WO2011135096A1

WO2011135096A1 - Radio base station, control node, and methods for supporting a serving cell change of a mobile terminal in a radio communications system

Info

Publication number: WO2011135096A1
Application number: PCT/EP2011/056920
Authority: WO
Inventors: Masatoshi Nakamata
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-04-30
Filing date: 2011-05-02
Publication date: 2011-11-03

Abstract

The invention relates to supporting a serving cell change of a mobile terminal (25) in a radio communications system (2), comprising radio cells (22, 23a - 23c), a radio base station (21a) spanning a first radio cell (22), with a first radio link (26), and a control node (24a, 24b) by the steps of : - sending (11), from the control node (24a) towards the radio base station, a radio link establish request message (31) comprising a radio resource parameter (32) concerning an establishing of a further radio link (29a- 29c) (21a- 21c) between the radio base station and the mobile terminal (25), - establishing (12), by the radio base station (21a- 21c), the further radio link, according to the radio link establish request message, - responding (13) to the radio link establish request message by sending, from the radio base station towards the control node (24a), a radio link establish response message (33), comprising a preconfiguration parameter set (34), the preconfiguration parameter set comprising radio configuration data (3411-3413) selected depending on the radio resource parameter (32), said radio configuration data to be used for continued transmission by the mobile terminal on the first radio link (26) following said serving cell change of the mobile terminal (25) from the first radio cell to a second radio cell (23a- 23c), and - forwarding (14), by the control node (24a), towards the mobile terminal, an active set update message comprising the selected radio configuration data.

Description

DESCRIPTION

TITLE

Radio base station, control node, and methods for supporting a serving cell change of a mobile terminal in a radio commu^¬ nications system

FIELD OF THE INVENTION

The present invention relates to a radio base station, con^¬ trol node, and methods for supporting a serving cell change of a mobile terminal in a radio communications system. Par^¬ ticularly, the present invention refers to a radio base sta^¬ tion comprising means for supporting of a serving cell change of a mobile terminal; a control node comprising means for supporting of a serving cell change of a mobile terminal; and corresponding methods for supporting a serving cell change of a mobile terminal.

BACKGROUND OF THE INVENTION As mentioned above, the present invention addresses a radio base station, control node, and methods for supporting a serving cell change of a mobile terminal in a radio communi^¬ cations system. In a radio communications system according to the specifica^¬ tions by the 3^rd Generation Partnership Project (3GPP) for Wideband Code Division Multiple Access (WCDMA) and High Speed Packet Access (HSPA) , Rel.8, a radio base station, or Node B, spans one or more radio cells. Within a radio cell, radio communications links, so-called Radio Links (RL) , are estab^¬ lished between the Node B and one or more User equipments (UE) . A control node, or Radio Network Controller (RNC) , man- ages and controls radio resources of its connected Node Bs and UEs within the cells spanned by the Node Bs .

Since Rel.5 of the above mentioned 3GPP specification, effort has been spent to increase bandwidth and throughput of data. The underlying concept is comprised in High Speed Packet Ac^¬ cess (HSPA) , with HSPA comprising corresponding parts for uplink (High Speed Uplink Packet Access, HSUPA) and downlink (High Speed Downlink Packet Access, HSDPA) . In this context, the Enhanced Dedicated Channel (E-DCH) was introduced. The E- DCH comprises channels for high speed uplink data transfer from the UE to the Node B.

With regard to radio links used for connections in the radio communications system, the Active Set of a UE comprises of a set of radio links between the UE and Node Bs to which the UE is connected and able to transmit data.

An Active Set Update (ASU) is necessary whenever a radio link has to be changed, removed from or added to the Active Set of a UE, e.g. due to changing radio conditions. For the Active Set Update, an Active Set Update message is used.

For supporting a serving cell change of a mobile terminal, the Enhanced Serving cell change procedure was specified in

3GPP, Rel.8. According to the specification document TS25.308 V9.1.0, chapter 9, Mobility procedures, a serving cell change facilitates the transfer of the role of serving radio link from one radio link belonging to the source cell to a radio link belonging to the target cell (non serving radio link) .

In this context, a Radio Link Set (RLS) of a UE is defined as a set of physical radio links established between the UE and its connected Node Bs . The network procedures "radio link set up" and "radio link addition" in order to modify the RLS, wherein a "radio link set up" is the physical creation and addition of a radio link, i.e. channel, to the RLS, while a "radio link addition" is the addition of an already existing radio link, i.e. channel, to the RLS. To prevent e.g. call loss for a UE moving from the coverage area of the source cell, serving the UE, to the target cell, not yet serving the UE, the RNC configures and coordinates the radio resources involved in the radio links between

Node B and UE .

