Patent Description:
The technology of the present disclosure relates generally to wireless communications among electronic devices in a network environment and, more particularly, to a method and apparatus for selecting MIMO mode.

Demand for data traffic on wireless communication system continues to increase. Since widespread commercialization of fourth generation (<NUM>) wireless systems, such as a Long Term Evolution (LTE) system or an LTE-Advanced (LTE-A) system standardized by the 3rd Generation Partnership Project (3GPP), next generation wireless systems are being developed. One such system, by the 3GPP, is a fifth generation (<NUM>) or New Radio (NR) wireless system.

To meet demand for higher data rates, wireless systems anticipate using presently unlicensed spectrum bands. High frequency bands (e.g. millimeter wave) can provide high data rates, but signal power may decrease quicker as signals propagate as compared to lower band systems. To provide a wider coverage area, beamforming techniques may be utilized at both a base station side and a user equipment (UE) side.

Polarization based MIMO (P-MIMO), also known as polarization multiplexing, can potentially double the data rate with no additional control/signaling overhead. Certain P-MIMO transmission techniques have been proposed and shown to deliver good results in favorable channel conditions, e.g., strong line of sight channel or channels with a dominant propagation direction. However, line of sight channels cannot be guaranteed in either indoor or outdoor environments, and high mobility use cases. <CIT> discloses systems for adaptation of MIMO mode in mmW Wireless Local Area Network (WLAN) systems. A first station (STA) may receive a mode change request from a second STA. The mode change request may indicate a mode change for a MIMO mode, a polarization mode, and/or an orthogonal frequency-division multiple access (OFDMA) mode. The mode change request may include one or more STA fields. The one or more STA fields may include a STA field associated with the first STA. Each of the one or more STA fields may include a MIMO mode subfield, a polarization mode subfield, and/or an OFDMA mode subfield.

In view of the above, there is a need in the art for methods and devices which are able to utilize P-MIMO transmission techniques, but also maintain a reliable communication method in situations where the communication channel is unfavorable for P-MIMO transmission.

The disclosed approach provides a method of operating an electronic device. The method includes determining a mode selection based on at least one of a capability of the electronic device or channel conditions of a communication channel between the electronic device and a base station. The mode selection indicates at least one of polarization based MIMO (P-MIMO) or beam MIMO (B-MIMO). The method further includes transmitting a signal to the base station to indicate a mode for communications over the communication channel according to the mode selection. The proposed solution is defined by the independent claims.

Embodiments will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout.

Described below, in conjunction with the appended figures, are various embodiments of systems and methods for selecting a communication mode in a wireless network. A communication mode selection procedure may be carried out by the respective devices in an automated manner to identify a desired mode for communication between an electronic device and a base station based on the electronic device's capabilities and/or the channel conditions of the communication channel between the electronic device and the base station. The procedure described herein may allow for the high data rates associated with polarization based MIMO while preventing communication interruptions due to unfavorable channel conditions.

In general, Multiple Input Multiple Output communication (MIMO) is implemented in LTE and involves the use of multiple transmission layers from multiple antennas at both sides of a link. The number of layers are less or equal to the number of antennas at the side which has the least antennas. For NR or in general at higher frequencies when beamforming is used, the receiving device (e.g. electronic device) identifies beam pairs (e.g. beams as seen from the terminal that reach the base station). For MIMO in mm-wave with beamforming, the electronic device identifies the strongest beams (with different beam ID) and selects the beams which are the strongest. For 2x2 MIMO, this corresponds to selecting the two strongest beam pairs. This process is defined as beam MIMO (B-MIMO) in this context. If the electronic device is restricted to operate dual transmit streams in a single direction but at orthogonal polarization we define this as polarization MIMO (P-MIMO). P-MIMO is then a subset of B-MIMO and P-MIMO condition applies when the electronic device identifies that the two beam pairs with different IDs are arriving from the same angle but with orthogonal polarization. Embodiments disclosed herein relate to identifying that the two strongest beam pairs actually are the same beam direction but with orthogonal polarization, communicating this between the two nodes (e.g. base station and electronic device or a first electronic device and a second electronic device) and thereby reducing the number of beam management processes. This results in the benefit of a reduction in related signaling and latency.

