Patent Description:
In a wireless system, it may be advantageous for a network to be permitted to schedule physical downlink control channel (PDCCH) candidates in a manner that is flexible, without scheduling them in a manner that burdens a user equipment to an unacceptable extent. Simple limits on blind detection and control channel element monitoring may be capable of protecting the user equipment from excessively burdensome requirements, but such limits may be sufficiently inflexible to limit the performance of the network, especially in a carrier aggregation (CA) scheme.

Thus, there is a need for an improved system and method for setting blind detection and control channel element monitoring limits in a carrier aggregation scheme.

<NPL>, discusses remaining aspects on Rel-<NUM> PDCCH enhancements for URLLC.

<NPL>, discusses remain issues on PDCCH enhancements for NR URLLC.

<NPL>, discusses remaining Issues on PDCCH Enhancements for URLLC.

<NPL>, discusses corrections on PDCCH enhancement for URLLC.

Specific embodiments are defined in the dependent claims.

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of a system and method for setting blind detection and control channel element monitoring limits in a carrier aggregation scheme provided in accordance with the present disclosure and is not intended to represent the only forms in which the present disclosure may be constructed or utilized. The description sets forth the features of the present disclosure in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the scope of the disclosure. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.

In a cellular system, a user equipment (UE) may monitor a physical downlink control channel (PDCCH) search space (SS) to obtain downlink control information (DCI) which provides control information for a UE's downlink operation. As used herein, the phrase "user equipment" is used as a countable noun even though the noun it contains ("equipment") may not be countable in ordinary English. Each time instance of a PDCCH SS may be referred to as a monitoring occasion (MO). In the new radio (NR) specification, to improve system latency and flexibility, the location of each MO can be arbitrary within a slot which consists of <NUM> or <NUM> orthogonal frequency division multiplexing (OFDM) symbols. However, such flexibility increases a UE's PDCCH monitoring complexity, and a UE capability signaling scheme which can limit the MO pattern within each slot is included in the release <NUM> NR specification. A network is required to provide a PDCCH SS configuration, which defines a set of monitoring occasions which satisfies the declared UE capability. The table of <FIG>, which is a part of the 3rd Generation Partnership Project (3GPP) specification TR <NUM>, describes the corresponding capability signaling. The table of <FIG> refers to FG-<NUM>-<NUM>, which is reproduced in the table of <FIG>.

A monitoring span mentioned in FG3-5b of the table of <FIG> consists of consecutive symbols within a slot, and a span pattern within a slot is determined based on the monitoring occasion (MO) pattern, a monitoring capability reported by the UE as a set of ordered pairs (X,Y), and the control resource set (CORESET) configuration for the user equipment (UE). Each ordered pair of numbers (X, Y) may be referred to as a "span-gap span-length pair" (within which X is the span-gap element, and Y is the span-length element). In particular, spans within a slot have the same duration, which is determined by max{maximum value of all CORESET durations, minimum value of Y in the UE reported candidate value} except possibly the last span in a slot which can be of shorter duration. The first span in the span pattern within a slot begins at the symbol of the smallest index for which a monitoring occasion is configured to the UE. The next span begins with an MO which is not included in the first span and the same procedure is applied to construct the following spans. The separation between any two consecutive spans within and across slots must satisfy the same (X,Y) limit, where X represents the minimum time separation of OFDM symbols of two spans and Y represents the maximum number of consecutive OFDM symbols for each span. In release <NUM> (Rel-<NUM>), the UE can report its monitoring capability from three possible sets: {(<NUM>,<NUM>)}, {(<NUM>,<NUM>), (<NUM>,<NUM>) }, {(<NUM>,<NUM>), (<NUM>,<NUM>), (<NUM>,<NUM>)}. One example is shown in <FIG>, where the CORESET configuration has one symbol and the UE reports {(<NUM>,<NUM>), (<NUM>,<NUM>), (<NUM>,<NUM>)}. Smaller 'X' will make monitoring more frequent, i.e., more challenging, from the perspective of the UE. Such nested capability signaling, i.e., a signaling scheme in which, when a UE sends to the network a declaration (or a "declaration of capabilities") indicating that it is capable of supporting a certain X value, it implies that it can also support larger X values, is reasonable in part because the larger X values are generally less burdensome for the UE. Upon receipt of such a declaration of capabilities, the network is expected to send, to the UE transmissions that comply with the declaration of capabilities, i.e., that are within the capabilities of the UE as declared to the network.

In release <NUM> (Rel-<NUM>) of the 3GPP, span-based PDCCH monitoring capability is specified as follows. A UE is required to support (X,Y) combinations selected from (<NUM>, <NUM>) (<NUM>, <NUM>) (<NUM>, <NUM>), as defined in UE feature <NUM>-5b as the combination (X, Y) for Rel-<NUM> PDCCH monitoring capability on the per-component carrier (per-CC) limit on the maximum number of non-overlapping control channel elements (CCEs) for ultra-reliable low-latency communication uRLLC. The UE reports the supported combinations per sub carrier spacing (SCS), and (<NUM>, <NUM>)(<NUM>, <NUM>)(<NUM>, <NUM>) is applicable for SCSs of <NUM> and <NUM>. If a UE reports the support of more than one combination of C(X, Y) for a given SCS, and if multiple combinations of C(X, Y) are valid for the span pattern, the maximum value of C of the valid combinations is applied. A combination C(X, Y) is valid if the span pattern satisfies X and Y of the given combination in every slot, including across slot boundaries.

