KR20140091686A - Srs optimization for coordinated multi-point transmission and reception - Google Patents

Abstract

 Certain aspects of the present disclosure relate to techniques for power control and SRS multiplexing for cooperative multi-point (CoMP) transmission and reception in heterogeneous networks (HetNet). Multiple SRS processes are supported with different physical and / or virtual cell IDs. Different power control offsets and procedures are associated with different SRS processes.

Description

[0001] SRS OPTIMIZATION FOR COORDINATED MULTI-POINT TRANSMISSION AND RECEPTION FOR COORDINATE MULTIPOINT TRANSMISSION AND RECEPTION [0002]

35 U.S.C. Priority claim under §119

This patent application claims priority from U.S. Provisional Application No. 61 / 542,669, filed October 3, 2011, entitled " SRS OPTIMIZATION FOR COORDINATED MULTI-POINT TRANSMISSION AND RECEPTION ", which application is assigned to the assignee of the present invention And are hereby expressly incorporated herein by reference.

Certain aspects of the present disclosure generally relate to wireless communications, and more particularly to techniques for power control and user multiplexing during cooperative multi-point (CoMP) transmission and reception in heterogeneous networks (HetNet).

Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multi-access networks capable of supporting multiple users by sharing available network resources. Examples of such multiple-access networks include, but are not limited to, code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) SC-FDMA) networks.

A wireless communication network may include multiple base stations (BSs) capable of supporting communication for multiple user equipments (UEs). The UE may communicate with the base station on the downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.

The base station may transmit data and control information to the UE on the downlink and / or receive data and control information on the uplink from the UE. On the downlink, transmissions from base stations may suffer interference due to transmissions from neighboring base stations. On the uplink, transmission from the UE may cause interference to transmissions from other UEs communicating with neighboring base stations. Interference can degrade the performance of both the downlink and the uplink.

Certain aspects of the present disclosure provide a method for wireless communication by a user equipment (UE). Transmitting the intended first sounding reference signal (SRS) to a first one or more base stations currently serving the UE and associated with a first cell identifier, transmitting the first sounding reference signal (SRS) Transmitting the intended second SRS to one or more base stations of the first and second SRSs, and adjusting the transmit power of the first and second SRS using discrete power control schemes.

Certain aspects of the present disclosure provide a method for wireless communication by a base station. The method includes configuring a UE to transmit a first sounding reference signal (SRS), which is generally presently serving a user equipment (UE) and intended for a first one or more base stations associated with a first cell identifier, Configuring the UE to transmit a second SRS intended for a second one or more base stations associated with a second cell identifier and for controlling the transmission power of the first and second SRS using separate power control schemes And transmitting one or more transmit power control (TPC) commands.

Certain aspects of the present disclosure provide a device for wireless communication by a user equipment (UE). The apparatus generally includes at least one processor and a memory coupled to the at least one processor, wherein the at least one processor is operative to determine, for the first one or more base stations currently serving the UE and associated with the first cell identifier, Transmitting the first SRS that is intended for the second one or more base stations associated with the second cell identifier, transmitting the second SRS intended for the second one or more base stations associated with the second cell identifier, And adjust the transmission power of the SRS.

Certain aspects of the present disclosure provide an apparatus for wireless communication by a first base station. The apparatus generally includes at least one processor and a memory coupled to the at least one processor, wherein the at least one processor is a first one or more base stations currently serving a user equipment (UE) Configure the UE to transmit the intended first sounding reference signal (SRS) to the second cell identifier, configure the UE to transmit the intended second SRS to the second one or more base stations associated with the second cell identifier And to transmit one or more transmit power control (TPC) commands for the UE to adjust the transmit power of the first and second SRS using discrete power control schemes.

Certain aspects of the present disclosure provide a computer program product comprising a computer-readable medium having stored thereon instructions. The instructions typically send a first sounding reference signal (SRS) intended for the first one or more base stations currently serving the UE and associated with the first cell identifier, and a second one associated with the second cell identifier And to control the transmit power of the first and second SRSs using separate power control schemes and to transmit the intended second SRS to the base stations.

Certain aspects of the present disclosure provide a computer program product comprising a computer-readable medium having stored thereon instructions. The instructions generally configure the UE to transmit a first sounding reference signal (SRS) intended for a first one or more base stations currently serving a user equipment (UE) and associated with a first cell identifier, Configuring the UE to transmit a second SRS intended for the second one or more base stations associated with the identifier and using one or more transmissions to the UE to adjust the transmit power of the first and second SRS using separate power control schemes And is executable by one or more processors to transmit power control (TPC) commands.

1 is a block diagram conceptually illustrating an example of a wireless communication network in accordance with certain aspects of the present disclosure.
2 is a block diagram conceptually illustrating an example of a frame structure of a wireless communication network, in accordance with certain aspects of the present disclosure.
2A illustrates an exemplary format for an uplink in long term evolution (LTE), in accordance with certain aspects of the present disclosure.
3 illustrates a block diagram conceptually illustrating an example of communication between a Node B and a user equipment device (UE) in a wireless communication network in accordance with certain aspects of the present disclosure.
Figure 4 illustrates an exemplary heterogeneous network (HetNet) according to certain aspects of the present disclosure.
Figure 5 illustrates an exemplary resource partition in a heterogeneous network, in accordance with certain aspects of the present disclosure.
6 illustrates an exemplary collaborative partitioning of subframes in a heterogeneous network, in accordance with certain aspects of the present disclosure.
7 is a diagram illustrating a range extended cell area in a heterogeneous network.
Figure 8 is a diagram illustrating a network with macro eNBs and remote radio heads (RRHs), in accordance with certain aspects of the present disclosure.
FIG. 9 is a diagram illustrating an exemplary sounding reference signal (SRS) enhancement, in accordance with aspects of the present disclosure.
10 is a diagram illustrating another exemplary sounding reference signal (SRS) enhancement, in accordance with aspects of the present disclosure.
FIG. 11 illustrates exemplary operations 1100 performed at a user equipment (UE), in accordance with certain aspects of the present disclosure.
12 illustrates exemplary operations 1200 performed in a base station (e.g., and eNB) in accordance with certain aspects of the present disclosure.

Aspects of the present disclosure provide techniques that can enhance sounding reference signal (SRS) procedures for use in Cooperative Multipoint (CoMP) systems. As will be described in greater detail below, UEs involved in CoMP operations can be configured to transmit two different sets of SRS signals. For example, a first set of SRSs may be intended only for a serving cell, while a second set of SRSs may be intended for co-reception of multiple cells.

