With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real ap...With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real applications. Then we generalize the method to such a case that an arbitrary number system can be utilized in the system. We form some conditions that should be satisfied when we want to create security keys, to encipher plaintexts or to decipher cryptograms. Finally, a qualitative analysis is made on the improved PR method with the results that the data redundancy R of enciphered text for the improved PR method is far smaller than that of the primitive PR method and its enciphering and deciphering procedures are accordingly sped up. Moreover, the security of the new scheme is by no means worse than that of the old one.展开更多
Orthogonal frequency division multiplexing (OFDM) is vastly used in wireless networks. Its superiority relies on the fact that information can be split in large amount of frequencies. Each frequency is called informat...Orthogonal frequency division multiplexing (OFDM) is vastly used in wireless networks. Its superiority relies on the fact that information can be split in large amount of frequencies. Each frequency is called information subcarrier. OFDM exhibits excellent annotation in channel fades and interferers as only a few subcarriers can be affected and consequently a small part of the original data stream can be lost. Orthogonality between frequencies ensures better spectrum management and obviates the danger of intersymbol interference. However, an essential problem exists. OFDM systems have high peak to average power ratio. This implies large fluctuations in signal power, ending up in increasing complexity of ADCs and DACs. Also, power amplifiers must work in a larger linear dynamic region. In this paper we present two new techniques for reducing Peak to Average Power Ratio (PAPR), that can be added in any OFDM system and we compare them with other existing schemes.展开更多
文摘With the goal of minimizing the enciphered data redundancy R , we first make a feasibility analysis on the PKCS which is based on the PR method, indicating its difficulties in real applications. Then we generalize the method to such a case that an arbitrary number system can be utilized in the system. We form some conditions that should be satisfied when we want to create security keys, to encipher plaintexts or to decipher cryptograms. Finally, a qualitative analysis is made on the improved PR method with the results that the data redundancy R of enciphered text for the improved PR method is far smaller than that of the primitive PR method and its enciphering and deciphering procedures are accordingly sped up. Moreover, the security of the new scheme is by no means worse than that of the old one.
文摘Orthogonal frequency division multiplexing (OFDM) is vastly used in wireless networks. Its superiority relies on the fact that information can be split in large amount of frequencies. Each frequency is called information subcarrier. OFDM exhibits excellent annotation in channel fades and interferers as only a few subcarriers can be affected and consequently a small part of the original data stream can be lost. Orthogonality between frequencies ensures better spectrum management and obviates the danger of intersymbol interference. However, an essential problem exists. OFDM systems have high peak to average power ratio. This implies large fluctuations in signal power, ending up in increasing complexity of ADCs and DACs. Also, power amplifiers must work in a larger linear dynamic region. In this paper we present two new techniques for reducing Peak to Average Power Ratio (PAPR), that can be added in any OFDM system and we compare them with other existing schemes.
