WO2013023354A1

WO2013023354A1 - User equipment assisted configuration of timing advance groups

Info

Publication number: WO2013023354A1
Application number: PCT/CN2011/078427
Authority: WO
Inventors: Wei Bai; Chunyan Gao; Jing HAN; Haiming Wang; Erlin Zeng
Original assignee: Renesas Mobile Corporation
Priority date: 2011-08-15
Filing date: 2011-08-15
Publication date: 2013-02-21

Abstract

A network sends to a user equipment UE configuration for a new secondary cell (SCell) and an indication to check a timing advance (TA) on it. The UE checks to see if the primary cell (PCell) TA is useable on the SCell by calculating the SCell TA and comparing it to the PCell TA. If the PCell TA is not useable on the SCell, the UE sends timing assistance information to the network informing that a TA other than the PCell TA is needed, and possibly a recommended TA group. The network uses the timing assistance information to select a TA group for the UE on the SCell.

Description

USER EQUIPMENT ASSISTED CONFIGURATION

OF TIMING ADVANCE GROUPS

TECHNICAL FIELD:

[0001] The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to synchronization and timing advance in a LTE system configured with carrier aggregation.

BACKGROUND:

[0002] The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

3 GPP third generation partnership project

CA carrier aggregation

CE control element

DL downlink

E-UTRA evolved universal terrestrial radio access

eNB evolved NodeB (base transceiver station in LTE/LTE-A)

LTE long term evolution (evolved UTRAN)

LTE-A LTE-advanced

MAC medium access control

PDCCH physical downlink control channel

RNTI radio network temporary identifier

RRC radio resource control

TA timing advance

TDOA timing difference of arrival

UE user equipment

UL uplink

[0003] Recent developments in the wireless communication arts divide a total system bandwidth into component carriers. Such systems are referred to as CA systems, and for example in the LTE system any given UE is to be configured with one primary component carrier (alternatively referred to as a primary cell or PCell) and one or more secondary component carriers (alternatively referred to as a secondary cell or SCell). CA is one of the key technological concepts to enable LTE-A to increase data throughput in the system, reduce transmission end-to-end delay, lower the per bit cost, and also enhance the performance scheme for more varied network deployment scenarios than are possible with more legacy cellular systems. There are various implementations for CA; the various component carriers may span different bandwidths or they may be equal, one or more S Cells may lie in the unlicensed band (industrial, scientific, medical or TV white spaces), one or more SCells may carry only data channels but no control channels (termed an extension carrier), and the various component carriers may not be contiguous in frequency with one another.

[0004] There is an agreement in the 3 GPP for LTE Release 10 (LTE-A) that only intra-band CA will be supported for UL, and there is to be only one TA for all the UL CCs. There is discussion that this restriction will not continue into Release 1 1 and beyond which contemplates inter-band carrier aggregation. Release 1 1 also is to include remote radio heads and repeaters for the eNB, which means multiple TAs will be necessary.

[0005] There have been no firm resolutions on how to implement multiple TAs in future 3 GPP specifications, but one view gaining acceptance is that there will be TA groups, each having one or more component carriers. All the component carriers within a given TA group should share the same TA value. Some of the early discussions along these lines can be seen at document R2-1 13285 by Huwai and HiSilicon entitled DISCUSSION ON TA GROUP MANAGEMENT; and also document R2-1 12876 by ZTE entitled GROUP MODEL FOR MULTIPLE TA [both documents from 3 GPP TSG-RAN WG2 meeting #74; Barcelona, Spain; 9-13 May 2011]. These discuss the need for a solution rather than proposing how the TA grouping issue might be resolved. [0006] Current discussions within the 3 GPP on this matter generally focus on two options for how a TA group should be configured. The first option is to configure the TA group in some implicit way, for example per frequency band, or according to the network deployment. The second option is to have the eNB explicitly configure the TA group using some methodology other than the implicit features above.

[0007] What is needed in the art is a way to identify just how to configure a TA group and what kind of factors should be taken into account for doing so. SUMMARY:

[0008] The foregoing and other problems are overcome, and other advantages are realized, by the use of the exemplary embodiments of this invention.

[0009] In a first exemplary embodiment of the invention there is a method comprising: in response to receiving a configuration for a new secondary cell, checking whether a timing value for a previously configured cell is useable for the new secondary cell; and for the case the checking finds that the timing value for the previously configured cell is not useable for the new secondary cell, compiling an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell.

