DESCRIPTION

Partitioning resources on a target side of a handover of a user equipment based on data traffic indication

Field of invention

The present invention generally relates to the field of mo- bile telecommunication networks and in particular to Long

Term Evolution (LTE) telecommunication networks, where relay nodes are used to increase a cell coverage. In particular, the present invention relates to a method for partitioning radio transmission resources within a telecommunication net- work on target side of a handover of a user equipment. Fur ^¬ ther, the present invention relates to a source side network element and to a target side network element for controlling a partitioning of radio transmission resources within a telecommunication network on a source and target side of a hand- over of a user equipment. Furthermore, the present invention relates to computer program for controlling the above described radio transmission resources partitioning method.

Art Background

In order to allow for cost efficient and flexible deployment solutions, within the third generation partnership project (3GPP) relaying is investigated as one of the new technolo- gies for Long Term Evolution (LTE) networks and in particular for Long Term Evolution Advanced (LTA-Advanced) networks. It has been shown that with the usage of a relay node (RN) or more relay nodes (RNs) the spatial coverage and/or the capac ^¬ ity of a base station (BS) can be significantly increased. Further, areas can be covered which without using RN would suffer from bad radio conditions. Such areas are located typically at the edge of a cell being served by a particular BS. 200900554

Apart from this main goal of coverage extension, introducing relay concepts can also help in (a) providing a high-bit-rate coverage in high shadowing environments, (b) reducing average radio-transmission power at a user equipment (UE) , thereby leading to long battery life, (c) enhancing the cell capacity and effective throughput, e.g., increasing cell-edge capacity and balancing cell load and (d) enhancing the overall per ^¬ formance and deployment cost of a Radio Access Network (RAN) .

Also the IEEE standardization bodies such as the IEEE 802.11 and IEEE 802.16 group notice and investigate the potential of relaying technology. In this respect it is mentioned that the specification IEEE 802.16 is influenced for instance by pre- standardization activities such as for instance Wireless World Initiative New Radio (WINNER) project (see http://www.ist-winner.org/), wherein investigations regarding RN are carried out. This means that telecommunication net- works relying on RN are achieving the level of maturity that is needed in ongoing standardization activities. The best evidence of this maturity is the IEEE 802.16 j standardization where RNs are added on top of the IEEE 802.16e standard. This recent development has increased the pressure to consider RN also in LTE standardization.

There are many kinds of relay systems proposed starting from the simplest amplify/forward RN, which is applied e.g. in single frequency Digital Video Broadcasting-Handhelds (DVB-H) networks ending up to the most complex one, which utilizes a network coding to improve the overall performance. The most common type of RN that is proposed for use of RN in cellular networks (cellular relaying) is a decode/forward type of RN, where an input signal is detected and typically decoded and retransmitted using the same procedure as in the original transmission. Such an approach is assumed in this document. 200900554

Cellular relaying can be realized at the different layers of a protocol stack, which layers are described by the well known Open Systems Interconnection Reference Model (OSI model) . A simple amplify and forward relaying can be realized at the Layer 1 of the protocol stack where the RN is required to have only (some part of) the PHY layer. Layer 2 RNs, which include the protocol stack up to the Media Access Control (MAC) / Radio Link Control (RLC) layers, enable the possibil ^¬ ity of doing decentralized radio resource management. Layer 3 or higher layer RNs could almost be considered as wireless base stations and support all the protocol layers of normal base stations. Layer 3 or higher layer relaying is assumed in this document for the sake of simplicity in notations. How ^¬ ever, the described radio resource partitioning procedure can easily be extended for other types of relays (e.g. layer 2) as well.

In order to make LTE-Advanced economically viable, it is re ^¬ quired to be as much backward compatible with 3GPP Release 8 as possible. This is especially important for the UE side, as it will allow users to benefit from relaying with their Release 8 terminals. Based on previous 3GPP experiences it is herein assumed that full backward compatibility is required from UE side, i.e. Release 8 and LTE-Advanced UEs should work equally well in Release 8 and LTE-Advanced networks. At the network side software and even hardware updates between stan ^¬ dard releases may be possible but preferably they should be as small as possible. Hence, from the viewpoint of a UE the serving network node respectively the current access point should function in exactly the same way as a Release 8 BS, which is called enhanced NodeB (eNB) . Due to this requirement the reduction of BS functionalities when defining a RN will be difficult and RNs need to support all main eNB functions of a BS respectively of an eNB. Due to this fact it is often assumed that RNs, which will be employed in future telecommu ^¬ nication networks, will be capable of flexible resource shar ^¬ ing with the eNB that controls them. Moreover, it is often assumed that (a) the telecommunication network will allow at 200900554

