CN109076371B - CQI reporting for flexible transmission mode switching - Google Patents

Abstract

User Equipment (UE) and base station (eNB) apparatus and methods for CQI reporting for flexible transmission mode switching. The UE includes: a memory; and processing circuitry configured to: generating a reporting message for an evolved node B (eNB) indicating a plurality of transmit (Tx) beams as preferred Tx beams. The processing circuitry determines Channel State Information (CSI) for at least two preferred Tx beams in response to a channel state information reference signal (CSI-RS), the CSI-RS being beamformed based on the plurality of preferred Tx beams, and the CSI comprising a transmission beam index for each of the preferred Tx beams. Reporting the determined CSI to the eNB, wherein the CSI is configured by the UE to indicate a preferred transmission mode based at least in part on a transmission beam index of each preferred Tx beam.

Description

CQI reporting for flexible transmission mode switching

Technical Field

Embodiments pertain to wireless communications. Some embodiments relate to wireless networks including 3GPP (third generation partnership project) networks, 3GPP LTE (long term evolution) networks, 3GPP LTE-a (LTE advanced) networks, and 5G networks, although the scope of the embodiments is not limited in this respect. Some embodiments relate to Channel Quality Indicator (CQI) derivation and reporting for flexible transmission mode switching.

Background

As different types of devices communicating with various network devices have increased, the usage of the 3GPP LTE system has increased. In recent years, cellular communications have evolved from low data rate voice and text messaging applications to high data rate applications with enormous useful applications, such as High Definition (HD) audio and video streaming media, full-feature internet connectivity, all of which have had a significant impact on the daily lives of the public. Fifth generation (5G) wireless systems are coming and are expected to enable greater speed, connectivity, and availability.

One area of development regarding 5G systems is to boost communication bandwidth for higher data rates than currently available. However, communication paths used in high-band communications tend to travel in a more line-of-sight manner and may be more susceptible to path loss due to obstructions (e.g., natural terrain, buildings and other structures, and vehicles). To address these challenges, it has been proposed to utilize beamforming and multiple-input multiple-output (MIMO) techniques. Furthermore, as User Equipment (UE) moves and/or rotates with usage, the surrounding environment changes, and the number of channel clusters that can be used for communication with an evolved node B (eNB) and the conditions also change.

A practical solution for flexible transmission mode switching is needed.

Drawings

In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. In the following figures of the drawings, some embodiments are shown by way of example and not limitation.

Fig. 1 is a functional diagram of a 3GPP network according to some embodiments.

Fig. 2 is a block diagram of a User Equipment (UE) in accordance with some embodiments.

Fig. 3 is a block diagram of an evolved node B (eNB) in accordance with some embodiments.

Fig. 4A-4B illustrate examples of multiple beam transmission scenarios with an eNB and a UE, in accordance with some embodiments.

Fig. 5A is a diagram illustrating Channel State Information (CSI) derivation and reporting for flexible transmission mode switching, in accordance with some embodiments.

Fig. 5B illustrates Downlink Control Information (DCI) based CSI derivation and reporting, in accordance with some embodiments.

Fig. 6-8 are flow diagrams illustrating example functionality for CQI derivation and/or reporting, according to some embodiments.

Fig. 9 illustrates a block diagram of a communication device (e.g., an eNB or UE) in accordance with some embodiments.

Detailed Description

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

The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. A number of examples are described in the context of a 3GPP communication system and its components. It should be understood that the principles of the embodiments may be applied, without limitation, in other types of communication systems (e.g., wi-Fi or Wi-Max networks, bluetooth or other personal area networks, zigbee or other home area networks, wireless mesh networks, etc.), unless expressly limited by the corresponding claims. Given the benefit of this disclosure, those skilled in the art will be able to devise suitable variations to implement the principles of the embodiments in other types of communication systems. Various embodiments may include structural differences, logical differences, electrical differences, processing differences, and other differences. Portions or features of some embodiments may be included in or substituted for those of others. Embodiments set forth in the claims encompass all currently known and later-presented equivalents of those claims.

Fig. 1 is a functional diagram of a 3GPP network according to some embodiments. The network includes a Radio Access Network (RAN) (e.g., E-UTRAN or evolved universal terrestrial radio access network, as depicted) 101 and a core network 120 (e.g., shown as Evolved Packet Core (EPC)) coupled together by an S1 interface 115. For convenience and simplicity, only a portion of the core network 120 and the RAN 101 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.RAN 101 includes an evolved node B (eNB) 104 (which may operate as a base station) for communicating with User Equipment (UE) 102. The enbs 104 may include macro enbs and Low Power (LP) enbs. In accordance with some embodiments, the eNB104 may send a downlink control message to the UE102 to indicate an allocation of Physical Uplink Control Channel (PUCCH) channel resources. The UE102 may receive a downlink control message from the eNB104 and may transmit an uplink control message to the eNB104 in at least a portion of the PUCCH channel resources. These embodiments will be described in more detail below.

The MME 122 is functionally similar to the control plane of a legacy Serving GPRS Support Node (SGSN). The MME 122 manages mobility aspects in access (e.g., gateway selection and tracking area list management). The serving GW 124 terminates the interface towards the RAN 101 and routes data packets between the RAN 101 and the core network 120. Further, it may be a local mobility anchor point for inter-eNB handover and may also provide an anchor for inter-3 GPP mobility. Other responsibilities may include lawful interception, charging, and some policy enforcement. The serving GW 124 and MME 122 may be implemented in one physical node or in separate physical nodes. The PDN GW 126 terminates the SGi interface towards the Packet Data Network (PDN). The PDN GW 126 routes data packets between the EPC 120 and the external PDN, and may be a key node for policy enforcement and charging data collection. It may also provide an anchor point for non-LTE access for mobility. The external PDN may be any kind of IP network as well as IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and the serving GW 124 may be implemented in one physical node or in separate physical nodes.

The enbs 104 (macro and micro enbs) terminate the air interface protocol and may be the first contact point for the UE 102. In some embodiments, the eNB104 may implement various logical functions for the RAN 101 including, but not limited to, RNCs (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 UE102 may be configured to communicate with the eNB104 over a multipath fading channel in accordance with an Orthogonal Frequency Division Multiple Access (OFDMA) communication technique. The OFDM signal may include a plurality of orthogonal subcarriers.

S1 interface 115 is an interface that separates RAN 101 from EPC 120. It is divided into two parts: S1-U, which carries traffic data between the eNB104 and the serving GW 124; and S1-MME, which is the signaling interface between eNB104 and MME 122. The X2 interface is an interface between enbs 104. The X2 interface includes two parts: X2-C and X2-U. X2-C is the control plane interface between eNBs 104, and X2-U is the user plane interface between eNBs 104.

In the case of cellular networks, LP cells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to increase network capacity in areas where phone usage is very dense (e.g., train stations). As used herein, the term Low Power (LP) eNB refers to any suitable relatively low power eNB for implementing a narrower cell (narrower than a macro cell), e.g., a femto cell, pico cell, or micro cell. Femtocell enbs are typically provided by mobile network operators to their residential or enterprise customers. A femto cell is typically the size of a residential gateway or smaller and is typically connected to a subscriber's broadband line. Once plugged in, the femto cell connects to the mobile operator's mobile network and provides additional coverage for the residential femto cell, typically ranging from 30 meters to 50 meters. Thus, the LP eNB may be a femto cell eNB as it is coupled through the PDN GW 126. Similarly, a picocell is a wireless communication system that typically covers a very small area, such as within a building (office, mall, train station, etc.), or more recently, within an aircraft. A picocell eNB may be connected to another eNB (e.g., a macro eNB) via an X2 link, typically through its Base Station Controller (BSC) functionality. Thus, the LP eNB may be implemented with a pico eNB, as it is coupled to a macro eNB via an X2 interface. A pico cell eNB or other LPeNB may include some or all of the functionality of a macro eNB. In some cases, this may be referred to as an access point base station or an enterprise femtocell.

In some embodiments, the downlink resource grid may be used for downlink transmissions from the eNB104 to the UE102, while uplink transmissions from the UE102 to the eNB104 may utilize similar techniques. The grid may be a time-frequency grid, referred to as a resource grid or a time-frequency resource grid, which is a physical resource in the downlink in each slot. This time-frequency plane representation is common practice for OFDM systems, making radio resource allocation intuitive. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in the radio frame. The smallest time-frequency unit in a resource grid is called a Resource Element (RE). Each resource grid includes a plurality of Resource Blocks (RBs) that describe the mapping of particular physical channels to resource elements. Each resource block includes a set of resource elements in the frequency domain and may represent a minimum share of resources that can currently be allocated. There are several different physical downlink channels conveyed using these resource blocks. Two example physical downlink channels are a physical downlink shared channel and a physical downlink control channel.

The Physical Downlink Shared Channel (PDSCH) carries user data and higher layer signaling to the UE102 (fig. 1). A Physical Downlink Control Channel (PDCCH) carries information on a transport format and resource allocation, etc. related to the PDSCH channel. It also informs the UE102 of transport format, resource allocation, and hybrid automatic repeat request (HARQ) information related to the uplink shared channel. Typically, downlink scheduling may be performed at the eNB104 (e.g., assigning control channel resource blocks and shared channel resource blocks to the UEs 102 within a cell) based on channel quality information fed back from the UEs 102 to the eNB104, and then downlink resource assignment information may be sent to the UEs 102 on a control channel (PDCCH) used for (assigned to) the UEs 102.

