Boosting Handwriting Text Recognition in Small Databases with Transfer Learning

In this paper we deal with the offline handwriting text recognition (HTR) problem with reduced training datasets. Recent HTR solutions based on artificial neural networks exhibit remarkable solutions in referenced databases. These deep learning neural networks are composed of both convolutional (CNN) and long short-term memory recurrent units (LSTM). In addition, connectionist temporal classification (CTC) is the key to avoid segmentation at character level, greatly facilitating the labeling task. One of the main drawbacks of the CNNLSTM-CTC (CLC) solutions is that they need a considerable part of the text to be transcribed for every type of calligraphy, typically in the order of a few thousands of lines. Furthermore, in some scenarios the text to transcribe is not that long, e.g. in the Washington database. The CLC typically overfits for this reduced number of training samples. Our proposal is based on the transfer learning (TL) from the parameters learned with a bigger database. We first investigate, for a reduced and fixed number of training samples, 350 lines, how the learning from a large database, the IAM, can be transferred to the learning of the CLC of a reduced database, Washington. We focus on which layers of the network could be not re-trained. We conclude that the best solution is to re-train the whole CLC parameters initialized to the values obtained after the training of the CLC from the larger database. We also investigate results when the training size is further reduced. The differences in the CER are more remarkable when training with just 350 lines, a CER of 3.3% is achieved with TL while we have a CER of 18.2% when training from scratch. As a byproduct, the learning times are quite reduced. Similar good results are obtained from the Parzival database when trained with this reduced number of lines and this new approach.Comment: ICFHR 2018 Conferenc

A Low-Complexity Double EP-based Detector for Iterative Detection and Decoding in MIMO

We propose a new iterative detection and decoding (IDD) algorithm for multiple-input multiple-output (MIMO) based on expectation propagation (EP) with application to massive MIMO scenarios. Two main results are presented. We first introduce EP to iteratively improve the Gaussian approximations of both the estimation of the posterior by the MIMO detector and the soft output of the channel decoder. With this novel approach, denoted by double-EP (DEP), the convergence is very much improved with a computational complexity just two times the one of the linear minimum mean square error (LMMSE) based IDD, as illustrated by the included experiments. Besides, as in the LMMSE MIMO detector, when the number of antennas increases, the computational cost of the matrix inversion operation required by the DEP becomes unaffordable. In this work we also develop approaches of DEP where the mean and the covariance matrix of the posterior are approximated by using the Gauss-Seidel and Neumann series methods, respectively. This low-complexity DEP detector has quadratic complexity in the number of antennas, as the low-complexity LMMSE techniques. Experimental results show that the new low-complexity DEP achieves the performance of the DEP as the ratio between the number of transmitting and receiving antennas decreasesProyectos Nacionales Españoles del Gobierno de España TEC2017-90093-C3-2-

Diseño de un radioenlace de servicio fijo de banda ancha entre las ciudades de Sevilla y Córdoba

Los radioenlaces de servicio fijo son una de las alternativas más importantes para establecer una comunicación entre dos puntos que estén relativamente alejados. Históricamente las comunicaciones por cable han sido más fiables y han avanzado tecnológicamente, con el objetivo de aumentar las tasas de transmisión hasta la actualidad, donde se alcanzan grandes anchos de banda con la tecnología de fibra óptica. La principal ventaja de los radioenlaces sobre los enlaces por cable como pueden ser la fibra óptica, es su instalación, ya que es mucho más sencillo instalar varias antenas en torres de comunicación que hacer una serie de obras por todo el recorrido por donde transcurra el cable. El mantenimiento de un radioenlace también es más sencillo, ya que los posibles puntos de fallo están focalizados, lo que hace que el tiempo de reparación sea más breve. El presente trabajo surge de la propuesta de realizar un radioenlace basado en la tecnología Packet Microwave, que sea red troncal entre dos grandes ciudades como pueden ser Sevilla y Córdoba. Se hará un previo estudio de las tecnologías que hay en el mercado que soporten Packet Microwave, así como de los equipos transceptores y antenas que soportan esta tecnología. Posteriormente se eligen los equipos que se consideran oportunos para el diseño de radioenlace y se hace un estudio de la viabilidad del mismo, así como un análisis de calidad e indisponibilidad para comprobar si se cumplen los objetivos de la ITU para radioenlaces de servicio fijo. Todos los estudios se han realizado con el software de planificación Xirio-Online. Debido a la distancia del radioenlace, a la orografía del terreno y a la banda de frecuencias en la que trabaja el radioenlace, es necesario dividir el trayecto en varios vanos. Finalmente se redacta una memoria con las descripciones técnicas de los elementos del radioenlace, incluyendo el pliego de condiciones y los planos.Fixed Service radio links are one of the most important alternatives for communication between two points that are relatively far. Historically wired communications have been more reliable and have advanced technologically, in order to increase transmission rates up to the present, when large bandwidths are achieved with fiber optic technology. The main advantage of the wireless links over wired links such as fiber optics is its installation, as it is much easier to install several antennas in communication towers to do a series of works throughout the tour which elapses Cable. Maintaining a wireless link is also easier, since the potential points of failure are focused, making repair time shorter. This work arises from the proposal for a system based on Packet Microwave technology, which is backbone network between two big cities such as Seville and Cordoba. A preliminary study of the technologies on the market that support Packet Microwave has be done and also transceiver and antennas that support this technology. Later the equipment that is considered appropriate for the design of wireless link and a study of its feasibility are chosen, as well as an analysis of quality and unavailability to check whether the objectives of the ITU for wireless fixed service are met. All studies were performed with planning software Xirio-Online. Because of the distance of the radio, to the terrain and the frequency band in which the radio link works, it is necessary to split the link in several bays. Finally a memory with the technical descriptions of the elements of the link, including the specification and plots, are included

Boosting offline handwritten text recognition in historical documents with few labeled lines

Article number 9438636In this paper we address the problem of offline handwritten text recognition (HTR) in historical documents when few labeled samples are available and some of them contain errors in the train set. Our three main contributions are: first, we analyze how to perform transfer learning (TL) from a massive database to a smaller historical database, analyzing which layers of the model need fine-tuning. Second, we analyze methods to efficiently combine TL and data augmentation (DA). Finally, we propose an algorithm to mitigate the effects of incorrect labeling in the training set. The methods are analyzed over the ICFHR 2018 competition database, Washington and Parzival. Combining all these techniques, we demonstrate a remarkable reduction of CER (up to 6 percentage points in some cases) in the test set with little complexity overhead