Periodic channel state information signaling using carrier aggregation - Patents.com

Abstract

To provide a method for periodic channel state information signaling that employs carrier aggregation, and to provide an apparatus and a computer readable medium.SOLUTION: A method may include a step for determining channel state information in an apparatus. The channel state information includes channel state information of a plurality of component carriers. The method may also include a step for reporting, by the apparatus, the channel state information including a plurality of reports in an aggregated form.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates generally to communications, and more particularly to communications over multiple carriers. More specifically, in some embodiments, the present invention provides a mechanism for periodic channel state information signaling using carrier aggregation. [Background technology]

[0002] There is no significant prior work on the relevant signaling details of periodic channel state information (CSI) using multiple parallel configurations in the case of multiple component carriers (CCs). Contributions in the 3rd Generation Partnership Project (3GPP) tend to focus on extending the payload of the Physical Uplink Control Channel (PUCCH) beyond 11 bits, thereby enabling new extended CSI formats.

[0003] There has been some discussion about component carrier activation and deactivation, and some discussion about the concept of primary component carriers (PCCs) and secondary component carriers (SCCs) in the radio access network 2 (RAN2). Summary of the Invention [Means for solving the problem]

[0004] In one embodiment, the invention is a method. The method includes determining, at an apparatus, channel state information, the channel state information including channel state information for a plurality of component carriers. The method also includes reporting, by the apparatus, the channel state information including a plurality of reports in aggregate form.

[0005] In a further embodiment, the present invention is an apparatus. The apparatus includes at least one memory including computer program code. The apparatus also includes at least one processor. The at least one memory and the computer program code are configured by the at least one processor to cause the apparatus to determine at least channel state information, the channel state information including channel state information for a plurality of component carriers. The at least one memory and the computer program code are also configured by the at least one processor to cause the apparatus to report the channel state information including a plurality of reports in aggregate form.

[0006] In a further embodiment, the invention is a computer-readable non-transitory medium encoded with information that, when executed in hardware, performs a process including determining channel state information, the channel state information including channel state information for a plurality of component carriers, and reporting the channel state information including a plurality of reports in aggregate form.

[0007] For a proper understanding of the present invention, reference should be made to the accompanying drawings, in which: [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 illustrates an example implementation for handling collisions between channel state information reports. [Figure 2] FIG. 1 illustrates a method according to some embodiments of the present invention. [Figure 3] 1 illustrates an apparatus according to some embodiments of the present invention. [Figure 4] FIG. 1 illustrates a technique for constructing rules for handling component carrier aggregation. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the Long Term Evolution (Advanced) (LTE-Advanced) of the 3rd Generation Partnership Project (3GPP) system, channel state information (CSI) feedback signaling with carrier aggregation, which may be part of 3GPP LTE Release 10 (3GPP LTE Rel-10), may be useful.

[0010] LTE-Advanced serves as an evolution of the LTE Release 8 (Rel-8) system and is capable of meeting the International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R) requirements for International Mobile Telecommunications - Advanced (IMT-Advanced). Carrier aggregation is one technology component that aims to provide higher bandwidth and higher peak data rates for the new system.

[0011] An efficient method for providing channel state information (CSI) reports for multiple component carriers (CCs) can help to efficiently use aggregated spectrum. The following describes aspects of periodic CSI signaling on the physical uplink control channel (PUCCH), and in particular rules and procedures related to configuring multiple CSI reports.

[0012] Periodic reporting of CSI, such as Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), and Rank Indicator (RI), is the primary mode of feedback signaling in LTE Elel-8. Periodic CSI reporting is performed on the PUCCH, and its payload size is typically limited to a maximum of 11 bits. Due to the limited payload size, the reports typically contain little or no information about the frequency domain behavior of the channel.

[0013] With carrier aggregation, periodic CSI may still be required. For example, LTE-Advanced (Rel-10) can support approximately five downlink (DL) CCs. Therefore, simply extending the reporting of multiple CCs as per Rel-8 would result in a larger report (e.g., 5 * 11 bits = 55 bits). This may not be useful from the perspective of uplink (UL) signaling. First, such high overhead may significantly limit the uplink capacity. Second, in many cases, it may be impossible to guarantee sufficient UL coverage for such a large payload. Therefore, some compression methods can be used to reduce the UL signaling load.

[0014] The simplest way to reduce the signaling load is to configure CSI reporting separately for each CC. This option would support standardization and maximize commonality with the Rel-8 specifications. Additionally, DL transmission modes could be configured separately for each DL CC, but this would complicate the joint coding of CSI reporting and at least increase the number of supported options.

[0015] There are many ways to handle component carriers in a communication system. For example, Medium Access Control (MAC) signaling can be used to explicitly activate and deactivate configured downlink (DL) component carriers. Alternatively, implicit deactivation of configured DL component carriers can be used. The configuration of DL / UL component carriers can be done within the user equipment's (UE's) aggregation capabilities. As a result, activation / deactivation can be done within the UE's capabilities as well.

