CN106033987B

CN106033987B - Method and device for enhancing sounding reference signal capacity

Info

Publication number: CN106033987B
Application number: CN201510125238.1A
Authority: CN
Inventors: 张晴川; 罗庆霖
Original assignee: Nokia Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2015-03-20
Filing date: 2015-03-20
Publication date: 2021-05-07
Anticipated expiration: 2035-03-20
Also published as: CN106033987A

Abstract

The invention relates to a method and a device for enhancing capacity of Sounding Reference Signal (SRS) in a Full-dimensional multiple-Input-multiple-Output (FD-MIMO) system. The invention provides an SRS (sounding reference signal) enhancing method and device for an FD-MIMO (field-emission multiple-input multiple-output) system, so that the SRS capacity is expanded. An evolved base station (eNB) broadcasting a plurality of predefined beams having different tilt angles; receiving RSRP reports for the beams by a User Equipment (UE); the inter-UE SRS resource allocation is then performed based on these reports.

Description

Method and device for enhancing sounding reference signal capacity

Technical Field

The present invention relates generally to the field of telecommunications, and more particularly to a method and apparatus for enhancing Sounding Reference Signal (SRS) capacity.

Background

With the development of Active Antenna arrays (Active Antenna Array), a Full-dimensional multiple-Input-multiple-Output (FD-MIMO) technology is proposed. The FD-MIMO adopts a large-scale two-dimensional active antenna array, and can provide service for a maximum number of mobile terminals at the same time and at the same frequency by utilizing both the height and the azimuth angle provided by the active antenna plane, thereby greatly improving the system capacity. For example, FD-MIMO may support high-order multi-user multiple-input multiple-output (MU-MIMO) transmission of up to 10 User Equipments (UEs).

However, due to Channel reciprocity of a Time Division Duplex (TDD) system, an uplink SRS for uplink Channel State Information (CSI) measurement may also be used for a downlink of the TDD. This allows the accuracy of the CSI based on SRS measurements to be affected by the number of UEs supported by the system. The increase in the number of supportable UEs in FD-MIMO systems also makes the acquisition of channel state information CSI therein facing unprecedented challenges. Orthogonal SRS resources in the existing next generation Long Term Evolution (LTE) system are not enough to support denser UEs in FD-MIMO system.

There is thus a need for an SRS enhancement mechanism for FD-MIMO systems to extend SRS capacity.

Disclosure of Invention

An objective of the present invention is to provide a method and an apparatus for enhancing SRS capacity, which can meet the SRS resource requirement in an FD-MIMO system.

The method provided by the invention can be used for enhancing the capacity of the sounding reference signal in a multi-input multi-output system, and comprises the following steps: the base station selects a plurality of elevation angles according to the maximum elevation angle range of the antenna; the base station respectively carries out weighting processing on the downlink reference signals based on a plurality of elevation angles so as to obtain a plurality of weighted reference signals; the base station sends a plurality of weighted reference signals to the user equipment; the base station receives a plurality of feedbacks from the user equipment respectively corresponding to each of a plurality of weighted reference signals; and the base station performs sounding reference signal allocation of the user equipment based on the plurality of feedbacks.

According to a preferred embodiment of the present invention, wherein the base station selecting the plurality of elevation angles according to a maximum elevation angle range further comprises determining the maximum elevation angle range according to a cell characteristic of the base station, dividing the maximum elevation angle range into L elevation angles, L being an integer.

According to yet another preferred embodiment of the present invention, wherein the dividing the maximum elevation angle range into L elevation angles further comprises dividing the maximum elevation angle range equally into L sub-ranges, and then calculating the angle value of the maximum elevation angle in each sub-range.

According to still another preferred embodiment of the present invention, the base station transmits a plurality of weighted sounding reference signals to the user equipment through a channel state information-reference signal process.

According to a further preferred embodiment of the present invention, wherein the plurality of feedbacks corresponding to each of the plurality of weighted reference signals is a reference signal received power or a channel quality indication.

According to a further preferred embodiment of the invention, wherein said multiple-input multiple-output system is a full-dimensional multiple-input multiple-output system.

