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发表于 2006-4-10 10:40:00
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<P>所以在中国用双频手机就可以了(900/1800).</P><P>到美国要用三频手机(900/1800/1900).因为大部分美洲国家用1900.</P><P>又多了一个850,就是为什么现在有的手机方案是四频的,现在南美和北美有用.</P><P>450好像是大灵通吧,CDMA有用这个频段.传输距离远,适合边远山区.</P><H3>GSM-900 and GSM-1800</H3><P>GSM-900 and GSM-1800 are used in most of the world.</P><UL><LI>GSM-900 uses 890 - 915 MHz to send information from the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Mobile+Station&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Mobile Station</FONT></A> to the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Base+Station+Subsystem&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Base Transceiver Station</FONT></A> (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Upstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>upstream</FONT></A>) and 935 - 960 MHz for the other direction (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Downstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>downstream</FONT></A>), providing 124 RF channels spaced at 200 kHz. Duplex spacing of 45 MHz is used. </LI></UL><P>In some countries the GSM-900 band has been extended to cover a larger frequency range. This 'extended GSM', E-GSM, uses frequency range 880 - 915 MHz (upstream) and 925 - 960 MHz (downlink), adding 50 traffic channels to the original GSM-900 band. The GSM specifications also describe 'railways GSM', <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=GSM-R&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>R-GSM</FONT></A>, which uses frequency range 876 - 915 MHz (uplink) and 921 - 960 MHz (downstream). R-GSM provides additional channels and specialized services for use by railway personnel.</P><P>All these variants are included in the GSM-900 specification.</P><UL><LI>GSM-1800 uses 1710 - 1785 MHz to send information from the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Mobile+Station&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Mobile Station</FONT></A> to the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Base+Station+Subsystem&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Base Transceiver Station</FONT></A> (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Upstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>upstream</FONT></A>) and 1805 - 1880 MHz for the other direction (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Downstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>downstream</FONT></A>), providing 374 channels. Duplex spacing is 95 MHz. </LI></UL><P>GSM-1800 is also called PCS in <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Hong+Kong&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Hong Kong</FONT></A> and the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=United+Kingdom&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>United Kingdom</FONT></A>.</P>
<H3>GSM-850 and GSM-1900</H3><P>GSM-850 and GSM-1900 are used in the United States, Canada, and many other countries in the Americas. GSM-850 is also sometimes called GSM-800.</P><UL><LI>GSM-850 uses 824 - 849 MHz to send information from the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Mobile+Station&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Mobile Station</FONT></A> to the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Base+Station+Subsystem&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Base Transceiver Station</FONT></A> (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Upstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>upstream</FONT></A>) and 869 - 894 MHz for the other direction (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Downstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>downstream</FONT></A>). </LI></UL><UL><LI>GSM-1900 uses 1850 - 1910 MHz to send information from the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Mobile+Station&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Mobile Station</FONT></A> to the <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Base+Station+Subsystem&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Base Transceiver Station</FONT></A> (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Upstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>upstream</FONT></A>) and 1930 - 1990 MHz for the other direction (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Downstream&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>downstream</FONT></A>). </LI></UL><P><a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=PCS&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>PCS</FONT></A> is an acronym for <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Personal+Communications+Service&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Personal Communications Service</FONT></A>, and merely represents the original name in North America for the 1900 MHz band. <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Cellular&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Cellular</FONT></A> is the term used to describe the 850 MHz band, as the original analog cellular mobile communication system was allocated in this spectrum. Providers commonly operate in one or both frequency ranges.</P><p><H3>GSM-400</H3><P>Another less common GSM version is GSM-400. It uses the same frequency as and can co-exist with old analog <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Nordic+Mobile+Telephone&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>NMT</FONT></A> systems. NMT is a first generation (<a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=1G&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>1G</FONT></A>) mobile phone system which was primarily used in <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Nordic+countries&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Nordic countries</FONT></A>, <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Eastern+Europe&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Eastern Europe</FONT></A> and <a href="http://www.answers.com/main/ntquery;jsessionid=sa6k9kx7jcvp?method=4&dsid=2222&dekey=Russia&curtab=2222_1&sbid=lc01b" target="_blank" ><FONT color=#008000>Russia</FONT></A> prior to the introduction of GSM. It operates in either 450.4 - 457.6 MHz paired with 460.4 - 467.6 MHz, or 478.8 - 486 MHz paired with 488.8 - 496 MHz.</P> |
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