NB-IoT物理层上行链路通信技术解析

NB-IoT作为物联网的主要技术,以其容量低、覆盖广、成本低和低功耗等优点在智慧城市建设中扮演着重要角色。主要从频率部署、上行传输方案、上行链路帧结构和上行物理信道几个方面解析,以便让读者更了解NB-IoT技术的物理层上行链路。     

一种CDMA系统反向功率控制的算法

本文简要介绍了基于ＩＳ－９５的ＣＤＭＡ系统反向信道功率控制的原理及其算法实现，从理论上分析了理想的精确功率控制和非精确功率控制对反向信道爱尔兰容量的影响，并对反向闭环功控算法和外环功率控制算法进行了仿真，得到爱尔兰容量最大的仿真算法。     

LTE网络上行共享信道功控参数优化研究

LTE无线系统中的反向功控主要用来使反向传输适应不同的无线传输环境,减少LTE网络中边缘用户的干扰。主要介绍了LTE反向功控原理,重点研究上行共享信道标称功率参数优化原理。从理论上研究LTE上行共享信道标称功率对LTE网络反向吞吐量的影响,并通过实际网络进一步验证上行共享信道标称功率功控参数对网络反向吞吐量的影响,并提出上行共享信道标称功率功控参数优化的建议。     

基于LabVIEW的LTE物理上行共享信道仿真

第三代移动通信技术的长期演进（LTE）系统上行信道采用单载波频分多址（SC-FDMA）方案,拥有较低的峰值平均功率比（PAPR）。首先介绍了LTE的时隙结构和物理资源,然后在3GPP 211协议的规范下,基于LabVIEW仿真了LTE物理上行共享信道过程,生成SC-FDMA信号。最后,仿真了LTE上行链路中SC-FDMA在不同调制方式和系统带宽中的PAPR。     

NB-IoT物理层下行链路通信技术解析

NB-IoT作为物联网的主要技术,以其容量低、覆盖广、成本低和低功耗等优点在智慧城市建设中扮演着重要角色。文章主要介绍了NB-IoT技术物理层下行链路的一些知识点,分析了NB-IoT的物理层结构。     

OFDM-FDMA Scheme for the Uplink of a Mobile Communication System

The Orthogonal Frequency Division Multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA and CDMA approaches with the OFDM modulation procedure which is particularly important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting subcarrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM transmission signal. A specific OFDM-FDMA uplink procedure is proposed and will be designed in this paper which can be seen as a combination of a specific subcarrier spreading scheme and subcarrier selection process. The resulting transmit signal consists of a periodic extension and multiple repetition of all modulation symbols and leads therefore to an extremely low computation complexity in the transmitter. Furthermore, the transmit signal shows simultaneously a constant envelope to avoid any non-linear effects in the amplification process. This uplink scheme can be considered as a trade off between low computation complexity and system performance. Prof. Hermann Rohling is with the Technical University Hamburg-Harburg, Germany where he has developed an international reputation in the field of OFDM transmission techniques. Previously Prof. Rohling was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. His research interests have included Wideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), signal theory, digital radar signal processing, detection, estimation and differential GPS for high precision navigation. Prof. Rohling is a member of Informationstechnische Gesellschaft (ITG), German Institute of Navigation (DGON) and a senior member of IEEE. He is chairman of the August 2005 International OFDM Workshop (InOWo 2005) in Hamburg, Germany. Martin Stemick received the Dipl.-Ing. degree in electrical engineering from the Technical University Hamburg Harburg (TUHH), Germany in 2004. Currently, he is a Ph. D. student and belongs to the scientific staff of the Department of Telecommunications, TUHH, Hamburg, Germany. His research interests include wireless OFDM-systems, with a current emphasis on resource allocation and equalization techniques.     

基于分布式检测和协作的自适应频谱感知机制

对当前备受关注的认知无线电多点协作频谱感知技术进行了系统归纳与总结.对频谱感知基本问题进行研究,指出了低信噪比情况下单节点检测存在的局限性;接着着重对基于能量检测的多点协作检测技术和多种数据合并算法等最新的研究情况进行了介绍和评价;最后提出了一种具有自适应优化功能的协作频谱感知机制,对控制信道和检测判决信道采用两种控制方式,采用较为稳健的拓扑控制方式,提高了检测网络的稳定性和运作效率.     

An Enhanced Link Adaptation Scheme Based on Cooperative Interference Prediction for MIMO-OFDM Systems

Dynamic inter-cell interference (ICI) causes channel quality indicator mismatch such that system throughput is reduced. In this paper, an enhanced link adaptation scheme based on cooperative interference prediction is proposed to reduce the mismatch. The scheme predicts the dynamic ICI within a cluster of base stations (BSs) for improving the link adaptation accuracy. With the dynamic ICI prediction, more accurate modulation and coding scheme can be selected without increasing the overhead over the air. System level simulations show that the proposed scheme significantly improves the system spectral efficiency (SE), especially the cell-edge SE.     

