Patent ID: 12238741

DETAILED DESCRIPTION OF THE INVENTION

As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).

In one embodiment, there is dynamic indication of ALs to a UE. Generally, if a UE is configured with multiple SS sets by the BS, the UE will monitor all possible SS sets and all the candidates configured in those SS sets irrespective of its channel quality or the payload size to be monitored. As shown inFIG.2, the UE will monitor CSS2and USS1in slot1and on all the configured ALs in both the SS sets. Therefore, on a total, (9+19) BDs need to be performed. For example, if the payload size of the DCI format to be monitored in the slot is higher than 108, then there is no need to monitor AL1in both the SS sets because AL1cannot carry bits higher than 108 bits. Similarly, if a UE has bad channel quality, then it is scheduled in higher ALs to satisfy the control channel PDCCH BLER.

The BS obtains the knowledge of the channel quality of the UE based on the measurement reports from the UE. Based on the channel quality, the BS can decide the subset of ALs that are most suitable for transmitting DCI. This method is applied to the UEs whose channel quality will remains constant for some time period. Along with the channel quality, the BS has the knowledge of the SS set configurations of a UE and the DCI formats that are going to be monitored in each SS set. For example, as shown inFIG.2, for a period of 10 milli-seconds, the UE will monitor DCI formats 2_0, 0_0/1_0 and 0_1/1_1. Hence, the possible payload sizes that the UE has to monitor will be known for 10 ms. The BS selects the ALs based on the channel quality of the UE and the payload sizes the UE is going to monitor for a certain period P and indicates the selected subset of ALs to the UE. For the example shown inFIG.2, if the BS indicates the UE to monitor only ALs4and8, the number of BDs is reduced significantly. If the UE selects control channel candidates dynamically by eliminating the candidates which are not indicated by the BS to the UE, the number of BDs will reduce.

This method helps to increase the scheduling flexibility of a UE. If certain ALs are excluded for a UE, the number of blind decoding attempts in a search space decreases. Therefore, control channel candidates can be scheduled in other search spaces configured for the UE, without the problem of over booking. Hence, the control channel scheduling flexibility of a UE is improved.

This subset of the ALs to be monitored by a UE will be signalled by the BS to the UE via Radio Resource Control (RRC) signalling, or Medium Access Control (MAC) Control Element (CE), or Layer 1 (L1) signalling. The time-period associated with the selected subset is also signalled along with the information on subset of ALs.

The ALs that are needed to be monitored is indicated by using a bitmap or an index to an existing table where the table contains various combinations of ALs. A set of time period values is preconfigured to the UE and an index of the set is indicated to the UE. The BS will indicate this time period and the bitmap or index using RRC signalling or MAC-CE signalling or L1 signalling. When the UE starts using the subset configuration it also starts the timer with the corresponding time period. When the timer expires, the UE performs any one of the following actions: (i) apply the old configuration for the next time period until it gets a new configuration, (ii) the UE monitors all the ALs as configured originally, (iii) it applies a default configuration, if a separate default configuration is provided by BS, (iv) it requests BS for a new configuration. A detailed explanation of this method using a flow chart is shown inFIG.3.

As illustrated inFIG.3, at step302, the BS configures a first Search Space (SS) configuration to a UE. At step304, the BS configures a second SS configuration. The second SS configuration may be a subset of ALs to be monitored based on a channel quality of the UE and an associated time period. At step306, the BS signals at least one of the first SS configuration and the second SS configuration. At step308, the UE monitors for DCI on ALs signalled by the BS. At step310, if UE receives new second SS configuration, the method loops back to step308and if the UE does not receive a new second SS configuration, the method proceeds to step312. At step312, if time period is not expired, the method loops back to step308and if the time period is expired, the method proceeds to step314. At step314, the UE performs any one of the following: adopting existing second SS configuration, requesting BS for new second SS configuration and utilizing first SS configuration, and utilizing a default second SS configuration.

In another embodiment, there is signalling of a PDCCH multiplication factor by the BS to the UE. According to this method, a rational value “k” is signalled to the UE by the BS. The UE will modify the number of candidates in all the search spaces based on the formula given below.
Modified number of candidates per AL=floor(configured number of candidates per AL*k)

If the value of k is configured as less than one, according to the above formula, the total number of candidates will reduce per SS set which in turn will reduce the number of BDs performed in a slot.

The value of k is signalled to the UE by using any one of RRC signalling, MAC-CE signalling and L1 signalling. The BS will change the value of k according to its need. For example, when this value is configured to 0, then the UE will stop monitoring the control channel.

This value of k is associated with a time period. The BS will indicate this time period using RRC signalling or MAC-CE signalling or L1 signalling. So, the ‘k’ value is valid only for the specified time period. The BS will configure a new value of k based on the need and a new time period. When the timer period associated with ‘k’ expires, the UE performs any one of the following actions: (i) apply the old value of ‘k’ for the next time period until it gets a new configuration, (ii) the UE will use the originally configured number of candidates per AL without any modification done by k, (iii) it applies a default value of ‘k’, if a separate default value is provided by BS, (iv) it requests BS for a new configuration.

