Reciprocity channel sounding reference signal multiplexing

Abstract

Systems and techniques are disclosed herein for enhancing the efficiency of the available bandwidth between a UE and a base station. The UE transmits sounding reference signals (SRS) to the base station. The base station characterizes the uplink channel based on the received SRS and, using reciprocity, applies the channel characteristics to the downlink channel. In applying the channel characteristics, the base station forms a beam for the UE based on the uplink channel information obtained from the SRS. The UE can include an antenna array, each UE transmits a different SRS, the base station receives these SRSs and uses them to characterize the downlink. Multiple UEs (or a single UE with multiple antennas) transmit SRSs simultaneously and with the same frequency allocation (non-orthogonal), but each UE transmits its own unique SRS. Further, multiple UEs (or a single UE with multiple antennas) can transmit their SRSs with unique time / frequency allocations (orthogonal).

Description

[0001] This application is a divisional application of the invention patent with application number 202010381029.4 and invention title "Reciprocal Channel Sounding Reference Signal Multiplexing", which is a divisional application of the invention patent with application number 201680015185.0 and invention title "A Method and Base Station for Reciprocal Channel Sounding Reference Signal Multiplexing" filed on February 5, 2016.

[0002] Cross-reference and priority requirements of related applications

[0003] This application claims priority and benefit from U.S. non-provisional application No. 14 / 866,778, filed September 25, 2015, and the latter claims benefit from U.S. provisional patent application No. 62 / 133,334, filed March 14, 2015, the entire contents of which are hereby expressly incorporated herein by reference. Technical Field

[0004] In general, this application relates to wireless communication systems, and more specifically, to beamforming downlink messages to a target receiver using channel state information obtained from uplink probe signals in non-orthogonal or orthogonal applications. Background Technology

[0005] Wireless communication networks can include multiple base stations capable of supporting communication between multiple user equipment (UEs). In recent years, the carrier frequencies used for communication between base stations and UEs have continued to increase, including larger bandwidths. To fully utilize these higher frequencies, more antennas are used in the same physical space. However, to make these higher frequency bands useful and approach the same coverage radius as existing technologies (e.g., 2G, 3G, or 4G), more (and more accurate) beamforming gain is required.

[0006] Furthermore, conventional systems employ various types of reference signals with varying fixed structures to provide sufficient measurement and estimation for adaptive multi-antenna operation in both the uplink and / or downlink directions. For example, a Channel State Information Reference Signal (CSI-RS) can be used on the downlink from the base station to assist in beamforming, a UE-specific Uplink Demodulation Reference Signal (DM-RS) can be used to specifically estimate channel information for the uplink, and each UE can use a Sounding Reference Signal (SRS) on the uplink to assist in scheduling (e.g., determining which frequency bands are good or bad for data). No single signal can achieve all of the above functions for a UE.

[0007] Reciprocity describes the ability of a station to use information from one channel (e.g., uplink) (e.g., multipath delay distribution) to determine information about another channel (e.g., downlink). Because existing methods require antenna-specific reference signals (e.g., CSI-RS in the LTE context), reciprocity cannot be used in cellular networks. Furthermore, CSI-RS and other types of signals do not scale well, becoming an increasingly significant problem as the demand for mobile broadband continues to grow. Summary of the Invention

[0008] To provide a basic understanding of the techniques discussed, some aspects of this disclosure are summarized below. This summary is not an exhaustive overview of all anticipated features of this disclosure, nor is it intended to identify key or essential elements of all aspects of this disclosure, or to describe the scope of any or all aspects of this disclosure. Its sole purpose is to present some concepts of one or more aspects of this disclosure in a generalized form as a prelude to the detailed description that follows.

[0009] In one aspect of this disclosure, a method includes: at a base station, receiving a sounding reference signal (SRS) from a user equipment (UE) via an uplink channel; the base station obtaining information about the uplink channel from the SRS and applying the information to a downlink channel; and based on the information obtained from the SRS, transmitting beamforming downlink communication from the base station to the UE via the downlink channel.

[0010] In another aspect of this disclosure, a method for communicating with a base station includes: transmitting multiple sounding reference signals (SRS) from multiple user equipment (UEs), wherein the multiple SRSs are transmitted using non-orthogonal physical resources via respective uplink channels; and receiving beamformed downlink communication from the base station, wherein the beamformed downlink communication is based on information about the uplink channels obtained from the multiple SRSs and applied to the downlink channels.

[0011] In another aspect of this disclosure, a method for communicating with a base station includes: arranging different sounding reference signals (SRS) corresponding to different antennas in a user equipment (UE) including multiple antennas; transmitting different sounding reference signals (SRS) from each of the multiple antennas from the UE; and receiving beamforming downlink communication from the base station, wherein the beamforming downlink communication is based on information obtained from the different SRS corresponding to each of the multiple antennas.

[0012] In another aspect of this disclosure, a method for communicating with a plurality of user equipments (UEs) includes: at a base station, receiving a plurality of sounding reference signals (SRS), wherein one SRS is received from each of the plurality of UEs, wherein each SRS is transmitted from each respective UE using orthogonal physical resources; obtaining information about a corresponding uplink channel from each SRS via the base station, and applying the information to a corresponding downlink channel; and, based on the information obtained from each SRS, transmitting beamforming downlink communication from the base station to each UE via the corresponding downlink channel.

[0013] In another aspect of this disclosure, a method for communicating with a base station includes: transmitting a plurality of narrowband sounding reference signals (SRS) from a user equipment (UE) at different frequency subbands during a subframe; and receiving beamforming downlink communication from the base station based on information obtained from the SRS corresponding to each of the different frequency subbands.

[0014] In another aspect of this disclosure, a base station includes: a transceiver configured to receive a sounding reference signal (SRS) from a user equipment (UE) via an uplink channel; and a processor configured to obtain information about the uplink channel from the SRS and apply the information to a downlink channel, wherein the transceiver is further configured to transmit beamforming downlink communication to the UE via the downlink channel based on the information obtained from the SRS.

[0015] In another aspect of this disclosure, a user equipment includes: multiple antennas; a processor configured to arrange different sounding reference signals (SRS) corresponding to different antennas in the multiple antennas; a transceiver configured to transmit different sounding reference signals (SRS) from each of the multiple antennas to a base station, and to receive beamforming downlink communication from the base station based on information obtained from the different SRS corresponding to each of the multiple antennas.

