WO2014114328A1

WO2014114328A1 - Enhanced serving cell change technique

Info

Publication number: WO2014114328A1
Application number: PCT/EP2013/051165
Authority: WO
Inventors: Alexander Sayenko; Karri Markus Ranta-Aho; Hans Thomas Hoehne
Original assignee: Nokia Solutions and Networks Oy
Current assignee: Nokia Solutions and Networks Oy
Priority date: 2013-01-23
Filing date: 2013-01-23
Publication date: 2014-07-31
Anticipated expiration: 2015-07-23

Abstract

There are provided measures for an enhanced serving cell change technique. Such measures exemplarily comprise issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity, scheduling dummy data for the mobile communication entity after issuance of the cell change order, monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring.

Description

DESCRIPTION

Title Enhanced serving cell change technique Technical Field

The present invention relates to an enhanced serving cell change technique. More specifically, the present invention exemplarily relates to measures (including methods, apparatuses and computer program products) for realizing an enhanced serving cell change technique.

Background

In cellular communication systems, mobility of mobile communication entities such as a user equipment or terminal is an essential issue, which generally depends on underlying paradigms and architectural aspects of the cellular communication system in question. Accordingly, specifics of a handover from a source network communication entity such as a base station to a target network communication entity such as a base station differ between the cellular communication systems.

Among others, in WCDMA and UMTS system, a mobile communication entity combines data from all radio links in an active set (of serving cells), thereby performing a soft handover. In contrast thereto, in a network deployment with high-speed downlink channels, also known as HSDPA, a mobile communication entity receives data only from one particular cell, i.e. a single serving cell, at a time.

Figure 1 shows a schematic diagram illustrating a communication network scenario, for which exemplary embodiments of the present invention are applicable.

As shown in Figure 1 , in a UTRAN-based communication network scenario, a radio network controller (RNC) representing a network control entity is connected, via an lub interface, with a plurality of Node B's (nB1 , nB2) representing network communication entities or base stations, each of which operates a cell (indicated by dashed blocks). A user equipment (UE) representing a mobile communication entity is connected with one Node B at a time. When moving from a first cell of nB1 to a second cell of nB2, the UE has to change the serving Node B or, stated in other words, the serving cell (as indicated by chain-dotted lines). While both Node B's are exemplified to be connected to a single RNC, it is noted to be also possible that nB1 and nB2 are connected to different RNC's which are connected to each other via an lur interface.

When assuming that the UE in performing a handover receives data only from one particular serving cell at a time, as is the case in HSDPA deployments, it is vital that the serving cell change is performed as fast and reliable as possible without interrupting an ongoing communication.

The process of changing the serving cell is generally based on a few RRC messages which are exchanged between the moving UE and the RNC (or the RNCs) of the source and target cells. When the UE requests serving cell change at the RNC, the RNC issues a corresponding RRC message and awaits receipt of a RRC "complete" indication from the UE, whereupon the UE is considered to be under the control of the specified new cell.

However, since the RRC messages can experience delays and can be even lost e.g. due to unfavorable communication conditions, the above-described serving cell change based on the exchange of RRC messages suffers from limited robustness in terms of both delay and reliability issues.

Among others, a mechanism which aims at increasing the robustness of the serving cell change based on the exchange of RRC messages is proposed for HSDPA deployments. Such mechanism called enhanced serving cell change (eSCC) allows the network to give the UE a pre-configu ration regarding the target serving cell and then activate this pre-configuration by sending a special cell change order from the target cell to the UE. The introduction of the eSCC mechanism was motivated by voice services, where the cell change interruption time should be as small as possible. Figure 2 shows a signaling diagram of a serving cell change procedure, for which exemplary embodiments of the present invention are applicable, i.e. the above- mentioned eSCC mechanism. As shown in Figure 2, the eSCC mechanism is based on preparatory measures. In this regard, the UE being connected with nB1 reports an event 1 a to the RNC, i.e. a RRC measurement report indicating that a common pilot channel of nB2 is registered and/or the power of a common pilot channel of nB2 has reached a certain level and, thus, that the cell of nB2 is a neighboring cell potentially available for handover. Upon receiving the event 1 a report from the UE, the RNC adds the nB2 to the active set of the UE and establishes a corresponding pre-configuration in the UE and in the nB2 for carrying out a potential handover.

As shown in Figure 2, the eSCC mechanism comprises the following operations. In step 1 , the UE detects the cell of nB2 as a new best cell, reports an event 1 d to the RNC, i.e. a RRC measurement report indicating the change of the best cell, and starts to listen for a cell change order from the target cell, i.e. the new best cell for which the event 1 d was generated. Upon receiving the event 1 d report from the UE, the RNC may ask the corresponding nB2 to send the cell change order to the UE in step 2, and the nB2 sends the cell change order as a special HS-SCCH order to the UE in step 3. In step 4, once the UE receives the cell change order, the UE applies the provided pre- configuration, i.e. reconfigures according to the pre-configuration, and thereby effectively changes the serving cell. Thereupon, the UE sends the RRC "complete" message to the RNC in step 5.

Only after completion of the procedure by receipt of the RRC "complete" message at the RNC, the RNC could provide the nB2 with actual data for downlink scheduling to the UE, and the nB2 could start with the scheduling of the actual data to the UE in a reliable manner. While the nB2 can of course transmit in the downlink direction even before a corresponding indication from the RNC, there would be no guarantee that the UE will listen to it.

