BR112017000190B1 - ASYMMETRIC DIRECTED CAPACITY METHODS FOR BEAM TRACKING IN MM-WAVE ACCESS SYSTEMS - Google Patents

Abstract

A method, an apparatus and a computer program product for operating a user equipment (UE) are provided. The apparatus establishes a wireless communication link with a millimeter wave base station (mmW-BS) based on a transmission beam from the mmW-BS, the transmission beam having a transmission beam direction, receives information from beamforming capability indicating one of at least one digital, analog, or hybrid beamforming capability associated with the mmW-BS, and scans N transmit beams from the mmW-BS for each of M beam directions reception of the UE based on the beamforming capability information and the transmit beam associated with the wireless communication link.

Description

CROSS REFERENCE TO RELATED ORDER

[0001] This application claims the benefit of United States Patent Application No. 14/332,330 entitled "ASYMMETRIC DIRECTED CAPACITY METHODS FOR BEAM TRACKING IN MM-WAVE ACCESS SYSTEMS" and filed on July 15, 2014, which is expressly incorporated by reference in its entirety.

FUNDAMENTALS Field

[0002] The present disclosure relates generally to communications systems, and more particularly to asymmetric directed capability methods of beam tracking in millimeter wave (mmW) access systems.

Fundamentals

[0003] Wireless communication systems are widely used to provide various telecommunication services such as telephony, video, data, messaging and transmissions. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (eg bandwidth, transmit power). Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, frequency division multiple access systems frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA) systems, and synchronous code division and time division multiple access (TD-SCDMA) systems.

[0004] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol that allows different wireless devices to communicate on a municipal, national, regional and even global level. An example of an emerging telecommunications standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by 3GPP (Third Generation Partnership Project). LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, reducing costs, improving services by making use of new spectrum, and better integration with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input, multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there is a need for improvements in LTE technology. Preferably, these enhancements should be applicable to other multiple access technologies and the telecommunications standards that use these technologies.

SUMMARY

[0005] In one aspect of the disclosure, a method, a computer program product, and an apparatus are provided. The apparatus establishes a wireless communication link with a millimeter wave base station (mmW-BS) based on a transmission beam from the mmW-BS, the transmission beam having a beam transmission direction, receives beamforming indicating one of at least one digital, analog, or hybrid beamforming capability associated with the mmW-BS, and scans N transmit beams from the mmW-BS for each of M beam directions reception of the UE based on the beamforming capability information and the transmit beam associated with the wireless communication link.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a diagram illustrating an example of a network architecture.

[0007] FIG. 2 is a diagram illustrating an example of an access network.

[0008] FIG. 3 is a diagram illustrating an example of an evolved Node B and user equipment in an access network.

[0009] FIG. 4 is a diagram of a device-to-device communications system.

[0010] FIG. 5 is a diagram illustrating an example of an mmW wireless communication system.

[0011] FIG. 6 is a diagram illustrating an exemplary scanning operation for a UE and an mmW-BS.

[0012] FIG. 7 is a diagram illustrating an exemplary scanning operation for a UE and an mmW-BS.

[0013] FIG. 8 is a flowchart of a wireless communication method.

[0014] FIG. 9 is a data flow diagram illustrating data flow between different modules/media/components in an exemplary apparatus.

[0015] FIG. 10 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

[0016] The detailed description presented below in connection with the accompanying drawings is intended to be a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a complete understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some cases, well-known structures and components are shown in block diagram form, in order to avoid obscuring such concepts.

[0017] Various aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatuses and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, steps, circuits, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and design limitations imposed on the overall system.

[0018] By way of example, an element, or any portion of an element, or any combination of the elements may be implemented with a "processing system", which includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGA), programmable logic devices (PLD), state machines, gate logic, discrete hardware circuits, and other suitable hardware. configured to perform the various functionalities described throughout this description. One or more processors in the processing system can run the software. Software shall be broadly interpreted to mean instructions, sets of instructions, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects , executables, chains of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0019] Therefore, in one or more exemplary embodiments, the described functions can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored in or encoded as one or more code instructions or on a computer-readable medium. Computer readable media include computer storage media. Storage media can be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media may comprise random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), compact disk ROM ( CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to transport or store the desired program code in the form of instructions or data structures, and that can be accessed by a computer. Combinations of the foregoing must also be included within the scope of computer-readable means.

[0020] FIG. 1 is a diagram illustrating an LTE network architecture 100. The LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS 100 may include one or more user equipment (UE) 102, a Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, and an Internet Protocol (IP) Operator Service 122. The EPS can interconnect with other access networks , but for simplicity these entities/interfaces are not shown. As shown, EPS provides packet switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure can be extended to networks providing circuit switched services.

[0021] The E-UTRAN includes Evolved Node B (eNB) 106 and another eNB 108, and may include a Multicast Coordination Entity (MCE) 128. The eNB 106 provides user and control plane protocol terminations for the UE 102. The eNB 106 may be connected to each other via an eNB 108 via a backhaul channel (eg, an X2 interface). ECM 128 allocates radio frequency/time resources for Evolved Broadcast Multimedia Multicast Services (MBMS) (eMBMS), and determines the radio configuration (eg, modulation and coding scheme (MCS)) for the eMBMS. The MCE 128 may be a separate entity or part of the eNB 106. The eNB 106 may also be referred to as a base station, a Node B, an access point, a base station transceiver, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), extended service set (ESS), or some other suitable terminology. The eNB 106 provides an access point to the EPC 110 for the UE 102. Examples of UEs 102 include a cell phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA ), satellite radio, global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, or any other operating device similar. UE 102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, an apparatus, a user agent, a mobile client, a client, or some other appropriate terminology.