The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms "system" and "network" are often used interchangeably. CDMA networks may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), cdma2000, and the like. UTRA technology includes wide band CDMA (WCDMA) and other variants of CDMA. CDMA2000 covers IS-2000, IS-95 and IS-856 standards. The TDMA network may implement radio technology such as Global System for Mobile Communications (GSM). The OFDMA network may be used in a wide variety of applications such as bulb UTRA, UMB, IEEE 802.11, And so on. UTRA and E-UTRA are part of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS using E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from the organization named as "3rd Generation Partnership Project (3GPP) ". CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2 (3GPP2) ". The techniques described herein may be used for the wireless networks and radio technologies described above as well as for other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in most of the following descriptions.

Figure 1 illustrates a wireless communication network 100 that may be an LTE network. The wireless network 100 may include a plurality of these bulged Node Bs (eNBs) 110 and other network entities. The eNB may be a station that communicates with user equipment (UEs), and may also be referred to as a base station, a Node B, an access point, and so on. Each eNB 110 may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" may refer to an eNB's coverage area and / or an eNB subsystem that serves this coverage area, depending on the context in which the term is used.

The eNB may provide communication coverage for macro cells, picocells, femtocells, and / or other types of cells. The macrocell covers a relatively large geographic area (for example, a radius of several kilometers) and may allow unrestricted access by UEs subscribed to the service. The picocell will cover a relatively small geographic area and may allow unrestricted access by UEs subscribed to the service. The femtocell will cover a relatively small geographic area (e. G., Home), and may be used by UEs associated with the femtocell (e.g., UEs in a closed subscriber group (CSG) UEs, etc.). ≪ / RTI > An eNB for a macro cell may be referred to as a macro eNB (i.e., a macro base station). The eNB for the picocell may be referred to as a pico eNB (i.e., pico base station). An eNB for a femtocell may be referred to as a femto eNB (i.e., femto base station) or a home eNB. In the example shown in Figure 1, the eNBs 110a, 110b, and 110c are macro eNBs for the macrocells 102a, 102b, and 102c, respectively. The eNB 110x may be a pico eNB for the pico cell 102x. The eNBs 110y and 110z may be femto eNBs for the femtocells 102y and 102z, respectively. The eNB may support one or more (e.g., three) cells.

The wireless network 100 may also include relay stations. The relay station receives a transmission of data and / or other information from an upstream station (e.g., eNB or UE) and transmits a transmission of data and / or other information to a downstream station (e.g., UE or eNB) Station. The relay station may also be a UE relaying transmissions to other UEs. In the example shown in FIG. 1, relay station 110r may communicate with eNB 110a and UE 120r to facilitate communication between eNB 110a and UE 120r. The relay station may also be referred to as a relay eNB, a relay, and so on.

The wireless network 100 may be a heterogeneous network that includes different types of eNBs, e.g., macro eNBs, pico eNBs, femto eNBs, relays, and the like. These different types of eNBs may have different transmission power levels in the wireless network 100, different coverage areas, and different impacts on interference. For example, macro eNBs may have a high transmit power level (e.g., 20 watts) while pico eNBs, femto eNBs, and relays may have lower transmit power levels (e.g., 1 watt) Lt; / RTI >

The wireless network 100 may support synchronous or asynchronous operation. In the case of synchronous operation, the eNBs may have similar frame timing, and transmissions from different eNBs may be approximately temporally aligned. In the case of asynchronous operation, the eNBs may have different frame timings and transmissions from different eNBs may not be temporally aligned. The techniques described herein may be used for synchronous or asynchronous operations.

The network controller 130 may be coupled to a set of eNBs and may provide coordination and control for these eNBs. The network controller 130 may communicate with the eNBs 110 via a backhaul. eNBs 110 may also communicate with each other indirectly or directly via, for example, a wired backhaul or a wireless backhaul.

The UEs 120 may be interspersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a terminal, a mobile station, a subscriber unit, a station, and so on. The UE may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless telephone, a wireless local loop (WLL) The UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, and the like. In Figure 1, a solid line with double arrows indicates the desired transmissions between the UE and the serving eNB, and the serving eNB is an eNB designed to serve the UE on the downlink and / or uplink. A dotted line with double arrows indicates the interfering transmissions between the UE and the eNB. In certain aspects, the UE may include an LTE Release 10 UE.

LTE utilizes 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 also commonly referred to as tones, bins, and the like. Each subcarrier may be modulated with data. In general, modulation symbols are transmitted in the frequency domain using OFDM and in the time domain using SC-FDM. The space between adjacent subcarriers can be fixed, and the total number of subcarriers (K) can be dependent on the system bandwidth. K may be equal to 128, 256, 512, 1024, or 2048 for a system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth can also be divided into sub-bands. For example, a subband may cover 1.08 MHz and may have 1, 2, 4, 8 or 16 subbands, respectively, for a system bandwidth of 1.25, 2.5, 5, 10, Can exist.

2 shows a frame structure used in LTE. The transmission time line for the downlink may be divided into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be divided into 10 subframes with indices of 0 to 9. Each subframe may include two slots. Thus, each radio frame may comprise 20 slots with indices of 0 to 19. Each slot consists of L symbol periods, for example L = 7 symbol periods in the case of a normal cyclic prefix (as shown in FIG. 2) or L = 6 symbol periods in the case of an extended cyclic prefix Lt; / RTI > 2L symbol periods in each subframe may be assigned indices of 0 to 2L-1. The available time frequency resources may be divided into resource blocks. Each resource block may cover N subcarriers (e.g., 12 subcarriers) in one slot.

