共查询到20条相似文献,搜索用时 15 毫秒
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fredric j. harris Elettra Venosa Xiaofei Chen Chris Dick 《Analog Integrated Circuits and Signal Processing》2014,78(3):633-644
In this paper we present a novel application of perfect reconstruction (PR), non-maximally decimated (NMD) filter banks whose assembly gives life to compact digital up converter and digital down converter for combined Third Generation Partnership Protocol, Long Term Evolution radios and Universal Mobile Telecommunications System radios, which are Wideband Code Division Multiple Access based. The design of the PR NMD analysis–synthesis chains in both transmit downlink and receive uplink has been optimized to maximize the performance according to the specific application scenario. In the receive uplink an 80-path, 40-to-1, PR NMD polyphase down converter channelizer accomplishes the pre-processing task of decomposing the whole input frequency range and of aliasing all the spectral fragments to base-band while reducing the signal sample rate. A selector block is in charge of connecting the ports, which contain the fragments belonging to the same band, to a proper PR 2-to-N up converter channelizer, which synthesizes them in base-band. The dual architecture, composed of small N-to-2 polyphase down converters followed by an 80-path, 2-to-40, up converter, has been designed for the transmit downlink. The down converters accomplish the pre-processing task of decomposing the input spectra and of simultaneously aliasing their fragments to base-band while reducing the input sample rate to 7.68 Msps. The 80-path, 1-to-40 up converter, accomplishes the task of recombining the spectral fragments at the desired center frequencies while increasing the signal sample rate to 307.2 Msps. 相似文献
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Shidong Zhou Yunzhou Li Ming Zhao Xibin Xu Jing Wang Yan Yao 《Communications Magazine, IEEE》2005,43(1):61-69
In future public mobile access with high data rates, one of the main challenges we face is spectral efficiency. In this article we will focus on the following new spectrally efficient downlink multiple access techniques that may be essential parts of China's Beyond 3G system development: dynamic code-division multiplexing, an adaptive multi-input multi-output technique in distributed wireless communications systems, and interleaver pattern division multi-access. 相似文献
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Christantus Obinna Nnamani Chidera Linda Anioke Cosmas Ikechukwu Ani 《International Journal of Electronics》2016,103(11):1857-1867
In long-term evolution (LTE) downlink transmission, modified least weighted delay first (MLWDF) scheduler is a quality of service (QoS) aware scheduling scheme for real-time (RT) services. Nevertheless, MLWDF performs below optimal among the trade-off between strict delay and loss restraints of RT and non-RT traffic flows, respectively. This is further worsened with the implementation of hybrid automatic retransmission request (HARQ). As these restraints grow unabated with increasing number of user demands, the performance of MLWDF further reduces. In order to ameliorate this situation, there is a need to directly incorporate the variations in user demands and HARQ implementation as parameters to the MLWDF scheduler. In this work, an improvement to the MLWDF scheduler is proposed. The improvement entails adding two novel parameters that characterise user demand and HARQ implementation. The scheduler was tested using varying three classes of service in QoS class identifiers (QCIs) table standardised by Third Generation Partnership Project for LTE network to characterise different services. It was also tested on the basis of packet prioritisation. The proposed scheduler was simulated with LTE-SIM simulator and compared with the MLWDF and proportional fairness schedulers. In terms of delay, throughput and packet loss ratio; the proposed scheduler increased overall system performance. 相似文献
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A multi-carrier simultaneous wireless information and power transfer (SWIPT) communication system including one base station (BS) and one user was investigated,where both uplink and downlink adopt orthogonal frequency division multiplexing (OFDM).In the downlink,the BS transmited information and power to the user simultaneously.In the uplink,the user transmited information to the BS by using the power harvested from the BS in the downlink.The weighted sum of the downlink and uplink achievable rates by jointly optimizing subcarrier allocation and power allocation of the uplink and downlink were aimed to maximized.An optimal algorithm to solve the joint resource allocation problem was proposed,which was based on the Lagrange duality method and the ellipsoid method.Finally,the result shows the performances of the proposed algorithm by computer simulations. 相似文献
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继第三代(3G)移动通信之后,长期演进(LTE)作为3G的演进,将是未来通信领域的主流技术。信道估计性能一定程度上决定了通信系统的可靠性,LTE系统上行采用基于块状导频的信道估计。通过MATLAB仿真分析了不同信道估计方法、不同插值方法及不同导频间隔对估计性能的影响,仿真结果可用于指导实际工程应用中信道估计参数的选择。 相似文献
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We study the problem of power efficient multiuser beamforming transmission for both uplink and downlink. The base station is equipped with multiple antennas, whereas the mobile units have single antennas. In the uplink, interference is canceled by successive decoding. In the downlink, ideal "dirty paper" precoding is assumed. The design goal is to minimize the total transmit power while maintaining individual SINR constraints. In the uplink, the optimization problem is solved by a recursive formula with low computational complexity. The downlink problem is solved by exploiting the duality between uplink and downlink; thus, the uplink solution carries over to the downlink. In the second part of the paper, we show how the solution can be applied to the problem of rate balancing in Gaussian multiuser channels. We propose a strategy for throughput-wise optimal transmission for broadcast and multiple access channels under a sum power constraint. Finally, we show that single-user transmission achieves the sum capacity in the low-SNR regime. We completely characterize the SNR-range where single-user transmission is optimal. 相似文献
