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DRAFT 2.0 04/30/97 Khursheed Khan St. Paul, Minnesota Brief comparison between US WEST Wireless Communications' technology of choice (CDMA) and the technology used/chosen by other providers in the Minneapolis - St. Paul wireless communications market Several providers in the Minneapolis-St. Paul market have chosen different wireless communications technologies to implement their respective PCS/Cellular systems. In order to succinctly describe these particular technologies, we need to first clarify some basic terminology and get fairly accustomed with the following acronyms: FDMA Frequency Division Multiple Access TDMA Time Division Multiple Access CDMA Code Division Multiple Access Cellular Band Frequency ranges in the 800 MHz to 900 MHz pes Band Frequency ranges in the 1800 MHz to 2000 MHz Most communications systems can be described by the elementary building blocks that they are comprised of. Let us assume a person makes a phone call from a cell phone. In what follows, we will trace the components of the communications system (from a systems level perspective) used in the generation-transmission-reception of this voice conversation. In the process, inherent features of the different technologies will be pointed out for comparison purposes. Once a speaker speaks into the handset, the on-board hardware/software elements extract the most critical components of this particular speech pattern and only these vital components of the speech are usually transmitted over the airwaves after necessary pre-processing has been carried out. To accomplish the extraction of these coefficients, various types of encoders/vocoders are normally used. Usually speech is sampled at double the frequency of the highest pitch of the human voice. Normally, this sampling rate is around 8000 samples/second. The sampled speech is then processed by the particular encoder/vocoder and after some more detailed processing, is usually chopped off into frames (approximately 22 milli-seconds of time duration) and transmitted over the airwaves. It is in the access of the airwaves that FDMA, TDMA, and CDMA technologies are most uniquely different. Below, short descriptions of the philosophies ofthe three main technology types is presented.