Communication of Channel State Information (CSI) for multiple transmission points

Abstract

A wireless communication system is evaluated based on the system's average cell throughput and / or its cell-edge throughput. Cell-edge users experience low received signal strength, and cell-edge performance is affected by inter-cell interference. Frequency reuse makes the system interference-limited when many or all cells transmit simultaneously on many or all time and frequency resources. Power boosting does not improve cell-edge performance because both the serving cell signal strength and the interfering signal strength are increased. [Solution] Embodiments of the present invention contemplate methods and systems for determining and communicating channel state information (CSI) for one or more transmission points (CSI reference signal resources). Embodiments further contemplate that determining a transmission state includes applying at least one transmission state parameter to the channel state information. Embodiments also contemplate reporting CSI based on the transmission state and / or at least one transmission state parameter applied thereto.

Description

[Background technology]

[0001] The present invention relates to the communication of channel state information (CSI) for multiple transmission points.

[0002] Wireless communication systems are evaluated based on the system's average cell throughput and / or its cell-edge throughput. Cell-edge users experience poor received signal strength, and cell-edge performance is affected by inter-cell interference (ICI). This is true for systems designed to operate with a frequency reuse factor of one or close to one. Summary of the Invention [Problem to be solved by the invention]

[0003] Such frequency reuse implies that the system becomes interference-limited when many or all cells may transmit simultaneously on many or all time and frequency resources. Furthermore, power boosting does not improve cell-edge performance because both the serving cell signal strength and the interfering signal strength are increased. [Means for solving the problem]

[0004] A detailed description of exemplary embodiments will now be described with reference to various drawings. While this description provides detailed examples of possible implementations, it should be noted that the details are intended to be illustrative and in no way limit the scope of application. As used herein, the article "a" is understood to mean, for example, "one or more" or "at least one" in the absence of further qualification or characterization.

[0005] Embodiments contemplate methods and systems for communicating transmission states. For example, a method for determining a transmission state includes applying at least one transmission state parameter to channel state information (CSI). The method also includes reporting the CSI based on the transmission state and the at least one transmission state parameter applied thereto, and applying a correction factor to the at least one transmission state.

[0006] Embodiments contemplate a wireless transmit / receive device (WTRU) configured, at least in part, to identify one or more transmission points. The one or more transmission points are configured for channel state information (CSI) reporting. The WTRU is further configured to generate CSI for the one or more transmission points. The WTRU may also be configured to transmit the CSI to one or more nodes in communication with the WTRU. Embodiments contemplate that the one or more transmission points include at least one antenna port in communication with the WTRU. Embodiments also contemplate that the one or more transmission points are CSI reference signal (CSI-RS) resources.

[0007] Embodiments contemplate one or more methods performed by a wireless transmit / receive unit (WTRU). One or more embodiments include identifying K transmission points, the K transmission points configured for channel state information (CSI) reporting, where K is an integer. Embodiments further include generating CSI for one or more of the K transmission points. Further, embodiments include transmitting the CSI to one or more nodes in communication with the WTRU. Also, embodiments include receiving at least one of a CSI reference signal (CSI-RS) or a common reference signal (CRS) transmitted by each of the K transmission points. Embodiments include identifying the K transmission points based at least in part on the received CSI-RS or CRS. In one or more embodiments, generating CSI includes generating at least one of a joint rank indication or a point-wise rank indication for one or more of the K transmission points. In one or more embodiments, generating the CSI includes generating a joint channel quality index (CQI), the joint CQI corresponding to a joint transmission over one or more of the K transmission points.

[0008] An embodiment contemplates a wireless transmit / receive device (WTRU) that, at least in part, identifies one or more transmission points, the one or more transmission points being configured for channel state information (CSI) reporting. The WTRU is configured to determine a transmission state of the one or more transmission points. The WTRU is configured to generate CSI for the one or more transmission points. The WTRU is further configured to receive an indication of a transmission state of each of the one or more transmission points, the indication of the transmission state including one or more of a transmission state, an interference state, a blanked state, or an unknown state. The WTRU is further configured to compare the determined transition state of the one or more transmission points with predetermined transition states of the one or more transmission points. The WTRU is also configured to transmit CSI of each of the one or more communication points to one or more nodes communicating with the WTRU when the transmission state of each of the one or more transmission points is a predetermined transmission state.

[0009] The following detailed description of the disclosed embodiments will be better understood when read in conjunction with the accompanying drawings, in which: For purposes of illustration, there are shown in the drawings exemplary embodiments; however, the subject matter is not limited to the specific elements and instrumentalities disclosed. [Effects of the Invention]

[0010] As described above, the present invention provides a wireless transmit / receive device (WTRU), and one or more methods performed by the WTRU, for communicating channel state information (CSI) for multiple transmission points such that the system is not interference limited and cell-edge performance is improved. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B]1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) used in the communication system shown in FIG. 1A. [Figure 1C] 1B is a system diagram illustrating an example radio access network and a corresponding core network used in the communication system illustrated in FIG. 1A. [Figure 2] FIG. 1 illustrates a non-limiting exemplary periodic feedback reporting sequence consistent with embodiments. [Figure 3A] FIG. 10 illustrates an example CSI-RS port mapping for a normal CP subframe consistent with an embodiment. [Figure 3B] FIG. 1 illustrates four resource element sets consistent with an embodiment. [Figure 4] FIG. 1 illustrates an exemplary wireless device configuration consistent with an embodiment. [Figure 5] FIG. 1 illustrates an exemplary method consistent with an embodiment. [Figure 6] FIG. 1 illustrates an exemplary wireless device configuration consistent with an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] 1A is a diagram of an example communication system 100 in which one or more disclosed embodiments may be implemented. Communication system 100 is a multiple-access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communication system 100 enables the multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, communication system 100 may use one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like. 1A, communications system 100 includes wireless transmit / receive units (WTRUs) 102a, 102b, 102c, and 102d, a radio access network (RAN) 104, a core network 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it should be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, and 102d is any type of device configured to operate and / or communicate in a wireless environment. For example, the WTRUs 102a, 102b, 102c, 102d are configured to transmit and / or receive wireless signals and include user equipment (UE), mobile stations, fixed or mobile subscriber units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, consumer electronics, and the like.

[0013] The communications system 100 also includes a base station 114a and a base station 114b. Each of the base stations 114a, 114b is any type of device configured to interface wirelessly with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the core network 106, the Internet 110, and / or the network 112. For example, the base stations 114a, 114b may be base transceiver stations (BTSs), Node Bs, eNode Bs, Home Node Bs, Home eNode Bs, site controllers, access points (APs), wireless routers, and the like. While the base stations 114a, 114b are each illustrated as a single element, it should be understood that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0014] The base station 114a is part of the RAN 104, which also includes other base stations and / or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, etc. The base station 114a and / or base station 114b are configured to transmit and / or receive radio signals in a particular geographic area (not shown) called a cell. A cell is further divided into cell sectors. For example, the cell associated with the base station 114a is divided into three sectors. Thus, in one embodiment, the base station 114a includes three transceivers, i.e., one transceiver for each sector of the cell. In another embodiment, the base station 114a uses multiple-input multiple-output (MIMO) technology and thus utilizes multiple transceivers for each sector of the cell.

[0015] The base stations 114a, 114b communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0016] More specifically, as noted above, the communications system 100 is a multiple-access system and uses one or more channel access schemes such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a and the WTRUs 102a, 102b, 102c in the RAN 104 implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which establishes the air interface 116 using wideband CDMA (WCDMA). WCDMA includes communications protocols such as High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA includes High-Speed ​​Downlink Packet Access (HSDPA) and / or High-Speed ​​Uplink Packet Access (HSUPA).

[0017] In another embodiment, the base station 114a and the WTRUs 102a, 102b, 102c implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which establishes the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A).

[0018] In another embodiment, the base station 114a and the WTRUs 102a, 102b, 102c implement a radio technology such as IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access, WiMAX), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and the like.

[0019] The base station 114b in FIG. 1A may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity within a localized area, such as a workplace, home, vehicle, campus, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another example, the base station 114b and the WTRUs 102c, 102d implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A, the base station 114b has a direct connection to the Internet 110. Therefore, the base station 114 b does not need to access the Internet 110 via the core network 106 .

[0020] The RAN 104 is in communication with the core network 106, which is any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. For example, the core network 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A , it should be understood that the RAN 104 and / or core network 106 may be in direct or indirect communication with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104 utilizing E-UTRA radio technology, the core network 106 may also be in communication with another RAN (not shown) that utilizes GSM radio technology.

[0021] The core network 106 also serves as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 includes a circuit-switched telephone network that provides plain old telephone service (POTS). The Internet 110 includes a worldwide system of interconnected computer networks and devices that use common communication protocols such as TCP, User Datagram Protocol (UDP), and IP in the Transmission Control Protocol / Internet Protocol (TCP / IP) Internet protocol suite. The networks 112 include wired or wireless communication networks owned and / or operated by other service providers. For example, the network 112 may include another core network connected to one or more RANs, which may use the same RAT as the RAN 104 or a different RAT.

[0022] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 include multi-mode capabilities, i.e., the WTRUs 102a, 102b, 102c, 102d include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102c shown in FIG. 1A is configured to communicate with a base station 114a that uses a cellular-based wireless technology and a base station 114b that uses an IEEE 802.11 wireless technology.

[0023] 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B, the WTRU 102 includes a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and other peripherals 138. It should be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0024] The processor 118 may be a general-purpose processor, a special-purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, and the like. The processor 118 performs signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 is coupled to the transceiver 120, which is coupled to the transmit / receive element 122. While FIG. 1B depicts the processor 118 and the transceiver 120 as separate components, it should be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0025] The transmit / receive element 122 is configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 is an antenna configured to transmit and / or receive RF signals. In another embodiment, the transmit / receive element 122 is an emitter / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In another embodiment, the transmit / receive element 122 is configured to transmit and receive both RF and light signals. It should be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0026] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may use MIMO technology. Thus, in one embodiment, the WTRU 102 includes multiple transmit / receive elements 122 (e.g., multiple antennas) that transmit and receive wireless signals over the air interface 116.

[0027] The transceiver 120 is configured to modulate signals that are transmitted by the transmit / receive element 122 and demodulate signals that are received by the transmit / receive element 122. As noted above, the WTRU 102 has multi-mode capabilities. Thus, the transceiver 120 includes multiple transceivers that enable the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11.

[0028] The processor 118 of the WTRU 102 is coupled to or receives user input data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light emitting diode (OLED) display unit). The processor 118 also outputs user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 accesses information from and stores data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 includes random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 includes a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 accesses information from and stores data in memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0029] The processor 118 is configured to receive power from the power source 134 and distribute and / or control the power to other components in the WTRU 102. The power source 134 is any suitable device that provides power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0030] The processor 118 is coupled to the GPS chipset 136, which is configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to or instead of information from the GPS chipset 136, the WTRU 102 receives location information from base stations (e.g., base stations 114a, 114b) over the air interface 116 and / or determines its location based on the timing of signals being received from multiple nearby base stations. It will be appreciated that the WTRU 102 acquires location information by any suitable location determination method while remaining consistent with an embodiment.

[0031] The processor 118 is further coupled to other peripherals 138, which include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, peripherals 138 include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photos or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth module, a frequency modulation (FM) radio unit, a digital music player, a media player, a video game player module, an internet browser, and the like.

[0032] 1C is a system diagram of the RAN 104 and the core network 106 according to one embodiment. As noted above, the RAN 104 uses E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 is also in communication with the core network 106.

[0033] The RAN 104 includes eNode-Bs 140a, 140b, and 140c, although it should be understood that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 140a, 140b, and 140c each include one or more transceivers that communicate with the WTRUs 102a, 102b, and 102c over the air interface 116. In one embodiment, the eNode-Bs 140a, 140b, and 140c implement MIMO technology. Thus, the eNode-B 140a, for example, uses multiple antennas to transmit wireless signals to and receive wireless signals from the WTRU 102a.

[0034] Each of the eNode-Bs 140a, 140b, 140c is associated with a particular cell (not shown) and is configured to handle radio resource management decisions, handover decisions, scheduling of users on the uplink and / or downlink, and the like. As shown in FIG. 1C, the eNode-Bs 140a, 140b, 140c can communicate with each other over an X2 interface.

[0035] 1C includes a mobility management gateway (MME) 142, a serving gateway 144, and a packet data network (PDN) gateway 146. Although each of the foregoing elements is illustrated as part of the core network 106, it should be understood that any one of these elements may be owned and / or operated by an entity other than the core network operator.

[0036] The MME 142 is connected to each of the eNode-Bs 142a, 142b, 142c in the RAN 104 via an S1 interface and acts as a control node. For example, the MME 142 is responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation / deactivation, selecting a particular serving gateway during initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 142 also provides a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies such as GSM or WCDMA.

[0037] The serving gateway 144 is connected to each of the eNode Bs 140a, 140b, 140c in the RAN 104 via an S1 interface. The serving gateway 144 generally routes and forwards user data packets to and from the WTRUs 102a, 102b, 102c. The serving gateway 144 also performs other functions, such as anchoring the user plane during inter-eNode B handovers, triggering paging when downlink data is available for the WTRUs 102a, 102b, 102c, managing and storing content for the WTRUs 102a, 102b, 102c, and the like.

[0038] The serving gateway 144 is also connected to a PDN gateway 146, which provides the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0039] The core network 106 facilitates communication with other networks. For example, the core network 106 provides the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communication between the WTRUs 102a, 102b, 102c and traditional landline communication devices. For example, the core network 106 includes or communicates with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that acts as an interface between the core network 106 and the PSTN 108. Additionally, the core network 106 provides the WTRUs 102a, 102b, 102c with access to networks 112, which may include other wired or wireless networks owned and / or operated by other service providers.

[0040] The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) system was introduced in 3GPP Release 8 (R8) (LTE Release 8 is referred to herein as LTE R8 or R8-LTE) to support higher data rates and spectral efficiency, among other fundamental reasons. In LTE, transmissions on the uplink are performed using Single Carrier Frequency Division Multiple Access (SC-FDMA). Specifically, SC-FDMA used in the LTE uplink is based on Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) technology. As used herein, the terms SC-FDMA and DFT-S-OFDM are used interchangeably.

[0041] In LTE, a wireless transmit / receive unit (WTRU), alternatively referred to as user equipment (UE), transmits on the uplink using a limited, contiguous set of allocated subcarriers in a frequency division multiple access (FDMA) arrangement, and in some embodiments, perhaps only a limited, contiguous set of allocated subcarriers in a frequency division multiple access (FDMA) arrangement. For example, if the overall orthogonal frequency division multiplexing (OFDM) signal or uplink system bandwidth consists of usable subcarriers numbered 1 through 100, then a first given WTRU may be assigned to transmit on subcarriers 1 through 12, a second WTRU may be assigned to transmit on subcarriers 13 through 24, and so on. While different WTRUs each transmit in, and perhaps only on, a subset of the available transmission bandwidth, an evolved Node B (eNodeB) serving the WTRUs receives a composite uplink signal across the entire transmission bandwidth.

[0042] LTE Advanced (which includes LTE Release 10 (R10) and future releases such as Release 11, and is referred to herein as LTE-A, LTE R10, or R10-LTE) is an enhancement to the LTE standard that provides a fully compliant 4G upgrade path for LTE and 3G networks. LTE-A supports carrier aggregation, and unlike LTE, multiple carriers are allocated to the uplink, downlink, or both.

[0043] Embodiments recognize that coordinated multi-point operation (CoMP) in the downlink refers to a set of possible schemes in which transmissions from multiple geographically separated transmission points are coordinated to improve system performance in terms of cell-edge throughput and / or system throughput. Examples of such schemes include joint transmission, in which multiple points simultaneously transmit information intended for one WTRU, dynamic point selection, in which one of a set of points is dynamically selected for transmission to one WTRU, and coordinated scheduling / coordinated beamforming, in which interference directed toward a WTRU scheduled from a first point is avoided by proper coordination of interfering transmissions from a second point.

[0044] In both LTE and LTE-A, as well as other wireless systems, system performance is evaluated based on average cell throughput and / or cell-edge throughput. While average cell throughput performance can be improved by increasing received signal strength using power boosting techniques, cell-edge users experience low received signal strength, and therefore cell-edge performance is primarily affected by inter-cell interference (ICI). This is particularly true for systems designed to operate with a frequency reuse factor of 1 or close to 1, as contemplated by OFDM-based 4G networks.

[0045] Embodiments contemplate that a wireless system is evaluated based on its average cell throughput and / or cell-edge throughput. Embodiments contemplate improving cell-average and / or cell-edge performance. Average cell performance is improved by increasing received signal strength using power boosting techniques. However, cell-edge users experience low received signal strength, and cell-edge performance is therefore affected by inter-cell interference (ICI). This is particularly prevalent in systems designed to operate with a frequency reuse factor of 1 or close to 1, as contemplated by OFDM-based 4G networks. Such frequency reuse results in a system that becomes particularly interference-limited when all cells transmit simultaneously on many or perhaps all time and frequency resources. Embodiments recognize that power boosting does not improve cell-edge performance because both the serving cell signal strength and the interfering signal strength are likely increased, which increases ICI, for example.

[0046] Embodiments contemplate other techniques used to improve cell-edge performance, such as coordinated multipoint operation (CoMP) transmission and reception. Multipoint transmission and reception embodiments involve transmission or reception from antennas that are not "very close," where "very close" is more than a distance of two to three wavelengths apart, causing most or perhaps all antennas to experience different long-term fading. In such transmission modes, multiple cells or transmission points are combined to improve the signal-to-interference-and-noise ratio (SINR) received at the WTRU.

