New schemes for increasing code rate of the OFDM based virtual OSTBC

In this paper we propose new schemes for increasing code rate of the orthogonal frequency division multiplexing (OFDM) based virtual orthogonal space time block coding (OSTBC). The proposed schemes are used for creating virtual 4×1 multiple input-single output (MISO) channel. These schemes include one base station (BS), one relay station (RS), both equipped with two antennas and one mobile station (MS) with a single antenna. One of the main disadvantages of the virtual OSTBC is its code rate, so we propose new schemes with greater code rate while preserving bit error rate (BER) of the scheme with virtual OSTBC. We proposed new schemes with greater code rate on the first hop while the code rate on the second hop remains the same. The code rates between BS and RS in the proposed schemes are 1, 4/5, 2/3 and 4/7, while in the scheme with virtual OSTBC the code rate is only 1/2. Also, we proposed subcarriers mapping in best to worst manner (BW) at RS in order to improve BER performance. The simulation results show that the proposed schemes maintain BER performance very close to the scheme with virtual OSTBC.