The E-SCC procedure as specified in the 3GPP specifications comprises a set of steps for configuring radio resources of Node Bs and the UE involved in the serving cell change. The E-SCC procedure is managed by the serving RNC (SRNC) of the UE.

However, the E-SCC procedure as specified has several disad- vantages. For instance, in case the serving RL becomes the non-serving RL, due to UE mobility as described above, the SRNC needs to reconfigure resources allocated to the serving RL . Furthermore, updated radio resource parameters need to be forwarded to the UE by Active Set Update message due to the change of the serving RL into a non-serving RL in order to maintain the connection.

This requires additional signalling between Node B and the RNC which might cause a delay of the handover. The delay in turn might cause a dropped call as, due to fast changing ra^¬ dio conditions, the serving RL radio conditions might already be insufficient while the radio link of the target cell which is to become the serving radio link is not yet properly con^¬ figured .

There might also be situations in which the E-SCC procedure as specified might not work as to incorrect radio resource configuration . The above problems might result in a degradation of service quality. Thus, there is still a need for an improved E-SCC procedure . SUMMARY OF THE INVENTION

Object of the present invention is improving of the E-SCC procedure to avoid the above mentioned problems.

This object is achieved by a radio base station comprising features according to claim 1, a control node comprising fea^¬ tures according to claim 2, and methods comprising features according to claims 3, 4 and 5.

Further embodiments of the present invention are provided with the corresponding dependent claims.

The object of the present invention is achieved by a radio base station for supporting a serving cell change of a mobile terminal in a radio communications system, the radio communi^¬ cations system comprising radio cells and a control node, with the radio base station spanning a first radio cell. The radio base station comprises means configured for receiving, from the control node, a radio link establish request mes^¬ sage, the radio link establish request message comprising a radio resource parameter concerning an establishing of a further radio link between the radio base station and the mobile terminal. Further, the radio base station comprises means for establishing the further radio link, according to the radio link establish request message, and for responding to the ra^¬ dio link establish request message by sending, towards the control node, a radio link establish response message, the radio link establish response message comprising a precon- figuration parameter set, the preconfiguration parameter set comprising radio configuration data selected depending on the radio resource parameter, said radio configuration data to be used for continued transmission by the mobile terminal on the first radio link following said serving cell change of the mobile terminal from the first radio cell to a second radio cell . By use of the radio base station supporting a serving cell change of a mobile terminal in a radio communications system, an improved service quality might be achieved compared to the E-SCC procedure as specified in 3GPP, Rel.8.

The object of the present invention is also achieved by a control node for supporting a serving cell change of a mobile terminal in a radio communications system, the radio communi^¬ cations system comprising radio cells and a radio base sta- tion spanning a first radio cell. The control node comprises means configured for sending, towards the radio base station, a radio link establish request message, the radio link estab^¬ lish request message comprising a radio resource parameter concerning an establishing of a further radio link between the radio base station and the mobile terminal. Further the control node comprises means configured for receiving, from the radio base station, a radio link establish response mes^¬ sage, the radio link establish response message comprising a preconfiguration parameter set, the preconfiguration parame- ter set comprising radio configuration data selected depend^¬ ing on the radio resource parameter. The radio configuration data is to be used for continued transmission by the mobile terminal on the first radio link following said serving cell change of the mobile terminal from the first radio cell to a second radio cell. Further, the control node comprises means configured for forwarding, towards the mobile terminal, an active set update message comprising the selected radio con^¬ figuration data. The object of the present invention is also achieved by a method for supporting a serving cell change of a mobile ter^¬ minal in a radio communications system, the radio communica^¬ tions system comprising radio cells, a control node, and a radio base station, with the radio base station spanning a first radio cell. The method comprises the following steps performed by the radio base station:

- receiving, from the control node, a radio link establish request message, the radio link establish request mes- sage comprising a radio resource parameter concerning an establishing of a further radio link between the radio base station and the mobile terminal;

establishing the further radio link, according to the radio link establish request message; and

responding to the radio link establish request message by sending, towards the control node, a radio link es^¬ tablish response message, the radio link establish re^¬ sponse message comprising a preconfiguration parameter set, the preconfiguration parameter set comprising radio configuration data selected depending on the radio resource parameter, said radio configuration data to be used for continued transmission by the mobile terminal on the first radio link following said serving cell change of the mobile terminal from the first radio cell to a second radio cell.

The object of the present invention is also achieved by a method for supporting a serving cell change of a mobile ter- minal in a radio communications system, the radio communica^¬ tions system comprising radio cells, a radio base station spanning a first radio cell, with the first radio cell com^¬ prising a first radio link, and a control node. The method comprises the following steps performed by the control node:

- sending, towards the radio base station, a radio link establish request message, the radio link establish re^¬ quest message comprising a radio resource parameter con^¬ cerning an establishing of a further radio link between the radio base station and the mobile terminal;

- receiving, from the radio base station, a radio link establish response message, the radio link establish re^¬ sponse message comprising a preconfiguration parameter set, the preconfiguration parameter set comprising radio configuration data selected depending on the radio re- source parameter, said radio configuration data to be used for continued transmission by the mobile terminal on the first radio link following said serving cell change of the mobile terminal from the first radio cell to a second radio cell; and

- forwarding, towards the mobile terminal, an active set update message comprising the selected radio configura- tion data.

