Layered Space-time Codes Research Articles

A vertical layered space-time code and its closed-form blind symbol detection

Vertical layered space-time codes have demonstrated the enormous potential to accommodate rapid flow data. Thus far, vertical layered space-time codes assumed that perfect estimates of current channel fading conditions are available at the receiver. However, increasing the number of transmit antennas increases the required training interval and reduces the available time in which data may be transmitted before the fading coefficients change. In this paper, a vertical layered space-time code is proposed. By applying the subspace method to the layered space-time code, the symbols can be detected without training symbols and channel estimates at the transmitter or the receiver. Monte Carlo simulations show that performance can approach that of the detection method with the knowledge of the channel.

Efficient algorithm for decoding layered space-time codes

Layered space-time codes have been designed to exploit the capacity advantage of multiple antenna systems in Rayleigh fading environments. A new efficient decoding algorithm based on QR decomposition is presented, which requires only a fraction of computational effort compared to the standard decoding algorithm requiring the multiple calculation of the pseudo inverse of the channel matrix.

A new approach to layered space-time coding and signal processing

The information-theoretic capacity of multiple antenna systems has been shown to be significantly higher than that of single antenna systems in Rayleigh-fading channels. In an attempt to realize this capacity, Foschini (1996) proposed the layered space-time architecture. This scheme was argued to asymptotically achieve a lower bound on the capacity. Another line of work has focused on the design of channel codes that exploit the spatial diversity provided by multiple transmit antennas (Tarokh et al. 1998, Hammons and Gamal 2000). In this paper, we take a fresh look at the problem of designing multiple-input-multiple-output (MIMO) wireless systems. First, we develop a generalized framework for the design of layered space-time systems. Then, we present a novel layered architecture that combines efficient algebraic code design with iterative signal processing techniques. This novel layered system is referred to as the threaded space-time (TST) architecture. The TST architecture provides more flexibility in the tradeoff between power efficiency, bandwidth efficiency, and receiver complexity. It also allows for exploiting the temporal diversity provided by time-varying fading channels. Simulation results are provided for the various techniques that demonstrate the superiority of the proposed TST architecture over both the diagonal layered space-time architecture in Foschini (1996) and the multilayering approach (Tarokh et al. (1999).