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One of the causes of intersymbol interference is multipath propagation in which a wireless signal from a transmitter reaches the receiver via multiple paths. The causes of this include reflection (for instance, the signal may bounce off buildings), refraction (such as through the foliage of a tree) and atmospheric effects such as atmospheric ducting and ionospheric reflection.
The impulse response of a root-raised cosine filter multiplied by T s, for three values of β: 1.0 (blue), 0.5 (red) and 0 (green).. The RRC filter is characterised by two values; β, the roll-off factor, and T s the reciprocal of the symbol-rate.
The raised-cosine filter is a filter frequently used for pulse-shaping in digital modulation due to its ability to minimise intersymbol interference (ISI). Its name stems from the fact that the non-zero portion of the frequency spectrum of its simplest form ( β = 1 {\displaystyle \beta =1} ) is a cosine function, 'raised' up to sit above the f ...
Not every filter can be used as a pulse shaping filter. The filter itself must not introduce intersymbol interference — it needs to satisfy certain criteria. The Nyquist ISI criterion is a commonly used criterion for evaluation, because it relates the frequency spectrum of the transmitter signal to intersymbol interference.
The first step of computing an eye pattern is normally to obtain the waveform being analyzed in a quantized form. This may be done by measuring an actual electrical system with an oscilloscope of sufficient bandwidth, or by creating synthetic data with a circuit simulator in order to evaluate the signal integrity of a proposed design.
A tutorial on the significance of Cyclic Prefix (CP) in OFDM Systems Archived 2023-10-05 at the Wayback Machine. Siemens demos 360 Mbit/s wireless; An Introduction to Orthogonal Frequency-Division Multiplex Technology; Short Introduction to OFDM – Tutorial written by Prof. Debbah, head of the Alcatel-Lucent Chair on flexible radio.
In digital communications, a turbo equalizer is a type of receiver used to receive a message corrupted by a communication channel with intersymbol interference (ISI). It approaches the performance of a maximum a posteriori (MAP) receiver via iterative message passing between a soft-in soft-out (SISO) equalizer and a SISO decoder. [1]
It provides a guard interval to eliminate intersymbol interference from the previous symbol. It repeats the end of the symbol so the linear convolution of a frequency-selective multipath channel can be modeled as circular convolution , which in turn may transform to the frequency domain via a discrete Fourier transform .