The object of the present invention is also achieved by a method for supporting a serving cell change of a mobile ter^¬ minal in a radio communications system, the radio communica- tions system comprising radio cells, a radio base station spanning a first radio cell, with the first radio cell com^¬ prising a first radio link, and a control node. The method comprises the following steps:

- sending, from the control node towards the radio base station, a radio link establish request message, the ra^¬ dio link establish request message comprising a radio resource parameter concerning an establishing of a further radio link between the radio base station and the mobile terminal,

- establishing, by the radio base station, the further radio link, according to the radio link establish request message,

- responding to the radio link establish request message by sending, from the radio base station towards the con- trol node, a radio link establish response message, the radio link establish response message comprising a pre- configuration parameter set, the preconfiguration parameter set comprising radio configuration data selected depending on the radio resource parameter, said radio configuration data to be used for continued transmission by the mobile terminal on the first radio link following said serving cell change of the mobile terminal from the first radio cell to a second radio cell, and

- forwarding, by the control node, towards the mobile ter- minal, an active set update message comprising the se^¬ lected radio configuration data. According to some embodiments of the present invention, the radio configuration data comprises an element, the element comprising data for configuring the radio link related to channelization code, signature sequence, and release indica- tor. This ensures that the radio link can be maintained and used after the serving cell change of the mobile terminal from the first radio cell to the second radio cell.

According to some embodiments of the present invention, the second radio cell is spanned by a second radio base station. This applies for inter-Node B serving cell change.

According to some embodiments of the present invention, the second radio base station is connected to the control node.

According to some embodiments of the present invention, the second radio base station is connected to a second control node using a connection to the control node. According to some embodiments of the present invention, the method further comprising the step of sending, from the control node to the radio base station, a radio link reconfigu^¬ ration request message comprising an indicator, said indicator indicating resources previously reserved for the radio configuration data to be unreserved from the radio base sta^¬ tion .

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the following description of the preferred embodiments of the invention read in conjunction with the attached drawings, in which : Fig. 1 shows an implementation of the present invention according to an embodiment of the present invention; Fig. 2 shows a radio communications system according to 3GPP Rel.8; and

Fig. 3 shows an implementation of the present invention according to a further embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In following the embodiments of the present invention are provided exemplary with regard to.

Fig. 1 shows an implementation of the present invention according to an embodiment of the present invention. The method 1 for supporting a serving cell change of a mobile terminal 25 in a radio communications system 2, the radio communications system 2 comprising radio cells 22, 23a, a radio base station 21a spanning a first radio cell 22, with the first radio cell 22 comprising a first radio link 26, and a control node 24a, 24b, comprises the following steps:

- In a first step 11, sending, from the control node 24a to^¬ wards the radio base station 21a, a radio link establish re^¬ quest message 31, the radio link establish request message (31) comprising

a radio resource parameter concerning an establishing of a further radio link 29a, 29b, 29c between the radio base sta^¬ tion 21a, 21b, 21c and the mobile terminal 25; - In a second step 12, establishing, by the radio base sta^¬ tion 21a, 21b, 21c, the further radio link 29a, 29b, 29c, ac^¬ cording to the radio link establish request message;

- In a third step 13, responding to the radio link establish request message by sending, from the radio base station 21a,

21b, 21c towards the control node 24a, a radio link establish response message, the radio link establish response message comprising a preconfiguration parameter set 34, the preconfiguration parameter set 34 comprising

radio configuration data selected depending on the radio re^¬ source parameter, said radio configuration data to be used for continued transmission by the mobile terminal 25 on the first radio link 26 following said serving cell change of the mobile terminal 25 from the first radio cell 22 to a further radio cell 23a, 23b, 23c; and - In a fourth step 14, forwarding, by the control node 24a, towards the mobile terminal 25, an active set update message comprising the selected radio configuration data.

Fig. 2 shows a radio communications system according to 3GPP Rel.8.