If the target cell knows that the UE has received the cell change order and has (already) carried out the instructed serving cell change, it can start sending the actual data in the downlink direction without waiting for an indication from the RNC that the latter has received the RRC "complete" message from the UE, thus avoiding unnecessary delays. However, with the eSCC mechanism, there exists an uncertainty on whether the UE has received the cell change order from the target cell and/or has (already) carried out the instructed serving cell change.

Referring to step 3 in the procedure of Figure 2, there is no way from the network point of view to know whether the UE has received the cell change order and, as a result, has (already) carried out the instructed serving cell change. The only way the network can detect, yet only later, that something went wrong with the cell change instruction is the absence of the RRC "complete" message of step 5 in the procedure of Figure 2. Only then, the network could re-issue the cell change instruction for the nB2 or take other actions. As a consequence, the serving cell change can fail e.g. due to drop of the cell change order or can take more time than actually required and/or acceptable, as the target cell must be quite conservative (in terms of guard time considerations) with regards to when it can schedule actual data in the downlink direction. Thereby, in view of the increased time and/or decreased reliability of the cell change procedure, the quality of communication could be significantly impacted, which is specifically detrimental to delay-critical and/or real-time services, such as voice.

In view thereof, there resides a problem in that the above-described cell change procedure is subject to increased cell change time and/or decreased cell change reliability, thus significantly impacting the quality of communication, especially delay- critical and/or real-time services.

Accordingly, there is a demand for an enhanced serving cell change technique which is superior in terms of cell change time and/or reliability.

Summary

Various exemplary embodiments of the present invention aim at addressing at least part of the above issues and/or problems and drawbacks. Various aspects of exemplary embodiments of the present invention are set out in the appended claims. According to an exemplary aspect of the present invention, there is provided a method comprising issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity, scheduling dummy data for the mobile communication entity after issuance of the cell change order, monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring.

According to an exemplary aspect of the present invention, there is provided an apparatus comprising an interface configured to connect to at least another apparatus, a memory configured to store computer program code, and a processor configured to cause the apparatus to perform: issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity, scheduling dummy data for the mobile communication entity after issuance of the cell change order, monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring. According to an exemplary aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to the aforementioned apparatus-related exemplary aspect of the present invention), is configured to cause the computer to carry out the method according to the aforementioned method-related exemplary aspect of the present invention.

The computer program product may comprise or may be embodied as a (tangible) computer-readable (storage) medium or the like, on which the computer-executable computer program code is stored, and/or the program is directly loadable into an internal memory of the computer or a processor thereof.

Advantageous further developments or modifications of the aforementioned exemplary aspects of the present invention are set out in the following.

By way of exemplary embodiments of the present invention, there is provided an enhanced serving cell change technique. The thus presented serving cell change technique can be applicable in HSDPA deployments, and can be superior in terms of cell change time and/or reliability as compared with a conventional eSCC mechanism.

Thus, improvement is achieved by methods, apparatuses and computer program products enabling/realizing an enhanced serving cell change technique.

Brief description of the drawings

In the following, the present invention will be described in greater detail by way of non- limiting examples with reference to the accompanying drawings, in which

Figure 1 shows a schematic diagram illustrating a communication network scenario, for which exemplary embodiments of the present invention are applicable, Figure 2 shows a signaling diagram of a serving cell change procedure, for which exemplary embodiments of the present invention are applicable,

Figure 3 shows a flowchart of a first example of a procedure according to exemplary embodiments of the present invention,

Figure 4 shows a flowchart of a second example of a procedure according to exemplary embodiments of the present invention, Figure 5 shows a signaling diagram of an exemplary implementation of the second example of a procedure according to exemplary embodiments of the present invention,

Figure 6 shows a flowchart of a third example of a procedure according to exemplary embodiments of the present invention,

Figure 7 shows a signaling diagram of an exemplary implementation of the third example of a procedure according to exemplary embodiments of the present invention, Figure 8 shows a flowchart of a fourth example of a procedure according to exemplary embodiments of the present invention, and

Figure 9 shows a schematic diagram illustrating an apparatus according to exemplary embodiments of the present invention.

Detailed description of drawings and embodiments of the present invention

The present invention is described herein with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present invention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied.

It is to be noted that the following description of the present invention and its embodiments mainly refers to specifications being used as non-limiting examples for certain exemplary network configurations and deployments. Namely, the present invention and its embodiments are mainly described in relation to WCDMA/UMTS specifications, particularly to HSDPA deployments thereof, being used as non-limiting examples for certain exemplary network configurations and deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the invention in any way. Rather, any other network configuration or system deployment, etc. may also be utilized as long as compliant with the features described herein. In particular, the present invention and its embodiments may be applicable in any cellular communication system and/or network deployment in which a serving cell change of a mobile communication entity is applicable, i.e. each cellular communication system with mobility of a mobile communication entity.

Hereinafter, various embodiments and implementations of the present invention and its aspects or embodiments are described using several variants and/or alternatives. It is generally noted that, according to certain needs and constraints, all of the described variants and/or alternatives may be provided alone or in any conceivable combination (also including combinations of individual features of the various variants and/or alternatives).