<FIG> is a schematic diagram of an exemplary network system <NUM> for implementing the disclosed techniques. It will be appreciated that the illustrated system is representative and other systems may be used to implement the disclosed techniques. The exemplary network system <NUM> includes a base station <NUM> that operates in accordance with a cellular protocol, such as a protocol promulgated by 3GPP or another standard. For instance, the network system <NUM> may operate in accordance with LTE, LTE-A, or a <NUM> NR standards. However, it is to be appreciated that the techniques described herein can be applied to substantially any wireless communication system that utilizes MIMO or multiple beams between respective devices.

The network system <NUM> of the illustrated example supports cellular-type protocols, which may include circuit-switched network technologies and/or packet-switched network technologies. The network system <NUM> includes a base station <NUM> that services one or more electronic devices <NUM>, designated as electronic devices 14a through 14n in <FIG>. The base station <NUM> may support communications between the electronic devices <NUM> and a network medium <NUM> through which the electronic devices <NUM> may communicate with other electronic devices <NUM>, servers, devices on the Internet, etc. The base station <NUM> may be an access point, an evolved NodeB (eNB) in a <NUM> network or a next generation NodeB (gNB) in a <NUM> or NR network as well as a second terminal (e.g. device to device communications). As utilized herein, the term "base station" may refer, generally, to any device that services user devices and enables communications between the user devices and the network medium or a second device and, thus, includes the specific examples above depending on the network implementation. It should be appreciated that while the term "base station" is used with regards to embodiments disclosed herein, the electronic device may communicate with any type of network node according to the disclosed embodiments, including, but not limited to, a second electronic device or a different type of network element.

In one embodiment, the network system <NUM> supports multi-beam operations between the base station <NUM> and the electronic devices <NUM> such that the base station <NUM> can transmit using a plurality of beams (generated with beamforming techniques, for example) and the electronic devices <NUM> can receive using one or more reception beams. During multi-beam operations, the base station <NUM> may retransmit certain messages (with or without differences) using each available transmit beam, which is referred to as beam sweeping. In particular, such beam sweeping may occur when the base station <NUM> communicates information to electronic devices <NUM> before establishing a specific, known beam for each electronic device <NUM>. For example, beam sweeping may be used to dynamically determine whether channel conditions are favorable for polarized MIMO (P-MIMO) communications, or whether beam MIMO (B-MIMO) should be used.

The base station <NUM> may include operational components for carrying out the wireless communications, the communication mode selection described herein and other functions of the base station <NUM>. For instance, the base station <NUM> may include a control circuit <NUM> that is responsible for overall operation of the base station <NUM>, including controlling the base station <NUM> to carry out the operations described in greater detail below. The control circuit <NUM> includes a processor <NUM> that executes code <NUM>, such as an operating system and/or other applications. The functions described in this disclosure document may be embodied as part of the code <NUM> or as part of other dedicated logical operations of the base station <NUM>. The logical functions and/or hardware of the base station <NUM> may be implemented in other manners depending on the nature and configuration of the base station <NUM>. Therefore, the illustrated and described approaches are just examples and other approaches may be used including, but not limited to, the control circuit <NUM> being implemented as, or including, hardware (e.g., a microprocessor, microcontroller, central processing unit (CPU), etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an application-specific integrated circuit (ASIC), etc.).

The code <NUM> and any stored data (e.g., data associated with the operation of the base station <NUM>) may be stored on a memory <NUM>. The code may be embodied in the form of executable logic routines (e.g., a software program) that is stored as a computer program product on a non-transitory computer readable medium (e.g., the memory <NUM>) of the base station <NUM> and is executed by the processor <NUM>. The functions described as being carried out by the base station <NUM> may be thought of as methods that are carried out by the base station <NUM>.

The memory <NUM> may be, for example, one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, the memory <NUM> includes a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the control circuit <NUM>. The memory <NUM> is considered a non-transitory computer readable medium.