[0010] In a second exemplary embodiment of the invention there is an apparatus comprising at least one processor; and at least one memory including computer program code. In this embodiment the at least one memory and the computer program code is configured, with the at least one processor, to cause the apparatus at least to perform: checking whether a timing value for a previously configured cell is useable for the new secondary cell in response to receiving a configuration for a new secondary cell; and for the case the checking finds that the timing value for the previously configured cell is not useable for the new secondary cell, compiling an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell. [0011] In a third exemplary embodiment of the invention there is a computer readable memory tangibly storing a computer program that is executable by at least one processor. In this embodiment the computer program comprises: code for checking, in response to receiving a configuration for a new secondary cell, whether a timing value for a previously configured cell is useable for the new secondary cell; and code for compiling, for the case the checking finds that the timing value for the previously configured cell is not useable for the new secondary cell, an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell. [0012] In a fourth exemplary embodiment of the invention there is a method comprising: utilizing timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment; and compiling a downlink message which identifies for the user equipment the selected timing group.

[0013] In a fifth exemplary embodiment of the invention there is an apparatus comprising at least one processor; and at least one memory including computer program code. In this fifth embodiment the at least one memory and the computer program code is configured, with the at least one processor, to cause the apparatus at least to utilize timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment; and further to compile a downlink message which identifies for the user equipment the selected timing group.

[0014] In a sixth exemplary embodiment of the invention there is a computer readable memory tangibly storing a computer program that is executable by at least one processor. In this embodiment the computer program comprises code for utilizing timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment. The computer program further comprises code for compiling a downlink message which identifies for the user equipment the selected timing group.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0015] Figure 1 is a schematic diagram showing a radio environment with a macro eNB, a remote repeater and two UEs; showing that whether a PCell and a SCell can be in the same TA group depends on the UE's location, and illustrating an environment in which exemplary embodiments detailed herein may be practiced to advantage.

[0016] Figure 2 is a flow diagram illustrating procedures by the eNB for using UE assistance information to configure a TA group for a newly configured SCell according to an exemplary embodiment of the invention.

[0017] Figure 3 is similar to Figure 2 but illustrating procedures by the UE. [0018] Figure 4 is an example of the signaling format with which the UE can provide the timing information to the eNB for configuring a TA group for the newly configured SCell according to an embodiment of these teachings.

[0019] Figures 5-6 are example MAC control elements for the eNB to configure the TA group for the newly configured SCell according to embodiments of these teachings.

[0020] Figures 7A-B are logic flow diagrams each illustrating the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, for practicing exemplary embodiments of these teachings from the respective perspectives of a UE and an eNB shown at Figures 1 and 8.

[0021] Figure 8 is a simplified block diagram of some of the devices shown at Figure 1 which are exemplary electronic devices suitable for use in practicing the exemplary embodiments of this invention.

DETAILED DESCRIPTION:

[0022] Figure 1 presents one exemplary but non-limiting CA environment in which embodiments of the invention might be practiced with advantage. In this deployment there is an eNB 22 in communication with two UEs, UEl and UE2, on two different UL frequency bands fl and £2. The eNB 22 also has a remotely located repeater 23, which is in communication with UE2 in the UL on f2. For simplicity assume fl is the PCell and f2 is an SCell. [0023] It is no difficulty for UEl if the PCell and the SCell are in the same TA group since UEl uses both those component carriers only for communications with the macro eNB 22. But keeping them in the same TA group would not be effective for UE2 since it sends UL transmissions on the PCell to the macro eNB 22 while also sending UL transmissions on the SCell to the remotely located repeater 23. UE2 will need different TA groups for the PCell and for the SCell. From this it is clear that whether a UE needs to have a different TA group will, in certain circumstances like that of Figure 1 , depend on the position of the UE.

[0024] On the carrier (SCell/f2) which is deployed with the repeater 23, most of the UEs will fall into the coverage of the macro eNB 22, simply because as Figure 1 shows the physical coverage area will typically be larger. In Figure 1 it is UEl that uses the SCell/f2 with the macro eNB 22. But lacking as it typically does position data for UEl , the eNB 22 is not able to distinguish whether UEl is in the SCell/f2 coverage area of the macro eNB 22 itself or in the coverage area of the repeater 23. Therefore the macro eNB 22 would in this situation have to configure the SCell/f2 in a separate TA group from the PCell/fl , but this is inefficient from both an implementation perspective and from a signaling overhead perspective. Using Figure 1 as an example, UEl will have to turn on two radiofrequency (RF) chains and operate two TA groups even if, as is true for UEl in Figure 1 , it is not necessary.

[0025] For this reason the inventors have concluded that efficiency is best improved if the eNB 22 could configure the TA group based on the real need at a given time. Below are detailed embodiments to do so in which the UE provides assistance to the eNB for configuring the TA groups. Further detail below also presents techniques for how to effectively change the TA groupings.