[0016] In another aspect of this disclosure, a computer-readable medium having program code recorded thereon includes program code comprising: code for enabling a base station to receive a sounding reference signal (SRS) from a user equipment (UE) via an uplink channel; code for enabling the base station to obtain information about the uplink channel from the SRS and apply the information to a downlink channel; and code for enabling the base station to transmit beamforming downlink communication to the UE via the downlink channel based on the information obtained from the SRS.

[0017] In another aspect of this disclosure, a computer-readable medium having program code recorded thereon includes program code comprising: code for causing a user equipment (UE) including multiple antennas to arrange different sounding reference signals (SRS) corresponding to different antennas among the multiple antennas; code for causing the UE to transmit different sounding reference signals (SRS) from each of the multiple antennas to a base station; and code for causing the UE to receive beamforming downlink communication from the base station, the beamforming downlink communication being based on information obtained from the different SRS corresponding to each of the multiple antennas.

[0018] In another aspect of this disclosure, a base station includes: a unit for receiving a sounding reference signal (SRS) from a user equipment (UE) via an uplink channel; a unit for obtaining information about the uplink channel from the SRS and applying the information to a downlink channel; and a unit for transmitting beamforming downlink communication to the UE via the downlink channel based on the information obtained from the SRS.

[0019] In another aspect of this disclosure, a user equipment (UE) including multiple antennas includes: units for arranging different sounding reference signals (SRS) corresponding to different antennas in the multiple antennas; units for transmitting different sounding reference signals (SRS) from each of the multiple antennas to a base station; and units for receiving beamforming downlink communication from the base station, wherein the beamforming downlink communication is based on information obtained from the different SRS corresponding to each of the multiple antennas. Other aspects, features, and embodiments of the invention will become apparent to those skilled in the art after reading the following description of specific, exemplary embodiments of the invention in conjunction with the accompanying drawings. While features of the invention are discussed with respect to certain embodiments and the drawings below, all embodiments of the invention may include one or more of the advantageous features discussed herein. In other words, while one or more embodiments are discussed as having certain advantageous features, one or more of these features may also be used according to the various embodiments of the invention discussed herein. Similarly, while exemplary embodiments are discussed below as device, system, or method embodiments, it should be understood that these exemplary embodiments can be implemented with a wide variety of devices, systems, and methods. Attached Figure Description

[0020] Figure 1 A wireless communication network is illustrated according to various aspects of this disclosure.

[0021] Figure 2 A wireless communication network that uses a probe reference signal to achieve beamforming at the base station is shown.

[0022] Figure 3 An exemplary subframe structure is shown.

[0023] Figure 4 An exemplary frame structure with periodic channel decorrelation for a synchronization subframe system is shown.

[0024] Figure 5 An exemplary frame structure with random channel decorrelation for a synchronization subframe system is shown.

[0025] Figure 6 An exemplary subframe structure for multiplexing SRS from a multi-antenna user equipment is shown.

[0026] Figure 7 An exemplary frame structure for extended-length SRS in low-interference environments is shown.

[0027] Figure 8 An exemplary frame structure for extended-length SRS in high-interference environments is shown.

[0028] Figure 9 This is a flowchart illustrating an exemplary method for channel estimation using uplink sounding reference signals, based on various aspects of this disclosure.

[0029] Figure 10 This is a flowchart illustrating an exemplary method for channel estimation using uplink sounding reference signals, based on various aspects of this disclosure.

[0030] Figure 11 This is a flowchart illustrating an exemplary method for channel estimation using uplink sounding reference signals, based on various aspects of this disclosure.

[0031] Figure 12 This is a flowchart illustrating an exemplary method for channel estimation using uplink sounding reference signals, based on various aspects of this disclosure.

[0032] Figure 13 This is a block diagram of an exemplary wireless communication device (e.g., a user equipment) according to an embodiment of the present disclosure.

[0033] Figure 14 This is a block diagram of an exemplary wireless communication device (e.g., a base station) according to an embodiment of the present disclosure. Detailed Implementation

[0034] The specific embodiments described below with reference to the accompanying drawings are intended merely to describe various configurations and not to indicate that the concepts described herein can be implemented only in these configurations. To provide a thorough understanding of the various concepts, the specific embodiments include certain details. However, it will be apparent to those skilled in the art that these concepts can be implemented without using these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring these concepts.

[0035] The technologies described in this article can be used in various wireless communication networks, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and others. The terms "network" and "system" are often used interchangeably. CDMA networks can implement wireless technologies such as Universal Terrestrial Radio Access (UTRA), CDMA 2000, and others. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. CDMA 2000 covers the IS-2000, IS-95, and IS-856 standards. TDMA networks can implement wireless technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement wireless technologies such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and others. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and its improved version (LTE-A) are new releases of UMTS that adopt E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization called the 3rd Generation Partnership Project (3GPP). CDMA2000 and UMB are described in documents from an organization called the 3rd Generation Partnership Project 2 (3GPP2). The technologies described herein can be used in the wireless networks and wireless technologies mentioned above, as well as other wireless networks and wireless technologies, such as next-generation (e.g., fifth-generation (5G)) networks.

[0036] Embodiments of this disclosure describe systems and techniques for enhancing the efficiency of available bandwidth utilization in wireless communication channels between a UE and a base station. In one embodiment, multiplexing such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), or Space Division Multiple Access (SDMA) can be used to help increase the efficiency of channel resource utilization. One way to implement SDMA or space division multiplexing is by utilizing beamforming. If the device has multiple antennas, it can transmit signals from all antennas simultaneously, while altering the phase of the signals from each antenna to produce constructive and destructive interference. The interference can be calibrated to produce constructive interference in certain directions and destructive interference in all other directions, thereby essentially transmitting a “beam” of information that does not produce interference in any other spatial region. Thus, multiple beams can be transmitted simultaneously in different directions without interference. To successfully perform beamforming, a multi-antenna device uses information about the channel between itself and its intended receiving device to generate a beam that will reach the receiver.

[0037] Therefore, according to embodiments of this disclosure, a base station can utilize channel reciprocity to use channel information obtained from the uplink channel from the UE to the base station for downlink applications. The UE can transmit a sounding reference signal (SRS) to the base station in a single subframe. The base station can then characterize the uplink channel based on the received SRS and, using reciprocity, apply the same channel characteristics back to the downlink channel for that UE. As part of applying this channel information downlink, the base station can form a beam for that UE based on the uplink channel information obtained from the SRS.

