Uplink Control Signaling for FDD-TDD Joint Carrier Aggregation

Abstract

To provide a method and a device for configuring carrier aggregation to UE using both time division duplex (TDD) and frequency division duplex (FDD) component carriers.SOLUTION: In a wireless communication system, connection is established to a first serving cell (101) designated as a PCell, connection is established to a second serving cell (105) designated as a SCell, the SCell (105) uses a different duplex mode different from the PCell (101), and the duplex modes for the PCell (101) and SCell (105) are selected from FDD and TDD modes. A mobile device receives a subframe scheduling message for the SCell (105) in a downlink subframe and selects an uplink subframe to send a scheduling message acknowledgement on the basis of the duplex mode of the PCell (101).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application relates generally to wireless communications, and more particularly to wireless telephone communications. [Background technology]

[0002] Cellular wireless networks include many base stations. Each base station transmits (downlink or DL) and receives (uplink or UL) data to and from mobile users within its coverage area. The rapid growth of data traffic in wireless cellular networks has created a need for rapid expansion of network capacity to meet growing user demand. Carrier aggregation provides one method for increasing network capacity. With carrier aggregation, a base station simultaneously transmits data to and receives data from mobile user equipment (UE) on multiple carriers in the same or different RF bands. For example, in cellular systems conforming to the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard, carrier aggregation is standardized for both intra-band and inter-band operation in LTE Releases 10 and 11. The cost of a mobile UE is largely dependent on the cost of its RF front end, which includes mixers, oscillators, and radio amplifiers designed to function in a specific RF band. To maximize return on their investment, mobile UE vendors strive for equipment that can be used in both frequency division duplex (FDD) and time division duplex (TDD) modes and in the most widely deployed RF bands across all geographic regions.

[0003] On the other hand, the cost of RF spectrum is a significant bottleneck in the deployment of ubiquitous and high-data-rate wireless communication systems. Cellular network operators acquire RF spectrum based on several factors, including the size of the allocated spectrum chunk (where higher RF bands are better) and optimized coverage (where lower frequency bands provide better in-building penetration). Furthermore, widespread adoption of a particular band ensures that mobile devices will support that band. Based on these factors, network operators may own spectrum in both FDD and TDD bands and may desire to configure carrier aggregation for UEs with both TDD and FDD component carriers. Summary of the Invention

[0004] In the illustrated example, a connection is established to a first serving cell designated as a primary serving cell (PCell), and a connection is established to a second serving cell designated as a secondary serving cell (SCell). The SCell uses a different duplex mode than the PCell. The duplex modes of the PCell and SCell are selected from FDD and TDD modes. A mobile device receives a subframe scheduling message for the SCell in a downlink subframe and selects an uplink subframe for sending a scheduling message acknowledgment based on the duplex mode of the PCell. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view of a network system in a heterogeneous deployment scenario in which a base station operates in an FDD mode and provides macro coverage at a macro cell site having three sectors.

[0006] [Figure 2]FIG. 10 is a subframe diagram of a mobile device scheduled to transmit a PUSCH on an FDD PCell in subframe 7 of radio frame nf+1.

[0007] [Figure 3] FIG. 10 is a subframe diagram of a scenario in which a mobile device is configured with an FDD SCell and a TDD PCell using TDD UL / DL configuration 2.

[0008] [Figure 4] FIG. 1 is a subframe diagram using an FDD secondary serving cell for a half-duplex TDD mobile device using TDD UL / DL configuration 1.

[0009] [Figure 5] FIG. 10 is a subframe diagram using a TDD cell as a secondary serving cell for an FDD-only mobile device.

[0010] [Figure 6] 2 is a block diagram of internal details of mobile user equipment and base stations operating in a network system such as the system of FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0011] A joint FDD and TDD design provides carrier aggregation in a wireless communication system. The signaling schemes described herein may be implemented in an Orthogonal Frequency Division Multiplexing (OFDM)-based cellular system operating in FDD and / or TDD modes, such as an LTE cellular network.

[0012] In one embodiment, the PCell operates in FDD mode and the SCell operates in TDD mode. In this configuration, the mobile device receives a physical downlink shared channel (PDSCH) from the TDD SCell in subframe n and sends a hybrid automatic repeat request acknowledgment (HARQ ACK) to the FDD PCell in subframe n+4.

