(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2015/0349855A1
`(43) Pub. Date:
`Dec. 3, 2015
`Sesia et al.
`
`US 20150349855A1
`
`(54)
`
`(71)
`
`(72)
`
`(21)
`(22)
`(86)
`
`AUTONOMOUS QUASI CO-LOCATION
`STATUS REDEFINITION BY RECEIVER IN
`COORONATED MULTIPOINT DOWNLINK
`
`Applicant: TELEFONAKTIEBOLAGET L M
`ERICSSON (PUBL), Stockholm (SE)
`Inventors: Stefania Sesia, Roquefort Les Pins (FR):
`Stefano Sorrentino, Solna (SE)
`14/761,129
`
`Appl. No.:
`
`PCT Fled:
`
`Jan. 17, 2014
`
`PCT NO.:
`S371 (c)(1),
`(2) Date:
`
`PCT/SE2O14/OSOOSO
`
`Jul. 15, 2015
`
`(60)
`
`Related U.S. Application Data
`Provisional application No. 61/753,685, filed on Jan.
`17, 2013.
`
`Publication Classification
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`(51) Int. Cl.
`H04B 7/02
`H04L 25/02
`H04L 5/00
`H04/24/08
`(52) U.S. Cl.
`CPC ............... H04B 7/024 (2013.01); H04W 24/08
`(2013.01); H04L 25/0202 (2013.01); H04L
`5/0048 (2013.01); H04W 88/08 (2013.01)
`ABSTRACT
`(57)
`User Equipment, UE (30), in a wireless radiocommunication
`network (10) supporting Coordinated Multi-Point, CoMP.
`transmissions may autonomously adopt an assumption of the
`quasi co-located (QCL) status of two (or more) antenna ports
`that is different from the default QCL status defined or sig
`naled by the network (10), in response to one or more esti
`mates of certain operating parameter values. The altered QCL
`status assumption allows the UE (30) to correct parameter
`estimates more accurately, and/or to reduce complexity in the
`parameter estimation correction.
`
`1"
`
`ASCERNAEFA CSAS
`F HE FRSAN SECON ANENA FORTS
`
`ESMATE ONE OR MORE WERELESS NEWORK
`OPERATNG PARANEERS
`
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`- 106
`PARAMETERS MEET - YES
`CRETERA FOR REENGING
`QC, SATS?
`
`- 102
`
`CA
`
`
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`
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`108
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`
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`AOO/CSY ACPA
`ASSUMPTION OF HEQCL STATUS,
`FFEREN FROH EFA
`QC STATUS, OF THE FRS AND
`SECON ANNA PORS
`
`TIE CSTATUS O CORRECTESTMATED PARAMETERS
`BETEEN FRSAN SECCEDANTENNA PORS
`
`1.
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`US 2015/0349855A1
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`N e
`CORE
`NETWORK
`40
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`RADiO COMMUNICAON
`NEWORK
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`FG.
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`Patent Application Publication
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`Dec. 3, 2015 Sheet 2 of 5
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`US 2015/0349855A1
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`ONE OF SYMBO
`NCDNG CYCC PREFX
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`t
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`FG. 2
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`RADiO FRAME (TFRAME - 10 ms)
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`FG. 3
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`Patent Application Publication
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`Dec. 3, 2015 Sheet 3 of 5
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`US 2015/0349855A1
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`4
`CONTROL. A.
`REGON
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`DAIA REGION
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`Patent Application Publication
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`Dec. 3, 2015 Sheet 4 of 5
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`US 2015/0349855A1
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`OC
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`A1
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`ASCERTAINA DEFAU QCL STATUS
`OF THE FRS AND SECCD ANTENNA PORS
`
`ESMATE ONE OR WORE, RELESS NEWORK
`OPERANG ARANEERS
`
`
`
`PARAMETERS MEET
`Xa
`CRERA FOR REENGING
`QCLSTATUS
`
`102
`
`04
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`AJONOMOUSLY ACPAN
`ASSUMPTION OF THE QCL STATUS,
`FFEREN FROM HE DEFA.
