Narrowband control channel decoding

Methods, systems, and devices for wireless communication are described. A user equipment (UE) may establish a connection with another wireless node, such as a base station or another UE. The connection may include a narrowband control region of a wideband system. The UE may identify a set of resources, which may include a set of subframes that have the same precoding or a set of resource blocks that have the same precoding, during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel within the narrowband. The UE may then decode the control channel using the DM-RS or a cell-specific reference signal (CRS), or both DM-RS and CRS. The UE may exclude resources of the narrowband region that include a control region for broadband communications.

BACKGROUND

Field of Disclosure

The following relates generally to wireless communication and more specifically to narrowband control channel decoding.

Description of Related Art

By way of example, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UEs). A base station may communicate with the communication devices on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).

In some cases, certain UEs may have limited operating capabilities. For example, device UE may not be designed for broadband communications. This may interfere with the ability of the UE to receive certain control information from a base station.

SUMMARY

Systems, methods, and apparatuses for a narrowband control channel decoding are described. A user equipment (UE) may establish a connection with another wireless node, such as a base station or UE. The connection may include a narrowband control region of a wideband system. The UE may identify a set of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel. The identified subframes or resource blocks may, for example, have the same precoding. The UE may decode the control channel (e.g., a physical downlink control channel (PDCCH)) using the DM-RS. In some examples, the UE may additionally or alternatively decode the control channel using a cell-specific reference signal (CRS). The UE may, in some examples, determine—e.g., via signaling received from another node—resources to exclude from the control channel. For instance, the UE may determine that the narrowband region includes a portion of control region for broadband communication, and the UE may exclude those resources.

A method of wireless communication is described. The method may include identifying a plurality of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, wherein the control channel comprises a narrowband region of a wideband system, and wherein the plurality of subframes have a same precoding for the DM-RS and decoding the control channel based at least in part on the DM-RS.

An apparatus for wireless communication is described. The apparatus may include means for identifying a plurality of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, wherein the control channel comprises a narrowband region of a wideband system, and wherein the plurality of subframes have a same precoding for the DM-RS and means for decoding the control channel based at least in part on the DM-RS.

A further apparatus is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be operable, when executed by the processor, to cause the apparatus to identify a plurality of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, wherein the control channel comprises a narrowband region of a wideband system, and wherein the plurality of subframes have a same precoding for the DM-RS and decode the control channel based at least in part on the DM-RS.

A non-transitory computer readable medium for wireless communication is described. The non-transitory computer-readable medium may store code for wireless communication, and the code may include instructions executable to identify a plurality of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, where the control channel comprises a narrowband region of a wideband system, and where the plurality of subframes have a same precoding for the DM-RS and decode the control channel based at least in part on the DM-RS.

Some examples of the method, apparatus, or non-transitory computer-readable medium described above may further include processes, features, means, or instructions for identifying two or more resource blocks (RBs) that have the same precoding within the narrowband region.

Some examples of the method, apparatus, or non-transitory computer-readable medium described above may further include processes, features, means, or instructions for excluding resources of the narrowband region that comprise a control region for broadband communications from the control channel.

Some examples of the method, apparatus, or non-transitory computer-readable medium described above may further include processes, features, means, or instructions for receiving a message indicating the resources of the narrowband region that comprise the control region for broadband communications. Some examples of the method, apparatus, or non-transitory computer-readable medium described above may further include processes, features, means, or instructions for determining the resources of the narrowband region that comprise the control region for the broadband communications based at least in part on the message.

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, the control channel comprises a control channel element (CCE) that comprises a set of resource element groups (REGs).

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, each REG of the set of REGs is distributed in time and frequency during the plurality of subframes within the narrowband region.

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, each REG of the set of REGs excludes resource elements that comprise DM-RS.

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, each REG of the set of REGs excludes resource elements that comprise a cell-specific reference signal (CRS).

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, a single precoder is applied for each physical resource block pair of the control channel.

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, two or more precoders are applied to resources with each physical resource block pair of the control channel.

In some examples of the method, apparatus, or non-transitory computer-readable medium described above, the control channel is decoded based at least in part on a cell-specific reference signal (CRS).

DETAILED DESCRIPTION

A user equipment (UE) may establish a connection with another wireless node, such as a base station or UE. The connection may include a narrowband control region of a wideband system, and the UE may decode a control channel received in the narrowband control region using demodulation reference signals (DM-RS) or cell-specific reference signals (CRS), or both, as described herein. Some of the example wireless systems described herein provide for automated communication known as Machine-to-Machine (M2M) communication or Machine Type Communication (MTC). M2M or MTC may refer to technologies or devices, such as UEs that communicate without human intervention. In some cases, UEs may operate according to certain constraints (e.g., narrowband operation) even though the UEs may be capable of more complex operation. While some devices, such as MTC devices, may have limited capabilities and may operate accordingly.

By way of example, while some devices (e.g., UEs or MTC devices) may have broadband capacity, other devices may be limited to narrowband communications. This narrowband limitation may, for example, interfere with the ability of a device to receive control channel information using the full bandwidth served by a base station. In some wireless communication systems, such as Long Term Evolution (LTE), an MTC device having limited bandwidth capability (or another device with similar capabilities) may be referred to as a category 0 device.

In some cases, MTC devices may have reduced peak data rates (e.g., a maximum transport block size may be 1000 bits). Additionally, an MTC device may have rank1transmission and one antenna for receiving. This may limit an MTC device to half-duplex communication (i.e., the device may not be capable of simultaneously transmitting and receiving). If an MTC device is half-duplex, it may have relaxed switching time (e.g., from transmission (Tx) to reception (Rx) or vice versa). For example, a nominal switching time for a non-MTC device may be 20 μs while a switching time for an MTC device may be 1 ms. MTC enhancements (eMTC) in a wireless system may allow narrowband MTC devices to effectively operate within wider system bandwidth operations (e.g., 1.4/3/5/10/15/20 MHz). For example, an MTC device may support 1.4 MHz bandwidth (i.e., 6 resources blocks). In some instances, coverage enhancements of such MTC devices may be achieved by power boosting of (e.g., of up to 15 dB).

According to the present disclosure, a UE, which may be an MTC device or another UE that supports narrowband operation, may establish a connection with another wireless node using a narrowband control region of a wideband system. The UE may identify a set of resources for a narrowband or MTC physical DL control channel (mPDCCH) within the narrowband control region based on a resource element indexing configuration associated with a cell-specific reference signal (CRS) based demodulation scheme. The UE may then receive the mPDCCH using the identified resources and demodulate the mPDCCH based on the CRS demodulation scheme. In some examples, the resource element indexing configuration may exclude the resource elements used for CRS. In some examples, the resource element indexing configuration may exclude the resource elements used for demodulation reference signals (DM-RS). In some examples, DM-RS resource elements may be indexed separately.

In some cases, a UE or a base station may determine which indexing configuration to use based on coverage and traffic consideration. For example, a UE without coverage enhancement needs may employ an alternative in which only CRS based modulation is used. On the other hand, a UE with coverage enhancement needs may use an alternative in which demodulation is based on both CRS and DM-RS.

The following description provides examples, and is not limiting of the scope, applicability, or examples set forth in the claims. Much of the following discussion describes examples related to MTC devices, but the description is not limited to such devices. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in other examples.

