Since the useable frequency spectrum is a scarce resource, future wireless systems should focus onrnnew technologies that provide high spectral efficiency and improved link reliability. Therncombination of Multiple Input Multiple Output (MIMO) wireless communication withrnOrthogonal Frequency Division Multiplexing (OFDM) is a very promising technology to meetrnthese requirements.rnAlthough MIMO OFDM systems have demonstrated very high spectral efficiency, the availablerncapacities of these systems are not fully exploited due to lack of low complex and, at the samerntime, optimal signal detection scheme. To this end, after reviewing the available detectionrntechniques, this thesis proposes a low complex MIMO signal detection technique which has nearrnoptimal performance.rnIt is found that among the MIMO signal detection techniques the Maximum Likelihood Decodingrn(MLD) has optimal performance; however, the corresponding computational complexity growsrnexponentially with the number of antennas and/or constellation size. The conventional detectionrnschemes such as ZF, MMSE, ZF with SIC and MMSE with SIC have relatively manageablerncomplexity; however, in general their BER performance is poor especially for large MIMO sizes.rnThe sphere decoding algorithms (SDAs), specifically the depth first sphere decoding (DF SD),rnachieves similar performance to MLD at relatively reasonable complexity, but it has very largernvariation of computational throughput. In order to reduce the complexity of DF SD, initial radiusrnsetting strategy is introduced in this thesis and, with this, enormous computational complexity isrnsaved. Fixed throughput SDAs, namely k best SDAs, are also analyzed and as a result, it isrnobtained that these schemes have performance degradation compared to the MLD. So, a hybridrnsphere decoding which combines the desirable features of the two SDAs is proposed in this thesisrnand simulation results show that the proposed scheme can achieve performance very close to thernMLD at very high computational throughput which is more than twice of that of k best SDAs.