The PDCCH delivers control information using CCEs (control channel elements). The PDCCH complex-valued symbols are first organized into quadruplets before being mapped to resource elements, and then arranged using a sub-block interleaver for rate matching. Each PDCCH is transmitted using one or more of these Control Channel Elements (CCEs), where each CCE corresponds to nine sets of four physical resource elements called Resource Element Groups (REGs). Four QPSK symbols are mapped to each REG. The PDCCH may be transmitted using one or more CCEs depending on the size of Downlink Control Information (DCI) and channel conditions. There may be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation levels, L =1, 2, 4, or 8).

According to an example embodiment, the UE102 may be configured to switch between single beam and dual beam transmission based on, for example, channel quality of one or more clusters of channels between the eNB104 and the UE 102. More specifically, and as explained below, a UE may be equipped with multiple antenna panels (e.g., 210A-210D), which enables the UE to boost signal quality through a wider angle of arrival (AoA), or to increase data rates by providing high rank transmission via beam aggregation.

As the UE moves and/or rotates and the resulting ambient environment changes, the preferred transmission may be switched between single beam transmission (e.g., rank 1 or 2) and dual beam transmission (e.g., rank 2, 3 or 4). For example, when at least two strong channel clusters are available during the link between the eNB and the UE, dual-beam transmission with a higher rank may be preferred, thereby enabling higher data rates. In instances when only one strong cluster of channels is feasible (e.g., in a line-of-sight (LoS) scenario), a single beam may be provided due to insufficient space. Since the eNB uses the Channel State Information (CSI) 160 to evaluate the condition of the cluster of communication channels for the beam, the CSI 160 (e.g., a channel quality indicator or CQI) may be used by the UE to indicate a preferred transmission mode to the eNB. Further, the eNB104 may provide an indicator 180 to the UE indicating whether CSI 160 of a single transmit beam or multiple transmit beams is required. In another embodiment, the eNB104 may provide an indicator 170 to the UE indicating a derivation method for one or more CSI characteristics (e.g., CQI). For example, the derivation indicator 170 may indicate whether mutual interference between at least two transmission beams should be considered when determining the CQI or whether the UE102 should determine the CQI without considering the mutual interference. In this regard, CQI reporting may be used to enable flexible transmission mode switching, where a preferred transmission mode (e.g., single or dual beam transmission) may be indicated by a UE or by an eNB.

As used herein, the term "circuitry" may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) or memory (shared, dedicated, or group) that executes one or more software or firmware programs, a combinational logic circuit, or other suitable hardware components that provide the described functionality. In some embodiments, the circuitry may be implemented in, or functions associated with, one or more software or firmware modules. In some embodiments, the circuitry may comprise logic operable, at least in part, in hardware. The embodiments described herein may be implemented as a system using any suitable configuration of hardware or software.

Fig. 2 is a functional diagram of a User Equipment (UE) according to some embodiments. The UE 200 may be adapted for use as the UE102 as depicted in fig. 1. In some embodiments, the UE 200 may include application circuitry 202, baseband circuitry 204, radio Frequency (RF) circuitry 206, front End Module (FEM) circuitry 208, and a plurality of antennas 210A-210D coupled together at least as shown. In some embodiments, other circuits or arrangements may include one or more elements or components of the application circuitry 202, the baseband circuitry 204, the RF circuitry 206, or the FEM circuitry 208, and in some cases may also include other elements or components. By way of example, "processing circuitry" may include one or more elements or components, some or all of which may be included in application circuitry 202 or baseband circuitry 204. As another example, a "transceiver circuit" may include one or more elements or components, some or all of which may be included in the RF circuitry 206 or the FEM circuitry 208. However, these examples are not limiting as the processing circuitry or transceiver circuitry may also include other elements or components in some cases.

The application circuitry 202 may include one or more application processors. For example, the application circuitry 202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor may include any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, etc.). The processor may be coupled to or may include memory/storage and may be configured to: the instructions stored in the memory/storage are executed to enable various applications or operating systems to run on the system.

The baseband circuitry 204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. Baseband circuitry 204 may include one or more baseband processors or control logic to process baseband signals received from the receive signal path of RF circuitry 206 and to generate baseband signals for the transmit signal path of RF circuitry 206. The baseband circuitry 204 may interface with the application circuitry 202 for generating and processing baseband signals and controlling operation of the RF circuitry 206. For example, in some embodiments, the baseband circuitry 204 may include a second generation (2G) baseband processor 204a, a third generation (3G) baseband processor 204b, a fourth generation (4G) baseband processor 204c, or other baseband processor 204d for other existing generations, generations in development or to be developed in the future (e.g., fifth generation (5G), 6G, etc.). The baseband circuitry 204 (e.g., one or more of the baseband processors 204 a-d) may process various radio control functions that enable communication with one or more radio networks via the RF circuitry 206. Radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, and the like. In some embodiments, the modulation/demodulation circuitry of the baseband circuitry 204 may include Fast Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, the encoding/decoding circuitry of the baseband circuitry 204 may include Low Density Parity Check (LDPC) encoder/decoder functionality, optionally including other techniques (e.g., block codes, convolutional codes, turbo codes, etc.) that may be used to support legacy protocols. Embodiments of modulation/demodulation and encoder/decoder functions are not limited to these examples, and may include other suitable functions in other embodiments.

In some embodiments, baseband circuitry 204 may include elements of a protocol stack, such as elements of an Evolved Universal Terrestrial Radio Access Network (EUTRAN) protocol, including, for example, a Physical (PHY) element, a Medium Access Control (MAC) element, a Radio Link Control (RLC) element, a Packet Data Convergence Protocol (PDCP) element, or a Radio Resource Control (RRC) element. The Central Processing Unit (CPU) 204e of the baseband circuitry 204 may be configured to: elements of the protocol stack are run for signaling of the PHY, MAC, RLC, PDCP, or RRC layers. In some embodiments, the baseband circuitry may include one or more audio Digital Signal Processors (DSPs) 204f. The audio DSP 204f may include elements for compression/decompression and echo cancellation, and may include other suitable processing elements in other embodiments. In some embodiments, the components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on the same circuit board. In some embodiments, some or all of the constituent components of the baseband circuitry 204 and the application circuitry 202 may be implemented together, for example, on a system on a chip (SOC).

In some embodiments, the baseband circuitry 204 may provide communications compatible with one or more radio technologies. For example, in some embodiments, baseband circuitry 204 may support communication with an Evolved Universal Terrestrial Radio Access Network (EUTRAN) or other Wireless Metropolitan Area Network (WMAN), wireless Local Area Network (WLAN), wireless Personal Area Network (WPAN). Embodiments in which the baseband circuitry 204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

The RF circuitry 206 may enable communication with a wireless network using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 206 may include switches, filters, amplifiers, and the like to facilitate communication with the wireless network. RF circuitry 206 may include a receive signal path, which may include circuitry to down-convert RF signals received from FEM circuitry 208 and provide baseband signals to baseband circuitry 204. RF circuitry 206 may also include a transmit signal path, which may include circuitry to up-convert baseband signals provided by baseband circuitry 204 and provide an RF output signal to FEM circuitry 208 for transmission.

In some embodiments, RF circuitry 206 may include a receive signal path and a transmit signal path. The receive signal path of the RF circuitry 206 may include mixer circuitry 206a, amplifier circuitry 206b, and filter circuitry 206c. The transmit signal path of the RF circuitry 206 may include filter circuitry 206c and mixer circuitry 206a. RF circuitry 206 may further include synthesizer circuitry 206d for synthesizing the frequencies used by mixer circuitry 206a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuit 206a of the receive signal path may be configured to: the RF signal received from the FEM circuitry 208 is downconverted based on the synthesized frequency provided by the synthesizer circuitry 206 d. The amplifier circuit 206b may be configured to: the downconverted signal is amplified, and the filter circuit 206c may be a Low Pass Filter (LPF) or a Band Pass Filter (BPF) configured to: unwanted signals are removed from the down-converted signal to generate an output baseband signal. The output baseband signal may be provided to baseband circuitry 204 for further processing. In some embodiments, the output baseband signal may be a zero frequency baseband signal, but this is not required. In some embodiments, mixer circuit 206a of the receive signal path may comprise a passive mixer, although the scope of the embodiments is not limited in this respect. In some embodiments, the mixer circuit 206a of the transmit signal path may be configured to: the input baseband signal is upconverted based on the synthesized frequency provided by the synthesizer circuit 206d to generate an RF output signal for the FEM circuit 208. The baseband signal may be provided by the baseband circuitry 204 and may be filtered by the filter circuitry 206c. Filter circuit 206c may include a Low Pass Filter (LPF), although the scope of the embodiments is not limited in this respect.

In some embodiments, mixer circuit 206a of the receive signal path and mixer circuit 206a of the transmit signal path may include two or more mixers and may be arranged for quadrature down-conversion or up-conversion, respectively. In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., hartley image rejection). In some embodiments, the mixer circuit 206a of the receive signal path and the mixer circuit 206a of the transmit signal path may be arranged for direct down-conversion or direct up-conversion, respectively. In some embodiments, the mixer circuitry 206a of the receive signal path and the mixer circuitry 206a 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, RF circuitry 206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry, and baseband circuitry 204 may include a digital baseband interface to communicate with RF circuitry 206. In some dual-mode embodiments, separate radio IC circuits may be provided for processing signals with respect to each spectrum, although the scope of the embodiments is not limited in this respect.

