Briefly explain the evaluation of the analog and digital cellular mobile system?

11. Briefly explain the evaluation of the analog and digital cellular mobile system?

Cellular telephone systems can be “Analog” or “Digital”. Older Cellular Systems (AMPS, TACS, NMT) are analog and newer systems (GSM, CDMA, PCS) are “Digital”. The major difference between the two systems is how the voice signal is transmitted between the phone and base station. Analog and Digital refer to this transmission mechanism. It is like audio cassettes and CDs. Audio cassettes are analog and CDs are digital.

In either system, the audio at the microphone always starts out as a voltage level that varies continuously over time. High frequencies cause rapid changes and low frequencies cause slow changes. With analog system the audio is directly modulated on to a carrier. This is very much like FM (not identical) radio where the audio signal is translated to the RF signal. 

With digital systems, the audio is converted to digitized samples at about 8000 samples per second or so. The digital samples are numbers that represent the time varying voltage level at specific points in time. These samples are now transmitted as 1s and 0s. At the other end the samples are converted back to voltage levels and smoothed out so that you get about the same audio signal. 

With analog transmissions, interference (RF noise or some other anomaly that affects the transmitted signal) gets translated directly in to the recovered signal and there is no check that the received signal is authentic. The neat thing about the digital is that the 1s and 0s cannot be easily confused or distorted during transmission plus extra data is typically included in the transmission to help, detect and correct any errors.