Detecting a downlink control structure for carrier aggregation

Technical field The present invention relates to methods for detecting downlink aggregation control structure in communication networks, and in particular to methods implemented in a user device (UE) used in a wireless communication network.

Background Art [0002] Long Term Evoiution (LTE) is a mobile network technology standard based on the 3GPP standard. It is a set of extensions for the UMTS (Universal Mobile Telecommunications System) system, designed to increase the speed of data transmission for users of mobile wireless networks, increase user bandwidth and more efficient use of radio frequency spectrum. Currently, 3GPP is standardizing LTE-Advanced as an LTE extension. [0003] Fig. 1 shows a heterogeneous mobile communication network system 10 in the LTEAdvanced or LTE Rel-10 standard. In this system 10, base stations 12, 14, also known as eNode B nodes (Evolved Node B), support the communication of a number of User Equipment (UE) 16, 18, e.g. mobile phones, laptops, devices PDA (persona! digital assistant) type. Base stations 12, 14 are stationary, each providing communication range in a certain geographical area. Base station 12 is a femtocell that is connected to the network_L service providers through a broadband connection and provides coverage on component carriers CC # 0 and CC # 1. Base station 14 is a macro cell and provides radio range on CC # 0 and CC # 1 component carriers at different distances for each component carrier, [0004] In the downlink channel, from base stations 12, 14 to UE 16, 18 devices, standard LTE uses Orthogonal Frequency Division Multiplexing (OFDM). OFDM technique is a method of digital modulation on many carriers, in which a large number of closely spaced orthogonal sub carriers are used to transfer data. Multi-access with orthogonal frequency division (OFDMA) is used as a downlink LTE multiplexing scheme. In OFDMA multi-access, subcarriers are allocated for a predetermined time for individual UEs. This enables simultaneous data transmission from a certain number of users.

[0005] The down channel supports physical channels that relay information from the upper layers of the LTE stack. The two physical downlink channels are the Physical Down link Shared Channel (PDSCH), which is used for data transmission, as well as the Physical Downlink Contro! Channel (PDCCH) ), which is used to transmit control information. The scheduling of data reception on the downlink (on the PDSCH channel) or data transmission on the uplink, on the Physical Uplink Shared Channel (PUSCH) to the UE is usually implemented via link control signaling down using the PDCCH.

[0006] Document: RESEARCH IN MOTION ET AL: "Carrier Indication for Carrier Aggregation", 3GPP DRAFT; R1-092417 (RIM-CARRIER INDICATION FOR CA), 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTER; 650, ROUTE DES LUCIOLES; F-06921 SOPHIA-ANTIPOLIS CEDEX; FRANCE, no. Los Angeles, USA; 20090624, 24 July 2009 (2009-06-24), ΧΡ050350931, [downloaded 2009-06-24]; refers to the indication of carriers for carrier aggregation.

Summary of the Invention [0007] The main element to be introduced in LTE-Advanced is carrier aggregation. Component carriers (CC) that are continuous or discontinuous in the frequency domain can be aggregated. The UE may be adapted to aggregate different numbers of CC carriers that may differ in uplink (UL) and downlink (UL) bandwidth. Carrier aggregation depends on the UE, each UE in the same cell may have a different carrier aggregation configuration.

[0008] When the UE is configured for carrier aggregation, the UE is adapted to simultaneously receive or transmit on all CC carriers that are aggregated. The UE may thus be simultaneously serialized on a number of CC carriers. The scheduling of downlink assignments and uplink assignments for each CC carrier can be done via an additional carrier pointer field of 0-3 bits in DCI format (s) for jjujcuyi iuzlcj i iu & i icj in piz.yfjcieł \ uu unuw, wsKći ^ nK riusnej rne occurs.

[0009] An example illustrating the aggregation of carriers for CC carriers and the corresponding assignment of the carrier index index to the CC carrier index for the PDCCH channel with the carrier indicator field in CC # 2, is shown in Figs. 2 and 3, respectively.

