WO2016064317A1 - Procédé et système de transmission de csi-rs - Google Patents

Procédé et système de transmission de csi-rs Download PDF

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Publication number
WO2016064317A1
WO2016064317A1 PCT/SE2014/051255 SE2014051255W WO2016064317A1 WO 2016064317 A1 WO2016064317 A1 WO 2016064317A1 SE 2014051255 W SE2014051255 W SE 2014051255W WO 2016064317 A1 WO2016064317 A1 WO 2016064317A1
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Prior art keywords
csi
transmission
channel quality
reset
wireless device
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PCT/SE2014/051255
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English (en)
Inventor
Ying Sun
Tao CUI
George JÖNGREN
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Telefonaktiebolaget L M Ericsson (Publ)
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Priority to PCT/SE2014/051255 priority Critical patent/WO2016064317A1/fr
Publication of WO2016064317A1 publication Critical patent/WO2016064317A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
    • H04L5/0035—Resource allocation in a cooperative multipoint environment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0057—Physical resource allocation for CQI
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/0073—Allocation arrangements that take into account other cell interferences
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0078—Timing of allocation
    • H04L5/0085—Timing of allocation when channel conditions change
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/30—TPC using constraints in the total amount of available transmission power
    • H04W52/32—TPC of broadcast or control channels
    • H04W52/325—Power control of control or pilot channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management

Definitions

  • the disclosure relates to Channel State Information (CSI), and more specifically to a method and arrangement applying Coordinated Multipoint (CoMP) transmission to a wireless device over two transmission points where the arrangement and the wireless device are configured with a CSI process associated with a CSI- Reference Signal resource configuration.
  • CSI Channel State Information
  • CoMP Coordinated Multipoint
  • LTE Long Term Evolution
  • 3GPP 3rd Generation Partnership Project
  • UMTS Universal Mobile Telecommunication System
  • UTRAN is the Radio Access Network (RAN) of a UMTS
  • E-UTRAN Evolved UTRAN
  • a wireless device also referred to as a User Equipment (UE) is wirelessly connected to a Radio Base Station (RBS) commonly referred to as an evolved NodeB (eNodeB or eNB) in LTE.
  • RBS is a general term for a radio network node capable of transmitting radio signals to a wireless device and receiving signals transmitted by a wireless device.
  • FIG. 1 illustrates a conventional RAN in an LTE system.
  • An eNodeB 101 serves a UE 103 located within the eNodeB's geographical area of service also called coverage area or cell.
  • the eNodeB 101 manages the radio resources in its cell and is directly connected to a Core Network (CN) node 105.
  • CN Core Network
  • LTE Long Term Evolution
  • RBS Radio Service Set
  • a pico base station represents one example of a Low Power Node (LPN) transmitting with low output power and covering a much smaller geographical area than a high power node like a macro base station.
  • LPN Low Power Node
  • Other examples of low power nodes are home base stations and relays.
  • interference mitigation techniques have the potential to substantially improve the user performance. Interference mitigation can either take place on the transmitter side or on the receiver side, or a combination of both. Interference mitigation techniques often explore the structure of the physical layer transmission of the radio access technology.
  • the most basic means to operate heterogeneous deployments is to apply frequency separation between the different layers, i.e. macro and pico cells operate on different non-overlapping carrier frequencies and thereby avoid any interference between the layers.
  • macro and pico cells operate on different non-overlapping carrier frequencies and thereby avoid any interference between the layers.
  • cell splitting gains are achieved when all resources can simultaneously be used by the under laid cells.
  • the drawback of operating layers on different carrier frequencies is that it may lead to resource-utilization inefficiency. For example, with low activities in the pico cells, it could be more efficient to use all carrier frequencies in the macro cell and then basically switch off the pico cells.
  • the split of carrier frequencies across layers is typically done in a static manner.
  • Other means to operate heterogeneous networks is to share radio resources on same carrier frequencies by coordinating transmissions across macro and under laid cells.
  • This type of coordination refers to as Inter-Cell Interference Coordination (ICIC) in which certain radio resources are allocated for the macro cells during some time period whereas the remaining resources can be accessed by the under laid cells without interference from the macro cell.
  • ICIC Inter-Cell Interference Coordination
  • this resource split can change over time to accommodate different traffic demands.
  • this way of sharing radio resources across layers can be made more or less dynamic depending on the implementation of the interface between the nodes.
  • an X2 interface has been specified in order to exchange different types of information between RBS.
  • RBS can inform other RBSs that it will reduce transmit power on certain resources.
  • Time synchronization between base station nodes is required to ensure that ICIC across layers will work efficiently in heterogeneous networks. This is in particular of importance for time domain based ICIC schemes where resources are shared in time on the same carrier.
  • CoMP transmission and reception refers to a system where the transmission and/or reception at multiple, geographically separated antenna sites is coordinated in order to improve system performance.
  • a point will thus be referred to as a transmission point even if the transmission point will also be configured for reception in an uplink context.
  • a transmission point might correspond to one of the sectors at a site, but it may also correspond to a site having one or more antennas all intending to cover a similar geographical area. Often, different points represent different sites. Antennas correspond to different points when they are sufficiently geographically separated and/or have antenna diagrams pointing in sufficiently different directions.
