With Satellite Internet On The Road ?

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有意思的一个东西。

我也来说两句 查看全部评论 相关评论

  • papaya (2007-8-03 22:05:57)

    GPRS、CDMA没有信号的时候,在外露营,如何联接INTERNET,如何与外界沟通?
  • papaya (2007-8-03 22:20:03)

    EBAY上看到一款可携带装置,不知在中国能否正常接收,海关是否放行。。。
  • papaya (2007-8-03 22:20:38)

    http://cgi.ebay.com/Portable-RV- ... QrdZ1QQcmdZViewItem


    This auctions is for a Portable Quick Setup Direcway/Hughesnet satellite internet system With Tripod DW 6000 Receiver/Transmitter ,all cables, power supplys and a Router for WiFi.   

    I used this system while on camping trips. It uses the same account as your home system. With a relitively unobstructed southern sky view, It alway preformed flawlessly and never had any issues. Once familiar with setup ,I could have it up and working in 15 to 20 minutes. Less time if you use the same Receiver/Transmitter you use with your home system. This auction does include everything that you need to set up and operate this system. Just the Tripod setup cost over $400 !  I have setup instructions all printed up  which I will include also. Any Q's Please email us. Ray

    This Comes with a D-link Router with Wifi  in case you have to set it up off your campsite to get a clear shot at a southern sky.

    This unit is free and clear, the contract period has expired.

    No telephone services required!

    NO CONTRACT required if you own your equipment.

    Connects directly to a PC or to multiple PC's via a router.

    Way faster than dial-up. Usually 900+ kbs down 160 up

    I paid $1600 for this satellite system and you can buy it now much cheaper!

    This equipment works great.

    Extra care will also be taken in packaging this satellite system to allow for safe delievery.  Local pickup encouraged if possible, it's quite bulky!  This dish will be disassembled for shipping.

    Please visit http://www.hughes.net for plans & installation details.

    America's #1 Choice for Broadband by Satellite.

    With HughesNet™, your super-fast, always-on, satellite Internet access is ready when you are—no dialing in, no waiting and no tied-up phone lines. You can download files in seconds, check email instantly and surf faster than you ever imagined. And HughesNet is compatible with Windows and Mac, so getting online anywhere in the contiguous U.S. is easy!

    Benefits

    Want to access more Web content, get more done and have more fun? Get ready to enjoy the benefits of high-speed Internet access from HughesNet™! Not only do you get high-speed access, but you also get to eliminate the frustration of dealing with a dial-up connection, logging in, and slow surfing speeds. Here are some things people love about HughesNet:

        * Available everywhere…today
        * It’s fast—just sit down at your computer and start surfing!
        * Flip through Web pages like turning the pages of a book
        * Download large files in minutes, not hours
        * Enjoy fast Internet music and video downloads
        * Compatible with Windows® and Macintosh® operating systems
        * Frees up your phone—no missed calls, no dialing in, no extra phone line needed

    [ 本帖最后由 papaya 于 2007-8-3 23:33 编辑 ]


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  • papaya (2007-8-03 22:41:43)

  • papaya (2007-8-03 22:57:09)

    http://www.svacomm.com/cn/satellite.asp?menuid=20&id=340


    地址: 湖南省长沙市国家高新区麓谷(玉兰路号)湘邮科技园6楼国邮通信
    邮编: 410205
    电话: (0731)8998854
    传真: (0731)8998672
    网址: www.postcast.com.cn

    国邮公司故障受理联系方式为:

    客户服务电话:4006770077

                  0731-8998770

    周末值班电话:13875878114
  • papaya (2007-8-03 23:24:53)

    http://www.macsimumnews.com/inde ... ac_part_i_the_costs

    I’ve had satellite Internet installed, and, after three days of test driving it, I’m pleased. It’s not a cheap option, but some of us have few broadband choices. I live on a small road in a suburb of Nashville, TN, that, though only 15 minutes from a major mall, isn’t serviced by DSL or cable. I can take advantage of Sprint wireless thanks to products such as the Franklin Wireless USB Modem, the first wireless broadband USB modem that supports the Mac. It’s a great product, but I wanted something faster. So, after being dissed by DirecTV I turned to HughesNet.

