WO2016077975A1

WO2016077975A1 - Evolved node-b and user equipment and methods for group sounding in full-dimension multiple-input multiple-output systems

Info

Publication number: WO2016077975A1
Application number: PCT/CN2014/091345
Authority: WO
Inventors: Yuan Zhu; Qinghua Li; Fangze TU; Xiaogang Chen
Original assignee: Intel IP Corporation
Priority date: 2014-11-18
Filing date: 2014-11-18
Publication date: 2016-05-26
Also published as: EP3222099A1; EP3222099A4; CN107006017B; CN107006017A

Abstract

An Evolved Node-B (eNB) configured to support group sounding at a multiple-input multiple-output (MIMO) antenna array. The eNB may include hardware processing circuitry configured to transmit, for reception at multiple User Equipments (UEs), a physical downlink control channel (PDCCH) data block that includes a masked group SRS request. The hardware processing circuitry configured to receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. The hardware processing circuitry may include one or more transceivers configured to be coupled to a multiple-input multiple-output (MIMO) antenna array that includes a grid of multiple antenna elements and the reception of the SRS from each of the multiple UEs may be performed at the MIMO antenna array.

Description

EVOLVED NODE-B AND USER EQUIPMENT AND METHODS FOR GROUP SOUNDING IN FULL-DIMENSION MULTIPLE-INPUT MULTIPLE-OUTPUT SYSTEMS

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relate to cellular communication networks including LTE networks. Some embodiments relate to multiple-input multiple-output (MIMO) systems. Some embodiments relate to sounding reference signals.

BACKGROUND

Base stations may employ multiple-input multiple-output (MIMO) antenna arrays in order to improve reception performance when communicating with mobile devices. A MIMO antenna array may include a large number of antenna elements in some cases, which may be beneficial in terms of diversity gain or the ability to receive signals from multiple mobile devices in common time and frequency resources. However, computational complexity involved in processing signals on the large number of antenna elements may be challenging or intractable. Accordingly, there is a general need for methods and systems for reducing or alleviating computational complexity related to MIMO antenna arrays.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of a 3GPP network in accordance with some embodiments；

FIG. 2 is a functional diagram of a User Equipment (UE) in accordance with some embodiments；

FIG. 3 is a functional diagram of an Evolved Node-B (eNB) in accordance with some embodiments；

FIG. 4 is an example of a multiple-input multiple-output (MIMO) antenna array in accordance with some embodiments；

FIG. 5 illustrates the operation of a method of group sounding in accordance with some embodiments；

FIG. 6 illustrates the operation of another method of group sounding in accordance with some embodiments； and

FIG. 7 illustrates examples of information elements (IEs) that may enable group sounding in accordance with some embodiments.

DETAILED DESCRIPTION

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

FIG. 1 is a functional diagram of a 3GPP network in accordance with some embodiments. The network comprises a radio access network (RAN) (e.g., as depicted, the E-UTRAN or evolved universal terrestrial radio access network) 100 and the core network 120 (e.g., shown as an evolved packet core (EPC) ) coupled together through an S1 interface 115. For convenience and brevity sake, only a portion of the core network 120, as well as the RAN 100, is shown.

The core network 120 includes mobility management entity (MME) 122, serving gateway (serving GW) 124, and packet data network gateway (PDN GW) 126. The RAN 100 includes Evolved Node-B’s (eNBs) 104 (which may operate as base stations) for communicating with User Equipment (UE) 102. The eNBs 104 may include macro eNBs and low power (LP) eNBs.

The MME is similar in function to the control plane of legacy Serving GPRS Support Nodes (SGSN) . The MME manages mobility aspects in access such as gateway selection and tracking area list management. The serving GW 124 terminates the interface toward the RAN 100, and routes data packets between the RAN 100 and the core network 120. In addition, it may be a local mobility anchor point for inter-eNB handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement. The serving GW 124 and the MME 122 may be implemented in one physical node or separate physical nodes. The PDN GW 126 terminates an SGi interface toward the packet data network (PDN) . The PDN GW 126 routes data packets between the EPC 120 and the external PDN, and may be a key node for policy enforcement and charging data collection. It may also provide an anchor point for mobility with non-LTE accesses. The external PDN can be any kind of IP network, as well as an IP Multimedia Subsystem (IMS) domain. The PDN GW 126 and the serving GW 124 may be implemented in one physical node or separated physical nodes.

The eNBs 104 (macro and micro) terminate the air interface protocol and may be the first point of contact for a UE 102. In some embodiments, an eNB 104 may fulfill various logical functions for the RAN 100 including but not limited to RNC (radio network controller functions) such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. In accordance with embodiments, UEs 102 may be configured to communicate OFDM communication signals with an eNB 104 over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signals may comprise a plurality of orthogonal subcarriers.