Control nodes, or RNCs 24a, 24b, are connected via an Iub in^¬ terface 27 with radio base stations, or Node Bs 21a, 21b, 21c. Each radio base station 21a, 21b, 21c spans one or more radio cells 22, 23a, 23b, 23c. A mobile terminal, or user equipment UE 25, is located in the coverage area of one of the radio cells 22, having a first radio link 26 to its serv^¬ ing base station 21a. Further radio links 29a, 29b, 29c to the serving base station 21a of the UE or to the further base stations 21b, 21c are established for improving overall re^¬ ception quality. A further RNC 24b can be connected to the RNC 24a by an Iur interface 28. The RNC 24a is in charge of resource allocations on the air interface, including re^¬ sources maintained in radio base stations controlled by the further RNC 24b. Therefore, control messages sent over the

Iub interface are similarly transferred via Iur interface 28 to instruct the further RNC 24b to forward the control mes^¬ sages to the related base stations 21c. Fig. 3 shows an implementation of the present invention. Particularly, Fig. 3 shows a message flow diagram illustrating a method according to embodiments of the present invention for supporting a serving cell change of a mobile terminal. In the scenario shown in Fig. 3, the control node 24a, or RNC, decided to setup a radio link 26 between the mobile ter^¬ minal 25, or UE, and a radio base station 21a, or Node B, spanning a first radio cell 22.

As already described above, a new radio link can be estab^¬ lished between the UE and the radio base station by adding an already existing radio link to the RLS or by adding a further physically created radio link to the RLS.

With regard to the radio links contained in the RLS, the ra^¬ dio links can further be distinguished in "serving" and "non- serving" radio links.

A serving radio link is a radio link which is used, amongst others, for controlling the communication connection to the connected UE, while a non-serving radio link is used as a further, redundant transmission channel to improve the over- all service quality. Generally, a serving radio link is lo^¬ cated in the radio cell with the best radio conditions for the mobile terminal.

During E-SCC procedure, it might occur that the roles of a serving radio link and a non-serving radio link are changed.

In the scenario shown in Fig. 3, a first radio link 26 has the role of a serving radio link according to the above defi^¬ nition .

In a first step 11, the control node 24a sends a radio link setup request message 31 towards the radio base station 21a, 21b, 21c comprising a radio resource parameter 32, e.g. "Non- serving RL preconfiguration setup", which provides informa- tion on a further radio link 29a, 29b, 29c to become the new serving radio link.

There are at least three situations foreseen: According to a first situation, the further radio link 29a, 29b, 29c which is to become the new serving radio link of the UE 25 is to be established in the same base station 21a.

In the following, to establish a radio link in this context means, as described above, to add an existing physical radio link to the RLS of the UE 25, or to set up, i.e. physically create a radio link in a further base station 21b, 21c which has not yet any radio link to the UE 25.

According to a second situation, the further radio link 29b, 29c to become the new serving radio link of the UE 25 is to be established not in the same base station 21a but in a fur- ther base station 21b, 21c.

According to a third situation, the further radio link 29a, 29b, 29c to become the new serving radio link of the UE 25 is either to be established in the same base station 21a or in a further base station 21b, 21c, as the control node 24a did not yet decide where the new serving radio link of the UE will be located.

Each of those situations may occur when a further radio link 29a, 29b, 29c of a UE 25 is to be established.

For example, if the first radio link 26 is the only radio link established between the first base station 21a and the UE 25, the first radio link 26 is the current serving radio link of the UE 25, and the radio resource parameter 32 may indicate that the new serving radio link to be established will be located in same base station.

If the new serving radio link will be established in a fur- ther base station 21b, 21c, the radio resource parameter 32 may indicate that the new serving radio link will not be lo^¬ cated in the same base station. In the case that the control node 24a did not yet decide on where the new serving radio link will be established, the ra^¬ dio resource parameter 32 may indicate that the new serving radio link will or will not be located in the same base sta- tion, i.e. the base station 21a should consider information for both cases.

The base station 21a, 21b, 21c receives the request 31 to es^¬ tablish a further radio link 29a, 29b, 29c.

In a second step 12, the base station 21a, 21b, 21c estab^¬ lishes the further radio link 29a, 29b, 29c according to the received information of the radio link setup request message 31.

In a third step 13, when establishing of the further radio link 29a, 29b, 29c is completed, the base station 21a, 21b, 21c responds to the request 31 by sending a radio link setup response message 33 towards the control node 24a.

The radio link setup response message 33 comprises a precon- figuration parameter set 34, e.g. "Non-serving RL preconfigu- ration info". The element 341 of the preconfiguration parameter set 34 defines a radio configuration data 3411, 3412, 3413 correspond^¬ ing to the location of the new serving radio link 29a, 29b, 29c related to the base station 21a.

Different radio configuration data are selected by the base station 21a according to the location of the new serving radio link 29a, 29b, 29c related to the base station 21a.

The element 341 can take several values:

- new serving RL in base station,

- new serving RL not in base station,

- new serving RL in base station as well as not in base station . Possible radio configurations are, thus, new serving RL in base station, new serving RL not in base station, new serving RL in base station as well as not in base station, with the element 341 taking the respective value.

