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Fundamentals of Channel Estimation


Channel Estimation Techniques

Channel Estimation is an auto-regressive process that may be performed with a number of iterations.

There are commonly three types of channel estimation approaches.
1. Pilot estimation 
2. Blind estimation 
3. Semi-blind estimation.

For Channel Estimation, CIR [↗] is used. The amplitudes of the impulses decrease over time and are not correlated.
For example,

y(n) = h(n) * x(n) + w(n)

where y(n) is the received signal, x(n) is the sent signal, and w(n) is the additive white gaussian noise

At the next stage,
h(n+1) = a*h(n) + w(n)

The channel coefficient will be modified as stated above at the subsequent stage. The scaling factor "a" determines the impulse's amplitude, whereas "h(n+1)" represents the channel coefficient at the following stage.

Pilot Estimation Method

To understand how a communication medium is currently behaving, a channel estimate is necessary. In order to monitor a channel's behavior in practice communication systems, channel estimation is performed at very short periodic intervals. For instance, a pilot bit is injected into an OFDM data frame at every 'n' th bit interval. The pilot signal is known to the receiver. The receiver analyzes the channel influence on the pilot signal and adjusts the channel estimate for the entire data packet in accordance.

This training sequence-based strategy, also known as the pilot estimation method, is very well-liked and also not too complex. The frame contains pilot bit sequences sent over the channel and known to the receiver.

Blind Estimation Method

No training or pilot symbol is sent when using the blind estimating approach. This method makes use of some hidden mathematical operations or properties of the provided data.

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