Abstract:
Methods, systems, apparatus and computer program products are provided to facilitate the configuration and allocation of cross-carrier control information associated with transmissions of a wireless communication system. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the disclosed subject matter. Therefore, it is to be understood that it should not be used to interpret or limit the scope or the meaning of the claims.

Description:
[0001]    The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/241,816, entitled “MULTIPLE CARRIER INDICATION AND DOWNLINK CONTROL INFORMATION INTERACTION,” filed Sep. 11, 2009, the entirety of which is hereby incorporated by reference. The present application claims priority to U.S. Provisional Application Ser. No. 61/248,816, entitled “DOWNLINK CONTROL INFORMATION FOR MULTI-CARRIER OPERATION,” filed Oct. 5, 2009, the entirety of which is hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present disclosure relates generally to the field of wireless communications and, more particularly, to improving the ability of a wireless communication system to provide control information in a multi-carrier environment. 
       BACKGROUND 
       [0003]    This section is intended to provide a background or context to the disclosed embodiments. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section 
         [0004]    Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems. 
         [0005]    Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal, or user equipment (UE), communicates with one or more base stations through transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the user equipment, and the reverse link (or uplink) refers to the communication link from the user equipment to the base stations. 
       SUMMARY 
       [0006]    The disclosed embodiments relate to systems, methods, apparatus and computer program products that facilitate the interaction of multi-carrier indicators and downlink control information in a wireless communication system. 
         [0007]    In one aspect of the disclosed embodiments, a method includes receiving a plurality of component carriers configured for a wireless communication device, where the plurality of component carriers includes a plurality of search spaces having one or more common search spaces and a plurality of user-specific search spaces. The method further includes receiving a cross-carrier indicator, where the cross-carrier indicator is configured to enable cross-carrier signaling for a first component carrier. The method also includes determining whether the cross-carrier indicator is present in a control information format carried on a second component carrier, based on an association of the control information format with a search space on the second component carrier. 
         [0008]    In one embodiment, the common search space includes two downlink control information (DCI) formats without carrier indicators, and the plurality of user-specific search spaces includes DCI formats, of at least two different sizes, with carrier indicators, where cross-carrier control is enabled for unicast traffic via carrier indicators and cross-carrier control is not enabled for broadcast traffic via carrier indicators. 
         [0009]    In one embodiment, the common search space includes DCI format(s) of a first size with a carrier indicator and DCI format(s) of a second size without a carrier indicator, and the plurality of user-specific search spaces includes DCI formats of at least two different sizes with carrier indicators, wherein cross-carrier control is enabled for unicast traffic via carrier indicators and not enabled for broadcast traffic via carrier indicators. 
         [0010]    In one embodiment, the common search space includes DCI formats of two different sizes with carrier indicators and the plurality of user-specific search spaces includes DCI formats of at least two different sizes with carrier indicators, wherein cross-carrier control is enabled for unicast traffic and broadcast traffic via carrier indicators. 
         [0011]    In one embodiment, the common search space includes DCI format(s) of a first size with a carrier indicator and DCI format(s) of a second size without a carrier indicator, and the plurality of user-specific search spaces includes two DCI formats with carrier indicators, wherein cross-carrier control is enabled for unicast traffic and broadcast traffic via carrier indicators. 
         [0012]    In one embodiment, the common search space includes DCI formats of three different sizes, comprising DCI formats of two sizes with carrier indicators and DCI format(s) of a third size without a carrier indicator, and the plurality of user-specific search spaces includes DCI formats of at least two different sizes with carrier indicators, providing backward compatibility with LTE Rel-8 broadcast traffic and unicast traffic. 
         [0013]    In one embodiment, the common search space includes DCI formats of four different sizes, comprising DCI formats of a first two sizes with a carrier indicator and DCI formats of a second two sizes without a carrier indicator, and the plurality of user-specific search spaces includes DCI formats at least two different sizes with carrier indicators, providing backward compatibility with LTE Rel-8 broadcast traffic and unicast traffic. 
         [0014]    In one disclosed embodiment, a method in a wireless communication system includes formatting control information, in a control channel of a communications carrier, with a cross-carrier control indicator, and scrambling the CRC of the control information with a scrambling code, wherein the scrambling code is selected based on a format of the control information and a location of the control information within a plurality of search spaces in the control channel. 
         [0015]    In another aspect, a first plurality of control information formats is associated with a first scrambling code and the at least one common search space, and a second plurality of control information formats, including the first plurality of control information formats, is associated with a second scrambling code and the plurality of user-specific search spaces, where the second scrambling code is different from the first scrambling code. 
         [0016]    In another disclosed embodiment, a method in a wireless communication device includes searching a plurality of search spaces in a control channel of a communications carrier for scrambled control information, blind-decoding the plurality of search spaces with a plurality of descrambling codes to extract the control information, and determining the presence of a cross-carrier control indicator based on a format of the control information and a location of the control information in the plurality of search spaces. 
         [0017]    In another aspect, a first plurality of control information formats is associated with a first descrambling code and at least one common search space, and a second plurality of control information formats, including the first plurality of control information formats, is associated with a second descrambling code and the plurality of user-specific search spaces, where the second descrambling code is different from the first descrambling code. 
         [0018]    Other disclosed embodiments include apparatus and computer program products for performing the disclosed methods. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Various disclosed embodiments are illustrated by way of example, and not of limitation, by referring to the accompanying drawings, in which: 
           [0020]      FIG. 1  illustrates a wireless communication system; 
           [0021]      FIG. 2  illustrates a block diagram of a communication system; 
           [0022]      FIG. 3  illustrates exemplary search space; 
           [0023]      FIG. 4  illustrates a set of exemplary aggregation levels associated with a search space; 
           [0024]      FIG. 5  illustrates another set of exemplary aggregation levels associated with a search space; 
           [0025]      FIG. 6  illustrates a system within which various embodiments may be implemented; 
           [0026]      FIG. 7  illustrates a block diagram of a wireless communication system for cross-carrier signaling; 
           [0027]      FIG. 8A  is a flowchart illustrating a method in accordance with an exemplary embodiment; 
           [0028]      FIG. 8B  is a flowchart illustrating a method in accordance with another exemplary embodiment; 
           [0029]      FIG. 8C  is a flowchart illustrating a method in accordance with yet another exemplary embodiment; 
           [0030]      FIG. 9  illustrates a system within which various embodiments may be implemented; and 
           [0031]      FIG. 10  illustrates an apparatus within which various embodiments may be implemented. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    In the following description, for purposes of explanation and not limitation, details and descriptions are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, it will be apparent to those skilled in the art that the various embodiments may be practiced in other embodiments that depart from these details and descriptions. 
         [0033]    As used herein, the terms “component,” “module,” “system” and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal). 
         [0034]    Furthermore, certain embodiments are described herein in connection with a user equipment. A user equipment can also be called a user terminal, and may contain some or all of the functionality of a system, subscriber unit, subscriber station, mobile station, mobile wireless terminal, mobile device, node, device, remote station, remote terminal, terminal, wireless communication device, wireless communication apparatus or user agent. A user equipment can be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a smart phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a laptop, a handheld communication device, a handheld computing device, a satellite radio, a wireless modem card and/or another processing device for communicating over a wireless system. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with one or more wireless terminals and can also be called, and may contain some or all of the functionality of, an access point, node, Node B, evolved NodeB (eNB) or some other network entity. A base station communicates over the air-interface with wireless terminals. The communication may take place through one or more sectors. The base station can act as a router between the wireless terminal and the rest of the access network, which can include an Internet Protocol (IP) network, by converting received air-interface frames to IP packets. The base station can also coordinate management of attributes for the air interface, and may also be the gateway between a wired network and the wireless network. 
         [0035]    Various aspects, embodiments or features will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that, the various systems may include additional devices, components, modules, and so on, and/or may not include all of the devices, components, modules and so on, discussed in connection with the figures. A combination of these approaches may also be used. 
         [0036]    Additionally, in the subject description, the word “exemplary” is used to mean serving as an example, instance or illustration. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. 
         [0037]    The various disclosed embodiments may be incorporated into a communication system. In one example, such communication system utilizes an orthogonal frequency division multiplex (OFDM) that effectively partitions the overall system bandwidth into multiple (N F ) subcarriers, which may also be referred to as frequency sub-channels, tones or frequency bins. For an OFDM system, the data to be transmitted (i.e., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK or M-QAM) used for data transmission. At each time interval, which may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the N F  frequency subcarriers. Thus, OFDM may be used to combat inter-symbol interference (ISI) caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth. 
         [0038]    Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations through transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link can be established through a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system. 
         [0039]    A MIMO system employs multiple (N T ) transmit antennas and multiple (N R ) receive antennas for data transmission. A MIMO channel formed by the N T  transmit and N R  receive antennas may be decomposed into N S  independent channels, which are also referred to as spatial channels, where N S ≦min{N T , N R }. Each of the N S  independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. A MIMO system also supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the base station to extract transmit beamforming gain on the forward link when multiple antennas are available at the base station. 