In LTE, the eNB may transmit the main synchronization signal (PSS) and the auxiliary synchronization signal (SSS) for each cell of the eNB. As shown in FIG. 2, the primary and secondary synchronization signals may be transmitted in symbol periods 6 and 5, respectively, of each subframe of subframes 0 and 5 of each radio frame with a normal cyclic prefix. The synchronization signals may be used by the UEs for cell detection and acquisition. The eNB may transmit a physical broadcast channel (PBCH) in symbol periods 0 through 3 of slot 1 of subframe 0. [ The PBCH can carry specific system information.

the eNB may transmit the Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe as shown in FIG. The PCFICH may carry the number of symbol periods (M) used for the control channels, where M may be equal to 1, 2, or 3, and may vary from subframe to subframe. M may also be equal to 4 in the case of a small system bandwidth with fewer than 10 resource blocks, for example. The eNB may transmit a physical HARQ indicator channel (PHICH) and a physical downlink control channel (PDCCH) in the first M symbol periods of each subframe (not shown in FIG. 2). The PHICH may carry information to support Hybrid Automatic Repeat Request (HARQ). The PDCCH may carry control information for downlink channels and information about resource allocation for UEs. The eNB may transmit a physical downlink shared channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink. Various signals and channels in LTE are publicly described in 3GPP TS 36.211 entitled " This Bulb Universal Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation ".

The eNB may transmit the PSC, SSC and PBCH at the center 1.08 MHz of the system bandwidth used by the eNB. The eNB may transmit PCFICH and PHICH over the entire system bandwidth of each symbol period, and these channels are transmitted in each symbol period. The eNB may send the PDCCH to groups of UEs in specific parts of the system bandwidth. The eNB may send the PDSCH to specific UEs in certain parts of the system bandwidth. The eNB can transmit PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to all UEs, transmit a PDCCH in a unicast manner to specific UEs, and transmit PDCCH in a unicast manner to specific UEs Can be transmitted.

Multiple resource elements may be available in each symbol period. Each resource element may cover one subcarrier of one symbol period and may be used to transmit one modulation symbol, which may be a real or a complex value. The resource elements that are not used for the reference signal in each symbol period can be arranged into resource element groups (REGs). Each REG may contain four resource elements in one symbol period. The PCFICH can occupy four REGs that can be spaced approximately equally from the symbol duration 0 to the frequency. The PCFICH may occupy three REGs that may be spread over frequency in one or more configurable symbol periods. For example, all three REGs for PHICH may belong to symbol substrate 0 or may be spread in symbol periods 0, 1 and 2. The PDCCH may occupy 9, 18, 32 or 64 REGs, which may be selected from the available REGs in the first M symbol periods. Only certain combinations of REGs may be allocated for the PDCCH.

The UE may know the specific REGs used for the PHICH and PCFICH. The UE may search for different combinations of REGs for the PDCCH. The number of combinations to be searched is typically less than the number of combinations allowed for the PDCCH. The eNB may send the PDCCH to the UE in any combination of combinations to be searched by the UE.

2A shows an exemplary format 200a for an uplink in LTE. The available resource blocks for the uplink may be divided into a data section and a control section. The control section may be formed at two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to the UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The design of FIG. 2a allows the data section to contain contiguous subcarriers, which allows a single UE to be allocated all adjacent subcarriers of the data section.

The UE may be allocated resource blocks of the control section to transmit control information to the eNB. The UE may also be allocated resource blocks of a data section to transmit data to the eNB. The UE may transmit control information on the physical uplink control channels (PUCCH) 210a and 210b through the allocated resource blocks of the control section. The UE may transmit both data and control information or only data on the physical uplink shared channel (PUSCH) 220a and 220b through the allocated resource blocks of the data section. The uplink transmission may span all of the slots of the subframe as shown in FIG. 2A and may hop for the frequency.

The UE may be within the coverage of multiple eNBs. One of these eNBs may be selected to serve the UE. The serving eNB may be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR), and so on.

The UE may operate in a dominant interference scenario where the UE can observe high interference from one or more interfering eNBs. Dominant interference scenarios can be caused by limited association. For example, in FIG. 1, UE 120y may be close to femto eNB 110y and may have high receive power for eNB 110y. However, the UE 120y may not be able to access the femto eNB 110y due to limited association, and then the macro eNB 110c (shown in Fig. 1) with lower received power or the lower received power <Lt; / RTI > 110z (also not shown in FIG. UE 120y may then observe strong interference from femto eNB 110y on the downlink and may also cause strong interference to eNB 110y on the uplink.

The dominant interference scenario may also occur due to the range extension, which is the scenario in which the UE is connected to the eNB with low path loss and low SNR among all the eNBs detected by the UE. For example, in FIG. 1, UE 120x may detect macro eNB 110b and pico eNB 110x and may have a lower path loss to eNB 110x than eNB 110b. It may be desirable for UE 120x to be connected to pico eNB 110x if the path loss for eNB 110x is lower than the path loss for macro eNB 110b. This may cause less interference to the wireless network for a given data rate for UE 120x.

In an aspect, communication of dominant interference scenarios may be supported by allowing different eNBs to operate on different frequency bands. A frequency band is used for communication and is a band of frequencies that can be given by (i) center frequency and bandwidth, or (ii) low and high frequencies. The frequency band may also be referred to as a band, a frequency channel, or the like. The frequency bands for the different eNBs may be selected such that the strong eNB communicates with its UEs while the UE is able to communicate with the eNBs in a dominant interference scenario. The eNB may be classified as a "weak" eNB or a "strong" eNB based on the power of received signals from the eNB received at the UE (and not based on the transmit power level of the eNB).

Figure 3 shows a block diagram of a base station or eNB 110 and a design of a UE 120 which are either one of the base stations / eNBs of Figure 1 and the UE 120 Lt; / RTI > In the case of a limited association scenario, the eNB 110 may be the macro eNB 110c of FIG. 1 and the UE 120 may be the UE 120y. eNB 110 may also be some other type of base station. The eNB 110 may have T antennas 334a through 334t and the UE 120 may have R antennas 352a through 352r where T? 1 and R? 1 to be.

At the eNB 110, the transmit processor 320 may receive data from the data source 312 and receive control information from the controller / processor 340. The control information may be for PBCH, PCFICH, PHICH, PDCCH, and the like. The data may be for a PDSCH or the like. The transmit processor 320 may process (e.g., encode and symbol map) data and control information to obtain data symbols and control symbols, respectively. The transmit processor 320 may also generate reference symbols for the PSS, SSS and cell-specific reference signals, for example. (TX) multiple-input multiple-output (MIMO) processor 330 may perform spatial processing (e.g., precoding) on data symbols, control symbols, and / And may provide T output symbol streams to T modulators (MOD) 332a through 332t. Each modulator 332 may process a separate output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 332 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. The T downlink signals from the modulators 332a through 332t may be transmitted via the T antennas 334a through 334t, respectively.