    The company offers five satellite Internet options. The Home plan is US$59.99 per month and offers download speeds of 700 Kbps and upload speeds of 128 Kbps. The Pro plan is $69.99 per month with download and upload speeds of 1000 Kbps and 200 Kbps, respectively. The ProPlus plan (the one I chose) is $79.99 per month with download and upload speeds of 1500 Kbps and 200 Kbps, respectively. The Small Office plan is $99.99 per month and offers download and upload speeds of 1500 Kbps and 300 Kbps, respectively. Then there’s the Business/Commercial plan, which is a whopping $179.99 per month with download and upload speeds of 2000 Kbps and 500 Kbps, respectively. The first three options use a .74 meter with one-watt dish, while the latter two use a .98 meter with two-watt dish.

    Speaking of which, another cost of satellite Internet access is the dish itself. The smaller dish is (with HughesNet’s current promotion and rebates) $274.98, while the bigger dish is $549.98. You can upgrade among the first three service/price plans with a software update, but can’t upgrade to the Small Office or Business plan without replacing your satellite. All the plans include the new HN7000s modem (more on it tomorrow). You’ll probably also want to spring an another $125 for a rock-solid pole mount for the dish. It can be installed on your roof, but you’ll have to sign a waiver that HughesNet isn’t responsible for potential problems—such as, if your roof starts leaking. The serviceman who installed my dish said that roof installations usually went well, but pointed out that the dish weighs about 75 pounds. When it’s sitting atop your roof and the wind is blowing 60 mph, that’s like having the dish shaken by two hefty men. You can see why damage is possible.

    I’ve found the speeds on my Pro plan to live up to HughesNet’s claims. Neither an overcast sky nor a thunderstorm had an apparent effect on my uploading and downloading abilities. I’ve been able to easily download movie trailers from the QuickTime Movie Trailer site and videos from YouTube, something I couldn’t do with dial-up (though “streaming” video is still jerky). I can download system updates from Apple and sizeable software products with ease—something that would take hours (and hours and hours) on dial-up, assuming my connection didn’t “choke” before the download was completed.

    I can use Skype to make calls, even long-distance ones. The audio quality is good, but there’s a noticeable lag in the conversation as data is uploaded and downloaded. Sadly, I’ve been unable to do video chatting with iChat. Though I have 1500 Kbps download speed and 200 Kbps upload speed (which seems to fall within iChat’s requirements), I keep getting a “lack of bandwidth” message. I plan to try another video chat product to see if the results differ. As for online gaming, sorry, but satellite Internet just doesn’t cut it.

    So how does its speeds compare to other options? Many cable companies and Internet service providers argue that cable modems are as much as 100 times faster than a dial-up Internet connection, running at 5 million bits per second (mbps). In theory, it’s possible, but a more realistic speed is 1-2 mbps, or about 20 to 40 times faster than a typical 56,000-bits-per-second (kbps) dial-up connection.

    One type of DSL technology, VDSL, can match cable’s performance. However, Internet service providers generally don’t offer VDSL, but rather the cheaper and slower ADSL or SDSL services. Your DSL speed can change depending on how you use the network.
    DSL providers often advertise speed of their service using a combination of two bandwidth numbers; pretty typically, “1.5 Mbps (downloads) / 128 Kbps (uploads).” The rated maximum bandwidth of a DSL connection often can’t be reached and actual DSL speeds vary between households based on a variety of factors.

    Mobile broadband providers claim they can provide users with typical speeds of 300-500 kbps and bursts of up to 2 Mbps. In my experience with Sprint’s mobile service, I’ve found that the latter speed burst never happened.

    Tomorrow, we’ll look at the HughesNet 7000S modem.
  • papaya (2007-8-03 23:25:52)

    http://www.macsimumnews.com/inde ... ughes_hn7000s_modem

    Yesterday I started a series on satellite Internet on the Mac, using my newly installed broadband satellite through HughesNet. Part 1 looked at the costs; today we’ll look at the modem itself: the HughesNet HN7000S modem, which obviously receives and transmits data over the satellite through the HughesNet network.