[0038] In another embodiment, the UE may include an antenna array (MIMO). In this case, each UE may transmit different SRSs, which the base station receives and subsequently uses for downlink transmissions for each of these antennas (or alternatively, multiple UEs with single antennas can be used to achieve the same effect). For example, multiple UEs (or a single UE with multiple antennas) may transmit SRS simultaneously and at the same frequency allocation (e.g., non-orthogonal), but each UE transmits its own unique SRS (based on a unique scrambling code or interleaving permutation, for example). In another example, multiple UEs (or a single UE with multiple antennas) may transmit their SRS with unique time / frequency allocations (orthogonal).

[0039] Figure 1According to various aspects of this disclosure, a wireless communication network 100 is shown. The wireless communication network 100 may include a plurality of UEs 102 and a plurality of base stations 104. Base station 104 may include evolved Node B (eNodeB). A base station may also be referred to as a base transceiver, Node B, or access point. Base station 104 may be a station communicating with UE 102, and may also be referred to as a base station, Node B, access point, etc.

[0040] Base station 104 communicates with UE 102, as indicated by communication signal 106. UE 102 can communicate with base station 104 via uplink and downlink. Downlink (or forward link) refers to the communication link from base station 104 to UE 102. Uplink (or reverse link) refers to the communication link from UE 102 to base station 104. Furthermore, base stations 104 can also communicate directly or indirectly with each other via wired and / or wireless connections, as indicated by communication signal 108.

[0041] UE 102 can be distributed throughout wireless network 100, as shown in the figure. Each UE 102 can be stationary or mobile. UE 102 can also be referred to as a terminal, mobile station, user unit, etc. UE 102 can be a cellular phone, smartphone, personal digital assistant, wireless modem, laptop computer, tablet computer, etc. Wireless communication network 100 is an example of a network used in various aspects of this disclosure.

[0042] Each base station 104 can provide communication coverage for a specific geographic area. In 3GPP, the term "cell," depending on the context in which it is used, can refer to a specific geographic coverage area of ​​a base station and / or a base station subsystem serving that coverage area. In this respect, base station 104 can provide communication coverage for macro cells, pico cells, femtocells, and / or other types of cells. Macro cells typically cover a relatively large geographic area (e.g., a radius of several kilometers), allowing unrestricted access for UEs with service subscriptions to a network provider. Pico cells typically cover a relatively small geographic area, allowing unrestricted access for UEs with service subscriptions to a network provider. Furthermore, femtocells can also typically cover a relatively small geographic area (e.g., a home), providing restricted access to UEs associated with that femtocell (e.g., UEs in a closed user group (CSG), UEs for users in a home, etc.) in addition to unrestricted access. A base station used for a macro cell can be called a macro base station. A base station used for a pico cell can be called a pico base station. A base station used for a femtocell can be called a femtocell or a home base station.

[0043] exist Figure 1In the examples shown, base stations 104a, 104b, and 104c are examples of macro base stations used to cover areas 110a, 110b, and 110c, respectively. Base stations 104d and 104e are examples of pico and / or femto base stations used to cover areas 110d and 110e, respectively. It should be understood that base station 104 can support one or more (e.g., two, three, four, etc.) cells.

[0044] Wireless network 100 may also include relay stations. A relay station is a station that receives data and / or other information transmissions from upstream stations (e.g., base stations, UEs, etc.) and transmits the same data and / or other information to downstream stations (e.g., another UE, another base station, etc.). A relay station may also be a UE used to relay transmissions to other UEs. A relay station may also be called a relay base station, a relay UE, a repeater, etc.

[0045] Wireless network 100 can support synchronous or asynchronous operation. For synchronous operation, base stations 104 can have similar frame timing, and transmissions from different base stations 104 are approximately aligned in time. For asynchronous operation, base stations 104 can have different frame timing, and transmissions from different base stations 104 are not aligned in time.

[0046] In some implementations, the wireless network 100 uses Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and Single-Carrier Frequency Division Multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide the system bandwidth into multiple (K) orthogonal subcarriers, which are often also referred to as tones, frequency points, etc. Data can be used to modulate each subcarrier. Typically, OFDM is used in the frequency domain and SC-FDM is used in the time domain to transmit modulation symbols. The spacing between adjacent subcarriers can be fixed, and the total number of subcarriers (K) depends on the system bandwidth. For example, for system bandwidths of 1.4, 3, 5, 10, 15, or 20 MHz, K can be equal to 72, 180, 300, 600, 900, or 1200, respectively. Furthermore, the system bandwidth can also be divided into subbands. For example, a subband can cover 1.08MHz, and for the corresponding system bandwidths of 1.4, 3, 5, 10, 15, or 20MHz, there can be 1, 2, 4, 8, or 16 subbands.

[0047] See now Figure 2 The diagram illustrates what can be used to enhance one or more UEs 102 and one or more base stations 104 (as shown above). Figure 1 Examples of systems demonstrating efficient use of available bandwidth in wireless communication channels between (the systems discussed). For the sake of simplicity, Figure 2A base station 104 and a UE 102 are shown, but it should be understood that embodiments of this disclosure can be extended to multiple UEs 102 and / or base stations 104. UEs 102 and base stations 104 can communicate with each other at various frequencies. For example, in one embodiment, UEs 102 and base stations 104 can communicate at frequencies below 6 GHz, while in another embodiment, they communicate at frequencies above 6 GHz; these are just two examples.

[0048] UE 102 broadcasts a Sounding Reference Signal (SRS) 202 received by base station 104. In one embodiment, SRS 202 may be omnidirectional, while in another embodiment, SRS 202 may be wide-beam transmission. Upon receiving SRS 202, base station 104 can explicitly or implicitly collect channel information for the uplink channel between UE 102 and base station 104 from SRS 202. Subsequently, base station 104 can use this uplink channel information to train its antenna to perform beamforming on downlink 204 destined for the same UE 102.

[0049] To maximize the benefits of reciprocity (by applying channel information obtained from SRS 202 in the uplink), base station 104 can quickly reapply this information (through training) to beamform (or focus) downlink transmissions to UE 102, minimizing the effects of channel decorrelation. To facilitate the rapid reapplication of this channel information in the downlink, embodiments of this disclosure use a short subframe structure. See now. Figure 3 The figure illustrates an exemplary subframe structure 300 that operates within short time frames to minimize the effects of decorrelation in the channel. In one embodiment, the short time frame may be approximately 500 microseconds, but it may also be shorter or longer. This short time frame allows the base station 104 to essentially “freeze” the channel state for the duration of the subframe, during which time the base station 104 can train and form beams for the downlink, subsequently providing downlink bursts.

