HK1253872B - Dynamically beamformed control channel for beamformed cells - Google Patents

Description

Dynamic beamforming control channel for beamformed cells

Claim priority

This patent application claims priority to U.S. Provisional Patent Application No. 62/238,606, filed on October 7, 2015, and entitled “DYNAMICALLY BEAMFORMEDPDCCH DESIGN FOR BEAMFORMED CELL,” which is hereby incorporated by reference in its entirety.

Technical Field

Embodiments relate to wireless communications. Certain embodiments relate to cellular communication networks, including 3GPP (3rd Generation Partnership Project) networks, 3GPP LTE (Long Term Evolution) networks, and 3GPP LTE-A (LTE-Advanced) networks, although the scope of the embodiments is not limited thereto. Certain embodiments relate to 5G communications. Certain embodiments relate to beamforming. Certain embodiments relate to beamforming in millimeter wave systems.

Background Art

As more and more people become users of mobile communication systems, there is a growing demand to utilize new frequency bands. As a result, cellular communications have expanded into the millimeter wave (mmWave) band. There is a growing demand to provide high data rates and low latency in communications, including communications in the mmWave band.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a functional block diagram of a 3GPP network according to certain embodiments;

FIG2 illustrates an example of two groups of cellular users to illustrate issues of interest that can be addressed using certain embodiments;

FIG3 illustrates an example of beamforming in accordance with certain embodiments;

FIG4 illustrates a resource element group (REG) design with 75 KHz subcarrier spacing in accordance with certain embodiments;

FIG5 illustrates a REG design with 750 KHz subcarrier spacing according to certain embodiments;

FIG6 illustrates another REG design with 750 KHz subcarrier spacing in accordance with certain embodiments;

7 illustrates control channel transmission according to symbol-level time multiplexing of UE grouping based on geometry and direction, in accordance with certain embodiments;

FIG8 illustrates evolved Node B (eNB) scheduling of downlink control information (DCI) transmission based on different beam directions in accordance with certain embodiments;

FIG9 is a functional block diagram of a user equipment (UE) according to certain embodiments;

FIG10 is a functional block diagram of an evolved Node B (eNB) according to certain embodiments; and

11 is a block diagram illustrating components of a machine capable of reading instructions from a machine-readable medium and performing any one or more of the methodologies discussed herein, according to certain example embodiments.

DETAILED DESCRIPTION

The following description and accompanying drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical processes, and other changes. Portions and features of certain embodiments may be included in other embodiments or substituted for those of other embodiments. The embodiments set forth in the claims include all available equivalents of those claims.

FIG1 is a functional block diagram of a 3GPP network according to certain embodiments. The network includes a radio access network (RAN) (e.g., as depicted, E-UTRAN or Evolved Universal Terrestrial Radio Access Network) 100 and a core network 120 (e.g., shown as an Evolved Packet Core (EPC)) coupled together via an S1 interface 115. For convenience and brevity, only a portion of the core network 120 and the RAN 100 are shown.

The core network 120 includes a mobility management entity (MME) 122, a serving gateway (serving GW) 124, and a packet data network gateway (PDN GW) 126. The RAN 100 includes an evolved Node B (eNB) 104 (which can operate as a base station) for communicating with a user equipment (UE) 102. The eNB 104 can include a macro eNB and a low power (LP) eNB. According to certain embodiments, the eNB 104 can receive uplink data from the UE 102 over a radio resource control (RRC) connection between the eNB 104 and the UE 102. The eNB 104 can send an RRC connection release message to the UE 102 to instruct the UE 102 to transition to an RRC idle mode of the RRC connection. The eNB 104 can further receive additional uplink data packets based on the stored context information.

The MME 122 manages mobility aspects of access, such as gateway selection and tracking area list management. The Serving GW 124 terminates the interface to the RAN 100 and routes data packets between the RAN 100 and the core network 120. Furthermore, it can be the local mobility anchor point for inter-eNB handovers and can also provide an anchor for inter-3GPP mobility. Other functions may include lawful interception, charging, and certain policy enforcement. The Serving GW 124 and the MME 122 can be implemented in one physical node or in separate physical nodes. The PDN GW 126 terminates the SGi interface to the packet data network (PDN). The PDN GW 126 routes data packets between the EPC 120 and external PDNs and can be a key node for policy enforcement and charging data collection. It can also provide an anchor point for mobility with non-LTE accesses. External PDNs can be any type of IP network, as well as the IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and the Serving GW 124 can be implemented in one physical node or in separate physical nodes. Furthermore, in the case where one less hop is required to transmit a message, the MME 122 and the Serving GW 124 can be overlapped in one physical node.

The eNB 104 (macro and micro) terminates the air interface protocol and can be the first point of contact for the UE 102. In certain embodiments, the eNB 104 can perform various logical functions of the RAN 100, including but not limited to RNC (Radio Network Controller) functions, such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. According to an embodiment, the UE 102 can be configured to communicate orthogonal frequency division multiple access (OFDMA) communication signals with the eNB 104 on a multi-carrier communication channel in accordance with an orthogonal frequency division multiple access (OFDMA) communication technique. The OFDM signal can include multiple orthogonal subcarriers.

The S1 interface 115 is the interface that separates the RAN 100 from the EPC 120. It is divided into two parts: S1-U, which carries traffic data between the eNB 104 and the Serving GW 124; and S1-MME, which is the signaling interface between the eNB 104 and the MME 122. The X2 interface is an interface between eNBs 104. The X2 interface consists of two parts, X2-C and X2-U. X2-C is the control plane interface between eNBs 104, while X2-U is the user plane interface between eNBs 104.

In cellular networks, LP cells are typically used to extend coverage to indoor areas where outdoor signals don't reach well, or to increase network capacity in areas with very dense phone usage, such as train stations. As used herein, the term low-power (LP) eNB refers to any suitable relatively low-power eNB used to implement narrower cells (narrower than macrocells), such as femtocells, picocells, or microcells. Femtocell eNBs are typically provided by mobile network operators to their residential or enterprise customers. Femtocells are typically the size of a residential gateway or smaller and are typically connected to a user's broadband line. Once plugged in, the femtocell connects to the mobile operator's mobile network and provides additional coverage, typically in the 30 to 50 meter range, for residential femtocells. Thus, an LP eNB can be a femtocell eNB because it is coupled through a PDN GW 126. Similarly, a picocell is a wireless communication system that typically covers a small area, such as within a building (office, shopping mall, train station, etc.) or (more recently) within an aircraft. A picocell eNB can typically be connected to another eNB via an X2 link, such as to a macro eNB via the base station controller (BSC) functionality of the macro eNB. Thus, an LP eNB can be implemented using a picocell eNB, as it is coupled to the macro eNB via the X2 interface. A picocell eNB or other LP eNB can incorporate some or all of the functionality of a macro eNB. In some cases, this can be referred to as an access point base station or enterprise femtocell.

