Nr-arfcn and channel grid, synchronous grid and GSCN

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Channel planning

TS 38.104 V17.4.0 5.4 section

NR-ARFCN And channel grid

The global frequency grid is defined as A group of RF Reference frequency F_REF Set . RF The reference frequency is used in signaling to identify RF channel 、SSB And other elements in the frequency domain .

The frequency range of the global frequency grid is 0 To 100 GHz .

RF The reference frequency is determined by the global frequency grid [0…3279165] Within the scope of NR-ARFCN（NR Absolute RF channel number ） Appoint .

N_REF by NR-ARFCN. The granularity of the global grid is ΔF_Global. NR-ARFCN And with MHz RF reference frequency in F_REF The relationship between is given by the following formula , among F_REF-Offs and N_REF-Offs See table 5.4.2.1-1.

effect ： Generally used to calculate F_REF（ RF reference frequency ,NR Cell center frequency point ） or N_REF（NR Cell absolute channel number ）, Know one and ask the other .

give an example ： In frequency 2000Mhz For example , obtain N_REF=400000.
$$2000\times 1000=0+5\times (N_{REF}-0)$$

surface 5.4.2.2-1 The results on the channel grid are given RF Mapping between reference frequency and corresponding resource elements , Can be used to identify RF Channel location . The mapping depends on the number of channels allocated in the channel RB total , And it applies to UL and DL.

Channel grid and RE The mapping relationship is the middle of the bandwidth RB Of 0 Number or 6 Number subcarrier and NR-ARFCN alignment , The following table .

The channel grid is defined as RF A subset of the reference frequency , It can be used to identify data in uplink and downlink RF Channel location . RF Channeled RF The reference frequency is mapped to the resource element on the carrier . For each operating frequency band , There is a frequency subset of the global frequency grid to which it applies , And form a particle size of ΔF_Raster Channel grid , The particle size may be equal to or greater than ΔF_Global .

• The channel grid is 100KHz Frequency band ：ΔF_Rater =20×ΔF_Global, That is to say, every 20 individual NP-ARFCN Is a valid channel grid , namely N_REF step 20.
• The operating frequency band is less than 3GHz, And the channel grid is 15KHz：ΔF_Rater =i x ΔF_Global,i ∈ {3 ,6}, That is to say, every i individual NR-ARFCN Is a valid channel grid , namely N_REF In steps of i .
• The operating frequency band is greater than 3GHz, And the channel grid is 15kHz or 60kHz：ΔF_Rater =i x ΔF_Global,i ∈ {1 ,2}, That is to say, every I individual NR-ARFCN Is a valid channel grid , namely N_REF In steps of i .
• There are two kinds of frequency bands for ΔF_Rater, See agreement for details .

Different frequencies use different channel grids , Only part of the content is given here . A detailed reference 38.104 Table 5.4.2.3-1 and 2.

Table: Applicable NR-ARFCN per operating band

NR operating band	ΔFRaster(kHz)	Uplink range of NREF (First – step size – Last)	Downlink range of NREF (First – step size – Last)
n1	100	384000 – <20> – 396000	422000 – <20> – 434000
n28	100	140600 – <20> – 149600	151600 – <20> – 160600
n41	15	499200 – <3> – 537999	499200 – <3> – 537999
	30	499200 – <6> – 537996	499200 – <6> – 537996
n78	15	620000 – <1> – 653333	620000 – <1> – 653333
	30	620000 – <2> – 653332	620000 – <2> – 653332
n79	15	693334 – <1> – 733333	693334 – <1> – 733333
	30	693334 – <2> – 733332	693334 – <2> – 733332

Sync grid

The synchronization grid indicates that when the explicit signaling of the synchronization block location does not exist, it can be used by UE The frequency position of the synchronization block obtained by the system .

A global synchronization grid is defined for all frequencies . SSB The frequency domain position of is defined as SS_REF, The corresponding number is GSCN. Define all frequency ranges SS_REF and GSCN The parameters of are shown in table 5.4.3.1-1.

When the terminal starts up and performs cell search , It can only detect according to the frequency band supported by the operator and the terminal SSB The signal , Conduct downlink time-frequency synchronization . Due to the small granularity of the global frequency grid NR-ARFCN The value range of is large , If blind detection is carried out directly according to the global frequency grid , The synchronization delay will be relatively large , In order to effectively reduce the synchronization delay of this process , The concept of synchronous grid is defined , And through the global synchronization channel number (GSCN,Global Synchronization Channel Number) To limit the scope of the search .

And N The multiplied part is the granularity of the frequency range .

Synchronize grid with SSB Resource elements （RE） The mapping relation of ：

The synchronization grid and subcarrier spacing of the synchronization block are defined separately for each frequency band . Corresponding to each frequency band SCS and GSCN Details refer to Table 5.4.3.3-1 and 2

such as ：

Table 5.4.3.3-1: Applicable SS raster entries per operating band (FR1)

NR operating band	SS Block SCS	SS Block pattern	Range of GSCN (First – Step size – Last)
n41	15kHz	Case A	6246 – <3> – 6717
	30kHz	Case C	6252 – <3> – 6714
n78	30kHz	Case C	7711 – <1> – 8051

​ give an example ： With n78 The starting frequency of 3300MHz, Calculate its corresponding GSCN
$$\begin{gathered} 3300(M)+120\times 30/1000(M)=3000(M)+N\times 1.44(M) \\ thisinSuch\; asfruitallInto\; theThat\text{'}s\; oktowardsOntakewholeOfword \\ N=212 \\ GSCN=7499+N=7711 \end{gathered}$$

Summary

With 3.5G Take the frequency band as an example , Global Grid , Channel grid 、 An example of synchronization grid is shown in the following figure ：

The global grid granularity is 15KHz、 The channel grid granularity is 30KHz、 The granularity of the synchronous grid is 1.44MKHz：