Short physical downlink control channel (sPDCCH) mapping design

Abstract

A method, network node and wireless device for receiving and/or mapping a physical downlink control channel, PDCCH, to resource elements of a time-frequency grid are provided in which the PDCCH is mapped to resource elements of the time-frequency grid by configuring resource element groups, REGs, each REG spanning one orthogonal frequency division multiplex, OFDM, symbol, and the PDCCH being at least two OFDM symbols. In accordance with one embodiment, the method includes receiving the PDCCH from the network node on one of a plurality of sets of physical resource blocks, PRBs.

Claims

1. A method in a wireless device for receiving information on a physical downlink control channel, PDCCH, signaled by a network node, the PDCCH being mapped to resource elements of a time-frequency grid, by configuring resource element groups, REGs, each REG spanning only one OFDM symbol, the method comprising: receiving radio resource control, RRC, signaling from the network node, the RRC signaling indicating to the wireless device to use a PDCCH resource block set with one of a distributed mapping or a localized mapping of control channel elements, CCEs, to REGs; receiving the PDCCH from the network node on one of a plurality of sets of physical resource blocks, PRBs, the PDCCH being at least two OFDM symbols, the PDCCH including at least one CCE, the at least one CCE being mapped to a subset of the REGs based on: for RRC signaling indicating a distributed mapping: the subset of the REGs being distributed in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs; and for RRC signaling indicating a localized mapping: the subset of the REGs being localized in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs.

2. The method of claim 1, wherein each REG consists of 1 PRB within 1 OFDM symbol including resource elements, REs, for demodulation reference signals, DMRS, applied to DMRS-based PDCCH.

3. The method of claim 1, wherein the RRC signaling indicates to the wireless device to use a demodulation reference signal, DMRS, based PDCCH resource block set.

4. The method of claim 1, wherein the subset of REGs is ordered by first incrementing each symbol in a time domain for a frequency, from a first OFDM symbol to a number of OFDM symbols of the PDCCH, and subsequently incrementing the frequency.

5. A wireless device for receiving information on a physical downlink control channel, PDCCH, signaled by a network node, the PDCCH being mapped to resource elements of a time-frequency grid, by configuring resource element groups, REGs, each REG spanning only one orthogonal frequency division multiplex, OFDM, symbol, the wireless device comprising: a transceiver configured to: receive radio resource control, RRC, signaling from the network node, the RRC signaling indicating to the wireless device to use a PDCCH resource block set with one of a distributed mapping or a localized mapping of control channel elements, CCEs, to REGs; receive the PDCCH from the network node on one of a plurality of sets of physical resource blocks, PRBs, the PDCCH being at least two OFDM symbols, the PDCCH including at least one CCE, the at least one CCE being mapped to a subset of the REGs based on: for RRC signaling indicating a distributed mapping: the subset of the REGs being distributed in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs; and for RRC signaling indicating a localized mapping: the subset of the REG being localized in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs.

6. The wireless device of claim 5, wherein each REG consists of 1 PRB within 1 OFDM symbol including resource elements, REs, for demodulation reference signals, DMRS, applied to DMRS-based PDCCH.

7. The wireless device of claim 5, wherein the subset of REGs is ordered by first incrementing each symbol in a time domain for a frequency, from a first OFDM symbol to a number of OFDM symbols of the PDCCH, and subsequently incrementing the frequency.

8. A method in a network node for mapping a physical downlink control channel, PDCCH, to resource elements of a time-frequency grid, the method comprising: determining available time-frequency resources to be configured as resource element groups, REGs; configuring a wireless device with radio resource control, RRC, signaling, the RRC signaling indicating to the wireless device to use a PDCCH resource block set with one of a distributed mapping or a localized mapping of control channel elements, CCEs, to REGs; and configuring REGs within a physical resource block, PRB, to map the PDCCH to the resource elements, each REG spanning only one orthogonal frequency division multiplex, OFDM, symbol, the PDCCH being at least two OFDM symbols, the PDCCH including at least one CCE, the at least one CCE being mapped to a subset of the REGs based on: for RRC signaling indicating a distributed mapping: the subset of the REGs being distributed in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs; and for RRC signaling indicating a localized mapping: the subset of the REGs being localized in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs.

9. The method of claim 8, wherein each REG consists of 1 PRB within 1 OFDM symbol including resource elements, REs, for demodulation reference signals, DMRS, applied to DMRS-based PDCCH.

10. The method of claim 8, wherein the RRC signaling indicates to the wireless device to use a demodulation reference signal, DMRS, based PDCCH resource block set.

11. The method of claim 8, wherein the subset of REGs is ordered by first incrementing each symbol in a time domain for a frequency, from a first OFDM symbol to a number of OFDM symbols of the PDCCH, and subsequently incrementing the frequency.

12. A network node for mapping a physical downlink control channel, PDCCH, to resource elements of a time-frequency grid, the network node comprising: processing circuitry configured to: determine available time-frequency resources to be configured as resource element groups, REGs; configure a wireless device with radio resource control, RRC, signaling, the RRC signaling indicating to the wireless device to use a PDCCH resource block set with one of a distributed mapping or a localized mapping of control channel elements, CCEs, to REGs; and configure REGs within a physical resource block, PRB, to map the PDCCH to the resource elements, each REG spanning only one orthogonal frequency division multiplex, OFDM, symbol, the PDCCH being at least two OFDM symbols, the PDCCH including at least one CCE, the at least one CCE being mapped to a subset of the REGs based on: for RRC signaling indicating a distributed mapping: the subset of the REGs being distributed in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs; and for RRC signaling indicating a localized mapping: the subset of the REGs being localized in groups of REGs, each group of REGs being mapped to frequency-consecutive PRBs.

13. The network node of claim 12, wherein each REG consists of 1 PRB within 1 OFDM symbol including resource elements, REs, for demodulation reference signals, DMRS, applied to DMRS-based PDCCH.