  • the CoMP coordination of transmission points in a so called cluster can either be distributed by means of direct communication between the different transmission points, or centralized by means of a central coordinating entity controlling the transmission at all the transmission points.
  • CoMP operation targets many different deployments, including coordination between sites and sectors in cellular macro deployments, as well as different configurations of Heterogeneous network deployments, where for instance a macro node coordinates the transmission with pico nodes within the macro coverage area.
  • Techniques for CoMP introduce dependencies in the scheduling or transmission/reception among different points, in contrast to conventional cellular systems where a point from a scheduling point of view is operated more or less independently from the other points.
  • Downlink CoMP operations may include, e.g., serving a certain UE from multiple points, either at different time instances or for a given subframe, on overlapping or not overlapping parts of the spectrum.
  • CoMP transmission schemes such as:
  • Dynamic Point Blanking where multiple transmission points coordinates the transmission so that neighboring transmission points may mute the transmissions on the time-frequency resource elements (TFREs) that are allocated to UEs that experience significant interference.
  • TFREs time-frequency resource elements
  • Dynamic Point Selection where the data transmission to a UE may switch dynamically (in time and frequency) between different transmission points, so that the transmission points are fully utilized.
  • Coordinated Beamforming where the transmission points coordinate their transmissions in the spatial domain by beamforming the transmission power in such a way that the interference to UEs served by neighboring transmission points is suppressed.
  • Joint Transmission where the signal to a UE is simultaneously transmitted from multiple transmission points on the same time/frequency resource.
  • the aim of joint transmission is to increase the received signal power and/or reduce the received interference.
  • the point selection may be based on instantaneous conditions of the channels, interference or traffic.
  • cell specific reference signals are transmitted in all downlink subframes.
  • the CRSs are used by the UE for channel estimation, to acquire channel-state information (CSI), and to perform cell selection and make handover decisions.
  • LTE also supports UE specific RS, i.e. demodulation reference signals (DMRS), for assisting channel estimation for demodulation purposes only.
  • DMRS demodulation reference signals
  • Physical Downlink Control Channels (PDCCH), Physical Downlink Shared Channels (PDSCH), and CRS are mapped on resource elements within a downlink subframe. Since the CRS is common to all UEs in the cell, the transmission of CRS cannot be easily adapted to suit the needs of a particular UE. This is in contrast to DMRS as each UE has DMRSs of its own placed in the data region of the downlink subframe as part of PDSCH.
  • the length of the PDCCH control region which can vary on subframe basis, is conveyed in the physical control format indicator channel (PCFICH).
  • PCFICH physical control format indicator channel
  • the PCFICH is transmitted within this control region, at locations known by UEs. After a UE has decoded the PCFICH, it thus knows the size of the control region and in which Orthogonal Frequency Division Multiplexing (OFDM) symbol the data transmission starts.
  • OFDM Orthogonal Frequency Division Multiplexing
  • PHICH physical hybrid-ARQ indicator channel
  • This channel carries acknowledgement (ACK/NACK) responses to a UE to inform if the uplink data transmission in a previous subframe was successfully decoded by the base station.
  • CSI-RS Channel State Information Reference Signal
  • the CSI-RSs are used by release 10 and 10+ UEs to determine CSI. Specifically, in release 10 it is used for transmission mode 9 (TM9) and in release 1 1 for transmission mode 10 (TM10).
  • TM9 transmission mode 9
  • TM10 transmission mode 10
  • the reason to introduce CSI- RS is to improve channel estimation for coherent demodulation even with the most extreme channel conditions including very fast channel variations in both the time and frequency domain without introducing much overhead.
  • introducing a new type of reference signal only targeting CSI is flexible and requires in general lower time/frequency density and therefore lower overhead per reference signal.
  • the CSI-RS resources are specifically configured for each wireless device by using Radio Resource Control (RRC) signaling.
  • RRC Radio Resource Control
  • the RRC signaling may occur periodically, see e.g. 3GPP TS 36.213 V1 1 .4.0, 2013-09, Sections 7.2.5-7.2.6.
  • an RRC configuration message may be transmitted periodically every 5 ms, i.e. every 5th subframe.
  • the RRC configuration message may be sent in an aperiodic manner, or may be triggered in a control message from the radio base station to a wireless device.
  • a CSI-RS resource is a group of resource elements in a certain subframe that occurs periodically, for instance every 20th subframe.
  • the CSI-RS utilizes an orthogonal cover code of length two to overlay two antenna ports on two consecutive time frequency resource elements (TFREs).
  • TFREs time frequency resource elements
  • Many different CSI-RS patterns are available. For the case of two CSI-RS antenna there are 20 different TFRE pair possibilities within a subframe. The corresponding number of patterns is 10 for four CSI-RS antenna ports, and 5 for eight CSI-RS antenna ports.
  • the term CSI-RS resource corresponds to a particular pattern present in a particular subframe. Thus two different CSI-RS patterns in the same subframe constitute two separate CSI-RS resources, as well as the same CSI-RS pattern in two different subframes.
  • the PDSCH TRFEs are mapped around the CSI- RS resources, so it is important that both the network and the UE are assuming the same CSI-RS resource configuration for the UE to be able to decode the PDSCH.
