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.Base station, which provides the connection between thecustomer s RSS and the PSTN.Operations, administration, and maintenance system,which provides such functions as radio link performancemanagement and billing.Residential Service System (RSS) The RSS offers two lines,which can be assigned for both residential and home officeuse or for two customers in the same 2-kilometer area.Oncean RSS is installed, the performance of the wireless link isvirtually indistinguishable from a traditional wired link.The wireless link is able to handle high-speed fax and datavia standard modems, as well as voice.The system supportssubscriber features such as call transfer, intercom, confer-ence call, and call pickup.The RSS has several components: a transceiver unit, res-idential junction unit (RJU), network interface unit, andpower supply.The transceiver unit consists of an integral 30- WIRELESS LOCAL LOOPS 461centimeter octogonal array antenna with a radio transceiverencased within a weatherproof enclosure.The enclosure ismounted on the customer premises and points toward thelocal base station.The RJU goes inside the house, where it interfaces withexisting wiring and telephone equipment.The Proximity Isystem supports two 32-kbps links for every house, enablingsubscribers to have a voice conversation and data connectionfor fax or Internet access at the same time.At this writing,work is under way to develop systems that can handle ISDNspeeds of 64 kbps and beyond.Further developments willresult in RSSs that can handle more lines per unit formedium-sized businesses or apartment blocks.The network interface unit (NIU), mounted internally orexternally, is a cable junction box that accepts connectionsfrom customer premises wiring.The unit also providesaccess for service provider diagnostics and contains lighten-ing protection circuitry.The power unit is usually mounted internally and con-nects to the local power supply (110/220 V ac).The powerunit provides the dc supply to the transceiver unit.Arechargeable battery takes over in the event of a power fail-ure and is capable of providing 12 hours of standby and 30minutes of talk time.Base Station The base station contains the radio frequency(RF) equipment for the microwave link between the cus-tomer s RSS and the PSTN, along with subsystems for callsignal processing, frequency reference, and network man-agement.This connection is via radio to the RSS and bymicrowave radio, optical fiber, or wireline to the localexchange.The base station is modular and can be configuredto meet a range of subscriber densities and traffic require-ments.The base station has several components: transceivermicrowave unit, cabinet, power supply, and network man-agement module.The base station s dual antenna transceiver microwave unitprovides frequency conversion and amplification functions. 462 WIRELESS LOCAL LOOPSEach unit provides three RF channels, the frequency of whichcan be set remotely.The unit can be configured for a maximumof 18 RF channels.The antennas are available in omnidirec-tional or sectored configurations, depending on populationdensities and geographic coverage.An omnidirectional systemcan support 600 or more customers, while a trisectoredantenna can serve more than 2000 customers.Base stations inrural areas can be sited up to 20 kilometers from a subscriber spremises.The base station can be configured with either an internal orexternal cabinet.The internal cabinet is for location in anequipment room, while the external cabinet is weather-sealedand vandal-proofed for outside locations.Both types of cabinetshouse the integrated transceiver system, transmission equip-ment, optional power system, and batteries.Aseparate powercabinet provides dc power to the base station from the local110/220 V ac source
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