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.
What are the techniques used in 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 meant by channel estimation?
Channel Estimation is the process of finding correlation between the array of complex numbers on the left and the array of complex numbers on the right. The detailed method of the estimation can very depending on the implementation.
What is least square channel estimation?
The least squares (LS) estimation is a common method for pilot-based channel estimation, as it offers good performance with reasonable complexity. In this paper, a pilot-based channel estimator design for a MIMO-OFDM system is described and two channel es- timator architectures are presented for the LS estimator.
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 blind channel estimation?
Blind channel estimation methods use statistics from the incoming data to estimate the channel without the need for pilot signal sequences. Since the success of these algorithms does not depend on the presence of pilot signal sequences, this method is a good candidate for mitigating the pilot contamination problem.
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 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 is CSI amplitude?
From Figure 1, we observe the CSI amplitude on the selected subcarrier indeed presents a sinusoidal-like peri- odic changing pattern over the time due to breathing. This observation suggests that we can identify breathing cycles by measuring the peak-to-peak time interval of sinusoidal CSI amplitudes.
Why do we do channel estimation?
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 Preamble in DFT?
A preamble is generated based on a length-L preamble sequence which is DFT precoded before being applied to a conventional OFDM modulator. The preamble can thus be seen as a DFTS-OFDM signal.
What is pilot carrier OFDM?
In each OFDM symbol, four of the subcarriers are dedicated to pilot signals in order to make the coherent detection robust against frequency offsets and phase noise. These pilot subcarriers occupy subcarriers -21, -7 , 7, and 21 and use BPSK. modulation. Pilot subcarriers transmit with a known data sequence.
What is guard interval in OFDM?
Guard Interval (802.11a/g/j/p OFDM) The Guard Interval is the ratio of the Cyclic Prefix “CP1) Contention period, or 2) Cyclic prefix” time to the inverse FFT. See Spectrum. time “T(IFFTInverse Fast Fourier Transform).” The guard interval is used to eliminate inter-symbol and inter-carrier interference.