14. The network node of claim 12, wherein the subset of REGs is ordered by first incrementing each symbol in a time domain for a frequency, from a first OFDM symbol to a number of OFDM symbols of the PDCCH, and subsequently incrementing the frequency.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

(2) FIG. 1 is a diagram of a time-frequency grid;

(3) FIG. 2 is a diagram of downlink subframe;

(4) FIG. 3 is a diagram of a downlink subframe showing 10 RB pairs and configuration of three ePDCCH regions;

(5) FIG. 4 is a diagram of CCE aggregation;

(6) FIG. 5 is a diagram showing a search space to be monitored by a wireless device;

(7) FIG. 6 is a flowchart of processing steps for PDCCH formation;

(8) FIG. 7 illustrates differences between a CCE and an eCCE;

(9) FIG. 8 is a downlink subframe having 4 parts belonging to an ePDCCH;

(10) FIG. 9 is a downlink subframe showing a different mapping of 4 eCCEs;

(11) FIG. 10 is a PRB based sREG and a fractioned PRB based SREG for 1 OFDM symbol;

(12) FIG. 11 is a block diagram of a wireless communication system constructed in accordance with principles set forth herein;

(13) FIG. 12 is a block diagram of a network node constructed in accordance with principles set forth herein;

(14) FIG. 13 is a block diagram of an alternative embodiment of a network node;

(15) FIG. 14 is a block diagram of a wireless device constructed in accordance with principles set forth herein;

(16) FIG. 15 is a block diagram of an alternative embodiment of a wireless device;

(17) FIG. 16 is a flowchart of an exemplary process in a network node;

(18) FIG. 17 is flowchart of an exemplary process for ascertaining a sPDCCH at a wireless device;

(19) FIG. 18 is an OFDM distribution scheme for a set of 18 PRBs;

(20) FIG. 19 is a 1-OFDM symbol sPDCCH localized scheme;

(21) FIG. 20 is a 2-OFDM symbol sPDCCH distributed scheme;

(22) FIG. 21 is a 2-OFDM symbol sPDCCH localized scheme; and

(23) FIG. 22 is an additional 2-OFDM symbol sPDCCH distributed scheme.

DETAILED DESCRIPTION

(24) Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to short physical downlink control channel (sPDCCH) mapping design. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

(25) As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.

(26) Note that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and/or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

(27) The term wireless device or user equipment (UE) used herein may refer to any type of wireless device communicating with a network node and/or with another wireless device in a cellular or mobile communication system. Examples of a wireless device are target device, device to device (D2D) wireless device, machine type wireless device or wireless device capable of machine to machine (M2M) communication, PDA, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles etc.

(28) The term “network node” used herein may refer to a radio network node or another network node, e.g., a core network node, MSC, MME, O&M, OSS, SON, positioning node (e.g. E-SMLC), MDT node, etc.

(29) The term “radio network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), nodes in distributed antenna system (DAS) etc.

(30) Although embodiments are described herein with reference to certain functions being performed by a network node, it is understood that the functions can be performed in other network nodes and elements. It is also understood that the functions of the network node can be distributed across network cloud so that other nodes can perform one or more functions or even parts of functions described herein.

(31) A flexible mapping for sPDCCH to the resource elements (REs) is proposed. The proposed mapping has various modes, each enabling exploitation of the particularity of the channel or of advanced transmission modes. In one mode, large frequency diversity is achieved, and in another mode, condensed frequency allocation for, e.g., beamforming based transmission mode, is enabled. The proposed mapping also can be extended to various numbers of OFDM symbols. In the following, examples are given for the case of one and two OFDM symbols used by sPDCCH, but the proposed design can be adapted to even larger number of OFDM symbols.

(32) The same scheme can be used to select localized or distributed placement, of one or two symbols sPDCCH, all controlled by a scheduling decision by the network node, e.g., eNB: the proposed design can achieve high frequency diversity or condensed frequency allocation; and the proposed design can be adapted to a sPDCCH time region of one to several OFDM symbols. With the proposed sPDCCH design, users with transmission modes relying on different reference signals, e.g., CRS and DMRS users, can coexist on the same sTTI. The proposed design allows unused resources on the sPDCCH to be utilized for the sPDSCH.

(33) To facilitate the definition of the sPDCCH mapping to resource elements, special entities are defined: sREG and sCCE. This follows the methodology used so far in the LTE specifications for defining PDCCH and ePDCCH, as described above. Note that the definition of the same mapping can also be performed without using these terms or by using equivalent terms.

(34) Even though longer length can be considered, the possible lengths for sPDCCH in the time domain are 1 or 2 OFDM symbols for sTTI operation. The REs of a PRB in a given OFDM symbol of the sTTI can built from one or more sREG. The number of REs in a sREG may also be variable in order to provide allocation flexibility and to support good frequency diversity.

(35) In one embodiment, two sREG configuration options for a sPDCCH are defined: PRB based sREG, which means that a sREG is built up with the complete number of REs in a PRB within 1 OFDM symbol (i.e., 12 REs per sREG for 1 OFDM symbol), or Fractioned PRB based sREG, which means that the number of REs in a PRB within 1 OFDM symbol is split and assigned to a sREG (e.g., 6 REs per sREG).
These two sREG configuration options are depicted in FIG. 10, considering 1 OFDM symbol sPDCCH (options 1a and 1b) with 6 REs per sREG and 2 OFDM symbol sPDCCH (options 2a and 2b) with 12 REs per sREG. Each index, i.e. {0, 1, 2, 3}, represents an sREG group. Thus, as depicted, for 1 OFDM symbol sPDCCH, up to two sREG groups can be configured and for 2 OFDM symbol sPDCCH up to four sREG groups. It can be seen that a sREG only spans a single OFDM symbol. As such, the sREG is spanning only one OFDM symbol in the time domain. This enables easy extension of the sPDCCH design to more OFDM symbols in the time domain. Following this principle (i.e., only one OFDM symbol spanned by a sREG, i.e., the sREG has a time domain length of only one OFDM symbol, which is applicable to any example), one can consider the alternative fractioned PRB based sREG in which resource elements of a OFDM symbol would be split into more than two sREG for instance. But one way to achieve a design adaptable to different number of OFDM symbols is apply a condition that a sREG only spans a single OFDM symbol.

