How is OFDM symbol duration calculated?
The sub-carrier frequency spacing delta_f =1/Ts= 1/(Td * N), Ts is the OFDM symbol duration,Td is the sampling symbol duration and equal to the smapling time interval。 Thus Td=1/fs, fs is the DAC sampling rate. Then we can calculate the bandwidth of the fignal.
When the symbol duration of OFDM symbol is 3.2 microseconds the used subcarrier frequencies are?
Each OFDM subcarrier is 312.5 KHz. 802.11ax introduces a longer OFDM symbol time of 12.8 μs, which is four times longer than the legacy symbol time of 3.2 μs. Subcarrier spacing is equal to the reciprocal of the symbol time.
Why OFDM is not suitable for uplink transmission for LTE?
OFDMA is used on the downling, but since it presents a high Peak-to-average Power Ratio it is not possible to use it on the uplink.
When do subcarriers interfere with each other in OFDM?
In OFDM systems, the subcarriers will interfere with each other only if there is a loss of orthogonality. For example, frequency error will cause the subcarrier frequencies to shift so that the spectral nulls will no longer be aligned resulting in inter-subcarrier-interference
How are the subcarriers of an OFDM signal orthogonal?
The subcarriers are orthogonal to each other, and 3. A guard interval is added to each symbol to minimize the channel delay spread and intersymbol interference. The following figure illustrates the main concepts of an OFDM signal and the inter-relationship between the frequency and time domains.
What is the long guard interval in OFDM?
The long Guard Interval (GI) and short Guard Interval (SGI) are functions built into OFDM that help to mitigate these effects. The long GI successfully protects OFDM transmissions under most conditions.
How many microseconds does an OFDM symbol take?
An entire OFDM symbol, as used in Wi-Fi on standard width channels, requires four microseconds to transmit. But not all of this time is used to transmit end user data. The Guard Interval represents the first .8 microseconds (800 nanoseconds) of the symbol time.