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长春光学精密机械与物... [2]
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会议论文 [2]
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2009 [1]
2006 [1]
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专题:长春光学精密机械与物理研究所
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Transceiving protocol designc for a free space optical communication system (EI CONFERENCE)
会议论文
2008 International Conference on Optical Instruments and Technology: Optical Systems and Optoelectronic Instruments, November 16, 2008 - November 19, 2008, Beijing, China
Hualong W.
;
Wanxin S.
;
Zhongbao X.
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浏览/下载:41/0
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提交时间:2013/03/25
A new transceiving protocol is demonstrated for a Free Space Optical (FSO) communication system
and it's discussed in two parts: the transmitting protocol and the receiving protocol. During the discussion of these two parts
the cooperation of them is also discussed. Different from wired communication
an FSO system modulates the data on a narrow beam of laser transmitting through the free space or the atmosphere
and the protocol presented in this paper is mainly optimized for terrestrial Free Space Optical links
in which the signal channel of the system is mainly the atmosphere. Due to the complex composition and activity of the atmosphere
this signal channel brings in great influence on the transmitting laser in it
for example
the absorption and scattering of the atmosphere molecules and aerosols
the scintillation of received laser power caused by the turbulence of the atmosphere
all of which results in a much higher Bit Error Rate (BER) of the communication system. Thus in designing a protocol for an FSO system
more effort should be taken in the encoding of the data stream
the synchronization of the data stream
error checking and exception handling. The main function of the transmitting protocol includes interfacing the outer input data with a parallel port
buffering the input data
encoding the input data stream
serializing the parallel data and output the serialized data. It also has an output management unit to manage the activity of each part of the transmitting protocol. The main function of the receiving protocol includes filtering and synchronizing the input serial data stream
paralleling the serial data stream
decoding the input data
error checking
exception handling and interfacing the outer receiver with a parallel port. The entire transceiving protocol could be programmed into a single FPGA chip to improve system integrity and reduce the system cost. The presented protocol could be taken as "protocol transparent" for outer interfaces
meaning that when interfacing the presented system to an outer system
you don't have to consider what protocol the outer system transceiving data stream is under
for example
the TCP/IP protocol or anything else
in the case that its I/O interface is a parallel port. Simulation and final experiment prove that the protocol presented is working fine at a certain bit rate scale. 2009 SPIE.
Lossless wavelet compression on medical image (EI CONFERENCE)
会议论文
4th International Conference on Photonics and Imaging in Biology and Medicine, September 3, 2005 - September 6, 2005, Tianjin, China
Zhao X.
;
Wei J.
;
Zhai L.
;
Liu H.
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提交时间:2013/03/25
An increasing number of medical imagery is created directly in digital form. Such as Clinical image Archiving and Communication Systems (PACS). as well as telemedicine networks require the storage and transmission of this huge amount of medical image data. Efficient compression of these data is crucial. Several lossless and lossy techniques for the compression of the data have been proposed. Lossless techniques allow exact reconstruction of the original imagery while lossy techniques aim to achieve high compression ratios by allowing some acceptable degradation in the image. Lossless compression does not degrade the image
thus facilitating accurate diagnosis
of course at the expense of higher bit rates
i.e. lower compression ratios. Various methods both for lossy (irreversible) and lossless (reversible) image compression are proposed in the literature. The recent advances in the lossy compression techniques include different methods such as vector quantization
wavelet coding
neural networks
and fractal coding. Although these methods can achieve high compression ratios (of the order 50:1
or even more)
they do not allow reconstructing exactly the original version of the input data. Lossless compression techniques permit the perfect reconstruction of the original image
but the achievable compression ratios are only of the order 2:1
up to 4:1. In our paper
we use a kind of lifting scheme to generate truly loss-less non-linear integer-to-integer wavelet transforms. At the same time
we exploit the coding algorithm producing an embedded code has the property that the bits in the bit stream are generated in order of importance
so that all the low rate codes are included at the beginning of the bit stream. Typically
the encoding process stops when the target bit rate is met. Similarly
the decoder can interrupt the decoding process at any point in the bil stream
and still reconstruct the image. Therefore
a compression scheme generating an embedded code can start sending over the network the coarser version of the image first
and continues with the progressive transmission of the refinement details. Experimental results show that our method can get a perfect performance in compression ratio and reconstructive image.
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