Claims:We Claim:
1. A multiuser multi-input multi output (MIMO) communication system (100), comprising:
a base station (102) in communication with a plurality of user equipment (104), wherein the base station (102) comprises:
an antenna array (106) having a plurality of directive antennas (106 A) coupled to a metasurface (106B) positioned on an upper side of the antenna array (106), wherein each of the plurality of directive antennas (106 A) is positioned such that a directive beam generated by each of the plurality of directive antennas (106 A) overlaps with each other, and wherein the metasurface comprises of a periodic arrangement of a plurality of unit cells with optimized dimensions to provide an improved directivity to a plurality of overlapping beams received from the antenna array;
a digital beamformer (108);
a location tracker (110) operably connected to the digital beamformer (108) and the antenna array (106) through a plurality of radio frequency chains (112) and one or more digital precoders (114), wherein the location tracker (110) is configured to identify a location of each of the plurality of user equipment (104) based on an estimation of direction of arrival of a service request signal; and
a controller unit (116) operably connected to the digital beamformer (108), the location tracker (110) and the antenna array (106) using a switch (118), wherein the controller unit (116) comprises:
one or more data storage devices (116A) configured to store instructions;
one or more communication interfaces (116B); and
one or more hardware processors (116C) operatively coupled to the one or more data storage devices (116A) via the one or more communication interfaces (116C), wherein the one or more hardware processors (116C) are configured by the instructions to:
identify one or more antennas from the plurality of directive antennas in the antenna array for the service request signal received from each of the plurality of user equipment;
identify, using the location tracker, a location of each of the plurality of user equipment based on the estimation of direction of arrival of the service request signal; and
direct, using the digital beamformer, a directive beam signal to one or more user equipment based on identified locations along estimated direction of arrival.

2. The multiuser multi-input multi output communication system of claim 1, wherein direction of arrival of the service request signal is estimated using a pre-computed dictionary matrix.

3. The multiuser multi-input multi output communication system of claim 2, wherein the pre-computed dictionary matrix is a function of antenna array look-ahead angles for a predefined antenna gain pattern resolution.

4. The multiuser multi-input multi output communication system of claim 1, wherein the directive beam signal using the digital beamformer is obtained by:
estimating a delay for each of the plurality of user equipment based on geometrical arrangement of the plurality of directive antennas of the antenna array and the identified location of each of the plurality of user equipment;
multiplying overlapping beams obtained from each of the plurality of directive antenna of the antenna array with a corresponding antenna gain to provide a plurality of resultant signals; and
summing the plurality of resultant signals added with corresponding estimated delay.

5. A processor implemented method (1100), comprising:
identifying (1102), via one or more hardware processors, one or more antennas from the plurality of directive antennas in the antenna array for the service request signal received from each of the plurality of user equipment;
identifying (1104), via one or more hardware processors, a location of each of the plurality of user equipment using the location tracker based on the estimation of direction of arrival of the service request signal; and
directing (1106), via one or more hardware processors, a directive beam signal to one or more user equipment using the digital beamformer based on identified locations along estimated direction of arrival.

6. The processor implemented method of claim 5, wherein direction of arrival of the service request signal is estimated using a pre-computed dictionary matrix.

7. The processor implemented method of claim 6, wherein the pre-computed dictionary matrix is a function of antenna array look-ahead angles for a predefined antenna gain pattern resolution.

8. The processor implemented method of claim 5, wherein the directive beam signal using the digital beamformer is obtained by:
estimating a delay for each of the plurality of user equipment based on geometrical arrangement of the plurality of directive antennas of the antenna array and the identified location of each of the plurality of user equipment;
multiplying overlapping beams obtained from each of the plurality of directive antenna of the antenna array with a corresponding antenna gain to provide a plurality of resultant signals; and
summing the plurality of resultant signals added with corresponding estimated delay.
, Description:TECHNICAL FIELD
The disclosure herein generally relates to antenna systems, and, more particularly, to system and method for multi-user MIMO with array of directive antennas.

