HK1219355B - Method and base station for selecting at least one parameter for downlink data transmission with a mobile user equipment - Google Patents

Description

Method and base station for selecting at least one parameter for downlink data transmission with a mobile user equipment

Priority application

This application claims priority to U.S. Provisional Patent Application Serial No. 61/841,230, filed on June 28, 2013, and to U.S. Patent Application Serial No. 14/109,211, filed on December 17, 2013, each of which is incorporated herein by reference in its entirety.

Technical Field

Embodiments relate to operations and communications performed by electronic devices in a wireless network.Some embodiments relate to selecting at least one parameter for downlink data transmission with a mobile user equipment.

Background Art

A typical wireless communication base station, such as a cellular system, may include multiple antennas. These multiple antennas can increase sensitivity to signals received in a desired direction, while decreasing sensitivity to signals received away from the desired direction. Additionally, the multiple antennas can direct transmitted signals in a desired direction. Both of these directional effects are desirable for users of user equipment (e.g., cellular phones). For example, transmitting and receiving signals directionally can improve reception for cellular phone users and reduce dropped calls.

Typically, the direction from the base station to the user is monitored computationally, and signals are provided to and from multiple antennas to exploit the directional effect. Therefore, there is a need to reduce the computational complexity of the directional effect from multiple communication systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a base station with multiple antennas, a user with user equipment, and multiple paths along which signals travel.

FIG2 shows a flow chart of an example of a method for selecting at least one parameter for downlink data transmission with a mobile user equipment.

FIG. 3 illustrates an example of a mobile client device on which the configurations and techniques described herein may be deployed.

FIG4 illustrates an example computer system that can be used as a computer platform for computing or networking the devices described herein.

DETAILED DESCRIPTION

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

In wireless communication systems, users have user equipment (UEs) that communicate wirelessly with base stations. For example, in a cellular phone system, a cellular phone user transmits wireless signals to and receives wireless signals from the base station. Transmitted and received signals typically traverse more than one physical path from the UE to the base station. For example, one path might be directly between the UE and the base station, while another path might include bouncing off buildings.

Figure 1 illustrates an example of a base station (BS) 102 with multiple antennas 104, a user with a user equipment (UE) 106, and multiple paths 108 and 110 along which signals travel between the base station 102 and the UE 106. Paths 108 and 110 each have their own phase, power, angle of arrival (AoA) at the base station 102, and angle of departure (AoD) from the base station 102. Paths 108 and 110 can change dynamically as the user moves. In some examples, the base station (BS) includes a relatively large number of antennas, e.g., 4, 8, 16, 32, etc. As the number of antennas increases, the accuracy of signal directionality also increases, and the computational complexity required to maintain this accuracy also increases. In some examples, the antennas 104 at the base station 102 are uniformly spaced along a single direction. In some examples, for systems using frequency division duplexing (FDD) for uplink (UL) and downlink (DL) signals, the UL phase and DL phase on each path or subpath are independent of each other.

2 illustrates a flow chart of an example method 200 for selecting at least one parameter for downlink data transmission with a mobile user device. The method may be performed by a wireless communication base station (e.g., base station 102) having multiple antennas (e.g., antenna 104) configured to wirelessly communicate with a mobile user device (e.g., user device 106).

At 202, method 200 receives an uplink sounding signal from a mobile user equipment. At 204, method 200 determines, from the received uplink sounding signal, a plurality of angles of arrival corresponding to a plurality of paths between the mobile user equipment and a plurality of antennas. At 206, method 200 transmits a plurality of downlink sounding signals from the plurality of antennas in the direction of a corresponding angle of arrival of the plurality of angles of arrival. Each downlink sounding signal may be a virtual antenna port relative to the mobile user equipment. At 208, method 200 receives channel state information from the mobile user equipment. At 210, method 200 composes, in response to the received channel state information, at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS) for downlink data transmission to the mobile user equipment. Method 200 is merely one example of a method for selecting at least one parameter for downlink data transmission with the mobile user equipment; other methods may also be used.