maximum 2 hops (BS-UE and BS-RN-UE) and (b) the network topology has a tree design (no connections between different RNs are allowed) , but again the described resource partition ^¬ ing procedure also works in the general case without these restrictions, indeed it will be applicable to intermediate RNs as well.

In the following there will be considered by way of example a common handover situation with reference to Figure 2. A user equipment UE is originally located within source coverage area CAl being spanned by a source relay node RNl . CAl and RNl are located within a source cell, which is spanned by a source base station BSl . The UE is connected to the source relay node RNl via a radio access link. The source relay node RNl is connected to the source base station BSl via a so called backhaul link.

The UE is moving into a target coverage area CA2, which is located within a target cell of the telecommunication net- work. The movement of the UE is indicated in Figure 2 with an arrow origination from the UE. The target coverage area CA2 is spanned by a target relay node RN2c, which is connected to a target base station BS2. The target base station BS2 spans the target cell. Apart from the target relay node RN2c there are further relay nodes RN2a and RN2b connected to the target base station BS2. Each of these further relay nodes RN2a and RN2b may serve further UE's, which for the sake of clarity are not depicted in Figure 2. In addition, further UE's may be connected directly to the target base station BS2. There- fore, the radio transmission resources, which are in total available for the target cell, have to be distributed among various radio links (access links between a UE and a RN, backhaul links between a RN and the target base station and/or direct links between a UE and the target base sta- tion) .

Further relay nodes may be connected to the source base sta ^¬ tion BSl and may serve further UE's and further UE's may be 200900554

connected directly to the base station BSl. For sake of clar ^¬ ity they are not depicted in Figure 2. Also in the source cell available resources have to be distributed among various radio links .

However, the handover from RNl to RN2c may fail or at least result in bad performance, if the resource partitioning is not properly done by the target base station BS2. For example, if assuming that in the non depicted coverage areas of RN2a and RN2b there have occurred high data traffic dynamics, most of the available radio transmission resources may be as ^¬ signed to backhaul and access links of RN2a and RN2b. If RNl wants to handover the UE to RN2c, the handover (HO) could fail because RN2c does not have enough radio transmission re- sources to accommodate the additional UE that RNl wants to handover to RN2c. Generally speaking, a HO of UEs to a target RN may fail because (i) there are not enough available radio transmission resources for the target RN access link and/or (ii) there are not enough available resources for target RN backhaul link. Therefore, an appropriate radio transmission resource partitioning may be necessary in order to improve the success probability of a HO procedure and therefore im ^¬ prove the overall network performance. If the handover is executed despite an insufficient availability of resources, then the performance of the UE that was handed over, or the other UEs, or both, will be degraded.

A radio transmission resource partitioning configuration is a slower procedure than a HO. When a HO is initiated the HO procedure needs to be performed quickly while the configura ^¬ tion of a new radio transmission resource partitioning could require longer time. Therefore, reconfiguring the resource portioning at the target BS when a HO request towards the target RN is received may not be sufficient in order to en- sure the success of a HO process.

A new radio transmission resource partitioning configuration may require signalling on the Broadcast Control Channel 200900554

(BCCH) because a radio transmission resource partitioning may involve a Multi-Media Broadcast over a Single Frequency Net ^¬ work (MBSFN) sub-frame allocation. These MBSFN subframes have been proposed initially to make UEs aware that normal trans- mission from the access point is suspended for that subframe and instead a so called Single Frequency Network (SFN) trans ^¬ mission, which is a coordinated transmission from several access points, is performed in that subframe. However instead of a SFN transmission any other operation can be done in- stead, including a backhauling transmission from a mother base station to its assigned RN.

