HK1190025A - Cross-scheduling for random access response - Google Patents

Description

Cross scheduling for random access response

Technical Field

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 cross-scheduling from one component carrier or cell to another component carrier or cell during a random access procedure.

Background

Definitions the following abbreviations that may be found in the specification and/or the drawings are as follows:

3GPP third generation partnership project

CA carrier aggregation

CC component carrier

CIF carrier indication field

C-RNTI cell RNTI

DL downlink

Node B/base station in eNB E-UTRAN system

E-UTRAN evolution UTRAN (LTE)

LTE Long term evolution

LTE-A Long term evolution-advanced

MAC medium access control

PCC/PCell primary component carrier/primary cell

PDCCH physical downlink control channel

PDU protocol data unit

P-RNTI paging RNTI

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

RACH random access channel

RA-RNTI random access RNTI

RAR random access response

RNTI radio network temporary identifier

SCC/SCell secondary component carrier/secondary cell

SI-RNTI System information RNTI

TA timing Advance

UE user equipment

UL uplink

UTRAN Universal terrestrial radio access network

Bandwidth extension beyond 20MHz in LTE-a (expected to be implemented in 3GPP release 11) is done via carrier aggregation CA that aggregates multiple component carriers CC together to form a larger bandwidth. This is illustrated in fig. 1A, where there are five release 8 compatible CCs aggregated to form one larger LTE-a bandwidth. There is at least one CC that is backward compatible with legacy (3 GPP release 8/9) user terminals, 20MHz wide, and has all control and traffic channel structures of release 8. FIG. 1A is an example; in practice there may be more or less than five CCs, they may not have equal bandwidth, they may not be frequency adjacent, and LTE-a considers the case where one or more packet CCs are in unlicensed spectrum. CCs may be aggregated in both time division duplex, TDD, and frequency division duplex, FDD, systems.

1A-1B illustrate different example scenarios in which CA may be employed. In fig. 1B there is a macrocell F1 (e.g., a conventional cellular base station) providing macro area coverage and there is also a Remote Radio Head (RRH) F2 controlled by the macrocell F1, the RRHs serving to improve throughput at hot spots (hot spots shown in fig. 1B with darker lines). Mobility is performed based on F1 coverage (shown in lighter hatching in fig. 1B). For example, F1 and F2 may operate on different frequency bands, e.g., F1= {800MHz, 2GHz } and F2= {3.5GHz } and so on. It is expected that the F2RRH cell may be aggregated with the underlay F1 macro cell. In this case, the UE will communicate with the F1 cell on one CC (typically a PCC) and the F2 cell on a different CC (scc). These different CCs are treated as different cells by the UE.

Fig. 1C illustrates a different CA scenario, which is similar to that of fig. 1B, but in which a frequency selective repeater is employed such that coverage is extended for one of the carrier frequencies. It is expected that F1 and F2 cells of the same eNB may be aggregated at coverage overlap. In this case, the UE also treats the different CCs as different cells, with the F1 and F2 cells operating on different frequencies/different CCs.

In LTE release 8, the PDCCH informing individual UEs which radio resources to allocate for their traffic can only be used to indicate PDSCH/PUSCH transmitted on its own DL CC or its paired ul CC (release 8 spectrum can be considered as only one CC because of the ex-situ knowledge of CA). In LTE-advanced, "cross-scheduling" may be available, meaning that the PDCCH may be used to indicate PDSCH/PUSCH resources transmitted on other CCs than its own DL CC and/or its paired UL CC. This cross-scheduling is useful for distributing traffic load among multiple carriers from the perspective of the transmitted PDDCH.

However, in the scenarios of fig. 1B-1C, the transmitters are at different distances from the UE, and therefore there is a propagation delay that needs to be compensated for. In LTE, the eNB signals the Timing Advance (TA) to the UE as detailed in 3GPP ts36.321v10.1.0(2011-03), section 5.2. Upon receiving the Timing Advance Command (TAC), the UE adjusts its uplink transmission timing as detailed in 3GPP ts36.321v10.1.0(2010-12) section 6.1.1. The timing advance command may be received in a random access response or in a MAC control element. The validity of the timing advance command is controlled by a TA timer in the UE. As long as the TA timer runs, the timing advance remains valid and uplink transmissions can occur on the shared channel. The TA timer is restarted whenever a timing advance command is received. At the expiration of the TA timer, uplink synchronization is required and no uplink transmission can occur on the shared channel. In order for the eNB to evaluate the timing adjustments needed at the UE, a random access procedure is typically started.