[0010] The use of a carrier pointer on a PDCCH is not without cost. The disadvantages of using the PDCCH carrier pointer include:

- Increased scheduling complexity on the PDCCH, since this scheduling may need to be performed jointly for a number of CC carriers.

- Data block size increased up to 3 bits for DCI formats if the carrier pointer is explicitly signaled.

- A possible increase in the number of blind decoding attempts for a CC carrier if the UE is expected to blindly detect if the carrier indicator field with a non-zero number of bits in DCI format is present and if the CC carriers may have different bandwidth.

[0011] From the UE device's point of view, the increase in the number of blind decoding attempts for the CC carrier is undesirable due to the increase in PDCCH processing delay and the increase in power consumption, especially if the UE device is required to perform additional blind detections all the time, but the benefits of PDCCH with configurable bindings are limited to certain situations. [0012] It would therefore be desirable to provide a carrier aggregation detection method that minimizes the number of PDCCH blind decoding attempts that the UE needs to perform for each CC carrier.

[0013] The present invention is defined by independent claims 1, 10, 11, 12, 13 and 14. Preferred embodiments are defined by the dependent claims.

[0014] According to one aspect, the present invention provides a method implemented in a UE used in a wireless communication network, a method implemented in a base station used in a wireless communication network, a method implemented in a wireless communication network, a UE device, a base station and a wireless communication network as defined in the claims. In one example, a method is provided for detecting the structure of carrier aggregation downlinks in a communication network in which data transmission is serialized through a physical downlink control channel (PDCCH), which method comprises steps, on the EU device:

receiving higher layer signaling that allows UE aggregation, and reading component carriers PDCCHs (CCs), with downlink control information (DCI) in the PDCCHs of each CC carrier are read according to one of a number of predefined formats derived from higher layer signaling.

[0015] Higher layer signaling enables or disables carrier aggregation and allows the minimum number of blind decoding attempts to be maintained, as well as the size of DCI format data locks when no cross-carrier control is needed (depending on the deployment scenario or network operator preferences). This higher layer signaling is only sent to UEs adapted for aggregation of carriers. The default setting adopted by both the eNodeB node and the UE prior to sending this higher layer signaling is the lack of cross-carrier control, i.e. all DCI formats contain zero-bit carrier indicator fields.

[0016] Since the PDCCH of each CC carrier is read according to the predetermined DCI format signaled to the UE, the UE's power consumption and PDCCH channel delay processing budget for the CC carrier may be reduced.

[0017] Higher layer signaling may indicate that the CC carrier is a host CC that is adapted to transmit PDCCH client CC carriers, the predetermined DCI format in the PDCCH channels for the main CC carrier includes an indicator field carrier with a non-zero number of bits.

[0018] Thus, PDCCH channels containing carrier indicators are transmitted only in a certain subset of CC carriers (e.g. K, where K = 1, ..., M, and M is the total number of CC carriers aggregated for the UE), called the main CC carriers .

[0019] The higher layer signaling may indicate that the CC carrier is a client CC carrier that does not transmit PDCCHs of other CC carriers, with the predetermined DCI format in the PDCCH channels for the client CC carrier having a carrier field of zero bit size.

[0020] PDCCH channels of client CC carriers may be transmitted on the main CC carrier. It is possible for the CC carrier to be at the same time the main CC carrier as well as the client CC carrier. In this case, the CC carrier may transmit PDCCHs of other CC carriers, as well as its PDCCH may be transmitted on other CC carriers.

[0021] Higher layer signaling may indicate that it is not required for the UE to detect PDCCHs on the client CC carrier. Instead, client CC carrier PDCCHs are transmitted on the main CC carrier. The method may further include the step of selectively reading CC carrier PDCCHs, such that the UE does not detect PDCCHs on this client CC carrier. [0022] The client CC carrier may thus be configured so that all PDCCHs (with a zero bit size indicator) for the UE are not transmitted on this CC carrier. Therefore, the UE is not required to detect any PDCCHs on the client CC carrier. In contrast, this configuration cannot be used if the client CC carrier is also at the same time the main CC carrier, This configuration is advantageous for the implementation of heterogeneous networks in which the CC carrier client interference level can be so high that the control channels do not can be sent reliably. Since no PDCCH channel detection is required for client CC carriers, energy savings in the UE may be achieved.

