By cognitive radio,the low Earth orbit（LEO） satellites may prefer to operate in the unlicensed spectrum which is open to all the users,and compete for the limited resources with terrestrial cognitive radio networks...
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By cognitive radio,the low Earth orbit（LEO） satellites may prefer to operate in the unlicensed spectrum which is open to all the users,and compete for the limited resources with terrestrial cognitive radio networks（CRNs）.The competition can be regarded as a game and analyzed with game *** particular unlicensed spectrum sharing problem is modeled here,and the special properties of ＂spatially-distinguished-interference＂ and the short period of the interactions between satellites and terrestrial CRNs are ***,the problem is formulated as a ＂partially-blind＂ finitely repeated prisoner＇s dilemma by game ***,we begin with two promising spectrum sharing schemes,which can be used to enforce the frequency reuse among the remotely located terrestrial CRN players as well as to overcome the observation *** analysis and comparison,it is proposed that the novel refreshing-contrite-tit-for-tat（R-CTFT） is the optimal spectrum sharing *** results verify that it can be used to utilize the spectrum most efficiently.
利用华北地区夏季日降水资料和NCEP/NCAR再分析环流资料,采用功率谱分析、Butterworth带通滤波等方法,对华北地区夏季降水低频特征与大气低频环流演变进行了综合分析。结果表明:(1)华北地区夏季降水存在低频特征,主要以准双周振荡为主。(2)500 h Pa高度场大气低频环流表现为闭合的高、低压系统;850 h Pa低频流场演变要复杂一些,但它们伴随高层低频系统移动会发生有规律的变化。500 h Pa高度场上,在35°N以北,低频系统向东移动,有时也从鄂霍次克海附近向西的扩展;在35°N以南,低频系统表现为由西北太平洋向西北移动,然后再向西移动。华北夏季降水主要是直接受中高纬度低频系统影响,低纬度低频系统很难直接影响华北地区,但它们可以通过偏南偏北气流的变化影响向华北地区的水汽输送或冷空气活动,进而加强或减弱华北地区的降水强度。(3)当500h Pa 40°N-60°N范围内有低频低压从西向东移近华北地区,并诱发850 h Pa气旋或切变线生成,从而在华北地区出现明显的降水过程;当500 h Pa低频低压向东移出而后部低频高压移来时,华北地区低层850 h Pa流场就会转为辐散气流或为一致的偏北气流,降水过程结束。(4)华北地区降水发生时,高、低空低频环流有较好的配合。
In this paper, we investigate the problem of code acquisition for band-limited direct-sequence spread-spectrum (DSSS) systems in the presence of sampling offset. By analyzing the detection output property of the tradi...
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In this paper, we investigate the problem of code acquisition for band-limited direct-sequence spread-spectrum (DSSS) systems in the presence of sampling offset. By analyzing the detection output property of the traditional noncoherent detection scheme with and without the existence of sampling offset, an improved acquisition scheme that utilizes two decision variables for joint detection is proposed. Numerical results show that the proposed scheme can offer better performance and is more robust to the variation of the sampling offset than the traditional scheme.
As a novel rapid acquisition scheme, the partial correlation with frequency sweeping (PC-FS) method is proposed for acquisition of direct-sequence spread-spectrum (DSSS) signal in the presence of Doppler shift. The ou...
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ISBN:
(纸本)9781627485852
As a novel rapid acquisition scheme, the partial correlation with frequency sweeping (PC-FS) method is proposed for acquisition of direct-sequence spread-spectrum (DSSS) signal in the presence of Doppler shift. The output performance of the PC-FS scheme is analyzed and a hardware structure which can largely accelerate the synchronization process is designed. Application results show that new acquisition scheme can provide a significant improvement in flexibility and efficiency over the PMF-FFT method. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Harbin University of Science and Technology
As a novel rapid acquisition scheme, the partial correlation with frequency sweeping (PC-FS) method is proposed for acquisition of direct-sequence spread-spectrum (DSSS) signal in the presence of Doppler shift. The ou...
详细信息
As a novel rapid acquisition scheme, the partial correlation with frequency sweeping (PC-FS) method is proposed for acquisition of direct-sequence spread-spectrum (DSSS) signal in the presence of Doppler shift. The output performance of the PC-FS scheme is analyzed and a hardware structure which can largely accelerate the synchronization process is designed. Application results show that new acquisition scheme can provide a significant improvement in flexibility and efficiency over the PMF-FFT method.
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