As a consequence of a new radio transmission resource parti ^¬ tioning configuration a new MBSFN sub-frame allocation may be needed in order to provide radio transmission resources for backhauling RNs to the respective mother BS. However, signal ^¬ ling on the BCCH occurs infrequently (for instance every 80 ms) . This may introduce a significant delay between the deci ^¬ sion for a new radio transmission resource partitioning and its configuration. In this respect it is mentioned that the signaling of a resource partitioning can be done over different control channels, e.g. the Physical Downlink Control Channel (PDCCH) for the scheduling, the BCCH for the configuration of MBSFN sub-frames, etc.

There may be a need for improving a partitioning of radio transmission resources in connection with a handover of a user equipment .

Summary of the Invention

This need may be met by the subject matter according to the independent claims. Advantageous embodiments of the present invention are described by the dependent claims.

According to a first aspect of the invention there is pro ^¬ vided a method for partitioning radio transmission resources 200900554

within a telecommunication network. The provided method comprises (a) preparing a handover of a user equipment from a source access point being assigned to a source side of the telecommunication network to a target access point being as- signed to a target side of the telecommunication network, (b) transferring a pre-announcement message from the source side to the target side indicating the handover of the user equip ^¬ ment, wherein the pre-announcement message is indicative for the amount of data traffic being associated with the user equipment, and (c) partitioning the radio transmission re ^¬ sources on the target side of the telecommunication network based on the pre-announcement message.

The described method is based on the idea that a new and ap- propriate radio transmission resource partitioning configura ^¬ tion on the target side of a handover (HO) can be achieved well timed before the handover is initiated i.e. before the target access point is requested to increase its load with the additional data load being associated with the user equipment (UE) . Thereby, the chance for completing the HO successfully may be enhanced because the necessary radio transmission resources for serving the UE on the target side can be reserved for the UE by the described partitioning pro ^¬ cedure on the target side.

Generally speaking, the new radio transmission resource partitioning is computed on the target side taking into account the data traffic that will probably be received soon. It is mentioned that also on the source side there might be carried out preparation (s) with respect to a future source side radio transmission resource partitioning, wherein identified radio transmission resources on the source side will be released after the handover occurs when the user is handed over.

Within this document the term "radio transmission resource" may particularly denote any kind of ability of the telecommu ^¬ nication network to transmit data independently whether the data are payload data, reference data, control data or the 200900554

like via a radio link between a transmitting network element and a receiving network element. Typically, for the data transfer the overall available radio transmission resource is subdivided into a plurality of minimum radio transmission re- source units. This minimum unit may be called a physical re ^¬ source block (PRB), a chunk and/or a slot. The minimum unit may be illustrated as a two-dimensional element within a co ^¬ ordinate system having a time-axis and a frequency-axis . For example, different radio transmission resources may be dis- tinct from each other by the fact that they relate to differ ^¬ ent times of the same frame and/or different frequencies, e.g. two radio transmission resources may relate to the same time but may relate to different frequencies, i.e. the data transmitted by using the two radio transmission resources may be transmitted on different frequencies. In general, radio transmission resources may be distinguishable from each other by any suitable parameter, e.g. frame number, subframe num ^¬ ber, time, used frequency band, coding scheme or the like. In advanced applications, further dimensions of resource units, in particular in the spatial domain, may exist, i.e. a re-use of resources in different spatial layers or beams.

The UE may be any type of communication end device, which is capable of connecting with an arbitrary telecommunication network access point such as a base station or a relay node.

Thereby, the connection may be established in particular via a wireless radio transmission link. In particular the UE may be a cellular mobile phone, a Personal Digital Assistant

(PDA) , a notebook computer and/or any other movable communi- cation device.

Preparing the HO may comprise performing of measurements by the UE in order to determine the radio link qualities between (a) the UE and the source access point on the one hand and (b) the UE and the target access point on the other hand.

Based on the measurement values being indicative for the re ^¬ spective radio link it may be decided which neighboring ac- 200900554

cess point is the most probable candidate for the target ac ^¬ cess point.

According to an embodiment of the invention the source access point of the user equipment is (a) a source base station or (b) a source relay node being connected to a source base sta ^¬ tion. Thereby, the source base station (BS) and, if applica ^¬ ble, also the source relay node (RN) are assigned to the source side of the telecommunication network.

According to the first alternative the UE before the HO is directly served by the source BS. In this document the con ^¬ nection between a UE and a serving BS is called a direct connection or a direct link.