[0024] In contrast, in other deployment scenarios, such as homogeneous networks, in which the frequency diversity gain may be more important, the diversity gain can also be used by the UE also in detecting PDCCHs on the client CC carrier.

[0025] The signaling of the upper layer may not indicate that the CC carrier is the client CC carrier or the main CC carrier, in this case the CC carrier can be considered a regular CC carrier that is used to transmit all of its PDCCH channels and only its PDCCH channels, wherein the predetermined DCI format in PDCCHs for ordinary CC carrier comprises a zero-bit carrier pointer field.

[0026] Thus, using upper layer signaling, the eNodeB may configure the CC carrier as one or more of the following types:

- CC Main Carrier: CC carrier that can be used to transmit client CC (s) PDCCHs and their own PDCCHs.

- CC client carrier: CC carrier whose PDCCH channels can be transmitted on the main CC carrier. The CC carrier client can also be used to transmit its own PDCCHs, if configured.

- Normal CC carrier: CC carrier that is used to transmit all of its PDCCHs and only its PDCCHs (same as in LTE Rel-8).

[0027] All PDCCHs transmitted on the main CC carriers always contain carrier indicators with a non-zero number of bits, even for PDCCHs that correspond to the main CC carriers. The current number of carrier pointer field bits may be a function of the current aggregate number of carriers for the UE (i.e. ceil (log2 M).). PDCCHs transmitted on client CC carriers or regular CC carriers do not contain carrier indicators with a non-zero number of bits.

[0028] Higher layer signaling can be used in a network to configure CC carriers as main CC carriers, client CC carriers and normal CC carriers in a semi-static manner as needed or changes in radio channel properties. For example, for a heterogeneous network with an uncoordinated distribution of femtocells, the interference properties of each of the CC carriers may change several times a day.

[0029] The signaling of the higher layer may depend on the UE, because some UEs may not be adapted for carrier aggregation. In addition, for a heterogeneous network, the interference properties for each of the CC carriers experienced by different UEs may be different. As shown in Fig. 1, UE 16 and UE 18 clearly experience different radio properties for CC # 0 and CC # 1.

[0030] The main CC carrier may have the same CC bandwidth as the client CC carrier for which they transmit PDCCHs. In this case, the CC carrier, which is part of the carrier aggregations, must have the same bandwidth size as at least one other CC carrier in this carrier aggregation in order for it to be a CC carrier, which can be the main or client CC carrier.

[0031] An advantage of the present invention is that the number of PDCCH blind decoding attempts that must be performed by the UE for main CC carriers is not doubled due to two different data block sizes for the same DCI format due to the difference in CC bandwidth. In conjunction with the use of predefined formats, as described above, the number of blind decoding attempts that inususes piz.epfu. Seeing the use of ut, the music should be the same as that given for the usual CC carrier.

Description of the figures [0032] [Fig: 1]

Fig. 1 is a diagram illustrating a heterogeneous LTE-Advanced or LTE Rel-10 heterogeneous mobile communication network.

[Fig. 2]

Fig. 2 shows the carrier aggregation scheme for CC carriers.

[Fig. 3]

Fig. 3 is a table illustrating examples of 3-bit carrier indicator fields.

[Fig. 4A]

Fig. 4A shows schematics scenarios for PDCCH-PDSCH channel binding for two CC carriers.

[Fig. 4B]

Fig. 4B is a schematic diagram of the PDCCH-PDSCH channel association scenarios for two CC carriers.

[Fig. 4C]

Fig. 4C is a schematic diagram of the PDCCH-PDSCH channel binding scenarios for two CC carriers.

[Fig. 5]

Fig. 5 is a block diagram showing a method in one embodiment of the present invention.