[0026] Reference is made to co-owned PCT Application PCT/CN201 1/070874 (filed on February 1 , 201 1 and entitled TIMING ADVANCE WITHOUT RANDOM ACCESS CHANNEL ACCESS) for two specific techniques by which the UE can get the TA on one component carrier from knowing TA on another component carrier. There it is detailed at equation (2) that:

TA_p— TA_S— 2 * [{T_DRP— T_DRS )— ( _DTP ~ T_DTS )] where: TAp is timing advance on the PCell;

TAs is timing advance on the SCell;

TDRP is the time at which the UE first receives a DL transmission on the PCell; TDRS is the time at which the UE first receives a DL transmission on the SCell; TDTP is the time at which the eNB sends a DL transmission on the PCell; and TDTS is the time at which the eNB sends a DL transmission on the SCell.

[0027] From this it follows that the UE could determine the DL reception timing difference between two cells by itself, without having to access any random access channel to get timing for a new cell. So as long as the UE could know the DL transmission timing difference between the two cells, the UE could simply add to or subtract from the timing advance TAp on the PCell (which the UE will know since it will always have a PCell configured) that timing 'difference value' or 'TA offset' that is relevant for the specific SCell in question.

[0028] This timing difference value may be signaled by the eNB, such as via a MAC control element or by RRC signaling. One example of the signaled timing difference value in the above-referenced PCT/CN201 1/070874 is [T_DTP-TDTS]- This allows the UE to know the time at which the eNB will transmit its DL transmission on the SCell, and solve for TAs and TUTS (time the UE is to transmit UL on the SCell) are then solved by the above equations. Another example of the signaled timing difference value is [TAp-TAs]. In this case the UE would listen on the SCell for the DL transmission and learn the TDRS from its reception time, then compute TUTS using equations provided in that co-owned application.

[0029] Once the UE has received and properly received and decoded the difference value signaled by the eNB, the above co-owned application details that the UE can calculate the TA value on the SCell based on any of the following equations: a. TAs - TAp - 2 * [(TDRP - TDRS) - (TDTP - TDTS)] b. TAs = TAP - 2 * [(T_DRp - T_DRS)] c. TAs - TAp +(TDRS - TDRP) + 2 * (TDTP - TDTS)]

[0030] Equation a may be used for example if the SCell is used as the UE's timing reference. Equation b may be used for example if there is no DL transmission timing difference; the UE could just calculate the TA value on the SCell without any difference signaling from the eNB. Equation c may be used for example if the PCell is used as the UE's timing reference. [0031] So in general the UE can calculate the TA value on the SCell based on the timing difference of DL reception between PCell and SCell. The teachings below build on this principal that the UE can calculate itself the TA value on SCell, sometimes with a timing difference value signaled by the eNB and sometimes without. [0032] According to these teachings, once a repeater 23 is deployed for a component carrier (SCell) and the eNB 22 configures this carrier for a UE, the UE first checks to see if it is in the coverage area of the repeater 23. The above-reference co-owned application also details how the UE might do this, by checking the TDOA. Recognize that the difference [TUT-TDT] between the time TDT at which the eNB 22 (or repeater 23) sends the DL transmission and the time TUT at which the UE sends its UL transmission is the same as the difference [TDT-TDR] between the time TDT and the time TDR at which the UE receives the eNB's (or repeater's) DL transmission. The timing advance is the round trip time, and equation (1) in that co-owned application reproduced below expresses the TA and the equivalence of these timin differences:

From this it follows that TA = 2 * (T_DR - T_DT) .

[0033] According to these teachings, the UE checks to see if it is in the coverage area of the repeater 23 by checking the TDOA and sending the result to the eNB 22 via the PUSCH. So long as both UE and eNB both understand the timing value which the UE provides, it can be the TA, the difference [TUT-TDT] which is equal to the difference [TDT-TDR], or some related timing difference derived from the TDOA. For convenience term this message the UE sends on the PUSCH as the UE assistance message, or similarly the UE's TDOA timing information in it as UE assistance information. It is from this message and the TDOA information it includes that the eNB 22 uses to configure the TA groups. [0034] Since the UE will not know, when first being configured for a new SCell, whether or not there is a repeater 23 operating on that SCell in the vicinity of the eNB 22 also operating on that SCell, the eNB 22 will indicate to the UE whether it should do the calculation (TDOA) for the newly configured SCell. In an embodiment the eNB 22 indicates this to the UE in the same RRC signaling that first configures the SCell for the UE. In a particular exemplary embodiment at this time the eNB 22 additionally indicates to the UE a threshold of tolerable timing differences. [0035] So in case the newly configured SCell is not deployed with a repeater 23, there is no need for the UE to check the position/timing and the eNB 22 can include the TA group configuration in the RRC signaling which first configures the SCell for the UE. But if the SCell is deployed with a repeater 23, Figure 1 makes clear that the eNB 22 does not know whether the SCell can be in the same TA group with the PCell and so cannot give the TA group in that initial RRC configuration signaling but will instead indicate to the UE that it is to do the TDOA calculation.

