数字家庭——传输与存储篇电力线传输与储存科技加持数位家庭逐渐成型

经过2004年的激情讨论后,表面上"数字家庭"这个名词似乎再也激不起产业界及分析师等权威人士的热情.然而情况却不然,随着网络的发展、生活习惯的改变及厂商推出的产品来观察,"数字家庭"这个名词正逐步转为动词,经过多年的酝酿,"数位家庭"终于逐渐成型.     

探询中国3G决策思维

2003年以后,全球3G市场进入新的阶段.跨国通信巨头们纷纷宣称,已经在WCDMA、cdma 2000两大标准方面取得了实质性进展,全面支持商用化.同时,集中开发WCDMA设备的欧洲厂商对于中国提出的TD-SCDMA也张开了怀抱,关于两大标准互补性的言论不绝于耳.香港和黄电讯在欧洲几国全面建设和运营3 G网络,中国的近邻日本、韩国3 G市场开始出现快速增长的迹象.这些经历无法代替一个关键性的角色,世界最大通信市场所在地的中国尚未吹响3G的号角.     

多名学者欲联名状告超星侵权网络盗版顽疾再刺业界神经

接连而至的官司,再次搅起版权领域的千层浪! 2007年4月17日,中国社科院研究员吴锐及其导师刘宝才的一纸诉状,将数字图书馆解决方案提供商北京世纪超星公司(下称"超星")推上了北京海淀区法院的被告席.     

告阿里巴巴商标侵权?这个玩笑开得太大了

一家国内最大的电子商务公司的商标被一家名不见经传的企业所拥有,听起来似乎很荒唐,然而细细深究,却更像是一个拙劣的玩笑. 11月6日,阿里巴巴网络有限公司(股份代号:1688)于香港联合交易所有限公司主板开始交易.开盘即达到30港元,较发行价13.5港元上涨122%,加上超额认购部分,融资17亿美元,市值超过200亿美元,创下中国互联网市值之最,同时也是全球最大互联网融资.     

iSCSI分析及其Linux驱动实现

iSCSI，是IETF制订的用于将SCSI数据块映射成以太网数据包的一项标准，是实现IP存储的重要技术之一。本文分析了iSCSI协议及其Linux系统中驱动的实现方法。     

IMS:在不断质疑中前进

IMS的出现为下一代网络的发展和业务的融合提供了一种思路和方式,但IMS本身依然还不是十分成熟,还存在着一些问题,如理解和评估困难、标准和产品脱节、商业模式不明确等,业界也有不同的声音.但尽管如此,IMS还是在一步步变成现实,这表现在标准化和运营商的网络部署和互操作性方面.     

周忆,走向国际舞台的公关丽人

2007年3月9日,周五,晚.位于北京王府井大街旁的金宝大厦小南国餐厅内一派喜庆.50多位中国主流的IT媒体总编辑们相聚在这里,他们是来祝贺周忆女士荣升IBM亚太区副总裁的.这个职务在历史上(包括IBM在内的所有跨国公司),从来没有降临到任何亚裔人士的头上.周忆的进步,表明了中国本土公关人才开始走向国际舞台.     

IEC TC47半导体器件标准化最新动态

1 IEC TC47年会召开 2007年11月5～9日,在法国图卢兹召开了IEC TC47、SC47A、SC47E及相关工作组会议,来自英国、美国、德国、日本、韩国和中国国家委员会的数十名代表参加了会议.     

CEO空缺团队各自为战英独立软件在华举步维艰

很难想象,一家在全球数一数二,进入中国市场长达4年之久的英国独立系统软件公司(Autonomy),其中国公司CEO职位目前竟然处于空缺状态. 在近日举行的2007年互联网大会上,发现代表英国独立系统软件公司上台演讲的不再是大中华区总裁伍昕,而是公司COO安迪·康特.而此前,担任这一演讲重任的几乎都是伍昕.而在其后进行的演讲秀中,伍昕虽然也上台亮相,但其身份却已变成北京赛金传媒科技有限公司(openv)的CEO.     

得胜：从广东制造走向世界品牌——专访广东得胜电子有限公司总经理杨志豪

在第十七届中国国际专业音响、灯光、乐器及技术展览会的五号馆,有一个布置精致、宽敞明亮的展台,这就是著名的广东得胜电子有限公司展台.展区的外面,是得胜公司推出的"集成应用"系统方案的宣传画.进入展区,整洁的展台上按产品类别展示着得胜牌传声器、耳机、扩音器及科声产品.透明的玻璃演出间,乐队正在里面投入地演奏.展区中得胜公司的工作人员正在接待来参观的客人.     

