What is an OFDM symbol?
Orthogonal frequency division multiplexing (OFDM) takes a digital information signal with bit rate Rb, maps n-bit words on to M = 2n symbols (each symbol being a complex number representing the amplitude and phase of an M-ary modulation scheme), splits the resulting symbol stream (rate Rs = Rb/n) into N parallel …
Which signal represents the OFDM scheme?
An OFDM carrier signal is the sum of a number of orthogonal subcarriers, with baseband data on each subcarrier being independently modulated commonly using some type of quadrature amplitude modulation (QAM) or phase-shift keying (PSK). This composite baseband signal is typically used to modulate a main RF carrier.
How is symbol synchronization done with OFDM?
One of the most popular and frequently used techniques is the transmission of one or several pilot symbols that are known in the receiver. A pilot symbol is a complete OFDM symbol where the value of each subcarrier is predefined and known in transmitter and receiver.
How does OFDM work with low thrpt?
When the symbols are long (upper part of the figure) – meaning low thrpt – the ISI is small i.e., we are able to decode the signal, as majority of the power is received without interference. Now, we want to transmit more symbols within this 1 second, so we put there 6 symbols (lower part of the figure).
How does the multipath response of OFDM work?
As we know from the theory – long symbols result in narrow Bandwidth (BW = ~1/T), and the multipath channel response is always selective (i.e., the different frequency components within a symbol are modified differently).
How does OFDM ( orthogonal frequency division multiplexing ) work?
As a side comment, it is imporant to note that the long or short symbols are always with respect to the channel impulse response (and its dispersion): can be „perceived” as long in the office environment (that does not impact the signal so much due to short CIR). This is where OFDM comes as a solution.