At UE 120, antennas 352a through 352r may receive downlink signals from eNB 110 and provide the received signals to demodulators (DEMODs) 354a through 354r, respectively. Each demodulator 353 can condition (e.g., filter, amplify, downconvert, and digitize) the respective received signal to obtain input samples. Each demodulator 354 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 356 may obtain received symbols from all R demodulators 354a through 354r, perform MIMO detection on received symbols if applicable, and provide detected symbols. The receive processor 358 processes (e.g., demodulates, deinterleaves, and decodes) the detected symbols, provides decoded data for the UE 120 to the data sink 360, / Processor < / RTI >

On the uplink, in the UE 120, the transmit processor 364 receives data from the data source 362 (e.g., for the PUSCH) and data from the controller / processor 380 (e.g., for the PUCCH) Control information can be received and processed. The transmit processor 364 may also generate reference symbols for the reference signal. The symbols from transmit processor 364 are precoded by TX MIMO processor 366 if applicable and further processed by modulators 354a through 354r (e.g., for SC-FDM, etc.) eNB < / RTI > At the eNB 110, uplink signals from the UE 120 are received by antennas 334 and demodulated by the demodulators 332 to obtain decoded data and control information transmitted by the UE 120. [ And may be detected by the MIMO detector 336 if applicable and further processed by the receive processor 338. [ The receive processor 338 may provide the decoded data to the data sink 339 and may provide the decoded control information to the controller /

The controllers / processors 340 and 380 can direct the operation at the base station 110 and the UE 120, respectively. Processor 340 / processor 340, receive processor 338 and / or other processors and modules at eNB 110 may perform or instruct operations and / or processes for the techniques described herein have. Memories 342 and 382 may store data and program codes for eNB 110 and UE 120, respectively. Scheduler 344 may schedule the UEs for data transmission on the downlink and / or uplink.

Example Resource Partitioning

According to certain aspects of the present disclosure, when the network supports Enhanced Inter-Cell Coordination (eICIC), the base stations are configured to reduce or eliminate interference by the interfering cells abandoning a portion of their resources You can negotiate resources to cooperate with each other. In accordance with the interference cooperation, the UE can access the serving cell even with severe interference by using the resources produced by the interfering cell.

For example, a femtocell with a closed access mode in the coverage area of an open macrocell (i.e., only a member femto UE can only access the cell in the closed access mode) calculates resources and effectively removes interference, (Within the coverage area of the femtocell) "coverage hole ". By negotiating the femtocell to yield the resources, the macro UE under the femtocell coverage area can continue to access the serving macrocell of the UE using these calculated resources.

In a radio access system using OFDM, such as the bulbed universal terrestrial radio access network (E-UTRAN), the computed resources may be time-based, frequency-based, have. When cooperative resource partitioning is time-based, the interfering cell may simply not use some of the subframes of the time domain. When cooperative resource partitioning is frequency based, the interfering cell can yield subframes in the frequency domain. In the case of a combination of frequency-based and time-based, the interfering cell may yield frequency and time resources.

4 illustrates that even when the macro UE 120y experiences severe interference from the femtocell y, as illustrated by the successive radio links 402, the eICIC may notify the macro UE 120y (e. G. 10 macro UE) as shown in Figure 4 accesses the macro cell 110c. The legacy macro-UE 120u (e.g., the Rel-8 macro-UE as shown in Fig. 4), as illustrated by the broken radio link 404, It may not be possible to access the storage unit 110c. The femto UE 120v (e.g., the Rel-femto UE as shown in Fig. 4) can access the femtocell 110y without any interference problems from the macrocell 110c.

According to certain aspects, networks may support eICIC, where different sets of partitioning information may exist. The first set of these sets may be referred to as semi-static resource partitioning information (SRPI). The second set of these sets may be referred to as adaptive resource partitioning information (ARPI). As the name implies, the SRPI is typically not changed often, and the SRPI may be sent to the UE so that the UE can use the resource partitioning information for the UE's own operations.

For example, resource partitioning may be implemented with frequency division duplexing (FDD) also with 8 ms periodicity (8 subframes) or 40 ms periodicity (40 subframes). According to certain aspects, it can be assumed that frequency division duplexing (FDD) can also be applied so that frequency resources can also be partitioned. For communications over the downlink (e. G., From cell node B to UE), the partitioning pattern may be divided into a plurality of subframes each having a system frame number (SFN) value that is a multiple of an integer N, The first sub-frame of the radio frame). This mapping can be applied to determine resource partitioning information (RPI) for a particular subframe. By way of example, a subframe that has a cooperative resource partition for the downlink (e.g., computed by the interfering cell) may be identified by an index such as:

IndexSRPI_DL = (SFN * 10 + subframe number) mod 8

For the uplink, the SRPI mapping may be shifted by, for example, 4 ms. Thus, an example for the uplink may be as follows.

IndexSRPI_UL = (SFN * 10 + subframe number + 4) mod 8

SRPI can use the following three values for each entry.

U (use): This value indicates that the subframe has been cleaned up from the dominant interference used by this cell (ie, the main interference cells do not use this subframe).

N (not used): This value indicates that the subframe is not to be used.

X (not known): This value indicates that the subframe is not statistically partitioned. The details of the resource usage negotiation between the base stations are unknown to the UE.

Another possible set of parameters for SRPI may be as follows.

U (use): This value indicates that the subframe has been cleaned up from the dominant interference used by this cell (ie, the main interference cells do not use this subframe).

N (not used): This value indicates that the subframe is not to be used.

X (not known): This value indicates that the subframe is not statistically partitioned (the details of the resource usage negotiation between the base stations are unknown to the UE).

C (common): This value can indicate that all cells can use this subframe without resource partitioning. This subframe may experience interference, and thus the base station may be selected to use this subframe only for UEs that do not experience significant interference.

The SRPI of the serving cell may be broadcast over air. In the E-UTRAN, the SRPI of a serving cell may be transmitted in a block of either a master information block (MIB) or a system information block (SIB). The predefined SRPI can be defined based on features of cells, such as macro cells, picocells (with open access) and femtocells (with closed access). In this case, the encoding of SRPI in the system overhead message may result in more efficient broadcasting through the air.

The base station may also broadcast the SRPI of the neighboring cell in the SIB of one of the SIBs. To this end, the SRPI may be transmitted along with its corresponding range of physical cell identifiers (PCIs).