Alternatively, this value of k is also configured independently per AL. This means, a UE is configured with as many k values as there are ALs. For example, when the number of ALs is five, a UE is indicated with a set {k1, k2, k3, k4, k5}. The number of candidates per each AL is modified according to the formula: Modified number of candidates for ALi=floor (configured number of candidates for ALi*ki) by using the corresponding k value. This method provides additional flexibility by reducing the number of candidates in some selected ALs and increasing in others. This set of k values are indicated to a UE by the BS using RRC signalling or MAC-CE signalling or L1 signalling. Alternatively, a table is configured to a UE where each entry in the table contains the set {k1, k2, k3, k4, k5}. An index to this table is indicated to the UE using higher layer signalling or MAC-CE signalling or L1 signalling.

These values of k, i.e., {k1, k2, k3, k4, k5} is associated with a time period. The BS indicates this time period using RRC signalling or MAC-CE signalling or L1 signalling. Therefore, this value is valid only for the specified time period. The BS will configure new values of k based on the need and a new time period. When the timer period associated with ‘ki’s expires, the UE performs any one of the following actions: (i) apply the old value of ‘ki’s for the next time period until it gets a new configuration, (ii) the UE will use the originally configured number of candidates per AL without any modification done by ‘ki’s, (iii) it applies a default value of ‘ki’s, if a separate default value is provided by BS, (iv) it requests BS for a new configuration. A detailed explanation of this method using a flow chart is shown inFIG.4.

As illustrated inFIG.4, at step402the BS configures SS configuration to a UE. At step404, the BS configures a second SS configuration. The second SS configuration includes a value of a multiplication factor (k) associated with one or more of ALs and an associated time period. At step406, the BS signals any of the first SS configuration and the second SS configuration. At step408, the UE updates the number of candidates in each AL in all SS sets based on received k. At step410, the UE monitors for DCI, based on the updated number of candidates in each AL. At step412, if UE receives new second SS configuration, the method loops back to step408. At step412, if the UE does not receive the new second SS configuration, the method proceeds to step414. At step414, if time period is identified to be expired, the method proceeds to step416. If the time period is not expired, the method loops back to step410. At step416UE performs any one of the following: adopting existing second SS configuration, requesting BS for new second SS configuration and utilizing first SS configuration, and utilizing a default second SS configuration.

In another embodiment, there is indication to a UE which type of SS set to monitor in a slot. In this method, the BS will signal the UE as to whether to monitor only CSS or only USS or both CSS and USS or neither CSS nor USS in a slot. This signalling will apply to the SS sets configured to a UE. If in a slot, a UE is signalled by the BS to monitor only CSS, the UE will perform BDs only in the SS sets that are configured as CSS. If it is signalled to monitor only USS, the UE will perform BDs only in the SS sets that are configured as USS. If it is signalled to monitor both CSS and USS, the UE will monitor in all the SS sets. If it is configured not to monitor both in CSS and USS, the UE won't perform BD in that slot. For example, considerFIG.1wherein in slot4, UE needs to monitor CSS2, USS1and USS2. If the gNB indicates that the UE needs to monitor only CSS in slot4, the UE has to monitor in CSS2only. This leads to considerable decrease in the number of BDs. A UE is signalled with a time period P and each slot within the time period is signalled with the above-mentioned configuration. Two bits are required per slot as there are four types of configurations available. Hence, if the time period P has N slots, then 2N bits are required for the configuration. This configuration and the associated time period can be signalled to the UE by the BS using RRC signalling or MAC-CE signalling or L1 signalling.

If a UE receives a new configuration before the time period expires, the UE will update its configuration according to the received signalling

This configuration and the associated time period can be signalled to the UE by the BS using RRC signalling or MAC-CE signalling or L1 signalling, the UE performs any one of the following actions: (i) apply the old configuration for the next time period until it gets a new configuration, (ii) the UE will monitor all the SS sets by considering the default configuration as both CSS and USS, (iii) it applies a default configuration, if a separate default configuration is provided by BS, (iv) it requests BS for a new configuration. A detailed explanation of this method using a flow chart is shown inFIG.5.

As illustrated inFIG.5, at step502the BS configures a first search space configuration to a UE. At step504, the BS configures a second search space configuration to the UE. The second SS configuration is type of SS to be one of monitored and not monitored for each slot in a given time period. At step506, the BS signals the at least one of the first search space configuration and the second search space configuration to the UE. At step508, the UE monitors for Downlink Control Information (DCI) in CSS/USS/Both/None in the slots within the time period based on the configuration corresponding to the slot. At step510, if UE receives new second search space configuration, the method loops back to step508. If UE does not receive new configuration, then the method proceeds to step512. At step512, if time period is not expired, the method loops back to step508. If time period is expired, the method proceeds to step514. At step514, the UE performs blind decoding by one of utilizing a default second SS configuration, adopting the existing second SS configuration, requesting the BS for a new second SS configuration and utilizing the first SS configuration when the new second SS configuration is not received by the UE before the timer expires.

