Outage analysis of opportunistic‐based hybrid decode‐amplify‐forward relaying in polar code environment

Outage analysis plays a vital role in wireless systems to determine reliable transmission and effective communication. Incremental hybrid decode‐amplify‐forward (IHDAF) relay offers a way of meeting the challenges of capacity and coverage improvement with great potential in cooperative communication networks. Therefore, opportunistic incremental hybrid relaying must be integrated with coding schemes to achieve full diversity. In this paper, the outage behavior of polar coded and distributed coded cooperative relaying schemes is analyzed. Simulation results show that opportunistic incremental HDAF using polar code offers an outage capacity of 17 b/s/Hz for 4 × 4 multiantenna and 45 b/s/Hz in 8 × 8 multiantenna systems with an outage of 10^?8 and 10^?13, respectively. Moreover, the polar coded opportunistic IHDAF system in 8 × 8 MIMO achieves 2 and 6 dB higher gains compared with amplify‐and‐forward (AF) and decode‐and‐forward (DF) relaying schemes. The closed‐form expression for outage probability has been derived through Marcum‐Q approximations and processed through Monte Carlo simulations.     

标准模型下完美前向安全的基于身份认证密钥交换

一轮Diffie-Hellman密钥交换(One-Round Diff ie-Hellman key exchange,OR-DHKE)协议被认为无法实现完美的前向安全性(Perfect Forward Secrecy,PFS)。基于身份的OR-DHKE协议也是如此,现有研究仅实现了弱的完美 前向安全性(wPFS)。基于Cremers等人对密钥交换协议完美前向安全性的研究,文章提出 一种新的具有完美前向安全的基于身份认证密钥交换方案。文章首先提出一种较弱安全性的 基于身份 OR-DHKE协议π₀,然后采用Cremers等人提出的SIG变换方法,将π₀转化为具有完美前 向安全的基于身份认 证密钥交换方案π₁。文章简要分析了CK、CK⁺、eCK和eCK-PFS安全模型的异同,在此 基 础上定义了基于身 份认证密钥交换协议分析的强安全模型ID-eCK-PFS。在ID-eCK-PFS模型下,协议π₀和π₁的安全性被规约为 求解判定性BDH(Decisional Bilinear Diffie-Hellman,DBDH)问题,规约过程未使用随 机预言机,实现了在标准模型下的完美前向安全性和可证明安全性。     

Outage performance of dual‐hop relaying systems over extended generalized‐K fading channels

The outage performance of the amplify‐and‐forward relaying strategies over mutually uncorrelated extended generalized‐K fading channels is addressed in this paper. The attention is dedicated to the analyses of the noise‐limited and also interference‐limited environment. The new analytical expression for outage probability of observed relaying system in the presence of thermal noise is derived using the method for approximating equivalent signal‐to‐noise ratio. In addition, the outage performance is studied for the dual‐hop system when only the single dominant co‐channel interference is inherent at the relay and destination node. The correctness of the proposed mathematical derivations is verified by simulations. Copyright © 2014 John Wiley & Sons, Ltd.     

Nd:GdYVO4与Nd:YVO4的激光特性比较

在相同的实验条件下,分别采用平平直腔和V型折叠腔对比了Nd:GdYVO4和Nd:YVO4两种晶体的基频和腔内倍频特性.采用平平直腔在抽运功率为10.64 W时分别获得了5.35 W、6.29 W的1.06 μm基频输出,光-光转换效率达50.3%、59.1%,斜效率达58.1%、68.8%;采用V型折叠腔KTP腔内倍频,在抽运功率为6.71 W时分别获得了1.73 W和2.34 W的稳定倍频绿光输出,光-光转换效率达25.8%、34.9%.比较得出,Nd:GdYVO4-KTP绿光激光器的平均输出功率及稳定性均低于Nd:YVO4-KTP绿光激光器.     

基于单向函数树的多播密钥安全性分析

文章对SMuG草案之一的基于单向函数树(OFT)的密钥管理方案的安全性进行了详细分析,指出OFT方案在实现前向安全和后向安全上的漏洞,提出了可以实现完整的前向安全和后向安全的OFT改进方案。     

机械泵驱动两相回路的储液器控温策略研究

本文阐述了一种机械泵驱动两相回路的储液器的控温原理,并对待选的两种控温策略进行了解释:一种是基于电压的PI控制,另一种是基于功率的PI控制。文中将它们作了近似等效转换,并用SINDA/FLUINT软件进行模拟。结果显示:当控温点上升时,两种不同控制策略的控温效果大体一致;但当控温点下降时,由于基于功率的PI控制策略包含有Peltier的制冷功能,可以比基于电压的PI控制策略更快到达控温点。另外,基于功率的PI控制策略在死区内的跳跃更少,其应当为优先选择的控制策略。     

双程前向近高斯型掺铒超荧光光纤光源的实验研究

研究了输出谱型为近高斯型的掺铒超荧光光纤光源,分析了高斯型光谱的自相干函数和影响平均波长稳定性的因素.采用双程前向光源结构,通过选择铒纤长度获得高斯型光谱输出,同时调节泵浦功率来优化铒纤的本征温度系数对光源的影响,得到铒纤长度10.05 m,泵浦功率为172 mW时,整体光路（除半导体泵浦激光器及其驱动电源）在全温－40 ℃~60 ℃测试条件下平均波长稳定性为66.651 ppm的近高斯型掺铒光纤光源.     

Mutually Pumped Phase Conjugation of Three Incoherent Beams with a Novel Photorefractive Crystal

Ｍｕｔｕａｌｌｙ　Ｐｕｍｐｅｄ　Ｐｈａｓｅ　Ｃｏｎｊｕｇａｔｉｏｎ　ｏｆ　Ｔｈｒｅｅ　Ｉｎｃｏｈｅｒｅｎｔ　Ｂｅａｍｓ　ｗｉｔｈ　ａ　Ｎｏｖｅｌ　Ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅ　ＣｒｙｓｔａｌＭｕｔｕａｌｌｙＰｕｍｐｅｄＰｈａｓｅＣｏｎｊｕｇａｔｉｏ...     

半导体激光泵浦的Nd:YVO4激光器的1.064 μm高效率连续输出

报道了半导体激光端面泵浦的Nd:YVO4激光器获得线偏振的1.064 μｍ激光高效率连续稳定输出。在半导体激光功率为1.5 W时，获得连续输出功率为837 kW的TEM00模，激光器泵浦阈值功率为140 kW，斜率效率达61.5％，光-光转换效率达56％，电-光转换效率达15％。     

预脉冲灯泵钛宝石可调谐激光器

利用预脉冲技术,可减小氙灯放电初始阻抗,使主放电电流脉冲前沿变陡,脉冲包络变窄,峰值变高,泵浦能量集中,有利于灯泵钛宝石激光输出。试验证明,在低能量（４７Ｊ）注入时,电光转换效率提高１８％,输出９５０ｍＪ;在高能量（１１６Ｊ）注入时,效率提高５％,输出能量１８１０ｍＪ。该激光器可调谐范围为６９５～９４０ｎｍ。