We
usually see one parameter “EARFCN” in our project network optimization
test. The full name is “EUTRA Absolute Radio Frequency Channel Number”.
This parameter is the central frequency that the LTE system used.
Generally the EARFCN is calculated by the 3GPP defined formula, so we
don’t know directly what the central frequency is. This document mainly
gives introduction about how to calculate EARFCN by central frequency
and how to calculate central frequency by EARFCN.
When
we do drive test by using TEMS Investigation tool, we can only see
EAUFCN through the test tool. When we use CNT in drive test，we can both see the DL,UL central frequency and the matched EARFCN，like
figure 21. What’s the relation between central frequency and EARFCN?
That is our main subject about how to calculate the relation result.
The carrier frequency in the
uplink and downlink is designated by the EUTRA Absolute Radio Frequency
Channel Number (EARFCN) in the range 0  65535. The relation between
EARFCN and the carrier frequency in MHz for the downlink is given by the
following equation, where FDL_low and NOffsDL are given in table
5.7.31 and NDL is the downlink EARFCN.
FDL = FDL_low + 0.1(NDL – NOffsDL)
The relation between EARFCN and
the carrier frequency in MHz for the uplink is given by the following
equation where FUL_low and NOffsUL are given in table 5.7.31 and NUL
is the uplink EARFCN.
FUL = FUL_low + 0.1(NUL – NOffsUL)

EUTRA Operating Band

Downlink

Uplink


F_{DL_low} [MHz]

N_{OffsDL}

Range of N_{DL}

F_{UL_low} [MHz]

N_{OffsUL}

Range of N_{UL}


1

2110

0

0 – 599

1920

18000

18000 – 18599


2

1930

600

6001199

1850

18600

18600 – 19199


3

1805

1200

1200 – 1949

1710

19200

19200 – 19949


4

2110

1950

1950 – 2399

1710

19950

19950 – 20399


5

869

2400

2400 – 2649

824

20400

20400 – 20649


6

875

2650

2650 – 2749

830

20650

20650 – 20749


7

2620

2750

2750 – 3449

2500

20750

20750 – 21449


8

925

3450

3450 – 3799

880

21450

21450 – 21799


9

1844.9

3800

3800 – 4149

1749.9

21800

21800 – 22149


10

2110

4150

4150 – 4749

1710

22150

22150 – 22749


11

1475.9

4750

4750 – 4949

1427.9

22750

22750 – 22949


12

729

5010

5010 – 5179

699

23010

23010 – 23179


13

746

5180

5180 – 5279

777

23180

23180 – 23279


14

758

5280

5280 – 5379

788

23280

23280 – 23379


…








17

734

5730

5730 – 5849

704

23730

23730 – 23849


18

860

5850

5850 – 5999

815

23850

23850 – 23999


19

875

6000

6000 – 6149

830

24000

24000 – 24149


20

791

6150

6150  6449

832

24150

24150  24449


21

1495.9

6450

6450 – 6599

1447.9

24450

24450 – 24599


…








33

1900

36000

36000 – 36199

1900

36000

36000 – 36199


34

2010

36200

36200 – 36349

2010

36200

36200 – 36349


35

1850

36350

36350 – 36949

1850

36350

36350 – 36949


36

1930

36950

36950 – 37549

1930

36950

36950 – 37549


37

1910

37550

37550 – 37749

1910

37550

37550 – 37749


38

2570

37750

37750 – 38249

2570

37750

37750 – 38249


39

1880

38250

38250 – 38649

1880

38250

38250 – 38649


40

2300

38650

38650 – 39649

2300

38650

38650 – 39649


41

2496

39650

39650 – 41589

2496

39650

39650 – 41589


42

3400

41590

41590 – 43589

3400

41590

41590 – 43589


43

3600

43590

43590 – 45589

3600

43590

43590 – 45589


NOTE: The
channel numbers that designate carrier frequencies so close to the
operating band edges that the carrier extends beyond the operating band
edge shall not be used. This implies that the first 7, 15, 25, 50, 75
and 100 channel numbers at the lower operating band edge and the last 6,
14, 24, 49, 74 and 99 channel numbers at the upper operating band edge
shall not be used for channel bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz
respectively.
Since now we have known the relation and formula, we can try to calculate central frequency and EARFCN.
For example: the central frequency is 2664 MHz, Band=7 FDD LTE system, what is the down link EARFCN?
Calculation progress is shown as below, from the formula:
FDL = FDLlow + 0.1(NDL – NOffsDL),
We know:
NDL=（FDL – FDLlow）×10+ NOffsDL，
Check from table 22 we can know when band =7, FDLlow=2620 ，NOffsDL=2750, we can put the correspondence relation to the formula, the calculation result is,
NDL=（2664 – 2620）×10+ 2750=3190
Finally we get the result when the central frequency is 2664MHz FDD LTE system, the down link EARFCN is 3190.
From EARFCN to central frequency
Then we can make a backward calculate. When we do LTE test, we know the EARFCN and how to calculate the central frequency?
For example down link EARFCN is 37762, what is the central frequency?
We can calculate as below, 37762 correspondence band is 38, we can check from table 22 that FDLlow=2570，NOffsDL=37750，we can put the correspondence relation to the formula , the calculation result is:
FDL = 2570 + 0.1(37762 – 37750)=2571.2
Finally we get the result that the central frequency is 2571.2MHz.
Through above calculation and formula
we can get almost all the EARFCN and Central frequency. But we must
observe one important and detail in our calculation: BAND. From below
table 2 and 3 we can see that the same down link and up link frequency
may be in different band. In table 2, band 3 and band 4 indicate that DL
and UL bandwidth have overlap. So when we calculate EARFCN, we should
confirm the system band first, then we can calculate them accurately and
correctly.
Table 31 FDD LTE highest and lowest frequency
Tool make
From the formula calculation and the detail progress shown，we
can make the EARFCN and central frequency search tool, which can give
immediately and convenient search in our network planning and
optimization work.EARFCN and central frequency is one important parameter for us to know LTE system. When we in one trial or commercial project. We must know the FDD LTE system frequency and bandwidth. If we know the operator’s frequency information detailed, that can help us to give some professional advice to our customers. 