According to still another preferred embodiment of the present invention, wherein the base station performing sounding reference signal allocation for the user equipment based on the plurality of feedbacks further comprises pairing the user equipments in an angle domain to group the user equipments, wherein the user equipments within the same group are separable in the angle domain.

According to a further preferred embodiment of the present invention, sounding signal resources within each group occupying the same time, frequency and code division resources can be transmitted within the group.

According to another preferred embodiment of the present invention, the number of the paired ue is determined by the number of the ues to be detected and the initial sounding reference signal orthogonal resource of the cell where the base station is located.

According to a further preferred embodiment of the present invention, wherein the weighting process is further based on the wavelength of the antenna and the distance between adjacent antennas in the same column.

The invention also provides a corresponding base station which can be used for enhancing the capacity of the sounding reference signal in the multi-input multi-output system.

The invention can clarify the corresponding relation between the UE and the angle, and multiplex the SRS transmission in a plurality of UEs on the elevation angle domain, thereby enhancing the SRS capacity in FD-MIMO.

Drawings

Some embodiments of the apparatus and/or method will be described hereinafter, by way of example only, and with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of a communication system employing FD-MIMO;

FIGS. 2(a) and 2(b) show the response in the elevation domain and the azimuth domain, respectively;

FIG. 3 is a flow diagram of a method according to one embodiment of the invention;

FIG. 4 is a schematic orientation diagram of a UE and an evolved node B (eNB) according to one embodiment of the present invention;

fig. 5(a) and 5(b) are schematic diagrams of SRS allocation according to a conventional manner and according to an embodiment of the present invention, respectively;

fig. 6 is a schematic structural diagram of a communication system according to an embodiment of the present invention, which includes a base station and a user equipment.

Detailed Description

Exemplary embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in the specification. It should be understood, however, that there is no intention to limit example embodiments to the specific forms disclosed, but on the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the invention.

In general, the orthogonal SRS resources used by multiple users are either in the frequency domain (e.g., by interleaved FDMA and multiple cyclic shifts, i.e., code division resources) or in the time domain (e.g., by different SRS subframe offsets). These resources are difficult to expand further. For example, a larger interleaving factor may shorten the length of the base sequence, thereby enlarging the inter-cell interference; larger cyclic shift, that is, the number of code division resources may aggravate the interference between different UEs in the same cell; a longer SRS subframe period may result in a decrease in tracking accuracy of a fading channel.

The application provides an enhanced mechanism of SRS transmission and allocation, and provides a corresponding method and a corresponding device. The methods and apparatus proposed by the present invention can be used to enhance SRS transmission and allocation when using a planar active antenna array. The method and the device provided by the invention can be used for a Time Division Duplex (TDD) system and a Frequency Division Duplex (FDD) system.

For FD-MIMO, it has steerable longitudinally placed antennas due to the deployment of a planar active antenna array. The multi-antenna channel has different characteristics in elevation compared to azimuth. For example, the angular domain response of the channel covariance matrix at altitude has better directionality than azimuth. In view of the above, the present invention multiplexes SRS transmission in multiple UEs in the elevation domain to enhance SRS capacity in FD-MIMO. The invention provides a new dimension to enhance the SRS capacity based on the elevation Angle of emission (AoD) domain.

In order to overcome the limitations in practical applications, the present invention also provides related Downlink (DL) reference signal transmission and feedback mechanisms, and SRS allocation based on corresponding UE reports. Based on these mechanisms, a base station, such as an evolved base station (eNB), can efficiently perform allocation of angular domain SRS.

Fig. 1 is a schematic diagram of a communication system employing FD-MIMO. The communication system 100 includes a cell including an eNB 101, a first user equipment (UE1)102, and a second user equipment (UE2) 103. The eNB 101 includes one active antenna array 111. The UE 1102 and the UE 2103 are located in a building covered by the cell, and the UE 1102 and the UE 2103 have different elevation angles with respect to the eNB 101.

