Performance analysis of wireless communication system over nonidentical cascaded generalised gamma fading channels

Multiplicative fading statistics usually encountered in different radio propagation environments. In this context, we evaluate and analyse the performance of a wireless communication system over the nonidentical cascaded generalised Gamma Fading Channels, also known as generalised Bessel‐K fading channel. To this end, the closed‐form expressions for the amount of fading (AOF), the outage probability (OP), the average symbol error probability (SEP), and the channel capacity are derived. In addition approximate expressions for the average SEP with maximal ratio combining (MRC) diversity are also provided. The low‐ and high‐power solutions for the channel capacity are also provided. Furthermore, simplified asymptotic average SEP expressions for MRC and selection combining (SC) are presented to gain the system performance with diversity. The proposed methodologies provide more flexibility to accommodate different radio propagation scenarios. To examine the accuracy of the proposed solutions, numerical and simulation results are compared and shown to fit for variety of fading parameters.     

空时分组编码用于提高系统容量的研究

该文在简单介绍空时分组编码的基础上,着重研究了对共道用户产生的干扰进行抵消抑制的技术。采用干扰抵消技术可以充分利用干扰信号的相关性进行有效的抵消处理,从增加共道用户的角度提高了系统的容量。并且文中提出了一种利用不同调制方式性能的不同,对共道用户进行分步解码来削弱共道干扰的空时分组编码传输系统策略。这种方法能够进一步提高系统的性能,尤其是增大了通信系统的容量。     

MIMO的反馈信道研究

该文提出了在闭环MIMO容量研究中引入了率失真理论的研究方法,推导出了反馈信道速率和闭环MIMO容量之间的数学关系。通过理论分析和仿真结果,得出了有关反馈信道速率与信噪比,天线数,闭环MIMO容量之间变化关系的四个重要结论。为实际的闭环MIMO系统设计提供了折衷反馈信道开销和闭环MIMO容量的依据,对系统设计有重要的指导意义.     

MIMO信道中衰落信号的空域相关性评估

将MIMO(多输入多输出)信道建立为Nakagami衰落信道,进一步推导单元天线接收多径衰落信号的空域相关系数的通用解析式,并在均匀分布、余弦分布、高斯分布和拉式分布的来波功率角谱下分别进一步评估接收信号的空域相关性,分析各参数对相关系数的影响,比较各种来波功率角谱下相关性的数值结果,这些对于准确分析MIMO系统性能与设计MIMO多天线系统是十分必要的.     

硝酸铵防吸湿性和防结块性研究

用十二烷基苯磺酸铈（ＣＤＢＳ）、硬脂酸铈（ＣＳＡ）和十八烷胺硝酸盐（ＯＮ）等添加剂包覆硝酸铵（ＡＮ）以防其吸湿和结块,分析了添加剂降低ＡＮ吸湿性和结块性的原因。结果表明,与纯ＡＮ相比,添加ＣＤＢＳ、ＣＳＡ和ＯＮ的ＡＮ的结块性和吸湿性明显降低,ＣＤＢＳ、ＣＳＡ和ＯＮ组成的复合添加剂对ＡＮ的防潮、抗结块效果优于单一添加剂。液相包覆处理法优于机械混合法。包覆温度和复合添加剂的添加次序是影响抗结块效果的两个主要因素。     

On Limits of Wireless Communications in a Fading Environment when Using Multiple Antennas

This paper is motivated by the need for fundamental understanding of ultimate limits of bandwidth efficient delivery of higher bit-rates in digital wireless communications and to also begin to look into how these limits might be approached. We examine exploitation of multi-element array (MEA) technology, that is processing the spatial dimension (not just the time dimension) to improve wireless capacities in certain applications. Specifically, we present some basic information theory results that promise great advantages of using MEAs in wireless LANs and building to building wireless communication links. We explore the important case when the channel characteristic is not available at the transmitter but the receiver knows (tracks) the characteristic which is subject to Rayleigh fading. Fixing the overall transmitted power, we express the capacity offered by MEA technology and we see how the capacity scales with increasing SNR for a large but practical number, n, of antenna elements at both transmitter and receiver.We investigate the case of independent Rayleigh faded paths between antenna elements and find that with high probability extraordinary capacity is available. Compared to the baseline n = 1 case, which by Shannon's classical formula scales as one more bit/cycle for every 3 dB of signal-to-noise ratio (SNR) increase, remarkably with MEAs, the scaling is almost like n more bits/cycle for each 3 dB increase in SNR. To illustrate how great this capacity is, even for small n, take the cases n = 2, 4 and 16 at an average received SNR of 21 dB. For over 99% of the channels the capacity is about 7, 19 and 88 bits/cycle respectively, while if n = 1 there is only about 1.2 bit/cycle at the 99% level. For say a symbol rate equal to the channel bandwith, since it is the bits/symbol/dimension that is relevant for signal constellations, these higher capacities are not unreasonable. The 19 bits/cycle for n = 4 amounts to 4.75 bits/symbol/dimension while 88 bits/cycle for n = 16 amounts to 5.5 bits/symbol/dimension. Standard approaches such as selection and optimum combining are seen to be deficient when compared to what will ultimately be possible. New codecs need to be invented to realize a hefty portion of the great capacity promised.     