`QC. STATUS, OF THE FIRST AND
`SECON AN ENNA PORS
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`UTIZE QC STATUS TO CORRECTES MATED PARAMETERS
`BETWEEN FRS AND SECON ANTENNA PORS
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`10
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`F.G. 5
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`Patent Application Publication
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`Dec. 3, 2015 Sheet 5 of 5
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`-"
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`PROCESSING
`CRCUTRY
`24
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`EMORY
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`23
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`PROCESSENG
`CRCUTRY
`34.
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`RADO
`CRCRY
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`TMEMORY
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`F.G. 7
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`Dec. 3, 2015
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`AUTONOMOUS QUASI CO-LOCATION
`STATUS REDEFINITION BY RECEIVER IN
`COORONATED MULTIPOINT DOWNLINK
`
`TECHNICAL FIELD
`0001. The present invention relates generally to wireless
`communication reception, and in particular to a system and
`method for autonomously redefining quasi co-location status
`for antenna points in Coordinated Multipoint downlink trans
`missions.
`
`BACKGROUND
`0002 3' Generation Partnership Project (3GPP) Long
`Term Evolution (LTE) technology is a mobile broadband
`wireless communication technology. A representative LTE
`network 10 is depicted in FIG. 1. In the LTE network 10,
`transmissions a base station (also referred to as Evolved
`NodeB, or eNB) 20 to one or more mobile stations (also
`referred to as user equipments, or UES) 30 are sent using
`orthogonal frequency division multiplexing (OFDM) in the
`downlink. Uplink transmissions from the UEs 30 to the eNo
`deB 20 use DFT-spread OFDM. The eNodeBs 20 transfer
`data and telephony through a core network 40 to and from
`other networks, such as the Internet 50, the Public Switched
`Telephone Network (PSTN) 60, or the like.
`0003. The basic LTE physical resource canthus be seen as
`a time-frequency grid as illustrated in FIG. 2, where each
`resource element corresponds to one subcarrier during one
`OFDM symbol interval (on a particular antenna port). An
`antenna port is defined such that the channel over which a
`symbol on the antenna port is conveyed can be inferred from
`the channel over which another symbol on the same antenna
`port is conveyed. See 3GPP TS 36.211, S5.2.1. Typically, an
`antenna port corresponds to a physical antenna or a combi
`nation of physical antennas. There is one resource grid per
`antenna port.
`0004 LTE additionally supports Multiple-input multiple
`output (MIMO) operation, in which both transmitter and
`receiver are equipped with multiple antenna ports, allowing
`for transmit diversity and closed-loop spatial multiplexing.
`0005. In the time domain, LTE downlink transmissions are
`organized into radio frames of 10 ms, with each radio frame
`consisting of ten equally-sized subframes of 1 ms, as illus
`trated in FIG. 3. A subframe is divided into two slots, each of
`0.5 ms time duration. The resource allocation in LTE is
`described in terms of physical resource blocks (PRB), where
`a resource block corresponds to one slot in the time domain
`and 12 contiguous 15 kHz Subcarriers in the frequency
`domain. Two consecutive (in time) resource blocks represent
`a resource block pair and correspond to the time interval upon
`which scheduling operates.
`0006 Transmissions in LTE are dynamically scheduled in
`each subframe, where the eNodeB 20 transmits downlink
`assignments/uplink grants to certain UES 30 via the (en
`hanced) physical downlink control channel (PDCCH and
`ePDCCH). The PDCCHs are transmitted in the first OFDM
`symbol(s) in each subframe and span (approximately) the
`whole system bandwidth. A UE30 that has decoded a down
`linkassignment, carried by a PDCCH, knows which resource
`elements in the subframe that contain data aimed for the UE
`30. Similarly, upon receiving an uplink grant, the UE 30
`knows which time/frequency resources it should transmit
`upon. In LTE downlink, data is carried by the physical down
`
`link shared channel (PDSCH) and in the uplink the corre
`sponding link is referred to as the physical uplink shared
`channel (PUSCH).