In a continuing development of 3GPP release 11, a new CA work item is described that "specifies support for using multiple timing advances in case of LTE uplink carrier aggregation" (see document RP-110451, section 4 Objective;3GPP TSG RAN Meeting #51; kansa city, USA; March15-18,2011). Multiple TAs are needed to handle non-co-located network-side receivers, such as the RRHs and frequency selective repeater scenarios shown in fig. 1B-1C.

3GPP release 10 specifies that cross-carrier scheduling can be used to schedule resources on a cell from another cell. The Carrier Indicator Field (CIF) allows the PDCCH of the serving cell addressed to the C-RNTI of the UE to identify the other cell where the scheduled resource is located, but section 11.1 of 3gpp36.300v10.3.0(2011-03) sets forth the following limitations:

cross-carrier scheduling is not applicable to PCell, i.e., PCell is always scheduled via its PDCCH;

cross-scheduling does not apply to this SCell when the PDCCH of the SCell is configured, i.e. it is always scheduled via its PDCCH;

cross-carrier scheduling applies when the PDCCH of the SCell is not configured, and this SCell is always scheduled via the PDCCH of one other serving cell.

In 3GPP release 10, cross-carrier scheduling is not specified for all RACH related steps, since RACH is only supported on PCell for release 10 and PCell cannot be scheduled from SCell. In configuring CA, each CA-capable UE is configured with one PCell and optionally one or more scells as its serving cell, but the UE still has only one RRC connection with the network. The PCell is the cell that provides the UE with its network access layer mobility information, which is done at RRC connection establishment, re-establishment or handover. The PCell is a cell used by the UE for PUCCH transmission, and unlike the SCell, once established can only be changed with a handover procedure without deactivating the PCell. Thus, radio link failure on the PCell triggers the re-establishment procedure of the UE, which is not the case if the failure is on the SCell. For more details on PCell and SCell, see 3GPP ts36.300v10.3.0(2011-03) section 7.5.

Cross-scheduling scenarios, such as those in fig. 1B-1C, are independent of the fact that multiple TAs may be required. For example, assume that the PCell that the UE has with macro cell F1 also has a configured SCell with RRH F2. If the UE loses its TA with the PCell, it will perform RACH on the PCell to obtain UL synchronization, but the UL resources granted in this RACH procedure on the PCell cannot fall in the SCell. The possibility of cross-scheduling radio resources during the RACH procedure would give the network added flexibility. The exemplary embodiments of the present invention detailed below enable cross-scheduling during RACH procedures, which is currently not possible in LTE or LTE-a.

Furthermore, in 3GPP release 10, the UE does not perform blind decoding in the common search space of the SCell, because it is not expected to receive system information (scheduled by PDCCH addressed to SI-RNTI), paging (scheduled by PDCCH addressed to P-RNTI), random access response (scheduled by PDCCH addressed to RA-RNTI) on the SCell. If a RACH procedure is supported on the SCell and the RAR of the SCell is scheduled from the SCell, the number of blind decodes that the UE needs to support will increase. From this point of view, it would still be beneficial to be able to signal RARs from the PCell so that the UE only needs to decode the PCell's common search space, even if cross-scheduling of scells is not configured.

Disclosure of Invention

In a first example embodiment of the present invention, there is an apparatus comprising: at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: performing a random access procedure in which a downlink random access response from the network node to the user equipment indicates a timing advance for a component carrier or cell or a group of component carriers or cells in the plurality of component carriers or cells to which the timing advance applies; and then operating the wireless radio on the indicated one or a set of component carriers or cells synchronized with the timing advance.

In a second example embodiment of the present invention, there is a method, comprising: performing a random access procedure in which a downlink random access response from the network node to the user equipment indicates at least a timing advance for a component carrier or cell, or a group of component carriers or cells, of the plurality of component carriers or cells to which the timing advance applies; and then operating the wireless radio on the indicated one or a set of component carriers or cells synchronized with the timing advance.

In a third example embodiment of the present invention, there is a computer readable memory storing a program of computer readable instructions which when executed by a processor result in actions comprising: performing a random access procedure in which a downlink random access response from the network node to the user equipment indicates at least a timing advance for a component carrier or cell, or a group of component carriers or cells, of the plurality of component carriers or cells to which the timing advance applies; and then operating the wireless radio on the indicated one or a set of component carriers or cells synchronized with the timing advance.