FIG. 1illustrates an example of a wireless communications system100in accordance with various aspects of the present disclosure. The system100includes base stations105, at least one UE115, and a core network130. The core network130may provide user authentication, access authorization, tracking, internet protocol (IP) connectivity, and other access, routing, or mobility functions. The base stations105interface with the core network130through backhaul links132(e.g., S1, etc.). The base stations105may perform radio configuration and scheduling for communication with the UEs115, or may operate under the control of a base station controller (not shown). In various examples, the base stations105may communicate, either directly or indirectly (e.g., through core network130), with one another over backhaul links134(e.g., X1, etc.), which may be wired or wireless communication links.

In some examples, the wireless communications system100is an LTE/LTE-Advanced (LTE-A) network. In LTE/LTE-A networks, the term evolved node B (eNB) may be generally used to describe the base stations105, while the term UE may be generally used to describe the UEs115, which may include MTC devices. The wireless communications system100may be a heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB or base station105may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” is a 3GPP term that can be used to describe a base station, a carrier, or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs115with service subscriptions with the network provider. A small cell is a lower-powered base station, as compared with a macro cell, that may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs115with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs115having an association with the femto cell (e.g., UEs115in a closed subscriber group (CSG), UEs115for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers).

The communication networks that may accommodate some of the various disclosed examples may be packet-based networks that operate according to a layered protocol stack and data in the user plane may be based on the IP. A radio link control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A medium access control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARM) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE115and the base stations105. The RRC protocol layer may also be used for core network130support of radio bearers for the user plane data. At the physical (PHY) layer, the transport channels may be mapped to physical channels.

As mentioned above, some types of wireless devices may provide for automated communication. Automated wireless devices may include those implementing Machine-to-Machine (M2M) communication or Machine Type Communication (MTC), which may allow devices to communicate with one another or a base station without human intervention. For example, M2M or MTC may refer to communications from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs115may be MTC devices, such as those designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging. An MTC device may operate using half-duplex (one-way) communications at a reduced peak rate. MTC devices may also be configured to enter a power saving “deep sleep” mode when not engaging in active communications. In some examples, the UEs115are category 0 UEs (e.g., narrowband MTC devices).

The communication links125shown in wireless communications system100may include uplink (UL) transmissions from a UE115to a base station105, or downlink (DL) transmissions, from a base station105to a UE115. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each communication link125may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies described above. Each modulated signal may be sent on a different sub-carrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, etc. As discussed below, the communication links125may include a narrowband control region. In some examples, a PDCCH (e.g., mPDCCH) may be transmitted on resources of the narrowband control region utilizing a certain resource element indexing configuration. The communication links125may transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources). Frame structures may be defined for FDD (e.g., frame structure type 1) and TDD (e.g., frame structure type 2).

A base station105may insert periodic pilot symbols such as CRS to improve the efficiency of wireless communication links125(e.g., to aid UEs115in channel estimation and coherent demodulation). Control channels, such as a PDCCH, may be demodulated based on CRS—e.g., according to a CRS-based demodulation scheme. CRS may include one of 504 different cell identities. They may be modulated using quadrature phase shift keying (QPSK) and power boosted (e.g., transmitted at 6 dB higher than the surrounding data elements) to make them resilient to noise and interference. CRS may be embedded in 4 to 24 resource elements in each resource block based on the number of antenna ports or layers (up to 4) of the receiving UEs115. In addition to CRS, which may be utilized by all UEs115in the coverage area110of the base station105, demodulation reference signal (DM-RS), which may also be referred to as UE-specific reference signals, may be directed toward specific UEs115and may be transmitted only on resource blocks assigned to those UEs115. DM-RS may include signals on 24 resource elements in each resource block in which they are transmitted. In some cases, two sets of DM-RS may be transmitted in adjoining resource elements. In some cases, additional reference signals known as channel state information reference signals (CSI-RS) may be included to aid in generating channel state information (CSI). On the uplink, a UE115may transmit a combination of periodic sounding reference signal (SRS) and uplink DM-RS for link adaptation and demodulation, respectively.

Wireless communication links125may also be established between UEs115in a configuration known as device-to-device (D2D) communications. One or more of a group of UEs115utilizing D2D communications may be within the coverage area110of a cell. Other UEs115in such a group may be outside the coverage area110of a cell, or otherwise unable to receive transmissions from a base station105. In some cases, groups of UEs115communicating via D2D communications may utilize a one-to-many (1:M) system in which each UE115transmits to every other UE115in the group. In some cases, a base station105facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out independent of a base station105. A device within a D2D implementation may be referred to as a node.

In some embodiments of the system100, base stations105or UEs115may include multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stations105and UEs115. Additionally or alternatively, base stations105or UEs115may employ multiple input multiple output (MIMO) techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data.

LTE systems may utilize orthogonal frequency division multiple access (OFDMA) on the DL and single carrier frequency division multiple access (SC-FDMA) on the UL. OFDMA and SC-FDMA partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones or bins. Each subcarrier may be modulated with data. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, K may be equal to 72, 180, 300, 600, 900, or 1200 with a subcarrier spacing of 15 kilohertz (KHz) for a corresponding system bandwidth (with guard band) of 1.4, 3, 5, 10, 15, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into sub-bands. For example, a sub-band may cover 1.08 MHz, and there may be 1, 2, 4, 8, or 16 sub-bands.

A frame structure may also be used to organize physical resources. Time intervals may be expressed in multiples of a basic time unit (e.g., the sampling period, Ts=1/30,720,000 seconds). Time resources may be organized according to radio frames of length of 10 ms (Tf=307200·Ts), which may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include ten 1 ms subframes numbered from 0 to 9. A subframe may be further divided into two 0.5 ms slots, each of which contains 6 or 7 modulation symbol periods (depending on the length of the cyclic prefix prepended to each symbol). Excluding the cyclic prefix, each symbol contains 2048 sample periods. In some cases, the subframe may be the smallest scheduling unit, also known as a transmission time interval (TTI). In other cases, a TTI may be shorter than a subframe or may be dynamically selected (e.g., in short TTI bursts or in selected component carriers using short TTIs).

A resource element (RE) may consist of one symbol period and one subcarrier (a 15 Khz frequency range). A resource block (RB) may contain 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain (1 slot), or 84 resource elements. Some REs may include DL reference signals (DL-RS). The DL-RS may include a CRS and a UE-specific RS (UE-RS) or demodulation reference signals (DM-RS). In some cases, reference signals may be transmitted on the resource blocks associated with PDSCH. The number of bits carried by each RE may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period). Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be for the UE.

Data may be divided into logical channels, transport channels, and physical layer channels. Channels may also be classified into Control Channels and Traffic Channels. DL physical channels may include physical broadcast channel (PBCH) for broadcast information, physical control format indicator channel (PCFICH) for control format information, PDCCH for control and scheduling information, physical HARQ indicator channel (PHICH) for HARQ status messages, physical downlink shared channel (PDSCH) for user data and physical multicast channel (PMCH) for multicast data. UL physical channels may include physical random access channel (PRACH) for access messages, physical uplink control channel (PUCCH) for control data, and physical uplink shared channel (PUSCH) for user data.