In another embodiment, there is concatenation of DCI payloads. This method is used when a UE is scheduled with multiple DCIs in the same slot frequently. The BS will indicate the UE to monitor for a concatenated DCI payload in a slot. The concatenation applies only to DCI formats that schedules data transmission. When a BS schedules a UE with multiple DCIs that schedules DL/UL data reception or transmission and among those multiple DCIs if some of the DCI's belong to same DCI format and same RNTI, the BS concatenates those DCIs (of same format and RNTI) and transmits to a UE. The UE is informed about the concatenation via RRC signalling or MAC-CE signalling or L1 signalling. For example, if a UE receives a configuration from the BS to monitor for ‘c’ concatenated DCI payloads for DCI formats 0_1/1_1, then the UE will monitor for the concatenated DCI payload. After receiving the concatenated payload, the UE will stop further monitoring. To maintain the BLER of the control channel, the size of the ALs is increased proportionately according to c i.e., aggregation level L becomes aggregation level cL. If the size of the modified AL crosses the size of the CORESET, then UE will not monitor in that AL.

An associated time period also will be indicated to the UE. The configuration given to the UE will be applied for the time period specified. This value of c and the associated time period are signalled to the UE using RRC signalling or MAC-CE signalling or L1 signalling. When the time period expires, the UE performs any one of the following actions: (i) apply the old configuration for the next time period until it gets a new configuration, (ii) the UE will go back to the original configuration, i.e., monitoring without concatenation, (iii) it applies a default configuration, if a separate default configuration is provided by BS, (iv) it requests BS for a new configuration. This concatenation signalling is applied only to the USS.

Alternatively, it is implemented in a way, whereas each USS is configured with a c value. The UE will monitor a USS for the concatenated payload of c DCIs. The USS that are configured with higher value of c will be monitored first i.e., the USSs are monitored in the descending order of c. The ALs for each USS will be increased by the factor of c i.e., AL of L becomes cL. The UE will stop further monitoring if the UE receives a concatenated payload. A detailed explanation of this method using a flow chart is shown inFIG.6.

As illustrated inFIG.6, at step602, the BS configures a first Search Space (SS) configuration to a UE. At step604, the BS configures a second SS configuration to the UE. The second SS configuration is at least one multiplication factor (c) for at least one SS set and an associated time period. At step606, the BS signals at least one of the first SS configuration and the second SS configuration to the UE. At step608, the UE updates the payload size of the SS sets and scale the AL size based on the signalled c value. At step610, UE monitors c concatenated DCIs in the SS sets with the associated payload sizes and AL size. The concatenated DCIs belong to one of the same format and same Radio Network Temporary Identifier (RNTI). At step612, if UE receives a new second SS configuration, the method loops back to step608. If UE does not receive new configuration, the method proceeds to step614. At step614, if time period is not expired, the method loops back to step610. If time period is expired, the method proceeds to step616. At step616, UE performs blind decoding by one of utilizing a default second SS configuration, adopting the existing second SS configuration, requesting the BS for a new second SS configuration and utilizing the first SS configuration when the new second SS configuration is not received by the UE before the timer expires.

In another embodiment, there is DCI for different process/carriers in PDSCH in carrier aggregation. In case of carrier aggregation, cross carrier scheduling can be employed where DCIs of secondary carriers are also carried in the control channel of the primary carrier. The DCIs of secondary carriers are associated with a carrier indicator. The UE has to perform blind decoding for all the DCIs present in the control channel of the primary carrier, which is power consuming. In order to reduce the number of blind decoding due to the DCI of the secondary carriers, the following method can be employed. In this method, the first DCI schedules the data channel for a process (primary carrier). This first DCI is monitored is decoded using BD. The DCIs to schedule the data channel(s) for other process (secondary carriers) will be transmitted in the data channel scheduled by first DCI. This would reduce the number of BDs because the UE doesn't have to monitor for other DCIs in the control channel of first process (primary carrier). A flag “DCIpresentInData” will be sent in DCI present in control channel indicating that other DCIs for secondary carriers are present in data channel and to stop further monitoring.

An alternate way is to transmit the subsequent DCI for every new process in data channel of previous process. For example, data region1carries DCI2for carrier2, data region2carries DCI3for carrier3and so on. In this case, one-bit flag is included at the end of DCI to indicate that further or next DCI is in corresponding data channel of current DCI. This flag is set to 0 in case of no further DCIs or alternatively, this flag is set to 1 in case of no further DCIs.

DCI bits for secondary carriers will be padded at the start of primary carrier's data channel before data bits. The number of DCI bits and the formats of different DCIs will be informed to UE in two ways. One way is to include a UE specific field in DCI within control channel of the primary along with stop flag indicator. This field indicates the number of DCIs and the formats of DCIs. Another way is to include the information at start of DCI payload part in data region like a header, so that the UE will receive the information about numbers and formats of DCIs included at the start of data region. The UE will use the information on the formats and number of DCIs to segregate between various DCIs and to segregate data bits from DCI bits. For the region in data channel containing DCIs, a lower modulation scheme and/or coding rate to meet a target BLER (for example <10−4) is used to increase the reliability for the control information transmission.

