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61.
62.
该文提出了一种在有限反馈条件下多输入单输出正交频分复用(MISO-OFDM)系统中基于最大化容量的波束成形方案。将OFDM符号的所有子载波分成若干簇,从码本中选择能够最大化该簇每个子载波平均容量的码字,作为该簇的波束成形向量。在低信噪比区域,求出了最优波束成形向量的闭合解;鉴于在高信噪比区域无法求出闭合解,基于簇内不同子载波信道频响之间的相关性提出了一种简化的次优算法以降低搜索最优解时的计算复杂度。仿真结果表明,在典型参数设置下,所提方案能够取得比其他已有方案更高的容量和更低的误码率。 相似文献
63.
在多用户MIMO通信网络中,该文提出一种新的放大转发双向中继策略,在第1时隙的多址传输中采用OFDMA,在第2时隙的广播传输中采用OFDM/SDMA,通过利用频率分集和空间分集提高了系统性能。针对双向中继传输的特点,采用两种方法在每个子载波上设计了中继波束形成矩阵,即信漏噪比(SLNR)准则和块对角化迫零(BDZF)准则。利用割集理论推导了该双向中继网络的容量域上界。仿真结论表明,所提出的双向中继策略在系统和速率性能上优于其他3种中继策略,并能逼近所推导的容量域上界。 相似文献
64.
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针对期望信号方向向量存在偏差会导致自适应波束形成算法的性能急剧下降这一问题,该文提出了一种基于二次型约束的鲁棒自适应波束形成算法。通过对期望信号波达方向附近范围内的方向向量的误差模值进行约束,来提高算法的鲁棒性,并在此约束条件下对权重向量进行优化求解,且优化解中的参数能够准确求出。该算法可有效地控制波束主瓣区域内信号的畸变,并能够抑制方向向量偏差所带来的影响,提高了系统的鲁棒性,同时使干扰和噪声的功率输出最小,保证了对干扰信号的抑制能力,改善了阵列输出的信干噪比,使其更接近最优值。仿真结果验证了所提算法的有效性与优越性。 相似文献
67.
Chenguang Lu Frank H. P. Fitzek Patrick C. F. Eggers 《Wireless Personal Communications》2007,43(2):573-587
In dense traffic areas, wireless local area networks (WLANs) suffer from interference problems due to the usage of the crowded
unlicensed ISM band and the lack of available spectrum. To mitigate these problems, a terminal side beamforming framework
is proposed—this beamforming is capable of focusing the transmission and the reception in the relevant direction of the access
point to exploit the directivity of the indoor propagation channel. It provides network transparency to achieve the backwards
compatibility to the existing WLAN networks, and vendor transparency to ease the system design process and thereby achieve
low complexity and costs. The beamforming enabled terminal benefits in terms of capacity, energy efficiency, and security
while it does not require any change on the network side costing network providers new investments. It will be an attractive
value-added feature as well as low-cost solution for the future WLAN terminal design opening the door for WLAN terminal manufacturers
to include the proposed solution into their product line. In this work, a WLAN terminal beamforming demonstrator has been
developed to demonstrate the capacity enhancement in real environments. Signal to interference ratio (SIR) improvement as
well as array gain were investigated by simulations with IEEE 802.11n cluster channel models and by experiments with the demonstrator
in a typical office environment. The comparable results of simulations and experiments show significant array gain and SIR
improvement. The significant capacity increase has been demonstrated in the experiments in both an interference free scenario
and an interference limited scenario. 相似文献
68.
Munhyoung Cho Chong Hyun Lee Jonghyun Lee Kyungchun Lee Joohwan Chun Jong-Heon Lee 《AEUE-International Journal of Electronics and Communications》2004,58(3):232-234
We present a new on-line internal calibration algorithm for a CDMA (code division multiple access) antenna array. The proposed calibration algorithm gives an accurate calibration vector, and as byproducts, the vector-channel parameters of an arbitrarily selected reference user. 相似文献
69.
《Digital Communications & Networks》2016,2(4):162-166
Interference alignment (IA) is well understood to approach the capacity of interference channels, and believed to be crucial in cellular networks in which the ability to control and exploit interference is key. However, the achievable performance of IA in cellular networks depends on the quality of channel state information (CSI) and how effective IA is in practical settings is not known. This paper studies the use of IA to mitigate inter-cell interference of cellular networks under imperfect CSI conditions. Our analysis is based on stochastic geometry where the structure of the base station (BS) locations is considered by a Poisson point process (PPP). Our main contribution is the coverage probability of the network and simulation results confirm the accuracy. 相似文献
70.
Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from performance deterioration when the length of Cyclic
Prefix (CP) is shorter than the Channel Impulse Response (CIR). The fundamental reason of this impairment is the InterCarrier
Interference (ICI) and Inter-Symbol Interference (ISI) introduced by the excessive multipath delay. Specifically, Multiple
Input Multiple Output (MIMO) beamforming is helpful in cancelling such interference since it can spatially suppress some of
the multipath. In this paper, we propose an ICI eliminating beamforming scheme employing a per-tone processing approach, thus
with moderate computational complexity. The ISI is removed by using a simple decision feedback equalizer, while the optimal
steering and combining vectors are then derived to maximize the Signal to Interference plus Noise Ratio (SINR). This method
not only achieves the beamforming benefit, but also significantly alleviates the ICI. Simulation results show that the proposed
algorithm can effectively reduce the system Symbol Error Rate (SER), permitting good performance for multipath delay profiles
that would break conventional links. 相似文献