mathilda555
Posts : 124 Join date : 2011-07-01
| Subject: Digital wireless communication? Tue Jan 17, 2012 11:38 am | |
| Motorola uses digital communication technology in the design of cellular phones. In digital communications, a speech or data signal is converted into bits by a mobile phone and transmitted over the air to a base station.A bit is a unit of information that can be either 0 or 1.Thus, a single bit can represent two levels of information. A speech signal is converted into a digital signal by taking samples of the speech signal at specified time intervals, and then quantizing these samples. A sample is simply the value of the speech signal at a single time instant.To quantize the sample, a number of acceptable levels is defined, and the level that is closest to the value of the speech signal at a sampling instant is assigned to that sample.A symbol consisting of multiple bits is assigned to each level, and these resulting symbols are transmitted over the air. The number of levels is determined by the length of the symbols. For instance, a symbol of length one bit can only represent two levels (0 and 1). A symbol of length two bits represents 4 levels (00, 01, 10, 11). ___________ snowmobile tours Vail | |
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