(36) In another embodiment, 1 OFDM symbol sPDCCH is defined for CRS based transmissions due to the advantage of early decoding for 2 OFDM symbol sTTI, while 2 or more OFDM symbol sPDCCH can be configured for one slot length TTI. As an alternative for 2 OFDM symbol sTTI configuration, 2 or more OFDM symbol sPDCCH can be used to allow a small sTTI band, i.e., to limit the number of frequency resources used for sTTI operation.

(37) In a further embodiment, for DMRS based transmissions with 2 OFDM symbol sTTI, assuming a design based on DMRS pairs in the time domain as in legacy LTE, a 2 OFDM symbol sPDCCH is defined. A 2 OFDM symbol sPDDCH is defined since wireless devices wait for the end of sTTI for channel estimation. In such case, DMRS is not shared between sPDCCH and sPDSCH in a given PRB of the sTTI. This gives more freedom for applying beamforming for sPDCCH. For DMRS with 1-slot sTTI, a 2 symbols sPDCCH is suitable. One DMRS pair for 1-slot TTI is preferred to be able to perform channel estimation for sPDCCH and early sPDCCH decoding.

(38) Thereby, considering the presence of potential reference signals in a sTTI such as DMRS, CRS or CSI-RS, those REs occupied by these signals within a PRB are not used for a given sREG.

(39) The number of sREG required to build up a sCCE for a given sPDCCH can vary, as well as their placement scheme among the frequency resources used for sTTI operation. Thus, in one embodiment, a sCCE is defined to be composed ideally by 36 REs like an eCCE or a CCE. For that, a sCCE is composed by either PRB based sREG or fractioned PRB based sREG relying on the number of OFDM symbols assigned for sPDCCH as further described below.

(40) In order to support good frequency diversity or a more localized placement, localized and distributed placement schemes of sREG building up the same sCCE are defined:

(41) Localized scheme: sREGs building the same sCCE can be localized in frequency domain to allow for a sPDCCH resource allocation confined in a limited frequency band. This facilitates the use of beamforming for DMRS based sPDCCH.

(42) Distributed scheme: A distributed sREG location can be used to allow frequency diversity gains. In this case, multiple wireless devices may have the sREG of their sPDCCH mapped to the same PRB on different REs. Distributing over a wide frequency range also more easily makes the sPDCCH fit into one single OFDM symbol. For wireless devices with DMRS based demodulation, user-specific beamforming is not recommended with distributed sCCE locations.

(43) In a further embodiment, these schemes, which are described below for building sCCE based on 1 OFDM symbol sPDCCH and 2 OFDM symbol sPDCCH, can be used for CRS and DMRS transmissions.

(44) Likewise, some embodiments take into account the following considerations:

(45) CRS and DMRS users can coexist on the same sTTI, since sPDCCH design is the same.

(46) If both CRS and DMRS users are given downlink control information (DCI) in the same PRB, this may be indicated to CRS users. Then, the CRS users know that some REs are not used for sCCE. Otherwise, CRS and DMRS users may be sent DCI in different PRBs.

(47) At least one set of PRBs that can be used for the sPDCCH is configured per user. It is recommended to support the configuration of several sets of PRBs used for sPDCCH so as to configure one set of PRBs following the localized sPDCCH mapping and another set with the distributed mapping. The wireless device can monitor both sets and the network node, could select the most favorable configuration/PRB set for a given sTTI and wireless device.

(48) In an embodiment, the set of PRBs assigned for the sPDCCH, which includes PRBs (not necessarily consecutive) from the available sTTI band, may be configured via higher layer signaling such as radio resource control (RRC) signaling. However, this may require a potential resource allocation refinement in the slow downlink control information (DCI) transmitted in PDCCH, e.g., a reduced set of PRBs or a specific set in case several sPDCCH sets were defined. For some of the schemes described herein, and for simplicity, a system bandwidth of 10 MHz (i.e. 50 PRBs) is assumed, of which a set of 18 PRBs (not necessarily consecutive physical PRBs) is assigned by the network node, for sPDCCH. All the schemes however can further comprise all system bandwidths.

(49) In an embodiment, the set of PRBs are configured independently, e.g., as a PRB bitmap. In another embodiment, the set is configured based on groups of PRBs. One example of an already-defined group of PRBs in LTE is called resource block group (RBG) and can be used as a basis in the proposed sPDCCH mapping. Then, all PRBs within the same PRB group, e.g., RBG, may be jointly used.

(50) In an embodiment, the PRBs or groups of PRBs included in the configured PRB set may be ordered according to a sequence signaled to the wireless device before mapping the sPDCCH to them.

(51) FIGS. 11-17 depict hardware and flowcharts that implement the features described above. FIG. 11 is a block diagram of a wireless communication system 10 constructed according to principles set forth herein. The wireless communication network 10 includes a cloud 12 which may include the Internet and/or the public switched telephone network (PSTN). Cloud 12 may also serve as a backhaul network of the wireless communication network 10. The wireless communication network 10 includes one or more network nodes 14A and 14B, which may communicate directly via an X2 interface in LTE embodiments, and are referred to collectively as network nodes 14. It is contemplated that other interface types can be used for communication between network nodes 14 for other communication protocols such as New Radio (NR). The network nodes 14 may serve wireless devices 16A and 16B, referred to collectively herein as wireless devices 16. Note that, although only two wireless devices 16 and two network nodes 14 are shown for convenience, the wireless communication network 10 may typically include many more wireless devices (WDs) 16 and network nodes 14. Further, in some embodiments, WDs 16 may communicate directly using what is sometimes referred to as a side link connection.

(52) The network node 14 includes an sREG configuration unit 18 configured to configure short resource element groups, sREGs, within a physical resource block, PRB, each sREG spanning one OFDM symbol. In some aspects, and in any example, the sREGs being within a PRB corresponds to the sREGs having a size in the frequency domain which is equal to the frequency domain size of one PRB, e.g. 12 subcarriers. In some aspects, each sREG extends in frequency over one PRB. The wireless device 16 includes a PRB monitoring unit 20 configured to monitor a plurality of sets of PRBs used for the sPDCCH, at least one set configured for localized sPDCCH mapping to resource elements and at least another set configured for distributed sPDCCH mapping to resource elements.