There are three basic aspects to method 200. In the first aspect, a mobile user equipment (UE) sends an uplink sounding/probing signal. The base station (BS) then determines or estimates the angle of arrival (AoA) of several valid paths. A frequency conversion method is also provided. In the second aspect, the BS sends sounding signals toward selected AoAs, with each sounding signal acting as a different antenna port toward the UE. The sounding signals are virtual antenna ports, such as DFT beamforming vectors. Depending on how many such AoAs are selected, different numbers of antenna ports can be assigned to the UE. The UE performs channel estimation and feeds back channel state information or beam selection information to the BS. In the third aspect, the BS composes an optimal rank indicator (RI), precoding matrix indicator (PMI), or modulation and coding scheme (MCS) for downlink (DL) data transmission. Each of these aspects is discussed in more detail below.

There are many potential advantages to using the methods described in this paper. For example, the method discussed in this paper for determining the angle of arrival from the uplink sounding signal is more efficient than schemes where the angle of arrival is not initially determined or estimated (where a relatively large search space can be explored at will). Another potential advantage is the new channel state feedback. In this design, the DL antenna ports are formed from DFT vectors as virtual antenna ports. This can be considered a subset of the current LTE code book, especially for the case of 8-tx antennas. In this design, the UL channel feedback is simplified to focus on rank determination and beam selection, which can reduce or simplify computations. In addition, frequency conversion algorithms suitable for handling different angles are provided.

The first aspect involves UL channel sounding for AoA estimation, where the UE is scheduled by the BS (eNB) to send a sounding signal from one of its antennas. Upon receiving a signal on the UL at the BS, the UE and/or BS estimates the AoA of the signal.

The following is an example of the AoA estimation algorithm. Using the ULA assumption, if there are N paths, the received signal in the frequency domain will be in the following format:

A：＝A ₁ β ₁ +…+A _N β _N (1)

in

is the spatial signature of the nth path, f _UL is the uplink frequency, F ₀ is the carrier frequency, and Δ is the antenna distance in terms of wavelength at F _0. The received signal has a number of DFT vectors in digital form.

By projecting the received signal towards different spatial features across angular space, one can find the main power peaks along the direction. The projection is as follows:

Considered to target:

θ∈[0，π)

where _ΔUL is the antenna spacing in terms of the UL wavelength. The peak power of this function on [0, pi) yields the estimated AoA of the primary path. This set of estimated AoAs is written as follows:

A _est :={A ₁ , A ₂ ,..., A _N } (3)

This is just one example of a suitable AoA estimation algorithm; other suitable algorithms may also be used.

The first aspect also includes frequency conversion for each path.

The uplink sounding signal and the downlink sounding signal may be on different frequencies. In response to the uplink sounding signal, determining the downlink sounding signal may include determining an uplink channel vector, multiplying the uplink channel vector by a diagonal matrix to form a product, and using the product as the downlink channel vector. In some examples, the diagonal matrix includes a complex exponential factor at the Mth row and the Mth column, the complex exponential factor having an exponent that varies with (M-1) times the frequency difference between the uplink sounding signal and the downlink sounding signal.

For a specific path, the UL channel and DL channel (DFT) vectors can be

as well as

The UL vector β _n,UL is determined by the UL channel sounding/estimation process. To obtain the DL vector β n,UL , the following transformation is applied:

This conversion process is applied to each valid direction it identifies. In the next step, the estimated DFT vector is used for DL beamforming. Additional steps help the UE switch its transmit antenna in the uplink probe.

The first aspect also includes UE antenna switching in UL exploration for multi-rank DL transmission.

The UE will switch its transmit antennas for the eNB in a predetermined manner during the UL sounding process to detect multi-rank transmission opportunities. This allows the eNB to determine whether it can distinguish antennas used to support DL multi-stream transmission. Generally, the AoA/AoD resolution increases with the number of antennas. Given a reasonable number of antennas (e.g., 8×8 or 16×1) and possible different antenna spacings, more accurate information on the beam direction and phase/power information can be obtained through DL active sounding in the second aspect.

