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MULTIMEDIA EXPERIMENTS AT THE UNIVERSITY OF PISA: FROM VIDEOCONFERENCE TO RANDOM FRACTALS

MULTIMEDIA EXPERIMENTS AT THE UNIVERSITY OF PISA: FROM VIDEOCONFERENCE TO RANDOM FRACTALS

May 2, 1995


Abstract


Real time multimedia applications are emerging over networks originally designed to support asynchronous services. The traffic generated by these applications represents a very critical component of the total traffic to be supported by future broadband telecommunication networks. The paper presents the experimental measurements carried out in Italy over a broadband network infrastructure represented by a 140 Mbit/s DQDB MAN. Particular interest was directed to multicast desktop conferencing tools based on software coding of voice and video. The two main traffic components, represented by traditional data traffic and packetized voice and video, were highly variable and bursty. Our measurements show that aggregated traffic offered to the broadband network is well described by self-similar processes which exhibit long range dependence. The interest of this analysis is directed to the performance evaluation of a broadband network which provides a best effort, asynchronous interconnection of several remote LANs. Some relevant effects of the arrival processes on network performances are presented by considering a model of the DQDB IEEE 802.6 network. Our work is directed to point out the need for more realistic traffic scenarios in the analysis of broadband telecommunication networks. The rationale behind this choice is that real sources correspond to the multiplexing of several traffic over the network and not to a single isolated video or voice source. This will be particularly true for LAN interconnections that will represent the first service to be provided by broadband networks in a business and educational environment.


Contents

1 Introduction

2 The network infrastructure

3 Application Areas

4 Traffic measurements

5 Self similar models of multimedia IP traffics and long range dependence

6 Simulation analysis

7 Conclusions

Acknowledgements

References

Author Information


1 Introduction

The wider broadband network infrastructure in Italy is represented by the interconnection of three MANs (Metropolitan Area Networks) in the towns of Pisa, Florence and Siena (see fig. 1).
The MANs will be interconnected to the European ATM network and to the ATM MAN set up in Naples as shown in figure 2.

fig. 2

The MAN "Tuscany" was realized in the framework of the Telecommunication Project (Progetto Finalizzato Telecomunicazioni) of the Italian National Research Council (CNR) during two distinct phases. The first phase corresponds to the initial configuration of the MANs in Pisa and Florence and their regional interconnection using a 34 Mbit/s link. The second phase corresponds to the actual configuration of 11 nodes in Pisa and 17 in Florence. During this phase the nodes already connected to the MAN "Tuscany" had extended their nodes with more LAN interfaces. Others were were provided by isochronous access and SMDS (Switched Multimegabit Data Service) access. At the end of the Telecommunication Project the MAN was extended also to the town of Siena realizing a regional wide broadband infrastructure. The architecture of the MAN "Tuscany" is organized into three switching levels: level 1 representing the Customer Access Network (CAN), level 2 representing the MAN Switching System MSS, i.e. the real multiple access network and level 3, the I-MSS (Inter MAN Switching System), which provides the interconnection of the MANs. The network was configured to offer a LAN bridging connection-less service over a regional area. Each Ethernet interface is interconnected to one or more Departmental LANs by means of multiprotocol routers, used to better control and filter the traffic from and to remote hosts. The end nodes of the network were located inside institutions of the National Research Council, Departments of the Universities of Pisa and Florence, Hospitals and other cultural or research organizations of particular interest in the framework of the experiments.

2 The network infrastructure

As shown in fig. 1 the present configuration of the MAN consists of a 34 Mbit/s backbone linking togheter the 140 Mbit/s MANs realized in Pisa, Florence and Siena. The MAN is realized by means of an optical transmission system based on the Plesiochronous Digital Hierarchy (PDH) and it consists of five network elements: The Customer Gateway is located on the customer premises and provides for the interconnection of customer equipments (LANs equipped with routers and audio/video codec if the nodes support an isochronous access). The Customer Access Network (CAN) interconnects the network access equipments to the actual multiple access network which is realized among the central offices of the Italian PTT: Telecom Italia. In Tuscany the CANs are essentially point-to-point interconnections of the customer premises to the nearest central office but they could be configured to provide a dual bus interconnection of several neighboring sites. Optically interconnected nodes have their access tributary multiplexed to an higher rate bearer carrier (the optical transmission system is running at 140 Mbit/s, in each direction, while only one of the four 34 Mbit/s tributaries is used as a Customer Access Network). The EGW and the CNIU are located within the local central offices of the Italian PTT. These network elements are directly connected to the MAN Switching System (MSS). The main function of the MSS is to provide a connection-less transport of fixed size segments (69 bytes) over a wide urban area (the MAN is based on the original QPSX proposal [20]). As shown in fig. 1, the MSS is realized by means of a folded dual bus topology in Pisa and Florence, while it is completely contained in the central office which hosts the dual bus of the MAN in the town of Siena. The forwarding of segments between the three remote MANs is realized by the Inter MAN Switching System (IMSS) which in Tuscany corresponds to a 34 Mbit/s backbone. The network elements responsible for the interconnection of the MANs are the Subnetwork Routers. These routers work at the level of DQDB segments and have to be distinguished from multiprotocol routers working at an higher level (such as IP). We have assumed that the three MANs are interconnected by an IMSS to highlight the third switching level (formally only independent Network Management zones are separated by an IMSS).