(53) FIG. 12 is a block diagram of a network node 14 for mapping an sPDCCH to resource elements of a time-frequency grid as discussed above. The network node 14 has processing circuitry 22. In some embodiments, the processing circuitry may include a memory 24 and processor 26, the memory 24 containing instructions which, when executed by the processor 26, configure processor 26 to perform the one or more functions described herein. In addition to a traditional processor and memory, processing circuitry 22 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry).

(54) Processing circuitry 22 may include and/or be connected to and/or be configured for accessing (e.g., writing to and/or reading from) memory 24, which may include any kind of volatile and/or non-volatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory). Such memory 24 may be configured to store code executable by control circuitry and/or other data, e.g., data pertaining to communication, e.g., configuration and/or address data of nodes, etc. Processing circuitry 22 may be configured to control any of the methods described herein and/or to cause such methods to be performed, e.g., by processor 26. Corresponding instructions may be stored in the memory 24, which may be readable and/or readably connected to the processing circuitry 22. In other words, processing circuitry 22 may include a controller, which may comprise a microprocessor and/or microcontroller and/or FPGA (Field-Programmable Gate Array) device and/or ASIC (Application Specific Integrated Circuit) device. It may be considered that processing circuitry 32 includes or may be connected or connectable to memory, which may be configured to be accessible for reading and/or writing by the controller and/or processing circuitry 22.

(55) The memory 24 is configured to store sPDCCH mappings. The processor 26 includes a sREG configuration unit 18 configured to configure short resource element groups, sREGs, within a physical resource block, PRB, the number of sREGs depending upon a number of orthogonal frequency division multiplex, OFDM, symbols of the sPDCCH, each sREG spanning one OFDM symbol. The network node 14 also includes a transceiver 28 configured to transmit the sPDCCH to a wireless device 16.

(56) FIG. 13 is a block diagram of an alternative embodiment of a network node 14 that includes a memory module 25, an sREG configuration module 19 and a transceiver module 29. The sREG configuration module 19 may be implemented in software executed by a processor to configure short resource element groups, sREGs, within a physical resource block, PRB. The transceiver module 29 may be implemented at least in part by software that may be executed by the processor to transmit the sPDCCH to the wireless device 16.

(57) FIG. 14 is a block diagram of a wireless device 16. The wireless device 16 has processing circuitry 42. In some embodiments, the processing circuitry may include a memory 44 and processor 46, the memory 44 containing instructions which, when executed by the processor 46, configure processor 46 to perform the one or more functions described herein. In addition to a traditional processor and memory, processing circuitry 42 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry).

(58) Processing circuitry 42 may include and/or be connected to and/or be configured for accessing (e.g., writing to and/or reading from) memory 44, which may include any kind of volatile and/or non-volatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory). Such memory 44 may be configured to store code executable by control circuitry and/or other data, e.g., data pertaining to communication, e.g., configuration and/or address data of nodes, etc. Processing circuitry 42 may be configured to control any of the methods described herein and/or to cause such methods to be performed, e.g., by processor 46. Corresponding instructions may be stored in the memory 44, which may be readable and/or readably connected to the processing circuitry 42. In other words, processing circuitry 42 may include a controller, which may comprise a microprocessor and/or microcontroller and/or FPGA (Field-Programmable Gate Array) device and/or ASIC (Application Specific Integrated Circuit) device. It may be considered that processing circuitry 42 includes or may be connected or connectable to memory, which may be configured to be accessible for reading and/or writing by the controller and/or processing circuitry 42.

(59) The memory 44 is configured to store the sPDCCH. The wireless device 16 also includes a transceiver 48 which includes an sPDCCH receiver 50 configured to receive the sPDCCH from the network node 14 on one of a plurality of sets of PRBs.

(60) FIG. 15 is a block diagram of an alternative embodiment of a wireless device 16 that includes a transceiver module 49 includes the sPDCCH receiver 50 which may be implemented in part by software executable by a processor.

(61) FIG. 16 is a flowchart of an exemplary process for mapping an sPDCCH to resource elements of a time-frequency grid. The process includes determining available time-frequency resources to be configured as sREGs (block S100). The process also includes configuring, via the sREG configuration unit 18, the sREGs within a PRB, to map the sPDCCH to the resource elements (block S102). In some embodiments, the number of sREGs depending upon a number of OFDM symbols of a sPDCCH. Also note that in some embodiments, the size of the sREG in the frequency domain is equal to 1 PRB which may be equal to 12 subcarriers.

(62) FIG. 17 is a flowchart of an exemplary process for mapping an sPDCCH to resource elements of a time-frequency grid. The process includes receiving, via the receiver 50, the sPDCCH from the network node 14 on one of a plurality of sets of PRBs (block S106).

(63) In some embodiments, distributed cases are defined and depicted in FIG. 18, which shows a 1-OFDM symbol sPDCCH distributed scheme for a set of 18 PRBs. These cases include an aggregation level of up to 4 (i.e., up to 4 sCCE per sPDCCH). Higher aggregation levels are possible as well. These cases aim at regular distribution of the sREG over the PRBs of the configured PRB set in the frequency domain. Some embodiments have the features that the unused PRBs shown in FIG. 18 can be further assigned for building other sCCEs for other wireless devices 16. Further, these unused PRBs may be used for sPDSCH allocation. The PRB indices shown in FIG. 18 represent the number of the sREG group within the sPDCCH PRB set (for this example, a set of 18 PRBs). For simplicity, the physical PRB number is not shown.

