Patent ID: 8165227

Claim:
A method for transmission in a communication system, the method comprising: encoding input bits at a certain rate; interleaving the encoded bits; inputting the interleaved encoded bits into an Orthogonal Frequency Division Multiplexing (OFDM) block generation unit, wherein the encoded bits are grouped into m-bits wherein m is greater than 2 and mapped to a differential amplitude phase shift keying (DAPSK) modulation symbol, wherein a first bit of an m-bit unit is used as an amplitude reference, while the rest of the bits of the m-bit unit other than the first bit are used as a phase reference, wherein values of the amplitude reference and the phase reference are generated using a differential modulation method of which previous symbols are used as an amplitude reference and a phase reference for a current symbol; inserting pilot bits into code bits of each OFDM block, wherein the pilot bits have a specific phase and a specific amplitude to be used as initial reference information to be used in a differential demodulation of DAPSK; applying the DAPSK modulation symbol to generate modulation symbols in each OFDM block; re-ordering the generated modulations symbols in each OFDM block to carry out neighboring differential modulation symbols over a neighboring subcarrier frequency, wherein an output of the modulation symbol re-ordering is defined as: m i ′=m i (i+N) mod 2N , where i=0, 1, 2, . . . , 2N−1, wherein mi is represented as an input to the re-ordering block and mi′ is an output of the re-ordering block; inserting guard tones into the re-ordered OFDM blocks of data at both ends of a frequency band in a frequency domain; and transmitting the OFDM blocks.