LTE EARFCN

We usually see one parameter “EARFCN” in our project network optimization test. The full name is “E-UTRA 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 2-1. What’s the relation between central frequency and EARFCN? That is our main subject about how to calculate the relation result. 

The professional name of EARFCN is defined detailed in 3GPP《TS 36.104》 protocol：

Table 2-1  Protocol definition

The carrier frequency in the uplink and downlink is designated by the E-UTRA 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 NOffs-DL are given in table 5.7.3-1 and NDL is the downlink EARFCN.          FDL = FDL_low + 0.1(NDL – NOffs-DL) The relation between EARFCN and the carrier frequency in MHz for the uplink is given by the following equation where FUL_low and NOffs-UL are given in table 5.7.3-1 and NUL is the uplink EARFCN.          FUL = FUL_low + 0.1(NUL – NOffs-UL)

The referred table 5.7.3-1 is below table 2-2. From the description of the protocol，we can see the central frequency has one - to - one correspondence relation with EARFCN.  NDL/uL is defined as DL/UL EARFCN. The range is 0-65535 and the value is changed from low to high according to the operating band that the central frequency in. 0-6599 are belong to FDD downlink use, 18000-245999 are belong to up link use,36000-45589 are both used by down link and up link.

Table 2-2  E-UTRA operating band

E-UTRA Operating Band	Downlink			Uplink
	FDL_low [MHz]	NOffs-DL	Range of NDL	FUL_low [MHz]	NOffs-UL	Range of NUL
1	2110	0	0 – 599	1920	18000	18000 – 18599
2	1930	600	6001199	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 – NOffs-DL), We know: NDL=（FDL – FDLlow）×10+ NOffs-DL， Check from table 2-2 we can know when band =7, FDLlow=2620 ，NOffs-DL=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 2-2 that FDLlow=2570，NOffs-DL=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 3-1  FDD LTE highest and lowest frequency E-UTRA Band UL frequencies (MHz) DL frequencies (MHz) lowest highest lowest highest 1 1920 1980 2110 2170 2 1850 1910 1930 1990 3 1710 1785 1805 1880 4 1710 1755 2110 2155 5 824 849 869 894 6 830 840 875 885 7 2500 2570 2620 2690 8 880 915 925 960 9 1749.9 1784.9 1844.9 1879.9 10 1710 1770 2110 2170 11 1427.9 1452.9 1475.9 1500.9 Table 3-2  TDD LTE highest and lowest frequency E-UTRA band UL/DL frequencies (MHz) lowest highest 33 1900 1920 34 2010 2025 35 1850 1910 36 1930 1990 37 1910 1930 38 2570 2620   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.