NG Toolset开发笔记--5GNR Resource Grid（3）
5/26号完成如下需求分析：
（3）CRB, Point A, BWP （refer to 38.211/38.213/38.104/38.331)
**Per carrier configurations:
FrequencyInfoDL and FrequencyInfoUL (FreqInfoUL only for FDD/SUL)
l absoluteFrequencySSB defines the center frequency of SSB (sc#0 of #prb10 of SSB, SSB occupies 20prbs in frequency domain)
l absoluteFrequencyPointA in freqInfoDL defines Point-A in DL, which is sc#0 of CRB#0
l absoluteFrequencyPointA in freqInfoUL defines Point-A in UL(for FDD/SUL only), which is sc#0 of CRB#0
However, the actual NR carrier is defined in scs-SpecificCarrier:
l offsetToCarrier defines the actual usable BW w.r.t. the carrier’s Point-A, which is the CRB 
as defined in 38.211 4.4.2.
l subcarrierSpacing defines scs of the carrier, which is parameter--nrScs in Section 1.3.1
l carrierBandwidth defines N_RB of the carrier, which is parameter---nrBw in Section 1.3.1, which is also the 
as defined in 38.211 4.4.2.
offsetToCarrier shall have no impact to Resource Grid implementation. Let offsetToCarrier = 0?
Rational as below:
k_SSB is the sc offset from sc#0/crb#0(Point-A) sc#0 of CRB N_SSB_CRB to sc#0 of ssb. Max value of k_SSB is 31.
Is it a valid configuration if offsetTocarrier * 12 * subcarrierSpacing > 32*15K + 12*15*N_SSB_CRB(for type ASSB) or 32*MIB.subCarrierSpacingCommon + 12*60*N_SSB_CRB (for type B SSB)? That’s, SSB lies outside of the actual usable carrier BW.
2018/6/9 comment: note that, N_SSB_CRB can be configured (Note: It’s NOT the absoluteFrequencyPointA in frequencyInfoDL IE),means that it may not be CRB0.
From one aspect, SSB is carrier level configuration, while BWP is per UE configuration. SSB applies when UE trying to do initial access. After that, UE shall apply BWP setting for all other channels/signals except SSB.
SIB1 is the same as SSB, which is carrier level configuration. After receiving SIB1, UE may be configured a UL BWP, which can be used to send Msg3/Msg5 (I am not very sure about that).
DL BWP is not configured until RrcReconfiguration?(RrcReconfiguration----CellGroupConfig---ServingCellConfigCommon---initialDownlinkBWP). It’s for EN-DC only, I think this issue will be solved in upcoming 2018-06 specs.
As defined in 38.211 4.4.2, resource grid is given w.r.t. Combination of (antenna port p, scs u, tx direction(UL/DL)).
For simplicity, 5GNR resource grid is defined w.r.t combination of only (antenna port p, tx direction(UL/DL)). The reference scs, refScs, is fixed to 15K for FR1 and 60K for FR2, so that nrScs >= refScs, and actual CRB-nrScs may occupy multiple CRB-refScs.
Point-A definition in 38.211 4.4.4.2 is a bit confusing. The point is that:
(1) CRB and Point-A(sc#0 of crb#0) is defined w.r.t. a NR carrier.
(2) Point-A is separately defined for UL/DL in case of FDD/SUL, otherwise, Point-A is the same in case of TDD.
(3) Center frequency of SSB is defined separately so that UE can perform initial access.
(4) PRB and VRB is defined w.r.t. a NR BWP(bandwidth part).
**Per BWP configurations:
Definition of BWP in 38.331:
Note: “code points” here simply means available combinations of n bits. For example, certain DCI field is 2bits, so four “code points” in total: 00/01/10/11.
All the important configurations in NR UL/DL are defined either in BWP-DownlinkCommon/BWP-UplinkCommon or BWP-DownlinkDedicated/BWP-UplinkDedicated.