The ARPI may indicate additional resource partition information with detailed information on "X" subframes in the SRPI. As discussed above, detailed information about 'X' subframes is typically known only to base stations, and the UE does not notify it.

Figures 5 and 6 illustrate examples of SRPI allocation in scenarios with macros and femtocells. A, U, N, X, or C is a subframe corresponding to a U, N, X, or C SRPI allocation.

FIG. 7 is a diagram 700 illustrating a range extended cellular region of a dual network. A low power class eNB, such as RRH 710b, may be extended from the cellular region 702 through enhanced cell-to-cell interference cooperation between the RRH 710b and the macro eNB 710a and through interference cancellation performed by the UE 720. [ The extended cell area 703 may be a range extended cell area 703. In enhanced cell-to-cell interference cooperation, the RRH 710b receives information about the interference state of the UE 720 from the macro eNB 710a. Information allows the RRH 710b to serve the UE 720 in the extended cellular region 703 and accepts the handoff of the macro eNB 710a when the UE 720 enters the extended cellular region 703 .

FIG. 8 is a diagram illustrating a network 800 that includes macro nodes and multiple remote radio heads (RRHs) in accordance with certain aspects of the present disclosure. Macro node 802 is connected to RRHs 804, 806, 808 and 810 using optical fibers. In certain aspects, the network 800 may be a homogeneous network or a heterogeneous network, and the RRHs 804-810 may be low power or high power RRHs. In an aspect, the macro node 802 coordinates all scheduling for itself and for RRHs in the cell. The RRHs may be composed of the same cell ID (ID) or different cell IDs as the macro node 802. If the RRHs are configured with the same cell ID, then the macro node 802 and the RRHs can operate as essentially one cell controlled by the macro node 802. [ On the other hand, if the RRHs and the macro node 802 are configured with different cell IDs, then the macro node 802 and the RRHs may inform the UE that all the control and scheduling may remain in the macro node 802, . ≪ / RTI > It should further be appreciated that processing for macro node 802 and RRHs 804, 806, 808, and 810 may not necessarily reside in a macro node. This may also be performed in a centralized manner at some other network device or entity that is associated with macros and RRHs.

As used herein, the term transmission / reception point ("TxP") generally refers to a geographically separated (e.g., Refers to the transmitting / receiving nodes.

In certain aspects, when each of the RRHs share the same cell ID as the macro node 802, control information is transmitted from the macro node 802 or using the CRS from the macro node 802 and all RRHs . The CRS is typically transmitted from each of the transmission points using the same resource elements, so that the signals collide. When each of the transmission points has the same cell ID, the CRS transmitted from each of the transmission points may not be distinguished. In certain aspects, when the RRHs have different cell IDs, the CRS transmitted from each of the TxPs using the same resource elements may or may not collide. Even when the RRHs have different cell IDs and the CRS collides, the advanced UEs can distinguish CRSs transmitted from each of the TxPs using interference cancellation techniques and advanced receiver processing.

In certain aspects, when all transmission points are configured with the same ID and the CRS is transmitted from all transmission points, the appropriate antenna virtualization is performed when there is an unequal number of physical antennas in the transmission macro nodes and / or RRHs . That is, the CRS is transmitted on the same number of CRS antenna ports. For example, if the node 802 and the RRHs 804, 806, and 808 each have four physical antennas and the RRH 810 has two physical antennas, the first antenna of the RRH 810 may include two CRSs Ports and the second antenna of RRH 810 may be configured to transmit using two different CRS ports. Alternatively, in the same deployment case, the macros 802 and RRHs 804, 806 and 808 can only transmit only two CRS antenna ports from the two selected ones of the four transmit antennas per transmission point have. On the basis of these examples, it should be appreciated that the number of antenna ports can be increased or decreased in proportion to the number of physical antennas.

As discussed above, when all the transmit antennas are configured with the same cell ID, the macro node 802 and the RRHs 804-810 can all transmit CRSs. However, if only the macro node 802 transmits the CRS, the AGC problems may cause the RRH to become unusable in the vicinity. In this scenario, CRS-based transmission from macro 802 may be received at low received power, while other transmissions originating from nearby RRH may be received at much higher power. This power imbalance can cause the above AGC problems.

In summary, typically, the difference between the same / different cell ID setups is related to control and legacy problems and other potential operations that rely on CRS. Scenarios with different cell IDs but with a conflicting CRS configuration may have similarities with the same cell ID setups, which by definition have a colliding CRS. Scenarios with different cell IDs but with conflicting CRSs have advantages compared to the same cell ID case where system features / components that are typically subject to cell IDs (e.g., scrambling sequences, etc.) can be more easily distinguished I have.

The exemplary configurations may be applicable to macro / RRH setups having the same or different cell IDs. In the case of different cell IDs, the CRS may be configured to collide, which may lead to scenarios similar to the same cell ID case, but system characteristics according to cell IDs (e.g., scrambling sequences, etc.) And the like.

In certain aspects, the exemplary macro / RRH entity may be provided to separate control / data transmissions within the transmission points of such macro / RRH setup. When the cell ID is the same for each transmission point, the PDCCH may be transmitted with the CRS from either the macro node 802 or from both the macro node 802 and the RRHs 804-810, May be transmitted together with the state low reference signal (CSI-RS). When the cell ID is different for some of the transmission points, the PDCCH may be transmitted with the CRS in each cell IDD group. The CRS transmitted from each cell ID group may or may not collide. UEs may not be able to distinguish CRSs transmitted from multiple transmission points with the same cell ID, but may be transmitted from multiple transmission points with different cell IDs (e.g., using interference cancellation or similar techniques) CRS can be distinguished.

In certain aspects, in the case where all transmission points are configured with the same cell ID, the separation of control / data transmissions may be achieved by transmitting control based on CRS transmissions from all transmission points and transmitting at least one transmission point And a UE transparent manner that associates the UEs. This allows cell splitting for data transmission over different transmission points while maintaining a common control channel. The above-mentioned term "association" refers to the configuration of antenna ports for a particular UE for data transmission. This differs from the association that can be performed in the context of handover. The control may be transmitted based on the CRS as discussed above. Separating control and data may enable a fast reconfiguration of the antenna ports used for data transmission of the UE as compared to going through the handover process. In certain aspects, cross-transmission point feedback may be enabled by configuring the antenna ports of the UE to coincide with the physical antennas of the different transmission points.