  • Non-Zero Power, NZP, or non-muted CSI- RS resources there is a possibility to configure both Non-Zero Power, NZP, or non-muted CSI- RS resources and Zero Power, ZP, or muted CSI-RS resources.
  • a ZP CSI-RS resource is simply an unused radio resource that can be matched to a NZP CSI- RS resource in an adjacent radio base station.
  • a ZP CSI-RS may be used to improve the Signal to Interference plus Noise Ratio (SINR) for the CSI-RS measurements in the cell of the adjacent radio base station.
  • SINR Signal to Interference plus Noise Ratio
  • the ZP CSI- RS resources may also be referred to or used as CSI-lnterference Management (CSI-IM) resources.
  • CSI-IM CSI-lnterference Management
  • CSI-IM resources are defined in the same physical locations of the time/frequency grid as the CSI-RS, but with zero power. These are intended to give a wireless device the possibility to measure the power of interfering signals without having it overlaid on top of a CSI-RS signal, which is usually much stronger than any surrounding interference. Raising the SINR level for CSI-RS measurements is particularly important in applications such as CoMP or in heterogeneous deployments. In the CoMP joint transmission scheme, the UE may probably need to measure the channel from non-serving cells and interference from the much stronger serving cell would in that case be devastating.
  • ZP CSI-RS is also needed in heterogeneous deployments where ZP CSI-RS in the macro-layer is configured so that it coincides with CSI-RS transmissions in the pico-layer. This avoids strong interference from macro nodes when UEs measure the channel to a pico node.
  • LTE Release 1 1 For the purpose of improved interference measurements new functionality was introduced in LTE Release 1 1 , where the network is able to configure a UE to measure interference on the CSI-IM resource.
  • the network can control the interference seen on an CSI-IM, by for example muting all transmission points within a CoMP coordination cluster on the CSI-IM, in which case the UE will effectively measure the inter-cluster interference.
  • an eNodeB it is essential that an eNodeB can accurately evaluate the performance of a UE given different CoMP transmission hypotheses; otherwise the dynamic coordination becomes meaningless.
  • the system needs to be able to track or estimate also different intra-cluster interference levels corresponding to different transmission and blanking hypotheses.
  • a UE can assume that no transmission points of interest are transmitting on this resource, and the received power can therefore be used as a measure of the interference plus noise.
  • the UE can effectively measure the interference observed from all other cells or transmission points, and this will be the relevant interference level in an upcoming data transmission.
  • the network can to a large extent control which transmission points that interfere a UE. Hence, there will be multiple interference hypotheses depending on which transmission points that are transmitting. Additionally, the network can choose to transmit interference from specific transmission points for the sole purpose of testing how that particular interference hypothesis affects the UE (seen e.g. via the CSI feedback). The network can try to make an assessment of what hypothesis that is most likely to occur for upcoming transmission time intervals. For UEs that are on the boundaries of a coordination cluster of transmission points, the dominant interferers may not be found within the cluster but from outside the cluster. Such inter-cluster interference cannot be controlled and will impact the CSI reports in an unknown way.
  • Each CSI process is associated with a CSI-RS resource configuration which may comprise both CSI-RS and CSI- IM resources.
  • a UE in TM10 can be configured with one to four CSI processes by higher layers and a CSI reported by the UE is associated to a certain CSI process. Since up to four CSI processes can be used for measurements and reported by the UEs spanning maximally three different CSI-IMs, the network can test different interference realizations simultaneously on the UE. Based on the effect fed back to the network through the CSI reports associated with the different CSI processes, the network may adapt its transmission scheme.
  • a CSI report may also be referred to as a channel quality report.
  • the network may measure the interference from adjacent cells using measurements in the CSI-IM resource. If more than one CSI processes are configured for the wireless device, it is possible for the network to also configure a ZP CSI-RS in the adjacent radio base station that overlaps with a CSI-IM for the CSI process configured for the wireless device.
  • the wireless device may feedback accurate CSI estimates also for the case when this adjacent cell is not transmitting.
  • measurements to support coordinated scheduling between radio base stations is enabled with the use of multiple CSI processes.
  • One CSI process feeds back CSI estimates for the full interference case and the other CSI process feeds back CSI estimates for the case when an adjacent cell, preferably a strong interfering cell, is muted.
  • up to four CSI processes may be configured for a wireless device, thereby enabling feedback of four different transmission hypotheses.
  • the wireless device may use an associated buffer or memory comprising one or multiple CSI measurements used to determine CSI estimates of the CSI process. However, how these CSI estimates are determined from the CSI measurements are up to the implementation of the wireless device.
  • a CSI measurement at least contains the estimated value of a signal to interference and noise ratio. The signal is measured on CSI-RS and the interference plus noise is measured on CSI-IM. Both are filtered to improve accuracy.
  • different measurement filters might be used for the signal and for the interference since the time when transmitting CSI-IM and CSI-RS may be different.
  • the format of the channel quality or CSI report is specified in detail and comprises CSI estimates in the form of Channel-Quality Indicator(s) (CQI), Rank Indicator (Rl), and Precoding Matrix Indicator (PMI).