The base station <NUM> includes communications circuitry that enables the base station <NUM> to establish various communication connections. For instance, the base station <NUM> may have a network communication interface <NUM> to communicate with the network medium <NUM>. Also, the base station <NUM> may have a wireless interface <NUM> over which wireless communications are conducted with the electronic devices <NUM>, including the multi-beam operations and procedures described herein. The wireless interface <NUM> may include a radio circuit having one or more radio frequency transceivers (also referred to as a modem), one or more antenna assemblies, and any appropriate tuners, impedance matching circuits, and any other components needed for the various supported frequency bands and radio access technologies.

The electronic devices <NUM> serviced by the base station <NUM> may be user devices (also known as user equipment or UEs) or machine-type devices. Exemplary electronic devices <NUM> include, but are not limited to, mobile radiotelephones ("smartphones"), tablet computing devices, computers, a device that uses machine-type communications, machine-to-machine (M2M) communications or device-to-device (D2D) communication (e.g., a sensor, a machine controller, an appliance, etc.), a camera, a media player, or any other device that conducts wireless communications with the base station <NUM>.

As shown in <FIG>, each electronic device <NUM> may include operational components for carrying out the wireless communications, the communication mode selection described herein and other functions of the electronic device <NUM>. For instance, among other components, each electronic device <NUM> may include a control circuit <NUM> that is responsible for overall operation of the electronic device <NUM>, including controlling the electronic device <NUM> to carry out the operations described in greater detail below. The control circuit <NUM> includes a processor <NUM> that executes code <NUM>, such as an operating system and/or other applications. The functions described in this disclosure document may be embodied as part of the code <NUM> or as part of other dedicated logical operations of the electronic device <NUM>. The logical functions and/or hardware of the electronic device <NUM> may be implemented in other manners depending on the nature and configuration of the electronic device <NUM>. Therefore, the illustrated and described approaches are just examples and other approaches may be used including, but not limited to, the control circuit <NUM> being implemented as, or including, hardware (e.g., a microprocessor, microcontroller, central processing unit (CPU), etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an application-specific integrated circuit (ASIC), etc.).

The code <NUM> and any stored data (e.g., data associated with the operation of the electronic device <NUM>) may be stored on a memory <NUM>. The code <NUM> may be embodied in the form of executable logic routines (e.g., a software program) that is stored as a computer program product on a non-transitory computer readable medium (e.g., the memory <NUM>) of the electronic device <NUM> and is executed by the processor <NUM>. The functions described as being carried out by the electronic device <NUM> may be thought of as methods that are carried out by the electronic device <NUM>.

The electronic device <NUM> includes communications circuitry that enables the electronic device <NUM> to establish various communication connections. For instance, the electronic device <NUM> may have a wireless interface <NUM> over which wireless communications are conducted with the base station <NUM>, including the multi-beam operations and procedures described herein. The wireless interface <NUM> may include a radio circuit having one or more radio frequency transceivers (also referred to as a modem), at least one antenna assembly, and any appropriate tuners, impedance matching circuits, and any other components needed for the various supported frequency bands and radio access technologies.

Other components of the electronic device <NUM> may include, but are not limited to, user inputs (e.g., buttons, keypads, touch surfaces, etc.), a display, a microphone, a speaker, a camera, a sensor, a jack or electrical connector, a rechargeable battery and power supply unit, a SIM card, a motion sensor (e.g., accelerometer or gyro), a GPS receiver, and any other appropriate components.

With reference to <FIG>, network system <NUM> may support multi-beam operations. Base station <NUM> may include a large antenna array <NUM> comprising individual antenna elements <NUM>. In an aspect, each antenna element <NUM> may be coupled to a respective radio chain of base station <NUM>. The base station <NUM> may use beam forming technique with the antenna array <NUM> to generate a plurality of transmit beams <NUM> directed to electronic devices <NUM>. In certain embodiments, base station <NUM> may have the capabilities to operate as a polarization based MIMO (P-MIMO) system in which the transmit beams <NUM> are dual polarized signals. More specifically, the individual beams <NUM> and <NUM> of a beam pair in a P-MIMO system can have orthogonal polarizations with respect to one another. For example, if beam pair <NUM> is transmitted in a P-MIMO system, first beam <NUM> is transmitted in the same direction, but with a polarization that is orthogonal to the polarization of second beam <NUM>.