The span pattern definitions of Rel-<NUM> have certain shortcomings, referred to herein as Problem <NUM>, Problem <NUM>, and Problem <NUM>. Problem <NUM> relates to the definition of span patterns in Rel-<NUM> not being optimized. <FIG> shows an example demonstrating this shortcoming. In <FIG>, it is assumed that the UE has reported the support of multiple combinations {(<NUM>,<NUM>),(<NUM>,<NUM>), (<NUM>,<NUM>)}. The span duration is defined as dspan = max(dCORESET,max, min Y) = max(<NUM>,<NUM>) = <NUM> , which results in the shown span pattern. dCORESET,max denotes the maximum of the CORESET lengths configured to the UE. Although the span pattern satisfies the time separation between the start of two consecutive spans and the upper limit on span length, it does not satisfy one required condition: Each MO must be fully contained within a span. As can be seen in <FIG>, the first MO <NUM> in the second row is not fully contained in one span. Therefore, the resulting span pattern is not compatible with the combination (<NUM>,<NUM>). It is not compatible with other combinations for the same reason, as the length of span is determined to be <NUM> and cannot be changed. The above search space configuration may not be configured to the UE, even though the UE is clearly capable of monitoring such a configuration by reporting the combination (<NUM>,<NUM>). Had the span length been determined to be <NUM>, the PDCCH MOs could be monitored according to the combination (<NUM>,<NUM>) with a resulting valid span pattern. Therefore, span pattern definition is not optimized in Rel-<NUM> and needlessly limits the flexibility of the network.

A second shortcoming, Problem <NUM>, which may also be referred to as hard splitting of the blind detection / control channel element (BD/CCE) limit per span across serving cells, may be understood as follows. For a single-cell operation, Table <NUM> and Table <NUM> from TS <NUM> (reproduced in the tables of <FIG> and <FIG>, respectively) determine the maximum number of PDCCH candidates and non-overlapping CCEs a UE is required to monitor per slot for different SCS configurations µ for a given pair (X, Y). In particular, Table <NUM> shows the maximum number <MAT> of monitored PDCCH candidates in a span of a span pattern (X, Y) for a downlink (DL) bandwidth part (BWP) with SCS configuration µ ∈ {<NUM>, <NUM>} for a single serving cell, and Table <NUM> shows the maximum number <MAT> of non-overlapped CCEs in a span of a span pattern (X, Y) for a DL BWP with SCS configuration µ ∈ {<NUM>, <NUM>} for a single serving cell.

Some of the constants in these tables have not yet been agreed to, and they are therefore shown as symbols, e.g., "M01" and "C01". Some embodiments disclosed herein are suitable for use with (i) any of various combinations of values for these constants or (ii) arbitrary combinations of values for these constants. It remains to determine the total number <MAT> of PDCCH candidates and total number <MAT> of non-overlapping CCEs for a set of scheduling cells with numerology µ and associated pair (X,Y).

A third shortcoming, Problem <NUM>, which may also be referred to as BWP switching and span-based PDCCH monitoring, may be understood as follows. As can be seen in Table <NUM> and Table <NUM> (in <FIG> and <FIG> respectively), span-based PDCCH monitoring, introduced in Rel-<NUM>, is only supported for subcarrier spacings (SCSs) of <NUM> and <NUM>. One reason for this is that higher SCSs may be associated with a short slot duration for which the required latency of uRLLC is ensured even with slot-based PDCCH monitoring, due to the short slot duration of higher SCSs. Another reason is that uRLLC applications may be served in serving cells with lower frequencies and smaller SCS due to increased link reliability.

With BWP switching, the switched BWP may have different SCS than the previously active BWP. To take this possibility into account, it may be advantageous to specify what the UE behavior should be when the network (gNB) switches BWP to a new BWP with a configuration for which span-based monitoring is not supported. Some embodiments therefore provide methods to define UE behavior for span-based PDCCH monitoring when BWP switching is carried out.

In some embodiments, Problem <NUM> may be addressed using a method to define the span pattern for a UE as follows. For a given set of reported combinations (X, Y) and the set of search space sets and CORESETs configured to the UE by the network, a span pattern is determined as follows. The input is the declared (or "reported") set of A = {(X, Y)} by the UE and the set of search spaces and CORESETs configured to the UE by the network on the serving cell. The output is the span pattern in the slot. In some embodiments, the method includes three steps, Step <NUM>, Step <NUM>, and Step <NUM>, as follows (with Step <NUM> having several sub-steps). Step <NUM> includes setting the set C of (X, Y)s that are compatible with the configured search spaces to be an empty set C = { }. Step <NUM> includes, for each (X, Y) ∈ A, performing three sub-steps, Step <NUM>-<NUM>, Step <NUM>-<NUM> and Step <NUM>-<NUM>, as follows. Step <NUM>-<NUM> includes determining the span duration dspan(Y) = max(dCORESET,max, Y), where dCORESET,max is the maximum of CORESET lengths among the configured CORESETs for the UE. Step <NUM>-<NUM> includes, for the span duration given in Step <NUM>-<NUM>, determining the span pattern as follows: a) generating a bitmap b(l), <NUM> ≤ l ≤ <NUM>, where b(l) = <NUM> if symbol l of any slot is part of a monitoring occasion, and b(l) = <NUM> otherwise. The first span in the span pattern begins at the smallest l for which b(l) = <NUM>. The next span in the span pattern begins at the smallest l not included in the previous span(s) for which b(l) = <NUM>. The span pattern resulting from Step <NUM>-<NUM> may be referred to as the "span pattern assuming the span-gap span-length pair, that includes a first set of control resource sets and a first set of search spaces. " Step <NUM>-<NUM> includes putting (X, Y) in the set C ← C ∪ {(X, Y)}, if the span pattern resulting from Step <NUM>-<NUM> satisfies the span condition according to the conditions, listed below, for a combination (X, Y) to satisfy a span pattern. Step <NUM> includes choosing, from the set C, either (i) the (X*, Y*) with the maximum value of <MAT> or (ii) the (X*, Y*) with the maximum value of <MAT>. The resulting span pattern is the span pattern determined in Step <NUM>-<NUM> for (X, Y) = (X*, Y*) with span duration dspan(Y*).

