Channel Estimation for OFDM and MC-CDMA
7.1 Pilot-Assisted Channel Estimation
In this treatise we concentrate our attention on the derivation and the performance analysis of decision-directed channel estimation methods, although we would also like to give a brief performance comparison between decision-directed and pilot-aided channel estimation methods. Our motivation is that any technique applicable to decision-directed channel estimation can be equally employed in the context of pilot-aided schemes and the difference in attainable performance can be predicted as outlined below.
The attainable performance of both the Decision-Directed (DD) and Pilot-Assisted (PA) channel estimation methods can be compared in the following simple way.
The performance of any PA channel estimation method expressed in terms of the achievable Mean Square Error (MSE) is upper bounded by the expression
where Ep is the total power associated with the transmitted pilots, N0 is the Gaussian noise variance and L is the number of non-zero CIR components.
On the other hand, in the case of DD channel estimation the corresponding performance bound, using the assumption of error-free decisions, can be described by
where Es is the average signal energy per transmitted complex baseband sample ...