         [0040]      FIG. 1  illustrates a wireless communication system within which the various disclosed embodiments may be implemented. A base station  100  may include multiple antenna groups, and each antenna group may comprise one or more antennas. For example, if the base station  100  comprises six antennas, one antenna group may comprise a first antenna  104  and a second antenna  106 , another antenna group may comprise a third antenna  108  and a fourth antenna  110 , while a third group may comprise a fifth antenna  112  and a sixth antenna  114 . It should be noted that while each of the above-noted antenna groups were identified as having two antennas, more or fewer antennas may be utilized in each antenna group. 
         [0041]    Referring back to  FIG. 1 , a first user equipment  116  is illustrated to be in communication with, for example, the fifth antenna  112  and the sixth antenna  114  to enable the transmission of information to the first user equipment  116  over a first forward link  120 , and the reception of information from the first user equipment  116  over a first reverse link  118 .  FIG. 1  also illustrates a second user equipment  122  that is in communication with, for example, the third antenna  108  and the fourth antenna  110  to enable the transmission of information to the second user equipment  122  over a second forward link  126 , and the reception of information from the second user equipment  122  over a second reverse link  124 . In a Frequency Division Duplex (FDD) system, the communication links  118 ,  120 ,  124   126  that are shown in  FIG. 1  may use different frequencies for communication. For example, the first forward link  120  may use a different frequency than that used by the first reverse link  118 . 
         [0042]    In some embodiments, each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of the base station. For example, the different antenna groups that are depicted in  FIG. 1  may be designed to communicate to the user equipment in a sector of the base station  100 . In communication over the forward links  120  and  126 , the transmitting antennas of the base station  100  utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different user equipment  116  and  122 . Also, a base station that uses beamforming to transmit to user equipment scattered randomly throughout its coverage area causes less interference to user equipment in the neighboring cells than a base station that transmits omni-directionally through a single antenna to all its user equipment. 
         [0043]    The communication networks that may accommodate some of the various disclosed embodiments may include logical channels that are classified into Control Channels and Traffic Channels. Logical control channels may include a broadcast control channel (BCCH), which is the downlink channel for broadcasting system control information, a paging control channel (PCCH), which is the downlink channel that transfers paging information, a multicast control channel (MCCH), which is a point-to-multipoint downlink channel used for transmitting multimedia broadcast and multicast service (MBMS) scheduling and control information for one or several multicast traffic channels (MTCHs). Generally, after establishing radio resource control (RRC) connection, MCCH is only used by the user equipments that receive MBMS. Dedicated control channel (DCCH) is another logical control channel that is a point-to-point bi-directional channel transmitting dedicated control information, such as user-specific control information used by the user equipment having an RRC connection. Common control channel (CCCH) is also a logical control channel that may be used for random access information. Logical traffic channels may comprise a dedicated traffic channel (DTCH), which is a point-to-point bi-directional channel dedicated to one user equipment for the transfer of user information. Also, a multicast traffic channel (MTCH) may be used for point-to-multipoint downlink transmission of traffic data. 
         [0044]    The communication networks that accommodate some of the various embodiments may additionally include logical transport channels that are classified into downlink (DL) and uplink (UL). The DL transport channels may include a broadcast channel (BCH), a downlink shared data channel (DL-SDCH), a multicast channel (MCH) and a Paging Channel (PCH). The UL transport channels may include a random access channel (RACH), a request channel (REQCH), an uplink shared data channel (UL-SDCH) and a plurality of physical channels. The physical channels may also include a set of downlink and uplink channels. 
         [0045]    In some disclosed embodiments, the downlink physical channels may include at least one of a common pilot channel (CPICH), a synchronization channel (SCH), a common control channel (CCCH), a shared downlink control channel (SDCCH), a multicast control channel (MCCH), a shared uplink assignment channel (SUACH), an acknowledgement channel (ACKCH), a downlink physical shared data channel (DL-PSDCH), an uplink power control channel (UPCCH), a paging indicator channel (PICH), a load indicator channel (LICH), a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), a physical downlink shared channel (PDSCH) and a physical multicast channel (PMCH). The uplink physical channels may include at least one of a physical random access channel (PRACH), a channel quality indicator channel (CQICH), an acknowledgement channel (ACKCH), an antenna subset indicator channel (ASICH), a shared request channel (SREQCH), an uplink physical shared data channel (UL-PSDCH), a broadband pilot channel (BPICH), a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH). 
         [0046]    Further, the following terminology and features may be used in describing the various disclosed embodiments: 
         [0047]    3G 3rd Generation 
         [0048]    3GPP 3rd Generation Partnership Project 
         [0049]    ACLR Adjacent channel leakage ratio 
         [0050]    ACPR Adjacent channel power ratio 
         [0051]    ACS Adjacent channel selectivity 
         [0052]    ADS Advanced Design System 
         [0053]    AMC Adaptive modulation and coding 
         [0054]    A-MPR Additional maximum power reduction 
         [0055]    ARQ Automatic repeat request 
         [0056]    BCCH Broadcast control channel 
         [0057]    BTS Base transceiver station 
         [0058]    CDD Cyclic delay diversity 
         [0059]    CCDF Complementary cumulative distribution function 
         [0060]    CDMA Code division multiple access 
         [0061]    CFI Control format indicator 
         [0062]    Co-MIMO Cooperative MIMO 
         [0063]    CP Cyclic prefix 
         [0064]    CPICH Common pilot channel 
         [0065]    CPRI Common public radio interface 
         [0066]    CQI Channel quality indicator 
         [0067]    CRC Cyclic redundancy check 
         [0068]    DCI Downlink control indicator 
         [0069]    DFT Discrete Fourier transform 
         [0070]    DFT-SOFDM Discrete Fourier transform spread OFDM 
         [0071]    DL Downlink (base station to subscriber transmission) 
         [0072]    DL-SCH Downlink shared channel 
         [0073]    DSP Digital signal processing 
         [0074]    DT Development toolset 
         [0075]    DVSA Digital vector signal analysis 
         [0076]    EDA Electronic design automation 
         [0077]    E-DCH Enhanced dedicated channel 
         [0078]    E-UTRAN Evolved UMTS terrestrial radio access network 
         [0079]    eMBMS Evolved multimedia broadcast multicast service 
         [0080]    eNB Evolved Node B 
         [0081]    EPC Evolved packet core 
         [0082]    EPRE Energy per resource element 
         [0083]    ETSI European Telecommunications Standards Institute 
         [0084]    E-UTRA Evolved UTRA 
         [0085]    E-UTRAN Evolved UTRAN 
         [0086]    EVM Error vector magnitude 
         [0087]    FDD Frequency division duplex 
         [0088]    FFT Fast Fourier transform 
         [0089]    FRC Fixed reference channel 
         [0090]    FS1 Frame structure type 1 
         [0091]    FS2 Frame structure type 2 
         [0092]    GSM Global system for mobile communication 
         [0093]    HARQ Hybrid automatic repeat request 
         [0094]    HDL Hardware description language 
         [0095]    HI HARQ indicator 
         [0096]    HSDPA High speed downlink packet access 
         [0097]    HSPA High speed packet access 
         [0098]    HSUPA High speed uplink packet access 
         [0099]    IFFT Inverse FFT 
         [0100]    IOT Interoperability test 
         [0101]    IP Internet protocol 
         [0102]    LO Local oscillator 
         [0103]    LTE Long term evolution 
         [0104]    MAC Medium access control 
         [0105]    MBMS Multimedia broadcast multicast service 
         [0106]    MBSFN Multicast/broadcast over single-frequency network 
         [0107]    MCH Multicast channel 
         [0108]    MIMO Multiple input multiple output 
         [0109]    MISO Multiple input single output 
         [0110]    MME Mobility management entity 
         [0111]    MOP Maximum output power 
         [0112]    MPR Maximum power reduction 
         [0113]    MU-MIMO Multiple user MIMO 
         [0114]    NAS Non-access stratum 
         [0115]    OBSAI Open base station architecture interface 
         [0116]    OFDM Orthogonal frequency division multiplexing 
         [0117]    OFDMA Orthogonal frequency division multiple access 
         [0118]    PAPR Peak-to-average power ratio 
         [0119]    PAR Peak-to-average ratio 
         [0120]    PBCH Physical broadcast channel 
         [0121]    P-CCPCH Primary common control physical channel 
         [0122]    PCFICH Physical control format indicator channel 
         [0123]    PCH Paging channel 
         [0124]    PDCCH Physical downlink control channel 
         [0125]    PDCP Packet data convergence protocol 
         [0126]    PDSCH Physical downlink shared channel 
         [0127]    PHICH Physical hybrid ARQ indicator channel 
         [0128]    PHY Physical layer 
         [0129]    PRACH Physical random access channel 
         [0130]    PMCH Physical multicast channel 
         [0131]    PMI Pre-coding matrix indicator 
         [0132]    P-SCH Primary synchronization signal 
         [0133]    PUCCH Physical uplink control channel 
         [0134]    PUSCH Physical uplink shared channel. 
         [0135]      FIG. 2  illustrates a block diagram of an exemplary communication system that may accommodate the various embodiments. The MIMO communication system  200  that is depicted in  FIG. 2  comprises a transmitter system  210  (e.g., a base station or access point) and a receiver system  250  (e.g., an access terminal or user equipment) in a MIMO communication system  200 . It will be appreciated by one of ordinary skill that even though the base station is referred to as a transmitter system  210  and a user equipment is referred to as a receiver system  250 , as illustrated, embodiments of these systems are capable of bi-directional communications. In that regard, the terms “transmitter system  210 ” and “receiver system  250 ” should not be used to imply single directional communications from either system. It should also be noted the transmitter system  210  and the receiver system  250  of  FIG. 2  are each capable of communicating with a plurality of other receiver and transmitter systems that are not explicitly depicted in  FIG. 2 . At the transmitter system  210 , traffic data for a number of data streams is provided from a data source  212  to a transmit (TX) data processor  214 . Each data stream may be transmitted over a respective transmitter system. The TX data processor  214  formats, codes and interleaves the traffic data for each data stream, based on a particular coding scheme selected for that data stream, to provide the coded data. 
         [0136]    The coded data for each data stream may be multiplexed with pilot data using, for example, OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (symbol mapped) based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding and modulation for each data stream may be determined by instructions performed by a processor  230  of the transmitter system  210 . 
         [0137]    In the exemplary block diagram of  FIG. 2 , the modulation symbols for all data streams may be provided to a TX MEMO processor  220 , which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor  220  then provides N T  modulation symbol streams to N T  transmitter system transceivers (TMTR)  222   a  through  222   t.  In one embodiment, the TX MIMO processor  220  may further apply beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted. 