PDCCH carries downlink control information (DCI) in control channel elements (CCEs), which may consist of nine logically contiguous resource element groups (REGs) located in the first few symbols of a resource block, where each REG contains 4 REs. In other examples, according to the present disclosure, a CCE (e.g., a CCE designed for MTC or narrowband communications) may include 4 non-contiguous REGs that contain 9 or more REs. MTC devices or other UEs115may use an evolved physical downlink control channel (ePDCCH) based on DM-RS or MTC PDCCH (mPDCCH) based on CRS, both of which may facilitate coordinated multi-point (CoMP), DL multiple-input-multiple-output (MIMO) enhancements, and inter-cell interference coordination (ICIC) or further enhanced ICIC. For example, instead of spanning the first few symbols in a subframe, like PDCCH, an ePDCCH or mPDCCH may span an entire subframe using selected subcarriers (e.g., it may be frequency-division multiplexed (FDM)). In some cases DM-RS based ePDCCH may be supported and in other cases CRS based PDCCH or mPDCCH may be supported. Thus, the ePDCCH or mPDCCH may be UE-specifically configured (e.g., each UE may be configured to monitor a different set of resources). In some cases, there may be two modes for ePDCCH or mPDCCH operation: localized ePDCCH and distributed ePDCCH. In a localized mode, a single precoder may be applied for each physical resource block (PRB) pair, such as of a control channel. In distributed mode, two or more precoders may be applied to, or may cycle through, the allocated resources within each PRB pair, such as of a control channel.

The DCI included in a PDCCH, ePDCCH, or mPDCCH may include information regarding DL scheduling assignments, UL resource grants, transmission scheme, UL power control, HARQ information, modulation and coding scheme (MCS) and other information. The size and format of the DCI messages can differ depending on the type and amount of information that is carried by the DCI. For example, if spatial multiplexing is supported, the size of the DCI message may be large compared to contiguous frequency allocations. Similarly, for a system that employs MIMO, the DCI may include additional signaling information. DCI size and format may also depend on the amount of information, as well as factors such as bandwidth, the number of antenna ports, and duplexing mode.

PDCCH can carry DCI messages associated with multiple users, and each UE115may decode the DCI messages that are intended for it. For example, each UE115may be assigned a cell radio network temporary identity (C-RNTI) and cyclic redundancy check (CRC) bits attached to each DCI may be scrambled based on the C-RNTI. To reduce power consumption and overhead at the user equipment, a limited set of CCE locations can be specified for DCI associated with a specific UE115. CCEs may be grouped (e.g., in groups of 1, 2, 4 and 8 CCEs), and a set of CCE locations in which the user equipment may find relevant DCI may be specified. These CCEs may be known as a search space. The search space can be partitioned into two regions: a common CCE region or search space and a UE-specific (dedicated) CCE region or search space. The common CCE region may be monitored by all UEs served by a base station105and may include information such as paging information, system information, random access procedures, and the like. The UE-specific search space may include user-specific control information. In some cases, CCEs may be indexed, and the common search space may start from CCE 0. The starting index for a UE specific search space may depend on the C-RNTI, the subframe index, the CCE aggregation level and a random seed. A UE115may attempt to decode DCI by performing a process known as a blind decode, during which search spaces are randomly decoded until the DCI is detected. During a blind decode, the UE115may attempt descramble all potential DCI messages using its C-RNTI, and perform a CRC check to determine whether the attempt was successful.

According to the present disclosure, a UE115, such as an MTC device, may establish a connection with another wireless node, such as a base station105or another UE. The connection may include a narrowband control region. The UE115may identify a set of resources for an mPDCCH within the narrowband control region based on an RE indexing configuration associated with a CRS based demodulation scheme. The UE115may then receive the mPDCCH using the identified resources and demodulate the mPDCCH based on the CRS based demodulation scheme. In some examples, the RE indexing configuration may exclude the REs used for CRS. In some examples, the RE indexing configuration may exclude the REs used for DM-RS. In some examples, DM-RS REs may be indexed separately.

FIG. 2illustrates an example of a wireless communications system200for CRS based control channel element in accordance with various aspects of the present disclosure. Wireless communications system200may include a UE115-a, which may be an example of a UE115described above with reference toFIG. 1. In some examples, UE115-ais an MTC device. Wireless communications system200may also include a base station105-a, which may be an example of a base station105described above with reference toFIG. 1. Base station105-amay transmit control information and data to any UE115within its coverage area110-avia downlink205, as generally described with respect toFIG. 1. For example, downlink205may be a narrowband connection that may not utilize the whole range of frequency tones of the cell. For example, the narrowband region may be selected based on the capabilities of the UE115-a. In some examples of the present disclosure, the actions performed by base station105-amay be performed by another UE115(not shown) according to D2D operations. Base station105-amay thus be referred to as a node; and other nodes, including certain UEs, of a system may perform the same or similar functions as base station105-a.

UE115-amay receive control information via a narrowband control region that may utilize selected frequency tones, and may extend through each symbol period of a subframe. The control information may utilize resources that are identified by an indexing scheme associated with CRS based demodulation. UE115-amay use the CRS (and, in some cases, DM-RS) transmitted by base station105-afor coherent demodulation of data conveyed by downlink205.

Thus, UE115-amay establish a connection with base station105-aincluding downlink205and receive data via downlink205utilizing a narrowband control region. UE115-amay identify a set of resources for a PDCCH (e.g., an mPDCCH designed for use by MTC devices) within the narrowband control region based on an RE indexing configuration associated with a CRS based demodulation scheme. UE115-amay then receive the PDCCH using the identified resources and demodulate the PDCCH based on a CRS. As described below with reference toFIGS. 3A, 3B, and 3C, in some examples the RE indexing configuration may exclude the REs used for CRS. In some examples, the RE indexing configuration may exclude the REs used for DM-RS. In some examples, DM-RS REs may be indexed separately.

FIG. 3Aillustrates an example of an indexing configuration301for CRS based control channel element in accordance with various aspects of the present disclosure. Indexing configuration301may represent aspects of downlink205described above with reference toFIG. 2Indexing configuration301may illustrate a configuration of 14 symbol periods (1 subframe) in the time domain and 12 tones (1 RB) in the frequency domain. Each RE may correspond to the time and frequency resource included in one symbol period on one tone. Indexing configuration301may include indexed control region REs305-aand non-indexed CRS REs310, whose configuration may be based on the number of antennas and layers used in the communication. In some cases the non-indexed REs may correspond to a maximum CRS configuration (i.e., for a maximum number of antenna ports).

The REs of indexing configuration301may be grouped into MTC resource element groups (mREGs) based on the indices. In some case, 9 REs may make up one mREG. A group of 4 mREGs (i.e., 36 REs) may make up an MTC control channel element (mCCE) and one or more mCCEs may contain an mPDCCH (e.g., the number of mCCEs per mPDCCH may depend on an aggregation level parameter of a UE115).

The REs of indexing configuration301may be divided into 16 mREGs, which may be distinguished according to their indices. For example, all of the indexed control region REs305-awith index 0 may correspond to a single mREG. As shown in indexing configuration301, the indexing of the REs may be done in a frequency-first-time-second manner. However, in some schemes the indexing may be done in a time-first-frequency-second manner. Irrespective of the indexing manner, the CRS REs310may be excluded from the indexing. For example, the indexing of REs may start at the RE for tone 1, symbol period 0, instead of starting at the RE element at tone 0, symbol period 0. The indexing may continue in a sequential manner, progressing through the tones and symbol periods while skipping CRS REs310. Although the tones of indexing configuration301are shown as contiguous, in some examples the tones may not be contiguous.

