Subspace Decomposition Channel Estimation for Multiple Virtual MIMO SC-FDMA Systems

In this paper, we investigate the use of a subspace decomposition MIMO channel estimation algorithm for the blind estimation of the multiple virtual MIMO (V-MIMO) channels in Single Carrier Frequency Division Multiple Access (SC-FDMA) systems in order to increase its spectral efficiency. Groups of multiplexed users are formed, where each user is equipped with a single antenna, to transmit on the same frequency and time resources. When deployed in a V-MIMO system that resembles the LTE standard parameters, the proposed blind algorithm can obtain accurate estimates of the V-MIMO channels for each active user over every block of transmitted data. In addition, it is necessary to have knowledge of the channels state information to perform the users grouping and frequency allocation (scheduling). According to the LTE standard, sounding reference signals are employed in conjugation with Interleaved-frequency division multiple-access (I-FDMA). By eliminating the need to transmit an entire block of pilot symbols for each active transmitter, this permits for additional bandwidth efficiency in V-MIMO SC-FDMA systems in which multiple users occupy the same set of subcarriers as indicated by the LTE standard. The advantages of employing our proposed blind subspace-based channel estimation algorithm are verified by simulations results over fading channels, which demonstrate its practicality for use in the resulting V-MIMO SC-FDMA scheme with reduced training.