In accordance with some embodiments, an eNB 104 may receive a group sounding reference signal (SRS) that includes a sum of an SRS from each of multiple UEs 102 during a group SRS transmission period and in group SRS frequency resources. The group SRS may enable the eNB 104 to form a channel dimension reduction matrix for complexity reduction during reception of traffic signals from the same UEs during traffic transmission periods. These embodiments are described in more detail below.

The S1 interface 115 is the interface that separates the RAN 100 and the EPC 120. It is split into two parts: the S1-U, which carries traffic data between the eNBs 104 and the serving GW 124, and the S1-MME, which is a signaling interface between the eNBs 104 and the MME 122. The X2 interface is the interface between eNBs 104. The X2 interface comprises two parts, the X2-C and X2-U. The X2-C is the control plane interface between the eNBs 104, while the X2-U is the user plane interface between the eNBs 104.

With cellular networks, LP cells are typically used to extend coverage to indoor areas where outdoor signals do not reach well, or to add network capacity in areas with very dense phone usage, such as train stations. As used herein, the term low power (LP) eNB refers to any suitable relatively low power eNB for implementing a narrower cell (narrower than a macro cell) such as a femtocell, a picocell, or a micro cell. Femtocell eNBs are typically provided by a mobile network operator to its residential or enterprise customers. A femtocell is typically the size of a residential gateway or smaller, and generally connects to the user's broadband line. Once plugged in, the femtocell connects to the mobile operator's mobile network and provides extra coverage in a range of typically 30 to 50 meters for residential femtocells. Thus, a LP eNB might be a femtocell eNB since it is coupled through the PDN GW 126. Similarly, a picocell is a wireless communication system typically covering a small area, such as in-building (offices, shopping malls, train stations, etc. ) , or more recently in-aircraft. A picocell eNB can generally connect through the X2 link to another eNB such as a macro eNB through its base station controller (BSC) functionality. Thus, LP eNB may be implemented with a picocell eNB since it is coupled to a macro eNB via an X2 interface. Picocell eNBs or other LP eNBs may incorporate some or all functionality of a macro eNB. In some cases, this may be referred to as an access point base station or enterprise femtocell.

In some embodiments, a downlink resource grid may be used for downlink transmissions from an eNB 104 to a UE 102, while uplink transmission from the UE 102 to the eNB 104 may utilize similar techniques. The grid may be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time-frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid correspond to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements and in the frequency domain, this represents the smallest quanta of resources that currently can be allocated. There are several different physical downlink channels that are conveyed using such resource blocks. With particular relevance to this disclosure, two of these physical downlink channels are the physical downlink shared channel and the physical down link control channel.

The physical downlink shared channel (PDSCH) carries user data and higher-layer signaling to a UE 102 (FIG. 1) . The physical downlink control channel (PDCCH) carries information about the transport format and resource allocations related to the PDSCH channel, among other things. It also informs the UE 102 about the transport format, resource allocation, and H-ARQ information related to the uplink shared channel. Typically, downlink scheduling (assigning control and shared channel resource blocks to UEs 102 within a cell) is performed at the eNB 104 based on channel quality information fed back from the UEs 102 to the eNB 104, and then the downlink resource assignment information is sent to a UE 102 on the control channel (PDCCH) used for (assigned to) the UE 102.

The PDCCH uses CCEs (control channel elements) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols are first organized into quadruplets, which are then permuted using a sub-block inter-leaver for rate matching. Each PDCCH is transmitted using one or more of these control channel elements (CCEs) , where each CCE corresponds to nine sets of four physical resource elements known as resource element groups (REGs) . Four QPSK symbols are mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of DCI and the channel condition. There may be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L＝1, 2, 4, or 8) .

FIG. 2 is a functional diagram of a User Equipment (UE) in accordance with some embodiments. FIG. 3 is a functional diagram of an Evolved Node-B (eNB) in accordance with some embodiments. It should be noted that in some embodiments, the eNB 300 may be a stationary non-mobile device. The UE 200 may be a UE 102 as depicted in FIG. 1, while the eNB 300 may be an eNB 104 as depicted in FIG. 1. The UE 200 may include physical layer circuitry 202 for transmitting and receiving signals to and from the eNB 300, other eNBs, other UEs or other devices using one or more antennas 201, while the eNB 300 may include physical layer circuitry 302 for transmitting and receiving signals to and from the UE 200, other eNBs, other UEs or other devices using one or more antennas 301. As will be described in more detail below, the

antennas

201, 301 may be multiple-input multiple-output (MIMO) antennas. The UE 200 may also include medium access control layer (MAC) circuitry 204 for controlling access to the wireless medium, while the eNB 300 may also include medium access control layer (MAC) circuitry 304 for controlling access to the wireless medium. The UE 200 may also include processing circuitry 206 and memory 208 arranged to perform the operations described herein, and the eNB 300 may also include processing circuitry 306 and memory 308 arranged to perform the operations described herein.