Cooperative Relaying Scheme for Orthogonal Frequency and Code Division Multiple Access Uplink System

Orthogonal frequency and code division multiplexing (OFCDM) which can be extended orthogonal frequency and code division multiple access (OFCDMA) has a good performance, because it can mitigate multi path interference while maintaining high data rate. Furthermore, cooperative OFCDM relaying system provides these advantages, and this system can effectively use the limited resource with respect to data rate and each terminal’s energy efficiency. Therefore we proposed cooperative OFCDMA relaying uplink system because of the user’s requirement of the high data rate at uplink. However, a throughput performance decreases when this system employs many relays in case of each relay allocated code channel to separate each relay’s signal. Therefore, in this paper, we present that the proposed system combines cyclic delay diversity due to complement throughput performance problem. DF (Decode-and-Forward) is assumed in this paper. It is considered that the users which want to send data to BS only decode the data from other users. In addition to that, we propose the adaptive cooperative communication for the OFCDMA uplink system. The proposed adaptive system can easily select the cooperative relay.     

AF-DSTC协同通信的节点选择策略研究

协同通信的节点选择问题是建立无线协同网络的一个关键问题,提出了一种AF-DSTC协同通信模型的分布式节点选择策略,通过对接收信噪比表达式的推导,以最大化接收端信噪比为基础,建立了一个仅与候选节点自身信道条件有关的选择函数,通过各候选节点的分布式运算来选择最优的协同节点。理论分析和仿真结果证明,该策略能够在性能上逼近理论最优的穷尽查找方法,并且能极大地减少实现复杂度。     

一种正交码时分多子信道扩谱方案及其在卫星通信中的应用

文中从提高卫星通信的抗干扰能力出发，基于M-ary扩频、直接序列扩频、跳频及正交频分复用等技术思想，提出了一种正交码时分多子信道扩谱调制（OC-TDMSCSSM）新技术，建立了数学模型，推导了信号格式，给出了实验系统的输出信号频谱，分析了其在加性白高斯噪声信道下误码率性能。理论分析与仿真表明，该方案与DS／FH系统相比，具有良好的误码性能及较强的抗干扰能力。     

Adaptive Channel Estimation Scheme Based on LTE Uplink in V2V Environments

Wireless Personal Communications - Vehicle communication can facilitate efficient coordination among vehicles on the road and enable future vehicular applications such as vehicle safety...     

一种变结构抗梳状谱干扰的通信体制

当代的电磁环境对通信抗干扰的要求不断提高,必须不断探索更有效的抗干扰方法以提高通信性能。在此背景下针对高斯信道提出一种变结构抗常见梳状谱干扰的通信体制,该方法主要利用双极性脉冲扩展二元相移键控调制的优势,在不同的信道环境下选择不同的调制方式并调节相应的调制参数。通过仿真分析可以预见,在梳状谱干扰通信信道下,该通信体制能够以较小的代价获得较好的抗干扰效果。     

A Proposed H-STCDD Scheme in Cooperative Communication System

In this paper, the hierarchical space time cyclic delay diversity (H-STCDD) scheme is proposed. Proposed scheme uses hierarchical modulation and achieves approximately full rate. It also uses a cyclic delay diversity scheme, which improves the benefit of channel coding particularly in high SNR environment between source to relay and source to destination. According to simulation result, proposed scheme has up to 2.2 dB better BER performance than conventional cooperative scheme at BER of 10^?3 and has similar BER performance with the STCDD scheme particularly in high SNR environment between source to relay and source to destination. Throughput of the proposed scheme is better than those of other cooperative schemes. Therefore proposed scheme is more efficient than other cooperative scheme and can be efficiently used in high SNR environment between source to relay and source to destination.     

广电网双向改造中降低上行通道噪声的方案选择

HFC网络回传噪声的“漏斗”效应及传输速率一直严重制约着广电网双向传输业务的发展,基于移动通信CDMA技术的S—CDMA则非常圆满地解决了这两个问题,对S—CDMA技术在广电网双向改造中的应用进行了简要论述。     

A Generic Quantitative Approach to the Scheduling of Synchronous Packets in a Shared Uplink Wireless Channel

The scheduling logic at the base station of a shared wireless medium supports time-dependent (synchronous) applications by allocating timely transmission grants. To this end, it must take into account not only the deadlines of the pending packets, but also the channel conditions for each potential sender, the requirements of nonsynchronous applications, and the packet retransmission strategy. With respect to these factors, we identify three scheduling scenarios and show that the scheduler logic faces a different challenge in addressing each of them. We then present a generic scheduling algorithm that translates all the factors relevant to each scenario into a common profit parameter, and selects the most profitable transmission instances.     

Uplink Resource Sharing and Power Management Scheme for an Underlay D2D Communication

Wireless Personal Communications - With the implementation of device-to-device (D2D) communication in primary cellular networks, there will be notable benefits such as increase in cellular...     

分布式协作通信网络中一种新的跨层设计方案

 提出了一种新的跨层设计方案,即选择中继重传方案(SN-RT,selective-node-based retransmission scheme).它把物理层中的协作分集技术和数据链路层中的自动请求重传(ARQ)协议有效地结合起来.在重传过程中,依据中继与目的节点间链路的瞬时信噪比选择一个最佳中继,联合源节点进行Alamouti空时编码.在Rayleigh衰落环境和MPSK调制下,给出了确切的吞吐量表达式.结果显示,相比于固定中继重传方案(FN-RT,fixed-node-based retransmission scheme),SN-RT跨层方案能明显进一步提升系统吞吐量.