BACKGROUND
With an increased inclination towards use of emerging 5th generation (5G), 6th generation (6G) and wireless fidelity (WI-FI) system deployments in wireless communication, simultaneous servicing of multiple user equipment (UEs) while maintaining faster speed has become an issue of paramount concern. Traditional systems utilize two configurations namely single user MIMO (Su-MIMO) and multi-user MIMO (mu-MIMO) to address such scenarios. In Su-MIMO, only one UE is serviced at any given point of time and hence to service multiple UEs, time division multiplexing (TDM) is employed, which results in reduced speeds. The other configuration mu-MIMO addresses the limitation of TDM by providing dedicated spatial beams to each of the UE and hence enables simultaneous servicing of multiple UE.s. However, mu-MIMO technology experiences problems of beamforming limitation and interference in mobile UEs. Thus, though there exists a number of methods that provide a solution for the simultaneous servicing of multiple UEs, they do not perform well in varying scenarios.
SUMMARY
Embodiments of the present disclosure present technological improvements as solutions to one or more of the above-mentioned technical problems recognized by the inventors in conventional systems. For example, in one embodiment, a multiuser multi-input multi output (MIMO) communication system is provided. The multiuser multi-input multi output (MIMO) communication system comprising: a base station in communication with a plurality of user equipment, wherein the base station comprises: an antenna array having a plurality of directive antennas coupled to a metasurface positioned on an upper side of the antenna array, wherein each of the plurality of directive antennas is positioned such that a directive beam generated by each of the plurality of directive antennas overlaps with each other, and wherein the metasurface comprises of a periodic arrangement of a plurality of unit cells with optimized dimensions to provide an improved directivity to a plurality of overlapping beams received from the antenna array; a digital beamformer; a location tracker operably connected to the digital beamformer and the antenna array through a plurality of radio frequency chains and one or more digital precoders, wherein the location tracker is configured to identify a location of each of the plurality of user equipment based on an estimation of direction of arrival of a service request signal; and a controller unit operably connected to the digital beamformer, the location tracker and the antenna array using a switch, wherein the controller unit comprises: one or more data storage devices configured to store instructions; one or more communication interfaces; and one or more hardware processors operatively coupled to the one or more data storage devices via the one or more communication interfaces, wherein the one or more hardware processors are configured by the instructions to: identify one or more antennas from the plurality of directive antennas in the antenna array for the service request signal received from each of the plurality of user equipment; identify, using the location tracker, a location of each of the plurality of user equipment based on the estimation of direction of arrival of the service request signal; and direct, using the digital beamformer, a directive beam signal to one or more user equipment based on identified locations along estimated direction of arrival.
In another aspect, a processor implemented method is provided. The method comprising identifying, via one or more hardware processors, one or more antennas from the plurality of directive antennas in the antenna array for the service request signal received from each of the plurality of user equipment; identifying, via one or more hardware processors, a location of each of the plurality of user equipment using the location tracker based on the estimation of direction of arrival of the service request signal; and directing, via one or more hardware processors, a directive beam signal to one or more user equipment using the digital beamformer based on identified locations along estimated direction of arrival.
In yet another aspect, a non-transitory computer readable medium is provided. The non-transitory computer readable medium comprising identifying, via one or more hardware processors, one or more antennas from the plurality of directive antennas in the antenna array for the service request signal received from each of the plurality of user equipment; identifying, via one or more hardware processors, a location of each of the plurality of user equipment using the location tracker based on the estimation of direction of arrival of the service request signal; and directing, via one or more hardware processors, a directive beam signal to one or more user equipment using the digital beamformer based on identified locations along estimated direction of arrival.
In an embodiment, the direction of arrival of the service request signal is estimated using a pre-computed dictionary matrix.
In an embodiment, the pre-computed dictionary matrix is a function of antenna array look-ahead angles for a predefined antenna gain pattern resolution.
In an embodiment, the directive beam signal using the digital beamformer is obtained by: estimating a delay for each of the plurality of user equipment based on geometrical arrangement of the plurality of directive antennas of the antenna array and the identified location of each of the plurality of user equipment; multiplying overlapping beams obtained from each of the plurality of directive antenna of the antenna array with a corresponding antenna gain to provide a plurality of resultant signals; and summing the plurality of resultant signals added with corresponding estimated delay.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles:
FIG. 1 illustrates an exemplary block diagram of a multiuser multi-input multi output (MIMO) communication system according to some embodiments of the present disclosure.
FIG. 2 illustrates an exemplary representation (not to scale) of a top view of an antenna array without a metasurface according to some embodiments of the present disclosure.