[0050] In the time domain, the communication between UE 102 and base station 104 can be divided into subframes (SF) 300, for example... Figure 3 The SF 300 shown is illustrated here. For ease of explanation, in... Figure 3A single subframe is shown; it should be understood that the structure of SF 300 can be extended to any number of subframes as needed or desired. Each SF 300 is divided into an uplink (UL) portion 302 and a downlink (DL) portion 304, which are separated by a transition portion U / D. As part of the UL portion 302, UE 102 can transmit various types of signals to base station 104. These may include, for example, SRS (used here to transmit beamforming at the base station, instead of uplink DMRS), uplink data, and optionally requests for information. A transition portion U / D is provided between the UL portion 302 and the DL portion 304. During the DL portion, base station 104 transmits various types of signals to UE 102, including, for example, User Equipment Reference Signals (UERS) and downlink data (e.g., in downlink bursts).

[0051] In some embodiments, base station 104 may use the SRS in UL section 302 to obtain multiple pieces of information that contribute to the downlink between UE 102 and base station 104. For example, based on the SRS, base station 104, which has multiple antennas, can train its antennas to beamform the DL data transmitted back to UE 102, thereby reducing, for example, interference to other wireless communication devices within the range of base station 104. Beamforming relies on information about the channel between UE 102 and base station 104, which base station 104 obtains based on the uplink SRS and then applies to the downlink based on reciprocity. As the channel changes over time (e.g., periodically or randomly), base station 104 can retrain its antennas, for example, based on subsequent SRS received from UE 102. This can occur, for example, if UE 102 is moving, or if other moving objects enter or leave an area that interferes with the uplink (or downlink) channel. According to embodiments of this disclosure, subframe 300 is provided as part of a synchronization system such that subframe 300 is provided repeatedly over time so that base station 104 can retrain beams to adapt to UE 102 movement and channel decorrelation (and / or other effects) associated with that movement.

[0052] Channel reciprocity allows base station 104 to apply information about the channel in the UL direction to estimate one or more channel attributes in the DL direction that can be used for beamforming of DL transmission. In this way, base station 104 can train its antenna based on the SRS from UE 102. Furthermore, the SRS may also include information allowing base station 104 to demodulate data received from UE 102 during the UL portion of SF 300. Additionally, base station 104 can determine, based on the SRS, scheduling information allowing base station 104 to schedule future SF 300 (e.g., frequency band, etc.) for communication with UE 102.

[0053] In some embodiments, multiplexing can be used to allow base station 104 to communicate with multiple UEs 102 during the DL portion 304 of an SF 300. Beamforming can be advantageous because it allows base station 104 to fully utilize spatial multiplexing as well as other types of multiplexing such as frequency multiplexing and / or code multiplexing. Thus, base station 104 can request multiple UEs 102 to transmit SRS during an SF 300, which allows base station 104 to retrain antennas for beamforming for each UE 102 with which it will communicate during the SF 300.

[0054] See now Figure 4 This figure illustrates an example of SF resource allocation for SF 400 in a multi-user MIMO (MU-MIMO) scenario. Figure 4 In the embodiments described herein, for simplicity of discussion, two UEs 102 are referred to as SRS 1 and SRS 2. It should be understood that in various embodiments, more UEs 102 may be included. Each UE 102 in a MU-MIMO system can make each SRS unique by using, for example, permutation or scrambling, thereby transmitting their SRS at the same time and according to the same frequency allocation without conflict (i.e., using non-orthogonal physical resources). In this case, base station 104 can request SRS from multiple UEs 102 during the same SF 400 by sending a request at the beginning of SF 400, during DL portion 402. This request may include information instructing UEs 102 how to scramble or permutate their specific SRS (e.g., SRS 1 for the first UE 102 and SRS 2 for the second UE 102) to avoid interference. Alternatively, UEs 102 may be notified of interference from other UEs 102 and decide to use permutation, scrambling, etc., to utilize non-orthogonal physical resources to transmit SRS. During the UL portion of SF 400, UE 102 may notify base station 104 of the permutation, scrambling, or other method to be used to generate a unique SRS.

[0055] See now Figure 5 , Figure 5 An alternative embodiment is described, in which UE 102 or base station 104 can determine the minimum processing gain (PG) required to compensate for poor channel performance (e.g., when UE 102 is far from base station 104). UE 102 can determine the minimum PG by monitoring the time required to successfully receive a SYNC signal from base station 104. Base station 104 can determine the minimum PG by monitoring the time required to establish a random access channel (RACH) with UE 102.

[0056] To achieve the minimum PG, it may be necessary to extend the length of the SRS beyond the portion of SF500 allocated to UL section 502. Base station 104 may request an extension of the SRS from UE 102 during DL section 504 at the beginning of SF 500 (in... Figure 5 As shown in SF 500, UE 102 may notify base station 104 during UL portion 502 of SF 500 that it needs to transmit an extended SRS. However, as shown in SF 500, UE 102 is still able to use non-orthogonal physical resources to transmit its extended SRS because there is no risk of its low-power signal affecting other UEs 102 in this environment. Therefore, base station 104 does not need to instruct other UEs 102 in this environment to modify their behavior, nor do other UEs 102 in this environment need to actively modify their behavior.

[0057] In another embodiment, a single UE 102 with multiple antennas (e.g., in a single-user MIMO (SU-MIMO) system) can transmit SRS from each of its antennas simultaneously and at the same frequency (i.e., using non-orthogonal physical resources) without collision by using permutations, scrambling, or different precoders for the span antennas to make each SRS of each antenna different from the other SRS of the other antennas. Figure 4 The SF 400 (originally described with reference to a single antenna on multiple UEs 102) illustrates this embodiment because multiple antennas on a single UE 102 are functionally similar to a single antenna on multiple UEs 102. In this case (see now for this alternative embodiment) Figure 4 During the DL section 402 at the beginning of SF 400, base station 104 may notify UE 102 how to generate a unique SRS for each antenna, or UE 102 may select its own unique SRS for each antenna and notify base station 104 what to look for.