The eNB 103 and the UE 102 can be configured to operate in various frequency bands. Recently, the mmWave band has seen greater use. mmWave is a radio wave with a wavelength range of 1 millimeter (mm)-10 mm, which corresponds to a radio frequency of 30 gigahertz (GHz)-300 GHz. mmWave exhibits unique propagation characteristics. For example, compared to low-frequency radio waves, mmWave suffers from higher propagation losses and has a poorer ability to penetrate objects, such as buildings, walls, etc. On the other hand, due to the smaller wavelength of mmWave, more antennas can be packed into a relatively small area, thereby allowing high-gain antennas with small form factors to be achieved.

Beamforming can address these and other concerns and enable high data rate transmission on mmWave links. For data transmission, analog and data beamformers are trained and optimized for the physical downlink shared channel (PDSCH) to ensure coverage and high data rates. It may be desirable to further provide beamforming for control channels, however, certain recent specification and architecture changes have complicated this effort. For example, hybrid antenna architectures impose limitations on control channel beamforming designs. With a hybrid antenna architecture design, the analog beamforming weights can change at most from one OFDM symbol to the next. Multiplexing multiple UEs in the same control region can degrade beamforming performance.

FIG2 illustrates an example of two groups of UEs 102, illustrating the problems that can arise with reduced beamforming performance. In the illustrated cell served by eNB 104, UEs 1, 3, and 4 are in the center of the cell and are receiving downlink (DL) traffic, while UEs 2 and 5 are near or at the cell edge and are transmitting uplink (UL) traffic. In the control region, eNB 104 will use different Tx beam directions to send five DCIs (equivalently, five PDCCHs) to each of UEs 1, 2, 3, 4, and 5 to schedule DL/UL data transmissions. If eNB 104 has a subarray-based hybrid beamforming architecture with four subarrays, each subarray may need to form separate beam directions 202, 204, 206, and 208 to serve each of UEs 1, 2, 3, 4, and 5. Because of the reduced Tx beamforming gain, resources for transmitting the PDCCH to UE 2 and UE 5 may occupy the control region.

Apparatus and methods according to various embodiments address these challenges by providing the transmission shown in FIG3 . FIG3 illustrates an example of beamforming according to certain embodiments. In a practical subarray-based hybrid beamforming system, symbol-level time division multiplexing (TDM) of multiple beams can support low-geometry UEs 102 with full beamforming gain in some symbols, while allowing spatial multiplexing of multiple beam directions in other symbols. In OFDM symbol (or, in discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbol) 1, for example, spatial multiplexing of multiple beam directions 302, 304, 306, and 308 can be provided to support UE 1, UE 4, and UE 3. In symbol 2, beam 310 can support low-geometry UE 2. Apparatus and methods according to various embodiments provide control channel elements (CCEs) per symbol and resource element groups (REGs) mapped to the control channels. Embodiments can provide flexible analog and digital beamforming, and a dynamic, fully flexible time division duplex (TDD) structure with reduced signaling and control overhead.The control channel can be TDD with the data channel or other channels in the same subframe.

The apparatus and methods implemented according to various embodiments can improve the blind detection speed per UE 102. Because the UE 102 searches per OFDM symbol, the UE 102 can first pick the OFDM symbol or resource with the highest power (because the eNB 104 can be directed to the UE 102 in this symbol) and then decode this OFDM symbol. The embodiments allow for adaption of the control region size from one to multiple symbols without defining reference signals (RS) and CCEs for each case. Although the embodiments are described as referring to OFDM symbols, the embodiments are not limited thereto and may include DFT-s-OFDM symbols in some embodiments.

REG and CCE formation

The format of REGs and CCEs depends on the subcarrier spacing and the demodulation reference signal (DM-RS) pattern.Embodiments allow the eNB 104 to adjust the beam direction per symbol because REGs are formed per symbol.

Figure 4 illustrates a resource element group (REG) design with 75 kHz subcarrier spacing (14 OFDM symbols per 0.2 ms subframe) in accordance with certain embodiments. One REG can contain eight resource elements (REs), spanning one OFDM symbol duration and a time-frequency resource unit of 12 subcarriers. Four REs 402 are reserved for DM-RS with orthogonal cover codes [1 1; 1 -1] in each symbol. At least these embodiments support opportunistic multi-user (MU) transmission of PDCCH for up to two streams. An example design of a REG with DM-RS positions is shown at 404, while another example of a REG with DM-RS positions is shown at 406. For example, one OFDM symbol can be transmitted according to a DM-RS pattern, where four REs 402 are reserved for DM-RS (in two groups of two consecutive REs) and where four REs are reserved for non-DM-RS (between the two groups of consecutive REs). It will be appreciated that other REG formats and DM-RS patterns can be readily extended from the example shown in Figure 4. In certain embodiments, a cell-specific frequency offset can be applied to the DM-RS pattern to help reduce or eliminate time-frequency conflicts from neighboring cells.

FIG5 illustrates a first example REG design with a subcarrier spacing of 750 kHz (70 OFDM symbols per 0.1 ms subframe) in accordance with certain embodiments. One REG contains six REs, spanning a time-frequency resource unit of 1 OFDM symbol duration and 12 subcarriers. Six REs 502 are reserved for DM-RS in each symbol, where every two adjacent DM-RSs have orthogonal cover codes [1 1; 1 -1]. At least these embodiments support opportunistic MU transmission of PDCCH for up to two streams. A first symbol 504 can have a first REG design as shown at 504, while another symbol 506 can have a different REG design as shown at 506. It will be appreciated that other REG formats and DM-RS patterns can be readily extended from the example shown in FIG5. After UE 102 enters or leaves a cell, or after UE 102 moves closer to or further away from eNB 104, the number of OFDM symbols used for transmission of control channels can be adjusted.

Figure 6 illustrates another REG design with 750 KHz subcarrier spacing in accordance with certain embodiments. Figure 6 illustrates a design with a single carrier waveform such that the REG spans two symbols, one symbol 602 being used for RS and the other symbol being used for control channel (e.g., PDCCH, ePDCCH, xPDCCH, etc.) transmission. Every four adjacent DM-RSs are grouped together with a cover code:

At least these embodiments support opportunistic MU transmission of PDCCH up to four streams.