In some embodiments, synthesizer circuit 206d may be a fractional-N synthesizer or a fractional-N/N +1 synthesizer, although the scope of embodiments is not so limited as other types of frequency synthesizers may be suitable. For example, the synthesizer circuit 206d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase locked loop with a frequency divider. The synthesizer circuit 206d may be configured to: the output frequency used by the mixer circuit 206a of the input synthesis RF circuit 206 is controlled based on the frequency input and the divider. In some embodiments, the synthesizer circuit 206d may be a fractional-N/N +1 synthesizer. In some embodiments, the frequency input may be provided by a Voltage Controlled Oscillator (VCO), but this is not required. The divider control input may be provided by the baseband circuitry 204 or the application processor 202, depending on the desired output frequency. In some embodiments, the divider control input (e.g., N) may be determined from a look-up table based on the channel indicated by the application processor 202.

Synthesizer circuit 206d of RF circuit 206 may include dividers, delay Locked Loops (DLLs), multiplexers, and phase accumulators. In some embodiments, the divider may be a dual-mode divider (DMD) and the phase accumulator may be a Digital Phase Accumulator (DPA). In some embodiments, the DMD may be configured to: the input signal is divided by N or N +1 (e.g., based on a carry) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable delay elements, a phase detector, a charge pump, and a D-type flip-flop. In these embodiments, the delay elements may be configured to decompose the VCO period into 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 206d may be configured to: a carrier frequency is generated as the output frequency, while in other embodiments the output frequency may 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 a plurality of signals at the carrier frequency having a plurality of different phases relative to each other. In some embodiments, the output frequency may be the LO frequency (fLO). In some embodiments, the RF circuitry 206 may include an IQ/polar converter.

FEM circuitry 208 may include a receive signal path, which may include circuitry configured to operate on RF signals received from one or more of antennas 210A-D, amplify the received signals, and provide amplified versions of the received signals to RF circuitry 206 for further processing. The FEM circuitry 208 may further include a transmit signal path, which may include circuitry configured to amplify signals provided by the RF circuitry 206 for transmission by one or more of the one or more antennas 210A-D.

In some embodiments, FEM circuitry 208 may include a TX/RX switch to switch between transmit mode and receive mode 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 the received RF signal and provide the amplified received RF signal as an output (e.g., to RF circuitry 206). The transmit signal path of the FEM circuitry 208 may include: a Power Amplifier (PA) to amplify an input RF signal (e.g., provided by RF circuitry 206); and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 210). In some embodiments, the UE 200 may include additional elements, such as memory/storage, a display, a camera, sensors, or an input/output (I/O) interface.

Fig. 3 is a functional diagram of an evolved node B (eNB) in accordance with some embodiments. It should be noted that in some embodiments, eNB 300 may be a stationary non-mobile device. The eNB 300 may be suitable for use as the eNB104 as depicted in fig. 1. The components of eNB 300 may be included in a single device or multiple devices. The eNB 300 may include physical layer (PHY) circuitry 302 and a transceiver 305, one or both of which may enable the use of one or more antennas 301A-B to transmit signals to and receive signals from the UE 200, other enbs, other UEs, or other devices. As an example, the physical layer circuitry 302 may perform various encoding and decoding functions, which may include: forming a baseband signal for transmission and decoding a received signal. For example, physical layer circuitry 302 may include LDPC encoder/decoder functionality, optionally including other techniques (e.g., block codes, convolutional codes, turbo codes, etc.) that may be used to support legacy protocols. Embodiments of modulation/demodulation and encoder/decoder functions are not limited to these examples, and other suitable functions may be included in other embodiments. As another example, the transceiver 305 may perform various transmit and receive functions (e.g., frequency conversion of signals between baseband range and Radio Frequency (RF) range). Thus, the physical layer circuit 302 and the transceiver 305 may be separate components or may be part of a combined component. Further, some of the described functions related to the transmission and reception of signals may be performed by a combination that may include one, any, or all of physical layer circuitry 302, transceiver 305, and other components or layers. The eNB 300 may further include medium access control layer (MAC) circuitry 304 to control access to the wireless medium. The eNB 300 may further include processing circuitry 306 and memory 308 arranged to perform the operations described herein. eNB 300 may also include one or more interfaces 310, which may enable communication with other components, including other eNB104 (fig. 1), components in EPC 120 (fig. 1), or other network components. Further, interface 310 may enable communication with other components that may not be shown in fig. 1, including components external to the network. The interface 310 may be wired or wireless or a combination thereof.

Antennas 210A-D (in the UE) and 301A-B (in the eNB) 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 transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, the antennas 210A-D, 301A-B may be effectively separated to exploit spatial diversity and the different channel characteristics that may result.

In some embodiments, the UE 200 or eNB 300 may be a mobile device and may be a portable wireless communication device (e.g., a Personal Digital Assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smart phone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a wearable device (e.g., a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.)), or other device that may receive or transmit information wirelessly). In some embodiments, the UE 200 or eNB 300 may be configured to: operate in accordance with 3GPP standards, although the scope of the embodiments is not limited in this respect. The mobile device or other device may be configured in some embodiments to operate in accordance with other protocols or standards, including IEEE 802.11 or other IEEE standards. In some embodiments, the UE 200, eNB 300, or other device may include one or more of a keypad, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

Although both the UE 200 and the eNB 300 are illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including Digital Signal Processors (DSPs), or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field Programmable Gate Arrays (FPGAs), application Specific Integrated Circuits (ASICs), radio Frequency Integrated Circuits (RFICs), and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processes operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware, and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include Read Only Memory (ROM), random Access Memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

It should be noted that in some embodiments, the apparatus used by the UE 200 or eNB 300 may include various components of the UE 200 or eNB 300 shown in fig. 2-3. Thus, the techniques and operations described herein with reference to the UE 200 (or 102) may be applicable to the apparatus of the UE. Moreover, the techniques and operations described herein with reference to eNB 300 (or 104) may be applicable to an apparatus of an eNB.

Fig. 4A-4B illustrate examples of multiple beam transmission scenarios with an eNB and a UE, in accordance with some embodiments. Although the example scenarios depicted in fig. 4A-4B may illustrate some aspects of the techniques disclosed herein, it should be understood that embodiments are not limited to these example scenarios. Embodiments are not limited to the number or types of components shown in fig. 4A-4B, nor to the number or arrangement of transmit beams shown in fig. 4A-4B.

Referring to fig. 4a, the enb104 has multiple antennas (e.g., two antennas 410) that may be used in various combinations and with various signal modifications for each combination to effectively produce multiple antenna ports 405 (e.g., P1-P4). In various embodiments within the framework of the illustrated example, each antenna port P1-P4 may be defined for one or more antennas 410. Each antenna port P1-P4 may correspond to a different transmission signal direction. Using different antenna ports, the eNB104 may transmit multiple layers through codebook-based or non-codebook-based precoding techniques. According to some embodiments, each antenna port corresponds to a beam antenna port specific CSI-RS signal transmitted via the respective antenna port. In other embodiments, there may be more or fewer antenna ports available at the eNB than the four antenna ports shown in fig. 4A.

On the UE side, there are multiple receive antennas 415. As shown in the example of fig. 4A, the UE has two receive antennas. Multiple receive antennas may be selectively used to produce receive beamforming. Receive beamforming may be advantageously used to increase the receive antenna gain in the direction in which the desired signal is received and to suppress interference from neighboring cells (provided of course that interference is received in a different direction than the desired signal).

Some aspects of the embodiments relate to enabling flexible transmission mode switching. Each antenna 410 (or 415) may have one or two antenna ports 405 associated with it, allowing transmission of up to two layers per antenna. A single antenna may thus provide rank 1 (i.e., a single antenna port per antenna) or rank 2 (two antenna ports per antenna) single beam transmission. The two antennas may provide dual beam transmission with a transmission rank of 2 (one port for each of the two antennas), 3, or 4 (two ports for each of the two antennas). As shown in fig. 4A, with two antennas of the eNB104 and a transmission rank of 4 (i.e., all four ports 405 are being used), two transmit (Tx) beams are used. In one embodiment, the eNB104 may indicate a preference for single or dual beam transmission to the UE (e.g., as explained with reference to fig. 5B). In this scenario, the UE may report back CSI (e.g., CQIs) for multiple Tx beams (e.g., the two Tx beams visible in fig. 4A). In another embodiment, the UE may indicate a preference for single or dual beam transmission to the eNB (e.g., as explained with reference to fig. 5A).

Additionally and in instances when dual beam transmission is selected (by the eNB or UE), the UE may apply a different derivation method when determining the CQI (e.g., the CQI may be derived using or without taking into account the mutual interference of the received beams). The eNB may also indicate a preference for a desired CQI derivation method (e.g., as explained herein below).

In the example scenario in fig. 4B, the eNB104 may transmit signals on multiple beams 420-440, any or all of which may be received at the UE 102. It should be noted that the number of beams or transmission angles shown are not limiting. Because beams 420-440 may be directional, the transmit energy from beams 420-440 may be focused in the directions shown. Thus, due to the relative position of UE102, UE102 may not necessarily receive a significant amount of energy from beam 440 in some cases.

