基于单射频的无线Mesh网多信道方法

无线网状网(Wireless Mesh Network,WMN)是一种新型的分布式宽带无线网络结构。典型的移动Ad Hoc网络具有节点移动性小、受电池动力限制和用户带宽需求大等特点,从而导致传统单信道的Ad Hoc结构不再满足WMN用户的需求。为了提供更大的带宽,多信道技术得到越来越多应用。探讨了WMN的网络结构与特点,对现有几种典型的多信道技术进行了比较,提出了一种基于单射频的无线Mesh网多信道的设计方案,不同网关节点所代理的节点使用不同的信道进行通信,从而避免了不同子网节点之间的信道干扰。通过NS2的仿真与分析表明,该方法在特定环境下的网络性能是传统单射频单信道方法的2倍。

LTE与2G/3G系统互操作研究

为确保现有移动用户良好的业务体验感知,LTE对不同系统间的互操作做了较为完备的规定,但带来了现网设备复杂的升级和高昂的投入。本文通过对其他运营商和技术制式实现方法的介绍,提出了LTE建设初期与2G/3G系统间互操作的要求。

利用SAA的无线Mesh网络容量增加方法

为了在不增加网络节点和网关下提高无线Mesh网络的容量,提出一种基于模拟退火算法(Simulated Annealing Algorithm,SAA)和整数线性规划(Integer Linear Programming,ILP)模型的容量增加方法。首先,将单射频单信道无线Mesh网络的拓扑结构建模成一个有向图。然后,在考虑干扰约束下,将容量增加问题构建成一个ILP模型。然后,利用模拟退火算法快速选择出可增加容量的链路。最后,通过ILP模型来增加这些链路的容量,使网络总吞吐量达到最大。仿真结果表明,提出的方法有效提高了网络吞吐量,且能够在较短时间内找到最优解。

基于空时频三维稀疏字典的单通道CSA多参数联合估计

针对单射频通道的压缩感知阵列(compressed sensing array,CSA),提出了一种基于稀疏重构的多参数联合估计方法.首先利用目标在空域和频域上的稀疏特性,以及线性调频(LFM)信号的自相关特性,构建了一种空-时-频三维稀疏字典用于回波信号的稀疏表达;然后基于压缩感知理论对回波信号的投影向量进行稀疏重构,能够直接估计出目标的速度、角度以及距离信息.仿真结果验证了多目标场景下本文所提出的多参数联合估计算法的有效性.

VoLTE发展与运营商部署策略分析

VoLTE(基于IP多媒体子系统的语音业务)技术的应用是LTE发展的主要趋势之一,是LTE网络的最终语音解决方案。VoLTE的部署对于促进LTE网络演进具有重要作用,何时部署VoLTE以及如何部署Vo LTE对于运营商的业务发展具有重要意义。文章介绍VoLTE业务及产业链发展情况,对CSFB(电路域回落)、SVLTE(LTE与语音网同步)、OTT(Over the Top)等几种VoLTE部署前的语音过渡方案进行分析,指出运营商的网络现状及部署VoLTE面临的主要问题,对比几种过渡方案的特点,探讨运营商部署VoLTE的策略。

A Low-Power,Single-Poly,Non-Volatile Memory for Passive RFID Tags

Single-poly,576bit non-volatile memory is designed and implemented in an SMIC 0.18μm standard CMOS process for the purpose of reducing the cost and power of passive RFID tag chips. The memory bit cell is designed with conventional single-poly pMOS transistors, based on the bi-directional Fowler-Nordheim tunneling effect, and the typical program/erase time is 10ms for every 16bits. A new ,single-ended sense amplifier is proposed to reduce the power dissipation in the current sensing scheme. The average current consumption of the whole memory chip is 0.8μA for the power supply voltage of 1.2V at a reading rate of 640kHz.

Ethanol injection is highly effective for hepatocellular carcinoma smaller than 2cm

AIM： To analyze the long-term prognosis in a cohort of western cirrhotic patients with single hepatocellular carcinoma treated with ethanol injection.METHODS： One-hundred forty-eight patients with solitan/hepatocellular carcinoma were enrolled. The tumor diameter was lower than 2 cm in 47 patients but larger in the remaining 101 patients. The impact of some pre- treatment clinical and laboratory parameters and of tu- mor recurrence on patients＇ survival was assessed.RESULTS： Among the pre-treatment parameters, only a tumor diameter of less than 2 cm was an independent prognostic factor of survival. The occurrence of new nodules in other liver segments and the neoplastic portal invasion were linked to a poorer prognosis at univariate analysis. Patients with a single hepatocellular carcinoma smaller than 2 cm showed a better 5-year cumulative survival （73.0% vs 47.9%） （P = 0.009）, 3-year local re- currence rate （29.1% vs 51.5%） （P = 0.011）, and 5-year distant intrahepatic recurrence rate （52.g% vs 62.8%） （P = 0.054） compared to patients with a larger tumor. CONCLUSION： The 5-year survival rate of patients with single hepatocellular carcinoma 〈 2 cm undergoing ethanol injection is excellent and comparable to that achieved using radiofrequency ablation.