[0047] Embodiments contemplate that the term "serving cell" is used for a single cell transmitting a Physical Downlink Control Channel (PDCCH) assignment, e.g., as defined in LTE R8 (single cell). Embodiments also contemplate that multiple CoMP categories are used, including joint processing (JP), where data is available at each point in a CoMP cooperating set. In JP embodiments, joint transmission (JT) is used, where a Physical Downlink Shared Channel (PDSCH) transmission is transmitted from multiple points, such as a portion of the CoMP cooperating set or possibly the entire CoMP cooperating set, at a time. Data to a single WTRU is transmitted simultaneously from multiple transmission points, e.g., to improve received signal quality (coherently or non-coherently) and / or actively cancel interference with other WTRUs. Embodiments also contemplate that dynamic cell selection is used in JP, where, e.g., a PDSCH transmission is transmitted from one point in the CoMP cooperating set at a time.

[0048] Another CoMP category is coordinated scheduling / coordinated beamforming (CS / CB), where data is available at the serving cell (i.e., data transmission is performed only from that point), and in some embodiments only at the serving cell, but user scheduling / beamforming decisions are made with coordination between cells corresponding to the CoMP cooperating set.

[0049] Embodiments contemplate that at least one CoMP category includes cell aggregation. Some or each transmission point has independent data to transmit to the WTRU on the same carrier frequency field. Some or each cell has its own data and / or signal flow to and from the WTRU. For example, some or each cell uses independent HARQ processes.

[0050] Embodiments contemplate that one or more CoMP sets include a CoMP cooperating set, where a geographically separated set of points are directly or indirectly participating in PDSCH transmission to the WTRU. This set may or may not be transparent to the WTRU. Another CoMP set is the CoMP transmission point(s), which is a point or set of points that are actively transmitting PDSCH to the WTRU. The set of CoMP transmission point(s) is a subset of the CoMP cooperating set. In a JT embodiment, the CoMP transmission points are points in the CoMP cooperating set. In a dynamic cell selection embodiment, a single point is a transmission point in some subframes, or possibly all subframes. This single transmission point dynamically changes in the CoMP cooperating set. For a CS / CB embodiment, the CoMP transmission point corresponds, for example, to a "serving cell."

[0051] Embodiments contemplate other CoMP sets, including a CoMP measurement set, which is the set of cells for which channel state / statistics information (for the link to the WTRU) is reported. In some embodiments, the CoMP measurement set is identical to the CoMP cooperating set. The actual WTRU report contains feedback for a subset of cells of the CoMP measurement cells, and in some embodiments only includes feedback for a subset of cells of the CoMP measurement cells, called reported cells.

[0052] Embodiments contemplate that channel state information (CSI) feedback is reported in the form of a rank (e.g., rank indicator (RI)), a precoder matrix index (PMI), and / or a channel quality indicator (CQI), where the PMI is calculated at the WTRU, for example, by quantizing the channel against a predefined codebook. The CSI feedback may include CQI / PMI / RI reports and is provided either periodic or aperiodic. Parameters used to control the information reported by the WTRU are based on the system bandwidth and / or are provided in radio resource control (RRC) connection setup, reconfiguration, and / or re-establishment messages. The information reported by the WTRU varies based on the transmission mode, which is defined in the same RRC message. Table 1 includes a summary of example reporting modes contemplated by embodiments.

[0053] [Table 1]

[0054] Although embodiments contemplate that periodic feedback is transmitted on a Physical Uplink Control Channel (PUCCH) channel, when a Physical Uplink Shared Channel (PUSCH) channel is present, periodic feedback is transmitted on that channel. Periodic reporting can use a sequence of one or more different types of reports. Such types include, for example, "Type 1" for reporting subband CQI, "Type 2" for reporting wideband CQI / PMI, "Type 3" for reporting RI, and "Type 4" for reporting wideband CQI. An exemplary reporting sequence is shown in FIG. 2, where the numbers in each rectangle correspond to the report types described above. In one or more embodiments, aperiodic feedback is requested by format 0 downlink control information (DCI) or a random access response (RAR) when the CQI request bit is set. In one or more embodiments, aperiodic feedback is transmitted on a PUSCH channel.

[0055] Embodiments contemplate that the types of periodic PUCCH feedback are further extended for eight transmit (Tx) antenna ports. Such types of periodic PUCCH feedback include a “Type 1” report supporting CQI feedback of a subband selected by the WTRU, a “Type 1a” report supporting subband CQI and second PMI feedback, a “Type 2,” “Type 2b,” and “Type 2c” report supporting wideband CQI and PMI feedback, a “Type 2a” report supporting wideband PMI feedback, a “Type 3” report supporting RI feedback, a “Type 4” report supporting wideband CQI, a “Type 5” report supporting RI and wideband PMI feedback, and a “Type 6” report supporting RI and PTI feedback. CSI feedback, such as that used in LTE R8 and R10, is designed to support single-cell operation and physical downlink shared channel (PDSCH) scheduling. CSI feedback represents the channel between itself and the serving cell and is reported to the serving cell, and in some embodiments, perhaps only to the serving cell.

[0056] Embodiments contemplate one or more WTRU feedback procedures for single-cell downlink operation. Embodiments recognize that for CoMP operation, the WTRU may be required to provide multiple feedbacks containing CSI information for different CoMP cells or transmission points required for various functions such as CoMP set determination, CoMP activation / deactivation, and / or downlink scheduling / beamforming. Multiple feedback configuration embodiments for CoMP implementations are contemplated. One or more embodiments contemplate addressing aspects of both the content and speed of the feedback mechanism.

[0057] Embodiments recognize that some feedback procedures defined up to R10 are optimized for the case where some or all transmission points (or antenna ports) of a cell are geographically close to each other. In deployments utilizing remote radio heads (RRHs), a set of geographically separated RRHs utilizes the same physical cell identity. In this scenario, using a WTRU to report CSI for some or all deployed antenna ports of the same cell using the method of R10 is inefficient because the channel quality of some antenna ports is likely to be much weaker than the channel quality of other antenna ports. Furthermore, signals transmitted from different RRHs have different characteristics that need to be taken into account by the WTRU in evaluating the CSI.

[0058] Embodiments contemplate techniques that enable a WTRU to efficiently report CSI for multiple transmission points. For example, embodiments contemplate techniques that a WTRU uses to efficiently report CSI feedback (e.g., reduce the amount of unnecessary reporting of CSI information). Further, for example, embodiments contemplate methods for a WTRU to evaluate CSI for a set of transmission points that are not geographically co-located.

[0059] Embodiments recognize that the CSI is evaluated and reported assuming that the reference signals are transmitted from a set of closely spaced antennas from the same physical transmission point and, therefore, that these physical transmission points share the same long-term path loss between them and the WTRU. If this assumption is not met, the CSI will not be useful (or optimal) to the network for scheduling. For example, the network will not be able to determine which transmission point or set of transmission points is most appropriate for scheduling a UE in a particular case.

[0060] Embodiments also recognize that the set of transmission points suitable for CoMP operation depends on the location of the WTRU in the cell. Embodiments contemplate one or more techniques for determining the appropriate set(s) of transmission points and / or an associated set of reference signals (e.g., CSI-RS), for example, configured for the WTRU.

[0061] As referred to herein, the phrase "transmission point" refers to any antenna port or a subset of geographically co-located antenna ports from a network that is transmitting to or receiving from a WTRU. The set of transmission points configured or activated for a given WTRU may or may not belong to the same physical cell identity. A transmission point transmits one CSI-RS or a set of CSI-RS. Embodiments contemplate that the phrase "CSI-RS resource" or "non-zero-power CSI-RS resource" refers to a set of CSI-RS reference signals and / or antenna ports transmitted from one transmission point or a set of transmission points. In one or more embodiments, the characteristics of these reference signals are provided to the WTRU by higher layers, such as, for example, RRC signaling. The WTRU is configured with one or more CSI-RS resources for CSI estimation and reporting. The phrase "transmission point" is alternatively used in conjunction with the phrase "CSI-RS resource," and in one or more embodiments, the CSI-RS resource corresponds to the transmission point. The transmission points also transmit at least one common reference signal (CRS), and the WTRU also measures the at least one CRS, eg, for CSI estimation and / or reporting, among other purposes.

[0062] As also referred to herein, a CSI-RS resource is a set of CSI-RS reference signals or antenna ports transmitted from one transmission (or possibly multiple transmission points). Characteristics of these reference signals are provided to the WTRU by higher layers. The WTRU is configured with one or more CSI-RS resources, e.g., for CSI estimation and / or reporting. As explained previously, the expression "transmission point" is replaced by "CSI-RS resource" when it is understood that a CSI-RS resource corresponds to a transmission point. Also, as used herein, a per-point rank indication (RI) corresponds to a recommended number of useful transmission layers (or ranks) for transmission from one transmission point. The per-point RI is equivalently referred to as "per-CSI-RS resource RI" when the associated CSI-RS resource is used for CSI measurements, or "per-CRS" or "per-cell" RI when a CRS is used for CSI measurements.

[0063] Furthermore, as referred to herein, per-point CQI corresponds to a channel quality indicator (CQI) applicable to the transmission of a codeword (or PDSCH transport block) from one transmission point. Per-point CQI is equivalently referred to as "per-CSI-RS-resource CQI" when possibly corresponding CSI-RS resources are used for CSI measurements, or "per-CRS" or "per-cell" CQI when possibly a common reference signal (CRS) is used for CSI measurements.

[0064] As referred to herein, a per-point pre-coding matrix indicator (PMI) or local pre-coding matrix indicator corresponds to a recommended pre-coding matrix (or precoder) for transmission from one transmission point. A per-point PMI is equivalently referred to as a “per-CSI-RS-resource PMI” possibly when the associated CSI-RS resource is used for CSI measurements, or a “per-CRS” or “per-cell” PMI possibly when a CRS is used for CSI measurements. For the same CSI-RS resource or point, embodiments contemplate that there may be multiple pre-coding matrix indicators (e.g., a first pre-coding indicator and a second pre-coding indicator, where the latter changes more quickly over time than the former) that jointly indicate a single pre-coding matrix.

[0065] Also, as referred to herein, a joint rank indication or common rank indication corresponds to a recommended number of useful transmission layers for joint transmission from multiple transmission points, e.g., corresponding to multiple CSI-RS resources.

[0066] An aggregated CQI or joint CQI corresponds to a CQI applicable to joint transmission of codewords from multiple transmission points corresponding to multiple CSI-RS resources. The aggregated CQI is estimated assuming that a certain precoding vector or precoding matrix is ​​used at some or each transmission point corresponding to the CSI-RS resources. The aggregated CQI is also estimated assuming a certain relationship between the precoders used at the transmission points corresponding to these CSI-RS resources. For example, among other possible assumptions, the relative phases between the precoders are assumed to be such that signals from the transmission points are combined coherently (with zero phase difference) or with a predetermined phase difference.

[0067] As referred to herein, aggregated PMI or global PMI corresponds to a recommended precoding matrix for transmissions from multiple transmission points corresponding to multiple CSI-RS resources, where the dimension of the recommended precoding matrix corresponds, for example, to the total number of antenna ports from at least one CSI-RS resource multiplied by the number of layers (or ranks).

[0068] As referred to herein, an inter-point phase indicator or combining indicator corresponds to a recommended inter-point phase difference for at least one transmission layer for at least one pair of precoding matrices used at a transmission point. The inter-point phase indicator is equivalently referred to as an “inter-CSI-RS resource indicator” when possibly an associated set of CSI-RS resources is used for CSI measurements, or an “inter-CRS” or “inter-cell” CQI when possibly a common reference signal (CRS) is used for CSI measurements.

[0069] Also, when referred to herein, the term "CSI of a set of transmission points" refers to any type of channel state information derived from any subset of this set of transmission points. For example, the CSI of a set of transmission points includes channel quality information, a rank indication, a precoding matrix indication, and / or any type of explicit or implicit feedback. The CSI of a set of transmission points, as disclosed herein, also includes a type of channel state information not previously defined that is a function of multiple transmission points.

[0070] Embodiments contemplate devices and techniques that can be used individually or in combination to efficiently evaluate and / or report CSI related to geographically separated transmission points. In one or more embodiments, the WTRU reports CSI for different transmission points (or CSI-RS resources) or subsets thereof configured for CSI reporting in different subframes. The subsets of transmission points are determined based on one or more of receiving the transmission points (or corresponding reference signals, such as CSI-RS) that are part of each subset from higher layers (e.g., RRC signaling or MAC signaling) and / or one or more characteristics of the signals received from the transmission points. For example, the signal characteristics may include, but are not limited to, the CSI-RS (Channel State Indicator Reference Signal) transmitted from each Tx point, the CRS (Common Reference Signal) transmitted from each point, the physical cell identity used to derive the reference signal transmitted from each point (e.g., a subset of transmission points is defined to correspond to all transmission points from a particular cell), and the quality metrics of the signal received from each transmission point (such as received signal strength, received signal quality, and / or channel quality information).

[0071] For example, two subsets of transmission points may be defined, where one subset corresponds to transmission points that are received at a relatively high power level for which accurate and timely CSI information is required (e.g., the “active” subset), and the other subset corresponds to transmission points that are received at a relatively low level for which CSI information is not required, at least very frequently (e.g., the “monitored” subset). The network may determine which transmission points are part of each subset and use radio resource control signaling to indicate the active and monitored subsets of Tx points. Alternatively, the WTRU may determine whether a transmission point belongs to the active or monitored group by determining whether the received signal strength is above or below a threshold (in some embodiments, perhaps above or below the threshold for a predefined period of time) that is signaled by the network via higher layers and / or that may be a function of, for example, the received signal strength of the best transmission point. Configuring the active set may be done, for example, by providing the WTRU with a set of non-zero power CSI-RS resources and / or in some embodiments a set of cell identities.

[0072] In another example, a first subset of transmission points (e.g., a “serving” subset) is defined as the set of transmission points used by the WTRU's serving cell, while other subsets of transmission points (e.g., “non-serving” subsets) are defined according to the cells from which they transmit. In another example, one subset includes a single particular transmission point identified as the “serving” transmission point, and at least one other subset includes at least one transmission point identified as an “assisting” transmission point. The subframes for which the WTRU reports CSI for a particular subset of transmission points are determined by a particular function of the system frame number and the subframe number. For example, the function is defined such that the subframes for which at least a portion of the CSI for a particular subset of transmission points is reported occur periodically. Embodiments acknowledge that different portions of CSI (e.g., RI and PMI / CQI) of the same transmission point use different periodic sets of subframes. The periodicity (and / or offset) is different for different subsets of transmission points or different types or portions of CSI. This may, for example, allow the WTRU to transmit CSI more frequently for a first subset of transmission points (the “active” or “serving” subset) than for a second subset of transmission points (the “monitored” or “non-serving” subset). The parameters of the particular function that determines in which subframes a particular subset is reported are supplied by a higher layer (e.g., RRC signaling). For example, the higher layer provides the periodicity and offset and / or portions of CSI for each subset of transmission points, perhaps via a single index from which these parameters can be derived. Embodiments also contemplate that the periodicity of the second subset is determined as a predetermined or signaled multiple of the periodicity of the first subset. Also, for example, one or more embodiments contemplate that for certain subsets, there may be no periodic reporting at all.For these subsets, CSI is reported if an aperiodic CQI / CSI request is received by the WTRU, and in some embodiments, perhaps only if an aperiodic CQI / CSI request is received by the WTRU.

[0073] Embodiments contemplate that the type of CSI reported for certain subsets of transmission points may differ from that for other subsets of transmission points. More generally, the CSI reporting mode, which defines which portions of CSI are reported in which subframes, may differ for each subset of transmission points. For example, CSI feedback for a first subset of transmission points may be configured for PUCCH CSI reporting mode 2-1 (subband CQI is reported), and CSI feedback for a second subset of transmission points may be configured for PUCCH CSI reporting mode 1-1 (wideband CQI is reported). In another example, CSI feedback for a first subset of transmission points may be configured for PUSCH reporting mode 2-2 (subband PMI and CQI are reported), and CSI feedback for a second subset of transmission points may be configured for PUSCH reporting mode 1-2 (wideband CQI and subband PMI are reported) or PUSCH reporting mode 3-1 (wideband PMI and subband CQI are reported).

[0074] One or more embodiments contemplate that the WTRU also reports a specific subset of CSI in a given subframe (n) if the WTRU receives an aperiodic CSI request in a previous subframe (n), where n is predefined or signaled. Such an aperiodic CSI request is signaled at the physical layer, for example, by setting a specific field of downlink control information (DCI) to at least one of a subset of values, where the DCI is signaling an uplink grant and is transmitted over another downlink control channel, such as the PDCCH or an enhanced control channel (E-PDCCH).The subset (or set of subsets) for which the WTRU reports CSI depends on: (1) characteristics of the downlink transmission containing the aperiodic CSI request; (2) the timing of the subframe (nk) in which the request is received or the subframe (n) in which the CSI is reported, possibly expressed in terms of system frame number and subframe number; (3) the set of CSI-RSs received (transmitted) in the same subframe as the aperiodic CSI request or the set of CSI-RSs received or transmitted in xy subframes of the aperiodic CSI request, where x is the subframe in which the aperiodic CSI request is received and y is a predetermined or configured value; and (4) the set of CSI-RSs received (transmitted) in the same subframe as the aperiodic CSI request or the set of CSI-RSs received or transmitted in xy subframes of the aperiodic CSI request, where x is the subframe in which the aperiodic CSI request is received and y is a predetermined or configured value. (5) a set of CSI-RSs received (transmitted) in the same subframe as the aperiodic CSI request or a set of CSI-RSs received or transmitted within xy subframes of the aperiodic CSI request (where x is the subframe in which the aperiodic CSI request is received and y is a predetermined or configured value); (6) characteristics of uplink transmission indicated by downlink control signaling containing the aperiodic CSI request; and / or (7) codepoint reservation of the aperiodic CSI request field indicating that the subset of transmission points for which CSI is reported corresponds to the subset of transmission points used for transmitting the downlink control signaling indicating the aperiodic CSI request.

