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!!""!#" 12-2 $"%% &''(''" )'&&&#intents" *+, -. / 01 / 01 / / 2 $"%% 2 )'(3(&'4 " &&5" &6'&" -." 7 $"%% 7  '6& " ' !"' " &&'#" 8 $"%% 8 9(" &''" 9'putXXXgetXXX0&1'&'!" :# Bundle myBundle = new Bundle(); myBundle.putDouble (“var1”, 3.1415); Double v1 = myBundle.getDouble(“var1”); &$;(0&$"6&"1< &$;(01< &$"0=$>6$21< &$"?#0&$1< &:@0&$6$$1< A $"%% A !" ! 9?9 B01 ?#*$;#, C!@ D $"%% D !" ! 9?9 B01 ?#*$;#, C!@ &E;01< &;&E"?#01< $;&"0=$F1< G $"%% G !" ! 9?9 B01 0$%1 ?#*$;&'(, C!@ &"C0F$F678A1< &E"?#0&1< @0&"#$%&'()*"&+ H $"%% H !)*+!,,+--,.,,,-) $I $"%% $I /-01)2 &$('&'"94'& &$" [...]... meters and take approximately 5 minutes to install Metricom believe that their system has almost unlimited scalability, and could cover the whole of the states if necessary 13 Ch 14 - Wireless and Mobile Data Characteristics This diagram allows you to compare the systems we've mentioned in this lesson The horizontal-axis uses a logarithmic scale to show the bit rate a system offers The vertical-axis... considerable drawback IR based nets are also further limited by the fact that their connections must be "line-of-sight" based This is not a problem for RF based LANs An interesting solution to the MAN question has been developed by an American company called Metricom They've developed a wireless system that breaks away from the usual wireless network topology that we saw in chapter 14.3 Instead of building... Wireless and Mobile Data Characteristics There are lots of different wireless data communication systems To help us understand them all we divide them into different categories, Local Area Networks, Metropolitan Area Networks and Wide Area Networks Some of the techniques used for wireless LANs and MANs are shown here, but we'll discuss those in a little more detail in the next slide Wide Area Networks have... and start working In some older buildings, pulling cable to every desktop can be expensive, so using a wireless solution can save money Of course, the usual drawbacks apply - the bit rate is much lower than that offered by other LAN technologies Typically IR and RF based LANs offer a bit rate of about 4 Mbps Compared with Ethernet, which is over 25 years old and yet manages 10 Mbps, that can be a considerable... such as GPRS and HSCSD will increase this bit rate AMPS offers coverage in several countries across the world with a bit rate similar to that found in GSM Future enhancements, such as circuit switched data, will offer higher bit rates than are currently available Metricom's system, which was discussed earlier offers a higher bit rate than current GSM or AMPS systems, but only provides mobility at the... American urban areas, the Bay Area in California, Seattle and Washington DC Metricom's solution is also being used by several campus based networks and by Sun Microsystems (among others) to cover their corporate campus The system uses the license free portion of the RF spectrum and utilizes a patented frequency hopping technique to provide security and maintain good link quality The pole top boxes are positioned... to a box that has a fixed connection All this routing is done automatically by the meshed network, there is no human intervention and no need for hand crafted routing tables 12 Ch 14 - Wireless and Mobile Data Characteristics Metricom's system currently offers a bit rate of 38 kbps, a speed they hope to increase to 56 kbps some time in 1999 They offer a public Internet access service in three American... are conceptually very similar, they all build on existing circuit switched mobile telephony infrastructures and they all add a packet switched service GPRS provides packet data services by building on the GSM infrastructure, PPDC provides packet data services by building on PDC and CDPD provides packet data services by building on the AMPS system 11 Ch 14 - Wireless and Mobile Data Characteristics... switched and packet switched On the circuit switched side are Satellite phones, the American mobile telephone standard AMPS, GSM and PDC HSCSD is a new data oriented circuit switched service for GSM, which will be discussed a little more in chapter 16 The oldest of the packet switched services is Mobitex; a dedicated packet switched network that has been available since 1986 The other three systems are... LAN marketplace there are two main solutions, using infra-red or radio waves None of these solutions pretends to offer mobility - they merely offer a slightly more flexible way of coupling your desktop computer to the LAN In some cases this wireless flexibility can be very desirable - laptop users do not need to continually plug and unplug network cables, they can simply move into the covered area and
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