One, BWP configuration

1. Introduction to BWP

1.1. BWP concept and meaning [reference 38211]

BWP is a continuous CRB in the resource grid. Its purpose and significance are mainly as follows:

The NR bandwidth is very large. The UE does not need to support the full bandwidth compulsorily. It only needs to support part of the bandwidth. This is also the origin of the name BWP (bandwidth part);
it saves power when it is unnecessary, because the larger the bandwidth, the more power is required The higher the consumption, so there is no need to keep the UE in a state of large bandwidth all the time;
flexible scheduling, including bandwidth size and frequency band location, is used to adapt to different service requirements and overcome frequency selective fading.

1.2, BWP configuration [reference 38213]

The configuration of BWP is divided into several different situations:

1. Initial BWP The
initial uplink and downlink BWP, that is, Initial DL BWP and initial UL BWP will be configured in SIB1. If the initial BWP is not configured, it will default to CORESET0. The initial BWP is mainly used for the initial access process, such as the reception of SIB1, the reception of RAR, Msg4, and the transmission of preamble and Msg4 during the random access process.

2. Activate the BWP
Activate the BWP, that is, the active BWP is the BWP configured for the UE after the initial access is completed. After the initial access is completed, the UE will have various service requirements, so the bandwidth of the active BWP is generally larger than the initial BWP.

3. Default BWP The
default BWP, that is, the default BWP is used for the UE to switch from an active BWP with a large bandwidth to a default BWP with a smaller bandwidth in order to reduce power consumption when the UE has no service requirements for a long time.

Once the BWP is to be configured, it needs to include some necessary parameters, including the SCS and CP of the BWP, the frequency domain position and size of the BWP (indicated by RIV), ID, and the generic parameters and dedicate parameters of the PDCCH and PDSCH in the BWP. The SCS and CP of PDCCH, PDSCH, etc. in the BWP are the same as the BWP. The bandwidth of the BWP can be any value within 275RB. According to the parameter locationAndBandwidth, an RIV (Resource Indicator Value) is indicated, and then the starting position of the BWP and the number of RBs are calculated by formulas. The reference point of the starting position is Point A.
A UE can be configured with 4 DL BWPs and 4 UL BWPs at most. If there is a SUL, there can be up to 4 BWPs on the SUL. At any particular moment, there can only be one activated uplink BWP and activated downlink BWP. The uplink and downlink data channels, control channels, and reference signals cannot be transmitted beyond the scope of the BWP. In the NR FDD system, in the NR TDD system, the uplink and downlink BWP are a pair, with the same ID and center frequency, but the bandwidth and subcarrier spacing can be different.

2. BWP frequency domain resources

According to the BWP calculation formula:

Among them $N_{BWP}^{size} = 275$ , $1\leq L_{RBs}<N_{BWP}^{size} - RB_{start}$

Get 12928 = 275*(L-1)+RBstart = 275(48-1) + 3 => L = 48, RBstart = 3;

This range is consistent with the frequency domain range of CORESET0.

The frequency domain resource of BWP1 is, which represents the entire cell bandwidth.

1099 = 275 * (276-L) + （274 - RBstart） L = 273 RBstart = 0

Two, CORESET configuration

controlResourceSetId	The CORESET associated with the search space determines the physical resources of the search space
frequencyDomainResources	Resources occupied by the frequency domain, each bit corresponds to a 6RB group in the BWP
duration	Number of symbols occupied in time domain
interleaved	Parameters dedicated to CCE-REG interleaving mapping
cce-REG-MappingType	The mapping relationship between CCE and specific REG
precoderGranularity	PDCCH precoding related configuration

ControlResourceSetId

The ControlResourceSetId IE concerns a short identity, used to identify a control resource set within a serving cell. The ControlResourceSetId = 0 identifies the ControlResourceSet#0 configured via PBCH (MIB) and in controlResourceSetZero (ServingCellConfigCommon). The ID space is used across the BWPs of a Serving Cell. The number of CORESETs per BWP is limited to 3 (including common and UE-specific CORESETs).

CORESET0 is defined in MIB or in the cell controlResourceSetZero of ServingCellConfigCommon.

