共查询到19条相似文献,搜索用时 46 毫秒
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在美国,有线电视运营商与小贝尔公司鏖战正酣,双方互相进入对方领域的争夺赛正在热热闹闹地上演。1.互相进入,鏖战正酣一方面,小贝尔公司(SBC、南方贝尔、Qwest、Verizon)积极争夺宽带市场控制权,以应对VoIP的挑战,它们还投资了上百亿美元升级公众网络,以为用户提供电视业务,这 相似文献
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1999年无线通信产品增长势头旺盛,其中蜂窝移动电话仍将快速发展,寻呼产品仍平稳增长。到2000年,中国蜂窝移动电话用户将达到3800万户以上,中国联通公司130移动电话也将翻番。届时,全国移动电话用户总数将达到4000万户。中国电信移动电话1997年已达到1323万户,1998年新增800万户(截至8月底完成684.25万户)中国联通130移动电话1998将年达到100万户。预计1999年中国电信移动电话用户将新增800—1000万户左右(含中国联通新增100万户),(包括CDMA DCS—1800移动电话)。 相似文献
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1994年全球无线通信用IC市场规模达20.89亿美元,占全球IC市场的2.3%。而随着蜂窝式无线电话风靡全球,使蜂窝式无线电通信IC在无线电通信IC的领域中占有举足轻重的份量。近年来,数字无线通信标准陆续出台,各国政府实施电信民营化的政策,最近世界四大贸易力量为了推动全球电信市场,在神户举行会 相似文献
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2003年的中国专业无线通信市场,常规模拟终端设备稳步增长,数字集群应用日益普及。TETRA和iDEN两大信息产业部规定的中国数字集群通信标准在国内铁路、公安等领域应用的深度与广度都得到进一步的扩大。而作为TETRA的全球市场领导者、iDEN标准的发起者和倡导者、全球能够同时提 相似文献
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2006年是多功能手机加速发展的一年.各种款式的多功能手机为用户带来了全新的体验。有关专家认为.2007年,多功能手机将成为手机市场竞争的新焦点。欧洲市场去年销售了5000多万部多功能手机,占多功能手机全球总销量的41%。在未来5年内.欧洲将继续占有最大的销量份额,而亚太地区将进一步巩固其全球销量第二的位置。多功能手机将把终端市场打造得更为精彩,使消费者的生活更加丰富多彩。集多种功能于一身的智能化手机,将成为无线通信技术领域一个新热点。[编者按] 相似文献
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摩托罗拉16年前投资中国,现已成为中国最大的外商投资企业,并在中国进出口500强企业中名列榜首。摩托罗拉是中国对讲机市场的领袖企业,是业内唯一能提供从零配件、产品到服务的全套解决方案的厂商。摩托罗拉希望与更多的国内企业合作,与国内企业共同成长是摩托罗拉的愿望。摩托罗拉在天津设有工厂及研发中心, 相似文献
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地铁专用无线通信系统为中心调度员、场段调度员、车站值班员等固定用户与列车司机、防灾、维修等移动用户之间提供无线通信需求,是保证行车安全、应急抢险的重要通信手段。文章结合实际工程案例,研究分析地铁各场景下无线链路规划,论述无线场强计算方法,为地铁专用无线覆盖设计提供必要的参考依据。 相似文献
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在现代电子产品中,无源器件数量超过有源器件数量十倍的现象非常普遍。在空间为主要因素的众多无线通讯产品如手机中,特别需要集成无源器件。这种器件的芯片级封装通过把所有电路无件紧密结合在芯片本身的焊盘位置内来优化印制电路板的空间利用。本提供了模拟的器件和实际达到的器件性能,也讨论了芯片级封装的优势和可靠性因素。 相似文献
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就计算机无线通信系统而言,天线的作用十分重要,正确选择计算机通信系统的天线装置是保证信息传输的重要前提。文中详细介绍了计算机无线通信天线装置的类型,计算机无线通信系统的天线选择及参数的设计。天线的选用需综合考虑匹配问题。 相似文献
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Vandana Milind Rohokale Sandeep Inamdar Neeli Rashmi Prasad Ramjee Prasad 《Wireless Personal Communications》2013,69(3):1087-1096
For wireless sensor networks (WSNs), energy is a scarce resource. Due to limited battery resources, the energy consumption is the critical issue for the transmission as well as reception of the signals in the wireless communication. WSNs are infrastructure-less shared network demanding more energy consumption due to collaborative transmissions. This paper proposes a new cooperative opportunistic four level model for IEEE 802.15.4 wireless personal area network. The average per node energy consumption is observed merely about 0.17 mJ for the cooperative wireless communication which proves the proposed mechanism to be energy efficient. This paper further proposes four levels of cooperative data transmission from source to destination to improve network coverage with energy efficiency. 相似文献
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Haijin Yan Watterson S.A. Lowenthal D.K. Kang Li Krishnan R. Peterson L.L. 《Mobile Computing, IEEE Transactions on》2006,5(11):1575-1590
In mobile devices, the wireless network interface card (WNIC) consumes a significant portion of overall system energy. One way to reduce energy consumed by a device is to transition its WNIC to a lower-power steep mode when data is not being received or transmitted. In this paper, we investigate client-centered techniques for energy efficient communication, using IEEE 802.11b, within the network layer. The basic idea is to conserve energy by keeping the WNIC in high-power mode only when necessary. We track each connection, which allows us to determine inactive intervals during which to transition the WNIC to sleep mode. Whenever necessary, we also shape the traffic from the client side to maximize sleep intervals-convincing the server to send data in bursts. This trades lower WNIC energy consumption for an increase in transmission time. Our techniques are compatible with standard TCP and do not rely on any assistance from the server or network infrastructure. Results show that during Web browsing, our client-centered technique saved 21 percent energy compared to PSM and incurred less than a 1 percent increase in transmission time compared to regular TCP. For a large file download, our scheme saved 27 percent energy on average with a transmission time increase of only 20 percent 相似文献
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Capacity of Wireless Communication Systems Employing Antenna Arrays,a Tutorial Study 总被引:3,自引:0,他引:3
Khalighi Mohammad Ali Raoof Kosai Jourdain Geneviève 《Wireless Personal Communications》2002,23(3):321-352
A tutorial study is performed on thecapacity of multiple antenna wireless communication systems.Multiple antenna structures can be classified into single-inputmultiple-outputs (SIMO), multiple-inputs single-output (MISO), andmultiple-inputs multiple-outputs (MIMO) systems. Assuming that thechannel is known at receiver, capacity expressions are providedfor each structure, under the conditions of quasi-static flatfading. Also, information rate limits are provided in each casefor some suboptimal structures or detection techniques that may beused in practice. Using simulations for the case of flat Rayleighfading, capacities of optimal/suboptimal implementations arecontrasted for each multi-antenna structure. Discussions are madeon system design, regarding implementation complexity andpractical limitations on achieving these capacities. Inparticular, the problem of fading correlation and required antennaspacing, effect of fast channel fading, and lack of channelknowledge at receiver are discussed. Providing the results of themost recent researches considering the capacity of multi-antennasystems, as well as some new results, this paper can give a goodperspective for designing appropriate architectures in differentwireless communication applications. 相似文献