(64) The aggregation level (AL) 1 (i.e., 1 sCCE=36 REs) comprises two cases as depicted in FIG. 18, where the differently shaded regions represent different sCCEs:

(65) Case 1 (AL 1) (denoted by the numeral 1 at the top of column 1): Fractioned PRB based sREG with a sREG=6 REs. Thereby, the sCCE is composed of 6 sREG highly and regularly distributed in the frequency domain, providing high frequency diversity. For that, 6 PRBs are used. This case may further comprise an offset to be signaled or computed to use sREG group 1 instead of sREG group 0. This allows efficient PRB utilization by sharing the PRB resources between (up to) two users.
Case 2 (AL 1) (denoted by the numeral 2 at the top of column 2): PRB based sREG, i.e., 1 sREG=12 REs (sREG group 0 and 1 together are seen as a single sREG in FIG. 18), or fractioned PRB based sREG with full PRB utilization, i.e. including sREG group 0 and sREG group 1 from each assigned PRB. Thereby, the sCCE is composed of either 3 PRB based sREG or 6 fractioned PRB based sREG moderately and regularly distributed in the frequency domain, i.e. over 3 PRBs. Thus, frequency diversity is still provided.

(66) The choice of using, sREG group 0 or sREG group 1 in FIG. 18 can, as mentioned above, be signaled or calculated. It can also be standardized or signaled that the wireless device 16 should monitor a set of sREG, thereby increasing the search space but allowing for the network node 14 to send sPDCCH to multiple wireless devices 16 sharing the same set of configured PRBs.

(67) The aggregation levels (ALs) 2 (i.e. 2 sCCE) and 4 (i.e. 4 sCCE) comprise four cases. These cases are depicted in FIG. 18, where areas in FIG. 18 that are shaded differently represent different sCCEs.

(68) Case 3 (AL 2) (denoted by the numeral 3 at the top of column 3): An extension of Case 1 with full PRB utilization, i.e., including sREG group 0 and sREG group 1 from each assigned PRB. Likewise, this case can be based on PRB based sREG. Thereby, the sCCE is composed of either 6 PRB based sREG or 12 fractioned PRB based sREG that are highly and regularly distributed in the frequency domain, i.e., over 6 PRBs. In some aspects, this case uses 6 sREG each of one full PRB, or using 12 sREG each of one fractioned PRB. So aspects are applicable to either definition of sREG size. This is in contrast to case 1, which is only applicable for fractioned PRB.

(69) Case 4 (AL 2) (denoted by the numeral 4 at the top of column 4): An extension of Case 2 including the consecutive PRB from each PRB used in Case 2.

(70) Case 5 (AL 4) (denoted by the numeral 5 at the top of column 5): An extension of Case 3 including the consecutive PRB from the PRBs used in Case 3.

(71) Case 6 (AL 4) (denoted by the numeral 6 at the top of column 6): An extension of Case 4 including the consecutive PRB from each PRB used in Case 4 as well as the last 3 PRBs within the PRB set.

(72) As described, Case 1 and Case 2 are the basis for all schemes. Therefore, in one embodiment, the Case 1 and Case 2 distribution schemes for 1 OFDM symbol sPDCCH can be achieved by the following formula. The sREG m of a sCCE composed of N_(sREG/sCCE) is given by

(73) $Y+\left[\frac{m*N_{\mathrm{sREG}/\mathrm{PRB}}*N_{\mathrm{PRB}}}{N_{\mathrm{sREG}/\mathrm{sCCE}}}\right],m=0,\mathrm{.Math.},N_{\mathrm{sREG}/\mathrm{sCCE}}-1$
where: Y is the wireless device-dependent offset based on signalling from the network node 14, and/or pseudo-random number that may be time dependent (for the example above, it is 0 or 1),
N.sub.PRB is the number of PRBs in the configured sPDCCH PRB set (for the example above, it is 18),
N.sub.sREG/sCCE is the number of sREG per sCCE (described above in each case), and
N.sub.sREG/PRB is the number of sREG assigned per PRB. This means that for fractioned PRB sREG, it is equal to 1 in Case 1 and for the other cases it is equal to 2. For PRB based sREG, it is always equal to 1.

(74) The above formula indicates the PRB number (location within the PRB set) of each sREG that builds up a sCCE by evenly distributing them over all available N.sub.sREG/PRB*N.sub.PRB sREG in the configured N.sub.PRB PRBs. In certain cases, a rougher granularity for the distribution and distribution of the sREGs over a sCCE evenly over the configured N.sub.PRB PRBs may be used. In this case, the equation becomes as follows.

(75) $Y+\left[\frac{m*N_{\mathrm{PRB}}}{N_{\mathrm{sREG}/\mathrm{sCCE}}}\right],m=0,\mathrm{.Math.},N_{\mathrm{sREG}/\mathrm{sCCE}}-1$
Note that the above equations assume that the network node 14 configures a sufficient number of PRBs to achieve a PRB-based frequency distribution. Likewise, this distribution scheme can be given directly by the network node 14 providing a sequence of PRBs or a sequence of groups of PRB.

(76) In one embodiment, the localized cases are defined and depicted in FIG. 19, wherein differently shaded regions represent different sCCEs. As depicted in FIG. 10, options 1a and 1b correspond to 1 OFDM symbol sPDCCH. FIG. 19 shows a 1-OFDM symbol sPDCCH localized scheme. For the localized scheme, the sREGs building the same sCCE are localized in the frequency domain, i.e., in consecutive PRBs, to allow for a sPDCCH resource allocation confined in a limited frequency band. This applies for PRB based sREG as well as fractioned PRB based sREG. The PRB index shown in FIG. 19 represents the number of the sREG group within the sPDCCH PRB set (for this example, a set of 18 PRBs). For simplicity, the physical PRB number is not shown.

(77) As an example and in one embodiment, the localized scheme cases (i.e., 1L, 2L and 3L in FIG. 19) for 1 OFDM symbol sPDCCH can be achieved by the following algorithm:

(78) Determine the number of sREGs, n_tot, needed to reach the number of REs, nr, for the given aggregation level

(79) Initialize the set of sREG to use, S={ }

(80) Initialize the frequency index to the frequency of the starting sREG, k=k0

(81) While n<n_tot

(82) For 1=1 to nr of OFDM symbol available for the sPDCCH

(83) Add sREG to S (in time domain until the nr of OFDM symbol available for sPDCCH is reached)

(84) n=n+1

(85) End For

(86) k=k+1 (go to the immediately following sREG in frequency domain relying on sREG definition)

(87) end While

(88) Note that the above algorithm assumes that n_tot is a multiple of the number of OFDM symbols available for the sPDCCH. A 2 OFDM symbol sPDCCH configuration is an extension of the 1 OFDM symbol sPDCCH configuration described above, for both distributed and localized schemes.