         [0138]    Each transmitter system transceiver  222   a  through  222   t  receives and processes a respective symbol stream to provide one or more analog signals, and further condition the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. In some embodiments, the conditioning may include, but is not limited to, operations such as amplification, filtering, up-conversion and the like. The modulated signals produced by the transmitter system transceivers  222   a  through  222   t  are then transmitted from the transmitter system antennas  224   a  through  224   t  that are shown in  FIG. 2 . 
         [0139]    At the receiver system  250 , the transmitted modulated signals may be received by the receiver system antennas  252   a  through  252   r,  and the received signal from each of the receiver system antennas  252   a  through  252   r  is provided to a respective receiver system transceiver (RCVR)  254   a  through  254   r.  Each receiver system transceiver  254   a  through  254   r  conditions a respective received signal, digitizes the conditioned signal to provide samples and may further processes the samples to provide a corresponding “received” symbol stream. In some embodiments, the conditioning may include, but is not limited to, operations such as amplification, filtering, down-conversion and the like. 
         [0140]    An RX data processor  260  then receives and processes the symbol streams from the receiver system transceivers  254   a  through  254   r  based on a particular receiver processing technique to provide a plurality of “detected” symbol streams. In one example, each detected symbol stream can include symbols that are estimates of the symbols transmitted for the corresponding data stream. The RX data processor  260  then, at least in part, demodulates, de-interleaves and decodes each detected symbol stream to recover the traffic data for the corresponding data stream. The processing by the RX data processor  260  may be complementary to that performed by the TX MIMO processor  220  and the TX data processor  214  at the transmitter system  210 . The RX data processor  260  can additionally provide processed symbol streams to a data sink  264 . 
         [0141]    In some embodiments, a channel response estimate is generated by the RX data processor  260  and can be used to perform space/time processing at the receiver system  250 , adjust power levels, change modulation rates or schemes, and/or other appropriate actions. Additionally, the RX data processor  260  can further estimate channel characteristics such as signal-to-noise (SNR) and signal-to-interference ratio (SIR) of the detected symbol streams. The RX data processor  260  can then provide estimated channel characteristics to a processor  270 . In one example, the RX data processor  260  and/or the processor  270  of the receiver system  250  can further derive an estimate of the “operating” SNR for the system. The processor  270  of the receiver system  250  can also provide channel state information (CSI), which may include information regarding the communication link and/or the received data stream. This information, which may contain, for example, the operating SNR and other channel information, may be used by the transmitter system  210  (e.g., base station or eNodeB) to make proper decisions regarding, for example, the user equipment scheduling, MIMO settings, modulation and coding choices and the like. At the receiver system  250 , the CSI that is produced by the processor  270  is processed by a TX data processor  238 , modulated by a modulator  280 , conditioned by the receiver system transceivers  254   a  through  254   r  and transmitted back to the transmitter system  210 . In addition, a data source  236  at the receiver system  250  can provide additional data to be processed by the TX data processor  238 . 
         [0142]    In some embodiments, the processor  270  at the receiver system  250  may also periodically determine which pre-coding matrix to use. The processor  270  formulates a reverse link message comprising a matrix index portion and a rank value portion. The reverse link message may comprise various types of information regarding the communication link and/or the received data stream. The reverse link message is then processed by the TX data processor  238  at the receiver system  250 , which may also receive traffic data for a number of data streams from the data source  236 . The processed information is then modulated by a modulator  280 , conditioned by one or more of the receiver system transceivers  254   a  through  254   r,  and transmitted back to the transmitter system  210 . 
         [0143]    In some embodiments of the MIMO communication system  200 , the receiver system  250  is capable of receiving and processing spatially multiplexed signals. In these systems, spatial multiplexing occurs at the transmitter system  210  by multiplexing and transmitting different data streams on the transmitter system antennas  224   a  through  224   t.  This is in contrast to the use of transmit diversity schemes, where the same data stream is sent from multiple transmitter systems antennas  224   a  through  224   t.  In a MIMO communication system  200  capable of receiving and processing spatially multiplexed signals, a precode matrix is typically used at the transmitter system  210  to ensure the signals transmitted from each of the transmitter system antennas  224   a  through  224   t  are sufficiently decorrelated from each other. This decorrelation ensures that the composite signal arriving at any particular receiver system antenna  252   a  through  252   r  can be received and the individual data streams can be determined in the presence of signals carrying other data streams from other transmitter system antennas  224   a  through  224   t.    
         [0144]    Since the amount of cross-correlation between streams can be influenced by the environment, it is advantageous for the receiver system  250  to feed back information to the transmitter system  210  about the received signals. In these systems, both the transmitter system  210  and the receiver system  250  contain a codebook with a number of precoding matrices. Each of these precoding matrices can, in some instances, be related to an amount of cross-correlation experienced in the received signal. Since it is advantageous to send the index of a particular matrix rather than the values in the matrix, the feedback control signal sent from the receiver system  250  to the transmitter system  210  typically contains the index of a particular precoding matrix. In some instances the feedback control signal also includes a rank index which indicates to the transmitter system  210  how many independent data streams to use in spatial multiplexing. 
         [0145]    Other embodiments of MIMO communication system  200  are configured to utilize transmit diversity schemes instead of the spatially multiplexed scheme described above. In these embodiments, the same data stream is transmitted across the transmitter system antennas  224   a  through  224   t.  In these embodiments, the data rate delivered to receiver system  250  is typically lower than spatially multiplexed MIMO communication systems  200 . These embodiments provide robustness and reliability of the communication channel. In transmit diversity systems each of the signals transmitted from the transmitter system antennas  224   a  through  224   t  will experience a different interference environment (e.g., fading, reflection, multi-path phase shifts). In these embodiments, the different signal characteristics received at the receiver system antennas  252   a  through  254   r  are useful in determining the appropriate data stream. In these embodiments, the rank indicator is typically set to 1, telling the transmitter system  210  not to use spatial multiplexing. 
         [0146]    Other embodiments may utilize a combination of spatial multiplexing and transmit diversity. For example in a MIMO communication system  200  utilizing four transmitter system antennas  224   a  through  224   t,  a first data stream may be transmitted on two of the transmitter system antennas  224   a  through  224   t  and a second data stream transmitted on remaining two transmitter system antennas  224   a  through  224   t.  In these embodiments, the rank index is set to an integer lower than the full rank of the precode matrix, indicating to the transmitter system  210  to employ a combination of spatial multiplexing and transmit diversity. 
         [0147]    At the transmitter system  210 , the modulated signals from the receiver system  250  are received by the transmitter system antennas  224   a  through  224   t,  are conditioned by the transmitter system transceivers  222   a  through  222   t,  are demodulated by a transmitter system demodulator  240 , and are processed by the RX data processor  242  to extract the reserve link message transmitted by the receiver system  250 . In some embodiments, the processor  230  of the transmitter system  210  then determines which pre-coding matrix to use for future forward link transmissions, and then processes the extracted message. In other embodiments, the processor  230  uses the received signal to adjust the beamforming weights for future forward link transmissions. 
         [0148]    In other embodiments, a reported CSI can be provided to the processor  230  of the transmitter system  210  and used to determine, for example, data rates as well as coding and modulation schemes to be used for one or more data streams. The determined coding and modulation schemes can then be provided to one or more transmitter system transceivers  222   a  through  222   t  at the transmitter system  210  for quantization and/or use in later transmissions to the receiver system  250 . Additionally and/or alternatively, the reported CSI can be used by the processor  230  of the transmitter system  210  to generate various controls for the TX data processor  214  and the TX MIMO processor  220 . In one example, the CSI and/or other information processed by the RX data processor  242  of the transmitter system  210  can be provided to a data sink  244 . 
         [0149]    In some embodiments, the processor  230  at the transmitter system  210  and the processor  270  at the receiver system  250  may direct operations at their respective systems. Additionally, a memory  232  at the transmitter system  210  and a memory  272  at the receiver system  250  can provide storage for program codes and data used by the transmitter system processor  230  and the receiver system processor  270 , respectively. Further, at the receiver system  250 , various processing techniques can be used to process the N R  received signals to detect the N T  transmitted symbol streams. These receiver processing techniques can include spatial and space-time receiver processing techniques, which can include equalization techniques, “successive nulling/equalization and interference cancellation” receiver processing techniques, and/or “successive interference cancellation” or “successive cancellation” receiver processing techniques. 
         [0150]    In LTE systems, the physical downlink shared channel (PDCCH) carries the data and signaling information to the user equipment; while the physical downlink control channel (PDCCH) carries a message known as downlink control information (DCI). The DCI includes information regarding the downlink scheduling assignments, uplink resource grants, transmission scheme, uplink power control, hybrid automatic return repeat request (HARQ) information, modulation and coding schemes (MCS) and other information. A DCI can be UE-specific (dedicated) or cell-specific (common) and placed in different dedicated and common search spaces within the PDCCH depending on the format of the DCI. A user equipment attempts to decode the DCI by performing a process known as a blind decode, during which a plurality of decode attempts are carried out in the search spaces until the DCI is detected. 
         [0151]    The size of the DCI messages can differ depending on the type and amount of information that is carried by the DCI. For example, if spatial multiplexing is supported, the size of the DCI message is larger compared to scenarios where contiguous frequency allocations are made. Similarly, for a system that employs MIMO, the DCI must include additional signaling information that is not needed for systems that do not utilize MIMO. Accordingly, the DCI has been categorized in different formats that are suited for different configurations. Table 1 summarizes the DCI formats that are listed as part of LTE Rel-8 specifications. It should be noted that the disclosed embodiments can also be implemented in conjunction with other DCI formats and/or sizes. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Exemplary DCI Formats 
               
