APPARATUSES AND METHOD USING ENHANCED CONTROL CHANNEL INFORMATION FOR TDD-FDD CARRIER AGGREGATION

Abstract

Apparatuses and methods for carrier aggregation are generally described herein. An evolved NodeB (eNB) may transmit downlink control information (DCI) on a control channel portion for a primary cell (PCell) downlink (DL) subframe. The DCI can include an offset field indicating an offset, relative to a first secondary cell (SCell) subframe, to identify a second SCell subframe for which the DCI is providing control information. Other apparatuses and methods are also described.

Description

TECHNICAL FIELD

Embodiments described herein pertain generally to wireless communications. More particularly, the present disclosure relates to carrier aggregation, even more particularly for situations in which the carriers to be aggregated operate using different duplexing technologies.

BACKGROUND

Current 3rd Generation Partnership Project (3GPP) long term evolution (LTE) specifications allow operators to provide carrier aggregation (CA) to improve peak data rates. Currently CA support is only available between bands operating using the same duplexing technology, at least in part due to difficulties in performing with cross-carrier scheduling when bands operate using different duplexing technologies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a system in which some embodiments may be implemented.

FIG. 2 illustrates an example scenario for carrier aggregation with a time-division duplex (TDD) primary cell (PCell) and a frequency-division duplex (FDD) secondary cell (SCell).

FIG. 3A illustrates cross-carrier scheduling in accordance with available systems.

FIG. 3B illustrates cross-carrier scheduling in accordance with some embodiments.

FIG. 4 illustrates components of a physical downlink control channel in accordance with some embodiments.

FIG. 5 is a flow chart of a method for TDD-FDD carrier aggregation in accordance with some embodiments.

FIG. 6 is a block diagram of the basic components of a communication station in accordance with some embodiments.

FIG. 7 is a block diagram of a machine for executing various embodiments.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram illustrating a system 100 in which some embodiments may be implemented. The system 100 includes a user equipment (UE) 102, which can communicate wirelessly with a PCell 104 over a wireless communication link 108. Communication link 108 includes one or more communication channels. These channels can include a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH) with downlink control information (DCI) transmitted on the downlink (or DCI not transmitted on the downlink), and any other channel for transmitting control (e.g. scheduling or power) information or data on the uplink or downlink. Because system 100 may support carrier aggregation (e.g. may be an LTE-A system) these channels may include one or more aggregated component carriers.

PCell 104 may be a cell associated with a macro network, such as, but not limited to, a radio access network or cellular network. For example, in some examples, PCell 104 can include a PCell in LTE-Advanced communication environments. In various embodiments, PCell 104 may be associated with a PCell network entity 106. The PCell network entity 106 will be referred to hereinafter as an evolved node B (eNB), however, it will be understood that a network entity can include one or more of any type of network module, such as an access point, a macro cell, including a base station (BS), node B, a relay, a peer-to-peer device, an authentication, authorization and accounting (AAA) server, a mobile switching center (MSC), a radio network controller (RNC), etc. Additionally, the network entity associated with PCell 104 may communicate with one or more other network entities of wireless and/or core networks, such as, but not limited to, wide-area networks (WAN), wireless networks (e.g. 802.11 or cellular network), the Public Switched Telephone Network (PSTN) network, ad hoc networks, personal area networks (e.g. Bluetooth®) or other combinations or permutations of network protocols and network types. Such network(s) may include a single local area network (LAN) or wide-area network (WAN), or combinations of LANs or WANs, such as the Internet.

In a various embodiments, UE 102 may communicate with one or more SCells 110 via one or more communication links 112. In some examples, the one or more SCells 110 may include SCells in LTE-Advanced communication environments. UE 102 may be configured to communicate simultaneously with PCell 104 and the one or more SCells 110, for example, via a plurality of antennas of UE 102. Communication link 112 may include one or more communication channels, which may include a PUCCH, a PUSCH with DCI transmitted on the downlink (or DCI not transmitted on the downlink), and any other channel for transmitting control (e.g. scheduling or power) information or data on the uplink or downlink.