[0013] In another embodiment, the PCell operates in TDD mode and the SCell operates in FDD mode. In this configuration, the mobile device receives a PDSCH from the FDD SCell in a downlink subframe and transmits a HARQ ACK corresponding to the PDSCH to the TDD PCell in a selected uplink subframe. The selected uplink subframe may be the first valid uplink subframe following the downlink subframe. In one example, the downlink subframe carrying the PDSCH is subframe n, and the selected uplink subframe is subframe n+k, where k≧4.

[0014] A mobile device may operate in half-duplex TDD mode, in which case it uses an uplink / downlink subframe configuration for a TDD PCell when transmitting on an FDD SCell.

[0015] In a deployment scenario for FDD-TDD joint carrier aggregation, FDD-TDD joint operation is proposed when a cellular network operator owns both FDD and TDD spectrum in the same geographic area. For example, 800 MHz of FDD spectrum and 2.6 GHz of TDD spectrum may be available in a given geographic area. Figure 1 illustrates a heterogeneous deployment scenario in which a base station 101 operates in FDD mode and provides macro coverage at a macro cell site with three sectors 102-104. A base station 105 is a low-power node that operates in TDD mode in a higher frequency band and controls a small cell 106. The small cell 106 can be used as a capacity booster to improve throughput at hot spots within the macro cell sector. In another scenario, the macro cell base station 101 can operate in TDD mode, and the hot spot base station 105 can operate in FDD mode. Base stations 101 and 105 may be owned and controlled by a single network operator, or by two or more different network operators in a radio access network (RAN) sharing arrangement.

[0016] In this general deployment scenario, the three modes of FDD-TDD joint operation are default single mode operation, carrier aggregation, and inter-node aggregation, as described below.

[0017] In carrier aggregation (CA), a UE can be configured to receive and transmit data on multiple component carriers (CCs). From a MAC layer perspective, data transmission is scheduled per component carrier (CC), either DL only or in both DL and UL directions. Therefore, each component carrier can be considered a serving cell, each with its own MAC scheduler. In an LTE system, an anchor cell provides mobility connectivity to the network and is called a primary serving cell (PCell). Depending on data traffic requirements, a base station can configure additional serving cells, known as secondary serving cells (SCells). In one deployment configuration, the primary and secondary serving cells are all collocated. In a different deployment configuration, the SCell can be deployed at a different location from the PCell, with a backhaul connection 107 (preferably with low latency and high throughput) connecting the PCell and SCell locations.

[0018] In FDD-TDD joint carrier aggregation operation, the PCell (and possibly some SCells) can be FDD and one or more SCells can be TDD, or vice versa. Requirements for FDD-DD joint carrier aggregation include a UE capable of multi-mode operation (as either a TDD UE or an FDD UE), inter-band carrier aggregation capability, UL carrier aggregation joint operation, which also requires the UE to support independent UL timing advances for different component carriers, and determination of the cell to which the UE sends uplink control information (UCI).

[0019] In the FDD-TDD joint carrier aggregation design, there is hybrid automatic repeat request (HARQ) scheduling and feedback consideration.

[0020] In LTE systems, some existing procedures for carrier aggregation and DL / UL signaling are agnostic about whether the configured serving cell operates in FDD or TDD mode. An important difference is the HARQ scheduling and HARQ feedback acknowledgment (HARQ-ACK) timeline. Using paired DL and UL carriers in FDD, UEs can be scheduled for DL ​​assignments and / or UL grants with 1-millisecond accuracy (in any subframe). Correspondingly, HARQ-ACK feedback for DL ​​assignments in subframe n is transmitted in subframe n+4 for normal HARQ operation. Similarly, DL HARQ-ACK feedback for UL grants in subframe n is transmitted on the Physical HARQ Indicator Channel (PHICH) in subframe n+4.

[0021] In comparison, TDD divides a radio frame into DL and UL subframes and provides a guard period to allow transition from DL to UL. This results in limited opportunities for DL / UL transmission and HARQ-ACK feedback. LTE systems define special subframes consisting of a DL portion (downlink pilot time slot or DwPTS), a guard period, and a UL portion (uplink pilot time slot or UpPTS).

[0022] There are seven TDD UL / DL configurations defined in LTE Releases 8 to 11, as shown in Table 1. The selection of a TDD UL / DL configuration for a given cell depends on several factors, including the DL and UL traffic rates observed in the cell, the need for good UL coverage (e.g., requiring a UL-heavy UL / DL configuration), and coexistence with other TDD wireless technologies, such as Time Division Synchronous Code Division Multiple Access (TD-SCDMA). [Table 1]

[0023] As shown in Table 1, when operating in TDD mode, limited UL subframes are available for transmitting data or uplink control information such as HARQ-ACK feedback, channel state information (CSI), and scheduling requests. In an UL subframe, the UE may be required to transmit HARQ-ACK feedback for a set of M DL subframes, referred to as the downlink associated set.