             
          
           
               
                 DCI 
                   
                 Number of Bits 
               
               
                 Format 
                 Purpose 
                 (10 MHz) 
               
               
                   
               
               
                 0 
                 Uplink Resource Grant 
                 42 
               
               
                 1 
                 Downlink Resource Assignment - single 
                 47 
               
               
                   
                 codeword 
               
               
                 1A 
                 Downlink Resource Assignment - single 
                 42 
               
               
                   
                 codeword/compact format 
               
               
                 1B 
                 Downlink Resource Assignment - rank-1 
                 46 
               
               
                   
                 transmission 
               
               
                 1C 
                 Downlink Resource Assignment - very compact 
                 26 
               
               
                   
                 format 
               
               
                 1D 
                 Downlink Resource Assignment - multi-user 
                 46 
               
               
                   
                 MIMO 
               
               
                 2 
                 Downlink Resource Assignment - closed-loop 
                 62 
               
               
                   
                 MIMO 
               
               
                 2A 
                 Downlink Resource Assignment - open-loop 
                 58 
               
               
                   
                 MIMO 
               
               
                 3 
                 Transmit Power Control Commands - PUCCH 
                 42 
               
               
                   
                 and PUSCH with 2-bit power adjustment 
               
               
                 3A 
                 Transmit Power Control Commands - PUCCH 
                 42 
               
               
                   
                 and PUSCH with 1-bit power adjustment 
               
               
                   
               
             
          
         
       
     
         [0152]    The size of a DCI format depends not only on the amount of information that is carried within the DCI message, but also on other factors such as the transmission bandwidth, the number of antenna ports, TDD or FDD operating mode, etc. For example, the exemplary sizes that are listed in Table 1 for different DCI formats are associated with a system bandwidth of 50 resource blocks, FDD, and four antennas at the eNodeB, corresponding to a 10 MHz bandwidth. 
         [0153]    In order to simplify the decoding of the DCI messages at the user equipment, the LTE Rel-8 specifications also require that DCI format 0 (used for uplink grants) and format 1A (used for downlink resource assignment) to always be the same size. However, due to different information fields in DCI format 0 and DCI format 1A and, for example, bandwidth differences between the uplink and downlink channels, the size of a format 0 DCI and format 1A DCI message can differ. Therefore, in situations where DCI formats 0 and 1A have different sizes, the smaller of the two is padded with zeroes to produce same DCI message size. In order to differentiate between format 0 and format 1A DCI messages, a single bit in both formats is provided that signals the presence of either format 0 or format 1A. 
         [0154]    It should be noted that in some systems, the DCI messages are also appended with cyclic redundancy check (CRC) bits to for error detection. The coded DCI bits are then mapped to control channel elements (CCEs) according to the DCI format. A PDCCH can carry DCI messages associated with multiple user equipments. A particular user equipment must, therefore, be able to recognize the DCI messages that are intended for that particular user equipment. To that end, a user equipment is assigned certain identifiers (e.g., a cell radio network temporary identifier—C-RNTI) that facilitate the detection of the DCI associated with that user equipment. To reduce signaling overhead, the CRC bits that are attached to each DCI payload are scrambled (e.g., masked) with the identifier (e.g., C-RNTI) associated with a particular user equipment and/or an identifier that is associated with a group of user equipments. In an operation known as a “blind decode,” the user equipment can descramble (or de-mask) all potential DCI messages using its unique identifier, and perform a CRC check on the DCI payload. If the CRC check passes, the content of the control channel is declared valid for the user equipment, which can then process the DCI. 
         [0155]    To reduce power consumption and overhead at the user equipment; a limited set of control channel element (CCE) locations can be specified, wherein the set of CCE locations include locations at which a DCI payload associated with a particular UE can be placed. In LTE Rel-8, a CCE consists of nine logically contiguous resource element groups (REGs), where each REG contains 4 resource elements (REs). Each RE is one frequency-time unit. CCEs can be aggregated at different levels (e.g., 1, 2, 4 and 8) depending on the DCI format and the system bandwidth. The set of CCE locations in which the user equipment can find its corresponding DCI messages are considered a search space. The search space can be partitioned into two regions: a common CCE region or search space and a UE-specific (dedicated) CCE region or search space. The common CCE region is monitored by all UEs served by an eNodeB and can include information such as paging information, system information, random access procedures and the like. The UE-specific CCE region includes user-specific control information and is configured individually for each user equipment. 
         [0156]      FIG. 3  illustrates an exemplary search space  300  on a PDCCH  302  that is divided into a common search space  304  and a UE-specific search space.  306 . It should be noted that while, for simplicity, the exemplary search space  302  of  FIG. 3  is illustrated as a collection of 32 logically contiguous CCE blocks, it is understood that the disclosed embodiments can be implemented using a different number of CCEs. Each CCE contains a fixed number of resource elements in non-contiguous locations. Alternatively, the CCEs may be arranged in non-contiguous locations within the resource blocks of one or more downlink control channels. Moreover, the common search space  304  and the UE-specific search space  306  may span overlapping CCEs. CCEs are numbered consecutively. The common search space always starts from CCE 0, while UE specific search space has starting CCE indices that depend on the UE ID (e.g., C-RNTI), the subframe index, the CCE aggregation level and other random seeds. 
         [0157]    In LTE Rel-8 systems, the number of CCEs, denoted by N CCE , available for PDCCH can be determined based on the system bandwidth, the size of the control region, and the configuration of other control signals, etc. The set of CCEs for the common search space ranges from 0 to min{16, N CCE -1}. For all the UEs, the set of CCEs for the UE-specific search space ranges from 0 to N CCE-1 , a superset of those for the common search space. For a specific UE, the set of CCEs for the UE is a subset of the entire set within the range from CCE 0 to CCE N CCE -1, depending on the configured identifier and other factors. In the example in  FIG. 3 , N CCE =32. 
         [0158]    The size of a search space, such as search space  302  of  FIG. 3 , or a set of CCE locations can be based upon an aggregation level. As noted earlier, the size of a DCI message can depend on the DCI format and the transmission bandwidth. The aggregation level specifies a number of logically or physically contiguous CCEs utilized to convey a single DCI payload. The common search space can include two possible aggregation levels, level-4 (e.g., 4 CCEs) and level-8 (e.g., 8 CCEs). In some systems, to reduce the computations that must be performed by a user equipment, aggregation level-4 of the common search space can be configured to accommodate a maximum of four DCI locations. Similarly, aggregation level-8 of the common search space can be configured to accommodate a maximum of 2 DCI locations.  FIG. 4  provides an exemplary diagram of a common search space  400  on a PDCCH  402  that is configured to accommodate four aggregation level-4 candidates  404  and two aggregation level-8 candidates  406 . Accordingly, there are a total of 6 candidates in the common search space  400  in the exemplary diagram of  FIG. 4 . 
         [0159]    The UE-specific search space can be configured to include four aggregation levels: 1, 2, 4 or 8, corresponding to 1, 2, 4 and 8 CCEs, respectively.  FIG. 5  provides an exemplary diagram of a UE-specific search space  500  on a PDCCH  502  that is configured to accommodate six aggregation level-1 candidates  504 , six aggregation level-2 candidates  506 , two aggregation level-4 candidates  508  and two aggregation level-8 candidates  510 . Accordingly, there are a total of 16 candidates in the UE-specific search space  500  in the exemplary diagram of  FIG. 5 . 
         [0160]    It should be noted in the example of  FIG. 5  that the starting CCE indices for the four aggregation levels are different and follow a so-called “tree-structure” used in LTE Rel-8. That is, for aggregation level L, the starting CCE index is always an integer multiples of L. Within each aggregation level, the search space is logically contiguous. The starting CCE index for each aggregation level can also depend on time (i.e., subframe number). In other contemplated embodiments, the starting CCE indices for each aggregation level may be the same or different. 
         [0161]    Further, as discussed earlier, for a given UE, the UE-specific search space is a subset of the set {0, N CCE -1}, where N CCE  is the total number of available CCEs. In the example shown in  FIG. 3 , N CCE =32. For example, due to the “tree-structure” and potentially different starting CCE indices for different aggregation levels, in a subframe, a UE may have CCE 9 as the starting CCE index for aggregation level 1, CCE 18 for aggregation level 2, CCE 4 for aggregation level 4, and CCE 8 for aggregation level 8. Since the UE-specific search space for each aggregation level is contiguous, the 2 candidates for aggregation level 4 for the UE are CCEs {4, 5, 6, 7} and CCEs {8, 9, 10, 11}. It should be further noted that the common search space  400  of  FIG. 4  and the UE-specific search space  500  of  FIG. 5  are provided to facilitate the understanding of the underlying concepts associated with the disclosed embodiments. Therefore, it should be understood that common and UE-specific search spaces with different number and configurations of candidate locations may be configured and used in accordance with the disclosed embodiments. 
         [0162]    Each candidate in the common search space and UE-specific search space represents a possible DCI transmission. If, for example, the DCI is for a specific user equipment, the CRC may be masked with a cell radio network temporary identifier (C-RNTI). If the DCI contains paging information or system information, for example, the CRC is masked with a paging RNTI (P-RNTI) or a system-information RNTI (SI-RNTI). In other examples, additional RNTIs or other codes may be used for masking the CRC. As noted earlier, a user equipment conducts a blind decode to discover the location of the control information. For instance, in the example UE-specific search space  500  that is depicted in  FIG. 5 , a user equipment may conduct up to 16 decode attempts to determine which of the UE-specific candidate locations  504 ,  506 ,  508 ,  510  (if any) contain the DCI information associated with that user equipment. Additional decoding attempts may be needed due to additional RNTIs, DCI formats and multiple PDCCH candidates. 
         [0163]    In some embodiments, the number of DCI blind decodes can be limited by configuring each user equipment (e.g., via higher layers using RRC signaling) to operate in one of several transmission modes in a semi-static manner. Table 2 provides an exemplary listing of different transmission modes. It should be noted that the disclosed embodiments can also be implemented in conjunction with other transmission modes that are not listed in Table 2. 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Exemplary Transmission Modes 
               
