What is channel estimation in OFDM?

What is channel estimation in OFDM?

Channel estimation plays an important part in an OFDM system. It is used for increasing the capacity of orthogonal frequency division multiple access (OFDMA) systems by improving the system performance in terms of bit error rate.

How many sub channels will be required for OFDM?

Each OFDM channel consists of 128 to 2048 sub-carriers and can occupy bandwidths from 1.25 MHz to 20 MHz. In addition, each of these sub-carriers is modulated using BPSK, QPSK, 16-QAM, or 64-QAM modulation, depending on the requirements of the physical channel.

How do you do channel estimation?

Channel estimation can be carried out in different ways: with or without the help of a parametric model, using frequency and/or time correlation properties in the wireless channel, blind methods or those based on training pilots, adaptive or non-adaptive methods.

What is channel estimation and Equalization?

Channel estimation provides information about distortion of the transmission signal when it propagates through the channel. This information is then used by equalizers so that the fading effect and/or co-channel interference can be removed and the original transmitted signal can be restored.

What are pilot symbols in channel estimation?

The pilot symbols are constructed to be nonoverlapping in frequency to allow simultaneous sounding of the multiple channels. The time- varying channel responses are tracked by interpolating a set of estimates obtained through periodically transmitted pilot symbols.

What is channel estimation in MIMO?

MIMO. systems use multiple antennas to transmit and receive. signals. Channel Estimation means to estimate channel. parameters from the received signal.

How do I calculate OFDM bandwidth?

Thus the bandwidth of the OFDM baseband signal is N/2*delta_f,delta_f is the sub-carrier frequency spacing. 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。

What processing step combines multiple OFDM?

IFFT
4. What processing step combines multiple OFDM subcarriers into a single signal for transmission? Explanation: IFFT combines multiple OFDM subcarriers into a single signal for transmission.

How is channel estimation done in wireless communication?

The process is done as follows. i) set a mathematical model to correlate ‘transmitted signal’ and ‘recieved signal’ using ‘channel’ matrix. ii) Transmit a known signal (we normally called this as ‘reference signal’ or ‘pilot signal’) and detect the received signal.

What is pilot insertion in OFDM?

The first model refers to that the pilots are inserted into all the subcarriers of one OFDM symbol with a certain period. The block-type can be adopted for slowly fading channel, that is, the channel can be considered as stationary within a certain period of OFDM symbols [7].

What is post equalization Sinr?

1Post-equalizer SINR refers to the SINR of the received signal after channel estimation and equalization stages of the baseband.

What is preamble in OFDM?

PHY Frame OFDM Symbols Preamble: The preamble is constructed from 7.5 special OFDM symbols without cyclic prefixes, and is 38.4 µs in duration. This frame segment is used for synchronization, automatic gain control and optionally for phase reference.

What are pilots in OFDM?

Training OFDM symbols or equivalently OFDM preambles are transmitted at the beginning of the transmission record, while pilot symbols (complex exponentials in time) are embedded in each OFDM symbol, and they are separated from information symbols in the frequency-domain [1–3].

What is channel estimation in 5G?

Channel estimation is essential in a Multiple Input Multiple Output (MIMO) wireless communication in 5G. In the MIMO system, numerous antennas are utilized on the sender and receiver sides for enhancing spectral efficiency and reliability. The channel estimation can improve the exactness of the received signal.

How do you calculate the number of subcarriers in OFDM?

Choosing the first subcarrier to have a frequency such that it has an integer number of cycles in a symbol period, and setting the spacing between adjacent subcarriers (subcarrier bandwidth) to be BSC = B/L, where B is the nominal bandwidth (equal to data rate), and L is the number of subcarriers, ensures that all …

What is perfect channel estimation?

Perfect channel estimate, returned as an NSC-by-NSYM-by-NR-by-NT complex array, where: NSC is the number of subcarriers. NSYM is the number of OFDM symbols. NR is the number of receive antennas. NT is the number of transmit antennas.

What is the importance of channel estimation in wireless communication?

Abstract: Channel estimation is an important technical issue in mobile communication system, the performance and capacity of mobile communication system are directly influenced by the speed and precision of channel estimation.

What are training symbols in OFDM?