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

Building Automation, Wireless Technology and the Internet• increased levels of integration within the DSP,• larger amounts of on-chip memory,• intelligent input/output (I/O) peripherals and,• coprocessor for accelerating specialized functions.A cellular base transceiver station (BTS) serves as the interfacebetween mobile terminals and the rest of the cellular network. The frequencyspectrum is allocated in 200-kHz channels, with each channel’sbandwidth supporting up to eight users concurrently.The BTS contains one transceiver for each channel that is allocatedto the cell. The BTS must send, receive, and process all of the cellulartransmissions in the cell. Besides the speech or data included in thecellular transmissions, timing, synchronization, and control data areused to make the cellular network function nearly seamlessly and transparentlyto the cell phone users as they roam among the cells.The size of a cell depends on the terrain and the amount of callingtraffic. Cell sizes range from a maximum radius of approximately 35 km(macrocells) to a few kilometers (microcells) or several hundred meters(picocells). Picocells are needed in densely populated areas.In a channel, a time division multiple access (TDMA) format isused so that all users share the same bandwidth. The TDMA has timeslots for eight users. The cellular data are transmitted in bursts and eachburst fits into an allocated time slot.The base-station controller (BSC) controls BTS functions for severalcells. It hands off communications from one BTS to another as a communicatingmobile terminal travels from cell to cell. It also performs speechcoding and rate adoption to seamlessly connect the calls between thecellular network and the public-switched (land-based) network.The transmit function involves channel encoding, interleaving, andencryption. The receive path must perform equalization, deinterleaving,channel decoding, and decryption.Speech CodingIn the transmit path, the digitized speech is first encoded. Speechencoding compresses the speech through processing that uses speechmodeling and prediction. Speech encoding also detects pauses in speechand ensures that the data generated during the pauses will not be transmitted.©2001 by The Fairmont Press, Inc. All rights reserved.