基于MMX指令实现G.728定点算法优化

ITU-T建议是国际电信联盟于1992年制定的比特率为16kb/s的低延时CELP类语音编码器.G.728AnnexG是其补充定点算法建议.该文首先介绍了G.728定点算法的特点和Intel MMX技术,然后详细讨论了用MMX指令对G.728的LD-CELP定点算法实现优化一些关键技术,最后给出了优化前后算法速度的对比.     

Influence of N2 and O2 annealing treatment on the optical bandgap of polycrystalline Ga2O3:Cu films

Cu-doped Ga₂O₃ thin films were deposited by electron beam evaporation with subsequent annealing at 1000 °C in N₂ and O₂ for 1 h. The influence of the annealing atmosphere on the crystal structure, surface morphology and optical properties of Ga₂O₃:Cu films was investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), and transmittance and photoluminescence (PL) spectroscopy. The optical bandgap deduced from the absorption spectrum was greater for the O₂ annealed than for N₂ annealed samples. In both cases the bandgap was wider than for bulk β-Ga₂O₃. The grain size and surface roughness were sensitive to the annealing atmosphere. Results confirmed that the annealed samples were polycrystalline β-Ga₂O₃ with some amorphous phase. We hypothesize that annealing in oxygen led to recrystallization of the Ga₂O₃:Cu film. Annealing treatment improved the crystal quality of Ga₂O₃:Cu films and the PL intensity of the samples increased.     

关于移动IP区域注册的一些探讨

在移动IP中,每当移动节点发生了切换,改变了转交地址的时候,就需要向家乡代理注册。如果访问网络和移动节点家乡网络的距离较远的话,这些注册的时延就可能比较大。同它相比,区域注册减小了移动节点域内切换时延,降低了到家乡网络的信令开销,减少了分组丢失。本文首先介绍区域注册的过程,分析它存在的一些问题,然后介绍优化途径及相应的技术难题。     

Rate adaptive resource allocation in orthogonal frequency division multiple access system using multi‐objective immune algorithm

Rate adaptive downlink resource allocation in orthogonal frequency division multiple access system is a constraint optimization problem, which is to maximize the minimum data rate of the user subject to constraint that total power cannot exceed a given value. How to handle the constraint is a key issue for constrained optimization problem. Different with the available schemes on constraint handling, the proposed algorithm converts the constraint into an objective. Then, the resource allocation is combined into a multi‐objective optimization problem. An improved multi‐objective optimization algorithm based on artificial immune system is proposed to solve it. The simulation results show that, compared with previous schemes, the proposed algorithm performs remarkable improvement in sum capacity. Copyright © 2013 John Wiley & Sons, Ltd.     

农村有线数字电视转换的另一种技术探索

农村有线电视网络基础比较差,要应对直播卫星和电信的IPTV冲击就必须进行数字化转换,而采用常规的有线电视数字化转换,就必须对有线电视网络进行升级改造。本文通过采用地面国标的单载波调制方式(ADTB-T),在农村有线进行数字电视转换试点的技术探索,探索在农村有线电视网络转换中替代传统的(DVB-C)技术模式,不需要进行有线电视网络改造,就能直接进行数字化转换。取得一些比较好的经验,与广电同仁共同探索分享,加快农村有线电视的数字化转换速度。     

矫正规则散光的光学演示模型研制

目的:研制规则散光眼镜片矫正规则散光的光学演示模型。方法:用几何光学成像演示器直观演示规则散光成像、规则散光透镜成像、规则散光透镜矫正规则散光。结果:直接观察到规则散光和散光透镜的成像状态-散光Sturm光锥及散光透镜矫正规则散光的光学效果。结论:规则散光眼镜片矫正规则散光的光学演示模型能观察到规则散光透镜矫正规则散光的光学效果,便于准确理解规则散光成像、规则散光透镜的成像、规则散光矫正的光学原理。     

迫弹激光引信用脉冲半导体激光电源的设计与应用

设计了适应于迫弹激光近炸引信的小体积、低电压、窄脉宽、高功率的脉冲半导体激光电源.采用电容充放电的模式,选用高速大功率MOSFET管作为开关,设计了相应的高速开关控制电路.激光电源模块的重复频率高达50kHz,常规热电池供电电压条件下的输出脉冲激光峰值功率为9W,光脉冲上升沿为4.2 ns,光脉宽为10 ns,为有效提...     

战术异构网络互联端到端QoS研究

战术异构通信网络的融合,需要更完善的端到端服务质量（Quality of Service,QoS）体系。在研究和分析战术异构通信网特点后,分析总结出战术异构通信网络端到端QoS研究内容,并参考下一代网络QoS框架结构,提出了基于策略的QoS架构模型。最后阐述了所涉及的关键技术,用于解决在战术异构通信网中不同业务在跨网络传输时端到端QoS保证,合理利用无线网络资源,有效提高数据传输性能等问题。     

Performance analysis of uplink spatial multiplexing MIMO MT‐CDMA over multipath fading channels

In this paper, we consider multiple‐input multiple‐output (MIMO) multi‐tone code division multiple access (MT‐CDMA) uplink transmission over multipath fading channels. The zero‐forcing vertical Bell Laboratories layered space‐time architecture (ZF V‐BLAST) algorithm and maximum ratio combining scheme are applied at the receiver. The average bit error rate (BER) expression is derived provided that the number of receive antennas is not less than that of transmit antennas. The BER expression is verified by simulations. Numerical results show that the numbers of transmit and receive antennas have significant effects on the BER performance of the considered system. Spatial and path diversity show different capabilities to improve the BER performance. The MIMO MT‐CDMA system based on the ZF V‐BLAST algorithm is capable of achieving a better BER performance and a higher capacity than the conventional MT‐CDMA system. Copyright © 2011 John Wiley & Sons, Ltd.