排序方式: 共有44条查询结果,搜索用时 31 毫秒
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徐卫 《中国电子科学研究院学报》2006,1(1):98-101
研究了智能天线在下行链路的应用。利用上行链路接收数据,建立分布式目标信道模型。估计移动用户的发射角、扩展角度和发射功率以及下行信道相关矩阵,确定下行链路的波束形成方法。即对频分复用(FDD)系统进行上行相关矩阵变换,构建下行信道协方差矩阵,利用最大合并比准则获得下行链路权值。计算机仿真证实了这种方法的有效性。 相似文献
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Non-orthogonal multiple access (NOMA) is regarded as a candidate radio access technique for the next generation wireless networks because of its manifold spectral gains. A two-phase cooperative relaying strategy (CRS) is proposed in this paper by exploiting the concept of both downlink and uplink NOMA (termed as DU-CNOMA). In the proposed protocol, a transmitter considered as a source transmits a NOMA composite signal consisting of two symbols to the destination and relay during the first phase, following the principle of downlink NOMA. In the second phase, the relay forwards the symbol decoded by successive interference cancellation to the destination, whereas the source transmits a new symbol to the destination in parallel with the relay, following the principle of uplink NOMA. The ergodic sum capacity, outage probability, outage sum capacity, and energy efficiency are investigated comprehensively along with analytical derivations, under both perfect and imperfect successive interference cancellation. To inquire more insight into the system outage performance, diversity order for each symbol in the proposed DU-NOMA is also demonstrated. The performance improvement of the proposed DU-CNOMA over the conventional CRS using NOMA is proved through analysis and computer simulation. Furthermore, the correctness of the author's analysis is proved through a strong agreement between simulation and analytical results. 相似文献
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从系统吞吐量、用户公平性等方面分析研究了HSDPA系统中支持非实时业务的三种经典分组调度算法RR、Max C/I和PF。针对PF算法重传时延过长问题,提出了一种结合混合自动请求重传HARQ的增强分组调度算法。该算法通过提高重传分组的优先级降低重传时延,有效地避免系统资源的浪费。MATLAB仿真结果表明,该算法在降低单用户重传时延的同时,仍能保证用户间的公平性和系统的吞吐量。 相似文献
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In the Long Term Evolution (LTE) downlink multicast scheduling, Base Station (BS) usually allocates transmit power equally among all Resource Blocks (RBs), it may cause the waste of transmit power. To avoid it, this paper put forward a new algorithm for LTE multicast downlink scheduling called the Energy-saving based Inter-group Proportional Fair (EIPF). The basic idea of EIPF is to calculate an appropriate transmitting power for each group according to its data rate respectively, and then follow the inter-group proportional fair principle to allocate RBs among multicast groups. The results of EIPF simulation show that the proposed algorithm not only can reduce the transmit power of BS effectively but also improve the utilization rate of energy. 相似文献
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以等离子体改变通讯信号特征为基本出发点,根据通用通讯信号特征参数,提出了利用等离子体改变通讯信号特征的基本思路、计算模型和计算方法.计算与分析表明,等离子体改变卫星通讯信号特征的原理是正确的,效果是明显的. 相似文献
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HSDPA(高速下行链路数据包接入)为WCDMA的增强演化版本犤1犦。提出了基于HSDPA系统中的一种自适应准入控制方案。这里给出的两个性能指标是新呼叫拒绝率(newcallblockingratio)和切换拒绝率(handoffcallblockingratio)。仿真性能的比较对象是固定预留资源分配比例的准入控制方案。仿真结果显示,自适应准入控制方案保证了一定的切换拒绝率,同时降低了新呼叫拒绝率。 相似文献
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Mário Marques da Silva Américo M. C. Correia Rui Dinis 《Wireless Personal Communications》2008,47(2):219-233
In this paper we present and evaluate a pre-distortion (PD) scheme for the downlink of Wideband-code division multiple access
(W-CDMA) systems considering a Rake in the receiver in order to exploit multipath diversity. Its performance is compared with
schemes without the PD at the base station (BS), and combined with a transmit diversity (TD) scheme to improve the performance
by exploiting spatial diversity. It is shown that the proposed PD scheme allows receivers (Mobile Stations) with very low
complexity, contrarily to the case where a post-processing multi-user detector (MUD) approach is adopted to improve the performance.
Therefore, the proposed PD scheme can be seen as an alternative to post-processing schemes.
相似文献
Mário Marques da SilvaEmail: |
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Asymmetric traffics cause downlink–uplink asymmetric interference. It can lead to a critical unbalance between a downlink and an uplink channel qualities in cell edge areas. This paper proposes an enhanced handoff scheme including an efficient uplink channel estimation method. The proposed handoff scheme determines an appropriate handoff-timing and handoff-direction according to an estimated uplink channel quality and a measured downlink channel quality. In the proposed scheme, an uplink or downlink, whose quality dominantly affects a link failure, becomes the main handoff-criterion. An efficient uplink channel estimation method is also proposed to exploit an uplink channel quality in handoff. The proposed method estimates an uplink signal strength from the measured downlink signal strength and predicts an uplink interference based on the interference-level information from neighbor base stations. We propose two different uplink estimation modes such as the simple and the precise modes. The simple estimation mode calculates the uplink channel quality for the overall bandwidth for a general handoff process. The precise estimation mode finds the best uplink band for the handoff user who wants an elaborate handoff process. In the elaborate handoff, a target base station allocates the best uplink band to a handoff user to provide the better uplink channel quality. Simulation results show that the proposed uplink estimation method can accurately compute the uplink channel quality of neighbor cells where the estimation error rate is less than 0.7% The simulation results also show that the proposed handoff scheme reduces handoff-call-dropping probability by up to 69% compared to LTE-Advanced system. In addition, the end-to-end delay of the proposed scheme can be better than that of LTE-Advanced system by 26%. 相似文献