously matches its multicast beam towards the group of user equipment.

According to a first implementation of the base station according to the fifth aspect, the base station is further configured to receive data from the base station according to the second implementation of the base station according to the first aspect, and send jointly with the base station according to the second implementation of the base station according to the first aspect, received data on a further multicast beam to the group of user equipment.

Thereby, the signal to noise ratio of a user equipment of the group is improved significantly.

According to a second implementation of the base station according to the fifth aspect, the base station is further configured to adjust a signal for reducing interference with the multicast beam of the base station according to the fourth implementation of the base station according to the first aspect.

Thereby, the forwarding of the channel information can be advantageously used for reducing interference between transmitted beams of the base stations in the telecommunications network. Further, there is the advantage that there is a better SINR for the user equipment, in particular user equipment of the group, and hence a more reliable transmission.

More specifically, it should be noted that the above apparatuses may be implemented based on a discrete hardware circuitry with discrete hardware components, integrated chips or arrangements of chip modules, or based on a signal processing device or chip controlled by a software routine or program stored in a memory, written on a computer-readable medium or downloaded from a network such as the internet.

It shall further be understood that a preferred embodiment of the invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

These and other aspects of the invention will be apparent and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which

Fig. la depicts a base station comprising an antenna array and a multicast group of user equipment according to the present invention;

Fig. lb depicts channel information reporting according to a further embodiment of the present invention;

Fig. 2 depicts a use case for multicast transmission over a combined area regarding v2X communication services according to a further embodiment of the present invention; and Fig. 3 depicts a schematic flow diagram regarding a multicast collaboration model according to the further embodiment of the present invention depicted in Fig. 2.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION Fig. la depicts a base station 100 for sending a multicast beam to a group of user equipment 150, 151, 152 in a telecommunications network, the base station 100 comprises an antenna array 110, and the base station 100 is configured to send multiple reference beams 121, 122, 123, 124, 125, 126, 127, wherein each of the multiple reference beams 121, 122, 123, 124, 125, 126, 127 is associated with an index. The base station 100 receives, from the group of user equipment 150, 151, 152, channel information associated with a subset of the sent reference beams, and send the multicast beam 140 to the group of user equipment 150, 151, 152 based on received channel information.

The user equipment 150, 151, 152 are forming a group, particularly a multicast group. The reference beams 121, 122, 123, 124, 125, 126, 127 are associated with an index for efficient identification, particularly for estimating channel information in a user equipment 150, 151, 152.

The base station 100 receives channel information from each user equipment of the group, the channel information comprises one complex scalar value per beam, in particular phase information and amplitude information along with the indices of the reference beams 121, 122, 123, 124, 125, 126, 127, in particular those beams which significantly contribute to the channel.

The phase information or phases are measured with respect to a certain reference, which is common for all beams that belong to the same base station. Knowing the phases and amplitudes of all Grid of Beam (GoB) reference beams would be equivalent to perfect channel information assuming orthogonal beams as used in a Direct Fourier Transformation (DFT). The base station 100 and the user equipment 150, 151, 152 uses the knowledge that some of the GoB beams are pointing to "other directions" or not towards the user equipment 150, 151, 152 and not to the spatial channel or beam to the respective user equipment 150, 151, 152. This advantageously reduces the complexity or dimensionality, since only channel information regarding a subset of reference beams 121, 122, 123, 124, 125, 126, 127 will be fed back or send from each user equipment 150, 151, 152 to the base station 100. Therefore, instead of using user equipment specific channel information, in particular a user equipment specific precoding technique, the base station 100 receives channel information not not making any assumption on a user equipment-specific transmit or receive strategy based on a subset of reference beams 121, 122, 123, 124, 125, 126, 127. Based on the received channel information the base station is enabled to form an appropriate, in particular an adapted multicast beam 140, which improves the signal to noise ratio for the group of user equipment 150, 151, 152. The base station 100 send the multicast beam 140 to the user equipment 150, 151, 152, in particular for providing an ultra-reliable low latency communication service to vehicles as a V2x service.