The base station selects the suitable radio configuration data depending on received radio resource parameter 32. The element 341 of the preconfiguration parameter set comprises radio configuration data 3411, 3412, 3413 to be used for con- tinued transmission by the UE 25 on the first radio link fol^¬ lowing a change of the UE from the first cell to a second cell. The element 341 defines the radio resources to be used by the UE later on in case the RL is not the serving RL of the UE.

Depending on the received radio resource parameter 32, the base station 21a sets up different preconfiguration parameter sets 34 which are provided towards the RNC 24a in the re^¬ sponse message 33.

If the base station 21a provides radio configuration data 3411, 3412, 3413 related to the element 341 corresponding to the case new serving RL in base station 21a in the precon- figuration parameter set (34), the following applies:

In case RNC indicates Node B "both case" in Preconfiguration Setup, there are following possibilities:

- Node B does not include Non-Serving RL Preconfiguration Info for the RL in the RL Addition/Setup Response in case Node B continues to use current configuration for both

- Node B includes information for "New serving RL is in the Node B" only in case it use the new configuration for the case and continue to use current configuration for other case .

- Node B includes information for "New serving RL is Not in the Node B" only in case it use the new configuration for the case and continue to use current configuration for other case . - Node B includes both information for "New serving RL is in the Node B" and "New serving RL is Not in the Node B in case the Node B use new different configuration for both cases

- Node B includes one information for "New serving RL is in the Node B and New serving RL is Not in the Node B in case the Node B use new same configuration for both cases

In a fourth step 14, the RNC 24a forwards towards the UE 25 an active set update message 35 comprising the radio configu- ration data provided by the base station. Those radio con^¬ figuration data have been selected by the base station 21a depending on the provided radio resource parameter. The RNC forwards the received radio configuration data to the UE which correspond to the location of the new serving RL .

-k -k -k -k -k -k -k -k -k -k

However, there are following limitations on ESCC in current NBAP/RNSAP specifications:

(Issue 1) .

1) Node B can not provide preconfiguration information when the serving RL(in the node B) becomes non-serving RL at RL Setup/Addition

For example for Intra Node B ESCC below

Node Bl (21a): Cell 1 (22) /Cell 2 (23a)

Case: UE (25) has HS-DSCH RL (26) over cell under Node B. RLs are established over Celll (22)/Cell2 (23b) at the same time and HS-DSCH setup ( Intra-Node SCC) at Cell 1 (22) and eSCC to Cell 2 (23a) later.

Since current NBAP/RNSAP does not allow Node B (21a) to pro^¬ vide preconfiguration information (34) when the serving RL becomes non-serving RL . Therefore an extra RL Reconfiguration procedure needs to be executed before ASU (35) as shown in figure 4. This would generates some delay for ASU procedure and lub signalling flow and for avoiding the delay, RNC shall force Node B to keep same configuration of serving RL for non- serving RL after ESCC.

Same problem is generated in Inter-Node B ESCC in Figure 5: Node Bl (21a): Celll (22), Node B2 (21b): Cell 2 (23b);

HS-DSCH is setup at Celll (22) and ESCC to Cell2 (23b);

(Issue 2)

In addition, the solution in which the Node B provides the information for preconfiguration for non-serving RL has drawback that Node B reserves the allocated resource for the pre- configuration until execution of ESCC or cancelling by execution of Synchronised RL Preparation Procedure (note : currently specification has no mean since the preconfiguration info itself does not exist) and Commit procedure. This introduces some delay and signalling load a lot, which is worth to be improved. (Issue 2)

For Issue 1, there is no complete solution and as in figure4 the Node B needs to execute extra RL Synchronisation proce- dure even in simple intra/inter-Node B ESCC.

For Issue 2, there is no solution so that Node B shall re^¬ serve the resource until the ESCC or RL Synchronisation Pro^¬ cedure .

There is the following solution for two situations. (Solution for Issue 1)

- Node B to include the information (34) in RL Setup/RL Addi- tion Response (33) separately than HS-DSCH Preconfiguration Info . HSUPA/E-DCH shall always work with HSDPA/HS-DSCH and serving cell for HS-DSCH and one for E-DCH shall be always identical .

E-DCH supports Soft Handover whereas HS-DSCH does not support. The cell that does not serve HS-DSCH but serve E-DCH is called non-serving (E-DCH) cell.

In case E-DCH is configured for a UE and a cell is changed from serving cell which operates E-DCH/HS-DSCH to non-serving cell which operates E DCH/HS-DSCH, the Node B does not need to provide any information for HS-DSCH since

HS-DSCH will not exist in the cell anymore but for E-DCH, it will exist in the non-serving cell.

HS-DSCH Preconfiguration contains the information for when the cell becomes the serving cell, "preconfiguration for HS-DSCH" is not needed for when the cell becomes non-serving cell .