In addition to reducing the number of BDs for a UE, this method will also increase the scheduling capacity of the network because there will be more free search spaces as DCIs for the UE is present in data region of primary. Hence these free locations in search spaces is given to control channel candidates of additional users scheduled, thus in this way more number UEs can be scheduled at a time by gNB. A detailed explanation of this method using a flow chart is shown inFIG.7.

As illustrated inFIG.7, at step702, a first DCI is sent in SS. At step704, if flag to indicate at least one second DCI is present in data channel is enabled in the first DCI, the method proceeds to step708. If flag in first DCI is not on, the method proceeds to step706. At step706, monitoring of the SS for the second DCI is continued. At step708, UE performs one of receiving subsequent DCI for a next process in a data channel of previous process and receiving at least one second DCI scheduled for the UE in the data channel of the primary process.

In one embodiment, a limit may be imposed on number of DCIs UE can receive in one format in a period of time. In this method, the BS will impose a limit on every DCI format in a time period so that the UE does not monitor for that format within the time period, once the limit has crossed. This limit is configured by the BS to the UE for all DCI formats or specified DCI formats. For example, if a UE is configured by the BS that the maximum number of DCIs it can receive in DCI format 0_0/1_0 is 3 for a time period of 10 ms, then the UE will stop monitoring in the SS sets that are configured to monitor for DCI format 0_0/1_0 after it has received 3 DCIs in the corresponding time window. The UE again will start monitoring for the DCI format 0_0/1_0 after the end of the time period, i.e., 10 ms. The BS can reconfigure the limit on each DCI format and the time period associated with it according to the need for a specific DCI format by a particular UE. This configuration is signalled to the UE by the BS using RRC signalling or MAC-CE signalling or L1 signalling or combination of both. A detailed explanation of this method using a flow chart is shown inFIG.8.

As illustrated inFIG.8, at step802the BS configures search space configuration to a UE. At step804, the BS signals the UE a value on number of DCIs a UE can receive for a format or a set of formats in a period of time. At step806, UE monitors all SS sets and counts number of DCIs received per format. At step808, it is determined if the UE has received new configuration. If it is identified that the UE has received new configuration, the method proceeds to step810. At step810, all the count values are reset to 0 and control is transferred back at step806. At step808, if the UE does not receive new configuration, the method proceeds to step812. At step812, it is determined if the number of DCIs received for a format exceeds the limit. If it is identified that the number of DCIs received for a format is exceeding the limit, the method proceeds to step814. At step814, the PDCCH candidates associated with the DCI formats that has exceeded the limit are not monitored, and PDCCH candidates corresponding to the DCI formats whose count has exceeded are removed in rest of the slots in the configured time period. At step812, if the number of DCIs received for a format are identified to not exceed the limit, the method proceeds to step816. At step816, it is determined if time period has expired. When it is identified that the time period has expired, the method proceeds to step818. At step818, the count values of the DCI format corresponding to expired time period are reset to zero and control is transferred back at step806. At step816, if time period is not expired, the method loops back to step806.

In one embodiment, there is Indication to stop doing BD. This method is applicable for the case where the UE performs blind decoding in some predefined order. The mapping of the control channel candidates will follow the order of CSS first and USS later i.e., the candidates from all the CSSs are fixed as valid candidates and the candidates from the USS are taken in the ascending order of the SS ID. Hence, BS will have the knowledge of what are the possible SS sets the UE will monitor on. This method is based on the BS knowledge on which SS sets the UE is going to monitor for PDCCH.

Consider an example where a UE will monitor for 5 USS in a slot with SS ids1,2,3,4and5referred to as USS1, USS2, USS3, USS4and USS5respectively. It is assumed that a DCI is scheduled in USS1and one DCI is scheduled in USS2in the slot. According to the current NR standards, the UE will monitor all the valid control channel candidates i.e., the UE will monitor all the USS in the slot. But in the example given above, the UE need not monitor in USS3,4and5. However, the UE will not stop monitoring in these USSs because there is no indication for the UE that says no DCI is present in USS3,4and5. Hence, the BDs performed by the UE in USS3,4and5leads to wastage of power.

In order to mitigate this problem, in the proposed method, the BS includes an indication field in the DCI which informs the UE whether to stop doing BDs or continue doing BDs. This indication will be a one-bit field that will be present in the DCI. This bit is present in all the DCIs that are being transmitted in the USSs. If the bit field is set to 0 in a DCI that is received in the USS with index i, then the UE will not perform BDs in the SS sets with index greater than i, else, the UE does BDs in SS sets with index greater than index i. In this case, the BS will set the bit to 0 in the DCI that is scheduled in the SS set with the highest index. In the DCIs that are scheduled in all other SS sets, this field is set to 1. Alternatively, if the bit field is set to 1 in a DCI that is received in the USS with index i, then the UE will not perform BDs in the SS sets with index greater than i, else, the UE does BDs in SS sets with index greater than index i. In this case, the BS will set the bit to 1 in the DCI that is scheduled in the SS set with the highest index. In the DCIs that are scheduled in all other SS sets, this field is set to 0.