[0022] The eNB 106 is connected to the EPC 110. The EPC 110 may include a Mobility Management Entity (MME) 112, a Home Subscriber Server (HSS) 120, other MMEs 114, a Gateway Server 116, a Gateway Broadcast Multimedia Multicast Services (MBMS) 124, a Broadcast Multicast Service Center (BM-SC) 126, and a packet data network (PDN) gateway 118. The MME 112 is the control node that processes signaling between the UE 102 and EPC 110. Generally, MME 112 provides bearer and connection management. All user IP packets are transferred through Server Gateway 116, which in turn is connected to PDN Gateway 118. PDN Gateway 118 provides UE IP address allocation as well as other functions. The PDN Gateway 118 and the BM-SC 126 are connected to the IP Services 122. The IP Services 122 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS streaming service (PSS), and/or other IP services. The BM-SC 126 can provide user MBMS service provisioning and delivery functions. The BM-SC 126 can serve as an entry point for content provider MBMS transmissions, can be used to authorize and initiate supporting MBMS services within a PLMN, and can be used to schedule and deliver MBMS transmissions. MBMS Gateway 124 can be used to distribute MBMS traffic to eNBs (e.g. 106, 108) belonging to a Broadcast Multicast Single Frequency Network (MBSFN) area transmitting a particular service, and can be responsible for managing sessions (start/stop) and to collect related eMBMS charging information.

[0023] In one aspect, the UE 102 is capable of communicating signals over the LTE network and a millimeter wave (mmW) system. Therefore, the UE 102 can communicate with the eNB 106 and/or the other eNB 108 over an LTE link. Furthermore, the UE 102 can communicate with a connection point (CP) or base station (BS) or mmW base station (mmW-BS) 130 (capable of mmW system communication) over an mmW link.

[0024] In another aspect, at least one of the other eNB 108 may be able to communicate signals through the LTE network and the mmW system. As such, an eNB 108 can be referred to as an LTE + mmW eNB. In another aspect, the CP/BS/mmW-BS 130 may be able to communicate signals through the LTE network and the mmW system. As such, the CP/BS/mmW-BS 130 can be referred to as an LTE + mmW CP/BS. The UE 102 can communicate with the other eNB 108 over an LTE link as well as over an mmW link.

[0025] In yet another aspect, the other eNB 108 may be able to communicate signals via the LTE network and the mmW system, while the CP/BS 130 is able to communicate via signals only via the mmW system. Therefore, the CP/BS 130 unable to signal the other eNB 108 over the LTE network can communicate with the other eNB 108 over an mmW backhaul link.

[0026] FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture. In this example, the access network 200 is divided into a number of cellular regions (cells) 202. One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202. The eNB of lower power class 208 can be a femto cell (eg home eNB (HeNB)), pico cell, micro cell, or remote radio header (RRH). The macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point for the EPC 110 for all UEs 206 in cells 202. There is no centralized controller, in this example, of an access network 200 , but a centralized controller can be used in alternative configurations. The eNB 204 is responsible for all radio related functions, including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the server gateway 116. An eNB can support one or multiple (e.g., three), cells (also referred to as a sector). The term "cell" may refer to the smaller coverage area of an eNB and/or an eNB subsystem serving its particular coverage area. Furthermore, the terms "eNB", "base station", and "cells" may be used interchangeably herein.

[0027] In one aspect, the UE 206 can communicate signals over the LTE network and a millimeter wave (mmW) system. Therefore, the UE 206 can communicate with the eNB 204 over an LTE link and communicate with a connection point (CP) or base station (BS) 212 (capable of mmW system communication) over an mmW link. In an additional aspect, the eNB 204 and CP/BS/mmW-BS 212 can communicate signals over the LTE network and the mmW system. As such, the UE 206 can communicate with the eNB 204 via an LTE link and an mmW link (when the eNB 204 is capable of mmW system communication), or communicate with the PC/BS 212 via an mmW link and an LTE access (when the CP/BS/mmW-BS 212 is capable of LTE network communication). In yet another aspect, the eNB 204 communicates the signals via the LTE network and the mmW system, while the CP/BS/mmW-BS 212 communicates the signals via the mmW system only. Therefore, the CP/BS/mmW-BS 212 unable to signal the eNB 204 over the LTE network can communicate with the eNB 204 over a mmW backhaul channel link.

[0028] The modulation and multiple access scheme employed by the access network 200 may vary depending on the particular telecommunications standard to be deployed. In LTE applications, OFDM is used in DL and SC-FDMA is used in UL to support both frequency division duplex (FDD) and time division duplex (TDD). As those skilled in the art will easily appreciate from the detailed description that follows, the various concepts presented here are well suited for LTE applications. However, these concepts can easily be extended to other telecommunications standards that employ other multiple access and modulation techniques. For example, these concepts can be extended to Optimized Data Evolution (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by 3GPP2 (3rd Generation Partnership Project 2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts can also be extended to Universal Terrestrial Radio Access (UTRA) employing wideband CDMA (W-CDMA) and other variants of CDMA such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM using OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in 3GPP organization documents. CDMA2000 and UMB are described in 3GPP2 organization documents. The actual wireless communication standard and multiple access technology employed will depend on the specific application and general design constraints placed on the system.

[0029] The eNB 204 can have multiple antennas that support MIMO technology. The use of MIMO technology allows the eNB 204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmission diversity. Spatial multiplexing can be used to transmit different data streams simultaneously on the same frequency. Data streams can be transmitted to a single UE 206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is accomplished by spatially precoding each data stream (i.e., applying one amplitude and one phase scaling) and then transmitting each precoded spatial stream through multiple transmit antennas in the DL. The spatially precoded data streams arrive at the UE(s) 206 with different spatial signatures, which allows each of the UE(s) 206 to retrieve one or more data streams destined for that UE 206. In the UL , each UE 206 transmits a spatially precoded data stream, which allows the eNB 204 to identify the source of each spatially precoded data stream.

[0030] Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming can be used to focus transmission energy in one or more directions. This can be achieved by spatially pre-coding the data for transmission over multiple antennas. To achieve good coverage at the cell edges, a single stream beamforming transmission can be used in combination with transmission diversity.

[0031] In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system that supports OFDM in DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced at precise frequencies. The spacing provides "orthogonality" that allows a receiver to retrieve data from the subcarriers. In the time domain, a guard interval (eg, cyclic prefix) can be added to each OFDM symbol to combat inter-symbol-OFDM interference. The UL can use SC-FDMA in the form of a DFT spread OFDM signal to compensate for high peak-to-average power ratio (PAPR).

