CDMA EV-DO反向链路控制算法与功率控制的结合

EV—DO是CDMA3G的一种高速数据传输技术，它具有独特的反向链路媒体介入控制算法机制，可以参与调整基站反向链路的状况．以优化小区的反向链路情况。除此之外，EV—DO仍然支持反向功率控制。结合两者的特点，共同优化小区反向链路、提高服务质量，是一个需要研究的方向。     

一种CDMA EVDO系统负荷算法的优化设计

CDMA EVDO系统是一种高速数据传输系统,数据传输本身具有传输突发性和传输速率波动大的特点.同时,由于CDMA EVDO系统前向采用满功率时分复用方式,只有反向采用码分复用方式,所以对于链路负荷的控制只集中在反向链路过载控制上面.针对数据系统,负荷控制算法的难点在于反向链路数据的突发性对系统造成的干扰,以及如何平衡系统吞吐量与抑制反向干扰.针对现有负荷算法自身的特点,文中设计了多条件下的对比测试实验,通过对测试数据进行分析,结合现有算法设计文中提出了一种切实可行的优化负荷算法,能够弥补现有负荷控制算法的不足.     

智能手机能拍出数码单反相机质量的照片吗?自己判断...

为了使智能手机拍照达到单反相机的效果,可以采用添加DSP的方法来改善ISP的图像处理.该方法有诸多好处,例如可以提供WRGB到RGB转换、失真校正、视频防抖和其他ISP增强功能;还可以实现许多其它功能,显著提高静态图像和视频片段的质量,如低光增强、HDR和超分辨率;另外降低了功率等.     

WCDMA功率控制技术的研究与实现

介绍了功率控制技术的作用和分类,以及宽带码分多址(WCDMA)系统反向闭环功率控制的技术标准和组成部分,分析得出了WCDMA系统反向功率控制实现的定时限制条件.讨论了影响功率控制技术性能的几个关键因素:信扰比(SIR)估计精度、步长选择、功控比特传输错误及功控时延等,并给出了仿真曲线和结果分析.最后给出了WCDMA系统前、反向功率控制技术基于FPGA的实现结构框图和测试结果.     

1xEV-DO与HSDPA技术分析与介绍

EV-DO和HSDPA的特点1xEV-DO是CDMA2000标准系列中专门提供高速分组数据业务的无线标准通信技术。与CDMA20001x相比,1xEV-DO技术有效地解决了数据业务在空中接口,特别是前向链路的传输瓶颈问题。目前CDMA20001x的峰值速率是153.6Kbps/单载波,而1xEV-DO Rev0、Rev A的前向链路速率分别高达2.4Mbps、3.072Mbps/单载波。1xEV-DO反向链路采用了反向导频、功率控制和速率控制等技术。反向导频技术使基站可以对终端进行相干解调,获得更大的接收增益;反向速率控制和功率控制技术的结合使基站对终端、系统负荷控制手段更灵活,更有…     

CDMA反向闭环功率控制仿真研究

反向闭环功率控制是CDMA通信系统中十分重要的一项技术。本文对CDMA闭环功率控制理论进行仿真研究及仿真结果作分析。     

CDMA蜂窝系统中基于模糊神经网络的反向链路功率控制

CDMA是一个干扰受限系统,反向链路功率控制对于克服“远近效应”和增加系统容量是非常重要的.本文提出了一种基于模糊神经网络(FNN)的自适应闭环功率控制算法,该算法动态地调整功率控制增量,使基站接收到的每个用户的发射功率相等.仿真结果表明,由于模糊神经网络能够较好地识别反向链路的时变特性,FNN功率控制算法比传统的固定步长功率控制方法取得了更好的控制性能和更大的系统容量.而且,FNN能够通过神经网络训练自动地调整隶属度函数和模糊规则,从而适合于实现在线系统识别和自适应控制.     

HDR电视系统关键技术研究

HDR是广播电视发展的一个主要方向,构建完善的端到端电视系统,是推动HDR电视发展的重要基础.本文首先介绍了HDR电视系统的基本概念和技术特征,然后立足于我国HDR电视的发展现状,研究分析了HDR电视系统采集、编辑、播出、传输、接收和显示各环节的关键技术.     

CDMA系统中的功率控制

功率控制是CDMA移动通信系统中最为重要的核心技术之一。该文主要介绍CDMA系统反向链路和前向链路的各种功率控制技术。首先介绍功率控制对于CDMA系统的重要性及功率控制的分类，然后分别介绍CDMA系统反向链路和前向链路的功率控制算法。     

索尼以强大阵容参展CCBN2016

2016年3月24～26日,索尼中国专业系统集团秉持“超越界限、定义未来”(Beyond Definition)的理念参展CCBN2016,着重展出4K摄像机的全线产品及部分主流高清应用方案,包括: 作为未来4K技术的发展方向,索尼展出了4K HDR技术,不但现场实时信号可以输出4K HDR图像,在后期制作中也可以得到4K HDR素材,在现场还有SDR和HDR素材的直观对比,方便观者对4K HDR直观的了解.     

