research - Technology Digital wireless services, which...

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Technology Digital wireless services, which include personal communications services, have been available in the United States since the mid-1990s, but they did not come into the mainstream until the middle years of the first decade of the 2000s. Digital represents the second generation (2G) of wireless communications; the first was various analog (defined by Merriam-Webster's Collegiate Dictionary as data represented by continuously variable physical quantities), systems that have been around for decades. Digital (defined by Webster's as calculation by numerical methods or by discrete units) encoding enables greater volumes of information to be sent and received by wireless devices and is capable of delivering higher sound quality and other features found wanting in analog service. The third generation (3G) of wireless communications is represented by mobile applications: wireless voice telephony, video calls, and broadband wireless (also known as WiFi). By June 2007 there were 200 million 3G subscribers, most of them in Japan and South Korea. In the United States, networks were in the process of being upgraded from the voice-centric 2G to the multimedia-oriented 3G. Using standards such as the nascent Wireless Application Protocol (WAP), 3G broadband services can deliver applications and data to wireless phones that double as handheld organizers, personal digital assistants (PDAs), or computers. WAPs that use displays and access the Internet utilize microbrowsers, browsers limited to small file sizes, to accommodate the low memory constraints of handheld devices and the low bandwidth limitations of a wireless handheld network. Major technical distinctions include whether a service uses analog or digital signals, what kind of signal separation scheme it employs to let multiple users share the same airwaves, and even what radio frequencies it uses. All these differences mean that portable phones and other wireless communications devices will work with some systems but not others, and in some locations but not all. This mélange of standards has resulted from technological change, proprietary competitive strategies of certain companies, and a failure to adopt wider standards before industry players invested heavily in any one technology. Commercial mobile radio service includes the cellular telephone industry. Cellular telephone systems use low power radio-telephone transceivers. The cellular infrastructure in use in the United States at the end of the 1990s was largely analog, meaning that continuous electrical signals send and receive information. This differs from communications systems that use digital signals to send and receive messages. Digital systems create virtually exact replicas of signals because they are fed through computers that assign binary codes comprised of zeroes and ones to each unit of information. Analog systems create only very good copies of signals.
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research - Technology Digital wireless services, which...

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