What is channel estimation in MIMO OFDM?
The channel estimation is carried out with conventional Least Square (LS) and Minimum Mean Square (MMSE) estimation algorithms. The performance of MIMO-OFDM system is evaluated on the basis of Bit Error Rate (BER) and Mean Square Error (MSE) level.
How is channel estimation done in OFDM?
Channel Estimation Overview The populated resource grid represents several subframes containing data. This grid is then OFDM modulated and passed through the model of the propagation channel. Channel noise in the form of additive white Gaussian noise (AWGN) is added before the signal enters the receiver.
Is OFDM used in MIMO?
It combines multiple-input, multiple-output (MIMO) technology, which multiplies capacity by transmitting different signals over multiple antennas, and orthogonal frequency-division multiplexing (OFDM), which divides a radio channel into a large number of closely spaced subchannels to provide more reliable …
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.
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 is channel estimation necessary?
Channel estimation plays an important role in a communication receiver. In order to mitigate hostile channel effects on the received signal, precise channel estimation is required to provide information for further processing of the received signal. Channel estimators can be categorized as non-data-aided or data-aided.
What is channel estimation in digital communication?
Channel estimation is a challenging problem in wireless communications. Transmitted signals are typically reflected and scattered, arriving at the receiver along multiple paths. When these paths have similar delays, they add either constructively or destructively, giving rise to fading.
What is channel estimation techniques in wireless communication?
Is OFDMA same as MU-MIMO?
OFDMA and MU-MIMO are complementary technologies. While OFDMA is ideal for low-bandwidth, small-packet applications such as IoT sensors, MU-MIMO increases capacity and efficiency in high-bandwidth applications like mission-critical voice calls and video streaming.
What is OFDM channel?
OFDM is a subset of frequency division multiplexing in which a single channel utilizes multiple sub-carriers on adjacent frequencies. In addition the sub-carriers in an OFDM system are overlapping to maximize spectral efficiency. Ordinarily, overlapping adjacent channels can interfere with one another.
How do you calculate the number of subcarriers in OFDM?
If you divide the channel bandwidth (20 MHz) by the subcarrier bandwidth (312.5 kHz) you will see that 802.11a/g comprises 64 subcarriers. This is referred to as 64-point FFT/IFFT. Each of these subcarriers is capable of being individually modulated to carry part of the current input data stream.
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.
Should I enable OFDMA and MU-MIMO?
So, which is better? OFMDA and MU-MIMO technologies complement each other. Each helps increase performance on the uplink and downlink. OFDMA is best with low-bandwidth applications while MU-MIMO better serves high-bandwidth applications.
What are downstream OFDM channels?
OFDM is used in the downstream and is a common channel shared by all compatible cable modems. OFDMA is used in the upstream by cable modems transmitting data to the CMTS.
What is the channel spacing used for OFDM subcarriers?
Subcarrier spacing is equal to the reciprocal of the symbol time. As a result of the longer symbol time, the subcarrier size and spacing decreases from 312.5 KHz to 78.125 KHz. The narrow subcarrier spacing allows better equalization and therefore enhanced channel robustness.