There is a conflict between increasing the image swath and improving the azimuth resolution in a conventional single-channel synthetic aperture radar (SAR) system. This paper introduces a method of realizing high-reso...
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There is a conflict between increasing the image swath and improving the azimuth resolution in a conventional single-channel synthetic aperture radar (SAR) system. This paper introduces a method of realizing high-resolution and wide-swath (HRWS) SAR imaging with a multiple-inputmultiple-output (MIMO) system based on a space-pulse phase coding (SPPC) technique, which makes it possible to discriminate and separate the echoes from multiple ambiguous range regions through coding the phases of the transmitted pulses in each spatial channel. Two coding schemes, referred to as the uniform-cyclic coding and the uniform-acyclic coding, respectively, are devised for discriminating the range-ambiguous echoes. By choosing a proper phase gradient factor, both coding schemes can be used to resolve the range ambiguities. The uniform-cyclic coding scheme presents a little better performance of the range ambiguity suppression, and the uniform-acyclic coding scheme can preserve the coherency of the range-ambiguous clutters. Simulation results have demonstrated the effectiveness of the proposed coding schemes.
Although multiple-inputmultiple-output (MIMO) technique is used in free space optical (FSO) systems to reduce the effect of atmospheric turbulence, however, employing this technique without sufficient attention to th...
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Although multiple-inputmultiple-output (MIMO) technique is used in free space optical (FSO) systems to reduce the effect of atmospheric turbulence, however, employing this technique without sufficient attention to the interference of laser beams not only does not reduce the effect of atmospheric turbulence, but also it can significantly degrade the performance of the FSO system. This study investigates that the average intensity of laser beams at the receiver aperture of MIMO FSO systems is very sensitive to small variations of path lengths between the transmitter and receiver. Therefore, the destructive interference that degrades the performance of MIMO FSO systems compared to equivalent single-input single-output (SISO) FSO ones is due to the difference in path lengths of laser beams between transmitter and receiver apertures. For this reason and in order to mitigate the interference effect, the authors compensate small changes of path lengths through adjusting the sending times and the initial parameters of laser beams in the transmitter apertures. The authors' analysis supported by numerical results show that the adjustment of laser parameters could increase the chance of peak intensity of MIMO-FSO systems to be higher than the peak intensity of equivalent SISO-FSO ones.
Using the Schnorr-Euchner (SE) enumeration for soft-input soft-output (SISO) sphere decoding is inefficient to implementation, because it calculates and sorts partial metrics of all constellation points exhaustively. ...
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ISBN:
(纸本)9781538643426
Using the Schnorr-Euchner (SE) enumeration for soft-input soft-output (SISO) sphere decoding is inefficient to implementation, because it calculates and sorts partial metrics of all constellation points exhaustively. In order to solve this problem, we use a low-complexity method which can be applied to the channel information and a-priori information enumerations for the SISO iterative K-best sphere decoding. In this paper, we present an algorithm that combines these two enumerations to reduce the operation complexity and do not need to sacrifice too much bit error rate (BER) performance.
The multiple-inputmultiple-output (MIMO) technique has been introduced to use in wireless networks to achieve the higher bit rate. Although the bit rate is increased, the throughput in wireless networks using MIMO te...
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ISBN:
(纸本)9781479975754
The multiple-inputmultiple-output (MIMO) technique has been introduced to use in wireless networks to achieve the higher bit rate. Although the bit rate is increased, the throughput in wireless networks using MIMO technique is not increased by the same ratio. A number of new media access control (MAC) protocols have been proposed to increase the throughput in the MIMO wireless networks, but more overheads are added into the transmission process. This study proposes a new MAC protocol called the extended contention period (ECP) protocol which increases the throughput in the wireless networks and reduces the overheads in the transmission process. We also develop a simulation model to evaluate the performance of the ECP protocol and compare with the carrier sense multiple access with collision avoidance (CSMA/CA) protocol.
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