[0058] See now Figure 6 The figure illustrates another MU-MIMO embodiment. In this embodiment, multiple UEs 102 (represented as users 1, 2, 3, and 4) can transmit corresponding SRS during the same SF 600. Figure 6In this embodiment, multiple UEs 102 can use a unique set of time and frequency allocations (i.e., using orthogonal physical resources) for the SRS from each corresponding UE 102. This may be necessary when UEs 102 are close to base station 104, resulting in very high power signals (i.e., very high UL signal-to-noise ratio (SNR)) being received at base station 104. Even with scrambling or permutation, such high-power signals can cause interference between each other, so the signals can be allocated to orthogonal physical resources to avoid collisions. These allocations can be contiguous portions of the system bandwidth. Alternatively, these allocations can be spaced between tones to reserve bandwidth between portions used by UEs 102. These allocations do not need to be symmetrical between UEs 102. For example, as shown in SF 600, two non-contiguous spectrum segments (represented by SRS 1 and SRS 2, respectively) can be allocated to the first UE 102 and the second UE 102 in a first time period, while contiguous spectrum blocks (represented by SRS 3 and SRS 4, respectively) can be allocated to the third UE 102 and the fourth UE 102 in a second time period. Typically, one or more contiguous or non-contiguous spectrum blocks can be allocated to UE 102 in one or more contiguous or non-contiguous time periods. Base station 104 can, for example, recognize, based on the very short time required to establish RACH with UE 102, that the power level of the signal received from UE 102 is very high and that orthogonal resources should be used for one or more of UE 102. Therefore, base station 104 can send instructions to UE 102 during the DL portion of SF 600 to allocate physical resources for the SRS of each UE 102. Alternatively, a given UE 102 may, for example, receive a SYNC (synchronization) signal from base station 104 in a very short time, recognize that it has a very high UL SNR, and notify base station 104 of the physical resource allocation required by UE 102 to achieve its SNR. Alternatively, UE 102 may suggest potential allocations to base station 104.

[0059] In another embodiment, a single UE 102 with multiple antennas (e.g., in a SU-MIMO system) can transmit SRS from each of its antennas during the same SF 600 period, but using a unique set of time and frequency allocations (i.e., using orthogonal physical resources). For example, as shown in SF 600, two non-contiguous spectrum segments (represented by SRS 1 and SRS 2, respectively) can be allocated to the first and second antennas of UE 102 in a first time period, while a single contiguous block of spectrum (represented by SRS 3 and SRS 4, respectively) can be allocated to the third and fourth antennas of UE 102 in a second time period. In this case, base station 104 can notify UE 102 of the resource allocation for each antenna during the DL portion 602 at the beginning of SF 600, or UE 102 can select its own resource allocation for each antenna and notify base station 104 what to look for.

[0060] See now Figure 7 This figure illustrates an embodiment of UE 102 with a narrowband power amplifier (PA). To fully utilize channel reciprocity (which allows base station 104 to beamform the DL channel based on UE 102's SRS), the SRS may need to cover the entire system bandwidth. If UE 102 has a narrowband PA, it may only cover one subband of the system bandwidth for any given transmission. As shown in frame structure 700, UE 102 may transmit multiple consecutive narrowband SRSs at interleaved frequencies (which together cover the entire system bandwidth). Base station 104 may collect and combine the multiple consecutive narrowband SRSs to obtain complete information about the system bandwidth of the downlink channel.

[0061] See now Figure 8 According to embodiments of this disclosure, information about a portion of the system bandwidth that is less than the full bandwidth may be sufficient to maintain channel reciprocity. Therefore, UE 102 can transmit only the amount of interleaved narrowband SRS required to reach the threshold for channel reciprocity, as shown in SF structure 800.

[0062] Figure 9 This document illustrates a flowchart of an exemplary method 900 for channel estimation using an uplink sounding reference signal, based on various aspects of this disclosure. Method 900 can be implemented in a base station 104. For simplicity of discussion, method 900 will be described with reference to a single base station 104, but it should be understood that the aspects described herein are applicable to any number of base stations 104. It should be understood that additional method blocks may be provided before, during, and after the blocks of method 900, and some of the blocks described may be substituted or removed for other embodiments of method 900.

[0063] At block 902, base station 104 receives SRS from UE 102 in uplink communication, as described according to the various embodiments above. For example, base station 104 may receive SRS as part of the uplink portion of a subframe, such as... Figure 3 As shown in the illustration. According to various embodiments of this disclosure, base station 102 can receive a single SRS from a single-antenna UE 102, receive multiple SRS corresponding to multiple antennas of a single UE 102, multiple SRS corresponding to a single antenna of multiple UEs 102, and / or multiple SRS corresponding to multiple antennas of multiple UEs 102. Furthermore, according to embodiments, SRS can also be provided to base station 104 based on non-orthogonal or orthogonal SRS.

[0064] At block 904, base station 104 extracts uplink information from the SRS received at block 902. This may include: information useful for demodulating uplink data included in the uplink portion of a subframe, scheduling information, and channel information about the uplink channel.

[0065] At block 906, base station 104 schedules downlink communication (e.g., downlink bursts as part of the downlink portion of a subframe) based on information extracted from SRS at block 904.

[0066] At block 908, base station 104 trains beamforming for one or more antennas of base station 104 based on channel information extracted from SRS received from UE 102. For example, based on this SRS, beamforming can be invariant to several antennas in the system, making embodiments of this disclosure backward compatible with future technologies including more antennas (e.g., 16, 32, etc.) in MIMO arrays.

[0067] At box 910, as part of the same subframe, base station 104 transmits a downlink burst comprising one or more reference signals (e.g., UERS) and downlink data. Using the beamform of the antenna of base station 104 trained based on channel information derived from the uplink SRS and applied to the downlink (by fully utilizing the reciprocity during the short time frame encapsulated by this subframe), base station 104 is able to better improve its utilization of higher frequencies while still providing an equivalent range substantially comparable to low-frequency / evolved technologies (e.g., 2G, 3G, 4G).

[0068] It should be understood that method 900 can be implemented using program code stored on a computer-readable medium. For example, the program code may enable a processor to implement blocks 902-910 after reading the code from a computer-readable medium. In some embodiments, the UE 102 and base station 104 of this disclosure may include such a processor, wherein the program code is stored in the computer-readable medium.

