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ABSTRACT This paper,presents,a new hybrid coding method for low bit-rate videoconferencing transmission,over ISDN. The use of both predictive,and transform coding techniques along with motion compensation allows to obtain bit-rates... more
ABSTRACT This paper,presents,a new hybrid coding method for low bit-rate videoconferencing transmission,over ISDN. The use of both predictive,and transform coding techniques along with motion compensation allows to obtain bit-rates suitable for ISDN applications. To that extend, a new quad,tree based segmentation technique to detect stationary,and,moving parts of an image is introduced. On the other hand, to fully exploit the statistical
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The transmission of video and audio services under quality restrictions over the available bandwidth in the broadband ISDN is a challenge over the next years. The specification of the ABR service allows one to obtain better resource... more
The transmission of video and audio services under quality restrictions over the available bandwidth in the broadband ISDN is a challenge over the next years. The specification of the ABR service allows one to obtain better resource utilization in ATM networks. This policy is only suitable for applications which traffic can be adapted to the available bit rate offered through
Research Interests: Quality Management, Adaptation, Queueing theory, Protocols, Quality of Service, and 11 moreATM networks, Feedback, Resource Management, Real Time, Traffic Shaping, asynchronous Transfer Mode, Multimedia Traffic, Service Operations Management and Quality of Services, Video on Demand, Bandwidth, and Resource Utilization
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The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include... more
The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include mechanisms for the integration of different technologies. New optical access technologies trends are: WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take into account the evolution of the installed legacy PONs to the next generation optical access networks. The present paper goes through such topics, focusing on the research being carried out to develop dynamic bandwidth algorithms for the 10 Gb/s new EPON standard (IEEE 802.3av). We summarize results and point out issues that will require further investigation. Postprint (published version)
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En les dues darreres decades ens hem acostumat a veure un vertiginos canvi tecnologic en I'area de les telecomunicacions que ens ha dut a observar els nous avencos, els nous sistemes, com a Pets completament usuals dins les nostres... more
En les dues darreres decades ens hem acostumat a veure un vertiginos canvi tecnologic en I'area de les telecomunicacions que ens ha dut a observar els nous avencos, els nous sistemes, com a Pets completament usuals dins les nostres vides. Res no ens sorpren, sembla que tot sigui possible, transmissio d'I natges, veu, documents, terminals que fan multiplicitat de funcions i presenten diversos tipus d'informacio simultaniament i en temps real. Aquesta carrera frenetica d'arribar a una comunicacio integral a distancia, de presentar multiplicitat de serveis al nostre abast, esta revolucionant i revolucionara el nostre sistema de vida. Es usual poder consultar les dades bancaries o treure diners en els caixers automatics: ja no ho es tant encomanar mercaderies als grans magatzems des de la propia liar o consultar algunes bases de dades del nostre municipi, del banc, o la borsa. Probablement en un futur immediat existiran terminals multimitja (veu, dades, imatge i video) q...
One of the most important problems to solve for the Ethernet Passive Optical Networks (EPON) is the design of a Dynamic Bandwidth Allocation algorithm for the upstream channel. It is a shared medium in time for data transmissions of... more
One of the most important problems to solve for the Ethernet Passive Optical Networks (EPON) is the design of a Dynamic Bandwidth Allocation algorithm for the upstream channel. It is a shared medium in time for data transmissions of different user devices (ONU). By means of a signalling protocol, the head-end (OLT) arbitrates the use of the upstream channel, not only to avoid collisions, but also to provide support to quality-of-service for the users of the network. Most of the solutions are based on a round-robin scheduling inside the cycle of transmission of every ONU in the EPON. In this paper we propose the combination of a fair bandwidth distribution algorithm with an ordering approach that grants transmissions according to the arrival time of frames. We show some simulation results over a simple topology considering two different scenarios: first with homogeneous or balanced network loads, and second with different traffic rates and misbehaving ONUs. In general, the combinatio...
Ethernet Passive Optical Networks (EPON) is being considered as a promising solution for the next generation broadband access networks. An open issue at the standard 802.3ah is Dynamic Bandwidth Allocation (DBA) algorithm. The DBA schemes... more
Ethernet Passive Optical Networks (EPON) is being considered as a promising solution for the next generation broadband access networks. An open issue at the standard 802.3ah is Dynamic Bandwidth Allocation (DBA) algorithm. The DBA schemes can help in providing quality of service issues. In this work we propose a new DBA algorithm which not only could provide a fair distribution of bandwidth, but also some control to delay experienced by user traffic. Ethernet Passive Optical Networks (EPON), remote scheduling, Dynamic Bandwidth Allocation (DBA), Quality of service (QoS).