3 Application Areas

The main target of the experiments carried out over the MAN "Tuscany" was to find user applications which could provide real services to the research community in a first step and to business/industrial users in a second phase. In this context the performances of the MAN should have been evaluated gaining experience on the possibilities offered by metropolitan area networks based on the DQDB proposal. The main application areas are: Among them, due to the relevant number of the sites involved in the specific subject, the main activities were carried out in the field of telemedicine and distance learning. The other application areas are more site-specific and, in several cases, they adopt multimedia solutions firstly experimented in the field of telemedicine and distance learning.

3.1 Multimedia experiments in the field of telemedicine

Among the 33 nodes connected to the network at 2 Mbit/s or 34 Mbit/s, more than one third of them are clinical or radiological departments of the main hospitals in the towns of Pisa, Florence and Siena. Since the beginning of the Telecommunication Project, Telemedicine represented the main application area. Imaging departments frequently consist of a number of units, each one either focusing on a cluster of clinical applications domains (e.g. neuroradiology, pediatric radiology, etc.) or on a specific technology (e.g. Computer Tomography and Magnetic Resonance units, Angiography unit, etc.) that may be far from each other. Moreover, it often happens that hospital imaging departments are supplemented by satellite units located at various distances from the main hospital. In order to maintain the logical unity of the imaging data acquired for a given patient in the various units belonging to the same imaging department, it is crucial to provide efficient trasmission of information among the individual units. The resources have to be shared depending on the needs of the different sites. In this scenario the two most important applications are remote consultation of diagnostic experts and image communications between the departments of radiology [15]. This tele-consulting process can be realized in real time or considering different separated phases for the diagnostic data aquisition and for the referral activity of the radiologist. Sequences of still images are produced by means of Computer Tomography (CT), Magnetic Resonance (MR) or Ultrasonography. Moving images are produced by new diagnostic methodologies often directed to record methabolic activities in a 3D presentation. The first experiments in the field of Teleradiology were carried on between the two main units composing the Dept. of Radiology of the University of Pisa. The logical configuration of the two departments is shown in fig. 3. Each one is cabled with several Ethernet LANs (twisted pair and thin coaxial cable) interconnecting several Pcs, workstations and diagnostic equipments such as CT and MR. A Computer tomograph is installed also in the S. Chiara hospital but, so far, it was impossible to extract digital images directly from this equipment due to the lack of open standardized access units. The main resources at the Radiology Unit of the S. Chiara Hospital are high definition scanners which can be used to digitalize radiological films produced using traditional X-ray equipments. In Cisanello Hospital the main apparatuses are the Computer Tomography and a Magnetic Resonance connected by fiber optical links to a central unit called DCX. The DCX is connected to a Juke Box of optical disks (OD), to an high resolution film printer and to a 2.6 Gbyte Worm where the digital images are stored. Among the equipments not shown in fig. 3 four ultrasonograph (two are color doppler) are connected to the network. The amount of images produced by the Radiological Departments in a year is around 400.000 units. By using a proprietary software on the workstations interconnected to the DCX via an Ethernet LAN, it is possible to operate on the images stored in remote radiological data bases. This powerful windows tool lets the radiologist reconstruct 3D images from a set of images produced by CT or MR. After each exam, which takes around half an hour for each patient, the radiologist can share the access to the database and discuss about the reports. Teleradiology experiments were started using file transfer sessions driven by an user friendly interface by which the radiologist could access a remote data base of images and data related to the patients. The consultation between experts was realized using trasmission of "talk" like messages on the video of the workstation. In a second phase an interactive voice communication was set up using the tools developed by the Lawrence Berkeley Laboratory and by the research community over the Internet for voice and video communication over a Multicast logical network based on an the IP infrastructure [3][13][16][19]. Although voice and video could be better transported by isochronous channels over the MAN, easier integration of multimedia services on cheap workstations [19] and a possible extension to a global multicast environment suggested the use of real time traffic over a completely asynchronous transport service offered by IP. The LAN to LAN interconnection service provided by the MAN represented an ideal environment where to carry out this kind of experiences. Voice and video interaction between two or more experts was developed in an open X-window environment using software source coding [13].