Performance evaluation of an adaptive self-organizing frequency reuse approach for OFDMA downlink

Orthogonal frequency division multiple access (OFDMA) is extensively utilized for the downlink of cellular systems such as long term evolution (LTE) and LTE advanced. In OFDMA cellular networks, orthogonal resource blocks can be used within each cell. However, the available resources are rare and so those resources have to be reused by adjacent cells in order to achieve high spectral efficiency. This leads to inter-cell interference (ICI). Thus, ICI coordination among neighboring cells is very important for the performance improvement of cellular systems. Fractional frequency reuse (FFR) has been widely adopted as an effective solution that improves the throughput performance of cell edge users. However, FFR does not account for the varying nature of the channel. Moreover, it exaggerates in caring about the cell edge users at the price of cell inner users. Therefore, effective frequency reuse approaches that consider the weak points of FFR should be considered. In this paper, we present an adaptive self-organizing frequency reuse approach that is based on dividing every cell into two regions, namely, cell-inner and cell-outer regions; and minimizing the total interference encountered by all users in every region. Unlike the traditional FFR schemes, the proposed approach adjusts itself to the varying nature of the wireless channel. Furthermore, we derive the optimal value of the inner radius at which the total throughput of the inner users of the home cell is as close as possible to the total throughput of its outer users. Simulation results show that the proposed adaptive approach has better total throughput of both home cell and all 19 cells than the counterparts of strict FFR, even when all cells are fully loaded, where other algorithms in the literature failed to outperform strict FFR. The improved throughput means that higher spectral efficiency can be achieved; i.e., the spectrum, which is the most precious resource in wireless communication, can be utilized efficiently. In addition, the proposed algorithm can provide significant power saving, that can reach 50% compared to strict FFR, while not penalizing the throughput performance.

     

Partial channel information feedback mechanism for FFR-based multi-channel systems

This article puts forward a partial channel state information(CSI) feedback scheme for fractional frequency reuse(FFR)-based orthogonal frequency division multiple access(OFDMA) systems.Efficient CSI feedback strategy plays an important role in opportunistic scheduling because base station(BS) can employ adaptive modulation and coding(AMC) technique to adaptively change transmission rates according to CSI feedback,and therefore the spectrum efficiency can be improved significantly.On the other hand,FFR is a...     

Interference management with adaptive fractional frequency reuse for LTE-A femtocells networks

This paper presents a novel interference management strategy, to adaptively choose the best fractional frequency reuse (FFR) scheme for macro and femto networks. The strategy aims to maximize the system throughput taking into account a number of system constraints. Here, the system constrains consist of the outage constraints of two-tier users and macrocell spectral efficiency requirement. The detailed procedures of our proposed strategy are: 1) A reference signal received power (RSRP) based selection algorithm is presented to adaptively select the optional FFR schemes satisfying the outage constraints. 2) Considering the macrocell spectral efficiency, the optimal FFR scheme is selected from the optional FFR schemes at MeNB side, to achieve the maximum system throughput in two-tier femtocell networks. We study the efficacy of the proposed strategy using an long term evolution advanced (LTE-A) system level simulator. Simulation results show that our proposed interference management strategy can select the best FFR scheme to maximize the system throughput, and the FFR schemes derived by using RSRP-based selection algorithm can be the effective solutions to deploy femtocells in macrocells.     

Downlink Transmit Power Allocation in Soft Fractional Frequency Reuse Systems

Downlink transmit power allocation schemes are proposed for soft fractional frequency reuse (FFR) in loose and tightly coordinated systems. The transmit powers are allocated so that the loss of spectral efficiency from the soft FFR is minimized, and the required cell edge user throughput is guaranteed. The effect of the soft FFR on spectral efficiency is evaluated depending on the power allocation schemes and the number of subbands. Results show that the loss of spectral efficiency from the soft FFR can be reduced by configuring an appropriate number of subbands in the loosely coordinated systems. In tightly coordinated systems, results show that the loss of spectral efficiency can be minimized regardless of the number of subbands due to its fast coordination.     

采用部分频率复用的小小区网络建模与分析

小小区组网技术被认为是解决迅速增长的移动数据量需求的方法。然而,密集的小小区组网会导致严重的小区间干扰。传统的部分频率复用方法不能完全照搬用在部署不规则的小小区网络内,急需一种合理高效建模采用频率复用小小区网络的方法,对其性能进行评估。利用随机几何理论对小小区网络考虑部分频率复用场景进行建模,推导了考虑部分频率复用的小小区网络下行覆盖概率和网络吞吐量的表达式。数值仿真结果显示：部分频率复用技术可以提高小小区网络下行覆盖概率,但是会降低网络图吞吐量。在满足覆盖概率约束条件下,得到了使得网络吞吐量最大的频率复用因子的表达式。以上结果对未来采用频率复用技术的小小区组网的具体实施具有重要的指导意义。     

Bandwidth Partitioning and SINR Threshold Analysis of Fractional Frequency Reuse in OFDMA Cellular Networks for Real Time and Best Effort Traffic

To achieve high capacity in cellular networks, frequency reuse factor of unity is used. However, it suffers from heavy co-channel interference at cell edge regions. This leads to poor Signal to Interference plus Noise Ratio (SINR) and hence poor performance. fractional frequency reuse (FFR) is one of the methods being considered to improve cell edge performance. In this work we present the impact of SINR threshold and bandwidth partitioning on the successful deployment of FFR scheme. We have considered both real time (RT) and best effort (BE) traffic. In FFR, the total frequency resource is divided logically into cell center and cell edge user bands. However, while frequency resource is partitioned into two segments, the amount of bandwidth required by cell center and cell edge users is quite different and influences the system performance. We developed the semi analytical approach to evaluate the average bandwidth required by cell center and edge band users. From the analysis and simulation results it is seen that while grade of service (GoS) fair based method of choosing bandwidth partitioning ratio is best for RT traffic, while the only feasible method for BE traffic is dividing the bandwidth based on probability of a user to be in a given band which we termed as ‘Probability’ method.     

