R. B. Gaikwad, Ankit shrivastava
In 4G/5G high speed systems the receiver should be able to recover the data i.e effective channel estimation is essential. Basically it is done to know or to predict the behaviour of wireless channel. We add extra bits with the data bits to know the behaviour of the channel these bits are called pilots. Now, it is achieved by using dedicated pilot symbols which consume a non negligible part of the throughput and power resources especially for large dimensional systems. The main objective of this paper is to quantify the rate of reduction of this overhead due to the use of a semi-blind channel estimation. Different data models and different pilot design schemes have been considered in this study. By using the Cramér Rao Bound (CRB) tool, the estimation error variance bounds of the pilot-based and semi-blind based channel estimators for a Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system are compared. In particular, for large MIMO-OFDM systems, a direct computation of the CRB is prohibitive and hence a dedicated numerical technique for its fast computation has been developed. Many key observations have been made from this comparative study. The most important one is that, thanks to the semi-blind approach, one can skip about 95% of the pilot samples without affecting the channel estimation quality.
Channel estimation, Semi-blind, CRB, MIMO- OFDM, large MIMO.