LS codes aided channel estimation for MIMO-OFDM systems in multipath channels

Abstract

High-data rate techniques in communication systems have gained considerable attraction in recent years. Strong candidates for these communication systems are Multiple Input Multiple Output (MIMO) systems, Orthogonal Frequency Division Multiplexing (OFDM) system and MIMO-OFDM systems. MIMO systems have shown their potential by improving the diversity gain with scheme as Space-Time Block Codes (STBC) and increasing the capacity gain significantly with scheme as Bell Lab Layered Space-Time Architecture (BLAST). However, it is difficult to get the both sides at the same time since transmit diversity comes at the cost of throughput and vice versa. Recently, Double Space Time Transmit Diversity (DSTTD) was proposed, which is a combination of STBC and BLAST to increase the diversity gain and data rates simultaneously. OFDM system is also one of the most promising techniques for the high data rate wireless communications in complex multipath fading environment. OFDM system is a special form of multi-carrier transmission where all the subcarriers are orthogonal each other. In OFDM system, the high data rate input stream is divided into many low-rate streams and transmitted in parallel. MIMO-OFDM systems have received considerable attentions in order to combat the multipath fading and increase system capacity. To take the advantages of the MIMO-OFDM system, the reliable channel estimation techniques are needed. For the single-antenna OFDM system, various channel estimation techniques such as least square (LS) and minimum mean square error (MMSE) estimators have been studied. However, these techniques are inadequate for channel estimation of MIMO-OFDM systems, since other transmission antennas act as interference. Smart codes have been studied previously by many researchers. LS codes, one of the smart codes based on a Golay complementary pairs (GCP), have the zero correlation zone (ZCZ) or Interference Free Window (IFW). Utilizing the ZCZ or IFW, it is propose...