[0069] Now transferred to Figure 10 This figure illustrates a flowchart of an exemplary method 1000 for channel estimation using a non-orthogonal uplink sounding reference signal, according to various aspects of this disclosure. Method 1000 can be implemented in UE 102. The described method 1000 is applicable to a single UE 102 with multiple antennas and multiple UEs 102, each with a single antenna. It should be understood that additional method blocks may be provided before, during, and after the blocks of method 1000, and some of the blocks described may be replaced or removed for other embodiments of method 1000.

[0070] At box 1002, UE 102 monitors the interference level. For a single UE 102 with multiple antennas, this involves monitoring the interference level of each antenna of that UE 102. For multiple UEs 102, each with a single antenna, this involves each UE 102 monitoring the interference level of its antenna.

[0071] At block 1004, UE 102 (which has multiple antennas) or UE 102 (each with a single antenna) determines whether permutation (interleaving) or scrambling coding will better overcome the interference monitored at block 1002. For example, this could involve UE 102 determining to use non-orthogonal coding (when the UE 102 is power-limited (e.g., low uplink SNR)) or to implement MU-MIMO on the downlink (e.g., when the multiple UEs 102 all have multiple antennas).

[0072] At box 1006, in response to the determination at box 1004, UE 102 uses a unique permutation or scrambling code (as determined at box 1004) to configure SRS for each of its antennas (or, for a single-antenna UE 102, each UE 102 for its respective antenna).

[0073] Using scrambled SRS (for each antenna of MIMO UE 102 or for each antenna of every UE 102, according to an embodiment), at block 1008, UE 102 (for each antenna or for each SRS of every UE 102) transmits the scrambled SRS to base station 104 via the uplink channel. In one embodiment, the full channel bandwidth and the full uplink subframe portion (as referred above) are used. Figure 3 (As discussed) to perform this transmission.

[0074] After base station 104 receives SRS from multiple antennas of UE 102 (or each antenna of UE 102, according to an embodiment) in the uplink portion of a subframe, base station 104 derives channel state information for the uplink channel based on the SRS and applies the derived channel state information to the downlink channel based on reciprocity. This includes training the antennas of base station 104 to beamform for UE 102.

[0075] As a result, at box 1010, UE 102 receives a beamformed downlink burst from base station 104 as part of the downlink portion of the same subframe (at multiple antennas of a single UE 102, or at each antenna of each of multiple UE 102).

[0076] It should be understood that method 1000 can be implemented using program code stored on a computer-readable medium. For example, the program code may enable a processor to implement blocks 1002-1010 after reading the code from a computer-readable medium. In some embodiments, the UE 102 and base station 104 of this disclosure may include such a processor, wherein the program code is stored in the computer-readable medium.

[0077] Figure 11 According to various aspects of this disclosure, flowcharts of an exemplary method 1100 for channel estimation using orthogonal uplink sounding reference signals are shown. Method 1100 can be implemented in UE 102. The described method 1100 is applicable to a single UE 102 with multiple antennas and multiple UEs 102, each with a single antenna. It should be understood that additional method blocks may be provided before, during, and after the blocks of method 1100, and some of the blocks described may be replaced or removed for other embodiments of method 1100.

[0078] At box 1102, UE 102 monitors the interference level. For a single UE 102 with multiple antennas, this involves monitoring the interference level of each antenna of that UE 102. For multiple UEs 102, each with a single antenna, this involves each UE 102 monitoring the interference level of its own antenna, as described above. Figure 10 As described.

[0079] At box 1104, UE 102 (which has multiple antennas) or UE 102 (each of which has a single antenna) determines whether the uplink SNR is high enough to allow the SRS to be orthogonal. At this time, different time / frequency combination physical resources are allocated to each SRS at each antenna (whether at a single UE 102 or at multiple UE 102).

[0080] At block 1106, in response to the decision at block 1104, UE 102 configures SRS for each of its antennas using a specific frequency / time combination (or, for a single-antenna UE 102, each UE 102 for its respective antenna). For example, the frequency allocated to each SRS may be continuous with other frequencies allocated to other SRSs, or may span tonal interleaving.

[0081] In cases where different frequency / time physical resources are allocated to the SRS for each antenna of MIMO UE 102 (or for each antenna of each UE 102, according to an embodiment), at block 1108, UE 102 (for each antenna or for each SRS of each UE 102) uses a unique frequency / time physical resource to transmit SRS to base station 104 via the uplink channel.

[0082] After base station 104 receives SRS from multiple antennas of UE 102 (or each antenna of UE 102, according to an embodiment) in the uplink portion of a subframe, base station 104 derives channel state information for the uplink channel based on the SRS and applies the derived channel state information to the downlink channel based on reciprocity. This includes training the antennas of base station 104 to beamform for UE 102.

[0083] As a result, at box 1110, UE 102 receives a beamformed downlink burst from base station 104 as part of the downlink portion of the same subframe (at multiple antennas of a single UE 102, or at each antenna of each of multiple UE 102).

[0084] It should be understood that method 1100 can be implemented using program code stored on a computer-readable medium. For example, the program code may enable a processor to implement blocks 1102-1110 after reading the code from a computer-readable medium. In some embodiments, the UE 102 and base station 104 of this disclosure may include such a processor, wherein the program code is stored in the computer-readable medium.

[0085] Now transferred to Figure 12 This figure illustrates a flowchart of an exemplary method 1200 for channel estimation using an uplink sounding reference signal, according to various aspects of this disclosure. Method 1200 can be implemented in a UE 102 with a narrowband power amplifier. It should be understood that additional method blocks may be provided before, during, and after the blocks of method 1200, and some of the blocks described may be substituted or removed for other embodiments of method 1200.

[0086] At box 1202, UE 102 determines whether the power amplifier is narrowband. As mentioned above, a narrowband power amplifier can cover only one subband of the system bandwidth for any given transmission.

[0087] At block 1204, in response to determining that the power amplifier of UE 102 is narrowband, UE 102 generates and transmits a series of consecutive SRSs interleaved across a large portion or the entire system bandwidth, as part of the uplink portion of a subframe according to the embodiments discussed above, such as... Figure 7 As shown in the figure.

[0088] In response, base station 104 receives consecutive SRS (continuous in time, interleaved in frequency), combines them to obtain a roughly complete view of the uplink channel information. Then, base station 104 uses reciprocity to apply this channel information to the downlink channel and beamforms the antenna accordingly.