FIG. 3 illustrates an exemplary representation (not to scale) of a lateral view of the microstrip antenna array coupled with the metasurface comprising of a periodic arrangement of a plurality of unit cells with optimized dimensions according to some embodiments of the present disclosure.
FIG. 4 illustrates an exemplary representation (not to scale) of a front view of a unit cell comprised in the metasurface according to some embodiments of the present disclosure.
FIG. 5 illustrates an exemplary representation (not to scale) of directive and overlapping beam formation from a lateral view of the microstrip antenna array coupled with the a metasurface according to some embodiments of the present disclosure.
FIG. 6 illustrates an exemplary representation (not to scale) of directive and overlapping beam formation from a side view of the microstrip antenna array according to some embodiments of the present disclosure.
FIG. 7 illustrates an exemplary block diagram of a radio frequency (RF) chain of the multiuser multi-input multi output (MIMO) communication system, according to some embodiments of the present disclosure.
FIG. 8 illustrates functioning of a location tracker in the multiuser multi-input multi output (MIMO) communication system, according to some embodiments of the present disclosure.
FIG. 9 shows a graph illustrating a sparse signal location estimation algorithm for location tracking, according to some embodiments of the present disclosure.
FIG. 10A and 11B illustrate a process of directive beam formation using a digital beamformer, according to some embodiments of the present disclosure.
FIG. 11 is an exemplary flow diagram illustrating a processor implemented method for multi-user MIMO with array of directive antennas, in accordance with an embodiment of the present disclosure.
FIG.12 is a Reflection Coefficient (S11) curve of the microstrip antenna array without the metasurface in a millimeter frequency range.
FIG. 13 is the Reflection Coefficient (S11) curve of the microstrip antenna array with the metasurface in a millimeter frequency range.
FIG. 14 illustrates gain plots for the microstrip antenna array without the metasurface for various values of theta, according to some embodiments of the present disclosure.
FIG. 15 illustrates gain plots for the microstrip antenna array with the metasurface for various values of theta, according to some embodiments of the present disclosure.
FIG. 16 is a 2-Dimensional radiation pattern of the microstrip antenna array without the metasurface according to some embodiments of the present disclosure.
FIG. 17 is the 2-Dimensional radiation pattern of the microstrip antenna array with the metasurface according to some embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS
Exemplary embodiments are described with reference to the accompanying drawings. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. Wherever convenient, the same reference numbers are used throughout the drawings to refer to the same or like parts. While examples and features of disclosed principles are described herein, modifications, adaptations, and other implementations are possible without departing from the scope of the disclosed embodiments. It is intended that the following detailed description be considered as exemplary only, with the true scope being indicated by the following claims.
The present disclosure is directed to simultaneous servicing of multiple user equipment’s (UE’s) for faster speeds. Conventional systems for simultaneous servicing of multiple user devices or user equipment pose a beamforming limitation. For example, in conventional systems, a base station comprises of multiple omni-directional antennas in form of an antenna array. Further, to provide individual beams, beamforming is employed and usually hybrid beamformers (to limit number of RF-IF chains) comprising analog and digital (precoder) beamformers are employed. The analog beamformer is controlled by phase shifters and can transmit or receive a signal only from one direction. To service multiple UE’s simultaneously, the antenna array must be divided into groups and each group is allocated to each UE. This division results in fewer elements in the antenna array available per UE, thus reducing the number of elements available for beamforming thereby affecting beam-width and also increase in side-lobes. This limitation can be overcome by using large antenna arrays. However, use of large antenna arrays increases footprint and power requirements. Another limitation of the conventional systems is interference in mobile UE. The conventional systems do not have efficient tracking methods as a functionality and hence beam switching in the mobile UE is difficult and would require reference signals for tracking the mobile UEs. Also, switching of beams is not easy as it requires changing phases of the phase shifters thereby increasing latency. Further, for fixed beams, high interference occurs in transitioning between two beams. Thus, the prevalent systems become impractical.
The system of the present disclosure overcomes the beam forming limitation by using a digital beamforming architecture comprising an antenna array system coupled with a metasurface to produce directional beam during beamforming and utilizes an efficient location tracking algorithm based on multiple signal classification (MUSIC) algorithm to avoid interference in mobile UE. In other words, a new directional antenna array arrangement combined with a location tracker and a beam-steering algorithm is employed. Since antenna elements themselves are directive, interference with other user devices can be significantly reduced particularly during downlink. Further, the system of the present disclosure can easily be incorporated in massive and millimeter wave MIMO which are typically used in the 5G next generation radio.