The following set of conditions for a combination (X, Y) to satisfy a span pattern may be employed in Step <NUM>-<NUM>. A span pattern may be considered to be "valid" for a combination (X, Y) if all of the following conditions hold: (i) there is a minimum time separation of X OFDM symbols (including the cross-slot boundary case) between the start of two spans (ii) each span is of length up to Y consecutive OFDM symbols of a slot, (iii) spans do not overlap on any OFDM symbol, (iv) every span is contained in a single slot, (v) the same span pattern repeats in every slot. (vi) the separation between consecutive spans within and across slots may be unequal but the same (X, Y) limit is satisfied by all spans, (vii) every monitoring occasion is fully contained in one span (that is, every PDCCH candidate is fully contained within a span), and (viii) the number of different start symbol indices of spans for all PDCCH monitoring occasions per slot is no more than <MAT> (where X is the minimum value reported by the UE). Any valid span pattern may be considered to "comply" with the declaration of capabilities of the UE, in the sense that it a member of the family of span patterns that the UE has declared itself to be capable of handling.

For example, if a UE is configured with the search space configurations shown in <FIG>, the resulting span pattern for (<NUM>,<NUM>) is not valid as one MO is not fully contained within a span. The resulting span pattern for (<NUM>,<NUM>) is valid as it satisfies all the conditions in the above table. The resulting span pattern for (<NUM>,<NUM>) is not valid as the time gap between the start of the first and second spans is <NUM>, which is less than <NUM>.

In some embodiments, Problem <NUM> may be addressed using a method to determine <MAT> and <MAT> and a rule to distribute the BD/CCE limits across different spans of the N cells, as follows. It is assumed that N scheduling cells with numerology µ and pair (X, Y) schedule a number of scheduled cells. As used herein, a span pattern is said to be "covered" by (X, Y) if the conditions in FG <NUM>-5b are satisfied for (X, Y). The conditions are also listed above, as set of conditions for a combination (X, Y) to satisfy a span pattern. Each of the methods taught herein for addressing Problem <NUM> and Problem <NUM> may use either the determination of span pattern of Rel-<NUM> or the method described above as a method for addressing Problem <NUM>.

Methods for addressing Problem <NUM> may use the concept of "aligned span patterns", discussed in further detail below. In some embodiments, BD/CCE limits per span can be determined as follows.

A method referred to herein as Method A may be employed to determine a BD limit, as follows. If a UE is configured with <MAT> downlink cells with Rel-<NUM> PDCCH monitoring capability with an associated combination (X, Y) and SCS configuration µ, where <MAT>, the UE is not required to monitor more than <MAT> PDCCH candidates per span on the active DL BWP(s) of scheduling cell(s) from the <MAT> downlink cells if the spans on different downlink cells from the <MAT> downlink cells are aligned (i.e., if together they form an aligned span pattern, discussed in further detail below), where <MAT> <MAT> is the number of downlink cells with Rel-<NUM> monitoring capability, i.e. span-based monitoring capability, with which the UE is configured, and <MAT> is the reference number of serving cells with Rel-<NUM> monitoring capability, and is reported by the UE as a capability.

The associated combination (X, Y) is the combination (X, Y) associated with the largest maximum number of <MAT>, if the UE indicates a capability to monitor PDCCH according to multiple (X, Y) combinations and a configuration of search space sets to the UE results in a span pattern with a separation of any two consecutive PDCCH monitoring spans that is equal to or larger than the value of X for two or more of the (X, Y) combinations.

A method referred to herein as Method B may be employed to determine a non-overlapping CCE limit, as follows. If a UE is configured with <MAT> downlink cells with Rel-<NUM> PDCCH monitoring capability with an associated combination (X, Y) and SCS configuration µ, where <MAT>, the UE is not required to monitor more than <MAT> non-overlapping CCEs per span on the active DL BWP(s) of scheduling cell(s) from the <MAT> downlink cells if the spans on different downlink cells from the <MAT> downlink cells are aligned (i.e., if together they form an aligned span pattern, discussed in further detail below), where <MAT> and <MAT> is the number of serving cells configured with Rel-<NUM> monitoring capability, i.e. span-based monitoring capability.

The associated combination (X, Y) is the combination (X, Y) associated with largest maximum number of <MAT>, if the UE indicates a capability to monitor PDCCH according to multiple (X, Y) combinations and a configuration of search space sets to the UE results in a span pattern with a separation of any two consecutive PDCCH monitoring spans that is equal to or larger than the value of X for two or more of the (X, Y) combinations.

It then remains to define (i) how to determine span determination in "per span" mentioned in Method A and B and (ii) how to determine whether the spans on different downlink cells from the <MAT> downlink cells are aligned. In one embodiment, which may be referred to as Embodiment <NUM>-A, the case of aligned spans may be defined as follows. The span pattern on a set of (X, Y) serving cells is considered to be aligned if every two spans on the same or two different cells either (i) have the same starting and ending symbols or (ii) the time gap between the start of the two spans is at least X symbols. An example is shown in <FIG>, where the UE is configured with N = <NUM> serving cells, CC1 and CC2, both with (X, Y) = (<NUM>,<NUM>). The span pattern is classified as aligned according to Embodiment <NUM>-A.

In another embodiment, which may be referred to as Embodiment <NUM>-B, the case of aligned spans may be defined as follows. The span pattern on a set of (X, Y) serving cells is considered to be aligned if every two spans on the same or two different cells either (i) have the same starting symbols or (ii) the time gap between the start of the two spans is at least X symbols. An example is shown in <FIG>, where the UE is configured with N = <NUM> serving cells, CC1 and CC2, both with (X, Y) = (<NUM>,<NUM>). The span pattern is classified as aligned according to Embodiment <NUM>-B. The definition of an aligned span pattern in Embodiment <NUM>-B can be stated alternatively as follows. A span pattern in the group of (X, Y) cells may be classified as aligned if the following condition is satisfied: For any span in any cell whose starting symbol is 'i', any other span in all cells in the group (including the cell itself) should have starting symbol 'j' satisfying either 'i=j' or '|i-j|>=X'. This rule can be applied within a slot or across slots. Alternatively, for any span in any cell whose starting symbol is 'i', there should be no span in any cell in the group (including the cell itself) which has starting symbol 'j' not satisfying either 'i=j' or '|i-j|>=X'. This rule can be applied within a slot or across slots.