[0036] Once the eNB 22 sends that indication for the UE to perform the calculation, the UE will compute the UL timing advance value, such as for example by any of the ways detailed in the referenced co-owned application and summarized above. The UE will then send to the eNB 22 the UE assistance message as soon as possible (in the next PUSCH). Above the eNB 22 gave to the UE a threshold of tolerable timing differences.

[0037] The UE will see whether the calculated TA value (for the newly configured SCell) has a larger difference than the threshold between the current TA value (for the already configured PCell). If yes the UE will then send the assistance information to the eNB 22. In an exemplary embodiment such assistance information informs whether the TA value for the SCell is the same or has a sufficiently small difference than the TA value for the macro eNB 22. The eNB 22 should set the TA group according to this message (i.e., if same or the difference is within the threshold then the eNB will set the SCell to be in the same TA group as the PCell; otherwise the SCell will be put in a different TA group). [0038] If there are more than two TA groups which are finally supported, the UE can also include in its UL assistance message a recommended TA group which this newly configured SCell should be added into. The UE can do this by comparing the calculated TA value with reference to the threshold against any other TA group it is aware of.

[0039] On the eNB 22 side, once it receives the UE assistant information the eNB should configure or re-configure the TA group, such as via a MAC control element CE. In an exemplary embodiment the MAC CE should contain at least the target TA group index, and the corresponding SCell index. Upon receiving this TA group modification MAC CE the UE should apply the new TA group as soon as possible. If the eNB 22 detects a non-synchronous UL for the newly configured SCell at any time, the eNB 22 can simply re-transmit the same MAC CE to help align the UE's timing on the SCell. [0040] Generally the UL TA is a user plane issue from the perspective of protocol stacks in the UE, and so all the TA calculations and TA adjustments in the UE will be done at the physical layer and/or at the MAC layer. This means that configuring the TA group via a MAC CE will be a robust solution. [0041] Figure 2 is a flow diagram detailing some of the actions taken by the eNB 22 according to an exemplary embodiment. At block 202 the eNB 22 decides to configure a new SCell to the UE. At block 204 the eNB 22 checks the network configuration; if there is no repeater deployed on that same SCell then block 206 becomes active and the eNB 22 will send R C signaling to configure the new SCell for the UE and this configuration signaling will also give the TA group of the SCell as being the same as the PCell.

[0042] If instead at block 204 there is a repeater 23 deployed on this same SCell then block 208 becomes active and the eNB 22 indicates to the UE to calculate the TA value, which the UE can do for example using the TDO A computation noted above. The eNB 22 then receives from the UE its UE assistance information at block 210. If that information indicates that a separate TA group from the PCell is not needed, then block 212 becomes active and the eNB configures the new SCell with the same TA group as the PCell. If instead the information indicates that a separate TA group from the PCell is needed, then block 214 becomes active and the eNB configures the new SCell with a TA group different from that used for the PCell. [0043] Figure 3 is a flow diagram detailing some of the actions taken by the UE for which is newly configured with an SCell according to an exemplary embodiment. At block 302 the UE receives the RRC configuration signaling that configures the new SCell for it. At block 304 the UE checks that RRC configuration signaling to see if there is an indication for the UE to calculate the TA on the new SCell. If no then the flow chart is complete; the UE uses the TA group for the PCell which may or may not be explicitly indicated in the RRC signaling. If yes then block 306 becomes active and the UE begins tracking the TA value on this SCell according to the indication received at block 302. If there was the indication that the UE should perform the calculations, then the RRC signaling also included a threshold tolerance value according to one exemplary embodiment.

[0044] Once computed the UE checks the TA value of the SCell which it computed against the TA value on the PCell which the UE already knows (since the PCell is always configured for the UE). If there is a threshold tolerance the UE applies it here. If the calculated TA value for the SCell is the same as (or within the tolerance as) the TA on the PCell, then block 310 becomes active and the UE indicates to the eNB 22 that the same TA group as the PCell can be used on the newly configured SCell. If the calculated TA value for the SCell is different from (or outside the tolerance) the TA on the PCell, then block 312 becomes active and the UE indicates to the eNB 22 that the newly configured SCell will need a different TA group than the PCell and the UE may also recommend a specific TA group (by reporting a TA group index with the SCell index for example). Regardless of whether block 310 or 312 were entered, both feed into block 314 where the UE receives from the eNB a TA group for the SCell and follows that TA group timing to send its UL data on the SCell.