In the context of the subject disclosure, certain expressions and their usage are as explained herein below.
f and phi may be interchangeably used.
? and theta may be interchangeably used.
Antenna array and microstrip antenna array ? and theta may be interchangeably used.
Referring now to the drawings, and more particularly to FIGS. 1 through 17, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments and these embodiments are described in the context of the following exemplary system and/or method.
Reference numerals of one or more components of the multiuser multi-input multi output (MIMO) communication system as depicted in the FIG.1 are provided in Table 1 below for ease of description:

Table 1:
Sr.No. Component Reference numeral
1 a base station 102
2 User Equipment 104
3 Antenna array 106
4 Digital Beamformer 108
5 Location Tracker 110
6 Radio Frequency (RF) chain 112
7 Digital precoder 114
8 Controller unit 116
9 Switch 118
10 Directive Antenna 106A
11 Metasurface 106B
12 Data storage device/Memory 116A
13 Communication interface 116B
14 Hardware processor 116C
FIG. 1 illustrates an exemplary block diagram of a multiuser multi-input multi output (MIMO) communication system according to some embodiments of the present disclosure. In an embodiment, multiuser multi-input multi output (MIMO) communication system 100, comprising: a base station 102 in communication with a plurality of user equipment’s 104. In an embodiment, the base station is operating as a transceiver which enables reception and transmission of communication signals to the plurality of the user equipment’s. In an embodiment, the user equipment may include a fixed user device or a mobile user device. In an embodiment, the communication signals are baseband signal which may include but not limited to a radio frequency (RF) signal, a microwave signal, a millimeter wave signal which are further modulated at the base station. In an embodiment, the base station 102 comprising: an antenna array 106 having a plurality of directive antennas 106A coupled to a metasurface 106B positioned on an upper side of the antenna array 106. FIG. 2 illustrates an exemplary representation (not to scale) of a top view of the antenna array without the metasurface according to some embodiments of the present disclosure. The antenna array 106 shown in FIG. 2 comprises a plurality of antennas that are directive in nature. In an embodiment, the antenna array is interchangeably referred as a microstrip antenna array and hereby used throughout the description. In an embodiment, the antenna array is square shaped and configured as a 4*4 planar array with one feed point, 16 patch directive antenna elements and no shorting pin added in design of the antenna array as implemented by the present disclosure. In an embodiment, series-corporate feed technique is applied in the design of the antenna array as implemented in the present disclosure. The total size of the antenna array is 35.522mm*25.88mm. In an embodiment, the optimized dimensions of the antenna array include single patch dimensions: W=3.5mm, L= 4 mm, substrate thickness = 0.787 mm. Here, a top conducting patch of copper material is used, and the substrate material used is RT- Duroid® 5880 having relative permittivity of 2.2 and loss tangent is considered to be 0.0045. The whole substrate is backed with ground plane having the same length and breadth as that of substrate. Such antenna array is an exemplary and the design specification of the antenna array shall not be construed as limiting the scope of the present disclosure.
FIG. 3 illustrates an exemplary representation (not to scale) of a lateral view of the microstrip antenna array coupled with the metasurface comprising of a periodic arrangement of a plurality of unit cells with optimized dimensions according to some embodiments of the present disclosure. As shown in FIG. 3, the metasurface comprises of a periodic arrangement of a plurality of unit cells with optimized dimensions to provide an improved directivity to a plurality of overlapping beams received from the antenna array. The total size of the antenna array is 39.1mm*28.9mm. The substrate material used in metasurface is Rogers RT- Duroid® 5880 having relative permittivity of 2.2 and loss tangent is considered to be 0.0045. The number of the plurality of unit cells comprised in the metasurface considered in the design of the present disclosure is 23*17. FIG. 4 illustrates an exemplary representation (not to scale) of a front view of a unit cell comprised in the metasurface according to some embodiments of the present disclosure. As shown in FIG. 4, inner dimensions of the unit cell are 1.5 mm*1.5mm and outer dimensions of the unit cell is 1.7mm*1.7mm. Optimization of the metasurface to provide improved directivity is achieved after performing many parametric iterations on the dimensions and number of the plurality of unit cells. In an embodiment, the metasurface used is two dimensional and consist of the plurality unit cells in the dimensions of subwavelength range.