  • CQI Channel-Quality Indicator
  • Rl Rank Indicator
  • PMI Precoding Matrix Indicator
  • the quality and reliability of the CSI estimates such as CQI, Rl and PMI are crucial for the radio base station in order to make the best possible scheduling decisions for the upcoming downlink transmissions.
  • the radio base station estimates the channel quality based on the content of the CSI report.
  • the CSI scheme used for CoMP does not scale with the size of clusters. For one UE, maximally four CSI processes and four CSI reports are supported as mentioned above. However, the four CSI processes are only sufficient for a CoMP transmission scheme based on dynamic point blanking in a cluster of three sectors or cells.
  • the three available CSI-IMs may e.g. be used to support two single interferer measurements and one joint interferer measurement. It is thus not possible to support larger clusters with more than three coordinated sectors or cells.
  • a flexible CSI-RS resource configuration allowing configuration of CSI-RS and CSI-IM based on a UE's individual geometry property could extend the size of a coordination cluster. However, more CSI-IM overhead will then be required.
  • Yet another eight CSI-IM resources (corresponding to 16 CSI- RS resources) are needed.
  • the maximum number of CSI-RS resource specified in 3GPP is 20 in a subframe, which thus limits the size of the coordination cluster.
  • a method for an arrangement of a wireless communication network applies coordinated multipoint transmission to a wireless device over at least two transmission points.
  • the arrangement and the wireless device are both configured with a CSI process, associated with a CSI-RS resource configuration.
  • the method comprises controlling transmission of CSI-RSs in accordance with the configured CSI process.
  • the method also comprises determining a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain.
  • the change comprises at least one of a change of transmission point and a change of transmission power for a CSI-RS.
  • the method further comprises controlling transmission of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process, and applying the change in the transmission of CSI-RSs.
  • an arrangement for a wireless communication network configured to apply coordinated multipoint transmission to a wireless device over at least two transmission points.
  • the arrangement and the wireless device are both configured with a CSI process, associated with a CSI-RS resource configuration.
  • the arrangement is further configured to control transmission of CSI-RSs in accordance with the configured CSI process, and determine a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain.
  • the change comprises at least one of a change of transmission point and a change of transmission power for a CSI- RS.
  • the arrangement is also configured to control transmission of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process, and apply the change in the transmission of CSI-RSs.
  • An advantage of embodiments is that CSI-RS resource reuse may be applied with good measurement accuracy without having to turn off the filtering functionality of the wireless devices, which in turn enables larger coordination clusters.
  • a further advantage of embodiments is that resetting of a filter state is simple to implement in the wireless device.
  • Another advantage of embodiments is that channel quality measurement accuracy is gradually increased over time thanks to the filtering without the need of an explicit configuration message.
  • Figure 1 is a schematic illustration of an LTE RAN according to prior art.
  • Figure 2 is a schematic illustration of an example scenario of a downlink CoMP deployment.
  • Figure 3 is a signaling diagram schematically illustrating the signaling between the UE and the eNodeB according to embodiments.
  • Figures 4a-e are flow charts schematically illustrating the method performed by the arrangement according to embodiments.
  • Figures 5a-c are block diagrams schematically illustrating the arrangement according to embodiments.
  • Embodiments are described in a non-limiting general context in relation to an example scenario in an UTRAN illustrated in Figure 2 with an eNodeB 101 applying downlink CoMP transmission to a UE 103 over two transmission points TP1 , TP2, in a coordination cluster 200.
  • the embodiments are described in the LTE environment, they could be applied for other wireless communication systems supporting coordinated multipoint transmission in the downlink.
  • the embodiments are described for a centralized solution where one eNodeB 101 controls the transmission from both transmission points TP1 and TP2, they could also be applied for a distributed solution with more than one eNodeB controlling the transmission from multiple transmission points, where the eNodeBs have direct and fast communication with each other to enable the coordinated transmission.
  • CSI-RS resources can be reused for spatially separated transmission points or during different time periods.
  • an algorithm needs to identify separated transmission points of a cluster and allocate the same CSI-RS resource for UEs in the separated points.
  • Such an algorithm is rather complex and computational intensive as it is based on a large amount of statistics.
  • possible impairments will be introduced due to non-perfect transmission point isolation.
  • the same CSI-RS resource is used by different transmission points of a cluster during different time periods.
  • an eNodeB controlling the CSI-RS transmission can identify to what CSI-RS transmission that a measurement in a CSI report corresponds to.
  • a problem with this solution is the UE measurement filtering. Since the UE is not aware of when the CSI-RS transmission changes from one transmission point to another, the reported channel quality measurement may be a filtered result of the measurements from two or more different transmission points. This may result in poor accuracy of the channel quality measurement and may destroy the potential downlink CoMP gain.
  • the UE filtering problem that occurs when reusing CSI-RS resources within a CoMP coordination cluster 200 is addressed by a solution where the UE 103 is requested to reset a channel quality measurement filter. This is done when the eNodeB 101 controlling the transmissions of CSI-RSs within the cluster 200 determines that there is a need for a change in the transmission of CSI-RSs due to reuse considerations.
