EP2603993A2

EP2603993A2 - Techniques for allocation of control channels

Info

Publication number: EP2603993A2
Application number: EP11816816.0A
Authority: EP
Inventors: Ping Wang; Yuwen Liu
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2010-08-13
Filing date: 2011-08-02
Publication date: 2013-06-19
Also published as: CN103119875A; EP2603993A4; WO2012021337A2; CN103119875B; WO2012021337A3

Abstract

Techniques are described for setting the Physical Downlink Control Channel search spaces for component carriers. If any component carrier is de-activated, the Carrier Indicator Fields (CIF) of remaining activated component carriers can be set to consecutive values. The User Element can utilize its identifier to determine the starting point Control Channel Elements in each subframe. The locations of Control Channel Elements for a component carrier can be determined based on its CIF. Accordingly, search spaces for different component carriers can potentially be closely spaced but not overlap.

Description

TECHNIQUES FOR ALLOCATION OF CONTROL CHANNELS

Related Art

This application claims the benefit of U.S. Provisional Application No.

61/373,788, filed August 13, 2010 (attorney docket no. P35732Z).

Field

The subject matter disclosed herein relates generally to techniques for allocating control channels in a wireless network.

Related Art

In a 3 GPP LTE compatible communication system, various channels are defined for uplink and downlink in the physical layer for signal transmission. For example, a Physical Uplink Shared Channel (PUSCH), a Physical Uplink Control Channel (PUCCH), and a Physical Random Access Channel (PRACH) are defined as uplink physical channels. Physical Downlink Shared Channel (PDSCH), a Physical Multicast Channel (PMCH), a Physical Broadcast Channel (PBCH), a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), and a Physical Hybrid ARQ (HARQ) Indicator Channel (PHICH) are defined as downlink physical channels.

The PDCCH can be used to transmit scheduling allocation control information and other control information. In a cellular communication system in which one base station (or Node-B) controls a plurality of User Equipments (UEs) or mobile stations, multiple UEs can receive control information through a PDCCH transmitted from the base station. The base station does not previously allocate different PDCCHs to each UE but transmits control information through an arbitrary PDCCH to an arbitrary UE at each time. The UE determines whether or not control information received through the PDCCH belongs to the UE based on a UE identifier masked with the cyclic redundancy code (CRC) field of the PDCCH. The UE performs decoding on each of the PDCCHs for the possible PDCCH formats and, when it is determined that the PDCCH corresponds to the UE, the UE accesses control information included in the PDCCH.

According to 3 GPP TS36.213 (2010), a PDCCH is transmitted on one, two, four, or eight (1, 2, 4, or 8) control channel elements (CCEs). In addition, each CCE is composed of nine (9) resource element groups (REGs), and each REG includes four resource elements (REs). Each resource element (RE) can be allocated for one subcarrier in the both frequency and time domain. A RE can include 4 bits.

A UE-specific search space carries control information specific to a particular UE and is monitored by at least one UE in a cell. The size of a search space is based on a number of PDCCH candidates and a size of CCE aggregation level. The size of the search space can be an integer times the size of a CCE aggregation level or the number of PDCCH candidates.

The number of combinations of PDCCH regions for transmission of control information may be large. For example, release 10 of 3GPP LTE advanced specifies that PDCCH search space design is to support carrier aggregation, including cross-carrier scheduling. Cross-carrier scheduling allows the PDCCH of a serving cell (or radio carrier) to schedule resources on another serving cell (or radio carrier) within one eNode B (eNB). For example, for two CCs, namely CCl and CC2, and both CCl and CC2 are configured with PDCCH, eNode B can use the PDCCHs on CCl (where CCl is the primary carrier of a UE) to schedule the PDSCH on CCl and PDSCH on CC2. From a UE perspective, PDCCH can be transmitted on primary component carrier (CC) instead of secondary CC. If the eNB configures the UE for cross-carrier scheduling, then UE monitors primary CC only for PDCCH. However, a problem exists in how to partition PDCCH search spaces used for the cross-carrier scheduling when PDCCH is transmitted on a primary carrier and each component carrier has a separate PDCCH search space.

Brief Description of the Drawings

Embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the drawings and in which like reference numerals refer to similar elements.

FIG. 1 depicts an example of devices connected using a wireless network. FIGs. 2 and 3 depict examples of allocation of search spaces for component carriers.

FIG. 4 depicts an example system that can use embodiments of the present invention.

FIG. 5 depicts an example process that can be used to determine search spaces for control channels. FIG. 6 depicts an example process that can be used to allocate search spaces for control channels.