Drawings

Fig. 1A is a schematic illustration of a radio spectrum in which cross-scheduling may be employed, where five component carrier bandwidths may be aggregated into a single LTE-advanced bandwidth.

Fig. 1B-1C illustrate different scenarios where a UE will require multiple independent timing advances for different cells/component carriers and are two example environments in which embodiments of the present invention may be advantageously implemented.

Fig. 2A-2B illustrate two MAC subheaders of one octet size as detailed at 3GPP ts36.321v10.1.0 (2011-03).

Fig. 2C illustrates a MAC random access response of six octets in size as detailed in 3GPP ts36.321v10.1.0 (2011-03).

Fig. 2D illustrates the MAC subheader and MAC random access response of fig. 2A-C assembled with optional padding bits into a MAC PDU for random access as detailed in 3GPP ts36.321v10.1.0 (2011-03).

Fig. 3A illustrates a random access response message according to first and second example implementations as further detailed herein.

Fig. 3B-3C illustrate random access response messages according to respective third and fourth example implementations as further detailed herein.

Fig. 4 is an example flow diagram illustrating various embodiments of the present invention from the perspective of a UE and eNB/network node.

Fig. 5 is a simplified block diagram of a UE and an eNB, which are example electronic devices suitable for use in example embodiments of the present invention.

Detailed Description

In 3GPP release 10, RACH procedure for UE is only possible on PCell, but release 11 is expected to allow it on SCell. Continuing with the background section above, the UE does not perform blind decoding in the common search space for any SCell, so it will not be able to receive any PDCCH addressed to the RA-RNTI on the SCell. Furthermore, if cross-carrier scheduling is configured for the SCell, cross-carrier scheduling needs to be supported for RACH related steps when introducing RACH for multi-TA on the SCell, since the UE does not monitor PDCCH on this SCell. There is currently no carrier indicator field, CIF, for the PDCCH addressed to the RA-RNTI for random access responses in LTE and LTE-a, since the RA-RNTI is in the common search space. As an overview, the non-contention RACH procedure in LTE and LTE-a is as follows. First, the eNB assigns a RACH preamble to the UE via proprietary signaling. Second, the UE then sends its assigned preamble on the RACH followed by a random access response by the eNB on the DL shared channel scheduled by the PDCCH and addressed to the RA-RNTI (mapped from the UE's message containing the preamble). The random access response assigns UL resources to the UE and gives absolute timing for UE synchronization. For contention-based RACH, the UE randomly selects a preamble. Fig. 2A-2D detail the conventional random access response of the network in more detail.

Fig. 2A-2D are taken from 3GPP ts36.321v10.1.0(2011-03), section 6.1.5, which describes a MAC PDU for random access, which conveys a random access response message of the network (to one or more UEs). A MAC PDU consists of a MAC header and zero or more MAC random access responses, optionally with padding bits as will be shown. The MAC PDU header itself is made up of one or more sub-headers, each of one octet (8 bits). Fig. 2A shows a subheader having: a one-bit field E, which is an extension flag indicating whether more fields exist in the MAC header; a one-bit field T, which is a type flag indicating whether the MAC subheader contains a random access ID (T = 1) or a backoff indicator (T = 0); and a six-bit field RAPID that identifies the RACH preamble UL transmitted by the UE on the RACH itself (given its index). Fig. 2B shows having another subheader with: a bit extension flag E; a one-bit type flag T; a four bit field BI, which is used by the UE to back off its timing for retransmission of RACH preambles in case of collision of its last RACH access attempt, given an overload condition in the cell; and the remaining two bits R are reserved but not currently used (always R = 0).

Fig. 2C shows the structure of the MAC random access response in six octets. There is one reserved bit R (R = 0) that is not currently used; eleven bits for a TA command that a given UE will apply a timing adjustment to synchronize with a carrier; twenty bits for indicating a granted UL resource to be used by the UE; and sixteen bits for the temporary C-RNTI now assigned to the UE, which the UE will use to identify itself after this random access response message. Fig. 2A-2C are arranged in a MAC PDU for random access as described in fig. 2D. The various subheaders are arranged one by one, followed by various MAC random access responses (RARs in fig. 2D) and the padding bits (if any) follow the last MAC random access response. Each individual UE obtains a subheader and a MAC random access response identified by the same index [1, 2, …, n ] in fig. 2D.