[0024] Table 2 shows the HARQ-ACK DL association set K for a TDD UL / DL configuration in an LTE system. The set of possible HARQ-ACK feedback states includes positive acknowledgement (ACK), negative acknowledgement (NACK), and discontinuous transmission (DTX). Therefore, the set of M elements {k0, k1, . . . , k M-1}, the UE transmits the DL subframes {n-k0,n-k1,...,nk M-1 ,nk}. The downlink control information (DCI) format for scheduling DL assignments or UL grants to a TDD serving cell includes a downlink assignment index (DAI) field. The downlink assignment index (DAI) field indicates to the UE the number of DL subframes for which HARQ-ACK feedback is expected. For example, for up to M DL subframes {n-k0, n-k1, . . . , k M-1 In UL subframe n, where} may request HARQ-ACK feedback, the DAI field may indicate to the UE that fewer than M subframes have actually been scheduled. The radio frame includes 10 subframes, denoted as subframes 0 through 9. In Table 2, the subframes in subsequent frames are denoted by subtracting nk. i For purposes of calculating (for i=0 to Ml), subframes may be denoted as 10 to 19, etc. [Table 2]

[0025] A design constraint for carrier aggregation in current LTE systems is that UCI is transmitted only on the physical uplink control channel (PUCCH) of the PCell. Therefore, efficient FDD-TDD HARQ-ACK feedback in carrier aggregation depends on which duplex mode (full duplex for FDD and half duplex for TDD) is operating on the PCell. Some design principles used in current LTE systems can be revisited for more efficient FDD-TDD operation. These include not introducing new TDD UL / DL configurations for FDD-TDD joint carrier aggregation operation and transmitting UCI only on the PUCCH of the PCell.

[0026] In the following sections, we consider different HARQ-ACK feedback designs for the cases where the PCell operates in either FDD or TDD mode. Note that these examples are illustrated using the specific case of a single SCell, but the designs may be generalized to carrier aggregation with multiple SCells.

[0027] In one scenario, the PCell operates in FDD mode and the SCell operates in TDD mode. When the network includes a mix of FDD and TDD cells, one advantage of operating the PCell in FDD mode is that all subframes of the FDD radio frame are valid UL subframes for UCI transmission. Therefore, when an additional serving cell is configured for TDD, the HARQ-ACK feedback timeline for any TDD UL / DL configuration can be followed for HARQ-ACK feedback on the PUCCH, since the UL subframes for the PCell are a superset of the TDD UL subframes. For single duplex mode carrier aggregation, an LTE Release 10 or Release 11 UE can be configured with either PUCCH format 1b or PUCCH format 3 with channel selection. The same PUCCH scheme can be configured as follows for FDD-TDD CA:

[0028] 1) If the UE detects a DL assignment on the physical downlink control channel (PDCCH) or the enhanced physical downlink control channel (EPDCCH), it schedules a PDSCH on a TDD SCell in any one of the M subframes associated with the uplink subframe.

[0029] a) When PUCCH format 3 is configured, the PUCCH resource is indicated by the transmit power control (TPC) field of the PDCCH that schedules the PDSCH on the SCell, where the TPC field indicates one of four semi-statically configured resources.

[0030] b) For the single SCell case, when PUCCH format lb with channel selection is configured, (a) When the PDSCH of the SCell is cross-scheduled from the PCell, a maximum of two resources may be indicated by dynamic PUCCH allocation based on the PDCCH / EPDCCH detected on the PCell. (b) Alternatively, if the PDSCH is self-scheduled to an SCell, the value of the TPC field of any PDCCH / EPDCCH that schedules the PDSCH in any DL subframe of the M DL subframes associated with the UL subframe indicates one of a set of four pairs of semi-statically configured PUCCH resources.

[0031] 2) If the UE does not detect a PDCCH / EPDCCH scheduling a PDSCH on the TDD SCell in any one of the M subframes associated with the uplink subframe, the UE transmits on the PUCCH of the FDD PCell in subframe n only if a PDSCH or PDCCH / EPDCCH indicating a semi-persistent scheduling (SPS) release is detected on the PCell in subframe n-4.

