Widely linear FRESH receiver for SAIC/MAIC with frequency offsets

Abstract

Widely linear (WL) receivers are able to fulfill single antenna interference cancellation (SAIC) of one rectilinear (R) (ASK, BPSK) or quasi-rectilinear (QR) (MSK, GMSK, OQAM) co-channel interference (CCI), a function which is operational in GSM handsets in particular. However, in most cases, SAIC technology loses its efficiency if the residual frequency offset (FO) of the CCI is above a very small fraction of the baud rate. It may be the case for airborne communications, due to high differential Doppler shifts. It may also be the case if we try to use SAIC/MAIC receivers to mitigate intrinsic inter-carrier interference (ICI) of FBMC-OQAM waveforms, which are candidate for 5G networks, and for which the ICI FO is equal to 50% of the (real) baud rate. In this context, the purpose of this paper is twofold. The first one is to extend, for an arbitrary propagation channel and from a MLSE-based approach, the SAIC/MAIC concept to R or QR signals with differential FO using WL FRESH filtering. The second one is to analyse both analytically and by simulations the impact of the residual CCI FO on the performance of the proposed SAIC/MAIC receiver.

Reception filter impact on widely linear fresh receiver performance for SAIC/MAIC with frequency offsets

“…The WL FRESH receiver introduced in [12] for SAIC/MAIC of a R CCI having a residual FO has been extended in this paper, for arbitrary propagation channels and from a pseudo MLSE-based approach, for low-pass filtered observations. Performance of the extended WL FRESH receiver have been analyzed for deterministic propagation channels with no delay spread, both analytically and by simulations, enlightening the impact of the low-pass filter bandwidth.…”

“…Performance of the extended WL FRESH receiver have been analyzed for deterministic propagation channels with no delay spread, both analytically and by simulations, enlightening the impact of the low-pass filter bandwidth. It has been shown that to maintain the whole potential of the WL FRESH receiver introduced in [12], the low-pass filter has to keep the CCI unfiltered. Extension of these results for QR signals will be presented elsewhere.…”

“…The WL FRESH receiver introduced in [12] for R signals exploits the conjugate SO cyclic frequency β = 2∆ f of x p (t) through the exploitation of the two-input FRESH observation vector x p,F2 (t), defined by…”

“…In the presence of a differential FO between the sources, the SAIC/MAIC receivers have to be extended using WL FRESH receivers. Such a WL FRESH receiver has been introduced recently in [12], for R and QR signals and for arbitrary propagation channels, using the pseudo-MLSE approach introduced in [13][14]. Performance of this receiver, jointly with the impact of the FO on the latter, have been analyzed both analytically and by simulations, showing off the great interest of this receiver whatever the value of the FO.…”

“…In this context, the purpose of this paper is twofold. The first one is to extend, for R sources with different FO, the WL FRESH receiver introduced in [12] to observations which are low-pass filtered. The second one is to analyze, both analytically and by simulations, the impact of the low-pass filtering on the performance of the extended WL FRESH receiver.…”