The second aspect includes DL sounding with precoded beams towards the effective UL AoA. In some examples, the virtual antenna ports are specifically designed based on _Aest from equation (3). The eNB informs the UE that N1 ports are supported in the transmission. N1 here can have values 1, 2, 4 or 8. The N1 element can be selected from _Aest to cover the effective directions in _Aest . The eNB then transforms the DFT vectors in A _N1 according to the above transformation equation. Now it uses their complex transpose as the definition (precoding) vector of the DL virtual CSI-RS port (as shown in step 2.1.2 later). It should be noted that due to the transformation and DL CSI-RS sounding of each path, this method works regardless of the size of the UL/DL frequency difference.

The second aspect also includes RS transmission on the selected A _N1 . The eNB applies the CSI-RS signal on the N1 virtual port. The resources sent on the port are predetermined and therefore known to the UE.

The second aspect also includes UE feedback design. The UE can measure and feed back channel state information or other measurements. There are several options: as in the first option, when N1 is small (e.g., less than 4), the UE uses equations (1) and (2) above, and an older codebook for RI/CQI/PMI feedback. As in the second option, when N1 is large (greater than 4), the UE first selects the number of ports down to less than 4 based on CSI-RS measurements and throughput considerations, and then calculates the best RI/CQI/PMI based on the selected beam. As in the third option, the BS can provide explicit phase/power feedback for each port.

The third aspect involves downlink (DL) data transmission. At this stage, the eNB has calculated a small set of DFT vectors suitable for data transmission toward the UE. Furthermore, the eNB knows how to combine these with the number of data layers being used. The eNB can use this information for data transmission (e.g., on the PDSCH).

While previous examples of wireless network connections have been provided with specific reference to 3GPP LTE/LTE-A, IEEE 802.11, and Bluetooth communication standards, it will be appreciated that various other WWAN, WLAN, and WPAN protocols and standards may be used in conjunction with the techniques described herein. These standards include, but are not limited to, other standards from 3GPP (e.g., HSPA+, UMTS), IEEE 802.16 (e.g., 802.16p), or the Bluetooth (e.g., Bluetooth 4.0, or similar standards defined by the Bluetooth Special Interest Group) family of standards. Other applicable network configurations may be included within the scope of the presently described communication network. It will be appreciated that any number of personal area networks, LANs, and WANs may be used, using any combination of wired or wireless transmission media to facilitate communication over such communication networks.

The embodiments described above may be implemented in one or a combination of hardware, firmware, and software. The various methods or techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in a tangible medium (e.g., flash memory, a hard drive, a portable storage device, a read-only memory (ROM), a random access memory (RAM), a semiconductor memory device (e.g., an electrically programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM)), a magnetic disk storage medium, an optical storage medium, and any other machine-readable storage medium or storage device), wherein when the program code is loaded into a machine (e.g., a computer or network device) and executed by the machine, the machine becomes an apparatus for implementing the various techniques.

Machine-readable storage medium or other storage devices may include any non-transient mechanism for storing information in a form readable by a machine (e.g., computer). In the case of executing program code on a programmable computer, computer equipment may include a processor, a processor-readable storage medium (including volatile and non-volatile memory and/or storage element), at least one input device, and at least one output device. One or more programs that can implement or utilize the various technologies described herein can use application programming interfaces (APIs), reusable controls, etc. This program can be implemented with high-level procedural or object-oriented programming languages to communicate with a computer system. However, (one or more) programs can be implemented as needed with assembly language or machine language. In any case, language can be compiled or translated language, and can be combined with hardware implementation.

FIG3 illustrates an example of a mobile device 300. The mobile device 300 may be a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a cell phone, or other type of mobile wireless computing device. The mobile device 300 may include one or more antennas 308 within a housing 302, the antennas 308 being configured to communicate with a hotspot, a base station (BS), an evolved Node B (eNodeB), or other type of WLAN or WWAN access point. The mobile device 300 may be configured to communicate using multiple wireless communication standards, including standards selected from 3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and Wi-Fi standard definitions. The mobile device 300 may use separate antennas for each wireless communication standard, or may use a shared antenna for multiple wireless communication standards. The mobile device 300 may communicate in a WLAN, a WPAN, and/or a WWAN.