In some embodiments, mobile devices or other devices described herein may be part of a portable wireless communication device, such as a personal digital assistant (PDA) , a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc. ) , or other device that may receive and/or transmit information wirelessly. In some embodiments, the mobile device or other device can be the UE 102 or eNB 104 configured to operate in accordance with 3GPP standards. In some embodiments, the mobile device or other device may be configured to operate according to other protocols or standards, including IEEE 802.11 or other IEEE standards. In some embodiments, the mobile device or other device may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

The

antennas

201, 301 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, the

antennas

201, 301 may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result. FIG. 4 is an example of a multiple-input multiple-output (MIMO) antenna array in accordance with some embodiments. Referring to FIG. 4, an example MIMO antenna array 400 shows a two-dimensional planar array with antenna elements arranged in a grid with M rows and N columns. In this example, half of the antenna elements may have a slant angle of positive 45 degrees while the other half of the antenna elements may have a slant angle of negative 45 degrees. Accordingly, the

elements

412, 422, 432 and other solid lines shown may have an angle of positive 45 degrees while the

elements

414, 424, 434 and other dashed lines shown may have an angle of negative 45 degrees.

One possible arrangement includes the values M ＝ 10 and N ＝ 2. With two layers in the MIMO antenna array 400, there are 40 antenna elements. The signals received at the 40 antenna elements may be different but correlated, especially when the spacing between elements is not large. Therefore, a diversity gain realized by the MIMO antenna array 400 with 40 antenna elements may not be as high as a diversity gain realized when 40 independent signals are received. However, the use of such a large number of antenna elements may increase diversity gains beyond those realized by antenna configurations with 4 or 8 antenna elements, for instance. Accordingly, the MIMO antenna array 400 may be considered a full-dimension MIMO (FD-MIMO) array in some cases.

Although the UE 200 and eNB 300 are each illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs) , and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field-programmable gate arrays (FPGAs) , application specific integrated circuits (ASICs) , radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements may refer to one or more processes operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer) . For example, a computer-readable storage device may include read-only memory (ROM) , random-access memory (RAM) , magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

In accordance with embodiments, the eNB 104 may include hardware processing circuitry configured to transmit, for reception at multiple UEs that may include the UE 102, a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs. The hardware processing circuitry may be further configured to apply the SRS-RNTI to a group SRS request to produce a masked group SRS request and to transmit a physical downlink control channel (PDCCH) data block that includes the masked group SRS request. The hardware processing circuitry may be further configured to receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. These embodiments are described in more detail below.

FIG. 5 illustrates the operation of a method of group sounding in accordance with some embodiments. It is important to note that embodiments of the method 500 may include additional or even fewer operations or processes in comparison to what is illustrated in FIG. 5. In addition, embodiments of the method 500 are not necessarily limited to the chronological order that is shown in FIG. 5. In describing the method 500, reference may be made to FIGs. 1-4 and 6-7, although it is understood that the method 500 may be practiced with any other suitable systems, interfaces and components. For example, reference may be made to the MIMO antenna array 400 in FIG. 4 described earlier for illustrative purposes, but the techniques and operations of the method 500 are not so limited.

In addition, while the method 500 and other methods described herein may refer to eNBs 104 or UEs 102 operating in accordance with 3GPP or other standards, embodiments of those methods are not limited to just those eNBs 104 or UEs 102 and may also be practiced on other mobile devices, such as a Wi-Fi access point (AP) or user station (STA) . Moreover, the method 500 and other methods described herein may be practiced by wireless devices configured to operate in other suitable types of wireless communication systems, including systems configured to operate according to various IEEE standards such as IEEE 802.11.

At operation 505 of the method 500, an SRS radio network temporary identifier (SRS-RNTI) may be transmitted for reception at multiple UEs, including the UE 102. The UEs may be assigned to an SRS group and the SRS-RNTI may be reserved for the SRS group and may enable the UE 102 to detect a group SRS request, as will be described below. In some embodiments, the transmission of the SRS-RNTI to the multiple UEs may include transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs. As an example, an information element (IE) of a radio resource control (RRC) control message may include the SRS-RNTI or an index of the SRS-RNTI that may refer to a pre-determined group of RNTIs known at the UE 102. The dedicated control message may be transmitted at any suitable time, including during a setup process for the connection between the eNB 104 and UE 102 or during an update process.