According to exemplary embodiments of the present invention, in general terms, there are provided measures and mechanisms for (enabling/realizing) an enhanced serving cell change technique.

Figure 3 shows a flowchart of a first example of a procedure according to exemplary embodiments of the present invention. Such procedure is operable at a target network communication entity, such as Node B nB2 in the exemplary network scenario of Figure 1 .

As shown in Figure 3, a procedure according to exemplary embodiments of the present invention comprises an operation (S310) of issuing a cell change order for a mobile communication entity, such as the UE, said cell change order instructing a serving cell change from a source network communication entity, such as nB1 , to a target network communication entity, such as nB2, an operation (S320) of scheduling dummy data for the mobile communication entity after issuance of the cell change order, an operation (S330) of monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and an operation (S340) of deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring.

In such procedure according to exemplary embodiments of the present invention, the dummy data scheduling may be performed immediately upon issuance of the cell change order, i.e. the operation S320 may be performed with no (intentional) delay or time gap after the operation S310, or upon elapse of a predetermined time after issuance of the cell change order, i.e. the operation S320 may be performed with some (intentional) delay or time gap after the operation S310.

Further, in such procedure according to exemplary embodiments of the present invention, the dummy data scheduling may be performed once or repeatedly in a predetermined number with a predetermined interval after issuance of the cell change order, i.e. the operation S320 may comprise a one-time or multiple-times scheduling of dummy data. For example, for the sake of safety, i.e. increasing reliability, the dummy data scheduling may be performed several times over several transmission time intervals (TTIs) of the target network communication entity. By performing such dummy data scheduling in N consecutive TTIs, ACK-to-NACK errors can be avoided, namely it can be avoided that a Node B receives a message which is not the same as that sent by a UE, such as e.g. that the Node B receives a NACK message (e.g. as a result of a reception error) although an ACK message would be expected.

According to exemplary embodiments of the present invention, it is assumed that, if a mobile communication entity has successfully received a cell change order from the target cell, i.e. the target network communication entity, and started to listen for downlink (high-speed) channels in the target cell as a result of the instructed serving cell change, then it should behave with regards to the downlink (high-speed) channels according to current specifications. Thus, any data scheduled over the downlink (highspeed) channels after the serving cell change should be responded accordingly by the mobile communication entity.

In view thereof, it is proposed that the network schedules dummy data and, based on presence/absence of ACK/NACK messages for the dummy data, which are provided as for legacy transmissions, thereby determines whether the mobile communication entity has successfully received that cell change order and has (already) carried out the instructed serving cell change, i.e. has (already) changed the serving cell. Accordingly, the presence/absence of ACK/NACK messages for the dummy data is utilized as an ACK/NACK indication for receipt and execution of the cell change order at the mobile communication entity. It is noted that, in monitoring receipt of an acknowledgment for the scheduled dummy data (operation S330), the mere presence of an UL transmission (e.g. an HS-DPCCH UL transmission) from the mobile communication entity, such as the UE, in response to the scheduled dummy data is sufficient to indicate a successful serving cell change, regardless of whether or not an ACK or NACK message is carried in such UL transmission. That is, an "acknowledgment for the scheduled dummy data" in the meaning of the present specification is not limited to an ACK/NACK message, as is exemplarily adopted for illustrative purposes in non-limiting examples described below.

Thereby, the cell change time could be shortened and/or the cell change reliability could be improved, without requiring any non-legacy behavior from the mobile communication entity, such as provision of an explicit ACK/NACK message for the cell change order as such.

Figure 4 shows a flowchart of a second example of a procedure according to exemplary embodiments of the present invention. Such procedure is operable at a target network communication entity, such as Node B nB2 in the exemplary network scenario of Figure 1 .

In the procedure of Figure 4, operations S410, S420, S430 and S440 basically correspond to operations S310, S320, S330 and S340 in the procedure of Figure 3, respectively. Accordingly, a detailed description thereof is not repeated, and reference is made to the description of Figure 3 above.

It is noted that the dummy data in the present example are actually empty data or no (real) data.

As shown in Figure 4, the dummy data scheduling in operation S420 comprises an operation (S422) of allocating the dummy (or empty) data for the mobile communication entity, and an operation (S424) of issuing an indication of a data allocation based on the dummy data allocation for the mobile communication entity. Based thereon, the monitoring operation (S430) comprises monitoring receipt of a negative acknowledgment (NACK), or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data, and the deciding operation (S440) comprises an operation (S442) of deciding that the mobile communication entity has carried out the instructed serving cell change when receipt of the negative acknowledgment, or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data is monitored (YES in S430), or an operation (S444) of deciding that the mobile communication entity has not carried out the instructed serving cell change when receipt of no (negative) acknowledgment, or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data is monitored (NO in S430). Figure 5 shows a signaling diagram of an exemplary implementation of the second example of a procedure according to exemplary embodiments of the present invention.

More specifically, the signaling diagram of Figure 5 illustrates an exemplary implementation of the procedure of Figure 4 in a HSDPA deployment (of a WC DMA/UMTS cellular communication system), wherein the exemplary network scenario of Figure 1 is adopted for explanatory purposes by way of example. In a HSDPA deployment, the HS-SCCH channel (in downlink) is used to indicate the UE that there is a (MAC-hs/ehs) data packet to it on HS-PDSCH channel(s), and the HS- PDSCH channel(s) (in downlink) is/are used to deliver an actual data packet. An ACK or NACK message on the HS-DPCCH channel (in uplink) is used to indicate whether a transmitted HS-PDSCH data packet was received correctly or not. In addition, CQI messages on the HS-DPCCH channel, which are time-multiplexed with ACK/NACK messages, are used by the Node B scheduler to determine the modulation and coding scheme to be used in the HS-PDSCH transmissions.