UE102 may receive a significant amount of energy from beams 420 and 430, as shown. As an example, beams 405-420 may be transmitted using different reference signals, and UE102 may determine Channel State Information (CSI) feedback or other information for beams 420 and 430. In some embodiments, each of the beams 420-430 is configured as a CSI reference signal (CSI-RS). In a related embodiment, the CSI-RS signal is part of a Discovery Reference Signaling (DRS) configuration. The DRS configuration may be used to inform the UE102 of the physical resources (e.g., subframes, subcarriers) where CSI-RS signals are to be found. In a related embodiment, the UE102 is also informed of any scrambling sequences to be applied to the CSI-RS.

In some embodiments, up to 2 MIMO layers may be transmitted within each beam by using different polarizations. More than 2 MIMO layers may be transmitted by using multiple beams. In a related embodiment, the UE is configured to discover available beams and report those discovered beams to the eNB prior to MIMO data transmission using an appropriate reporting message. Based on the reporting message, the eNB104 may determine an appropriate beam direction for a MIMO layer to be used for data communication with the UE 102. In various embodiments, there may be up to 2, 4, 8, 16, 32, or more MIMO layers depending on the number of MIMO layers supported by the eNB104 and the UE 102. In a given scenario, the number of MIMO layers that may actually be used will depend on the quality of the signaling received at the UE102 and the availability of reflected beams that arrive at the UE102 at divergent angles, such that the UE102 can distinguish between the data carried on the separate beams.

In the example scenario in fig. 4B, the UE102 may determine the angles of the beams 420 and 430 or other information (e.g., CSI feedback, including Channel Quality Indicator (CQI) or otherwise). UE102 may also determine this information when received at other angles (e.g., beam 440 as shown). Beam 440 is bounded using a dashed line configuration to indicate that it may not necessarily transmit at the indicated angle, but UE102 may determine the beam direction of beam 440 using techniques such as receive beamforming. This situation may occur, for example, when the transmitted beam reflects from an object near the UE102 and arrives at the UE102 according to its reflection rather than angle of incidence.

In some embodiments, the UE102 may send one or more Channel State Information (CSI) messages to the eNB104 as reporting messages. However, embodiments are not limited to dedicated CSI messages, as the UE102 may include the related reporting information in a control message or other type of message that may or may not be dedicated to communicating CSI type information.

As an example, the first signal received from the first eNB104 may include a first directional beam 420 based at least in part on the first CSI-RS signal and a second directional beam 430 based at least in part on the second CSI-RS signal. The UE102 may determine a Rank Indicator (RI) of the first CSI-RS and an RI of the second CSI-RS, and may send the two RIs in CSI messages. In some embodiments, the UE102 may also determine a CQI, a Precoding Matrix Indicator (PMI), a reception angle, or other information about one or both of the first signal and the second signal. Such information may be included in one or more CSI messages along with one or more RIs. In some embodiments, the UE102 performs Reference Signal Received Power (RSRP) measurements, received Signal Strength Indication (RSSI) measurements, reference Signal Received Quality (RSRQ) measurements, or some combination thereof, using CSI-RS signals.

As an example, the first signal received from the eNB104 may include a first directional beam based at least in part on the first CSI-RS signal and a second directional beam based at least in part on the second CSI-RS signal. The UE102 may determine a first CSI measurement for the first directional beam and a second CSI measurement for the second directional beam based on the received CSI-RS. The CSI measurements may include a Channel Quality Indicator (CQI), a Rank Indicator (RI), and a Precoding Matrix Indicator (PMI). The CQI may be used by the eNB transmitter to select one of several modulation alphabet and code rate combinations. The RI may be used to inform the transmitter of the number of useful transmission layers for the current MIMO channel, and the PMI may be used to indicate a codebook index (depending on the number of transmit antennas) of the precoding matrix applied at the transmitter. The code rate used by the eNB may be based on CQI. The PMI may be a vector that is calculated by the cell station and reported to the eNB.

In this regard, the CQI may be an indication of the downlink mobile radio channel quality experienced by the UE. The CQI allows the UE to propose to the eNB the optimal modulation scheme and coding rate for a given radio link quality so that the resulting transport block error rate will not exceed a certain value (e.g., 10%). In some embodiments, the UE may report a wideband CQI value that refers to the channel quality of the system bandwidth. The UE may also report sub-band CQI values per sub-band for a certain number of resource blocks that higher layers may configure.

The PMI within the CSI may indicate an optimal precoding matrix to be used by the eNB for given radio conditions. The PMI value may refer to a codebook table. The network configuration PMI reports the number of resource blocks represented. In some embodiments, to cover system bandwidth, multiple PMI reports may be provided. PMI reporting may also be provided for closed loop spatial multiplexing, multi-user MIMO, and closed loop rank 1 precoding MIMO modes.

According to example embodiments, the UE may control the transmission mode (e.g., single or dual beam transmission) by providing an indication (or preference) for the transmission mode in the CSI reported to the eNB (as explained herein below). In yet another example, transmission mode selection may be controlled by the eNB, and the eNB may indicate a preference that CSI information is needed for multiple (e.g., 2) transmit beams.

Fig. 5A is a diagram illustrating Channel State Information (CSI) derivation and reporting for flexible transmission mode switching, in accordance with some embodiments. Referring to fig. 5A, there is a CSI derivation shown in the high band system formed by the eNB and the UE. Transmit (Tx) and receive (Rx) beamforming may be used in the system to increase cell coverage and/or improve signal quality. Initially, beamformed Reference Signals (RSs) 510a are transmitted periodically to enable the UE to acquire and maintain the preferred (optimal) Tx beam 515a and the candidate Tx beams 520a. The acquired optimal TX beam 515a and candidate TX beam 520a are transmitted to the eNB. When the eNB intends to transmit data to the UE, a channel state information reference signal (CSI-RS) 525a, which may be beamformed based on the reported optimal Tx beam 515a and/or candidate beam 520a, is transmitted to the UE for channel quality measurement, so that the eNB may determine an actual modulation coding scheme, the number of streams, and the optimal Tx beam at the current stage.

In some instances (e.g., due to movement of the UE), the wireless link between the eNB and the UE may change, and the transmission mode may be switched based on, for example, these conditions changing. For example, when there are multiple strong channel clusters (e.g., at least two channel clusters), high rank transmission (e.g., dual beam transmission mode) may be supported, while low rank transmission is enabled when spatial freedom is insufficient. For flexible switching between different ranks (e.g., between single-mode and dual-mode transmissions), the following CQI reporting techniques may be used:

the CSI report transmitted from the UE to the eNB may contain Tx beam specific CSI information. More specifically, and for two example Tx beams (e.g., one preferred/optimal Tx beam and one candidate Tx beam), the CSI information may include an implicit or explicit index Tx1 of one candidate Tx beam; RI1, PMI1, and CQI1 of the candidate beam Tx1; an implicit or explicit index Tx2 of another candidate Tx beam; and RI2, PMI2, CQI2 of the candidate beam Tx 2. The beam index may be an explicit or implicit beam index. The explicit beam index may be a beam number transmitted from the eNB (e.g., for the first of the 48 possible beams, the explicit beam index would be 1). The implicit beam index may be associated with an antenna port number used to transmit the beam.

CSI reporting

According to an example embodiment, different transmission modes including dual beam transmission and single beam transmission may be distinguished via flexible CSI/CQI reporting as follows:

(1) In an instance when the beam index Tx2 is different from the beam index Tx1 (and/or any of RI, PMI, and CQI is different between beams), a preference for dual beam transmission is indicated to the eNB by the UE.

(2) In the example when Tx1, RI1, PMI1, and CQI1 are equal to Tx2, RI2, PMI2, CQI2, respectively, the UE may indicate a preference for single beam transmission to the eNB; and

(3) As an alternative to (2), if the beam index Tx2 is the same as the beam index Tx1 while RI2, PMI2, and CQI2 are set to zero, the UE indicates a preference for single beam transmission to the eNB.

The UE may use any of examples (1) - (3) above to report beam index and CSI information, indicating a preference for single beam transmission or dual beam transmission, and triggering flexible transmission mode switching.

Referring again to fig. 5A, CSI information 530a, 535A, e.g., for the optimal and candidate beams, may be reported to the eNB. The beam index (and/or CSI for each beam) may be different. Based on the different values, the UE may indicate a preference for dual-beam transmission to the eNB. The downlink data 540a may then be transmitted using the two Tx beams 550a and 560 a.

In another example, the UE may set the indices Tx2, RI2, PMI2, and CQI2 equal to (even though they may be different from) Tx1, RI1, PMI1, and CQI1, thereby indicating a preference for single beam transmission to the eNB.

In yet another example, the UE may set RI2, PMI2, and CQI2 equal to zero, thereby indicating a preference for single beam transmission to the eNB.