At operation 510, a common RRC IE that includes SRS sequence parameters may be transmitted by the eNB 104. The SRS sequence parameters may enable determination of a group SRS bit sequence at the UEs that may be used by the UEs for group sounding, as will be described below. The group SRS bit sequence may be used at the UE 102 to form the SRS transmitted by the UE 102. As an example, the bit sequence may be input to encoder functions such as forward error correction (FEC) , interleaving, bit-to-symbol mapping or others to produce modulated symbols for transmission. As described previously, the modulated symbols may be used to form an OFDM signal for the SRS in some embodiments.

FIG. 7 illustrates examples of information elements (IEs) that may enable group sounding in accordance with some embodiments. The common RRC IE may be transmitted in one or more broadcast control messages that are receivable at the multiple UEs. An example of one such common RRC IE is shown in FIG. 7, in which a common SRS IE 705 (which may be included in RRC or other control messages) may include other SRS parameters or information 710 (which may be empty in some cases) and an SRS configuration index 720. The SRS configuration index 720 may be an index (such as an index in a range like 0-1023) that refers to a pre-defined SRS bit sequence or may be an input, such as a seed value or similar, for a formula or other algorithm that may generate the SRS bit sequence at the UEs. It should be noted that the SRS bit sequence used for group sounding is not limited to a special group SRS bit sequence reserved for group sounding, although such arrangements may be used. The SRS bit sequence may be any suitable SRS sequence, and in some cases, the SRS bit sequence used for group sounding may also be used other UEs in different time and/or frequency resources for non-group sounding. As shown in FIG. 7, the common SRS IE 705 may be a “SoundingRS-UL-ConfigCommonAperiodic-r13” IE or similar from 3GPP or other standards, but these embodiments are not limiting.

At operation 515, dedicated SRS configuration IEs that include cyclic shifts for the UEs may be transmitted to each of the multiple UEs. An example in FIG. 7 shows a dedicated SRS IE 755 that may include other SRS parameters or information 760 (which may be empty in some cases) and an SRS cyclic shift 770 for the UE 102. The SRS transmitted by the UE 102 may be determined by applying the cyclic shift for the UE 102 to the previously described SRS. In some embodiments, the cyclic shifts for some or all of the UEs may be different, which may result in some or all of the UEs transmitting different SRSs in the same set of REs during common or overlapping time periods to the eNB 104. As shown in FIG. 7, the dedicated SRS IE 755 may be a “SoundingRS-UL-ConfigDedicated” IE or similar from 3GPP or other standards, but these embodiments are not limiting.

At operation 520, the SRS-RNTI may be applied to a group SRS request to produce a masked group SRS request. A PDCCH data block that includes the masked group SRS request may be transmitted at operation 525. In some embodiments, the application of the SRS-RNTI to the group SRS request may include application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request.

At operation 530, a group SRS may be received from the multiple UEs. The eNB 104 may include one or more transceivers configured to be coupled to a MIMO antenna array that includes a grid of multiple antenna elements, and reception of the group SRS may be performed at the MIMO antenna array. Accordingly, each of the multiple UEs may transmit an SRS (or a cyclically shifted version of an SRS) during a group SRS transmission period and in group SRS frequency resources, and the sum of the transmitted SRSs (weighted by a channel for each SRS) may form, or contribute to, the group SRS signal.

At operation 535, a composite received sample vector for the UEs at the MIMO antenna array may be determined. The determination may include the use of a fast Fourier transform (FFT) , matched-filtering or other techniques. As an example, when the SRS are OFDM signals, an FFT operation may be performed on the received signal at each antenna element during an OFDM symbol period to produce an FFT sample for each resource element (RE) or sub-carrier. Accordingly, each RE (or at least multiple REs) may then be associated with a received sample vector of length equal to the number of antenna elements in the MIMO antenna array. Therefore composite received sample vectors may actually be determined for each RE, and the determination of the multiple composite received sample vectors may be performed jointly in some cases. For instance, the FFT operations inherently operate on multiple REs. Embodiments are not limited to such implementations, however.

The following FD-MIMO model may be employed for illustration of concepts. On each RE, an FFT value may be extracted from FFT operations performed on each antenna element to form a composite received sample vector for the RE, which may be modeled as

y＝HPx+n

In the model, the received sample vector y is of dimension N_r×1, H is anN_r×N_c matrix, Pis anN_r×N_pmatrix, x is an N_p×1 data symbol vector, n is an N_r×1 noise vector, N_r is the number of receiving antennas, N_t is the number of antenna elements, and N_p is the number of layers. For example, if the antenna array is a 2D antenna array as shown in FIG. 4, N_t＝2NM and N_t may be significantly larger than 8. For example, when N ＝ 2 and M ＝ 10, N_t＝40.