Detailed Description

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments.

Embodiments of the invention may be used in a variety of applications. Some embodiments of the invention may be used in conjunction with various devices and systems, for example, a transmitter, a receiver, a transceiver, a transmitter-receiver, a wireless communication station, a wireless communication device, a wireless Access Point (AP), a modem, a wireless modem, a Personal Computer (PC), a desktop computer, a mobile computer, a laptop computer, a notebook computer, a tablet computer, a server computer, a handheld computer, a handheld device, a Personal Digital Assistant (PDA) device, a handheld PDA device, a network, a wireless network, a Local Area Network (LAN), a Wireless LAN (WLAN), a Metropolitan Area Network (MAN), a Wireless MAN (WMAN), a Wide Area Network (WAN), a Wireless WAN (WWAN), devices and/or networks operating in accordance with existing IEEE 802.11, 802.1 la, 802.1 lb, 802. l ie, 802.1 lg, 802.11 h, 802. Hi, 802.1 1η, 802.16, 802.16d, 802.16e, 802.16m, 3 GPP standards, physical layer description of 3 GPP LTE advanced 3621 1 release 10, and/or future versions and/or derivatives and/or Long Term Evolution (LTE) of the above standards, a Personal Area Network (PAN), a Wireless PAN (WPAN), units and/or devices which are part of the above WLAN and/or PAN and/or WPAN networks, one way and/or two-way radio communication systems, cellular radio-telephone communication systems, a cellular telephone, a wireless telephone, a Personal Communication Systems (PCS) device, a PDA device which incorporates a wireless communication device, a Multiple Input Multiple Output (MIMO) transceiver or device, a Single Input Multiple Output (SIMO) transceiver or device, a Multiple Input Single Output (MISO) transceiver or device, a Multi Receiver Chain (MRC) transceiver or device, a transceiver or device having "smart antenna" technology or multiple antenna technology, or the like.

Some embodiments of the invention may be used in conjunction with one or more types of wireless communication signals and/or systems, for example, Radio Frequency (RF), Infra Red (IR), Frequency-Division Multiplexing (FDM), Orthogonal FDM

(OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), Time-Division Multiplexing (TDM), Time-Division Multiple Access (TDMA), Extended TDMA (E- TDMA), General Packet Radio Service (GPRS), Extended GPRS, Code-Division Multiple Access (CDMA), Wideband CDMA (WCDMA), CDMA 2000, Multi-Carrier Modulation (MDM), Discrete Multi-Tone (DMT), Bluetooth (RTM), ZigBee (TM), or the like.

Embodiments of the invention may be used in various other apparatuses, devices, systems and/or networks.

FIG. 1 depicts an example of devices connected using a wireless network. The network can be compliant with any variety of IEEE 802.16 or 3 GPP LTE as well as variations and revisions thereof. 3 GPP LTE is described in 3 GPP LTE Rel-9 (2009) specifications as well as variations thereof. In the downstream or downlink case, the generically -named transmitters 102 and/or 202 above may be interchangeably referred to as a base station (BS), Node B (NB), enhanced Node B (eNB), or access point (AP). In various embodiments, for the downlink, the transmitter can also be

interchangeably referred to as network entities such as a Mobile Switching Center

(MSC), Serving GPRS Support Node (SGSN), or Mobility Management Entity (MME). In the downlink case, receivers 104 and/or 204 above may be interchangeably referred to as a mobile station (MS), subscriber station (SS), user equipment (UE), station (STA), machine-type communication (MTC) device, or machine-to-machine (M2M) device at the system level herein. Further, the terms BS, NB, eNB, AP, MSC, SGSN, and MME may be conceptually interchanged, depending on which wireless protocol is being used, so a reference to BS herein may also be seen as a reference to any of NB, eNB, AP, MSC, SGSN, and MME. Similarly, a reference to MS or SS herein may also be seen as a reference to any of UE, STA, an MTC device, or M2M device.

At the 3GPP RANl#61bis meeting in Dresden, Germany from June 28 to July 2,

2010, conclusions were made concerning PDCCH search space design. First, the same hashing function (i.e., offset between search spaces for different component carriers (CCs)) is not to be a function of the subframe number. Rather, the CC-specific offset is to be a function at least of a Carrier Indicator Field (CIF). In addition, no additional Radio Resource Control (RRC) signaled parameters are to be used and the additional refinements are for further study. Such conclusions can further be formulated as the following equation (1), (2), and (3):

⁵ = (⁵S + OFFSET _n)mod(N_CCE>k) (1)

Equations (2) and (3) are re-used from PDCCH search space design in section 9.1.1 of Release 9 (TS36.213 (2010)).