Thus, mPDCCH may be constructed based on mREGs and mCCEs. For example, a normal CP may result in 144 REs for an mREG: 12 tones×14 symbols−24 CRS=144 REs. In some cases, each PRB pair may include 16 mREGs regardless of subframe type, CP type, PRB pair index, subframe index, etc. For example, there may be 9 REs per mREG for normal CP and there may be 8 REs per mREG for extended CP. Due to the presence of other signals, the number of available REs for mPDCCH may not be fixed and may be different for different mREGs in a PRB pair. For example, some indexed control region REs305-amay be occupied by other signals. In some cases, a control channel, such as mPDCCH, may include a CCE, such as a mCCE, which may include a set of REGs, such as mREGs. Each REG of the set of REGs may be distributed in time and frequency, such as during subframes within a narrowband control region. In some cases, each REG of the set of REGs excludes resource elements which include DM-RS. In some cases, each REG of the set of REGs excludes resource elements which include a CRS.

mCCEs may be defined by selecting 4 indices (and thus, 4 mREGs). Accordingly, a first group (Group #0) may include mREGs whose REs are indexed with the numbers 0, 4, 8, and 12. A second group (Group #1) may include mREGs whose REs are indexed with the numbers 1, 5, 9, and 13. A third group (Group #2) may include mREGs whose REs are indexed with the numbers 2, 6, 10, and 14. And the fourth group (Group #3) may include mREGs whose REs are indexed with the numbers 3, 7, 11, and 15.

When an mCCE is formed by 4 mREGs, the mCCE may be formed by a single mREG group. However, in some cases mCCE may be formed by 8 mREGs or two mREG groups (e.g., Group #0 and Group #2 or Group #1 and Group #3). In some cases, the location of mREGs in an mREG group may depend on the mode of mPDCCH, and the detailed mapping may depend on the number of PRB pairs configured for mPDCCH. For localized mPDCCH, mREGs of the same group may come from the same PRB pair. Additionally, for localized mPDCCH, each mCCE may be defined within a PRB pair. For distributed mPDCCH, mREGs of the same group may come from different PRB pairs (i.e., each mCCE may be defined across several PRB pairs). For example, an mCCE may consist of mREG 0 from PRB pair 0, mREG 4 of PRB pair 1, mREG 8 of PRB pair 2, and mREG 12 of PRB pair 3. In some examples, the four PRB pairs may be contiguous, while in other examples the four PRB pair may not be contiguous.

The number of available REs per mCCE for mPDCCH may not be fixed and may be different for different mCCEs. However, mREG grouping-based mCCE definition may help equalize the number of available REs per mCCE (e.g., 2 CRS ports, normal CP, normal subframes).

In some cases, each UE may be configured with up to K=2 mPDCCH resource sets. Each resource set may be separately configured with M=2, 4, or 6 PRB pairs. Additionally, each resource set may be configured with either localized or distributed mode. Regarding the search space for localized mPDCCH, the candidates may be spaced in as many different PRB pairs as possible in order to exploit sub-band scheduling for mPDCCH. The search space for distributed mPDCCH may be similar to PDCCH described above with reference toFIG. 1. In some cases, the REs occupied by other signals known to the UE may be rate-matched around by mPDCCH (e.g., legacy control region, CRS, UE-specifically configured channel state information reference signals (CSI-RS), etc.).

FIG. 3Billustrates an example of an indexing configuration302for narrowband control channel decoding in accordance with various aspects of the present disclosure. Indexing configuration302may represent aspects of downlink205described above with reference toFIG. 2Indexing configuration302may illustrate a configuration of 14 symbol periods (1 subframe) in the time domain the and 12 tones (1 RB) in the frequency domain. Each RE may correspond to the time and frequency resource included in one symbol period on one tone. Indexing configuration302may include indexed control region REs305-band non-indexed DM-RS REs315. In some cases, the number of DM-RS REs315may be based on the cyclic prefix (CP). For example, an mREG may include 24 DM-RS REs for a normal CP and may include 16 DM-RS for extended CP. Indexing configuration302may include aspects of indexing configuration301described with reference toFIG. 3A.

The REs of indexing configuration302may be indexed according to a frequency-first-time-second manner, and may exclude DM-RS REs315. For example, the REs may be indexed in a progressive manner until a DM-RS RE315is encountered. When a DM-RS RE315is encountered, the DM-RS RE315may not be indexed. The indexing of the REs may resume when a non-DM-RS RE is encountered. In some examples, a UE115may use the DM-RS REs315in combination with CRS to determine channel and interference estimation. As described above with reference toFIG. 3A, the REs of indexing configuration302may be grouped into mREGs based on the indices. Thus, 9 REs may make up one mREG. A group of 4 mREGs (i.e., 36 REs) may make up an mCCE and one or more mCCEs may contain an mPDCCH.

UEs115may combine CRS and DM-RS REs for channel/interference estimation. Such a scheme may be used for CRS and DM-RS base mPDCCH decoding. Additionally, such a scheme may promote interference cancellation from ePDCCH or mPDCCH transmissions, thus possibly increasing its compatibility with ePDCCH (which may be based on a configuration similar to indexing configuration302).

FIG. 3Cillustrates an example of an indexing configuration303for narrowband control channel decoding in accordance with various aspects of the present disclosure. Indexing configuration302may represent aspects of downlink205described above with reference toFIG. 2Indexing configuration303may illustrate a configuration of 14 symbol periods (1 subframe) in the time domain the and 12 tones (1 RB) in the frequency domain. Each RE may correspond to the time and frequency resource included in one symbol period on one tone. Indexing configuration303may include indexed control region REs305-cand indexed DM-RS REs320. In some cases, the number of DM-RS REs315may be based on the cyclic prefix (CP). For example, an mREG may include 24 DM-RS REs for a normal CP and may include 16 DM-RS for extended CP. Indexing configuration303may include aspects of indexing configuration301and302described with reference toFIGS. 3A and 3B.

According to indexing configuration303, all REs of a control region may be indexed (i.e., both control region REs305-cand DM-RS REs320). Although shown indexed in a frequency-first-time-second manner, in some cases the REs of resource block pair may be indexed in a time-first-frequency-second manner. Regardless of the manner of indexing, the indexed control region REs305-cmay be indexed separately from the DM-RS REs20. For example, the indexing of first resource block may progress in a sequential manner, skipping over DM-RS REs320. Accordingly, the DM-RS REs320of first resource block may be indexed in a similar sequential manner, skipping over the control region REs305-c. The indexing for DM-RS REs320may continue in the second resource block. Although shown in regards to resource blocks which carry DM-RS, the indexing configuration303may be used to index resource blocks which carry other reference signals (e.g., CRS). As described above with reference toFIG. 3A, the REs of indexing configuration303may be grouped into mREGs based on the indices. Thus, 9 REs may make up one mREG. A group of 4 mREGs (i.e., 36 REs) may make up an mCCE and one or more mCCEs may contain an mPDCCH.