In another embodiment, which may be referred to as Embodiment <NUM>-C, the case of aligned spans may be defined as follows. The span pattern on a set of (X, Y) serving cells is considered to be aligned if every two spans on the same or two different cells either (i) have the same ending symbols or (ii) the time gap between the start of the two spans is at least X symbols. An example is shown in <FIG>, where the UE is configured with N = <NUM> serving cells, CC1 and CC2, both with (X, Y) = (<NUM>,<NUM>). The span pattern is classified as aligned according to Embodiment <NUM>-C.

The definition of an aligned span pattern in Embodiment <NUM>-C can be stated alternatively as follows. A span pattern in the group of (X, Y) cells may be classified as aligned if the following condition is satisfied: For any span in any cell whose ending symbol is 'i', any other span in all cells in the group (including the cell itself) should have ending symbol 'j' satisfying either 'i=j' or '|i-j|>=X'. This rule can be applied within a slot or across slots. Alternatively, for any span in any cell whose ending symbol is 'i', there should be no span in any cell in the group (including the cell itself) which has ending symbol 'j' not satisfying either 'i=j' or '|i-j|>=X'. This rule can be applied within a slot or across slots.

In another embodiment, which may be referred to as Embodiment <NUM>-D, the case of aligned spans may be defined as follows. The span pattern on a set of (X, Y) serving cells is considered to be aligned if every two spans on the same or two different cells either (i) have the same starting or ending symbols or (ii) the time gap between the start of the two spans is at least X symbols. An example is shown in <FIG>, where the UE is configured with N = <NUM> serving cells, CC1 and CC2, both with (X, Y) = (<NUM>,<NUM>). The span pattern is classified as aligned according to Embodiment <NUM>-D. The definition of an aligned span pattern in Embodiment <NUM>-D can be stated alternatively as follows. A span pattern in the group of (X, Y) cells may be classified as aligned if the following condition is satisfied: For any span in any cell whose starting symbol is 'i_start' and ending symbol is "i_end", any other span in all cells in the group (including the cell itself) whose starting symbol is "j_start" and ending symbol is "j_end", satisfies either 'i_start=j_start' or 'i_end=j_end' or '|i_start-j_start|>=X'. This rule can be applied within a slot or across slots. An alternative description of the above condition is as follows: for any span in any cell whose starting symbol is "i_start" and ending symbol is "i_end", there should be no span in any cell in the group (including the cell itself) which has starting symbol 'j_start' and ending symbol "j_end" not satisfying either 'i_start=j_start' or 'i_end=j_end' or '|i_start-j_start|>=X'. This rule can be applied within a slot or across slots.

In another embodiment, which may be referred to as Embodiment <NUM>, the case of aligned spans may be defined as follows. The span pattern is determined jointly for the (X, Y) cells. If the resulting span pattern is "covered" by (X, Y), the case is classified as aligned. For the purpose of Ctotal/Mtotal, "span" is determined according the joint pattern instead of the individual patterns of each cell. The following procedure is employed to determine if the spans on different downlink cells from the <MAT> downlink cells are aligned according to this embodiment. The input is a group of N downlink serving cells CC <NUM>, CC <NUM>,. , CC N with indices <NUM>, <NUM>,. , N, each with an associated (X, Y) pair. The procedure includes four steps, Step <NUM>, Step <NUM>, Step <NUM>, and Step <NUM>, as follows. Step <NUM> includes letting Si i = <NUM>,. , N, be the union of all the search space sets configured in serving cell with index i. Step <NUM> includes defining the set S to be the union of sets Si among all the serving cells. A bit map, for the determination of the span pattern in Step <NUM>, is obtained follows. A bitmap b(l), <NUM> ≤ l ≤ <NUM> is generated, where (i) b(l) = <NUM> if symbol l of any slot on any cell among the group of serving cells is part of a monitoring occasion, and (ii) b(l) = <NUM> otherwise. The first span in the span pattern begins at the smallest l for which b(l) = <NUM>. The next span in the span pattern begins at the smallest l not included in the previous span(s) for which b(l) = <NUM>. Step <NUM> includes determining the span pattern for a virtual cell with the same numerology as that of the N cells based on (i) the set of all search spaces S and the obtained bitmap b(l), and (ii) the set of values of {(X, Y)} reported by the UE. The determination is based on a Rel-<NUM> span pattern determination. Step <NUM> includes determining, by the UE, that the span pattern determined in Step <NUM> is an aligned span pattern if (X, Y) covers the span pattern determined in Step <NUM> and that it is not an aligned span pattern otherwise.

Example <NUM>: The UE is configured with N = <NUM> serving cells both with (X, Y) = (<NUM>,<NUM>) as shown in <FIG>. MOs on CC <NUM> correspond to search space sets associated with a length-<NUM> CORESET <NUM> and a length-<NUM> CORESET <NUM>. The span pattern is obtained is determined to be <NUM>. The associated (X, Y) is equal to (<NUM>,<NUM>) so this is a (<NUM>,<NUM>) cell. MOs on CC <NUM> correspond to search space sets associated with two length-<NUM> CORESETs and two length-<NUM> CORESETs. The span pattern is obtained as <NUM>. Both (<NUM>,<NUM>) and (<NUM>,<NUM>) cover this span pattern. But assuming that (<NUM>,<NUM>) has a larger per-span single-cell BD/CCE limit than (<NUM>,<NUM>), pair (<NUM>,<NUM>) is associated with this cell and therefore CC <NUM> too is a (<NUM>,<NUM>) cell. CC3 is also configured with two search spaces associated with two different CORESETs. To determine whether the span patterns on these three cells are aligned or not, the procedure of Embodiment <NUM> is employed to determine the span pattern for a virtual cell considering all the MOs (search spaces on all cells). The span pattern of the virtual cell is found to be <NUM> which is covered by (<NUM>,<NUM>), so these two cells are categorized as aligned. As such, in <FIG>, the three (<NUM>,<NUM>) cells CC1, CC2 and CC3 are considered to be aligned as the union of all search spaces results in span pattern that is covered by (<NUM>, <NUM>).