As mentioned above, while a single RNC is exemplarily illustrated, which is assumed to commonly serve both nB1 and nB2, it is equally feasible that nB1 and nB2 are served by different RNCs being connected via an lur interface, in which case the RNC illustrated in Figure 5 represents the RNC of the target Node B nB2.

As shown in Figure 5, such procedure according to exemplary embodiments of the present invention is based on or realized within the eSCC mechanism as illustrated in Figure 2. Namely, steps 1 to 5 in the procedure of Figure 5 basically correspond to steps 1 to 5 in the procedure of Figure 2, respectively. Accordingly, a detailed description thereof is not repeated, and reference is made to the description of Figure 2 above.

It is noted that in such exemplary HSDPA-related implementation in the context of the eSCC mechanism, the cell change order includes an instruction to activate a pre- configuration for carrying out the instructed serving cell change, while such pre- configuration has previously been provided to the mobile communication entity, e.g. the UE, and the target network communication entity e.g. the nB2, by a network control entity, e.g. the RNC (of the nB2), as exemplarily illustrated in Figure 2 above. Further, the cell change order is provided as a special HS-SCCH order, i.e. on the HS-SCCH channel.

As shown in Figure 5, in such procedure according to exemplary embodiments of the present invention, the dummy (or empty) data scheduling comprises that the nB2 of the target cell issues and provides a HS-DSCH data allocation on the HS-SCCH channel, but does not provide any HS-DSCH (real/actual) packet (e.g. a MAC-hs/ehs packet) on the HS-PDSCH channel. If the UE has successfully performed the serving cell change and thus already listens to the downlink high-speed channels in the target cell of the nB2, then the UE - as a result of the HS-DSCH data allocation received on the HS- SCCH channel - would try to decode data on the HS-PDSCH channel. However, since the nB2 did (intentionally) not send any data on the HS-PDSCH channel, the UE would fail in data decoding and thus respond with a NACK message, e.g. a HARQ NACK message, on the HS-DPCCH channel. Based on the receipt/presence of the NACK message for the scheduled dummy (or empty) data as a result of the monitoring, the nB2 can conclude/decide that the UE listens to its cell, i.e. has already carried out the instructed serving cell change to the nB2 cell. Otherwise, if the UE has not yet performed the serving cell change and thus does not listen to the downlink high-speed channels in the target cell of nB2 yet, there would be no feedback from the UE (on the HS-DPCCH channel) as a result of the monitoring, and the nB2 can conclude/decide that the UE does not listen to its cell, i.e. has not carried out the instructed serving cell change to the nB2 cell.

Upon concluding/deciding that the UE listens to its cell, i.e. has already carried out the instructed serving cell change to the nB2 cell, the nB2 can start scheduling actual data for the UE in the downlink direction. Such actual data to be transmitted to the UE could have been provided by/from the RNC to the nB2 together with the order to send the cell change order in step 2 or at any time after that. In view of the preceding positive conclusion regarding the execution of the serving cell change, the thus scheduled actual data could reliably be assumed to be listened by the UE.

As in the legacy eSCC mechanism of Figure 2, as a result of successfully carrying out the instructed serving cell change, the UE could further provide a RCC "complete" message which is forwarded by the nB2 to the RNC (of the nB2) in step 5. Namely, the nB2 could obtain a confirmation for the serving cell change from the UE and forward the confirmation to its RNC. However, in contrast to the legacy eSCC mechanism of Figure 2, the nB2 does not need to wait for an indication of the receipt of such confirmation from its RNC so as to be able to reliably conclude/decide execution of the instructed serving cell change by the UE, thus saving time in the cell change.

Figure 6 shows a flowchart of a third example of a procedure according to exemplary embodiments of the present invention. Such procedure is operable at a target network communication entity, such as Node B nB2 in the exemplary network scenario of Figure 1 .

In the procedure of Figure 6, operations S610, S620, S630 and S640 basically correspond to operations S310, S320, S330 and S340 in the procedure of Figure 3, respectively. Accordingly, a detailed description thereof is not repeated, and reference is made to the description of Figure 3 above.

It is noted that the dummy data in the present example are (actual/real) data which are predefined or recognizable as dummy data, e.g. a sequence of a predetermined number or zeros, a data string with a specific code pattern at the beginning, or the like. As shown in Figure 6, the dummy data scheduling in operation S620 comprises an operation (S622) of allocating the dummy data for the mobile communication entity, and an operation (S624) of issuing an indication of a data allocation and a dummy data packet based on the dummy data allocation for the mobile communication entity. Based thereon, the monitoring operation (S630) comprises monitoring receipt of a (positive) acknowledgment (ACK), or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data, and the deciding operation (S640) comprises an operation (S642) of deciding that the mobile communication entity has carried out the instructed serving cell change when receipt of the (positive) acknowledgment, or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data is monitored (YES in S630), or an operation (S644) of deciding that the mobile communication entity has not carried out the instructed serving cell change when receipt of the (positive) acknowledgment, or any other e.g. HS-DPCCH UL transmission, for the scheduled dummy data is not monitored (NO in S630), but rather receipt of a negative acknowledgment or no acknowledgment for the scheduled dummy data is monitored.