In an embodiment, each of the plurality of directive antennas comprised in the antenna array is positioned such that a directive beam generated by each of the plurality of directive antennas overlap with each other. This results in enhancement of coverage area. FIG. 5 illustrates an exemplary representation (not to scale) of directive and overlapping beam formation from a lateral view of the microstrip antenna array coupled with the metasurface according to some embodiments of the present disclosure. In an embodiment, the plurality of unit cells comprised in the metasurface are arranged in such a way that when a resultant signal beam from the antenna array is passed through it, directivity of the resultant signal beam is improved along with gain. This results into high focused beam which is a key requirement of the 5G systems. In an embodiment, frequency range is considered in the 5G millimeter wave spectrum starting from 25GHz. The metasurface is placed above the antenna array structure. The metasurface changes its impedance when a beam is passed through it in such a way which provided the resultant focused beam.
FIG. 6 illustrates an exemplary representation (not to scale) of directive and overlapping beam formation from a side view of the microstrip antenna array according to some embodiments of the present disclosure. In an embodiment, the antenna array and the metasurface are arranged in such a way that at least 20% overlapping of main beam is present at output of the antenna array. The output of the antenna array which includes multiple overlapping beams is scanned continuously for detecting any user equipment present within a coverage area of a 5G network.
In an embodiment, the base station further comprises a digital beamformer 108, a location tracker 110 operably connected to the digital beamformer 108 and the antenna array 106 through a plurality of radio frequency chains 112 and one or more digital precoders 114, and a controller unit 116 operably connected to the digital beamformer 108, the location tracker 110 and the antenna array 106 using a switch 118. In an embodiment, the plurality of radio frequency chains 112 includes a plurality of transmit radio frequency (RF) chains and a plurality of receive RF chains. Similarly, the one or more precoders 114 include transmit precoders and receive precoders and the switch 118 may function as a transmit switch or a receive switch.
In an embodiment, when a user equipment 104 is detected by the plurality of directive antennas 106A comprised in the antenna array 106, an analog signal received from the user equipment 104 is transferred from the antenna array 106 to the plurality of receive RF chains 112 and this analog signal is converted into a digital signal. FIG. 7 illustrates an exemplary block diagram of a radio frequency (RF) chain of the multiuser multi-input multi output (MIMO) communication system, according to some embodiments of the present disclosure. As can be seen in FIG. 7, the RF chain is a cascade of electronic components and sub-units which may include amplifiers, filters, mixers, attenuators and detectors. The RF chain represents a single radio and all of its supporting architecture including mixers, amplifiers, and analog/ digital converters, linear noise amplifier (LNA), radio frequency (RF) switches, and RF attenuators going into frequency conversion, could be used for up conversion or down conversion, depending upon requirement. The RF chain then goes to analog to digital converter (ADC) drivers and the ADC for conversion to bits which mean the RF signal is converted to bits. As can be seen in FIG. 7, frequency generation blocks are present in middle, which can be driven from a variety of sources and distributed around the system with timing management. The timing management frequency generation blocks are shared with output side or transmit side of a generic signal chain. On the output side, a digital to analog converter (DAC) goes into an amplifier for the mixer, which results into frequency conversion, filtering out followed by switching out.
The digital signal obtained from the plurality of receive RF chains 112 is provided to the location tracker 110. In an embodiment, the location tracker 110 is configured to identify a location of each of the plurality of user equipment’s 104 based on estimation of direction of arrival of a service request signal. In an embodiment, the service request signal is received from each of the plurality of user equipment. In an embodiment, the direction of arrival of the service request signal is estimated using a pre-computed dictionary matrix. In an embodiment, the pre-computed dictionary matrix is a function of antenna array look-ahead angles for a predefined antenna gain pattern resolution. FIG. 8 illustrates functioning of the location tracker in the multiuser multi-input multi output (MIMO) communication system, according to some embodiments of the present disclosure. In an embodiment, the dictionary matrix is computed only once during design phase based on antenna gain pattern by resampling/interpolating/decimating the antenna gain pattern to a requisite resolution and constructing the dictionary matrix given the antenna array look-ahead angles, wherein the dictionary matrix is of the form provided below as:
? = ¦(G(?_1,f_1 )&G(?_1,f_2 )&G(?_1,f_(N_2 ) )@G(?_2,f_1 )&G(?_2,f_2 )…&G(?_2,f_(N_2 ) )@G(?_3,f_1 )&G(?_3,f_2 )&G(?_3,f_(N_2 ) ) )
?