[0045] Returning to Figure 1, assume now that the UE1 is mobile and moves into the coverage area of the repeater 23. Or similarly assume the mobile UE2 moves out of the coverage range of the repeater 23. In either case it is advantageous that the mobile UE, after the initial configuration of the SCell, continue to monitor the TA difference in case the mobile UE moves into or out of repeater 23 coverage. Once the UE detects the TA difference larger than the threshold and reports that information to the eNB 23, the eNB 23 will be able to re-set the TA group dynamically. The UE should continue this monitoring anytime it has an SCell configured, even if at that initial configuration the SCell was put into the same TA group with the PCell.

[0046] Figures 4-6 give non-limiting examples of the various signaling noted above. Figure 4 is an exemplary UE assistance signaling and specifically indicates whether the SCell will need a different TA group from the PCell. The single bit "F" in Figure 4 is a binary flag to show if the UE's computed TA value for the SCell is the same or similar as the TA value for the PCell under the macro eNB 22 coverage. The three-bit field "TA group ID" gives the index for the TA group which the UE recommends. [0047] Figure 5 is an exemplary MAC CE which the eNB 22 uses, after setting the TA group for the SCell according to the Figure 4 information, to inform the UE of the TA group (indicated as "TA Group ID") that the eNB 22 has configured for the SCell (indicated as "Cell Index"). [0048] Figure 6 is another embodiment of a MAC CE. The single bit flag "E" is an extension flag informing the UE whether there is an extension after the first two octets (rows), of which there is one extension in Figure 6. Bit positions CI through C7 are the bitmap of each carrier. The three-bit field "TA group ID" identifies the allocated TA group. From Figure 6, all the carriers whose corresponding bit(s) is/are set in first octet are in the TA group identified in the second octet. Each extension bit enables two more octets and one additional TA group in this same MAC CE.

[0049] In an embodiment, if the newly configured SCell is not deployed with a repeater 23, the eNB 22 can more simply configure the TA group for it using the SCell initial configuration RRC signaling.

[0050] One technical effect of these teachings is that they enable the eNB 22 to configure the TA group according to the real need, without introducing implementation difficulties or additional signaling overhead. Additionally, they enable the network to change the TA group configuration on the fly (dynamically), without resorting to any C-plane procedure (only User-plane) and so the performance robustness is easily acceptable. And these embodiments in which the UE routinely monitors its own TA calculation enables the UE to know by itself, on the fly, if there is a need to change the TA group for a given component carrier, without it being necessary to lose synchronization.

[0051] Figures 7A-B are each a logic flow diagram which may be considered to illustrate the operation of a method, and a result of execution of a computer program stored in a computer readable memory, and a specific manner in which components of an electronic device are configured to cause that electronic device to operate. The various blocks shown in each of Figures 7A-B may also be considered as a plurality of coupled logic circuit elements constructed to carry out the associated function(s), or specific result of strings of computer program code stored in a memory.

[0052] Such blocks and the functions they represent are non-limiting examples, and may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.

[0053] Figure 7A details particular exemplary embodiments of the invention from the perspective of the UE (or one or more components thereof, more generally termed an apparatus which may or may not be the entire UE). At block 702 of Figure 7 A the UE/apparatus, in response to receiving a configuration for a new secondary cell, checks whether a timing value for a previously configured cell is useable for the new secondary cell. Then at block 704, for the case the checking of block 702 finds that the timing value for the previously configured cell is not useable for the new secondary cell, the UE/apparatus compiles an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell.

[0054] Further portions of Figure 7A are optional and may or may not be combined with one another in various embodiments. Block 706 stipulates that the previously configured cell noted first at block 702 comprises a primary cell on which the UE received the configuration for the new secondary cell. Block 708 states that the checking of block 702 is conditional on the UE receiving, in addition to the configuration for the new secondary cell stated at block 702, an indication to calculate a timing advance for the new secondary cell. Block 710 which may be combined with block 708 has the additional step of the UE/apparatus calculating the timing advance for the new secondary cell. Block 710 has further detail that the checking first said at block 702 comprises comparing whether the calculated timing advance for the new secondary cell is within a threshold difference from the timing value for the previously configured cell. And block 712 summarizes the embodiment in which the UE/apparatus identifies a recommended timing group in the compiled uplink message to indicate the new secondary cell's need for another timing group.