SCells 110 may be small cells or low power cells, controlled by or otherwise associated with one or more network entities 114 or modules, such as, but not limited to a low-power access point, such as a picocell, femtocell, microcell, WiFi hotspot, etc. However, embodiments are not limited thereto. For example, the SCell 110 can be co-located with the PCell 104 in the eNB 106. Additionally, similarly to PCell 104, SCells 110 may communicate with one or more other network entities of wireless and/or core networks.

Additionally, system 100, which may include PCell 104 and one or more SCells 110, may comprise a Wideband Code Division Multiple Access (W-CDMA) system, and PCell 104 and one or more SCells 110 may communicate with one or more UEs 102 according to this standard. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system. The various devices coupled to the network(s) (e.g. UE 102 and/or network entities serving PCell 104 and/or SCells 110) may be coupled to the network(s) via one or more wired or wireless connections.

The system 100 may support both frequency-division duplex (FDD) and time-division duplex (TDD) duplexing modes. Efficient TDD and FDD spectrum usage through TDD-FDD joint operations becomes more important in light of ever-increasing throughput and capacity needs. Carrier aggregation (CA) is one concept that can enhance TDD-FDD joint operations.

Cross-carrier scheduling is an important aspect of CA that helps operators achieve better load balancing across multiple carriers as well as avoid performance degradation due to control channel interference in heterogeneous network (HetNet) deployments. In some available systems, CA for LTE is available only between bands operating using same duplexing technology, i.e., between multiple FDD bands or between multiple TDD bands. However, the need for TDD-FDD carrier aggregation is increasing as more eNBs and UEs become capable of supporting both FDD and TDD.

Introducing support for FDD/TDD CA may create issues with control channel design, arising primarily from disparate availability of downlink (DL) and uplink (UL) subframes over time between a TDD Component Carrier (CC) and an FDD CC. Embodiments provide a control channel design to help overcome these and other issues. Embodiments described below are described referring to a TDD PCell 104 and an FDD SCell 110, but it will be appreciated that embodiments are not limited thereto. Furthermore, FDD and TDD cells can be co-located in one network entity, or FDD and TDD cells can be non-co-located with ideal backhaul, or FDD and TDD cells can be non-co-located with non-ideal backhaul.

FIG. 2 illustrates an example scenario for CA with a TDD PCell 104 and an FDD SCell 110. If cross carrier scheduling is enabled, the UE 102 will look for control channel portions, for example the Physical Downlink Control Channel (PDCCH) evolved PDCCH (ePDCCH) or other control channel, in the TDD PCell 104 only. According to current 3GPP standards, the control channel portion of a DL subframe of PCell 104 can contain allocation information relevant to the SCell 110 subframes that coincide with the current PCell 104 DL subframe, using identification fields such as a Carrier Indicator Field (CIF) to identify carriers.

As shown in FIG. 2, depending on the DL/UL configuration of the TDD PCell 104, there could be several UL and DL subframes in the FDD SCell 110 without any coincident DL subframe in the TDD PCell 104. As a result, an eNB such as the network entity 106 (FIG. 1) cannot schedule resources in many FDD subframes because there are fewer DL subframes in the TDD PCell 104 available to carry the scheduling information. Radio resources in those FDD subframes will thus be wasted.

To address these and other concerns, embodiments provide enhancements to the control channel design so that a control channel portion (e.g., PDCCH, ePDCCH, etc.) of a TDD DL subframe can carry scheduling information for multiple FDD subframes preceding the next available TDD DL subframe. Embodiments additionally provide radio resource control (RRC) signaling between eNBs and UEs to configure a TDD-FDD CA-capable UE to receive and use cross-carrier and cross-subframe scheduling information provided in various embodiments.

FIG. 3A illustrates cross-carrier scheduling in accordance with available systems. PDCCH 300 can carry cross-carrier scheduling 302 for a TDD PCell subframe and the PDCCH can additionally carry cross-carrier scheduling 304 for the current FDD SCell 110 subframe 306.

In contrast, in some embodiments, the TDD PCell 104 control channel portion can carry scheduling information for up to the number of FDD subframes that might occur before the next TDD DL subframe by transmitting this scheduling information in one or more DCIs, as needed based on the number of FDD subframes, on a control channel portion for a PCell 104 DL subframe.