The embodiments described herein support distributed and centralized REG-to-CCE mapping, as well as multiple CCE aggregation levels. Centralized REG mapping is used for UE-specific DCI. A CCE consists of multiple REGs within adjacent RBs in the same symbol. Distributed REG mapping is used to transmit cell-specific control information or UE-specific scheduling information. Distributed REG mapping can be used when closed-loop beamforming is not available.

Indication of the size of the DL control region

The size of the DL control region can vary dynamically based on cell conditions (e.g., the number of UEs 102 scheduled in a transmission time interval (TTI)). The UE 102 uses the size of the control region to determine the symbol at which to begin decoding the PDSCH. Embodiments provide a mechanism for signaling the size of the control region to the UE 102.

In at least some embodiments, the eNB 104 can send control region size information in a UE-specific DCI. At least these embodiments can be used when the control region size changes frequently or more dynamically. For a UE 102 assigned in a TTI, after correctly decoding the DCI, the starting position of the PDSCH can be determined accordingly. In some embodiments, the control region size information can be sent in a 3-bit field in the UE-specific DCI, although embodiments are not limited to any particular size for the control region size information field. A UE 102 not assigned in a TTI can perform a blind search for the maximum allowed control region size (e.g., a maximum of eight symbols in a 750 kHz subcarrier design, or a maximum of three symbols in a 75 kHz subcarrier design). If no DCI is found, in at least these embodiments, the UE 102 can enter power saving until a subsequent TTI and then perform a blind search again. The maximum allowed control region size can be predefined or configured by higher layers in the master system information block (MIB), the system information block (SIB), or in dedicated RRC signaling.

In another embodiment, a synchronization signal can be used to indicate the control region size. At least these embodiments can be used when the control region size changes less frequently (e.g., is semi-static). In at least these embodiments, a control format indicator (CFI) channel can be repeatedly mapped to the central subcarriers in each control channel OFDM symbol. This synchronization signal for indicating the control region size can have a basic sequence that is at least somewhat similar to the LTE secondary synchronization signal (SSS), and the root index can be used to carry the CFI value information. The CFI channel signal in each symbol can use the same beamforming weights as the control channel. Therefore, the UE 102 can ignore control channel symbols whose channel energy is below a threshold and correctly decode the CFI channel or the control channel to reduce or eliminate blind detection.

Illustrative Examples

In an embodiment, UE 102 can use previously trained Rx beamforming to receive the control channel. As described below, eNB 104 can use different beamforming schemes.

For example, in some embodiments, the eNB 104 can transmit multiple control channels intended for multiple UEs 102 in different beam directions by employing DL multi-user multiple input multiple output (MU-MIMO) transmission, while DL digital beamforming is trained through channel state information reference signal (CSI-RS) or sounding RS.

In other embodiments, the eNB 104 can transmit multiple control channels to multiple UEs 102 in the same or similar directions from the eNB 104 to maximize or enhance Tx beamforming gain. These embodiments are illustrated in FIG7 .

FIG7 illustrates symbol-level time-multiplexed control channel transmissions based on geometry- and direction-based UE groupings, in accordance with certain embodiments. As shown in FIG7 , eNB 104 can group UEs based on their estimated signal-to-noise ratio (SINR) (or geometry) and beam direction. eNB 104 can then transmit UE-specific control channels based on the user groupings. For example, UE 1 and UE 2 can be low-geometry UEs requiring high beamforming gain, while UE 3, UE 4, and UE 5 can be high-geometry UEs capable of supporting MU MIMO. To accommodate the different required beamforming gains and beam directions, UE Group 1 and UE Group 2 are allocated different symbols for control channel transmissions in beam directions 702, 704, and 706 with the same or different aggregation levels. For example, a higher aggregation level can be used for transmissions to UE Group 2. Consequently, UE 1 and UE 2 can decode one or more DL DCI symbols for UE Group 2 because this symbol or group of symbols will have higher energy than the symbols for UE Group 1. In other embodiments, as described earlier herein, any or all of UE 1, UE 2, UE 3, UE 4, and UE 5 may scan up to a maximum number of symbols to decode the control channel and determine where the PDSCH may begin.

In certain embodiments, as shown in FIG8 , eNB 104 can schedule multiple UEs 102 in one or more beam directions, including both DL DCI and UL DCI. As shown in FIG8 , for example, if it is desired to receive a different UE 102 in each beam direction, a symbol can be simultaneously transmitted to multiple beam directions. For example, Tx Beam Set 1 can be simultaneously transmitted in beam directions 802 and 804. Because UL users UE 1 and UE 2 are typically not the same users as downlink users UE 3, UE 4, and UE 5, the example embodiment illustrated in FIG8 can be implemented by at least eNB 104. Similar Tx Beam Sets can be included; for example, eNB 104 can also simultaneously transmit Tx Beam Set 2 and Tx Beam Set 3 to other groups.

In the above embodiments, the DM-RS can be scrambled using a UE-specific sequence and can use a DM-RS port association rule similar to that of the ePDCCH. For DL transmissions from multiple transmission points, a DM-RS port is associated and the aggregated channel is estimated for decoding. The UE 102 can perform a blind search on a per-symbol basis, using a similar search space for each symbol. Optionally, in some embodiments, the UE search space can be designed as follows:

Where Δ _CCE represents a UE-specific CCE offset, which can be configured via dedicated RRC signaling, N _CCE is the number of CCEs in a subframe, and L is the aggregation level. The control channel symbols of one UE 102 can be different in different subframes to achieve diversity gain.

Apparatus for performing various embodiments

FIG9 is a functional block diagram of a user equipment (UE) 900 according to certain embodiments. UE 900 may be suitable for use as UE 102, as depicted in FIG1 . In certain embodiments, UE 900 may include application circuitry 902, baseband circuitry 904, radio frequency (RF) circuitry 906, front-end module (FEM) circuitry 908, and one or more antennas 910, coupled together at least as shown. In certain embodiments, other circuits or devices may include one or more elements and/or components of application circuitry 902, baseband circuitry 904, radio frequency (RF) circuitry 906, front-end module (FEM) circuitry 908, and in some cases, may also include other elements and/or components. As an example, "processing circuitry" may include one or more elements and/or components, some or all of which may be included in application circuitry 902 and/or baseband circuitry 904. As another example, "transceiver circuitry" may include one or more elements and/or components, some or all of which may be included in RF circuitry 906 and/or FEM circuitry 908. However, these examples are not limiting, as the processing circuit and/or the transceiver circuit may in some cases further include other elements and/or components.