[0055] Finally, block 714 of Figure 7 A describes signaling after the UL message is compiled. The UE sends the uplink message first compiled at block 704, and the UE receives in response, from the macro eNB on the PCell, the MAC message with the CE noted with respect to Figures 5-6 as identifying the new SCell and the TA group for use on the new SCell. The UE then sends an UL message on the new SCell (for example, the UE sends data on a physical uplink shared channel) using a TA associated with the identified TA group. The TA group identified in the CE may or may not be the recommended timing group of block 712, depending on what other factors the eNB takes into account in its selection of which TA group to associate with the SCell for this UE. [0056] Figure 7B details particular exemplary embodiments of the invention from the perspective of the eNB 22 (or one or more components thereof, more generally termed an apparatus which may or may not be the entire eNB 22). At block 752 the apparatus/eNB utilizes timing assistance information, received from a UE on a PCell, to select a timing group to associate with a SCell for the UE. At block 754 the apparatus/eNB compiles a DL message which identifies for the UE the selected timing group. [0057] Further portions of Figure 7A are optional and may or may not be combined with one another in various embodiments. Block 756 stipulates that the timing assistance information is received from the UE in response to the eNB sending to the UE configuration information for the SCell, and also an indication for the UE to send the timing assistance information. As noted above the sending of the indication is conditional on there being a repeater operating on the SCell. To be relevant such a repeater must be operating near enough the eNB that a UE moving between them will somewhere have radio coverage for data (shorter than broadcast typically) by both the eNB and the repeater on the SCell. For brevity we term this nearness as the repeater being within 'radio proximity' to the eNB, and this is shown in block 756 also. Or the eNB 22 can simply check the network configuration whether there is a repeater 23 under the eNB's own control that is operating on the SCell. Block 758 summarizes the embodiment in which the eNB also sends to the UE, with the indication from block 756, a threshold difference for use by the UE to determine whether a timing value for the PCell is useable for the SCell. With or without the threshold difference, ion an example above it was detailed that the eNB sends the configuration information and the indication on the PCell in a single RRC message as block 756 mentions.

[0058] From the specific examples above it follows that if the timing assistance information of block 752 that the eNB receives indicates that the timing value for the PCell is not useable for the secondary cell, then the selected timing group of block 752 is different from a first timing group which is associated with the PCell. Similarly if the received timing assistance information indicates it is useable then the selected timing group of block 752 is the first timing group (which is associated with the PCell). If the UE timing assistance information also includes a recommended timing group, then the eNB may (but is not required to) use the UE-recommended TA group as the timing group which is selected at block 752.

[0059] And finally block 760 provides that the compiled DL message of block 754 is a MAC message with a CE that identifies both the selected timing group and the SCell. The eNB sends this MAC message to the UE on the PCell.

[0060] Reference is now made to Figure 8 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 8 there is a first network access node/macro eNB 22 coupled via an XI interface to a second network access node/repeater 23, which are adapted for communication over respective wireless links 70A, 70B with an apparatus 20 such as mobile terminals or termed more generally as a user equipment UE. The macro eNB 22 may be further communicatively coupled to further networks (e.g., a publicly switched telephone network PSTN and/or a data communications network/Internet), possibly via a higher network node such as a serving gateway in the case of the LTE system. [0061] The UE 20 includes processing means such as at least one data processor (DP) 20A, storing means such as at least one computer-readable memory (MEM) 20B storing at least one computer program (PROG) 20C, communicating means such as a transmitter TX 20D and a receiver RX 20E for bidirectional wireless communications with the macro eNB 22 and with the repeater 23 via one or more antennas 20F. Within the memory 20B of the first UE 20 is also the TA comparator and the UE assistance information compiler 20G for checking the calculated TA and for putting together the UE assistance message s detailed above.

[0062] The macro eNB 22 also includes processing means such as at least one data processor (DP) 22A, storing means such as at least one computer-readable memory (MEM) 22B storing at least one computer program (PROG) 22C, and communicating means such as a transmitter TX 22D and a receiver RX 22E for bidirectional wireless communications with its associated user devices 20 via one or more antennas 22F and a modem 22H. The macro eNB 22 also has stored in its memory at block 22G the logic or enabling software to configure the TA groups for the various SCells it configures for different UEs according to the UE assistance information they report on the PUSCH. The repeater 23 is similarly functional with blocks 23A, 23B, 23C, 23D, 23F and 23H. [0063] While not particularly illustrated for the UE 20, that device is also assumed to include as part of its wireless communicating means a modem which may in one exemplary but non limiting embodiment be inbuilt on an RF front end chip so as to carry the respective TX 20D and RX 20E.