FIG. 3B illustrates cross-carrier scheduling in accordance with some embodiments. In accordance with some embodiments, the PDCCH 308 in the TDD PCell 104 can carry cross-carrier resource allocation information 304, 310, 312, 314 for more than one consecutive subframe starting from the current subframe 316 in the FDD SCell 110. To make this possible, in embodiments, each DCI will include an offset field indicating an offset, relative to a first SCell 110 subframe, to identify the corresponding SCell 110 subframe for which each DCI is providing control information. This control information can include, for example, scheduling information described earlier herein with respect to CA. In some embodiments, the offset field can take the form of an Offset Indicator Field (OIF) as described below with respect to Table 1, although embodiments are not limited thereto.

FIG. 4 illustrates components of a PDCCH in accordance with some embodiments. As shown in FIG. 4, the PDCCH will include at least one DCI. While one DCI is shown, embodiments are not limited to any particular number of DCIs.

The DCI includes a CIF, an OIF, and other DCI fields. The number of bits to be included in the OIF will be based on the maximum ratio of UL to DL subframes in the TDD PCell 104. Depending on the possible DL/UL configurations, there could be maximum of a certain number of UL subframes between a DL or special (S) subframe before the next DL subframe in the TDD PCell 104, and accordingly there can be a maximum ratio of UL to DL subframes in the TDD PCell 104. In accordance with current 3GPP standards, there will be a maximum number of three such UL subframes between DL subframes, and accordingly the PDCCH will carry up to four DCIs, one for SCell subframe coincident with the current PCell subframe and a maximum of three DCIs for SCell subframes coincident with subframes between the current subframe and the next DL subframe in the TDD PCell 104. The number of bits used for the OIF proposed for various embodiments is thus two bits long to hold values in the range of 0 to 3, based on the above-described maximum ratio of UL to DL subframes, wherein the OIF indicates a subframe offset with the current subframe being offset 0. For example, a DCI with OIF set to “01” may convey the scheduling information for the associated UE for the next DL subframe in the FDD SCell 110. However, embodiments are not limited to any particular range or to any particular length of the OIF.

As shown in FIG. 4, the DCI will also include a CIF preceding the OIF to identify the carrier corresponding to the DCI. This allows the PDCCH to convey scheduling information for subframes of several carriers.

The eNB 106 will transmit a configuration message to the UE 102 prior to transmitting DCIs. The configuration message can be a message otherwise involved with configuring CA for UEs, although embodiments are not limited thereto. The configuration message will include an indicator indicating that the control channel portion of PCell 104 DL subframes is capable of including control information for more than one SCell 110 subframe. The configuration message can be included as part of RRC signaling in accordance with a standard of the 3GPP family of standards, although embodiments are not limited thereto. The configuration message notifies the UE 102 that DCIs transmitted in the control channel portion of subsequent PCell DL subframes will include the offset field (e.g., OIF) described earlier herein.

The indicator can be included as a field of a cross-carrier scheduling configuration information element (IE) within the configuration message. An example cross-carrier scheduling configuration IE containing such an indicator is shown in Table 1. However, it will be understood that Table 1 is just an example and other IEs with other fields can be used, or fields can have other names than those shown in Table 1.

TABLE 1
cross carrier scheduling configuration information elements.
CrossCarrierSchedulingConfig-r10 ::= SEQUENCE {
schedulingCellInfo-r10           CHOICE {
own-r10                          SEQUENCE {-- No cross carrier scheduling
cif-Presence-r10 BOOLEAN
oif-Presence-rxx BOOLEAN
},
other-r10                        SEQUENCE {-- Cross carrier scheduling
schedulingCellId-r10             ServCellIndex-r10,
pdsch-Start-r10                  INTEGER (1..4)
}
}
}

Upon receiving an IE in an RRC message including the indicator (e.g., the oif-Presence-rxx field), the UE 102 will thereby be notified that the UE 102 should expect, and parse, OIFs in any received DCIs in order to access control information for corresponding subframes. The presence or absence of the OIF field in DCIs will be semi-static, meaning that any UE 102 configured with the above-described RRC message will continue to look for the OIF in all control channel portions received in the configured serving cell (e.g., PCell 104) until the eNB 106 or other eNB transmits another RRC message to indicate otherwise. Additionally, the eNB 106 will only include the OIF fields in control channel portions intended for the UEs configured to receive it, to help ensure backward compatibility for legacy UEs that do not employ the proposed solution. At a later point, the eNB 106 may to transmit a reconfiguration message, to indicate that the eNB 106 will subsequently refrain from transmitting control information for more than one SCell subframe within a single PCell DL subframe control channel portion.