Fig. 2(a) and 2(b) show the responses of UE 1102 and UE 2103 in the elevation domain and azimuth domain, respectively. As can be seen from fig. 2(a) and 2(b), the difference between the angles corresponding to the best responses of UE 1102 and UE 2103 in the elevation domain is more significant than in the azimuth. And, for each UE, the difference between its best response in the elevation domain and the other responses is also more significant than the azimuth. Thus, the responses of different UEs in the elevation domain have less overlap than in the azimuth, and thus it is easier to distinguish the channels of different UEs in the elevation domain.

Unlike the conventional time/frequency SRS resource allocated by the eNB, AoD is actually determined by the propagation environment. Therefore, using AoD as SRS multiplexing resource, the following technical problems need to be solved:

the response of different UEs in the elevation domain depends on the physical location of the UE itself and the propagation environment, so the UEs are not necessarily able to be separated;

even if separation is possible, the correspondence between the UE and the angle is uncertain.

To solve the aforementioned technical problems, the present invention employs specific terminal feedback based on a downlink reference signal using vertical weight values (i.e., weight values including elevation angle information or altitude information). The main processes of the method proposed by the present invention are roughly as follows: the eNB broadcasting a plurality of predefined beams with different tilt angles; receiving resource Reference Signal Power (RSRP) or Channel Quality Indicator (CQI) reports of the UE for the beams; the inter-UE SRS resource allocation is then performed based on these reports. Specifically, according to an embodiment of the present invention, a method for enhancing sounding reference signal capacity in a mimo system includes: the base station selects a plurality of elevation angles according to the maximum elevation angle range of the antenna; the base station respectively carries out weighting processing on the downlink reference signals based on a plurality of elevation angles so as to obtain a plurality of weighted reference signals; the base station sends a plurality of weighted reference signals to the user equipment; a base station receives a plurality of feedbacks from the user equipment respectively corresponding to each of the plurality of weighted reference signals; and the base station allocates the sounding reference signal of the user equipment based on the plurality of feedbacks.

A method flow 300 according to one embodiment of the invention is described below with reference to fig. 3.

At step 310, a maximum elevation angle range is determined. The maximum elevation range may be determined according to the specific propagation environment, i.e. the characteristics of the cell in which the base station is located. For example, the maximum elevation range may be predetermined according to the specific location where the target serving object or target user (e.g., UE) of the eNB is located. In particular, the maximum elevation range may be determined from the relative horizontal distance and relative height difference of the eNB and the target serving object or target UE. For example, according to the highest point of the target service object or the relative horizontal distance and the relative height difference between the highest target UE and the eNB, it is determined that the included angle between the highest point of the eNB and the target service object or the highest target UE and the horizontal plane is θ_maxI.e. theta_maxRepresents the maximum possible elevation separation angle; according to the lowest point of the target service object or the relative horizontal distance and the relative height difference between the lowest target UE and the eNB, determining the highest point of the target service object from the eNB or the lowest target UE to form an included angle theta with the horizontal plane_minI.e. theta_minRepresenting the smallest possible elevation separation angle. Theta_maxMinus theta_minI.e. the maximum elevation range.

When the specific location where the target service object is located or the distribution of the target UEs changes, the maximum elevation angle range may also be dynamically adjusted according to the change.

At step 320, the maximum elevation angle range is further partitioned. The maximum elevation angle range can be equally divided into L sub-ranges to obtain L elevation angles. And the maximum value of L is not more than the maximum number of CSI-RS processes supported by the system. The angle value for the maximum elevation angle in each sub-range can be calculated according to equation (1).

Equation (1)

Where θ is the angle value of the maximum elevation angle in the ith sub-range.

It can also be based on the concrete of the target service objectThe division of sub-ranges is dynamically adjusted by changes in the location or target UE distribution. For example, when UEs in a certain sub-range are too dense, the sub-range may be further divided. For example, the number of UEs in the sub-range l exceeds the highest threshold V_hAnd for a predetermined duration, the sub-range/may be further divided. According to another embodiment, when the UE density in a certain sub-range is too low, the sub-range may be merged with a neighboring sub-range. For example, the number of UEs in the sub-range l is below the lowest threshold V_lAnd for a predetermined duration, molecular range l may be combined with adjacent sub-ranges (e.g., l +1 or l-1).