Figure 7 shows a signaling diagram of an exemplary implementation of the third example of a procedure according to exemplary embodiments of the present invention. More specifically, the signaling diagram of Figure 7 illustrates an exemplary implementation of the procedure of Figure 6 in a HSDPA deployment (of a WC DMA/UMTS cellular communication system), wherein the exemplary network scenario of Figure 1 is adopted for explanatory purposes by way of example. In a HSDPA deployment, the HS-SCCH channel (in downlink) is used to indicate the UE that there is a (MAC-hs/ehs) data packet to it on HS-PDSCH channel(s), and the HS- PDSCH channel(s) (in downlink) is/are used to deliver an actual data packet. An ACK or NACK message on the HS-DPCCH channel (in uplink) is used to indicate whether a transmitted HS-PDSCH data packet was received correctly or not. In addition, CQI messages on the HS-DPCCH channel, which are time-multiplexed with ACK/NACK messages, are used by the Node B scheduler to determine the modulation and coding scheme to be used in the HS-PDSCH transmissions.

As mentioned above, while a single RNC is exemplarily illustrated, which is assumed to commonly serve both nB1 and nB2, it is equally feasible that nB1 and nB2 are served by different RNCs being connected via an lur interface, in which case the RNC illustrated in Figure 7 represents the RNC of the target Node B nB2.

As shown in Figure 7, such procedure according to exemplary embodiments of the present invention is based on or realized within the eSCC mechanism as illustrated in Figure 2. Namely, steps 1 to 5 in the procedure of Figure 7 basically correspond to steps 1 to 5 in the procedure of Figure 2, respectively. Accordingly, a detailed description thereof is not repeated, and reference is made to the description of Figure 2 above.

It is noted that in such exemplary HSDPA-related implementation in the context of the eSCC mechanism, the cell change order includes an instruction to activate a pre- configuration for carrying out the instructed serving cell change, while such pre- configuration has previously been provided to the mobile communication entity, e.g. the UE, and the target network communication entity e.g. the nB2, by a network control entity, e.g. the RNC (of the nB2), as exemplarily illustrated in Figure 2 above. Further, the cell change order is provided as a special HS-SCCH order, i.e. on the HS-SCCH channel. As shown in Figure 7, in such procedure according to exemplary embodiments of the present invention, the dummy data scheduling comprises that the nB2 of the target cell issues and provides a HS-DSCH data allocation on the HS-SCCH channel, as well as a HS-DSCH dummy packet, i.e. a HS-DSCH packet with dummy data (e.g. a MAC- hs/ehs packet (with or without payload data)) on the HS-PDSCH channel. If the UE has successfully performed the serving cell change and thus already listens to the downlink high-speed channels in the target cell of the nB2, then the UE - as a result of the HS- DSCH data allocation received on the HS-SCCH channel - would decode the HS- DSCH dummy packet on the HS-PDSCH channel. Normally, the UE would succeed in data decoding and thus respond with an ACK message, e.g. a HARQ ACK message, on the HS-DPCCH channel. Based on the receipt/presence of the ACK message for the scheduled dummy data as a result of the monitoring, the nB2 can conclude/decide that the UE listens to its cell, i.e. has already carried out the instructed serving cell change to the nB2 cell. If the UE has listened to the HS-SCCH and HS-PDSCH but failed to decode the HS-PDSCH (i.e. the HS-DSCH dummy data), it will send an HARQ NACK message. The nB2 can then as well conclude/decide that the UE listens to its cell. Otherwise, if the UE has not yet performed the serving cell change and thus does not listen to the downlink high-speed channels in the target cell of nB2 yet, there would be no feedback, i.e. no ACK/NACK message, from the UE (on the HS-DPCCH channel) as a result of the monitoring, and the nB2 can conclude/decide that the UE does not listen to its cell, i.e. has not carried out the instructed serving cell change to the nB2 cell.

Figure 8 shows a flowchart of a fourth example of a procedure according to exemplary embodiments of the present invention. Such procedure is operable at a target network communication entity, such as Node B nB2 in the exemplary network scenario of Figure 1 .

In the procedure of Figure 8, operations S810, S830, S840 and S850 basically correspond to operations S310, S320, S330 and S340 in the procedure of Figure 3, respectively. Accordingly, a detailed description thereof is not repeated, and reference is made to the description of Figure 3 above.