According to the second alternative (bl) the source RN is connected to the source BS via a radio link and (b2) the UE before the HO is served by the source RN. In this document the connection between a RN and its serving BS (mother BS) is called a backhaul link. Further, the radio connection between a UE and a serving RN is called access link.

At this point it is mentioned that on the source side there may be of course at least one further UE and/or one further RN. Thereby, the further RN may preferably also be connected via a backhaul link to the source BS. The further UE may be connected directly to the source BS via a direct link or to one on the RN' s via an access link.

According to a further embodiment of the invention the target access point of the user equipment is (a) a target base sta ^¬ tion or (b) a target relay node being connected to a target base station. Thereby, the target BS and, if applicable, also the target RN are assigned to the target side of the telecom- munication network.

The various connections on the target side may be denominated in accordance with the various connections on the source side 200900554

10

described above. Specifically, the connection between the UE and the target BS may be called a direct link, the connection between the UE and the target RN may be called an access link and the connection between the target RN and the target BS may be called a backhaul link.

Further, in accordance with additional network elements (i.e. further RN' s and/or further UE' s) on the source side there may also be further network elements assigned to the target side. The described partitioning of the radio transmission resources may take into account these further network ele ^¬ ments on the target side. Specifically, radio transmission resources may be taken from at least one direct link, from at least one access link and/or from at least one backhaul link associated with at least one of the further network element in order to have enough radio transmission resources avail ^¬ able for the expected amount of data being associated with the UE which is supposed to be handed over to the target side of the telecommunication network.

According to a further embodiment of the invention the target side of the telecommunication network comprises (a) the target base station and a relay node being connected to the tar ^¬ get base station and (b) partitioning the radio transmission resources on the target side is carried out at the target base station or is negotiated between the target base station and the relay node being connected to the target base sta ^¬ tion .

According to the first alternative the radio transmission re ^¬ source partitioning is done centrally at the target BS, which has the full responsibility to allocate available resources for directly serving UE (s) (direct link(s)), for the communi ^¬ cation with connected RN(s) (backhaul link(s)) and for the RN(s) to serve their UE (s) (access link(s)).

According to the second alternative the radio transmission resource partitioning is negotiated among the target BS and 200900554

11

its connected RN(s) . Thereby, a connected RN respectively the connected RN may be the target RN representing the target ac ^¬ cess point .

According to a further embodiment of the invention partitioning the radio transmission resources on the target side is carried out at a central unit that is responsible to perform the partitioning of radio transmission resources for one or more base stations . Such a central unit could be a so called Self Organizing Network (SON) entity that is responsible for configurations of several base stations and/or relay nodes.

According to a further embodiment of the invention the source side is a source cell and the target side is a target cell. This may mean that the described radio transmission resource partitioning method can be carried out for so called inter cell HO, wherein the UE is handed over from a source cell to a target cell of the telecommunication network. Thereby, at least one RN is involved in the handover. The relay node(s) may be situated within the source cell and/or within the tar ^¬ get cell. Accordingly, the described method may contribute in order to increase the success rate for such inter cell HO.

According to a further embodiment of the invention the pre- announcement message is transferred from a source base sta ^¬ tion to a target base station. If at least one RN is involved on the source side and/or on the target side, i.e. if the UE is attached to a RN on the source side and/or on the target side, no additional messages may be needed between theses RN and their serving BS 's, i.e. between a source RN and the source BS and/or a target RN and the target BS. Thereby, the respective BS may have all information regarding the access links for the served UE. This information may particularly include the radio transmission resource assignment to the re- spective access link and/or to the respective backhaul link. This information may have already been transferred from the respective RN to its serving BS. In this respect it is men ^¬ tioned that such an information flow to the source BS and/or 200900554

12

the target BS is requested by a centralized approach for con ^¬ trolling a HO in a relay enhanced telecommunication network, wherein solely a BS is responsible for controlling the HO of the UE.

Further, it is mentioned that (a) the source BS may represent the source access point for the UE before the HO or (b) the target BS station may represent the target access point for the UE after the HO. In the above mentioned centralized ap- proach no more signaling information is necessary both on the source side and on the target side. In case of a decentral ^¬ ized approach, wherein a RN is at least partially responsible for radio resource partitioning, there may be an exchange of appropriate messages on the source side and/or on the target side. On the source side such an appropriate message may in ^¬ clude information for the source BS in order to enable the source BS to form the described pre-announcement message. On the target side such an appropriate message may include in ^¬ formation for the target RN representing the target access point for a proper radio resource partitioning on the target side in due time before the HO of the UE is carried out.