             
          
           
               
                 Transmission 
                   
               
               
                 Mode Number 
                 Description 
               
               
                   
               
               
                 1 
                 Single Antenna Port - Port 0 
               
               
                 2 
                 Transmit Diversity 
               
               
                 3 
                 Open-Loop Spatial Multiplexing 
               
               
                 4 
                 Closed-Loop Spatial Multiplexing 
               
               
                 5 
                 Multi User MIMO 
               
               
                 6 
                 Closed-Loop Rank 1 Precoding 
               
               
                 7 
                 Single Antenna Port - Beam Forming with UE- 
               
               
                   
                 Specific Reference Signal 
               
               
                 8 
                 Single- or Dual-Layer Transmission with UE- 
               
               
                   
                 Specific Reference Signal 
               
               
                   
               
             
          
         
       
     
         [0164]    In one embodiment, each transmission mode may be associated with two downlink DCI formats of different sizes, one of which is always DCI format 1A. In this example, the DCI formats 0 and 1A can be forced to be of the same size (e.g., via zero-padding, if needed, as described above). Therefore, each transmission mode has a maximum of two associated DCI format sizes: one corresponding to formats 0/1A and the other corresponding to another DCI format. Using the common and user-specific search spaces that are illustrated in  FIGS. 3 through 5 , the maximum number of blind decodes can be calculated as: (2 DCI sizes)×(6+16 search candidates)=44. In another embodiment, in order to support UL MIMO, a third DCI format size may be introduced in the UE-specific search space, such that the maximum number of blind decodes becomes (2 DCI sizes)×6+(3 DCI sizes)×16=60. It should be noted that the maximum number of decode attempts can be generalized as: N DCI =(total number of DCI sizes)×(number of search candidates). 
         [0165]    Table 3 provides an exemplary listing of seven transmission modes and associated DCI formats. It should be noted that the listing in Table 3 is only provided to facilitate the understanding of the underlying concepts. However, the disclosed embodiments are equally applicable to additional transmission modes and/or DCI format configurations associated with both the uplink and downlink transmissions. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Exemplary Transmission Modes and Associated DCI Formats 
               
             
          
           
               
                   
                 Transmission 
                 First 
                 Second 
               
               
                   
                 Mode Number 
                 DCI Format(s) 
                 DCI Format 
               
               
                   
                   
               
               
                   
                 1 
                 0 and 1A 
                 1 
               
               
                   
                 2 
                 0 and 1A 
                 1 
               
               
                   
                 3 
                 0 and 1A 
                 2A 
               
               
                   
                 4 
                 0 and 1A 
                 2 
               
               
                   
                 5 
                 0 and 1A 
                 1D 
               
               
                   
                 6 
                 0 and 1A 
                 1B 
               
               
                   
                 7 
                 0 and 1A 
                 1 
               
               
                   
                   
               
             
          
         
       