When the number of antenna elements is relatively large, matrix computations and other computations may be prohibitively high, especially when such computations may have to be performed at every RE. Accordingly, a reduction in computational complexity may be realized by virtualizing the total number of antenna elements N_t to a smaller number. As an example, the smaller number of virtual elements may be 1, 2, 4 or 8, which may be compatible with the number of antenna ports available for channel state information reference signals (CSI-RS) in 3GPP or other standards.

The above model may be re-written as

y＝HP_cP_dx+n＝HP_dx+n

The matrix P_c is an N_t×N_c matrix, P_d is anN_c×N_p matrix and

is the effective channel matrix of dimension N_r×N_c and N_t＝N_cK. Accordingly, the number of columns in the effective channel matrix may be reduced, for instance, from the previous example value of 40 to 8.

As part of the model, an average co-variance matrix estimate may be determined by receiving individual SRSs from multiple UEs, forming an average channel estimate

for each user, and forming an average co-variance matrix estimate by averaging (with respect to the UEs) matrix products of individual average channel estimates with their corresponding Hermitian transpose as

In this equation, the right hand side is a singular value decomposition (SVD) of the average co-variance matrix estimate, and the “H” notation on the vectors and matrices denotes a Hermitian transpose. The columns of the matrix V are the eigenbeams of the average co-variance matrix estimate, and the diagonal entries of the matrix S are the eigenvalues. The previous result may also be obtained by utilizing the received sample vectors associated with the individual SRS from the multiple UEs instead of the channel estimates, as

In any case, the eigenbeams associated with the strongest eigenvalues may be selected as the columns of the matrix P_c. As an example, if the strongest 8 eigenbeams are selected, the effective channel matrix

also has 8 columns.

An improvement in the computational aspect of the above processes may be realized through group sounding. As mentioned previously, the group SRS received at the MIMO antenna array may include a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. The matrix product of a received sample vector for the group SRS with its Hermitian transpose may average out to the same result as the above SVD. That is, the matrix product of the summation of individual SRSs includes a sum of matrix products of individual SRS (as desired in the last equation) and a number of cross products between SRSs of different UEs. Statistically, the cross products may average to zero, as they result from different UEs transmitting on different channels. Therefore, the desired SVD above may be obtained through the use of group sounding.

At operation 540, an averaged co-variance matrix estimate may be determined using a matrix product of the group SRS received sample vector and a transpose of the group SRS received sample vector. It should be noted that the averaging may actually result from more than a single group SRS received sample vector. That is, group SRS received sample vectors from multiple time periods in which the group SRS is transmitted by the group of UEs may be used at operation 540. At operation 545, a set of eigenbeams and eigenvalues for the averaged co-variance matrix estimate may be determined using SVD or other suitable techniques. A reduced set of eigenbeams from the set of eigenbeams may be selected at operation 550 and at operation 555, the reduced set of eigenbeams may be included in a channel dimension reduction matrix as columns. In some embodiments, the selected eigenbeams for the reduced set may be associated with the eigenvalues of the highest magnitude.

It should be noted that the above operations may take place at each RE or at multiple REs, and each of those REs may be associated with a channel dimension reduction matrix. In addition, for each RE, a traffic received sample vector based at least partly on received signals at the antenna elements of the MIMO antenna array may be determined for the UE 102 during a traffic transmission period for the UE 102. The traffic transmission period may be exclusive to the group SRS transmission period and may also be exclusive to other SRS transmission periods for other UEs.

At operation 560, the channel dimension reduction matrix for a particular RE may be applied to the traffic received sample vector for the RE to produce a reduced dimension received sample vector that may be modeled according to the effective channel described earlier. As the effective channel after the virtualization may have much fewer dimensions that the full-dimension channel, as described earlier, decoding or demodulation operations may also be simplified. Accordingly, the reduced dimension received sample vector may be demodulated at operation 565 to produce a decoded symbol from a constellation (or corresponding data bits) or soft decision of the symbols or bits for a particular RE. In addition, similar operations may be performed at other REs, and decoded symbols or bits (hard decisions) or soft decisions from some or all of those operations may be further processed with an FEC decoder or other techniques to produce one or more decoded data blocks.

The eNB 104 may also coordinate with other eNBs, such as neighboring eNBs. In some cases, those eNBs or UEs supported by them may cause interference to the eNB 104, during group sounding periods or other periods. For the estimation of the channel covariance matrix as part of a group sounding, it may be beneficial that UEs supported by the neighboring eNBs or other eNBs refrain from transmission of sounding signals during group sounding periods of the eNB 104. Coordination between the eNB 104 and the neighboring eNBs or other eNBs may be performed through suitable inter-eNB coordination techniques. For instance, signaling formats and related procedures for inter-eNB signaling included as part of 3GPP, LTE or other standards may be used. Accordingly, an information element (IE) in such a standard may be defined, created or modified to include relevant information that may enable eNBs to reduce or avoid interference to each other during group sounding or other sounding periods.