In another embodiment, which may be referred to as Embodiment <NUM>, the case of aligned spans may be defined as follows, using a single-cell to CA (X, Y) transform. Prior to applying to CA hard splitting equations (the equations specifying <MAT> and <MAT>), a group of cells is identified via association to the same (X, Y) according to the single-cell max BD/CCE limit rule. This rule states that if multiple pairs of (X, Y) satisfy the span pattern, the cell is associated with the pair (X, Y) with the largest BD/CCE limit per span. As is shown below, it may be possible that the span pattern on the virtual cell is not covered by the pair (X, Y) but with a new pair (X', Y'). <FIG> shows an example of an aligned case, with two (<NUM>,<NUM>) cells and the virtual cell. The virtual cell is not covered by (<NUM>,<NUM>).

As can be seen from <FIG>, the span pattern on CC1 and CC2 is covered by both pairs (<NUM>,<NUM>) and (<NUM>,<NUM>). According to the max BD/CCE limit rule, both cells are associated to be (<NUM>,<NUM>) cells and the BD/CCE limit for (<NUM>,<NUM>) would be applied for each span on these cells for the non-CA case. On the other hand, with CA and hard splitting, the virtual cell would not be a (<NUM>,<NUM>) cell so according to Embodiment <NUM> and <NUM> this would be an unaligned case. Although (<NUM>,<NUM>) does not cover the virtual cell, (<NUM>,<NUM>) does. Since (<NUM>,<NUM>) also covers each individual cell, one UE behavior is to assume the individual cells as (<NUM>,<NUM>) and consider this case as an aligned case. As such, the following definition of an aligned span pattern may be used, based on a non-CA (X, Y) to CA (X,Y) transform: For a set of cells with the same numerology and the same associated pair (X, Y), a span pattern is defined for each cell. Additionally, a virtual cell is defined as having the set of search spaces that are the union of all SSs across all the cells according to Embodiment <NUM>. Let P be the set of pairs (X, Y) reported by the UE and let Pall be a subset of P including all the pairs which cover the span pattern on the virtual cell. If Pall is non-empty, then the set of search spaces is deemed to correspond to an aligned span pattern. The virtual cell is associated with a pair (Xall, Yall) ⊂ Pall with a maximum single-cell BD/CCE limit per span according to Table <NUM> and Table <NUM>. The aligned case is associated with (Xall, Yall) and the span pattern on the virtual cell is applied to all the cells.

For the example shown in <FIG>, P = Pall = {(<NUM>,<NUM>)} so the set of search spaces corresponds to an aligned span pattern, with the associated pair (Xall, Yall) = (<NUM>,<NUM>) and the span pattern shown for the virtual cell.

In another embodiment, which may be referred to as Embodiment <NUM>, the applicable span for determining the total BD/CCE limit per span may be defined as follows. Once the span pattern is classified as aligned according to any one of Embodiments <NUM>-A, <NUM>-B, <NUM>-C, <NUM>-D, and <NUM>, a span for monitoring of <MAT> non-overlapping CCE or <MAT> PDCCH candidates given in Method A and Method B is determines as follows.

For Embodiment <NUM>-A, <NUM>-B, <NUM>-C or <NUM>-D, for each set of overlapping spans, a span with largest length is chosen to define per-span limits in Method A and Method B. The determined span pattern on the virtual cell is used to define per-span in Method A and Method B. In other words, the UE is not required to monitor more than <MAT> PDCCH candidates or <MAT> non-overlapping CCEs per span on the active DL BWP(s) of scheduling cell(s) from the <MAT> downlink cells where span is determined according to Embodiment <NUM>-A or <NUM>-B or <NUM>-C or <NUM>-D.

For each of Embodiment <NUM> and <NUM>, the determined span pattern on the virtual cell may be used to define per-span limits in Method A and Method B. In other words, the UE is not required to monitor more than <MAT> PDCCH candidates or <MAT> non-overlapping CCEs per span on the active DL BWP(s) of scheduling cell(s) from the <MAT> downlink cells where span is determined according to Embodiment <NUM> or <NUM>.

Example <NUM>: This example considers the scenario in Example <NUM> where the span patterns on the three cells have been determined to be aligned. The UE is not required to monitor more than <MAT> PDCCH candidates or <MAT> non-overlapping CCEs per first span, i.e., {symbol <NUM>, <NUM> and <NUM>} or second span, i.e., {symbol <NUM>, <NUM> and <NUM>} or third span, i.e., {symbol <NUM>, <NUM> and <NUM>} on the active DL BWP(s) of CC1 and CC <NUM>.

Example <NUM>: This example considers the case of <FIG> with (i) the SCS configuration µ = <NUM>, and (ii) the UE reporting a CA capability for <MAT> cells. <MAT> and <MAT> in Table <NUM> and Table <NUM>, (iii) the total number of configured DL cells being <MAT> among which <MAT> cells are associated with (X, Y) = (<NUM>,<NUM>) and µ = <NUM>, and (iv) the search space configuration, the span pattern on each cell, and the span pattern on the virtual cell, being defined as shown in <FIG>, according to method A and method B, the resulting total number of PDCCH candidates and non-overlapping CCEs may be determined as follows: <MAT> and <MAT>.

This accordingly gives the following limits. The BD limit may be given by: (i) in the first span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored PDCCH candidates on CC <NUM>}+ {Number of monitored PDCCH candidates on CC <NUM>} ≤ <NUM> (ii) in the second span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored PDCCH candidates on CC <NUM>}+ {Number of monitored PDCCH candidates on CC <NUM>}≤ <NUM>, and (iii) in the third span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored PDCCH candidates on CC <NUM>}+ {Number of monitored PDCCH candidates on CC <NUM>}≤ <NUM>.

The CCE limit may be given by (i) in the first span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored non-overlapping CCEs on CC <NUM>}+ {Number of monitored non-overlapping CCEs on CC <NUM>}≤ <NUM> , (ii) in the second span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored non-overlapping CCEs on CC <NUM>}+ {Number of monitored non-overlapping CCEs on CC <NUM>}≤ <NUM>, and (iii) in the third span, i.e., symbols <NUM>, <NUM> and <NUM>: {Number of monitored non-overlapping CCEs on CC <NUM>}+ {Number of monitored non-overlapping CCEs on CC <NUM>}≤ <NUM>.