In an embodiment, the processing circuitry can configure the transceiver circuitry to scan multiple OFDM symbols of a downlink subframe to detect the highest energy OFDM symbol among the multiple OFDM symbols. The processing circuitry can configure the transceiver circuitry to receive a value for the number of OFDM symbols to be scanned, wherein the value is not provided in a Physical Hybrid ARQ Indicator Channel (PHICH). For example, the value for the number of OFDM symbols to be scanned can be received in a DCI or in a synchronization signal. When the relative distance to the eNB 104 changes, the hardware processing circuitry can further configure the transceiver circuitry to scan the multiple OFDM symbols again to detect whether the highest energy OFDM symbol has changed. When the UE 900 does not receive the value for the number of OFDM symbols, the hardware processing circuitry can further configure the transceiver circuitry to blindly search up to a threshold number of OFDM symbols to detect control channel information.

The processing circuitry can configure the transceiver circuitry to decode the downlink control channel in the OFDM symbol with the highest energy.In an embodiment, the downlink control channel may be received from the eNB 104 in no more than one OFDM symbol.

In some embodiments, the UE 900 may receive the UL-formatted DCI in a first OFDM symbol of the plurality of OFDM symbols and receive the DL DCI in an OFDM symbol different from the first OFDM symbol.

The application circuitry 902 may include one or more application processors. For example, the application circuitry 902 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and specialized processors (e.g., graphics processors, application processors, etc.). The processor(s) may be coupled to and/or include memory/storage and may be configured to execute instructions stored in the memory/storage, thereby enabling various applications and/or operating systems to run on the system.

The baseband circuitry 904 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 904 may include one or more baseband processors and/or control logic to process baseband signals received from the receive signal path of the RF circuitry 906 and to generate baseband signals for the transmit signal path of the RF circuitry 906. The baseband circuitry 904 may interface with the application circuitry 902 for generating and processing baseband signals and for controlling the operation of the RF circuitry 906. For example, in some embodiments, the baseband circuitry 904 may include a second generation (2G) baseband processor 904a, a third generation (3G) baseband processor 904b, a fourth generation (4G) baseband processor 904c, and/or one or more other baseband processors 904d for other existing generations, generations in development, or generations to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 904 (e.g., one or more of the baseband processors 904a-d) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 906. The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency offset, etc. In some embodiments, the modulation/demodulation circuitry of the baseband circuitry 904 may include fast Fourier transform (FFT), precoding, and/or constellation mapping/demapping functions. In some embodiments, the encoding/decoding circuitry of the baseband circuitry 904 may include convolution, tail-biting, turbo, Viterbi, and/or low-density parity check (LDPC) encoder/decoder functions. Embodiments of the modulation/demodulation and encoder/decoder functions are not limited to these examples and may include other suitable functions in other embodiments.

In some embodiments, the baseband circuitry 904 may include protocol stack elements, including, for example, elements of the Evolved Universal Terrestrial Radio Access Network (EUTRAN) protocol, including, for example, physical (PHY), medium access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), and/or radio resource control (RRC) elements. The central processing unit (CPU) 904e of the baseband circuitry 904 may be configured to execute protocol stack elements for signaling at the PHY, MAC, RLC, PDCP, and/or RRC layers. In some embodiments, the baseband circuitry may include one or more audio digital signal processors (DSPs) 904f. The one or more audio DSPs 904f may include elements for compression/decompression and echo cancellation, and in other embodiments may include other suitable processing elements. The components of the baseband circuitry may be appropriately combined in a single chip, a single chipset, or, in some embodiments, placed on the same circuit board. In some embodiments, some or all of the components of the baseband circuitry 904 and the application circuitry 902 may be implemented together, such as, for example, on a system on a chip (SOC).

In some embodiments, the baseband circuitry 904 may provide for communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 904 may support communications with the Evolved Universal Terrestrial Radio Access Network (EUTRAN) and/or other wireless metropolitan area networks (WMANs), wireless local area networks (WLANs), and wireless personal area networks (WPANs). Embodiments in which the baseband circuitry 904 is configured to support radio communications using more than one wireless protocol may be referred to as multi-mode baseband circuitry.

RF circuitry 906 can enable communication with a wireless network using modulated electromagnetic radiation over a non-solid medium. In various embodiments, RF circuitry 906 can include switches, filters, amplifiers, and the like to facilitate communication with the wireless network. RF circuitry 906 can include a receive signal path that can include circuitry to downconvert RF signals received from FEM circuitry 908 and provide baseband signals to baseband circuitry 904. RF circuitry 906 can also include a transmit signal path that can include circuitry to upconvert baseband signals provided by baseband circuitry 904 and provide RF output signals to FEM circuitry 908 for transmission.

In certain embodiments, RF circuitry 906 may include a receive signal path and a transmit signal path. The receive signal path of RF circuitry 906 may include a mixing circuit 906a, an amplifier circuit 906b, and a filter circuit 906c. The transmit signal path of RF circuitry 906 may include a filter circuit 906c and the mixing circuit 906a. RF circuitry 906 may also include a synthesizer circuit 906d for synthesizing frequencies used by the mixer circuits 906a of the receive and transmit signal paths. In certain embodiments, the mixer circuit 906a of the receive signal path may be configured to down-convert the RF signal received from FEM circuitry 908 based on the synthesized frequency provided by the synthesizer circuit 906d. The amplifier circuit 906b may be configured to amplify the down-converted signal, and the filter circuit 906c may be a low-pass filter (LPF) or a band-pass filter (BPF) configured to remove unwanted signals from the down-converted signal to generate an output baseband signal. The output baseband signal may be provided to baseband circuitry 904 for further processing. In some embodiments, the output baseband signal can be a zero-frequency baseband signal, although this is not a requirement. In some embodiments, the mixing circuit 906a of the receive signal path can include a passive mixer, although the scope of the embodiments is not limited in this regard. In some embodiments, the mixing circuit 906a of the transmit signal path can be configured to up-convert the input baseband signal based on the synthesized frequency provided by the synthesizer circuit 906d, thereby generating an RF output signal for the FEM circuit 908. The baseband signal can be provided by the baseband circuit 904 and filtered by the filter circuit 906c. The filter circuit 906c can include a low-pass filter (LPF), although the scope of the embodiments is not limited in this regard.