[0075] In one example, the characteristics of the downlink transmission including the aperiodic CSI request may be determined by: (1) an indication from downlink control signaling (e.g., PDCCH) including the aperiodic CSI request for the UE (e.g., the indication is provided by a specific codepoint(s) of an existing field, such as a CQI request field, or perhaps a field in a previously undefined DCI format); (2) the transmission point(s) used to transmit the downlink control channel (e.g., evolved PDCCH, etc.) including the aperiodic CSI request (e.g., if the downlink control signaling is conveyed through an enhanced control channel, the WTRU may not be able to determine the CSI request for the UE); The subset of transmission points reporting I may correspond to the set of transmission points used for transmitting the enhanced control channel, (3) the cell from which the downlink control signaling including the aperiodic CSI request is transmitted (e.g., the WTRU reports CSI for the subset of transmission points corresponding to this cell, and in some embodiments, the WTRU reports CSI for only the subset of transmission points corresponding to this cell), and / or (4) the subset of cells for which feedback is provided according to the value of the CSI request field (e.g., the WTRU reports CSI for the subset of transmission points corresponding to a subset of cells).

[0076] One or more embodiments contemplate that the WTRU reports CSI for a subset of transmission points within a given subframe, determined according to one or more of the following: (1) determination of a maximum number M of transmission points or subsets of transmission points and / or subsets of CSI-RS resources for which CSI should be reported, where this value is predetermined or signaled by higher layers; and / or (2) selection of up to M transmission points or subsets thereof for which the value(s) of an associated metric are the largest among all transmission points (or subsets thereof) configured for CSI reporting and / or exceed a certain threshold. The associated metric represents the quality of the signal received from the corresponding transmission point(s) and / or the expected performance of the transmission on these transmission points. In one or more embodiments, this metric is associated with each transmission point or each subset of transmission points.

[0077] Embodiments also contemplate that a single metric may be associated with the selection of the M transmission points. For example, the selection of a transmission point may be based on one or more of: (1) the wideband CQI of the transmission point or the best possible wideband CQI across precoding matrices for a subset of transmission points; (2) the subband CQI if the report is for a particular subband, or the maximum of the subband CQIs across subbands using the best precoding matrix (for the subset of transmission points); (3) the received signal strength (RSRP) from the transmission point(s); (4) the received signal quality (RSRQ) from the transmission point(s); (5) the expected throughput for a hypothetical transmission from the selected transmission point; and / or (6) the maximum rank for a hypothetical transmission from the selected transmission point (where the same or different layer(s) and / or flow(s) are received from several or each transmission point).

[0078] Embodiments contemplate that the WTRU selects up to M transmission points according to one or more of: (1) selecting the transmission point that provides the best channel quality, e.g., as measured by CQI, RSRP, and / or RSRQ, etc., or the like, possibly given at least one precoding matrix; and (2) adding another transmission point to the reported set of transmission points if, and in some embodiments only if, the performance metric (e.g., throughput or SINR, etc.) improves beyond a predefined threshold. In one or more embodiments, the metrics related to the selection of the M transmission points described herein persist for a predefined period of time. For example, if the metrics rely on CQI reports, then the transmission point is selected if the measured quality is greater / less than a threshold for a period of time.

[0079] Embodiments contemplate that an activation state is defined for transmission point(s) or a subset(s) thereof. Within a given subframe, the WTRU reports CSI for transmission point(s) and / or subset(s) thereof that are in an “active” state. In one or more embodiments, the WTRU does not measure the quality of reference signal(s) associated with inactive transmission point(s) or subset(s) thereof. The activation state is determined using one or more of: (1) setting an initial activation state to either “active” or “inactive” after configuration of the transmission point(s) or subset(s) thereof; and / or (2) explicit activation or deactivation through receipt of an activation or deactivation command. The command may be conveyed by signaling with one or more of the following characteristics, for example: the DCI is scrambled using a Radio-Network Identifier (RNTI) indicating the use of at least one CoMP feature, the DCI indicates at least one radio resource allocation (e.g., a downlink allocation) such that the DCI indicates that CoMP is applicable to the transmission, and / or any of the above characteristics where the physical layer signaling, such as from reception of PDCCH control signaling (e.g., DCI), includes an indication (e.g., one bit) of activation and / or deactivation of at least one CoMP feature. Furthermore, the command may be conveyed by one or both of MAC layer signaling (e.g., a MAC control element) and / or RRC signaling.Embodiments contemplate that implicit deactivation occurs when one or more conditions are detected, such as, for example, a metric associated with the transmission point or a subset thereof falls below a threshold, the WTRU reports one or more measurements that trigger the network to begin utilizing the transmission point or a subset thereof for transmissions to the WTRU, and / or a timer that was started (or re-started) upon the last transmission from the network utilizing the transmission point(s) or a subset thereof expires.

[0080] For one or more of the signaling methods described above, one or more embodiments contemplate the WTRU sending a HARQ A / N to acknowledge the activation / deactivation of the CoMP capability. Furthermore, the signaling procedure is built based on, for example, an index table (e.g., 00, 01, 10, 11) to the CSI reporting / mode and / or CoMP set to report, and / or feedback format, and / or configuration of feedback resources to use.

[0081] Embodiments contemplate techniques used to indicate a set of transmission points in the uplink for CSI or measurement reporting and / or a set of transmission points in downlink control signaling (such as a DCI format of the PDCCH or enhanced PDCCH) for aperiodic CSI requests or data transmissions. For example, a WTRU indicates (or causes a WTRU to indicate) a transmission point(s) or a subset(s) of transmission points via a bitmap, where each bit position corresponds to a particular transmission point or subset thereof. In another example, the subset of transmission point(s) is implicitly indicated by characteristics of the transmission of the associated signaling (e.g., CQI report, DCI, etc.), the subframe timing of the transmission of the associated signaling, the transmission points used to transmit the associated signaling, etc. In another example, a predefined sequence of bits is used to replace CSI for transmission points for which CSI is not reported. In another example, an index is associated with some or each CSI-RS resource within the configuration. The WTRU reports this index together with the associated CSI report. The index may be explicitly provided or may be implicitly determined at the WTRU according to, for example, the order of received configurations in the RRC messages.

[0082] Embodiments contemplate CSI feedback components for a set of K transmission points. Measurements used as a basis for determining CSI feedback are derived from at least one of the following sets of signals: CSI-RS reference signals, CRS reference signals, and / or other types of reference signals. Such reference signals are A, B, CSI-RS, CRS, CRS-2, CRS-3, CRS-4, CRS-5, CRS-6, CRS-7, CRS-8, CRS-9, CRS-10, CRS-11, CRS-12, CRS-13, CRS-14, CRS-15, CRS-16, CRS-17, CRS-18, CRS-19, CRS-20, CRS-21, CRS-22, CRS-23, CRS-24, CRS-25, CRS-26, CRS-27, CRS-28, CRS-29, CRS-30, CRS-31, CRS-32, CRS-33, CRS-34, CRS-35, CRS-36, CRS-37, CRS-38, CRS-39, CRS-40, CRS-41, CRS-42, CRS-43, CRS-44, CRS-45, CRS-46, CRS-47, CRS-48, CRS-49, CRS-50, CRS-51, CRS-52, CRS-53, CRS-54, CRS-55, CRS-56, CRS-57, CRS-58, CRS-59, CRS-60, CRS-61, CRS-62, CRS-63, CRS-64, CRS-64, CRS-72, CRS-73, CRS-74, CRS-75, CRS-76, CRS-81, CRS-82, CRS-83, CRS-84, CRS-95, CRS-106, CRS-117, CRS-128, CRS-137, CRS-148, CRS-159, CRS-168, CRS-179, CRS-189, CRS-190, CRS-191, CRS-192, CRS- k (reference signal) antenna ports. Several or each transmission point antenna port configurations and one or more mapping techniques for the associated reference signals are contemplated by embodiments.

[0083] One or more embodiments may involve a WTRU using a "joint rank indication" RI that is achieved for joint transmission over some or all of the set of K transmission points. joint or "common rank indication." The joint rank indication may be interpreted, for example, as a recommended number of useful transmission layers (or ranks) for joint transmission over K transmission points. The WTRU may report a per-point rank indication RI corresponding to the recommended number of useful transmission layers (or ranks) for transmission on the k-th transmission point, and in some embodiments only on the k-th transmission point. k The per-point rank indication may also be referred to as a "per-CSI-RS resource rank indication," for example, when the CSI evaluation is based on CSI-RS measurements.

[0084] Embodiments contemplate that the point-by-point rank indication may include an unconditional point-by-point rank indication and / or a conditional point-by-point rank indication. Unconditional Point-by-Point Rank Indication RI k indicates transmission to the WTRU (and in some embodiments, possibly only the WTRU) via transmission point k without any assumptions regarding the precoding utilized on the other transmission points of the other TWRU(s). kindicates a transmission to the WTRU (and, in some embodiments, perhaps only the WTRU) via transmission point k, assuming that transmissions to other WTRUs are made on other transmission points using one or more precoders. One or more precoders are indicated by the WTRU for other transmission points whose use will cause the most interference to the WTRU. Alternatively or additionally, in one or more embodiments, one or more precoders are indicated by the WTRU for other transmission points whose use will cause the least interference to the WTRU. The one or more precoders include a “zero” precoder (e.g., no transmission or “mute”). A precoder from a subset of precoders is indicated by the WTRU for other transmission points, such as from the set of allowed precoders or from outside the set of restricted precoders. The use of such a precoder enables the WTRU to correctly receive data from the associated transmission point. The WTRU receives data independently from the associated multiple transmission points. The rank indication(s) may be reported, for example, for an entire frequency band or for a particular set of subbands.

[0085] In one or more embodiments, the WTRU reports at least one channel quality index (CQI) corresponding to at least one combination of transmission parameters (e.g., modulation, code rate, transport block size) such that a single PDSCH transport block (e.g., codeword) occupying a certain CSI reference resource can be received with a transport block error probability not exceeding a predetermined threshold (e.g., 0.1). Different types of CQIs are defined based on the assumed type of transmission over the K transmission points, as described herein.

[0086] Embodiments may refer to the CQI as a "joint CQI" or an "aggregated CQI" (CQI joint) and "CQI per point" or "CQI per CSI-RS resource" (CQI k ) and other types of CQI. joint ) contains the CQI for the joint transmission of the codeword over all K transmission points of the set. When a WTRU uses joint CQI, an assumption is made regarding the transmission state of the points in the set for which CQI is being fed back. For example, the points are in one of the following states: transmitting to the WTRU, interfering with the WTRU (e.g., transmitting to another WTRU), muted (e.g., blanked), or unknown. The unknown state(s) indicates that the WTRU makes no assumption regarding the transmission state of the points, and the points are in one of the three previously defined states. Points that are assumed to be transmitting to the WTRU transmit coherently or non-coherently. The WTRU feeds back coherent joint (or aggregated) CQI and non-coherent joint (or aggregated) CQI based on the assumptions made for the points that transmit. The joint (or aggregated) CQI includes coherent joint CQI and non-coherent joint CQI. Coherent joint (or aggregated) CQI assumes that symbols of a codeword are transmitted over up to K transmission points using a determined relationship between the precoders used at each of the K transmission points, possibly according to a combining matrix or combining indicator described herein. For example, the relative phase between the precoders is assumed to be such that signals from the transmission points are combined coherently (with zero phase difference) or with a predetermined phase difference. Non-coherent joint (or aggregated) CQI assumes that symbols of a codeword are transmitted over up to K transmission points without a determined relationship between the precoders used at some or each of the K transmission points.

[0087] Embodiments contemplate, for example, evaluating CQI for transmissions from multiple transmission points. In one or more embodiments, the WTRU may evaluate the received signal strength S of at least one resource element where a CSI-RS or CRS signal is known to be present according to the WTRU configuration. RS,i Estimate the ratio P c,i is determined between the energy per resource element (EPRE) of this reference signal (CSI-RS or CRS) and the EPRE of the PDSCH transmission of at least one resource element. The WTRU determines the signal strength S PDSCH Evaluate the signal-to-interference ratio (SIR) of a hypothetical PDSCH transmission as the ratio between S and the interference I, where S PDSCH is at least one (S RS,i / P c,i ) term functions, e.g., S PDSCH =Sum_over_i(S RS,i / P c,i ) etc. The interference I is estimated, for example, by measuring the energy from other resource elements provided by the network, among other techniques.

[0088] CQI per point or CQI per CSI-RS resource (CQI k ) contains the CQI for the transmission of the codeword to this WTRU via the kth transmission point, and in some embodiments perhaps only via the kth transmission point. The point-by-point CQI is the unconditional point-by-point CQI k and conditional point-wise CQI k Includes unconditional point-by-point CQI k denotes the CQI of the transmission of a codeword to this WTRU via transmission point k (and possibly only via transmission point k), without any assumptions about the precoding utilized on other transmission points for other WTRUs or for independent data to the WTRU. kindicates the CQI for the transmission of a codeword to this WTRU via transmission point k (and possibly only via transmission point k), assuming that the other WTRUs' transmissions are made at the other transmission points using one or more precoders. The precoder(s) are indicated by the WTRU for the other transmission points whose use will cause the most interference to the WTRU. The precoder(s) are indicated by the WTRU for the other transmission points whose use will cause the least interference to the WTRU. The precoder(s) include a "zero" precoder (e.g., no transmission or "mute"). A precoder from a subset of precoders is indicated by the WTRU for the other transmission points, e.g., from the set of allowed precoders or from outside the set of restricted precoders. The use of such a precoder enables the WTRU to correctly receive data from the associated transmission point. The CQI is reported, for example, for the entire frequency band or for a specific set of subbands.

[0089] If more than one of the above types / subtypes of CQI are reported for at least one codeword, the WTRU reports, for a first type / subtype of CQI applicable to a first codeword, the difference between the value of this first type / subtype of CQI and the value of a second type / subtype of CQI applicable to the same codeword or a second codeword, e.g., the second type / subtype of CQI for a codeword is differentially coded with respect to the respective first type / subtype of CQI.

[0090] One or more embodiments contemplate the WTRU reporting at least one precoding matrix indicator (PMI) applicable to the set of K transmission points, where the PMI includes a global precoding matrix indicator, a local precoding matrix indicator, and an interference precoding matrix indicator.

[0091] At least one global precoding matrix indicator has dimensions (A1+A2+…A K )xRI joint corresponds to a global (or "aggregated") precoding matrix W of the K transmission points. This matrix is joint In one or more embodiments, the interpretation of the global (or aggregated) PMI is based on the last reported Joint Rank Indication RI. joint Depends on.

[0092] The local (or "per point" or "per CSI-RS resource") precoding matrix indicator for transmission point k is k xRI k matrix W k This matrix contains the RI from the kth transmission point. k represents the precoder recommended for transmission of data for this WTRU over each of the layers. The interpretation of the local (or point-by-point) PMI is the sum of the last reported point-by-point rank indicator RI k Depends on.

[0093] The precoding matrix indicator for transmission point k is the matrix Y k The matrix includes: k = k th transmission point + ...

[0094] Embodiments may include a precoding matrix W′ for one or more transmission points k1. kIt is contemplated that the set of precoders corresponds to a set of precoders. The set of precoding matrices includes a group of precoder matrices. This set corresponds to a set of precoder(s) not used by transmission point k1 to ensure that the WTRU correctly receives possibly independent data from other transmission point(s) (e.g., k2). This set corresponds to a set of precoder(s) from which transmission point k1 selects a precoder if transmission point k1 chooses not to use a precoder identified by a precoder matrix indication fed back by the WTRU.

[0095] Embodiments may be implemented using a local (or point-wise) precoding matrix W k It is contemplated that the at least one precoding matrix indicator corresponding to ≡ ... - Precoding matrix W according to a predefined mapping k The rank indication RI corresponds to the last reported point-by-point interpretation. k Depends on a single index i k and, - Precoding matrix W according to a predefined mapping k Corresponding to the last reported point-by-point rank indication RI k One or two indices i depending on 1k and / or i 2k and the first index i 1k corresponds to a property of the precoding matrix that does not change on a short-term basis, e.g., at least one set of weights (or beams) that are applied to at least one group of antenna ports, and this at least one group of antenna ports has a point-wise rank indication RI k Depends on the second index i 2k is a property of the precoding matrix that changes on a short-term basis, e.g., RI kFor each of the transmission layers, there corresponds a beam selected from each of the groups of antenna ports and combining information (eg, co-phasing) between these beams. Embodiments contemplate that whether a single index or two indexes are reported for this transmission depends on higher layer signaling or configuration and / or the number of antennas at the transmission point.

[0096] Embodiments contemplate that the one or more precoding matrix indicators corresponding to the global precoding matrix W include one or more of the following: - For each transmission point k, the local precoding matrix W as described previously k At least one point-wise precoding matrix indicator (e.g., i k or vs. i 1k , i 2k ). - Dimension(RI1+RI2+…+RI k )xRI joint The matrix W that combines comb The interpretation of the Joint Rank Indication RI, which corresponds to the last reported joint and possibly a point-by-point rank indicator RI k At least one combining indicator i, depending on the possible set of comb (or point-to-point indicator or CSI-RS resource-to-resource indicator). The combining matrix W comb is the RI of the combined set of transmission points joint For each of the transmission layers, it indicates which beam (if any) of the last reported local precoder of each transmission point is used, as well as co-phase information between the beams of these transmission points. This indicator also provides, for example, relative amplitude information. The global precoding matrix W corresponding to this set of precoding matrix indicators is obtained using the following example formula (rows separated by semicolons): W=[W10…0;0 W20…0;0 0 W k …0;0…0 W K ]xW comb

[0097] Embodiments may include one or more combining indicators i comb is intended to include one or more of the following: - A specific combination matrix W with a predefined mapping comb at least one index to - whether the global (or aggregated) precoding matrix is ​​such that each layer is transmitted via at most one transmission point (i.e., the matrix W comb is an identity matrix), and - At least one indication of the phase difference (or correction) that must be applied to or between the local (or per-point) precoders of each transmission point, per transmission layer. In more or more embodiments, the phase difference of a particular "reference" per-point precoder is fixed to 0, in which case the phase difference is referred to as "inter-point phase information."

