基于波长间插复用的载波抑制双边带调制的ROF系统的研究

本文提出了一种基于波长间插复用的载波抑制双边带(ODSB-SC)新型射频光纤传输(ROF)系统,该系统采用马赫曾德尔调制器(MZM)实现了ODSB-SC调制信号,通过两个马赫曾德尔干涉仪(MZI)的级联实现了三路光射频(RF)信号的解复用。理论分析了系统的工作原理,采用光子模拟软件设计出了一个10GHz、15GHz和25GHz的三路射频(RF)信号经过波长间插复用的ODSB-SC的ROF系统,给出了三路RF信号复用及解复用前后的频谱图、Q值及眼图,讨论了MZI的延时时间对解复用出来的RF复用信号性能的影响,得出了两个MZI的最佳延时时间τ1、τ2分别为0.1ns、0.06ns的结论。

基于频率间插复用和SSB的DWDM-RoF系统

设计了一个基于频率间插复用的DWDM-RoF系统,将相邻的多个单边带调制的信道交织在一起,使每个信道载波与边带之间的空闲频段得到利用,大大提高了带宽利用率。同时提出一种使用AWG的解复用器结构。实验对四个间隔为25GHz的信道进行频率间插复用,毫米波频率为60GHz,携带2Gb/s的数据用光纤传输50km,结果表明,系统信道间串扰对系统影响不大,同时验证了所设计的解复用器可行。

平顶级联马赫-曾德尔型间插复用器的研制

对级联Mach-Zehnder干涉仪进行了理论分析和计算机模拟,并成功制作了50 GHz的平顶二级级联Mach-Zehnder干涉仪型间插复用器,整个结构由3个耦合器和2组干涉臂组成.实际得到的光谱分布与计算机模拟的曲线基本相符,1 dB带宽达到了0.304 nm,占复用波长间隔的76%,得到了比较理想的平顶型的光谱分布,整个器件的附加损耗约为1 dB.

基于波长间插复用的载波抑制双边带射频光纤传输系统

提出了一种基于波长间插复用的载波抑制双边带(ODSB-SC)射频光纤传输(ROF)系统,该系统采用马赫曾德尔调制器(MZM)实现了ODSB-CS调制信号,采用马赫曾德尔干涉仪(MZI)实现了两路RF信号的解复用,并采用光子模拟软件设计出了一个15GHz和25GHz的两路射频(RF)信号经过波长间插复用的ODSB-SC的ROF系统,讨论了MZI的延时时间对解复用出来的RF复用信号性能的影响。

基于帧间数据复用的稀疏CNN加速器设计

卷积神经网络(CNN)被广泛应用于目标检测等任务场景中。然而,传统的CNN加速器只对单帧图像进行加速处理,没有对视频任务中连续帧之间存在的数据冗余特性进行加速处理。目前利用帧间数据复用的CNN加速器存在稀疏度低、模型规模大以及计算复杂度高的缺点。为解决上述问题,通过可学习步长的低精度量化方法提高差分帧的稀疏度,提出量化因子2的幂次约束实现一个硬件友好的量化方法。使用Winograd算法降低卷积算子的计算复杂度,并在此基础上提出输入通道位图压缩方案,利用激活和权重的稀疏性跳过无效的零值计算。基于YOLOv3-tiny网络,使用ImageNet ILSVRC2015 VID部分数据集和DAC2020数据集,在现场可编程门阵列(FPGA)平台上对所提出的量化方法和稀疏CNN加速器进行验证。实验结果表明,在平均精度均值损失小于2%的条件下,该量化方法实现了4 bit位宽的全整形量化。得益于帧间数据复用,所设计的稀疏加速器实现了814.2×10^(9)operation/s的性能和201.1×10^(9)operation/s/W的能效比,与其他基于FPGA的同类型加速器相比,所设计的加速器提供了1.77~8.99倍的性能提升以及1.91~5.56倍的能效比提升。

漫谈各种复用技术

介绍各种复用技术 ,包括频分复用、时分复用和码分复用等 。

医院血透中心设计方法研究

本文通过细说透析治疗间、水处理间、复用间等用房的功能意义及相互关系，归纳总结了医院血透中心设计方法。

New subspace algorithm for blind channel estimation in OFDM systems

In order to increase the transmission efficiency,a subspace-based algorithm for blind channel estimation using second-order statistics is proposed in orthogonal frequency division multiplexing (OFDM) systems.Because the transmission equation of OFDM systems does not exactly have the desired structure to directly derive a subspace algorithm,the algorithm first divides the OFDM signals into three parts,then,by exploiting the redundancy introduced by the cyclic prefix (CP) in OFDM signals,a new equation with Toeplitz channel matrix is derived.Based on the equation,a new blind subspace algorithm is developed.Toeplitz structure eases the derivation of the subspace algorithm and practical computation.Moreover the algorithm does not change the existing OFDM system,is robust to channel order overdetermination,and the channel zero locations.The performances are demonstrated by simulation results.