Fig. 5B illustrates Downlink Control Information (DCI) based CSI derivation and reporting, in accordance with some embodiments. In another embodiment, the selection of the transmission mode may be controlled by the eNB. For example, a new Beam Search Algorithm (BSA) value 520b may be added in Downlink Control Information (DCI) 510b transmitted by the eNB to the UE. For example, when BSA value 520b is equal to a predetermined (and known to the UE) value x, the eNB needs a dual-beam Channel State Information (CSI) report for dual-beam transmission purposes. Similarly, when BSA value 520b is equal to another predetermined (and known to the UE) value y, the eNB needs a single CSI report for the purpose of single beam transmission. In the particular example in fig. 5B, BSA value 520B indicates a preference for dual-beam transmission, and CSI information 530B and 540B (for Tx beams 1 and 2, respectively) are communicated back to the eNB.

CQI derivation

In the example when dual beam transmission is used, the transmitted signals of the two different beams will interfere with each other at the UE. In this regard, whether CQI derivation takes into account that mutual interference should be consistent between the eNB and the UE (and known by both).

According to example embodiments, CQI derivation without considering mutual interference may be set to a default configuration (and may be known to both the eNB and the UE as a default configuration).

In the absence of mutual interference, the CQI may be derived based on the following formula:

P _sig /(P _intf +P _noise )，

wherein, P _sig Is the signal power, P _intf Is the interference power, P _noise Is the noise power. Using this CQI derivation technique, the eNB can perform flexible central scheduling and the computational complexity of the UE during CQI derivation is simplified. For example, if the eNB is equipped with two separate RF chains, the cell capacity can be optimized by deciding whether to send a single beam to two users or whether to send dual beams to one user.

According to another example embodiment, CQI derivation based on consideration of mutual interference may be set to a default configuration.

If mutual interference is considered, then additive interference will be added, resulting in the following equation:

P _sig /(P _intf +P _{mutual，intf} +P _noise ) Wherein P is _mutual,intf Is the additive mutual interference power. The eNB and the UE may optimize Tx beam selection between dual beams by considering mutual interference. For example, in instances when two non-ideal backhaul enbs are grouped to achieve beam aggregation, such a mechanism may reduce overhead for information exchange.

In yet another example, the eNB may configure the 1-bit indicator through higher layer signaling via, for example, a Master Information Block (MIB), a System Information Block (SIB), radio Resource Configuration (RRC) signaling, and/or Downlink Control Information (DCI). The indicator may be used by the eNB to inform the UE to derive the CQI with or without consideration of mutual interference (e.g., based on indicator bit values).

In yet another embodiment, the eNB may indicate a preference for the CQI derivation method (e.g., whether to consider mutual interference) based on the beam search algorithm indicated by the BSA value (e.g., 520B in fig. 5B) in the DCI. For example, if BSA requires dual-beam CSI, the UE may calculate CQI based on mutual interference from dual beams.

Fig. 6-8 are flow diagrams illustrating example functionality for CQI derivation and/or reporting, according to some embodiments. The example processes in each of flowcharts 600 and 800 may be performed by UE102 or by a UE device having a different architecture. The example process in flowchart 700 may be performed by eNB104. In particular, the processes in each flowchart are machine-implemented processes that may operate autonomously (i.e., without user interaction). Moreover, it is important to note that the processes in each flowchart are well-characterized embodiments that can be implemented as described; further, in various embodiments, a portion of the processing may be implemented without the other portion. The following additional notes and examples section details the various combinations contemplated, without limitation. It should also be noted that, in various embodiments, certain processing operations may be performed in a different order than depicted in fig. 6-8.

Referring to fig. 1-6, an example process 600 may be performed by the UE 102. More specifically, at 610, the ue102 reports multiple transmit (Tx) beams as preferred Tx beams (e.g., beams 515a, 520 a) to an evolved node B (eNB) 104. At 620, the ue102 receives a channel state information reference signal (CSI-RS) 525a, which is beamformed based on a plurality of preferred Tx beams. At 630, in response to CSI-RS 525a, ue102 determines Channel State Information (CSI) for at least two preferred Tx beams (e.g., CSI 530a for the first beam and CSI 535a for the second beam), wherein the CSI comprises a transmission beam index for each preferred Tx beam. At 640, the ue102 reports the determined CSI (530 a and 535 a) to the eNB104. The reported CSI may be configured by the UE to indicate a preferred transmission mode based at least in part on the transmission beam index. For example, the following CSI reporting techniques may be used:

(1) In an instance when the beam index Tx2 is different from the beam index Tx1 (and/or any of RI, PMI, and CQI is different between beams), a preference for dual-beam transmission is indicated to the eNB by the UE (in this regard, a dual-beam transmission mode may be determined based on only the difference in transmission beam indexes);

(2) In the example when Tx1, RI1, PMI1, and CQI1 are equal to Tx2, RI2, PMI2, CQI2, respectively, the UE may indicate to the eNB a preference for single beam transmission; and (3) as an alternative to (2), if the beam index Tx2 is the same as the beam index Tx1 while RI2, PMI2, and CQI2 are set to zero, the UE indicates a preference for single beam transmission to the eNB.

At 650, the ue102 receives a Downlink (DL) data transmission 540a from the eNB according to the indicated preferred transmission mode.

Referring to fig. 1-5B and 7, example process 700 may be performed by eNB104. More specifically, at 710, the enb104 receives multiple transmit (Tx) beams from the User Equipment (UE) 102 as preferred Tx beams (e.g., beams 515a, 520 a). At 720, the enb104 transmits a channel state information reference signal (CSI-RS) 525a to the UE 102. The CSI-RS 525a is beamformed based on a plurality of preferred Tx beams (e.g., 515a and/or 520 a). At 730, the enb104 receives Channel State Information (CSI) for at least two preferred Tx beams from the UE102 (530 a, 535 a), the CSI including a transmission beam index for each Tx beam. At 740, the enb determines a transmission mode based at least in part on the transmission beam indices of the at least two preferred Tx beams in the CSI. The transmission mode may be, for example, a single beam transmission mode or a dual beam transmission mode, as discussed above with reference to fig. 6. At 750, the enb104 initiates a Downlink (DL) data (540 a) transmission according to the determined transmission mode.

Referring to fig. 1-5B and 8, an example process 800 may be performed by the UE 102. More specifically, at 810, the ue102 receives a channel state information reference signal (CSI-RS) 525a, CSI-RS 525a from the eNB104 that is beamformed based on a plurality of preferred Tx beams (e.g., 515a, 520 a). At 820, the ue102 receives Downlink Control Information (DCI) 510b from the eNB104. The DCI 510b includes an indicator (e.g., 520 b) of a transmission mode. At 830, in response to the CSI-RS and based on the transmission mode, the UE102 determines Channel State Information (CSI) for one or more preferred Tx beams (e.g., 530b, 540 b). At 840, the ue102 reports the determined CSI (530 a, 540 b) to the eNB104. At 850, the ue102 receives a Downlink (DL) data (e.g., 540 a) transmission from the eNB104 according to a transmission mode that is based on the determined CSI.

Fig. 9 is a block diagram of a communication device (e.g., an eNB or UE) in accordance with some embodiments. In alternative embodiments, the communication device 800 may operate as a stand-alone device or may be connected (e.g., networked) to other communication devices. In a networked deployment, the communication device 900 may operate in the role of a server communication device, a client communication device, or both, in a server-client network environment. In an example, the communication device 900 can act as a peer-to-peer communication device in a peer-to-peer (P2P) (or other distributed) network environment. The communication device 900 may be a UE, eNB, PC, tablet PC, STB, PDA, mobile phone, smart phone, web appliance, network router, switch or bridge, or any communication device capable of executing instructions (sequential or otherwise) that specify actions to be taken by the communication device. Further, while only a single communication device is shown, the term "communication device" should also be taken to include any collection of communication devices 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 cloud computing, software as a service (SaaS), other computer cluster configurations.

Examples as described herein may include, or may operate on, logic or multiple components, modules, or mechanisms. A module is a tangible entity (e.g., hardware) capable of performing specified operations and may be configured or arranged in a certain manner. In an example, a circuit can be arranged (e.g., internally or with respect to an external entity such as other circuits) as a module in a specified manner. In an example, all or a portion of one or more computer systems (e.g., a stand-alone, client, or server computer system) or one or more hardware processors may be configured by firmware or software (e.g., instructions, application portions, or applications) as a module that operates to perform specified operations. In an example, the software may reside on a communication device readable medium. In an example, software, when executed by underlying hardware of a module, causes the hardware to perform specified operations.

Accordingly, the term "module" is understood to encompass a tangible entity, whether physically constructed, specifically configured (e.g., hardwired), or temporarily (e.g., temporarily) configured (e.g., programmed) to operate in a specified manner or to perform part or all of any of the operations described herein. Considering the example of temporarily configuring modules, each module need not be instantiated at any one time. For example, where the modules include a general purpose hardware processor configured using software, the general purpose hardware processor may be configured as respective different modules at different times. Thus, software may configure a hardware processor to, for example, form a particular module at one instance in time and form a different module at a different instance in time.

A communication device (e.g., computer system) 900 may include a hardware processor 902 (e.g., a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), a hardware processor core, or any combination thereof), a main memory 904, and a static memory 906, some or all of which may communicate with each other via an interlink (e.g., bus) 908. The communication device 900 may further include a display unit 910, an alphanumeric input device 912 (e.g., a keyboard), and a User Interface (UI) navigation device 914 (e.g., a mouse). In an example, the display unit 910, the input device 912, and the UI navigation device 914 may be a touch screen display. The communication device 900 may additionally include a storage device (e.g., drive unit) 916, a signal generation device 918 (e.g., a speaker), a network interface device 920, and one or more sensors 921 (e.g., a Global Positioning System (GPS) sensor, compass, accelerometer, or other sensor). The communication device 900 may include an output controller 928, 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, card reader, etc.).