[0032] FIG. 3 is a block diagram of a base station 310 in communication with a UE 350 in an access network. The base station 310 can be, for example, an eNB of an LTE system, a point of connection (CP)/access point/base station of a millimeter wave (mmW) system, an eNB capable of communicating signals across the system LTE and the mmW system, or a point of connection (CP)/access point/base station capable of communicating signals via the LTE system and the mmW system. The UE 350 may be able to communicate signals via the LTE system and/or the mmW system. In DL, packets from the network core upper layer are provided to a controller/processor 375. In DL, controller/processor 375 provides header compression, encryption, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations for the UE 350 based on several priority indicators. Controller/processor 375 is also responsible for HARQ operations, retransmission of lost packets, and signaling to UE 350.

[0033] The transmit (TX) processor 316 implements various signal processing functions. Signal processing functions include encoding and interleaving to facilitate forward error correction (FEC) in the UE 350, and mapping to signal constellations based on various modulation schemes (e.g. BPSK (binary phase-shift keying), QPSK ( quadrature phase-shift keying), M-PSK (M-phase-shift keying), M-QAM (M-quadrature amplitude modulation)). The encoded and modulated symbols are then divided into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a channel. that carries a stream of time-domain OFDM symbols. The OFDM stream is spatially pre-coded to produce multiple spatial streams. Channel estimates from a channel estimator 374 can be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each 318TX transmitter can modulate an RF carrier with a respective spatial stream for transmission.

[0034] At the UE 350, each RX receiver 354 receives a signal through its respective antenna 352. Each RX receiver 354 retrieves modulated information about an RF carrier and provides the information to the receive (RX) processor 356. The processor RX 356 implements various signal processing functions. The RX processor 356 can perform spatial processing on the information to retrieve the spatial streams destined for the UE 350. If multiple spatial streams are destined for the UE 350, they can be combined by the RX processor 356 into a single stream of OFDM symbols. The RX processor 356 then converts the OFDM symbol stream from the time domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the signal constellation points most likely transmitted by base station 310. These indicative decisions may be based on channel estimates calculated by channel estimator 358. decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by base station 310 over the physical channel. The data and control signals are then provided to the 359 controller/processor.

[0035] The controller/processor 359 can be associated with a memory 360 that stores program codes and data. Memory 360 may be referred to as a computer-readable medium. In DL, controller/processor 359 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data store 362. Various control signals may also be provided to the data store 362. The controller/processor 359 is also responsible for detecting errors using an acknowledgment (ACK) protocol and /or negative acknowledgment (NACK) to support HARQ operations.

[0036] In the UL, a data source 367 is used to provide upper layer packets to the controller/processor 359. Similar to the functionality described in connection with the DL transmission by the base station 310, the controller/processor 359 provides the compression of header, encryption, packet segmentation, and reordering and multiplexing between logical and transport channels based on radio resource allocations by base station 310. Controller/processor 359 is also responsible for HARQ operations, retransmission of lost packets, and signaling for the base station 310.

[0037] The channel estimates obtained by a channel estimator 358 from a reference or feedback signal transmitted by the base station 310 can be used by the TX processor 368 to select the appropriate modulation and encoding schemes, and to facilitate the spatial processing. The spatial streams generated by the TX processor 368 can be provided to the antenna 352 via different separate transmitters 354TX. Each 354TX transmitter can modulate an RF carrier with a respective spatial stream for transmission.

[0038] The UL transmission is processed at the base station 310 in a similar manner to that described in connection with the receiver function at the UE 350. Each RX receiver 318 receives a signal through its respective antenna 320. Each RX receiver 318 retrieves the modulated information over an RF carrier and provides the information to an RX 370 processor.

[0039] The controller/processor 375 may be associated with a memory 376 that stores program codes and data. Memory 376 may be referred to as a computer-readable medium. At the UL, control/processor 375 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover upper layer packets from UE 350. Upper layer packets from the UE 350 controller/processor 375 may be provided to the backbone network. Controller/processor 375 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.

[0040] FIG. 4 is a diagram of a device-to-device communications system 400. The device-to-device communications system 400 includes a plurality of wireless devices 404, 406, 408, 410. The device-to-device communications system a-device 400 may overlap with a cellular communications system, such as, for example, a wireless wide area network (WWAN). Some of the wireless devices 404, 406, 408, 410 can communicate together in device-to-device communication using WWAN DL/UL spectrum, some can communicate with base station 402, and some can do both. For example, as shown in FIG. 4, wireless devices 408, 410 are in device-to-device communication and wireless devices 404, 406 are in device-to-device communication. Wireless devices 404, 406 are also communicating with base station 402.

[0041] The exemplary methods and apparatus discussed below are applicable to any of a variety of device-to-device wireless communication systems, such as a wireless device-to-device communication system based on FlashLinQ, WiMedia , Bluetooth, ZigBee, or Wi-Fi based on the IEEE 802.11 standard. To simplify the discussion, exemplary methods and apparatus are discussed within the context of LTE. However, one skilled in the art will appreciate that the exemplary methods and apparatus are more generally applicable to a variety of other wireless device-to-device communication systems.

[0042] A mmW communication system can operate in very high frequency bands (eg, 10.0 GHz to 300.0 GHz) where the carrier wavelength is on the order of a few millimeters. An mmW system can operate with the help of a number of antennas and beamforming to overcome a channel having low gain. For example, heavy attenuation in high carrier frequency bands can limit the range of a transmitted signal to a few tens of meters (for example, 1 to 50 meters). In addition, the presence of obstacles (eg walls, furniture, people, etc.) can block the propagation of high frequency millimeter waves. As such, propagation characteristics of high carrier frequencies necessitate the need for directional beamforming between the mmW-BS and the UE that focuses the transmission energy in specific spatial directions corresponding to the dominant scatterers, reflectors and/or diffraction paths. space to overcome the loss. Beamforming can be implemented through an array of antennas (e.g. phased arrays) cooperating to beamform a high frequency signal in a particular direction to receiving devices, and therefore extend the reach of the signal. . While an mmW system can operate in a stand-alone mode, the mmW system can be implemented in conjunction with more established lower frequency (and lower bandwidth) systems such as LTE.