从OFC2001会议看DW DM全光网中的无源器件

概述了在 2 0 0 1年 OFC会议上出现的新型光无源器件 ,介绍了光无源器件的最新进展 ,着重分析了几种用于

TRANSMIT ANTENNA SELECTION IN V-BLAST SYSTEM

In order to reduce the cost of Radio Frequency (RF) chains in the spatial multiplexing systems with Vertical-Bell Labs Layered Space-Time (V-BLAST) nonlinear receiver, a novel transmit antenna selection cri-terion is proposed with the motivation of minimizing the Vector Symbol Error Rate (VSER). In the proposed scheme, both the number of substreams and the mapping of substreams to antennas are dynamically adjusted based on the knowledge of channel. Simulation results illustrate that the proposed two-step selection criterion outperforms the existing eigenmode based selection criterion by 0.3dB at a VSER of 10?3.

NAND flash service lifetime estimate with recovery effect and retention time relaxation

A service life model of NAND flash and threshold voltage shift process is proposed to calculate the service life and endurance.The relationships among achievable program/erase(P/E) cycles,recovery time,bad block rate and storage time are analyzed.The achievable endurance and service life of a NAND flash are evaluated based on a flash cell degradation and recovery model by varying recovery time,badblock rate,and storage time.It is proposed to improve the service lifetime of solid state disk by both relaxing the bad block rate limitation and retention time while extending the recovery time.The results indicate that endurance can be improved by 17 times if the storage time guarantee is reduced from 10 a to 1 a with 105 s recovery time inserted between cycles.

Realization of 40 GHz Short Time Windows and Their Applications in High Speed Optical Time Division Multiplexing Systems

Optical Time Division Multiplexing （OTDM） is known to be capable of transmitting single channel high bit rate data stream with low speed electro-optical components. A cost-effective, compact and stable short time window with low insert loss, low phase noise, low timing-jitter and high speed performance is essential for ultra-high speed OTDM systems using phase and amplitude modulation formats. In this paper, we review three promising methods to obtain 40 GHz short time window including Electro-Absorption Modulator （EAM）, Dual-Parallel Mach-Zehnder Modulator （DPMZM） and Fiber Loop-Polarization Modulator （FL-PolM）. Sub-picosecond short pulse source generation, optical time division denlaltiplexing and clock recovery are realized respectively by using the short time window based on the three methods. By using DPMZM based pulse source and EAM based Clock Recovery （CR） and dermltiplexer, error free transmission of 640 Goit/s （160 Gbaud/s Pol-Mux DQPSK） single channel signal over 400 km single mode fiber is proven to be experimentally successful.

NOVEL ICI CANCELLATION ALGORITHM IN OFDM SYSTEMS

The Bit Error Rate (BER) caused by Inter Carrier Interference (ICI) increases greatly with the increase of frequency offset in Orthogonal Frequency Division Multiplexing (OFDM) systems. According to a typical OFDM signal model, this letter proves that the coefficient matrix of ICI is a unitary matrix whose inverse matrix is much easier to get, and then proposes a new ICI cancellation method with less computation complexity by sending typical pilot symbols. Compared with two existing ICI cancellation methods, self-cancellation and windowing cancellation, it is shown that the proposed algorithm can cancel ICI better and overcome the limitation of the two traditional methods.

Rate-aware optimal transmission power analysis in wireless ad hoc networks

The problem of transmission power control in a rate-aware way is investigated to improve the throughput of wireless ad hoc network. The behavior of basic IEEE 802.11 DCF is approximated by the p-persistent CSMA through a Markov chain model. The throughput model takes hidden terminals, muhi-hop flow and concurrent interference into account. Numerical results show that the optimal transmission power derived from this model could balance the tradeoff between spatial reuse and data rate and hence yield maximum throughput.

Narrow-channel-spacing 32-channel AWG multiplexer with an innovative alignment method

A 32-channel 50 GHz spaced arrayed-waveguide grating(AWG) with our innovative configuration has been designed and fabricated.The performance of the device has been fully tested by using a system that consists of a tunable laser light source (TLS), an optical power meter and a polarization controller.The insertion loss (IS) of the device is 4.2-7.4 dB.The crosstalk is about -28 dB.The IS uniformity is less than 3.3 dB.With our configuration,the performance of the device has been enhanced effectively and the difficulty in alignment process has been decreased obviously.