However, for E-DCH, "preconfiguration for E-DCH" is needed for when the cell becomes non-serving cell from serving cell.

- The E-DCH information which needs to be reconfigured is information for E-HICH/E-RGCH . E-AHCH will not exist in serving cell. E-AGCH will not exist in non-serving cell.

Based on figures 1-3 and the respective description, the al- ready described steps are further detailed below:

Stepl (11) : At RL Setup/Addition (31), for newly established RL (29a, 29b, 29c) by the procedure or RL already existed (26) in the Node B before the procedure, the SRNC (24a) can include an information (32) which allows the Node B in RL

Setup/Addition Response (33) to include preconfiguration info (34, e.g. called Non-Serving RL Preconfiguration Setup) related to the established RL (26, 29a, 29b, 29c) which is used by the UE when the RL becomes the non-serving RL from serving RL after the ESCC. Within the information (32), the SRNC provides the information on whether the new serving RL (29a, 29b, 29c)

is in the Node B (i.e. same Node B) is not in the Node B

is either of "in the Node B" or "not in the Node B" when the RL (26) becomes non-serving RL .

For RL Addition, Node B includes the preconfiguration info (34) also for existing RL (before the RL addition), not only for established RL .

E.g.

- RL1 is established and RL1 (26) is serving RL .

- RL2 (29a, 29b, 29c) is established:

-- The RL Addition Request contains the HS-DSCH Preconfigura^¬ tion Setup for RL2 (new RL) and invented Non-Serving RL Preconfiguration Setup (32) for RL1(26, existing RL)

-- The RL Addition Response contains HS-DSCH Preconfiguration Info for RL2 (new RL) and Non-Serving RL Preconfiguration Setup (34) for RL1(26, existing RL)

Similarly, it is introduced to include the existing HS-DSCH Preconfiguration Setup/Info for existing RL (26) into RL Ad- dition Request/Response messages which is new for specifica^¬ tion, due to this, the following signalling is possible:

RL1 is established as non-serving RL and when the RL is established the SRNC did not pre-configure the HS-DSCH info for the RL1.

RL2 is added and SRNC want to preconfigure the HS-DSCH resource for RL1.

Step2 (13) : If the Node B wants to update/provide some infor- mation (3411, 3412, 3413, e.g. E-DCH FDD DL Control Channel Information) for the change of role for the RL (26) to non- serving RL from the serving RL, which needs to be delivered to UE by ASU, the Node B includes the information (34, e.g. called Non-Serving RL Preconfiguration Info) for the indi- cated case above in RL Setup/Addition Response (33) .

Node B assigns the all information in the E-DCH FDD DL Control Channel Information freely. However, this case when serving RL becomes non-serving RL, the Node B can only change the following information in the IE: - E-RGCH/E-HICH Channelisation Code

E-RGCH Signature Sequence

E-HICH Signature Sequence

E-RGCH Release Indicator In case "serving E-DCH RL is either of "in the Node B" or

"not in the Node B"", the Node B may include two information, i.e. information for each case or one information which is common for both cases. Step3: At RL Reconfiguration (61, 63, 64, 65) after SRNC de^¬ cides to execute ESCC (60) which changes the role of the RL to non-serving RL, the Node B (21a) selects pre-configured information (34, 341, 3411, 3412, 3413) based on the Serving E-DCH RL ID (62) in the RL Reconfiguration Prepare message (61) .

Figure 6 describes the signalling flow using the solution for Intra-Node B ESCC. Figure 7 describes the signalling flow using the solution for Inter-Node B ESCC.

Due to this solution, it does not need to execute RL Synchro^¬ nisation Procedure.

Figures 8 and 9 contain use case where Node B needs to in^¬ clude E-DCH FDD DL Control Channel Information for both cases: new serving RL is and is not in the Node B. Figure 8 describes the signalling flow using the solution for another embodiment where a new RL is added in the Node B where currently the serving RL is established but indicating that the new serving RL may be "in the Node B" or "not in the Node B". Afterwards, the new serving RL is established in the other Node B ..

Node B (21a): Cell 1 (22) /2 (23a)

Node B (21b): Cell 3 (23b) /4

Flow :

a) RL1 (26)- call setup on serving cell

b) RL3 (29b)- ela ASU (35)

i) Radio link addition information - RGCH/HICH RL3 Non- serving RLS

ii) "Target cell preconfiguration information", HICH/RGCH RL3 - serving RL

iii) "E-DCH RL Info other cells" - HICH/RGCH RL1 - non-serving RLS c) RL2 (29a)- ela ASU (preconfiguration info for RL2) i) Radio link addition information - RGCH/HICH RL2 non- serving RL serving RLS

ii) "Target cell preconfiguration information", HICH/RGCH - serving RLS

iii) "E-DCH RL Info other cells" - HICH/RGCH RL3 - non- serving RLS

- HICH/RGCH RL1 - non-serving RL serv- ing RLS

d) RL3 - eld

Figure 9 describes the signalling flow using the solution for another embodiment where a RL is established in a Node B which is different to the Node B where the currently serving RL is established and indicating that the new serving RL may be "not in the Node B". Afterwards, the new serving RL is switched into the other Node B and back into the previous Node B.