FIG. 6 illustrates the operation of another method of group sounding in accordance with some embodiments. As mentioned previously regarding the method 500, embodiments of the method 600 may include additional or even fewer operations or processes in comparison to what is illustrated in FIG. 6 and embodiments of the method 600 are not necessarily limited to the chronological order that is shown in FIG. 6. In describing the method 600, reference may be made to FIGs. 1-5 and 7, although it is understood that the method 600 may be practiced with any other suitable systems, interfaces and components. In addition, embodiments of the method 600 may refer to eNBs 104, UEs 102, APs, STAs or other wireless or mobile devices.

It should be noted that, although not limited as such, the method 600 may be practiced at the UE 102 while the method 500 may be practiced at the eNB 104. Some of the operations included in one of the

methods

500, 600 may be similar to operations included in the other method, and some or all of the discussion related to one of the

methods

500, 600 may be applicable to the other method. For example, the method 500 may include transmission of a message by the eNB 104 while the method 600 may include reception of a similar or related message at the UE 102. Accordingly, some or all of the descriptions of the message may apply to both

methods

500, 600.

At operation 605, an SRS radio network temporary identifier (SRS-RNTI) associated with an SRS group may be received from the eNB 104. The SRS-RNTI may be received in a dedicated control message for the UE 102. In some embodiments, the SRS group may include the UE 102 and other UEs. At operation 610, a common RRC IE that includes SRS sequence parameters may be received at the UE 102, and the SRS sequence parameters may enable determination of a group SRS bit sequence at the UE 102. In some embodiments, the RRC IE may be the common SRS IE 705 or similar. At operation 615, a dedicated SRS configuration IE that includes a cyclic shift for the UE 102 may be received. In some embodiments, the dedicated SRS configuration IE may be the dedicated SRS IE 755 or similar.

At operation 620, a PDCCH data block that includes a group SRS request may be received at the UE 102. The SRS-RNTI may be applied to the PDCCH data block to detect the group SRS request at operation 625. In some embodiments, the application of the SRS-RNTI to the PDCCH data block may include application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request. At operation 630, an SRS may be transmitted at the UE 102. The transmission may be in response to the detection of the group SRS request, and the SRS may be transmitted during a transmission time period and in frequency resources for group SRS transmission by the SRS group. The SRS signal may be formed, as previously described, using the group SRS bit sequence and the cyclic shift for the UE 102.

An Evolved Node-B (eNB) is disclosed herein. The eNB may include hardware processing circuitry configured to transmit, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs and to apply the SRS-RNTI to a group SRS request to produce a masked group SRS request. The hardware processing circuitry may be further configured to transmit a physical downlink control channel (PDCCH) data block that includes the masked group SRS request and receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. The hardware processing circuitry may include one or more transceivers configured to be coupled to a MIMO antenna array that includes a grid of multiple antenna elements. The reception of the SRS from each of the multiple UEs may be performed at the MIMO antenna array. In some embodiments, the MIMO antenna array may include a two-dimensional planar array of antenna elements. In some embodiments, the MIMO antenna array may be a full-dimension MIMO antenna array that includes at least 16 elements. The hardware processing circuitry may be further configured to determine a group SRS received sample vector based at least partly on received signals at the antenna elements of the MIMO antenna array during the group SRS transmission period.

The hardware processing circuitry may be further configured to determine an averaged co-variance matrix estimate based at least partly on a matrix product of the group SRS received sample vector and a transpose of the group SRS received sample vector and to determine a set of eigenbeams and eigenvalues for the averaged co-variance matrix estimate. The hardware processing circuitry may be further configured to select, according to the magnitude of the corresponding eigenvalues, a reduced set of eigenbeams from the set of eigenbeams, and to form a channel dimension reduction matrix. In some embodiments, the columns of the channel dimension reduction matrix may include the reduced set of eigenbeams. The hardware processing circuitry may be further configured to determine, for one of the UEs, a traffic received sample vector based at least partly on received signals at the antenna elements of the MIMO antenna array during a traffic transmission period for the UE. The hardware processing circuitry may be further configured to apply the channel dimension reduction matrix to the traffic received sample vector to form a reduced dimension traffic received sample vector and to demodulate the reduced dimension traffic received sample vector to produce a decoded data symbol or one or more soft metrics for the data symbol.