A UE-specific search is carried out on four aggregation levels of 1, 2, 4, or 8. Section 9.1.1 of PDCCH search space for Rel-8/9 is specified as follows: the set of PDCCH candidates to monitor are defined in terms of search spaces, where a search space

S^_Q at aggregation level L, L e {l,2,4,8} , is defined by a set of PDCCH candidates. The

CCEs corresponding to PDCCH candidate m of the search space are given by equation (2), where Y_k is defined according to (3), and i = 0 to L-l and m = 0 to M^(L)-1. Value M^^L) is the number of PDCCH candidates to monitor in a given search space. In the example of FIG. 2 (below), value M^(L) _can be 6, 6, 2, or 2 for respective aggregation levels (L) of 1, 2, 4, or 8.

For a UE-specific search space at aggregation level L , the variable Y_k is defined by equation (3), where Υ__λ = «_RNTI≠ 0 , A = 39827 , D = 65537 and k = , n_s is the slot number within a radio frame. Value Yk depends on the index of the subframe, where Y_i is the initial Cell Radio Network Temporary Identifier (C-RNTI) of UE at the RRC-Connected state. Parameters A and D can be constants and be known to both eNB and UE.

Parameter OFFSET^ in equation (1) is added into the Rel-8 and 9 PDCCH search space equations in order to support the Rel-10 aggregated component carriers for a given UE. According to equation (1), a search space for a kth subframe can be defined as a sum of (a) a search space and (b) Search space can identify the first CCE number to search. Multiplication by mod(N_{CCE k}) can guarantee the final is less than N_{CCE k}. Therefore, a PDCCH search space offset can be based on equations (l)-(3) for Rel-10 PDCCH search space.

In various embodiments, parameter OFFSET^ in equation (1) can be based on CIF values that increase or decrease in a consecutive manner. For example, the spacing between CIF values can be set to increment or decrement by 1. An eNB can configure CIF values via RRC signaling and the CIF values can be sorted by ascending or descending order. The eNB can partition the PDCCH search space according to the sorting order. Activated component carriers (CC) can be dynamically changed at each sub frame due to the interference level of the aggregated CC. CIF can be re-assigned to activated CC via RRC signaling so that CIF values increase or decrease with no gaps in CIF values. Accordingly, a gap between PDCCH search spaces for different CCs can be potentially reduced by providing CIF values that are re-configurable to be consecutive values.

Section 5.3.3, entitled Downlink Control Information, of 3GPP TS36.212 VIO.1.0 (2011) specifies that a 3 -bit CIF can be added into the PDCCH on a component carrier. The CIF value can range from '000' to Ί 11 '. However, other number of bits can be used for CIF values. In an embodiment, if the PDCCH search space for CC1 has a CIF = 000, then the PDCCH search space is for the primary carrier, whereas for CIF values other than 000 (e.g., 001 to 1 11), the search space is for a secondary carrier. Any CIF value other than '000' can be used to assign PDSCH or PUSCH resources in one of multiple secondary component carriers. The CIF value '000' can be configured by the eNB field via RRC signaling to allow cross-carrier scheduling occur in the primary carrier.

Accordingly, a 3 -bit CIF field is added into the PDCCH, but the CIF value is configured by RRC signaling. For example, the PDCCH on a primary carrier can be used to transmit PDSCH for a primary carrier and PDSCH for a secondary carrier.

The configuration for the CIF can be semi-static and UE-specific (i.e., not system- specific or cell-specific). The aggregated component carriers can be configured for a given UE via the RRC signaling. The activated component carriers can be dynamically changed at each sub frame due to the interference level of the aggregated component carriers for a given UE via the activation or deactivation command transmitted in a MAC message before the aggregated component carriers are re-configured via the RRC signaling served by one or more component carriers. The configuration command via RRC signaling can be semi-static, which means that only the RRC re-configuration command can modify the CIF parameters.

In accordance with some embodiments, for a given UE, (i) the index of the sorted {CIF_k,n} of the activated CCs in the configured CCs and (ii) the number of the activated CCs in the configured CCs for a given UE (vActive cc k) can be adopted into the parameter OFFSET^ design of equation (1) above. Additionally, the number of the activated CCs in the configured CCs for a given UE can be dynamically changed. In various

embodiments, the following equation (4) can be used to determine the parameter OFFSET_kn:

where:

f({CIFk,n }) represents an index of an activated and configured CC at k^th subframe per radio frame for a UE;

NCCE, k represents the number of CCEs at k^th subframe per radio frame for a UE; and

VActive cc, k represents the number of activated CCs in the configured

CCs at k^th subframe per radio frame for a UE.

