📄 wireless nirvana.htm
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<TD vAlign=top align=middle bgColor=#e8edf4><SPAN
class=title-bold-large>Wireless Nirvana
</SPAN></TD></TR></TBODY></TABLE><BR><BR><A id=tocLink name=toc>
<TABLE style="PADDING-RIGHT: 2em" cellSpacing=2 cellPadding=2 width="22%"
align=left background="Wireless Nirvana.files/bg_toc.gif" border=0>
<TBODY>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-bold>Contents</SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-4
title="Network Details "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-4">Network
Details </A></SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-5
title="IP Packet Architecture "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-5">IP
Packet Architecture </A></SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-6
title="Using the Networks "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-6">Using
the Networks </A></SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-7
title="Throughput Versus Latency "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-7">Throughput
Versus Latency </A></SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-8 title="Pricing It Out "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-8">Pricing
It Out </A></SPAN></TD></TR>
<TR>
<TD vAlign=top align=left width="100%" colSpan=2><SPAN
class=medium-normal><A id=hd_AN0007584743-9
title="But Is It Secure? "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#AN0007584743-9">But
Is It Secure? </A></SPAN></TD></TR></TBODY></TABLE><A name=AN0007584743-3>
<CENTER>
<P><STRONG>Unattainable? hardly. wireless heaven is so close you can touch
it-or at least see a picture of it on your cell phone or PDA.
Next-generation cellular data technologies bring bliss in the form of IP
packet networking. </STRONG></P></CENTER>
<P class=medium-normal>It all seems so sexy on TV-the image of a luscious
plate of pasta on their buddy's cell phone gets the other guys drooling.
You know you want it. Now you can have it-if not the spaghetti, the data
service.</P>
<P class=medium-normal>After years of anticipation, next-generation
cellular-data services are being deployed worldwide. In the United States,
AT&T Wireless, Cingular Wireless and T-Mobile (formerly VoiceStream)
are deploying GPRS (General Packet Radio Service) data technology in their
GSM (Global System for Mobile Communications)
<STRONG><EM>networks</EM></STRONG>, while Alltel, Sprint PCS, U.S.
Cellular and Verizon Wireless are deploying
<STRONG><EM>CDMA</EM></STRONG>2000 1XRTT. These new services give a big
boost to networking options for remote-access solutions.</P>
<P class=medium-normal>Both IP packet networking technologies offer
substantial speed improvements over previous cellular technologies,
including CDPD or circuit-switched data services. Is this wireless heaven?
Yes and no. GPRS and 1XRTT (which stands for "one-carrier
radio-transmission technology") are a huge step forward and will enable a
broad range of new wireless applications, but in terms of performance,
they are more like dial-up than broadband and require some care to fully
exploit their capabilities. In particular, you'll need to consider
throughput, latency, <STRONG><EM>security</EM></STRONG>, usage costs,
service coverage, IP-address and data-session management, and intranet
interconnections.</P><A name=AN0007584743-4>
<CENTER>
<H3><A id=hd_toc title="Network Details "
href="http://web11.epnet.com/citation.asp?tb=1&_ug=sid+55725B2C%2D1A6E%2D4291%2D99B0%2DA6A8441EF92B%40sessionmgr6+dbs+a3h+cp+1+F22C&_us=frn+1+hd+False+hs+True+cst+0%3B2+or+Date+fh+False+ss+SO+sm+ES+sl+0+dstb+ES+mh+1+ri+KAAACBTB00061445+22DE&_uso=tg%5B2+%2D+tg%5B1+%2DAB+tg%5B0+%2DAB+db%5B0+%2Da3h+hd+False+clv%5B0+%2DY+op%5B2+%2DAnd+op%5B1+%2DAnd+op%5B0+%2D+cli%5B0+%2DFT+st%5B2+%2D+st%5B1+%2Dcdma+st%5B0+%2Dnetwork++security+mdb%5B0+%2Dimh+DD39&cf=1&fn=1&rn=1#toc">Network
Details </A></H3></CENTER>
<P class=medium-normal>Although they're different in almost every other
detail, both GPRS and 1XRTT are packet-switched-the most important
improvement over earlier technologies. Data services for GSM and
<STRONG><EM>CDMA</EM></STRONG> were circuit-switched and emulated modem
connections. With packet switching, a user's modem (whether a data-capable
mobile telephone, PC Card modem or PDA with integrated modem) uses only
the radio channel when sending and receiving packets. Thus, packet
switching uses scarce radio resources more efficiently than does GSM or
<STRONG><EM>CDMA</EM></STRONG> circuit-switched data services, and
theoretically provides users with an always-on, always-virtually-connected
experience. Because cellular networks, even digital ones, were designed
for circuit-switched voice communications, packet switching requires new a
infrastructure to handle authentication for data services, IP-address
management and <STRONG><EM>network</EM></STRONG> interconnections.</P>
<P class=medium-normal>To the user or IT manager, GPRS and 1XRTT provide
very similar services, namely the transport of IP packets to and from
mobile terminals. The connection to the packet data service is
functionally equivalent to a connection to an ISP. The connection begins
at the mobile terminal, such as a notebook computer. A mobile application
interfaces to a TCP/IP protocol stack, which interfaces to the wireless
modem, which is inserted in the computer or, in the case of a data-capable
cell phone, connected by a serial cable, USB cable, infrared or Bluetooth.
The modem presents a PPP interface or NDIS interface. NDIS, normally used
by Ethernet devices in a Microsoft Windows environment, offers better
plug-and-play capabilities and is typical for PC Card devices; PPP suits
tethered devices, such as mobile telephones. In the case of GPRS, the PPP
connection terminates in the device; in 1XRTT, the PPP connection
terminates in the <STRONG><EM>network</EM></STRONG>. Although this
difference illustrates <STRONG><EM>CDMA's</EM></STRONG> greater use of IP
protocols within its infrastructure, it hardly matters to users.</P>
<P class=medium-normal>Across the air, GPRS and 1XRTT use different
approaches, though end users probably will never know the difference. GPRS
takes the GSM time-division approach: Each 200-KHz radio channel is
divided into eight time slots. Normally, one time slot supports one voice
user, but for packet data, GPRS can combine up to four time slots for
effective throughputs of about 40 Kbps. 1XRTT, in comparison, is a DSSS
(direct-sequence spread-spectrum) system that uses a much wider, 1.25-MHz
radio channel and different codes to designate channels. Compared to prior
<STRONG><EM>CDMA</EM></STRONG> versions, 1XRTT introduces high-speed
supplemental channels that can operate at 16 times the fundamental
voice-call channel rate. This technology allows burst rates of 144 Kbps,
though typical user rates are generally 40 Kbps to 60 Kbps. In both GPRS
and 1XRTT, a medium-access protocol controls which user gets to send
packets at what time; data users must contend for radio resources with
other data users and voice users. Operators can specify how much of their
system capacity to allocate to data and to voice. Both technologies can
take advantage of idle voice capacity to boost data capacity, though the
converse also holds true-in a cell busy with voice traffic, only a small
amount of capacity may be left for data.</P>
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