As can be seen from fig. 2A-2D, there are no bits or fields indicating on which CCs/cells the UL resources identified in fig. 2C may fall; conventionally, the network and the UE understand that they will fall on the same CC/cell in which the RACH falls. To allow cross-carrier scheduling for random access response, according to an example embodiment, the CC/serving cell/group is indicated in the MAC random access response. There are various ways to implement such an indication, four example ways of which are detailed below. Each of them can be considered to explicitly indicate the CC/serving cell/group to which the TA applies (and also where the UL resource allocation falls if the UL grant is included in the random access response). Each of these example implementations is customized to seamlessly integrate with existing LTE-a signaling categories and formats, and of course may be modified for easier adoption in other wireless systems.

In LTE-a, different configured CCs/cells of a UE may be arranged into TA groups; all CCs/cells in an individual group may apply the same TA. Thus, for example, if there is a PCell, SCell #1, and SCell #2 configured for a UE, in one case PCell and SCell #1 may be in one TA group while SCell #3 is in a different TA group, and in another case, each of the three configured cells has their own timing and none of them are grouped under the same TA.

The first implementation assumes at most only two TA groups. The UE knows how its configured cells are grouped by TA, so identifying the TA group for the UE also identifies the group of CCs/cells that are members of the TA group. This first implementation is illustrated in fig. 3A, where a first bit position 302A of a first octet of a random access response 300A is used to indicate which TA group applies to the TA command. For example, X =0 may indicate that the UE is to use the CC/cell on which this random access response 300A is sent, and X =1 may indicate that the UE is used with other CCs/cells. In the second implementation, the bits shown in fig. 3A labeled cell index 308 are used for this purpose, but for this first implementation, for the case where there is no UL resource grant 306A in the random access response 300A (or if there is only one CC/cell in the TA group of the UE indicated by bit 302A), those bits 308A are reserved bits 310 and are not used to signal information. In this first implementation, for the case where the random access response 300A does not include a UL resource grant 306A and/or if there is more than one CC/cell in the indicated TA group, those bits 308A indicate the index of the particular CC/cell within the TA group identified at the first bit position 302A to which the UL resource grant 306A applies. Regardless of whether UL resource grant 306A is present, the UE applies the indicated TA304A to all CCs/cells in the TA group identified in this TA group identifier bit 302A. Specifically, the first bit position 302A in the first octet of fig. 3A is defined to indicate a TA group, unlike its conventional use, which is reserved/unused in fig. 2C.

The second implementation dispenses with the above assumptions for the second implementation and therefore there may be more than two TA groups. This second implementation is also shown in fig. 3A and uses the first bit position 302A of the first octet as a flag to indicate the presence of CC/cell/group information included in the random access response 300A (i.e., the TA and UL resources identified in the random access response are for a different CC/cell than the CC/cell on which the random access response was sent). For example, X =1 indicates that there is CC/cell/group information in this random access response 300A, so TA and granted UL resources are for the indicated CC/cell/group, and X =0 indicates no CC/cell/group, so TA and granted UL resources are for the same CC/cell/group on which the random access response itself is sent. Alternatively, it may be specified that X =1 means that the random access response 300A is a new format including a CC/cell/group index, and the actual index at 308A indicates the specific CC/cell/TA group to which the TA at field 304A applies. For case X =1, the cell index is indicated by some of the bit positions in the last two octets of the random access response, which are shown as three cell index bits within the fifth octet in fig. 3A. For the X =0 case, these bits 308A will be reserved and unused.

Fig. 2C shows these latter two bits (with bits 308A and 310) as being for the temporary C-RNTI field. There is no need to signal the temporary C-RNTI in the random access response generated by the non-contention-based RACH because the network assigns a preamble to the UE that already has an RNTI assigned to it (the network informs the UE of its RACH preamble assignment using the RNTI). Thus, as with the first implementation, the second implementation also redefines the bit meanings from their conventional understanding. The random access response 300A of fig. 3A (or any of the various implementations described herein) may also be further adapted to support contention-based RACH by adding a seventh octet to give space for the CC/cell index 308A, without being able to omit the temporary C-RNTI in the fifth and sixth octets of fig. 2C.