`0007 Demodulation of sent data requires estimation of the
`radio channel, which is done by using transmitted reference
`symbols (RS), i.e., symbols known a priori by the receiver. In
`LTE, cell specific reference symbols (CRS) are transmitted in
`all downlink subframes and, in addition to assisting downlink
`channel estimation, they are also used for mobility measure
`ments performed by the UEs 30. LTE also supports UE
`specific RS aimed only for assisting channel estimation for
`demodulation purposes, referred to as demodulation refer
`ence symbols (DMRS). Because the DMRS is precoded, in
`MIMO operations, with the same precoding matrix as that
`used for the PDSCH transmission, the DMRS cannot be used
`to generate Channel Quality Indicator (CQI), Precoding
`Matrix Index (PMI), or Rank Indicator (RI) feedback values.
`Accordingly, another reference signal, referred to as the
`Channel State Information Reference Signal (CSI-RS), is
`cell-specific and used by UEs 30 to generate CQI, PMI, and
`RI. Although the CSI-RS is similar to CRS, the CSI-RS is
`transmitted much less frequently than CRS.
`0008 FIG. 4 illustrates how the mapping of physical con
`trol/data channels and signals can be done on resource ele
`ments within a downlink subframe. In this example, the
`PDCCHs occupy the first out of three possible OFDM sym
`bols, so in this particular case the mapping of data could start
`already at the second OFDM symbol. Since the CRS is com
`monto all UEs 30 in the cell, the transmission of CRS cannot
`be easily adapted to suit the needs of a particular UE30. This
`is in contrast to UE-specific RS which means that each UE 30
`has RS of its own placed in the data region of FIG. 4 as part of
`PDSCH.
`0009 Coordinated Multipoint (CoMP) refers to a set of
`techniques in LTE that enable dynamic coordination of trans
`mission and reception over a variety of different base stations
`20. CoMP utilizes the phenomenon of inter-cell interference
`(ICI) to improve overall quality for UEs 30, particularly at
`cell borders, and improve utilization of the network. The
`concept of a transmission point is heavily used in CoMP. In
`this context, a transmission point (or simply a point) corre
`sponds to a set of antenna ports covering essentially the same
`geographical area in a similar manner. Thus a point might
`correspond to one of the sectors at a site, but it may also
`correspond to a site having one or more antenna ports all
`intending to cover a similar geographical area. Often, differ
`ent points represent different sites. Antenna ports correspond
`to different points when they are Sufficiently geographically
`separated and/or having antenna diagrams pointing in Suffi
`ciently different directions. Stated differently, a transmission
`point is a set of antenna ports that are geographically collo
`cated.
`0010 Techniques for CoMP entail introducing dependen
`cies in the scheduling or transmission/reception among dif
`ferent points, in contrast to conventional cellular systems
`where, from a scheduling point of view, each point is operated
`substantially independently from the other points. DL CoMP
`operations may include, e.g., serving a certain UE 30 from
`multiple points, either at different time instances or for a
`given subframe, on overlapping or not overlapping parts of
`the spectrum. Dynamic Switching between transmission
`points serving a certain UE30 is often referred to as dynamic
`point selection (DPS). Simultaneously serving a UE30 from
`multiple points on overlapping resources is often referred to
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`Dec. 3, 2015
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`as joint transmission (JT). The point selection may be based,
`e.g., on instantaneous conditions of the channels, interfer
`ence, or traffic. CoMP operations are intended to be per
`formed, e.g., for data (PDSCH) channels and/or control chan
`nels. Such as ePDCCH. Because CoMP downlink
`transmissions to a particular UE30 may emanate from points
`associated with different eNodeBs 20, the UE30 is generally
`discussed hereinas exchanging information with the network
`10, rather than particular eNodeBs 20. Those of skill in the art
`will readily realize that a UE30 may transmit information to
`or from the network 10 via one or more eNodeBs 30.