Node B (21a) : Cell 1 (22)

Node B (21b) : Cell 3 (23b) Flow : a) RL1 (26)- call setup on serving cell

b) RL3 (29b)- ela ASU (35, preconfiguration info

341,3411,3412, 3413 for RL3)

c) RL3 - eld,

d) RL1 - eld

(Solution for Issue 2)

At anytime after the RL Setup/Addition (31,33), if SRNC wants to release Preconfiguration Information (34, 341, 3411, 3412, 3413) before the execution of the ESCC due to some rea^¬ sons (e.g. removal of potential serving RL in the other Node B etc), the SRNC informs Node B about the removal (1000) of the non-HS-DSCH Pre-configuration .

Figure 10 describes the solution for 2 cells within one Node B.

Flow :

a) RL1 (26)- call setup on serving cell

b) RL2 (29a)- ela ASU (35, including non-serving RL precon- figuration info for RL1)

c) Decision in SRNC to release reserved resources for non- serving RL1 allocated earlier

c) Release request (1000) sent to Node B indicating the pre^¬ viously reserved resources which have been reported previ^¬ ously in the non-serving RL preconfiguration info (34, 341, 3411, 3412, 3413) related to RL1. While embodiments and applications of this invention have been shown and described above, it should be apparent to those skilled in the art, that many more modifications (than mentioned above) are possible without departing from the in^¬ ventive concept described herein. The invention, therefore, is not restricted except in the spirit of the appending claims. Therefore, it is intended that the foregoing detailed description should be regarded as illustrative rather than limiting . LIST OF ABBREVIATIONS:

3GPP 3rd generation partnership project

ASU Active Set update

ESCC Enhanced Serving Cell Change

HSPA High Speed Packet Access

HSDPA High Speed Downlink Packet Access

HSUPA High Speed Uplink Packet Access

NBAP Node B Application Part (a signalling protocol between Node B and RNC on Iub interface)

RNC Radio Network Controller

RNSAP Radio Network Subsystem Application Part (a signalling protocol between RNCs on Iur interface)

SRNC Serving RNC

RRC Radio ressource control

RL Radio Link

UE User Equipment

WCDMA Wideband Code Division Multiple Access

LIST OF REFERENCES:

1 Method

11 first step

12 second step

13 third step

14 fourth step

2 radio communications system

21a radio base station

21b second radio base station

21c third radio base station

22 first radio cell

23a second radio cell

23b third radio cell

23c fourth radio cell

22, 23a,

23b, 23c radio cells

24a control node

24b second control node

25 mobile terminal

26 first radio link

27 Iub interface

28 Iur interface

29a second radio link

29b third radio link

29c fourth radio link

31 radio link establish request message

32 a radio resource parameter

33 radio link establish response message 34 preconfiguration parameter set

3411, 3412,

3413 radio configuration data

35 active set update message

60 decision on enhanced serving cell change 61 radio link reconfiguration prepare message

62 Serving E-DCH Radio Link Indicator

63 radio link reconfiguration commit message

64 cell change order message radio resource control reconfiguration message non-serving RL preconfiguration release request message

Claims

Radio base station (21a) for supporting a serving cell change of a mobile terminal (25) in a radio communica^¬ tions system (2), the radio communications system (2) comprising radio cells (22, 23a, 23b, 23c), a control node (24a, 24b) , with the radio base station (21a) spanning a first radio cell (22), with the first radio cell (22) comprising a first radio link (26),

the radio base station (21a) comprising means configured for

- receiving (11), from the control node (24a), a radio link establish request message (31), the radio link es^¬ tablish request message (31) comprising

a radio resource parameter (32) concerning an establishing of a further radio link (29a, 29b, 29c) between the radio base station (21a) and the mobile terminal (25) ,

- establishing (12) the further radio link (26), according to the radio link establish request message (31) , and

- responding (13) to the radio link establish request message (31) by sending, towards the control node

(24a) , a radio link establish response message (33) , the radio link establish response message (33) compris^¬ ing

a preconfiguration parameter set (34), the preconfigu- ration parameter set (34) comprising

radio configuration data (3411, 3412, 3413) selected depending on the radio resource parameter (32), said radio configuration data (3411, 3412, 3413) to be used for continued transmission by the mobile terminal (25) on the first radio link (26) following said serving cell change of the mobile terminal (25) from the first radio cell (22) to a second radio cell (23a, 23b, 23c) .