FIG3 also shows a microphone 320 and one or more speakers 312, which can be used for audio input to and audio output from the mobile device 300. The display screen 304 can be a liquid crystal display (LCD) screen, or other types of display screens (e.g., organic light emitting diode (OLED) displays). The display screen 304 can be configured as a touch screen. The touch screen can use capacitive, resistive, or another type of touch screen technology. The application processor 314 and the graphics processor 318 can be coupled to the internal memory 316 to provide processing and display capabilities. The non-volatile memory port 310 can also be used to provide data input/output options for the user. The non-volatile memory port 310 can also be used to expand the storage capacity of the mobile device 300. The keyboard 306 can be integrated with the mobile device 300 or can be wirelessly connected to the mobile device 300 to provide additional user input. A touch screen can also be used to provide a virtual keyboard. A camera 322 located on the front side (display screen) or back side of the mobile device 300 can also be integrated into the housing 302 of the mobile device 300.

4 is a block diagram illustrating an example computer system machine 400 on which any one or more of the methods discussed herein may be executed. The computer system machine 400 may be embodied as a base station 102, an antenna 104, a user device 106, or any other computing platform described or referenced herein. In alternative embodiments, the machine operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine may operate as a server or client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. The machine may be a portable or non-portable personal computer (PC) (e.g., a laptop or netbook), a tablet computer, a set-top box (STB), a gaming console, a personal digital assistant (PDA), a mobile phone or smartphone, a web appliance, a network router, a switch or bridge, or any machine capable of executing (sequentially or otherwise) instructions for specifying actions for the machine. Further, while a single machine is illustrated, the term "machine" shall also be taken to include any collection of machines that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein.

The example computer system machine 400 includes a processor 402 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), or both), a main memory 404, and a static memory 406, which communicate via an interconnect 408 (e.g., a link, a bus, etc.). The computer system machine 400 may also include a video display unit 410, an alphanumeric input device 412 (e.g., a keyboard), and a user interface (UI) navigation device 414 (e.g., a mouse). In one embodiment, the video display unit 410, the input device 412, and the UI navigation device 414 are touch screen displays. The computer system machine 400 may also include a storage device 416 (e.g., a drive unit), a signal generating device 418 (e.g., a speaker), an output controller 432, a power management controller 434, and a network interface device 420 (which may include one or more antennas 430, transceivers, or other wireless communication hardware, or be operable to communicate with one or more antennas 430, transceivers, or other wireless communication hardware), and one or more sensors 428 (e.g., a global positioning sensor (GPS) sensor, a compass, a position sensor, an accelerometer, or other sensor).

The storage device 416 includes a machine-readable medium 422 on which is stored one or more data structures and instructions 424 (e.g., software) embodying or utilizing any one or more of the methodologies or functionality described herein. The instructions 424 may also reside, completely or at least partially, within the main memory 404, the static memory 406, and/or within the processor 402 during execution of the instructions by the computer system machine 400, and the instructions 424, together with the main memory 404, the static memory 406, and the processor 402, constitute a machine-readable medium.

Although the machine-readable medium 422 is shown as a single medium in the example embodiment, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and processors) that store one or more instructions 424. The term "machine-readable medium" shall also include any tangible medium that can store, encode, or carry instructions for execution by a machine, causing the machine to perform any one or more of the methods of the present disclosure, or can store, encode, or carry data structures utilized by or associated with such instructions.

Transmission media may also be used to send or receive instructions 424 over a communications network 426 via a network interface device 420 utilizing any one of the known transmission protocols (e.g., HTTP). The term "transmission media" shall include any tangible medium that can store, encode, or carry instructions for execution by the machine, including digital or analog communication signals or other intangible media that facilitate communication of such software.

It should be understood that the functional units or performances described in this specification are referenced or labeled as components or modules to emphasize the independence of their implementation. For example, a component or module can be implemented as a hardware circuit comprising a very large scale (VLSI) circuit or gate array, a readily available semiconductor (e.g., a logic chip, a transistor, or other discrete components). A component or module can also be implemented in a programmable hardware device (e.g., a field programmable gate array, a programmable array logic, a programmable logic device, etc.). A component or module can also be implemented in software run by various types of processors. The identified component or module of executable code can, for example, include one or more physical blocks or logical blocks of computer instructions, which can, for example, be organized as an object, a program, or a function. However, the executable nature of the identified component or module does not need to be physically located together, but can include different instructions stored in different locations, which, when logically combined together, include the component or module and achieve the stated purpose of the component or module.