[0032] When the PCell is operated in FDD mode, HARQ-ACK feedback may be optimized for the TDD SCell. Specifically, the HARQ-ACK timing for the PDSCH transmitted on the TDD SCell tracks the HARQ-ACK timing on the FDD PCell. Thus, the UE transmits HARQ-ACK feedback on the PUCCH of the PCell in subframe n for the PDSCH detected on the TDD SCell in subframe n-4. When PUCCH format 3 is configured, the PUCCH resource is indicated by the TPC field of the PDCCH / EPDCCH that schedules the PDSCH on the TDD SCell. Similarly, when PUCCH format 1b with channel selection is configured, up to two PUCCH resources corresponding to the SCell PDSCH are indicated by the TPC field of the PDCCH / EPDCCH that schedules the PDSCH on the SCell. This scheme eliminates the need for a downlink association set (M=1 for any UL / DL configuration). Therefore, there is no need for a DAI field in the DCI format for scheduling DL assignments or UL grants to TDD SCells when the PCell is operating in FDD mode, as the HARQ-ACK timing tracks the FDD PCell HARQ-ACK timing.

[0033] Another consideration is how to multiplex the HARQ-ACK bits on the PUSCH when the UE transmits on the PUSCH. In LTE Release 11 TDD, the number of HARQ-ACK bits transmitted on the PUSCH for configured serving cells depends on the size of the DL association set M or the DAI value included in the DL assignment or UL grant transmitted on the PDCCH / EPDCCH. Subframes from 0 to 9 can be indicated by the DAI value of the PDCCH / EPDCCH. In contrast, for FDD serving cells in LTE Release 11, the number of HARQ-ACK bits is based on the number of configured serving cells and the downlink transmission mode configured for each FDD serving cell.

[0034] FIG. 2 illustrates carrier aggregation with a PCell in FDD mode and an SCell in TDD UL / DL configuration 2. For the TDD SCell, the DL assignment for the SCell in DL subframes 4 and 5 of radio frame nf is f The UE acknowledges (HARQ-ACK feedback) the data in UL subframe 2 of radio frame n. f The DL assignment for the SCell in special subframe 1 of +1 is made in radio frame n f In contrast, in an FDD PCell, since the FDD PCell has a pair of CCs for DL ​​and UL, each DL subframe n can always be uniquely associated with the corresponding UL subframe, which is the fourth subsequent subframe (n+4). For example, in radio frame n f The DL assignment in subframe 8 of f It is acknowledged in UL subframe 2 of radio frame n+1. f If an UL grant is sent in addition to the DL assignment in subframe 8 of n, the UE will send HARQ-ACK feedback on the PUSCH if the UE is not configured for simultaneous PUCCH and PUSCH transmission. The DAI field is not required for FDD because the feedback in UL subframe n+4 corresponds to the DL assignment sent on the PDSCH in DL subframe n.

[0035] In FDD-TDD joint carrier aggregation operation, the HARQ-ACK feedback on the PUSCH may need to take into account the HARQ-ACK feedback for the FDD cell. However, in the current FDD-only carrier aggregation operation, the downlink control information (DO) format does not have a DAI field. Two possible solutions to efficiently support FDD-TDD joint carrier aggregation operation are described below.

[0036] Solution 1: Keep the current design where the DCI format does not have a DAI field in FDD cells.

[0037] 1) For PUSCH transmission in an FDD serving cell

[0038] a) Place the HARQ-ACK bit according to the serving cell index, where 0 is the PCell, 1 is the first SCell, etc.

[0039] b) For FDD cells, generate 1 or 2 HARQ-ACK bits depending on whether the configured transmission mode supports 1 or 2 transport blocks, respectively.

[0040] c) For the cth TDD cell, depending on whether the configured transmission mode supports one transport block or two transport blocks, B c DL or 2B c DL where B c DL =M.

[0041] In an alternative embodiment, the UE may select a DL associated set {nk m}, m=0,···,M-1 in the most recently detected PDCCH / EPDCCH that schedules the PDSCH on the SCell Determine the HARQ-ACK feedback for the TDD SCell based on the value of JPEG0007787141000003.jpg1033. Therefore, for this TDD cell, the number of HARQ-ACK bits generated is JPEG0007787141000004.jpg1129.

[0042] d) Figure 2 shows an example for an SCell using TDD UL / DL configuration 2. Radio frame n fIn UL subframe 2 of radio frame n+1, the UE f The UE transmits HARQ-ACK feedback corresponding to the detected DL assignment in subframes 4 and 5 of the TDD SCell and subframe 8 of the FDD PCell.

[0043] 2) For PUSCH transmission in TDD serving cell

[0044] a) If PUSCH transmission is not adjusted based on a detected PDCCH / EPDCCH with DCI format 0 / 4, The same bit ordering and number of generated bits are followed as described above for PUSCH transmission in an FDD serving cell with JPEG0007787141000005.jpg1024.