In the above example, the DCIs are scheduled in USS1and2and no DCI is scheduled in USS3,4and5. According to the given method, the indication bit will be disabled (for example by setting to 0) in the DCI scheduled in USS1, and, the indication bit will be enabled (for example by setting to 1) in the DCI scheduled in USS2. Hence, the UE will stop monitoring in the USS3,4and5thus saving the power. A detailed explanation of this method using a flow chart is shown inFIG.9.

As illustrated inFIG.9, at step902the BS configures Search Space (SS) configuration to a UE. At step904, the UE receives a Downlink Control Information (DCI) in a Search Space (SS) sent by the BS. At step906, UE starts blind decoding procedure in a slot. At step908, BD is continued. At step910, if the monitored DCI in SS with id “i” has indicator bit=1, the method proceeds to step914. If the monitored DCI in SS with id “i” does not have indicator bit=1, the method proceeds to step912. At step912, PDCCH candidates corresponding to SS id>i are removed from PDCCH candidates for blind decoding. At step914, if all the candidates (in all SS) are not monitored, the method loops back to step908.

As an alternative, the total number of DCIs present in a search space is indicated in all DCIs of the search space. This is done for all search spaces individually. This will provide the user an idea about number of DCIs present in each search space. For e.g., let N represent the number of DCIs scheduled in a particular search space and the number ‘N’ is indicated in all DCIs in that search space. After receiving the Nth DCI of the search space, UE will skip the blind decoding for the remaining part of current search space and start monitoring the next search space. Therefore, this information reduces unnecessary blind decoding attempts and saves power. This method does not require that DCIs should be received in any order. The BS will append this information anywhere in the DCI. The number of bits required to indicate this information depends on the number of DCIs that can be scheduled to a UE in a search space. If a UE can be scheduled with N DCIs in a search space, then ceil(log2N) are required to indicate this signalling. A detailed explanation of this method using a flow chart is shown inFIG.10.

As illustrated inFIG.10, at step1002, UE starts blind decoding procedure in a slot. At step1004, blind decoding procedure is continued. At step1006, UE receives a DCI which indicates number of DCIs scheduled in a SS as N. At step1008, if UE receives N DCIs in the SS, the method proceeds to step1010. At step1010, remaining Physical Downlink Control Channel (PDCCH) candidates for blind decoding present in the SS are removed, and then blind decoding procedure is resumed in other SS, at step1004. At step1008, if the UE does not receive N DCIs in the SS, the method loops back to step1004.

In order to reduce number of BD attempts made by a UE to receive DCI, a BS will indicate the total number of DCIs scheduled for a UE in the slot, in every DCI. When a UE receives a DCI, which indicates the UE that it is scheduled with N DCIs in that slot, then UE will stop doing blind decoding after receiving all the N DCIs. This method does not assume that DCIs are received in any order. The BS can append this information anywhere in the DCI. The number of bits required to indicate this information depends on the number of DCIs that can be scheduled to a UE in a slot in a component carrier. If a UE is scheduled with N DCIs per slot per component carrier, then ┌log_2N┐ are required to indicate this signalling. A detailed explanation of this method using a flow chart is shown inFIG.11.

As illustrated inFIG.11, at step1102, UE starts blind decoding procedure in a slot. At step1104, blind decoding procedure is continued. At step1106, UE receives a DCI which indicates number of DCIs scheduled in a Slot as N. At step1108, if UE receives N DCIs in this slot, the method proceeds to step1110. At step1110, the remaining PDCCH candidates for blind decoding present in this slot are removed and then blind decoding procedure is resumed in other slot, at step1104. At step1108, if UE does not receive N DCIs in this slot, the method loops back to step1104.

The above two alternatives i.e., indicating number of DCIs per search space and indicating number of DCIs per slot, are applied only for DCI that schedules unicast data transmission or reception.

In one embodiment, there is bitmap indication of search spaces to be monitored to reduce number of blind decoding attempts. When a UE is configured with multiple SS, there can be scenario where there is no DCI for the UE in some of the search spaces in certain slot. However, in any slot, UE will perform BDs on all the SS that are applicable for that slot based on the periodicity and offset. This leads to wastage of power. For e.g., inFIG.2, there are 4 search spaces configured to a UE as CSS1, USS1, CSS2& USS2with different periodicity for each search space. As per the diagram, in slot2, the UE needs to monitor CSS1based on the periodicity and offset of CSS1. However, if the BS is not planning to send any DCI in CSS1in slot2, the BDs performed by UE on CSS1in slot2are unnecessary. In case of more search spaces configured to UE (a maximum of 10 search spaces configured for a UE), there will be more number of unnecessary blind decoding attempts. In this method, a bitmap of size equal to the number of configured search space to the UE is provided to the UE.

The bitmap contains ones in bits corresponding to the search spaces that may contain DCI for that UE and zeros in other bits. This bitmap indicates the presence of DCI in the search spaces and will be informed to the UE, so that the UE knows which search spaces are to be monitored.