FIG. 5 is a flow chart of a method 500 for TDD-FDD carrier aggregation in accordance with some embodiments. The example method 500 is described with respect to elements of FIG. 1-4. The eNB 106 can perform at least some operations of the method 500.

In operation 502, the eNB 106 transmits DCI on a control channel portion 308 (FIG. 3B) for a single PCell DL subframe. Each DCI includes an offset field as described earlier herein with respect to FIG. 3B to indicate an offset, relative to a first SCell subframe, to identify an SCell subframe for which each corresponding DCI is providing control information.

In operation 504, the eNB 106 transmits a configuration message to UE 102, the message including an indicator to notify the UE 102 that the UE 102 is to parse the offset field of each DCI. As described earlier herein, the eNB 106 will transmit the configuration message prior to transmitting the DCI. The eNB 106 may subsequently transmit a reconfiguration message, to indicate that control information will no longer be transmitted for more than one SCell 110 subframe within a single PCell 104 control channel portion.

FIG. 6 is a block diagram of the basic components of a communication station 600 in accordance with some embodiments. The communication station 600 may be suitable as a UE 102 (FIG. 1) or as an eNB 106 or network entity 114 (FIG. 1). The communication station 600 may support methods for carrier aggregation, in accordance with embodiments described above with respect to FIG. 1-5. It should be noted that when the communication station 600 acts as an eNB 106 or network entity 114, the communication station 600 may be stationary and non-mobile.

In some embodiments, the communication station 600 may include one or more processors and may be configured with instructions stored on a computer-readable storage device. When the communication station 600 serves as a UE 102 (FIG. 2), the instructions may cause the communication station 600 to receive a configuration message including an indicator to indicate that control channel portions of at least some PCell DL subframes shall include control information for more than one SCell subframe. As described earlier herein, the indicator instructs the communication station 600 to parse an offset field of downlink control information (DCI) transmitted by the PCell. The offset field indicates an offset, relative to a first SCell subframe, to identify a second SCell subframe for which the corresponding DCI is providing control information.

When the communication station 600 serves as an eNB 106 (FIG. 1), the instructions will cause the communication station 600 to transmit DCI as described earlier herein with respect to FIGS. 1-5 on a control channel portion for a PCell DL subframe, for one or more SCell subframes. The communication station 600 will also transmit a configuration message, such as the RRC messages described earlier herein, including an indicator to indicate that the control channel portion of PCell DL subframes are capable of including control information for more than one SCell subframe.

The communication station 600 may include physical layer circuitry 602 having a transceiver 610 for transmitting and receiving signals to and from other communication stations using one or more antennas 601. The physical layer circuitry 602 may also comprise medium access control (MAC) circuitry 604 for controlling access to the wireless medium. The communication station 600 may also include processing circuitry 606 and memory 608 arranged to perform the operations described herein. In some embodiments, the physical layer circuitry 602 and the processing circuitry 606 may be configured to perform operations detailed in FIGS. 1-5.

In accordance with some embodiments, the MAC circuitry 604 may be arranged to contend for a wireless medium and configure frames or packets for communicating over the wireless medium and the physical layer circuitry 602 may be arranged to transmit and receive signals. The physical layer circuitry 602 may include circuitry for modulation/demodulation, upconversion/downconversion, filtering, amplification, etc.

In some embodiments, the processing circuitry 606 of the communication station 600 may include one or more processors. In some embodiments, two or more antennas 601 may be coupled to the physical layer circuitry 602 arranged for transmitting and receiving signals. The memory 608 may store information for configuring the processing circuitry 606 to perform operations for configuring and transmitting message frames and performing the various operations described herein. The memory 608 may comprise any type of memory, including non-transitory memory, for storing information in a form readable by a machine (e.g., a computer). For example, the memory 608 may comprise a computer-readable storage device, read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices and other storage devices and media.