XX

As shown in Figure 8, the thus exemplified procedure according to exemplary embodiments of the present invention further comprises an operation (S820) of obtaining at least one control parameter for the dummy data scheduling from a network control entity, e.g. a RNC of the target network communication entity, and the dummy data scheduling of operation S830 is performed in accordance with the at least one control parameter. By virtue of such operations S820 and S830 according to Figure 8, the Node B behavior with regards to issuing the dummy data according to exemplary embodiments of the present invention can be controlled by the network control entity serving the target network communication entity, e.g. the RNC of the nB2 according to the exemplary network scenario of Figure 1 . Such control can be based on the (type of) service to be provided to the UE, the (type of) data to be transmitted to the UE, or the like. For example, in case the Node B behavior with regards to issuing the dummy data according to exemplary embodiments, as described in connection with Figures 3 to 7, is (considered to be) only needed or desired for delay-critical and/or real-time services, such as voice, and is (considered to be) not needed or desired in any other case, the RNC can effect a corresponding control of the nB2. Such control can relate to any details of the dummy data scheduling at the nB2, including one or more of the variant of dummy data scheduling (i.e. the procedure of Figure 4/5 or the procedure of Figure 6/7), the timing of the dummy data scheduling with respect to the issuance of the cell change order (i.e. immediate or delayed execution of the dummy data scheduling), the non-/repetition of the dummy data scheduling (i.e. execution of the dummy data scheduling once or repeatedly), or the like.

Accordingly, a network control entity according to exemplary embodiments of the present invention is configured to perform a corresponding control of a network communication entity, which is a target network communication entity in a serving cell change of a mobile communication entity, in terms of dummy data scheduling in the context of the serving cell change being instructed by the target network communication entity. In this regard, the network control entity according to exemplary embodiments of the present invention is configured to set at least one control parameter for the dummy data scheduling depending on predetermined criteria, e.g. a (type of) service, data, or the like, and to provide the thus set control parameter/s for the target network communication entity either directly e.g. via the lub interface (in case it is the network control entity serving the target network communication entity) or indirectly, over the network control entity serving the target network communication entity, e.g. via the lur interface (in case it is not the network control entity serving the target network communication entity). Such provision of control parameter/s for the dummy data scheduling could be effected prior to, together with or after provision of an order to send a cell change order to the target network communication entity.

It is noted that, while obtaining the control parameter/s is illustrated to take place after issuance of the cell change order in Figure 8, the control parameter/s could also be obtained prior to issuance of the cell change order, e.g. prior to or together the order to send the cell change order from the RNC, as illustrated in any one of Figures 2, 5 and 7 above.

Further, it is noted that obtaining at least one control parameter for the dummy data scheduling and performing the dummy data scheduling accordingly (i.e. the operations S820 and S830 of Figure 8) could also be integrated in the procedures of any one of Figures 5 and 7 as well.

In view of the above, exemplary embodiments of the present invention provide for an enhanced serving cell change technique, which can provide for a faster and more reliable serving cell change as compared with legacy serving cell change techniques.

The enhanced serving cell change technique according to exemplary embodiments of the present invention can be applicable in HSDPA deployments, and which can be superior in terms of cell change time and/or reliability as compared with a conventional eSCC mechanism. In this regard, it is an advantage that the time gap in user plane connectivity is shortened, and the robustness for the target cell detecting the successful reception of the HS-SCCH order triggering the serving cell change at the UE is improved. As the RNC may provide actual user data to the target Node B already at the time where it signals the target Node B to issue the HS-SCCH order or shortly thereafter, the target Node B can start scheduling the actual user data as soon as it is clear that the UE has carried out the serving cell change. Hence, the conventional delay for waiting for an indication of receipt of the RRC signaling RRC" complete" at the RNC is saved, and any (meanwhile) uncertainty with regards to the execution of the instructed serving cell change at the UE is reduced. Further, the enhanced serving cell change technique according to exemplary embodiments of the present invention can be applicable on a legacy radio interface, i.e. without requiring any modifications to current specifications for the radio interface and/or the behavior of an involved mobile communication entity.

The above-described procedures and functions may be implemented by respective functional elements, processors, or the like, as described below.

While in the foregoing exemplary embodiments of the present invention are described mainly with reference to methods, procedures and functions, corresponding exemplary embodiments of the present invention also cover respective apparatuses, network nodes and systems, including both software and/or hardware thereof.

Respective exemplary embodiments of the present invention are described below referring to Figure 9, while for the sake of brevity reference is made to the detailed description of respective corresponding configurations/setups, schemes, methods and functionality, principles and operations according to Figures 3 to 8.

In Figure 9, the solid line blocks are basically configured to perform respective operations as described above. The entirety of solid line blocks are basically configured to perform the methods and operations as described above, respectively. With respect to Figure 9, it is to be noted that the individual blocks are meant to illustrate respective functional blocks implementing a respective function, process or procedure, respectively. Such functional blocks are implementation-independent, i.e. may be implemented by means of any kind of hardware or software, respectively. The arrows and lines interconnecting individual blocks are meant to illustrate an operational coupling there-between, which may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or wireless) and on the other hand may also comprise an arbitrary number of intermediary functional entities not shown. The direction of arrow is meant to illustrate the direction in which certain operations are performed and/or the direction in which certain data is transferred.

Further, in Figure 9, only those functional blocks are illustrated, which relate to any one of the above-described methods, procedures and functions. A skilled person will acknowledge the presence of any other conventional functional blocks required for an operation of respective structural arrangements, such as e.g. a power supply, a central processing unit, respective memories or the like. Among others, memories are provided for storing programs or program instructions for controlling the individual functional entities to operate as described herein.

Figure 9 shows a schematic diagram illustrating an apparatus according to exemplary embodiments of the present invention. In view of the above, the thus illustrated apparatus 10 is suitable for use in practicing the exemplary embodiments of the present invention, as described herein.