Joint Link Allocation and Rate Assignment Algorithm for Multi-Channel Wireless Networks

This paper presents a link allocation and rate assignment algorithm for multi-channel wireless networks. The objective is to reduce network con-flicts and guarantee the fairness among links. We first design a new network model. With this net-work model, the multi-channel wireless network is divided into several subnets according to the num-ber of channels. Based on this, we present a link allocation algorithm with time complexity O（l^2）to al-locate all links to subnets. This link allocation algo-rithm adopts conflict matrix to minimize the network contention factor. After all links are allocated to subnets, the rate assignment algorithm to maximize a fairness utility in each subnet is presented. The rate assignment algorithm adopts a near-optirml al-gorithm based on dual decomposition and realizes in a distributed way. Simulation results demonstrate that, compared with IEEE 802.11b and slotted see-ded channel hopping algorithm, our algorithm de-creases network conflicts and improves the net-work throughput significantly.

Numerical study and acceleration of LBM-RANS simulation of turbulent flow

The coupled models of LBM （Lattice Boltzmann Method） and RANS （Reynolds-Averaged Navier-Stokes） are more practical for the transient simulation of mixing processes at large spatial and temporal scales such as crude oil mixing in large-diameter storage tanks. To keep the efficiency of parallel computation of LBM, the RANS model should also be explicitly solved; whereas to keep the numerical stability the implicit method should be better for PANS model. This article explores the numerical stability of explicit methods in 2D cases on one hand, and on the other hand how to accelerate the computation of the coupled model of LBM and an implicitly solved RANS model in 3D cases. To ensure the numerical stability and meanwhile avoid the use of empirical artificial lim- itations on turbulent quantities in 2D cases, we investigated the impacts of collision models in LBM （LBGK, MRT） and the numerical schemes for convection terms （WENO, TVD） and production terms （FDM, NEQM） in an explic- itly solved standard k-e model. The combination of MRT and TVD or MRT and NEQM can be screened out for the 2D simulation of backward-facing step flow even at Re = 107. This scheme combination, however, may still not guarantee the numerical stability in 3D cases and hence much finer grids are required, which is not suitable for the simulation of industrial-scale processes.Then we proposed a new method to accelerate the coupled model of LBM with RANS （implicitly solved）. When implemented on multiple GPUs, this new method can achieve 13.5-fold accelera- tion relative to the original coupled model and 40-fold acceleration compared to the traditional CFD simulation based on Finite Volume （FV） method accelerated by multiple CPUs. This study provides the basis for the transient flow simulation of larger spatial and temporal scales in industrial applications with LBM-RANS methods.

CARRIER FREQUENCY OFFSET ESTIMATION FOR INTERLEAVED OFDMA UPLINK BASED ON SUBSPACE PROCESSING

This paper investigates Carrier Frequency Offset (CFO) estimation in the uplink of the Orthogonal Frequency-Division Multiple Access (OFDMA) systems with the interleaved subcarrier assignment. CFOs between the transmitters and the uplink receiver will destroy orthogonality among different subcarriers, hence resulting in inter-carrier interference and multiuser interference. A two-stage frequency offset estimation algorithm based on subspace processing is proposed. The main advantage of the proposed method is that it can obtain the CFOs of all users simultaneously using only one OFDMA block. Compared with the previously known methods, it not only has a relatively low implementation complexity but is also suitable for random subchannel assignment.

Content based error resilience coding using redundant coding, reference frame modification, and mode decision

Quality degradation occurs during transmission of video streaming over the error-prone network. By jointly using redundant slice, reference frame selection, and intra/inters mode decision, a content and end-to-end rate-distortion based error resilience method is proposed. Firstly, the intra/inter mode decision is implemented using macro-block(MB) refresh, and then redundant picture and reference frame selection are utilized together to realize the redundant coding. The estimated error propagation distortion and bit consumption of refresh MB are used for the mode and reference frame decision of refresh MB. Secondly, by analyzing the statistical property in the successive frames, the error propagation distortion and bit consumption are formulated as a function of temporal distance. Encoding parameters of the current frame is determined by the estimated error propagation distortion and bit consumption. Thirdly, by comparing the rate-distortion cost of different combinations, proper selection of error resilience method is performed before the encoding process of the current frame. Finally, the MB mode and bit distribution of the primary picture are analyzed for the derivation of the texture information. The motion information is subsequently incorporated for the calculation of video content complexity to implement the content based redundant coding. Experimental results demonstrate that the proposed algorithm achieves significant performance gains over the LA-RDO and HRP method when video is transmitted over error-prone channel.

Optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing in cognitive radio network

In order to improve the throughput of cognitive radio(CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple users and one fusion center. The frame structure of cooperative spectrum sensing was divided into multiple transmission time slots and one sensing time slot consisting of local energy detection and cooperative overhead. An optimization problem was formulated to maximize the throughput of CR network, subject to the constraints of both false alarm probability and detection probability. A joint optimization algorithm of sensing time and number of users was proposed to solve this optimization problem with low time complexity. An allocation algorithm of cooperative users was proposed to preferentially allocate the users to the channels with high utilization probability. The simulation results show that the significant improvement on the throughput can be achieved through the proposed joint optimization and allocation algorithms.