共查询到19条相似文献,搜索用时 109 毫秒
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无线携能通信(SWIPT)技术是解决无线网络能量受限问题的有效方法,该文研究一个由基站(BS)和多用户组成的多载波SWIPT系统,其上行和下行链路均采用正交频分复用(OFDM)技术。在下行链路中,基站向用户同时进行信息与能量传输;在上行链路中,用户利用从基站接收的能量向基站回传信息。该文以最大化上下行加权和速率为目标,联合优化上行和下行的子载波分配和功率分配,提出基于拉格朗日对偶法和椭球法的最优联合资源分配算法。计算机仿真结果证实了该算法的有效性。 相似文献
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在存在一个半双工自适应窃听者的通信模型中,分析了采用非正交多址(Non-orthogonal Multiple Access,NOMA)技术合作系统的性能。提出了一种新型的合作NOMA方案,该方案在中继转发时,强用户可充当中继协助转发弱用户信号,而弱用户采用全双工技术向窃听者发送干扰信号,提高了通信链路的安全性和用户的服务质量。合法接收端采用连续干扰消除(SIC)技术,以解码来自叠加信号的各个消息。在已知窃听信道统计信道状态信息(CSI)的情况下,分别推导了2个用户的安全中断概率和中断概率的闭合表达式,并通过Monte-Carlo仿真验证。理论分析和数值模拟结果均表明所提出的NOMA用户合作方案在保密率方面优于非合作方案的性能。 相似文献
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干扰是无线蜂窝网络面临的主要问题之一。蜂窝网络干扰对齐能消除干扰的影响从而提高系统信道容量。经典蜂窝网络下行链路干扰对齐算法仅优化单个用户自身信道容量,从而限制了蜂窝小区整体信道容量的提升。从提高蜂窝小区总信道容量出发,该文提出一种蜂窝网络下行链路单反馈干扰对齐算法。构建了蜂窝网络下行链路干扰对齐数学模型;在用户端以最大化用户SINR为目标构造接收矩阵;而在基站端以最大化小区总信道容量为目标构造预编码矩阵,并通过梯度投影算法来求解该优化问题。实验结果表明,相比于传统蜂窝小区下行链路干扰对齐算法,新算法可有效提高蜂窝网络下行链路信道容量。 相似文献
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本文研究了在智能天线在FDD-CDMA中的下行链路的应用,利用上行链路接收数据,估计了下行链路的信道相关矩阵和对其它小区用户的相对干扰总量,给出下行链路的波束形成方法,即在保证一定的有效发送功率的同时,使得对其他小区的用户干扰最小。计算机仿真表明:(在多小区蜂窝CDMA环境中,采用上述方法比仅保证用户方向的最大发送功率,有更小的中断率。 相似文献
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W C D M A 系统是基于 C D M A 接入方式的网络,其技术特点更接近 CDMA, 因而与 GSM 存在诸多不同。同时,由于 3G网络的综合数据业务的特点,对网络设计提出了更高的要求。 一、链路预算与上行覆盖 链路预算是无线网络规划的基本工具,链路预算的结果决定小区的覆盖半径。在GSM系统中, 上行链路和下行链路是基本平衡的,小区半径可以由基站下行信号电平高于某一设计要求的门限值决定。 在WCDMA 系统中, 上行链路和下行链路的平衡并非网络设计目标。 基站功率在下行由小区所有用户及信令共享,因而不会成为覆盖受限链路。由于… 相似文献
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在蜂窝系统中,由于干扰的存在,用户性能受到影响,特别是对于小区边缘用户,其通信质量较差。干扰对齐作为一种能够消除干扰、提高系统容量的技术,近年来受到广泛关注。针对多天线两小区蜂窝系统的边缘用户,本文给出了一种系统开销小、需要天线数少的线性干扰对齐算法。该算法利用发送端预编码矢量消除小区内干扰,利用接收端干扰抑制矢量消除小区间干扰。采用本文算法后,在每个小区有 个用户、基站有 根发送天线、用户有 根接收天线的情况下,只需 和 就可以实现上下行的干扰对齐,整个系统可以达到 的自由度,并且在下行链路中不需要小区间反馈,而在上行链路中只需要较小的小区间反馈。仿真结果表明,本文提出的算法能够以较小的开销实现比以往的算法更好的性能。 相似文献
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A novel application on the recently emerging wireless Personal Communications Systems (PCS) is the multimedia communication. In this paper, we evaluate multimedia communications capability and quality of service characteristics of one of the PCS standards, Personal Access Communications System's (PACS) packet channel (PPC) using simulation modeling. The performance of PPC's slot aggregation and data-sense multiple access techniques are studied by considering the downlink and uplink in a single cell and combined uplink/downlink in two cells and changing various parameters such as the number of users and certain protocol parameters. Interconnection of PPC with the Internet is discussed next. Frame rates of MPEG-1 coded images transmitted in a PACS cell as IP datagrams are determined. Handover characteristics of PPC downlink are studied by changing different parameters such as the cell size, the speed of the mobile host and time between handovers. The results clearly establish that multimedia communication on PPC is only feasible at lower bandwidths and frame rates and only a few users per cell can be supported. Careful tuning of PPC protocol parameters is required. There is one parameter whose variation gives opposite results on the downlink and uplink. 相似文献