The storage device 916 may include a communication device readable medium 922 on which is stored one or more sets of data structures or instructions 924 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein. The instructions 924 may also reside, completely or at least partially, within the main memory 904, static memory 906 or within the hardware processor 902 during execution thereof by the communication device 900. In an example, one or any combination of the hardware processor 902, the main memory 904, the static memory 906, or the storage device 916 may constitute communication device readable media.

While the communication device-readable medium 922 is shown to be a single medium, the term "communication device-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 924.

The term "communication device-readable medium" can include any medium that can store, encode or carry instructions for execution by communication device 900 and that cause communication device 900 to perform any one or more of the techniques of this disclosure, or that can store, encode or carry data structures utilized by or associated with such instructions. Non-limiting examples of communication device readable media may include solid state memory and optical and magnetic media. Specific examples of the communication device readable medium may include: non-volatile memory (e.g., semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices); magnetic disks (e.g., internal hard disks and removable disks); a magnetic optical disk; random Access Memory (RAM); and CD-ROM and DVD-ROM disks. In some examples, the communication device readable medium may include a non-transitory communication device readable medium. In some examples, the communication device readable medium may include a communication device readable medium that is not a transitory propagating signal.

The instructions 924 may further be transmitted or received over a communication network 926 using a transmission medium via the network interface device 920 utilizing any one of a number of transfer protocols (e.g., frame relay, internet Protocol (IP), transmission Control Protocol (TCP), user Datagram Protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks can 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., referred to as

Is known as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards, referred to as £ r @>

IEEE 802.16 family of standards), IEEE 802.15.4 family of standards, long Term Evolution (LTE) family of standards, universal mobile telecommunications network (UMTS) family of standards, peer-to-peer (P2P) networks, and the like. In an example, the network interface device 920 may include one or more physical jacks (e.g., ethernet jacks, coaxial jacks, or telephone jacks) or one or more antennas for connecting to the communication network 926. In an example, the network interface device 920 may include multiple antennas for wireless communication using at least one of single-input multiple-output (SIMO), MIMO, or multiple-input single-output (MISO) techniques. In some examples, the network interface device 920 may wirelessly communicate using multi-user MIMO techniques. Term(s) for"transmission media" shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the communication device 900, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software.

Additional notes and examples:

example 1 is an apparatus of a User Equipment (UE), the apparatus may include: a memory; and processing circuitry coupled to the memory, the processing circuitry configured to: generating a reporting message for an evolved node B (eNB), the reporting message indicating a plurality of transmit (Tx) beams as preferred Tx beams; determining Channel State Information (CSI) for at least two preferred Tx beams in response to a channel state information reference signal (CSI-RS), the CSI-RS being beamformed based on the plurality of preferred Tx beams, and the CSI including a transmission beam index for each preferred Tx beam; reporting the determined CSI to the eNB, wherein the CSI is configured by the UE to: indicating a preferred transmission mode based at least in part on a transmission beam index of each preferred Tx beam; and processing a Downlink (DL) data transmission from the eNB, the downlink data transmission associated with the indicated preferred transmission mode.

In example 2, the subject matter of example 1 optionally includes: wherein the processing circuitry comprises baseband processing circuitry, and wherein the CSI for each of the at least two preferred Tx beams further comprises: a Rank Indicator (RI); a Precoding Matrix Indicator (PMI); and a Channel Quality Indicator (CQI).

In example 3, the subject matter of any one or more of examples 1-2 optionally includes: wherein the preferred transmission mode comprises: a single beam transmission mode when the transmission beam index is the same for the preferred Tx beam; or a dual-beam transmission mode when the transmission beam index is different for the preferred Tx beam.

In example 4, the subject matter of any one or more of examples 1-3 optionally includes: wherein the plurality of preferred Tx beams includes at least a first Tx beam and a second Tx beam.

In example 5, the subject matter of example 4 optionally includes: wherein the CSI includes first CSI associated with the first Tx beam and second CSI associated with the second Tx beam.

In example 6, the subject matter of example 5 optionally includes: wherein the processing circuit is further configured to: indicating the preferred transmission mode to the eNB by setting a transmission beam index, RI, PMI and CQI in the second CSI to be equal to a corresponding transmission beam index, RI, PMI and CQI in the first CSI.

In example 7, the subject matter of any one or more of examples 5-6 optionally includes: wherein the processing circuit is further configured to: indicating the preferred transmission mode to the eNB by setting RI, PMI and CQI in the second CSI to be equal to zero.

In example 8, the subject matter of any one or more of examples 6-7 optionally includes: wherein the indicated preferred transmission mode is a single beam transmission mode.

In example 9, the subject matter of any one or more of examples 5-8 optionally includes: wherein the processing circuit is further configured to: obtaining RI, PMI and CQI measurements of the first CSI and the second CSI.

In example 10, the subject matter of example 9 optionally includes: wherein the processing circuit is further configured to: indicating a dual beam transmission mode to the eNB when the RI, PMI and CQI measurements of the first CSI are different from the RI, PMI and CQI measurements of the second CSI.

In example 11, the subject matter of any one or more of examples 1-10 optionally includes: a transceiver; and an antenna assembly coupled to the transceiver, wherein the transceiver is configured to transmit and receive signals using the antenna assembly.

In example 12, the subject matter of example 11 can optionally include: wherein the transceiver is further configured to: receive Downlink Control Information (DCI) from the eNB, the DCI including a Beam Search Algorithm (BSA) value.

In example 13, the subject matter of example 12 optionally includes: wherein the processing circuit is further configured, based on the BSA value, to: for single beam transmission mode, reporting CSI for only one preferred Tx beam; or reporting CSI of the at least two preferred Tx beams for a dual beam transmission mode.

In example 14, the subject matter of any one or more of examples 9-13 optionally includes: wherein the processing circuit is further configured to: applying the indicated CQI derivation method to obtain CQI measurements for the first CSI and the second CSI using an indication from the eNB associated with the CQI derivation method.

In example 15, the subject matter of example 14 can optionally include: wherein the CQI derivation method is based on one of: obtaining, at the UE and during dual beam transmission from the eNB, CQI measurements without regard to interference between the first Tx beam and the second Tx beam; or obtaining a CQI measurement at the UE and during dual beam transmission from the eNB taking into account interference between the first Tx beam and the second Tx beam.

Example 16 is a method for flexible transmission mode switching, comprising: by a User Equipment (UE): reporting a plurality of transmit (Tx) beams as preferred Tx beams to an evolved node B (eNB); receiving a channel state information reference signal (CSI-RS) beamformed based on the plurality of preferred Tx beams; determining Channel State Information (CSI) for at least two preferred Tx beams in response to the CSI-RS, the CSI including a transmission beam index for each preferred Tx beam; reporting the determined CSI to the eNB, wherein the CSI is configured by the UE to: indicating a preferred transmission mode based at least in part on a transmission beam index of each preferred Tx beam; and receiving a Downlink (DL) data transmission from the eNB according to the indicated preferred transmission mode.

In example 17, the subject matter of example 16 optionally includes: wherein the processing circuitry comprises baseband processing circuitry, and wherein the CSI for each of the at least two preferred Tx beams further comprises: a Rank Indicator (RI); a Precoding Matrix Indicator (PMI); and a Channel Quality Indicator (CQI).

In example 18, the subject matter of any one or more of examples 16-17 optionally includes: wherein the transmission mode comprises: a single beam transmission mode when the transmission beam index is the same for the preferred Tx beam; or a dual-beam transmission mode when the transmission beam index is different for the preferred Tx beam.

In example 19, the subject matter of any one or more of examples 16-18 optionally includes: wherein the plurality of preferred Tx beams includes at least a first Tx beam and a second Tx beam.

In example 20, the subject matter of example 19 optionally includes: wherein the CSI includes a first CSI associated with the first Tx beam and a second CSI associated with the second Tx beam.

In example 21, the subject matter of example 20 optionally includes: indicating the preferred transmission mode to the eNB by setting a transmission beam index, RI, PMI and CQI in the second CSI to be equal to a corresponding transmission beam index, RI, PMI and CQI in the first CSI.

In example 22, the subject matter of any one or more of examples 20-21 optionally includes: indicating the preferred transmission mode to the eNB by setting RI, PMI and CQI in the second CSI to be equal to zero.

In example 23, the subject matter of any one or more of examples 21-22 optionally includes: wherein the indicated preferred transmission mode is a single beam transmission mode.

In example 24, the subject matter of any one or more of examples 20-23 optionally includes: obtaining RI, PMI and CQI measurements of the first CSI and the second CSI.

In example 25, the subject matter of example 24 can optionally include: indicating a dual beam transmission mode to the eNB when the RI, PMI and CQI measurements of the first CSI are different from the RI, PMI and CQI measurements of the second CSI.

In example 26, the subject matter of any one or more of examples 16-25 optionally includes: receive Downlink Control Information (DCI) from the eNB, the DCI including a Beam Search Algorithm (BSA) value.