  • the channel quality measurement filter may also be referred to as a layer 1 filter, a channel quality estimation filter, an interference measurement filter, a signal quality measurement filter, a CSI measurement filter, or simply as a measurement filter.
  • the eNodeB 101 can dynamically perform transmission point switching and change of transmission power for transmission points within the cluster 200 with good measurement accuracy without having to affect the internal filtering algorithm of the UE.
  • the measurement states are reset which means that the UE filtering is always kept on. From one reset of the filter until a new reset is requested, the channel quality measurement accuracy is gradually increased without the need of an explicit configuration message. Furthermore, resetting the filter state of the UE is simple to implement.
  • Another advantage of embodiments is that the eNodeB may be allowed to control the overhead introduced by the sending of a request to reset the filter based on the load situation and on the importance of the data to be coordinated. Only when the load is moderate and the data is important, the eNodeB may use its possibility to reset the filtering.
  • the request for resetting the filter may be transmitted to the UE in different ways.
  • it may be transmitted in an uplink scheduling grant comprising a request for an aperiodic CSI report, either as an extra bit or as a special format such as a special Modulation and Coding Scheme (MCS) format.
  • MCS Modulation and Coding Scheme
  • it may be a special Media Access Control (MAC) control element that is interpreted as the request.
  • the special MAC control element may or may not be piggybacked on a data transmission.
  • Still another alternative is to send the request as a separate bit in a downlink assignment. Also in this case the downlink assignment may or may not be sent together with a data transmission.
  • the request may be comprised in an RRC signaling message.
  • the request may in embodiments be associated with different CSI processes.
  • a UE When a UE receives the request to reset the filter, it may reset the states of all, or possibly a subset of, the filters related to a CSI process.
  • the filters comprise aperiodic CSI report related filters and periodic CSI report related filters. If all the filters are reset, the first periodic and aperiodic CSI reports after the reset will be based on fresh channel quality measurements. Consecutive CSI reports will be based on the filtered results until the next reset message from an eNodeB is received.
  • the UE may reset only the aperiodic CSI report related filters or only the periodic CSI report related filters.
  • any periodic CSI report will be ignored by the eNodeB. Only after reception of an aperiodic CSI report, the channel quality update may be performed. Furthermore, if the reset is only applied to aperiodic CSI report related filtering, it may be possible for an eNodeB to have an extra trigger for the reset of aperiodic CSI report related filtering when data is expected to be transmitted.
  • CoMP coordination of transmission points in a so called cluster can either be distributed by means of direct communication between the different transmission points, or centralized by means of a central coordinating entity controlling the transmission at all the transmission points.
  • the example scenario used hereinafter to describe embodiments of the invention is a centralized solution where the central coordinating entity is an eNodeB 101 controlling the transmission at two transmission points TP1 and TP2 of a cluster 200.
  • the transmission points may e.g. be remote radio units controlled by the eNodeB 101 .
  • the eNodeB 101 and the UE 103 served by the eNodeB 101 are both configured with a same CSI process associated with a CSI-RS resource configuration.
  • the CSI-RS resource configuration comprises one CSI-RS resource.
  • Time domain reuse of the CSI-RS resource is applied. Therefore, the two transmission points TP1 and TP2 share the CSI-RS resource in time.
  • transmission point TP1 is transmitting CSI- RS in accordance with the CSI-RS resource configuration, and at time instance t1 +t there is a switch of transmission point and transmission point TP2 is transmitting CSI-RS in accordance with the CSI-RS resource configuration.
  • transmission point TP1 may again be the transmission point that transmits CSI- RS.
  • the scenario with two transmission points is just one non-limiting example, and that the switch of transmission of CSI-RS may very well involve more than two transmission points. The procedure is described in the following with reference to the signaling diagram in Figure 3:
  • the eNodeB 101 configures a CSI-RS resource, for example with a certain subframe periodicity and offset, to be reused in time between the transmission points TP1 and TP2.
  • the CSI-RS periodicity is 5ms meaning that the CSI-RS is transmitted every 5 th subframe, and the offset is 0 meaning that the CSI-RS transmission starts in subframe 0.
  • the eNodeB 101 also configures the UE 103 with the same CSI-RS resource, and the CSI-RS resource configuration is sent to the UE 103 using RRC signaling in S31 1 .
  • the UE 103 receives the RRC signaling and configures the CSI-RS resource according to the RRC configuration message in 312.
  • the UE 103 then returns an RRC reconfiguration complete message to the eNodeB 101 in S313 to confirm that the CSI resource configuration is completed and that the UE 103 is prepared to measure the CSI- RS starting from subframe 0, with a periodicity of 5ms.
  • the eNodeB 101 may instruct the different transmission points TP1 and TP2 to transmit CSI-RS according to the configured CSI process, dynamically shifting between transmitting from TP1 to transmitting from TP2. For example, initially, the eNodeB 101 determines the channel quality for the channel between transmission point TP1 and the UE 103.
  • the UE will measure the CSI-RS and will continuously send CSI reports to the eNodeB so that the eNodeB can determine the channel quality, but this signaling is not illustrated in the signaling diagram.
  • the eNodeB wants to determine the channel quality for the channel between transmission point TP2 and the UE 103 instead, and therefore determines to switch the transmission of CSI-RS to transmission point TP2 in 315, thus reusing the same CSI-RS resource for the other transmission point in the time domain.
