On the use of Pseudo-Noise Ranging with high-rate spectrally-efficient modulations

In this paper, we study the feasibility of coupling the PN ranging with filtered high-order modulations, and investigate the simultaneous demodulation of a high-rate telemetry stream while tracking the PN ranging sequence. Accordingly, we design a receiver scheme that is able to perform a parallel cancellation, in closedloop, of the ranging and the telemetry signal reciprocally. From our analysis, we find that the non-constant envelope property of the modulation causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be limited by properly sizing the receiver loop bandwidth. Our study proves that the use of filtered high-order modulations combined with PN ranging outperforms the state-of-the-art in terms of spectral efficiency and achievable data rate, while having comparable ranging performanc

Geometric morphometric approach in the study of the footprint variation in children between 6 and 12 years of age

Introduction. Footprint evaluation is a widely used method for determination of foot morphology. Generally, variation in footprint have been associated to vertical variation of the plantar vault, with particular attention to the middle longitudinal arch (MLA). In the children, MLA tends to be lower and accentuates naturally when approaching adolescence (Forriol and Pascual, 1990). Thought this condition is mostly asymptomatic, permanence of lower MLA after development is associated to flatfoot. In this study the morphology of the baropodometrical footprint was analysed by using geometric morphometric approach (Slice, 2000). This method permits to quantify the geometrical look of the anatomical structures by mean of coordinate system method. Material and methods. The footprints of 50 children with age spanning from 6 to 12 years were sampled using an electronic baropodometry. The external profile of the footprints were reduced to 50 equally spaced landmarks and superimposed using the Procrustes superimposition method. A principal component analysis was performed to evaluate the morphological variability of the footprints and sex and age difference were observed. Results. geometric morphometric results show that principal variations are localized in the medial region of the isthmus and are associated to a narrowing/widening of the footprint. No sex and age differences were observed, a part from a small group with age spanning from 6 to 9 years, showing a wider footprint. Conclusions. It is thought that principal modification of the MLA occurs in the pre-school years (Stavlas et al, 2005). The results of this analysis show an high variability of the footprint geometry, suggesting that ongoing development of the foot structure takes place also during school ages. Although these results are preliminary, they should carefully considered in the treatment of the flatfoot in children, considering that the development of the foot proceeds also after 6 year

RNN BCJR: a fully trainable version of the additive BCJR algorithm

We present a new version of the additive BCJR algorithm based on a recurrent neural network whose structure reflects an underlying trellis diagram. Starting from a matrix version of the equations of the additive BCJR algorithm, we derive the equivalent trainable recurrent neural network model, named Recurrent Neural Network (RNN) BCJR. The RNN BCJR consists of a linear layer to form the edge metrics from the state and input metrics, followed by a SOFTMAX/max* layer to marginalize the edge metrics back to the state and output spaces. We derive the recursions for delta propagation to train the two-layer mixing matrices from the output cost function. Unlike the previous approaches, the proposed RNN BCJR can completely replace the BCJR and is trainable from the cost functions of the outputs. The trained RNN BCJR achieves the same optimal performance as the BCJR when the model is known but at the same time can adapt itself to model mismatch, thus outperforming BCJR

On the use of PN Ranging with High-rate Spectrally-efficient Modulations in Satellite Payload Telemetry Links

Pseudo Noise (PN) ranging is a ranging technique that has been recently introduced in near-Earth space research (SR) missions. For these, at the state-of-the-art, the PN ranging signal is combined with a high-rate telemetry stream binary modulated in phase. The coupling of the two, together with the 10 MHz bandwidth constraint imposed for this class of missions, translates into a data rate bound of approximately 10 Mbps. The purpose of this article is to prove the feasibility of overcoming the current data rate limitation by defining a communication architecture that foresees the coupling of the PN ranging signal with a high-order modulated telemetry stream. To achieve the goal, we study the feasibility of pairing the PN ranging with filtered high-order modulations in satellite payload telemetry links and investigate the simultaneous demodulation of the telemetry stream while tracking the ranging sequence. Accordingly, we design a receiver scheme that is able to perform a closed-loop parallel cancellation of the ranging and the telemetry signal, reciprocally. From our analysis, we find that the non-constant envelope property, characterizing the considered modulation set, causes an additional jitter on the PN ranging timing estimation that, on the other hand, can be controlled and reduced by properly sizing the receiver loop bandwidth, without limiting the timing synchronization dynamic. Our study proves that the use of filtered high-order modulations combined with PN ranging outperforms the state-of-the-art in terms of spectral efficiency and achievable data rate while having comparable ranging performance