In some embodiments, the UEs may be assigned to an SRS group and the SRS-RNTI may be reserved for the SRS group. In some embodiments, the application of the SRS-RNTI to the group SRS request may include application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request. In some embodiments, the transmission of the SRS-RNTI to the multiple UEs may include transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs. The hardware processing circuitry may be further configured to transmit, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs. In some embodiments, the SRS received from each of the multiple UEs may be based at least partly on the group SRS bit sequence. The hardware processing circuitry may be further configured to transmit, to each of the multiple UEs, a dedicated SRS configuration IE that includes a cyclic shift for the UE. In some embodiments, the SRS received from each of the multiple UEs may be further based at least partly on the cyclic shift for the UE and the cyclic shifts for at least some of the UEs may be different. In some embodiments, the SRS-RNTI may be reserved for common data blocks included in the PDCCH, the common data blocks intended for multiple UEs.

A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors to perform operations for transmission and reception of signals at an Evolved Node-B (eNB) is disclosed herein. The operations may configure the one or more processors to transmit, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs and to apply the SRS-RNTI to a group SRS request to produce a masked group SRS request. The operations may further configure the one or more processors to transmit a physical downlink control channel (PDCCH) data block that includes the masked group SRS request and to receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. In some embodiments, the reception of the SRS from each of the multiple UEs may be performed at a MIMO antenna array to which one or more transceivers included at the eNB are configured to be coupled. In some embodiments, the transmission of the SRS-RNTI to the multiple UEs may include transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs. The operations may further configure the one or more processors to transmit, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs. In some embodiments, the SRS received from each of the multiple UEs may be based at least partly on the group SRS bit sequence.

A method of transmitting and receiving signals at an Evolved Node-B (eNB) is also disclosed herein. The method may include transmitting, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs and applying the SRS-RNTI to a group SRS request to produce a masked group SRS request. The method may further include transmitting a physical downlink control channel (PDCCH) data block that includes the masked group SRS request and receiving a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources. In some embodiments, the reception of the SRS from each of the multiple UEs may be performed at a MIMO antenna array to which one or more transceivers included at the eNB are configured to be coupled. In some embodiments, the transmission of the SRS-RNTI to the multiple UEs may include transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs. The method may further include transmitting, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs. In some embodiments, the SRS received from each of the multiple UEs may be based at least partly on the group SRS bit sequence.

A User Equipment (UE) is also disclosed herein. The UE may include hardware processing circuitry configured to receive, from an Evolved Node-B (eNB) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) associated with an SRS group that includes the UE and other UEs. The hardware processing circuitry may be further configured to receive a physical downlink control channel (PDCCH) data block that includes a group SRS request and to apply the SRS-RNTI to the PDCCH data block to detect the group SRS request. The hardware processing circuitry may be further configured to transmit, in response to the detection of the group SRS request, an SRS during a group SRS transmission period and in group SRS frequency resources. In some embodiments, the application of the SRS-RNTI to the PDCCH data block may include application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request. In some embodiments, the SRS-RNTI may be received in a dedicated control message for the UE. The hardware processing circuitry may be further configured to receive, from the eNB, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UE. In some embodiments, the transmitted SRS may be based at least partly on the group SRS bit sequence. The hardware processing circuitry may be further configured to receive, from the eNB, a dedicated SRS configuration IE that includes a cyclic shift for the UE. In some embodiments, the transmitted SRS may be further based at least partly on the cyclic shift for the UE.

The Abstract is provided to comply with 37 C. F. R. Section 1.72 (b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or 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

An Evolved Node-B (eNB) comprising hardware processing circuitry configured to:

transmit, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs；

apply the SRS-RNTI to a group SRS request to produce a masked group SRS request；

transmit a physical downlink control channel (PDCCH) data block that includes the masked group SRS request； and

receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources.
The eNB according to claim 1, wherein:

the hardware processing circuitry includes one or more transceivers configured to be coupled to a multiple-input multiple-output (MIMO) antenna array that includes a grid of multiple antenna elements； and

the reception of the SRS from each of the multiple UEs is received through the MIMO antenna array.
The eNB according to claim 2, wherein the MIMO antenna array includes a two-dimensional planar array of antenna elements.
The eNB according to claim 2, wherein the MIMO antenna array is a full-dimension MIMO antenna array that includes at least 16 antenna elements.
The eNB according to claim 2, the hardware processing circuitry further configured to determine a group SRS received sample vector based at least partly on received signals at the antenna elements of the MIMO antenna array during the group SRS transmission period.
The eNB according to claim 5, the hardware processing circuitry further configured to:

determine an averaged co-variance matrix estimate based at least partly on a matrix product of the group SRS received sample vector and a transpose of the group SRS received sample vector；

determine a set of eigenbeams and eigenvalues for the averaged co-variance matrix estimate；

select, according to the magnitude of the corresponding eigenvalues, a reduced set of eigenbeams from the set of eigenbeams；