BWP generic parameters:
l locationAndBandwidth defines 
and 
by table-lookup. However the table is not specified yet.
l subcarrierSpacing is defined for this BWP, which may be different from the scs of NR carrier
l cyclicPrefix, which is the parameter---nrCp in section 1.3.2
For simplicity, only one BWP (with bwp-index=0) shall be configured.
**SCS summary for initial access:
Ssb scs: blindly decoded by UE?
One exception is NR n41:
15k with case A, and 30k with case C are both supported. However, according to 38.213 4.1, 1st symbol indexs of SSB for both case A and case C are the same.
So basically, UE can’t determine whether scs-ssb is 15k or 30k. It doesn’t affect UE’s behavior since 38.211 7.4.3.1 stats that there are two types of SSB: type A and type B:
Type A SSB covers both 15k and 30k scs-ssb.
Question: eventually, UE had to determine scs-ssb, since UE need scs-ssb and scs-pdcch to determine type-0 CSS, as specified in 38.213 13. How to determine scs-ssb for NR n41?
2018/6/9 comment: one possible solution is that the detected BW of ssbis different for 15k and 30k.
**Time/Frequency Synchronization during initial access
In general, time synchronization is realized as below:
*UE detects a valid SSB(with its 1st symbol) and determines its ssb-index1 (through dmrs for pbch, and possible payload of pbch--- 
as specified in 38.212 7.1.1)
*UE detects next valid SSB(with its 1st symbol) and determines its ssb-index2
*from ssb-index1 and ssb-index2, UE can determine the half-frame timing.
Contents of MIB(from PBCH):
And frequency synchronization is realized as below:
*from MIB(PBCH), UE determine k_SSB (k_SSB is the #scs between sc#0 of ssb and point-A sc#0 of CRB N_SSB_CRB, so UE can determine Point-A).
*from k_SSB, UE determine type-0 CSS(common search space)
*UE receive SIB1 (for EN-DC, there is no SIB1, contents of the missed SIB1 are sent to UE via RrcReconfiguration via MCG-LTE RRC signalling)
*when SIB1 is received, UE can determine Point-A, GSCN of SSB, and N_SSB_CRB accordingly. (2018/6/10 comment)
Scs of SIB1/msg2/msg4 is determined from subCarrierSpacingCommon from MIB
**Conclusions:
(1) SIB1 will not be simulated, and will be updated according to upcoming 3GPP specs in 2018-06.
(2) Additional carrier specific parameters:
Carrier specific parameters shall separate UL/DL in case of FDD
l nrCcOpBand: operating band of NR carrier
l nrCcGridStart: as defined by offsetToCarrier of SCS-specificCarrier, value range is: [0, 2199] in PRB
l nrCcGridSize: as defined by carrierBandwidth of SCS-specificCarrier
l nrCcGridScs: as defined by subcarrierSpacing of SCS-specificCarrier
l nrCcSsbScs: subcarrier spacing of SSB, 15K/30K for FR1 and 120K/240K for FR2; should be configured in UI, and determined by UE in live network
(3) Additional BWP specific configurations :
Separate settings for UL/DL in case of FDD
l nrBwpStart: starting position of BWP in PRB
l nrBwpSize: size of BWP in PRB
l nrBwpScs: subcarrier spacing of BWP, 15K/30K/60K for FR1 and 60K/120K for FR2
l nrBwpMu: u of BWP, 0/1/2 for FR1 and 2/3 for FR2
l nrBwpCp: cyclic prefix of BWP
l All other parameters listed in previous‘Frame Structure’ section
(4) SSB specific configurations:
l nrNSsbCrb: the N_SSB_CRB
l nrKSsb: k_SSB, value range is [0,31] for FR1 and [0,15] for FR2
l nrMibScsCommon: as defined by subCarrierSpacingCommon in MIB, 15K/30K for FR1 and 60K/120K for FR2
l nrMibRmsiPdcch: as defined by pdcch-ConfigSIB1 in MIB, value range is [0, 255]