Patent Description:
<CIT> provides an MBSFN configuration method and a device, which may implement flexible configuration of an MBSFN, and improve radio resource utilization of a system. The method includes: determining, by a base station, a subframe configuration of an MBSFN subframe that is used to bear a physical multicast channel PMCH, where the subframe configuration includes a cyclic prefix CP type and/or a reference signal pattern; and sending, by the base station, MBSFN configuration infor-mation to user equipment UE, where the MBSFN configu-ration information is used to indicate the subframe configu-ration of the MBSFN subframe, where the CP type includes a normal CP, an extended CP, or another CP, and a length of the another CP is different from a length of the normal CP or a length of the extended CP. The present invention is applicable to the communications field.

The dependent claims describe advantageous optional embodiments. The scope of protection of the invention is solely limited by the appended claims.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with reference signal transmission using a reference signal design for cellular broadcast, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. In some aspects, memory <NUM> and/or memory <NUM> may comprise a non-transitory computer-readable medium storing one or more instructions for wireless communication. For example, the one or more instructions, when executed by one or more processors of the base station <NUM> and/or the UE <NUM>, may perform or direct operations of, for example, process <NUM> of <FIG> and/or other processes as described herein.

In some aspects, UE <NUM> may include means for determining a set of resources, in a set of physical multicast channel symbols between a first cell acquisition subframe and a second cell acquisition subframe, means for receiving a first type of reference signal and a second type of reference signal, means for receiving one or more reference signal transmissions in accordance with the set of resources, and/or the like. In some aspects, such means may include one or more components of UE <NUM> described in connection with <FIG>, such as controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, and/or the like.

In some aspects, base station <NUM> may include means for determining a set of resources, in a set of physical multicast channel symbols between a first cell acquisition subframe and a second cell acquisition subframe, for transmitting a first type of reference signal and a second type of reference signal, means for receiving one or more reference signal transmissions in accordance with the set of resources, and/or the like. In some aspects, such means may include one or more components of base station <NUM> described in connection with <FIG>, such as antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like.

<FIG> is a block diagram conceptually illustrating an example <NUM> of a frame structure that includes cell acquisition subframes (CASs) and physical multicast channel (PMCH) symbols, in accordance with various aspects of the present disclosure.

A communications system, such as a <NUM> cellular broadcast communication system, may include reception scenarios with a threshold inter-site distance. For example, a rooftop reception scenario may be associated with inter-site distances of greater than <NUM> kilometer (km), up to <NUM>, and/or the like. Rooftop reception scenarios with a threshold inter-site distance may result in a threshold delay spread. A candidate numerology for such a scenario may be selected to have a threshold duration of a cyclic prefix to cover the threshold delay spread of a channel.

As shown in <FIG>, example <NUM> shows CASs and PMCHs in a frame structure for, for example, a rooftop reception scenario. As shown, the frame structure includes a first CAS, a plurality of PMCH symbols, and a second CAS. A time from a start of the first CAS to a start of the second CAS may be <NUM> milliseconds (ms) and each CAS may have a duration of <NUM>. This results in a <NUM> spacing between the first CAS and the second CAS forming a PMCH region for PMCH symbols. In some aspects, the PMCH symbols may be between the first CAS and the second CAS, which may be consecutive CASs. In some aspects, PMCH symbols are interspersed by periodic occurrences of a CASs. In other words, a first portion of the PMCH symbols may be between a first CAS and a second CAS, a second portion of the PMCH symbols may be between the second CAS and a third CAS, and/or the like.

A first candidate numerology for the PMCH region (e.g., for a scenario with a threshold delay spread) includes a transmission time duration of <NUM> microseconds (µs) and a cyclic prefix duration of <NUM>, which results in a symbol duration of <NUM> and a subcarrier spacing (SCS) of <NUM> hertz (Hz). As a result, in the first candidate numerology, <NUM> PMCH symbols occur in the PMCH region. Alternatively, a second candidate numerology for the PMCH region (e.g., for a scenario with a threshold delay spread) includes a transmission time duration of <NUM> and a cyclic prefix duration of <NUM>, which results in a symbol duration of <NUM> and an SCS of <NUM>. As a result, in the second candidate numerology, <NUM> PMCH symbols occur in the PMCH region.

