Echo Cancellation in DMT modems is a means to improve transmission performance. It consists in extending the downstream (DS) and upstream (UP) frequency bands so that they become adjacent or even overlap, and relaxing at the same time the existing filters. Modern cancellers make use of FIR filters that emulate the echo-path, and adaptive algorithms that estimate the correspondent coefficients. In this article, we start from the Circulant Decomposition Canceller (CDC), an efficient algorithm recently developed for ADSL, and explore new kinds of decomposition, based on the diagonalization properties of the Discrete Cosine and Sine Transforms (DCT, DST).
The European GNSS, Galileo is currently in its InOrbit Validation (IOV) phase where four satellites are available for computing the user position. Galileo E1 OS and GPS C/A represent a very effective constellation pair in a consumer grade receiver: the signals are conveyed on the same analog path and measurements can be combined in a single position, velocity and time (PVT) solution, provided that the Galileo to GPS Time Offset (GGTO) is available. Algorithms for GGTO estimation are presented in this paper, including a real-time implementation on a compact hardware receiver, based on the Teseo-II chipset. Experimental results are provided, showing the benefit in terms of accuracy and availability of the Galileo plus GPS multiconstellation solution respect to the GPS only case. Also analyzed are the effects on the GGTO estimate of different ionospheric models, namely: GPS Klobuchar and Galileo NeQuick. Both simulated scenarios and real, recorded Galileo IOV samples from a roof antenna are used in the validation of the proposed algorithms.
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