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广东:通信业捐助抗非典医护人员 (特约记者 陈治焕 石易)非典疫情发生以来,广东省通信行业一方面采取各项措施,保障通信畅通、确保抗击非典取得最后胜利,另一方面,以实际行动支援抗击非典,通过各种具有电信行业特点的方式,向抗非典一线医护人员捐助资金、物资和设备。

Performance Analysis and Parameter Optimizing Rules of LT Codes

As a new class of forward error correcting encoding algorithm,Luby Transform codes are suitable for the erasure channel environment based on the packet communication.The encoding,decoding algorithms and the implementation of LT codes are summarized in the paper.Meanwhile simulations of the ideal soliton distribution and robust soliton distribution are conducted to evaluate the performance of LT codes in terms of successful decoding probability,mean degree and decoding time over the erasure channel.The parameter optimization rules of LT codes are deeply discussed and proposed in the paper.The research results are of great practical importance for improving the real time performance in the erasure correction applications.

A Joint Encryption and Error Correction Method Used in Satellite Communications

Due to the ubiquitous open air links and complex electromagnetic environment in the satellite communications,how to ensure the security and reliability of the information through the satellite communications is an urgent problem.This paper combines the AES(Advanced Encryption Standard) with LDPC(Low Density Parity Check Code) to design a secure and reliable error correction method — SEEC(Satellite Encryption and Error Correction).This method selects the LDPC codes,which is suitable for satellite communications,and uses the AES round key to control the encoding process,at the same time,proposes a new algorithm of round key generation.Based on a fairly good property in error correction in satellite communications,the method improves the security of the system,achieves a shorter key size,and then makes the key management easier.Eventually,the method shows a great error correction capability and encryption effect by the MATLAB simulation.

Deterministic Secure Quantum Communication with Cluster State and Bell-Basis Measurements

We present a novel protocol for deterministic secure quantum communication by using the lour-qubit cluster state as quantum channel. It is shown that two legitimate users can directly transmit the secret messages based on Bellbasis measurements and classical communication. The present protocol makes use of the ideas of block transmission and decoy particle checking technique. It has a high capacity as each cluster state can carry two 5its of information, and has a high intrinsic efficieney 5ecause almost all the instances except the decoy checking particles （its numSer is negligible） are useful. Furthermore, this protocol is feasible with present-day technique.

Universities and Global Market

The article interested in the universities in the global market. Author briefly describes the situation of the many universities of the point of view of education, research, orientation, system of financing and management of the universities. The whole article is based on the author＇s practical experiences. The research objective was to determine how the professional community is looking at private universities and state universities. It was based on the opinion of the quality of graduates and the number of academic staff who are working at state universities These academics have mostly negative view of private universities as well as the knowledge of graduates of these private schools. However, the opinion ofstaffin practice, especially managers in manufacturing companies, trading companies, companies selling services, as well as senior officials in government, are not so negative. By contrast in certain areas such as marketing, business, management, Information and Communication Technology etc., was rather neutral or positive. The politicians were interested about these information with regard to educational reform （reform of universities is still not actual--note the author） and the expected necessary cuts of spending to higher education from the state budget. Unfortunately, the research project due to political changes in 2009 was not completed and obtained only partial results. Despite of this fact the author decided to process the article below Opinions on the topic of public vs. private univeristies were mainly obtained informally from experts from academic area （both public and private）, managers, various specialists, but also from the students themselves. In conclusion man can say that the demand for people who are able to quickly demonstrate their knowledge in practice is still stronger. The title becomes second-rate （unfortunately not quite in the public and state administration）. Very strong demand is the active practice of communication in English （it fulfilles especially private universities） Graduates of technical universities in the classical fields are sought less in the labor market. Very high pressure is developed by state universities to private. This implies a lack of professors and associate professors who can work in full time at private universities which are more flexible and better adapt to labor market requirements. Stronger position have private universities that are in any way connected with foreign partners from developed countries

A Novel Low Density Parity Check Coded Differential Amplitude and Pulse Position Modulation Free-Space Optical System for Turbulent Channel

Based on the proposed partly equidifferent mapping and its specific Differential Amplitude and Pulse Position Modulation(DAPPM) demodulation, a modified FSO scheme for turbulent channel is designed and analyzed. The novel Low Density Parity Check(LDPC) coded 4×4 and 4×8 DAPPM Free-Space Optical communication(FSO) system is constructed. The Monte Carlo simulation results show approximately 2d B transmit power reduction against classical LDPC-DAPPM at the identical Bit-Error-Rate in strong turbulent channel. The proposed partly equidifferent mapping is compatible with other modulations, so it enables widespread adoption in other coded FSO systems.

A novel construction method of QC-LDPC codes based on CRT for optical communications

A novel construction method of quasi-cyclic low-density parity-check(QC-LDPC) codes is proposed based on Chinese remainder theory(CRT). The method can not only increase the code length without reducing the girth, but also greatly enhance the code rate, so it is easy to construct a high-rate code. The simulation results show that at the bit error rate(BER) of 10^(-7), the net coding gain(NCG) of the regular QC-LDPC(4 851, 4 546) code is respectively 2.06 dB, 1.36 dB, 0.53 dB and 0.31 dB more than those of the classic RS(255, 239) code in ITU-T G.975, the LDPC(32 640, 30 592) code in ITU-T G.975.1, the QC-LDPC(3 664, 3 436) code constructed by the improved combining construction method based on CRT and the irregular QC-LDPC(3 843, 3 603) code constructed by the construction method based on the Galois field(GF(q)) multiplicative group. Furthermore, all these five codes have the same code rate of 0.937. Therefore, the regular QC-LDPC(4 851, 4 546) code constructed by the proposed construction method has excellent error-correction performance, and can be more suitable for optical transmission systems.