Unlike the first and second implementations, which redefine certain bits of the existing format, the third implementation utilizes the new format for random access responses, illustrated by way of example in fig. 3B. The preamble bit 302B is a type flag indicating that this random access response 300B has a new format, followed by a three-bit CC/cell/group index 308C and an 11-bit TA command 304A. When the random access response 300B of this new format is two octets in length, then there is no available space for signaling any UL grant resources; the UE may use this random access response 300B in two octet format in a non-contention-based RACH procedure to obtain an updated TA value (e.g., if its TA timer has expired). But if there is an UL resource need indication then three more octets can be appended to the shown random access response 300B, which under the current understanding in LTE-a would occupy 20 bits, thus leaving the last 4 bits of the fifth/last octet unused.

As with the third implementation, the fourth implementation is also the new format for the random access response 300C shown in fig. 3C and may be used to signal the TA command 304C and CC/cell index 308C with or without granted UL resources. But for fig. 3C there is no type flag 302B and instead the bit is reserved and not used to signal information. In this case, the network may use RRC signaling to explicitly configure the random access response 300C that the UE should use this new format. Or alternatively its use may be implicit whenever cross scheduling is configured and RACH is configured on the cell. In either case, when the UE finds its matching preamble ID (e.g., RAPID in the subheader in fig. 2A), it knows how to interpret the random access response.

This configuration of the random access response format (either explicit or implicit in RRC signaling) may be used in any of the above embodiments. For the case where it is used with the second and third implementations, the first bit 30-2A, 302B may then simply be reserved without conveying any information for the UE. For the case it is used with the first implementation, the first bit 302A may still identify the TA group, or instead it may be reserved, in which case the UE implicitly knows to apply TA304A in the random access response 300A to all CCs/cells that are members of the same TA group as the CC/cell identified by index 308A.

In both the third and fourth implementations, for the case where the random access response 300B, 300C does not identify any granted UL resources, once the UE acquires UL synchronization on the new CC/cell in accordance with the RACH procedure of which the random access response 300B, 300C is part, the network may inform the UE of the granted UL resources using the normal PDCCH (addressed to the C-RNTI of the UE) with the carrier indication field. Each of the random access responses detailed above for the RACH procedure, whether contention-based or non-contention-based, is addressed to the RA-RNTI.

Also for the third and fourth implementations, it is convenient to put those new formats of random access responses 300B, 300C as the last entry/entries in the MAC PDU (see fig. 2D) in order to facilitate backward compatibility with legacy user equipments reading their regular random access responses in that same PDU. The first and second implementations are the same size as a conventional random access response and do not need to be segregated to guarantee backward compatibility in the same PDU.

For any of the above implementations, it is also convenient for the network to always send a random access response on the PCell, identifying in the random access response the CC/cell/TA group to which the TA (and UL resources if included) applies.

Using either of the above implementations or a modification of any of them, the UE then follows a RACH procedure for the indicated CC/cell/group, which includes applying the TA to the indicated CC/cell/group, starting its TA timer for the CC/cell/group, transmitting the PUSCH on the granted UL resources on the indicated CC/cell, and transmitting at a TA-dependent time.

One technical effect of the embodiments is to support cross-carrier scheduling during RACH procedures without impacting the physical layer blind decoding effort by the UE. Furthermore, the random access response detailed above is scheduled by the PDCCH addressed to the RA-RNTI in the UE's common search space, whether contention-based or contention-free, and thus the PDCCH addressed to the RA-RNTI is not changed. Thus, these techniques reduce the number of blind decodings that the UE needs to support as well as the PDCCH overhead, since the individual random access responses for different UEs for different cells can be put in one random access response PDU, which is the same as the existing random access responses for different UEs, where cross-scheduling is not allowed as is conventional (so all random access responses are for the same CC/cell).

The above embodiments are summarized and combined in fig. 4, which fig. 4 is a logic flow diagram illustrating the operation of a method and the results of execution of computer program instructions, according to an example embodiment of the present invention. According to these example embodiments, a random access procedure is performed at block 402, wherein a downlink random access response from the network node to the user equipment indicates at least a timing advance and an explicit indication identifying one component carrier or cell or a group of component carriers or cells among a plurality of component carriers or cells to which the timing advance applies. The wireless radio is operated at block 404 on one or a set of component carriers or cells synchronized with the timing advance of block 402.