    The HN7000S, which was released last July, is compatible with Mac and Windows operating systems and connects effortlessly with your computer via an Ethernet connection (Monday I’ll go through the installation process, and offer some tips you need to know if you sign up for the HughesNet service). The HN7000S is self-hosting, and there’s no software to load. The modem automatically upgrades software when new versions become available. And, unlike with Internet satellite set-ups in the past, no phone line is needed. The modem uses two-way satellite communication for setup and operation. HughesNetT delivers high-speed Internet access totally via satellite, so need neither a phone line nor dial-up data modem.

    While the HN7000S is a big improvement (or so I’m told) over its predecessors, like all satellite Internet systems, you’ll have to deal with transmission latency. Latency refers to the amount of time it takes a packet of data to travel across a network. With satellite service, that data makes a pretty long journey, traveling up to the satellite and back (about 45,000 miles). This round trip adds about a half a second delay to the total time your computer takes to communicate with a web site or host server. Most back-office applications, e-commerce transactions, and common business applications work just fine over HughesNet. Business applications that require response times in fractions-of-a-second (such as web hosting, VoIP, and video conferencing) aren’t recommended over satellite.

    I’ve tried VoIP and video conferencing, and they work with the HughesNet system, but not smoothly. My son Matt and his friend Jake are planning to give online gaming a whirl. Again, it’s not recommended and I’m dubious they’ll have much luck, but I’ll pass along their results when they finished their experiments.

    Can you run a VPN using HughesNet for business? Yep, but running a VPN client over satellite isn’t an ideal configuration. If you choose to run VPN over satellite, your data speeds may be reduced by as much as 50–75 percent. Of course, you can restore your connection to full speed by simply disabling your VPN client when your session is over. However, HughesNet technical support does not provide help with configuring or troubleshooting problems associated with VPN clients. However, part II: HughesNet does offer an end-to-end VPN accelerator solution for large corporations and government agencies. This accelerator delivers higher connection speeds over VPN. Go here for more info.

    One final note: the HN7000 unit lets users take advantage of the second generation satellite broadband application “DVB-S2,” which provides enhancements through increased NOC capacity and out-route traffic. In addition, the new application will allow the system to adjust to obtain the best transmission rates.

    Monday: setting up a home network with multiple computers on the HughesNet system.
  • papaya (2007-8-03 23:26:49)

    http://www.macsimumnews.com/inde ... t_iii_setting_it_up

    In this, the third and final part of this series, I look at setting up satellite Internet on a Mac. I recently had such a service installed at my home office via HughesNet. So far we’ve looked at the costs in Part 1 and the modem itself in Part II. So how do you ago about implementing it?

    First, you’ll need a repairman to come to your home or business and do the actual installation of the satellite dish and the modem (both of these are covered in our previous installments). Once the physical components are in place, the HN7000S modem must be attached to a Mac via an Ethernet cable, which will “talk” to the HughesNet satellite to get your connection up and going for the first time. This takes about 30 minutes. After this, you’re good to go. Unless you want to set up a network. Which I did.

    And that’s where I ran into problems. After unplugging the modem from my desktop Mac, I connected it (again, via Ethernet) to my AirPort Extreme Base Station (though you can use other routers). I tried accessing the Internet and my desktop Mac connected just fine. However, while I could download email, I couldn’t send email. Nor could I get any other Macs on the AirPort network online except my desktop system.

    Finally, after much hair pulling, weeping, gnashing of teeth and unfruitful calls to the (very friendly) HughesNet support number, I finally discovered (with the help of my friend and fellow HughesNet user, Steve Foster) the solution to my problems. It’s a simple one, but I would never have figured it out on my own.

    Here’s the solution—and what you must do if you’re setting up a network that uses satellite Internet (see the graphic below):

    1) Open up the AirPort Administration Utility.