     
         [0166]    In the exemplary listing of Table 3, DCI formats 0 and 1A (which both have the same size) are always selected as one of the possible DCI formats for all transmission modes. However, each transmission mode is also associated with another DCI format that can vary based on the transmission mode. For example, DCI format 2A can be associated with transmission mode 3, DCI format 1B can be associated with transmission mode 6 and DCI format 1 can be associated with transmission modes 1, 2 and 7. The listing of Table 3 further illustrates that two or more of the transmission modes can have identical DCI formats. For example, in the exemplary listing of Table 3, transmission modes 1, 2 and 7 are all associated with DCI formats 0/1A and DCI format 1. 
         [0167]    The number of decodes associated with a blind decode scheme can increase in systems where multiple component carriers (CCs) are used. In some systems, multiple carriers may be used to increase the overall system bandwidth. For example, two 10 MHz component carriers and four 20 MHz component carriers can be aggregated to extend the bandwidth of an LTE system to 100 MHz. Such component carriers may span a contiguous portion of the spectrum or reside on non-contiguous portions of the spectrum. 
         [0168]      FIG. 6  illustrates a system  600  that can be used in accordance with the disclosed embodiments. The system  600  can include a user equipment  610 , which can communicate with an evolved Node B (eNB)  620  (e.g., a base station, access point, etc.) one or more component carriers 1 through N (CC 1 -CC N ). While only one user equipment  610  and one eNB  620  are illustrated in  FIG. 6 , it will be appreciated that the system  600  can include any number of user equipment  610  and/or eNBs  620 . The eNB  620  can transmit information to the user equipment  610  over forward (downlink) channels  632  through  642  on component carriers CC 1  through CC N . In addition, the user equipment  610  can transmit information to the eNB  620  over reverse (uplink) channels  634  through  644  on component carriers CC 1  though CC N . In describing the various entities of  FIG. 6 , as well as other figures associated with some of the disclosed embodiments, for the purposes of explanation, the nomenclature associated with a 3GPP LTE or LTE-A wireless network is used. However, it is to be appreciated that the system  600  can operate in other networks such as, but not limited to, an OFDMA wireless network, a CDMA network, a 3GPP2 CDMA2000 network and the like. 
         [0169]    In LTE-A based systems, the user equipment  610  can be configured with multiple component carriers utilized by the eNB  620  to enable a wider overall transmission bandwidth. As illustrated in  FIG. 6 , the user equipment  610  can be configured with “component carrier 1”  630  through “component carrier N”  640 , where N is an integer greater than or equal to one. While  FIG. 6  depicts two component carriers, it is to be appreciated that the user equipment  610  can be configured with any suitable number of component carriers and, accordingly, the subject matter disclosed herein and the claims are not limited to two component carriers. In one example, some of the multiple component carriers can be LTE Rel-8 carriers. Thus, some of the component carrier can appear as an LTE Rel-8 carrier to a legacy (e.g., an LTE Rel-8 based) user equipment. Component carrier  630  through  640  can include respective downlinks  632  through  642  as well as respective uplinks  634  through  644 . 
         [0170]    In multi-carrier operations, the DCI messages associated with different user equipments can be carried on a plurality of component carriers. For example, the DCI on a PDCCH can be included on the same component carrier that is configured to be used by a user equipment for PDSCH transmissions (i.e., same-carrier signaling). Alternatively, or additionally, the DCI may be carried on a component carrier different from the target component carrier used for PDSCH transmissions (i.e., cross-carrier signaling). For example, with reference to  FIG. 6 , a downlink assignment on “component carrier 1”  630  can be indicated to the user equipment  610  via PDCCH on “component carrier N”  640 . Cross-carrier signaling facilitates the operations of heterogeneous networks where, for example, due to the time division multiplex (TDM) nature of the downlink control signaling structure, some of the component carriers can have unreliable control information transmissions due to frequency dependent propagation and/or interference characteristics. Therefore, in some examples, due to strong interference from neighboring cells, the transmission of control information may be advantageously carried on a different component carrier with less interference. In other examples, some of the component carriers may not be backward compatible or may not even carry control information. As a result, a different component carrier can be used to provide the control signaling. 
         [0171]    In some embodiments, a carrier indicator field (CIF), which may be semi-statically enabled, may be included in some or all DCI formats to facilitate the transmission of PDCCH control signaling from a carrier other than the target carrier for PDSCH transmissions (cross-carrier signaling). In one example, the carrier indicator field comprises 1-3 bits that identify particular component carriers in a system that utilizes multiple component carriers. In another example, the carrier indicator field comprises a fixed 3 bits that identify particular component carriers in a system that utilizes multiple component carriers. In general, the number of CIF bits required is given by ceiling[log 2 (N UE )] if the carrier indicator (CI) is UE specific, where N UE  is the number of carriers configured per UE. If the CI is cell specific (i.e., common to all UEs in the cell), then the number of bits required to support CIF is given by ceiling[log2(M)], where M is the number of carriers configured for the cell. The inclusion of the carrier indicator field as part of the DCI allows a component carrier to be linked with another component carrier. 
         [0172]      FIG. 7  illustrates a communications system  700  in one embodiment. In  FIG. 7 , communication system  700  includes a node, depicted as a serving evolved Base Node (eNB)  702  that schedules and supports multiple carrier operation for an advanced user equipment (UE)  704 . In some instances, the eNB  702  can also support single carrier operation for a legacy UE  706 . For the benefit of the advanced UE  704 , the serving eNB  702  encodes a Carrier Indication (CI)  708  on first channel  710  on a first carrier  712  for scheduling an assignment or grant  714  for a second channel  716  on a second carrier  718 . In a first instance, there is more than one uplink channel (i.e., second channel)  720  on the second carrier  718  that is designated by the CI  708 . In a second instance, there is a downlink second channel  722  on the second carrier  718  that is designated by the CI  708 . 
         [0173]    In one aspect, the serving eNB  702  performs cross-carrier assignments in multiple carrier wireless communication using a receiver  723 , transmitter  724 , a computing platform  726  and an encoder  728 . The computing platform  726  accesses a user-specific code  730  and generates the assignment or grant  714  according to the CI  708  for the more than one uplink channel  720  or downlink second channel  722  on the second carrier  718 . The encoder  728  encodes at least one of a user-specific search space  732  using the user-specific code  730  and a common search space  734  to provide the CI  708 . The transmitter  724  transmits the first channel  710  on the first carrier  712  containing the assignment or grant  714 . 
         [0174]    Similarly, the advanced UE  704  handles cross-carrier assignments in multiple carrier wireless communication using a receiver  743 , a transmitter  744 , a computing platform  746  and a decoder  748 . The computing platform  746  accessing a user-specific code  750 . The receiver  742  receives the first channel  710  on the first carrier  712 . The decoder  748  decodes at least one of the user-specific search space  732  using the user-specific code  750  and the common search space  734  to detect the CI  708 . The transmitter  744  or the receiver  742  utilize the assignment or grant  714  for the first channel  710  on the first carrier  712  according to the CI  708 . 
         [0175]    In an exemplary implementation, LTE-A supports multi-carrier operation. A UE may be configured with multiple carriers. Different carriers may experience different levels of interference. Also, some carriers may not be backward compatible with legacy UEs (e.g., LTE Rel-8) devices, and some even do not carry any control signals. As a result, it may be desirable to have cross-carrier control signaling such that one carrier can transmit PDCCH scheduling PDSCH transmissions over a different carrier. 
         [0176]    One issue addressed by the system of  FIG. 7  concerns implementation of a carrier indicator field at eNB  702 , including whether the CIF is applied to unicast traffic only, broadcast traffic only, or both unicast and broadcast traffic, and the implications on the design of DCI formats for cross-carrier signaling in view of some systems for which DCI format 1A is present in both the common search space and the UE-specific search space and can be used to schedule both unicast traffic and broadcast traffic. Unicast traffic is point-to-point transmission between the eNB  702  and one of the UEs  704 ,  706 . Broadcast traffic is a downlink only point-to-multipoint connection between the eNB  702  and multiple UEs  704 ,  706 . 
         [0177]    In one embodiment (Option I), the eNB  702  may signal cross-carrier operation by extending the LTE Rel-8 DCI formats with CIF bits. The eNB  702  can apply a CIF to DCI formats in the UE-specific search space only, using it with both downlink DCI formats configured for the specific downlink transmission mode, and with DCI format 0 for uplink scheduling. This may include defining new downlink DCI formats, 1A plus one other, and a new DCI format 0. The new DCI formats may be designated 1A′ (1A prime), 1B′, 1D′, 2′, 2A′ and 0′. As a result, with this embodiment, the common search space uses DCI formats 1A/0 and 1C, and the UE specific search space uses new DCI formats 1A′/0′ and 1B′/1D′/2′/2A′. It should be noted that the same design may also be applied to any other DCI formats in the UE-specific search space, e.g., DCI 2B supporting dual-layer beamforming, new DCI format(s) supporting UL MIMO operation, etc. Other embodiments described below may also be applicable to any other DCI formats in the UE-specific search space too. 
         [0178]    In this embodiment, because the CIF is not included in the common search space, the three DCI formats 1A/ 0  and 1C can remain unchanged (i.e., LTE Rel-8 compatible) and may be used for single carrier broadcast traffic, and DCI formats 1A′ and 0′ can be used for cross-carrier unicast traffic. While this option does not support cross-carrier signaling for broadcast traffic via DCI formats, such signaling may be resolved by redesigning System Information Blocks (SIB) or Master Information Blocks (MIB) to include information for one or more other carriers, or by dedicated layer 3 (RRC) signaling. 
         [0179]    In a variation of the first embodiment (Option IA), rather than extending the DCI formats with a CIF, the eNB  702  may re-use reserved bits in DCI format 1A for carrier indication when they are not needed, such as when the DCI is scrambled by a Paging RNTI (P-RNTI), System Information RNTI (SI-RNTI) or a Random Access RNTI (RA-RNTI) based scrambling code. For example, the Hybrid Automatic Repeat Request (HARQ) process number and/or the Downlink Assignment Index (TDD only) are reserved bits in LTE Rel-8 which may be used to embed the CIF. As a result, DCI format 1A′ may have the same size as format 1A, but may still provide for cross-carrier signaling for broadcast traffic. The same DCI format design principle (i.e., an embedded CIF), may be applied to the other embodiments described below. 
         [0180]    In another embodiment (Option II), the eNB  702  may apply the CIF to both the UE specific search space and the common search space. In this case, the CIF is applied to DCI formats 1A, 0 and 1C in the common search space, both downlink DCI formats configured for the specific transmission mode, and DCI format 0 for uplink scheduling in the UE specific search space. Related DCI formats 1A and one other format, and DCI format 0 are modified by CIF bits (by extension or embedding as described above), resulting in formats 1A′, 1B′/1D′/2′/2A′, 1C′ and 0′. As a result, the common search space will use DCI formats 1A′/0′ and 1C′, and the UE-specific search space will use the same DCI formats as in Option I above (1A′/0′, 1B′/1D′/2′/2A′). 
         [0181]    Compared with Option I, the Option II embodiment provides for the UE to have cross-carrier signaling in both the common search space and the UE-specific search space for both unicast and broadcast traffic. However, the Option II embodiment is not backward compatible with LTE Rel-8 as it includes modifications to DCI formats 1A and 1C for carrying broadcast traffic. 
         [0182]    In another embodiment (Option III), the eNB  702  may apply the CIF to both the UE specific search space and the common search space, but may limit the use of CIF to DCI formats 1A/0 in the common search space (CIF is not applied to DCI format 1C). As with the Option II embodiment, the CIF can be applied to both downlink DCI formats configured for the specific downlink transmission mode, and to DCI format 0 for the uplink scheduling, in the UE specific search space. Related DCI formats 1A and one other format, and DCI format 0 are modified by CIF bits (by extension or embedding) resulting in formats 1A′, 1B′/1D′/2′/2A′ and 0′. DCI format 1C is not changed. As a result, the common search space includes DCI formats 1A′ and 1C, and the DCI formats used in the UE specific search space are the same as for Options I and II (i.e., 1A′/0′, 1B′/1D′/2′/2A′). 
         [0183]    Compared with Options I and II, the Option III embodiment provides for the UE to have cross-carrier signaling in both the common search space and in the UE specific search space for both unicast traffic and broadcast traffic (using DCI format 1A only). The Option III embodiment is also backward compatible with LTE Rel-8 via DCI format 1C, which remains unchanged. 
         [0184]    In another embodiment (Option IV), the eNB  702  may apply a CIF to DCI formats in both the common search space and the UE specific search space: to DCI formats 1A, 0 and 1C in the common search space, to both downlink DCI formats configured for the specific downlink transmission mode, and to DCI format 0 for uplink scheduling in the UE specific search space. DCI formats 1A or 1C, or both 1A and 1C, may be maintained (i.e., unmodified) for backward compatibility for broadcast traffic and/or unicast traffic. 
         [0185]    More particularly, based on the foregoing description of the Option IV embodiment, the following exemplary alternatives may be considered for common search space blind decoding, where there are 2 locations defined for CCE aggregation level 8 and 4 locations defined for CCE aggregation level 4: 
         [0186]    Alternative 1: 3 DCI sizes 1A′/0′, 1C′, 1A→3(4+2)=18 blind decodes. 
         [0187]    Alternative 2: 3 DCI sizes 1A′/0′, 1C′, 1C→3(4+2)=18 blind decodes. 
         [0188]    Alternative 3: 3 DCI sizes 1A′/0′, 1C, 1A→3(4+2)=18 blind decodes. 
         [0189]    Alternative 4: 4 DCI sizes 1A′/0′, 1C′, 1A, 1C→4(4+2)=24 blind decodes. 
         [0190]    For each of the four alternatives, the UE specific search space is the same as Options I and II with 32 blind decodes. Accordingly, under Option IV, either 50 (18+32) or 56 (24+32) blind decodes may be required, in comparison to 44 blind decodes in LTE Rel-8, to obtain the flexibility of cross-carrier signaling and backward compatibility with LTE Rel-8 unicast traffic or broadcast traffic, or both unicast and broadcast traffic. 
         [0191]    Table 4 summarizes the embodiments described above: 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Summary of Embodiments 
               