According to a further embodiment of the invention (a) the source access point is a source relay node being connected to a source base station, (b) the target access point is a tar ^¬ get relay node being connected to a target base station and (c) the pre-announcement message is transferred from the source relay node to the target relay node.

In this further embodiment of the invention a HO from a source RN to a target RN is considered. Thereby, the source BS may be different from the target BS, i.e. the source side is a source cell and the target side is a target cell. In this respect it is mentioned that other configurations of a HO, wherein either on the source side or on the target side the UE is connected to the respective BS via a direct link, are from a technical point of view simplifications of this case . 200900554

13

Generally speaking, the serving RN respectively the source RN pre-announces to the target RN the amount of UE data traffic that it will try soon to handover to the target RN. The tar- get BS can use this information received indirectly from the source RN respectively directly from the source BS and, if applicable also corresponding information from other neighboring RN(s) respectively BS (s) in order to pre- configure a resource partitioning that will better accommo- date the data traffic that the source BS respectively the source RN and, if applicable also the neighboring BS (s) re ^¬ spectively the neighboring RN(s), will try to handover to it and/or to its connected RN(s).

It is mentioned that the source BS may aggregate the indica ^¬ tions from several of its subordinate RNs and only send a comprehensive indication to the target BS respectively to the target RN. This may provide the advantage that the signaling load within the telecommunication network may be signifi- cantly reduced.

According to a further embodiment of the invention (a) the source access point of the user equipment is a source base station, (b) the target access point of the user equipment is a target relay node being connected to a target base station and (c) the source base station and the target base station are the same entity within the telecommunication network. This may mean that the described radio transmission resource partitioning method can be carried out for so called intra- cell HO, wherein the UE is handed over from a source access point to a target access point and wherein both access points are assigned to the same cell of the telecommunication net ^¬ work .

According to a further embodiment of the invention the method further comprises (a) carrying out the handover of the user equipment from the source access point to the target access point, and (b) partitioning radio transmission resources on 200900554

14

the source side based on the amount of data traffic that is associated with the user equipment. This may provide the ad ^¬ vantage that the radio transmission resources, which are no more needed after the HO of the UE can be assigned to one or more other radio connections on the source side. Thereby, the radio connections, which may be provided with more radio transmission resources, may be a direct link, an access link and/or a backhaul link between different types of network elements on the source side. The mentioned network elements may be UE (s), RN(s) and/or BS (s) . Only when the UE is handed over the new partitioning radio transmission resources may take place and the free radio transmission resources may be used e.g. for another UE.

The partitioning procedure may be carried out based on a value of the pre-announcement message, which value is indica ^¬ tive for the amount of data traffic being associated with the user equipment .

It is mentioned that the radio transmission resource parti ^¬ tioning on the source side can also be pre-announced before the handover of the UE is carried out. However, this source side radio transmission resource, which will be released on the source side because of the handover, cannot be used for other network elements before the UE has left the source side .

According to a further embodiment of the invention (a) parti ^¬ tioning radio transmission resources on the target side com- prises allocating radio transmission resources for the user equipment, and (b) after partitioning the radio transmission resources and before carrying out the handover of the user equipment the allocated radio transmission resources are used for another radio data transfer. This may mean that the tar- get BS can temporarily use these allocated radio transmission resources for another purpose until the UE is handed over from the source side to the target side, wherein the target BS or a target RN represents the target access point. The al- 200900554

15

located radio transmission resources may also be denoted pre- assigned and/or reserved radio transmission resources.

For example, the allocated radio transmission resources may be used by UE (s) being directly connected to the target BS. But since the target BS needs the full flexibility to quickly cancel this allocation of radio transmission resources, these resources should be used only for services such as for in ^¬ stance best effort services, which can accept such a quick resource withdrawal. Therefore, the allocated radio transmis ^¬ sion resources should only be assigned to backhaul and access links or direct links (if a target access point is a target base station) after the UE has been handed over to the target side .

