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Exact Analysis of MIMO Channel Estimation Based on Superimposed Training

Addad Mouad, Toaba Hanane Meriem, Djebbari Ali

Journal of Telecommunications and Information Technology

2024

nr 2

104--112

In this paper, channel estimation capabilities of a multiple-input multiple-output (MIMO) system using superimposed training sequences are investigated. A new expression for estimation-error variance is derived. It is shown that the training sequences must be balanced and must have specific correlation properties. The latter are required only in a specific zone. Sequences that satisfy these criteria exist and are referred to as zero-correlation zone (ZCZ) solutions. Consequently, by using balanced ZCZ sequences, harmful direct current (DC) offset can be removed. Owing to their zero-cross correlation, interference from other transmitting antennas may be eliminated. Furthermore, a closed-form expression of the estimation-error variance can be obtained due to their impulse-like autocorrelation. To increase the number of antennas in the MIMO system, a new construction of ZCZ sequence set is proposed, in which all sequences are balanced.

Low-Complexity Estimation of Carrier and Imbalance Parameters in Direct-Conversion Receivers

Gappmair W., Koudelka O.

Advances in Electronics and Telecommunications

2013

Vol. 3, no. 5

32--38

Due to aggressive goals for future communication systems, direct-conversion receivers are an attractive option in terms of compactness and power dissipation. But the price to pay is an additional impairment introduced by IQ mismatch and DC offset, which might be compensated by appropriately designed DSP algorithms. In this context, recovery of carrier and imbalance parameters has been investigated in many publications available from the open literature. For the current paper, however, we first derive the Cramer-Rao lower bound (CRLB) as the theoretical limit of the jitter variance for joint estimation of carrier frequency/phase, IQ gain/phase imbalance, and DC offset; to this end, the correlation of the noise components – in numerous contributions tacitly neglected – is explicitly taken into account. In the sequel, by means of several simplification steps, we present an approximate closed-form solution for the recovery of carrier and balance parameters, whose jitter performance is verified to be close to the CRLB, underlining this way the efficiency of the proposed method.