3.2 Multimedia experiments in distance learning

Another main application area of broadband telecommunications, carried out over the network infrastructure in Pisa, is in the field of tele education and distance learning. These activities were either supported by isochronous connections offered by the DQDB network or by the queue arbitrated best effort access provided by the MAN. The experiments were also extended to the field of telemedicine with interesting applications in hypermedia WWW servers in support of medical imaging. The University of Pisa was infact the first Italian site to develop a WWW server (http://www.unipi.it) in the framework of the activities of the SERRA (SERvizio Reti Ateneo) project. The SERRA staff of the University of Pisa is maintaining the first Italian Veronica and Archie server and one of the main Italian news server in collaboration with the Institute CNUCE of the National Research Council. Hypermedial communication was adopted in the field of distance learning in teleradiology, setting up the first European Radiological WWW server (http://www.rad.unipi.it:7080/IRMosaicHome.html) which is focusing on high quality diagnostic images related to a specific liver disease ("Diagnosis, treatment and follow-up of hepatocellular carcinoma"). There are basically three types of tele-education activities studied and experimented at the University of Pisa: the ones based on the use of switched communication by means of Narrow Band ISDN, the ones carried out by using the semi-permanent G.703 access to the MAN and the ones related to desktop conferencing based on multicast IP and following the activities of the Mbone. The first experiments related to ISDN need expensive codecs (usually H.261, also known as px64Kbit/s codecs) which can be connected to a 2B+D Basic Rate Interface to provide a dial on demand service of slow-motion videoconferencing. The fixed transmission rate of the network implies a control feedback on the coding process which decreases the quality of the received video sequence when there is an high scene activity. To increase the performance of the system without using a more expensive access to ISDN (Primary Rate Interface), it is possible to make a diviplexing of the trasmitted stream over 2 or 3 Basic Rate Interfaces by means of inverse multiplexers [8]. The best quality available by commercial H.261 codec employing a fixed trasmission rate system is obtained by using a 2 Mbit/s link. One of the most relevant characteristics of the DQDB/QPSX MAN is that it provides an isochronuos access for real time communications. The communication is garanteed in bandwidth and delay since the pre-arbitrated functions [14] of the DQDB can be considered equivalent to a Time Division Multiplexing scheme. By contacting the Network Management Center it is possible to allocate a semi-permanent connection at 2 Mbit/s between two nodes of the network provided by isochronous interfaces. A very expensive hardware codec is still necessary and moreover the MAN does not provide a multipoint isochronous service. For this reason only point to point connection could be established. One of the most interesting experiments in this area was carried out during the final workshop related to the national Telecommunication Project held in Pisa last May. During the demonstration an isochronous connection between the Conference Center of the University of Pisa and the Department of Information Engineering was set up as shown in fig. 4. A speech of Prof. A. Roveri, Director of the Italian CNR Telecommunication Project, was transmitted in real time from the Department of Information Engineering to the Conference Hall. The third and most important activity in the field of distance learning was carried out over the MAN in a multicast IP environment [3][16][19]. Already before the interconnection of Italy to the Mbone, the transmission of voice and video over a completely asynchronous infrastructure was experimented between the Department of Information Engineering and the Institute of Radiology in Pisa [2]. Soon after the logical connection of the MAN to the Mbone, these experiments were extented over wider geographical areas. The Department of Information Engineering of the University of Pisa was the first Italian site to send voice and video over the Mbone. Some mounths later Steve Deering, author of the first IP multicast proposal was invited in Pisa to multicast a seminar from Consorzio Pisa Ricerche (a research consortium in Pisa), connected to the MAN by an SMDS access. These experiments on tele education and distance learning were successively proposed in the field of remote consulting between radiologists and physicians [2] and in the area of remote sensing for environmental monitoring [9]. The interest in this area is mainly due to the following reasons: The activities in the field of multicast IP communication were carried out with the support of the SERRA project. In the framework of this cooperation several video conferences with the Pisa Section of the National Institute for Nuclear Physics (INFN) were carried out. The INFN laboratory is not directly connected to the MAN "Tuscany", but these experiments showed easy interoperability among users reached by different communication facilities (i.e. leased lines, SMDS service, MANs, etc.). Although voice and video could be better transported over guaranteed bandwidth and delay channels, this easier integration of multimedia services on cheap workstations [13] and a possible extension to a global multicast environment produce an increasing interest on real time traffic over a completely asynchronous transport service offered by IP over LANs, MANs and ATM networks. With respect to broadband networking, a complementary context in the field of multimedia communications is represented by the down sizing (in terms of remote stations and link capacity) proposed by activities such as the Cornell University See-Me project, which is realizing an increasing compatibility between the Mbone and multimedia tools for Pcs and Macs. The first Italian reflector was set up at the Department of Information Engineering of the University of Pisa in collaboration with the SERRA (its address is indy.iet.unipi.it).