The }) can be the index number of each CC. Index values can increase in a consecutive manner. For example, with reference to the example of FIG. 2 (described below /IC/ ^ }) can be 0 for CC1 and 1 for CC3.

Value NCCE, k can be determined based on a number of OFDM symbols for control channels in each subframe and based on system bandwidth. The number of the CCEs at each subframe can be adopted into the parameter OFFSET^ in order to achieve dynamically spaced offsets among the PDCCH search spaces of the activated CCs in the configured CCs at each subframe per radio frame. Table 1 depicts an example of number of CCEs for a subframe. Table 1 : Number of Control Channel Elements in each subframe in case of 2 TX antenna and Ng=l/6 for Normal Cyclic Prefix

The eNB can signal to the UE how many OFDM symbols are in each subframe using Physical Control Format Indicator Channel (PCFICH). In Table 1 , the downlink system bandwidth is represented by 1.4MHz, 3.0MHz, and so forth. The UE can determine the number of OFDM symbols and system bandwidth from information transmitted in the primary broadcasting control channel (PBCH), where a PBCH is composed of 40 information bits including 3 bits for downlink system bandwidth, 8-bits for system frame number (SFN), 3 bits for Physical HARQ Indicator Channel (PHICH) configuration, 10 bits for spare bits, and 16 bits for CRC.

Referring again to equation (4), the number of activated CCs, VActive cc_{, k}, can be specified in a MAC layer command sent by an eNB to a UE. In the example of FIG. 2 (below), VActive cc, k is 2. In some cases, the UE can itself determine the number of activated CCs by reducing the number of activated CCs by the number of CCs with excessive interference.

In some cases, one or more of the values used to solve equations (l)-(4) can be transmitted to the UE from an eNB so that the UE determines the locations of the search spaces. The UE can determine the CCEs to search based on equations (l)-(4). The UE can utilize its identifier (C-RNTI) to derive the starting point of CCEs in each subframe according to equations (l)-(4) and then detect all the possible number ( ⁽ⁱ⁾ ) of the candidate PDCCHs at each aggregation level.

FIG. 2 depicts an example of allocation of a search space for component carriers.

At the kth subframe per radio frame, component carriers for a given UE can be configured as CC 1 , CC2, and CC3. RRC signaling can be used to indicate the component carrier identifiers for CC1, CC2, and CC3 as respective CIF_k,i=000, CIF_k;2=001, and CIF_k3=010. The activated component carriers are CC1 and CC3, such that and CIF_k,3=010 via the activation or deactivation commands of a MAC layer. In this example, the component carrier CC2 is subject to the heavy interference. In some cases, a UE can use a MAC message to indicate interference levels of PDCCH search spaces to the eNB. In some cases, a UE can use measurement reportings to eNB to indicate interference levels of PDCCH search spaces to the eNB. The eNB can use a MAC message to deactivate one or more CCs with unacceptable interference levels.

Because the values of the CIFs for the active CC, namely CC1 and CC3, (i.e., and CIF_k,3=010) are not consecutive values, large spaces between the PDCCH search spaces of the activated component carriers (e.g., CCE numbers) can result. Large spaces between PDCCH search spaces can lead to the non-continuous search space design and high blocking probability for cross-carrier scheduling. High blocking probability can occur if the small system bandwidth (1.4MHz) is not large and a PDCCH search space for one CC overlaps with another CC. For example, when the number of scheduled CCs is large and a number of CCEs is small, the CCEs as the PDCCHs of the different CCs may overlap, which shall result in the blocking. Blocking can be when two CCs access a PDCCH in a CCE but the PDCCH contains PDCCH intended for one of the CC.

The sorted ascending index of the CIF values (CIF_k,i=000, CIF_k,3=010) for the activated CCs can be set to 0 and 1 so that CIFk,i=000 and CIFk,3=001).

In accordance with an embodiment, the search spaces for CC1 and CC3 can be provided in the search space for CC1. In the example of FIG. 2, PDSCH on CC1 is not subject to heavy interference but PDSCH on CC2 is subject to heavy interference.

Accordingly, PDSCH on CC2 shall not be scheduled via the PDCCH on CC1 by eNode B. Instead, the PDCCH on CC1 used to schedule PDSCH on CC3 can be moved to the position of PDCCH search space on CC1 occupied by the previous PDCCH search space that would have been used to schedule the PDSCH on CC2. In other words, for this UE, PDSCH for CC2 is deactivated. PDCCH on CCl can be used to schedule PDSCH on CC3. The CCEs that store PDCCH for CCl and PDSCH for CC2 and CC3 may be in different groups of CCEs. The CCE numbers associated with search spaces for CCl and CC3 can be determined using equation (1) above.