The BS will take into consideration of parameters like the traffic of the UE, previous scheduling patterns for the UE, number of UEs in the cell, channel quality of the UE, compromise in scheduling flexibility etc. before deciding the bitmap. The bitmap is informed to the UE directly or an index to a table containing all combinations of configured search spaces is given. The table will be formed by the UE based on search space configuration given by RRC messages.

The bitmap indication is done in two ways, semi periodic and dynamic. In semi periodic approach, a bitmap is configured for a time period before scheduling and the BS will allocate the DCIs to the UE as per the bitmap. This bitmap is indicated to the UE by RRC message, MAC CE or DCI. The UE performs BD according to the bitmap until the timer expires. Once the time period of the bitmap ends, the UE will start monitoring all the search space as usual until it receives a new bitmap. After receiving the new bitmap, UE follows bitmap pattern for monitoring further, thus saving power.

Using RRC signalling: This bitmap signalling should be of higher periodicity than the RRC message containing the configuration of the search spaces and ALs. Using DCI: This bitmap is indicated through DCI and be associated with a timer. Here, the bitmap is transmitted in advance to the UE. i.e., signalling is provided before (n-j)th slot for the scheduling to be done on nth slot, where j is the time when BS decides to schedule.

In dynamic approach, the BS schedules and knows the exact SS where the DCI for the UE is present. Hence a bitmap per slot is defined only for slots where there is no scheduled DCI in allocated search space. Here the bitmap indication is done dynamically and for each slot independently using a separate dedicated channel. There are fixed RBs in a specific region in the BWP. The gNB (alternatively referred as BS) fills those RBs with the bitmap. The UE will decode those RBs first, get the bitmap and perform BD according to the bitmap. For e.g., inFIG.2, gNB sends a 4-bit bitmap to the UE indicating which search space to be monitored. For slot2, the bitmap will be 0011, hence the UE knows that it has to monitor only in USS1& USS2. This will avoid unnecessary monitoring of search spaces. A detailed explanation of this method using a flow chart is shown inFIG.12.

As illustrated inFIG.12, at step1202the BS configures Search Space (SS) configuration to a UE. At step1204, the BS configures a bitmap of SS to be monitored by the UE. At step1206, the BS signals one of the bitmap and an index of the table containing all combinations of bitmaps. At step1208, the UE continues monitoring of DCI as per configuration till the bitmap/index is received from the BS. At step1210, if UE receives new bitmap/index, then the method proceeds to step1212. If UE does not receive new bitmap/index, then the method loops back to step1208. At step1212, SS is monitored for which corresponding bit in bitmap is enabled. At step1214, UE stops monitoring for remaining SS.

In one embodiment, there is prior transmission of high priority DCI. If multiple DCIs with different priority levels are configured to a UE by the BS, there can be vacant search spaces between the DCIs. Also, there can be low priority DCI present in between two high priority DCIs. Hence to get all high priority DCIs, UE has to do blind decoding for all search space including SS containing low priority DCIs. In order to avoid this, the BS schedules all high priority DCIs first and then schedule low priority DCIs in search spaces. The final high priority DCI contains an indicator at the end to indicate the end of high priority DCIs, UE will stop monitoring further after receiving this indicator field if it can afford to lose low priority DCIs. It will be a one-bit indication if the DCI is present in USS.

For the DCI present in CSS, the indication will be done using a dedicated field included in CSS. This field can be a bitmap for the group of users receiving the CSS. For the stop message indicating end of high priority DCIs to any user the corresponding bit will be one. Alternatively, the field can be a user indicator dedicated to a particular user containing the UE index. This user indicator will be included for all users receiving CSS in a similar manner. In this way after receiving all important DCIs, UE stops BD and hence enable low power consumption. A detailed explanation of this method using a flow chart is shown inFIG.13.

As illustrated inFIG.13, at step1302the BS configures search space configuration to a UE. At step1304, the BS segregates the scheduled DCI into high priority and low priority DCIs and schedules all high priority DCIs prior to low priority DCI. At step1306, the UE continue monitoring for the DCI in the SS, as per configuration. At step1308, if Indicator for last DCI with high priority is received, then the method proceeds to step1310, else, when the UE does not receive indicator for last DCI with high priority, the method loops back to step1306. At step1310, UE will be able to afford loss of low priority DCI. At step1312, UE does not monitor for low priority DCIs.

In one embodiment, there is SS location of next DCI in previous. In this method, each DCI contains the information about location of the search space of the next DCI in a round robin way. This method does not assume that UE performs monitoring in any specific order. Even if the UE does not perform BD in any order, whenever any DCI is decoded, the information about the search space of another DCI is obtained and so on. A separate field for indication of next SS to be monitored will be included in DCI. For the DCIs coming in CSS, indication is done separately for each UE. The indicator field per user contains UE index and the SS index of the next DCI for that UE. This will be done individually within the DCI for all UEs receiving that DCI. In USS, this per user indicator field will be disabled and only the SS index will be included. For example, DCI1contains SS location of DCI2and so on and the last DCI (DCI N) contains SS location of first DCI (DCI1) as shown inFIG.14. In this method, when the SS index of the next DCI is indicated in a DCI, the UE performs BD and obtains all the DCIs present in that SS. UE will not monitor if it gets that SS index again in any other DCI. For example, inFIG.14, DCI1contains indication of USS1hence once DCI1is received, UE will go to indicated USS1and obtain both DCI2& DCI3by decoding USS1. Here DCI2in USS1contains location of USS1again. In this case, since USS1is already monitored, the UE will ignore the repeated locations. A detailed explanation of this method using a flow chart is shown inFIG.15.