In some cases, the starting index for different RBs may be different, which may result in a more uniform mREG size. For example, the first RB may start from mREG 0 while a second RB may start from mREG 8. Alternatively, if an mCCE follows the same grouping concept (e.g., an mCCE has mREGs 0/4/8/12) the starting index for the first RB may be the same as the starting index for the second RB. In such examples, each mREG may have an average of 10.5 REs. In some cases, the mREG definition may exclude both DM-RS and CRS REs. Or, in some examples, the actual CRS ports may be excluded from the mREG definition.

FIG. 4illustrates an example of a process flow400for narrowband control channel decoding in accordance with various aspects of the present disclosure. Process flow400may include a UE115-b, which may be an example of a UE115described above with reference toFIGS. 1-2(e.g., an MTC device). Process flow400may also include a base station105-b, which may be an example of a base station105described above with reference toFIGS. 1-2. In some examples of the present disclosure, the actions performed by base station105-bmay be performed by another UE115(not shown) according to D2D operations.

At message405, UE115-band base station105-bmay establish a connection based on a narrowband control region. In some cases, the narrowband control region may not include all the frequency tones supported by base station105-b.

At block410, UE115-band base station105-bmay identify a set of resources in the narrowband control region based at least in part on an RE indexing configuration associated with a CRS based demodulation scheme. In some examples the RE indexing configuration excludes a set of REs associated with a CRS configuration as described above with reference toFIG. 3A(e.g., based on a CRS configuration that includes a maximum number of CRS ports). In some examples, the RE indexing configuration excludes a set of REs associated with a DM-RS configuration as described above with reference toFIG. 3B. In some examples, the RE indexing configuration includes a set of separately indexed REs associated with a DM-RS configuration as described above with reference toFIG. 3C. In some cases, resources of the narrowband region which include a control region, such as for broadband communication from the control channel, may be excluded. Base station105-bmay, for instance, transmit (and UE115-bmay receive) a message indicating a size, or resources, of a broadband control region to be excluded from the set of resources. Similarly, base station105-bmay transmit (and UE115-bmay receive) a message indicating the resources of the narrowband region which include the control region for broadband communications. The UE115-b, or another base station105, may determine the resources of the narrowband region which includes the control region for the broadband communications based at least in part on the message.

At message415, base station105-bmay transmit (and UE115-bmay receive) a PDCCH (e.g., an mPDCCH) based on the set of resources. The transmission may also include CRS for demodulation and, in some cases, DM-RS.

At message415, UE115-bmay demodulate the PDCCH based on a CRS (e.g., using CRS transmitted by base station105-b). In some examples, the demodulation of the PDCCH is also based on a DM-RS. UE115-bmay identify a number of subframes during which to monitor a DM-RS for decoding the PDCCH. In some cases, the PDCCH may include a narrowband region within a wideband system. In some cases, the number of subframes may have the same precoding for the DM-RS. UE115-bmay decode the PDCCH based at least in part on the DM-RS. In some cases, UE115-bmay map a set of modulation symbols to the set of resources. In some cases, UE115-bmay identify two or more RBs that have the same precoding, such as RBs with the same precoding within the narrowband region. The RBs which have the same precoding may be a part of the PDCCH.

In some examples, (not shown) base station105-bmay transmit (and UE115-bmay receive) a second PDCCH, in a manner similar to message415, using a same precoding as the PDCCH according to a bundling configuration or using a different precoding from the PDCCH according to a predetermined precoding pattern. In some examples, the PDCCH and the second PDCCH include the same content and may be transmitted in a different frequency resource or a different time resource. In some cases, UE115-bmay identify two or more RBs that have the same precoding, such as RBs with the same precoding within the narrowband region. The RBs which have the same precoding may be a part of the second PDCCH.

Additionally, bundling of mPDCCH may be supported, which may improve mPDCCH decoding performance. In such instances, the same precoding may be assumed over multiple RBs and/or multiple subframes. When TTI bundling is used (i.e., when mPDCCH is transmitted over multiple frames), time-domain precoding may be helpful. In an alternative example, different precoding may be assumed, but the precoding may be predetermined or known at the UE (e.g., some precoding cycling in different RBs and/or subframes). In the case an MTC device only supports 6-RB operation, a larger fast Fourier transform (FFT) size (e.g., 8-RB) may be used to improve bandwidth edge performance.

In some cases, include those in which mPDCCH rate matching is used, a UE may assume that the legacy control region is not used for mPDCCH. Additionally, the legacy control region may be assumed to be the maximum possible size. Accordingly, if the system bandwidth is 10 RBs or less, 4 control symbols may be assumed for the legacy control region. Otherwise, 3 control symbols may be assumed for the legacy control size. Alternatively, instead of assuming the maximum possible legacy control region, the size of the legacy control region may be indicated to the UE. In such instances, the indicated control region size may include zero-size (i.e., no legacy control region) so that other carrier types (e.g., an LTE-U carrier, which may not have a legacy control region) or operations may be covered.

FIG. 5shows a block diagram500of a UE115-cconfigured for narrowband control channel decoding in accordance with various aspects of the present disclosure. UE115-cmay be an example of aspects of a UE115described with reference toFIGS. 1-4. UE115-cmay include a receiver505, a CRS based PDCCH module510, or a transmitter515. UE115-cmay also include a processor. Each of these components may be in communication with one another.

The receiver505may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a CRS based control channel element, etc.). Information may be passed on to the CRS based PDCCH module510, and to other components of UE115-c. The receiver505may receive a PDCCH based on a set of resources. In some examples, the receiver505may receive a message indicating a size of the broadband control region to be excluded from the set of resources. The receiver505may also receive a second PDCCH using a same precoding as the PDCCH according to a bundling configuration. In some examples, the receiver505may receive a second PDCCH using a different precoding from the PDCCH according to a predetermined precoding pattern. Additionally or alternatively, the PDCCH and the second PDCCH may include the same content and may be transmitted in a different frequency resource or a different time resource. In some cases, the receiver505may receive a message indicating the resources of the narrowband region which include the control region for broadband communications.

The CRS based PDCCH module510may establish a connection with a node (such as a UE115or base station105), where the connection may include a narrowband control region, and the CRS based PDCCH module510may identify a set of resources in the narrowband control region based on a resource element indexing configuration associated with a CRS based demodulation scheme. The CRS based PDCCH module510may also receive a PDCCH based on the set of resources, and it may demodulate the PDCCH based at least in part on a CRS. In some cases, the CRS based PDCCH module510may identify a plurality of subframes during which to monitor a DM-RS for decoding a control channel associated with a node. The control channel may include a narrowband region and may be within a wideband system. In some cases, the plurality of subframes may have a same precoding for the DM-RS. The CRS based PDCCH module510may further decode the control channel based at least in part on the DM-RS.

The transmitter515may transmit signals received from other components of UE115-c. In some embodiments, the transmitter515may be collocated with the receiver505in a transceiver module. The transmitter515may include a single antenna, or it may include a plurality of antennas.

FIG. 6shows a block diagram600of a UE115-dfor narrowband control channel decoding in accordance with various aspects of the present disclosure. UE115-dmay be an example of aspects of a UE115described with reference toFIGS. 1-5. UE115-dmay include a receiver505-a, a CRS based PDCCH module510-a, or a transmitter515-a. UE115-dmay also include a processor. Each of these components may be in communication with one another. The CRS based PDCCH module510-amay also include a narrowband connection module605, a resource identification module610, and a demodulation module615.