In certain aspects, UE-specific reference signals enable this operation (e.g., in the context of LTE-A, Rel-10 and its evolution). CSI-RS and DM-RS are reference signals used in the LTE-A context. The interference estimate may be performed based on CSI-RS muting or may be facilitated by CSI-RS muting. Control capacity problems may exist because the PDCCH capacity may be limited when the control channels are common to all transmission points in the case of the same cell ID setup. The control capacity can be extended by using FDM control channels. A relay PDCCH (R-PDCCH) such as an enhanced PDCCH (e-PDCCH) or its extensions can be used to supplement or increase or replace the PDCCH control channel.

SRS Issues in CoMP Scenarios

In the CoMP design, one challenge is to identify and group transmission points (with UL and / or DL CoMP sets) that participate in CoMP operations with minimal overhead. The SRS channel is mainly used for UL channel sounding. In the context of CoMP, SRS is often used to identify the cell closest to the UE. The current LTE SRS channel in Release 8-10 is designed without many considerations for CoMP operations. As a result, existing CoMP designs can result in dimensional constraints or design complexity in the case of various CoMP scenarios.

Aspects of the present disclosure provide techniques that can enhance sounding reference signal (SRS) procedures for use in Cooperative Multipoint (CoMP) systems. As will be described in greater detail below, UEs participating in CoMP operations can be configured to transmit two different sets of SRS signals. For example, the first set of SRSs may be intended only for serving cells, while the second set of SRSs may be intended for co-reception of multiple cells.

Sounding reference signals (SRS) are transmitted on the uplink by the UE, causing the receiving nodes to estimate the quality of the channel at different frequencies. In the CoMP system, the SRS may cause the receiving nodes to determine the closest transmission point, e.g., to dynamically switch transmission points serving the UE via the uplink or downlink. The techniques presented herein may be applied to periodic SRS (e.g., SRS transmissions scheduled to be sent periodically) and aperiodic SRS (e.g., single SRS transmissions triggered by downlink transmissions).

The SRS is used by the base station to estimate the quality of the uplink channel for large bandwidths outside the interval allocated to a particular UE. These measurements can not be obtained with the auxiliary reference signal DRS because they are always associated with the physical uplink shared channel (PUSCH) and the physical uplink control channel (PUCCH) and are limited to the UE allocated bandwidth. Unlike DRS associated with physical uplink control and shared channels, the SRS is not necessarily transmitted on any physical channel. If the SRS is transmitted on a physical channel, the SRS can be stretched over a larger frequency band. The information provided by the estimates is used to schedule uplink transmissions on resource blocks of good quality.

The SRS is typically transmitted from the UE with a cell ID (e.g., PCI of the serving cell) detectable by a given transmission point. However, as used herein, a UE may transmit two sets of SRSs using different cell IDs.

The pico eNB may have its own physical cell identification (PCI) or cell ID along with the X2 connection to the macro eNB. The pico eNB has its own scheduler operation and can be linked to multiple macro eNBs. The RRH may or may not have the same PCI as the macro eNB and may provide good backhaul by having a fiber connection to the macro eNB. In the case of RRH, the scheduler operation can be performed only on the macro eNB side. Femto eNBs may have limited associations, and no consideration has been given to CoMP schemes.

The SRS techniques presented herein may be applied to a number of different downlink (DL) CoMP scenarios. For example, in the first scenario (scenario 1) there may be a homologous development using CoMP in the site. In the second scenario (scenario 2) there may be homogeneous development using high power RRHs connected by fibers.

In the third scenario (scenario 3), the macro eNB and the RRH (s) and / or the pico eNB (s) have different PCIs. In this scenario, the common reference signal CRS, the main synchronization signal PSS, the auxiliary synchronization signal SSS and the physical broadcast channel PBCH are all transmitted from the macro eNB and the pico eNBs. In such a scenario, the cell splitting gain can be easily achieved by scheduling different users for different RRHs, but DL CoMP transmissions based on CSI-RS or CRS require enhanced feedback from the UE.

In the fourth scenario (scenario 4), the macro eNB and the RRH (s) have the same PCI. In one case, only the macro eNB transmits CRS, PSS, SSS and PBCH, while in other cases both macro eNB and RRH transmit CRS, PSS, SSS and PBCH. For RRH with the same cell ID, the macros eNB and RRH effectively form a "super-cell" using centralized scheduling. A single frequency network (SFN) gain can be achieved, but a cell splitting gain can not be achieved. The SRS channel can be used to identify the closest RRH and based on this it is possible to perform cell splitting by transmitting only to the UEs close to the RRHs.

In scenario 3, each RRH will have different PCIs, and the SRS channel from each RRH will have a different configuration, sequence, and so on. For DL CoMP and uplink (UL) CoMP, each RRH will need to try the SRS sent from the other RRHs. Alternatively, in scenario 4, all RRHs will attempt to decode the SRS transmissions of the same UE, with the RRHs having the same PCI. Depending on the received signal strength, DL and UL CoMP sets may be formed. However, the design difficulty is the dimension of the SRS channels, i.e., more UEs can force the SRS channel limitations.

As noted above, aspects of the present disclosure provide techniques that can enhance sounding reference signal (SRS) procedures for use in cooperative multipoint (CoMP) systems. According to the techniques presented here, a UE participating in CoMP operations can be configured to transmit two different sets of SRS signals. For example, a first set of SRSs may be intended only for serving cells, and a second set of SRSs may be intended for co-reception of multiple cells.

For example, one possible enhancement to scenario 3 is for one eNB (macro eNB, RRH, pico eNB, or femto eNB) to allocate its PCI and other PCIs to SRS transmissions. Such PCI may be a virtual or group PCI signaled or exchanged over fiber or X2 connection between all participating nodes. All nodes capable of receiving this SRS may participate in DL or UL CoMP with the UE. For non-CoMP operation, all of the nodes can receive the SRS belonging to the PCI of the asset. Moreover, for DL or UL CoMP operation, each node may receive an SRS belonging to a virtual or group PCI.

Figure 9 illustrates an example of transmitting SRS with group PCI. For example, the UE is served by RRH2 for non-CoMP operation. Therefore, the UE transmits the first SRS together with the PCI of RRH2. However, the UE also sends an SRS (specifying the group PCI) that is mapped to another PCI for possible CoMP operations from RRH1, RRH2, RRH3 and macro eNBs.