form a channel dimension reduction matrix, wherein the columns of the channel dimension reduction matrix include the reduced set of eigenbeams.
The eNB according to claim 6, the hardware processing circuitry further configured to:

determine, for one of the UEs, a traffic received sample vector based at least partly on received signals at the antenna elements of the MIMO antenna array during a traffic transmission period for the UE；

apply the channel dimension reduction matrix to the traffic received sample vector to form a reduced dimension traffic received sample vector； and

demodulate the reduced dimension traffic received sample vector to produce a decoded data symbol or one or more soft metrics for the data symbol.
The eNB according to claim 1, wherein the UEs are assigned to an SRS group and the SRS-RNTI is reserved for the SRS group.
The eNB according to claim 1, wherein the application of the SRS-RNTI to the group SRS request includes application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request.
The eNB according to claim 1, wherein the transmission of the SRS-RNTI to the multiple UEs includes transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs.
The eNB according to claim 1, wherein:

the hardware processing circuitry is further configured to transmit, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs；

the SRS received from each of the multiple UEs is based at least partly on the group SRS bit sequence.
The eNB according to claim 11, wherein:

the hardware processing circuitry is further configured to transmit, to each of the multiple UEs, a dedicated SRS configuration IE that includes a cyclic shift for the UE；

the SRS received from each of the multiple UEs is further based at least partly on the cyclic shift for the UE； and

the cyclic shifts for at least some of the UEs are different.
The eNB according to claim 1, wherein the SRS-RNTI is reserved for common data blocks included in the PDCCH, the common data blocks intended for multiple UEs.
A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors to perform operations for transmission and reception of signals at an Evolved Node-B (eNB) , the operations to configure the one or more processors to configure the eNB to:

transmit, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs；

apply the SRS-RNTI to a group SRS request to produce a masked group SRS request；

transmit a physical downlink control channel (PDCCH) data block that includes the masked group SRS request； and

receive a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources.
The non-transitory computer-readable storage medium according to claim 14, wherein the reception of the SRS from each of the multiple UEs is performed at a multiple-input multiple-output (MIMO) antenna array to which one or more transceivers included at the eNB are configured to be coupled.
The non-transitory computer-readable storage medium according to claim 14, wherein:

the transmission of the SRS-RNTI to the multiple UEs includes transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs；

the operations further configure the eNB to transmit, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs； and

the SRS received from each of the multiple UEs is based at least partly on the group SRS bit sequence.
A method of transmitting and receiving signals at an Evolved Node-B (eNB) , the method comprising:

transmitting, for reception at multiple User Equipments (UEs) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) for detection of a group SRS request at the UEs；

applying the SRS-RNTI to a group SRS request to produce a masked group SRS request；

transmitting a physical downlink control channel (PDCCH) data block that includes the masked group SRS request； and

receiving a group SRS that includes a sum of an SRS from each of the multiple UEs during a group SRS transmission period and in group SRS frequency resources.
The method according to claim 17, wherein the reception of the SRS from each of the multiple UEs is performed at a multiple-input multiple-output (MIMO) antenna array to which one or more transceivers included at the eNB are configured to be coupled.
The method according to claim 17, wherein:

the transmission of the SRS-RNTI to the multiple UEs includes transmissions of the SRS-RNTI in dedicated control messages for each of the multiple UEs；

the method further comprises transmitting, to the multiple UEs, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UEs； and

the SRS received from each of the multiple UEs is based at least partly on the group SRS bit sequence.
A User Equipment (UE) comprising hardware processing circuitry configured to:

receive, from an Evolved Node-B (eNB) , a sounding reference signal (SRS) radio network temporary identifier (SRS-RNTI) associated with an SRS group that includes the UE and other UEs；

receive a physical downlink control channel (PDCCH) data block that includes a group SRS request；

apply the SRS-RNTI to the PDCCH data block to detect the group SRS request； and

transmit, in response to the detection of the group SRS request, an SRS during a group SRS transmission period and in group SRS frequency resources.
The UE according to claim 20, wherein the application of the SRS-RNTI to the PDCCH data block includes application of the SRS-RNTI to cyclic redundancy check (CRC) bits of the group SRS request.
The UE according to claim 20, wherein the SRS-RNTI is received in a dedicated control message for the UE.
The UE according to claim 20, wherein:

the hardware processing circuitry is further configured to receive, from the eNB, a common Radio Resource Control (RRC) information element (IE) that includes SRS sequence parameters to enable determination of a group SRS bit sequence at the UE； and

the transmitted SRS is based at least partly on the group SRS bit sequence.
The UE according to claim 23, wherein:

the hardware processing circuitry is further configured to receive, from the eNB, a dedicated SRS configuration IE that includes a cyclic shift for the UE；and

the transmitted SRS is further based at least partly on the cyclic shift for the UE.