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本文提出一种基于有限反馈的波束和用户选择方案,在这种方案中,用户端利用一个随机正交码本对其信道方向信息(CDI)进行量化,计算其最大信号与干扰加噪声功率比(SINR),并把这些信息反馈给基站;基站根据接收到的这些反馈信息,按照和容量最大的准则选择出多个正交波束以及相应的多个用户.和sharif等人最近提出的方案相比,我们提出的方案能根据系统参数,如用户数和信噪比(SNR),对选择的波束成形矢量及其对应的用户的数量和集合进行调整,当用户数量较小时,和容量性能得到了很大的提升,同时避免了选择波束成形矢量时的用户冲突,另外,基站也不需要广播波束成形矢量给各个用户. 相似文献
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A novel cross layer scheduling algorithm is proposed for real-time (RT) traffic in multiuser downlink multiple-input multiple-output orthogonal frequency division multiple access (MIMO-OFDMA) wireless systems. The algorithm dynamically allocates resources in space, time and frequency domain based on channel state information (CSI), users' quality of service (QoS) requirements and queue state information (QSI). To provide higher data rate and spectrum efficiency, adaptive modulation and coding (AMC) is employed. The proposed algorithm can improve cell throughput and increase the number of users that can be supported while guaranteeing users' QoS requirements and fairness among all users. Simulation results indicate that the proposed algorithm can achieve superior performance. 相似文献
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Coordinated multi-point (CoMP) is known to be one of the key technologies for long-term evolution (LTE)-advanced systems. CoMP technology can improve system capacity and the quality of wireless communication services for users in LTE networks. However, in practice, the actual performance of CoMP technology is limited by the switching capacity of the backhaul network among distributed base stations as well as its latencies. In this paper, we propose a new cloud radio access network architecture based on RF signal soft-switching to solve this problem. Furthermore, we introduce a narrow-band parallel processing technique on a common public radio interface in downlink and uplink to reduce the volume of data as well as the latencies in the transmission process among base band units and remote radio units. By combining theoretical analysis with computer simulations, we show that the technique is valid both for downlink and uplink, i.e., it does not degrade the performance of downlink and uplink propagation between BBU pool and user equipments. Moreover, the computational time of the narrow-band parallel processing technique is less than that of the standard technique. 相似文献
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Balasubramanian A. Liu L. Miller S.L. 《Wireless Communications, IEEE Transactions on》2010,9(2):605-613
A wireless communication system where a common base station is scheduled to transmit information to multiple mobile users on a time division (TD) basis is considered. The capacity region of this system is found for the two user case and the optimal scheduling scheme is proposed which achieves the boundary of the capacity region. Furthermore, the optimal scheduling scheme is found for the case when the remote mobile users can perform downlink cooperation and the achievable rate region of the downlink cooperative system is characterized. Finally, a simple iterative algorithm is proposed for finding the resource allocation parameters and the scheduling scheme for the cooperative system. 相似文献