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 is channel estimation techniques?
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 in digital communication?
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.
Why do we need 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.
How is channel estimation done in 5g?
Introduction. The general approach to channel estimation is to insert known reference pilot symbols into the transmission and then interpolate the rest of the channel response by using these pilot symbols. For an example showing how to use this channel estimation approach, see NR PDSCH Throughput.
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 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 channel matrix?
A steel based matrix mainly used on cylinder machines and hand platens. Due to the flexible locator Original matrix works well with the curves on a cylinder machine. Learn More.
What is pilot contamination in massive MIMO?
Pilot contamination occurs when two terminals use the same pilot sequence (also known as reference signal). It can be suppressed by using different pilots in adjacent cells – for example, by having a large number of pilots sequences and switching randomly between them.
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 imperfect channel?
Imperfect channel state information (I-CSI) and imperfect transceiver hardware often happen in wireless communication systems due to the time-varying and random characteristics of both wireless channels and hardware components.
What is MIMO channel capacity?
It is known that the channel capacity in a MIMO communication system depends on the number of transmit and received antennas, the signal-to-noise ratio, the channel state, and the autocorrelation or covariance matrix of the transmitted signal vector [1].
What is SVD in MIMO?
MIMO transmission based on. singular value decomposition (SVD) is an effective mathematical technique to obtain the MIMO. channel capacity [1], [3].
What is LTE channel estimation?
To facilitate the estimation of the channel characteristics, LTE uses cell-specific reference signals (pilot symbols) inserted in both time and frequency. These pilot symbols provide an estimate of the channel at given locations within a subframe.
What is pilot 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 imperfect CSI?
Imperfect channel state information (CSI) always hinders the practical implementation of interference alignment (IA) in current mobile communication systems, where channel estimation error, delay and frequency offset are major factors that cause the unmatched CSI with unignorable error.
Why MIMO is used?
Multiple-Input Multiple-Output (MIMO) is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. All wireless products with 802.11n support MIMO. The technology helps allow 802.11n to reach higher speeds than products without 802.11n.
What are the types of MIMO?
There are two primary types of MIMO: single-user (SU) and multiuser (MU). In SU-MIMO systems, data streams can only interact with one device on the network at a time.
What is channel rank?
The rank of the channel matrix is thus an indicator of how many data streams can be spatially multiplexed on the MIMO channel. The rank and condition of a channel matrix also exist for every possible matrix dimension and thus for every possible MIMO constellation!
What is SVD precoding?
In case of an ideal radio channel knowledge the SVD based precoding procedure, which is applied at the transmitter site, is going to consider all possible Eigenmodes which results in a perfect separation of all signals at the receive antenna output and into a minimum bit-error-rate (BER).
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 many symbols are there in OFDM?
OFDM can generate a new symbol (composed of 48 subcarriers) every 4 microseconds. Based on that, it’s possible to signal 250,000 symbol transitions every second on each of the subcarriers.
Why cyclic prefix is used in OFDM?
The purpose of the cyclic prefix is to combat ISI and intra-symbol interference. The cyclic prefix is a guard time made up of a replica of the time-domain OFDM waveform. The basic premise is to replicate part of the back of the OFDM signal to the front to create the guard period, as shown in Figure 3.31.
What is instantaneous CSI?
Instantaneous CSI (or short-term CSI) means that the current channel conditions are known, which can be viewed as knowing the impulse response of a digital filter.
What is 2×2 MIMO and 4×4 MIMO?
MIMO indicates the number of transmit and receive antennas. The number of transmit antennas also determines the number of streams. The more streams an access point has, the greater the transfer rate. A 2×2 MIMO device can transmit 867 Mbit/s, while a 4×4 MIMO device reaches 1.7 Gbit/s.