共查询到20条相似文献,搜索用时 122 毫秒
1.
本文首先介绍了LTE系统中OFDMA、SC-FDMA多址接入技术的原理以及信号实现过程,然后对两种多址接入方式进行了分析比较,验证OFDMA接入技术的PAPR(峰均比)高于SC-FDMA,并给出了仿真结果,最后,提出研究降低OFDMA系统PAPR算法的必要性。 相似文献
2.
正交频分多址(OFDMA)是以OFDM调制为基础的新一代无线接入技术,在这种方式中,多址是通过给每个用户分配可用子载波总数的一部分来实现的。介绍了一种OFDMA下行链路的实时动态子载波分配算法,算法根据各个子载波对各个用户的瞬时信道增益,在使系统总的发送功率最小的准则下,为各用户分配最优的子载波组。最后用MATLAB语言仿真实现了该算法.仿真结果表明该算法性能要优于传统的静态子信道方案。 相似文献
3.
4.
5.
随着宽带无线通信的发展,目前的多址技术已经满足不了系统的需求,为了适应更宽的带宽的传输,必须引进增强型的多址接入技术。介绍了4G系统讨论的其中两种热点多址方案,即:Nx-SCFDMA(Nx单载波频分多址接入)、clusteredDFT-S—OFDMA(clustered离散傅里叶变换扩展频分多址接入),主要从方案的实现原理、CM(立方量度)性能和FFT(快速傅里叶变换)复杂度方面进行分析和比较。 相似文献
6.
7.
《无线电通信技术》2021,(1):86-95
针对椭圆球面波函数(PSWFs)非正弦通信系统多个用户如何共享时频资源进行通信的问题,展开基于PSWFs的非正弦通信系统正交多址接入技术研究。首先,基于PSWFs的信号特性,提出了PSWFs非正弦通信系统频分多址(PSWFs-FDMA)、时分多址(PSWFs-TDMA)和阶分多址接入(PSWFs-ODMA)方法。其次,与循环前缀正交频分复用(CP-OFDM)对比分析了调制信号的能量聚集性、频谱效率和相邻子波带间的干扰,证明所提正交多址技术的可行性。最后,在双选择信道下,将PSWFs-TDMA/FDMA、PSWFs-ODMA与CP-OFDM对比分析了系统吞吐量,与正交频分多址接入(OFDMA)对比了不同接入方式的误码性能。理论与仿真分析表明,PSWFs非正弦通信系统正交多址能够比CP-OFDM通信系统提高约1.4倍的系统吞吐量。在多径信道下,PSWFs-ODMA增加时宽情况下的误码性能最好;在双选择信道,多普勒频移较小的中低速场景下,PSWFs-TDMA/FDMA的误码性能比OFDMA要好。 相似文献
8.
机会波束成形(Opportunistic Beamforming,OBF)技术通过加大、加快信道的波动来提高多用户分集增益,将之使用在正交频分复用多址接入(OFDMA)系统中,可以使得系统的吞吐量最大化。在OFDMA系统中,通过对所有子载波进行分簇,可以实现在牺牲系统性能很少的情况下,大大降低系统反馈量。研究了对分簇OFDMA系统使用OBF技术来提高系统吞吐量,并进一步研究了在训练阶段使用多个随机加权向量进行多波束成形,然后从中选择最好的一个来实现数据阶段的波束成形。仿真证明,采用多波束机会波束成形技术能提高OFDMA系统吞吐量。 相似文献
9.
10.
11.
12.
Wireless Networks - In this paper, we present an analytical framework for the performance evaluation of Radio Resource Allocation (RRA) in Orthogonal Frequency Division Multiple Access (OFDMA)... 相似文献
13.
Huan Cong Nguyen Elisabeth de Carvalho Ramjee Prasad 《Wireless Personal Communications》2010,52(1):119-131
Inheriting all the advantages of Orthogonal Frequency Division Multiplexing (OFDM), plus the ability to offer a fine level
of bit granularity and dynamic subcarrier allocation for multiuser diversity, the Orthogonal Frequency Division Multiple Access
(OFDMA) has emerged as a potential candidate for multiple access technique for future broadband wireless networks. However,
the benefits of OFDMA come with stringent requirements on synchronization, especially in the uplink. Unless the timing offsets
(TOs) and carrier frequency offsets (CFOs) among users in the uplink are kept under tolerable ranges, inter-symbol interference
(ISI), inter-channel interference (ICI) and multi-user interference (MUI) will occur, which degrade the overall system performance
severely. Accurate estimation of TOs and CFOs is required for each user, so that they can be accounted for at the user’s side
or compesated for at the base station. This paper proposes a novel method to estimate jointly TOs and CFOs in the time-domain
for multi-user in the OFDMA uplink. The method is shown to offer good accuracy, while maintaining a reasonable complexity
compared to conventional estimation schemes. 相似文献
14.