[0045] b) If PUSCH transmission is adjusted based on a detected PDCCH / EPDCCH carrying UL DCI format 0 / 4:

[0046] i) In the cth TDD cell, JPEG0007787141000006.jpg1030, where JPEG0007787141000007.jpg1013 is the detected DAI value for DCI format 0 / 4.

[0047] ii) In one embodiment, the bit order is determined according to the cell index, as described above for PUSCH transmitted on an FDD serving cell.

[0048] iii) In another embodiment, the HARQ-ACK bits generated for one or more FDD serving cells are appended to the HARQ-ACK bits for the TDD serving cell (so they are the least significant bits). Thus, when a UL grant is detected for subframe n in the TDD serving cell, if there is no PDSCH or SPS release DCI in subframe n-4 of the FDD serving cell, the bit mapping is the same as in the TDD-only carrier aggregation case.

[0049] Solution 2: In the FDD serving cell, add a DAI field to the DCI format. This DAI field may indicate (to the UE) the total number of subframes for which feedback is required for any configured TDD serving cell. This solution avoids any possible ambiguity between the base station and the UE if the UE fails all scheduling assignments in the DL associated set for UL subframe n.

[0050] The DAI field may be 2 bits in length, although in other embodiments, a 1-bit DAI field may be defined. This is used to indicate (to the UE) that feedback is required for at least one configured TDD serving cell with JPEG0007787141000008.jpg1025. Other values ​​are not excluded, as the main purpose is to inform the UE to include HARQ-ACK feedback for TDD cells when transmitting PUSCH in an FDD cell.

[0051] This solution is also applicable to TDD PCell and FDD SCell, since the UL grant for the FDD SCell may include a DAI field to indicate the number of DL subframes of the TDD PCell that require HARQ-ACK feedback. Thus, whenever at least one TDD serving cell is configured for the UE, the DAI field may be present for the PDCCH / EPDCCH of the FDD serving cell.

[0052] Alternatively, the DAI field is present only for an FDD serving cell when the subframe is also a UL subframe corresponding to a linked DL associated set for at least one of the configured TDD serving cells.

[0053] FIG. 2 shows the UE receiving the data in radio frame n. f This indicates that the UE is scheduled to transmit PUSCH on the FDD PCell in subframe 7 of the TDD serving cell +1. Also, there is a DL assignment in subframe 1 (special subframe) of the TDD SCell in the same frame. Even if the UE fails this DL assignment, the value of the DAI field in the UL grant for UL subframe 7 indicates how many DL subframes require HARQ-ACK feedback. This mechanism allows the UE to determine that it failed to detect one or more DL assignments in the TDD serving cell.

[0054] An interesting deployment scenario arises when the PCell operates in TDD mode and at least one SCell operates in FDD mode. Following the design constraint that PUCCH transmissions occur only on the PCell, this limits the HARQ-ACK feedback opportunities for the FDD SCell. Essentially, it forces the FDD SCell to follow the HARQ-ACK feedback timeline of the TDD PCell. In the case of a DL-only FDD serving cell without a paired UL carrier, this is the default behavior. However, when the FDD serving cell has a paired UL carrier, it makes sense to consider more efficient means for transmitting HARQ-ACK feedback corresponding to the PDSCH on the FDD SCell. These considerations become even more important in the following scenarios:

[0055] Figure 3 shows a scenario in which a UE is configured with an FDD SCell and a TDD PCell using TDD UL / DL configuration 2. Consider the case in which the UE is scheduled for PDSCH reception in a DL subframe of the FDD SCell, which is an UL subframe according to the TDD UL / DL configuration of the PCell, as shown in Figure 3. According to current FDD procedures, the UE should transmit corresponding feedback in subframe 6, which is a special subframe on the TDD PCell. One solution to this problem is to configure the UE to transmit HARQ-ACK feedback on the PUCCH of the SCell. Two possible implementations of this solution are (a) simultaneous PUCCH-PUCCH transmission on both the PCell and SCell, or (b) time-division multiplexed PUCCH transmission. In this solution, the UE transmits PUCCH on the FDD SCell only if the UL subframe of the SCell corresponds to the DL subframe of the TDD PCell. Alternatively, if the subframe is an UL subframe for both FDD and TDD serving cells, the PUCCH is transmitted on the PCell.