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The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include... more
The access network infrastructure plays an important role in the overall performance of the network, next generation access networks (NGA) must be able to access diverse services, and should incorporate adequate architectures that include mechanisms for the integration of different technologies. New optical access technologies trends are: WDM, 10 Gb/s, and longer reach/higher splits. It is also important to take
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ABSTRACT The usage of the DECT as a RLL application has many advantages such as high quality voice encoding (ADPCM at 32 kbps), full ISDN compatibility when assigning double slot to the connection, and no need of frequency planning. DECT... more
ABSTRACT The usage of the DECT as a RLL application has many advantages such as high quality voice encoding (ADPCM at 32 kbps), full ISDN compatibility when assigning double slot to the connection, and no need of frequency planning. DECT was first designed as an indoor system with low spectral efficiency. Although it has only 120 different channels, it is capable of a high quality in the environment it has been designed for. When trying to apply it outdoors, it will be necessary to reuse those few frequencies many times, resulting in a system that is limited mainly by co-channel interference. We have studied several ways to increase the system capacity by limiting the co-channel interference and we have evaluated the impact on the system performance by simulation. Among the most significant improvements studied are the the use of directive and adaptive antennas
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ABSTRACT In this paper we present a fast splitting algorithm (FSA) for a signal that when combined with the wavelet transform for each interval and an optimality criterion, leads to the best progressive tiling of the time-frequency plane.... more
ABSTRACT In this paper we present a fast splitting algorithm (FSA) for a signal that when combined with the wavelet transform for each interval and an optimality criterion, leads to the best progressive tiling of the time-frequency plane. Given a set of basic regions and a cost function defined over this set, we find the minimum cost cover of the signal and establish the conditions for progressive analysis. We show how when progressive conditions are verified this method can be modelled with simple structures such as trellis diagrams or ordinary Petri nets. The FSA includes the splitting induced by the double tree algorithm (DTA) [8], and allows better signal analysis and coding efficiency. We also present two heuristic approaches (basis regions with bounded maximum length, and best past splitting) that can reduce properly the complexity of the FSA maintaining the improvements of the method
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The Digital European Cordless Telecommunication System (DECT) is gaining acceptance in environments different to the ones the system has been designed for. In particular in the radio local loop (RLL) and in personal communication services... more
The Digital European Cordless Telecommunication System (DECT) is gaining acceptance in environments different to the ones the system has been designed for. In particular in the radio local loop (RLL) and in personal communication services (PCS) applications. The main difference between indoors, where DECT was supposed to work, and outdoors is that in this latter environment the signal propagation is
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ABSTRACT Multimedia traffic is carried over multi-access channels using random multi-access protocols (RMAP) to access the common channel by users' equipment. The main goal of any RMAP is that the network is shared by all users in... more
ABSTRACT Multimedia traffic is carried over multi-access channels using random multi-access protocols (RMAP) to access the common channel by users' equipment. The main goal of any RMAP is that the network is shared by all users in a fair way. RMAP must also be able to cope with the QoS that different multimedia traffic requires. Current protocols proposed for multimedia traffic are very sophisticated and difficult to analyze because they use distributed queues. The main goal of this paper is to present a common methodology to analyze multimedia RMAP. The results obtained by this procedure include the computation not only of the expected values but the distributions of the final interdeparture time and the departure burst size
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ABSTRACT The present paper suggests both an ATM customer premises network architecture as an associated generic flow control (GFC) MAC algorithm for the broadband customer premises network (B-CPN). This ATM local network incorporates a... more
ABSTRACT The present paper suggests both an ATM customer premises network architecture as an associated generic flow control (GFC) MAC algorithm for the broadband customer premises network (B-CPN). This ATM local network incorporates a ring architecture and is based on a new class of shared-medium access protocol. The access control operates over an unidirectional slotted ring network with spatial reuse by a destination release procedure. Under this access mechanism two levels of traffic with requested quality of service (QoS) are supported: real-time and non-real-time traffic. This access protocol is described and its performance is analyzed
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ABSTRACT This paper shows a new class of shared-medium access mechanism, named reset-window with buffer insertion protocol, applied to the ATM customer premises network architecture. The broadband local network consists of a... more