`0011. One of the principles guiding the design of the LTE
`system is transparency of the network 10 to the UE 30. In
`other words, the UE30 is able to demodulate and decode its
`intended channels without specific knowledge of scheduling
`assignments for other UEs 30 or network deployments.
`DMRS or UE-specific RS are employed for demodulation of
`data channels and possibly certain control channels (ePD
`CCH). UE-specific RS relieves the UE from having to know
`many of the properties of the transmission and thus allows
`flexible transmission schemes to be used from the network
`side. This is referred to as transmission transparency (with
`respect to the UE30).
`0012 Geographical separation of RS ports implies that
`long term channel properties from each port towards the UE
`30 are in general different. Example of such long term prop
`erties include the received power for each port, the delay
`spread, the Doppler spread, the received timing (i.e., the
`timing of the first significant channel tap), the number of
`significant channel taps, the frequency shift, and the Doppler
`spread. It is noted that transmitter impairments, such as fre
`quency shift with respect to a nominal reference frequency
`and propagation delays in the equipment, affect the equiva
`lent channel perceived by the UE.Therefore, RS ports that are
`physically collocated but associated with significantly differ
`ent transmitter impairments may be perceived by the UE30 as
`having different long term channel properties.
`0013. According to the LTE terminology, it is said that two
`antenna ports are quasi co-located (QCL) with respect to a
`certain long term channel property X when such long term
`channel property X may be assumed to be the same for both
`ports by the UE 30. Conversely, it is said that two antenna
`ports are not quasi co-located (QCL) with respect to a certain
`long term channel property X when Such long term channel
`property X shall not be assumed to be the same for both ports
`by the UE30.
`0014 UEs 30 may exploit knowledge of the QCL assump
`tions in a number of ways. For example, the complexity of
`channel estimation algorithms may be reduced by avoiding
`individual estimation of channel properties that are QCLed
`between different antenna ports. Another advantage is the
`possibility of extracting channel properties from certain ports
`which allow accurate estimation and applying them to other
`QCLed ports that do not allow equally good estimation. Other
`applications are also possible, one example being the indica
`tion of QCL assumptions between DMRS and CSI-RS. Since
`estimation of long term channel properties from DMRS is
`challenging, the DMRS QCL assumptions in LTE allow esti
`mating selected long term channel properties from a signaled
`CSI-RS resource and applying them to DMRS, to aid DMRS
`estimation. Other UE30 implementations might exploit QCL
`between CSI-RS and DMRS by jointly exploiting certain
`channel properties from both RS types, and applying them to
`aid estimation of either or both such RS types.
`
`00.15 QCL properties are either defined in the standard or
`signaled by the network 10 to the UE 30, according to the
`deployment and propagation scenario. LTE Rel-11 defines
`QCL of Doppler shift and Doppler spread between CRS,
`CSI-RS and DMRS. Furthermore, delay spread and propaga
`tion delay are QCLed between a CSI-RS resource and
`DMRS. There are at least three technical problems deriving
`from this situation.
`0016 First, it is impossible to configure correct QCL
`assumptions when DMRS based transmission occurs from
`multiple points (i.e., joint transmission on the same
`resources) which are characterized by different frequency
`shift and/or propagation delay and/or delay spread. Second,
`demodulation performance degrades unnecessarily when
`CRS and/or CSI-RS SINR are low. Third, when compensa
`tion of all the above mentioned mismatches is required, the
`UE complexity increases.
`0017. The Background section of this document is pro
`vided to place embodiments of the present invention in tech
`nological and operational context, to assist those of skill in the
`art in understanding their scope and utility. Unless explicitly
`identified as such, no statement herein is admitted to be prior
`art merely by its inclusion in the Background section.