In order to effectively communicate using a P-MIMO configuration, the electronic device <NUM> must support such configuration. Further, the electronic device <NUM> can predict communication channel conditions of the communication channel between the base station and the electronic device <NUM> in order to determine whether P-MIMO communication is feasible or desirable.

With reference to <FIG>, shown is an exemplary flow diagram representing steps that may be carried out by the electronic device <NUM> when executing logical instructions to carry out MIMO mode selection. The flow diagram depicts an exemplary method for determining whether an electronic device <NUM> supports a P-MIMO configuration. Although illustrated in a logical progression, the blocks of <FIG> may be carried out in other orders and/or with concurrence between two or more blocks. Therefore, the illustrated flow diagrams may be altered (including omitting steps or adding steps not shown in order to enhance description of certain aspects) and/or may be implemented in an object-oriented manner or in a state-oriented manner.

Beginning at block <NUM>, the electronic device <NUM> determines at least one of a type, an amount, or a location of antenna arrays included as part of wireless interface <NUM>. For example, the electronic device <NUM> may determine that its wireless interface <NUM> includes co-located orthogonal antenna arrays. In another example, the electronic device <NUM> may determine that its wireless interface <NUM> includes an arbitrary number of antenna arrays or antenna arrays in an arbitrary location on the electronic device <NUM>. At block <NUM>, electronic device <NUM> considers whether it has co-located orthogonal arrays. If electronic device <NUM> does not have co-located orthogonal arrays, electronic device <NUM> indicates that it has B-MIMO capability only at block <NUM>. If electronic device <NUM> has co-located orthogonal arrays, electronic device <NUM> considers at block <NUM> whether it is configured to be restricted to P-MIMO only. If electronic device <NUM> is not restricted to P-MIMO only, electronic device <NUM> indicates, at block <NUM>, that it has dynamic P-MIMO capabilities. An electronic device <NUM> having dynamic P-MIMO capabilities may choose to alternate operation between P-MIMO and B-MIMO. In certain embodiments, the electronic device <NUM> with dynamic P-MIMO capabilities may request either P-MIMO or B-MIMO depending on estimated or determined communication channel conditions as described later in reference to <FIG>. If the electronic device <NUM> is configured to be restricted to P-MIMO only, the electronic device <NUM> indicates that it has static P-MIMO capabilities at block <NUM>. If the electronic device <NUM> has static P-MIMO capabilities, it may only operate using P-MIMO communications. In certain embodiments, the electronic device <NUM> with static P-MIMO capabilities operates using P-MIMO communications regardless of the communication channel conditions. When the electronic device <NUM> communicates to the base station <NUM> that it supports P-MIMO as a capability, it can also specify whether it has the capability or configuration to communicate with P-MIMO in the up-link direction, down-link direction, or both.

Turning now to <FIG>, an electronic device <NUM> may estimate channel conditions based on a beam sweep <NUM> performed by a base station <NUM>. <FIG> is a signaling diagram of communication between the base station <NUM> and the electronic device <NUM> on a wireless communication channel. At <NUM>, the base station <NUM> performs a beam sweep <NUM> by transmitting one or more pilot signals <NUM>. Each pilot signal <NUM> may be indicative of the particular beam on which it has been transmitted. Thereby, the electronic device <NUM> can receive the beam sweep <NUM> and identify the particular beams of the beam sweep <NUM> which shows most favorable transmission characteristics. In certain embodiments where the base station <NUM> includes omni-directional antennas, the communication channel is sounded by pilot signals (e.g. Channel State Information-Reference Signals (CSI-RS) in the down-link case and Sounding Reference Signal (SRS) in the up-link case). A pilot signal is transmitted from each antenna element on the base station <NUM> in a dedicated time frequency resource and received by all antennas at the receive side (e.g. electronic device <NUM>). The receiver node then has the full channel matrix. By computing a singular value decomposition (SVD), the modes associated with the strongest singular values can be identified and addressed by the electronic device <NUM> with different streams. If the electronic device <NUM> identifies that two singular values are associated with the same directional properties it can conclude that they are orthogonally polarized. If the two strongest singular values are identified as being orthogonal from polarization perspective the electronic device <NUM> can assume that P-MIMO condition apply.

