This letter introduces a new low-complexity frequency-domain equalizer for continuous phase modulations (CPM). The derivation of a fractionally spaced representation for circular block-based CPM leads, without any approximation, to a simple yet efficient frequency-domain equalization. The proposed equalizer is compared to the state-of-the-art approaches. Simulation results show the equivalence in terms of performance with a lower or similar complexity.

In this paper, we present two Data-Aided channel estimators for Continuous Phase Modulation (CPM) in the case of transmissions over doubly-selective channels. They both capitalize on the Basis Expansion Model (BEM), widely used for OFDM systems and for Single Carrier transmission with linear modulation. However, in the case of CPM signals, we need to work on a over-sampled received signal (fractionally-spaced representation) as the equalization techniques are also working on the over-sampled received signal. The first one is a classical Least Squares (LS) estimation of the BEM parameters whereas the second channel estimator introduces first a parametric dependence on the paths delays. Indeed, in the case where those delays are known (by estimation or by geometrical consideration as for the aeronautical channel by satellite), the second LS estimation on the BEM parameters is improved and less computationally demanding. Simulations results are provided and show good performance of our parametric LS estimation.

In this paper, we consider single carrier continuous phase modulations (CPM) over frequency selective time-varying channels. In this context, we propose a new low-complexity frequency-domain equalizer based on the minimum mean square error (MMSE) criterion exploiting efficiently the band structure of the associated channel matrix in the frequency domain. Simulations show that this band-MMSE equalizer exhibits a good performance complexity trade-off compared to existing solutions.

In this paper, we present a generalized polyphase representation for Continuous Phase Modulation (CPM) signals suited to the detection over frequency-selective channels. We first develop two different equalizers based on this representation and relate them to the State of Art. We also derive a Least Squares (LS) channel estimation and an improved LS estimation using a priori on the channel. Simulation results show the equivalence between existing equalizers and also show that our channel estimation leads only to a small degradation in term of Bit Error Rate (BER) in the case of an aeronautical communication over a satellite link.

Dans cet article, nous proposons d’étudier différents algorithmes d’égalisation pour signaux à Modulation de Phase Continue (continuous phase modulation, CPM) dans le domaine fréquentiel à l’aide d’une représentation polyphase du signal. Par cette approche unifiée, nous montrons l’équivalence analytique de ces égaliseurs sous certaines hypothèses liées au canal de transmission, les liens, ainsi que leurs limitations dans certains cas.

In this paper, we present a new data-aided carrier-recovery method for Continuous Phase Modulation (CPM) signals over frequency-selective channels. We first present a linear model of the received signal based on Mengali representation over selective channels and show how to use it to perform joint channel and carrier-frequency estimation. We also derive a low-complexity version of the estimator. Simulation results show that this method performs better than the optimal method suited to the Additive White Gaussian Noise (AWGN) channels.

Les modulations à phase continue (CPM) se distinguent des autres modulations de par leur enveloppe constante et une phase continue. Ses deux dernières caractéristiques mettent en lumière les avantages de l'utilisation de la CPM. Tout d'abord une enveloppe constante entraîne une puissance constante de l'onde porteuse et donc à un bon rendement en puissance. Cela peut être très utile lors de l'amplification du signal notamment par les relais satellites. Ensuite la continuité de la phase permet d'obtenir une forte efficacité spectrale. En conséquence les CPM sont utilisées dans de nombreux standards tels que le GSM, l'AIS, RCS2... Nous verrons lors de ce séminaire une introduction aux CPM et à leurs récepteurs associés ainsi que les contributions apportées par nos deux thèses.