The thus illustrated apparatus 10 may represent a (part of a) network communication entity, such as a base station or Node B, according to exemplary embodiments of the present invention. Specifically, it may represent a (part of a) target network communication entity which acts as a target network communication entity in a serving cell change of a mobile communication entity. It may be configured to perform a procedure and/or exhibit a functionality as described (for nB2) in any one of Figures 3 to 8. Referring to the exemplary network scenario of Figure 1 , it may be connectable to a mobile communication entity such as a UE and a network control entity such as a RNC.

As indicated in Figure 9, according to exemplary embodiments of the present invention, the apparatus 10 comprises a processor 1 1 , a memory 12 and an interface 13, which are connected by a bus 14 or the like.

The processor 1 1 and/or the interface 13 may also include a modem or the like to facilitate communication over a (hardwire or wireless) link, respectively. The interface 13 may include a suitable transceiver coupled to one or more antennas or communication means for (hardwire or wireless) communications with the linked or connected device(s), respectively. The interface 13 is generally configured to communicate with at least one other apparatus, as illustrated with regards to the UE and the RNC. The memory 12 may store respective programs assumed to include program instructions or computer program code that, when executed by the respective processor, enables the respective electronic device or apparatus to operate in accordance with the exemplary embodiments of the present invention. For example, the memory 12 may store a pre-configuration with regards to the target cell of a serving cell change, or any other data or information usable in the context of the behavior describe herein.

In general terms, respective devices/apparatuses (and/or parts thereof) may represent means for performing respective operations and/or exhibiting respective functionalities, and/or the respective devices (and/or parts thereof) may have functions for performing respective operations and/or exhibiting respective functionalities.

When in the subsequent description it is stated that the processor (or some other means) is configured to perform some function, this is to be construed to be equivalent to a description stating that a (i.e. at least one) processor or corresponding circuitry, potentially in cooperation with computer program code stored in the memory of the respective apparatus, is configured to cause the apparatus to perform at least the thus mentioned function. Also, such function is to be construed to be equivalently implementable by specifically configured circuitry or means for performing the respective function (i.e. the expression "processor configured to [cause the apparatus to] perform xxx-ing" is construed to be equivalent to an expression such as "means for xxx-ing"). In its most basic form, according to exemplary embodiments of the present invention, the apparatus 10 or its processor 1 1 is configured to perform issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity, scheduling dummy data for the mobile communication entity after issuance of the cell change order, monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring. Accordingly, stated in other words, the apparatus 10 at least comprises respective means for issuing a cell change order, means for scheduling dummy data, means for monitoring receipt of an acknowledgment for the scheduled dummy data, and means for deciding whether the mobile communication entity has carried out the instructed serving cell change.

For further details regarding the operability/functionality of the individual apparatuses, reference is made to the above description in connection with any one of Figures 3 to 8, respectively.

According to exemplarily embodiments of the present invention, the processor 1 1 , the memory 12 and the connector 13 may be implemented as individual modules, chips, chipsets, circuitries or the like, or one or more of them can be implemented as a common module, chip, chipset, circuitry or the like, respectively.

According to exemplarily embodiments of the present invention, a system may comprise any conceivable combination of the thus depicted devices/apparatuses and other network elements, which are configured to cooperate as described above. In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device.

Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Such software may be software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is preserved. Such hardware may be hardware type independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components. A device/apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device/apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor. A device may be regarded as a device/apparatus or as an assembly of more than one device/apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example. Apparatuses and/or means or parts thereof can be implemented as individual devices, but this does not exclude that they may be implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person. Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) medium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

The present invention also covers any conceivable combination of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are applicable.

In view of the above, there are provided measures for an enhanced serving cell change technique. Such measures exemplarily comprise issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity, scheduling dummy data for the mobile communication entity after issuance of the cell change order, monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring.

Even though the invention is described above with reference to the examples according to the accompanying drawings, it is to be understood that the invention is not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

List of acronyms and abbreviations

ACK [Positive] Acknowledgement

CQI Channel Quality Indicator

ehs enhanced high speed

eSCC enhanced Serving Cell Change

HARQ Hybrid Automatic Repeat Request

hs high speed

HS-DPCCH High-Speed Dedicated Physical Control Channel

HS-DSCH High-Speed Downlink Shared Channel

HS-PDSCH High-Speed Physical Downlink Shared Channel

HS-SCCH High-Speed Shared Control Channel

HSDPA High-speed Downlink Packet Access

MAC Medium Access Control

NACK Negative Acknowledgement

nB Node B (UTRAN base station)

RNC Radio Network Controller

RRC Radio Resource Control

TTI Transmission Time Interval

UE User Equipment

UMTS Universal Mobile Telecommunications System UTRAN Universal Terrestrial Radio Access Network WCDMA Wideband Code Division Multiple Access

Claims

1. A method comprising

issuing a cell change order for a mobile communication entity, said cell change order instructing a serving cell change from a source network communication entity to a target network communication entity,

scheduling dummy data for the mobile communication entity after issuance of the cell change order,

monitoring receipt of an acknowledgment for the scheduled dummy data from the mobile communication entity, and

deciding whether the mobile communication entity has carried out the instructed serving cell change on the basis of the monitoring.

2. The method according to claim 1 , wherein the scheduling comprises

allocating the dummy data for the mobile communication entity, and

issuing an indication of a data allocation based on the dummy data allocation for the mobile communication entity.