4 Traffic measurements

The experiments carried out in the fields of telemedicine and tele-education in Pisa show that multimedia applications are the new frontier for asynchronous global networking. The importance of these applications will growth up when present broadband islands will be interconnected by a global high capacity backbone. In this evolutionary scenario, the performance evaluation of such a complex infrastructure will be heavely influenced by the study of these new traffic components. Their modeling and implications on teletraffic theory are the present challenge in trying to build up new networks with statistically guaranteed quality of service (QoS). In the following we present an analysis of the traffic traces obtained by considering voice and video sources. The main tools considered in our experiments are in the public domain: NV for VBR video, VAT for audio, WB for shared whiteboard. A first analysis of the traces is directed to obtain the interarrival time distribution and the packet length distribution of the traffic process. With reference to this analysis we can compare the typical data traffic with the characteristics of voice and video traffic. In both cases we consider the actual traffic pattern obtained by means of tcpdump used as an Ethernet analyzer. Although the maximum achievable time resolution is lower than the one obtainable by dedicated hardware (such as a protocol analyzer), we will show in the following that the time resolution is enough for our studies. To make a comparison, a typical packet lenght distribution of the traffic offered to a broadband IP network is shown in fig. 5. The data were obtained filtering the traffic transmitted from several locally interconnected LANs to one of the access interfaces of the DQDB MAN (Department of Information Engineering). Over the LANs traditional applications, such as ftp, data base access (mainly www) and telnet, were continuosly running. In fig. fig. 6-8 the packet length distributions generated by a single video source (NV) are shown. In the first case (fig. 6) the coder was configured to send a maximum of 256 Kbit/s, with slowly moving greyscale images. In the second case (fig. 7) we consider the trasmission of a color video at the same peak rate and with a greater scene activity. In the third case (fig. 8) the trasmission of a "fixed" grayscale scene was recorded. All the experiments highlight that there is a great difference with respect to the distributions obtained considering traditional data applications. The same situation comes out when we consider the interarrival time distribution of the generated packet traffic (the interarrival time is measured from the beginning of a packet to the beginning of the next one). The traditional traffic produces a plot which is well fitted by an exponential distribution while the interarrival time plot obtained by video sources are characterized by a bimodal distribution (fig. 9-10) even if we have a completely static scene. The interarrival time distribution of the source corresponding to 256 Kbit/s (slow motion) grayscale video is shown in fig. 9, while in fig. 10 it is shown the plot obtained for a 256 Kbit/s color video with frequent scene changes. The presence of the first peak is due to the high presentation frequency of some values of the interarrival time between packets within a burst corresponding to the trasmission of a single frame; the second peak is due to the inter-frame tim e delimited by the last packet of a frame and the first packet of the next one. Each trace was 15 minutes long and was obtained considering the video trasmission between two Silicon Graphics INDY workstations connected to an isolated Ethernet LAN monitored by a Sun workstation runnig tcpdump. The measurements of packet voice traffic were obtained using VAT with PCM coding and unicast trasmission. In this case the interarrival time distribution can be considered almost deterministic (the interarrival time is very close to 80 msec). The randomness of the process is related only to the talking activity of the speaker. A classical model adopted for this process is the ON-OFF 2 state Markov process enabling and disabling a deterministic train. Starting from these measurements the interest of our work was related to the performance evalation of a network loaded by several heterogenous traffic sources corresponding to multimedia applications.