[0043] In one aspect, the specific orientations of transmitted beams in an mmW system may need to be determined reliably and with minimal latency. Furthermore, spatial directions may need to be maintained and/or tracked as a UE moves relative to the mmW-BS and the dominant scatterers. Arbitrary UE rotations (e.g., UE rotations by the user's hand) and signal blocking in the UE (e.g., caused by the user's hand covering portions of the UE) over time may require reorientation via beamforming to avoid link failure with mmW-BS. Note that such issues are not normally a concern in LTE and other wireless communication standards, because propagation and blocking losses are negligible and performance generally does not rely on the success of the beamforming scheme (harvesting the matrix gain through a large number of antennas). In certain respects, higher ranking schemes that benefit from spatial diversity are often used to maximize throughput in LTE, however such schemes are difficult to implement in mmW systems due to radio frequency (RF) complexity and bandwidth constraints. cost.

[0044] In one aspect, an mmW-BS and a UE in an mmW system may have different capacities (also referred to as asymmetric capacities). For example, the mmW-BS and the UE may have a different number of antennas, a different number of antenna subarrays, different types of subarrays (linear, planar, etc.), different types of beamforming architecture (e.g., digital, analogue/RF, hybrid), and/or different transmit power. As discussed below, such differences in capabilities between the mmW-BS and the UE can be taken advantage of to efficiently implement a beam scanning procedure (also referred to as a beam scan).

[0045] In another aspect, a first UE (for example, wireless device 404) and a second UE (for example, wireless device 406) may be configured for device-to-device communications in an mmW system and may have different capacities. For example, the first UE and the second UE can have a different number of antennas, a different number of antenna subarrays, different types of subarrays (linear, planar, etc.), different types of beamforming architecture (e.g., digital, analogue/RF, hybrid), and/or different transmit power. These differences in capabilities between the first UE and second UE can be taken advantage of to effectively implement a beam tracking procedure between the first and second UEs.

[0046] FIG. 5 is a diagram illustrating an example of an mmW communication system 500. The mmW communication system 500 includes the UE 502 and the mmW-BS 504. In one aspect, the UE 502 and the mmW-BS 504 can perform synchronization initial and discovery to establish a communication link. For example, UE 502 and mmW-BS 504 may establish a communication link along path 506. After performing initial synchronization and discovery, UE 502 and mmW-BS 504 may each have an estimate of one L number of directions (also referred to as directions or beamforming angles) corresponding to L dominant paths from the mmW-BS 504 to the UE 502. In one aspect, L is an integer greater than 1 (for diversity reasons) . In one aspect, the mmW-BS 504 and/or the UE 502 can have an estimate of the relative strength of these L dominant paths which allows initial beamforming to be performed on the most dominant path.

[0047] In one aspect, the remaining L-1 dominant paths are tracked in both the UE 502 and the mmW-BS 504 to ensure a smooth switch from the most dominant path (e.g., the 506 path) to the L dominant paths to any of the remaining L-1 other paths (for example, path 514 that reflects off surface 522) if and when the need arises. For example, such a need to switch from the most dominant path to any of the remaining L-1 paths may arise in a case where the most dominant path is unexpectedly blocked by an obstruction (due to the mobility of the UE 502) or if the Material properties (of reflectors and scatterers) change as a function of angles.

[0048] In one aspect, the UE 502 and/or the mmW-BS 504 may have one or more beamforming capabilities that may facilitate tracking (also referred to as scanning) of the previously discussed dominant L-1 paths and the respective benefits. In one aspect, the beamforming capability which may be a device in the mmW communication system 500 has a greater number of antennas than another device in the mmW communication system 500. For example, the mmW-BS 504 may have a higher number of antennas than the UE 502. This differential in the number of antennas between the mmW-BS 504 and the UE 502 can allow the mmW-BS 504 to scan through more instructions and/or sectors within a time interval of than UE 502, for the purposes of learning the respective beam direction. For example, mmW-BS 504 can use its increased number of antennas to scan each of its possible beamforming angles (e.g., the angles corresponding to beams 508, 510, and/or 512) faster than the UE 502 may scan each of its possible beamforming angles (e.g., the angles corresponding to beams 516, 518 and/or 520) in a given time interval.

[0049] In one aspect, the beamforming capability may be an analog beamforming capability. For example, the mmW-BS 504 may have an analogue beamforming capability that may allow the mmW-BS 504 to transmit a single beam (e.g., beam 510 along path 506) over an RF chain available to a time. The term RF chain refers to a combination of power amplifier, digital-to-analog converter, and mixer, when referring to the transmit side of a modem, or to a combination of a low-noise amplifier, demixer, and a analog to digital converter, when referring to the receiver side of a modem. In one aspect, the beamforming capability may be a digital beamforming capability. For example, the mmW-BS 504 may have a digital beamforming capability corresponding to the same number of RF chains as the number of antennas, which may enable the mmW-BS 504 to simultaneously transmit several beams (e.g., beams 508 , 510, and/or 512), by emitting electromagnetic energy in multiple directions at the expense of peak gain. In one aspect, the beamforming capability can be a hybrid beamforming capability with the number of RF chains being more than one and less than the number of antennas. For example, the mmW-BS 504 can have a hybrid beamforming capability that can allow the mmW-BS 504 to transmit a beam from each of the RF chains of the mmW-BS 504. beam can be an array of multiple antenna subarrays. For example, the UE 502 may have multiple antenna subarrays that allow the UE 502 to transmit beams from each of the antenna subarrays in different directions (e.g., the respective directions of beams 516, 518, and 520) to overcome RF obstructions. , such as a UE user's hand, inadvertently blocking the path of a beam.