HDR satellite codec with concatenated multilevel codes

The performance of a high data rate (HDR) codec based on a multidimensional modulation code derived from multilevel codes is evaluated for a satellite channel. The codec reliably supports HDR transmission for broadband ISDN over a 72 MHz satellite transponder and is designed to be used with an 8 PSK modem. Results show that significant coding gain with higher spectral efficiency can be achieved compared to uncoded QPSK     

Channel estimation and error correction for UWOC system with vertical non-line-of-sight channel

Recently, underwater wireless optical communication (UWOC) system has placed more attention towards increasing data rate, high accuracy, higher bandwidth and providing highly secured transmission. Generally, light propagation in underwater medium is disturbed due to some degrading effects such as turbulence, scattering and absorption which will degrade the performance. Therefore, channel estimation is essential and need to adapt suitable correction techniques that compensate the errors due to those effects. In this work, channel estimation and error correction technique are proposed for the UWOC system with vertical non-line-of-sight channel based on MIMO-OFDM approach. Initially, input sequence error is eliminated by HVD Turbo coding method and error rectified signal is modulated with M-ary OAM-PPM modulation technique. Modulated signal is transmitted through Vertical NLOS channel. During transmission, the signal undergoes scattering, absorption and channel fading. In receiver side, channel characteristics are estimated by invariant embedding method. Finally, estimated signal is demodulated and decoded by same techniques. MATLAB environment is used to implement the proposed work. Resultant performances like channel capacity, BER, SNR, data rate, receiving power and MSE for different water types like pure sea water, ocean water, costal water and turbid water are compared and results are examined.

     

Resource Allocation in High Data Rate Mesh WPAN: A Survey Paper

IEEE 802.15.3 High data rate wireless personal area networks (HDR WPANs) have been developed to communicate with devices within 10 m at high speed. A mesh network made up of a parent piconet and several child piconets can support multi-hop communications. Wireless mesh networks (WMNs) have been expected to be the ultimate solution for the next decade wireless networking, showing rapid progress and many new inspiring applications. The international standardization organizations formed working groups to address the problem of standardization for WMNs. These groups were the IEEE 802.15.5 (mesh extensions for WPANs),the IEEE 802.11s (mesh extensions for WLANs), and the IEEE 802.16a (mesh extensions for WiMAX). The IEEE 802.15.5 standard is the standard which defines specifications for including multi-hop functionality in the legacy 802.15.3 and 802.15.4 low data rate (LDR) WPAN networks. The impetus for a WPAN to operate in a mesh topology is to increase the network coverage without increasing the transmit power, to increase the route reliability via route redundancy, self-configuration, and efficient use of device battery life. In the case of meshed WPANs, multiple WPAN clusters compete for channel time in a shared superframe. Therefore, it is essential to determine the channel time requirements of each cluster with a certain number of devices and to determine how these clusters can compete to the shared channel time. In this paper, we investigate the different resource allocation mechanisms related to the meshed HDR WPANs for the 802.15.3 and the 802.15.5 standards. We introduce the single hop and the multi-hop IEEE 802.15.3 WPAN architectures. This is followed by the introduction of the IEEE 802.15.5 standard that provides the mesh capabilities for extending the coverage area of HDR WPANs. The current on-going research issues for resource allocation, including beacon interference, reservation collision etc., in both meshed 802.15.3 and 802.15.5 are alluded to.     

Understanding and Improving the Spatial Reuse in Multihop Wireless Networks

The importance of spatial reuse in wireless ad-hoc networks has been long recognized as a key to improving the network capacity. In this paper, we show that (i) in the case that the achievable channel rate follows the Shannon capacity, spatial reuse depends only on the ratio of the transmit power to the carrier sense threshold; and (ii) in the case that only a set of discrete data rates are available, as a control knob for sustaining achievable data rates, tuning the transmit power provides more sophisticated rate control over tuning the carrier sense threshold, provided that there is a sufficient number of power levels available. Based on the findings, we then propose a decentralized power and rate control algorithm to enable each node to adjust, based on its signal interference level, its transmit power and data rate. The transmit power is so determined that the transmitter can sustain a high data rate, while keeping the adverse interference effect on the other neighboring concurrent transmissions minimal. Simulation results have shown that, as compared to existing carrier sense threshold tuning algorithms, the proposed power and rate control algorithm yields higher network capacity.     