3. The method according to claim 2, wherein the dummy data comprise empty data.

4. The method according to claim 2 or 3, wherein

the deciding yields that the mobile communication entity has carried out the instructed serving cell change when receipt of a negative acknowledgment for the scheduled dummy data is monitored, or

the deciding yields that the mobile communication entity has not carried out the instructed serving cell change when receipt of no acknowledgment for the scheduled dummy data is monitored

5. The method according to claim 1 , wherein the scheduling comprises

allocating the dummy data for the mobile communication entity, and

issuing an indication of a data allocation and a dummy data packet based on the dummy data allocation for the mobile communication entity.

6. The method according to claim 5, wherein

the deciding yields that the mobile communication entity has carried out the instructed serving cell change when receipt of a positive acknowledgment for the scheduled dummy data is monitored, or

the deciding yields that the mobile communication entity has not carried out the instructed serving cell change when receipt of a negative acknowledgment or no acknowledgment for the scheduled dummy data is monitored.

7. The method according to any one of claims 1 to 6, wherein

the dummy data scheduling is performed immediately upon issuance of the cell change order or upon elapse of a predetermined time after issuance of the cell change order.

8. The method according to any one of claims 1 to 7, wherein

the dummy data scheduling is performed once or repeatedly in a predetermined number with a predetermined interval after issuance of the cell change order.

9. The method according to any one of claims 1 to 8, further comprising

scheduling actual data for the mobile communication entity when the deciding yields that the mobile communication entity has carried out the instructed serving cell change, and/or

obtaining a confirmation for the serving cell change from the mobile communication entity and forwarding the confirmation to a network control entity.

10. The method according to any one of claims 1 to 9, further comprising

obtaining at least one control parameter for the dummy data scheduling from a network control entity,

wherein the dummy data scheduling is performed in accordance with the at least one control parameter.

1 1. The method according to any one of claims 1 to 10, wherein the cell change order includes an instruction to activate a pre-configuration for carrying out the instructed serving cell change, said pre-configuration having previously been provided to the mobile communication entity and the target network communication entity by a network control entity.

12. The method according to any one of claims 1 to 1 1 , wherein

the method is operable at or by the target network communication entity, and/or the method is operable in a high-speed downlink packet access deployment of a cellular communication system.

13. An apparatus comprising

an interface configured to connect to at least another apparatus,

a memory configured to store computer program code, and

a processor configured to cause the apparatus to perform:

14. The apparatus according to claim 13, wherein the processor is configured to cause the apparatus to perform the scheduling by

allocating the dummy data for the mobile communication entity, and

15. The apparatus according to claim 14, wherein the dummy data comprise empty data.

16. The apparatus according to claim 14 or 15, wherein the processor is configured to cause the apparatus to decide that the mobile communication entity has carried out the instructed serving cell change when receipt of a negative acknowledgment for the scheduled dummy data is monitored, or

decide that the mobile communication entity has not carried out the instructed serving cell change when receipt of no acknowledgment for the scheduled dummy data is monitored

17. The apparatus according to claim 13, wherein the processor is configured to cause the apparatus to perform the scheduling by

allocating the dummy data for the mobile communication entity, and

issuing an indication of a data allocation based on the dummy data allocation and a dummy data packet for the mobile communication entity.

18. The apparatus according to claim 17, wherein the processor is configured to cause the apparatus to

decide that the mobile communication entity has carried out the instructed serving cell change when receipt of a positive acknowledgment for the scheduled dummy data is monitored, or

decide that the mobile communication entity has not carried out the instructed serving cell change when receipt of a negative acknowledgment or no acknowledgment for the scheduled dummy data is monitored.

19. The apparatus according to any one of claims 13 to 18, wherein the processor is configured to cause the apparatus to perform

the dummy data scheduling immediately upon issuance of the cell change order or upon elapse of a predetermined time after issuance of the cell change order.

20. The apparatus according to any one of claims 13 to 19, wherein the processor is configured to cause the apparatus to perform

the dummy data scheduling once or repeatedly in a predetermined number with a predetermined interval after issuance of the cell change order.

21. The apparatus according to any one of claims 13 to 20, wherein the processor is configured to cause the apparatus to perform scheduling actual data for the mobile communication entity when the deciding yields that the mobile communication entity has carried out the instructed serving cell change, and/or

22. The apparatus according to any one of claims 13 to 21 , wherein the processor is configured to cause the apparatus to perform

obtaining at least one control parameter for the dummy data scheduling from a network control entity, and

the dummy data scheduling in accordance with the at least one control parameter.

23. The apparatus according to any one of claims 13 to 22, wherein the cell change order includes an instruction to activate a pre-configuration for carrying out the instructed serving cell change, said pre-configuration having previously been provided to the mobile communication entity and the target network communication entity by a network control entity.

24. The apparatus according to any one of claims 13 to 23, wherein

the apparatus is operable as or at the target network communication entity, and/or

the apparatus is operable in a high-speed downlink packet access deployment of a cellular communication system.

25. A computer program product comprising computer-executable computer program code which, when the program is run on a computer, is configured to cause the computer to carry out the method according to any one of claims 1 to 12.

26. The computer program product according to claim 25, wherein the computer program product comprises a computer-readable medium on which the computer- executable computer program code is stored, and/or wherein the program is directly loadable into an internal memory of the processor.