`
`SUMMARY
`0018. The following presents a simplified summary of the
`disclosure in order to provide a basic understanding to those
`of skill in the art. This summary is not an extensive overview
`of the disclosure and is not intended to delineate the scope of
`the invention. The sole purpose of this Summary is to present
`Some concepts disclosed herein in a simplified form as a
`prelude to the more detailed description that is presented later.
`0019. According to one or more embodiments described
`and claimed herein a UE in a CoMP downlink may autono
`mously adopt an assumption of the quasi co-located (QCL)
`status of two (or more) antenna ports that is different from the
`default QCL status defined or signaled by the network, in
`response to one or more estimates of certain operating param
`eter values. The altered QCL status assumption allows the UE
`to correct parameter estimates more accurately, and/or to
`reduce complexity in the parameter estimation correction.
`0020. One embodiment relates to a method of operating a
`User Equipment UE in the downlink of a wireless radiocom
`munication network operative to transmit signals from a plu
`rality of transmission points. Two or more antenna ports are
`defined or signaled by the network to be quasi co-located
`(QCL), or not, with respect to a given long term channel
`property, whereby the antenna ports are QCL if the given long
`term channel property may be assumed to be the same for
`both antenna ports by the UE (30). The UE ascertains, by
`predefinition or signaling from the network, a default QCL
`status of the first and second antenna ports, and estimates one
`or more wireless network operating parameters. The UE
`autonomously adopts an assumption of the QCL status, dif
`ferent from the default QCL status, of the first and second
`antenna ports, in response to the one or more parameter
`estimates.
`0021. Another embodiment relates to a User Equipment
`(UE) operative in a wireless radiocommunication network
`transmitting signals from a plurality of transmission points.
`Two or more antenna ports are defined or signaled by the
`network to be quasi co-located (QCL), or not, with respect to
`a given long term channel property, whereby the antenna
`ports are QCL if the given long term channel property may be
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`assumed to be the same for both antenna points by the UE.
`The UE includes radio circuitry operative to receive signals
`from the network, memory, and processing circuitry opera
`tively connected to the memory and radio circuitry. The pro
`cessing circuitry operative to ascertain, by predefinition or
`signaling from the network, a default QCL status of the first
`and second antenna ports; estimate one or more wireless
`network operating parameters, and autonomously adopt an
`assumption of the QCL status, different from the default QCL
`status, of the first and second antenna ports, in response to the
`one or more parameter estimates.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0022. The present invention will now be described more
`fully hereinafter with reference to the accompanying draw
`ings, in which embodiments of the invention are shown. How
`ever, this invention should not be construed as limited to the
`embodiments set forth herein. Rather, these embodiments are
`provided so that this disclosure will be thorough and com
`plete, and willfully convey the scope of the invention to those
`skilled in the art. Like numbers refer to like elements through
`Out
`0023 FIG. 1 is a functional block diagram of a Long Term
`Evolution (LTE) radiocommunication network 10.
`0024 FIG. 2 depicts a LTE downlink physical resource.
`0025 FIG.3 depicts an LTE time-domain structure.
`0026 FIG. 4 shows a mapping of LTE physical control
`signaling, data link and cell specific reference signals within
`a downlink subframe.
`0027 FIG. 5 is a flow diagram of a method of operating a
`UE 30 in an LTE network.
`0028 FIG. 6 is a functional block diagram of an eNodeB
`20.
`0029 FIG. 7 is a functional block diagram of a UE30.