    2) Click on the Network option.

    3) Disable the “Distribution IP addresses” option.

    That’s it. Once I did that, things have worked perfectly (you will also need to set smtp.hughes.net as your outgoing mail server). The Internet access has worked fine through rain, though we haven’t had any bad storms since I’ve had this set-up. I’ll keep you updated on the situation as things, such as the weather, change.

    My recommendation? If you have other Internet options, be sure to check ‘em out. But if, like me, DSL and cable are out of the question and if you can bear the upfront expenses and rather steep monthly charge, I’d certainly recommend HughesNet. The satellite Internet connection has been MUCH faster than I had expected—and it’s made my daily work (and play) much more enjoyable.
  • papaya (2007-8-03 23:28:06)

    http://www.macsimumnews.com/inde ... _satellite_internet

    Recently, I did a three-part series on setting up satellite Internet on a Mac for those who have no other recourse to broadband access (you can read ‘em here: Part 1, Part II and Part III). I’ve had the system for over two weeks now, so how do I feel?

    I didn’t like paying the upfront costs (about 400 bucks) and I don’t like the monthly fee ($69.95). But I can’t get DSL or cable, wireless systems such as EVDO aren’t fast enough and fiber optic is just a dream, so I have little choice. That said the satellite Internet from HughesNet is faster than I thought and pretty reliable. It’s worked in rain without much slow-down and overcast skies don’t seem to affect it at all. Internet gaming doesn’t work, VOiP and video chatting are wanky at best.

    My main complaint: for some reason, I occasionally have to unplug the HughesNet modem from my AirPort Extreme Base Station (I have a network set up) and plug it into my desktop Mac to “reboot” the system (it’s not really rebooting, but that’s the best term I can think of). Then I can reconnect the modem to the Base Station and everything is fine.

    But the bottom line is this: my daily work is much faster. I’d say the Internet satellite saves me at least an hour a day in work time, so it’s more than worth the money. I wish I had other options where I live, but I don’t. For those in my situation, I’d certain recommend satellite Internet.
  • papaya (2007-8-04 22:26:15)

    卫星宽带高速接入因特网--网民的新梦?

    --------------------------------------------------------------------------------

    http://www.sina.com.cn 2001年04月18日 14:45 财经时报

      卫星宽带高速接入因特网的业务正在渐渐兴起,中国通信广播卫星公司迫不及待制定了卫星走入家庭的实施计划,雄心勃勃要营造中国“最e的家庭”卫星宽带高速接入因特网的业务正在渐渐兴起。继去年双威网络通讯公司卫星高速互联网宽带接入服务推出后,中国通信广播卫星公司也迫不及待制定了卫星走入家庭的实施计划,并成立中星在线业务部,雄心勃勃要营造中国“最e的家庭”。


      据了解,在美国,休斯公司和吉莱特公司已为几万户家庭提供了卫星宽带高速接入的服务,吉莱特公司还有意进军中国卫星接入市场。但有业内人士分析,由于种种原因,卫星接入要真正走进中国的普通家庭,还有很长的路要走。

      国内卫星接入市场硝烟渐起

      据了解,国内最早介入卫星接入业务的是电信系统。广东信网通公司从1999年开始在中国率先推出了高速互联网卫星接入,产品是“星网通”。当时由于国内普通用户的上网费用极其昂贵,使用DDN上网大约需要2万元。因此使用卫星接入技术市场发展空间很大,不但在出口带宽方面有优势,使用效果好,在卫星信道的费用上也极具竞争力。“对卫星接入业务来说,当时可谓是千载难逢的好机会。”中国通信广播卫星公司中星在线总经理黄锐说。但由于信网通的股东对此业务兴趣不大,加上电信管理机制不顺等原因,信网通最终没有将此业务很好地开展下去。