ABSTRACT This paper shows a new class of shared-medium access mechanism, named reset-window with buffer insertion protocol, applied to the ATM customer premises network architecture. The broadband local network consists of a unidirectional slotted ring network with spatial reuse by the destination release procedure. Under this access mechanism two levels of traffic with requested quality of service (QoS) are supported: real-time and non-real-time traffic
The actual trend to integrated services has to be simulated by and accompanied by a group of applications that take profit out of new facilities. Through the paper, a multimedia application oriented to both remote diagnostic and... more
The actual trend to integrated services has to be simulated by and accompanied by a group of applications that take profit out of new facilities. Through the paper, a multimedia application oriented to both remote diagnostic and consultation between physicians and specialists is presented. This application is designed to manage medical images (both static and dynamic), and offers edition facilities of multimedia documents (voice, image, text and data), document interchange, videotelephony conferencing and screen synchronization. The multimedia application is a software development made on a UNIX workstation including sound acquisition and reproduction devices within its original hardware, and an attached video camera with an associated DSP card. The user interface is based on the SUN windowing environment called Open Windows, which assists medical staff. The communication was developed using the TCP/IP suite protocols (IP, TCP, UDP), and tested over different local area networks (FDDI, Ethernet) and low speed links (asynchronous line using the SLIP protocol)
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ABSTRACT The new advances in multimedia technology and telematic environments provide powerful tools that have been applied to several heterogeneous fields with successful results. The area of telediagnostic and remote consultation... more
ABSTRACT The new advances in multimedia technology and telematic environments provide powerful tools that have been applied to several heterogeneous fields with successful results. The area of telediagnostic and remote consultation between physicians will be one that can obtain more benefits. In this work a telediagnostic system applied to teleradiology is presented. The system is built on a Unix software/hardware standard platform, a specific DSP, video card, and an audio and video acquisition and reproduction devices, that incorporate multimedia facilities. The dialogue between physicians is established either interactively on real time, or non interactively through multimedia mail. At low level the transferred information is conveyed on a multimedia structure with TCP/IP protocols over the main public or private telematic networks. The users dispose of a set of multimedia editors to manipulate data, text, voice, images and video over a window environment, that along with the synchronisation of the two remote screens and applications, facilitate the interchange of information between remote sites
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This paper presents an analysis of the aggregate traffic of variable bit rate (VBR) MPEG-1 sources. The aggregate traffic was implemented by the superposition of different copies of a real sample obtained at the output of an MPEG coder.... more
This paper presents an analysis of the aggregate traffic of variable bit rate (VBR) MPEG-1 sources. The aggregate traffic was implemented by the superposition of different copies of a real sample obtained at the output of an MPEG coder. These copies were offset a random time interval, that was not forced to be a multiple of the interframe time. The
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Service disciplines are one of the most important aspects in high speed networks in order to provide guarantee performance services. The earliest deadline first (EDF) discipline is considered delay optimal. It minimizes the maximum delay... more
Service disciplines are one of the most important aspects in high speed networks in order to provide guarantee performance services. The earliest deadline first (EDF) discipline is considered delay optimal. It minimizes the maximum delay of all packets because it selects the packet with the smallest deadline in each service time. In this paper we present the performance of a
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Current telecommunications includes plenty of services and applications for final users. New standards are currently being discussed such as 802.14 for HFC networks, or DAVIC for access networks with new technologies such as HFC, ADSL,... more
Current telecommunications includes plenty of services and applications for final users. New standards are currently being discussed such as 802.14 for HFC networks, or DAVIC for access networks with new technologies such as HFC, ADSL, FTTC and FTTH, including new MAC multi-access protocols. Different types of traffic are defined depending on the service they are carried on: CBR, VBR, ABR
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Despite there are several ATMIB-ISDN physical configurations recommended by ITU-T [ 11, as centralized B-NT2, distributed B-NT2, multi-access B-TE, the main actual development is based on centralized configurations. The shared ATM access... more
Despite there are several ATMIB-ISDN physical configurations recommended by ITU-T [ 11, as centralized B-NT2, distributed B-NT2, multi-access B-TE, the main actual development is based on centralized configurations. The shared ATM access is intended as an complementary ...