[0056] An alternative solution is to schedule HARQ-ACK feedback corresponding to a DL assignment on an FDD SCell to be transmitted in the first valid UL subframe of the TDD PCell. Specifically, for a PDSCH detected in subframe n on an FDD SCell, the UE may transmit the corresponding HARQ-ACK feedback in the first valid UL subframe n+k, where k≧4. In the example of Figure 3, the HARQ-ACK feedback is transmitted on the PCell in subframe 7.

[0057] Aperiodic or periodic CSI reporting can be configured in a manner similar to the single duplex mode carrier aggregation case. In periodic CSI reporting, the priority of CSI reports is based on the PUCCH reporting type and serving cell index. When a PCell operates in TDD mode, some constraints are imposed on the channel quality indicator (CQI) / precoding matrix indicator (PMI) reporting periodicity of an FDD SCell depending on the TDD UL / DL configuration of the PCell. For example, if the PCell uses UL / DL configuration 5, a reporting periodicity of 2 ms may imply frequent dropping of CSI reports for an FDD SCell. Therefore, if a periodic CSI reporting occasion or subframe coincides with a DL subframe of a TDD PCell, the UE does not transmit a CSI report.

[0058] Generally, full-duplex capability is required for UEs that support FDD-TDD carrier aggregation. However, it is possible for half-duplex UEs to enjoy some of the benefits of FDD-TDD CA. For example, an LTE Release 11 TDD UE with a radio resource control (RRC) connection to a TDD serving cell may be configured to receive a PDSCH on a secondary serving cell that uses the same TDD UL / DL configuration as the primary serving cell. When an SCell operates in FDD mode, the UE may be configured to apply the same UL / DL configuration as the TDD PCell.

[0059] Figure 4 illustrates the use of an FDD secondary serving cell for a half-duplex TDD UE using TDD UL / DL configuration 1. As shown in Figure 4, subframes {2, 3, 7, 8} and {0, 1, 4, 5, 6, 9} are not valid DL or UL subframes, respectively, for a half-duplex TDD UE on an FDD SCell. While this subframe restriction may initially seem like a waste of network resources, it allows the base station to assign other UEs (such as FDD UEs or other TDD UEs with full-duplex capability) to the unused resources. Furthermore, the performance of UEs with half-duplex capability is comparable to TDD-only carrier aggregation where the same UL / DL configuration is configured in each serving cell.

[0060] Similarly, a UE that supports only FDD duplex mode can be configured to receive downlink shared channel (DL-SCH) data on the PDSCH of an SCell, where the SCell is actually deployed on a TDD carrier. This scenario is possible when an FDD band overlaps in frequency with a TDD band. For example, 3GPP Band 7 is an FDD band that overlaps in frequency with 3GPP TDD Band 41. An operator with spectrum in this RF region can choose to operate as either a TDD or FDD carrier. When operated as a TDD carrier, an FDD-only UE can be configured to receive data on this carrier by configuring the UE with a limited set of subframes that match the DL subframes on the TDD carrier.

[0061] FIG. 5 illustrates the use of a TDD cell as a secondary serving cell for an FDD-only UE. The UE can be configured with a bitmap indicating which subframes it should monitor for DL-SCH data. Frame (a) of FIG. 5 shows an example in which a TDD carrier is configured to operate in UL / DL configuration 1. An FDD-only UE can be configured with a secondary serving cell on this TDD component carrier. Traditionally, an FDD-only UE monitors all subframes of a radio frame for DCI transmitted on the PDCCH or EPDCCH. However, on this TDD carrier, the FDD-only UE does not need to waste energy monitoring the PDCCH / EPDCCH for DCI that may not be transmitted in subframes {2, 3, 7, 8} because those subframes are designated for the UL. Thus, the FDD UE is configured with a bitmap specifying a limited set of subframes on which it should monitor DCI.

[0062] As shown in frame (b) of Figure 5, an FDD-only UE monitors for DL-SCH data from an SCell in a limited set of subframes {0, 4, 5, 9}. The bitmap specifying this limited set of subframes may be semi-statically configured by RRC signaling.

[0063] In a different embodiment, a UE may be configured with an extended bitmap that indicates (a) subframes to monitor for DCI and (b) subframes in which detected DL assignments on the PDSCH are limited to fewer OFDM symbols than the maximum number of OFDM symbols in the subframe. This allows the UE to receive the PDSCH in the special subframe. For example, when a TDD cell applies a normal cyclic prefix in the downlink, special subframe configuration 11 includes 11 OFDM symbols. Thus, an FDD-only UE is configured to receive DL assignments up to the 11th OFDM symbol in this subframe.

[0064] Frame (c) of Figure 5 shows a limited set of subframes including special subframes {1, 6}. FDD-only UEs may be configured to receive data less than the total number of OFDM symbols in the special subframes.