In some embodiments, the mixing circuit 906a of the receive signal path and the mixing circuit 906a of the transmit signal path may include two or more mixers and may be arranged for orthogonal down-conversion and/or up-conversion, respectively. In some embodiments, the mixing circuit 906a of the receive signal path and the mixing circuit 906a of the transmit signal path may include two or more mixers and may be arranged for image suppression (e.g., Hartley image suppression). In some embodiments, the mixing circuit 906a of the receive signal path and the mixing circuit 906a may be arranged for direct down-conversion and/or direct up-conversion, respectively. In some embodiments, the mixing circuit 906a of the receive signal path and the mixing circuit 906a of the transmit signal path may be configured for superheterodyne operation.

In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, the RF circuitry 906 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry, and the baseband circuitry 904 may include a digital baseband interface to communicate with the RF circuitry 906. In some dual-mode embodiments, separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.

In certain embodiments, the synthesizer circuit 906d may be a fractional-N synthesizer or a fractional N/N+1 synthesizer, although the scope of the embodiments is not limited thereto, as other types of frequency synthesizers may be suitable. For example, the synthesizer circuit 906d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase-locked loop with a frequency divider. The synthesizer circuit 906d may be configured to synthesize the output frequency used by the mixing circuit 906a of the RF circuit 906 based on a frequency input and a frequency divider control input. In certain embodiments, the synthesizer circuit 906d may be a fractional N/N+1 synthesizer. In certain embodiments, the frequency input may be provided by a voltage-controlled oscillator (VCO), although this is not a requirement. The frequency divider control input may be provided by the baseband circuit 904 or the application circuit 902 depending on the desired output frequency. In certain embodiments, the frequency divider control input (e.g., N) may be determined from a lookup table based on a signal indicated by the application circuit 902.

The synthesis circuit 906d of the RF circuit 906 may include a frequency divider, a delay-locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the frequency divider may be a dual-mode frequency divider (DMD) and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by N or N+1 (e.g., based on the implementation) to provide a fractional frequency division ratio. In some example embodiments, the DLL may include a set of series-connected, adjustable delay elements, a phase detector, a charge pump, and a D-type flip-flop. In these embodiments, the delay elements may be configured to divide the VCO cycle into up to Nd equal phase groups, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

In some embodiments, the synthesizer circuit 906d can be configured to generate a carrier frequency as an output frequency, while in other embodiments, the output frequency can be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with a quadrature generator and divider circuit to generate multiple signals at the carrier frequency with multiple different phases relative to each other. In some embodiments, the output frequency can be the LO frequency (fLO). In some embodiments, the RF circuit 906 can include an IQ/polarization converter.

The FEM circuitry 908 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 910, amplify the received signals, and provide an amplified version of the received signals to the RF circuitry 906 for further processing. The FEM circuitry 908 may also include a transmit signal path that may include circuitry configured to amplify signals for transmission provided by the RF circuitry 906 for transmission by one or more of the one or more antennas 910.

In certain embodiments, the FEM circuitry 908 may include a TX/RX switch to switch between transmit and receive modes of operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include a low noise amplifier (LNA) to amplify received RF signals and provide the amplified received RF signals as outputs (e.g., to the RF circuitry 906). The transmit signal path of the FEM circuitry 908 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by the RF circuitry 906), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 910). In certain embodiments, the UE 900 may include additional components such as, for example, memory/storage, a display, a camera, sensors, and/or input/output (I/O) interfaces.

FIG10 is a functional block diagram of an evolved Node B (eNB) 1000 according to certain embodiments. It should be noted that in certain embodiments, eNB 1000 may be a stationary, non-mobile device. eNB 1000 may be suitable for use as eNB 104, as depicted in FIG1 . eNB 1000 may include physical layer circuitry 1002 and a transceiver 1005, one or both of which may enable the use of one or more antennas 1001 to transmit or receive signals to or from UE 900, other eNBs, other UEs, or other devices. As an example, physical layer circuitry 1002 may perform various encoding and decoding functions, including forming baseband signals for transmitting and decoding received signals. As another example, receiver 1005 may perform various transmit and receive functions, such as converting signals between baseband and radio frequency (RF) ranges. Thus, physical layer circuitry 1002 and transceiver 1005 may be separate components or may be part of a combined component. Additionally, some of the described functions may be performed by a combination that may include one, any, or all of the physical layer circuitry 1002 , the transceiver 1005 , and other components or layers.

In certain embodiments, the transceiver 1005 can transmit a downlink control channel to the UE 102, 900 (FIGS. 1 and 9) in an OFDM symbol (or a discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbol) of a downlink subframe. A first OFDM symbol in the plurality of OFDM symbols can be transmitted using first beamforming parameters, and a second OFDM symbol in the plurality of OFDM symbols can be transmitted using second beamforming parameters different from the first beamforming parameters. In an embodiment, any or all of these downlink control channels can be transmitted in no more than one OFDM symbol, although embodiments are not limited thereto. It will be appreciated that any number of control channels can be transmitted, and embodiments are not limited to two control channels. For example, only one control channel can be transmitted, or three or more control channels can be transmitted.

As described earlier herein with reference to at least Figures 4-6, any or all OFDM symbols in the control region can be transmitted using different DM-RS patterns. For example, a first OFDM symbol can be transmitted according to a first DM-RS pattern and a second OFDM symbol can be transmitted according to a second DM-RS pattern that is different from the first DM-RS pattern. In some embodiments, the second DM-RS pattern can vary from the first DM-RS pattern according to a cell-specific frequency offset pattern. In some embodiments, at least one OFDM symbol can include only a reference signal (RS).

In some embodiments, one OFDM symbol can be transmitted in a first beam direction and another OFDM symbol can be transmitted in a second beam direction different from the first beam direction. In at least these embodiments, UEs 102 in a cell served by eNB 1000 can be divided into at least two groups based on proximity to a cell edge. eNB 1000 can transmit a first OFDM symbol to one of the at least two groups and a second OFDM symbol to the other of the at least two groups.

In an embodiment, the eNB 1000 can transmit a UL-formatted downlink control indicator (DCI) in a first beam direction on a first OFDM symbol and transmit the downlink DCI in a second direction and in the first OFDM symbol.