[0050] In another aspect, the beamforming capability may be that a device in the mmW communication system 500 has a higher antenna switching speed than another device in the mmW communication system 500. For example, the mmW-BS 504 can have a higher antenna switching speed than the UE 502. In such an example, the higher antenna switching speed of the mmW-BS 504 can be taken advantage of by configuring the mmW-BS 504 to scan different directions and/or sectors while the UE transmits a beam in a fixed direction. In another example, the UE 502 may have a higher antenna switching speed than the mmW-BS 504. In such an example, the higher antenna switching speed of the UE 502 can be taken advantage of by configuring the UE 502 to scan different directions and/or sectors while the mmW-BS 504 transmits a beam in a fixed direction.

[0051] Beam tracking is typically performed by the UE 502 and/or the mmW-BS 504 after an initial synchronization and discovery phase, where a first estimate of the beam angles has already been obtained by the UE 502 and/or the mmW- BS 504. Therefore, it should be noted that early phase discovery is characterized by poor signal-to-noise ratio (SNR) conditions, whereas beam tracking is characterized by reasonable link margin/SNR.

[0052] Beam-tracking algorithms typically use the angles learned in the initial synchronization and discovery period as an initial value (also referred to as a seed value) and to subsequently fine-tune these angles within a narrow range over the course of a period of time where the dynamic range of the angle is small. For example, if UE 502 travels at 100 mph and the distance between UE 502 and mmW-BS 504 is 100 m, the angle of a path (e.g. path 506) from mmW-BS 504 for UE 502 it can change on the order of 2.5 degrees every 100.0 milliseconds (ms). In such an example, when UE 502 is following path 506 in the direction of beam 518, UE 502 may search over a narrow range (e.g., an angle range t that includes angles θ3 and θ4 with respect to beam angle 518 in the Fig. 5) around your initialized angle to arrive at the best estimate of the follow-up phase angle. For example, θ3 can be the seed value of +2.0 degrees and θ4 can be the seed value -2.0 degrees. Therefore, the speed of the tracking process can be considerably increased by exploiting the asymmetric capabilities in mmW-BS 504 and UE 502.

[0053] In one aspect, the mmW-BS 504 can have a digital beamforming capability with NK numbers of RF chains and the UE 502 can have both an RF chain (e.g., the UE 502 has a single former analog or RF beam) or at most two RF chains (e.g. UE 502 has a hybrid beamformer). The presence of multiple RF chains can reduce the time required for beam tracking by a factor of the number of multiple RF chains, since multiple directions can be searched at the same time using these RF chains. For example, when the mmW-BS 504 has digital beamforming capability with at least two RF chains, the mmW-BS 504 can simultaneously transmit a beam along the initialized direction for a Kth path, such as path 506, and an Ith path, such as path 514, (where K Φ I) in a time interval. UE 502 may configure its antenna to cycle through its possible directions one at a time to determine the best path for each path pair (e.g., the Kth and Ith paths).

[0054] In one aspect, UE 502 may have multiple antenna subarrays. Multiple antenna subarrays with UE 502 can ensure signaling diversity to overcome dynamic signaling deficiencies, such as a physical obstruction of a signal path. For example, such a physical obstruction could be a user's hand or body part blocking a signal path. In this regard, with the mmW-BS 504 beaming along a single direction, the UE 502 can use each of its antenna subarrays to check for a quality signal received from a different direction, thus speeding up the tracking process. by the number of antenna subarrays available with the UE 502. For example, when the UE 502 has at least two antenna subsystems, the mmW-BS 504 can correct its beamformer to that of the initialized direction for the Ith path 514, while UE 502 cycles through the antenna subarrays in different directions (e.g., beam directions 516, 518 and/or 520) to determine the best direction (e.g., beam direction 520) for the Ith path 514 in time reduced tracking with respect to a case where the UE 502 has no antenna subarrays.

[0055] In one aspect, when the mmW-BS 504 has digital beamforming capability UE 502 has multiple antenna subarrays, the mmW-BS 504 and UE 502 can employ these capabilities simultaneously to significantly increase the speed of the beamforming process. tracking performed by the mmW-BS 504 and the UE 502. For example, the mmW-BS 504 can transmit a beam along the initialized direction for the Kth path and the Ith path (where K Φ I), and the UE 502 can do the cycle through its subarrays of antennas in different directions to determine the best direction for any path in the reduced tracking time. In another aspect, and as discussed below in relation to FIG. 7, when the UE 502 has the digital or hybrid beamforming capability, the UE 502 can employ the digital or hybrid beamforming capability to significantly increase the speed of the tracking process.

[0056] FIG. 6 is a diagram illustrating an example frame structure 600 for a sweep operation for UE 502 and mmW-BS 504. In the aspect of FIG. 6, UE 502 and mmW-BS 504 can each have a single antenna. As shown in FIG. 6, the mmW-BS 504 can transmit a beam in a single direction (e.g., "D1" direction) during each of a number of time slots (e.g., slot 1 602, slot 2 604, U slot 606 ) . As further shown in FIG. 6, the UE 502 may scan each of its U number of possible directions (e.g. directions "D1" to "DU") during each of the corresponding time slots (e.g. slot 1 602, slot 2 604, interval U 606) to determine the best path for the beam from the mmW-BS 504. For example, each of the time intervals (eg, interval 1 602, interval 2 604, interval U 606) can be the same length. In such an example, the duration of scan period 1 in FIG. 6 can be equivalent to the total of the U time slots needed for the UE 502 to scan each of its U directions.

[0057] The mmW-BS 504 may subsequently transmit a beam in another direction (eg "D2" direction), while the UE 502 scans each of its U number of possible directions to determine the best path for the mmW beam -BS 504. As shown in FIG. 6, the mmW-BS 504 can transmit a beam in a single direction (e.g., "D2" direction) during each of a number of time slots (e.g., slot 1 608, slot 2 610, U slot 612 ) . As further shown in FIG. 6, the UE 502 may scan each of its U number of possible directions (e.g. directions "D1" to "DU") during each of the corresponding time slots (e.g. slot 1 608, slot 2 610, interval U 612) to determine the best path for the beam from the mmW-BS 504. For example, each of the time intervals (eg interval 1 608, interval 2 610, interval U 612) can be the same length. In such an example, the duration of scan period 2 in FIG. 6 can be equivalent to the total of the U time slots needed for the UE 502 to scan each of its U directions.