According to a further embodiment of the invention the pre- announcement message comprises an identification of the tar ^¬ get side of the telecommunication network. This identifica ^¬ tion may be for instance an ID symbol of the target access point, the target BS and/or if applicable the target RN. Gen ^¬ erally speaking, in the pre-announcement message instead of having only the amount of data traffic being associated with the UE also an identification tag for each candidate for a target BS respectively target RN could be added to the infor- mation about the data traffic which is supposed to be handed over in due time.

It has to be mentioned that also further or other information may be added to the pre-announcement message. Such informa- tion may be for instance (a) at what time the HO is expected, (b) the quality of service of the data traffic that will be handed over and/or (c) any other information that may impact the forthcoming radio resource partitioning.

It is mentioned that the described method may be simultaneous applied for different UEs, which are originally assigned to the source side and which may be handed over to different target sides. In this case, it is possible to group the in- 200900554

16

formation about different data traffics per target BS and send different HO pre-announcement message to different tar ^¬ get sides (target base stations), or the source BS could send the same information with a cumulative message to all neighboring BS (including information also designated to other BS(s)) . This could help to inform the involved BS also about the current or expected future status of neighboring sides of the telecommunication network. Further, such a cumulative information could be useful for radio transmission re- source partitioning, data load balancing, interference coor ^¬ dination, etc.

Further, the pre-announcement message may comprise a time-out information. This time-out information may indicate how long an accomplished partitioning of the radio transmission re ^¬ sources (in order to be ready for accepting the amount of data traffic being associated with the UE) is supposed to be valid. This may avoid that radio transmission resources are allocated for a too long time waiting for an HO of UEs that will never happen and that the allocated radio transmission resources cannot be used by other RN(s) and/or other UE (s) in the future .

According to a further aspect of the invention there is pro- vided a source side network element for controlling a parti ^¬ tioning of radio transmission resources within a telecommunication network in connection with a handover of a user equipment from a source access point being assigned to a source side of the telecommunication network to a target access point being assigned to a target side of the telecommunica ^¬ tion network. The provided source side network element com ^¬ prises a transmitting unit for transmitting a pre- announcement message from the source side to the target side indicating the handover of the user equipment, wherein the pre-announcement message is indicative for the amount of data traffic being associated with the user equipment and wherein the preannouncement message is adapted for controlling the 200900554

17

partitioning of the radio transmission resources on the target side.

Also this aspect of the invention is based on the idea that a new and appropriate radio transmission resource partitioning configuration can be provided on the target side of a HO in due time before the target access point is requested to in ^¬ crease its load with the additional data load being associ ^¬ ated with the user equipment .

With respect to the HO the source side network element is lo ^¬ cated on the source side of the telecommunication network. The described source side network element may be the above mentioned source BS or the above mentioned source RN.

According to a further aspect of the invention there is pro ^¬ vided a target side network element for controlling a parti ^¬ tioning of radio transmission resources within a telecommunication network in connection with a handover of a user equip- ment from a source access point being assigned to a source side of the telecommunication network to a target access point being assigned to a target side of the telecommunica ^¬ tion network. The provided target side network element com ^¬ prises a receiving unit for receiving a pre-announcement mes- sage from the source side to the target side indicating the handover of the user equipment, wherein the pre-announcement message is indicative for the amount of data traffic being associated with the user equipment and wherein the prean- nouncement message is adapted for controlling the partition- ing of the radio transmission resources on the target side.

Also this aspect of the invention is based on the idea that an appropriate adaptation of a radio transmission resource partitioning configuration can be provided on the target side of a HO in due time before the HO is actually carried out.

With respect to the HO the target side network element is lo ^¬ cated on the target side of the telecommunication network. 200900554

18

The described source side network element may be the above mentioned target BS or the above mentioned target RN.

According to a further aspect of the invention there is pro- vided a computer program for partitioning radio transmission resources within a telecommunication network. The computer program, when being executed by a data processor, is adapted for controlling the above described method for partitioning radio transmission resources within a telecommunication net- work.

As used herein, reference to a computer program is intended to be equivalent to a reference to a program element and/or to a computer readable medium containing instructions for controlling a computer system to coordinate the performance of the above-described method.

The computer program may be implemented as computer readable instruction code in any suitable programming language, such as, for example, JAVA, C++, and may be stored on a computer- readable medium (removable disk, volatile or non-volatile memory, embedded memory/processor, etc.) . The instruction code is operable to program a computer or any other programmable device to carry out the intended functions. The com- puter program may be available from a network, such as the World Wide Web, from which it may be downloaded.