Combining wind farms with concentrating solar plants to provide stable renewable power

We evaluate the extent to which a combination of wind power and concentrating solar power (CSP) may lead to stable and even baseload power by taking advantage of: 1) spatiotemporal balancing of solar and wind energy resources and 2) storage capabilities of CSP plants. A case study is conducted for the region of Andalusia in Spain. To this end, spatiotemporal variability of modeled CSP and wind capacity factors in a 3-km spatial resolution grid were analyzed based on principal component analysis (PCA) and canonical correlation analysis (CCA). Results reveal that renewable baseload power can be obtained in the study region by locating wind farms and CSP plants using balancing patterns derived from CCA and PCA. In addition, the power fluctuation reduction attained from these patterns was substantially higher than those obtained by interconnecting randomly-located wind farms and CSP plants across the study region. Results were particularly meaningful for the winter season. Upon considering storage capability of the CSP plants, results proved better. The main difference was a higher firm capacity value associated with spring and summer seasons. For the other seasons, the contribution of thermal storage capabilities of the CSP plants to stable power proved less relevant.     

南通市水资源供需平衡与承载力研究

近年来,江苏省南通市水质性缺水和季节性缺水问题严重制约了社会经济的发展。为实现可持续发展,利用2015、2020、2030规划年南通市用水和供水系统的水量数据,分析了水资源供需平衡,建立了水资源承载力模型,并以总人口数为目标函数,求解最优化目标。最后通过情景模拟,探讨了不同组合(水量、水质、供水季节)、不同阶段的水资源承载力。结果表明,未来南通市水资源将出现超载情况,2015年可能出现水质性缺水问题;2020年水质问题有所改善,季节性缺水逐渐出现;2030年季节性缺水问题凸显。     

提高深层稠油蒸汽驱排液能力技术研究

蒸汽驱如何提高井组产液量,使采注比≥1．2是成功的关键,对深层稠油油田蒸汽驱而言更为重要。文章以高升油田蒸汽驱先导性试验为例,蒸汽驱后,油层温度大幅度提高,生产井井底温度高达200℃～300℃,引发出一系列新问题为背景,阐述其形成的原因并在此分析的基础上,针对蒸汽驱采油工艺上的难点和出现的主要问题,开展了相关配套技术研究及部分研究成果试验应用,进而提出了一套适合深层稠油蒸汽驱提高排液能力的方式与方法,为下一步深层稠油蒸汽驱采油工艺技术配套提供依据。     

Prospects and challenges of using hydropower for electricity generation in Lebanon

In a region characterized by low water resources, Lebanon stands as an exceptional country in the Middle East. Several waterways present ample opportunity for utilization of hydropower. Before the civil war, several projects were undertaken to generate electricity through hydropower. A total installed capacity of 283 MW has aided Lebanon in supplementing its need of electricity from local renewable sources, thus reducing the overall bill of imported energy. The available hydropower generation constitutes currently 4–7% of the electricity generation depending on rainfall, with future plans expected to install another 205 MW of capacity. This use is in competition with water diversion for irrigation. Four different scenarios were analyzed to indicate the share of hydropower in the total production of electricity, with and without future irrigation and power projects, indicating that, by 2020, hydropower's share of electricity generation will vary between a maximum of 6.9% and a minimum of 1.2% depending on government plans regarding water use. Current value of potential energy available when water from the Litani river is used for hydropower is estimated to be around 20 cents per m³. Water uses planned should take this value into account.