Low Complexity Remote Radio Unit Selection and Adaptive Bit Partition Algorithm in Cooperative Distributed MIMO Systems

For multi-user cooperative Distributed MIMO (D-MIMO) systems, a low-complexity Remote Radio Unit (RRU) selection and adaptive bit partition algorithm is proposed to maximize the transmission Signal-to-Interference-Noise Ratio (SINR). Considering limited feedback, each user can adaptively select an RRU cluster to maintain the best communication quality. Under this condition, only one codebook is utilized for quantizing the Channel State Information (CSI) with variable dimensions, which effectively reduces the codebook storage amount. Furthermore, we propose an adaptive bit partition algorithm, which separately allocates bits to quantize the desired channels and interference channels. The optimal solution is achieved through an optimization theory to minimize the effect of inter-cell interference. Simulation results show that the proposed algorithm substantially improves the performance compared to other non-adaptive schemes.

Low Power Single-Chip RF Transceiver for Human Body Cormunication

Human body communication is proposed as a promising body proximal comanunication tech- nology for body sensor networks. To achieve low power and slmll volume ill the sensor nodes, a Ra-dio Frequency （RF） application-specific integrated circuit transceiver tbr Human Body Commnunication （HBC） is presented and the characteristics of HBC are investigated. A high data rate On-Off Keying （OOK）/Frequency-Shift Keying （FSK） modulation protocol and an OOK/FSK delrodulator circuit are introduced in this paper, with a data-rate-to-carrier-frequency ratio up to 70%. A low noise amplifier is proposed to handle the dynamic range problem and improve the sensitivity of the receiver path. In addi-tion, a low power autonmatic-gain-control system is realized using a novel architecture, thereby render-ing the peak detector circuit and loop filter unneces-sary. Finally, the complete chip is fabricated. Simula-tion results suggest receiver sensitivity to be-75 dBm. The transceiver shows an overall power con-smxption of 32 mW when data rate is 5 Mbps, de-livering a P1dB output power of - 30 dBm.

Efficient Scheme for One-Way Quantum Computing with Radiofrequency SQUID Qubits by Adiabatic Passage

We proposed an efficient scheme for constructing a quantum controlled phase-shift gate and generating thecluster states with rf superconducting quantum interference devices (SQUIDs)coupled to a microwave cavity throughadiabatic evolution of dark eigenstates.During the operation,the spontaneous emission is suppressed since the rf SQUIDsare always in the three lowest flux states.Considering the influence from the cavity decay with achievable experimentalparameters,we numerically analyze the success probability and the fidelity for generating the two-SQUID maximallyentangled state and the controlled phase-shift gate by adiabatic passage.

A method to estimate crop effects at higher frequencies by modeling and microwave radiometric data

To use the 0th-order τ-ω model to retrieve soil moisture from radiometric data at frequencies higher than the C band, the characteristics of the effective single scattering albedo ω and the opacity rof vegetation must be studied. In this paper, the co and r values of corn for the C, X, and Ku bands were retrieved by matching the simulations of a high-order matrix-doubling model to the τ-ω model. First, the brightness temperature of the matrix-doubling was validated by a truck-mounted radiometer in a field experiment, where the vegetation emission contributions were validated with aluminum foil to mask the soil emission. Then an emissivity database of corn fields for different growing seasons was established for a variety of soil conditions. With the transmissivity of corn determined from the database, the effective single scattering albedos of corn for different heights at the C, X, and Ku bands and at a 55° viewing angle were derived. To verify the accuracy of the derived co and τ values, we used SMEX02/PSR aircraft data and the Qp model to retrieve the soil moisture; the RMSE between the retrieval and the measurements was 4.76% at the C band and 5.36% at the X band.

A VHF band HTS filter based on modified single-spiral resonators for radio astronomy application

A 10-pole quasi-elliptic bandpass filter （BPF） with a relatively wide passband in the very high frequency （VHF） band was de- signed and fabricated using YBCO thin films deposited on both sides of a LaAIO3 substrate. Single-spiral resonators were modified to generate strong coupling and reduce the parasitic coupling, We analysed the coupling polarities between the modi- fied resonators. Two pairs of attenuation poles were introduced in the filter for sharp cut-off response. The measurements showed that the filter has a centre frequency of 255.8 MHz, fractional bandwidth of about 12.3%, insertion loss of smaller than 0.265 dB, and the return loss in the passband of better than 17.5 dB, in zood a^reement with computer simulations.

Electromagnetically Induced Transparency and Absorption of A Monochromatic Light Controlled by a Radio Frequency Field

Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency （RF） field. Both electrom^gnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.

Frequency-domain terahertz transmission spectra of Mn_3 and Mn_(12) single-molecule magnets

Frequency-domain terahertz transmission spectra of Mn3 and Mn12 single molecule magnets （SMMs） have been measured at different temperatures, and hence the anisotropic parameters O2 and D4 of the spin Hamiltonian H = D2Sz^2 ＋ D4Sz^4 have been calculated. For Mn12 SMM, D2=-10.9 GHz and D4=-2.59×10^-2 GHz, while for Mn3 SMM, D2=-22.0 GHz and D4 can be con- sidered negligible. This suggests Mn3 SMM can be considered as a simpler and more suitable candidate for magnetic quantum tunneling research.