[0058] The mmW-BS 504 can transmit beams in the last direction of its P number of possible directions in a similar manner to the previously discussed transmissions with respect to scan periods 1 and 2 in FIG. 6. For example, the mmW-BS 504 can transmit a beam in the last of its possible directions (eg "DP" direction) during each of the corresponding time slots (eg slot 1 614, slot 2 616, range U 618). As further shown in FIG. 6, the UE 502 may scan each of its U number of possible directions (e.g. directions "D1" to "DU") during each of the corresponding time slots (e.g. slot 1 614, slot 2 616, interval U 618) to determine the best path for the beam from the mmW-BS 504. For example, each of the time intervals (eg, interval 1 614, interval 2 616, interval U 618) can be the same length. In such an example, the length of the P-scan period in FIG. 6 can be equivalent to the total of the U time slots needed for the UE 502 to scan each of its U directions.

[0059] FIG. 7 is a frame structure 700 illustrating an exemplary scan operation for UE 502 and mmW-BS 504. In the configuration of Fig. 7, the UE 502 can have multiple antenna subarrays and the mmW-BS 504 can have a digital beamforming capability. As shown in FIG. 7, the mmW-BS 504 can transmit beams in a number P of possible directions (e.g. directions "D1" to "DP") by simultaneously transmitting two beams in two different directions (e.g. a first beam in direction "D1" " and a second beam in the direction "D2") during each of the corresponding time slots (e.g. slot 1 702, slot 2 704, slot U/2 706) of a scan period. As further shown in FIG. 7, the UE 502 can scan two different directions (for example, the "D1" direction and "D2" direction of a first time slot, the "D3" direction and "D4" direction in a second time slot, and and so on) from its U number of possible directions during each of the corresponding time intervals (e.g., interval 1 702, interval 2 704, interval U/2 706) to determine the best path for the mmW-BS beams 504. For example, each of the time slots can be the same length. In such an example, the duration of scan period 1 in FIG. 7 can be equivalent to the total U/2 time slots required for the mmW-BS 504 to transmit beams to each of its P directions.

[0060] As further shown in FIG. 7, the mmW-BS 504 can simultaneously transmit two beams in two different directions (for example, a first beam in the "D3" direction and a second beam in the "D4" direction) during each of the corresponding time intervals (for example, gap 1 708, gap 2 710, gap U/2 712). As further shown in FIG. 7, the UE 502 can check two different directions (for example, the "D1" direction and the "D2" direction of a first time slot, the "D3" direction and the "D4" direction in a second time slot, and and so on) from its U number of possible directions during each of the corresponding time intervals (e.g., interval 1 708, interval 2 710, interval U/2 712) to determine the best path for the mmW-BS beams 504. For example, each of the time slots can be the same length. In such an example, the duration of scan period 2 in FIG. 7 can be equivalent to the total L/2 time slots required for the mmW-BS 504 to transmit beams to each of its P directions.

[0061] As shown in FIG. 7, the mmW-BS 504 can transmit beams in the last two directions of its P number of possible directions by simultaneously transmitting two beams in two different directions (for example, a first beam in direction "DP-1" and a second beam in direction " DP") during each of the corresponding time slots (e.g. slot 1 714, slot 2 716, slot U/2 718). As further shown in FIG. 7, the UE 502 can check two different directions (for example, the "D1" direction and the "D2" direction of a first time slot, the "D3" direction and the "D4" direction in a second time slot, and and so on) from its U number of possible directions during each of the corresponding time intervals (e.g., interval 1 714, interval 2 716, interval U/2 718) to determine the best path for the mmW-BS beams 504. For example, each of the time slots can be the same length. In such an example, the length of the P/2 verification period in FIG. 7 can be equivalent to the total of the U/2 time slots needed for the UE 502 to scan each of its U directions.

[0062] It should be understood that in the aspect of FIG. 6, UE 502 and mmW-BS 504 are equipped with only one antenna and that none of the capabilities of UE 502 and mmW-BS 504 are being used. As such, in an example, when the mmW-BS 504 equipped with an antenna transmits beams in four possible directions (e.g. U = 4), four scan periods (one scan period per direction) will be needed to cover all four directions (for example, directions "D1" to "D4") of the mmW-BS 504. In the aspect of FIG. 7, however, UE 502 may receive beamforming capability information associated with the mmW-BS and may modify the scanning operation to take advantage of one or more of the capabilities indicated in the beamforming capability information. For example, the beamforming capability information may indicate that the mmW-BS 504 has digital beamforming capability and therefore can transmit two or more beams in different directions in a single time slot. Once the UE 502 is informed of such digital beamforming capability of the mmW-BS through the received capability information, the UE 502 can determine that multiple beams can be transmitted by the mmW-BS 504 in different directions in a single slot. of time. Therefore, the UE 502 can implement its two antenna subarrays to simultaneously scan for beams in two different directions in one time interval to significantly increase the speed of the scanning operation.

[0063] For example, in the aspect of FIG. 7, when the mmW-BS 504 transmits beams in four possible directions (e.g. U=4), two scan periods (one scan period for two directions) would be required to cover all four directions (e.g. directions " D1" to "D4") of mmW-BS 504. Therefore, if the time slots in Figs. 6 and 7 are configured to be equal in duration, the sweep operation in the aspect of FIG. 7 will require half the number of scan periods with half the number of time intervals per each scan period as required in the FIG. 6 to UE 502 to scan all possible directions of the mmW-BS 504.

[0064] In one aspect, the UE 502 may send beamforming capability information associated with the UE 502 to the mmW-BS 504. For example, the beamforming capability information may indicate that the UE 502 has two antenna subsystems and therefore can scan beams in two different directions in a single time interval. Therefore, the mmW-BS 504 having a digital beamforming capability can transmit two beams having different directions in each time slot, as shown in FIG. 7, thus leveraging the digital beamforming capability to significantly increase the speed of the scanning operation.