ControlResourceSetId defines the unique control resource set ID in the cell (it cannot be repeated across BWP). The maximum number of CORESET for each BWP is 3 (including public and UE-specific CORESET)

frequencyDomainResources

Frequency domain resources for the CORESET. Each bit corresponds a group of 6 RBs, with grouping starting from the first RB group (see 38.213, section 10.1) in the BWP. The first (left-most / most significant) bit corresponds to the first RB group in the BWP, and so on. A bit that is set to 1 indicates that this RB group belongs to the frequency domain resource of this CORESET. Bits corresponding to a group of RBs not fully contained in the bandwidth part within which the CORESET is configured are set to zero. Corresponds to L1 parameter 'CORESET-freq-dom' (see 38.211, section 7.3.2.2).

For each CORESET in a DL BWP of a serving cell, a respective frequencyDomainResources provides a bitmap. The bits of the bitmap have a one-to-one mapping with non-overlapping groups of 6 consecutive PRBs, in ascending order of the PRB index in the DL BWP bandwidth of $N_{RB}^{BWP}$ PRBs with starting common RB position $N_{BWP}^{start}$ where the first common RB of the first group of 6 PRBs has common RB index $6\left \lceil N_{BWP}^{start}/6 \right \rceil$ .

The RB group is defined in Section 38.213, 10.1, and each bit represents 6 RBs, starting from the first RB group of the BWP.

frequencyDomainResources provides a bitmap, and each bit in the bitmap maps a 6 RB group. The PRBs between groups are continuous but not overlapping. The PRBs are arranged in ascending order, the total number is $N_{RB}^{BWP}$ , the starting RB is $N_{BWP}^{start}$ , and the index of the first PRB in the first group is $6\left \lceil N_{BWP}^{start}/6 \right \rceil$ . The bit value of 1 in the Bitmap indicates that the corresponding 6 PRBs belong to the CORESET, and the value of 0 indicates that the corresponding 6 PRBs do not belong to the CORESET.

Note that the RB corresponding to the first bit of frequencyDomainResources does not necessarily start from the first RB of the BWP. For example $N_{RB}^{BWP} = 3$ , the PRB represented by the first bit is PRB index 6, and the RB with PRB index 3~5 cannot be used CORESET.

According to the calculation in the previous section, the BWP frequency domain resource in the figure below is L = 273, and RBstart = 0.

FrequencyDomainResources with ControlResourceSetId = 1 has 9 zeros in front, which means that none of the first 54 (0~53) PRBs are frequency domain resources of the CORESET.

CORESET1 is 54~149PRB in the frequency domain, 96 RBs in total, and 1 symbol in the time domain.

CORESET2 is 54~77PRB in the frequency domain, a total of 24 RBs, and 1 symbol in the time domain.

Three, PDCCH-ConfigCommon and PDCCH-Config

PDCCH-ConfigCommon

The IE PDCCH-ConfigCommon is used to configure cell specific PDCCH parameters provided in SIB as well as during handover and PSCell/SCell addition.

The PDCCH-ConfigCommon information element is used to configure cell-level PDCCH parameters, and is used when cell SIB messages, handover messages, and PSCell/SCell are added. It mainly includes the definition of CORESET0 and the search space indicating the BWP to receive paging, SIB1, SIBs, and RAR.

PDCCH-ConfigCommon field descriptions

commonControlResourceSet

An additional common control resource set which may be configured and used for RAR/paging/system information. If the network configures this field, it uses a ControlResourceSetId other than 0 for this ControlResourceSet.

Additional CORESET, used for RAR/paging/system information. If the network is configured with this domain, use this additional CORESET.

commonSearchSpaceList

A list of additional common search spaces. If the network configures this field, it uses the SearchSpaceIds other than 0.

Additional public search space. If the network is configured with this domain, the additional public search space is used, otherwise CORESET0 is used.

controlResourceSetZero

Parameters of the common CORESET#0. The values are interpreted like the corresponding bits in MIB pdcch-ConfigSIB1. Even though this field is only configured in the initial BWP (BWP#0) controlResourceSetZero can be used in search spaces configured in other DL BWP(s) than the initial DL BWP if the conditions defined in 38.213, section 10 are satisfied.