      第二家进军卫星接入业务的是号称2000年卫星市场大“黑马”的双威网络通讯公司,该公司采用休斯公司的技术,与电信163合作,在各地共同推出名为“Turbo163(高速163)”的卫星高速互联网宽带接入服务。该公司业务发展迅猛,不到三个月的时间,便与北大、清华谈妥了上千个远程教育卫星小站的合作意向,其用户数量发展到了1000多家。据业内人士分析,该公司当时的业务扩张,是基于不计成本进行规模扩张的结果,当时该公司用户使用400K的专线、不限流量的接入使用,每月的费用仅为1000元,根本不存在赢利。今年下半年由于科技股泡沫的破灭,该公司管理层变更,其运作费用也提高到了每月2600元。

      最为雄心勃勃的应属中国通信广播卫星公司,该公司推出了名为中星在线的高速因特网卫星接入和多媒体广播服务,采用美国休斯公司的技术,中星在线总经理黄锐说,该公司为用户提供的是远高于现在DDN因特网接入速度的400K,可以带动30-50台机器同时运转,每月的使用费用为2500元,应该是中国用户所能接受的具有市场竞争力的结合点。

      据了解,除中广卫、双威公司外,东方网络公司等也在开展卫星接入业务,甚至吉通、网通等公司也对卫星接入业务有着深厚的兴趣,地面上宽带接入硝烟弥漫的战争已升上了天空。

      休斯与吉莱特争夺美国家庭

      据了解,卫星宽带接入系统已经为美国大众所接受,并走入了美国家庭。美国400万户家庭中有10%是住在独院的,这种居住环境,使用卫星接入设备较铺设通讯光缆更为经济实用,专家预计其中会有1/3的用户使用卫星接入设备,这个市场是非常庞大的。世界两大卫星通信公司休斯和吉莱特早就为争夺这一市场展开了激烈竞争。

      休斯公司早在60年代就已经从单纯卫星制造业务介入到卫星终端数据接收业务,1999年该公司将其空间技术制造公司卖给了波音,成为一个纯粹的卫星通信运营公司。该公司现已为美国50多个州的10000多个加油站,及几个大型超市连锁店开展业务,占有65%的市场份额。创建于1987年的吉莱特卫星通信公司是休斯最强劲的竞争对手,该公司在美国的市场占有率已达20%以上,新增市场的市场占有率超过了休斯,其发展势头很猛。

      据悉,休斯公司与美国在线等公司合作,1997年开始进军美国家庭,现已发展10万用户,该公司预计今后三年将发展150万用户。美国家庭使用该公司产品,安装终端产品设备需要100美元,由于公司对用户的每月流量有一定的限制,使用费用较低,约为30美元,与使用ADSL和CABLEMODEM的费用价位差别不大。

      吉莱特公司与微软、EchoStar通信公司合作,联合推出可将高速互联网接入和卫星直播电视集成在一起的Gila-to-home业务,后更名为StarBand。该产品2000年底推向市场,正在为2万名互联网用户提供免费试用,该产品的使用在流量上对客户没有限制,费用约为每月60美元。

      业内人士分析:休斯公司实力强大,进入该领域时间长,客户占有率高,有一套自己成熟的服务体系;吉莱特公司在星上互动方面的技术领先于休斯,并将其产品定位在民品化上,尽量使用市场能买到的大众通信产品做零部件,很受美国人的欢迎,最后鹿死谁手很难预测。

      家庭卫星接入还有多远

      在谈到卫星宽带接入与光缆接入可能出现的天网与地网的竞争时,几乎所有的卫星通讯公司都不约而同的表示,卫星宽带与光缆宽带接入不会构成竞争,它们之间只是一种补充关系。

      积极筹措进军中国卫星接入市场的吉莱特公司高级工程师王宝钧认为,卫星宽带高速接入因特网的最大优势在于它广阔的覆盖性。从理论上讲,卫星宽带接入可以到达任何地方,特别是到达光缆宽带接入达不到的地方,如地广人稀或地貌复杂的地方。这些地方铺设光缆的费用极大,而且由于居住区分散,利用效率不高,可能会得不偿失,而如果使用卫星通信,则完全可以以低得多的成本更好地满足需要。