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ABSTRACT We present a methodology to analyze functions in l2 in terms of self-similar discrete-time biorthogonal functions at different resolution levels. We call these functions discrete-time biorthogonal wavelets, and they verify in l2... more
ABSTRACT We present a methodology to analyze functions in l2 in terms of self-similar discrete-time biorthogonal functions at different resolution levels. We call these functions discrete-time biorthogonal wavelets, and they verify in l2 the same properties that biorthogonal wavelets do in L2, including self-similarity. Discrete multiresolution analysis is also defined
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ABSTRACT In this paper, the performance of filters implied in the discrete wavelet transform approach is compared with a set of filters of common application in image processing. A multidimensional multirate codec is designed in which the... more
ABSTRACT In this paper, the performance of filters implied in the discrete wavelet transform approach is compared with a set of filters of common application in image processing. A multidimensional multirate codec is designed in which the best subband decomposition and coding is jointly obtained by minimization of a rate-distortion criterion. We also introduce the idea of directional sensitivity based on the initial sampling lattice. This allows the codec to adapt better to the spectral content of the signal. Finally, taking as a starting point the continuous wavelet transform, we propose a discrete multiresolution analysis that would lead to new discrete transforms of special interest when analyzing discrete scalings and shiftings: the completely discrete wavelet transform.
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ABSTRACT In this paper we present a family of orthonormal transforms for functions in l2 in which basis functions have compact support and verify a self-similarity criterion at different resolution levels. First, we define the... more
ABSTRACT In this paper we present a family of orthonormal transforms for functions in l2 in which basis functions have compact support and verify a self-similarity criterion at different resolution levels. First, we define the discrete-time orthogonal wavelet transform, a transform that verifies a set of orthonormality properties on a self-similar discrete multiresolution analysis. We relax the constrains imposed on this transform generalizing the concept of self- similarity and defining the generalized discrete-time orthogonal wavelet transform. In this case, it is possible to obtain different levels of self-similarity and more degrees of freedom in the design of basis functions. Finally, a discrete-time self-similar multi-function transform and a discrete-time multi-wavelet transform are presented, and the criteria that basis functions must verify to become an orthonormal transform are pointed out.
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ABSTRACT This paper describes the Three Dimensional Laplacian Pyramid Coding as an extension of previously reported work on static images. The algorithms that we present when applied to image sequences gives high compression rates being... more
ABSTRACT This paper describes the Three Dimensional Laplacian Pyramid Coding as an extension of previously reported work on static images. The algorithms that we present when applied to image sequences gives high compression rates being very useful for videotelephone or videoconference applications. The image sequence is splitted into subsequences which are composed of a small number of images then the three dimensional algorithms are applied. The coding scheme is based on the construction of spatial/temporal pyramid structures defined on arbitraiy sampling lattices. A three dimensional treatment study of sampling rate conversion using matrix notation is also presented.
ABSTRACT This paper proposes a fast splitting algorithm (FSA) for a signal that when combined with an optimally criterion defined in the frequency domain leads to coherent tilings of the time- frequency plane. For a given set of basis... more
ABSTRACT This paper proposes a fast splitting algorithm (FSA) for a signal that when combined with an optimally criterion defined in the frequency domain leads to coherent tilings of the time- frequency plane. For a given set of basis regions formed by allowed subsets of the signal and a cost function defined over this set, we find the minimum cost cover of the signal by means of a fast algorithm. We show how when an additive cost measure is defined over the subband decomposition induced by a given filter bank, the method admits a solution in the form of a progressive orthogonal tiling. When progressive conditions are verified this method can be modelled with simple structures such as trellis diagrams or ordinary Petri nets. The extension of this method to bidimensional signals and conditions for fast algorithms are also discussed. The set of partitions obtained by the double tree algorithm is included in those considered by the FSA, allowing the later better signal analysis. We also present two approaches that reduced properly the complexity of the FSA maintaining the improvements of the method. The first one is based in constraining the set of basis regions to those with dyadic support, while the second one bounds the maximum support of basis regions.
A pyramidal image structure is presented that uses algorithms defined on arbitrary nonrectangular sampling lattices. An adaptive technique is also developed that assigns to the pyramidal structure an optimum sampling lattice as a function... more
A pyramidal image structure is presented that uses algorithms defined on arbitrary nonrectangular sampling lattices. An adaptive technique is also developed that assigns to the pyramidal structure an optimum sampling lattice as a function of the frequency content of the original image. Two algorithms, one in the frequency domain and the other in the spatial domain are used to select the optimum sampling lattice