In: Categories » Electronics and communication » Wireless and mobile computing » Proprietary Networks
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ARDIS (DATATAC) Advanced Radio Data Information Services (Ardis) sometimes referred to as the DataTAC network, is a two-way radio service that is based on Motorola’s RD-LAP technology. It was originally created and jointly owned by Motorola and IBM to serve IBM field technicians. Coverage includes about 90 percent of the urban business population in the U.S with more than 400 metropolitan areas in the United States, Puerto Rico, and the Virgin Islands. The network is based on packet-data transfer using data rates as high as 19.2 Kbps. Some areas may not offer rates as high as 19.2 Kbps if they are not enhanced with RD-LAP. Frequencies and protocols are proprietary to Motorola. Modulation at the physical layer is Gaussian Frequency Shift Keying (GFSK). RICOCHET Ricochet is the only wireless packet data network today that was built from the ground up to handle high speed data, up to 128 Kbps. Modems are available from third-party sources that allow connection to laptop computers by at least one Pocket PC. The network has about 41,000 customers in 15 markets as of July 2001 but the parent company, Metricom, has filed for Chapter 11 in bankruptcy court, so anything could happen to Ricochet. On August 8, 2001, Metricom ceased operations of Ricochet but the company is negotiating with third parties to buy the Ricochet network. If a third party can buy the network at a really good price, then Ricochet may continue in some form. As of the publishing this article, the outcome is unknown. The high costs of building out a nationwide network far exceeded the revenue, and current economic conditions make financing very difficult. The Ricochet radio network utilizes several elements including microcell radios and wired access points. This provides true Wireless Internet access to information—regardless of where it resides either on the Web or the intranet, in an email message or a video clip. In many ways the Ricochet network functions similarly to a wireless Ethernet network. Acquisition is a necessary first step for each radio on the network. The user radio, when first turned on, must locate neighboring radios and Ricochet modems by sending out synchronization packets. On acknowledgment from neighboring radios, it must then get the authorization from the name server. Only then does it join the network. The network operates in two Industrial, Scientific, Medical (ISM) bands of regulated, unlicensed spectrum, the 900 MHz band and the 2.4 GHz band, in addition to the licensed 2.3 GHz Wireless Communications Systems (WCS) spectrum. The physical layer uses Frequency Hopping Spread Spectrum (FHSS) technology. MOBITEX OR RAM MOBILE DATA Mobitex enjoys wide acceptance as a global standard for wireless data networks. This technology was originally developed by Swedish Telecom as a private network similar in purpose to the Ardis network. The network became commercial in 1986. Since then, many networks have been deployed in Europe, the United States, and Australia. The frequency varies by country but the United States and Canada mainly use 900 MHz. In the United States, Mobitex is operated by RAM Mobile Data, a subsidiary of Bell South. There are over 1,200 base stations installed nationwide with service in more than 7,700 cities and towns, covering approximately 93 percent of America’s urban business population. Mobitex technology offers six distinguishing features that other networks lack: • Transparent, seamless roaming • Store-and-forward • Dependability (99.99 percent) • Interoperability and connectivity options • Capacity to support millions of subscribers • Security second to none Channels use 12.5 kHz bandwidth and support a data rate of 8 Kbps. The network operates in the United States at 935 MHz to 940 MHz for the downlink (base to mobile) and 896 MHz to 901 MHz for the uplink (mobile to base). OMNISKY OmniSky’s Wireless Internet service uses the CDPD packetbased network, encompassing over 172 million people. The first service began in May 2000. Data rates are 19.2 Kbps and users are offered a flat-rate monthly fee for unlimited service. Much of Omnisky’s success can be attributed to the partners it has chosen to work with: Palm, Handspring, HP, and Compaq. However, Omnisky should be feeling the competition when cellular begins next-generation service.
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