¦(G(?_(N_1 ),f_1 )&(?_(N_1 ),f_2 )&(?_(N_1 ),f_(N_2 ) ) )
FIG. 9 shows a graph illustrating a sparse signal location estimation algorithm for location tracking, according to some embodiments of the present disclosure. As shown in FIG. 9, the antenna array look-ahead angles are expressed in form of discretized elevation and azimuth angles. In FIG. 9, outlined dots denote a search space and filled dots indicate users/user equipment(s) present at those locations. It is analyzed from FIG. 9 that number of users/UE may be at any point in elevation and azimuth axis and not at all the point(s) which means number of users/UE (say five users) represented by the filled dot are less that total discrete points.
As can be seen in FIG. 8, the location of each of the plurality of user equipment’s (104) based on the estimation of direction of arrival of the service request signal is identified by applying the sparse signal location estimation algorithm. In an embodiment, the sparse signal location estimation algorithm includes (i) representing the service request signal by Y as Y=?X+n, wherein ? is the precomputed dictionary matrix, X is a transmitted signal to be estimated and n is noise in the received signal, (ii) constructing a covariance matrix R as R=YY^H, wherein Y^H is a Hermitian matrix of Y, (iii) performing singular value decomposition on R to get Eigen values (?) and Eigen vectors (U). (iv) splitting U into signal subspace U_s and noise subspace U_n, (v) projecting dictionary matrix ? onto noise subspace U_n by P_sub=1/(?_(i=1)^K¦??_(n_i)^H U_(n_i ) U_(n_i)^H f?), and (vi) selecting maximum value in the P_sub matrix as estimated direction of arrival of the service request signal.
In an embodiment, a digital signal is obtained from the location tracker (110) which is passed to the one or more digital precoders 114 that pre-code the digital signal into multiple data streams as per channel characteristics. In an embodiment the one or more digital precoders 114 include a transmit precoder and a receive precoder and act as the digital beamformer 108 itself.
In an embodiment, the digital beamformer 108 generates weights along the estimated direction of arrival as per the signal received and direct a directive beam signal to one or more user equipment based on identified locations along estimated direction of arrival. Unlike, conventional systems utilizing analog beamformer and hybrid beamformers, use of phase shifters is eliminated in the present disclosure due to use of digital beamformer which results in cost reduction. FIGS. 10A and 10B illustrate a process of directive beam formation using the digital beamformer, according to some embodiments of the present disclosure. As shown in FIGS. 10A and 10B, the directive beam signal using the digital beamformer 108 is obtained by estimating a delay for each of the plurality of user equipment’s 104 based on geometrical arrangement of the plurality of directive antennas 106A of the antenna array 106 and the identified location of each of the plurality of user equipment 104. In other words, delay for each antenna of the antenna array 106, wherein the delay (t) for m^th antenna is given by t_m (?)=(m-1)dsin(?)/?. Further, overlapping beams obtained from each of the plurality of directive antenna 106A of the antenna array 106 are multiplied with corresponding antenna gain to provide a plurality of resultant signals; and summing up each of the plurality of resultant signals added with corresponding estimated delay. In other words, the estimated delay is added to the resultant signal of each antenna and signals from all antennas are summed to obtain a single signal which is transmitted along the estimated direction of arrival. As shown in FIGS. 10 A and 10B, g_m (?,?) represents gain of m^th antenna and t_m (?,?) represents delay of the m^th antenna element with respect to a reference antenna for a source at azimuth angle ? and elevation angle F.More specifically, the digital beamformer (108) utilizes information received from the location tracker (110) to generate some weights as shown in FIG. 10A and these weights are applied to a transmitting signal for varying phase and power of main beam in such a way that it directs itself towards direction of the user equipment location which is identified by the location tracker. The signal/information to be transmitted is multiplied by the weights before it is transmitted. Selection of the weights depends on factors such as user location, channel state information, and the like. In an embodiment, the controller unit 116 informs the digital beamformer about the user location, channel state information and using this information the digital beamformer 108 allocates weight to a signal before transmission. Similarly, at the receive digital precoder, information received from the antenna array remains same, but it delayed. In-order to determine original transmitted signal, received signals are multiplied by weights and are delayed in such a way that all the signals are combined to a single signal by adding them thereby resulting the signal that has been transmitted.