Some aspects described herein may provide a reference signal design and enable use of the reference signal design for a PMCH region for the candidate numerologies. In some aspects, the reference signal design for the candidate numerologies may be based at least in part on a joint time-frequency-plane design over a subset of subcarriers of PMCH symbols in the PMCH region. In some aspects, the reference signal design for the candidate numerologies may be associated with a threshold level of reference signal density (e.g., a threshold packing) to enable channel estimation. In some aspects, the reference signal design may enable correction of a residual carrier frequency offset (CFO).

<FIG> are block diagrams conceptually illustrating examples <NUM>/<NUM>/<NUM> of reference signal transmission patterns for a single type of reference signal within an example frame structure, in accordance with various aspects of the present disclosure.

A UE (e.g., UE <NUM>) and/or a BS (e.g., BS <NUM>) may define a reference signal transmission pattern with respect to a frequency spacing, Fd, of subcarriers and a time stagger, Td, of symbols. As shown in <FIG>, the reference signal transmission patterns result in a reference signal once in each Fd * Td subcarriers of a PMCH symbol configured with a value for Fd and Td. Across a group of Td PMCH symbols, a reference signal occurs once in each Fd subcarrier collectively (e.g., when coalesced). Within each PMCH symbol, the reference signal subcarriers have a periodicity of Fd * Td.

In some aspects, the time stagger may be based at least in part on a coherence time of a channel. For example, for a channel that changes relatively fast, a relatively small time stagger may be used. In contrast, for a channel that changes relatively slow, a relatively large time stagger may be used to enable channel estimation. In some aspects, the UE and/or the BS may store configuration information indicating the frequency spacing, the time stagger, and/or one or more other parameters for determining a resource for a reference signal, as described herein. In some aspects, the BS may dynamically configure and/or reconfigure resources for reference signal transmission.

As shown in <FIG>, example <NUM> includes a first reference signal transmission pattern. The first reference signal transmission pattern is associated with a frequency spacing of <NUM> and a time stagger of <NUM>. As a result, a reference signal in PMCH symbol <NUM> (denoted PMCH<NUM>) is in subcarrier <NUM>, a reference signal in PMCH symbol <NUM> (denoted PMCH<NUM>) is in subcarrier <NUM>, and/or the like based at least in part on a frequency spacing of <NUM>. Similarly, a reference signal is, again, in subcarrier <NUM> in PMCH symbol <NUM> (denoted PMCH<NUM>) based at least in part on a time stagger of <NUM>. In some aspects, the BS and/or the UE may store information identifying the first reference signal pattern, such as a mapping of resources in PMCH symbols. Additionally, or alternatively, the BS and/or the UE may dynamically determine the first reference signal pattern (and/or one or more other reference signal patterns described herein) based at least in part on an equation, as described in more detail herein.

As shown in <FIG>, example <NUM> includes a second reference signal transmission pattern. The second reference signal transmission pattern is associated with a frequency spacing of <NUM> and a time stagger of <NUM>. As a result, a reference signal in PMCH symbol <NUM> is in subcarrier <NUM>, a reference signal in PMCH symbol <NUM> is in subcarrier <NUM>, and/or the like based at least in part on a frequency spacing of <NUM>. Similarly, a reference signal is, again, in subcarrier <NUM> in PMCH symbol <NUM> based at least in part on a time stagger of <NUM>. In this case, the second reference signal transmission pattern may be termed a monotonic reference signal transmission pattern.

As shown in <FIG>, example <NUM> includes a third reference signal transmission pattern. The third reference signal transmission pattern is associated with a frequency spacing of <NUM> and a time stagger of <NUM>, but is a non-monotonic reference signal transmission pattern. As a result, a reference signal in PMCH symbol <NUM> is in subcarrier <NUM>; a reference signal in PMCH symbol <NUM> is in subcarrier <NUM>; a reference signal in PMCH <NUM> is in subcarrier <NUM>; and a reference signal in PMCH symbol <NUM> is in subcarrier <NUM>. In other words, in the non-monotonic reference signal transmission pattern, the time stagger pattern is non-sequential with regard to the offset from subcarrier <NUM> across sequential PMCH symbols.