             
          
           
               
                   
                   
                   
                 UE-Specific 
               
               
                   
                 Option 
                 Common Search Space 
                 Search Space 
               
               
                   
                   
               
               
                   
                 I 
                 1A/0, 1C 
                 1A′, 1B′/1D′/2′/2A′ 
               
               
                   
                 IA 
                 1A/0, 1C (reserved bits in 1A) 
                 1A′, 1B′/1D′/2′/2A′ 
               
               
                   
                 II 
                 1A′/0′, 1C′ 
                 Same as above 
               
               
                   
                 III 
                 1A′/0′, 1C 
                 Same as above 
               
               
                   
                 IV 
                 1A′/0′, 1C′, 1A 
                 Same as above 
               
               
                   
                   
                 1A′/0′, 1C′, 1C 
               
               
                   
                   
                 1A′/0′, 1C, 1A 
               
               
                   
                   
                 1A′/0′, 1C, 1A, 1C 
               
               
                   
                   
               
             
          
         
       
     
         [0192]    Other options for the common search space contemplated herein include, without limitation, {1A/0, 1C′} or {1A/0, 1C, 1C′}, where the CIF is only introduced to DCI format 1C instead of DCI format 1A/0. 
         [0193]      FIG. 8A  is a flowchart illustrating the operations of a method  800  that are carried out in accordance with an exemplary embodiment. The method  800  may be performed by a user equipment, such as the advanced UE  704  depicted in communication system  700 . 
         [0194]    The method  800  of  FIG. 8A  begins, at operation  802 , by receiving a plurality of component carriers configured for a wireless communication device, the plurality of component carriers comprising a plurality of search spaces comprising one or more common search spaces and a plurality of user-specific search spaces. The method continues, at operation  804 , by receiving a cross-carrier indicator configured to enable cross-carrier signaling for a first component carrier and, at operation  806 , by determining whether the cross-carrier indicator is present in the control information format carried on a second component carrier, based on an association of the control information format with a search space on the second component carrier. 
         [0195]    In one embodiment, cross-carrier operation may be configured and signaled to the UE by an upper layer of the communication protocol (e.g., the radio resource control layer) and the carrier indication may be constrained to 0 bits when there is no cross-carrier signaling, and 3 bits when cross-carrier signaling is implemented, where the use of a fixed number of bits (e.g., 3) reduces complexity by eliminating the need to signal and detect the number of CI bits being used. Such signaling may be specific to both uplink (UL) and/or downlink (DL) carrier assignments. Such signaling may be specific to a user equipment. Additionally, such signaling may be specific to an individual component carrier. It is important that there is a common interpretation between the upper layer scheduler and the UE with respect to the meaning of the carrier indicator. Table 5, below, illustrates an example of how the CI bits might be mapped to designated component carriers in a set of five (5) component carriers for a user equipment, when scheduling data transmissions on these five (5) component carriers for the user equipment is carried by the first component carrier. It will be appreciated that the bit map illustrated in Table 5 is exemplary and that other bit maps are possible. 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Exemplary CIF Bit-Mapping 
               
             
          
           
               
                 CIF 
                 CARRIER ASSIGNMENTS 
               
               
                   
               
               
                 000 
                 Single Carrier (Carrier 1) 
               
               
                 001 
                 Carrier 2 
               
               
                 010 
                 Carrier 3 
               
               
                 011 
                 Carrier 4 
               
               
                 100 
                 Carrier 5 
               
               
                   
               
             
          
         
       
     
         [0196]    The UE carrier configuration may include a unique identifier of each carrier that can be used for the carrier identification. Also, to enable the flexibility to address more carriers than can be directly addressed by the 3-bit indicator, the carrier indexing can be specific to the carrier of the PDCCH that makes the assignments. For example, if there are 10 carriers, the UE may address the first five carriers based on one PDCCH in a first carrier and the other five carriers based on another PDCCH in a second carrier. Also, by limiting the cross-carrier signaling to specific carrier subsets, the total number of blind decodes can be limited. 
         [0197]    As described above, with respect to the details of incorporating a CIF within the various DCI formats, the CI is generally applicable to all DCI formats that can carry UE specific UL or DL assignments. DCI formats 0, 1, 1A, 1B, 1D, 2 and 2A are used for UE specific assignments with C-RNTI scrambling, and can include the CIF for cross-carrier operation. DCI formats 1C, 3, and 3A are not used for UE-specific purposes and are located in the common search space. In order to provide for backward compatibility with LTE Rel-8 UEs that will use the same common search spaces, DCI formats 1C, 3 and 3A may not include a CIF. However, in LTE Rel-8, DCI formats 0 and 1A are used in both the common and UE specific search spaces. To insure backward compatibility with LTE Rel-8, for DCI formats in the common search space, DCI formats 0 and 1A with a carrier indicator can be distinguished from DCI formats 0 and 1A without a carrier indicator by the specific RNTI used for CRC scrambling. For example, DCI formats 0 and 1A with a carrier indicator could have a CRC scrambled exclusively by C-RNTI, while DCI formats 0 and 1A without a carrier indicator could have a CRC scrambled, for example, with an SI-RNTI, a P-RNTI or an RA-RNTI. 
         [0198]    In various embodiments, an LTE-A UE (e.g., UE  704 ) could attempt to decode DCI formats 0 and 1A, both with and without a CIF in the common search space. DCI formats 0 and 1A with C-RNTI based CRC scrambling would be assumed to include a CIF, while DCI formats 0 and 1A with SI/P/RA-RNTI based CRC scrambling would be assumed to not include a CIF. By doing so, the number of blind decodes is only increased by 6 (2 DCI sizes×3 RNTIs). However, the false alarm probability is not increased compared to LTE Rel-8. This is because the false alarm probability is not only a function of the number of blind decodes, but also a function of the number of RNTIs used for the de-scrambling operation. In this approach, the total number of de-coding operations is still maintained. Table 6 summarizes the relationships among DCI formats, CRC scrambling, search spaces and carrier indication described above. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 DCI Formats With Carrier Indicators 
               
             
          
           
               
                   
                   
                 SEARCH 
                 CARRIER 
               
               
                 DCI FORMAT 
                 SCRAMBLING 
                 SPACE 
                 INDICTOR 
               
               
                   
               
               
                 0, 1, 1A, 1B, 1D, 2, 2A 
                 C-RNTI 
                 UE Specific 
                 YES 
               
               
                 1C, 3, 3A 
                 SI/P/RA-RNTI 
                 Common 
                 NO 
               
               
                 0, 1A 
                 TEMP C-RNTI, 
                 Common 
                 NO 
               
               
                   
                 SI/P/RA-RNTI 
               
               
                 0, 1A 
                 C-RNTI 
                 Common 
                 YES 
               
               
                   
               
             
          
         
       
     