As illustrated inFIG.15, at step1502the BS configures search space configuration to a UE. At step1504, UE starts blind decoding procedure in a slot. At step1506, the UE may decode Downlink Control Information (DCI) present in the slot. At step1508, UE receives an indication of SS index of consecutive DCI present in the slot. At1510, it is determined if the consecutive DCI is present in a Common SS (CSS). If DCI is identified to be present in the CSS, UE specific indicator field including UE index and the SS index of the consecutive DCI for that UE is identified, at step1514. At step1510, when the DCI is found not to be present in CSS but present in USS, UE specific indicator field will be disabled and only the SS index will be included, at step1512. Further, at step1518, if SS index indicated is already monitored, then the method proceeds to step1516where the SS index is ignored and not monitored again. If SS index indicated is not monitored, then the method proceeds to step1520. At step1520, the indicated SS is monitored.

In one embodiment, there is using of DMRS correlation, channel estimate correlation and SINR estimation to reduce BD attempts. A UE will detect energy on the possible DMRS locations of every candidate CCE. If the estimated energy of a candidate CCE is below a certain threshold value, UE will eliminate or deprioritize the PDCCH candidates associated with that CCE. For example, in per 5G-NR, the channel coefficients within the REG bundle are expected to be highly correlated with each other. This assumption is valid because the REGs within the REG bundle are to be contiguous in time and/or frequency domain and precoder/beamformer applied on the REG bundle are to be same. Here, both data symbols and DMRS symbols are precoded using the same precoder/beamformer.

The DMRS sequence are derived based on a pseudo-random sequence, which is initialized using a seed. The seed is unique for a given UE which makes the DMRS sequence of a UE specific SS unique. The UE estimates the channel coefficients on DMRS resource elements of a REG bundle using its DMRS sequence. If that REG bundle is allocated to that UE, then the correlation between the estimated channel coefficients corresponding to the different REGs of the same REG bundle will be significantly higher than the case where the REG bundle is allocated to some other UE or is not allocated to any UE. This variation in correlation value is used to eliminate or deprioritize the PDCCH candidates associated with that REG bundle. If the detected energy and/or the channel correlation value is significantly smaller, the UE will eliminate the corresponding PDCCH candidate and thereby the number of PDCCH candidates are reduced which in turn reduces the number of blind decoding attempts. To avoid any misdetection of DCI, UE can deprioritize the PDCCH candidate wherein the detected energy or the channel correlation value is just below the threshold values. Though the deprioritizing method is not reducing the worst-case blind decoding attempts, it helps the UE to detect the DCI earlier than the normal behaviour of the UE. Further, the UE will estimate a Signal to Noise plus Interference Ratio (SINR) on the DMRS resource elements and map to the possible Aggregation Level (AL) set. The UE will prioritize the PDCCH candidates based on the detected energy, the correlation value between the channel estimates and the estimated SINR for the early detection of DCI. If the mapping table of SINR to AL set is predefined or configured from BS using any one of RRC signalling, MAC-CE or DCI, the number of blind decoding attempts is reduced.

Flow chart of the method described above is shown inFIG.16, wherein the flow chart includes steps1602through1622. The steps are explained in detail as follows: The UE starts with initial PDCCH candidates list. For each PDCCH candidate from the initial PDCCH candidates list, the UE finds the DMRS correlation value between the received DMRS sequence and its original DMRS sequence using the DMRS correlator. Based on at least one DMRS correlation threshold, UE updates the initial PDCCH candidate list and forms the 1st updated PDCCH candidate list. The update is any one of a deletion of the PDDCH candidate and de-prioritization of the PDDCH candidate.

For each PDCCH candidate from the first updated PDCCH candidates list, the UE finds the channel correlation value between the estimated channel coefficients corresponding to the different REGs of the same REG bundle using the channel correlator. Based on at least one channel correlation threshold, UE updates the first updated PDCCH candidate list and forms the second updated PDCCH candidate list. The update is any one of a deletion of the PDDCH candidate and de-prioritization of the PDDCH candidate. For each PDCCH candidate from the 2nd updated PDCCH candidates list, UE estimates the SINR on the DMRS resource elements using the SINR estimator and map the estimated SINR to the possible aggregation level (AL) set. Based on the possible AL set, UE updates the 2nd PDCCH candidate list and forms the final updated PDCCH candidate list. The update is any one of a deletion of the PDDCH candidate and de-prioritization of the PDDCH candidate. UE starts the blind decoding process with the final PDCCH candidates list. It is to be noted that, the deletion of PDCCH candidates will reduce the number of blind decoding attempts for the UE and de-prioritization of PDCCH candidates will help the UE for the early detection of PDCCH.

