OFDM Flashcards
OFDM - short for ?
Orthogonal Frequency Division Multiplexing
How does OFDM transmit data?
By using multiple closely spaced orthogonal sub-carriers that are transmitted in paralel within the single channel.
How many subcarriers are used in a usual FDM data stream?
One
Why is guard band used in FDM?
To avoid interference between adjacent channels.
What is IFFT used for ?
To convert subcarriers from frequency domain to time domain at the transmitter side.
What is FFT used for?
To convert the receiving signal from time domain into frequency domain.
What does orthogonal mean in terms of subcarriers?
It means that peak of one carrier occurs at null of the other.
What is a Resource Element?
RE represents 15kHz OFDM symbol which carries N bits depending on the modulation (QPSK, QAM etc.)
What is a Resource Block?
Set of 12 Subcarriers each transmiting 7 OFDM symbols.
How long does a single RB last in time domain?
0.5 ms
What is a Scheduling block?
Scheduling block represents 2 RBs.
