Code-aware joint estimation of carrier phase and SNR for linear modulation schemes

Closed-form CRLBs for SNR estimation from turbo-coded square-QAM-modulated signals

“…In order to satisfy the ever increasing demand in high data rates, the use of turbo codes in conjunction with high-order QAMs has been already adopted in many current and upcoming wireless communication standards such as 4G long-term evolution (LTE), LTE-advanced (LTE-A) and beyond (LTE-B) [6,7]. Recently, it has been shown in (see [8][9][10][11] and references therein) that the SNR estimation performance can be substantially enhanced by exploiting some priors that are delivered during the decoding process of the transmitted bits. Indeed, over a wide range of practical SNRs, CA estimation was found to perform nearly the same as DA estimation.…”

“…In fact, a bunch of advanced NDA SNR estimtors have been recently proposed in [13][14][15][16][17] for both constant and time-varying single-input multipleoutput (SIMO) channels. SNR estimators suited for turbo-coded single-input single-output (SISO) systems have also been recently reported in the open literature (see [8][9][10] and references therein). The performance of such estimators is usually assessed in terms of error variance; yet it still requires to be gauged against an absolute benchmark that sets the minimum achievable variance for all the unbiased estimators.…”

“…In CA estimation, however, such stochastic CRLBs were derived analytically for the very basic case of coded BPSK transmissions only [11] and their closed-form expressions for higher-order modulations have not been reported yet. A compelling illustration of the literature limitation persisting so far is that code-aided SNR estimators have been very often compared in performance to the DA CRLBs ( as recently done in [9] and [11] ) . The latter might offer an accurate benchmark for BPSK signals, but become excessively optimistic 2 in the presence of higher-ordermodulated signals, especially at low SNR values (see section V for more details).…”