In the example of FIG. 2, according to some embodiments, when CC2 is deactivated, the CIF values for CCl, CC2, and CC3 are not be changed if RRC signaling or other manners of communication are not available to re-configure CIF values for CCl and CC3. In other words, the deactivation of CC2 may not change the CIF values of CCl and CC3.

In an embodiment, a UE can report to the eNB the interference to which each CC is subject. The eNB can determine which CCs to activate or de-activate. The eNB can reconfigure the CIF values of PDCCH search spaces to consecutive values by RRC signaling. In various embodiments, the CIFs of the activated component carriers can be re-configured to ascending or descending order and the index of the sorted CIFs can be consecutive. Accordingly, the PDCCH search spaces for the different component carriers can be closely spaced or potentially consecutive in CCE numbering. This can potentially reduce the blocking probability for the cross-carrier scheduling.

Positions of the PDCCH search spaces per aggregation level in the activated component carriers can be dynamically changed within all the Control Channel Element (CCE) regions of the component carriers carrying the scheduled CCs. It is noted that one PDCCH search space can be transmitted using one, two, four, or eight (1,2,4, or 8) control channel elements (CCEs), each CCE can include nine resource elements group (REGs), each REG can contain four resource elements (REs), and each RE can be a subcarrier in both frequency and time domains.

If the search space for the primary carrier (CIF = 000) has heavy interference, another search space can be assigned a CIF =000 and becomes the primary carrier search space (and can be used for cross-carrier scheduling). RRC signaling from eNode B can reconfigure another CC as the primary component carrier of this UE.

Another example is provided in FIG. 3. Configured component carriers for a given

UE can be CCl, CC2, CC3, CC4, and CC5 at the kth subframe per radio frame. The CIF for the component carriers can be CIF_k,2=001, CIF_k,3=010, CIF_k,4=01 1, and CIFk,5=100, respectively. In this example, component carriers CC2 and CC4 are subject to the heavy interference. Accordingly, the activated component carriers are CCl, CC3, and CC5, with respective CIF_k;1=000, CIF_k3=010, and CiF_k;5=100. It can be seen that the values of CIFs are not consecutive values, which can result in large spaces between the search spaces of the activated component carriers. According to various embodiments, the sorted ascending index of the CIF values (CIF_k;1=000, CIF_k3=010, and CIF_k,5=100) for the activated CCs can be re-configured to 000, 001, and 010 using RRC signaling.

In this other example, the PDCCH search space for CC 1 can be used as control channels for CC3 and CC5. Different consecutive groups of CCEs can be used as control channels for CCl, 3, and 5.

The following provides an example determination of search spaces for UE-specific PDCCH. For example, an initial C-RNTI (Ύ ) can be 100, which can be signaled by eNB to UE via RRC signaling. For the first subframe (k=0), Yo can be derived by eNB from equation (3), where A=39827 and D=65537:

Y₀ = (39827* 100) mod(65537) = 50480.

The eNB can use UE Contention Resolution Identity MAC Control Element described in TS36.321 to signal Y₀ to UE.

For L = 1, M^^L) corresponds to 6. Accordingly, value m ranges from 0 to (A ^-l), 0 to 5. Value i ranges from 0 to L-l, or 0. For 20MHz bandwidth and 3 OFDM symbols for PDCCH overhead, value NccE_,k = 87. The following values are determined for equation (2):

for m = 0, S_k,o ^(L) = 1 * {(50480+0)mod(floor(87/l))}+0 = 20; for m = l, S_k,₀ ^(L) = 1 * {(50480+1 )mod(floor(87/ 1 ))} +0 = 21; for m = 2, S_k,₀ ^(L> = 1 * {(50480+2)mod(floor(87/l))}+0 = 22; for m = 3, S_k,o ^(L) = 1 * {(50480+3)mod(floor(87/l))}+0 = 23; for m = 4, S_k,₀ ^(L) = 1 * {(50480+4)mod(floor(87/l))}+0 = 24; and for m = 5, S_k,o ^(L) = 1 * {(50480+5)mod(floor(87/l))}+0 = 25.