[0098] By way of example and not limitation, embodiments may provide one indication per transmission point of the quantized timing offset Δτ of at least one transmission layer (reference is to the timing of one particular transmission point), one indication per transmission point of the phase difference (or correction) that must be applied to the precoder of this transmission point for coherent combining per transmission layer (i k,comb ), and / or two indications per transmission point of the phase difference (or correction) to be applied to the precoder of this transmission point for coherent combining per transmission layer (i 1k,comb and i 2k,comb), where: Single point indication 1k,comb corresponds to a property of the phase correction that does not change on a short-term basis, such as the M most significant bits of the quantized phase correction, Single point indication 2k,comb corresponds to a property of the phase correction that varies on a short-term basis, such as the L least significant bits of the quantized phase correction.

[0099] Embodiments contemplate that the one or more precoding matrix indicators corresponding to the global (or aggregated) precoding matrix W also include: - for each transmission point k, properties of the global (or aggregated) precoding matrix that do not change on a short-term basis, e.g., at least one set of weights (or beams) to be applied to at least one group of antenna ports of transmission point k (at least one group of antenna ports is subject to a per-point rank indication RI); k or Joint (or Common) Rank Indication RI joint (depending on 1k , -i 1k The set of indices of is a single joint (or aggregated) long-term precoding index i 1joint linked to, and / or - Properties of the global precoding matrix W that change on a short-term basis, e.g., RI joint For each of the transmission layers, an index i corresponds to the beam selected from each of the groups of antenna ports from all transmission points and the combining information (e.g., co-phasing) between these beams. 2comb .

[0100] Embodiments contemplate that the global (or aggregated) precoding matrix W includes a single index i1 (and possibly a single index i1) that corresponds to a property of the global precoding matrix that does not change on a short-term basis. For example, index i1 corresponds to a set of weights and / or beams that are applied to a transmission point. The global (or aggregated) precoding matrix W includes an index i1 for each transmission point k. 2k Contains the index i 2k corresponds to a property of each local (or pointwise) precoding matrix that varies on a short-term basis. For example, 2k , ...

[0101] For example, if a WTRU receives one tier from two transmission points each with four x-pol transmit antennas, a signal y=Wx+z is received, where y is the nth tier of the received signal. r is a 1 x 1 vector, where x is the nth of the transmitted signal i ×1 vector, and (n l = 1), z is n r × 1 noise vector, and W is n r ×n l is the precoding matrix. The four ports assigned to transmission point "a" are denoted as a1, a2, a3, a4, and the four ports assigned to transmission point "b" are denoted as b1, b2, b3, b4. The precoding matrix is ​​mapped to the antenna ports as follows: W → [a1, a2, b1, b2, a3, a4, b3, b4] T The following codebook structure can be used (see also Table 2):

[0102]

number

[0103]

number

[0104] v m =[1 e j2Πn / 32 e j4Πn / 32 e j6Πn / 32 ] T

[0105] [Table 2]

[0106] The same long-term / wideband PMI i1 is used by both transmission points. Each transmission point uses its own short-term / narrowband PMI i2 (i 2a and i 2b Index i1 requires 4 bits of feedback, but index i 2a requires 4 bits, and the index i 2b For example, precoding at transmission point a requires two bits i1 and i 2a Precoding at transmission point b requires i1, i 2a , and i 2b An alternative transmission point b may, for example, require feedback i1 and i 2b At the transmission point b, only 2a To remove the dependency on , the codebook at each transmission point contains (see Tables 3 and 4):

[0107] [Table 3]

[0108] [Table 4]

[0109] In this case, some or each transmission point receives, for example, i1 (4 bits) as well as respective i2 (4 bits each).

[0110] Precoding matrix W' k The set of Λ contains indices (and possibly single indices) that correspond to groups of precoding matrices according to a predetermined mapping. The interpretation of a group of precoding matrices is based on the last reported pointwise rank indication RI k and / or depending on a precoding matrix indicator corresponding to the desired precoding matrix to be used for this WTRU. The set of precoding matrices includes, for example, multiple indices, each indicative of a specific precoding matrix according to a predetermined mapping, whose grouping constitutes the set.

[0111] In one or more embodiments, the WTRU may include at least one power adjustment indicator PAI for at least one transmission point. k Power Adjustment Indicator PAI k

[0033] In one or more embodiments, the WTRU reports channel state information assuming a certain type of single-point or multi-point transmission from the network. Such a transmission hypothesis may be referred to herein as a "transmission state." A transmission state may be a hypothesis that, for at least one transmission point, this transmission point is in a state where ... - being transmitted to the WTRU according to the reported point-by-point or aggregated precoding matrix indicator - transmitting to another WTRU according to the reported point-by-point or aggregated precoding matrix indicator; and / or - Not transmitting to any WTRU (e.g. muted or blanked) This includes assumptions about which In one or more embodiments, for a given transmission condition, no assumptions are made about at least one transmission point.

[0112] A transmission point may be in a transmission state such as transmitting (T), interfering (I) (e.g., unwanted transmission to another WTRU), blanked (B), and / or unknown (U). For example, for n points, n There are up to five possible Transmission State Vectors (TSVs). Some or each Transmission State Vector is indicated by one or more Transmission State Indicators (TSIs). A TSI is a scalar value that maps to a TSV or the TSV itself. Additionally or alternatively, the TSI is a bitmap that represents the TSVs. Also, for example, a WTRU may feedback with hypotheses about five points, including two transmitting points, two interfering points, and one blanked / muted point. An exemplary corresponding TSI includes a vector such as [TTIIB]. An exemplary corresponding TSI includes a value that maps to a vector such as [TTIIB]. Additional transmission states or TSIs are defined to indicate whether the joint transmission is assumed to be coherent (i.e., using a combining indicator or point-to-point phase information) or non-coherent.

[0113] Embodiments contemplate that the WTRU may be configured to report CSI for certain possible transmission states, and in some embodiments perhaps only for certain possible transmission states. For example, the WTRU may be configured to report CSI for two points and configured to report CSI for the next transmission state. - a single transmission from a first point (or, using the previous terminology, e.g., [TI]) that a second point transmits to another WTRU; - a single transmission from the first point (or, using the previous terminology, e.g., [TB]) without the second point transmitting to any WTRU; - a single transmission from a second point (or, using the previous terminology, e.g., [IT]) that the first point transmits to another WTRU; - a single transmission from the second point (or, using the previous terminology, e.g., [BT]) where the first point does not transmit to any WTRU, and / or - Joint transmission from both points (or, using the previous terminology, e.g., [TT]). Embodiments contemplate that the set of transmission states and / or the set(s) of TSVs for which the WTRU potentially reports CSI may be configured by higher layers.

[0114] Embodiments contemplate that transmission state selection is controlled by the network. The network determines the transmission state or TSI value(s) (e.g., TSI value(s) corresponding to a CSI report). The network indicates, via higher layer signaling, the TSI and / or TSV for the WTRU to use. The network indicates, for example, the TSI and / or TSV for the WTRU to use for periodic or aperiodic feedback grants. The TSI is used for one instance of aperiodic feedback or for the duration of a semi-persistent aperiodic feedback grant. In one or more embodiments, the TSI is associated with one or more subframe numbers. This association is pre-configured by higher layer signaling. In one or more embodiments, the TSI and / or TSV are based on previous feedback. For example, the WTRU feeds back an indicator that indicates to the network that the TSI and / or TSV have changed. The new TSI and / or TSV cycle to another pre-configured value. For example, the WTRU may feedback an indicator to the network that the TSI and / or TSV must be changed, and the network may be prompted to indicate the new TSI and / or TSV to the WTRU before another CSI feedback is performed by the WTRU.

[0115] In one or more embodiments, the TSI / TSV selection is controlled by the WTRU. For example, the WTRU feeds back the TSI and / or TSV to inform the network about the conditions under which the CSI feedback was calculated. The WTRU determines the value(s) of the TSI and / or TSV. For example, for n points, the WTRU may select 4 nThe WTRU selects from among possible TSI and / or TSV values. For example, the WTRU selects from a subset of possible TSI and / or TSV values. The subset of possible TSI and / or TSV values ​​is signaled to the WTRU. For example, the subset is signaled to the WTRU by one or more methods described above with respect to network-controlled TSI and / or TSV selection (e.g., by replacing the TSI with a TSI set). For example, the subset of possible values ​​includes a TSV with a single point in transmission (T). In some embodiments, no other conditions for the other points are used (e.g., DPS without muting). For example, the subset of possible values ​​includes a TSI with at least two points in transmission (T) and the other points blanked (B) (e.g., joint transmission with blanking). The WTRU feeds back an indicator to the network that the selected TSI and / or TSV have changed. The new TSI and / or TSV are, for example, pre-configured or fed back by the WTRU.

[0116] As explained above, the WTRU may select a set of possible transmission states or a set of possible values ​​(e.g., four possible values ​​in one embodiment). nn values, where n is the number of points. The TSI(s) and / or TSV(s) are selected based on the number of points required to achieve a preconfigured performance threshold. For example, the WTRU selects the TSI(s) and / or TSV(s) that require the fewest (or the most) points to be transmitted to achieve a preconfigured performance threshold (e.g., maximize SINR, minimize BLER, maximize throughput, or the like). The TSI(s) and / or TSV(s) are selected based on the number of points that need to be blanked to achieve a preconfigured performance threshold. For example, the WTRU selects the TSI(s) and / or TSV(s) that require the fewest (or the most) points to be blanked to achieve a preconfigured performance threshold (e.g., maximize SINR, minimize BLER, maximize throughput, or the like). The TSI(s) and / or TSV(s) are selected based on constraints on non-transmitting points. For example, the WTRU selects the TSI(s) and / or TSV(s) (fewest (or most) unknown points) that impose the fewest (or most) constraints on non-transmitting points to achieve a preconfigured performance threshold (e.g., maximize SINR, minimize BLER, maximize throughput, or the like). In one or more embodiments, the TSI(s) and / or TSV(s) are selected based on CQI and / or rank (e.g., (RI)). For example, the WTRU selects the TSI(s) and / or TSV(s) with the highest CQI and / or highest rank (e.g., (RI)).

[0117] Additionally or alternatively, the TSI(s) and / or TSV(s) are selected based on throughput or the amount of bits transferred. For example, the WTRU selects the TSI(s) and / or TSV(s) that maximizes the total throughput or the total amount of bits transferred in a subframe when the network complies with the recommended CSI (e.g., including both CQI and RI). In one or more embodiments, the WTRU selects the TSI and / or TSV from a subset of allowable TSIs and / or TSVs. The subset of allowable TSIs and / or TSVs includes TSI(s) that are in a transmitting (T) state and correspond to points that satisfy one or more of the following criteria: exceeding a minimum acceptable path loss threshold, achieving a minimum point-by-point CQI threshold, and / or exceeding a point-by-point CQI difference when compared to a maximum point-by-point CQI threshold.

[0118] Embodiments contemplate that, in evaluating the CSI for a transmission state, the WTRU may use one or more parameters, including parameters related to, corresponding to, or specific to that transmission state (as previously described) and / or the type of CSI being reported (e.g., whether the CSI feedback includes a combining indicator, or whether it is used for coherent or non-coherent joint transmission). For example, the WTRU may use one or more of the following example transmission state-specific parameters: (1) an assumed PDSCH transmit power from each point (or an assumed ratio of PDSCH EPRE to CSI EPRE for each point), a correction factor for the assumed PDSCH transmit power from each point, and / or an offset to an estimated CQI index, or the like.

[0119] In one or more embodiments, the use of such transmission-based parameters (e.g., in combination with a WTRU selection mechanism for a transmission state based on maximum throughput (or CQI or rank)) allows CSI for each such transmission state to be reported if, from the network's perspective, using a transmission state that uses more resources (or uses reporting of more CSI bits) provides benefits compared to a state that consumes fewer resources. In some embodiments, for the same transmission state, different parameters are also applied for different assumed ranks.

[0120] For example, the WTRU may be configured to report CSI for up to two transmission points where the set of transmission conditions reported by the WTRU includes one or more of a single transmission from a first point (with a second point possibly interfering), a single transmission from a second point (with a second point possibly interfering), a joint transmission from both points, and / or the like (e.g., using transmission points).

[0121] Embodiments contemplate that the estimated CQI indices for each of the transmission states may be, for example, 8, 6, and 9, respectively, in certain subframes (e.g., in the absence of correction factors). Thus, the WTRU reports CSI for a joint transmission (e.g., doubling the cost of such a transmission from the network's perspective) even if the incremental benefit over a single transmission is minimal. In some embodiments, when the method of applying correction factors to assumed PDSCH transmit powers described herein is used, the WTRU applies, for example, a correction factor of 0 dB to each single-point transmission state and a correction factor of −3 dB to the joint transmission state. Furthermore, such correction factors (e.g., when applied) may result in estimated CQI indices of 8, 6, and 6, causing the UE to report CSI corresponding to, for example, a single transmission from the first point (CQI=8).

[0122] Embodiments contemplate that the value(s) of the applied correction factor are defined or provided for several or each type of transmission condition (e.g., 2 dB for joint transmission, 0 dB for single-point transmission, 1 dB for single-point transmission with muting at other points, or the like). Alternatively, the value(s) of the correction factor are a function of the number of transmission points that are not or are assumed not to be interfering with the WTRU. In one or more embodiments, the value(s) of the correction factor are, for example, a function of the number of transmission points that are assumed to be transmitting to the WTRU.

[0123] Embodiments contemplate that the value(s) of the correction factor (or parameters used to derive the correction factor) are also predefined. Alternatively, the value(s) of the correction factor (or parameters used to derive the correction factor) are signaled by the network, e.g., using higher layer (e.g., RRC) signaling. Such signaling of parameters allows the network to adjust the likelihood of reporting CSI for certain transmission conditions based on current conditions such as network load, among other conditions. For example, when there is low system load, one or more WTRUs report CSI for joint transmission because there is excess capacity, perhaps significant excess capacity, in the network. In that case, for other considerations, one or more embodiments contemplate that the correction factor for joint transmission is decreased. Alternatively or additionally, one or more embodiments contemplate that the correction factor is increased, perhaps when the system has a heavier load, among other reasons.

[0124] Embodiments contemplate one or more techniques used to provide a correction factor for each transmission state. One or more embodiments contemplate that a correction factor (e.g., already signaled) for an assumed ratio of PDSCH EPRE to CSI-RS EPRE is provided as part of each configured CSI-RS resource (corresponding to a transmission point). Such a correction factor is applied, for example, to estimate CSI for a transmission state involving joint transmission from that transmission point and at least one additional point to the WTRU. Alternatively, a new value for the assumed ratio of PDSCH EPRE to CSI-RS EPRE applicable to a joint transmission is provided directly (rather than applying a correction factor to the assumed ratio of PDSCH EPRE to CSI-RS EPRE applicable to a single-point transmission). A similar approach is also used to provide parameters used for a transmission state with one transmission point and muting from at least one other transmission point or a transmission state with muting from one transmission point.

[0125] Alternatively or additionally, embodiments contemplate that a correction factor associated with the assumed PDSCH transmit power (e.g., from each of the points) is provided from some and / or all permissible transmission states. For example, rather than explicitly listing each possible transmission state, a correction factor is provided as a function of the number of transmission points transmitting to the WTRU and / or the number of transmission points not transmitting to any WTRU (e.g., muted) for any given transmission state. In one or more embodiments, correction factors of 0 dB, 2 dB, and 4 dB are defined for transmission state(s) involving transmission to the WRU (and / or being muted), e.g., from a single transmission point, two transmission points, and / or three transmission points, respectively. Furthermore, a correction factor (e.g., applied together with the correction factor) for the number of points transmitting to the WTRU is defined for the number of transmission points that are muted (e.g., not transmitting to the WTRU).

[0126] Embodiments contemplate that a WTRU configured to report CSI for one or more transmission points (or CSI-RS resources) must report CSI for a subset of these transmission points in certain cases, and in some embodiments perhaps only a subset of these transmission points in certain cases, for the following reasons:

[0127] the transmission state recommended by the WTRU or requested by the network uses transmissions from a subset of the transmission points, and in some embodiments possibly only from a subset of the transmission points; Due to payload constraints, e.g. in case of periodic reporting, the WTRU may report feedback components for a subset of transmission points or CSI-RS resources, and in some embodiments may do so only in specific cases. Embodiments contemplate one or more methods described herein for indicating one or more subsets of transmission points to which a report including a CSI feedback component applies.

