Table of Contents
What is OFDM encoding?
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.
Why is OFDM preferred?
OFDM advantages & disadvantages Immunity to selective fading: One of the main advantages of OFDM is that is more resistant to frequency selective fading than single carrier systems because it divides the overall channel into multiple narrowband signals that are affected individually as flat fading sub-channels.
What is PAPR in OFDM?
The PAPR is the relation between the maximum power of a sample in a given OFDM transmit symbol divided by the average power of that OFDM symbol. In simple terms, PAPR is the ratio of peak power to the average power of a signal. This ratio of the peak to average power value is termed as Peak-to-Average Power Ratio.
What is the principle of OFDM signal processing?
The OFDM concept is based on spreading the high speed data to be transmitted over a large number of low rate carriers. The carriers are orthogonal to each other and frequency spacing between them are created by using the fast Fourier transform (FFT).
Why is a cyclic prefix required in an OFDM?
To combat the intersymbol interference (ISI) in a multipath channel, a cyclic prefix (CP) is inserted in the OFDM symbol. Cyclic prefix is inserted to avoid intersymbol interference due to the multipath channel.
What is OFDM modulation technique?
Orthogonal frequency division multiplexing (OFDM) is a modulation technique that is used in several applications ranging from cellular systems (3GLTE, WiMAX), wireless local area networks (LANs), digital audio radio, underwater communications, and even optical light modulation.
Why OFDM is efficient?
Why OFDM Is Efficient? OFDM, like FDM, separates the channel bandwidth into multiple narrow-band subcarriers to carry the information. This not only permits the removal of the guard bands, but since the subcarriers are completely unrelated, they can even overlap each other. This is why OFDM is so bandwidth efficient.
Why is PAPR important?
The peak-to-average power ratio (PAPR) of a signal waveform is an important metric as a small value implies that the power amplifier used to transmit signals can operate more efficiently and thus save battery in the UE (see also Section 11.3. 1.1).
How does PAPR affect OFDM?
In fact, the high PAPR is one of the most detrimental aspects in an OFDM system as it decreases the signal-to-quantization noise ratio (SQNR) of the analog-digital convertor (ADC) and digital-analog convertor (DAC) while degrading the efficiency of the power amplifier in the transmitter.
How is OFDM typically realized at the transmitter?
The inverse fast Fourier transform can therefore be used to realise the basic OFDM signal at the transmitter and the FFT can be used to recover (de-multiplex) the symbols at the receiver.
Why guard interval is provided in OFDM?
Guard Interval (802.11a/g/j/p OFDM) time “T(IFFTInverse Fast Fourier Transform).” The guard interval is used to eliminate inter-symbol and inter-carrier interference. Each symbol is transmitted for a slightly longer time, extended symbol time T(s), than the active (or useful) symbol time T(IFFT).