[0065] In either embodiment (using a limited set of subframes including only DL subframes or including DL and special subframes), if the UL carrier is FDD, the HARQ-ACK timeline should follow FDD procedures, e.g., if a DL assignment is received in subframe n, the UE sends HARQ-ACK feedback in subframe n+4.

[0066] 6 is a block diagram illustrating internal details of a mobile UE 601 and a base station 603, such as an eNB, operating in a network system such as the system of FIG. 1. The mobile UE 601 may communicate with multiple base stations 603 in a carrier aggregation operation. The mobile UE 601 may represent any of a variety of devices, such as a server, a desktop computer, a laptop computer, a mobile phone, a personal digital assistant (PDA), a smartphone, or other electronic device. In some embodiments, the electronic mobile UE 601 communicates with the eNB 602 based on the LTE or Evolved Universal Terrestrial Radio Access (E-UTRA) protocol. Alternatively, other communication protocols, now known or developed in the future, may be used.

[0067] The mobile UE 601 includes a processor 603 coupled to a memory 604 and a transceiver 605. The memory 604 stores (software) applications 606 for execution by the processor 603. These applications may include any known or future application useful to an individual or organization. These applications may fall into categories such as operating systems (OS), device drivers, databases, multimedia tools, presentation tools, internet browsers, emailers, voice over internet protocol (VOIP) tools, file browsers, firewalls, instant messaging, finance tools, games, word processors, or other. Regardless of the exact type of application, at least some of the applications may instruct the mobile UE 601 to periodically or continuously transmit UL signals to a base station (eNB) 602 via the transceiver 605.

[0068] The transceiver 605 includes uplink logic, which may be implemented by execution of instructions that control the operation of the transceiver. Some of these instructions may be stored in memory 604 and executed as needed by the processor 603. Components of the uplink logic may include the physical (PHY) layer and / or medium access control (MAC) layer of the transceiver 605. The transceiver 605 includes one or more receivers 607 and one or more transmitters 608.

[0069] The processor 603 may send or receive data to various input / output devices 609. A subscriber identity module (SIM) card stores and retrieves information used to make calls over the cellular system. A Bluetooth baseband unit may be provided for wireless connection to a microphone and handset for sending and receiving voice data. The processor 603 may send information to a display unit for interaction with a user of the mobile UE 601 during the call process. The display may also display pictures received from the network, from a local camera, or from other sources such as a universal serial bus (USB) connector. The processor 603 may also send video streams received from various sources such as the cellular network or a camera via the RF transceiver 605 to the display.

[0070] The eNB 602 includes a processor 610 coupled to a memory 611, symbol processing circuitry 612, and a transceiver 613 via a backplane bus 614. The memory stores applications 615 for execution by the processor 610. Such applications may include any known or future applications useful for managing wireless communications. At least some of the applications 615 may direct the eNB 602 to manage transmissions to or from the mobile UE 601. The eNB 602 may operate in FDD or TDD mode and may communicate with a base station (not shown) for carrier aggregation.

[0071] The transceiver 613 includes an uplink resource manager that enables the eNB 602 to selectively allocate uplink Physical Uplink Shared Channel (PUSCH) resources to the mobile UE 601. Components of the uplink resource manager may include a physical (PHY) layer and / or a medium access control (MAC) layer of the transceiver 613. The transceiver 613 includes at least one receiver 617 for receiving transmissions from various UEs within range of the eNB 602 and at least one transmitter 616 for transmitting data and control information to various UEs within range of the eNB 602.

[0072] The uplink resource manager executes instructions that control the operation of the transceiver 613. Some of these instructions may be located in the memory 611 and executed as needed by the processor 610. The resource manager controls the transmission resources allocated to each UE 601 served by the eNB 602 and broadcasts control information over the PDCCH. The UE 601 may receive TTD UL / DL configuration instructions from the eNB 602.

[0073] The symbol processing circuitry 612 performs demodulation using known techniques. The random access signal is demodulated in the symbol processing circuitry 612. During transmission and reception of voice data or other application data, the receiver 617 may receive a random access signal from the UE 601. The random access signal is encoded to request a preferred message size for the UE 601. The UE 601 determines the preferred message size by using a message threshold provided by the eNB 602.