According to an embodiment of the present invention antenna weights or antenna coefficients are determined in the base station 100 based on an algorithm. The user equipment 150, 151, 152 only send, to the base station 100, the phase information, amplitude information and the indices associated with the strongest beams. Based on these indices, the amplitudes and phases the base station 100 determines the channel matrix H between M reference beams and K user equipment. The effective channel matrix H models the combined effect of transmitted reference beams and the propagation channel. And let U be a reduced channel matrix, which is defined similar to H, based on the subset of reference beams. The entries are taken from the user equipment 150, 151, 152 feedback regarding index of the reference beam 121, 122, 123, 124, 125, 126, 127, phase and amplitude of each reference beam per user equipment. Entries for which no feedback value is available are set to zero, because this beam has negligible contribution to the respective user equipment 121, 122, 123, 124, 125, 126, 127.

The columns of H are weighted individually, which optionally can be done based on the max- min-SINR criterion, in particular using the inverse path gain concept, which means the weaker the channel, the stronger is the weight. Other weighting concepts are possible.

By summing up all columns, we obtain the vector u.

Let Ufuii be the MxM DFT matrix, where each column corresponds to one beam, forming a GoB grid of beam. Let U be the reduced matrix, containing only beams that contribute to the given group of users to be served by a multicast beam. The antenna weights w _n are given as the product w=U*u. Fig. lb depicts channel information reporting according to a further embodiment of the present invention. Fig. lb shows user equipment 150, 151, 152, a base station 100 and a further base station 180 in a telecommunications network. The base station 100 and the further base station 180 are part of a single frequency network in the telecommunications network.

A single frequency network is or SFN is a broadcast or multicast telecommunications network where several transmitters or base stations 100, 180 simultaneously send the same signal over the same frequency channel, in particular simultaneously sending the multicast beam to a group of user equipment 150, 151, 152.

The user equipment 150, 151, 152 is further configured to receive, from a further base station 180, multiple further reference beams 131, 132, 133, each of the multiple further reference beams 131, 132, 133 is associated with an index, determine conditions of a channel associated with each of the received further reference beams 131, 132, 133, select a subset of the received further reference beams, and send, to the base station 100, further channel information associated with the subset of the received further reference beams.

Each base station 100, 180 comprises an antenna array 110, 190. Each base station 100, 180 is configured to send multiple reference beams 121, 122, 123, 124, 125, 126, 127, 131, 132, 133 each of the multiple reference beams 121, 122, 123, 124, 125, 126, 127, 131, 132, 133 is associated with an index. The base station 100 receives, from the group of user equipment 150, 151, 152, channel information associated with a subset of the sent reference beams 121, 122, 123, 124, 125, 126, 127, 131, 132, 133, and send the multicast beam 140 to the group of user equipment 150, 151, 152 based on received channel information.

The user equipment 150, 151, 152 are forming a group, particularly a multicast group. The reference beams 121, 122, 123, 124, 125, 126, 127, 131, 132, 133 are associated with an index for efficient identification, particularly for estimating channel information in a user equipment 150, 151, 152. In this embodiment as depicted in Fig. lb the base station 100 is configured to send received channel information and data to the further base station 180. Optionally the channel information is sent via an XN-interface 170 of the telecommunications network. The further base station 180 is configured to receive data from the base station 100. In this embodiment the further base station 180 send jointly with the base station 100 received data on a further multicast beam 160 to the group of user equipment 150, 151, 152. Optionally, the further base station 180 direct its multicast beam 160 to other user equipment in a different geographical area of the single frequency network.

Fig. 2 depicts a use case for multicast transmission over a combined area regarding v2X communication services according to a further embodiment of the present invention.

In this embodiment Fig. 2 depicts a use case for 5G or also called new radio for offering an ultra-reliable low latency communication (uRLLC) service for a group of vehicles 250, 251 based on multicast beamforming.