The following are additional examples which are categorized as aligned or unaligned according to Embodiment <NUM>. <FIG> shows an aligned case: CC <NUM>, CC <NUM> and CC <NUM> are categorized as aligned as (<NUM>,<NUM>) covers the span pattern on the virtual cell. <FIG> and <FIG> show an unaligned case. This case differs from that of <FIG> in that an MO with a length-<NUM> CORESET <NUM> has been added on CC <NUM>. In this case, (<NUM>,<NUM>) no longer covers the resulting span pattern as the time gap between the last span in the first slot and the first span in the second slot is less than <NUM>. <FIG> is an example of an aligned case: (<NUM>,<NUM>) covers the span pattern on the virtual cell. <FIG> is an example of an unaligned case: it differs from <FIG> in that MOs associated with a length-<NUM> CORESET on CC <NUM> have been added, and (<NUM>,<NUM>) no longer covers the resulting span pattern on the virtual cell.

The reason CC <NUM>, <NUM> and <NUM> in <FIG> are considered unaligned is that the resulting span pattern on the virtual cell is no longer covered by (<NUM>,<NUM>). This is because, as part of the span definition, every MO is required to be contained within one span. As can be seen, on CC <NUM> there is a length-<NUM> MO, part of which appears in the first span on the virtual cell and part of which appears in the second span on the virtual cell.

Unaligned span patterns may be handled as follows. Once a span pattern is defined as unaligned, how the PDCCH candidates, or non-overlapping CCEs may be distributed among different spans across the cells may be specified. To this end, the following provide three different interpretations of <MAT>.

In an embodiment which may be referred to as Embodiment <NUM>, or as Interpretation <NUM>, a uniform distribution may be used. In this embodiment, the UE is not required to monitor more than <MAT> non-overlapping CCEs or <MAT> PDCCH candidates for any set of spans across the active DL BWP(s) of scheduling cell(s) from the downlink cells, with at most one span per scheduling cell for each set. Both <MAT> and <MAT> may be based on a declaration of capabilities sent to the network by the UE.

In an embodiment which may be referred to as Embodiment <NUM>, or as Interpretation <NUM>, alignment-based cell partitioning may be used. In this embodiment, the UE is not required to monitor more than <MAT> non-overlapping CCEs or <MAT> PDCCH candidates for any set of spans across the active DL BWP(s) of scheduling cell(s) from the downlink cells, where the set of spans are not aligned with each other.

It is possible that the set of cells associated with (X, Y) are such that the resulting span pattern is unaligned but if some of the cells are excluded they would be classified as aligned according to the definition given in one of Embodiments <NUM>-A to <NUM>-D, <NUM> and <NUM>. In that case a number of cell groups may be defined such that in each group the cells are aligned with each other. In <FIG> (an example in which CC1, CC2 and CC3 are unaligned according to Embodiment <NUM> since (<NUM>, <NUM>) does not cover the virtual cell span pattern), cell <NUM> and <NUM> are grouped together and cell <NUM> is grouped by itself. <MAT> and <MAT> are scaled by the fraction of cells in a group to obtain the total BD/CCE limit for each group.

In some embodiments, alignment-based cell grouping may be used. In a set of N serving cells with indices <NUM>,. ,N with the same (X, Y) and numerology µ , a number of groups of cells may be formed using five steps, Step-<NUM> Step-<NUM>, Step-<NUM>, Step-<NUM>, and Step-<NUM>, as follows.

For group l with Nl cells, Embodiment <NUM> is employed by using <MAT> and <MAT> in place of <MAT> and <MAT> to determine the BD/CCE limit per span across the cells.

In an embodiment which may be referred to as Embodiment <NUM>, or as Interpretation <NUM>, time-domain span merging may be used. For a set of cells associated with (X, Y) that are classified as unaligned, it may be the case that removing a certain number of spans on some of the cells will result in their being classified as aligned. <FIG> shows an example. The resulting span pattern in the virtual cell is not covered by (<NUM>,<NUM>) so the case is considered unaligned. (<NUM>,<NUM>) does not cover the span pattern because there is an MO which is not fully contained in one span. If the four spans in symbols <NUM>, <NUM>, <NUM>, and <NUM> are excluded, all other spans will result in an aligned case. Once these four spans are added the case will become unaligned. Instead of considering the case as unaligned and uniformly distributing the BD/CCE limit across all spans according to Embodiment <NUM>, it may be beneficial to consider the four spans of symbols <NUM>, <NUM>, <NUM>, and <NUM> as one "super span" (a method that may be referred to as "span merging") and apply two equations on it as shown in <FIG>. For each of symbols <NUM> and <NUM>, symbols <NUM> and <NUM>, symbols <NUM> and <NUM> and symbols <NUM> and <NUM> one separate equation is defined, resulting in four different independent equations.

The following pseudo-code can be used to determine the set of "super-spans" for a set of cells classified as unaligned according to any of the Embodiments <NUM>-A to <NUM>.

BD/CCE limit determination: Once the above method has given the set Γ of super-spans on the virtual cell, BD/CCE candidates may be distributed across a set of spans contained in a super-span SPi ∈ Γ across the active DL BPW(s) of the scheduling cells. This may result in the following specification: For a super-span SPi, the UE is not required to monitor more than <MAT> non-overlapping CCEs and more than <MAT> PDCCH candidates for any set of spans across the active DL BWP(s) of scheduling cell(s) from the <MAT> downlink cells with at most one span per scheduling cell for each set, where the spans are contained in super-span SPi.

Taking <FIG> as an example, the final set of super-spans on the virtual cell includes L = <NUM> super-spans, SP<NUM> = {<NUM>,<NUM>,<NUM>,<NUM>},SP<NUM> = {<NUM>,<NUM>},SP<NUM> = {<NUM>,<NUM>},SP<NUM> = {<NUM>,<NUM>} and SP<NUM> = {<NUM>,<NUM>}. For the first super-span SP<NUM> there are four spans across the cells: two spans on CC1, one span on CC2 and one span on CC3. What the UE is expected to monitor in these spans is shown in <FIG> with the two equations. For SP<NUM>, SP<NUM>, SP<NUM> or SP<NUM> there is exactly one span on each cell within the super-span.