[0065] It should be understood that the aspects disclosed in FIGS. 6 and 7, where mmW-BS 504 is configured to transmit beams and UE 502 is configured to scan beams, represent example configurations. In other aspects, UE 502 may be configured to transmit beams and mmW-BS 504 may be configured to scan beams in a similar manner to the scan operations described above with respect to FIGS. 6 and 7.

[0066] FIG. 8 is a flowchart 800 of a wireless communication method. The method may be performed by a UE (e.g. UE 502, apparatus 902/902'). It should be noted that the blocks indicated with dashed lines in FIG. 8 (for example, blocks 806, 810 and 812) represent optional blocks.

[0067] In block 802, the UE establishes a wireless communication link with an mmW-BS based on a transmit beam from the mmW-BS, the transmit beam having a transmit beam direction. For example, UE 502 can establish a wireless communication link with mmW-BS 504 based on transmission beam 510 along path 506.

[0068] In block 804, the UE receives beamforming capability information indicating one of at least one hybrid analog or digital beamforming capability related to the mmW-BS. In another aspect, the beamforming capability information indicates an antenna switching speed of the mmW-BS.

[0069] In block 806, the UE sends beamforming capability information associated with the UE to the mmW-BS. In one aspect, UE 502 may send beamforming capability information indicating a hybrid, analog, or digital beamforming capability. In another aspect, the beamforming capability information associated with the UE indicates that the UE includes multiple antenna subarrays. In another aspect, the beamforming capability information associated with the UE indicates an antenna switching speed of the UE.

[0070] In block 808, the UE scans N transmit beams from the mmW-BS for each of the M receive beam directions of the UE based on the beamforming capability information and the transmit beam associated with the transmit link wireless communication. In one aspect, the UE analyzes the N transmission beams using multiple antenna subarrays in a single time slot. In one aspect, the UE scans the N transmit beams, setting antenna weights and/or a phase and amplitude for the N beam transmission directions. In one aspect, the N transmit beams include N transmit beam directions within an angular range T of the transmit beam direction of the wireless communication link. In one aspect, the scan is further based on the beamforming capability information associated with the UE.

[0071] In block 810, the UE determines one or more preferred scanned beams of the defined transmit beam among the N transmit beams. In one aspect, the determination is performed by the UE by comparing a signal quality of scanned beams to a threshold and selecting one or more beams that meet or exceed the threshold.

[0072] Finally, in block 812, the UE sends information indicating the preferred ones among the one or more scanned beams.

[0073] FIG. 9 is a conceptual data flow diagram 900 illustrating data flow between different modules/media/components in an exemplary apparatus 902. The apparatus may be a UE. The apparatus includes a module 904 that receives beamforming capability information indicating one of at least one digital, analog, or hybrid beamforming capability related to the mmW-BS (e.g., the mmW-BS 950) , a module 906 that establishes a wireless communication link with an mmW-BS based on a transmission beam from the mmW-BS, the transmission beam having a transmission beam direction, a module 908 that scans N transmission beams of the mmW-BS for each M UE receiving beam directions based on the beamforming capability information and the transmit beam associated with the wireless communication link, a module 910 that determines one or more preferred scan beams of the transmit beam defined among the N transmit beams, a module 912 that sends beamforming capability information (via the transmit module 914) associated with the UE to the mmW-BS 950, and a module 914 that sends information indicating the one or more preferred scanned beams.

[0074] The apparatus may include additional modules that execute each of the blocks in the above flow diagram of FIG. 8. As such, each of the blocks in the above flowchart of FIG. 8 may be realized by a module and the apparatus may include one or more of said modules. The modules may be one or more hardware components specifically configured to carry out the indicated processes, implemented by a processor configured to perform the established processes, stored within a computer-readable medium for execution by a processor, or some combination thereof. .

[0075] FIG. 10 is a diagram 1000 illustrating an example of a hardware implementation for an apparatus 902' employing a processing system 1014. Processing system 1014 may be implemented with a bus architecture, represented generally by bus 1024. Bus 1024 may include any number of interconnecting buses and bridges, depending on the specific application of the 1014 processing system and the overall design constraints. Bus 1024 links together various circuitry, including one or more processors and/or hardware modules, represented by processor 1004, modules 904, 906, 908, 910, 912, and 914, and computer-readable medium/memory 1006. 1024 can also connect other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore will not be described further.

[0076] The processing system 1014 may be coupled to a transceiver 1010. The transceiver 1010 is coupled to one or more antennas 1020. The transceiver 1010 provides a means for communicating with various other apparatuses over a transmission medium. Transceiver 1010 receives a signal from one or more antennas 1020, extracts information from the received signal, and provides the extracted information to processing system 1014, specifically, receiver module 904. Furthermore, transceiver 1010 receives the information from the processing system 1014, specifically the transmit module 914, and based on the received information, generates a signal to be applied to one or more antennas 1020. The processing system 1014 includes a processor 1004 coupled to a readable medium by computer/memory 1006. Processor 1004 is responsible for general processing, including execution of software stored on computer readable medium/memory 1006. The software, when executed by processor 1004, causes processing system 1014 to perform the various functions described above for any particular device. The computer-readable medium/memory 1006 may also be used to store data that is manipulated by the processor 1004 when running the software. The processing system further includes at least one of modules 904, 906, 908, 910, 912, and 914. The modules may be software modules running on processor 1004 resident/stored on computer readable medium/memory 1006, one or more hardware coupled to processor 1004, or some combination thereof. Processing system 1014 may be a component of UE 350 and may include memory 360 and/or at least one of TX processor 368, RX processor 356, and controller/processor 359.