10 illustrates another example of transmitting SRS with group PCI. An example illustrates a border situation where a UE is served by one eNB (eNB0), but is on the boundary between eNB0 and another macro eNB (eNB1). In this example, RRH2 has the same PCI as eNB0 (as in Scenario 4), and RRH3 has the same PCI as eNB1. In this situation, the UE can transmit the PCI of the neighboring node (PCI1) in addition to its own PCI (PCI0). The macro eNB0 may schedule the UE to send SRS according to PCI1 as well as PCI0. The macro eNBs, eNB1 and eNB0, can be jointly transmitted or received by the UE.

Using separate power control, SRS For Multiplexing

When the UE is configured by at least two SRS configurations, different SRSs may be multiplexed according to different techniques. For example, the UE may be configured to switch between two SRS configurations utilizing Time Division Multiplexing (TDM). This TDM approach has little or no effect on the peak to average ratio and can therefore be a desirable solution. Alternatively, the UE may be configured to transmit two SRS configurations via frequency division multiplexing (FDM) using different cyclic shifts or different combs, - It is possible to increase the peak-to-average ratio when transmitted in a frame.

During TDM SRS transmission opportunities, one SRS may be intended only for the serving cell (the serving cell's transmission points). Another SRS may be intended for joint reception of multiple cells (transmission points of multiple cells). According to certain aspects, two different power control schemes may be used for different SRS configurations.

For example, the first power control scheme may be referred to as power control scheme A (PC_A) and may include multiple receive points (e.g., four transmit points as shown in FIG. 9) Can be used for SRS targeting. The second power control scheme may be referred to as power control scheme B (PC_B) and may be used for SRS to target a single cell receive point.

The PC_A may cause the SRS that targets multiple cells to be transmitted at a higher power offset than the SRS that only targets the serving transmission points. PC_A can also enable outer loop power control and potentially separate transmit power control (TPC) commands from the PUSCH and PUCCH commands can be used (which means that the transmit power for the SRS is transmitted over the PUSCH and PUCCH It does not need to be tied directly to the power commands).

A PC_B evening control scheme (e.g., RRH2 in the example shown in FIG. 9) that targets serving reception points or points may utilize an offset that is different from the PC_A power control scheme. In this case, the SRS may be transmitted with a different power offset, and the external power control loop may be disabled, and / or PC_B may use the same TPC as the PUSCH and the outer loop different from the different PC_A when the predetermined power off can be used Can be used.

The signaling impact of the enhancements described above is that the eNB needs to signal multiple SRS configurations to the UE. The participating nodes need to exchange information about the intended common SRS configuration for DL CoMP or UL CoMP. There may also be additional signaling to support multiple power control levels for different SRS configurations or alternatively to support delta offset between different SRS configurations.

The effect on the UE transmission is that the UE transmits multiple SRSs using different configurations (time, frequency, shift and comb) and possibly different power offsets. The effect on eNB reception is that the eNB can receive SRS with multiple configurations from the same UE and the eNB can execute multiple power control loops for different SRSs.

In alternate embodiments, three or more SRS configurations may be used by the UE and / or eNBs and RRHs.

FIG. 11 illustrates exemplary operations 1110 performed by a user equipment (UE) in accordance with aspects of the present disclosure. Operations 1100 begin at 1102 with the UE sending a first sounding reference signal (SRS) that is currently serving the UE and intended for one or more base stations associated with the first cell identifier. At 1104, the UE transmits a second SRS intended for joint reception by one or more base stations associated with the second cell identifier. At 1106, the UE adjusts the transmit power of the first and second SRS using separate power control schemes.

12 illustrates exemplary operations 1200 performed by a base station (BS) in accordance with aspects of the present disclosure. Operations 1200 may include transmitting a user equipment (UE) message at 1202 to the BS to send a first sounding reference signal (SRS) intended for one or more base stations currently serving the UE and associated with a first cell identifier Begin by constructing. At 1204, the BS configures the UE to transmit the intended second SRS to the other or a plurality of base stations associated with the second cell identifier. At 1206, the BS transmits one or more transmit power control (TPC) commands to the UE to adjust the transmit power of the first and second SRS using separate power control schemes.

Those skilled in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may refer to voltages, currents, electromagnetic waves, magnetic fields, , Light fields or light particles, or any combination thereof.

Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both . To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented in hardware or software depends upon the design constraints imposed on the particular application and the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array Capable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of an algorithm or method described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integrated into the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal. In general, when the operations illustrated in the figures are present, these operations may have corresponding counterparts with similar numbering + functional components.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted via one or more instructions or code on a computer-readable medium. Computer-readable media includes both communication media and computer storage media including any medium that facilitates the transfer of a computer program from one place to another. The storage medium may be any available media that can be accessed by a general purpose computer or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise any form of computer-readable medium, such as RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, Purpose computer or any other medium which can be accessed by a general purpose processor or a special purpose processor. Also, any connection means is appropriately referred to as a computer-readable medium. For example, if the software is transmitted from a web site, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, Wireless technologies such as coaxial cable, fiber optic cable, twisted pair, DSL, or infrared, radio, and microwave are included within the definition of the medium. The discs and discs used herein may be a compact disc (CD), a laser disc, an optical disc, a digital versatile disc (DVD), a floppy disc, Ray disc in which discs usually reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

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

Claims (38)