Description of Embodiments of the Invention [0033] Fig. 4A, Fig. 4B and Fig. 4C show possible scenarios for associating PDCCH-PDSCH channels for the example of two CC carriers. In Fig. 4A, PDCCH 20, 22 are on the same CC 24, 26 as PDSCH 28, 30 for which they are scheduling. In Fig. 4B, PDCCH channels 32, 34 are on a different carrier component 36, 38 than the PDSCH channels 42, 40 for which they are scheduling. In Fig. 4C, both PDCCHs 44, 46 are on one component carrier 48, although the PDCCHs 44, 46 are scheduling for PDSCH 50, 52 on components 48, 54.

[0034] According to the control structure used in the present invention, the CC 24 and 26 carriers are ordinary CC carriers, the CC 36, 38 carriers are both the main and client CC carriers, the CC 48 carrier is the main CC carrier and the CC 54 carrier is client support CC.

[0035] Referring to Fig. 5, in one embodiment of the present invention, the CC carriers PDCCHs are read according to one of a number of predefined formats derived from higher layer signaling between an eNodeB (e.g. base station 12) and the device UE (e.g. UE 16 device).

[0036] In step 70, it is determined whether the UE is required to detect DCI formats with carrier indicator fields with a non-zero bit number. The default setting adopted by both eNodeB and UE is no aggregation of carriers. Thus, in the absence of the higher layer signaling received, at step 72, the UE assumes that the CC carrier is a normal CC carrier and reads the PD carrier of the CC carrier according to the predetermined DCI format in the PDCCH channels with a zero bit size indicator field.

[0037] Conversely, if the UE receives higher layer signaling from the eNodeB, e.g., the carrierjnd_config signal, switching to carrier aggregation mode, then in step 74 the UE determines whether the downlink CC carrier is the main CC carrier. If the higher layer signaling from an eNodeB node, e.g. signal control_cc_config, indicates that the CC carrier is the main CC carrier, in step 76 the UE reads the CC carrier PDCCH channels according to the predetermined DCI format with a carrier pointer field having a non-zero number of bits. The physical signal processing and PDCCH detection procedure can be the same as the Rel-8 processing and procedure as specified in the documents TS 36.211 and TS 36.213.

[0038] If the higher layer signaling from the eNodeB, e.g. the control_cc_config signal, instead indicates that the CC carrier is a client CC carrier, in step 78 the UE determines that the downlink CC carrier is a client CC carrier. Then, at step 80, the UE determines whether it is required for this UE to detect PDCCH channels for this client CC, via higher layer signaling from the eNodeB, e.g., client_cc_config signal.

[0039] If it is required for the UE to detect PDCCHs, in step 82 the UE reads the PDCCH channels of the CC in accordance with a predetermined DCI format with a carrier indicator field of zero bit size. The physical signal processing and PDCCH detection procedure can be the same as the Rel-8 processing and procedure as specified in the documents TS 36.211 and TS 36.213.

[0040] If the UE is not required to detect PDCCHs on the client CC carrier, then in step 84 the UE does not attempt to detect PDCCHs.

[0041] If the UE does not receive the control__cc_config signal (i.e., the upper layer signaling does not indicate that the CC carrier is a primary or client carrier), in step 86 the UE device assumes that the downlink CC carrier is a normal CC carrier. The UE reads the PDCCH channels of the ordinary CC carrier according to the predetermined DCI format in the PDCCH channels with a zero bit size indicator field. The physical signal processing and PDCCH detection procedure can be the same as the Rel-8 processing and procedure as specified in TS 36.211 and TS 36.213.

[0042] The UE may thus detect the downlink aggregation control structure in a manner that minimizes the number of PDCCH blind decoding attempts that the UE is required to make to the required LTE Rel-8 standard (up to 44 times).

[0043] It will be understood that in the light of the above explanations, the present invention may be implemented by means of software, firmware and / or hardware in a variety of ways as will be understood by one of ordinary skill in the art.

Industrial Applicability [0044] The present invention provides a method of controlling access to mobile communication networks.

List of references [0045] mobile communication network femtocell node eNodeB

16, 18 UE device

20, 22, 32, 34, 44, 46 PDCCH

24, 26, 36, 38, 48, 54 CC carrier (component carrier) 28, 30, 40, 42, 50, 52 PDSCH channel