In example 27, the subject matter of any one or more of examples 16-26 optionally includes: receiving Downlink Control Information (DCI) from the eNB, the DCI including a Beam Search Algorithm (BSA) value; and based on the BSA value: for single beam transmission mode, reporting CSI for only one preferred Tx beam; or reporting CSI of the at least two preferred Tx beams for a dual beam transmission mode.

In example 28, the subject matter of any one or more of examples 26-27 optionally includes: based on the BSA value: for single beam transmission mode, reporting CSI for only one preferred Tx beam; or reporting CSI of the at least two preferred Tx beams for a dual beam transmission mode.

In example 29, the subject matter of any one or more of examples 24-28 optionally includes: receiving an indication associated with a CQI derivation method from the eNB; and applying the indicated CQI derivation method to obtain CQI measurements for the first CSI and the second CSI.

In example 30, the subject matter of example 29 optionally comprising: wherein the CQI derivation method is based on one of: obtaining, at the UE and during dual beam transmission from the eNB, CQI measurements without regard to interference between the first Tx beam and the second Tx beam; or obtaining a CQI measurement at the UE and during dual beam transmission from the eNB taking into account interference between the first Tx beam and the second Tx beam.

Example 31 is at least one machine readable medium, which when executed by a machine, causes the machine to perform any one of the methods of examples 16-30.

Example 32 is an apparatus comprising means for performing any of the methods of examples 16-30.

Example 33 is a User Equipment (UE) device, comprising: means for reporting a plurality of transmit (Tx) beams as a preferred Tx beam to an evolved node B (eNB); means for receiving a channel state information reference signal (CSI-RS), the CSI-RS beamformed based on the plurality of preferred Tx beams; means for determining Channel State Information (CSI) for at least two preferred Tx beams in response to the CSI-RS, the CSI including a transmission beam index for each preferred Tx beam; means for reporting the determined CSI to the eNB, wherein the CSI is configured by the UE to: indicating a preferred transmission mode based at least in part on a transmission beam index of each preferred Tx beam; and means for receiving a Downlink (DL) data transmission from the eNB according to the indicated preferred transmission mode.

In example 34, the subject matter of example 33 optionally includes: wherein the CSI for each of the at least two preferred Tx beams further comprises: a Rank Indicator (RI); a Precoding Matrix Indicator (PMI); and a Channel Quality Indicator (CQI).

In example 35, the subject matter of any one or more of examples 33-34 can optionally include: wherein the transmission mode comprises: a single beam transmission mode when the transmission beam index is the same for the preferred Tx beam; or a dual-beam transmission mode when the transmission beam index is different for the preferred Tx beam.

In example 36, the subject matter of any one or more of examples 33-35 optionally includes: wherein the plurality of preferred Tx beams includes at least a first Tx beam and a second Tx beam.

In example 37, the subject matter of example 36 can optionally include: wherein the CSI includes a first CSI associated with the first Tx beam and a second CSI associated with the second Tx beam.

In example 38, the subject matter of example 37 optionally includes: means for indicating the preferred transmission mode to the eNB by setting a transmission beam index, RI, PMI, and CQI in the second CSI to be equal to a corresponding transmission beam index, RI, PMI, and CQI in the first CSI.

In example 39, the subject matter of any one or more of examples 37-38 optionally includes: means for indicating the preferred transmission mode to the eNB by setting RI, PMI, and CQI in the second CSI to be equal to zero.

In example 40, the subject matter of any one or more of examples 38-39 optionally includes: wherein the indicated preferred transmission mode is a single beam transmission mode.

In example 41, the subject matter of any one or more of examples 37-40 optionally includes: means for obtaining RI, PMI and CQI measurements for the first CSI and the second CSI.

In example 42, the subject matter of example 41 can optionally include: means for indicating a dual beam transmission mode to the eNB when the RI, PMI, and CQI measurements of the first CSI are different from the RI, PMI, and CQI measurements of the second CSI.

In example 43, the subject matter of any one or more of examples 33-42 optionally includes: means for receiving Downlink Control Information (DCI) from the eNB, the DCI including a Beam Search Algorithm (BSA) value.

In example 44, the subject matter of example 43 can optionally include: means for reporting CSI for only one preferred Tx beam for a single beam transmission mode based on the BSA value; or means for reporting CSI of the at least two preferred Tx beams for a dual beam transmission mode based on the BSA value.

In example 45, the subject matter of any one or more of examples 41-44 optionally includes: means for receiving an indication associated with a CQI derivation method from the eNB; and means for applying the indicated CQI derivation method to obtain CQI measurements for the first CSI and the second CSI.

In example 46, the subject matter of example 45 optionally includes: wherein the CQI derivation method is based on one of: obtaining, at the UE and during dual beam transmission from the eNB, CQI measurements without regard to interference between the first Tx beam and the second Tx beam; or obtaining a CQI measurement at the UE and during dual beam transmission from the eNB taking into account interference between the first Tx beam and the second Tx beam.

Example 47 is an apparatus of an evolved node B (eNB), the apparatus comprising processing circuitry configured to: receiving a plurality of transmit (Tx) beams as a preferred Tx beam from a User Equipment (UE); beamforming a channel state information reference signal (CSI-RS) based on an indication of a plurality of transmit (Tx) beams from a User Equipment (UE) as preferred Tx beams; determining a transmission mode based on a transmission beam index in CSI of at least two preferred Tx beams from the UE using Channel State Information (CSI) of the at least two preferred Tx beams, wherein the transmission mode is a single beam transmission mode or a dual beam transmission mode; and initiating a Downlink (DL) data transmission according to the determined transmission mode.

In example 48, the subject matter of example 47 optionally includes: wherein the processing circuit is further configured to: obtaining a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a Channel Quality Indicator (CQI) for each preferred Tx beam based on the CSI.

In example 49, the subject matter of example 48 optionally comprising: wherein the processing circuit is further configured to: initiating DL data transmission according to a single beam transmission mode when the RI, PMI and CQI of a first of the preferred Tx beams is equal to the RI, PMI and CQI of a second of the preferred Tx beams.

In example 50, the subject matter of any one or more of examples 48-49 optionally includes: wherein the processing circuit is further configured to: when the RI, PMI, and CQI of the at least one preferred Tx beam are equal to zero, DL data transmission is initiated according to the single beam transmission mode.

In example 51, the subject matter of any one or more of examples 48-50 optionally includes: wherein the processing circuit is further configured to: initiating DL data transmission according to a dual-beam transmission mode when a transmission beam index, RI, PMI and/or CQI of a first preferred Tx beam of the preferred Tx beams is different from a corresponding transmission beam index, RI, PMI and/or CQI of a second preferred Tx beam of the preferred Tx beams.

In example 52, the subject matter of any one or more of examples 47-51 optionally includes: wherein the processing circuit is further configured to: generating an indicator for transmission to the UE during a dual beam transmission mode of at least two Tx beams, the indicator indicating a CQI derivation mode, wherein the CQI derivation mode specifies whether mutual interference between the at least two Tx beams is considered during CQI derivation.

Example 53 is a method for flexible transmission mode switching, comprising: by evolved node B (eNB): receiving a plurality of transmit (Tx) beams as a preferred Tx beam from a User Equipment (UE); transmitting a channel state information reference signal (CSI-RS) to the UE, the CSI-RS being beamformed based on the plurality of preferred Tx beams; receiving Channel State Information (CSI) of at least two preferred Tx beams from the UE, the CSI including a transmission beam index of each preferred Tx beam; determining a transmission mode based on a transmission beam index in the CSI of the at least two preferred Tx beams, wherein the transmission mode is a single beam transmission mode or a dual beam transmission mode; and initiating a Downlink (DL) data transmission according to the determined transmission mode.

In example 54, the subject matter of example 53 can optionally include: wherein a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a Channel Quality Indicator (CQI) are obtained for each preferred Tx beam based on the CSI.

In example 55, the subject matter of example 54 optionally includes: wherein when a transmission beam index, RI, PMI and/or CQI of a first preferred Tx beam of the preferred Tx beams is equal to a transmission beam index, RI, PMI and/or CQI of a second preferred Tx beam of the preferred Tx beams, DL data transmission is initiated according to a single beam transmission mode.

In example 56, the subject matter of any one or more of examples 54-55 optionally includes: when the RI, PMI, and CQI of the at least one preferred Tx beam are equal to zero, DL data transmission is initiated according to the single beam transmission mode.

In example 57, the subject matter of any one or more of examples 54-56 optionally includes: initiating DL data transmission according to a dual-beam transmission mode when a transmission beam index, RI, PMI and CQI of a first preferred Tx beam of the preferred Tx beams is different from a transmission beam index, RI, PMI and CQI of a second preferred Tx beam of the preferred Tx beams.

In example 58, the subject matter of any one or more of examples 53-57 optionally includes: transmitting an indicator regarding a CQI derivation mode to the UE during a dual beam transmission mode of at least two Tx beams, wherein the CQI derivation mode specifies whether mutual interference between the at least two Tx beams is considered during CQI derivation.

Example 59 is at least one machine readable medium which, when executed by a machine, causes the machine to perform any one of the methods of examples 53-58.

Example 60 is an apparatus comprising means for performing any of the methods of examples 53-58.

