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.In developingcountries, where lack of a universal wired telecommunica-tions infrastructure can limit economic growth, DECT per-mits the creation of a wireless local loop (WLL), therebyavoiding the considerable time and expense required to laywire lines.WLLs can be implemented in several ways, whichare summarized in Figure D-1.In a small cell installation in densely populated urban ordowntown areas, the existing telephone network can be usedas a backbone that connects the base stations for each DECT DIGITALLY ENHANCED CORDLESS TELECOMMUNICATIONS 85PSTNRelay MicrowaveStation LinkFiber tothe CurbBaseStationFigure D-1 DECT supports the deployment of wireless local loops thatoffer a high degree of configuration flexibility and cost savings over conven-tional wireless and wireline solutions.cell.These DECT base stations may be installed on tele-phone poles or other facilities.Customer boxes (i.e., trans-ceivers) installed on the outsides of houses and officebuildings connect common phone, fax, and modem jacksinside.Through the transceivers, customers use their tele-phone, fax, and modem equipment to communicate with thebase stations outside.In addition, customers can use DECT-compliant mobile phones, which can receive and transmitcalls to the same base station.In larger cell installations, such as suburban or ruralareas, fiberoptic lines may provide the backbone that con-nects local relay stations to the nearest base station.Theserelay stations transmit and receive data to and from cus-tomer boxes.In these installations, the customer box musthave a direct line of sight to the relay station.Network feeds over long distances may be accomplished viamicrowave links, which is more economical than having toinstall new copper or fiber lines.Large cells can be convertedeasily into smaller cells by installing additional base units orrelay stations.Since DECT system has a self-organizing air 86 DIGITALLY ENHANCED CORDLESS TELECOMMUNICATIONSinterface, no top-down frequency planning is necessary, asis the case with other wireless connection techniques suchas GSM or its derivative Digital Cellular System 1800(DCS 1800).While most WLL installations focus on regular telephoneand fax services, DECT paves the way for enhanced services.Multiple channels can be bundled to provide wider bandwidth,which can be tailored for each customer and billed accordingly.Among other things, this allows the mapping of ISDN servicesall the way through the network to the mobile unit.Wireless LANsIn many data applications with low bit rate requirements,DECT can be a cost-effective solution.One example isremote wireless access to corporate LANs.By bundlingchannels, full-duplex transmission of up to 480 kbps per fre-quency carrier is theoretically possible.For multiple datalinks, a DECT base station can be complemented by addi-tional DECT base stations controlled by a DECT server.Thisforms a multicell system for higher traffic requirements.With a transparent interface to ISDN, data access and video-conferencing through wireless links can be realized.Suchinstallations also may include such services as voice mail,automatic call back, answering and messaging services,data on demand, and Internet access.SummaryDECT is a radio access technology.As such, it has beendesigned and specified to work with many other types of net-works, including the PSTN, ISDN, GSM, and the Internet,as well as LANs and telephone systems in office buildingsand homes.DECT modules incorporated into building con-trol and security systems provide intelligent systems thatallow automatic control and alerting to augment or replacetoday s customized telemetry and wired systems.DECT also DIRECT BROADCAST SATELLITE 87may find its way into the home, providing automatic securityalerting in the event of unauthorized entry, fire, or flood;remote telephone control of appliances; and return channelsfor interactive television
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