A single-frequency network (SFN) over multiple base stations 200, 280, 290 is created, where the base station 200, 280, 290 simultaneously multicast the information via a multicast beam 240, 260, 295 to a number of vehicles 250, 251, 252, 253, 254, 255 within a certain geographical area. The base station 200, 290 are delivering localized URLLC services to the group of vehicles 250, 251 in the associated base station's coverage area.

The base station 280 is located in a 4G telecommunications network, the 4G network further comprises a multimedia broadcast multicast service gateway 285, a broadcast multicast service center 286 and a V2x server 287.

The 5G telecommunications network provides localized uRLLC multicast data transmission with multicast beamforming according to the present invention.

The channel information and the data or information is exchanged between the base stations 200, 290 and the further base station 280 via the Xn interface 270. This has the advantage that the base stations 200, 280, 290 are enabled to send simultaneously the same signal on their multicast beam 240, 260, 295 to the vehicles 250, 251, 252, 253, 254. Further, the sending of the channel information and data as described above advantageously supports a selective provision of services for vehicles close to the base stations 200, 290 and for those vehicles far away.

In a further embodiment of the present invention the sending of channel information only from the base station 200, 290 to the further base station is alternatively useable for reducing interference for beams from the further base station 280. This is achieved by sending the channel information, particularly phase, amplitude and the index of the interferer beams, to the further base station 280, 290.

Therefore, based on this received channel information the antenna weights of the further base station 280 are adjusted in such a way that the directions of the beams to the base station 200, 290 user are suppressed, in particular by using zero forcing or a MMSE-type MIMO base station.

This also has the advantage to prioritize the uRLLC services provided by the base stations 200, 290 against the services of the further base station 280. Thereby, the group of vehicles or user equipment 250, 251 has a better SINR and hence a more reliable communication link.

Particularly, in this embodiment the base station 200, 290 in Fig. 2 provides the uRLLC service by sending the multicast beam to the group of vehicles 250, 251 without involving a lot of network elements or entities in the telecommunications network, in particular further base stations, signaling gateway SGW, packet data gateway PGW or V2X application server or similar. This reduction of involved network elements and network entities has the advantage to reduce the latency significantly.

Fig. 3 depicts a schematic flow diagram regarding a multicast collaboration model according to the further embodiment of the present invention depicted in Fig. 2. Fig. 3 depicts a telecommunications network comprising a base station 300 and a further base station 380. Both base stations 300, 380 are part of a single frequency network as already described above. Fig. 3 also shows a group of user equipment 350, 351, 352, and user equipment 353, 354, 355.

In step 301 of the schematic flow diagram the base station 300 send multiple reference signals or beams, also called CSI-RS, to the each of the multiple reference signals is associated with an index.

In step 302 each of the user equipment 350, 351, 352 determine conditions of a channel associated with each of the received reference signals, in particular determining phase information, amplitude and index of the reference signal. Each user equipment 350, 351, 352 select a subset of the received reference signals.

In step 303 each user equipment 350, 351, 352 sends channel information associated with the subset of the received reference signals to the base station 300.

In step 304 the base station 300 uses the subset of the reference signals for the determining of the antenna weights for the antenna array of the base station 300 based on the grid of beams concept as described above. In step 305 the base station 300 sends the multicast signal or multicast beam, in particular a uRLLC multicast signal, to the user equipment 350, 351, 352 or a vehicle comprising a user equipment 350, 351, 352 for further processing in the user equipment 350, 351, 352.

In step 306 the base station 300 send received channel information and data to the further base station 380 via the XN interface for further processing in the further base station 380, in particular forwarding the data to a localized multimedia broadcast multicast service entity 390.

In step 307 the further base station 380 sends the multicast data signal to the other user equipment 353, 354, 355 in the network coverage area of the further base station 380. While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. From reading the present disclosure, other modifications will be apparent to a person skilled in the art. Such modifications may involve other features, which are already known in the art and may be used instead of or in addition to features already described herein.

The invention has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Although the present invention has been described with reference to specific features and embodiments thereof, it is evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded simply as an illustration of the invention as defined by the appended claims, and are contemplated to cover any and all modifications, variations, combinations or equivalents that fall within the scope of the present invention.

The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 760809.