      据了解,我国曾建设兰州─西宁─拉萨光缆线路,并对此进行大力的宣传,但由于西藏的电信市场本来就非常有限而又高度分散,致使这条光缆的利用率微乎其微,而且光缆上的全部收入连维护费用都难以维持。

      中国通信广播卫星公司总裁周泽曾表示,卫星的作用不可能被其他通信手段完全替代,它是地面网很重要的补充。而且,地面网容易受到破坏,经常听到有光缆被挖断的事件,而空间网不容易受到破坏。再加上卫星最大的特点就是具有一点对多点的广播功能,比地面网经济得多。

      但据了解,由于我国居民居住环境趋于集中,加上国内光缆铺设的速度很快,卫星接入设备及费用仍偏高等原因,卫星接入因特网目前还很难走入家庭。吉莱特与中广卫公司都坦言,虽然他们都将目标定位于家庭,但到目前为止,其业务主要集中在网吧、学校、机关、企业等,接入家庭也是通过居民小区间接接入,在国内还没有开展居民直接卫星接入因特网的业务。

      对此,中广卫公司的黄锐解释说,因为我国居民居住环境、居住条件以及生活习惯不同于美国,美国许多家庭都是独院居住,有很大的空间可以安装卫星接入设备,也就是那个“大锅盖”;中国居民多在小区居住,不要说费用承担的问题,就是设备安装也存在空间上的不足,现在讲卫星接入进入家庭还是通过小区,整个小区的居民共用一套卫星接入设备。

      据了解,卫星接入系统能在美国大行其道的原因还在于美国人喜欢自己动手的习性。在美国,卫星接入设备就象日用品一样在超市里由居民自由选购,相当一部分美国人有自己动手的兴趣,因此很受美国人喜爱,这在中国显然是不适用的。

      但不论是中广卫还是吉莱特都表示,随着卫星宽带接入技术的发展,此业务的成本费用还会有很大的降价空间,加上我国居民的居住条件、生活水平不断得到改善,卫星宽带进入中国家庭的时代不会久远。记者李亮/文(完)
  • papaya (2007-8-04 22:32:32)

    几种可能的宽带卫星接入的解决方案
      多媒体技术是一种新兴的信息交流方式,它不是简单的把声音、文字、图形和图像等几种媒体叠加后呈现在人们面前,而是通过有机的信息集成,为人们提供最优的视听品质。随着多媒体应用的逐步普及,传统的网络框架已不再适用,全交换和高速接入已成为新型网络结构的两大特点。因此,对网络技术的基本要求也相应加强。
      
      首先,多媒体通信网络必须有足够的带宽。数据传输速率应该在100Mbit/s以上,才能满足各类多媒体通信应用的需求;其次,网络必须保证多媒体通信的实时性和可靠性。语音和图像的延时都要小于0.25s,静止的图像要求小于1s,对于共享数据要求没有误码;再有,系统必须保证精确的同步,这包括媒体间同步和媒体内同步;多媒体通信的最大特点就是交互性。它不仅要求具有高质量的多媒体数据传播能力,还要求具有一定的信息反馈能力,能及时传送用户的反馈信息。
      
      一般现有的电信网、计算机网和CATV网,虽然都可以用来传送多媒体信息,然而都各自存在不同的缺陷。加之全球范围内的Internet接入、交互式多媒体业务、电视会议和其他带宽密集型应用的迅速增长,要求有更加灵活和成本低廉的宽带解决方案。
      
      针对上述多媒体通信的要求,鉴于卫星宽带接入的特点,现主要提出两种加速因特网传输的卫星接入方案:一种是利用卫星的高速下载和地面反馈的外交互的方式,该方案是基于当前因特网信息流量非对称性(接收数据量往往远大于发送数据量)而提出的,采用卫星链路作为下行数据链路,将其他通信网络如电话拨号。局域网等作为上行数据链路。另一种是利用宽带卫星的双向传输,例如Teledesic系统可以给用户提供16kbps~2.048Mbps的传输速率。
      