CORESET0 configuration parameter, which has the same meaning as MIB pdcch-ConfigSIB1. Although this parameter is only configured in the initial BWP, this parameter can also be used in other search spaces of other BWPs.

pagingSearchSpace

ID of the Search space for paging. Corresponds to L1 parameter 'paging-SearchSpace' (see 38.213, section 10). If the field is absent, the UE does not receive paging in this BWP (see 38.213, section 10).

The search space used for paging messages, if this field is not configured, means that the UE does not receive paging messages in this BWP.

ra-SearchSpace

ID of the Search space for random access procedure. Corresponds to L1 parameter 'ra-SearchSpace' (see 38.214?, section FFS_Section) If the field is absent, the UE does not receive RAR in this BWP. This field is mandatory present in the DL BWP(s) if the conditions described in TS 38.321 [3], subclause 5.15 are met.

随机接入所用搜索空间，如果不配置该域，表示UE在该BWP不接收RAR消息。

searchSpaceOtherSystemInformation

ID of the Search space for other system information, i.e., SIB2 and beyond. Corresponds to L1 parameter 'osi-SearchSpace' (see 38.213, section 10) If the field is absent, the UE does not receive other system information in this BWP.

接收其它SIB（SIB2及其它）消息所用搜索空间，如果不配置该域，表示UE在该BWP不接收其它SIB消息。

searchSpaceSIB1

ID of the search space for SIB1 message. If the field is absent, the UE does not receive SIB1 in this BWP. (see 38.213, section 10)

接收SIB1所用搜索空间，如果不配置该域，表示UE在该BWP不接收SIB1消息。

searchSpaceZero

Parameters of the common SearchSpace#0. The values are interpreted like the corresponding bits in MIB pdcch-ConfigSIB1. Even though this field is only configured in the initial BWP (BWP#0) searchSpaceZero can be used in search spaces configured in other DL BWP(s) than the initial DL BWP if the conditions described in Spec38.213 [13], section 10 are satisfied.

CORESET0的参数，该参数与MIB pdcch-ConfigSIB1的含义一致。尽管该参数只在初始BWP配置，该参数也可以用于其他BWP的其它搜索空间。

PDCCH-Config

The PDCCH-Config IE is used to configure UE specific PDCCH parameters such as control resource sets (CORESET), search spaces and additional parameters for acquiring the PDCCH.

PDCCH-Config信元用于配置UE专用PDCCH参数，例如CORESET、搜素空间，以及获取PDCCH的其它参数。

PDCCH-Config field descriptions

controlResourceSetToAddModList

List of UE specifically configured Control Resource Sets (CORESETs) to be used by the UE. The network configures at most 3 CORESETs per BWP per cell (including UE-specific and common CORESETs).

controlResourceSetToAddModList指示了UE专用的CORESET，对于每个小区的每个BWP，网络最多配置3个CORESET（包括UE专用和公用CORESET）

downlinkPreemption

Configuration of downlink preemption indications to be monitored in this cell. Corresponds to L1 parameter 'Preemp-DL' (see 38.214, section 11.2)

FFS_RAN1: LS R1-1801281 indicates this is "Per Cell (but association with each configured BWP is needed)" => Unclear, keep on BWP for now.

searchSpacesToAddModList

List of UE specifically configured Search Spaces. The network configures at most 10 Search Spaces per BWP per cell (including UE-specific and common Search Spaces).

UE专用搜索空间，对于每小区的每个BWP，网络最多配置10个搜索空间。（包括UE专用和公共搜索空间）

四、搜索空间

searchSpaceId

Identity of the search space. SearchSpaceId = 0 identifies the searchSpaceZero configured via PBCH (MIB) or ServingCellConfigCommon and may hence not be used in the SearchSpace IE. The searchSpaceId is unique among the BWPs of a Serving Cell.

搜索空间ID，PBCH(MIB)或者ServingCellConfigCommon配置的搜索空间ID为0。searchSpaceId在一个小区的所有BWP中唯一。

controlResourceSetId

The CORESET applicable for this SearchSpace. Value 0 identifies the common CORESET#0 configured in MIB and in ServingCellConfigCommon. Values 1..maxNrofControlResourceSets-1 identify CORESETs configured in System Information or by dedicated signalling. The CORESETs with non-zero controResourceSetId locate in the same BWP as this SearchSpace.