[0128] Embodiments contemplate that when a WTRU reports feedback for multiple cells, a point indicator (PI) and / or a CSI-RS resource indicator explicitly indicate the transmission point or set of transmission points for which the feedback report pertains. The PI includes the PCI of the transmission point. The PI includes a network-provided bitmap implementation, where a 1 in a particular bit position represents a particular transmission point or CSI-RS resource configured by higher layers. This bitmap is signaled to the WTRU by higher layer RRC signaling, or provided, for example, in an uplink DCI (which triggers aperiodic feedback on PUSCH) or a Random Access Response Grant. This bitmap is static, semi-static, or dynamic based on the CoMP measurement set. The PI includes an n-bit stream, where the possible n-tuples are 2 n transmission points. The PI includes an ordered list of indexes, possibly in binary format, where some or each index in the list indicates a particular transmission point or configured CSI-RS resource. This type of point indicator is useful for providing ranking information between points. In one or more embodiments, the PI indicates a set of, e.g., size M (out of N possible transmission points), for selecting, e.g., M recommended points. The PI includes an indicator related to a particular point in the TSV. The PI includes a combination index r, where

[0129]

number

[0130] and the set

[0131]

number

[0132] , 1≦s i ≦N,s i i+1 contains the M sorted transmission indices,

[0133]

number

[0134] For some or each particular feedback, which of the transmission points the feedback report relates to is determined based on the indicator.

[0135] Alternatively or additionally, embodiments contemplate that a subset of transmission points may be jointly indicated along with a selected subset of subbands into a point-subband-indicator (PSI). - a bitmap in which a 1 in a particular bit position represents a particular combination of transmission point and subband, and / or If the WTRU indicates a set of size M (out of N possible combinations of transmission points and subbands), then a combination index r is used to select, for example, M recommended combinations of points and subbands, where

[0136]

number

[0137] and the set

[0138] ​

number

[0139] , 1≦s i ≦N,s i i+1 contains M sorted point subband combination indices,

[0140]

number

[0141] is Contains one or more of:

[0142] In some embodiments, the PI or PSI is - in the same subframe as the feedback component to which it applies. If multiple PIs or PSIs are transmitted in the same subframe, the association between the PIs (or PSIs) and the feedback information is predetermined by the bit order, and / or - Subframes, in some embodiments according to a predetermined rule, occurring before the subframe in which the feedback information is transmitted. In other words, the subset of transmission points corresponds to the most recently transmitted PI or PSI. For example, the WTRU transmits a PI or PSI (e.g., periodically) in a first set of predetermined subframes and the associated feedback in a second set of predetermined subframes. The PI or PSI applicable to the feedback transmitted in a given subframe of the second set is, for example, the most recently transmitted PI or PSI in the first set. ​, and PSI. Embodiments contemplate that at least one benefit of the PI or PSI is to enable savings on feedback overhead, since the WTRU feeds back reports on the strongest n cells (and in some embodiments, only the strongest n cells) and discards feedback reports on any other cells. The feedback report includes a PI to indicate to the network which transmission point the feedback is for.

[0143] The indication of which transmission points the feedback pertains to may be explicit or implicit. For example, the transmission points are implicitly determined based on transmission point-specific scrambling. In one or more embodiments, the subset of transmission points is implicitly and / or uniquely determined from the timing of the subframe (frame number and subframe number) in which the feedback is transmitted. The WTRU transmits feedback components for the subset of transmission points in a first subframe, provided that the WTRU transmitted an indication that feedback was provided for this subset of transmission points in a second-previous subframe. In some embodiments, the WTRU transmits feedback components for the subset of transmission points in a first subframe only, provided that the WTRU transmitted an indication that feedback was provided for this subset of transmission points in a second-previous subframe. The second subframe is, for example, the most recent subframe in a pre-determined set of subframes. The indication may indicate a single bit, a PI, or a PSI, and / or may be encoded as a specific code point for a previously undefined or modified report type.

[0144] In one or more embodiments, the subset of transmission points is implicitly determined from the most recently transmitted transmission status indicator (TSI), PI, or PSI and subframe timing according to a preconfigured set of rules, e.g., according to a particular mode of periodic reporting. For example, within a set of periodically occurring subframes, the transmission points for which feedback is provided are cycled among the transmission points indicated in the most recently transmitted PI. In another example, the transmission points correspond to the first indicated transmission point in the most recently transmitted PI in a first set of subframes and the second indicated transmission point in the most recently transmitted PI in a second set of subframes. This can be useful for several reasons, e.g., when it is desired to transmit feedback for a first transmission point more frequently than for a second transmission point.

[0145] Embodiments contemplate that in one or more of the aforementioned techniques, the subset of transmission points to which a certain feedback component is applied may also depend on the type of feedback (CQI, PMI, or PI). For example, the WTRU reports an aggregated CQI for transmissions from two points in a given subframe, along with a per-point PMI for one of the two points. This can be useful for several reasons, such as when per-point PMI for the other point has already been provided in a previous subframe.

[0146] Embodiments contemplate techniques for determining which of the above-described CSI feedback components and types are reported to the network and / or in which subframe(s). In one example, a WTRU reports at least one CSI feedback component of at least one type or subtype (if applicable) in a given subframe (n), e.g., if it received an aperiodic CSI report in a previous subframe (nk), where k is predefined or signaled. In one embodiment, an aperiodic CSI request in subframe (n) triggers the WTRU to report at least one CSI feedback component of at least one type or subtype (if applicable) in different subframes for different transmission points. For example, feedback for transmission point 1 is transmitted in subframe n+k1, feedback for transmission point 2 is transmitted in subframe n+k2, and so on. The set of {k1, k2, ...} is, for example, predefined or signaled.

[0147] Embodiments contemplate that for a given set of transmission points, the set of CSI components, reported types and subtypes, and associated conditions (as described herein) are determined according to at least one of the following: - characteristics of the downlink transmission including the aperiodic CSI report, such as an indication from downlink control signaling (e.g., PDCCH) including the aperiodic CSI report for the WTRU, for example, this indication being provided by a specific codepoint(s) of an existing field such as a CQI request field or possibly a field in a contemplated but not yet defined DCI format, the set of antenna ports or reference signals used to transmit the downlink control signaling (CRR or DM-RS), and / or the cell from which the downlink control signaling including the aperiodic CSI request is to be transmitted; - the timing of the subframe (nk) in which the request is received or the subframe (n) in which the CSI is reported, expressed in terms of the system frame number and / or subframe number; - characteristics of uplink transmissions indicated by downlink control signaling containing aperiodic SCSI requests; - higher layer signaling (e.g. RRC configuration), - (PUSCH) CSI reporting mode, - whether all transmission points are transmitting the same (dependent) or different (independent) data, and / or - A combination of the above, such as reserving a codepoint in the Aperiodic CSI Request field to indicate that the set or type / subtype of the reported CSI components corresponds to the timing of the subframe in which the request is received.

[0148] Embodiments contemplate one or more examples of the relevant conditions shown (such as, but not limited to, the following): - Point-by-point CQI reported k whether it is unconditional or conditional, and perhaps in the latter case whether the condition is for minimum interference (e.g., "no transmission" or "zero precoder") or maximum interference; - whether coherent or non-coherent aggregated CQI (or joint CQI) must be reported; - Combined indicators comb or the combination matrix W comb Which of the following must be reported? - whether the report is broadband or specific subband; - whether a long-term (first) precoding matrix indication or a short-term (second) precoding matrix indication is reported; - whether the interference precoding matrix corresponds to maximum or minimum interference; - Precoding matrix W' k corresponds to a set from which the transmission point must select a precoding matrix or a set from which the transmission point must not select a precoding matrix, and / or - Indication of the Transmission State Vector (or Transmission State Indicator, TSI).

[0149] Embodiments contemplate one or more examples of sets, types, and subtypes of CSI components that are reported following an aperiodic request. The aggregated or joint CSI may be reported using a common (or joint) rank indication (RI). joint ), a point-by-point rank indication (RI) for a particular transmission point k, such as a transmission point identified as a "serving transmission point" k ), an aggregated CQI (or joint CQI) for at least one codeword (CQI joint ), and / or global precoding matrix indicator(s), and the like. The aggregated CSI (or joint CSI) includes one or more of a transmission state indicator or transmission state indicator (TSI). The aggregated CSI (or joint CSI) includes a CQI per primary point and at least one CQI per delta point (e.g., for a secondary transmission point). The aggregated CSI (or joint CSI) includes a muting pattern that indicates points that the WTRU should assume to be blanked for the reported feedback. The aggregated CSI (or joint CSI) includes a vector of point indicators (PIs). One or more embodiments contemplate that the PIs map to points (indicated by the TSI) in the transmission state vector. The aggregated CSI (or joint CSI) includes one or more associated conditions. The per-point CSI for a subset of transmission points is represented by a per-point rank indication (RI).k ), point-wise CQI for at least one codeword (CQI k ), point-wise (or local) precoding matrix indicator(s), precoding matrix indicator(s) W' k , a PI, a corresponding element of the transmission state vector, a primary CQI or a delta CQI (related to the primary CQI), and / or at least one associated condition per transmission point.

[0150] Embodiments contemplate that for reporting modes in which the feedback type is for WTRU-selected subbands, the WTRU may also indicate, for example, whether several transmission points, or perhaps each transmission point, have identical subsets of subbands, and / or whether they are orthogonal to each other, and / or whether they overlap. In one or more embodiments, this is achieved by transmitting a point-subband indicator (PSI) as described herein. For several reasons, such as when there is at least partial overlap of subsets, the WTRU provides a combination of aggregated (or joint) CSI and, in some embodiments, point-wise CSI. Embodiments contemplate that a bitmap may be used to indicate to the transmission points which type of CSI is applicable to which subbands.

[0151] Embodiments contemplate that report types can be fed back using pre-existing modes where different CSI reports are mapped to existing fields. For example, aperiodic PUSCH feedback modes 1-2 are reused when the WTRU feeds back multiple PMIs, one per transmission point, rather than feeding back multiple PMIs, perhaps one per subband.

[0152] In one or more embodiments, the WTRU is triggered by the network with aperiodic feedback, and the WTRU provides a new ranking of transmission points to change the periodicity / offset of some or each point. The WTRU uses such parameters in periodic feedback until new (or fresh) aperiodic feedback is triggered. Embodiments contemplate that aperiodic CSI reporting for CoMP includes any combination of at least one of the following: - Transmission Status Indicator (TSI); - Point Indicator (PI) and a combination index indicating the M subbands selected by the UE; - a combination index indicating the N points selected by the UE; - a combination index indicating a point-subband combination (PSI) selected by the UE; - Aggregated or per-point RI (RIa or RIp) and - Aggregated or point-by-point wideband CQI (W-CQIa or W-CQIp) and - aggregated or per-point sub-band CQI (S-CQIa or S-CQIp); - Aggregated or point-by-point M-band CQI (M-CQIa or M-CQIp) and - Aggregated or point-by-point wideband PMI (W-PMIa or W-PMIp) and - an aggregated or point-wise wideband first PMI (W-PMI1a or W-PMI1p) (where PMI1 corresponds to the first precoding matrix in the 2-PMI method introduced in Rel-10); and - an aggregated or point-wise wideband second PMI (W-PMI2a or W-PMI2p) (where PMI2 corresponds to the second precoding matrix in the 2PMI method introduced in Rel-10); and - Aggregated or point-wise sub-band PMI (S-PMIa or S-PMIp) and - an aggregated or per-point sub-band first PMI (S-PMI1a or S-PMI1p); - an aggregated or point-by-point sub-band second PMI (S-PMI2a or S-PMI2p); - Aggregated or point-by-point M-band PMI (M-PMIa or M-PMIp) and - Aggregated or point-by-point M-band first PMI (M-PMI1a or M-PMI1p) and - Aggregated or point-by-point M-band second PMI (M-PMI2a or M-PMI2p) and - a wideband point-to-point phase indicator; - a subband point-to-point phase indicator; - With M-band inter-point phase indicator. Embodiments contemplate that point-to-point phase indicators (e.g., wideband, sub-band, and / or M-band) may be linked to multiple phase values ​​in various situations, such as when there are more than two cooperating points.

[0153] Embodiments contemplate that the Rel-10 aperiodic reporting mode can be modified and / or augmented to accommodate efficient CoMP feedback reporting. The modes are defined as mode x y, where x indicates whether the CQI feedback is for wideband, network-configured subbands, or WTRU-selected subbands. Also, y indicates whether there is no PMI feedback, a single PMI feedback, or multiple PMI feedback. In one or more embodiments, one or more previously undefined dimensions can be added to some or all of the modes to indicate assumptions regarding the selection of TSVs, such as whether the feedback is for a) all points in the CoMP measurement set, b) network-selected TSVs, or c) WTRU-selected TSVs. As an example, a contemplated mode could take the form mode x y z, where z represents an assumption regarding the selection of TSVs. In either some or all three of the point selection assumptions, the WTRU is instructed to provide aggregated or per-point feedback for each individual report type. The aperiodic CQI reporting mode is configured by higher layer signaling (eg, in the parameter cqi-ReportModeAperiodic).

[0154] In one or more embodiments, the existing aperiodic CSI reporting mode can be reused and is applicable to any of the three assumptions regarding TSVs. In that case, either the uplink DCI or the random access response grant (used to trigger aperiodic feedback) can be used to instruct the WTRU about the assumption regarding the selection of the TSV (all points, network-selected TSV, and / or UE-selected TSV). In the case of network-selected TSVs, the aperiodic feedback trigger also includes the network-selected TSI. The TSI is included, for example, as an extension to the CSI request field. The aperiodic feedback trigger (e.g., uplink DCI or random access response grant) can also indicate whether aggregated feedback or point-by-point feedback is requested for some or each individual report type.

[0155] In embodiments where the WTRU selects the TSV, the aperiodic feedback report includes the TSI and the PI and / or PSI. Embodiments contemplate using specific aperiodic feedback for a subset of the points to transmit, for scenarios where the PI in such a situation has a large number of points that the WTRU selects to transmit in the TSV. In that case, even if one aperiodic feedback does not include feedback for all points in the TSV, the aggregated CQI is conditioned only on the points indicated by the entire TSV or PI(s).

[0156] Embodiments contemplate that a hierarchy of points may be provided by either the WTRU or the network (e.g., based on, for example, ranking the CQI for each point), with this hierarchy being used such that some or all feedback reports for points other than the highest ranked point are differential to, for example, the feedback report of the highest ranked point.

[0157] Embodiments contemplate one or more techniques for use in periodic CSI reporting for WTRUs configured with multiple transmission points or CSI-RS resources.

[0158] In one or more embodiments, the WTRU reports CSI periodically, e.g., according to a configured (PUCCH) CSI reporting mode and / or submode, which defines which pre-determined report types are transmitted in which reporting instances.

[0159] Embodiments contemplate that the WTRU reports at least one CSI component and / or additional type indication(s) of at least one type or subtype (where applicable), possibly combined with at least one associated condition, in an existing report type or a previously undefined report type transmitted as part of a modified or previously undefined reporting mode, as described herein. For example, the following report types are defined: - Combined indicators comb , - A common (or joint) rank indication RI with an existing precoding type indication (PTI) or a currently defined type indication (see below) joint , - Precoding indicator i for each first (long-term) point1k The first (long-term) point-by-point indicator combined with 1kcomb , - Common (or Joint) Rank Indicator RI joint The first (long-term) point-by-point indicator combined with 1kcomb , - Precoding indicator i for each first (long-term) point 1k and the common (or joint) rank indicator RI joint The first (long-term) point-by-point indicator combined with 1kcomb , - local precoding indicator i for each second (short-term) point 2k Second (short-term) point-by-point indicators combined with 2kcomb , - Point-by-point indicators for each transmission point 1k , i 2k and the combined indicator i comb a global (or aggregated) precoding matrix indicator, including - An indicator of whether CSI feedback for a given transmission point or CSI-RS resource (or set thereof) will be reported later.

[0160] The WTRU reports at least one transmission status indicator (TSI). The WTRU sends different reports to report feedback for different TSI(s). The WTRU sends different reports to report feedback for different sets of TSI(s). In one or more embodiments, the sets of TSI(s) overlap. The reports are sent, for example, with their own periodicity and subframe offset(s).

[0161] In one or more embodiments, an indication of which point a feedback report pertains to is jointly transmitted with another report. As an example, the rank and point indicator are jointly transmitted in a previously undefined report type. A single value corresponds to rank 1 using point #1 (possibly only point #1 in some embodiments), rank 2 using point #1 (possibly only point #1 in some embodiments), rank 1 using point #2 (possibly only point #2 in some embodiments), and / or rank 2 using point #2 (possibly only point #2 in some embodiments), and / or the like.

[0162] The joint report includes phase correction values ​​that provide feedback information for JT CoMP. For example, the joint report includes rank 1 using points #1 / #2 with phase correction θ1, rank 1 using points #1 / #2 with phase correction θ2, and the like. The joint report includes phase correction θ n The joint report includes rank 1 using points #1 / #2 with phase correction θ, rank 2 using points #1 / #2 with phase correction θ, and so on. n rank 2 using points #1 / #2 with 1 / 2, rank 2 using points #1 / #2 with each point transmitting independent data, and the like.

[0163] One or more combinations of the above two sets of values ​​may also be used for systems that support any combination of JT and DPS. Furthermore, for non-coherent systems, phase correction is removed from the joint report. The identification of points #1 and #2 is previously fed back in another report type (e.g., PI).

[0164] The PI is transmitted jointly with the cell's report. In one or more embodiments, the PI is transmitted once. The eNB assumes that the feedback report pertains to that transmission point until a further PI is transmitted. In one or more embodiments, the WTRU feeds back the PI at regular intervals, e.g., using a particular periodicity / subframe offset. The WTRU feeds back the PI even if the PI has not changed. This reduces the impact of error propagation (e.g., when an incorrect PI is decoded at the eNB).

[0165] In one or more embodiments, a PI is sent instead of an RI. For example, a PI / RI report includes a flag indicating whether the PI / RI report is for a PI or an RI. For example, there is a pre-configured pattern that determines whether a report is for an RI or a PI. The pre-configured pattern indicates that every xth instance of reporting an RI is replaced with a PI. When a PI is fed back in this manner, further report types that are fed back are for that transmission point, for example, until another PI is fed back.