Example 61 is a computer-readable medium comprising instructions that, when executed on processing circuitry of a User Equipment (UE), cause the UE to: receiving a channel state information reference signal (CSI-RS) from an evolved node B (eNB), the CSI-RS beamformed based on a plurality of preferred Tx beams; receiving Downlink Control Information (DCI) from the eNB, the DCI including an indicator of a transmission mode; determining Channel State Information (CSI) for one or more preferred Tx beams in response to the CSI-RS and based on the transmission mode; reporting the determined CSI to the eNB; and receiving a Downlink (DL) data transmission from the eNB according to a transmission mode, the transmission mode based on the determined CSI.

In example 62, the subject matter of example 61 can optionally include: wherein the DCI includes a Beam Search Algorithm (BSA) value indicating the transmission mode.

In example 63, the subject matter of examples 61-62 optionally includes: wherein the dual beam transmission mode is associated with at least a first Tx beam and a second Tx beam of the preferred Tx beams, and wherein the instructions further cause the UE to: deriving a first Channel Quality Indicator (CQI) of the first Tx beam and a second CQI of the second Tx beam based on the CQI derivation method.

In example 64, the subject matter of example 63 optionally includes: wherein the instructions further cause the UE to: obtaining, at the UE, the first CQI and the second CQI without considering interference between the first Tx beam and the second Tx beam; or obtaining, at the UE, the first CQI and the second CQI taking into account interference between the first Tx beam and the second Tx beam.

The foregoing detailed description includes reference to the accompanying drawings, which form a part hereof. The drawings show, by way of illustration, specific embodiments that can be practiced. These embodiments are also referred to herein as "examples". These examples may include elements in addition to those shown or described. However, examples including the elements shown or described are also contemplated. Moreover, it is also contemplated to use examples of any combination or permutation of those elements (or one or more aspects thereof) shown or described with respect to a particular example (or one or more aspects thereof) or with respect to other examples (or one or more aspects thereof) shown or described herein.

The publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. The usage in the incorporated references is in addition to the usage in this document if the usage between this document and those incorporated by reference is inconsistent; for irreconcilable inconsistencies, the usage in this document controls.

In this document, the terms "a" or "an" are used to include one or more than one, regardless of any other instances or usages of "at least one" or "one or more," as is common in patent documents. In this document, the term "or" is used to refer to a non-exclusive "or" such that "a or B" includes "a but not B," "B but not a" and "a and B," unless otherwise specified. In the appended claims, the terms "including" and "in which" are used as the plain-english equivalents of the respective terms "comprising" and "wherein". Furthermore, in the following claims, the terms "comprising" and "including" are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such term in a claim are still considered to be within the scope of that claim. Furthermore, in the following claims, the terms "first," "second," and "third," etc. are used merely as labels, and are not intended to imply a numerical order of their objects.

The above description is intended to be illustrative and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with other examples. Other embodiments may be utilized, for example, by those skilled in the art, upon reading the foregoing description. The Abstract is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing detailed description, various features may be combined together to simplify the present disclosure. However, the claims may not set forth every feature disclosed herein as embodiments may feature a subset of the features. Moreover, embodiments may include fewer features than are disclosed in a particular example. Thus, the following claims are hereby incorporated into the detailed description, with the claims standing on their own as separate embodiments. The scope of the embodiments disclosed herein should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims (19)

1. An apparatus for use in a User Equipment (UE), the apparatus comprising:

at least one processor configured to cause the UE to:

generating a reporting message for a base station, the reporting message indicating a plurality of transmit Tx beams as preferred Tx beams, wherein the preferred Tx beams include at least a first Tx beam and a second Tx beam, wherein the first Tx beam is a preferred beam and the second Tx beam is a candidate beam;

determining channel state information, CSI, for the first Tx beam and the second Tx beam in response to a channel state information reference signal, CSI-RS, the CSI-RS being beamformed based on the plurality of preferred Tx beams, and the CSI including a transmission beam index, a rank indicator, RI, a precoding matrix indicator, PMI, and a channel quality indicator, CQI, for each preferred Tx beam;

reporting the determined CSI to the base station, wherein the CSI is configured by the UE to: indicating a preferred transmission mode based at least in part on a transmission beam index of the second Tx beam, and/or setting values of the RI, the PMI, and the CQI, wherein the preferred transmission mode is a single beam transmission mode or a dual beam transmission mode; and

processing a downlink, DL, data transmission from the base station, the downlink data transmission associated with the indicated preferred transmission mode.

2. The apparatus of claim 1, wherein the preferred transmission mode comprises:

the single beam transmission mode when the transmission beam index is the same for the preferred Tx beam; or

The dual beam transmission mode when the transmission beam index is different for the preferred Tx beam.

3. The apparatus of claim 1, wherein the CSI includes first CSI associated with the first Tx beam and second CSI associated with the second Tx beam.

4. The apparatus of claim 3, wherein the at least one processor is further configured to cause the UE to:

indicating the preferred transmission mode to the base station by setting a transmission beam index, RI, PMI and CQI in the second CSI to be equal to a corresponding transmission beam index, RI, PMI and CQI in the first CSI.

5. The apparatus of claim 3, in which the at least one processor is further configured to cause the UE to:

indicating the preferred transmission mode to the base station by setting RI, PMI and CQI in the second CSI to be equal to zero.

6. The apparatus of claim 4 or 5, wherein the indicated preferred transmission mode is the single beam transmission mode.

7. A method for flexible transmission mode switching, comprising: by a user equipment, UE:

reporting a plurality of transmit Tx beams as preferred Tx beams to a base station, wherein the preferred Tx beams comprise at least a first Tx beam and a second Tx beam, wherein the first Tx beam is a preferred beam and the second Tx beam is a candidate beam;

receiving a channel state information reference signal, CSI-RS, beamformed based on the plurality of preferred Tx beams;

determining channel state information, CSI, for the first Tx beam and the second Tx beam in response to the CSI-RS, the CSI including a transmission beam index, a rank indicator, RI, a precoding matrix indicator, PMI, and a channel quality indicator, CQI, for the first Tx beam and the second Tx beam;

reporting the determined CSI to the base station, wherein the CSI is configured by the UE to: indicating a preferred transmission mode based at least in part on a transmission beam index of the second Tx beam, and/or setting values of the RI, the PMI, and the CQI, wherein the preferred transmission mode is a single beam transmission mode or a dual beam transmission mode; and

receiving a downlink, DL, data transmission from the base station in accordance with the indicated preferred transmission mode.

8. The method of claim 7, wherein the transmission mode comprises:

the single beam transmission mode when the transmission beam index is the same for the preferred Tx beam; or

The dual beam transmission mode when the transmission beam index is different for the preferred Tx beam.

9. The method of claim 7, wherein the CSI includes a first CSI associated with the first Tx beam and a second CSI associated with the second Tx beam.

10. The method of claim 9, further comprising:

indicating the preferred transmission mode to the base station by setting a transmission beam index, RI, PMI and CQI in the second CSI equal to a corresponding transmission beam index, RI, PMI and CQI in the first CSI.

11. The method of claim 9, further comprising:

indicating the preferred transmission mode to the base station by setting RI, PMI and CQI in the second CSI to be equal to zero.

12. The method of claim 10 or 11, wherein the indicated preferred transmission mode is the single beam transmission mode.

13. At least one machine readable medium which, when executed by a machine, causes the machine to perform any of the methods of claims 7-12.

14. An apparatus comprising means for performing any of the methods of claims 7-12.

15. An apparatus for use in a base station, the apparatus comprising at least one processor configured to cause the base station to:

receiving a plurality of transmit Tx beams as preferred Tx beams from a User Equipment (UE), wherein the preferred Tx beams include at least a first Tx beam and a second Tx beam, wherein the first Tx beam is a preferred beam and the second Tx beam is a candidate beam;

beamforming a channel state information reference signal, CSI-RS, based on an indication of a plurality of Tx beams from a user equipment, UE, as preferred transmit Tx beams;

determining a transmission mode based on set values of a transmission beam index, a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), and a Channel Quality Indicator (CQI) in CSI of the second Tx beam using Channel State Information (CSI) of the first Tx beam and the second Tx beam from the UE, wherein the transmission mode is a single beam transmission mode or a dual beam transmission mode; and

initiating downlink, DL, data transmission according to the determined transmission mode.

16. The apparatus of claim 15, in which the at least one processor is further configured to cause the base station to:

initiating DL data transmission according to the single beam transmission mode when the RI, PMI and CQI of the first Tx beam is equal to the RI, PMI and CQI of the second Tx beam.

17. The apparatus of claim 15, in which the at least one processor is further configured to cause the base station to:

and when the RI, PMI and CQI of the second Tx wave beam are equal to zero, initiating DL data transmission according to the single wave beam transmission mode.

18. The apparatus of claim 15, in which the at least one processor is further configured to cause the base station to:

initiating DL data transmission according to the dual-beam transmission mode when the transmission beam index, RI, PMI and/or CQI of the first Tx beam is different from the corresponding transmission beam index, RI, PMI and/or CQI of the second Tx beam.

19. The apparatus of claim 15, in which the at least one processor is further configured to cause the base station to:

generating an indicator for transmission to the UE during the dual beam transmission mode of at least two Tx beams, the indicator indicating a CQI derivation mode, wherein the CQI derivation mode specifies whether to account for mutual interference between the at least two Tx beams during CQI derivation.

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