The antennas 601 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated for spatial diversity and the different channel characteristics that may result between each of the antennas and the antennas of a transmitting station.

In some embodiments, the communication station 600 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

In some embodiments, the communication station 600 may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or another device that may receive and/or transmit information wirelessly.

Although the communication station 600 is illustrated as having several separate functional elements, two or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements of the communication station 600 may refer to one or more processes operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory memory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media.

FIG. 7 is a block diagram of a machine 700 for executing various embodiments. In alternative embodiments, the machine 700 may operate as a standalone device or may be connected (e.g., networked) to other machines.

The machine (e.g., computer system) 700 may include a hardware processor 702 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 704 and a static memory 706, some or all of which may communicate with each other via an interlink (e.g., bus) 708. The machine 700 may further include a power management device 732, a graphics display device 710, an alphanumeric input device 712 (e.g., a keyboard), and a user interface (UI) navigation device 714 (e.g., a mouse). In an example, the graphics display device 710, alphanumeric input device 712 and UI navigation device 714 may be a touch screen display. The machine 700 may additionally include a storage device 716 (i.e., drive unit), a signal generation device 718 (e.g., a speaker), a network interface device/transceiver 720 coupled to antenna(s) 730, and one or more sensors 728, such as a global positioning system (GPS) sensor, compass, accelerometer, or other sensor. The machine 700 may include an output controller 734, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, card reader, etc.)

The storage device 716 may include a machine readable medium 722 on which is stored one or more sets of data structures or instructions 724 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 724 may also reside, completely or at least partially, within the main memory 704, within the static memory 706, or within the hardware processor 702 during execution thereof by the machine 700. In an example, one or any combination of the hardware processor 702, the main memory 704, the static memory 706, or the storage device 716 may constitute machine readable media.

While the machine readable medium 722 is illustrated as a single medium, the term “machine readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 724.

The term “machine readable medium” may include any medium that is capable of storing, encoding, or carrying instructions 724 for execution by the machine 700 and that cause the machine 700 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with instructions 724. Non-limiting machine readable medium examples may include solid-state memories, and optical and magnetic media. In an example, a massed machine readable medium comprises a machine readable medium with a plurality of particles having resting mass. Specific examples of massed machine readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), or Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.

The instructions 724 may further be transmitted or received over a communications network 726 using a transmission medium via the network interface device/transceiver 720 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.).

Although the present inventive subject matter has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. One of ordinary skill in the art would recognize that various features of the described embodiments may be combined in accordance with the disclosure. Moreover, it will be appreciated that various modifications and alterations may be made by those of ordinary skill in the art without departing from the scope of the disclosure.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

1. An evolved Node B (eNB) for performing carrier aggregation, the eNB comprising hardware processing circuitry to: transmit downlink control information (DCI) on a control channel portion for a primary cell (PCell) downlink (DL) subframe, the DCI including an offset field indicating an offset, relative to a first secondary cell (SCell) subframe, to identify a second SCell subframe for which the DCI is providing control information.

2. The eNB of claim 1, wherein the offset field includes a number of bits based on a ratio of DL subframes to uplink (UL) subframes in the PCell, the ratio being configured in accordance with a standard of the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) family of standards.

3. The eNB of claim 2, wherein the offset has a value ranging from 0 to 3 subframes.

4. The eNB of claim 1, wherein the hardware processing circuitry is further configured to: transmit a configuration message to a user equipment (UE) prior to transmitting the DCI, the configuration message including an indicator to indicate that the control channel portion of PCell DL subframes are capable of including control information for more than one SCell subframe.

5. The eNB of claim 4, wherein the configuration message notifies the UE that DCI transmitted in the control channel portion of subsequent PCell DL subframes will include the offset field.

6. The eNB of claim 5, wherein the indicator is included as a field of a cross-carrier scheduling configuration information element (IE).