[0166] Embodiments contemplate that the granularity of the PMI and phase offset is reduced. For example, the phase offset is jointly coded with the PMI of at least one of the transmission points. The PMI is subsampled, certain PMIs are associated with certain phase offsets, and feedback of a particular PMI at least implicitly indicates a subset of the transmission point's possible phase offsets. Embodiments contemplate that another indicator is used by the network to determine the offset from the subset. For example, the phase offset is fed back when another feedback report type is scheduled. For example, a flag is transmitted by the WTRU indicating the report type for which the instance is being used.

[0167] Embodiments contemplate that for modes in which the WTRU selects subbands in some or each bandwidth portion, the report type includes at least one of the following: For some or each point, the WTRU selects at least one subband in some or all bandwidth portions (the set of bandwidth portions spans the entire bandwidth). Thus, for some points, for each point, the WTRU has a different set of subbands, For some or each point, the WTRU selects one subband in some or all bandwidth portions, so that the same set of subbands applies to some or all points; For some or all bandwidth portions, the WTRU selects at least one subband / point combination, where the WTRU provides, for example, a label indicating both the subband in the bandwidth portion and the point to which it is applicable.

[0168] The CSI that the WTRU periodically reports is subject to at least one associated condition as described herein, which is determined using at least one of the following: - higher layer signaling, such as configured reporting modes and submodes, and / or - Last reported PTI or last reported Type Indication (possibly newly defined).

[0169] In one or more embodiments, report types for multiple cells are combined. A reporting mode allows for combining report types for multiple cells. For example, multiple transmission points use the same rank. In this reporting mode, one RI is transmitted for multiple transmission points. This reporting mode configures the WTRU to, for example, feed back one RI, n wideband CQIs, n wideband PMIs, and multiple subband CQIs and PMIs if configured (e.g., for n points).

[0170] Embodiments contemplate examples of periodic CSI reporting according to existing or previously undefined reporting modes. For example, in at least one reporting mode / sub-mode, the WTRU reports: - a report type that includes a common (or joint) rank indicator in a first set of reporting instances separated by a first periodicity; - in a second set of reporting instances (excluding the reporting instances belonging to the first set) separated by a second periodicity, at least one wideband aggregated (or joint) CQI and at least one wideband combining indicator i comb Report types containing, and / or - in a third set of reporting instances (excluding reporting instances belonging to the first set or the second set) separated by a third period, at least one subband aggregated (or joint) CQI and at least one subband combining indicator i comb Report types that include: Embodiments contemplate that the described reporting modes are useful in combination with periodic reporting configured for several transmission points or for each transmission point separately.

[0171] Also, for example, in at least one reporting mode / sub-mode, the WTRU reports: - within a first set of reporting instances separated by a first periodicity, a report type determined by the WTRU according to techniques described herein, the report type including a common (or joint) rank indicator, a per-point rank indicator of at least one transmission point, and a precoding type indicator (PTI); - in a second set of reporting instances (excluding reporting instances belonging to the first set) separated by a second period, one long-term (first) point-by-point precoding matrix indicator and possibly one point-by-point long-term combining indicator i for several or each transmission point (possibly at different reporting instances in some embodiments) when the first value is set in the latest PTI transmitted by the WTRU; 1k,comb and, At least one wideband aggregated (or joint) CQI for several or each transmission point (possibly in different reporting instances), one wideband short-term (second) per-point precoding matrix indicator, and one per-point (short-term) wideband combining indicator i, when a second value is set in the latest PTI transmitted by the WTRU. 2kcomb and Report types containing, and / or - within a third set of reporting instances (excluding reporting instances belonging to the first and second sets) separated by a third period; at least one wideband aggregated (or joint) CQI and / or at least one wideband short-term (second) per-point precoding matrix indicator and / or at least one per-point (short-term) wideband combining indicator i for several or each transmission point (possibly in different reporting instances) when a first value is set in the latest PTI transmitted by the WTRU; 2kcomb and / or at least one subband aggregated (or joint) CQI and / or at least one subband short-term (second) precoding matrix indicator and / or at least one (short-term) subband combining indicator i for several or each transmission point (possibly in different reporting instances) when a second value is set in the latest PTI transmitted by the WTRU; 2kcomb Report types that include:

[0172] In one or more of the example subbands described above, the WTRU sets the precoding type indicator to a first value, e.g., when the WTRU determines that the precoding matrix indicator per long-term point and / or the combining indicator per long-term point has changed significantly for at least one transmission point since a previous transmission of the precoding type indicator that was set to the first value. Alternatively, the WTRU sets the precoding type indicator to the first value periodically, e.g., every N subframes or reporting instances, to prevent error propagation. In one or more embodiments, the value of N is configured, e.g., by higher layer signaling.

[0173] One or more embodiments contemplate reporting modes / sub-modes, such as, for example, a WTRU reporting: In a first set of reporting instances separated by a first period, a common (or joint) rank indicator, a precoding type indicator (PTI), and a WTRU the WTRU sets a joint precoding type indicator (JPTI) to a first value if different layers must be transmitted from different transmission points (the combining matrix is ​​an identity matrix); and / or The WTRU sets the JPTI to a second value if at least one layer must be transmitted from a different transmission point. A report type including a JPTI determined according to at least one of: - in a second set of reporting instances (possibly excluding reporting instances belonging to the first set) separated by a second period, one long-term (first) per-point precoding matrix indicator for each transmission point (possibly in different reporting instances), with the first value set in the most recent PTI transmitted by the WTRU; and / or at least one wideband aggregated (or joint) CQI and / or one wideband short-term (second) per-point precoding matrix indicator for several or each transmission point (possibly in different reporting instances) when the second value is set in the latest PTI transmitted by the WTRU, and one wideband combining indicator i when the second value is set in the latest JPTI reported by the WTRU; comb A report type that includes at least one of the following: - reporting instances separated by a third period (possibly excluding reporting instances belonging to the first or second set); within the third set, at least one wideband aggregated (or joint) CQI and / or one wideband short-term (second) per-point precoding matrix indicator for several or each transmission point (possibly in different reporting instances) when the second value is set in the latest PTI transmitted by the WTRU, and one wideband combining indicator i when the second value is set in the latest JPTI reported by the WTRU; comb Report types that include:

[0174] At least one subband aggregated (or joint) CQI and / or one subband short-term (second) point-by-point precoding matrix indicator for several or each transmission point (possibly in different reporting instances) if the second value is set in the latest PTI transmitted by the WTRU, and one subband combining indicator i if the second value is set in the latest JPTI reported by the WTRU. comb .

[0175] Embodiments contemplate one or more techniques in which the periodic feedback is based on independent periods and / or feedback. Stated somewhat differently, embodiments contemplate implementing periodic CSI feedback based on transmitting periodic CSI reports in multiple sets of subframes, some or each of which is defined by at least a period and / or an offset. In such embodiments, the CSI reports transmitted in a particular set of subframes are - a transmission point, a set of transmission points or a set of CSI-RS resources; - transmission status (e.g., reports on joint or single-point transmission), - relevant terms and conditions, and / or - Report type (e.g. whether the WTRU reports rank indicator or CQI / PMI feedback) Embodiments contemplate that the period and / or offset of a given set of subframes may be derived from parameters indicated, for example, by a higher layer.

[0176] In one or more embodiments, the WTRU transmits CSI reports for some combinations of report types and transmission points, or in some embodiments, all possible combinations of report types and transmission points, each in a different set of subframes. For example, the WTRU transmits RI for point 1 in subframe set A, RI for point 2 in subframe set B, CQI / PMI for point 1 in subframe set C, CQI / PMI for point 2 in subframe set D, etc.

[0177] In one or more embodiments, the WTRU transmits a CSI report for some type of feedback that is applicable to several or all transmission points in a single set of subframes. This is useful for several reasons, e.g., some types of CSI information are common among transmission points. For example, an RI may be common to all transmission points, a transmission state, or linked to the RI of a specific transmission point. In this case, the information is transmitted in a single set of subframes rather than one set of subframes per transmission point, thus saving overhead. The same technique applies, for example, to a transmission state indicator (TSI) or a PI that indicates an ordered set of transmission points.

[0178] In one or more embodiments, a given set of subframes is linked to a particular set of transmission points (or CSI-RS resources) or transmission state (e.g., joint transmission) on a semi-static basis. To minimize overhead, the WTRU determines that a certain type of CSI associated with a certain transmission point or transmission state will be transmitted if, and in some embodiments, perhaps only if, certain one or more conditions are satisfied. For example, the conditions are associated with a transmission state determined by the WTRU. The WTRU transmits CSI feedback for a certain transmission point if, and in some embodiments only if, this transmission point is used for transmission to the WTRU according to the determined transmission state. Also, for example, another condition is that a metric (e.g., wideband CQI) associated with the transmission point or state is better than the metric associated with the best transmission point or state minus a threshold. If the WTRU determines that a certain transmission point or transmission state does not satisfy the conditions for transmission, the WTRU indicates this to the network in a separate type of report, such as a TSI or a report of a previously undefined type, e.g., in a separate set of subframes specific to that transmission point. In one or more embodiments, the transmission of CSI feedback for one or more transmission points is conditioned, e.g., on the most recently transmitted value of this report.

[0179] In one or more embodiments, the linkage between the sets of subframes and the transmission points is dynamic. For example, the transmission points are ranked by the WTRU using at least one quality criterion (e.g., highest RI or highest wideband CQI, etc.). The WTRU indicates this ranking in a previously undefined report type that includes a PI, transmitted in a specific set of subframes. Based on the most recently transmitted PI, the CSI for the highest-ranked transmission point is transmitted in a first set of subframes, the CSI for the second-highest transmission point is transmitted in a second set of subframes, and so on. This technique allows, for example, for feedback for more important transmission points to be transmitted more frequently than for less important points.

[0180] Embodiments contemplate that the report type is fed back when the WTRU provides a new ranking of transmission points. The periodicity / offset of each transmission point is pre-configured and / or tied to a rank provided by the WTRU. In one or more embodiments, the WTRU transmits at least two lists, one with "good" transmission points requiring higher periodicity and the other with "bad" transmission points requiring lower periodicity. The number of lists increases, for example, with the required periodicity granularity. The WTRU also reports a PI containing the list of points using higher layer signaling.

[0181] When a WTRU is configured to feed back CSI for multiple transmission points using one of the aforementioned techniques, a feedback report collision occurs if there is an overlap between the sets of subframes. In one or more embodiments, the order of transmission point priority is pre-configured by the network, e.g., when a collision occurs for the same report type, and in some embodiments, pre-configured only when a collision occurs for the same report type. When two transmission points feed back scheduled reports for the same resource, the WTRU feeds back a report for the transmission point with the higher priority. In one or more embodiments, the WTRU selects the transmission point to be fed back. The feedback CSI includes, for example, a PI to indicate which point the feedback relates to.

[0182] Embodiments contemplate that periodic feedback is based on transmitting reports for multiple points. For various reasons, such as to perform periodic CSI reporting, the WTRU is configured with any of the available Rel-10 reporting modes for single-point feedback. Embodiments contemplate that the modes be augmented by including previously undefined report types to include TSI and / or PI. Contemplated report types are previously undefined independent report types or provided jointly with any other report type (e.g., a report type that combines RI with TSI). In that case, some or all other feedback report types are conditioned on the point(s) indicated in the most recently transmitted report type that included TSI and / or PI. In one or more embodiments, the TSI is transmitted with a higher periodicity than the PI or other report types, and the PI is transmitted to indicate which point within the TSV (indicated by the TSI) future reports are conditioned on. Alternatively or additionally, some or all feedback reports include a TSI and / or PI that indicate which point the particular report pertains to.

[0183] In one or more embodiments, CSI components for multiple points are reported in the same subframe. For example, existing report types (e.g., 1, 1a, 2, 2a, 2b, etc.) can be maintained, modified, or extended so that the type of CSI information provided in the report is provided for multiple points rather than a single point. Embodiments contemplate that this may result in an increase in the number of reports or the information payload of each report, but may facilitate maintaining the time organization of existing periodic modes, for example, regardless of the number of transmission points.

[0184] Embodiments contemplate one or more techniques applicable to one or more particular report types, such as, but not limited to, the following. - in reports 1 and 1a containing subband CQI for the best WTRU selected subband of the BW portion, the WTRU reports both points (and possibly a single subband at both points) or one subband at each point; In reports that include CQI (e.g., 1, 1a, 2, 2b, 2c, 4), the WTRU reports at least one of the following (it is contemplated that per-point CQI may or may not involve a mute hypothesis): Point-wise CQI of the first codeword of each point, some or each of which is relative to the first codeword of each point, spatially differential point-wise CQI of the second codeword of each point (if RI>1); a point-wise CQI for the first codeword of a point, a differential point-wise CQI for the first codeword of each other point (some or each of which is relative to the first codeword of the first point), a differential point-wise CQI for the second codeword of each point (some or each of which is relative to either the first codeword of the first point or the first codeword of each point) (e.g., if RI>1), and / or Aggregated CQI for the first codeword, assuming joint transmission from some or all points; spatially differential aggregated CQI for the second codeword, assuming joint transmission from some or all points (e.g., RI>1); - In reports that include PMI or secondary PMI (e.g., 1a, 2, 2b, 5), Per-point PMI for some or each point with fewer than eight antenna points, second PMI for some or each point with eight antenna ports; for some or each point other than the first point, at least one phase offset between the first point and this point, and / or one or more combining indicators (e.g., a single indicator pointing to a co-phase matrix between points), and / or - if at least one point has eight antenna ports, Report 2a or 2c includes the first PMI for a point with eight antenna ports, and in some embodiments, report 2a or 2c includes only the first PMI for a point with eight antenna ports.

[0185] In one or more embodiments, contemplated report types that include TSI also include an order of points (e.g., a vector of points) for which the CSI is fed back. In that case, the feedback report that occurs after the TSI and order of points have been fed back is for the first point. A previously undefined single-bit flag may be added to any of the contemplated report types, and after feeding back a predefined value for the flag, the point for which future reports are conditioned cycles to the next point in the vector of ordered points. Alternatively or additionally, in one or more embodiments, the order of points is signaled by the network to the WTRU.

[0186] In one or more embodiments, the WTRU is configured in Rel-10 periodic feedback mode. Embodiments contemplate that the WTRU is configured with a period and / or offset that associates a subframe number with a point and / or TSI and / or PI. Some or all feedback reports are conditioned on the point to which the subframe is associated, and in some embodiments, some or all feedback reports must be conditioned on the point to which the subframe is associated.

[0187] In one or more embodiments, report types that include TSI and / or PI or higher signaling or subframe numbers also include, either explicitly or implicitly, information regarding whether the feedback report is for aggregated or point-by-point values. Aggregated feedback is achieved by removing the conditioning of report types to the most recently reported PI and / or by conditioning some or all aggregated report types to the most recently fed back TSI. Alternatively or additionally, aggregated feedback is achieved by transmitting differential values ​​conditioned on feedback of preselected points. The preselected points are determined by a metric such as, but not limited to, the highest point-by-point CQI. For example, point 1 is considered a reference point, and thus, when the PI indicates point 1 feedback, the CQI represents the point-by-point CQI of point 1. In one or more embodiments, when the PI indicates other points, the CQI represents a differential value (compared to the point-by-point CQI of point 1), for example, to provide an aggregated CQI.

[0188] Embodiments contemplate periodic feedback based on cycling between transmission points and / or transmission states. In one or more embodiments, the WTRU is configured with one of the Rel-10 reporting modes augmented by allowing certain feedback report types to cycle through points. For example, if RI is configured, the WTRU feeds back at least one value for every point (i.e., aggregate RI), and in some embodiments, perhaps only one value for every point. In one or more embodiments, several or each successive RI report represents a different point rank. The point for which the RI report is configured can be obtained by cycling through a vector of points. The vector of points is, for example, implicitly determined from the most recent TSI and / or PI, or explicitly fed back by the WTRU in a previously undefined report type, or pre-configured by the network via higher layer signaling. In one or more embodiments, when the WTRU uses RI cycling, the periodicity per point of the RI report is N points *M RI *N pd (where N points is the total number of points, and the reporting interval of the RI report is the CQI / PMI report period N as defined in, for example, 3GPP TS 36.213. pd Integer multiples of (M RI )

[0189] When wideband CQI / PMI reporting is configured, the WTRU cycles through the or each point for each successive report on CQI / PMI, where the periodicity at which the or each point CQI / PMI is reported is N points *N pdThe embodiments contemplate that when a PMI is represented by two parts (e.g., PMI1 and PMI2), the point cycling for each precoding matrix may be dependent or independent. For example, in single point reporting mode 2-1, when PTI=0, the following order of reporting is configured: W-PMI1, W-CQI / W-PMI2, W-CQI / W-PMI2 W-CQI / W-PMI2, W-PMI1, W-CQI / W-PMI2, W-CQI / W-PMI2, W-CQI / W-PMI2… (Where W means wideband, PMI1 means first precoder matrix indicator, and PMI2 means second precoding matrix indicator.) When cycling through points, the following example demonstrates that the cycling of W-PMI1 and W-PMI2 is dependent. W-PMI1 a , W-CQI / W-PMI2 a , W-CQI / W-PMI2 a W-CQI / W-PMI2 a , W-PMI1 b , W-CQI / W-PMI2 b , W-CQI / W-PMI2 b , W-CQI / W-PMI2 b …

[0190] In one or more dependent ways, embodiments contemplate that cycling occurs with respect to one report type (e.g., PMI1), and in some embodiments perhaps only one report type, with other report types being conditioned on the points used for the cycled report type. Alternatively, embodiments contemplate that cycling is independent. W-PMI1 a , W-CQI / W-PMI2 a , W-CQI / W-PMI2 b W-CQI / W-PMI2 c , W-PMI1 b , W-CQI / W-PMI2 a, W-CQI / W-PMI2 b , W-CQI / W-PMI2 c … (where lettered subscripts are used to denote different points). Embodiments contemplate that the concepts of dependent cycling and independent cycling may be attributed to either of the report types. For dependent cycling, in some embodiments, one report type is considered an anchor upon which the point dependency of another report type is conditioned. For example, for the case where both wideband CQI / PMI and subband CQI are configured, if the subband CQI is anchored to the wideband CQI, the point upon which the subband report is conditioned depends on the point for the most recent wideband CQI. As an illustrative example, in mode 2-0, for a single point and two bandwidth portions, the reporting may be W-CQI, S-CQI1, S-CQI2, S-CQI1, S-CQI2, W-CQI, S-CQI1, S-CQI2, S-CQI1, S-CQI2… (The numbered subscripts indicate the subband numbers).