A System Level Energy Model and Energy-Quality Evaluation for Integrated Transceiver Front-Ends

As CMOS technology scales down, digital supply voltage and digital power consumption goes down. However, the supply voltage and power consumption of the RF front-end and analog sections do not scale in a similar fashion. In fact, in many state-of-the-art communication transceivers, RF and analog sections can consume more energy compared to the digital part. In this paper, first, a system level energy model for all the components in the RF and analog front-end is presented. Next, the RF and analog front-end energy consumption and communication quality of three representative systems are analyzed: a single user point-to-point wireless data communication system, a multi-user code division multiple access (CDMA)-based system and a receive-only video distribution system. For the single user system, the effect of occupied signal bandwidth, peak-to-average ratio (PAR), symbol rate, constellation size, and pulse-shaping filter roll-off factor is analyzed; for the CDMA-based multi-user system, the effect of the number of users in the cell and multiple access interference (MAI) along with the PAR and filter roll-off factor is studied; for the receive-only system, the effect of 1/f noise for direct-conversion receiver and the effect of IF frequency for low-IF architecture on the RF front-end power consumption is analyzed. For a given communication quality specification, it is shown that the energy consumption of a wireless communication front-end can be scaled down by adjusting parameters such as the pulse shaping filter roll-off factor, constellation size, symbol rate, number of users in the cell, and signal center frequency     

Performance analysis of hexagonal cellular networks in fading channels

This paper analyzes the location‐dependent performance metrics of coverage probability and spectral efficiency in hexagonal cellular networks under Rayleigh fading with a general distribution for shadowing and also including two special cases of no shadowing and lognormal shadowing. The effects of system parameters such as frequency reuse factor, transmission probability of base stations, and signal‐to‐interference‐plus‐noise ratio gap from Shannon capacity are accurately characterized. The proposed approach is applied to fractional frequency reuse (FFR) scheme where the impact of FFR on spectral efficiency is evaluated. Numerical results show that (i) in a lognormal‐shadowed Rayleigh fading channel with the shadowing standard deviation of 12 dB, the cell area wide spectral efficiency is degraded by approximately 40% compared with when there is Rayleigh fading without shadowing; (ii) the improvement in spectral efficiency achieved by FFR over the universal frequency reuse increases as the transmission probability increases and the shadowing becomes less severe; and (iii) in Rayleigh fading without shadowing environment where all the base stations are actively transmitting, FFR achieves approximately 20% improvement in spectral efficiency in the cell edge area. Interestingly, this improvement increases to about 30% if a 3‐dB signal‐to‐interference‐plus‐noise ratio gap from Shannon capacity is further accounted. Copyright © 2015 JohnWiley & Sons     

Resource Allocation with Partitioning Criterion for Macro-Femto Overlay Cellular Networks with Fractional Frequency Reuse

The interference mitigation technique based on fractional frequency reuse (FFR) provides improved cell-edge performance with similar overall cell capacity as that of systems with the frequency reuse factor of one. Furthermore, frequency sub-band allocation by FFR has the benefit of allowing flexibility for the deployment of femto-cells through frequency partitioning. Determination of a proper frequency partitioning criterion between the cell-center and the cell-edge, and between the cells with femto-cells is an important issue. In addition, time resource partitioning introduces another degree of freedom to the design of time-frequency resource allocation. In this paper, we propose a novel time-frequency resource allocation mechanism using FFR for a macro-femto overlay cellular network. Feasible frequency sub-band and time resource is allocated to the cell-center and the cell-edge region in a cell by the proposed partitioning criterion and the time partitioning ratio. We provide a guideline for how to determine the partitioning criterion for the regions and how to design the amount of time resource. We derive the average capacity of macro-cells and femto-cells, and introduce a new harmonic mean metric to maximize the average capacity of the regions while achieving the fairness among users in a cell.     

一种面向CR-NOMA系统的动态功率分配算法

在密集小区的认知无线电非正交多址（cognitive radio non-orthogonal multiple access, CR-NOMA）网络场景下,针对用户采取Underlay方式复用时信道频带利用率低的问题,提出了一种基于能效的组合用户动态功率分配算法. 该算法在保证主用户服务质量前提下,基于用户之间的干扰和信干噪比,优化了组合多用户的接入方案,使信道接入用户数量最大且提高了频带利用率. 同时,根据增益排序下的功率差额配比改进了剩余功率再分配方案,使空闲功率重新利用更加合理和有效. 仿真结果表明,本文算法可以有效实现接入用户数量最大化的同时提高了频谱利用率.