For two CCs (CCl and CC2), CIF₀,o = 000 and CIF₀,i =010, then v_Active_cc,k = 2. For CIFo_,o = 000, X{CIF_k,n}) = 0 and for CiF₀,i =010,X{CIF_k,n}) = 1. Therefore, equation (4) can be:

for CIF_0,o(CCl), OFFSET_k;0 = 0*floor[87/2] = 0 and

for CIF₀,i(CC2), OFFSET_k;1 = l*floor[87/2] =43.

Accordingly, equation (1) can be determined. For CIFo,o (CCl), the starting CCE of candidate PDCCH, S_k is 20 + OFFSET^ = 20, and candidate PDCCHs for L = 1 are located in CCE numbered 20 (m=0), 21 (m=l), 22(m=2), 23 (m=3), 24 (m=4), and 25 (m=5). For CIF₀,i (CC2), the starting CCE of candidate PDCCH, S_k,i ^(L) , is 20 +

OFFSETk,i = 63, and all the candidate PDCCHs for L = 1 are located in CCE numbered 63 (m=0), 64 (m=l), 65 (m=2), 66 (m=3), 67 (m=4), and 68 (m=5).

UE can directly find CCEs numbered 20-25 and 63-68 to locate the UE-specific PDCCH for respective CCl and CC2. A UE can perform a sequential search. Candidate PDCCHs can be in sequential CCEs. In a UE-specific search space, the UE finds its PDCCH by inspecting a set of consecutive CCEs on which PDCCH could be mapped in every subframe. If no CRC error is detected when the UE uses its RNTI to de-mask the CRC on a PDCCH, the UE determines that PDCCH carries its own control information. The PDCCH candidate could correspond to different PDCCH formats. There are four PDCCH formats, i.e., 0, 1, 2 or 3. If the UE fails to decode any PDCCH candidates for a given PDCCH format, then the UE can try to decode candidates for other PDCCH formats. This process can be repeated for all possible PDCCH formats until all directed PDCCHs are successfully decoded that can be present in UE-specific search space.

FIG. 4 depicts an example system that can use embodiments of the present invention. Computer system 400 may include host system 402 and display 422.

Computer system 400 can be implemented in a handheld personal computer, mobile telephone, set top box, or any computing device. Host system 402 may include chipset 405, processor 410, host memory 412, storage 414, graphics subsystem 415, and radio 420. Chipset 405 may provide intercommunication among processor 410, host memory 412, storage 414, graphics subsystem 415, and radio 420. For example, chipset 405 may include a storage adapter (not depicted) capable of providing intercommunication with storage 414.

Processor 410 may be implemented as Complex Instruction Set Computer (CISC) or Reduced Instruction Set Computer (RISC) processors, x86 instruction set compatible processors, multi-core, or any other microprocessor or central processing unit. In various embodiments, processor 410 or radio 420 can be configured to identify control channel search spaces in the manners described herein.

Host memory 412 may be implemented as a volatile memory device such as but not limited to a Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), or Static RAM (SRAM). Storage 414 may be implemented as a non- volatile storage device such as but not limited to a magnetic disk drive, optical disk drive, tape drive, an internal storage device, an attached storage device, flash memory, battery backed-up SDRAM (synchronous DRAM), and/or a network accessible storage device.

Graphics subsystem 415 may perform processing of images such as still or video for display. An analog or digital interface may be used to communicatively couple graphics subsystem 415 and display 422. For example, the interface may be any of a High-Definition Multimedia Interface, DisplayPort, wireless HDMI, and/or wireless HD compliant techniques. Graphics subsystem 415 could be integrated into processor 410 or chipset 405. Graphics subsystem 415 could be a stand-alone card communicatively coupled to chipset 405.

Radio 420 may include one or more radios capable of transmitting and receiving signals in accordance with applicable wireless standards such as but not limited to any version of IEEE 802.1 1, IEEE 802.16, and 3GPP LTE advanced. For example, radio 420 may include at least a physical layer interface and media access controller.

FIG. 5 depicts an example process in accordance with an embodiment. The process of FIG. 5 can be performed by a UE to identify a PDCCH, PDSCH, or other search space for control channel information. Block 501 includes receiving one or more parameters that can be used to determine search space locations for control channels. For example, the one or more parameters can include value Y_i. A UE can receive Y-i from an eNB. In some cases, all the Yk-i (k=l,2,3,...,10) can be derived from equation (3) when Y-i is known by both UE and eNB. This value Y_i can be used to solve equation (3), which can in turn be used to solve equations (2) and (1). In addition, the one or more parameters can include CIF values of activated component carriers. The CIF values can be used to solve equation (4), which can be used to solve equation (1). The search spaces can correspond to particular CCEs.