It is stated in a way that blocks 402 and 404 are interpreted on both the network node/eNB and the UE (or one or more components thereof). On the network side, the eNB compiles and transmits a DL random access response at block 402. Although the network node remains synchronized on one or a set of CCs/cells, it receives the UE's UL transmission on the UL resources granted in the random access response (if such UL resources are granted, and if the network node still does not transmit and receive on the one or the set of CCs/cells), so its synchronization is consistent with the TA provided to the UE in the random access response. On the UE side, the UE receives the DL random access response of block 402, applying the TA to one or a set of CCs/cells as indicated in the random access response and transmitting the PUSCH (if any) on the indicated resources.

The remaining blocks of fig. 4 are optional embodiments, any of which may be combined with blocks 402 and 404, and any of which are interpreted on both the network side and the UE side of the wireless partition.

Block 406 describes various implementations in which the DL random access response grants UL resources to the UE, in which case the UE transmits PUSCH on uplink resources on the indicated one or set of component carriers or cells to which the timing advance is applied. The network node receives the same PUSCH.

Block 408 describes the first implementation above; the random access response (300A) identifies the set of component carriers or cells by a single bit (302A) indicating the timing advance set. For the case where there is more than one CC/cell in the indicated group and there is also a UL resource grant in the random access response, the random access response also includes an index identifying one component carrier or cell within the timing advance group (308A). In this case, the TA applies to all CCs/cells in the group (whether or not any UL resource grant is included), and the UL resource grant applies only to the identified one CC/cell within the TA group.

Block 410 describes the second implementation above; the random access response (300A) identifies one or more carriers or cells or groups by an index (308A), and further includes a flag bit (302A) indicating that the index is included in the random access response.

Block 412 describes the third implementation above; the random access response (300B) identifies one component carrier or cell or group by an index (308B), and the random access response further includes a flag bit (302B) indicating the format of the random access response, with or without the CC/cell/group index included in the random access response. It is also generalized whether this third implementation includes two options for UL resource grants: the random access response (300B) may be shorter (e.g., two octets in length) if it lacks any identification of uplink resources granted to the UE; and it may be longer (e.g., at least four octets in length) if it does not identify the uplink resources granted to the UE.

Block 414 describes the fourth implementation above, where the format is explicitly indicated to the UE (whether the response includes CC/cell/group index) in addition to the random access response itself; the random access response (300C) identifies one or a group of component carriers or cells by an index (308C), and identifies the format of the random access response in RRC signaling between the network node and the UE. The two options of whether this fourth implementation also includes UL resource grants are the same as in block 412, but the RRC signaling indicates whether the CC/cell/group index is included in the random access response.

Block 416 depicts the fourth implementation above, wherein the format of the random access response is implicit; the random access response (300C) identifies one or a group of component carriers or cells by an index (308C), and whether the random access response includes such an index is in a format that is implicit from the RACH and cross-carrier scheduling being configured (where the RACH is used in the random access procedure first set forth at block 402). The two options of whether the fourth implementation also includes UL resource grants are the same as in block 412, but the implicit indication indicates whether a CC/cell/group index is included in the random access response.

Although not explicitly shown in fig. 4, if the random access response of block 402 is considered to be a first RAR, from the network perspective it may schedule the first and other random access responses on the PCC/PCell (of the plurality of CCs/cells of block 402), regardless of which CC/cell the timing advance of the first and other random access responses applies. In addition, the network may transmit a MAC PDU including a plurality of random access responses to the UE of block 402 as well as other UEs. In this case, the network will set the first random access response within the PDU to follow all other random access responses that lack a display indication identifying the one or group of CCs/cells to which their respective TAs apply.

In a particular embodiment, the network may use RRC signaling to explicitly configure the user equipment with the new format random access response detailed above. This configuration of the UE is different from the explicit or implicit format indication identifying the random access response format as detailed in the above example.

The various blocks shown in fig. 4 may be viewed as method steps and/or as operations resulting from operations of computer program code embodied on a memory and executed by a processor and/or as a plurality of coupled logic circuit elements constructed to perform the associated functions.

Reference is now made to fig. 5 for illustrating a simplified block diagram of various electronic devices and apparatus suitable for use in implementing exemplary embodiments of the present invention. In fig. 5, a wireless network 1 is adapted to communicate with an apparatus, such as a mobile communication device referred to above as a UE10, over a wireless link 11 via a network access node, such as a node B (base station), and more particularly an eNB 12. The network 1 may include a Network Control Element (NCE) 14, which may include mobility management entity/gateway MME/S-GW functionality specified for LTE/LTE-a. NCE14 also provides connectivity to different networks, such as a telephone network and/or a data communication network (e.g., the internet).