In some embodiments, Problem <NUM> may be addressed using either of two possible methods to define UE behavior when a BWP is switched for the case of span-based PDCCH monitoring. The following embodiments provide the two behaviors corresponding to these two possibilities.

In one embodiment, which may be referred to as Embodiment <NUM>, switching to an invalid BWP may be treated as an error case. If, on a serving cell, the UE is configured with Rel-<NUM> (span-based) PDCCH monitoring for an active BWP, the UE is not expected to be instructed to switch to a new BWP with a configuration for which span-based PDCCH monitoring cannot be applied (invalid BWP configuration). For example, a BWP configuration with SCS of <NUM>, <NUM> or <NUM> may be an invalid BWP configuration for span-based PDCCH monitoring. It may be seen that Embodiment <NUM> makes it an error case for the UE to be configured with span-based PDCCH monitoring for a cell and an invalid configuration for the active BWP of the cell.

As an alternative behavior, the UE can be provided with a fallback operation in case of switching to an invalid BWP. In such an embodiment, which may be referred to as Embodiment <NUM>, a fallback UE behavior for switching to an invalid BWP is defined. If the UE is configured with span-based PDCCH monitoring on a serving cell with an active BWP configuration applicable to span-based PDCCH monitoring, and if the UE is instructed to switch to a new BWP and the new BWP configuration is invalid for span-based PDCCH monitoring, the UE falls back to slot-based PDCCH monitoring on the new BWP. This is equivalent to the network reconfiguring the cell with slot-based PDCCH monitoring. An example may be a circumstance with a serving cell with SCS = <NUM> configured with span-based PDCCH monitoring on the active BWP, in which the network indicates to the UE to switch to a new BWP with an SCS configuration of <NUM>. After switching to the new BWP, the UE no longer performs span-based PDCCH monitoring, and instead the UE performs the PDCCH monitoring based on slot.

As mentioned above, if a UE is configured only with <MAT> downlink cells for which the UE is provided monitoringCapabilityConfig-r16 = r16monitoringcapability and with associated PDCCH candidates monitored in the active DL BWPs of the scheduling cell(s) using SCS configuration µ , and with <MAT> of the <MAT> downlink cells using combination (X, Y) for PDCCH monitoring, where <MAT>, a DL BWP of an activated cell is the active DL BWP of the activated cell, and a DL BWP of a deactivated cell is the DL BWP with index provided by firstActiveDownlinkBWP-Id for the deactivated cell, the UE is not required to monitor more than <MAT> <MAT> PDCCH candidates or more than <MAT> <MAT> non-overlapped CCEs either (i) per set of spans on the active DL BWP(s) of all scheduling cell(s) from the <MAT> downlink cells, if a first condition holds or (ii) per set of spans across the active DL BWP(s) of all scheduling cells from the <MAT> downlink cells, with at most one span per scheduling cell for each set of spans, if the first condition does not hold, where <MAT> is a number of configured cells with SCS configuration j. The first condition holds if and only if the union of PDCCH monitoring occasions on all scheduling cells from the <MAT> downlink cells results to PDCCH monitoring according to the combination (X, Y) and any pair of spans in the set is within Y symbols, where first X symbols start at a first symbol with a PDCCH monitoring occasion and next X symbols start at a first symbol with a PDCCH monitoring occasion that is not included in the first X symbols. The first condition holds if the span pattern is an aligned span pattern.

In the above, the determination of monitoring capability depends on whether the first condition holds or not. As such, the UE may, in operation, check whether the first condition holds. The first condition involves the union of PDCCH MOs, as discussed above; an example of an aligned span pattern (i.e., a span pattern for which the first condition holds) is illustrated, for example, in <FIG>. Since the PDCCH MOs may vary from slot to slot, whether the span pattern is an aligned span pattern (i.e., whether the first condition holds) may also vary from slot to slot, and the corresponding PDCCH monitoring capability determination may vary from slot to slot. In some embodiments, all slots of a set of slots (e.g., a set of as many as <NUM> slots of the SS configuration) may be defined to be unaligned if at least one slot within the set of slots is unaligned, i.e., if at least one slot of the set of slots does not satisfy the first condition. Such a definition, however may increase the processing burden imposed on a UE since only one slot may be unaligned out of large number of slots, and it may therefore be necessary for the UE to check a large number of slots (i.e., all of the slots in the set of slots) before processing any slot of the set of slots. In some embodiments, this processing burden may be alleviated by instead defining all slots to be unaligned only if every slot is unaligned (i.e., only if for each slot of the set of slots the first condition does not hold). While this method does reduce the burden on the UE, it also puts considerable restrictions on the network configuration.

In other embodiments, the processing burden imposed on a UE may be alleviated if, when any one of the slots of the set of slots is unaligned, unaligned slots occur with relatively high frequency. For example, the processing burden imposed on a UE may be alleviated if the network is required to send either (i) a search space configuration in which all of the slots are aligned (contain aligned span patters), or (ii) a search space configuration in which at least one in every P slots is unaligned, where P is a relatively small number, e.g., a number between <NUM> and <NUM> (e.g., P = <NUM>). If the UE is able to assume that the network will comply with such a requirement, then the UE need only check any P (e.g., any <NUM>) consecutive slots to determine whether the first condition holds, for the entire set of slots.