At step 330, a weighting value is calculated. The weighting value for each sub-range may be calculated according to equation (2). Each weight value contains an elevation angle information, which corresponds to a sub-range. Those skilled in the art will appreciate that in other 3GPP releases, weighting values containing elevation angle information can also be obtained in other ways, and that weighting values containing elevation angle information obtained in other ways can be used to achieve the objects of the present invention.

Equation (2)

Where λ and d represent the wavelength and the distance between adjacent antennas in the antenna column, respectively.

At step 340, the reference signal is weighted. For example, the eNB may transmit a reference signal derived according to equation (2) on the mth element of the nth antenna column.

Equation (3)

Wherein q is_nIs the original symbol in the sequence of reference symbols.

By weighting the original reference symbol sequence, reference symbols containing elevation information can be obtained. That is, the same element in the antenna array may be at the same time and the sameThe carriers transmitted over frequency increase the dimensionality of the elevation domain. That is, carriers having the same time and the same frequency can be distinguished in the elevation domain. E.g. reference signal

Containing elevation information corresponding to the elevation sub-range l.

At step 350, weighted reference signals obtained by vertical weighting values may be transmitted using multiple CSI-RS processes

The CSI-RS process may be defined by LTE Rel 11, although as protocol standards evolve, the newly defined CSI-RS port for FD-MIMO may also be used to transmit weighted reference signals. For LTE Rel10 and previous releases, multiple CSI-RS processes are not supported, and the same objective can be achieved by sending CSI-RS weighted by different weights alternately at different time slots.

At step 360, feedback corresponding to the transmitted reference signal is received. The feedback may be fed back to the eNB by each UE receiving the reference signal. Each may measure RSRP of beams corresponding to L elevation angles (or heights) by the UE and then report the RSRP to the eNB. The feedback received at step 360 may be an RSRP report or a CQI report.

At step 370, the UE is allocated an SRS. Step 370 may include determining an elevation range for each UE. The elevation angle corresponding to each UE may be determined after the eNB receives vertical RSRP reports (i.e., RSRP reports containing elevation angle information or altitude information) from all I UEs. RSRP includes available

Wherein L ═ 1, …, L; i is 1, …, I. The eNB may determine how to enhance SRS capacity in the elevation domain based on these reports. When the eNB uses these reports, it is necessary to modify the uplink power control for SRS transmission according to each UE

For example, when dividing the 4 elevation sub-ranges (i.e., L-4), if the eNB serves 5 target UEs (i.e., I-5) and the received feedback is as shown in table 1, it can be seen that the UE1 has the strongest signal strength on the elevation sub-range 1, the UE1 has a signal strength on the elevation sub-range 1 that is significantly higher than the other sub-ranges, the UE2 has a signal strength on the elevation sub-range 3 that is significantly higher than the other sub-ranges, the UE3 has a signal strength on the elevation sub-range 1 that is significantly higher than the other sub-ranges, the UE4 has a signal strength on the elevation sub-ranges 2 and 3 that is significantly higher than the other sub-ranges, and the UE5 has a signal strength on the elevation sub-ranges 1 and 3 that is significantly higher than the other sub-ranges. It can thus be determined that UE1 corresponds to elevation sub-range 1, UE2 corresponds to elevation sub-range 3, UE3 corresponds to elevation sub-range 1, UE4 corresponds to elevation sub-ranges 2 and 3, and UE5 corresponds to elevation sub-ranges 1 and 3.

	l＝1	l＝2	l＝3	l＝4
					i＝1	0dB	-15dB	-17dB	-20dB
i＝2	-16dB	-19dB	-3dB	-15dB
					i＝3	-2dB	-17dB	-3dB	-15dB
i＝4	-16dB	-1dB	-4dB	-13dB

i＝5

-3dB

-10dB

-5dB

-12dB

TABLE 1

Fig. 4 illustrates one possible location relationship between the UE and the eNB as determined by the feedback in table 1. Where the E-axis represents the height and the X-axis represents the position with the same height as the eNB.