Block 502 includes identifying interference levels of search spaces for assigned common carriers. A UE can indicate interference levels of the component carriers (e.g., in dB) to the eNB using measurement reporting messages described in TS 36.331 (201 1). For example, a UE can determine PDCCH search space locations based on equations (1)- (4). UE may report the interference levels of carriers to eNB and eNB can determine the PDCCH search space locations for each CC.

Block 503 includes receiving updated carrier identifiers for active component carriers. In some cases, if an activated component carrier experiences too high an interference level, the eNB can decide to de-activate the component carrier. CIF can be re-assigned to activated component carriers via RRC signaling so that CIF values increase or decrease for activated component carriers with no gaps in CIF values. The eNB can set search space locations for each CC by adjusting CIF values used to solve equations (1)- (4).

In some cases, the UE can determine which component carriers have too high an interference level. The UE can determine to de-activate certain component carriers and accompanying search spaces and indicate the decision to the eNB. The eNB can determine new CIF values to assign to previously assigned and active component carriers and accompanying search spaces. The eNB can communicate the new CIF values to the UE.

In some cases, the UE can identify the component carriers with too high interference level to the eNB. The eNB can determine to de-activate component carriers with too high interference level and accompanying search spaces and indicate the decision to the UE. The eNB can determine new CIF values to assign to previously assigned and active component carriers and accompanying search spaces. The eNB can communicate the new CIF values to the UE.

Block 504 includes investigating assigned search spaces of active component carriers to determine whether its control channel is present. For all aggregation levels (1, 2, 4, and 8), the UE can detect search spaces. The UE may detect search spaces until finding a PDCCH that is unmasked by its RNTI. In some cases, the primary component carrier PDCCH is used to transmit PDSCH for secondary component carriers.

FIG. 6 depicts an example process that can be used to allocate search space locations for control channels. The process of FIG. 6 can be used by an eNB to allocate PDCCH, PDSCH, or other control channel search spaces to a UE.

Block 601 includes requesting to transmit one or more parameters useful to determine frequency band search space locations of control channels. The one or more parameters can include variable Y_i, which can be used to solve equation (3), which can in turn be used to solve equations (2) and (1). In addition, the one or more parameters can include CIF values of activated component carriers. The CIF values can be used to solve equation (4), which can be used to solve equation (1).

Block 602 includes determining component carriers that experience unacceptable interference levels. The interference levels can be measured by the eNB or by the UE and communicated to the eNB. Component carriers with excessively high interference levels can be determined to be unusable until further consideration. Component carriers with acceptable interference levels can be determined to be usable. Associated search spaces for those component carriers can remain active.

Block 603 includes selectively modifying CIF values of usable component carriers to sequential values in response to any component carrier being unusable.

Block 604 includes requesting to transmit modified CIF values of usable component carriers. The eNB can request to transmit the re-assigned CIF values to at least one UE. Thereafter, a UE can use the re-assigned CIF values to identify CCE that can potentially store PDCCH, PDSCH, or other control channel information for the usable component carriers.

The graphics and/or video processing techniques described herein may be implemented in various hardware architectures. For example, graphics and/or video functionality may be integrated within a chipset. Alternatively, a discrete graphics and/or video processor may be used. As still another embodiment, the graphics and/or video functions may be implemented by a general purpose processor, including a multicore processor. In a further embodiment, the functions may be implemented in a consumer electronics device.

Embodiments of the present invention may be implemented as any or a combination of: one or more microchips or integrated circuits interconnected using a motherboard, hardwired logic, software stored by a memory device and executed by a microprocessor, firmware, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA). The term "logic" may include, by way of example, software or hardware and/or combinations of software and hardware.

Embodiments of the present invention may be provided, for example, as a computer program product which may include one or more machine-readable media having stored thereon machine-executable instructions that, when executed by one or more machines such as a computer, network of computers, or other electronic devices, may result in the one or more machines carrying out operations in accordance with

embodiments of the present invention. A machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs (Compact Disc-Read Only Memories), and magneto-optical disks, ROMs (Read Only Memories), RAMs (Random Access Memories), EPROMs (Erasable Programmable Read Only Memories), EEPROMs (Electrically Erasable Programmable Read Only Memories), magnetic or optical cards, flash memory, or other type of media / machine-readable medium suitable for storing machine-executable instructions.

The drawings and the forgoing description gave examples of the present invention. Although depicted as a number of disparate functional items, those skilled in the art will appreciate that one or more of such elements may well be combined into single functional elements. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of the present invention, however, is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is at least as broad as given by the following claims.