(89) As depicted in FIG. 10, options 2a and 2b correspond to 2 OFDM symbol sPDCCH. Based on this, and as a further embodiment, the distributed cases are defined and depicted in FIG. 20, which shows a 2-OFDM sPDCCH distributed scheme for a set of 19 PRBs. These cases comprise an aggregation level of up to 8 (i.e., up to 8 sCCE per sPDCCH) and a regular distribution in the frequency domain. This embodiment further assumes that the unused PRBs shown in FIG. 20 can be further assigned for building other sCCE for other wireless devices 16 following the description below as well as the possibility to be used for sPDSCH allocation. For simplicity, the physical PRB number is not shown.

(90) The aggregation level (AL) 1 (i.e. 1 sCCE=36 REs) comprises three cases which can be built up based on fractioned PRB sREG, as depicted in FIG. 20:

(91) Case 7 (AL 1): Fractioned PRB based sREG, i.e. sREG=6 REs. Thereby, the sCCE is composed of 6 sREG moderately distributed in frequency domain. For that, 2 PRBs are used.

(92) Case 8 (AL 1): Fractioned PRB based sREG. Thereby, the sCCE is composed of 6 sREG highly and regularly distributed in frequency domain. For that, 6 PRBs are used with one sREG per PRB while varying the OFDM symbol position. Thus, high frequency and time diversity are achieved. This case further includes an offset to be signaled or computed to start using sREG 2 instead of sREG 0 (or sREG group 1 or 3). This allows efficient PRB utilization by sharing the PRB resources between (up to) four users.
Case 9 (AL 1): Fractioned PRB based sREG. Thereby, the sCCE is composed of 6 fractioned PRB based sREG moderately and regularly distributed in the frequency domain, i.e. over 3 PRBs. Thus, frequency diversity is still provided. The sREG are paired in the time domain to use all OFDM symbols in the same PRB. This case further includes an offset to be signaled or computed to start using the sREG pair {1, 3} instead of sREG pair {0, 2}. This allows efficient PRB utilization by sharing the PRB resources between (up to) two users.

(93) As depicted in FIG. 20, each differently shaded region represents a different sCCE:

(94) Case 10 (AL 2): An extension of Case 8 by including the time domain adjacent fractioned PRB based sREG, i.e., a sREG pair in the time domain per PRB. Alternatively, this case can be built as a Case 9 extension by making a regular distribution of sREG pairs over 6 PRBs. Thereby, the sCCE is composed of sREG pairs highly and regularly distributed in the frequency domain, providing high frequency diversity. This case further comprises an offset to be signaled or computed to start using the sREG pair {1, 3} instead of sREG pair {0, 2}. This allows efficient PRB utilization by sharing the PRB resources between (up to) two users.

(95) Case 11 (AL 2): An extension of Case 9 with full PRB utilization, i.e., including sREG pairs {0, 2} and {1, 3} from each assigned PRB. Likewise, this case can be based on PRB based sREG. Thereby, the sCCE is composed of either 6 PRB based sREG (2 sREG per PRB) or 12 fractioned PRB based sREG (4 sREG per PRB) moderately and regularly distributed in the frequency domain, i.e. over 3 PRBs. In some aspects, both 6 full-PRBs or 12 half-PRBs will provide a same or corresponding result.

(96) Case 12 (AL 4): An extension of Case 11 including the consecutive PRB from each PRB used in Case 11.

(97) Case 13 (AL 4): An extension of Case 10 with full PRB utilization from each assigned PRB. Likewise, it can be based on PRB based sREG. Thereby, the sCCE is composed of either 12 PRB based sREG or 24 fractioned PRB based sREG highly and regularly distributed in the frequency domain, i.e. over 6 PRBs.

(98) Case 14 (AL 8): An extension of Case 13 including the consecutive PRB from each PRB used in Case 13.

(99) Case 15 (AL 8): An extension of Case 12 including the consecutive PRB from each PRB used in Case 12 as well as the last 3 PRBs within the PRB set.

(100) In one embodiment, the localized cases of FIG. 10, options 2a and 2b are defined and depicted in FIG. 21, which shows a 2-OFDM symbol sPDCCH localized scheme. For the localized scheme, the sREGs building the same sCCE are localized in the frequency domain, i.e., in consecutive PRBs, to allow for a sPDCCH resource allocation confined in a limited frequency band. This applies for PRB based sREG as well as fractioned PRB based sREG. The PRB index shown in FIG. 21 represents the number of the sREG group within the sPDCCH PRB set (for this example, a set of 18 PRBs). For simplicity, the physical PRB number is not shown.

(101) As a further embodiment, a sCCE can be defined to be composed ideally of 48 REs instead of 36 REs. Therefore, for 2 OFDM symbol sPDCCH, a sCCE is composed of either 2 PRB based sREG, i.e., 1 sREG=1 PRB=48 REs, or 8 fractioned PRB based sREG, i.e., 1 sREG=6 REs (4 sREG per PRB). Thus, a full PRB is utilized for the same user. Besides, an aggregation level of 3 sCCE can be further considered. These cases are depicted in FIG. 22 which shows an additional 2-OFDM symbol sPDCCH distributed scheme for a set of 18 PRB s.

(102) These cases comprise a regular distribution in the frequency domain. One embodiment further provides that the unused PRBs shown in FIG. 22 can be further assigned for building other sCCE for other wireless devices 16 as well as the possibility to be used for sPDSCH allocation. The PRB index shown in FIG. 22 represents the number within the sPDCCH PRB set (for this example, a set of 18 PRBs). For simplicity, the physical PRB number is not shown.