      下面分析几种具体的卫星宽带接入的解决方案。
      
      方案一:卫星与传统的Modem或专线相结合接入Internet
      
      该方案其工作原理如下:用户的电脑装配一张卫星网络PCI卡,并和一个大约75厘米口径的卫星接收天线相连。所有低带宽。外向的信息(如网址要求)通过调制解调器从电话网络上送出,但所有高带宽。内向的信息(比如一个图像丰富的网站)都从卫星上直接发射到用户的电脑上。用户在浏览器软件上单击一个网址,网址要求信号由调制解调器送出到用户的ISP。在这个要求信号离开用户PC机之前,用户端软件附加了一个IP头码到要求信号上。这个附加码指示用户ISP把要求信号转到网络运行中心,NOC接到要求信号后,把附加码去除,然后根据用户要求到相应的网站去获取所需信息,再将信息上传到卫星,以高速高带宽送到用户的接收天线,再到用户的PC机上或配置机顶盒STB(set top box)的视频接收机中。这种卫星高速数据接入系统充分利用互联网不对称传输特点,采用DirecPC技术,用户端只需14.4kbps以上Modem基本上网配置。卫星网络PCI卡。用户端软件和0.75m卫星接收天线等设备即可。系统的交互速率可达200-400kbps,最高可达3Mbps高速单向广播式数据文件下载。
      
      该系统比较适合于单向的远程教学,也可以用于会议电视及为各类教育机构、大中院校、成人教育等开设交互式远程教育课程等。但采用Modem拨号上网要受限于线路速度,最高不超过56kbps,而且上网的费用相对较高。即使采用光缆或卫星及微波等无线信道的专线连接方式能提高上行速度,但由于需要建立联网的站点且费用较高,使得它只适合于业务量大的单位和机构团体,不适合于广大个体用户。目前很多公司都采用这种类似的卫星宽带接入方式,如中国通信广播卫星公司推出的"中星在线"、广东电信推出的"星网通"业务以及科利华公司开发的卫星宽频互动教育平台等。
      
      方案二:卫星与有线电视网相结合接入Internet
      
      为了寻求一种对个体用户来说上网快、费用低、投资少、见效快的途径,不妨考虑卫星与有线电视网相结合的新型上网方式。有线电视网的HFC网络是采用光纤和同轴电缆混合铺设,具有成本低。信号质量好。频带宽的特点,给家庭用户高速、快捷上网开辟了一条新途径。
      
      由Internet的高速接入供应商、本地ISP有线电视台(CATV网络)和用户终端组成。国际出口就是一个Internet高速接入供应商,在这里建立卫星上行的主站,下行数据经过发射无线送到卫星转发器。在有线电视台设立卫星接收站,把收到的数据经过电缆数据调制器。上变频器,变成有线电视网络需要的射频RF,用户在家中使用带有数据广播接收卡的计算机,将电缆中的信号解调并接收。同时用户的计算机配普通电话Modem,拨号到本地ISP,把用户的请求信息传送到对方。本地ISP在此起到路由的作用,沟通用户和远端的国际出口局。这样从地面Internet上行到卫星与有线下行,构成了一条完整的双向数据通路。
      
      这种新的接入Internet的方法充分利用了现有的CATV网的现状和卫星不对称单向广播的特点。有线电视网络仍然采用当前的单向传输,而卫星也采用单向广播传输,用户的回传信息则通过地面的Internet传送到信息源。这种方式,有线台就不必要建设卫星上行站,而有线电视网也不必要进行双向改造,这就大大减少了资金的投入,缩短了建网的时间。从卫星到有线整个信道具有宽带特点,且价格低廉,让用户充分享受到高速上网的服务,是一种比较理想的宽带接入方式。
      
      方案三:卫星与VSAT系统结合的双向传输网络
      
      前述两种方案都利用地面网来实现信息的回传问题,但是地面网的信道比较拥挤,可能常常会发生阻塞和故障,此时不妨考虑利用VSAT网来接入Internet。由于VSAT系统具有覆盖范围大。结构灵活。组网迅速方便。易于实现多级连接,用户终端接入方式灵活等优点,使得它完全可以作为地面网的补充,甚至在某些场合成为唯一的可行方案。
      