         [0199]      FIG. 8B  is a flowchart illustrating the operations of a method  850  in a communications system that are carried out in accordance with an exemplary embodiment. The method  850  may be performed by a base station, such as the serving node (eNB)  702  depicted in communication system  700 . 
         [0200]    The method  850  begins at operation  852  by formatting control information, in a control channel of a communications carrier, with a cross-carrier control indicator. The method concludes at operation  854  by scrambling the control information with a scrambling code, where the scrambling code is selected based on a format of the control information and a location of the control information within a plurality of search spaces in the control channel. 
         [0201]      FIG. 8C  is a flowchart illustrating the operations of a method  870  in a UE that are carried out in accordance with an exemplary embodiment. The method  870  may be performed by a user equipment, such as the advanced UE  704  depicted in communication system  700 . 
         [0202]    The method  870  begins at operation  872  by searching a plurality of search spaces in a control channel of a communications carrier for scrambled control information. The method continues at operation  874  by blind-decoding the plurality of search spaces with a plurality of descrambling codes to extract the control information. The method concludes at operation  876  by determining the presence of a cross-carrier control indicator based on a format of the control information and a location of the control information in the plurality of search spaces. 
         [0203]    For purposes of simplicity of explanation, the operations in  FIGS. 8A ,  8 B and  8 C are shown and described as a series of acts. However, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts can, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts can be required to implement a methodology in accordance with the disclosed embodiments. 
         [0204]    As indicated above (see, e.g., Table 1), DCI formats 3 and 3A are size-matched with DCI formats 1A and 0, which means that modified DCI formats 3′ and 3A′ with carrier information can be defined to size-match DCI formats 1A′ and 0′. The modifications can be made in the same way; size-matching via zero-padding or size-matching by defining a specific use for existing but unused reserve bits. The later approach is possible because DCI formats 3/3A are in the common search space and the CIF size in the common search space is preferably based on cell-specific multi-carrier configurations. 
         [0205]    Alternatively, the CIF can be introduced in DCI formats 3/3A via the transmit power control (TPC) bits in those two DCI formats, such that the TPC commands can address not only the carrier in question, but other carriers as well. This cross-carrier power control can be useful under high interference conditions when the selected component carrier can deliver more reliable power control commands to a group of user equipments. 
         [0206]    If carrier information (CI) is included in the 1A/1C DCI formats for broadcast, and the size of the CIF is allowed to vary, it would be beneficial to signal the carrier information as early as possible. The signaling can be explicit or implicit. One example of explicit signaling is to use reserved bits in the PBCH to signal the presence and/or the size of the CI. After PBCH decoding, the UE is aware of the CI field and can determine the PDCCH payload size to search for SIB/Paging decoding. For implicit signaling, UEs may perform blind decodes of PDCCH formats which are used to signal resource allocations for system information, paging and or random access responses. The presence and/or the size of the CI can be determined from the results of the blind decoding. 
         [0207]    Alternatively, cross-carrier broadcast can be realized via a new SI-RNTI (or P/RA-RNTI) for PDCCH CRC scrambling (vs. explicit CI in PDCCH). The new SI-RNTI can be taken from reserved RNTIs (0000 and FFF4-FFFD, currently reserved in LTE Rel-8 for future use), or other RNTIs. 
         [0208]    Yet another alternative is to use one PDCCH to signal the same broadcast content for two or more component carriers, at the expense of scheduling restrictions. 
         [0209]      FIG. 9  illustrates an exemplary system  600  capable of supporting the various operations described above. As discussed in connection with  FIG. 6 , the system  600  includes an eNB  620  that can transmit and/or receive information, signals, data, instructions, commands, bits, symbols and the like.  FIG. 9  also illustrates a user equipment  610 , that is in communication with the eNB  620  using “component carrier 1”  630  through “component carrier N”  640 . The user equipment  610  can transmit and/or receive information, signals, data, instructions, commands, bits, symbols and the like. Moreover, although not shown, it is contemplated that the system  600  can include additional base stations and/or user equipment. 
         [0210]    In some embodiments, the eNB  620  can include a scheduler  922  that allocates resources on a link (e.g., downlink or uplink) to the user equipment  610  and/or any other user equipment (not shown) that is served by the eNB  620 . The scheduler  922  can select resource blocks (RBs) on one or more subframes that are intended to carry data associated with the user equipment  610 . For example, the scheduler  922  can assign RBs of downlink subframes for data transmitted to the user equipment  610  and the scheduler  922  can assign RBs of uplink subframes for data transmitted by the user equipment  610 . The allocated RBs can be indicated to the user equipment  610  via control channel signaling (e.g., control information messages) included on a control channel such as PDCCH. The eNB  620  may also include a search space configuration component  924  that can enable the configuration of search spaces associated with one or more control information messages. The search space configuration, component  924  can operate in association with one or more of the “component carrier 1”  630  through “component carrier N”  640 . For example, the search space configuration component  924  can configure two or more search spaces to be shared among control information messages associated with two or more component carrier transmissions. 
         [0211]    In some embodiments, the user equipment  610  that is shown in  FIG. 9  can include a carrier group component  912  that can be configured to group of one or more component carriers. The carrier group component  912  can, for example, be configured to group the component carriers based on the DCI size of the control information carried on the component carriers. The carrier group component  912  can also be configured to group the component carriers based on the transmission mode used by the communication system. The user equipment  610  can also include a control channel monitor component  914  that allows the user equipment  610  to monitor the control channels of “component carrier 1”  630  through “component carrier N”  640 . Moreover, a selection component  916  within the user equipment  610  can be configured to allow the selection of a group of component carriers, as well as the selection of a particular component carrier within the group of component carriers. The user equipment  610  can also include a detection component  918  that enables the detection of the control information messages that are carried on the control channels of “component carrier 1”  630  through “component carrier N”  640 . For example, the detection component  918  can be configured to conduct a blind decode of the DCI messages within a search space. 
         [0212]      FIG. 10  illustrates an apparatus  1000  within which the various disclosed embodiments may be implemented. In particular, the apparatus  1000  that is shown in  FIG. 103  may comprise at least a portion of a base station or at least a portion of a user equipment (such as the eNB  620  and the user equipment  610  that are depicted in  FIG. 6  and  FIG. 10 ) and/or at least a portion of a transmitter system or a receiver system (such as the transmitter system  210  and the receiver system  250  that are depicted in  FIG. 2 ). The apparatus  1000  that is depicted in  FIG. 10  can be resident within a wireless network and receive incoming data via, for example, one or more receivers and/or the appropriate reception and decoding circuitry (e.g., antennas, transceivers, demodulators and the like). The apparatus  1000  that is depicted in  FIG. 10  can also transmit outgoing data via, for example, one or more transmitters and/or the appropriate encoding and transmission circuitry (e.g., antennas, transceivers, modulators and the like). Additionally, or alternatively, the apparatus  1000  that is depicted in  FIG. 10  may be resident within a wired network. 
         [0213]      FIG. 10  further illustrates that the apparatus  1000  can include a memory  1002  that can retain instructions for performing one or more operations, such as signal conditioning, analysis and the like. Additionally, the apparatus  1000  of  FIG. 10  may include a processor  1004  that can execute instructions that are stored in the memory  1002  and/or instructions that are received from another device. The instructions can relate to, for example, configuring or operating the apparatus  1000  or a related communications apparatus. It should be noted that while the memory  1002  that is depicted in  FIG. 10  is shown as a single block, it may comprise two or more separate memories that constitute separate physical and/or logical units. In addition, the memory while being communicatively connected to the processor  1004 , may reside fully or partially outside of the apparatus  1000  that is depicted in  FIG. 10 . It is also to be understood that one or more components, such as the scheduler  1022 , the search space configuration component  1024 , the carrier group component  1012 , the control channel monitor component  1014 , the selection component  1016  and/or the detection component  1018  that are shown in  FIG. 10 , can exist within a memory such as memory  1002 . 
         [0214]    It will be appreciated that the memories that are described in connection with the disclosed embodiments can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM) and direct Rambus RAM (DRRAM). 
         [0215]    It should also be noted that the apparatus  1000  of  FIG. 10  can be employed with a user equipment or mobile device, and can be, for instance, a module such as an SD card, a network card, a wireless network card, a computer (including laptops, desktops, personal digital assistants PDAs), mobile phones, smart phones or any other suitable terminal that can be utilized to access a network. The user equipment accesses the network by way of an access component (not shown). In one example, a connection between the user equipment and the access components may be wireless in nature, in which access components may be the base station and the user equipment is a wireless terminal. For instance, the terminal and base stations may communicate by way of any suitable wireless protocol, including but not limited to Time Divisional Multiple Access (TDMA), Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiplexing (OFDM), FLASH OFDM, Orthogonal Frequency Division Multiple Access (OFDMA) or any other suitable protocol. 
         [0216]    Access components can be an access node associated with a wired network or a wireless network. To that end, access components can be, for instance, a router, a switch and the like. The access component can include one or more interfaces, e.g., communication modules, for communicating with other network nodes. Additionally, the access component can be a base station (or wireless access point) in a cellular type network, wherein base stations (or wireless access points) are utilized to provide wireless coverage areas to a plurality of subscribers. Such base stations (or wireless access points) can be arranged to provide contiguous areas of coverage to one or more cellular phones and/or other wireless terminals. 
         [0217]    It is to be understood that the embodiments and features that are described herein may be implemented by hardware, software, firmware or any combination thereof. Various embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. As noted above, a memory and/or a computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD) and the like. Therefore, the disclosed embodiments can be implemented on non-transitory computer readable media. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. 
         [0218]    Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL), then the coaxial cable, fiber optic cable, twisted pair, or DSL are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
         [0219]    Generally, program modules may include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes. 
         [0220]    The various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, at least one processor may comprise one or more modules operable to perform one or more of the steps and/or actions described above. 
         [0221]    For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor and/or external to the processor, in which case it can be communicatively coupled to the processor through various means as is known in the art. Further, at least one processor may include one or more modules operable to perform the functions described herein. 
         [0222]    The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). Additionally, cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). Further, such wireless communication systems may additionally include peer-to-peer (e.g., user equipment-to-user equipment) ad hoc network systems often using unpaired unlicensed spectrums, 802.xx wireless LAN, BLUETOOTH and any other short- or long-range, wireless communication techniques. The disclosed embodiments can also be used in conjunction with systems that use multiple component carriers. For example, the disclosed embodiments can be used in conjunction with LTE-A systems. 
         [0223]    Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique that can be utilized with the disclosed embodiments. SC-FDMA has similar performance and essentially a similar overall complexity as those of OFDMA systems. SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. SC-FDMA can be utilized in uplink communications where lower PAPR can benefit a user equipment in terms of transmit power efficiency. 
         [0224]    Moreover, various aspects or features described herein may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques. The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier or media. For example, computer-readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., compact disk (CD), digital versatile disk (DVD), etc.), smart cards, and flash memory devices (e.g., EPROM, card, stick, key drive, etc.). Additionally, various storage media described herein can represent one or more devices and/or other machine-readable media for storing information. The term “machine-readable medium” can include, without being limited to, wireless channels and various other media capable of storing, containing, and/or carrying instruction(s) and/or data. Additionally, a computer program product may include a computer readable medium having one or more instructions or codes operable to cause a computer to perform the functions described herein. 
         [0225]    Further, the steps and/or actions of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Further, in some embodiments, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user equipment (e.g.  610   FIG. 12 ). In the alternative, the processor and the storage medium may reside as discrete components in a user equipment (e.g.,  610   FIG. 12 ). Additionally, in some embodiments, the steps and/or actions of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a machine readable medium and/or computer readable medium, which may be incorporated into a computer program product. 
         [0226]    While the foregoing disclosure discusses illustrative embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described embodiments as defined by the appended claims. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within scope of the appended claims. Furthermore, although elements of the described embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any embodiment may be utilized with all or a portion of any other embodiments, unless stated otherwise. 
         [0227]    To the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim. Furthermore, the term “or” as used in either the detailed description or the claims is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.