`
`DETAILED DESCRIPTION
`
`0030. It should be understood at the outset that although
`illustrative implementations of one or more embodiments of
`the present disclosure are provided below, the disclosed sys
`tems and/or methods may be implemented using any number
`of techniques, whether currently known or in existence. The
`disclosure should in no way be limited to the illustrative
`implementations, drawings, and techniques illustrated below,
`including the exemplary designs and implementations illus
`trated and described herein, but may be modified within the
`Scope of the appended claims along with their full scope of
`equivalents. In particular, although terminology from 3GPP
`LTE has been used in this specification to exemplify the
`invention, this should not be seen as limiting the scope of the
`invention to only the aforementioned system. Other wireless
`systems, including but not limited to WCDMA, WiMax,
`UMB and GSM, may also benefit from exploiting the ideas
`described herein.
`0031 One fundamental property of DL CoMP is the pos
`sibility to transmit different signals and/or channels from
`different geographical locations (transmission points). One
`of the principles guiding the design of the LTE system is
`transparency of the network 10 to the UE30. In other words,
`the UE 30 is able to demodulate and decode its intended
`channels without specific knowledge of scheduling assign
`ments for other UEs 30 or network 10 deployments. Signaling
`
`has been defined in 3GPP in order to make Sure that the UE30
`has sufficient information to correctly set its demodulation
`parameters.
`0032 Because of this distributed transmission scheme, the
`received signal will be characterized by mismatches. For
`example, the signals transmitted from different transmission
`points may be (or be perceived as being) received at different
`timing instants, mainly due the different path lengths between
`the transmission points and the UE30. Signals may also be
`(or be perceived as being) received with different frequency
`error (due to clock differences at different transmission points
`and Doppler shifts). Alternatively or additionally, signals may
`be (or be perceived as being) received with different average
`channel gain.
`0033. It is important that the UE30 be capable of compen
`sating for the effects of the above-mentioned mismatches in
`order to set correctly the most important parameters related to
`the demodulation. In particular, the UE 30 must be able to
`correctly compensate the timing difference and/or frequency
`error, and must be able to correctly estimate the SNR depend
`ing on which transmission point(s)transmits the data channel.
`0034. This leads to a high increased complexity in the UE
`30 if good performance must be maintained under typical
`CoMP scenarios. Additionally, as mentioned above, certain
`QCL assumptions—referred to herein as default QCL
`assumptions—are defined by specifications or signaled by the
`network 10 in order to allow for proper estimation. LTE
`Rel-11 defines QCL of Doppler shift and Doppler spread
`between CRS, CSI-RS and DMRS. Furthermore, delay
`spread and propagation delay are QCLed between a CSI-RS
`resource and DM RS.
`0035 More specifically, in some CoMP scenarios,
`PDSCH (or ePDCCH) transmission occurs from multi
`points, and CRSs are sent by each transmission point, each
`with a different cell ID. According to the LTE Rel-11 speci
`fication, the network 10 signals the QCL assumptions for
`Doppler shift and Doppler spread, i.e., the network 10 will
`inform the UE30 regarding which CRS may be considered as
`collocated with DMRS and CSI-RS with respect to Doppler
`shift and Doppler spread. However, if the UE 30 uses this
`QCL assumption, it will estimate a frequency error based on
`the signaled CRSs, while the actual frequency error the UE30
`experiences on PDSCH will be different, due to the multi
`point transmission strategy.
`0036. At least three technical problems deriving from this
`situation are identified: First, it is impossible to configure
`correct QCL assumptions when DMRS based transmission
`occurs from multiple points (joint transmission on same
`resources) which are characterized by different frequency
`shift and/or propagation delay and/or delay spread. Second,
`demodulation performance degrades unnecessarily when
`CRS and/or CSI-RS SINR are low. Third, the UE complexity
`increases when compensation of all the above mentioned
`mismatches is required.
`0037 According to an exemplary embodiment, these
`problems can be solved by, for example, introducing a multi
`fold decision region defined such that the UE 30 autono
`mously optimizes and dynamically changes the default QCL
`assumptions between two (or more) antenna ports in order to
`perform proper estimation of timing, frequency error, and
`average channel gain, and compensates for these mismatches
`only when it is needed. The decision region can, for example,
`be determined by a combination of parameters and measure
`mentS.