Step 370Grouping the target UEs may also be included. Can use the set

To represent the UE_iElevation mode (or altitude mode). In particular, two UEs may be distinguished in the angular domain if their elevation patterns have a significant difference. Also, the value of each UE that is most significantly different in elevation pattern from the other values may be used to determine the UE's separation angle, so that uncertainty between the UE and the angle may be eliminated. The following technical problems can thus be solved: the correspondence of different UEs in the elevation domain depends on the physical location of the UE itself and the propagation environment, so the UEs are not necessarily able to be separated; even if separation is possible, the correspondence between the UE and the angle is uncertain. For example, if it is determined that there is an elevation angle different from UE2 in the elevation angle to which UE1 corresponds, then this UE1 may be distinguished from UE2 in the elevation domain, i.e., UE1 may be grouped into the same group as UE 2.

In short, the problem of SRS allocation in the elevation domain can be represented by the following reuse form:

determining UE groups (assuming number of groups K) such that G is for each group_kAll exist in a subset

i∈G_kWhich satisfies the following conditions:

condition 1:

all exist

Condition 1:

all exist

Those skilled in the art will appreciate that the grouping of UEs can also be derived according to other ways, and that groupings derived according to other ways can all be used to achieve the objects of the invention. One possible way is: the value most different from the other values in the elevation pattern of each UE is first obtained according to condition 1, and then the best UE grouping is determined according to condition 2.

For example, the eNB may first determine a pair of UEs over an angular domain to group the UEs, wherein the UEs in the pair of UEs are distinguishable from each other over the angular domain. The number of UE pairs depends on the difference between the number of UEs that need to be detected (or UEs that need to be served) and the initial sounding reference signal orthogonal resource of the cell in which the base station is located, i.e. the conventional SRS orthogonal resource. Then, in each group of UEs, the same SRS with the same time, frequency and code division resources may be transmitted.

For the embodiments corresponding to table 1, UE1 and UE2 may be grouped into the same group, UE3 and UE4 may be grouped into the same group, and UE5 may be grouped separately.

For UEs in the same group, they may be allocated channels with the same time and frequency. In addition, the number of UEs in each group is not particularly limited, and the same group may include more than two UEs.

Fig. 5(a) and 5(b) are diagrams of SRS allocation according to a conventional manner and according to an embodiment of the present invention, respectively. Wherein the real envelope represents a first frequency domain comb and the imaginary envelope represents a second frequency domain comb, i.e., both are different frequency-division resources; while different hatchings surrounded by the envelope indicate that different cyclic shifts, i.e. different code division resources, are used on the respective subcarriers.

As can be seen from fig. 5(a), for the conventional SRS allocation manner, one code division resource can only carry the service of one UE, specifically, on the first frequency domain comb, the first code division resource carries the service of UE1, the second code division resource carries the service of UE2, and so on. As shown in fig. 5(b), according to the SRS allocation method of the present invention, one code division resource may carry traffic of more than two UEs, for example, a first code division resource on a first frequency domain comb may simultaneously carry traffic of UE1 and UE 2. The SRS is distributed according to the method provided by the invention, and the capacity of the SRS can be obviously enhanced without changing channel time, frequency and code division resources.

Fig. 6 is a schematic structural diagram of a communication system 60 according to an embodiment of the present invention, which includes a base station 600 and a user equipment 602.

Base station 600 includes an angle builder 610, a weighting processor 612, a transmitter 640, a receiver 650, and an SRS allocator 660. The weighting processor 612 may further include a weight calculator 620 and a multiplier 630. Wherein angle builder 610 may be configured to perform

steps

310 and 320 of method flow 300, weight calculator 620 may be configured to perform step 330 of method flow 300, multiplier 630 may be configured to perform step 340 of method flow 300, transmitter 640 may be configured to perform step 350 of method flow 300, receiver 650 may be configured to perform step 360 of method flow 300, and SRS allocator 660 may be configured to perform step 370 of method flow 300.

Angle builder 610 may further obtain the elevation angle corresponding to the target UE from SRS allocator 660 to dynamically adjust the maximum elevation angle range, as well as the division of the elevation angle range.