[0089] At box 1206, UE 102 receives a beamformed downlink burst from base station 104 as part of the same subframe.

[0090] It should be understood that method 1200 can be implemented using program code stored on a computer-readable medium. For example, the program code may enable a processor to implement blocks 1202-1206 after reading the code from a computer-readable medium. In some embodiments, the UE 102 and base station 104 of this disclosure may include such a processor, wherein the program code is stored in the computer-readable medium.

[0091] Figure 13This is a block diagram illustrating an exemplary wireless communication device 1300 according to an embodiment of the present disclosure. The wireless communication device 1300 may be a UE 102 as discussed above. As shown, the UE 102 may include a processor 1302, a memory 1304, an SRS configuration module 1308, a transceiver 1310 (which includes a modem 1312 and an RF unit 1314), and an antenna 1316. These components may communicate directly or indirectly with each other, for example, via one or more buses.

[0092] Processor 1302 may include: configured to execute the document referenced above. Figure 1 The UE 102 described herein and discussed in more detail above refers to a central processing unit (CPU), digital signal processor (DSP), application-specific integrated circuit (ASIC), controller, field-programmable gate array (FPGA) device, another hardware device, firmware device, or any combination thereof. Specifically, processor 1302 can be used in conjunction with other components of UE 102 (including related information module 1308) to perform various functions associated with orthogonal or scrambled SRS, as described in more detail above. Furthermore, processor 1302 can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, several microprocessors, one or more microprocessors combined with a DSP core, or any other such architecture.

[0093] Memory 1304 may include cache memory (e.g., the cache memory of processor 1302), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory devices, hard disk drives, other forms of volatile and non-volatile memory, or combinations of different types of memory. In one embodiment, memory 1304 includes a non-transitory computer-readable medium. Memory 1304 may store instructions 1306. Instructions 1306 may include, when executed by processor 1302, causing processor 1302 to perform the operations described herein in conjunction with embodiments of this disclosure, referring to UE 102. Instructions 1306 may also be referred to as code. The terms “instruction” and “code” should be interpreted broadly to include any type of computer-readable statement. For example, the terms “instruction” and “code” may refer to one or more programs, routines, subroutines, functions, procedures, etc. "Instructions" and "codes" can include a single computer-readable statement or multiple computer-readable statements.

[0094] SRS configuration module 1308 can be used in various aspects of this disclosure. For example, SRS configuration module 1308 can be used to measure interference at an antenna or antenna set of UE 102. In one embodiment, SRS configuration module 1308 can then determine whether a permutation or scrambling overcomes the measured interference and configure SRS for each antenna using a unique permutation or scrambling. In another embodiment, SRS configuration module 1308 can determine whether it is necessary for SRS transmission to use orthogonal time and frequency resources (i.e., physical channel resources), and it can configure each antenna of UE 102 to use orthogonal time and frequency resources for SRS transmission.

[0095] As shown in the figure, transceiver 1310 may include modem subsystem 1312 and radio frequency (RF) unit 1314. Transceiver 1310 may be configured to communicate bidirectionally with other devices (e.g., base station 104). Modem subsystem 1312 may be configured to modulate and / or encode data from related information 1308 and other aspects of UE 102 (e.g., processor 1302 and / or memory 1304) according to modulation and coding schemes (MCS) (e.g., low-density parity-check (LDPC) coding scheme, turbo coding scheme, convolutional coding scheme, etc.). RF unit 1314 may be configured to process modulated / coded data from modem subsystem 1312 (regarding outbound transmissions) or transmissions originating from another source (e.g., UE 102 or base station 104) (e.g., perform analog-to-digital conversion or digital-to-analog conversion, etc.). Although shown as integrated with transceiver 1310, modem subsystem 1312 and RF unit 1314 can be separate devices coupled together at UE 102 to enable UE 102 to communicate with other devices.

[0096] RF unit 1314 can provide modulated and / or processed data (e.g., data packets (or specifically, data messages containing one or more data packets and other information)) to antenna 1316 for transmission to one or more other devices. For example, this may include, according to embodiments of this disclosure, transmission of… Furthermore, antenna 1316 can also receive data messages transmitted from other devices and provide the received data messages for processing and / or demodulation at transceiver 1310. Although… Figure 13 Antenna 1316 is shown as a single antenna, but antenna 1316 may include multiple antennas with similar or different designs in order to maintain multiple transmission links.

[0097] Figure 14According to this disclosure, a block diagram of an exemplary base station 104 is shown. Base station 104 may include a processor 1402, a memory 1404, a beamforming module 1408, a transceiver 1410 (which includes a modem 1412 and an RF unit 1414), and an antenna 1416. These components may communicate directly or indirectly with each other, for example, via one or more buses.

[0098] Processor 1402 may have various features as a particular type of processor. For example, these may include configurations for executing the functions described herein with reference to the above. Figure 1 The CPU, DSP, ASIC, controller, FPGA device, another hardware device, firmware device, or any combination thereof described in the base station 104 are used to describe the operation. The processor 1402 can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, several microprocessors, one or more microprocessors combined with a DSP core, or any other such structure.

[0099] Memory 1404 may include cache memory (e.g., cache memory of processor 1402), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, solid-state memory devices, one or more hard disk drives, memristor-based arrays, other forms of volatile and non-volatile memory, or combinations of different types of memory. In some embodiments, memory 1404 may include non-transitory computer-readable media. Memory 1404 may store instructions 1406. Instructions 1406 may include instructions that, when executed by processor 1402, cause processor 1402 to perform the operations described herein in conjunction with embodiments of this disclosure, referring to base station 104. Furthermore, instructions 1406 may also be referred to as code, wherein code can be broadly interpreted to include any type of computer-readable statement.

[0100] Beamforming module 1408 can be used in various aspects of this disclosure. For example, beamforming module 1408 can involve: extracting information from SRS received by UE 102, and using the extracted information to train beamforming for the downlink between the one or more antennas 1416 and UE 102.

[0101] As shown, transceiver 1410 may include modem subsystem 1412 and radio frequency (RF) unit 1414. Transceiver 1410 may be configured to communicate bidirectionally with other devices (e.g., UE 102 and / or another core network unit). Modem subsystem 1412 may be configured to modulate and / or encode data according to MCS (e.g., LDPC coding scheme, turbo coding scheme, convolutional coding scheme, etc.). RF unit 1414 may be configured to process modulated / coded data from modem subsystem 1412 (regarding outbound transmissions) or transmissions originating from another source (e.g., UE 102) (e.g., performing analog-to-digital conversion or digital-to-analog conversion, etc.). Although shown as integrated with transceiver 1410, modem subsystem 1412 and RF unit 1414 may be separate devices coupled together at base station 104 to enable base station 104 to communicate with other devices.