  • the switch is completely transparent for the UE which continues to measure the CSI-RS according to the CSI process and to report CSI reports based on the measurements regardless of which transmission points that transmits.
  • a request to reset the UE's channel quality measurement filter corresponding to the CSI process is sent to the UE in S316 when the eNodeB has switched to transmit CSI- RS from transmission point TP2.
  • the procedure of switching back and forth between transmission point TP1 and TP2 may continue.
  • a new request for resetting the UE filter is sent to the UE.
  • the UE When the UE receives the request to reset the channel quality measurement filter in S316, the UE resets the filter 317.
  • the first CSI report transmitted after the reset in S318 will thus e.g. comprise a fresh CQI value based on CSI-RS measurements from a newly reset filter.
  • the UE continues to perform channel quality estimation based on the CSI-RS measurements performed every 5ms according to the configured periodicity and offset of the CSI-RS resource continuously applying the filtering scheme of the UE.
  • the CSI report is used by the eNodeB 101 to update the channel quality estimation of the corresponding transmission hypothesis measurement in 319.
  • the procedure of requesting a filter reset from the UE when a change of the CSI-RS transmission is performed may comprise a check that the filter has actually been reset by the UE before the CSI-RS change is actually applied. This may be done in different ways depending on how the request to reset the filter is transmitted to the UE:
  • the eNodeB may determine whether the grant has been received by the UE by detecting if the uplink transmission as expected from the uplink scheduling grant is done. If the grant is received by the UE, also the request for resetting the filtering is received, and the eNodeB can go ahead and apply the change of the CSI- RS transmission without risking inaccurate CSI measurement reporting. How this may be done is further detailed below. A similar method may be performed when the request for resetting the UE filter is comprised in a downlink assignment, or in a MAC control element which is piggybacked on a data transmission.
  • a response message confirming that the filter reset has been done may be defined and sent by the UE to the eNodeB.
  • the eNodeB may check that the UE has reset the filter.
  • the eNodeB has thus sent a request to reset the filter in the UE.
  • the eNodeB also performs a reception.
  • the eNodeB may check if the UE has reset the filter successfully through one of the following alternatives: a.
  • the eNodeB can check the expected reception of the uplink transmission on PUSCH to determine if the UE has reset the filter successfully. If energy is detected on PUSCH e.g.
  • the determination of whether the UE has successfully reset the CSI measurement filter may be based on the feedback ACK/NACK transmitted on PUCCH. If no energy is detected on the expected transmission resource for ACK/NACK on PUCCH, the UE has probably not received the downlink assignment and has therefore not reset the CSI filters either. Otherwise, the eNodeB may consider that the UE has reset the filter.
  • the schedDelay is the scheduling delay from when the UE receives the grant/assignment to when it transmits the uplink transmission. It is assumed that UE performs filter reset and transmits the uplink feedback within 4ms.
  • t_eNBDecoding is the time period that the eNodeB needs for receiving the uplink transmission.
  • #OfRetransmissions is the number of retransmissions that the UE performs for the reset request transmission.
  • the eNodeB may use the filter reset time in order to determine if a received CSI report should be used for estimating the channel quality for the CSI-RS situation before the filtering reset or after the filtering reset.
  • the transmission time of the CSI report has to be estimated.
  • the transmission time may be estimated as follows:
  • t_csiSent the time of the configured previous CSI report transmission occasion.
  • t_csiSent t_currentCsiReceivedTime - 4ms -#OfRetransmission * 8 - t_eNB Decoding
  • t_currentCsiReceivedTime is the receive time of the current aperiodic CSI report. If the transmission time of the CSI report t_csiSent is after the time t when the UE has reset its filter, the CSI report is considered to be sent after the CSI-RS transmission change, and otherwise it is considered to be sent before the change.
  • the CSI report corresponds to the measurement of the old CSI-RS transmission scheme or the CSI-RS transmission performed before the change
  • the measurement is used to update the old channel quality estimate.
  • the channel quality estimation for the transmission scheme of only transmitting from TP1 is thus updated based on the CSI report sent by the UE before subframe 40.
  • the measurement is used to update the new channel quality estimate.
  • the channel quality estimation for the transmission scheme of only transmitting from TP2 is thus updated based on the CSI report.
  • Figure 4a is a flowchart illustrating one embodiment of a method for an arrangement 500 of a wireless communication network.
  • the arrangement applies coordinated multipoint transmission to a wireless device 550 over two or more transmission points TP1 and TP2.
  • the two transmission points TP1 and TP2 may thus form a CoMP coordination cluster.
  • the arrangement and the wireless device are both configured with a CSI process associated with a CSI-RS resource configuration.
  • the CSI-RS resource configuration may in embodiments comprise a CSI-IM resource configuration.
  • the arrangement 500 may in a centralized embodiment comprise a network node such as an eNodeB controlling the transmission performed by the at least two transmission points.
  • the transmission points may be remote radio units or antennas covering different sectors of the network node's coverage area.
  • the arrangement may comprise more than one network node. Each network node may control the transmission performed by at least one of the transmission points.