Optimal resource allocation in uplink SC-FDMA systems 总被引:1,自引:0,他引:1
We present algorithms for resource allocation in Single Carrier Frequency Division Multiple Access (SC-FDMA) systems, which is the uplink multiple access scheme considered in the Third Generation Partnership Project-Long Term Evolution (3GPP-LTE) standard. Unlike the well-studied problem of Orthogonal Frequency Division Multiple Access (OFDMA) resource allocation, the "subchannel adjacency" restriction, whereby users can only be assigned multiple subchannels that are adjacent to each other, makes the problem much harder to solve. We present a novel reformulation of this problem as a pure binary-integer program called the set partitioning problem, which is a well studied problem in operations research. We also present a greedy heuristic algorithm that approaches the optimal performance in cases of practical interest. We present simulation results for 3GPP-LTE uplink scenarios. 相似文献
15.
Gao Peng Meng Dexiang Song Zhiyuan Tu Guofang Graduate University of Chinese Academy of Sciences Beijing China China Mobile Group Design Institute Co. Ltd. Beijing China 《中国通信》2010,7(1):23-29
In Orthogonal Frequency Division Multiple Access (OFDMA) systems, such as Long Term Evolution (LTE) and so on, the resources used by each user are orthogonal, and the OFDMA systems performances are mainly affected by the inter-cell interference. Therefore, the inter-cell interference mitigation technology becomes a hotspot. The objective of interference mitigation technologies used in OFDMA systems are to increase cell-edge throughput and average cell throughput. In this paper, the Resource Block Planning (BRBP) based scheme is proposed to mitigate the inter-cell interference and improve the cell-edge throughput. Comparison between the simulation results of BRBP and Round Robin (RR) illustrates that the enhanced performance of BRBP. 相似文献
16.
Yang Xiang Wei Gang 《电子科学学刊(英文版)》2005,22(6):586-593
This paper utilizes the cross-layer architecture to implement adaptive resource allocation in Orthogonal Frequency Division Multiple Access (OFDMA) based on the broadband wireless access system. According to the cross-layer architecture, the information in link layer is used for adaptive resource allocation in OFMDA. A new cross-layer adaptive resource allocation algorithm is developed which can guarantee the users to be in minimum average waiting time in link-layer and get the better spectrum utilization. Numerical results show that our scheme is appealing and can get about half of average waiting time less and 0.5 bps/Hz spectrum utilization more than the scheme in 1EEE802.16a. 相似文献
17.
Juan I. del-Castillo María A. Santos Jose M. Villalón 《Telecommunication Systems》2013,52(4):2721-2732
Broadband Wireless Access (BWA) is gaining interest due to the increasing demand of high-quality mobile wireless systems. In this context Orthogonal Frequency Division Multiple Access (OFDMA) is one of the most promising and researched physical transmission technologies. In OFDMA, data have to be mapped into a time-frequency matrix before the actual transmission. Efficiency, power consumption, Quality of Service (QoS) and complexity factors should be taken into account by mapping algorithms. In this paper, we focus on the OFDMA resource allocation problem in BWA networks. Through extensive simulation in different scenarios, performance of several resource allocation algorithms is evaluated. 相似文献
18.
Orthogonal Frequency Division Multiple Access (OFDMA) is an emerging multiple access technology. In this paper, we consider OFDMA in the context of fixed wireless networks. This paper addresses the problem of assigning subcarriers and bits to point-to-point wireless links in the presence of cochannel interference and Rayleigh fading. The objective is to minimize the total transmitted power over the entire network while satisfying the data rate requirement of each link. We formulate this problem as a constrained optimization problem and present centralized algorithms. The simulation results show that our approach results in an efficient assignment of subcarriers and transmitter power levels in terms of the energy required for transmitting each bit of information. However, centralized algorithms require knowledge of the entire network topology and channel characteristics of every link. In a practical scenario, that would not be the situation and there is a need for distributed rate allocation algorithms. To address this need, we also present a distributed algorithm for allocating subcarriers and bits in order to satisfy the rate requirements of the links. 相似文献
19.
In conventional Orthogonal Frequency Division Multiple Access (OFDMA) cellular systems, the fundamental cause of inter-cell interference (ICI) is that the signals from serving Base Station (BS) and interference BSs, are modulated by same exponential bases, at same subcarrier. In this letter, an effective OFDMA cellular mobile system based on multiple fractional Fourier transform (FrFT) angle reuse scheme is proposed. In this system, FrFT angle is regarded as new resource, which can be optimally allocated to each BS of cellular system. Because chirp bases, generated by different FrFT with optimally allocated angle, are mutually approximately orthogonal at same subcarrier, ICI can be perfectly suppressed. Both theory and simulations show the essential advantages over conventional OFDMA cellular systems for ICI suppression and bit error rate. 相似文献
20.
全球微波接入互操作性(WiMAX)是4G的核心技术,其物理层采用正交频分复用(OFDM)/正交频分多址(OFDMA)技术,帧同步是实现这一技术的关键。因此,对WiMAX物理层进行了Simulink建模仿真,同时基于IEEE 802.16d下行链路帧结构提出新的帧同步算法。该算法用长导频符号中的第1个OFDM符号进行粗同步来估计FFT窗的可能起始位置,然后用第2个OFDM符号进行细同步来确定FFT窗的起始位置。最后,将帧同步算法用嵌入式Matlab function模块嵌入WiMAX Simulink模型中。仿真结果表明,新算法在较低的信噪比或多径衰落环境下仍可产生脉冲型定时度量,较之传统算法定时估计更准确。 相似文献