The eNB 1000 may also include medium access control (MAC) circuitry 1004 for controlling access to the wireless medium. Antennas 910, 1001 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, or other types of antennas suitable for transmitting RF signals. In certain MIMO embodiments, antennas 910, 1001 may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may be obtained. In FD MIMO embodiments, a two-dimensional planar antenna array structure may be used, with antenna elements positioned in both vertical and horizontal directions, as described earlier herein.

In some embodiments, the UE 900 or eNB 1000 may be a mobile device and may be a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capabilities, a netbook, a wireless phone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a wearable device (such as a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.)), or other device that can wirelessly receive and/or transmit information. In some embodiments, the UE 900 or eNB 1000 may be configured to operate in accordance with 3GPP standards, although the scope of the embodiments is not limited in this regard. In some embodiments, the mobile device or other device may be configured to operate in accordance with other protocols or standards, including IEEE 802.11 or other IEEE standards. In some embodiments, the UE 900, eNB 1000, or other device may include one or more of a keyboard, a display, a non-volatile storage port, multiple antennas, a graphics processor, an application processor, a speaker, and other mobile device components. The display may be an LCD screen including a touch screen.

FIG11 illustrates a block diagram of an example machine 1100 on which any one or more of the techniques (e.g., methods) discussed herein may be performed. In alternative embodiments, the machine 1100 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine 1100 may operate as a server machine, a client machine, or both in a server-client network environment. In an example, the machine 1100 may act as a peer machine in a peer-to-peer (P2P) (or other distributed) network environment. The machine 1100 may be a UE, an eNB, an MME, a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile phone, a smartphone, a network appliance, a network router, a switch or bridge, or any machine capable of executing instructions (sequential or otherwise) specifying actions to be taken by the machine. Further, while a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as in cloud computing, Software as a Service (SaaS), and other computer cluster configurations.

As described herein, example can include or can be operated on logic or multiple components, modules or mechanisms.Module is the tangible entity (for example, hardware) that can perform the specified operation and can be configured or arranged in an ad hoc manner. In an example, circuit can be arranged in a specified manner (for example, internally or about an external entity such as other circuits) as a module. In an example, all or part of one or more computer systems (for example, independently, client or server computer systems) or one or more hardware processors can be configured as a module for performing the specified operation by firmware or software (for example, instruction, application part or application). In an example, software can reside on a computer-readable medium. In an example, when performed by the underlying hardware of a module, software causes hardware to perform the specified operation.

Thus, the term "module" is understood to include tangible entities, being entities that are physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., provisionally) configured (e.g., programmed) to operate in a prescribed manner or to perform some or all of any of the operations described herein. Considering examples where modules are temporarily configured, each module need not be instantiated at any one moment in time. For example, where a module comprises a general-purpose hardware processor configured using software, the general-purpose hardware processor can be separately configured as different modules at different times. Thus, software can configure a hardware processor, for example, to constitute a particular module at one moment and to constitute a different module at a different moment.

The machine (e.g., a computer system) 1100 may include a hardware processor 1102 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 1104, and a static memory 1106, some or all of which may communicate with each other via a connection (e.g., a bus) 1108. The machine 1100 may further include a display unit 1110, an alphanumeric input device 1112 (e.g., a keyboard), and a user interface (UI) navigation device 114 (e.g., a mouse). In an example, the display unit 1110, the input device 1112, and the UI navigation device 1114 may be a touch screen display. The machine 1100 may additionally include a storage device (e.g., a drive unit) 1116, a signal generating device 1118 (e.g., a speaker), a network interface device 1120, and one or more sensors 1121, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensors. The machine 1100 may include an output controller 1128, such as a serial (e.g., universal serial bus (USB)), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.).

The storage device 1116 may include a computer-readable medium 1122 having stored thereon one or more data structures or instructions 1124 (e.g., software) that embody or are utilized by any one or more of the techniques or functions described herein. The instructions 1124 may also reside, completely or at least partially, within the main memory 1104, within the static memory 1106, or within the hardware processor 1102 during execution thereof by the machine 1100. In an example, one or any combination of the hardware processor 1102, the main memory 1104, the static memory 1106, or the storage device 1116 may constitute a computer-readable medium.

Although the computer-readable medium 1122 is described as a single medium, the term "computer-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 1124. When the machine 1100 operates as an eNB, the computer-readable medium 1122 can instruct one or more processors of the eNB to detect the location of user equipment (UE) in a cell served by the eNB; and to transmit a downlink control channel to the UE in a plurality of orthogonal frequency division multiplexing (OFDM) symbols of a downlink subframe, the number of OFDM symbols being set based on at least one of a cell load and the location of the plurality of UEs.

The term "computer-readable medium" may include any medium that is capable of storing, encoding, or executing instructions executed by the machine 1100 and causing the machine 1100 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding, or executing data structures used by such instructions or data structures associated with such instructions. Non-limiting examples of computer-readable media may include solid-state memory, and optical and magnetic media. Specific examples of computer-readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; random access memory (RAM); and CD-ROM and DVD-ROM disks. In some examples, the computer-readable medium may include non-transitory computer-readable media. In some examples, the computer-readable medium may include computer-readable media that is not a transient propagating signal.

The instructions 1124 may further be sent or received over the communication network 1126 using a transmission medium via the network interface device 1120 using any of a number of transmission protocols (e.g., frame relay, Internet Protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.) Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), a mobile telephone network (e.g., a cellular network), a plain old telephone (POTS) network, and a wireless data network (e.g., the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as IEEE, the IEEE 802.16 family of standards known as IEEE), the IEEE 802.15.4 family of standards, the Long Term Evolution (LTE) family of standards, the Universal Mobile Telecommunications System (UMTS) family of standards, a peer-to-peer (P2P) network, and others. In an example, the network interface device 1120 may include one or more physical jacks (e.g., Ethernet, coaxial, or telephone jacks) or one or more antennas to connect to the communication network 1126. In an example, the network interface device 1120 may include multiple antennas to communicate wirelessly using at least one of single-input multiple-output (SIMO), MIMO, FD-MIMO, or multiple-input single-output (MISO) technology. In some examples, the wireless interface device 1120 may communicate wirelessly using FD-MIMO technology. The term "transmission medium" should be taken to include any intangible medium capable of storing, encoding, or carrying instructions for execution by the machine 1100, and includes digital or analog communication signals or other intangible media to facilitate communication of such software.