  • the method comprises:
  • - 420 Determining a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain.
  • the change may comprise a change of transmission point for transmitting CSI-RS or a change of transmission power for transmitting CSI-RS, or both.
  • - 430 Controlling transmission of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process.
  • the request to reset the channel quality measurement filter may be comprised in an uplink scheduling grant comprising a request for an aperiodic CSI report, in a downlink assignment, or in a RRC signaling message.
  • the channel quality measurement filter may be associated with an aperiodic
  • CSI report a periodic CSI report, or both.
  • Figure 4b is a flowchart illustrating another embodiment of the method performed by the arrangement.
  • the method may comprise the following in addition to the transmission control and determining described in step 410-430 above: - 440: Determining whether the channel quality measurement filter has been reset by the wireless device.
  • the method may comprise the following in addition to the transmission control and determining described in step 410-430 above:
  • the request to reset the channel quality measurement filter is comprised in an uplink scheduling grant comprising a request for an aperiodic CSI report or in a downlink assignment, as described in bullet A above. It is illustrated that the method may comprise the following in addition to the transmission control and determining described in step 410-430 above:
  • - 436 Receive an uplink transmission from the wireless device as expected from the uplink scheduling grant or the downlink assignment.
  • - 437 Determine whether the uplink scheduling grant or the downlink assignment has been received by the wireless device based on the received uplink transmission. In embodiments, the determining is based on at least one of a detected energy and a check sum control of the received uplink transmission, as described in bullets a. and b. above.
  • Figure 4e is a flowchart illustrating another embodiment of the method performed by the arrangement.
  • the method may comprise the following in addition to the transmission control, determining, and applying described in step 410-450 in embodiments above:
  • - 470 Receiving a channel quality report associated with the CSI process from the wireless device.
  • - 480 Determining whether the channel quality report was transmitted by the wireless device after the time when the filter was reset based on an estimated channel quality report transmission time.
  • the method further comprises: - 490: Updating a first channel quality estimate based on the channel quality report, the first channel quality estimate being associated with CSI-RSs transmitted after applying the change.
  • the method further comprises: - 491 : Updating a second channel quality estimate based on the channel quality report, the second channel quality estimate associated with CSI-RSs transmitted before applying the change.
  • An embodiment of an arrangement 500 for a wireless communication network configured to apply coordinated multipoint transmission to a wireless device 550 over at least two transmission points, TP1 , TP2, is schematically illustrated in the block diagram in Figures 5a and 5b.
  • the arrangement 500 and the wireless device 550 are both configured with a CSI process, associated with a CSI-RS resource configuration.
  • the CSI-RS resource configuration may comprise a CSI- IM resource configuration.
  • the arrangement comprises a network node 500 controlling the transmission performed by the two transmission points TP1 , TP2.
  • the arrangement 500 comprises more than one network node, 510, 520, each network node controlling the transmission performed by one of the two transmission points TP1 , TP2.
  • the arrangement is in both the centralized and the distributed solution further configured to control transmission of CSI-RSs in accordance with the configured CSI process, and to determine a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain.
  • the change may comprise a change of transmission point for a CSI-RS, a change of transmission power for a CSI-RS, or both.
  • the arrangement is further configured to control transmission of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process.
  • the channel quality measurement filter is associated with an aperiodic CSI report and/or a periodic CSI report.
  • the request to reset the channel quality measurement filter may be comprised in an uplink scheduling grant comprising a request for an aperiodic CSI report, in a downlink assignment, or in a RRC signaling message.
  • the arrangement is further configured to apply the change in the transmission of CSI- RSs.
  • the arrangement is further configured to determine whether the channel quality measurement filter has been reset by the wireless device, and to apply the change in the transmission of CSI-RSs when it is determined that the channel quality measurement filter has been reset.
  • the arrangement may be further configured to determine whether the channel quality measurement filter has been reset by receiving a message from the wireless device confirming that the channel quality measurement filter has been reset. It is in this embodiment determined that the channel quality measurement filter has been reset based on the received message.
  • the request to reset the channel quality measurement filter is comprised in an uplink scheduling grant comprising a request for an aperiodic CSI report or in a downlink assignment
  • the arrangement is configured to determine whether the channel quality measurement filter has been reset by receiving an uplink transmission from the wireless device as expected from the uplink scheduling grant or the downlink assignment, by determining whether the uplink scheduling grant or the downlink assignment has been received by the wireless device based on the received uplink transmission, and by determining that the channel quality measurement filter has been reset when it is determined that the uplink scheduling grant or the downlink assignment has been received.
  • the arrangement may be further configured to determine whether the uplink scheduling grant or the downlink assignment has been received by the wireless device based on at least one of a detected energy and a check sum control of the received uplink transmission.
  • the arrangement may be further configured to determine a time when the filter was reset, receive a channel quality report associated with the CSI process from the wireless device, and determine whether the channel quality report was transmitted by the wireless device after the time when the filter was reset based on an estimated channel quality report transmission time.
  • the arrangement may be configured to update a first channel quality estimate based on the channel quality report, the first channel quality estimate being associated with CSI-RSs transmitted after applying the change.
  • the arrangement may be configured to update a second channel quality estimate based on the channel quality report when, the second channel quality estimate associated with CSI-RSs transmitted before applying the change.