Claims

Claims What is claimed is:

1. A computer-implemented method performed at a user element, the method comprising:

selectively receiving updated component carrier identifiers in response to excessive interference on one or more component carriers and

determining locations of control channels for one or more active component carriers using a search space allocated for at least one active component carrier, the locations of control channels for the one or more active component carriers are based in part on component identifiers, the identifiers being sequential in value, and based in part on a number of active component carriers and based in part on a number of common carrier elements available for control channels of a subframe.

2. The method of claim 1, further comprising:

determining interference levels of one or more component carriers and requesting to identify component carriers that have excessive interference levels, wherein the updated component carrier identifiers correspond to component carriers whose interference level is not excessive.

3. The method of claim 1, further comprising:

receiving at least one parameter useful to identify a location of a control channel associated with one or more component carriers.

4. The method of claim 3, wherein the at least one parameter comprises a value of an initial Cell Radio Network Temporary Identifier.

5. The method of claim 3, wherein the at least one parameter comprises a carrier indicator field value.

6. The method of claim 1, wherein the determining locations of control channels comprises: determining a location of a base common carrier element for a k sub frame using the user element's identifier;

determining common carrier elements at the k^th sub frame based in part on the location of the base common carrier element, a number of common carrier elements for a k^th sub frame, a carrier aggregation level, and number of Physical Downlink Control Channel candidates to monitor in a given search space, and an offset, wherein

the offset is based in part on component identifiers, a number of active component carriers, and a number of common carrier elements available for control channels of a subframe.

7. The method of claim 1, wherein the determining locations of control channels comprises determining locations of control channels for one or more active secondary component carriers using a search space allocated for an active primary component carrier.

8. The method of claim 7, wherein the control channels for one or more active component carriers comprise a Physical Downlink Control Channel for a primary component carrier and a Physical Downlink Shared Channel information for one or more active secondary component carriers.

9. The method of claim 1, wherein the control channels for one or more active component carriers comprise a Physical Downlink Control Channel for a primary component carrier and a Physical Downlink Shared Channel information for one or more active secondary component carriers.

10. A communications apparatus comprising:

logic to request to allocate one or more component carriers to a user element;

logic to request to transmit one or more parameters that can be used by the user element to determine control channel locations for one or more component carriers;

logic to determine allocated component carriers that have excessive interference; and logic to request to transmit identifiers of component carriers that do not have excessive interference, the identifiers being sequential in value.

The apparatus of claim 10, wherein

the one or more component carriers comprise a primary carrier and at least one secondary carrier;

the control channel locations comprise control channel elements identified based in part on the identifiers and based in part on the one or more parameters; and

the control channel locations associated with the primary carrier used to convey control channels for the at least one secondary carrier.

The apparatus of claim 10, wherein the one or more parameters comprises a value initial Cell Radio Network Temporary Identifier.

A system comprising:

a display device;

at least one antenna; and

a processor configured to:

receive updated component carrier identifiers and determine locations of control channels for one or more active component carriers using a search space allocated for at least one active component carrier, the locations of control channels for the one or more active component carriers are based in part on component identifiers, the identifiers being sequential in value, and based in part on a number of active component carriers and based in part on a number of common carrier elements available for control channels of a subframe.

The system of claim 13, wherein the processor is also configured to:

determine interference levels of one or more component carriers and request to identify component carriers that have excessive interference levels, wherein the updated component identifiers correspond to component carriers whose interference level is not excessive.

15. The system of claim 13, wherein the processor is also configured to:

receive at least one parameter useful to identify a location of a control channel associated with one or more component carriers.

16. The system of claim 15, wherein the at least one parameter comprises a value of an initial Cell Radio Network Temporary Identifier.

17. The system of claim 15, wherein the at least one parameter comprises a carrier indicator field value.

18. The system of claim 13, wherein to determine locations of control channels, the processor is to:

determine a location of a base common carrier element for a k"¹ sub frame using the user element's identifier and

determine common carrier elements at the k"¹ sub frame based in part on the location of the base common carrier element, a number of common carrier elements for a k^th sub frame, a carrier aggregation level, and number of Physical Downlink Control Channel candidates to monitor in a given search space, and an offset, wherein

19. The system of claim 13, wherein to determine locations of control channels, the processor is to determine locations of control channels for one or more active secondary component carriers using a search space allocated for an active primary component carrier.

20. The system of claim 13, wherein the control channels for one or more active component carriers comprise a Physical Downlink Control Channel for a primary component carrier and a Physical Downlink Shared Channel information for one or more active secondary component carriers.