5 Self similar models of multimedia IP traffics and long range dependence

A continuos time process is a self similar process or a scaling process with parameter H (Hurst parameter) if X(at) and have identical finite dimensional distributions for all . Self-similar processes exhibit long range dependence. Considering the autocorrelation function r(k) and the power spectral density , long range dependence implies that:

where the simbol ~ stands for "has the form" and . A discrete-time, wide-sense stationary process Xn, with an autocorrelation function having the previous hyperbolic decay is called exactly (second order) self-similar if the aggregated time series have the same correlation structure of Xn [18]. The analysis of the experimental data corresponding to the multiplexing of several multimedia sources shows the self similar nature of the traffic offered to a broadband network. This behaviour can be confirmed by considering the Index of Dispersion for Counts IDC [10] which could be evaluated by the number of arrivals in a time interval of width t. The value of the IDC at time n is obtained as:

.

This function of n can be expressed as a weighted sum of the autocorrelation coefficients of the random sequence . This property maps the long range dependence of the IDC to the long range dependence of the process [4]. The self-similar property can be confirmed by comparing IDC functions obtained using different time intervals t. These IDC plots are almost identical independently on the time scale, i.e. on t, over several orders of magnitude [4]. The self similar stochastic process we considered as a mathematical model of the traffic offered to the DQDB MAN belongs to a particular class of Gaussian stationary processes called fractional Gaussian noises (fGn) [18]. An fGn process is completely characterized by its mean value , its variance and Hurst parameter H which completely defines its autocorrelation function:

For large values of n the IDC function of a fGn has the form . This gives us the possibility to extimate the Hurst parameter of an actual traffic process plotting the IDC curve obtained from the experimental results in a double logarithmic scale diagram. The asymptotic slope of the obtained line corresponds to the value 2H-1. Isolated video sources and traditional data traffic are well described by self similar processes. Isolated voice sources are, on the contrary, well described by ON-OFF models and by MMPP models [12].

6 Simulation analysis

A simulation analysis obtained considering the multiplexing of several actual traffic traces offered to an Ethernet LAN shows that the aggregated traffic process is self similar [6]. The model was obtained using Alta Group's BONeS Designer [1]. From the measurements analysis presented above we obtained isolated traces of multimedia sources. We offered to the model of the LAN 5 traces corresponding to NV sessions, 5 traces recording VAT sessions, 5 traces corresponding to WB sessions and 5 traces taken from the simultaneous use of VAT and NV applications. During the experimental measurements the peak rate offered by VBR coded sources was maintained to 1024 Kbps (512 Kbps when it was produced the mixed session of NV and VAT). The first interesting result is that the IDC curves of the resulted traffic, produced by this single Ethernet simulation, show that increasing the number of multimedia sources gives a self similar process with an increasing Hurst parameter (H). To highlight the implications of the long range characteristics of multimedia traffics on the performance evaluation and dimensioning of modern telecommunication networks, we considered the model of a DQDB MAN similar to the one set up in Tuscany [7]. The model refers to the functions of the medium access control protocol described in the IEEE 802.6 standard [14]. It was realized using Designer [1] to carry out trace driven simulations of the MAN by offering to the model different loading conditions which give the possibility to make a performance comparison with different mathematical source models. The architecture of a DQDB subnetwork is made up of two unidirectional buses that permit the transmission of information between a certain number of stations that represent the traffic sources. The DQDB access technique does not provide a fair access [11], in terms of mean access delay and mean throughput. The stations that are physically located near the Head of the transmission bus (named forward bus), although slowed down by the reservation of downstream stations, are privileged with respect to other stations even if they offer to the network the same load. This behaviour becomes evident when the network is large and the total offered load is close to the capacity of the bus. The simulation results [5] are related to the analysis of an ideal DQDB looped bus composed of 15 equally spaced stations separated by a distance of around 600 meters. The simulation was carried out considering the not isochronous traffic class and disabling the BWB Mechanism [11] proposed by the AT&T Bell's Labs to solve the unfairness problem. The bit rate was assumed equal to 150 Mbps, the payload of the segments was assumed equal to 48 octets and the local queues were assumed equal to 1000 segments. Every station generates the same percentage of the total offered load. Considering a total offered load of about 95% of the capacity of the bus (the network is symmetrical and we consider the process of trasmission over a single bus) we obtained that the steady state distribution of the normalized throughput of the stations is fair (fig. 11). This was due to the contained dimension of the network which exhibits an increasing unfairness if the distance among the stations increase and if an higher bit rate are adopted at the physical level [11]. The model was loaded with three different types of traffic: a real data trace, Poisson processes and Fractional Gaussian Noise processes. Although the steady state distribution of the throughput of the nodes is fair (fig. 11), there are significant differences for what is concerning mean access delay (fig. 12). The curve associated to the real trace corresponds to the worst results (the segments experiment the higher delays accessing the network and the unfairness). The Poisson trace is the most optimistic giving a lower delay and less unfairness also in this not extremely critical conditions of extension and capacity of the dual bus. The fractional gaussian noise process gives intermediate results. Although fractional Gaussian noises represent the simpler class of self-similar stochastic models, the behaviour of real traffic is closer to them than poissonian or renewal processes.