[0102] RF unit 1414 can provide modulated and / or processed data (e.g., data packets (or more specifically, data messages containing one or more data packets and other information)) to antenna 1416 for transmission to one or more other devices. For example, this may include using beamforming to transmit information to UE 102 according to embodiments of this disclosure. Furthermore, antenna 1416 can also receive data messages transmitted from other devices and provide the received data messages for processing and / or demodulation at transceiver 1410. Although Figure 14 Antenna 1416 is shown as a single antenna, but antenna 1416 may include multiple antennas with similar or different designs in order to maintain multiple transmission links.

[0103] Information and signals can be represented using any of a variety of different techniques and methods. For example, the data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0104] A general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, or any combination thereof, used to perform the functions described herein, may be used to implement or execute the various exemplary blocks and modules described in conjunction with the disclosure herein. The general-purpose processor may be a microprocessor, or it may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, several microprocessors, one or more microprocessors combined with a DSP core, or any other such architecture).

[0105] The functions described herein can be implemented in hardware, processor-executed software, firmware, or any combination thereof. When implemented in processor-executed software, these functions can be stored on a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Other examples and implementations also fall within the scope of this disclosure and its appended claims. For example, due to the nature of software, the functions described above can be implemented using processor-executed software, hardware, firmware, hardware wiring, or any combination thereof. Features used to implement the functions can be physically located in multiple locations, including distributed ones, such that portions of the functions are implemented in different physical locations. Furthermore, as used herein (including the claims), the word "or" as used in a list item (e.g., "or" used in list items ending with phrases such as "at least one of" or "one or more of") indicates an inclusive list, such that, for example, the list [at least one of A, B, or C] means: A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0106] As will be understood by those skilled in the art, many improvements, substitutions, and changes can be made to the materials, apparatus, structure, and methods of use of the devices disclosed herein, depending on the specific application at the time, without departing from the spirit and scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the specific embodiments shown and described herein, as they are merely illustrative in nature, but should be fully commensurate with the appended claims and their functional equivalents.

Claims

1. A method for communicating with a base station, comprising: At a user equipment (UE) that includes multiple antennas, different detection reference signals (SRS) are arranged corresponding to different antennas in the multiple antennas. During the uplink period of a subframe, the UE transmits different sounding reference signals (SRS) from each of the multiple antennas, wherein the subframe includes the uplink period and the downlink period, and wherein the SRS transmitted from the antennas of the multiple antennas is extended such that the extended SRS is transmitted during the uplink period of the subframe and during at least a portion of the downlink period of the subframe; and During the downlink period of the subframe, beamforming downlink communication is received from the base station, the beamforming downlink communication being based on information obtained from the different SRS corresponding to each of the multiple antennas.

2. The method according to claim 1, wherein, The SRS includes information for demodulating data transmitted by the UE during the uplink period of the subframe.

3. The method according to claim 1, wherein, Use non-orthogonal physical resources to deploy each SRS.

4. The method according to claim 3, wherein, Each SRS is configured using permutation or scrambling to avoid conflicts with other SRSs corresponding to the multiple antennas.

5. The method according to claim 1, wherein, Use orthogonal physical resources to deploy each SRS.

6. The method according to claim 5, wherein, During one or more time periods of the subframe, one or more blocks of spectrum are allocated to each of the multiple antennas.

7. A user equipment (UE), comprising: Multiple antennas; The processor is configured to arrange different detection reference signals (SRS) corresponding to different antennas in the multiple antennas. as well as The transceiver is configured as follows: During the uplink period of a subframe, different Sounding Reference Signals (SRS) are transmitted from each of the multiple antennas to the base station, wherein the subframe includes the uplink period and the downlink period, and wherein the SRS transmitted from the antennas of the multiple antennas is extended such that the extended SRS is transmitted during the uplink period of the subframe and during at least a portion of the downlink period of the subframe. During the downlink period of the subframe, beamforming downlink communication is received from the base station, the beamforming downlink communication being based on information obtained from the different SRS corresponding to each of the multiple antennas.

8. The user equipment according to claim 7, wherein, The SRS includes information for demodulating data transmitted by the UE during the uplink period of the subframe.

9. The user equipment according to claim 7, wherein, Use non-orthogonal physical resources to deploy each SRS.

10. The user equipment according to claim 9, wherein, Each SRS is configured using permutation or scrambling to avoid conflicts with other SRSs corresponding to the multiple antennas.

11. The user equipment according to claim 7, wherein, Use orthogonal physical resources to deploy each SRS.

12. The user equipment according to claim 11, wherein, During one or more time periods of the subframe, one or more blocks of spectrum are allocated to each of the multiple antennas.

13. A computer-readable medium having program code recorded thereon, the program code comprising: Code for enabling a user equipment (UE) including multiple antennas to arrange different detection reference signals (SRS) corresponding to different antennas in the multiple antennas; Code for enabling the UE to transmit different Sounding Reference Signals (SRS) from each of the multiple antennas to the base station during the uplink period of a subframe, wherein the subframe includes the uplink period and the downlink period, and wherein the SRS transmitted from the antennas of the multiple antennas is extended such that the extended SRS is transmitted during the uplink period of the subframe and during at least a portion of the downlink period of the subframe; and Code for enabling the UE to receive beamforming downlink communication from the base station during the downlink period of the subframe, the beamforming downlink communication being based on information obtained from the different SRS corresponding to each of the multiple antennas.

14. The computer-readable medium according to claim 13, wherein, The SRS includes information for demodulating data transmitted by the UE during the uplink period of the subframe.

15. The computer-readable medium according to claim 13, wherein, Use non-orthogonal physical resources to deploy each SRS.

16. The computer-readable medium of claim 15, wherein, Each SRS is configured using permutation or scrambling to avoid conflicts with other SRSs corresponding to the multiple antennas.

17. The computer-readable medium according to claim 13, wherein, Use orthogonal physical resources to deploy each SRS.

18. The computer-readable medium of claim 17, wherein, During one or more time periods during the subframe, one or more blocks of spectrum are allocated to each of the multiple antennas.

Images