In certain embodiments, pilot signals <NUM> are transmitted by the base station <NUM> in beams as described above. Transmit beam sweeps are performed by the base station <NUM> where each beam has a unique beam ID. The electronic device <NUM> performs a receive beam sweep and identifies beam pairs. In some embodiments, an electronic device <NUM> with collocated dual polarized antennas sweeps both polarizations independently. Likewise, the base station <NUM> can sweep both polarizations independently. It should be appreciated that the polarizations at the base station <NUM> are not necessarily aligned to the polarizations at the electronic device <NUM>. As the electronic device <NUM> knows which receive beams correspond to the same direction, but with different polarization, it can detect if P-MIMO conditions apply also in this case.

At <NUM>, the electronic device <NUM> identifies at least two strongest beam pairs having the same beam direction and orthogonal polarization. The electronic device <NUM> can determine whether the signal strength of the at least two strongest beam pairs is greater than a signal strength of any other beam pairs by a predetermined ratio. The electronic device <NUM> then selects a communication mode based on the determination of whether the signal strength of the at least two strongest orthogonally polarized beam pairs is greater than a signal strength of any two other beam pairs by the predetermined ratio. If the signal strength of the at least two strongest orthogonally polarized beam pairs is greater than a signal strength of any two of the other beam pairs in the beam sweep <NUM> by the predetermined ratio, then the electronic device <NUM> can determine that P-MIMO conditions apply on the communication channel. In this situation, the electronic device <NUM> indicates a request for P-MIMO communications and transmits this request via a request signal <NUM> to the base station <NUM> at <NUM>. At <NUM>, upon receiving the request signal <NUM>, the base station <NUM> can activate or de-activate P-MIMO communications based on the request indicated by the electronic device <NUM> in the request signal <NUM>.

With reference to <FIG>, shown is an exemplary flow diagram representing steps that may be carried out by the electronic device <NUM> when executing logical instructions to determine channel conditions and/or select a communication mode. Complimentary operations of the base station <NUM> are shown in <FIG>, which shows an exemplary flow diagram representing steps that may be carried out by the base station <NUM> when executing logical instructions to carry out activation or deactivation of P-MIMO communications. Although illustrated in a logical progression, the blocks of <FIG> may be carried out in other orders and/or with concurrence between two or more blocks. Therefore, the illustrated flow diagrams may be altered (including omitting steps or adding steps not shown in order to enhance description of certain aspects) and/or may be implemented in an object-oriented manner or in a state-oriented manner. Also, the method represented by <FIG> may be carried out apart from the method of <FIG> and vice versa.

Turning first to <FIG>, at block <NUM>, the electronic device <NUM> determines or estimates communication channel conditions. This step may include some or all of the steps of the beam sweep and analysis operations described above with respect to <FIG>. Determining channel conditions can also include determining whether there is line of sight, a dominant mode, a dominant beam direction, or multiple available modes between the base station <NUM> and the electronic device <NUM>. At <NUM>, the electronic device <NUM> determines whether the communication channel conditions are acceptable for P-MIMO communications. If the channel conditions are acceptable for P-MIMO, the electronic device <NUM> transmits a P-MIMO request signal to base station <NUM> at block <NUM>. For example, the electronic device <NUM> can determine that channel conditions are acceptable for P-MIMO if the receive beam sweep <NUM> analysis indicates P-MIMO conditions on the communication channel and/or if there is a line of sight, or dominant mode between the base station <NUM> and the electronic device <NUM>. If the channel conditions are unacceptable or not conducive for P-MIMO, the electronic device <NUM> transmits a B-MIMO request signal to the base station <NUM> at block <NUM>. For example, the electronic device <NUM> can determine that channel conditions are not acceptable for P-MIMO if the receive beam sweep <NUM> analysis indicates that P-MIMO conditions are not present on the communication channel and/or if there is no line of sight between the base station <NUM> and the electronic device <NUM>. After sending a request for B-MIMO, the electronic device <NUM> can transmit configuration data indicating a first polarization of a first radio frequency signal and a second polarization of a second radio frequency signal to be transmitted as a beam pair by the base station <NUM>. Alternatively, the electronic device <NUM> may also request Single Input Single Output (SISO) communications when the communication channel does not support more than a single stream.