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The directional properties of the uplink (UL) and downlink (DL) channel are compared experimentally for a duplex distance of 68 MHz. It is found that the first- and second-order moments of the power azimuth spectrum, for all practical purposes, can be assumed to be identical for the UL and DL bands 相似文献
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针对LTE系统中多用户下行吞吐量难以预测的问题,从LTE 系统的时域和频域资源出发,结合用户位置、终端类型以及下行MIMO模式等内容,分析了多用户条件下时域和频域调度算法的特点、影响因素和作用过程。并在此基础上建立了多用户下行吞吐量分析和估算模型,进而应用此模型对具体实例进行了预测和分析,从而对多用户性能分析工作起到一定的指导作用。 相似文献
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《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1984,72(11):1583-1593
In this paper the integration of ALOHA random-access schemes and TDMA techniques in a multibeam packet satellite network are analyzed. The uplink channels operate according to a slotted-ALOHA protocol, while the downlink channels use a TDMA strategy. Two different models are described. In the first model, each transponder on-board the satellite is permanently connected to a preassigned spot beam. The second model uses a number of transponders lower than the number of spot beams. Some different strategies of transmission are proposed in the latter model, able to provide full interconnection among earth stations by channel-hopping capability of the transponders. The performance of the models is evaluated through queueing theory analysis and extensive computer simulations. The obtained results suggest the second model as an efficient candidate for the implementation of a multibeam packet satellite network. In that case, the system parameters must be carefully chosen in order to avoid possible instability conditions. 相似文献
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In wireless networks, sleep-based power saving mechanisms can reduce the energy consumption at the expense of additional packet delay. This paper proposes a queueing model to analyze the packet queueing delay. Compared with the existing models which consider downlink traffic only, both downlink and uplink traffic are considered in the analysis. 相似文献
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To take advantage of the multiuser diversity resulted from the variation in channel conditions among the users,it has become an interesting and challenging problem to efficiently allocate the resources such as subcarriers,bits,and power.Most of current research concentrates on solving the resource-allocation problem for all users together in a centralized way,which brings about high computational complexity and makes it impractical for real system.Therefore,a coalitional game framework for downlink multi-user resource allocation in long term evolution(LTE) system is proposed,based on the divide-and-conquer idea.The goal is to maximize the overall system data rate under the constraints of each user’s minimal rate requirement and maximal transmit power of base station while considering the fairness among users.In this framework,a coalitional formation algorithm is proposed to achieve optimal coalition formation and a two-user bargaining algorithm is designed to bargain channel assignment between two users.The total computational complexity is greatly reduced in comparison with conventional methods.The simulation results show that the proposed algorithms acquire a good tradeoff between the overall system throughout and fairness,compared to maximal rate and max-min schemes. 相似文献
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针对高速移动时分双工长期演进(TDD-LTE,time division duplex-long term evolution)上行单载波频分多址(SC-FDMA,single carrier-frequency division multiple access)系统,提出了一种新型的变换域时变信道估计方法.在所定义的变换域中,基于两块导频符号的信道参数估计,提出利用基于判决导向的非线性内插方法来估计数据符号的信道参数.为了便于SC-FDMA系统均衡,推导给出了变换域信道与频域信道的转换表达式,利用该式可以直接将变换域信道参数估计转化为频域信道响应.计算机仿真结果表明,新方法的性能远远优于传统方法的估计性能,且具有低的计算复杂度. 相似文献
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LTE系统中的上行协同主要基于软合并技术,且适用于具备理想传输条件的小区间,因而在实际网络中部署受限。根据TD-SCDMA系统中的多小区联合检测原理提出了基于干扰抑制合并的上行协同技术,并应用于不具备理想传输条件的小区间。试验表明,基于软合并的上行协同技术可以提升主测小区边缘用户的平均吞吐量达89.9%,而基于干扰抑制合并的上行协同技术则可提升29.3%,两者的有机结合可有效提升全网用户感知。 相似文献
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The call admission control (CAC) for mobile communications is one of the most important engineering issues since it belongs to the category of resource management and the radio spectrum is a very scarce resource. In future mobile cellular systems, the CAC scheme should be efficient for multimedia services as well as for voice services. This paper proposes an advanced CAC scheme for mobile multimedia communications. A characteristic of the proposed scheme is that it takes account of the traffic (load) asymmetry between uplink and downlink in mobile multimedia environments, we evaluate the performance of the proposed scheme using Markov analysis. The performance measures on which we focus are the utilization of resources and the blocking probabilities of handoff calls and new calls. We present some numerical examples with practically meaningful parameter values. As a result, we show that the proposed CAC scheme can be a good choice for mobile multimedia systems such as the International Mobile Telecommunications-2000 systems 相似文献