[0064] At least one of the PROGs 20C, 22C in the UE 20 and in the macro eNB 22 is assumed to include program instructions that, when executed by the associated DP 20A, 22A, enable the device to operate in accordance with the exemplary embodiments of this invention as detailed more fully above. In this regard the exemplary embodiments of this invention may be implemented at least in part by computer software stored on the MEM 20B, 22B which is executable by the DP 20A, 22 A of the respective devices 20, 22; or by hardware; or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Electronic devices implementing these aspects of the invention need not be the entire UE 20, or macro eNB 22, but exemplary embodiments may be implemented by one or more components of same such as the above described tangibly stored software, hardware, firmware and DP, or a system on a chip SOC or an application specific integrated circuit ASIC or a digital signal processor DSP or a modem or a subscriber identity module commonly referred to as a SIM card. [0065] Various embodiments of the UE 20 can include, but are not limited to: cellular telephones; data cards, USB dongles, personal portable digital devices having wireless communication capabilities including but not limited to laptop/palmtop/tablet computers, digital cameras and music devices, and Internet appliances. [0066] Various embodiments of the computer readable MEM 20B, 22B include any data storage technology type which is suitable to the local technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DP 20 A, 22 A include but are not limited to general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and multi-core processors. [0067] Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description. While the exemplary embodiments have been described above in the context of the LTE and LTE-A systems, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems such as for example UTRAN, WCDMA and others as adapted for carrier aggregation. [0068] Some of the various features of the above non-limiting embodiments may be used to advantage without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

Claims

CLAIMS: What is claimed is:

1. A method, comprising:

in response to receiving a configuration for a new secondary cell, checking whether a timing value for a previously configured cell is useable for the new secondary cell; and

for the case the checking finds that the timing value for the previously configured cell is not useable for the new secondary cell, compiling an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell.

2. The method according to claim 1, in which the previously configured cell comprises a primary cell on which is received the configuration for the new secondary cell.

3. The method according to claim 2, in which checking whether the timing value for the previously configured cell is useable for the new secondary cell is conditional on receiving, in addition to the configuration for the new secondary cell, an indication to calculate a timing advance for the new secondary cell.

4. The method according to claim 3, the method further comprising calculating the timing advance for the new secondary cell;

and in which checking whether the timing value for the previously configured cell is useable for the new secondary cell comprises comparing whether the calculated timing advance for the new secondary cell is within a threshold difference from the timing value for the previously configured cell.

5. The method according to any one of claims 1 through 4, in which the compiled uplink message indicates that another timing group is needed for the new secondary cell by identifying a second timing group recommended by a user equipment executing the method.

6. The method according to claim 5, further comprising the user equipment sending the compiled uplink message to a macro eNodeB on the previously configured cell which is a primary cell from which is received the configuration for the new secondary cell.

7. The method according to claim 6, further comprising:

in response to sending the compiled uplink message, receiving from the macro eNodeB on the primary cell a medium access control message comprising a control element that identifies the new secondary cell and a timing advance group for use on the new secondary cell; and thereafter

the user equipment sending an uplink message on the new secondary cell using a timing advance associated with the identified timing advance group.

8. An apparatus comprising

at least one processor; and

at least one memory including computer program code;

in which the at least one memory and the computer program code is configured, with the at least one processor, to cause the apparatus at least to perform:

9. The apparatus according to claim 8, in which the previously configured cell comprises a primary cell on which is received the configuration for the new secondary cell.

10. The apparatus according to claim 9, in which in which the at least one memory and the computer program code is configured with the at least one processor to cause the apparatus at least to perform the checking conditional on the apparatus receiving, in addition to the configuration for the new secondary cell, an indication to calculate a timing advance for the new secondary cell.

1 1. The apparatus according to claim 10, in which the at least one memory and the computer program code is configured with the at least one processor to cause the apparatus at least to further calculate the timing advance on the secondary cell;

and in which the checking is done by comparing whether the calculated timing advance for the new secondary cell is within a threshold difference from the timing value for the previously configured cell.

12. The apparatus according to any one of claims 8 through 11 , in which the compiled uplink message indicates that another timing group is needed for the new secondary cell by identifying a second timing group recommended by the apparatus, in which the apparatus comprises a user equipment.

13. The apparatus according to claim 12, in which the at least one memory and the computer program code is configured with the at least one processor to cause the apparatus at least to further perform:

sending the compiled uplink message to a macro eNodeB on the previously configured cell which is a primary cell from which is received the configuration for the new secondary cell.

14. The apparatus according to claim 13, in which the at least one memory and the computer program code is configured with the at least one processor to cause the apparatus at least to further:

after sending the compiled uplink message, receive from the macro eNodeB on the primary cell a medium access control message comprising a control element that identifies the new secondary cell and a timing advance group for use on the new secondary cell; and thereafter

send an uplink message on the new secondary cell using a timing advance associated with the identified timing advance group.

15. A memory tangibly storing a computer program that is executable by at least one processor, in which the computer program comprises:

code for checking, in response to receiving a configuration for a new secondary cell, whether a timing value for a previously configured cell is useable for the new secondary cell; and

code for compiling, for the case the checking finds that the timing value for the previously configured cell is not useable for the new secondary cell, an uplink message indicating that another timing group, different from a first timing group which comprises the previously configured cell, is needed for the new secondary cell.