[0191] The embodiments contemplate that when cycling through points, the following illustrates an example of cycling dependency between sub-band CQI and wide-area CQI. W-CQI a , S-CQI 1,a , S-CQI 2,a , S-CQI 1,a , S-CQI 2,a , W-CQI b , S-CQI 1,b , S-CQI 2,b , S-CQI 1,b , S-CQI 2,b … In that case, the periodicity of the wideband CQI is N points *H*N pd(where H is an integer multiple used to determine the periodicity of wideband CQI / wideband PMI reporting as defined, for example, in 3GPP TS 36.213.

[0192] For one or more embodiments, the following provides an example of cycling dependency between wideband and sub-band CQI. W-CQI a , S-CQI 1,a , S-CQI 2,a , S-CQI 1,b , S-CQI 2,b , W-CQI b , S-CQI 1,a , S-CQI 2,a , S-CQI 1,b , S-CQI 2,b … One or more embodiments contemplate that the subband reports cycle through some or all bandwidth portions of at least one point in successive reports before cycling through a point. Alternatively or additionally, the order of cycling can be reversed, with some or all subband reports for different points being cycled through while keeping the bandwidth portion constant in successive reports before cycling through the bandwidth portion. Embodiments contemplate that the cycling and / or cycling dependency can be applicable for any combination of report types and any reporting mode. In one or more embodiments, the cycling occurs across all points and across two hypotheses: aggregated or point-by-point feedback.

[0193] Embodiments contemplate techniques for reporting channel state information from multiple transmission points using measurement reports generated at the RRC layer. In one or more embodiments, a WTRU may estimate the received signal strength (RSRP) and / or received signal quality (RSRQ) and / or path loss of a subset of transmission points of a certain cell based on measuring the transmitted CSI-RS reference signal(s) for the subset of transmission points.

[0194] Embodiments also contemplate that a WTRU estimates the received signal strength (RSRP) and / or received signal quality (RSRQ) and / or path loss for a subset of transmission points of a certain cell based on measuring a previously undefined type of reference signal(s) transmitted for this subset of transmission points (referred to as Transmission Point Reference Signals or TP-RS). The TP-RS is transmitted for and received by CoMP-capable WTRUs in accordance with this method during, and in some embodiments only during, specific subframes whose patterns are provided by higher layers, defined as "multipoint measurement" subframes. Such subframes are included as a subset of MBSFN subframes, for example, to prevent legacy WTRUs from attempting to perform certain measurements and associated processing in these subframes.

[0195] Embodiments contemplate that TP-RS transmitted from different (adjacent) transmission points are transmitted in different OFDM symbols to prevent loss of accuracy due to potential power imbalance between the signals received from these points.

[0196] Using the CSI-RS or TP-RS for its measurements, the WTRU separately reports the RSRP or RSRQ values ​​for some or each transmission point of the same cell(s) and / or different cell(s). Based on the RRC measurement reports, the network explicitly configures the WTRU with a subset of transmission points for CSI reporting. Embodiments contemplate that the higher layer RSRP measurements per CSI-RS or per TP-RS are used by the network, for example, to manage the set of CSI-RS resources used by the WTRU for CSI measurement reporting, among other reasons.

[0197] More specifically, the WTRU is configured with a list of transmission points, CSI-RS, or TP-RS (ports) to measure, possibly as part of its measurement configuration, which includes at least a subset of CSI-RS or TP-RS configurations corresponding to one or a combination of a list of CSI-RS or TP-RS related to a serving cell (e.g., CSI-RS or TP-RS transmitted from the WTRU's serving cell, primary serving cell, or possibly secondary cell), a list of CSI-RS or TP-RS related to a particular PCI, and / or a list of CSI-RS or TP-RS related to any PCI.

[0198] Embodiments contemplate that the configuration of the CSI-RS or TP-RS used for higher layer measurements includes at least one of the following configuration parameters: - Antenna port count (for example, 1, 2, 4, or 8), - resource configuration (e.g., CSI-RS or TP-RS resource element configuration); - Subframe configuration (e.g., subframes in which CSI-RS or TP-RS are transmitted); - the assumed ratio of PDSCH EPRE to CSI-RS EPRE (e.g., Pc value); - at least one parameter used to derive the initial value of the pseudo-random sequence for the CSI-RS, such as a virtual cell identity. In one or more embodiments, some or each of the ports or some or each of a subset of the ports has its own pseudo-random sequence initialization configuration; and / or - Associated PCI - This parameter is included if the CSI-RS or TP-RS corresponds to a cell different from the serving cell or Pcell. Furthermore, this parameter is included if the CSI-RS of a different cell is configured with respect to RS RSP measurements. In one or more embodiments, the network configures a complete or partial set of the parameters described above for some or all of the CSI-RS included in the higher layer measurement set, for example, at the WTRU.

[0199] Alternatively or additionally, one or more embodiments contemplate that a subset of the previously described configurations are common across the configured transmission points (e.g., certain parameters are provided for some or all transmission points) for multiple reasons, such as to optimize signaling. The remaining subsets are provided to the WTRU separately for some or each transmission point configuration. For example, the antenna port count is a common parameter, and the resource configuration, subframe configuration, and / or pseudo-random sequence configuration are different for some or each provided transmission point (CSI-RS or TP-RS).

[0200] In another example, the subframe configuration is also a common configuration parameter across transmission points configured for higher layer measurements. More specifically, in such an example, the WTRU measurement set configuration includes one subframe configuration and potentially one antenna port configuration (or alternatively, a default antenna port configuration (e.g., 2) is assumed), followed by a list of independent transmission point (e.g., CSI-RS or TP-RS) parameter configurations, including, but not limited to, resource configurations and / or pseudo-random sequence configurations.

[0201] As a further example, one CSI-RS or TP-RS configuration may have multiple subsets of ports, each with its own sequence generation. This allows the network flexibility to manage different CSI-RS configurations for different WTRUs. In this case, the WTRU is informed of multiple sequence initiators and ports to which some or each initialization is applicable. Alternatively or additionally, the WTRU attempts to blindly decode and / or measure the RSRP of CSI-RS transmitted (and detected) in the configured cell. To assist the WTRU in blindly decoding the CSI-RS or TP-RS, the WTRU is provided with a subframe configuration for searching for the CSI-RS, taking into account a default antenna port count (e.g., a two-antenna port configuration) or a given configured antenna port count. Additionally or alternatively, embodiments contemplate the network configuring at least some subframes to be used for blind decoding. In these or any other subframes, the same sequence generation initialization is used for some or all CSI-RS or TP-RS resources. The sequence generation initialization is obtained, for example, by the actual PCI of the macrocell.

[0202] Embodiments contemplate that the WTRU considers some or all possible resource elements on which the CSI-RS for the antenna port count is transmitted to detect potential CSI-RS transmissions. In one or more embodiments, when reporting higher layer measurements to the network, the WTRU reports the resource element(s) on which the CSI-RS was detected along with the RSRP. This allows the network to determine which CSI-RS the measurement corresponds to and / or to correctly configure the CSI-reporting set and / or CoMP set. In one or more embodiments, the WTRU reports a resource configuration index (or resourceConfig parameter) indicating the location of these resource elements along with the RSRP. To further assist the WTRU in decoding transmission points, in one or more embodiments, the network provides scrambling configurations for the CSI-RS points that the WTRU decodes (or at least attempts to decode) in the configured subframes.

[0203] Alternatively or additionally, one or more embodiments contemplate CSI-RS whose sequences are cyclic shifts of each other (e.g., no longer Gold sequences but closer to CAZAC sequences), in which case the scrambling configuration does not need to be provided to the WTRU in advance. In that case, some or all cooperating points share the same root sequence. One or more embodiments contemplate the root sequence being conditioned on the subframe number, e.g., pre-configured by the network and signaled to the WTRU via higher layers. One or more embodiments also contemplate the WTRU maintaining and / or measuring measurement quality for some or each transmission point, e.g., used for evaluation of reporting metrics or measurement criteria.

[0204] For example, and without limitation, the measurement configuration message provides one or a combination of information to the WTRU. For example, this information includes a set of measurement identities to be used for multi-point CSI-RS or multi-point TP-RS reporting that may or may not belong to the serving cell physical identity (and, in some embodiments, perhaps only for multi-point CSI-RS or multi-point TP-RS reporting). This information includes a set of measurement identities associated with at least one measurement object that the WTRU can use across some or all cells and / or transmission points. Furthermore, this information includes instructions to configure the WTRU to measure CSI-RS or TP-RS per transmission point (e.g., serving cell) for a configured PCI. This configuration may be specific to a measurement identity, measurement object, or reporting configuration, or alternatively, apply across some or all measurement identities and / or events. In another example, this information includes, in addition to a list of CSI-RS or TP-RS, instructions to configure the WTRU to measure CRS. In another example, the WTRU determines which transmission points it should measure, and perhaps in some embodiments should measure, based on the presence of a list. The measurement identities on which these measurements have been made (and in some embodiments perhaps must be made) and on which the WTRU can use them for criteria evaluation are explicitly indicated in the measurement configuration message. Alternatively, the WTRU applies these across some or all measurement identities. In another example, this information includes an explicit indication of which measurement identities the measurements of the transmission points in the subset are applicable to.

[0205] The WTRU is configured with one or more measurement events, although the range of measurement events and measurement identities varies across different deployments and networks. For example, the measurement events include event A4. In this example, the quality of a neighboring cell becomes better than a configured threshold for a configured period of time. When configured with instructions to measure CSI-RS or TP-RS of multiple transmission points, this event is interpreted by the WTRU as the quality of a transmission point becoming better than a configured threshold for a configured period of time. Furthermore, the WTRU limits transmission of this event to transmission points in the serving cell, and in some embodiments, perhaps only transmission points in the serving cell.

[0206] In another example of a measurement event, the event is when the quality of a transmission point of the serving cell drops below a configured threshold. This is also configured by setting the "reportOnLeave" bit of event A4. In one example, the quality of the transmission point becomes better than the quality of a transmission point in the CSI-reporting set or CoMP set by a threshold value for a configured period of time. This corresponds, for example, to a previously undefined event used to maintain the CoMP set.

[0207] Because the WTRU is performing measurements for multiple transmission points in the same cell or in different cells, for example to enable correct measurement criterion evaluation and comparison with other cells also configured with multiple transmission points, the WTRU uses one or a combination of various measurements. In one example, the WTRU performs CRS measurements on the serving cell and / or neighboring cells in addition to CSI-RS or TP-RS measurements on some or all configured transmission points; in some embodiments, the CRS measurements are R10 CRS measurements. In this example, the measurements are used as a basis for comparison for other events. In another example, the WTRU uses the best measured transmission point of some or each cell as a basis for comparison for other events (e.g., to evaluate and trigger event A3, the WTRU takes into account the quality of the best transmission point in the serving cell, and in some embodiments only takes into account the quality of the best transmission point in the serving cell). In another example, the WTRU uses the first CSI-RS or TP-RS of some or each configured subset, if configured. In another example, the WTRU uses a function or average value of CSI-RS or TP-RS measured from different physical channel identities or different subsets (e.g., alternatively, the CSI-RS or TP-RS used in the formula is a CSI-RSM or TP-RS (e.g., a CSI report set) in the configured CoMP set).

[0208] In another example, the WTRU uses some or all transmission point measurements and treats them as measurements from different cells. Then, some or all configured events are triggered for transmission points in the same serving cell. For example, event A3 is triggered when there is a change in the best transmission point in the serving cell or when there is a change in the best cell compared to some or all transmission points in the serving cell. In another example, the WTRU triggers an event if the transmission points for which a criterion is met belong to the same subset (e.g., certain events are triggered if the criterion is met for a transmission point). In one or more embodiments, the WTRU only triggers an event if the transmission points for which a criterion is met belong to the same subset (e.g., certain events are only triggered if the criterion is met for a transmission point).

[0209] In one or more contemplated embodiments, measurements taken on the CSI-RS or TP-RS are used to evaluate transmission point-specific configured events and / or to perform transmission point measurement quality reporting. In such embodiments, neighboring cell measurements performed on the legacy CRS are used independently for other events and / or reporting configurations. Embodiments contemplate, for example, that a measurement configuration (e.g., measConfig) requires the WTRU to perform intra-frequency measurements on a set of transmission points on the serving cell and / or a different cell(s). In one or more embodiments, the WTRU is also required to perform inter-frequency measurements on a set of transmission points on another frequency.

[0210] In one or more embodiments, the WTRU is configured with a measurement object and / or reporting configuration that possibly explicitly indicates to the WTRU that the configured event or configuration applies to the CSI-RS or TP-RS measurements. This is done using one or a combination of the following: - A new measurement object is defined for transmission point measurements on CSI-RS or TP-RS. In one or more embodiments, multiple measurement objects for one frequency are defined (e.g., one measurement object for cell evaluation and one measurement object for transmission point evaluation). The reporting configuration includes a new CoMP set management event or an existing event configuration. Embodiments contemplate that at least one measurement entity is configured to have an associated measurement object that includes a transmission point CSI-RS list or a transmission point TP-RS list and / or a reporting configuration; One or more previously undefined purposes are contemplated in the reporting configuration reportConfig. For example, one purpose corresponds to a purpose set to "reportMeasCSI_RS". Embodiments contemplate that when a reporting configuration with a purpose set to "reportMeasCSI_RS" is received by a WTRU, the WTRU performs measurements on a reference signal (e.g., CSI-RS or TP-RS) of a transmission point. The reporting configuration includes an event-triggered configuration with an additional purpose and / or identifier that this reporting configuration is used for CSI-RS measurements. The reporting configuration is used, for example, to request the WTRU to measure the listed CSI-RS and report them within a configured time period, - The measurement object contains a transmission point CSI-RS configuration or a transmission point TP-RS configuration (e.g., a list of transmission points for performing CSI-RS or TP-RS measurements). When referred to below, this list is called "pointsForWhichToReportMeasCSI_RS", and the configuration is according to any of the previously described configurations and / or - The reporting configuration includes the "pointsForWhichToReportMeasCSI_RS" information.

[0211] Embodiments contemplate that the reporting configuration is used in conjunction with any of the previously described techniques for configuring a WTRU with measurement criteria (e.g., events). A measurement report is triggered when the criteria of the associated event(s) are met for a transmission point in the list. In one or more embodiments, the WTRU is requested to measure and / or report a set of transmission points, e.g., by a one-shot request for transmission point measurements. For example, this is achieved by using a reporting configuration (e.g., reportConfig). Embodiments contemplate that one or more previously undefined intents (reportMeasCSI_RS) previously described are used to instruct the WTRU to perform measurements on the configured transmission point list and, in some embodiments, report them. reportConfig sets the intent to reportMeasCSI_RS and configures or does not configure an event trigger for a given configuration. The WTRU reports the measurements, possibly as soon as it has measured some or all of the requested measurement points, or sends a report, e.g., after a configured period of time. In one or more embodiments, upon expiration of the timer, the WTRU reports some or all of the measured and / or detected CSI-RS.

[0212] In one or more embodiments, the list of transmission points or CSI-RS to measure is provided as part of a measurement object (e.g., an intra-frequency measurement object). The measurement object includes a list of CSI-RS, TP-RS, and / or transmission points that the WTRU will measure, and in one or more embodiments, perhaps must measure. When referred to below, this list is referred to as pointsForWhichToReportMeasCSI_RS. In such an example, the reporting configuration includes a report type or purpose (e.g., reportMeasCSI_RS) and further includes reporting criteria, where the reporting criteria include an existing event (e.g., event 4) or a previously undefined event. Alternatively or additionally, the reporting configuration sets the purpose to “reportMeasCSI-RS” (in some embodiments, perhaps only sets the purpose to “reportMeasCSI-RS”) and does not configure any events. In that case, the WTRU uses the presence of such a reporting intent to indicate that it will measure, acquire (or at least attempt to acquire) the provided transmission point CSI-RS, and report the measurement quantity, for example, after it has been measured or within a configured time.

[0213] In one or more embodiments, the WTRU is configured with at least one measurement identity for transmission point CSI-RS reporting that combines at least one of the reportConfig and / or corresponding measurement objects (e.g., including CSI-RS configuration, pointsForWhichToReportMeasCSI_RS) with purpose "reportMeasCSI_RS" set.

[0214] In one or more embodiments, for some or each measId, embodiments contemplate that the corresponding reportConfig includes an object set to "reportMeasCSI_RS". In some embodiments, the WTRU performs measurements on the CSI-RS on the frequencies in the associated measObject. For example, if no Assistant information for CSI-RS is provided to the WTRU, the WTRU detects (or at least attempts to detect) CSI-RS on configured subframes, possibly on known possible resource elements of CSI-RS for a given antenna configuration, and measures the configured measurement quantity (e.g., RSRP). As a further example, the WTRU performs measurements on the transmission point CSI-RS or transmission point TP-RS found in cellForWhichToReportMeasCSI_RS.