A method for wireless communication by a user equipment (UE)
Transmitting an intended first sounding reference signal (SRS) to a first one or more base stations currently serving the UE and associated with a first cell identifier;
Transmitting an intended second SRS to a second one or more base stations associated with a second cell identifier; And
And adjusting transmit power of the first and second SRS using separate power control schemes. 2. The method of claim 1, wherein the UE is configured to periodically transmit at least one of the first and second SRSs. 2. The method of claim 1, wherein the UE is configured to aperiodically transmit at least one of the first and second SRS. 2. The method of claim 1 wherein adjusting the transmit power of the first and second SRS using discrete power control schemes comprises:
Adjusting the first SRS using a first power control scheme; And
Adjusting the second SRS using a second power control scheme; Wherein the first power control scheme allows the first SRS to be transmitted at a different transmit power than the first SRS. 5. The method of claim 4, wherein the first power control scheme utilizes transmit power control (TPC) commands from a base station and an external power control loop. 6. The method of claim 5, wherein the second power control scheme does not use an external power control loop. 6. The method according to claim 5, wherein the TPC commands of the first power control scheme are different from TPC commands applied to different physical uplink channels. 2. The method of claim 1, wherein the second cell identifier comprises a virtual cell identifier associated with a plurality of base stations participating in cooperative multipoint (CoMP) operations with the UE. Lt; / RTI > 2. The method of claim 1, wherein the second cell identifier comprises a cell identifier associated with a neighboring cell. A method for wireless communication by a first base station,
Configuring the UE to send an intended first sounding reference signal (SRS) to a first one or more base stations currently serving the user equipment (UE) and associated with a first cell identifier;
Configuring the UE to send an intended second SRS to a second one or more base stations associated with a second cell identifier; And
(TPC) commands for the UE to adjust the transmit power of the first and second SRS using separate power control schemes. Way. 11. The method of claim 10, wherein the UE is configured to periodically transmit at least one of the first and second SRSs. 11. The method of claim 10, wherein the UE is configured to aperiodically transmit at least one of the first and second SRSs. 11. The method of claim 10, wherein the one or more TPC commands comprise TPC commands utilized in an external power control loop of the first power control scheme. 14. The method of claim 13, wherein the one or more TPC commands further comprise individual TPC commands utilized in an external power control loop of the second power control scheme. 14. The method of claim 13, further comprising transmitting TPC commands applied by the UE to adjust transmit power of one or more other physical uplink channels. 11. The method of claim 10, wherein the second cell identifier comprises a virtual cell identifier associated with a plurality of base stations participating in cooperative multipoint (CoMP) operations with the UE. Way. 11. The method of claim 10, wherein the second cell identifier comprises a cell identifier associated with a neighboring cell. An apparatus for wireless communication by a user equipment (UE)
Means for sending an intended first sounding reference signal (SRS) to a second one or more base stations currently serving the UE and associated with a first cell identifier;
Means for transmitting a second SRS intended for a second one or more base stations associated with a second cell identifier; And
And means for adjusting transmit power of the first and second SRS using separate power control schemes. 19. The apparatus of claim 18, wherein the UE is configured to periodically transmit at least one of the first and second SRSs, the apparatus for wireless communication by a user equipment (UE) 19. The apparatus of claim 18, wherein the UE is configured to aperiodically transmit at least one of the first and second SRSs. 19. The method of claim 18, wherein adjusting the transmit power of the first and second SRS using discrete power control schemes comprises:
Adjusting the first SRS using a first power control scheme; And
And adjusting the second SRS using a second power control scheme; Wherein the first power control scheme allows the first SRS to be transmitted at a different transmit power than the first SRS. 22. The apparatus of claim 21, wherein the first power control scheme utilizes transmit power control (TPC) commands from a base station and an external power control loop. 23. The apparatus of claim 22, wherein the second power control scheme does not employ an external power control loop. 24. The apparatus of claim 22, wherein the TPC commands of the first power control scheme are different from TPC commands applied to different physical uplink channels. 19. The method of claim 18, wherein the second cell identifier comprises a virtual cell identifier associated with a plurality of base stations participating in cooperative multipoint (CoMP) operations with the UE. Lt; / RTI > 19. The apparatus of claim 18, wherein the second cell identifier comprises a cell identifier associated with a neighboring cell. An apparatus for wireless communication by a first base station,
Means for configuring the UE to send a first sounding reference signal (SRS) intended for a first one or more base stations currently serving a user equipment (UE) and associated with a first cell identifier;
Means for configuring the UE to transmit a second SRS intended for a second one or more base stations associated with a second cell identifier; And
And means for transmitting one or more transmit power control (TPC) commands for the UE to adjust transmit power of the first and second SRS using separate power control schemes. . 28. The apparatus of claim 27, wherein the UE is configured to periodically transmit at least one of the first and second SRS. 28. The apparatus of claim 27, wherein the UE is configured to aperiodically transmit at least one of the first and second SRS. 28. The apparatus of claim 27, wherein the one or more TPC commands comprise TPC commands utilized in an external power control loop of the first power control scheme. 32. The apparatus of claim 30, wherein the one or more TPC commands further comprise individual TPC commands utilized in an external power control loop of the second power control scheme. 31. The apparatus of claim 30, further comprising means for transmitting TPC commands applied by the UE to adjust transmit power of one or more other physical uplink channels. 28. The base station of claim 27, wherein the second cell identifier comprises a virtual cell identifier associated with a plurality of base stations participating in cooperative multipoint (CoMP) operations with the UE. Device. 28. The apparatus of claim 27, wherein the second cell identifier comprises a cell identifier associated with a neighboring cell. An apparatus for wireless communication by a user equipment (UE)
At least one processor; And
A memory coupled to the at least one processor;
Wherein the at least one processor comprises:
Transmit an intended first sounding reference signal (SRS) to the first one or more base stations currently serving the UE and associated with a first cell identifier;
Transmit an intended second SRS to a second one or more base stations associated with a second cell identifier; And
And configured to adjust the transmit power of the first and second SRS using separate power control schemes. An apparatus for wireless communication by a first base station,
At least one processor; And
A memory coupled to the at least one processor;
Wherein the at least one processor comprises:
Configure the UE to send a first sounding reference signal (SRS) intended for a first one or more base stations currently serving a user equipment (UE) and associated with a first cell identifier;
Configure the UE to send an intended second SRS to a second one or more base stations associated with a second cell identifier; And
And to transmit one or more TPC commands for the UE to adjust transmit power of the first and second SRS using separate power control schemes. A computer program product comprising a computer readable medium having stored thereon instructions,
The instructions,
Transmit an intended first sounding reference signal (SRS) to the first one or more base stations currently serving the UE and associated with the first cell identifier;
Transmit an intended second SRS to a second one or more base stations associated with a second cell identifier; And
A computer program product executable by one or more processors to adjust the transmit power of the first and second SRS using discrete power control schemes. A computer program product comprising a computer readable medium having stored thereon instructions,
The instructions,
Configure the UE to send a first sounding reference signal (SRS) intended for a first one or more base stations currently serving a user equipment (UE) and associated with a first cell identifier;
Configure the UE to send an intended second SRS to a second one or more base stations associated with a second cell identifier; And
A computer program product, executable by one or more processors, for sending one or more transmit power control (TPC) commands for the UE to adjust transmit power of first and second SRS using discrete power control schemes .

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