(103) In some cases, one subframe cannot be divided into short TTIs each of length 2 symbols. Then, the subframe may be chosen such that one or more of the TTIs are in fact of length 3. In one embodiment, the third symbol will have sREGs with index 4 and 5, extending case 2b of FIG. 10. In another embodiment, the same number of sREGs are used, and the third symbol will have sREG with index 2 or 3, identical to the second symbol in case 2b of FIG. 10, and the sREG with index 2 and three will then consist of double number of REs

(104) In summary, a flexible mapping for sPDCCH to the resource elements (REs) is proposed. The mapping has various modes, each enabling exploitation of the channel or the advanced transmission modes. In one mode, large frequency diversity is achieved. In another mode condensed frequency allocation for a beamforming based transmission mode is enabled. The proposed mapping also can be extended to various number of OFDM symbols. With the proposed mapping, users with transmission modes relying on different reference signals, e.g. CRS and DMRS users, can coexist on the same sTTI.

(105) Thus, according to one aspect, a method in network node 14 for mapping a short physical downlink control channel (sPDCCH) to resource elements of a time-frequency grid is provided. The method includes determining available time-frequency resources to be configured as short resource element groups (sREGs) (S100). The method also includes configuring sREGs within a physical resource block (PRB), to map the sPDCCH to the resource elements, each sREG spanning one OFDM symbol (S102). In any aspect, the spanning of one OFDM symbol refers to a time domain, e.g. the sREG is on a length of time of only one symbol. In any aspect, the sREG being within a PRB may refer to the sREG in the frequency domain, e.g. having a frequency extent or number of subcarriers which is one PRB.

(106) According to this aspect, in some embodiments, an sREG consists of 1 PRB within 1 OFDM symbol including REs for at least one of cell-specific reference signal (CRS), and demodulation reference signals (DMRS) applied to DMRS-based sPDCCH. In some embodiments, an sREG consists of 1 PRB within 1 OFDM symbol including REs for at least one of CRS, and DMRS, applied to CRS-based sPDCCH. In some embodiments, the sREGs are configured to be one of localized in a frequency domain (to facilitate beam forming) and distributed in the frequency domain (to achieve frequency diversity gain). In some embodiments, the method further includes configuring a wireless device 16 by radio resource control (RRC) signaling to use a CRS, based sPDCCH resource block set with one of distributed or localized mapping of short control channel elements (sCCE), to sREGs. In some embodiments, the method further includes configuring a wireless device 16 by RRC signaling to use a DMRS based sPDCCH resource block set with one of distributed or localized mapping of sCCE to sREGs. In some embodiments, the method further includes configuring an sPDCCH PRB set with at least a set of PRBs and one of localized and distributed sCCE to sREG mapping. In some embodiments, 1 OFDM symbol sPDCCH is defined for CRS based transmissions. In some embodiments, for CRS based sPDCCH, with 2 or 3 sPDCCH symbol short transmission time intervals (sTTI), a number of OFDM symbols per RB set is one of 1 and 2. In some embodiments, for CRS based sPDCCH, with 1 slot (sTTI), a number of OFDM symbols per RB set is one of 1 and 2. In some embodiments, a 2 OFDM symbol sPDCCH is defined for DMRS-based transmissions. In some embodiments, for DMRS based sPDCCH, with 2 sPDCCH symbol sTTI, a number of OFDM symbols per RB set is 2. In some embodiments, for DMRS based sPDCCH, with 3 symbol sTTIs, a number of OFDM symbols per RB set is 3. In some embodiments, for DMRS based sPDCCH, with 1 slot sTTIs, a number of OFDM symbols per RB set is 2.

(107) According to another aspect, a network node 14 for mapping a short physical downlink control channel, sPDCCH, to resource elements of a time-frequency grid is provided. The network node 14 includes processing circuitry 22 configured to determine available time-frequency resources to be configured as short resource element groups, sREGs. The processing circuitry 22 is further configured to configure sREGs within a physical resource block, PRB, to map the sPDCCH to the resource elements, each sREG spanning one OFDM symbol.

(108) In some embodiments, an sREG consists of 1 PRB within 1 OFDM symbol including REs for at least one of CRS and DMRS applied to DMRS-based sPDCCH. In some embodiments, an sREG consists of 1 PRB within 1 OFDM symbol including REs for at least one of CRS and DMRS applied to CRS-based sPDCCH. In some embodiments, the sREGs are configured to be one of localized in a frequency domain and distributed in the frequency domain. In some embodiments, the processing circuitry 22 is further configured to configure a wireless device 16 by RRC signaling to use a CRS based sPDCCH resource block set with one of distributed or localized mapping of short control channel elements (sCCE) to sREGs. In some embodiments, the processing circuitry 22 is further configured to configure a wireless device 16 by RRC signaling to use a DMRS based sPDCCH resource block set with one of distributed or localized mapping of sCCE to sREGs. In some aspects, the distributed/localized mapping is of a plurality of sREGS (each being 1 PRB in frequency) to a sCCE. In some embodiments, the processing circuitry 22 is further configured to configure an sPDCCH PRB set with at least a set of PRBs, and one of localized and distributed sCCE to sREG mapping. In some embodiments, 1 OFDM symbol sPDCCH is defined for CRS based transmissions. In some embodiments, for CRS based sPDCCH, with 2 or 3 sPDCCH symbol sTTI, a number of OFDM symbols per RB set is one of 1 and 2. In some embodiments, for CRS based sPDCCH, with 1 slot sTTI, a number of OFDM symbols per RB set is one of 1 and 2. In some embodiments, a 2 OFDM symbol sPDCCH is defined for DMRS-based transmissions. In some embodiments, for DMRS-based sPDCCH, with 2 sPDCCH symbol sTTI, a number of OFDM symbols per RB set is 2. In some embodiments, for DMRS-based sPDCCH, with 3 symbol sTTI, a number of OFDM symbols per RB set is 3. In some embodiments, for DMRS-based sPDCCH, with 1 slot sTTI, a number of OFDM symbols per RB set is 2.

(109) According to another aspect, a network node 14 for mapping a short physical downlink control channel (sPDCCH), to resource elements of a time-frequency grid to achieve one of high frequency diversity and condensed frequency allocation. The network node 14 includes a memory module 45 configured to store a mapping of the sPDCCH to resource elements of a time-frequency grid. The network node 14 further includes a short resource element group (sREG) configuration module 19 configured to configure sREGs within a physical resource block, PRB, to map the sPDCCH to the resource elements, each sREG spanning one OFDM symbol.