The UE10 includes a controller, such as a computer or Data Processor (DP) 10A, a computer-readable memory medium embodied as a memory (MEM) 10B storing a program of computer instructions (PROG) 10C, and a suitable Radio Frequency (RF) transmitter and receiver 10D for bidirectional wireless communication with the eNB12 via one or more antennas (two shown). The eNB12 also includes a controller, such as a computer or Data Processor (DP) 12A, a computer-readable memory medium embodied as a memory (MEM) 12B storing a program of computer instructions (PROG) 12C, and a suitable RF transmitter and receiver 12D for communicating with the UE10 via one or more antennas (two shown). The eNB12 is coupled to NCE14 via a data/control path 13. The path 13 may be implemented as an S1 interface known in LTE/LTE-a. The eNB12 may also be coupled to another eNB via a data/control path 15, which may be implemented as an X2 interface as known in LTE/LTE-a.

At least one of PROG10C and PROG12C is assumed to include program instructions that, when executed by an associated DP, enable the device to operate in accordance with the exemplary embodiments of this invention as detailed above. That is, example embodiments of the present invention may be implemented at least in part by computer software executable by the DP10A of the UE10 and/or the DP12A of the eNB12, or by hardware, or by a combination of software and hardware (and firmware).

For the purpose of describing example embodiments of the present invention, it may be assumed that the UE10 also includes an RA response bitmap or algorithm 10E that may interpret the bit meaning of the random access response message it receives in accordance with the embodiments detailed above, in conjunction with rules as to whether cross-scheduling and RACH are configured (e.g., implicit format of the fourth implementation). eNB12 has similar functionality in block 12E, while eNB12 also has a random access response format filled with bits.

In general, the various embodiments of the UE10 can include, but are not limited to, cellular telephones, Personal Digital Assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, internet appliances permitting wireless internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The computer-readable MEMs 10B and 12B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, slave memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DP10A and DP12A may be of any type suitable to the local technical environment and may include one or more of general purpose computers, special purpose computers, microprocessors, Digital Signal Processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.

In general, the various example embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in embodied firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, embodied software and/or firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof, wherein the embodied executable software may be special purpose general purpose elements.

It should thus be appreciated that at least some aspects of the exemplary embodiments of the inventions may be implemented in various components such as integrated circuit chips and modules and that the exemplary embodiments of the inventions may be implemented in apparatus that is embodied in an integrated circuit. The one or more integrated circuits may include circuitry (and possibly firmware) for embodying at least one or more of one or more data processors, one or more digital signal processors, baseband circuitry, and radio frequency circuitry that may be configured for operation in accordance with example embodiments of the present invention.

Although the example embodiments have been described above in the context of an LTE-advanced system, it should be understood that the example embodiments of the present invention are not limited to use with only this one particular type of wireless communication system that uses carrier aggregation.

In addition, the various names used for the described parameters and channels (e.g., RACH, PDCCH, TA) are not intended to be limiting in any respect, as any suitable name may identify these parameters. The use of LTE-a in the specific example does not limit the broader aspects of the invention that are feasible for many CA systems other than LTE-a that use cross-scheduling.

In addition, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

Claims (22)

1. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to:

performing a random access procedure in which a downlink random access response from a network node to a user equipment indicates a timing advance for a component carrier or cell, or a group of component carriers or cells, of a plurality of component carriers or cells to which the timing advance applies; and then

Operating a wireless radio on one or a set of component carriers or cells of the indication synchronized with the timing advance.

2. The apparatus of claim 1, wherein:

the downlink random access response further indicates uplink resources granted to the user equipment, an

The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to operate the wireless radio to transmit or receive using uplink resources on the component carrier or cell or a group of component carriers or cells to which the timing advance applies.

3. The apparatus of claim 2, wherein the random access response further indicates the component carrier or cell for which the uplink resources are on by an index.

4. The apparatus of claim 1, wherein the random access response further identifies the set of component carriers or cells by a single bit indicating a timing advance set,

wherein the timing advance is applied to all component carriers or cells within the group.

5. The apparatus according to claim 1, wherein the random access response further identifies the component carrier or cell or a group of component carriers or cells by an index, and the random access response further comprises a flag bit indicating that the index is included in the random access response.