In examples <NUM>/<NUM>/<NUM>, after initial downlink synchronization and physical broadcast channel (PBCH) acquisition, a residual CFO may be correctable using reference signals and/or phase-locked loops (PLLs). For example, with a time stagger of Td, a PLL may be used to correct a residual CFO of up to <NUM>/(<NUM> * Td * Tsymb) where Tsymb represents the symbol duration (e.g., <NUM> for the first candidate numerology and <NUM> for the second candidate numerology). For the first candidate numerology, using a PLL, a UE may correct up to <NUM> of residual CFO. Similarly, for the second candidate numerology, using a PLL the UE may correct up to <NUM> of residual CFO. However, the residual CFO for some scenarios, may be approximately <NUM>.

Some aspects described herein provide a second type of reference signal to enable residual CFO compensation for scenarios where a large channel coherence time results in a larger time-stagger parameter Td of the first type of reference signal to improve reference signal overhead. For example, a UE may receive a first type of reference signal for channel estimation and a second type of reference signal for channel estimation and CFO correction in scenarios with greater than a threshold residual CFO (e.g., greater than is correctable using only the first type of reference signal). In this case, the second type of reference signal may be a sparse reference signal that occurs in the same subcarrier(s) of every PMCH symbol to correct residual CFOs.

In some aspects, the second type of reference signal may be defined as sparse in the frequency domain based at least in part on occurring once in each physical resource block (PRB) (e.g., with a frequency of <NUM>). In some aspects, the second type of reference signal may be defined as sparse in the frequency domain based at least in part on occurring once in a bandwidth of a PMCH symbol, as described herein.

In some aspects, a BS may scramble and a UE may de-scramble the plurality of types of reference signals. For example, the BS may scramble the plurality of types of reference signals based at least in part on an identifier corresponding to a multicast-broadcast single-frequency number (MBSFN) area identifier. In some aspects, the plurality of types of reference signals may be jointly scrambled using the same reference signal scrambling pattern. Additionally, or alternatively, the plurality of types of reference signals may be scrambled using different scrambling patterns for each type of reference signal.

In some aspects, the BS and/or the UE may determine reference signal resources (e.g., reference signal locations within available resources) based at least in part on one or more equations. For example, a reference signal location (e.g., for the first type of reference signal) is specified as a vertical shift v with respect to a particular subcarrier of a PMCH symbol and is based at least in part on a periodicity in a subcarrier domain for the PMCH symbol. In this case, a UE determines the reference signal as a function of the vertical shift, which is based at least in part on a system frame number (SFN), an orthogonal frequency division multiplexing (OFDM) symbol index for the PMCH symbol with respect to an immediately previous CAS, a time stagger parameter, a frequency offset, a quantity of PMCH symbols that occur between two consecutive CASs in the PMCH region, a multicast-broadcast single-frequency network (MBSFN) area identifier, an MBSFN cell identifier, and/or the like.

As an example, a UE and/or a BS may determine v based at least in part on an equation of the form: <MAT> where <MAT> represents a quantity of symbols in the PMCH region between two consecutive CASs (e.g., which may be based at least in part on whether the first candidate numerology or the second candidate numerology is used) and nsymb represents a PMCH symbol index within the PMCH region between two consecutive CASs (e.g., from <NUM> to <MAT>). In this way, the UE and/or the BS determines the vertical shift in the subcarrier domain, with respect to a reference subcarrier (e.g., subcarrier <NUM>) for a monotonic uniform reference signal transmission pattern, such as is illustrated by examples <NUM> and <NUM> and by a first type of reference signal in example <NUM>, as described in more detail herein. In some aspects, a vertical shift for a type-<NUM> MBSFN reference signal pattern may be included in an equation for a reference-signal sequence mapping to a complex-valued modulation symbol of the form: <MAT> where ñs represents an absolute slot number and the '<NUM>(ñs mod <NUM>)' term represents a vertical shift. Similarly, for a type-<NUM> MSFN reference signal pattern the equation may be of the form: <MAT> where '<NUM>(ñs mod <NUM>)' represents the vertical shift. Expanding out the '<NUM>(ñs mod <NUM>)' term, results in an equation of the form (for Fd = <NUM> and Td = <NUM> or2): <MAT> where ns is a symbol index of the symbols within the two CASs (with a quantity of symbols between the CASs of <NUM>).

