针对正交频分复用(orthogonal frequency division multiplexing,OFDM)系统峰值平均功率比(peak average power ratio,PAPR)大的问题,提出了降低PAPR的联合算法。该算法在改进的部分传输序列(part transmission sequences,PTS)算法的基...针对正交频分复用(orthogonal frequency division multiplexing,OFDM)系统峰值平均功率比(peak average power ratio,PAPR)大的问题,提出了降低PAPR的联合算法。该算法在改进的部分传输序列(part transmission sequences,PTS)算法的基础上,加入压扩技术。联合算法在不增加系统复杂度的情况下,可有效地减小OFDM系统的PAPR。仿真结果表明:当子载波分组数为16、随机分组方式、4倍过采样、内层分组数为4、CCDF(complementary cumulative distribution function)为10-3时,联合算法与传统的PTS算法相比,PAPR减小了4.8 dB。展开更多
The United States,Russia and China are militarily and economically among the most powerful countries in the post-Cold War period,and the interactions between the three powers heavily influence the international system...The United States,Russia and China are militarily and economically among the most powerful countries in the post-Cold War period,and the interactions between the three powers heavily influence the international system.However,different conclusions about this question are generally made by researchers through qualitative analysis,and it is necessary to objectively and quantitatively investigate their interactions.Monthly-aggregated event data from the Global Data on Events,Location and Tone(GDELT)to measure cooperative and conflictual interactions between the three powers,and the complementary cumulative distribution function(CCDF)and the vector autoregression(VAR)method are utilized to investigate their interactions in two periods:January,1991 to September,2001,and October,2001 to December,2016.The results of frequencies and strengths analysis showed that:the frequencies and strengths of USA-China interactions slightly exceeded those of USA-Russia interactions and became the dominant interactions in the second period.Although that cooperation prevailed in the three dyads in two periods,the conflictual interactions between the USA and Russia tended to be more intense in the second period,mainly related to the strategic contradiction between the USA and Russia,especially in Georgia,Ukraine and Syria.The results of CCDF indicated that similar probabilities in the cooperative behaviors between the three dyads,but the differences in the probabilities of conflictual behaviors in the USA-Russia dyad showed complicated characteristic,and those between Russia and China indicated that Russia had been consistently giving China a hard time in both periods when dealing with conflict.The USA was always an essential factor in affecting the interactions between Russia and China in both periods,but China’s behavior only played a limited role in influencing the interactions between the USA-Russia dyad.Our study provides quantitative insight into the direct cooperative and conflictual interactions between the three dyads since the end of the Cold War and helps to understand their interactions better.展开更多
文摘针对正交频分复用(orthogonal frequency division multiplexing,OFDM)系统峰值平均功率比(peak average power ratio,PAPR)大的问题,提出了降低PAPR的联合算法。该算法在改进的部分传输序列(part transmission sequences,PTS)算法的基础上,加入压扩技术。联合算法在不增加系统复杂度的情况下,可有效地减小OFDM系统的PAPR。仿真结果表明:当子载波分组数为16、随机分组方式、4倍过采样、内层分组数为4、CCDF(complementary cumulative distribution function)为10-3时,联合算法与传统的PTS算法相比,PAPR减小了4.8 dB。
基金The Second Tibetan Plateau Scientific Expedition and Research(STEP)program,No.2019QZKK0608Talent Start Project of Beijing Normal University。
文摘The United States,Russia and China are militarily and economically among the most powerful countries in the post-Cold War period,and the interactions between the three powers heavily influence the international system.However,different conclusions about this question are generally made by researchers through qualitative analysis,and it is necessary to objectively and quantitatively investigate their interactions.Monthly-aggregated event data from the Global Data on Events,Location and Tone(GDELT)to measure cooperative and conflictual interactions between the three powers,and the complementary cumulative distribution function(CCDF)and the vector autoregression(VAR)method are utilized to investigate their interactions in two periods:January,1991 to September,2001,and October,2001 to December,2016.The results of frequencies and strengths analysis showed that:the frequencies and strengths of USA-China interactions slightly exceeded those of USA-Russia interactions and became the dominant interactions in the second period.Although that cooperation prevailed in the three dyads in two periods,the conflictual interactions between the USA and Russia tended to be more intense in the second period,mainly related to the strategic contradiction between the USA and Russia,especially in Georgia,Ukraine and Syria.The results of CCDF indicated that similar probabilities in the cooperative behaviors between the three dyads,but the differences in the probabilities of conflictual behaviors in the USA-Russia dyad showed complicated characteristic,and those between Russia and China indicated that Russia had been consistently giving China a hard time in both periods when dealing with conflict.The USA was always an essential factor in affecting the interactions between Russia and China in both periods,but China’s behavior only played a limited role in influencing the interactions between the USA-Russia dyad.Our study provides quantitative insight into the direct cooperative and conflictual interactions between the three dyads since the end of the Cold War and helps to understand their interactions better.