The controller unit 116 further comprises one or more data storage devices or memory 116A configured to store instructions; one or more communication interfaces 116B; and one or more hardware processors 116C operatively coupled to the one or more data storage devices 116A via the one or more communication interfaces 116B, wherein the one or more hardware processors 116C are configured by the instructions to co-ordinate and schedule the plurality of directive antennas 106A comprised in the antenna array 106 and feeds that service the plurality of user equipment’s 104.
The one or more hardware processors 116C can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, graphics controllers, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor(s) are configured to fetch and execute computer-readable instructions stored in the memory. In the context of the present disclosure, the expressions ‘processors’ and ‘hardware processors’ may be used interchangeably. In an embodiment, the one or more hardware processors 116C can be implemented in a variety of computing systems, such as laptop computers, notebooks, hand-held devices, workstations, mainframe computers, servers, a network cloud and the like.
In an embodiment, the communication interface(s) or input/output (I/O) interface(s) (116B) may include a variety of software and hardware interfaces, for example, a web interface, a graphical user interface, and the like and can facilitate multiple communications within a wide variety of networks N/W and protocol types, including wired networks, for example, LAN, cable, etc., and wireless networks, such as WLAN, cellular, or satellite. In an embodiment, the I/O interface(s) can include one or more ports for connecting a number of devices to one another or to another server.
The one or more data storage devices or memory (116A) may include any computer-readable medium known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or non-volatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes.
In an embodiment, the one or more hardware processors 116C are configured to perform a method for multi-user MIMO with array of directive antennas, which can be carried out by using methodology, described in conjunction with FIG. 11, and use case examples.
FIG. 9 is an exemplary flow diagram illustrating a processor implemented method for multi-user MIMO with array of directive antennas, in accordance with an embodiment of the present disclosure. The steps of the method 1100 of the present disclosure will now be explained with reference to the components or blocks of the multiuser MIMO communication system 100 as depicted in FIG. 1 and the steps of flow diagram as depicted in FIG. 9. Although process steps, method steps, techniques or the like may be described in a sequential order, such processes, methods and techniques may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps to be performed in that order. The steps of processes described herein may be performed in any order practical. Further, some steps may be performed simultaneously.
Referring to the steps of the method 1100 depicted in FIG. 11, in an embodiment of the present disclosure, at step 1102, the one or more hardware processors 116C are configured to identify one or more antennas from the plurality of directive antennas in the antenna array for a service request signal received/obtained from each of the plurality of user equipment. Further, at step 1104, the one or more hardware processors 116C are configured to identify, using the location tracker, a location of each of the plurality of user equipment based on an estimation of direction of arrival of the service request signal. At step 1106 of FIG. 11, the one or more hardware processors 116C are configured to direct, using the digital beamformer, a directive beam signal to one or more user equipment based on identified locations along estimated direction of arrival.
EXPERIMENTAL RESULTS
The multiuser MIMO communication system 100 of the present disclosure was simulated using Ansys HFSS for its reflection coefficient (S11) curve. FIG. 12 is a Reflection Coefficient (S11) curve of the microstrip antenna array without metasurface in a millimeter frequency range. From FIG.12, it may be noted that recorded reflection coefficient (S11) is –32.6dB at a resonant frequency of 28.1GHz. The value of S11 is below –10dB within a frequency range of 27.4GHz to 28.7GHz and bandwidth observed is 1.3GHz.
FIG. 13 is a Reflection Coefficient (S11) curve of the microstrip antenna array with the metasurface in a millimeter frequency range. From FIG. 13, it may be noted that recorded reflection coefficient (S11) is –27.8dB at a resonant frequency of 27.9GHz. The value of S11 is below –10dB within a frequency range of 27.5GHz to 28.6GHz and bandwidth observed is 1GHz.