7 Conclusions

In the paper we presente the activities carried out in the field of multimedia communications at the University of Pisa. The presence of a broadband infrastructure in Tuscany gives the opportunity to experiment multicast IP voice and video services in the metropolitan area. The main application areas are Telemedicine and Distance Learning and several others are emerging. The IP network protocol seems to be a very promising candidate to provide global multimedia services over broadband islands interconnected by an ATM network. Quality of Service and traffic control will be some of the most relevant issues in this evolutionary process. The experiences carried out with actual applications over the Mbone give the possibility to face the problem of a correct performance evaluation. The analysis of real traffic and of its long range dependence confirms a self similar nature of the traffic offered to a broadband network. This behaviour is now observed in several different context: VBR video streams, packet traffic over the ISDN D-channels, traffic over LANs and broadband backbones [17]. Our simulation analysis highligths that this long-memory property has to be taken in careful account in the dimensioning of the future global telecommunication network. This will be possibile only if new simulation and mathematical tools will be developed in the new promising field of a fractal queueing theory.

Acknowledgements

This work was partially supported by the SERRA Committee and by the Project Murst 60% (1994) "Multimedia traffic measurements over not isochronous broadband networks". The authors want to express their best gratitude to Dr. Michele Pagano for his contribution to this work.


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Author Information

Stefano Giordano was born in Pisa in 1963. He worked with CNUCE Institute of the CNR at the ASTRA Project and in support of the UNESCO RINAF project. He graduated in Electronics Engineering at the University of Pisa in 1990. From 1993 he is researcher in the field of telecommunication at the Department of Information Engineering of the University of Pisa where he takes lectures on Telecommunication Networks, Digital Signal Processing and Electrical Communications. His main areas of interest are Broadband Communications, Telecommunication Networks Analysis and Design, Simulation of Communication Networks and Systems, Multimedia communications and source coding.

Giuseppe Pierazzini was born in Pisa in 1941, he graduated in physics in 1966. He started his research activities in high energy physics at University of Orsay in Paris and at CERN in Geneva. He continued his research collaborating with CERN and at the Nuclear Physics Laboratory of Protvino near Moskow. He is now full professor of Physics at the Department of Physics of the University of Pisa where he is involved in high energy experiments with CERN about the simmetry between matter and anti-matter. For his work he is involved in computer science problems and local and remote high speed data communications. In particular he was pioneering the subject of satellite (OTS) communications in support of nuclear physics (Stella Project). He is the now Director of the Pisa Section of the National Institute of Nuclear Physics and the General Director of the SERRA project, deeply involved in networking activities in support of research and education.

Franco Russo was born in Nola (Naples) in 1937, he was graduated in Electronics Engineering at the University of Pisa in 1962. He was with the Center for Methods and Devices for Radio Trasmission of the National Council of Research from 1963 to 1981. From that date he joined the Faculty of Engineering at the University of Pisa teaching Electrical Communications. From 1981 he is full professor at the University of Pisa where now he teachs Digital Signal Processing. He was the Director of the Computer Center of the Faculty of Engineering, of the Center for Automatics and Bioengineering and of the Dept. of Information Engineering. He is member of the Scientific Council of the National Group of Information Theory and Telecommunications of the National Research Council in Italy. Currently his main interests are related to ATM switching, Synchronization, Image, Voice and Video coding, Broadband Telecommunications.


Stefano Giordano
Stefano Giordano
giordano@iet.unipi.it
Department of Information Engineering, Via Diotisalvi, 2 56126 PISA - ITALY Phone: +39-50-568539

Giuseppe Pierazzini

Giuseppe Pierazzini
pierazzini@pisa.infn.it

Franco Russo

Franco Russo
russo@iet.unipi.it
Department of Information Engineering, Via Diotisalvi, 2 56126 PISA - ITALY Phone: +39-50-568645

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