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`0038 More specifically, the multifold decision region cor
`responds to a set of conditions, such as for example DMRS
`SNR, CSR-SNR, modulation, speed, and PDSCH PRB allo
`cation (as discussed more fully herein), according to which
`the UE 30 dynamically and autonomously changes the
`default QCL assumptions in order to properly estimate the
`parameters and perform proper compensation. Additionally,
`these embodiments limit the complexity in the UE30 but still
`guarantee high demodulation performance under CoMP (that
`is, no performance loss compared to the full complexity UE
`30 behavior).
`0039 Thus, embodiments provide for dynamically
`Switching QCL assumptions for a RS port depending on the
`resources associated to such RS port, or to a channel to be
`demodulated by exploiting such RS port. Such dynamic
`Switching may, for example, be based on signaling from the
`network 10 to the UE30 (e.g., by scheduling grants or RRC
`messages) or it may be autonomous in the UE30.
`0040. One specific application of such embodiments is
`enhanced and/or simpler channel estimation based on DL
`DMRS (associated, e.g., to PDSCH or ePDCCH reception).
`In this case, switching between different QCL behaviors is
`determined by one or more of the following parameters and/
`or measurements: CRS SNR, CSI-RSSNR, DMRS SNR,
`System bandwidth, PDSCH PRB allocation, ePDCCH PRB
`allocation, Modulation, Transmission rank, Coding Rate,
`Modulation and Coding Scheme (MCS), Nominal spectral
`efficiency for the associated Scheduled transmission, Single?
`Multipoint DMRS transmission, Reference Signal Received
`Power (RSRP) and/or Reference Signal Received Quality
`(RSRO) measurements for a given cell, including a non
`serving cell. Other parameters and/or measurements may of
`course be considered as Switching criteria. It is noted that the
`above parameters/measurements should be known at least by
`the UE 30 prior to the decision on which QCL assumption
`should be used.
`0041. One fundamental observation associated with these
`embodiments is that some long term channel properties may
`be efficiently estimated for a certain RS type (e.g., DM RS)
`only when the SNR (or SINR) is sufficiently good and the
`scheduled bandwidth (BVV) is sufficiently large. It is also
`observed that the required BW is actually a function of the
`SNR or SINR. Other parameters may also contribute, to a
`lesser extent, to estimation accuracy. On the other hand, in the
`general case, certain RS such as DM RS do not have a struc
`ture that allows for accurate parameters estimation; therefore
`QCL assumptions with other RS are needed to improve
`DMRS-based channel estimation.
`0042. This problem may be solved by dynamic optimiza
`tion of the QCL assumptions—specific examples of which
`are described in numbered embodiments of the present inven
`tion.
`
`Embodiment 1
`
`0043. In a first basic embodiment, the UE 30 autono
`mously, after estimation of a certain set of parameters (e.g.,
`PDSCH PRB allocation, and/or other switching criteria
`explained in the following), adapts the QCL assumptions in
`order to optimize performance, or to reduce complexity while
`maintaining optimal performance. Note that the phrase “set of
`parameters' can include a set having one or more parameters.
`One or more of the following sub-variants can be used in
`conjunction with this general first embodiment.
`
`Embodiment 1.1
`0044) Under the conditions of embodiment 1, the UE 30
`sends a capability bit to indicate the Support of this autono
`mous, dynamic optimization of the QCL assumptions.
`0045. This allows the network 10 to adapt its decisions on
`transmission schemes to be scheduled. The network 10 may
`be aware of the QCL assumptions definitions A and B in
`embodiment 1.3 described below, as well as of the QCL
`Switching criteria, and can exploit this in order to increase the
`deployment freedom.
`
`Embodiment 1.2
`0046 Under the conditions of embodiments 1, or 1.1, the
`network 10 may reconfigure the QCL assumptions as well as
`the corresponding triggering criteria in the UE30.