FIG. 14 illustrates rectangular gain plots for the microstrip antenna array without the metasurface for various values of theta which is an angle measured off z-axis, according to some embodiments of the present disclosure. It is observed in FIG. 14 that value of gain is 13.3dB for Phi=0 and 11.4dB for Phi=90 plane. Further, directivity obtained is measured with beamwidths which are quite in good range including beamwidth of 23 degrees for phi=90 and 18 degrees for phi=0 degrees. These lower beamwidths make beam narrower which is quite an important feature in the 5G technology for focused beams used in beamforming.
FIG. 15 illustrates rectangular gain plots for the microstrip antenna array with the metasurface for various values of theta which is an angle measured off z-axis, according to some embodiments of the present disclosure. It is observed in FIG. 14 that value of gain is 16.6dB for Phi=0 and 15.9dB for Phi=90 plane. Further, directivity obtained is measured with beamwidths of 18.9 degrees for phi=90 and 14.7 degrees for phi=0 degrees. These lower beamwidths make beam narrower which is quite an important feature in the 5G technology for focused beams used in beamforming.
FIG. 16 is a 2-Dimensional radiation pattern of the microstrip antenna array without the metasurface according to some embodiments of the present disclosure. The 2-Dimensional radiation pattern as depicted in FIG. 16 provides a polar plot representation of the rectangular gain plots shown in FIG. 14 for the microstrip antenna array without metasurface for various values of theta and phi.
FIG. 17 is a 2-Dimensional radiation pattern of the microstrip antenna array with the metasurface according to some embodiments of the present disclosure. The 2-Dimensional radiation pattern as depicted in FIG. 17 provides a polar plot representation of the rectangular gain plots shown in FIG. 15 for the microstrip antenna array with the metasurface for various values of theta and phi.
The written description describes the subject matter herein to enable any person skilled in the art to make and use the embodiments. The scope of the subject matter embodiments is defined by the claims and may include other modifications that occur to those skilled in the art. Such other modifications are intended to be within the scope of the claims if they have similar elements that do not differ from the literal language of the claims or if they include equivalent elements with insubstantial differences from the literal language of the claims.
The embodiments of present disclosure herein provide a scalable solution that handles simultaneous servicing of multiple UE’s for faster speeds using a directional antenna array arrangement combined with a location tracker and beam-forming algorithm. The system of the present disclosure provides design flexibility in terms of size, shape, cable, connector all fully customizable with no tooling cost, has minimum footprint, light weight, low profile and can easily be incorporated in massive and mmWave MIMO which are typically used in 5G next generation radio (NR). The system of present disclosure is scalable to other bands such as Wi-Fi, 6G and the like.
It is to be understood that the scope of the protection is extended to such a program and in addition to a computer-readable means having a message therein; such computer-readable storage means contain program-code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The hardware device can be any kind of device which can be programmed including e.g. any kind of computer like a server or a personal computer, or the like, or any combination thereof. The device may also include means which could be e.g. hardware means like e.g. an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of hardware and software means, e.g. an ASIC and an FPGA, or at least one microprocessor and at least one memory with software processing components located therein. Thus, the means can include both hardware means and software means. The method embodiments described herein could be implemented in hardware and software. The device may also include software means. Alternatively, the embodiments may be implemented on different hardware devices, e.g. using a plurality of CPUs.
The embodiments herein can comprise hardware and software elements. The embodiments that are implemented in software include but are not limited to, firmware, resident software, microcode, etc. The functions performed by various components described herein may be implemented in other components or combinations of other components. For the purposes of this description, a computer-usable or computer readable medium can be any apparatus that can comprise, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purposes of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope of the disclosed embodiments. Also, the words “comprising,” “having,” “containing,” and “including,” and other similar forms are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
Furthermore, one or more computer-readable storage media may be utilized in implementing embodiments consistent with the present disclosure. A computer-readable storage medium refers to any type of physical memory on which information or data readable by a processor may be stored. Thus, a computer-readable storage medium may store instructions for execution by one or more processors, including instructions for causing the processor(s) to perform steps or stages consistent with the embodiments described herein. The term “computer-readable medium” should be understood to include tangible items and exclude carrier waves and transient signals, i.e., be non-transitory. Examples include random access memory (RAM), read-only memory (ROM), volatile memory, nonvolatile memory, hard drives, CD ROMs, DVDs, flash drives, disks, and any other known physical storage media.
It is intended that the disclosure and examples be considered as exemplary only, with a true scope of disclosed embodiments being indicated by the following claims.