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排序方式: 共有16条查询结果,搜索用时 46 毫秒
1.
下行SDM/OFDMA系统中基于效用函数的多用户调度算法   总被引:3,自引:0,他引:3       下载免费PDF全文
许宁  周蓓  王莹  张平 《电子与信息学报》2008,30(6):1428-1431
该文研究了空分复用/正交频分多址(SDM/OFDMA)无线通信系统中的多用户调度问题,针对该系统的空时频三维调度特点,提出一种基于效用函数的多用户调度算法.该算法利用空间多用户分集获得增益,同时兼顾系统的整体效率和用户的个体效用.通过计算机仿真验证了算法具有和穷举搜索算法相近的性能,但算法复杂度大大降低.  相似文献
2.
Cell search algorithms for the 3G long-term evolution   总被引:2,自引:0,他引:2  
This article presents downlink initial synchronization and cell identification algorithms for long term evolution (LTE) of third-generation (3G) mobile communication systems, which are based on synchronization channel (SCH) and cell specific pilot symbols, respectively. The key features of the proposed scheme are: it can improve performance of the frequency synchronization through oversampling of the SCH, it can support a large number of target cells by modulating a cell-specific pilot sequence over two symbols within a subframe, and it can guarantee cell identification performance by maximally ratio combining the frequency domain differential cross-correlation. Simulations show that the proposed scheme has a potential use in 3G LTE.  相似文献
3.
频率复用作为提高小区边缘用户性能的有效方式已被广为研究.然而,如何在提高小区边缘用户性能的同时,使频谱利用率得到有效提高仍是一个有待解决的问题.在以正交频分多址(OFDMA)为基本多址方式的第4代(4G)系统中该问题尤为突出.为此,该文提出了一种OFDMA系统中的频率复用方法,通过抑制小区间干扰提高小区边缘用户性能;同时,根据小区中心与小区边缘通信环境的差异,分别对其实施不同的频率复用策略使频率复用系数接近于1以提高频谱利用率.仿真结果表明,与未经过频率规划的全频率复用相比,该文提出的频率复用方法提高了系统吞吐量并显著改善了小区边缘用户性能.  相似文献
4.
在正交频分多址接入系统中采用正比公平算法可以兼顾吞吐量和公平性,有效地提高系统性能.结合正比公平算法,该文提出一种应用于正交频分多址接入系统保证服务质量的分组调度算法.为防止需求速率高但瞬时信道状况差的用户分配过多的子载波,算法使用了动态变化的权重因子.在一次调度过程中,剩余子载波的权重因子可以随着子载波的分配而更新.仿真结果证明,在满足实时业务服务质量的前提下,该算法比正比公平算法具有更好的公平性.  相似文献
5.
Efficient radio resource allocation is essential to provide quality of service (QoS) for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically allocates radio resources based on user's channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process (dMMPP), and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users.  相似文献
6.
We propose and demonstrate an improved Ethernet passive optical network (EPON) architecture supporting bandwidth-scalable physical layer local area network (LAN) emulation. Due to the use of orthogonal frequency division multiple access (OFDMA) technology for the LAN traffic transmission, there is no need to change the existing EPON architecture. Only one receiver at each optical network unit (ONU) is required to detect both LAN traffic and EPON downstream traffic, which makes the proposed system simple and cost-effective. Moreover, flexible assignment of LAN traffic bandwidth is realized by allocating different number of subcarriers or using different modulation formats. The 250 Mb/s 4-quadrature amplitude modulation (4-QAM) and 500 Mb/s 16-QAM OFDM LAN traffic are successfully emulated with the EPON traffic in our experiment.  相似文献
7.
The growth in mobile communication will accelerate over the next years. Today most of the mobile subscribers use cellular services only. But this will change in the near future towards broadband wireless access services like WiFi and WiMAX. This paper describes a fundamental overview of the broadband wireless access technologies and outlines the market view, major trends and introduces OFDM technologies. New developments for integration of broadband wireless access into the operators' infrastructure are also discussed.  相似文献
8.
Distributed multipoint systems (DMS) are important and timely for the move to future broadband wireless communication systems.Traditional studies on DMS have mainly focused on the issues with the spatial division multiple access such as precoding techniques,which only consider a narrowband case.This paper addresses the downlink radio resource management of the orthogonal frequency division multiple access DMS (OFDMA-DMS),including power allocation between users or subcarriers,and distributed antenna selection.Signal models with incoherent and coherent transmitters are built.To maximize the system throughput,for the incoherent transmitter case,a strategy based on the iterative water-filling power allocation is proposed to approach the optimality.As for the coherent case,where coherent additions of the signal could occur at the users,the problem is transformed into an integer programming which is solvable.Numerical results show that the gain from the coherent transmitter is promising.And to achieve a near-optimal solution,only part of the DA ports will be used,which have better channel conditions.  相似文献
9.
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.  相似文献
10.
范达  曹志刚 《电子学报》2007,35(4):629-633
 在OFDMA系统中,通过为每个用户分配不同的子载波可以实现并行数据传输.采用Interleaved子载波分配方法可以提高频率分集和系统容量,但是发射机和接收机之间的载波频率偏移会破坏子载波间的正交性,从而导致本用户的载波间干扰(ICI)以及用户间干扰(MUI).本文提出了一种基于子空间的两阶段频偏搜索方法,该方法只采用一个OFDMA符号块就可以实现Interleaved-OFDMA上行链路多个用户频偏的联合估计,并且不需要知道接入的用户个数及用户所占用的子信道,因此适用于随机分配子信道的情况.仿真结果验证了算法的精确度和有效性.  相似文献
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