16. The memory according to claim 15, in which the previously configured cell comprises a primary cell on which is received the configuration for the new secondary cell.

17. The memory according to claim 15, in which code for checking operates conditional on receiving, in addition to the configuration for the new secondary cell, an indication to calculate a timing advance for the new secondary cell.

18. The memory according to claim 17, in which the computer program comprises further comprises code for calculating the timing advance on the secondary cell;

and in which the code for checking whether the timing value for the previously configured cell is useable for the new secondary cell operates to compare whether the calculated timing advance for the new secondary cell is within a threshold difference from the timing value for the previously configured cell.

19. A method comprising:

utilizing timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment; and

compiling a downlink message which identifies for the user equipment the selected timing group.

20. The method according to claim 19, in which the timing assistance information is received from the user equipment in response to a network node, which executes the method, sending to the user equipment configuration information for the secondary cell and an indication for the user equipment to send the timing assistance information.

21. The method according to claim 20, in which the network node which executes the method comprises an eNodeB, and the indication is sent conditional on a repeater operating on the secondary cell in radio proximity to the eNodeB.

22. The method according to claim 21, in which the eNodeB further sends with the indication a threshold difference for use by the user equipment to determine whether a timing value for the primary cell is useable for the secondary cell.

23. The method according to claim 21, in which the configuration information and the indication are sent on the primary cell in a single radio resource control message.

24. The method according to any one of claims 19 through 23, wherein:

for the case the received timing assistance information indicates that the timing value for the primary cell is not useable for the secondary cell, the selected timing group is different from a first timing group which is associated with the primary cell; else the selected timing group is the first timing group.

25. The method according to claim 24, wherein for the case the received timing assistance information indicates that the timing value for the primary cell is not useable for the secondary cell, the selected timing group is recommended by the user equipment in the timing assistance information.

26. The method according to any one of claims 19 through 23, in which the compiled downlink message is a medium access control message comprising a control element, and the control element identifies the selected timing group and the secondary cell; and the method further comprises sending the medium access control message to the user equipment on the primary cell.

27. An apparatus comprising

at least one processor; and at least one memory including computer program code;

in which the at least one memory and the computer program code is configured, with the at least one processor, to cause the apparatus at least to:

utilize timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment; and

compile a downlink message which identifies for the user equipment the selected timing group.

28. The apparatus according to claim 27, in which the timing assistance information is received from the user equipment in response to the apparatus sending to the user equipment configuration information for the secondary cell and an indication for the user equipment to send the timing assistance information.

29. The apparatus according to claim 28, in which the apparatus comprises an eNodeB, and the indication is sent conditional on a repeater operating on the secondary cell in radio proximity to the eNodeB.

30. The apparatus according to claim 29, in which the at least one memory and the computer program code is configured with the at least one processor to cause the eNodeB to further send with the indication a threshold difference for use by the user equipment to determine whether a timing value for the primary cell is useable for the secondary cell.

31. The apparatus according to claim 29, in which the configuration information and the indication are sent on the primary cell in a single radio resource control message.

32. The apparatus according to any one of claims 27 through 31, wherein:

33. The apparatus according to claim 32, wherein for the case the received timing assistance information indicates that the timing value for the primary cell is not useable for the secondary cell, the selected timing group is recommended by the user equipment in the timing assistance information.

34. The apparatus according to any one of claims 27 through 31, in which the compiled downlink message is a medium access control message comprising a control element, and the control element identifies the selected timing group and the secondary cell;

and the at least one memory and the computer program code is configured with the at least one processor to cause the apparatus further to send the medium access control message to the user equipment on the primary cell.

35. A memory tangibly storing a computer program that is executable by at least one processor, in which the computer program comprises:

code for utilizing timing assistance information, received from a user equipment on a primary cell, to select a timing group to associate with a secondary cell for the user equipment; and

code for compiling a downlink message which identifies for the user equipment the selected timing group.

36. The memory according to claim 35, in which the timing assistance information is received from the user equipment in response to the computer program executing code for sending to the user equipment configuration information for the secondary cell and an indication for the user equipment to send the timing assistance information.

37. The memory according to claim 36, in which the memory and the at least one processor are disposed within an eNodeB, and the indication is sent conditional on a repeater operating on the secondary cell in radio proximity to the eNodeB.

38. The memory according to any one of claims 35 through 37, wherein:

39. The memory according to claim 38, wherein for the case the received timing assistance information indicates that the timing value for the primary cell is not useable for the secondary cell, the selected timing group is recommended by the user equipment in the timing assistance information.

40. The memory according to any one of claims 35 through 37, in which the compiled downlink message is a medium access control message comprising a control element, and the control element identifies the selected timing group and the secondary cell; and the computer program further comprises code for sending the medium access control message to the user equipment on the primary cell.