[0215] In one or more embodiments, for some or each measId, embodiments contemplate that the corresponding reportConfig includes an object set to reportMeasCSI_RS. In some embodiments, the WTRU considers all transmission points (CSI-RS) detected on a given cell and matches the value of "cellForWhichToReportMeasCSI_RS" included in the corresponding measObject in the VarMeasConfig applicable to event reporting and / or event triggering provided in the corresponding ReportConfig.

[0216] In one or more embodiments, a previously undefined measurement object is configured in the WTRU. The measurement object includes pointsForWhichToReportMeasCSI_RS. At least one measurement identity is configured in which such measurement object and / or reporting configuration is linked, possibly to enable the WTRU to take measurements for transmission points for the serving cell and / or any other cells, for example, among other reasons. In one or more embodiments, for some or each measID, the corresponding measurement object includes cellForWhichToReportMeasCSI_RS. Embodiments contemplate that the WTRU considers all transmission points (CSI-RS) detected on a given cell and matches the value of “cellForWhichToReportMeasCSI_RS” contained in the corresponding measObject in the VarMeasConfig applicable to event reporting and / or event triggering provided in the corresponding ReportConfig.

[0217] Embodiments contemplate autonomous removal of measurement configurations. In one or more embodiments, the WTRU autonomously removes one or more measurement configurations for a number of reasons, such as when a serving cell change occurs, for example, if the transmission points to be measured correspond to transmission points that are present in the serving cell (and perhaps only in some embodiments). By way of further example, embodiments contemplate a serving cell change and / or handover occurring, where the WTRU autonomously removes one or a combination of the following measurement configurations: - a measurement identity with a corresponding reportConfig with purpose "reportMeasCSI_RS", - a measurement identity with a corresponding measObject with a list of CSI-RS to measure (for example, this is used when a previously undefined measurement object is introduced for CSI-RS measurements), - reportConfig with reportMeasCSI_RS set to the desired value, and / or The cellForWhichToReportMeasCSI_RS is removed from the WTRU's memory for the given measurement object.

[0218] When a criterion (e.g., reporting configuration) corresponding to one of the measurement events for a transmission point is satisfied and / or when the WTRU decides to transmit a measurement report according to a request in the reporting configuration. The WTRU triggers a measurement report, which is sent to the network and includes some or all of the following information: measurement identity, serving cell physical channel identity, transmission point(s) identity that triggered the event and corresponding measurement results (the transmission point identity corresponds to the transmission point index provided in the original configuration message, which is either an explicit index or implicitly determined by the WTRU based on the order of the transmission point configuration (alternatively, the transmission point identity is indicated in the report by providing a virtual cell ID provided as part of the measurement list, e.g., for scenarios where a virtual ID is provided to the WTRU), the subset to which the CSI-RS or TP-RS triggering the event corresponds, and / or measurements of other transmission points are also included in the report. In case of blind detection, embodiments contemplate that the RE in which the reference signal was detected is indicated in the report. The network uses this measurement report to determine a CoMP set and configure the WTRU with the set, which determines the set of transmission points for which the WTRU performs CSI reporting. One or more embodiments extend equally to transmission points in a secondary serving cell (Scell), where in some embodiments a specific Scell ​​offset is also defined.

[0219] Embodiments contemplate measuring CSI-RS for one or more different subsets of transmission points. In one or more embodiments, the WTRU measures sets of CSI-RS associated with different transmission points (or subsets thereof) in different subframes. The subframes during which the WTRU measures the set of CSI-RS for a particular subset of transmission points occur on a periodic basis. In this case, the periodicity and / or offset of the subframes during which the CSI-RS are measured is different for some or each subset of transmission points. In one or more embodiments, the WTRU measures the subframe configuration (I CSI-RS The WTRU measures the CSI-RS reference signal of a transmission point according to the number of antennas (antennaPortsCount parameter and / or subframeConfig parameter) and / or the number of antennas specific to this transmission point (antennaPortsCount parameter). In other words, the WTRU is provided with multiple non-zero power CSI-RS configurations instead of, for example, a single non-zero power CSI-RS configuration. This technique allows for greater flexibility in configuring CSI-RS transmissions in networks comprising, for example, multiple transmission points in the same geographical area.

[0220] The WTRU is also provided with a set of zero-power CSI-RS (or muting patterns) for some or each transmission point (or a subset thereof) occurring in different subframes for the different transmission points (or a subset thereof). The WTRU uses knowledge of the existence of these muting patterns for at least the following purposes: PDSCH decoding and / or CSI calculation adjustment, such as interference estimation and / or estimation of a desired signal occurring in the same OFDM symbol as a muted resource element. In one or more embodiments, there is one muting pattern (possibly a single muting pattern in some embodiments) defined for estimating interference for some or all types of CQI, or separate muting patterns defined for estimating interference for some or each type of CQI, such as aggregated CQI, point-by-point CQI without muting assumptions at other points, and / or point-by-point CQI with muting assumptions at other points.

[0221] In one or more embodiments, the WTRU measures sets of CSI-RS associated with different transmission points in the same subframe but in different resource elements. This technique has the advantage that, for example, the phase difference between the transmission points can be measured more accurately because the signals are measured in the same subframe.

[0222] More specifically, in one or more embodiments, CSI-RS associated with different transmission points are transmitted and / or measured by the WTRU in different OFDM symbols in the time domain. Such embodiments minimize problems resulting from received power imbalances between signals transmitted from different transmission points with different path losses to them. In some embodiments, the WTRU measures the CSI-RS reference signals of a transmission point according to a CSI reference signal configuration (and / or number of antenna ports) specific to this transmission point rather than a CSI reference signal configuration (resourceConfig parameter) common to some or all transmission points. Such a reference signal configuration is indicated, for example, by an integer ranging from 0 to 31 for some or each transmission point (for example), and is provided by higher layer signaling or physical layer signaling.

[0223] FIG. 3A shows an example CSI-RS port mapping for a normal CP subframe. According to the number of TX antennas of a transmission point, one set of the illustrated CSI-RS ports is used for CSI measurement. In some embodiments, perhaps only one set of the illustrated CSI-RS ports is used for CSI measurement. One or more embodiments contemplate that simultaneous CSI measurement of multiple transmit ports in the same subframe can be achieved. For example, in a multipoint transmission system including a macro eNB with four Tx antennas and three remote radio heads, each with two TX antennas, the CSI-RS is transmitted as shown in FIG. 3B. In FIG. 3B, the four illustrated resource elements (rows 1 and 7 of columns 10 and 11) are used for CSI measurement of the macro eNB. The three illustrated 2 resource element sets (e.g., third row of columns 5 and 6 for the 2CSI-RS port and the 4CSI-RS port, and third row of columns 12 and 13 for the 4CSI-RS port) are used for CSI measurements of three remote radio heads, such as remote radio head A, B, and / or C. The WTRU is configured to measure the CSI-RS transmitted from the macro eNB and the CSI-RS transmitted from at least one of the remote radio heads. Because these are transmitted in different OFDM symbols, there is no measurement degradation due to a potential power imbalance between the CSI-RS transmitted from the two nodes.

[0224] In one or more embodiments, CSI-RS is transmitted and / or received by CoMP-capable WTRUs during (and in some embodiments, possibly only during) specific subframes defined as "multipoint measurement" subframes, the pattern of which is provided by higher layers. In some embodiments, such subframes are included as a subset of MBSFN subframes to prevent legacy WTRUs from attempting to perform certain measurements and related processing in these subframes.

[0225] In one or more embodiments, different transmission points (or subsets thereof) are associated with different values ​​of the ratio of PDSCH EPRE to CSI-RS EPRE (or pC parameter) used to derive at least the CQI. Sometimes, or in some embodiments, whenever the WTRU estimates CSI associated with a given transmission point (or subset thereof), the WTRU determines an appropriate value of the ratio for this transmission point (or subset thereof) and uses this to calculate the CSI. The ratio value for each transmission point or subset thereof is provided by higher layers (e.g., RRC signaling). In one or more embodiments in which the WTRU estimates CSI based on at least one common reference signal (CRS), the WTRU estimates the CSI associated with a given transmission point, for example, by using a value of cell-specific RS EPRE (parameter referenceSignalPower) that is specific to this transmission point.

[0226] Embodiments contemplate that the RS received from a signal at Tx point m on subcarrier k can be expressed as:

[0227]

number

[0228] where (m, τ) is the timing offset from Tx point m,

[0229]

number

[0230] is the RS symbol received on subcarrier k without timing offset, and N is the number of FFT points. The received DM-RS symbols are

[0231]

number

[0232]

number

[0233] The received data symbols are given by

[0234]

number

[0235]

number

[0236] The RS signal or user j received from Tx points m1 and m2 on subcarrier k and OFDM symbol l is given by

[0237]

number

[0238]

number

[0239] If the timing of the phase information during transmission cannot be reported, the best precoder

[0240]

number

[0241] and

[0242]

number

[0243] teeth,

[0244]

number

[0245]

number

[0246] Embodiments may then find the cross term

[0247]

number

[0248] and

[0249]

number

[0250] It is recognized that since is not optimized, the received signal (or sum-rate) is not maximized.

[0251] On the other hand, if relative timing or phase information can be measured and reported (such measurements can be accurate, for example, by measuring the CSI-RS of both transmission points in the same subframe as described in Section 4.4),

[0252]

number

[0253] and

[0254]

number

[0255] can be jointly determined by maximizing equation (7). Embodiments recognize that this may require a large quantized codebook.

[0256] Therefore, embodiments contemplate a technique to compensate for the loss of total rate due to timing offset, which is achieved by changing equation (7) to

[0257]

number

[0258]

number

[0259] This can be shown by rewriting it as

[0260] The phase correction matrix term V is

[0261]

number

[0262] or

[0263]

number

[0264] , allowing equation (10) or (11) to be optimized, and therefore the effective precoder matrix is

[0265]

number

[0266] or

[0267]

number

[0268] It can be either of the following.

[0269] In this scenario, the timing offset can either be reported separately or included in the phase correction matrix term, i.e., Phase adjustment

[0270]

number

[0271] Or simply the timing offset Δτ is measured from the RS, quantized and reported separately to the eNB, and the phase correction matrix term V is reported separately to the eNB. Alternatively, phase adjustment

[0272]

number

[0273] is the phase correction matrix term

[0274]

number

[0275] and jointly reported to the eNB.

[0276] In view of the description herein and with reference to FIG. 4, example embodiments contemplate, at least in part, a wireless transmit / receive device (WTRU) configured to identify 402 one or more transmission points. The one or more transmission points are configured for channel state information (CSI) reporting. The WTRU is further configured to generate 404 CSI for the one or more transmission points. The WTRU is also configured to transmit 406 the CSI to one or more nodes in communication with the WTRU. Embodiments contemplate that the one or more transmission points include at least one antenna port in communication with the WTRU. Embodiments also contemplate that the one or more transmission points are CSI reference signal (CSI-RS) resources. Embodiments contemplate that the WTRU is further configured to receive 408 an indication of the one or more transmission points via signaling from one or more logical layers above the WTRU's physical layer.

[0277] Embodiments contemplate that the WTRU, at 410, is further configured to determine the one or more transmission points based at least in part on at least one characteristic of a signal transmitted from the one or more transmission points, respectively. Embodiments contemplate that the at least one characteristic is, for example, at least one of signal strength, signal quality, or channel quality. Embodiments contemplate that the WTRU, at 412, is further configured to identify one or more subsets of the one or more transmission points. Embodiments contemplate that the one or more transmission points are further configured for CSI reporting in one or more subframes. Embodiments contemplate that the WTRU, at 414, is further configured to transmit CSI of the at least one subset in at least one subframe. Embodiments contemplate that the at least one subframe is determined based at least in part on at least one of a system frame number or a subframe number. Embodiments contemplate that the WTRU, at 416, is further configured to transmit CSI for at least one subset in at least one subframe in at least one of a periodic manner or an aperiodic manner.

[0278] Embodiments contemplate one or more methods performed by a wireless transmit / receive unit (WTRU). Referring to FIG. 5, one or more embodiments include, at 502, identifying K transmission points, the K transmission points configured for channel state information (CSI) reporting, where K is an integer. Embodiments further include, at 504, generating CSI for one or more of the K transmission points. Further, embodiments include, at 506, transmitting the CSI to one or more nodes in communication with the WTRU. Also, embodiments include, at 508, receiving at least one of a CSI reference signal (CSI-RS) or a common reference signal (CRS) transmitted by the K transmission points, respectively. Embodiments contemplate identifying the K transmission points based at least in part on the received CSI-RS or CRS. In one or more embodiments, generating CSI includes, at 510, generating at least one of a joint rank indication or a point-by-point rank indication for one or more of the K transmission points. In one or more embodiments, generating the CSI includes, at 512, generating a joint channel quality index (CQI), the joint CQI corresponding to the joint transmission over one or more of the K transmission points.

[0279] Embodiments contemplate that the joint transmission over one or more of the K transmission points is a joint transmission of at least one codeword. Embodiments contemplate that the joint CQI includes, for example, at least one of a coherent joint CQI and a non-coherent joint CQI. Embodiments also contemplate that generating CSI includes, at 514, generating a precoding matrix indicator (PMI) for one or more of the K transmission points.

[0280] Referring to FIG. 6, embodiments contemplate a wireless transmit / receive device (WTRU), at least in part, identifying one or more transmission points at 602, the one or more transmission points configured for channel state information (CSI) reporting. At 604, the WTRU is configured to determine a transmission state of the one or more transmission points. At 606, the WTRU is configured to generate CSI for the one or more transmission points. At 608, the WTRU is further configured to receive an indication of the transmission state of each of the one or more transmission points, the indication of the transmission state including, for example, one or more of a transmission state, an interference state, a blanked state, or an unknown state. At 610, the WTRU is further configured to compare the determined transition state of the one or more transmission points with predetermined transition states of the one or more transmission points. At 612, the WTRU transmits the CSI of each of the one or more communication points to one or more nodes communicating with the WTRU when the transmission state of each of the one or more transmission points is the predetermined transmission state.

[0281] Although features and elements are described above in particular combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with the other features and elements. Furthermore, the methods described herein are implemented in a computer program, software, or firmware embodied in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted via wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, read-only memory (ROM), random-access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software is used to implement a radio frequency transceiver used in a WTRU, UE, terminal, base station, RNC, or any host computer. [Industrial Applicability]

[0282] The present invention can be generally applied to wireless communication systems. [Explanation of symbols]

[0283] 100 Communication Systems 102a, 102b, 102c, 102d WTRU 104 RAN 106 Core Network 110 Internet 114a base station 118 processors 120 Transceiver (transmitter / receiver) 122 Transmitting / Receiving Elements (Antennas)

Claims

1. 1. A wireless transmit / receive unit (WTRU), comprising: Memory and at least, receiving first configuration information indicating one or more sets of channel state information reference signal (CSI-RS) resources; receiving second configuration information associating at least one of the one or more sets of CSI-RS resources with a feedback report; determining a received signal strength ratio (RSRP) to be reported in the feedback report, the RSRP determined using at least a first CSI-RS resource in the at least one of the one or more sets of CSI-RS resources; determining a CSI-RS resource indicator that identifies the first CSI-RS resource used to determine the RSRP; generating the feedback report including the determined RSRP and the CSI-RS resource indicator; Sending the feedback report to the network device and a processor configured to A WTRU comprising:

2. The WTRU of claim 1 , wherein the second configuration information includes a reporting configuration.

3. The WTRU of claim 2 , wherein the reporting configuration indicates at least one of a purpose or a type of the feedback report.

4. 2. The WTRU of claim 1, wherein the processor is further configured to determine a received signal quality (RSRQ) using a second CSI-RS resource in the at least one of the one or more sets of CSI-RS resources.

5. The WTRU of claim 4 , wherein the processor is further configured to indicate the determined RSRQ in the feedback report.

6. 2. The WTRU of claim 1, wherein the CSI-RS resource indicator identifying the first CSI-RS resource used to determine the RSRP comprises at least one of a bitmap or an ordered list of indices.

7. 10. The WTRU of claim 1, wherein the one or more sets of CSI-RS resources include non-zero-power CSI-RS resources.

8. The WTRU of claim 1 , wherein the CSI-RS resource indicator identifying the first CSI-RS resource used to determine the RSRP includes a resource configuration index.

9. 1. A method implemented by a wireless transmit / receive unit (WTRU), comprising: receiving first configuration information indicating one or more sets of channel state information reference signal (CSI-RS) resources; receiving second configuration information associating at least one of the one or more sets of CSI-RS resources with a feedback report; determining a received signal strength ratio (RSRP) to be reported in the feedback report, the RSRP determined using at least a first CSI-RS resource in the at least one of the one or more sets of CSI-RS resources; determining a CSI-RS resource indicator that identifies the first CSI-RS resource used to determine the RSRP; generating the feedback report including the determined RSRP and the CSI-RS resource indicator; sending the feedback report to a network device; A method for providing the above.

10. The method of claim 9 , wherein the second configuration information includes a report configuration, the report configuration indicating at least one of a purpose or a type of the feedback report.

11. determining a received signal quality (RSRQ) using a second CSI-RS resource in the at least one of the one or more sets of CSI-RS resources; including the RSRQ in the feedback report sent to the network device; The method of claim 9 further comprising:

12. 10. The method of claim 9, wherein the CSI-RS resource indicator identifying the first CSI-RS resource comprises at least one of a bitmap or an ordered list of indices.

13. 10. The method of claim 9, wherein the one or more sets of CSI-RS resources include non-zero-power CSI-RS resources.

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