In fact, the component or the module of executable code can be a single instruction or many instructions, and can even be distributed on several different code segments across several storage devices and between different programs.Similarly, operational data can be identified and illustrated in this article in component or module, and can be embedded in and organized into the data structure of any appropriate type in any suitable form.Operational data can be collected as a single data set, or can be distributed in different locations (comprising on different storage devices), and can only exist as the electronic signal on system or network at least in part.Component or module can be active or passive, comprise the agent that can be operated to perform desired function.

Additional examples of embodiments of the presently described methods, systems, and devices include the following non-limiting configurations. Each of the following non-limiting examples can be independent, or can be combined in any permutation or with any one or more other examples provided below or the entire disclosure.

Example 1 includes a subject matter embodied by a method for selecting at least one parameter for downlink data transmission with a mobile user device, the method being executable by a wireless communication base station having multiple antennas configured for wireless communication with the mobile user device, the method comprising: receiving an uplink sounding signal from the mobile user device; determining, from the received uplink sounding signal, multiple angles of arrival for corresponding multiple paths between the mobile user device and the multiple antennas; sending, from the multiple antennas, multiple downlink sounding signals in the direction of corresponding ones of the multiple angles of arrival, each downlink sounding signal being a virtual antenna port with respect to the mobile user device; receiving channel state information from the mobile user device; and composing, in response to the received channel state information, at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS) for downlink data transmission to the mobile user device.

In Example 2, the subject matter of Example 1 may optionally include: wherein each downlink sounding signal originates from a different location from the perspective of the mobile user equipment.

In Example 3, the subject matter of one or any combination of Examples 1-2 may optionally include, wherein determining a plurality of angles of arrival for a corresponding plurality of paths between the mobile user equipment and the plurality of antennas from the received uplink sounding signal comprises using an angle of arrival estimation algorithm.

In Example 4, the subject matter of Example 3 optionally includes: wherein the angle of arrival estimation algorithm: projects the received uplink sounding signal toward different spatial features across angular space; determines a peak from the projections; and employs the peak as the estimated angle of arrival.

In Example 5, the subject matter of one or any combination of Examples 1-4 can optionally include: wherein the uplink sounding signal and the downlink sounding signal are on different frequencies.

In Example 6, the subject matter of Example 5 optionally includes: wherein determining the downlink sounding signal in response to the uplink sounding signal includes: determining an uplink channel vector; multiplying the uplink channel vector by a diagonal matrix to form a product; and employing the product as the downlink channel vector.

In Example 7, the subject matter of Example 6 optionally includes: wherein the diagonal matrix includes complex exponential factors in the Mth row and the Mth column, and the complex exponential factors have exponents that vary with (M-1) times the frequency difference between the uplink sounding signal and the downlink sounding signal.

In Example 8, the subject matter of one or any combination of Examples 6-7 may optionally further include: forming a complex transpose of the product; and using the complex transpose as a definition vector of a downlink virtual channel state information reference signal port.

In Example 9, the subject matter of one or any combination of Examples 6-8 may optionally further include applying a channel state information reference signal on multiple virtual antenna ports.

In Example 10, the subject matter of one or any combination of Examples 1-9 may optionally further include: for a case where the number of virtual antenna ports is greater than four, selecting the number of virtual antenna ports down to less than four based on channel state information reference signal measurements.

Example 11 includes a subject matter embodied by a wireless communication base station having multiple antennas configured to wirelessly communicate with a mobile user device, the wireless communication base station including a circuit configured to perform the following operations: receiving an uplink sounding signal from the mobile user device; determining multiple arrival angles for corresponding multiple paths between the mobile user device and the multiple antennas from the received uplink sounding signal; sending multiple downlink sounding signals from the multiple antennas toward corresponding ones of the multiple arrival angles, each downlink sounding signal being a virtual antenna port with respect to the mobile user device; receiving channel state information from the mobile user device; and composing at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS) for downlink data transmission to the mobile user device in response to the received channel state information.