[0077] In one embodiment, the apparatus 902/902' for wireless communication includes means for establishing a wireless communication link with an mmW-BS based on a transmission beam from the mmW-BS, the transmission beam having a direction of the transmit beam, means for receiving beamforming capability information indicating one of at least one digital, analog, or hybrid beamforming capability related to the mmW-BS, means for scanning N transmit beams from of the mmW-BS for each of the M receive beam directions of the UE based on the beamforming capability information and the transmit beam associated with the wireless communication link, means for determining one or more preferred scanned beams of the transmit beam defined among the N transmit beams, means for sending information indicating the preferred one or more scanned beams, means for sending the beamforming capability information associated with the UE to the mmW-BS. The aforementioned means may be one or more of the aforementioned modules of apparatus 902 and/or the processing system 1014 of apparatus 902' configured to perform the functions recited by the aforementioned means. As described above, processing system 1014 may include TX processor 368, RX processor 356, and controller/processor 359. As such, in one configuration, the aforementioned means may be TX processor 368, RX processor 356, and controller/processor 359 configured to perform the functions recited by the aforementioned means.

[0078] It is understood that the specific order or hierarchy of blocks in the flow/disclosed graphic processes is an illustration of exemplary approaches. Based on design preferences, it is understood that the specific order or hierarchy of blocks in the process graphics/flow can be rearranged. Also, some blocks can be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not intended to be limited to the specific order or hierarchy presented.

[0079] The foregoing description is provided to enable anyone skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but full scope is to be given under the claims, wherein reference to a singular element is not intended to mean "one and only one" unless specifically so declared, but rather "one or more". The word "exemplary" is used here to mean "to serve as an example, case or illustration". Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically noted otherwise, the term "one" refers to one or more. Combinations such as "at least one of A, B, or C," "at least one of A, B, and C," and "A, B, C, or any combination thereof include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as "at least one of A, B, or C", "at least one of A, B, and C , "and" A, B, C, or any combination thereof may be just A, just B, just C, A and B, A and C, B and C, or A and B and C, where such combinations may contain a member or more members of A, B, or C. All structural and functional equivalents to elements of the various aspects described throughout this disclosure, which are known or later become known to those skilled in the art are hereby expressly incorporated by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is expressly recited in the claims. No claim element is to be construed as a means plus the function of, unless the element is expressly recited using the phrase "means to".

Claims (15)

1. Method (800) of wireless communication to a user equipment, UE, (102, 206, 502, 902) comprising: establishing (802) a wireless communication link with a millimeter wave base station, mmW- BS, (130, 204, 504, 950) based on a transmit beam from the mmW-BS (130, 204, 504, 950), the transmit beam having a transmit beam direction; receiving (804) beamforming capability information indicating one of at least one digital, analog or hybrid beamforming capability associated with the mmW-BS (130, 204, 504, 950), the method characterized in that beamforming capability information includes an indication of an antenna switching speed of the mmW-BS (130, 204, 504, 950); and further comprising scanning (808) N transmit beams (508, 510, 512) from the mmW-BS (130, 204, 504, 950) for each of the M receive beam directions (516, 518, 520 ) of the UE (102, 206, 502, 902) based on the beamforming capability information and the transmit beam associated with the wireless communication link. 2. Method, according to claim 1, characterized in that it additionally comprises: determining one or more preferred swept beams of a transmission beam defined from the N transmission beams; and sending information indicating the one or more preferred scanned beams. 3. Method, according to claim 1, characterized in that it additionally comprises sending beamforming capability information associated with the UE to the mmW-BS, wherein the scan is additionally based on the beamforming capability information associated with the EU. 4. Method according to claim 3, characterized in that: the beamforming capability information associated with the UE indicates that the UE comprises a plurality of antenna subarrays; and scanning the N transmission beams comprises scanning the N transmission beams using the plurality of antenna subarrays in a single time slot. 5. Method according to claim 1, characterized in that the N transmission beams comprise N transmission beam directions within an angular range T of the transmission beam direction. 6. Method, according to claim 5, characterized in that the scan comprises configuring antenna weights and/or a phase and amplitude for the N transmission beam directions. 7. Method, according to claim 2, characterized by the fact that the determination comprises comparing a signal quality of the scanned beams with a threshold. 8. User equipment apparatus, UE, (102, 206, 502, 902) for wireless communication comprising: means (906) for establishing a wireless communication link with a millimeter wave base station, mmW-BS, (130, 204, 504, 950) based on a transmission beam from the mmW-BS (130, 204, 504, 950), the transmission beam having a transmission beam direction; means (904) for receiving beamforming capability information indicating one of at least one digital, analog or hybrid beamforming capability associated with the mmW-BS (130, 204, 504, 950), the apparatus characterized in that that the beamforming capability information includes an indication of an antenna switching speed of the mmW-BS (130, 204, 504, 950); and further comprising means (908) for scanning N transmit beams (508, 510, 512) from the mmW-BS (130, 204, 504, 950) to each of the M receive beam directions (516, 518 , 520) of the UE (102, 206, 502, 902) based on the beamforming capability information and the transmit beam associated with the wireless communication link. 9. UE, according to claim 8, characterized in that it additionally comprises: means for determining one or more preferred scanned beams of a transmission beam defined among the N transmission beams; and means for sending information indicating the one or more preferred scanned beams. 10. UE, according to claim 8, characterized in that it additionally comprises means for sending beamforming capability information associated with the UE to the mmW-BS, wherein the scan is additionally based on the forming capability information beams associated with the UE. 11. UE, according to claim 10, characterized by the fact that: the beamforming capability information associated with the UE indicates that the UE comprises a plurality of antenna subarrays; and the means for scanning the N transmission beams is configured to scan the N transmission beams using the plurality of antenna subarrays in a single time slot. 12. UE, according to claim 8, characterized by the fact that the N transmission beams comprise N transmission beam directions within an angular range T of the transmission beam direction. 13. UE, according to claim 12, characterized by the fact that the means for scanning are configured to configure antenna weights and/or a phase and an amplitude for the N transmission beam directions. 14. UE, according to claim 8, characterized by the fact that the means for determination are configured to compare a signal quality of the scanned beams with a threshold. 15. Memory characterized by the fact that it comprises instructions stored therein, the instructions being executed by a computer to carry out the method as defined in any one of claims 1 to 7.