In the current 3GPP specification (<NUM>), the periodicity of MOs may be as large as <NUM> slots. In some embodiments, to reduce the burden on the UE, the network is required to send a search space configuration in which, when any of the slots does not satisfy the first condition (i.e., any slot is unaligned), at least M slots out of every N consecutive slots are unaligned. Alternatively, this behavior may be tied to slot index. For example, the network may be required to send a search space configuration in which, when any of the slots is unaligned, at least M slots out of every N slots, starting from a slot with an index N1 satisfying (N1 mod N) = <NUM> and ending at a slot with an index N2 satisfying (N2 mod N) = N-<NUM>, are unaligned. The duration of a slot depends on subcarrier spacing, and the frequency of unaligned slots may alternatively be described with an absolute amount time such as <NUM> or <NUM> radio frame length. In this case, the network may be required to send a search space configuration in which, when any of the slots in the search space configuration is unaligned, at least M slots out of every T are unaligned, where T is an interval of time (e.g., in ms). Alternatively, this behavior can be tied to certain time indexes, such as subframe index which is indexed every <NUM>, radio frame index which is indexed every <NUM> etc. For example, the network may be required to send a search space configuration in which, when any of the slots in the SS configuration is unaligned, at least M slots in every radio frame are unaligned. In some embodiments, to significantly reduce the burden on the UE, N and T are considerably smaller than <NUM>, and than the duration of <NUM> slots, respectively.

In some embodiments in which a network is in communication with a UE, methods as outlined in <FIG> (from the perspective of the network) and <FIG> (from the perspective of the UE), may be performed. Referring to <FIG>, the network may: receive, at <NUM>, from the UE, a declaration of capabilities of the UE; send, at <NUM>, to the UE, a first search space (SS) configuration for a first component carrier in a carrier aggregation (CA) scheme; and send, at <NUM>, to the UE, a second search space configuration for a second component carrier in the carrier aggregation (CA) scheme. Referring to <FIG>, the UE may: send, at <NUM>, to the network, a declaration of capabilities; receive, at <NUM>, from the network, a first search space configuration for a first component carrier in the carrier aggregation (CA) scheme; and receive, at <NUM>, from the network, a second search space configuration for a second component carrier in the carrier aggregation (CA) scheme.

As used herein, an "aligned span pattern" corresponding to a plurality of sets of monitoring occasions is either (i) a plurality of span patterns, each of which corresponds to a respective set of monitoring occasions and all of which are aligned with each other according to a definition of one of the embodiments disclosed herein, or (ii) a span pattern corresponding to the union of the sets of monitoring occasions (i.e., corresponding to a virtual cell configured with the union of the sets of monitoring occasions). As used herein, an "aligned slot" is a slot in which the span pattern is an aligned span pattern, an "unaligned span pattern" is a span pattern that is not an aligned span pattern, and an "unaligned slot" is a slot in which the span pattern is an unaligned span pattern.

As used herein, a "set" of things is one or more of the things, e.g., a set of control resource sets includes one or more control resource sets and a set of search spaces includes one or more search spaces. As used herein, "a portion of" something means "at least some of" the thing, and as such may mean less than all of, or all of, the thing. As such, "a portion of" a thing includes the entire thing as a special case, i.e., the entire thing is an example of a portion of the thing. As used herein, the word "or" is inclusive, so that, for example, "A or B" means any one of (i) A, (ii) B, and (iii) A and B.

The methods described herein may be performed by one or more processing circuits (e.g., a processing circuit of the network, or a processing circuit of the UE). Such processing circuits may be configured to send or receive data (e.g., through other elements, such as a radio transmitter or receiver). The term "processing circuit" is used herein to mean any combination of hardware, firmware, and software, employed to process data or digital signals. Processing circuit hardware may include, for example, application specific integrated circuits (ASICs), general purpose or special purpose central processing units (CPUs), digital signal processors (DSPs), graphics processing units (GPUs), and programmable logic devices such as field programmable gate arrays (FPGAs). In a processing circuit, as used herein, each function is performed either by hardware configured, i.e., hard-wired, to perform that function, or by more general-purpose hardware, such as a CPU, configured to execute instructions stored in a non-transitory storage medium. A processing circuit may be fabricated on a single printed circuit board (PCB) or distributed over several interconnected PCBs. A processing circuit may contain other processing circuits; for example, a processing circuit may include two processing circuits, an FPGA and a CPU, interconnected on a PCB.

As used herein, when a method (e.g., an adjustment) or a first quantity (e.g., a first variable) is referred to as being "based on" a second quantity (e.g., a second variable) it means that the second quantity is an input to the method or influences the first quantity, e.g., the second quantity may be an input (e.g., the only input, or one of several inputs) to a function that calculates the first quantity, or the first quantity may be equal to the second quantity, or the first quantity may be the same as (e.g., stored at the same location or locations in memory) as the second quantity.

Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of "<NUM> to <NUM>" or "between <NUM> and <NUM>" is intended to include all subranges between (and including) the recited minimum value of <NUM> and the recited maximum value of <NUM>, that is, having a minimum value equal to or greater than <NUM> and a maximum value equal to or less than <NUM>, such as, for example, <NUM> to <NUM>. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein.

Claim 1:
A method performed by a network, comprising:
receiving (<NUM>; <NUM>), by the network from a first user equipment, UE, a declaration of capabilities of the first UE;
sending (<NUM>; <NUM>), by the network, to the first UE, a first search space, SS, configuration for a first component carrier in a carrier aggregation, CA, scheme; and
sending (<NUM>; <NUM>), by the network, to the first UE, a second search space configuration for a second component carrier in the carrier aggregation scheme,
wherein:
the first search space configuration comprises a first set of monitoring occasions,
the second search space configuration comprises a second set of monitoring occasions, MOs,
determining an (X, Y) pair that is satisfied by both the first set of monitoring occasions and the second set of monitoring occasions, wherein the (X, Y) pair refers to a span-gap span-length pair complying with the declaration of capabilities of the first UE;
the method characterized by
determining a union of the first set of monitoring occasions and the second set of monitoring occasions;
determining a span pattern based on the union; and
determining whether the (X, Y) pair is satisfied by the span pattern,
wherein the (X, Y) pair is determined to be satisfied by the span pattern when the (X, Y) pair covers by the span pattern and wherein the (X, Y) pair is determined not to be satisfied by the span pattern when the (X, Y) pair is not covered by the span pattern;
implementing a control channel elements, CCE, limit, wherein the limit is based on whether the (X, Y) pair is satisfied by the span pattern.