Efficient near maximum-likelihood decoding of multistratum space-time codes

Multistratum space-time codes combine the layered transmission strategy of V-BLAST with space-time block coding in order to achieve high data rates and at the same time exploit transmit diversity. Simple detection schemes like successive interference cancellation severely suffer from the strong correlation between the strata, so true maximum-likelihood detection needs to be performed instead, which can be efficiently realized by the sphere decoding algorithm. However, most implementations known from the literature still have relatively high complexity, especially for low signal to noise ratio. Therefore, we propose several modifications that can reduce the computational effort by orders of magnitude while achieving at least near optimum performance.