The receiver505-amay receive information which may be passed on to CRS based PDCCH module510-a, and to other components of UE115-d. The CRS based PDCCH module510-amay perform the operations described above with reference toFIG. 5. The transmitter515-amay transmit signals received from other components of UE115-d.

The narrowband connection module605may establish a connection with a node (such as a UE115or base station105), where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In some cases, the narrowband connection module605may exclude resources of the narrowband region which include a control region for broadband communications from the control channel.

The resource identification module610may identify a set of resources in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In some examples, the resource element indexing configuration excludes a set of resource elements associated with a CRS configuration. In some examples, the resource element indexing configuration excludes a set of resource elements associated with a DM-RS configuration. In some examples, the resource element indexing configuration includes a set of separately indexed resource elements associated with a DM-RS configuration. The CRS demodulation scheme may, for instance, be based on a CRS configuration that includes a maximum number of CRS ports. In some cases, the resource identification module610identifies a plurality of subframes during which to monitor a DM-RS for decoding a control channel associated with a node. The control channel may include a narrowband region of a wideband system and the plurality of subframes may have a same precoding for the DM-RS. The resource identification module610may identify two or more RBs that have the same precoding within the narrowband region. In some cases, the resource identification module610may determine the resources of the narrowband region which include the control region for the broadband communications based at least in part on a message. In some cases, the resource identification module610may exclude resources of the narrowband region which include a control region for broadband communications from the control channel.

The demodulation module615may demodulate the PDCCH based on a CRS as described above with reference toFIGS. 2-4. In some cases, the demodulation may also be based on a DM-RS. The demodulation module615may decode the control channel based at least in part on the DM-RS.

FIG. 7shows a block diagram700of a CRS based PDCCH module510-bfor narrowband control channel decoding in accordance with various aspects of the present disclosure. The CRS based PDCCH module510-bmay be an example of aspects of a CRS based PDCCH module510described with reference toFIG. 5 or 6. The CRS based PDCCH module510-bmay include a narrowband connection module605-a, a resource identification module610-a, and a demodulation module615-a. Each of these modules may perform the functions described above with reference toFIG. 6. The CRS based PDCCH module510-bmay also include a DM-RS module705, and a symbol mapping module710.

The DM-RS module705may be configured such that the demodulation of the PDCCH may be based on a DM-RS as described above with reference toFIGS. 2-4. In some cases the DM-RS module705may decode the control channel based at least in part on the DM-RS.

The symbol mapping module710may map a set of modulation symbols to the set of resources, where the mapping excludes a broadband control region from the set as described above with reference toFIGS. 2-4.

FIG. 8shows a diagram of a system800including a UE115configured for narrowband control channel decoding in accordance with various aspects of the present disclosure. System800may include UE115-e, which may be an example of a UE115described above with reference toFIGS. 1-7. UE115-emay include a CRS based PDCCH module810, which may be an example of a CRS based PDCCH module510described with reference toFIGS. 5-7. UE115-emay also include a channel estimation module825. UE115-emay also include components for bi-directional voice and data communications including components for transmitting communications and components for receiving communications. For example, UE115-emay communicate bi-directionally with UE115-for base station105-c.

UE115-emay also include a processor module805, and memory815(including software (SW)820), a transceiver module835, and one or more antenna(s)840, each of which may communicate, directly or indirectly, with one another (e.g., via buses845). The transceiver module835may communicate bi-directionally, via the antenna(s)840or wired or wireless links, with one or more networks, as described above. For example, the transceiver module835may communicate bi-directionally with a base station105or another UE115. The transceiver module835may include a modem to modulate the packets and provide the modulated packets to the antenna(s)840for transmission, and to demodulate packets received from the antenna(s)840. While UE115-emay include a single antenna840, UE115-emay also have multiple antennas840capable of concurrently transmitting or receiving multiple wireless transmissions.

The channel estimation module825may estimate channel conditions and generate channel state information (CSI) reports based on the channel estimates. In some examples, CRS may be used for channel estimation. A wireless communications link may then be updated based on the CSI.

The memory815may include random access memory (RAM) and read only memory (ROM). The memory815may store computer-readable, computer-executable software/firmware code820including instructions that, when executed, cause the processor module805to perform various functions described herein (e.g., narrowband control channel decoding, etc.). Alternatively, the software/firmware code820may not be directly executable by the processor module805but cause a computer (e.g., when compiled and executed) to perform functions described herein. The processor module805may include an intelligent hardware device, (e.g., a central processing unit (CPU), a microcontroller, an ASIC, etc.)

FIG. 9shows a block diagram900of a base station105-dconfigured for narrowband control channel decoding in accordance with various aspects of the present disclosure. Base station105-dmay be an example of aspects of a base station105or a UE115described with reference toFIGS. 1-8. Base station105-dmay include a receiver905, a base station CRS based PDCCH module910, or a transmitter915. Base station105-dmay also include a processor. Each of these components may be in communication with one another. In some examples of the present disclosure, the structure of base station105-dmay be found in a UE115by operating according to D2D operations.

The receiver905may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to a CRS based control channel element, etc.). Information may be passed on to the base station CRS based PDCCH module910, and to other components of base station105-d.

The base station CRS based PDCCH module910may establish a connection with a UE115, where the connection may include a narrowband control region, identify a set of resources for the UE115in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme, transmit a PDCCH to the UE115using the set of resources, and transmit a CRS in a same resource block as the set of resources.

The transmitter915may transmit signals received from other components of base station105-d. In some embodiments, the transmitter915may be collocated with the receiver905in a transceiver module. The transmitter915may include a single antenna, or it may include a plurality of antennas. In some examples, the transmitter515may transmit a message indicating a size of the broadband control region to be excluded. In some examples, the transmitter515may transmit a second PDCCH using a same precoding as the PDCCH according to PDCCH bundling configuration. In some examples, the transmitter515may transmit a second PDCCH using a different precoding from the PDCCH according to a predetermined precoding pattern. The PDCCH and the second PDCCH may include the same content and may be transmitted in a different frequency resource or a different time resource.

FIG. 10shows a block diagram1000of a base station105-efor narrowband control channel decoding in accordance with various aspects of the present disclosure. Base station105-emay be an example of aspects of a base station105described with reference toFIGS. 1-9. Base station105-emay include a receiver905-a, a base station CRS based PDCCH module910-a, or a transmitter915-a. Base station105-emay also include a processor. Each of these components may be in communication with one another. The base station CRS based PDCCH module910-amay also include a BS narrowband connection module1005, a BS resource identification module1010, a PDCCH module1015, and a CRS module1020. In some examples of the present disclosure, the structure of base station105-emay be found in a UE115by operating according to D2D operations.

The receiver905-amay receive information which may be passed on to base station CRS based PDCCH module910-a, and to other components of base station105-e. The base station CRS based PDCCH module910-amay perform the operations described above with reference toFIG. 9. The transmitter915-amay transmit signals received from other components of base station105-e.

The BS narrowband connection module1005may establish a connection with a UE115, where the connection may include a narrowband control region as described above with reference toFIGS. 2-4.

The BS resource identification module1010may identify a set of resources for the UE115in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4.

The PDCCH module1015may transmit a PDCCH to the UE115using the set of resources as described above with reference toFIGS. 2-4.