[0016] A newly configured component carrier may always be in a default "inactive" state. An activation command may be required to activate this newly configured component carrier. Furthermore, DL component carriers can be activated and deactivated individually. A subset of configured DL component carriers can be activated / deactivated by a single activation / deactivation command.

[0017] An uplink (UL) primary component carrier (PCC) and a DL PCC can be configured per UE. The UL PCC can be used to transmit L1 uplink control information. In some embodiments, the DL PCC cannot be deactivated. If a DL PCC experiences a radio link failure (RLF), it can trigger recovery differently than if another DL PCC experiences an RLF. However, these implementations are just one example of how component carriers can be handled.

[0018] The following description focuses on rules and procedures for handling multiple CSI reporting configurations. Such rules for handling multiple CSI reporting configurations can be useful when CSI for multiple CCs is transmitted simultaneously in the same subframe. This situation can be described as the state that exists when multiple configurations collide.

[0019] The rules and procedures may relate to processing periodic CSI reporting for carrier aggregation using PUCCH in multiple parallel configurations, which may be CC-specific.

[0020] For each configured DL CC, a periodic CSI reporting mode can be configured. Here, disabled reporting is considered a special configuration case of reporting mode. In other words, when reporting is disabled, it can be considered as periodic reporting with a frequency of "never." This configuration can be done using RRC signaling and includes parameters such as periodicity, subframe offset, reporting mode, and PUCCH resource to use for reporting.

[0021] For a Primary Component Carrier (PCC), the UE can start reporting CQI after receiving the CQI configuration via Radio Resource Control (RRC) signaling. This process follows a similar procedure as in Rel-8.

[0022] For a secondary component carrier (SCC), the UE may start reporting CQI according to the RRC configuration after receiving an activation command for a given CC in medium access control (MAC) signaling.

[0023] In case of CC deactivation, the UE may stop reporting the CSI of this CC, in other words, the UE is not required to report on an inactive CC.

[0024] In some embodiments, when periodic reports for two or more CCs collide, the following complementary rules arise, which are numbered for identification purposes. Unless otherwise specified, these numbers should not be taken as indicating a fixed order, e.g., 2 must come after 1 and before 3.

[0025] Option 1 is multiplexing. In this option, if the PUCCH resources of the conflicting CSI reports are located on the same or adjacent PRBs, all CSI reports can be transmitted simultaneously. Each UE can be configured to exclude this option and always drop conflicting CSI reports according to the following options regarding prioritization:

[0026] Option 2 gives priority to less frequent reports. In this option, the CC configuration with the lowest periodicity takes precedence and other concurrent reports are dropped. In the case of equal periodicity, similar to option 4 described below, CSI corresponding to a predetermined CC is transmitted and CSI(s) corresponding to other CC(s) are dropped.

[0027] Option 3 gives priority to the rank indicator. In this option, reports containing RI are given priority over CQI / PMI. If there is a need to transmit them simultaneously, CQI / PMI will be dropped.

[0028] Option 4 is to rank different CCs separately. The priorities of different CCs can be configured separately. This can be done, for example, by RRC configuration. This configuration indicates the order in which CSI from different CCs is prioritized. In case of a collision, the CSI of the CC with the higher priority is transmitted and the other CSI is dropped.

[0029] Option 5 gives the primary component carrier a higher priority than the secondary component carrier, where the CSI report of the PCC takes precedence over the SCC.

[0030] Various combinations of different options are also possible. For example, option 2 can be combined with option 3. Option 1 can also be combined with options 2, 3, 4, or 5 if some, but not all, CSI reports are located on the same or adjacent PRBs. Thus, for example, the first single CSI report according to one of options 2 to 5 is selected, after which other CSI reports on the same or adjacent PRBs are also selected and transmitted.

[0031] The reporting configuration for DL ​​PCCs can follow Rel-8 principles. For SCC(s), the CSI report can mask activation / deactivation commands received via MAC signaling. For example, there can be a bitmap indicating which SCCs are active or inactive.

[0032] An example implementation for handling conflicts between CSI reports can be summarized in a block diagram in Figure 1. The embodiment of Figure 1 illustrates a decision tree that may be one way of implementing some embodiments of the present invention.

[0033] As shown in Figure 1, when the need arises to simultaneously transmit CSI reports for two or more CCs (the first "Yes" branch from the top of the diagram), the device may first check whether the PUCCH resources configured for the transmission of the CSI reports are on a single PRB or on adjacent PRBs. One reason for imposing such a constraint is that transmission on multiple non-adjacent PUCCHs violates the single-carrier property and may increase cubic metric and out-of-band emissions.