The invention may be realized by means of a computer program respectively software. However, the invention may also be re- alized by means of one or more specific electronic circuits respectively hardware. Furthermore, the invention may also be realized in a hybrid form, i.e. in a combination of software modules and hardware modules .

It has to be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with ref ^¬ erence to method type claims whereas other embodiments have 200900554

19

been described with reference to apparatus type claims. How ^¬ ever, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the method type claims and features of the appa ^¬ ratus type claims is considered as to be disclosed with this application .

The aspects defined above and further aspects of the present invention are apparent from the example of embodiment to be described hereinafter and are explained with reference to the example of embodiment. The invention will be described in more detail hereinafter with reference to an example of em ^¬ bodiment but to which the invention is not limited.

Brief Description of the Drawings

Figure 1 shows a transactional flow diagram illustrating a message flow between various network elements which in accordance with an embodiment of the invention are adapted for carrying out a radio transmission resources partitioning in due time before a handover of a user equipment from a source relay node to a target relay node is carried out.

Figure 2 shows a common handover of a UE from a source relay node to a target relay node, wherein source relay node and target relay node are connected to different base stations.

Detailed Description

The illustration in the drawing is schematically.

Figure 1 shows a transactional flow diagram illustrating a message flow between a source RN and a target RN in order to 200900554

20

(a) pre-announce a possible HO of a non depicted UE from the source RN to the target RN and (b) to carry out a radio transmission resources partitioning in due time before the HO. The source RN corresponds to the relay node RNl depicted in Figure 2. The target RN corresponds to the relay node RN2c depicted in Figure 2. The source RN is connected to a source BS, which corresponds to the base station BSl depicted in Figure 2. The target RN is connected to a target BS, which corresponds to the base station BS2 depicted in Figure 2.

The source RN (and each RN being backhauled by the source BS) collects measurements from its attached UEs which are ex ^¬ pected to be handed over. Thereby, the node id (ID) of a can ^¬ didate BS/RN and the amount of traffic (TP) expected to be handed over with the UE to each of the candidate BS/RN can be determined. In the scenario shown in Figure 1, for each can ^¬ didate BS and RN information about the ID and about the TP have been acquired by the respective RN. This information is inserted into a RN-to-BS indication message 110 sent from the source RN to the source BS.

The source BS may collect such information received from dif ^¬ ferent backhauled RNs together with information for UEs being directly connected to the source BS. Then, available informa- tion about ID and TP at the source BS are grouped per neighbouring target BS and backhauled target RNs and are separately sent to the neighbouring target BSs . Thereby, a BS-to-BS indication message 120 is employed for each target BS and each RN being connected to the target BS.

The source BS may also send all information without grouping according to the target BS. The target BS may select from re ^¬ ceived message only the relevant information regarding itself and connected RNs.

In the following the procedure is explained for the source RN and source BS for the sake of clarity. However, it is obvi ^¬ ously done at each RN and BS within the telecommunication 200900554

21

network. The source BS may also aggregate the indications from several of its subordinate source RNs and only send a comprehensive indication to the neighbouring target BSs and target RNs .

Upon receiving these messages 120 from the neighbouring source BSs, each target BS performs the resource partitioning taking into account the amount of traffic that should be ex ^¬ pected to be handed over soon to it and its backhauled RNs. The new resource partitioning is announced to its backhauled RNs, i.e. the target BS in Figure 1, by means of a resource partitioning indication message 130. However, only when the load balancing and/or the HO of UEs between source RN and target RN (see reference numeral 150 in Figure 1) have been performed, the resource partitioning is really confirmed from the target BS to its backhauled target RN by a resource par ^¬ titioning confirmation message 170. Otherwise, if the HO is going to be rejected anyhow there is no need to take the ad ^¬ ditional traffic into account.

According to the embodiment described here after accomplish ^¬ ing the HO there is further carried out a resource partition ^¬ ing on the source side of the telecommunication network. Before actually accomplishing the HO this resource partitioning is pre-announced from the source BS to the source RN by means of a resource partitioning indication message 140. After having accomplished the HO and the resource partitioning also on the source side (see reference numeral 150) a corresponding resource partitioning confirmation message 160 is sent from the source BS to the source RN.