Turning now to <FIG>, at block <NUM>, the base station <NUM> receives the request signal from the electronic device <NUM>. At block <NUM>, the base station <NUM> determines whether the request signal indicates P-MIMO. If the request signal indicates P-MIMO, the base station <NUM> activates P-MIMO at block <NUM>. If the request signal does not indicate P-MIMO, the base station <NUM> de-activates P-MIMO at block <NUM> (or maintains B-MIMO if P-MIMO is already de-activated. ) In certain embodiments, the base station <NUM> can activate or de-activate P-MIMO by Radio Resource Control (RRC) signaling. Further, the base station <NUM> can activate P-MIMO in the up-link direction, the down-link direction, or both, based on the electronic device's <NUM> request.

In certain embodiments, the base station <NUM> activates or de-activates P-MIMO based only on the capabilities of the electronic device <NUM>, as described with regards to <FIG>. In these embodiments, the electronic device <NUM> transmits a signal to the base station indicating the electronic device's <NUM> capabilities with regards to communication via P-MIMO, and the base station <NUM> responds by activating or de-activating P-MIMO based on the device's capabilities and/or configuration.

In other embodiments, the base station <NUM> activates or de-activates P-MIMO based only on communication channel conditions as estimated or determined by the electronic device <NUM>, as described with regards to <FIG>. The electronic device <NUM> transmits a signal to the base station indicating whether the channel conditions support P-MIMO communications, and the base station <NUM> responds by activating or de-activating P-MIMO based on the communication channel conditions.

In still other embodiments, the base station <NUM> activates or de-activates P-MIMO based on both the capabilities of the electronic device <NUM> (e.g. in <FIG>) and the communication channel conditions (e.g. in <FIG>). The electronic device <NUM> transmits a signal to the base station indicating the electronic device's <NUM> capabilities with regards to communication via P-MIMO. If the electronic device <NUM> has P-MIMO capabilities, it also communicates an indication whether the channel conditions support P-MIMO communications, and the base station <NUM> responds by activating or de-activating P-MIMO based on the electronic device's <NUM> capabilities and the communication channel conditions.

In further embodiments, if P-MIMO feature is activated, a decision is made regarding whether beams corresponding to the same physical antenna element but different polarization should or should not be in the same beam group. More specifically, the decision is whether the beam IDs of the polarization pair should or should not be in the same beam group. This decision depends on whether multiplexing MIMO is allowed with beams in the same beam group.

The embodiments disclosed herein may also apply to larger scale MIMO where each dual polarized beam pair has a common beam management process.

Claim 1:
A method of operating an electronic device (<NUM>) in a communication network comprising the electronic device and a network node, the method comprising:
determining a mode selection based on channel conditions of a communication channel between the electronic device (<NUM>) and the network node (<NUM>), the mode selection indicates one of polarization based MIMO, P-MIMO, or beam MIMO, B-MIMO; and
transmitting a signal to the network node (<NUM>) to indicate a mode for communications over the communication channel according to the mode selection, wherein the channel conditions are determined by:
performing a receive beam sweep (<NUM>) to identify a plurality of beam pairs; and
identifying (<NUM>) two strongest beam pairs having a same beam direction and orthogonal polarizations;
wherein the mode selection indicates a request for P-MIMO to the network node based on a determination condition that signal strength of the two strongest beam pairs having the same beam direction and orthogonal polarization is greater by a predetermined ratio than a signal strength of any other beam pairs of the identified plurality of beam pairs and when said determination condition for P-MIMO is not fulfilled the mode selection indicates a request for beam-MIMO communication to the network node.