2. Control node (24a) for supporting a serving cell change of a mobile terminal (25) in a radio communications system (2), the radio communications system (2) comprising radio cells (22, 23a, 23b, 23c),

a radio base station (21a) spanning a first radio cell (22), with the first radio cell (22) comprising a first radio link (26),

the control node (24a) comprising means configured for

- sending (11), towards the radio base station (21a), a radio link establish request message (31), the radio link establish request message (31) comprising

- receiving (13), from the radio base station (21a), a radio link establish response message (33) , the radio link establish response message (33) comprising

radio configuration data (3411, 3412, 3413) selected depending on the radio resource parameter (32), said radio configuration data (3411, 3412, 3413) to be used for continued transmission by the mobile terminal (25) on the first radio link (26) following said serving cell change of the mobile terminal (25) from the first radio cell (22) to a second radio cell (23a), and

- forwarding (14), towards the mobile terminal (25), an active set update message (35) comprising

the selected radio configuration data (3411, 3412, 3413) .

Method for supporting a serving cell change of a mobile terminal (25) in a radio communications system (2), the radio communications system (2) comprising radio cells (22, 23a, 23b, 23c), a control node (24a, 24b), a radio base station (21a) , with the radio base station (21a) spanning a first radio cell (22), with the first radio cell (22) comprising a first radio link (26),

the method comprising the following steps performed by the radio base station:

- establishing (12) the further radio link (26), ac- cording to the radio link establish request message

(31) , and

radio configuration data (3411, 3412, 3413) selected depending on the radio resource parameter (32), said radio configuration data (3411, 3412, 3413) to be used for continued transmission by the mobile terminal (25) on the first radio link (26) following said serving cell change of the mobile terminal (25) from the first radio cell (22) to a second radio cell (23a) .

Method for supporting a serving cell change of a mobile terminal (25) in a radio communications system (2), the radio communications system (2) comprising radio cells (22 , 23a, 23b, 23c) ,

a radio base station (21a) spanning a first radio cell (22), with the first radio cell (22) comprising a first radio link (26), a control node (24a),

the method comprising the following steps performed by the control node:

- sending (11), towards the radio base station (21a), a radio link establish request message (31), the radio link establish request message (31) comprising a radio resource parameter (32) concerning an establishing of a further radio link (29a, 29b, 29c) between the radio base station (21a) and the mobile terminal (25) ,

the selected radio configuration data (3411, 3412, 3413) .

Method (1) for supporting a serving cell change of a mobile terminal (25) in a radio communications system (2), the radio communications system (2) comprising ra^¬ dio cells (22, 23a, 23b, 23c),

a radio base station (21a) spanning a first radio cell (22), with the first radio cell (22) comprising a first radio link (26), and a control node (24a, 24b), the method (1) comprising the following steps:

- sending (11), from the control node (24a) towards the radio base station (21a) , a radio link establish re^¬ quest message (31), the radio link establish request message (31) comprising

a radio resource parameter (32) concerning an establishing of a further radio link (29a, 29b, 29c) between the radio base station (21a, 21b, 21c) and the mobile terminal (25) ,

- establishing (12), by the radio base station (21a, 21b, 21c), the further radio link (29a, 29b, 29c), ac^¬ cording to the radio link establish request message (31) ,

- responding (13) to the radio link establish request message (31) by sending, from the radio base station (21a, 21b, 21c) towards the control node (24a) , a radio link establish response message (33) , the radio link establish response message (33) comprising

radio configuration data (3411, 3412, 3413) selected depending on the radio resource parameter (32), said radio configuration data (3411, 3412, 3413) to be used for continued transmission by the mobile terminal (25) on the first radio link (26) following said serving cell change of the mobile terminal (25) from the first radio cell (22) to a further radio cell (23a, 23b, 23c) , and

- forwarding (14), by the control node (24a), towards the mobile terminal (25) , an active set update message (35) comprising

the selected radio configuration data (3411, 3412, 3413) .

Method according any of claims 3 to 5, wherein the ra^¬ dio configuration data (3411, 3412, 3413) comprises an element, the element comprising data related to chan^¬ nelization code, signature sequence, and release indi^¬ cator .

Method according to any of claims 3 to 6, wherein the second radio cell (23b) is spanned by a second radio base station (21b) .

8. Method according to any of claims 3 to 7, wherein the second radio base station (21b) is connected to the control node (24a) . Method according to any of claims 3 to 8, wherein the second radio base station (21b) is connected to a sec^¬ ond control node (24b) using a connection (28) to the control node. Method according to any of claims 3 to 9, the method further comprising the step of

sending, from the control node (24a) to the radio base station (21a, 21b, 21c) , a radio link reconfiguration request message (1000) comprising an indicator, said indicator indicating resources previously reserved for the radio configuration data to be unreserved from the radio base station (21a, 21b, 21c) .