Space Time Block Coded Vector OFDM with ML Detection

Space time block coding (STBC) is a popular technique to improve diversity gain of conventional OFDM systems. Vector OFDM (VOFDM) is a transmission technology that exploits signal space dimension to reduce the effect of spectral nulls on OFDM subcarriers. Space time block coded vector OFDM (STBC VOFDM) tries to extract advantages of both these techniques, thereby improving the reliability of the communication system. This paper illustrates the characteristics of STBC VOFDM systems with maximum likelihood (ML) detection in an i.i.d (independent and identically distributed) multipath complex Rayleigh channel with D channel taps. The expression for diversity gain in STBC VOFDM for most vector blocks is derived as 2{min(M, D)}, where M denotes the number of elements in each vector block and D denotes the number of channel taps. It can be observed that the diversity order in STBC VOFDM has improved by a factor of 2 when compared with VOFDM.