A method performed by a wireless communication node, comprising: determining a third-type reference signal, RS, based on a signaling indication, wherein a pattern of the third-type RS comprises a superposition of a first pattern of a first-type RS and a second pattern of a second-type RS, wherein the first pattern does not overlap with a pattern of a cell-specific reference signal, CRS, in a Long Term Evolution, LTE, system and the second pattern is identical to the pattern of the CRS in the LTE system; determining a first sequence of the first-type RS, wherein the first sequence is a sub-sequence of a second sequence of a CRS, wherein a length of the second sequence is 2 N RB max , DL and a length of the first sequence is 2, wherein N RB max , DL is a maximum downlink bandwidth in LTE system; and transmitting the physical downlink channel data according to the third-type RS, wherein the determining a first sequence r l,n s ( i ) of the first-type RS is performed based on r l , n s i = 1 2 1 − 2 ⋅ c 2 m i + j 1 2 1 − 2 ⋅ c 2 m i + 1 , i = 0,1 c init = 2 10 ⋅ 7 ⋅ n s + 1 + l + 1 ⋅ 2 ⋅ N ID cell + 1 + 2 ⋅ N ID cell + N CP wherein the value of m i is predefined, N ID cell is a physical cell identity, PCID, n s is a time slot index, l is an orthogonal frequency-division multiplexing, OFDM, symbol index, N CP depends on a cyclic prefix, CP, type and has a value of 0 or 1, and c init is an initialization value of a pseudo-random sequence c (·), wherein the first-type RS is a NarrowBand Internet of Things, NB-IOT, reference signal, the second-type RS is a CRS, LTE reference signal, and the third-type RS is a superposition of the first and second types of reference signals. determining a third-type reference signal, RS, based on a signaling indication, wherein a pattern of the third-type RS comprises a superposition of a first pattern of a first-type RS and a second pattern of a second-type RS, wherein the first pattern does not overlap with a pattern of a cell-specific reference signal, CRS, in a Long Term Evolution, LTE, system and the second pattern is identical to the pattern of the CRS in the LTE system; determining a first sequence of the first-type RS, wherein the first sequence is a sub-sequence of a second sequence of a CRS, wherein a length of the second sequence is 2 N RB max , DL and a length of the first sequence is 2, wherein N RB max , DL is a maximum downlink bandwidth in LTE system; and transmitting the physical downlink channel data according to the third-type RS, wherein the determining a first sequence r l,n s ( i ) of the first-type RS is performed based on r l , n s i = 1 2 1 − 2 ⋅ c 2 m i + j 1 2 1 − 2 ⋅ c 2 m i + 1 , i = 0,1 c init = 2 10 ⋅ 7 ⋅ n s + 1 + l + 1 ⋅ 2 ⋅ N ID cell + 1 + 2 ⋅ N ID cell + N CP wherein the value of m i is predefined, N ID cell is a physical cell identity, PCID, n s is a time slot index, l is an orthogonal frequency-division multiplexing, OFDM, symbol index, N CP depends on a cyclic prefix, CP, type and has a value of 0 or 1, and c init is an initialization value of a pseudo-random sequence c (·), wherein the first-type RS is a NarrowBand Internet of Things, NB-IOT, reference signal, the second-type RS is a CRS, LTE reference signal, and the third-type RS is a superposition of the first and second types of reference signals. <EOS>