By exploiting diversity techniques, the information capacity of communications systems can be significantly increased. Research has recently been focused on a set of codes that introduce spatial and temporal correlation into signals transmitted from multiple antennas to provide diversity and coding gain at the receiver. Such codes are called space-time codes. The paper provides an overview of various space-time coding techniques, which include space-time trellis coding, space-time block coding, concatenated space-time coding, differential space-time coding, space-frequency coding and layered space-time codes. We present some of the latest research in these topics, in addition to presenting some design criteria and example codes.
Abstract:In this paper, the new detection scheme proposed by Tarokh and Alamouti is investigated and expanded to two schemes of two transmit two receive antennas and four transmit one receive antennas. Previously, Tarokh and Alamouti, based on the simple transmit diversity scheme proposed by Alamouti, have provided two new detection methods to decode signals at the receiver without channel information. We expand their work to two and four transmit antennas with different number of receive antennas. We also demonstrate that the two methods are in fact the same with one being a special case of the other. The theory and detailed derivation of detection formulas for three cases, Tarokh and Alamouti work, two transmit two receive antennas and four transmit one receive antennas are presented.
In this paper, a mathematical model for generating AWGN and Rayleigh fading is presented and argued based around the generation of Gaussian distributed numbers. This paper is focused on a multiple input multiple output (MIMO) channel model for the design and implementation of space-time coded MIMO modem systems such that the complexity of the design is as much as possible pushed into the digital domain and that the architecture is computationally efficient, driving the emphasis and complexity of implementation into software. We present an FPGA architecture to yield a Rayleigh fading and AWGN model for MIMO systems requiring up to four transmit and two receive antennas while requiring only a slight increase in logic resource over a single input single output model. The design entry was in VHDL and the target FPGA was the Xilinx Spartan 3 XC3S4000.
The paper reports on experimental investigations which have been made on four model RO/RO ferries. One of these was based on a 1/100th scale model of the Herald of Free Enterprise. Two of the other models were modified versions of the Herald of Free Enterprise, which were so modified that they did not decrease the efficient concept of the vehicle throughput of a conventional vessel. The tests revealed that the capsize times of these modified RO/RO vessels were increased by 350% for one vessel and 500% for the other vessel. The modified vessels should meet SOLAS 90 + 50 regulations. A fourth model was fitted with two equally spaced transverse bulkheads. This model also had good damage stability characteristics. The paper also summarizes the history of some of the past RO/RO ferry disasters.
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