A method of processing a broadcast signal in a transmitter, the method comprising: bit interleaving Physical Layer Pipe, PLP data; mapping the bit interleaved PLP data into constellations using a Quadrature Amplitude Modulation, QAM; performing Multi-input Multi-Output, MIMO, encoding on a first signal and a second signal of the PLP data mapped into the constellations; building a first frame including the MIMO encoded first signal and a second frame including the MIMO encoded second signal; inserting a first preamble, P1, symbol at a beginning of the first frame and a P1 symbol at a beginning of the second frame; and inserting an additional first preamble, AP1, symbol consecutively after the P1 symbol of the first frame and an AP1 symbol consecutively after the P1 symbol of the second frame, wherein the P1 symbol of the first frame or the second frame includes a main part, a first guard interval and a second guard interval, wherein the first guard interval carries a frequency shifted version of a part of the main part while the second guard interval carries a frequency shifted version of the other part of the main part, wherein (fsh) of frequency shift is applied to the first and second guard intervals, wherein the AP1 symbol of the first frame or the second frame includes an additional main part, a third guard interval and a fourth guard interval, wherein the third guard interval carries a frequency shifted version of a part of the additional main part while the fourth guard interval carries a frequency shifted version of the other part of the additional main part, wherein (-fsh) of frequency shift is applied to the third and fourth guard intervals, wherein the first frame and the second frame each further includes a pilot signal of a specific pilot pattern and Layer 1-pre, L1-pre, signaling data, wherein the L1-pre signaling data includes information for indicating the specific pilot pattern included in the corresponding frame and information for indicating a guard interval of the corresponding frame, wherein the P1 symbol of the first frame or the second frame includes information for indicating a preamble format, wherein the L1-pre signaling data are carried through at least one second preamble, P2, symbol within each frame, and wherein the at least one P2 symbol is located consecutively after the AP1 symbol of the first frame or the second frame. bit interleaving Physical Layer Pipe, PLP data; mapping the bit interleaved PLP data into constellations using a Quadrature Amplitude Modulation, QAM; performing Multi-input Multi-Output, MIMO, encoding on a first signal and a second signal of the PLP data mapped into the constellations; building a first frame including the MIMO encoded first signal and a second frame including the MIMO encoded second signal; inserting a first preamble, P1, symbol at a beginning of the first frame and a P1 symbol at a beginning of the second frame; and inserting an additional first preamble, AP1, symbol consecutively after the P1 symbol of the first frame and an AP1 symbol consecutively after the P1 symbol of the second frame, wherein the P1 symbol of the first frame or the second frame includes a main part, a first guard interval and a second guard interval, wherein the first guard interval carries a frequency shifted version of a part of the main part while the second guard interval carries a frequency shifted version of the other part of the main part, wherein (fsh) of frequency shift is applied to the first and second guard intervals, wherein the AP1 symbol of the first frame or the second frame includes an additional main part, a third guard interval and a fourth guard interval, wherein the third guard interval carries a frequency shifted version of a part of the additional main part while the fourth guard interval carries a frequency shifted version of the other part of the additional main part, wherein (-fsh) of frequency shift is applied to the third and fourth guard intervals, wherein the first frame and the second frame each further includes a pilot signal of a specific pilot pattern and Layer 1-pre, L1-pre, signaling data, wherein the L1-pre signaling data includes information for indicating the specific pilot pattern included in the corresponding frame and information for indicating a guard interval of the corresponding frame, wherein the P1 symbol of the first frame or the second frame includes information for indicating a preamble format, wherein the L1-pre signaling data are carried through at least one second preamble, P2, symbol within each frame, and wherein the at least one P2 symbol is located consecutively after the AP1 symbol of the first frame or the second frame.