Additionally, or alternatively, for a non-monotonic uniform reference signal transmission pattern, as is illustrated by example <NUM>, the UE and/or the BS may determine v as: <MAT> where <MAT> represents a permutation from {<NUM>,<NUM>,. , Td} → {<NUM>,<NUM>,. , Td} that is based at least in part on a non-monotonic pattern that may be based at least in part on at least one of SFN or <MAT>.

Additionally, or alternatively, the UE and/or the BS may determine v using a piecewise equation. For example, the UE and/or the BS may determine v using a first equation for nsymb = {<NUM>, <NUM>} and a second equation for nsymb = {<NUM>,<NUM>,. ,<NUM>}, which may enable determination of a non-uniform reference signal transmission pattern (e.g., a reference signal transmission pattern with a plurality of sub-patterns) for the first type of reference signal illustrated by examples <NUM> and <NUM>, as described herein.

When the shift is based at least in part on the MBSFN area identifier or MBSFN cell identifier, a vshift parameter may be introduced for determining the reference signal transmission pattern. In this case, a composite shift may be represented as: <MAT> where vshift is based at least in part on the MBSFN area identifier or MBSFN cell identifier. As a result, the UE and/or the BS may determine subcarrier indices k in a PMCH symbol for the first type of reference signal as: <MAT> where <MAT> where <MAT> represents a quantity of subcarriers for PMCH transmission.

In some aspects, when the UE and the BS are to determine a reference signal transmission pattern that includes a second type of reference signal, the UE and the BS may determine another set of subcarrier indices k for the second type of reference signal. In this case, as described herein, subcarrier indices for the second type of reference signal may be the same for each PMCH symbol, and a subcarrier location for the second type of reference signal may be based at least in part on the MBSFN area identifier or the MBSFN cell identifier. For example, when the second type of reference signal is to occur once in each PRB, as described above, the UE and/or the BS may determine subcarrier indices (which are the same for each PMCH symbol in an MBSFN area) as: <MAT> where v'shift is based at least in part on the MBSFN area identifier and <MAT> represents a quantity of subcarriers in a PRB (e.g., which may be based at least in part on which of the candidate numerologies is used).

As shown in <FIG>, example <NUM> includes a fourth reference signal transmission pattern. The fourth reference signal transmission pattern is associated with a frequency spacing of <NUM> and a time stagger of <NUM> and an additional type of reference signal for CFO correction. As a result, a first occurrence (e.g., a first resource) of a first type of reference signal in PMCH symbol <NUM> is in subcarrier <NUM>, a second occurrence (e.g., a second resource) of the first type of reference signal in PMCH symbol <NUM> is in subcarrier <NUM>, and/or the like. Here, a second type of reference signal is associated with a frequency spacing of <NUM> and a time stagger of <NUM>. As a result, occurrences of the second type of reference signal (e.g., resources for the second type of reference signal) are in a subcarrier <NUM> of each PMCH, thereby enabling correction of a residual CFO of approximately <NUM>.

As shown in <FIG>, example <NUM> includes a fifth reference signal transmission pattern that includes a plurality of sub-patterns for the first candidate numerology. For example, the fifth reference signal transmission pattern includes, for a first type of reference signal, a frequency spacing of <NUM> and a time stagger of <NUM> for PMCH symbols <NUM> and <NUM> and a frequency spacing of <NUM> and a time stagger of <NUM> for PMCH symbols <NUM> to <NUM>. This may reduce an amount of initial buffering of data that may occur before PMCH decoding is complete. In this case, the second type of reference signal is associated with a frequency spacing of <NUM> and a time stagger of <NUM>, resulting in the second type of reference signal occurring in each PMCH at the same subcarrier.