`
`Embodiment 1.3
`0047 Under the condition of embodiments 1, 1.1, or 1.2 at
`least the following QCL assumptions for CRS are present:
`0.048 A: Default Rel-11 QCL assumptions (i.e., CRS,
`CSI-RS and DMRS are QCL with respect to certain long
`term channel properties), and
`0049 B: DMRS shall not be assumed as QCL with any
`other RS.
`Embodiment 1.3 can also define a triggering criterion for
`QCL assumption B, e.g., the UE30 adopts QCL assumption
`B when the associated PDSCH BW is larger than 2 PRBs.
`Other triggering criteria are of course possible, as discussed
`further below. Similarly, other definitions of assumption Bare
`possible. As with other QCL assumptions, individual long
`term channel properties may be collocated between different
`RS types in the definition of assumption B and additional
`assumptions may be introduced. When the triggering criteria
`apply, the UE 30 ignores the default QCL assumption that
`CRSs are QCLed with DMRSs and will use assumptions B
`instead. One important point is to define triggering conditions
`such that the UE30 does not need to rely on QCL of DMRS
`with other RS when such triggering conditions apply. Using
`this embodiment, the network 10 can deploy PDSCH multi
`point transmission, even when CRSs are sent independently
`from the different transmission points, without any joint pro
`cessing, without loss in performance. The network 10 pref
`erably performs multipoint transmission only when the trig
`gering condition(s) for assumption B apply.
`
`Embodiment 1.4
`0050. Under the conditions of embodiment 1, the UE 30
`does not inform the network 10 about the dynamic QCL
`adaptation and the network 10 is not aware that the UE 30
`performs dynamic QCL assumptions Switching. In other
`words, the QCL assumptions A and B (and possibly others),
`as well as the Switching criteria, are autonomously defined by
`the UE 30. If the UE 30 applies embodiment 1.4 correctly,
`multipoint transmission is still applicable on the network 10
`side, as it is shown by simulation results that sensitivity to at
`least incorrect frequency shift is only critical at medium-high
`SNR levels, i.e., the SNR levels at which the UE 30 should
`apply assumption B. At low SNR levels, the UE 30 would
`need to exploit QCL between DM RS and other RS types
`(assumption A) but the performance loss due to inaccurate
`channel properties estimation due to multipoint combining
`would be limited.
`
`Ex.1010
`APPLE INC. / Page 10 of 14
`
`

`

`US 2015/0349855A1
`
`Dec. 3, 2015
`
`0051. A second problem mentioned above associated with
`the use of default QCL assumptions occurs when the CRSs or
`CSI-RSs are received with very low SNR, compared to
`DMRSs. In this case, demodulation performance of DMRS
`based transmission degrades. This problem is addressed by
`embodiment of the present invention described below.
`
`estimation of the following UE parameters: CRS SNR, CSI
`RS SNR, DMRS SNR, and/or Modulation. Note that the
`eNodeB 20 knows the System bandwidth, UE-specific
`PDSCHPRB allocation and UE-specific modulation, and the
`transmission scheme used for PDSCH single or multipoint
`PDSCH transmission).
`
`Embodiment 2
`0.052. In a second basic embodiment, the UE30 autono
`mously, after estimation of certain parameters (e.g., CRS
`SNR, CSI-RSSNR, DMRSSNR, System bandwidth, and/or
`other Switching criteria), adapts QCL assumptions in order to
`optimize performance or to reduce complexity while main
`taining optimal performance.
`
`Embodiment 2.1
`0053. Under the conditions of embodiment 2, the UE 30
`sends a capability bit to indicate the Support of this autono
`mous, dynamic optimization of the QCL assumptions. This
`allows the network 10 to adapt its decisions on transmission
`schemes to be scheduled. The network 10 is aware of the QCL
`assumptions A and B in Embodiment 2.3 described below, as
`well as of the QCL switching cri