To further illustrate the devices, systems, and methods disclosed herein, a non-limiting list of examples is provided below:

In Example 1, for an evolved Node B (eNB), the apparatus includes a hardware processing circuit and a transceiver circuit, the hardware processing circuit being configured to configure the transceiver circuit to: send a downlink control channel to a user equipment (UE) in an orthogonal frequency division multiplexing (OFDM) symbol of a downlink subframe, the first OFDM symbol being configured to be sent in a first direction using a first beamforming parameter, and the second OFDM symbol being configured to be sent in a second direction different from the first beamforming parameter using a second beamforming parameter different from the first beamforming parameter.

In Example 2, the subject matter of Example 1 can optionally include: wherein the eNB is configured to dynamically adjust the beam direction of the OFDM symbol in a subsequent subframe based on cell conditions in a cell served by the eNB.

In Example 3, the subject matter of any one of Examples 1-2 can optionally include: wherein the search space of the downlink control channel is limited to one OFDM symbol.

In Example 4, the subject matter of any of Examples 1-3 can optionally include: wherein the first OFDM symbol is sent according to a demodulation reference signal (DM-RS) pattern, wherein four resource elements (REs) are reserved for the DM-RS, in two groups of two consecutive REs; and wherein four REs are reserved for non-DM-RS between the two groups of consecutive REs.

In Example 5, the subject matter of Example 4 can optionally include: wherein the second DM-RS pattern differs from the first DM-RS pattern according to a cell-specific frequency offset pattern.

In Example 6, the subject matter of any one of Examples 1-2 can optionally include: wherein the hardware processing circuit further configures the transceiver circuit to send a first OFDM symbol to a first group of UEs close to a cell edge and to send a second OFDM symbol to a second group of UEs farther from the cell edge than the first group of UEs.

In Example 7, the subject matter of any of Examples 1-6 can optionally include: wherein the hardware processing circuit further configures the transceiver circuit to send an uplink-formatted downlink control indicator (DCI) in a first analog beam direction on a first OFDM symbol and to send a downlink DCI in a second direction and in the first OFDM symbol.

In Example 8, the subject matter of any one of Examples 1-7 can optionally include wherein the hardware processing circuitry further configures the transceiver circuitry to transmit, in the UE-specific DCI, an indication of a number of OFDM symbols in which the control channel is to be transmitted.

In Example 9, the subject matter of Example 8 can optionally include wherein the hardware processing circuitry further configures the transceiver circuitry to dynamically adjust, between subframes, a number of OFDM symbols in which the control channel is to be transmitted.

In Example 10, the subject matter of any one of Examples 1-9 can optionally include wherein the hardware processing circuitry further configures the transceiver circuitry to transmit in a secondary synchronization signal (SSS) an indication of a number of OFDM symbols in which the control channel is to be transmitted.

In Example 11, the subject matter of any one of Examples 1-10 can optionally include wherein the hardware processing circuitry further configures the transceiver circuitry to adjust a number of OFDM symbols used to transmit the control channel after the UE enters or leaves the cell.

In Example 12, the subject matter of any one of Examples 1-11 can optionally include eight or more antennas.

In Example 13, the subject matter of any one of Examples 1-12 can optionally include the antenna being configured in a subarray-based hybrid antenna architecture (HAA).

In Example 14, the subject matter of any one of Examples 1-13 can optionally include: wherein the downlink control channel is time division duplexed with the data channel within a subframe.

Example 15 includes an apparatus for a user equipment (UE), the apparatus comprising a transceiver circuit and a hardware processing circuit, the hardware processing circuit configuring the transceiver circuit to scan multiple orthogonal frequency division multiplexing (OFDM) symbols of a downlink subframe to detect the highest energy OFDM symbol among the multiple OFDM symbols; and to decode a downlink control channel in the highest energy OFDM symbol, the downlink control channel being received from an evolved Node B (eNB) in no more than one OFDM symbol.

In Example 16, the subject matter of Example 15 can optionally include wherein the hardware processing circuitry further configures the transceiver circuitry to receive a value for the number of OFDM symbols to be scanned.

In Example 17, the subject matter of Example 16 can optionally include: wherein the value for the number of OFDM symbols to be scanned is received in downlink control information (DCI).

In Example 18, the subject matter of Example 16 can optionally include: wherein the value for the number of OFDM symbols to scan is received in a synchronization signal.

In Example 19, the subject matter of any one of Examples 15-18 can optionally include: wherein, when the relative distance to the eNB changes, the hardware processing circuit further configures the transceiver circuit to scan the multiple OFDM symbols again to detect whether the highest energy OFDM symbol has changed.

In Example 20, the subject matter of any one of Examples 15-19 can optionally include: wherein the hardware processing circuit further configures the transceiver circuit to receive uplink-formatted downlink control information (DCI) in the first OFDM symbol of the multiple OFDM symbols and to receive downlink DCI in an OFDM symbol different from the first OFDM symbol.

In Example 21, the subject matter of any of Examples 15-20 can optionally include: wherein, when the UE does not receive a value for the number of OFDM symbols, the hardware processing circuit further configures the transceiver circuit to blindly search up to a threshold number of OFDM symbols to detect control channel information.

In Example 22, the subject matter of any one of Examples 15-21 can optionally include: wherein the hardware processing circuit comprises a baseband processor to process the control channel.

In Example 23, a computer-readable medium stores instructions for execution by one or more processors to perform operations for communications for an evolved Node B (eNB), the operations being configured to: detect a location of a user equipment (UE) in a cell served by the eNB; and send a downlink control channel to the UE in a plurality of orthogonal frequency division multiplexing (OFDM) symbols of a downlink subframe, the number of OFDM symbols being set based on at least one of a cell load and a location of the UE.

In Example 24, the subject matter of Example 23 can optionally include: wherein a downlink control channel of the plurality of control channels is sent in no more than one OFDM symbol.

In Example 25, the subject matter of any of Examples 23-24 can optionally include: wherein the first OFDM symbol is sent according to a first demodulation reference signal (DM-RS) pattern and the second OFDM symbol is sent according to a second DM-RS pattern different from the first DM-RS pattern.

In Example 26, the subject matter of any one of Examples 23-25 can optionally include: wherein the eNB is configured for millimeter wave (mmWave) communication.