As shown in <FIG>, example <NUM> includes a sixth reference signal transmission pattern that includes a plurality of sub-patterns for the second numerology. For example, the sixth reference signal transmission pattern includes, for a first type of reference signal, a frequency spacing of <NUM> and a time stagger of <NUM> for PMCH symbol <NUM> and a frequency spacing of <NUM> and a time stagger of <NUM> for PMCH symbols <NUM> to <NUM>. In this case, the first PMCH symbol is a densely packed symbol (e.g., the first PMCH symbol includes greater than a threshold quantity of reference signals), which may improve channel estimation relative to other reference signal patterns. Furthermore, the sixth reference signal transmission pattern may reduce an amount of initial buffering of data that may occur before PMCH decoding is complete. In this case, the second type of reference signal is associated with a frequency spacing of <NUM> and a time stagger of <NUM>, resulting in the second type of reference signal occurring in each PMCH at the same subcarrier.

In some aspects, a BS may signal, to a UE, dense packing of reference signals in the first PMCH symbol. For example, the BS may transmit a system information block (SIB) message, a downlink control information (DCI) message, and/or the like to cause the UE to omit one or more PMCH symbols from a reference signal mapping equation described above, and to use a dense packing configuration for the one or more PMCH symbols. In some aspects, the BS may override a reference signal mapping equation for one or more other PMCH symbols using a SIB message, a DCI message, and/or the like, thereby enabling dynamic configuration of the reference signal transmission patterns, values for the frequency offset and/or the time stagger, and/or the like.

In some aspects, the BS may configure a particular transport block size (TBS) for the PMCH symbols. For example, the BS may configure a relatively small TBS for the densely packed first PMCH symbol and a relatively large TBS for other sparsely packed PMCH symbols. In this case, the BS may transmit an indication of a scaling factor for scaling TBSs based at least in part on a quantity of reference signals for which resources are allocated in a PMCH symbol.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with various aspects of the present disclosure. Example process <NUM> is an example where a UE (e.g., UE <NUM> and/or the like) performs operations associated with reference signal design for numerologies.

As shown in <FIG>, in some aspects, process <NUM> may include determining a set of resources, in a set of physical multicast channel symbols between a first cell acquisition subframe and a second cell acquisition subframe, for receiving a first type of reference signal and a second type of reference signal (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may determine a set of resources, in a set of physical multicast channel symbols between a first cell acquisition subframe and a second cell acquisition subframe, for receiving a first type of reference signal and a second type of reference signal, as described above. In some aspects, the first type of reference signal is for channel estimation, and the second type of reference signal is for channel estimation and carrier frequency offset estimation.

As further shown in <FIG>, in some aspects, process <NUM> may include receiving one or more reference signal transmissions in accordance with the set of resources (block <NUM>). For example, the UE (e.g., using receive processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive one or more reference signal transmissions in accordance with the set of resources, as described above.

As used herein, "approximately" may, depending on the context refer to a value that is within a threshold amount of a stated value, such as within <NUM>%, within <NUM>%, and/or the like.

Claim 1:
A method of wireless communication performed by a user equipment, UE (<NUM>), comprising:
determining (<NUM>) a set of resources, in a set of physical multicast channel symbols between a first cell acquisition subframe and a second cell acquisition subframe, for receiving a first type of reference signal, and
wherein the first type of reference signal is for channel estimation, wherein one or more resources, of the set of resources, corresponding to the first type of reference signal and in each physical multicast channel symbol, of the set of physical multicast channel symbols, are defined based at least in part on a vertical shift parameter corresponding to a shift relative to an initial subcarrier, wherein the vertical shift parameter is based at least in part on a system frame number,
an orthogonal frequency division multiplexing symbol index, a time stagger parameter and a quantity of physical multicast channel symbols occurring between the first cell acquisition subframe and the second cell acquisition subframe; and
receiving one or more reference signal transmissions in accordance with the set of resources.