Peak-to-mean power control in OFDM, Golay complementary sequences,and Reed-Muller codes

We present a range of coding schemes for OFDM transmission using binary, quaternary, octary, and higher order modulation that give high code rates for moderate numbers of carriers. These schemes have tightly bounded peak-to-mean envelope power ratio (PMEPR) and simultaneously have good error correction capability. The key theoretical result is a previously unrecognized connection between Golay complementary sequences and second-order Reed-Muller codes over alphabets Z₂h. We obtain additional flexibility in trading off code rate, PMEPR, and error correction capability by partitioning the second-order Reed-Muller code into cosets such that codewords with large values of PMEPR are isolated. For all the proposed schemes we show that encoding is straightforward and give an efficient decoding algorithm involving multiple fast Hadamard transforms. Since the coding schemes are all based on the same formal generator matrix we can deal adaptively with varying channel constraints and evolving system requirements     

多用户自适应调制及功率分配

为了满足新一代无线通信系统的高数据速率、高频谱效率的通信要求,本文提出了基于正交频分复用(OFDM)技术的自适应调制、子载波分配及功率分配方法,它采用的多址方式是码分多址(CDMA).通过上行信道返馈获知下行信道参数,在一定服务质量要求(QoS)、一定传输速率下,通过本文的优化分配算法,使系统的频谱利率最高,所有子载波的发射功率之和最小.将本方法应用在下行同步信道环境下,系统具有较快的收敛速度;与非自适应OFDM比较,用户发射功率有较大降低,是一种工程可适用方案.     

Performance Evaluation for Medium Voltage MIMO-OFDM Power Line Communication System

Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)scenario due to the fast development of in-home PLC.The aim of this paper is to evaluate the link-level performance of a medium voltage(MV)MIMO-OFDM communication system based on transmission link under underground power line channel.The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise.We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city,Jiangxi province,China.Based on the measured channel,we design the frame structure based on an IEEE standard for broadband over power line networks[1]to support MV MIMO-OFDM transmission.According to designed frame structure,we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance.Finally,the link-level performance for both spatial multiplexing and spatial diversity are evaluated.Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.     

多路高速光纤图像传输系统设计及实现

设计了基于内嵌高速收发器RocketIO的现场可编程门阵列(FPGA)的多路光纤图像传输系统,能够对Camera Link接口模式的高速大容量图像数据进行实时传输。详细给出了系统总体结构设计、硬件实现中需要注意的问题和若干关键的软件功能模块,包括并口转换模块、图像传输控制逻辑和RocketIO的设计和配置。实验显示传输系统的三通道有效数据传输速率达7.2Gb/s,传输线路稳定可靠,满足光电探测设备对传输带宽的需求。     

A flexible downlink scheduling scheme in cellular packet data systems

Fast downlink scheduling algorithms play a central role in determining the overall performance of high-speed cellular data systems, characterized by high throughput and fair resource allocation among multiple users. We propose a flexible channel-dependent downlink scheduling scheme, named the (weighted) alpha-rule, based on the system utility maximization that arises from the Internet economy of long-term bandwidth sharing among elastic-service users. We show that the utility as a function of per-user mean throughput naturally derives the alpha-rule scheme and a whole set of channel-dependent instantaneous scheduling schemes following different fairness criteria. We evaluate the alpha-rule in a multiuser CDMA high data rate (HDR) system with space-time block coding (STBC) or Bell Labs layered space-time (BLAST) multiple-input multiple-output (MIMO) channel. Our evaluation shows that it works efficiently by enabling flexible tradeoff between aggregate throughput, per-user throughput, and per-user resource allocation through a single control parameter. In other words the Alpha-rule effectively fills the performance gap between existing scheduling schemes, such as max-C/I and proportional fairness (PF), and provides an important control knob at the media-access-control (MAC) layer to balance between multiuser diversity gain and location-specific per-user performance.     

Power control and capacity analysis for a packetized indoormultimedia DS-CDMA network

This paper proposes a packetized indoor wireless system using direct-sequence code-division multiple-access (DS-CDMA) protocol. The indoor radio environment is characterized by slow Rayleigh fading with or without lognormal shadowing. The system supports multimedia services with various transmission rates and quality of service (QoS) requirements and allows for seamless interfacing to asynchronous transfer mode (ATM) broadband networks. All packets are transmitted with forward error correction (FEC) using convolutional code for voice packets and Bose-Chaudhuri-Hocquenghem (BCH) code for data packets with an automatic retransmission request (ARQ) protocol and for video packets without ARQ. A queueing model is used for servicing data transmission requests. A power control algorithm is proposed for the system, which combines closed-loop power control with channel estimation to give the best performance. The cell capacity of each traffic type and various multimedia traffic configurations in both single-cell and multiple-cell networks are evaluated theoretically under the assumption of perfect power control. The effect of power control imperfection on the capacity using the proposed power control algorithm is investigated by computer simulation