[0074] When the mobile device 601 receives a PDSCH from the TDD SCell 105 in subframe n, the mobile device 601 transmits a HARQ-ACK to the FDD PCell 101 in subframe n+4. When the mobile device 601 receives a PDSCH from the FDD SCell 105 in a downlink subframe, the mobile device 601 transmits a HARQ-ACK corresponding to the PDSCH to the TDD PCell 101 in a selected uplink subframe. The selected uplink subframe may be the first valid uplink subframe following the downlink subframe. For example, the downlink subframe carrying the PDSCH is subframe n, and the selected uplink subframe is subframe n+k, where k≧4.

[0075] Changes may be made in the described embodiments, and other embodiments are possible, within the scope of the invention.

Claims

1. 1. A method for wireless communication, comprising: establishing a connection with a first base station designated as a primary serving cell (PCell); establishing a connection with a second base station designated as a secondary serving cell (SCell) that uses a different mode of operation than the PCell; receiving a subframe scheduling message from the SCell in a downlink subframe; generating a scheduling message acknowledgment in response to receiving the subframe scheduling message; selecting an uplink subframe for transmitting a scheduling message acknowledgement to the PCell based on an operation mode of the PCell; A method comprising:

2. 10. The method of claim 1, The method, wherein an operation mode of the PCell and the SCell is selected from a frequency division duplex (FDD) mode and a time division duplex (TDD) mode.

3. 10. The method of claim 1, the PCell operates in a frequency division duplex (FDD) mode and the SCell operates in a time division duplex (TDD) mode; The method comprises: receiving a physical downlink shared channel (PDSCH) from the TDD SCell in subframe n; sending a Hybrid Automatic Repeat Request Acknowledgement (HARQ ACK) to the FDD PCell in subframe n+4; and The method further comprises:

4. 10. The method of claim 1, the PCell operates in a time division duplex (TDD) mode and the SCell operates in a frequency division duplex (FDD) mode; The method comprises: receiving a physical downlink shared channel (PDSCH) in downlink subframe n from the FDD SCell; sending a hybrid automatic repeat request acknowledgement (HARQ ACK) to the TDD PCell in a first uplink subframe n+k (k≧4) following the downlink subframe n; The method further comprises:

5. 10. The method of claim 1, The method, wherein the downlink subframe is subframe n and the selected uplink subframe is the first uplink subframe n+k (k≧4) following subframe n.

6. 10. The method of claim 1, The method further includes operating in half-duplex time division duplex (TDD).

7. 7. The method of claim 6, The method further includes using an uplink / downlink subframe configuration for the PCell operating in a frequency division duplex (TDD) mode when transmitting to the SCell operating in a TDD mode.

8. A user equipment (UE), 1. A processor, comprising: establishing a connection with a first base station designated as a primary serving cell (PCell); establishing a connection with a second base station designated as a secondary serving cell (SCell) that uses a different mode of operation than the PCell; the processor configured to a receiver configured to receive a subframe scheduling message from the SCell in a downlink subframe; a transmitter configured to select an uplink subframe for transmitting a scheduling message acknowledgement to the PCell based on an operation mode of the PCell; Including, The UE, wherein the processor is further configured to generate a scheduling message acknowledgement in response to receiving the subframe scheduling message.

9. 9. The UE of claim 8, A UE, wherein an operation mode of the PCell and the SCell is selected from a frequency division duplex (FDD) mode and a time division duplex (TDD) mode.

10. 9. The UE of claim 8, the PCell operates in a frequency division duplex (FDD) mode and the SCell operates in a time division duplex (TDD) mode; the receiver is further configured to receive a physical downlink shared channel (PDSCH) from the TDD SCell in subframe n; The UE, wherein the transmitter is further configured to send a hybrid automatic repeat request acknowledgement (HARQ ACK) to the FDD PCell in subframe n+4.

11. 9. The UE of claim 8, the PCell operates in a time division duplex (TDD) mode and the SCell operates in a frequency division duplex (FDD) mode; the receiver is further configured to receive a Physical Downlink Shared Channel (PDSCH) in downlink subframe n from the FDD SCell; The UE, wherein the transmitter is further configured to send a hybrid automatic repeat request acknowledgement (HARQ ACK) to the TDD PCell in a first uplink subframe n+k (k≧4) following the downlink subframe n.

12. 9. The UE of claim 8, The UE, wherein the downlink subframe is subframe n, and the selected uplink subframe is the first uplink subframe n+k (k≧4) following subframe n.

13. 9. The UE of claim 8, A UE operating in half-duplex time division duplex (TDD).

14. 14. The UE of claim 13, A UE that uses an uplink / downlink subframe configuration for the PCell operating in a time division duplex (TDD) mode when transmitting to the SCell operating in a frequency division duplex (FDD) mode.

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