HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New Millenniumpattern in order to increase carrier-to-interference ratios, reduce network-interferencelevels, control hand-off boundaries or redistributetraffic loads.Smart antennas will be used with code division multiple access(CDMA) technology in mobile cellular and personal-communicationservices(PCS) networks as well as fixed-terminal-wireless-local-loopsystems. Smart antennas are emerging as a major component ofwideband CDMA standards for third-generation mobile systems inNorth America, Europe, and Asia.The technology of smart antennas evolved from phased-array techniquesused in military and radar applications. These advanced electronicsconcepts are now practical for wireless communications networks.A smart antenna platform uses a phase-array antenna to synthesizecustom antenna patterns.In Advanced Mobile Phone System (AMPS) networks, smart antennascreate narrowbeam antenna patterns that track subscribers asthey move around the cell site. The narrow antenna beams improve callquality. Smart antennas can provide network-wide interference control,traffic-load balancing, resource allocation and dynamic network management.In the CDMA operating mode, the smart antenna uses a phasedarray to create custom sector-antenna patterns through a process calledsector synthesis. This is done with software management. Sector synthesiscontrols the azimuth angles, beamwidths and gains.Service providers can match antenna patterns for the different sectorsof a CDMA cell. The smart antenna system monitors traffic loadingand interference levels on the CDMA links. The smart system then respondsto the traffic load and interference levels by creating antennapatterns that are used to equalize traffic loads and reduce interference.In cellular networks, traffic loads are unevenly distributed acrosscells and sectors. A cell may have one sector near the blocking point,while the cell’s other two sectors are lightly loaded.Traffic load balancing is used to shift the traffic load from heavilyloaded sectors to underused sectors. This results in a reduction in thepeak loading levels and allows an increase in the traffic or networkcapacity. Without traffic load balancing, only about 1/2 of the subscribersin the highly loaded spot receive acceptable service.Smart antennas also allow rotation of the azimuth angle of thesectors in order to shift hand-off boundaries. A feature called soft hand-©2001 by The Fairmont Press, Inc. All rights reserved.