Symbolrate
The symbol rate, also referred to as a step or speed as the modulation rate in the digital transmission technology and communications technology, the number of symbols transmitted per unit time. It is typically expressed as symbols per second using the baud unit, abbreviated Bd.
General
Each symbol is assigned a certain, usually fixed, the number of information-carrying bits on the line code. The information-carrying bits that are transmitted per unit time can be in the bit rate, measured in bits per second, abbreviated bps expressed. Per symbol is only the information of a bit assigned to the bit rate corresponding to the symbol rate.
In conventional narrowband transmissions, such as telephone modems, the symbol rate is less, or at low bit rates and is equal to the bit rate. For frequency spreading, such as Direct Sequence Spread Spectrum (DSSS ), and code division multiple access (CDMA), in which case the symbols are also referred to as chip, the symbol rate ( chip rate ) is higher than the bit rate.
Related to bandwidth
The symbol rate is related to the symbol duration, also known as unit intervals (UI ) refers to the following relationship together:
A sequence of individual symbols is transmitted with the duration time and strung together with a certain symbol rate for data transmission. Through pulse shaping filter, such as the raised cosine filter, while the junction is formed from a symbol to the next. The aim of the pulse shaping, there is, inter alia, signal changes abruptly, due to minimize the switching from one symbol to the next symbol, and to replace it by as "smooth" transition curves. This leads to a certain degree of undesirable cross-talk icon, which can be measured using an eye diagram.
The necessary for a given symbol rate bandwidth results primarily directly from the symbol rate and can be equated to a first rough approximation to it. The bandwidth required depends inter alia on the type of pulse shaping, and carrier -based transmission method and the type of modulation and the modulation index.