该搜索空间所用的CORESET，0指示为PBCH(MIB)或者ServingCellConfigCommon配置的CORESET#0，其他数值指示为SIB或者专用信令配置的CORESET。非0的CORESET与该搜索空间在同一个BWP中。

common

Configures this search space as common search space (CSS) and DCI formats to monitor.

ue-Specific

Configures this search space as UE specific search space (USS). The UE monitors the DCI format with CRC scrambled by C-RNTI, CS-RNTI (if configured), and SP-CSI-RNTI (if configured)

搜索空间有common和ue-Specific两种，common表示公共搜索空间。ue-Specific表示UE专用搜索空间，此时DCI用C-RNTI，CS-RNTI、或SP-CSI-RNTI进行CRC加扰。

monitoringSlotPeriodicityAndOffset、duration、monitoringSymbolsWithinSlot参数确定了该搜索空间在CORESET中的周期和持续时间。

duration

Number of consecutive slots that a SearchSpace lasts in every occasion, i.e., upon every period as given in the periodicityAndOffset. If the field is absent, the UE applies the value 1 slot. The maximum valid duration is periodicity-1 (periodicity as given in the monitoringSlotPeriodicityAndOffset).

搜索空间持续的时隙数量，如果没有该参数，表示持续1个时隙。最大持续时隙数量比周期少1个时隙。

monitoringSlotPeriodicityAndOffset

Slots for PDCCH Monitoring configured as periodicity and offset. If UE is configured to monitor DCI format 2_1, only the values 'sl1', 'sl2' or 'sl4' are applicable. Corresponds to L1 parameters 'Montoring-periodicity-PDCCH-slot' and 'Montoring-offset-PDCCH-slot' (see 38.213, section 10)

以时隙为单位的PDCCH监测周期和偏移，如果UE监测DCI format 2_1 ，则只有'sl1', 'sl2' or 'sl4'可以使用。

monitoringSymbolsWithinSlot

The first symbol(s) for PDCCH monitoring in the slots configured for PDCCH monitoring (see monitoringSlotPeriodicityAndOffset and duration). The most significant (left) bit represents the first OFDM in a slot. The least significant (right) bit represents the last symbol. The bit(s) set to one identify the first OFDM symbol(s) of the control resource set within a slot. Corresponds to L1 parameter 'Montoring-symbols-PDCCH-within-slot' (see 38.213, section 10)

PDCCH监测时隙中监测的第一个符号。最左边（最大一位）的bit表示时隙中第一个符号，最右边（最小一位）的bit表示时隙中最后一个符号。设置为1的bit位表示监测的第一个符号的位置。

其它参数：

nrofCandidates

Number of PDCCH candidates per aggregation level. Corresponds to L1 parameter 'Aggregation-level-1' to 'Aggregation-level-8'. The number of candidates and aggregation levels configured here applies to all formats unless a particular value is specified or a format-specific value is provided (see inside searchSpaceType). (see 38.213, section 10)

每种聚合等级的候选PDCCH数量。

searchSpaceType

Indicates whether this is a common search space (present) or a UE specific search space as well as DCI formats to monitor for.

指示该搜索空间是公共搜索空间还是UE专用的搜索空间，以及监测的DCI格式。

如下指示

有两个searchSpace，搜索空间1和搜索空间8，都是使用CORESET0的资源。

搜索空间1的监测周期为1 slot，也就是每个slot进行监测。监测的符号为每个slot的符号0，搜索空间类型为公共搜索空间，监测DCI格式为formate0-0和format1-0。

搜索空间8的监测周期为40 slot，偏移为slot 21，连续监测两个时隙，也就是21、22。监测的符号为每个slot的符号0，搜索空间类型为公共搜索空间，监测DCI格式为formate0-0和format1-0。

接收SIB1用搜索空间0，接收其它SIBs用搜索空间8，接收寻呼和RAR消息都用搜索空间1。

Mobile public network 5G configuration (2)