In Example 12, the subject matter of Example 11 may optionally include: wherein each downlink sounding signal originates from a different location from the perspective of the mobile user equipment.

In Example 13, the subject matter of one or any combination of Examples 11-12 may optionally include: wherein determining multiple arrival angles for multiple paths corresponding to the mobile user equipment and the multiple antennas from the received uplink sounding signal includes: using an arrival angle estimation algorithm.

In Example 14, the subject matter of Example 13 optionally includes: wherein the arrival angle estimation algorithm: projects the received uplink sounding signal toward different spatial features across angular space; determines a peak from the projections; and employs the peak as the estimated arrival angle.

In Example 15, the subject matter of one or any combination of Examples 11-14 can optionally include: wherein the uplink sounding signal and the downlink sounding signal are on different frequencies.

In Example 16, the subject matter of Example 15 optionally includes: wherein determining the downlink sounding signal in response to the uplink sounding signal includes: determining an uplink channel vector; multiplying the uplink channel vector by a diagonal matrix to form a product; and employing the product as the downlink channel vector.

In Example 17, the subject matter of Example 16 optionally includes: wherein the diagonal matrix includes complex exponential factors in the Mth row and the Mth column, the complex exponential factors having exponents that vary with (M-1) times the frequency difference between the uplink sounding signal and the downlink sounding signal.

In Example 18, the subject matter of one or any combination of Examples 16-17 optionally includes: wherein the circuit is further configured to: form a complex transpose of the product; and use the complex transpose as a definition vector for the downlink virtual channel state information reference signal port.

In Example 19, the subject matter of one or any combination of Examples 16-18 may optionally include, wherein the circuit is further configured to: apply a channel state information reference signal across the plurality of virtual antenna ports.

Example 20 includes a subject matter embodied by a method for selecting at least one parameter for downlink data transmission with a mobile user device, the method being executable by a wireless communication base station having multiple antennas configured for wireless communication with the mobile user device, the method comprising: receiving an uplink sounding signal from the mobile user device; using an arrival angle estimation algorithm; determining, from the arrival angle estimation algorithm, multiple arrival angles for corresponding multiple paths between the mobile user device and the multiple antennas; sending, from the multiple antennas, multiple downlink sounding signals in the direction of corresponding ones of the multiple arrival angles, each downlink sounding signal being a virtual antenna port with respect to the mobile user device, each downlink sounding signal originating from a different location from the perspective of the mobile user device, the uplink sounding signal and the downlink sounding signal having different frequencies; receiving channel state information from the mobile user device; and composing, in response to the received channel state information, at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS) for downlink data transmission to the mobile user device.

The abstract is provided to allow the reader to ascertain the nature and gist of the technical disclosure. The abstract is submitted with the understanding that it will not be used to limit or interpret the scope and meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims (16)