The CRS module1020may transmit a CRS in a same resource block as the set of resources as described above with reference toFIGS. 2-4. In some examples, the CRS demodulation scheme may be based on a CRS configuration comprising a maximum number of CRS ports.

FIG. 11shows a block diagram1100of a base station CRS based PDCCH module910-bfor narrowband control channel decoding in accordance with various aspects of the present disclosure. The base station CRS based PDCCH module910-bmay be an example of aspects of a base station CRS based PDCCH module910described with reference toFIGS. 9-10. The base station CRS based PDCCH module910-bmay include a BS narrowband connection module1005-a, a BS resource identification module1010-a, a PDCCH module1015-a, and a CRS module1020-a. Each of these modules may perform the functions described above with reference toFIG. 10. The base station CRS based PDCCH module910-bmay also include and a BS symbol mapping module1105.

The BS symbol mapping module1105may map a set of modulation symbols to the set of resources, where the mapping excludes a broadband control region from the set as described above with reference toFIGS. 2-4.

FIG. 12shows a diagram of a system1200including a base station105configured for narrowband control channel decoding in accordance with various aspects of the present disclosure. System1200may include base station105-f, which may be an example of a base station105described above with reference toFIGS. 1-11. Base station105-fmay include a base station CRS based PDCCH module1210, which may be an example of a base station CRS based PDCCH module910described with reference toFIGS. 9-11. Base station105-fmay also include components for bi-directional voice and data communications including components for transmitting communications and components for receiving communications. For example, base station105-fmay communicate bi-directionally with base station105-gor base station105-h.

In some cases, base station105-fmay have one or more wired backhaul links. Base station105-fmay have a wired backhaul link (e.g., S1 interface, etc.) to the core network130. Base station105-fmay also communicate with other base stations105, such as base station105-gand base station105-hvia inter-base station backhaul links (e.g., an X2 interface). Each of the base stations105may communicate with UEs115using the same or different wireless communications technologies. In some cases, base station105-fmay communicate with other base stations such as105-gor105-hutilizing base station communication module1225. In some embodiments, base station communication module1225may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between some of the base stations105. In some embodiments, base station105-fmay communicate with other base stations through core network130. In some cases, base station105-fmay communicate with the core network130through network communications module1230.

Base station105-fmay include a processor module1205, memory1215(including software (SW)1220), transceiver modules1235, and antenna(s)1240, which each may be in communication, directly or indirectly, with one another (e.g., over bus system1245). The transceiver modules1235may be configured to communicate bi-directionally, via the antenna(s)1240, with the UEs115, which may be multi-mode devices. The transceiver module1235(or other components of the base station105-f) may also be configured to communicate bi-directionally, via the antennas1240, with one or more other base stations (not shown). The transceiver module1235may include a modem configured to modulate the packets and provide the modulated packets to the antennas1240for transmission, and to demodulate packets received from the antennas1240. The base station105-fmay include multiple transceiver modules1235, each with one or more associated antennas1240. The transceiver module may be an example of a combined receiver905and transmitter915ofFIG. 9.

The memory1215may include RAM and ROM. The memory1215may also store computer-readable, computer-executable software code1220containing instructions that are configured to, when executed, cause the processor module1210to perform various functions described herein (e.g., a CRS based control channel element, selecting coverage enhancement techniques, call processing, database management, message routing, etc.). Alternatively, the software1220may not be directly executable by the processor module1205but be configured to cause the computer, (e.g., when compiled and executed), to perform functions described herein. The processor module1205may include an intelligent hardware device, (e.g., a CPU, a microcontroller, an ASIC, etc.). The processor module1205may include various special purpose processors such as encoders, queue processing modules, base band processors, radio head controllers, digital signal processor (DSPs), and the like.

The base station communications module1225may manage communications with other base stations105. The communications management module may include a controller or scheduler for controlling communications with UEs115in cooperation with other base stations105. For example, the base station communications module1225may coordinate scheduling for transmissions to UEs115for various interference mitigation techniques such as beamforming or joint transmission.

FIG. 13shows a flowchart illustrating a method1300for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1300may be implemented by a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method1300may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, a UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects the functions described below using special-purpose hardware.

At block1305, the UE115may establish a connection with a node (such as a UE115or base station105), where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1305may be performed by the narrowband connection module605as described above with reference toFIG. 6.

At block1310, the UE115may identify a set of resources in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1310may be performed by the resource identification module610as described above with reference toFIG. 6.

At block1315, the UE115may receive a PDCCH based on the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1315may be performed by the receiver505as described above with reference toFIG. 5.

At block1320, the UE115may demodulate the PDCCH based at least in part on a CRS as described above with reference toFIGS. 2-4. In certain examples, the operations of block1320may be performed by the demodulation module615as described above with reference toFIG. 6.

FIG. 14shows a flowchart illustrating a method1400for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1400may be implemented by a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method1400may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, a UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects the functions described below using special-purpose hardware. The method1400may also incorporate aspects of method1300ofFIG. 13.

At block1405, the UE115may establish a connection with a node (such as a UE115or base station105), where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1405may be performed by the narrowband connection module605as described above with reference toFIG. 6.

At block1410, the UE115may identify a set of resources in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1410may be performed by the resource identification module610as described above with reference toFIG. 6.

At block1415, the UE115may map a set of modulation symbols to the set of resources, where the mapping excludes a broadband control region from the set as described above with reference toFIGS. 2-4. In certain examples, the operations of block1415may be performed by the symbol mapping module710as described above with reference toFIG. 7.

At block1420, the UE115may receive a PDCCH based on the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1420may be performed by the receiver505as described above with reference toFIG. 5.

At block1425, the UE115may demodulate the PDCCH based at least in part on a CRS as described above with reference toFIGS. 2-4. In certain examples, the operations of block1425may be performed by the demodulation module615as described above with reference toFIG. 6.

FIG. 15shows a flowchart illustrating a method1500for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1500may be implemented by a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method1500may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, a UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects the functions described below using special-purpose hardware. The method1500may also incorporate aspects of methods1300, and1400ofFIG. 13 or 14.

At block1505, the UE115may establish a connection with a node (such as a UE115or base station105), where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1505may be performed by the narrowband connection module605as described above with reference toFIG. 6.

At block1510, the UE115may identify a set of resources in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1510may be performed by the resource identification module610as described above with reference toFIG. 6.

At block1515, the UE115may receive a PDCCH based on the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1515may be performed by the receiver505as described above with reference toFIG. 5.

At block1520, the UE115may demodulate the PDCCH based at least in part on a CRS as described above with reference toFIGS. 2-4. In certain examples, the operations of block1520may be performed by the demodulation module615as described above with reference toFIG. 6.

At block1525, the UE115may receive a second PDCCH using a same precoding as the PDCCH according to a bundling configuration or a different precoding from the PDCCH according to a predetermined precoding pattern as described above with reference toFIGS. 2-4. In certain examples, the operations of block1525may be performed by the receiver505as described above with reference toFIG. 5.

FIG. 16shows a flowchart illustrating a method1600for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1600may be implemented by a wireless node such as a base station105or a UE115(e.g., in operating in D2D mode) or its components as described with reference toFIGS. 1-12. For example, the operations of method1600may be performed by the base station CRS based PDCCH module910as described with reference toFIGS. 9-12. In some examples, a base station105may execute a set of codes to control the functional elements of the base station105to perform the functions described below. Additionally or alternatively, the base station105may perform aspects the functions described below using special-purpose hardware.