(110) According to yet another aspect, a method in a wireless device 16 for receiving information on a short physical downlink control channel (sPDCCH) signaled by a network node 14, the sPDCCH being mapped to resource elements of a time-frequency grid, by configuring short resource element groups (sREGs) is provided. The method includes receiving the sPDCCH from the network node 14 on one of a plurality of sets of PRBs S106.

(111) According to this aspect, in some embodiments, the sPDCCH is of 2 OFDM symbols. In some embodiments, the method further includes receiving an indication of a sequential order of PRBs from the network node 14.

(112) According to another aspect, a wireless device 16 for receiving information on a short physical downlink control channel (sPDCCH) signaled by a network node 14, the sPDCCH being mapped to resource elements of a time-frequency grid, by configuring short resource element groups (sREGs) is provided. The wireless device 16 includes a transceiver 48 configured to receive the sPDCCH from the network node 14 on one of a plurality of sets of PRBs.

(113) According to this aspect, in some embodiments, the sPDCCH is of 2 OFDM symbols. In some embodiments, the transceiver 48 is further configured to receive an indication of a sequential order of PRBs from the network node 14.

(114) According to yet another aspect, a wireless device 16 for receiving information on a short physical downlink control channel (sPDCCH), signaled by a network node 14, the sPDCCH being mapped to resource elements of a time-frequency grid, by configuring short resource element groups (sREGs) is provided. The wireless device 16 includes a transceiver module 49 configured to receive the sPDCCH from the network node 14 on one of a plurality of sets of PRBs.

(115) Some embodiments include:

Embodiment 1

(116) A method in network node for mapping a short physical downlink control channel, sPDCCH, to resource elements of a time-frequency grid to achieve one of high frequency diversity and condensed frequency allocation, the method comprising:

(117) determining available time-frequency resources to be configured as short resource element groups, sREGs; and

(118) configuring sREGs within a physical resource block, PRB, to map the sPDDCH to the resource elements, the number of sREGs depending upon a number of orthogonal frequency division multiplex, OFDM, symbols of the sPDCCH, each sREG spanning one OFDM symbol.

Embodiment 2

(119) The method of Embodiment 1, wherein the sREGs are configured to be one of localized in a frequency domain to facilitate beam forming and distributed in the frequency domain to achieve frequency diversity gain.

Embodiment 3

(120) The method of Embodiment 1, wherein 1 OFDM symbol sPDCCH is defined for cell-specific reference symbol, CRS, based transmissions and at least two OFDM symbol sPDCCH is defined for short transmission time interval, sTTI, operation.

Embodiment 4

(121) The method of Embodiment 1, wherein a 2 OFDM symbol sPDCCH is defined for demodulation reference symbols, DMRS-based transmissions.

Embodiment 5

(122) A network node for mapping a short physical downlink control channel, sPDCCH, to resource elements of a time-frequency grid to achieve one of high frequency diversity and condensed frequency allocation, the network node comprising:

(123) processing circuitry including a memory and a processor: the memory configured to store a mapping of the sPDCCH to resource elements of a time-frequency grid; and the processor configured to configure short resource element groups, sREGs, within a physical resource block, PRB, to map the sPDDCH to the resource elements, the number of sREGs depending upon a number of orthogonal frequency division multiplex, OFDM, symbols of the sPDCCH, each sREG spanning one OFDM symbol.

Embodiment 6

(124) The network node of Embodiment 5, wherein the sREGs are configured to be one of localized in a frequency domain to facilitate beam forming and distributed in the frequency domain to achieve frequency diversity gain.

Embodiment 7

(125) The network node of Embodiment 5, wherein 1 OFDM symbol sPDCCH is defined for cell-specific reference symbol, CRS, based transmissions and at least two OFDM symbol sPDCCH is defined for short transmission time interval, sTTI, operation.

Embodiment 8

(126) The network node of Embodiment 5, wherein a 2 OFDM symbol sPDCCH is defined for demodulation reference symbols, DMRS-based transmissions.

Embodiment 9

(127) A network node for mapping a short physical downlink control channel, sPDCCH, to resource elements of a time-frequency grid to achieve one of high frequency diversity and condensed frequency allocation, the network node comprising:

(128) a memory module configured to store a mapping of the sPDCCH to resource elements of a time-frequency grid; and

(129) a short resource element group (sREG) configuration module configured to configure short resource element groups, sREGs, within a physical resource block, PRB, to map the sPDDCH to the resource elements, the number of sREGs depending upon a number of orthogonal frequency division multiplex, OFDM, symbols of the sPDCCH, each sREG spanning one OFDM symbol.

Embodiment 10

(130) A method in a wireless device for obtaining a short physical downlink control channel, sPDCCH, signaled by a network node, the sPDCCh being mapped to resource elements of a time-frequency grid, by configuring short resource element groups, sREGs, the method comprising:

(131) receiving signaling from the network node, the signaling including a sPDCCH; and

(132) decoding the signaling to obtain the sPDDCH.

Embodiment 11

(133) A wireless device for obtaining a short physical downlink control channel, sPDCCH, signaled by a network node, the sPDCCh being mapped to resource elements of a time-frequency grid, by configuring short resource element groups, sREGs, the wireless device comprising:

(134) a transceiver configured to receive signaling from the network node;

(135) processing circuitry including a memory and a processor;

(136) the memory configured to store the sPDCCH; and

(137) the processor configured to decode the signaling to obtain the sPDCCH.

Embodiment 12

(138) A wireless device for obtaining a short physical downlink control channel, sPDCCH, signaled by a network node, the sPDCCh being mapped to resource elements of a time-frequency grid, by configuring short resource element groups, sREGs, the wireless device comprising:

(139) a transceiver module configured to receive signaling from the network node;

(140) a memory module configured to store the sPDCCH; and

(141) a decoder configured to decode the signaling to obtain the sPDCCH.

(142) As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, and/or computer program product. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

(143) Some embodiments are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby provide a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

(144) These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

(145) The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

(146) It is to be understood that the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

(147) Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the “C” programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

(148) Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments can be combined in any way and/or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

(149) It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.