      除了使用VSAT网或地面网外,我们可以考虑使用双向VSAT小站通过卫星链路的回传信道来实现双向传输。一般来说小站的回传速率远小于下行广播速率,因此考虑采用星型(star network)的VSAT系统。该系统的大量高速数据通过主站天线发射至卫星转发器,下行则通过数字视频广播(DVB)传送至各个远端的VSAT小站,最后再通过相应的数据接口设备传送到某一用户的电脑,或是通过与局域网相连的某一PC机传送给多个用户。
      
      由于主站与远端站间需要进行交互传输,因此远端站需要安装一个宽带双向(two-way)终端。如果远端小站只接收Internet内容,则只需安装单向(one-way)终端。一个双向终端主要包括室外单元(ODU)和室内单元(IDU)。ODU包括RF部分的天线和HPA。IDU则配有机顶盒(set top box)用于提供宽带交互式卫星系统网络接入的数据接口,连接ODU和用户的PC。用户的需求和反馈信息通
  • 杨逍 (2007-8-06 19:28:27)

    PPY负责买一个,其他TX去哪FB都拉上他
  • 笑忘书 (2007-8-08 11:01:45)

    越来越精彩了·
  • 老乐 (2007-8-08 23:34:04)

    越来越FB了
  • papaya (2008-2-01 14:32:02)

    从08年初这次雪灾的情况来看,这玩意越来越重要了。

    +发电机+电脑基本上能与外界沟通了。
  • papaya (2008-2-01 14:47:44)

    DW7000卫星通信系统简介
       主要应用
        解决一些偏远地区的通信难题。专业解决地面网络不能通信的地区,用卫星链路提供互联网接入、语音通信、收发传真等服务。特别适合石油、矿业及时传输地面检测站获取的信息。
    普及卫星电视广播和卫星电视教育,传送广播电视、商业数据信号 。用于水利建设的管理,以达到传输监测水文变化情况,防止和减少自然灾害的损失的目的。
        卫星通信的优势
        1.通信距离远、应用范围广
        DW7000卫星通信系统属于广义上的宇宙通信范畴,所以具有良好的覆盖性和广播性。全球任何地方都可以提供服务。卫星通信可以很方便地跨越几千公里,连接其他通信手段所无法达到的边远地区、居住点、家庭和移动的车船、个人。而且无论两通信点近在只尺或远在几千公里以外,它们的传输距离和传输时间是相同的。卫星通信设备可方便地组成星形或网状网络,用于数据传送、数据搜集、电话通信等方面。
        2.通信电路开通迅速、简便
        在VSAT星状网络当中,终端只是通过单跳就可以同中心站通信,无须中途转接,无第三方设备参与,避免了地面通信手段多次转接、电路迂回的缺点。用户就无需进行大量的基础设施建设,完全跳过了通常网络建设中的线路铺设问题。因此,卫星通信是最直接、最简洁的接入方式。
        3.通信系统稳定可靠
       由于避免了在地面电路通信中存在的多次转接、电路迂回带来的高故障率,卫星通信系统具有很高的稳定性和可靠性。
        4.投资少、见效快
        在VSAT网络建设中,卫星资源由卫星运行公司管理、测控。卫星通信系统的主要工程是主站的建设。而小站的安装十分简便,安装、调试迅速。所以VSAT网络建设周期短,投入使用迅速。
        5.运行、管理灵活、方便
        基于卫星通信的结构特点,其主站具有很强的操作和运行的管理、监控功能。而且是主站对全网、对主站每个小站的直接管理和监控。对主站本身发出的信号从卫星转发回质量的监控。这也是保证系统高可靠的前提。主站(HUB)设备具有很强的管理功能。卫星通信系统的组态,运行,每个小站的加入、退出,小站的业务设定均由主站操作。小站基本是无人值守的。系统的扩容、通信网络结构的重组、通信小站的搬迁,均通过主站设置完成。