6. The apparatus of claim 1, wherein the random access response further identifies the component carrier or cell or group of component carriers or cells by an index, and whether the random access response includes the format of the index is identified by one of: radio resource signalling between the network node and the user equipment; and implicitly according to the random access channel and cross-carrier scheduling being configured.

7. The apparatus according to any one of claims 1 to 6, wherein the apparatus comprises the network node or one or more components thereof.

8. The apparatus of claim 7, wherein the random access response comprises a first random access response, and the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to further:

scheduling the first and further random access responses on a primary component carrier or primary cell of the plurality of component carriers or cells regardless of which component carrier or cell or which set of component carriers or cells the timing advance of the first and further random access responses applies to.

9. The apparatus of claim 7, wherein the random access response comprises a first random access response, and the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to further:

transmitting a medium access control protocol data unit comprising a plurality of random access responses to the user equipment and to other user equipments, wherein the first random access response is arranged to follow within the protocol data unit all other random access responses lacking a displayed indication of a component carrier or cell or group of component carriers or cells to which a respective timing advance for identifying all other random access responses applies.

10. The apparatus according to any one of claims 1 to 6, wherein the apparatus comprises the user equipment or one or more components thereof.

11. A method, comprising:

performing a random access procedure in which a downlink random access response from a network node to a user equipment indicates at least a timing advance for a component carrier or cell, or a group of component carriers or cells, of a plurality of component carriers or cells to which the timing advance applies; and then

Operating a wireless radio on one or a set of component carriers or cells of the indication synchronized with the timing advance.

12. The method of claim 11, wherein:

the downlink random access response further indicates uplink resources granted to the user equipment, an

Operating the wireless radio comprises transmitting or receiving using uplink resources on the component carrier or cell or a group of component carriers or cells to which the timing advance applies.

13. The method according to claim 12, wherein the random access response further indicates by an index the component carrier or cell for which the uplink resources are on.

14. The method of claim 11, wherein the random access response further identifies the set of component carriers or cells by a single bit indicating a timing advance set,

wherein the timing advance is applied to all component carriers or cells within the group.

15. The method according to claim 11, wherein the random access response further identifies the component carrier or cell or group of component carriers or cells by an index, and the random access response further comprises a flag bit indicating that the index is included in the random access response.

16. The method according to claim 11, wherein the random access response further identifies the component carrier or cell or group of component carriers or cells by an index, and whether the random access response comprises the format of the index is identified by one of: radio resource signalling between the network node and the user equipment; and implicitly according to the random access channel and cross-carrier scheduling being configured.

17. The method of any one of claims 11 to 16, performed by the network node or one or more components thereof, and wherein the random access response comprises a first random access response;

the method further comprises the following steps:

scheduling the first and further random access responses on a primary component carrier or primary cell of the plurality of component carriers or cells regardless of which component carrier or cell or which set of component carriers or cells the timing advance of the first and further random access responses applies to.

18. The method of any one of claims 11 to 16, performed by the network node or one or more components thereof, and wherein the random access response comprises a first random access response;

the method further comprises the following steps:

transmitting a medium access control protocol data unit comprising a plurality of random access responses to the user equipment and to other user equipments, wherein the first random access response is arranged to follow within the protocol data unit all other random access responses lacking a display indication identifying a component carrier or cell or group of component carriers or cells to which the respective timing advance of the all other random access responses applies.

19. The method according to any of claims 11 to 16, wherein the device explicitly configures a format of the downlink random access response by the network node via radio resource control signaling.

20. A computer readable memory storing a program of computer readable instructions which when executed by a processor result in actions comprising:

performing a random access procedure in which a downlink random access response from a network node to a user equipment indicates at least a timing advance for a component carrier or cell, or a group of component carriers or cells, of a plurality of component carriers or cells to which the timing advance applies; and then

Operating a wireless radio on one or a set of component carriers or cells of the indication synchronized with the timing advance.

21. The computer readable memory of claim 20, wherein:

the downlink random access response further indicates uplink resources granted to the user equipment, an

Operating the wireless radio comprises transmitting or receiving using uplink resources on the component carrier or cell or group of component carriers or cells to which the timing advance applies.

22. The computer-readable memory of claim 20, wherein the random access response comprises a first random access response, and the actions further comprise:

scheduling the first and further random access responses on a primary component carrier or primary cell of the plurality of component carriers or cells regardless of which component carrier or cell or which set of component carriers or cells the timing advance of the first and further random access responses applies to.