The hardware used to implement the various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The angle builder, SRS distributor, etc. may be any conventional processor, controller, microcontroller, or state machine. The modules and circuits may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Alternatively, some steps or methods may be performed by circuitry that is specific to a given function.

The previous description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for enhancing sounding reference signal capacity in a multiple-input multiple-output system, the method comprising:

the base station selects a plurality of elevation angles according to the maximum elevation angle range of the antenna;

the base station respectively carries out weighting processing on the downlink reference signals based on the plurality of elevation angles to obtain a plurality of weighted reference signals;

the base station sends the weighted reference signals to user equipment;

the base station receiving a plurality of feedbacks from the user equipment respectively corresponding to each of the plurality of weighted reference signals; and

the base station performs sounding reference signal allocation of the user equipment based on the plurality of feedbacks;

wherein the base station performing sounding reference signal allocation for the user equipment based on the plurality of feedbacks further comprises pairing the user equipment in an angle domain to group the user equipment, wherein user equipment within a same group are separable in the angle domain; and is

Wherein the sounding signal resources occupying the same time, frequency and code division resources in each group are transmitted in the group;

wherein the maximum elevation range is determined based on a location at which a target user device is located, the target user devices having a relative difference in elevation therebetween.

2. The method of claim 1, wherein the base station selecting a plurality of elevation angles according to a maximum elevation angle range further comprises determining the maximum elevation angle range according to cell characteristics of the base station, dividing the maximum elevation angle range into L elevation angles, L being an integer.

3. The method of claim 2, wherein dividing the maximum elevation angle range into L elevation angles further comprises dividing the maximum elevation angle range equally into L sub-ranges and then calculating an angle value for the maximum elevation angle in each sub-range.

4. The method of claim 1, wherein the base station transmits a plurality of weighted sounding reference signals to the user equipment through a channel state information-reference signal process.

5. The method of claim 1, wherein a plurality of feedbacks corresponding to each of the plurality of weighted reference signals are reference signal received power or channel quality indications.

6. The method of claim 1, wherein the multiple-input multiple-output system is a full-dimensional multiple-input multiple-output system.

7. The method of claim 1, wherein the number of paired ues is determined by the number of ues to be detected and the initial sounding reference signal orthogonal resource of the cell in which the base station is located.

8. The method of claim 1, wherein the weighting process is further based on a wavelength of the antenna and a distance between adjacent antennas in the same column.

9. A base station for enhancing sounding reference signal capacity in a multiple-input multiple-output system, comprising:

an angle builder configured to select a plurality of elevation angles according to a maximum elevation angle range of the antenna;

a weighting processor configured to weight downlink reference signals based on the plurality of elevation angles, respectively, to obtain a plurality of weighted reference signals;

a transmitter configured to send the plurality of weighted reference signals to a user equipment;

a receiver configured to receive a plurality of feedbacks from the user equipment respectively corresponding to each of the plurality of weighted reference signals; and

a sounding reference signal allocator configured to perform sounding reference signal allocation for the user equipment based on the plurality of feedbacks;

wherein the sounding reference signal allocator is further configured to pair the user equipments in an angle domain to group the user equipments, wherein user equipments within a same group are separable in an angle domain; and

10. The base station of claim 9, wherein the angle builder is further configured to determine the maximum elevation angle range according to cell characteristics of the base station, the maximum elevation angle range being divided into L elevation angles, L being an integer.

11. The base station of claim 10, the angle builder further configured to evenly divide the maximum elevation range into L elevation angles.

12. The base station of claim 9, wherein the transmitter is further configured to send a plurality of weighted sounding reference signals to the user equipment over a channel state information-reference signal process.

13. The base station of claim 9, wherein the plurality of feedbacks corresponding to each of the plurality of weighted reference signals are reference signal received power or channel quality indications.

14. The base station of claim 9, wherein the multiple-input multiple-output system is a full-dimensional multiple-input multiple-output system.

15. The base station according to claim 9, wherein the number of paired ues is determined by the number of ues to be detected and the initial sounding reference signal orthogonal resource of the cell in which the base station is located.

16. The base station of claim 9, wherein the weighting process is further based on a wavelength of the antenna and a distance between adjacent antennas in the same column.