[0034] If the conflicting reports meet the criteria, the reports are sent according to their respective settings, as shown, for example, in the second-to-top "Yes" branch in the diagram. If the conflicting reports do not meet the criteria, as shown, for example, in the lower "No" branch, only the report with the highest priority is sent. The highest priority can be determined using options 2, 3, 4, or 5 above, or a combination of these.

[0035] Alternatively, multiplexing functionality can be configured, for example to restrict cell edge user equipment (UE) to transmitting no more than one CSI report at a time in any case.

[0036] The conditions for simultaneous transmission of multiple PUCCH format 2 / 2a / 2b resources can be met as follows (NxPUCCH format 2 / 2a / 2b).

[0037] First, for the k-th PUCCH format 2 / 2a / 2b resource, a physical resource block (PRB) index m can be defined as follows: JPEG0007785265000001.jpg641In formula, N (2) PUCCH is the resource index configured by the higher layer for the periodic CSI transmitted on the PUCCH, and N RB SC is the number of subcarriers (SC) per PRB (there can be 12 subcarriers per resource block).

[0038] The criterion for simultaneous transmission of multiple PUCCH format 2 / 2a / 2b resources can be formulated as follows: JPEG0007785265000002.jpg636where b is an integer, n∈[0,1,...,N], and N is a predetermined integer. The integer b can be defined as b=min(m(k)). This criterion ensures that simultaneously transmitted PUCCH resources are on the same side of the system bandwidth. There are two special cases: n=0 and n=1.

[0039] n=0: PUCCH resources exist on the same PRB.

[0040] n=1: The PUCCH resource is on an adjacent PRB.

[0041] In principle, a PUCCH resource can reside on several adjacent PRBs. To cover this case as well, the criterion can be checked consecutively, i.e., m(k) are sorted in ascending order, N=1, b=min(m(k)), and the criterion is checked starting from the smallest m(k). If this is met, update N=m(k)+1 for the latest k and continue.

[0042] Some embodiments of the present invention may have various advantages. For example, some embodiments of the present invention may enable independent configuration for each CC, thereby allowing Rel-8 functionality to be reused as much as possible. Furthermore, since there is no existing solution for handling collisions between CSI reports, the above method may be widely implemented through standards, etc. Furthermore, it is expected that enabling multiplexing of CSI when transmitting them on a single or adjacent PRBs will provide performance benefits and ensure sufficient coverage.

[0043] Figure 2 illustrates a method according to some embodiments of the present invention. The method may be performed by an apparatus, such as a terminal, user equipment, or mobile node. The method of Figure 2 includes a step 210 of determining channel state information in the apparatus. The channel state information includes channel state information for multiple component carriers. The method also includes a step 220 of periodically reporting, by the apparatus, the channel state information comprising multiple reports in aggregate form. The aggregate form may include multiple independent reports. The periodic reporting step 220 may be performed via a physical uplink control channel.

[0044] The method may include a step of preparing 215 an aggregated configuration, which may include dropping at least channel state information reports for at least one configuration based on priority, where a configuration of component carriers may include more than one report.

[0045] After selecting the channel state information of a first component carrier for inclusion in the aggregation based on a priority, it is also possible to select other channel state information corresponding to component carriers with the same or adjacent physical resource blocks for inclusion in the aggregation. This priority can be, for example, the least periodic report. In other words, the highest priority can be assigned to the component carrier that sends reports least frequently.

[0046] As can be understood from the above description, information can be encoded on a computer-readable non-transitory medium that, when executed in hardware, performs a process corresponding to the process disclosed in Figure 2 or any other process described herein. By non-transitory medium, we mean that the medium is not a transitory signal. Examples of non-transitory medium include computer-readable medium, computer distribution medium, computer-readable storage medium, and computer program product.

[0047] Channel state information of component carrier configurations with equal periodicity may be prioritized according to a predetermined rank of the component carriers. Channel state information of component carrier configurations comprising a rank indicator may be prioritized higher than channel state information of component carrier configurations comprising a channel quality indicator or a precoding matrix indicator. Alternatively or additionally, multiple component carrier configurations may be individually assigned predetermined priorities. Channel state information of a primary component carrier may be prioritized higher than channel state information of a secondary component carrier.

[0048] 3 illustrates an apparatus according to some embodiments of the present invention. The apparatus may include at least one memory 310 containing computer program code 320. The apparatus may also include at least one processor 330. The apparatus may be configured to communicate with a base station or an enhanced Node B using a transceiver 340 including a receiver portion 343 and a transmitter portion 347. The apparatus may communicate with the base station or other network element via a wireless link 360, which may be a cellular wireless link, using an antenna 350. The apparatus may be configured to prepare a report regarding downlink (DL) quality of, for example, component carriers of the wireless link 360.