At block1605, the wireless node may establish a connection with a UE, where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1605may be performed by the BS narrowband connection module1005as described above with reference toFIG. 1.

At block1610, the wireless node may identify a set of resources for the UE in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1610may be performed by the BS resource identification module1010as described above with reference toFIG. 1.

At block1615, the wireless node may transmit a PDCCH to the UE using the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1615may be performed by the PDCCH module1015as described above with reference toFIG. 1.

At block1620, the wireless node may transmit a CRS in a same resource block as the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1620may be performed by the CRS module1020as described above with reference toFIG. 1.

FIG. 17shows a flowchart illustrating a method1700for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1700may be implemented by a wireless node such as a base station105or a UE115(e.g., in operating in D2D mode) or its components as described with reference toFIGS. 1-12. For example, the operations of method1700may be performed by the base station CRS based PDCCH module910as described with reference toFIGS. 9-12. In some examples, a base station105may execute a set of codes to control the functional elements of the base station105to perform the functions described below. Additionally or alternatively, the base station105may perform aspects the functions described below using special-purpose hardware. The method1700may also incorporate aspects of method1600ofFIG. 16.

At block1705, the wireless node may establish a connection with a UE, where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1705may be performed by the BS narrowband connection module1005as described above with reference toFIG. 1.

At block1710, the wireless node may identify a set of resources for the UE in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1710may be performed by the BS resource identification module1010as described above with reference toFIG. 1.

At block1715, the wireless node may map a set of modulation symbols to the set of resources, where the mapping excludes a broadband control region from the set as described above with reference toFIGS. 2-4. In certain examples, the operations of block1715may be performed by the symbol mapping module710as described above with reference toFIG. 7.

At block1720, the wireless node may transmit a message indicating a size of the broadband control region to be excluded as described above with reference toFIGS. 2-4. In certain examples, the operations of block1720may be performed by the transmitter915as described above with reference toFIG. 9.

At block1725, the wireless node may transmit a PDCCH to the UE using the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1725may be performed by the PDCCH module1015as described above with reference toFIG. 1.

At block1730, the wireless node may transmit a CRS in a same resource block as the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1730may be performed by the CRS module1020as described above with reference toFIG. 1.

FIG. 18shows a flowchart illustrating a method1800for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1800may be implemented by a wireless node such as a base station105or a UE115(e.g., in operating in D2D mode) or its components as described with reference toFIGS. 1-12. For example, the operations of method1800may be performed by the base station CRS based PDCCH module910as described with reference toFIGS. 9-12. In some examples, a base station105may execute a set of codes to control the functional elements of the base station105to perform the functions described below. Additionally or alternatively, the base station105may perform aspects the functions described below using special-purpose hardware. The method1800may also incorporate aspects of methods1600, and1700ofFIG. 16 or 17.

At block1805, the wireless node may establish a connection with a UE, where the connection may include a narrowband control region as described above with reference toFIGS. 2-4. In certain examples, the operations of block1805may be performed by the BS narrowband connection module1005as described above with reference toFIG. 1.

At block1810, the wireless node may identify a set of resources for the UE in the narrowband control region based at least in part on a resource element indexing configuration associated with a CRS based demodulation scheme as described above with reference toFIGS. 2-4. In certain examples, the operations of block1810may be performed by the BS resource identification module1010as described above with reference toFIG. 1.

At block1815, the wireless node may transmit a PDCCH to the UE using the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1815may be performed by the PDCCH module1015as described above with reference toFIG. 1.

At block1820, the wireless node may transmit a CRS in a same resource block as the set of resources as described above with reference toFIGS. 2-4. In certain examples, the operations of block1820may be performed by the CRS module1020as described above with reference toFIG. 1.

At block1825, the wireless node may transmit a second PDCCH using a same precoding as the PDCCH according to PDCCH bundling configuration or a different precoding from the PDCCH according to a predetermined precoding pattern as described above with reference toFIGS. 2-4. In certain examples, the operations of block1825may be performed by the transmitter915as described above with reference toFIG. 9.

FIG. 19shows a flowchart illustrating a method1900for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method1900may be implemented by a wireless node such as a base station105or a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method1900may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, a UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects of the functions described below using special-purpose hardware.

At block1905, the UE115may identify a set of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, where the control channel comprises a narrowband region of a wideband system, and where the set of subframes have a same precoding for the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block1905may be performed by the resource identification module610as described with reference toFIGS. 6 and 7.

At block1910, the UE115may decode the control channel based on the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block1910may be performed by the demodulation module615as described with reference toFIGS. 6-7, or the DM-RS module705as described with reference toFIG. 7.

FIG. 20shows a flowchart illustrating a method2000for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method2000may be implemented by a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method2000may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, the UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects of the functions described below using special-purpose hardware.

At block2005, the UE115may identify a set of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, where the control channel comprises a narrowband region of a wideband system, and where the set of subframes have a same precoding for the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block2005may be performed by the resource identification module610as described with reference toFIGS. 6 and 7.

At block2010, the UE115may decode the control channel based on the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block2010may be performed by the demodulation module615as described with reference toFIGS. 6-7, or the DM-RS module705as described with reference toFIG. 7.

At block2015, the UE115may identify two or more resource blocks (RBs) that have the same precoding within the narrowband region as described above with reference toFIGS. 2-4. In certain examples, the operations of block2015may be performed by the resource identification module610as described with reference toFIGS. 6 and 7.

FIG. 21shows a flowchart illustrating a method2100for narrowband control channel decoding in accordance with various aspects of the present disclosure. The operations of method2100may be implemented by a UE115or its components as described with reference toFIGS. 1-12. For example, the operations of method2100may be performed by the CRS based PDCCH module510as described with reference toFIGS. 5-8. In some examples, the UE115may execute a set of codes to control the functional elements of the UE115to perform the functions described below. Additionally or alternatively, the UE115may perform aspects of the functions described below using special-purpose hardware.

At block2105, the UE115may identify a set of subframes during which to monitor a demodulation reference signal (DM-RS) for decoding a control channel associated with a node, where the control channel comprises a narrowband region of a wideband system, and where the set of subframes have a same precoding for the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block2105may be performed by the resource identification module610as described with reference toFIGS. 6 and 7.

At block2110, the UE115may decode the control channel based on the DM-RS as described above with reference toFIGS. 2-4. In certain examples, the operations of block2110may be performed by the demodulation module615as described with reference toFIGS. 6-7, or the DM-RS module705as described with reference toFIG. 7.

At block2115, the UE115may exclude resources of the narrowband region that comprise a control region for broadband communications from the control channel as described above with reference toFIGS. 2-4. In certain examples, the operations of block2115may be performed by the narrowband connection module605or the resource identification module610as described with reference toFIGS. 6-7.

Thus, methods1300,1400,1500,1600,1700,1800,1900,2000, and2100may provide for narrowband control channel decoding. It should be noted that methods1300,1400,1500,1600,1700,1800,1900,2000, and2100describe possible implementation, and that the operations and the steps may be rearranged or otherwise modified such that other implementations are possible. In some examples, aspects from two or more of the methods1300,1400,1500,1600,1700,1800,1900,2000, and2100may be combined.