  • the network nodes 500, 510, 520, of the arrangement may comprise a processing circuit 501 , 51 1 , 521 , configured to control the transmission over the transmission points TP1 , TP2, and a memory 502, 512, 522, storing instructions that, when executed by the respective processing circuit, cause the arrangement to control transmission of CSI-RSs in accordance with the configured CSI process, and to determine a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain.
  • the change may comprise a change of transmission point for a CSI-RS or a change of transmission power for a CSI-RS or both.
  • the instructions when executed by the processing circuit cause the arrangement to control transmission of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process, and apply the change in the transmission of CSI-RSs.
  • the network nodes 510, 520 may comprise a communication interface each 514, 524, allowing the communication between the two network nodes 510, 520.
  • the processing circuits described above may comprise a Central Processing Unit (CPU) which may be a single unit or a plurality of units.
  • the memory may be a non-volatile memory, e.g. an EEPROM (Electrically Erasable Programmable Read-Only Memory), a flash memory or a disk drive.
  • the memory may correspond to a computer program product (CPP) comprising a computer program.
  • the computer program comprises code means which when run on the wireless device and the access node respectively causes the CPU to perform steps of the methods described earlier with reference to Figures 4a-4e.
  • the arrangement 500 comprises a first means for controlling transmission 531 of CSI-RSs in accordance with the configured CSI process.
  • the arrangement 500 also comprises means for determining 532 a change in the transmission of CSI-RSs for reusing resources of the CSI process in time domain, wherein the change comprises at least one of a change of transmission point and a change of transmission power for a CSI-RS.
  • the arrangement 500 further comprises a second means for controlling transmission 533 of a request to the wireless device to reset a channel quality measurement filter associated with the CSI process, and means for applying 534 the change in the transmission of CSI- RSs.
  • the means described above are functional means which may be implemented in hardware, software, firmware or any combination thereof. In one embodiment, the means are implemented as a computer program running on a processor.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne un procédé exécuté dans un système d'un réseau de communication sans fil, le système appliquant une transmission multipoint coordonnée dispositif sans fil sur au moins deux points de transmission. Le système et le dispositif sans fil sont tous les deux configurés avec un processus CSI associé à une configuration de ressources CSI-RS. Le procédé comprend les étapes consistant à commander (410) la transmission de Signaux CSI-RS en fonction de la configuration CSI procédé. Le procédé consiste à : déterminer (420) un changement de la transmission de CSI-RS pour la réutilisation des ressources du processus CSI dans le domaine temporel, le changement comprenant au moins un changement de point de transmission et/ou un changement de puissance de transmission pour un CSI-RS; contrôler (430) la transmission d'une demande au dispositif sans fil pour réinitialiser un filtre de mesurage de qualité de canal associé au processus CSI-RS, et appliquer (450) le changement à la transmission de CSI-RS.
PCT/SE2014/051255 2014-10-24 2014-10-24 Procédé et système de transmission de csi-rs WO2016064317A1 (fr)

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US10659128B2 (en) 2016-05-19 2020-05-19 Telefonaktiebolaget Lm Ericsson (Publ) Radio network node, wireless device and methods performed therein
WO2017200439A1 (fr) * 2016-05-19 2017-11-23 Telefonaktiebolaget Lm Ericsson (Publ) Nœud de réseau radio, dispositif sans fil et procédés mis en œuvre dans ce dernier
WO2018006974A1 (fr) * 2016-07-08 2018-01-11 Telefonaktiebolaget Lm Ericsson (Publ) Procédés et dispositifs de remise à zéro d'une estimation de canal de récepteur radio
WO2018044116A1 (fr) * 2016-09-01 2018-03-08 Samsung Electronics Co., Ltd. Procédé et appareil d'acquisition d'informations d'état de canal de liaison descendante et de liaison montante
US10484064B2 (en) 2016-09-01 2019-11-19 Samsung Electronics Co., Ltd. Method and apparatus for downlink and uplink CSI acquisition
DE102016123893A1 (de) 2016-12-08 2018-06-14 Immatics Biotechnologies Gmbh T-Zellrezeptoren mit verbesserter Bindung
CN110463071B (zh) * 2017-03-24 2023-02-28 高通股份有限公司 用于无线通信中的波束发现和波束成形的技术
CN110463071A (zh) * 2017-03-24 2019-11-15 高通股份有限公司 用于无线通信中的波束发现和波束成形的技术
CN110637419A (zh) * 2017-05-17 2019-12-31 高通股份有限公司 用于部分式频带重新调谐的csi-rs配置
CN110637419B (zh) * 2017-05-17 2023-04-25 高通股份有限公司 用于部分式频带重新调谐的csi-rs配置
US11689319B2 (en) 2017-05-17 2023-06-27 Qualcomm Incorporated CSI-RS configuration for partial band retuning
CN112752333A (zh) * 2019-10-31 2021-05-04 中国电信股份有限公司 上行信道功率控制方法、装置、终端以及存储介质
CN112752333B (zh) * 2019-10-31 2024-03-29 中国电信股份有限公司 上行信道功率控制方法、装置、终端以及存储介质

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