[0049] In the process, the at least one memory 310 and the computer program code 320 can be configured by the at least one processor 330 to cause the device to determine at least channel state information. The channel state information can be channel state information for multiple component carriers. The at least one memory 310 and the computer program code 320 can also be configured by the at least one processor 330 to cause the device to at least periodically report the channel state information comprising multiple reports in aggregate form.

[0050] The at least one memory 310 may be any suitable type of memory, such as on-board memory of a controller chip, a hard drive, various types of random access memory (RAM) or read-only memory (ROM), etc. The computer program code 320 may be any suitable type of computer instructions. The computer program code 320 may be provided in compiled or interpreted form. The processor 330 may be any suitable processing device, such as, but not limited to, a central processing unit (CPU), a controller, or an application specific integrated circuit (ASIC).

[0051] A technique for building rules for handling component carrier aggregation is shown in Figure 4. As shown in Figure 4, the technique can begin by selecting 410 a prioritization technique from a variety of techniques. Four such techniques are shown, although others are possible.

[0052] The first of the four techniques shown is to prioritize by report frequency / periodicity 420. That is, CC reports that are reported less frequently can be given higher priority than CC reports that are reported more frequently, and vice versa.

[0053] The second of the four techniques shown is prioritization by prioritizing RI over CGI / PMI 430 (and vice versa), where the most important aspects of the CC report can be given higher priority than aspects that the system deems less important.

[0054] 4 is prioritizing by ranking CCs in an individual, predetermined manner 440. In this technique, each individual CC can be assigned a predetermined ranking and prioritized according to this predetermined ranking.

[0055] 4 is prioritizing 450 by giving CSI reports for PCCs priority over CSI reports for SCCs. This technique allows reports for PCCs to be given priority if both reports for PCCs and SCCs are not feasible. As with the other priority schemes, this can be reversed, if desired, to give SCCs higher priority than PCCs.

[0056] Finally, in addition to the selected CC report from the various available CC reports, the system may multiplex 460 any "nearby" reports, where "nearby" may mean reports related to the same or adjacent physical resource blocks (PRBs).

[0057] Those skilled in the art will readily appreciate that the above-described invention can be implemented with steps in a different order and / or with hardware elements in different configurations than those disclosed. Thus, while the present invention has been described in terms of these preferred embodiments, certain modifications, variations, and alternative configurations will become apparent to those skilled in the art without departing from the spirit and scope of the invention. For example, while some embodiments of the present invention have been described in the context of a 3GPP system, it will be understood that the present invention may also be applied to other systems, such as an Evolved Terrestrial Radio Network (E-UTRAN). Accordingly, reference should be made to the appended claims in determining the metes and bounds of the present invention. [Explanation of symbols]

[0058] 210 Determine channel state information 215 Preparation for Consolidation 217 Missing CSI report for at least one setting 220 Periodically reporting channel state information

Claims

1. 1. A method for use in a user equipment (UE), the method comprising: If two channel state information (CSI) reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, one of the two CSI reports being a CSI report including a rank indicator (RI), and one of the two CSI reports being a CSI report including a channel quality indicator (CQI), transmitting only the CSI report including the RI on the physical uplink control channel; If two CSI reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, and each of the two CSI reports is a CSI report including a rank indicator (RI), transmitting only the CSI including the RI associated with a highest priority on the physical uplink control channel; the two CSI reports are configured by radio resource control (RRC) signaling; A method characterized by:

2. a baseband processor; a radio frequency (RF) transceiver; A user equipment (UE) comprising: The processor and RF transceiver If two channel state information (CSI) reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, one of the two CSI reports being a CSI report including a rank indicator (RI), and one of the two CSI reports being a CSI report including a channel quality indicator (CQI), transmitting only the CSI report including the RI on the physical uplink control channel; two CSI reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, and each of the two CSI reports is a CSI report including a rank indicator (RI); transmitting only the CSI including the RI associated with the highest priority on the physical uplink control channel; It can be operated as follows: the two CSI reports are configured by radio resource control (RRC) signaling; A UE characterized by:

3. Non-transitory computer-readable storage medium having executable code stored thereon wherein the executable code, when executed by a processor, If two channel state information (CSI) reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, one of the two CSI reports being a CSI report including a rank indicator (RI), and one of the two CSI reports being a CSI report including a channel quality indicator (CQI), transmitting only the CSI report including the RI on the physical uplink control channel; two CSI reports are to be transmitted on a physical uplink control channel, each of the two CSI reports being associated with a respective one of a plurality of component carriers, and each of the two CSI reports is a CSI report including a rank indicator (RI); transmitting only the CSI including the RI associated with the highest priority on the physical uplink control channel; a user equipment (UE) to perform the above; the two CSI reports are configured by radio resource control (RRC) signaling; A non-transitory computer-readable storage medium comprising:

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