The accompanying drawings and the foregoing description provide examples of the present disclosure. Although depicted as multiple separate functional items, those skilled in the art will appreciate that one or more of such elements can be well combined into a single functional element. Alternatively, a particular element can be divided into multiple functional elements. Elements of one embodiment can be added to another embodiment. For example, the order of the processes described herein can be varied and is not limited to the manner described herein. In addition, the actions of any flowchart do not need to be implemented in the order shown; nor do they necessarily need to be performed in all actions. Furthermore, those actions that do not depend on other actions can be performed in parallel with other actions. However, the scope of the present disclosure is not limited in any way by these specific examples. Whether or not explicitly given in the specification, a large number of variations are possible, such as differences in structure, size, and use of materials. The scope of the present disclosure is at least as broad as given in the following claims.

Claims (24)

1. An apparatus for a base station, the apparatus comprising hardware processing circuitry and transceiver circuitry, the hardware processing circuitry being configured to: In the orthogonal frequency division multiplexing (OFDM) symbols of the downlink subframe, a downlink control channel is transmitted to a user equipment (UE), wherein a first OFDM symbol in the OFDM symbol is configured to be transmitted using a first beamforming parameter in a first direction, and a second OFDM symbol in the OFDM symbol is configured to be transmitted using a second beamforming parameter different from the first beamforming parameter in a second direction different from the first direction. 2. The apparatus of claim 1, wherein the base station is configured to dynamically adjust the beam direction of OFDM symbols in subsequent subframes based on cell conditions in the cell served by the base station. 3. The apparatus according to any one of claims 1-2, wherein the search space of the downlink control channel is limited to one OFDM symbol. 4. The apparatus according to any one of claims 1-2, wherein the first OFDM symbol is transmitted according to a demodulation reference signal DM-RS pattern, wherein four resource elements (REs) are reserved for DM-RS in two sets of two consecutive REs; and wherein four non-DM-RS REs are reserved between the two sets of two consecutive REs. 5. The apparatus of claim 4, wherein the second DM-RS pattern differs from the first DM-RS pattern according to a cell-specific frequency offset pattern. 6. The apparatus according to any one of claims 1-2, wherein the hardware processing circuitry further configures the transceiver circuitry to: Send the first OFDM symbol to the first group of UEs that are close to the cell edge and send the second OFDM symbol to the second group of UEs that are farther from the cell edge than the first group of UEs. 7. The apparatus according to any one of claims 1-2, wherein the hardware processing circuitry further configures the transceiver circuitry to: Uplink-formatted downlink control information (DCI) is transmitted in the first analog beam direction on the first OFDM symbol, and downlink DCI is transmitted in the second direction and on the first OFDM symbol. 8. The apparatus according to any one of claims 1-2, wherein the hardware processing circuitry further configures the transceiver circuitry to: The UE-specific downlink control information (DCI) transmits an indication of the number of OFDM symbols for which the downlink control channel will be transmitted. 9. The apparatus of claim 8, wherein the hardware processing circuitry further configures the transceiver circuitry to: The number of OFDM symbols that will be transmitted in the downlink control channel is dynamically adjusted between subframes. 10. The apparatus according to any one of claims 1-2, wherein the hardware processing circuitry further configures the transceiver circuitry to: The auxiliary synchronization signal SSS is used to transmit an indication of the number of OFDM symbols that will be transmitted in the downlink control channel. 11. The apparatus according to any one of claims 1-2, wherein the hardware processing circuitry further configures the transceiver circuitry to: When a UE enters or leaves a cell, the number of OFDM symbols used for transmitting downlink control channels is adjusted. 12. The apparatus according to any one of claims 1-2, further comprising: eight or more antennas. 13. The apparatus according to any one of claims 1-2, further comprising: an antenna configured in a subarray-based hybrid antenna architecture (HAA). 14. The apparatus according to any one of claims 1-2, wherein the downlink control channel is time-division duplexed with the data channel within a subframe. 15. An apparatus for a user equipment (UE), the apparatus comprising a transceiver circuit and a hardware processing circuit, the hardware processing circuit configuring the transceiver circuit to: Multiple Orthogonal Frequency Division Multiplexing (OFDM) symbols are scanned in the downlink subframe, wherein a first OFDM symbol of the multiple OFDM symbols is transmitted by the base station in a first direction using a first beamforming parameter, and a second OFDM symbol of the multiple OFDM symbols is transmitted by the base station in a second direction different from the first beamforming parameter and different from the first direction; and Decode the downlink control channel, which is received from the base station in no more than one OFDM symbol. 16. The apparatus of claim 15, wherein the hardware processing circuitry further configures the transceiver circuitry to: Receive the value of the number of the plurality of OFDM symbols to be scanned. 17. The apparatus according to any one of claims 15-16, wherein the value of the number of the plurality of OFDM symbols to be scanned is received in downlink control information (DCI). 18. The apparatus according to any one of claims 15-16, wherein the value of the number of the plurality of OFDM symbols to be scanned is received in a synchronization signal. 19. The apparatus according to any one of claims 15-16, wherein, when the relative distance to the base station changes, the hardware processing circuit further configures the transceiver circuit to: The multiple OFDM symbols are scanned again to detect whether the highest-energy OFDM symbol has changed. 20. The apparatus according to any one of claims 15-16, wherein the hardware processing circuitry further configures the transceiver circuitry to: Uplink-formatted downlink control information (DCI) is received in the first OFDM symbol of the plurality of OFDM symbols, and downlink DCI is received in OFDM symbols different from the first OFDM symbol. 21. The apparatus according to any one of claims 15-16, wherein when the UE does not receive a value for the number of the plurality of OFDM symbols, the hardware processing circuitry further configures the transceiver circuitry to blindly search for up to a threshold number of OFDM symbols to detect control channel information. 22. The apparatus according to any one of claims 15-16, wherein the hardware processing circuitry includes a baseband processor for processing the control channel. 23. A base station, comprising: A means for transmitting a downlink control channel to a user equipment (UE) in an orthogonal frequency division multiplexing (OFDM) symbol of a downlink subframe, wherein a first OFDM symbol in the OFDM symbol is configured to be transmitted using a first beamforming parameter in a first direction, and a second OFDM symbol in the OFDM symbol is configured to be transmitted using a second beamforming parameter different from the first beamforming parameter and in a second direction different from the first direction. 24. A user equipment (UE), comprising: An apparatus for scanning multiple orthogonal frequency division multiplexing (OFDM) symbols of a downlink subframe, wherein a first OFDM symbol of the multiple OFDM symbols is transmitted by a base station in a first direction using a first beamforming parameter, and a second OFDM symbol of the multiple OFDM symbols is transmitted by the base station using a second beamforming parameter different from the first beamforming parameter and in a second direction different from the first direction; and A means for decoding a downlink control channel received from the base station in no more than one OFDM symbol.