7. The eNB of claim 6, wherein the configuration message is transmitted using radio resource control (RRC) messaging in accordance with a standard of the 3GPP family of standards.

8. The eNB of claim 4, wherein the hardware processing circuitry is further configured to transmit a reconfiguration message, subsequent to transmitting the configuration message, to indicate that the eNB will subsequently refrain from transmitting control information for more than one SCell subframe within a single PCell DL subframe control channel portion.

9. The eNB of claim 1, wherein the PCell and the SCell are co-located.

10. The eNB of claim 1, wherein the PCell and the SCell are non-co-located with ideal backhaul.

11. The eNB of claim 1, wherein the PCell operates using time-division duplex (TDD) technology and the SCell operates using frequency-division duplex (FDD) technology.

12. A user equipment (UE) configured for carrier aggregation, the UE comprising physical layer circuitry to: receive a configuration message including an indicator to indicate that control channel portions of at least some primary cell (PCell) downlink (DL) subframes shall include control information for more than one SCell subframe, wherein the indicator instructs the UE to parse an offset field of downlink control information (DCI) transmitted by the PCell, the offset field indicating an offset, relative to a first secondary cell (SCell) subframe, to identify a second SCell subframe for which the corresponding DCI is providing control information.

13. The UE of claim 12, wherein the offset field includes a number of bits based on a maximum ratio of DL subframes to uplink (UL) subframes in the PCell, the maximum ratio being configured in accordance with a standard of the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) family of standards.

14. The UE of claim 12, wherein the physical layer circuitry is further configured to: receive a plurality of sets of DCI on a control channel portion of a single PCell DL subframe; andparse offset fields from each DCI of the plurality to access corresponding control information for a plurality of SCell subframes.

15. The UE of claim 12, wherein the indicator is included as a field of a cross-carrier scheduling configuration information element (IE) and wherein the configuration message is received in a radio resource control (RRC) messaging.

16. A non-transitory computer-readable medium that stores instructions for execution by one or more processors to cause a machine to perform carrier aggregation operations including: operating a time-division duplex (TDD) primary cell (PCell) and a frequency division duplex (FDD) secondary cell (SCell);transmitting a plurality of downlink control information (DCI) on a control channel portion for a PCell DL subframe, each DCI of the plurality including an offset field indicating an offset, relative to a first SCell subframe, to identify a second SCell subframe for which the corresponding DCI is providing control information, the offset field including a number of bits based on a maximum ratio of DL subframes to uplink (UL) subframes in the PCell, the maximum ratio being configured in accordance with a standard of the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) family of standards.

17. The non-transitory computer-readable medium of claim 16, wherein the operations further comprise: transmitting a configuration message to a user equipment (UE) prior to transmitting the DCI, the configuration message including a field of a cross-carrier scheduling configuration information element (IE) indicating that a control channel portion of a PCell downlink (DL) subframe is configured to include control information for more than one SCell subframe.

18. The non-transitory computer-readable medium of claim 16, wherein the configuration message is transmitted using radio resource control (RRC) messaging in accordance with a standard of the 3GPP family of standards.

19. A method for carrier aggregation, the method comprising: transmitting a plurality of downlink control information (DCI) on a control channel portion for a single primary cell (PCell) downlink (DL) subframe, each DCI including an offset field indicating an offset, relative to a first secondary cell (SCell) subframe, to identify an SCell subframe for which each corresponding DCI is providing control information; andtransmitting a configuration message to a user equipment (UE) prior to transmitting the plurality of DCI, the configuration message including an indicator to notify the UE that the UE is to parse the offset field of each DCI.

20. The method of claim 19, wherein the offset field includes a number of bits based on a maximum ratio of DL subframes to uplink (UL) subframes in the PCell, the maximum ratio being configured in accordance with a standard of the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) family of standards.

21. The method of claim 19, further comprising: transmitting a reconfiguration message, subsequent to transmitting the configuration message, to indicate that control information will no longer be transmitted for more than one SCell subframe within a single PCell control channel portion.

22. The method of claim 19, further comprising: operating the PCell using time-division duplex (TDD) technology; andoperating the SCell using and a frequency-division duplex (FDD) technology.