1. A method for selecting at least one parameter for downlink data transmission with a mobile user equipment, the method being performed by a wireless communication base station having multiple antennas configured to wirelessly communicate with the mobile user equipment, the method comprising: Receive uplink probe signal from the mobile user equipment; An angle of arrival (AHA) estimation algorithm is used to determine multiple angles of arrival for multiple paths corresponding to the mobile user equipment and the multiple antennas from the received uplink probe signal, wherein the angle of arrival estimation algorithm: projects the received uplink probe signal toward different spatial features across the angular space; determines a peak value from the projection; and uses the peak value as the estimated angle of arrival. Multiple downlink probe signals are transmitted from the multiple antennas in the direction of the corresponding angle of arrival among the multiple angles of arrival, each downlink probe signal being about the virtual antenna port of the mobile user equipment; Receive channel status information from the mobile user equipment; and In response to received channel state information, the downlink data transmission to the mobile user equipment is configured to include at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS). 2. The method of claim 1, wherein, from the perspective of the mobile user equipment, each downlink probe signal originates from a different location. 3. The method of claim 1, wherein the uplink probe signal and the downlink probe signal are at different frequencies. 4. The method of claim 3, wherein determining the downlink probe signal in response to the uplink probe signal comprises: Determine the uplink channel vector; Multiply the uplink channel vector by a diagonal matrix to form a product; and The product is used as the downlink channel vector. 5. The method of claim 4, wherein the diagonal matrix includes a complex exponential factor at the Mth row and Mth column, the complex exponential factor having an exponent that varies with (M-1) times the frequency difference between the uplink probe signal and the downlink probe signal. 6. The method of claim 4, further comprising: The complex transpose that forms the product; and The complex transpose is used as the definition vector of the downlink virtual channel state information reference signal port. 7. The method of claim 4, further comprising: Channel state information reference signals are applied to multiple virtual antenna ports. 8. The method of claim 1, further comprising: For cases where the number of virtual antenna ports is greater than four, the number of virtual antenna ports is reduced to four or less based on channel state information reference signal measurements. 9. A wireless communication base station having multiple antennas configured to wirelessly communicate with a mobile user equipment, the wireless communication base station including circuitry configured to perform the following operations: Receive uplink probe signal from the mobile user equipment; An angle of arrival (AHA) estimation algorithm is used to determine multiple angles of arrival for multiple paths corresponding to the mobile user equipment and the multiple antennas from the received uplink probe signal, wherein the angle of arrival estimation algorithm: projects the received uplink probe signal toward different spatial features across the angular space; determines a peak value from the projection; and uses the peak value as the estimated angle of arrival. Multiple downlink probe signals are transmitted from the multiple antennas in the direction of the corresponding angle of arrival among the multiple angles of arrival, each downlink probe signal being about the virtual antenna port of the mobile user equipment; Receive channel status information from the mobile user equipment; and In response to received channel state information, the downlink data transmission to the mobile user equipment is configured to include at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS). 10. The wireless communication base station of claim 9, wherein, from the perspective of the mobile user equipment, each downlink probe signal originates from a different location. 11. The wireless communication base station as claimed in claim 9, wherein the uplink detection signal and the downlink detection signal are at different frequencies. 12. The wireless communication base station of claim 11, wherein determining the downlink detection signal in response to the uplink detection signal comprises: Determine the uplink channel vector; Multiply the uplink channel vector by a diagonal matrix to form a product; and The product is used as the downlink channel vector. 13. The wireless communication base station of claim 12, wherein the diagonal matrix includes a complex exponential factor at the Mth row and Mth column, the complex exponential factor having an exponent that varies with (M-1) times the frequency difference between the uplink probe signal and the downlink probe signal. 14. The wireless communication base station of claim 12, wherein the circuit is further configured to: The complex transpose that forms the product; and The complex transpose is used as the definition vector of the downlink virtual channel state information reference signal port. 15. The wireless communication base station of claim 12, wherein the circuit is further configured to: Channel state information reference signals are applied to multiple virtual antenna ports. 16. A method for selecting at least one parameter for downlink data transmission with a mobile user equipment, the method being performed by a wireless communication base station having multiple antennas configured to wirelessly communicate with the mobile user equipment, the method comprising: Receive uplink probe signal from the mobile user equipment; Use the angle of arrival estimation algorithm; The angle of arrival estimation algorithm determines multiple angles of arrival for multiple paths corresponding to the mobile user equipment and the multiple antennas, wherein the angle of arrival estimation algorithm: projects received uplink probe signals toward different spatial features across the angular space; determines a peak value from the projection; and uses the peak value as the estimated angle of arrival; Multiple downlink probe signals are transmitted from the multiple antennas in the direction of a corresponding angle of arrival among multiple angles of arrival. Each downlink probe signal is about a virtual antenna port of the mobile user equipment. From the perspective of the mobile user equipment, each downlink probe signal originates from a different location. The uplink probe signal and the downlink probe signal have different frequencies. Receive channel status information from the mobile user equipment; and In response to received channel state information, the downlink data transmission to the mobile user equipment is configured to include at least one of a rank indicator (RI), a precoding matrix indicator (PMI), or a modulation and coding scheme (MCS).