We propose low-complexity equalizers for Alamouti space-time coded orthogonal frequency-division multiplexing (OFDM) systems in timeand frequency-selective channels, by extending the approach formerly proposed for single-antenna OFDM systems. The complexity of the proposed algorithm is linear in the number of subcarriers by exploiting the band structure of the frequency-domain channel matrix an...

We investigate effects of ordering in blocked matrix–matrix multiplication. We find that submatrices do not have to be stored contiguously in memory to achieve near optimal performance. Instead it is the choice of execution order of the submatrix multiplications that leads to a speedup of up to four times for small block sizes. This is in contrast to results for single matrix elements showing t...

In this paper, block distance matrices are introduced. Suppose F is a square block matrix in which each block is a symmetric matrix of some given order. If F is positive semidefinite, the block distance matrix D is defined as a matrix whose (i, j)-block is given by Dij = Fii+Fjj−2Fij . When each block in F is 1 × 1 (i.e., a real number), D is a usual Euclidean distance matrix. Many interesting ...

Inverse scattering methods capable of compressive imaging are proposed and analyzed. The methods employ randomly and repeatedly (multiple-shot) the single-input-single-output (SISO) measurements in which the frequency, the chosen incidence and the sampling angle are related in a precise way and are capable of recovering exactly (point of extended) scatterers of sufficiently low sparsity. For po...