It is mentioned that the messages 110 and 140 can be obvi ^¬ ously also sent between target BS and target RN when they are on a source side of a handover. The same holds for message 130, which may be also sent at the source side. Further, the message 130 between target BS target RN and the message 140 between source BS and source RN may be combined. This may mean that the messages 130 and 140 may have the same format. 200900554

22

For the same reason, also messages 160 and 170 may be com ^¬ bined.

It has to be mentioned that (a) the resource partitioning in- dication message 130 from the target BS to the target RN and (b) the resource partitioning indication message 140 from the source BS to the source RN does not have a time order. In Figure 1 the resource partitioning indication message 130 from the target BS to the target RN occurs first. However, also the reverse time order of the two resource partitioning indication messages may be possible. At the source side, the resource partitioning indication message 140 may also occur before the BS-to-BS indication message 120. The same also holds for the resource partitioning confirmation messages 160 and 170 between (a) the target BS and the target RN and (b) the source BS and the source RN.

It is further mentioned that in Figure 1 it is illustrated the message flow for implementing the indication or the pre- announcement of the data traffic that the source RN will try to handover soon to the target RN if the decentralized ap ^¬ proach for handover is assumed. The RN-to-BS indication message 110 and the Resource partitioning indication message 130 may be not needed in case the centralized approach for hand- over is used, because it is assumed that information regard ^¬ ing the access links (between RN and served UEs) have already been transferred from the RNs to the respective BS (and therefore the RN-to-BS indication message 110 may not be needed) as requested by the centralized approach. The cen- tralized approach does not require that BS involves RNs, therefore it is not needed that the RNs are informed about the resource partitioning by means of the resource partition ^¬ ing indication message 130, instead the BS decides centrally.

The described method for partitioning radio transmission re ^¬ sources within a telecommunication network based on a data traffic pre-announcement message may particularly comprise the following advantages: 200900554

23

(A) The HO of UEs to target RNs may be accomplished with a higher success probability. If enough radio transmission re ^¬ sources can be used for the backhaul and access link on the target side the HO of the UE from the source access point (e.g. the source RN) to the target access point (e.g. the target RN) will be successful. Radio transmission resource configurations can be started in advance before the actual HO takes place. Even if the radio transmission resource recon- figuration procedure requires more time than the HO and/or if the HO needs to be completed quickly, an appropriate radio transmission resource configuration will be in place once it is needed.

(B) The target BS can use pre-assigned resources for other purpose until UEs are handed over from the source RN to the target RN. For example, the pre-assigned resources can be used by UEs directly connected to the target BS. However, since the target BS needs the full flexibility to withdraw or to cancel the allocation of these pre-assigned resources, these resources should be used only for services that can ac ^¬ cept such a cancellation or a withdrawal, respectively. Such non challenging services are e.g. best effort services. The pre-assigned resources are then really assigned to the back- haul and access links only when UEs are actually handed over to the target RN.

(C) The load balancing can be performed taking into account the pre-assigned resources to the backhaul and access links at the target RN. Therefore, if there are available resources identified by the target BS for the target RN, the load bal ^¬ ancing can trigger a UE handover from the source RN (which is overloaded) to the target RN.

(D) The described pre-announcing of the new resource parti ^¬ tioning (and therefore the new MBSFN sub-frame configuration in case it is used for backhauling traffic) helps to quickly establish the new resource partitioning as soon as it is con- 200900554

24

firmed because the RN could already announce to its served UEs the sub-frames used as MBSFN sub-frames according to the new resource partitioning. In any case (as discussed above) these may be resources used by BS for serving directly con- nected UEs while the resource partitioning is not yet con ^¬ firmed.

It should be noted that the term "comprising" does not ex ^¬ clude other elements or steps and "a" or "an" does not ex- elude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be con ^¬ strued as limiting the scope of the claims.

0900554

25 st of re ference s igns :

110 RN-to-BS indication message 120 BS-to-BS indication message 130 resource partitioning indication message 140 resource partitioning indication message 150 load balancing and/or HO 160 resource partitioning confirmation message 170 resource partitioning confirmation message

BSl source base station

BS2 target base station

CAl source coverage area

CA2 target coverage area

RNl source relay node

RN2a relay node

RN2b relay node

RN2c target relay node

UE user equipment