Multiple input multiple output (MIMO) techniques are widely employed in modern wireless systems. The most prominent approaches to MIMO communication are space-timecoding (STC) and spatial multiplexing (SM). Less stud...
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Multiple input multiple output (MIMO) techniques are widely employed in modern wireless systems. The most prominent approaches to MIMO communication are space-timecoding (STC) and spatial multiplexing (SM). Less studied is a hybrid technique called adaptive MIMO switching (AMS), which may be employed by fixing the transmission rate and selecting between space-time block coding and SM transmission modes based on instantaneous channel conditions to achieve the most efficient link. This study presents a hardware implementations of a selector algorithm and a detector employing it. The detector is designed for a 2 x 2 MIMO system and was implemented on an Altera Cyclone II FPGA. In addition, two transmission protocols with decision feedback from the receiver to the transmitter via a low-rate feedback channel are introduced and the feasibility of switching for high-data-rate transmissions is discussed.
A hypersonic vehicle is covered by a plasma sheath during reentry, which seriously attenuates the power of electromagnetic (EM) waves and generates the so-called "radio blackout" phenomenon when the equivale...
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A hypersonic vehicle is covered by a plasma sheath during reentry, which seriously attenuates the power of electromagnetic (EM) waves and generates the so-called "radio blackout" phenomenon when the equivalent frequency of plasma is greater than the carrier frequency. However, the parameters of plasma sheath vary randomly with time and axial distance. The variation produces some random time slots where the equivalent frequency of plasma is lower than the carrier frequency, so the EM waves can penetrate the plasma sheath. Random time slots cause receiver unable to receive information with the form of complete frame, resulting in the traditional communication methods being no longer applicable. In order to receive the complete frame in random time slots and make full use of the spatial-temporal resources of the plasma sheath channel, we construct a spatial-temporal-varying plasma sheath channel mode, propose an adaptivespace-time short-frame fountain code (ASTSFFC), and study the relationship between the ASTSFFC parameters and the characteristics of the channel. The ASTFFC has the characteristics of no-rate and short-frame, which can adapt to the short-time and random of the plasma sheath. In addition, ASTFFC contains an adaptive multilevel coding matrix to deal with the massive changes of plasma sheath parameters during reentry. Simulation shows that the proposed method achieves higher utilization of spatial-temporal resources of plasma sheath channel, and improves the reliability of communication by adaptively adjusting the coding strategy. When the plasma equivalent frequency is lower than the carrier frequency, information can be transmitted at high speed. Even when the plasma equivalent frequency is close to the carrier frequency, information can also be transmitted correctly.
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