In another embodiment, there is use of DMRS location to indicate additional information. For example, in 5G-NR, the DMRS locations within the CORESET is fixed (1st, 5th and 9th RE in an RB). By making the location of the DMRS flexible, it is possible to convey additional information implicitly to the UE regarding the further behaviour of DCI detection procedure. Following are the 4 possible DMRS RE positions in a REG in a symbol with the same reference signal density: {1st, 5th, and 9th}; {2nd, 6th and 10th}; {3rd, 7th and 11th}; and {4th, 8th and 12th}.

There are four combinations of positions. 2 bits of information can be conveyed using the position of the DMRS. Following are the two example configurations that is conveyed to the UE using these two bits of information.

UE may be configured with a set of priority table for DCI candidates based on AL. The two-bit is used to select a table from the set. The set of CCE's can be divided into (up to) 4 sub-regions. The two-bit information is used to inform the UE in which sub-region, the actual DCI data starts. Introducing flexible DMRS positions will increase the number of channel estimations per PDCCH candidate. Hence, this method is more beneficial when a simpler, and a low-cost algorithm is employed at the UE to detect the presence of DMRS first and then estimating the channel upon the detection of DMRS. For example, to detect the presence of the DMRS, UE can use RSRP based DMRS detection algorithm in all the possible DMRS position combinations within the DCI candidates. Following are the steps involved:

Generate reference DMRS sequences for each of the OFDM symbol in the SS. For a selected combination of the DMRS position, extract all the complex received symbols from the corresponding REs in all the OFDM symbols within the SS. Compute the RSRP from the extracted complex symbols with the help of generated reference DMRS sequences and detect the presence of DMRS using RSRP based algorithms. If DMRS is not detected, select the next combination of DMRS position and repeat from step2.

If DMRS is detected, obtain the implicit information conveyed by this particular DMRS position. Flow chart of the above steps are shown inFIG.17.

As illustrated inFIG.17, at step1702reference DMRS sequences are generated for each of the OFDM symbol in the search space. At step1704, one combination of positions of the DMRS sequences may be chosen. At step1706, RSRP may be computed using the received signal at the selected combination and reference DMRS sequences. At step1708, detection of DMRS is determined. If DMRS is detected, then the method proceeds to step1710. If DMRS is not detected, then the method loops back to step1704. At step1710, information conveyed by the position of the DMRS is obtained.

In another embodiment, there is indication to reduce PDCCH candidates. In this method, each SS is configured with additional information about the sub-region within the CORESET in which the PDCCH candidates should be monitored. If a PDCCH candidate do not start in the signalled sub-region, then it is considered as an invalid PDCCH candidate. CORESET is divided into multiple sub-regions. The CORESET sub-region is a set of consecutive CCE's within the CORESET. The number of sub-regions will be a fixed value (ideally 2 or 4). Each sub-region will have a unique bit sequence to identify them. The BS will signal the CORESET sub-region to be monitored using appropriate signalling methods. The UE, while trying to decode a PDCCH candidate, first checks if the PDCCH candidate starts in the signalled sub-region within the CORESET. Only PDCCH candidates starting in the signalled sub-region is considered to be valid and are processed further.

The information about the sub-region can be signalled using RRC/MAC-CE signalling or using the DMRS positions as described in Method12. Consider a simplified scenario where a CORESET having 8 CCE's is configured a SS with 4 PDCCH candidates of AL1. A possible distribution of PDCCH candidates is shown inFIG.18. In the figure, 1st PDCCH candidate contains CCE4, 2nd candidate contains CCE6, 3rd candidate contains CCE8and the 4th candidate contains CCE2. The CORESET is divided into two sub-regions with sub-region1consisting of CCE's1to34and sub-region2consisting of CCE's5to8. If the BS indicates to UE to consider PDCCH candidates in sub-region1, the UE will try to decode only PDCCH candidates1and4. Flow chart of the above method is given inFIG.19. The list of steps involved includes signalling, by the BS, first information about a plurality of sub-regions within a CORESET, at step1902; signalling the UE with the second information about at least one sub-region to be monitored amongst the plurality of sub-regions, at step1904; dividing the CORESET into multiple sub-regions based on the first information, at step1906; generating a list of all possible PDCCH candidates, at step1908; selecting a PDCCH candidate from the list of all possible PDCCH candidates, at step1910; determining if the PDCCH candidate start within the at least one sub-region in the second information, at step1912; and decoding/processing the PDCCH candidate when the PDCCH candidate is identified to be starting within the at least one sub-region in the second information, at step1914, and selecting a next PDCCH candidate when the PDCCH candidate is identified not to be starting within the at least one sub-region in the second information, loop to step1910.

In the above detailed description, reference is made to the accompanying drawings that form a part thereof, and illustrate the best mode presently contemplated for carrying out the invention. However, such description should not be considered as any limitation of scope of the present invention. The structure thus conceived in the present description is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence.