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GIANNI IMMOVILLI

Professore emerito
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

- Circuito demodulatore di frequenza a correlazione ampiezza fase [Brevetto]
L., Calandrino; Immovilli, Gianni
abstract

L'invenzione riguarda un circuito demodulatore di frequenza che utilizza la dipendenza statistica fra le deviazioni di frequenza e di ampiezza prodotte dal rumore, che si sovrappone alla oscillazione modulata, al fine di migliorare il rapporto segnale/rumore di uscita. Tale circuito demodulatore può essere chiamato a correlazione ampiezza-fase.

2002 - Admission control in T/CDMA systems supporting voice and data applications [Articolo su rivista]
Casoni, Maurizio; Immovilli, Gianni; Merani, Maria Luisa
abstract

This paper analyses the behavior of two hybrid time-code division multiple-access (T/CDMA) architectures on the up-link of a macrocellular mobile radio system. For the examined schemes two categories of users-voice and data-share the domain of available resources, made up of time slots and codewords, through two. alternative assignment strategies. Both solutions attribute voice users one single resource pair, i.e., one time slot and a single code to employ on that time slot, but differ in the way data users requests. are accommodated: they are either simultaneously granted several codes over the same time slot or are assigned a single code over several distinct time slots. Call admission control is performed by a channel assignment algorithm which dynamically attributes resources only if specified levels of transmission quality are met on the radio channels. The blocking and the outage probability of the two classes of users are determined and compared, showing that one of the proposed schemes exhibits better performance and allows to satisfyingly serve a significant percentage of data users.

2001 - Integrating voice and data applications in T/CDMA architectures [Articolo su rivista]
Casoni, Maurizio; Immovilli, Gianni; Merani, Maria Luisa
abstract

This letter analyzes the behavior of two time-code division architectures serving voice and data applications on the uplink of a cellular system. Both solutions attribute speech users one code over a timeslot, whereas data users are granted several codes over the same timeslot or a single code over several time slots. Call admission control dynamically attributes resources if specified levels of transmission quality are met. The blocking probability of the two classes of users is determined, demonstrating that the multicode T/CDMA approach performs better than the multislot solution and than a pure CDMA system.

2001 - Performance Evaluation of an Interference based admission control schemein T/CDMA systems with voice and dat users [Relazione in Atti di Convegno]
Casoni, Maurizio; Immovilli, Gianni; Merani, Maria Luisa
abstract

This paper analizes the behaviour of two-time code division architectures serving voice and data users on the uplink of a cellular system.

2001 - Performance evaluation of an interference based admission control scheme in T/CDMA systems with voice and data users [Relazione in Atti di Convegno]
Casoni, M.; Immovilli, G.; Merani, M. L.
abstract

This paper analyzes the behavior of two time-code division architectures serving voice and data applications on the uplink of a cellular system. Both solutions attribute speech users one code over a time slot, whereas data users are granted several codes over the same time slot or a single code over several time slots. Call admission control is performed by a channel assignment algorithm which dynamically attributes resources if specified levels of transmission quality are met. The blocking probability of the two classes of users is determined, and it is demonstrated that the multicode T/CDMA approach performs better than the multislot solution and than a pure CDMA system.

2000 - Channel Allocation Schemes Providing QoS in Wireless Networks [Relazione in Atti di Convegno]
Casoni, Maurizio; Immovilli, Gianni; Merani, Maria Luisa
abstract

In this paper we propose a new class of interference adaptive dynamic channel allocation policies, tailored to provide different QoS degrees in a cellular mobile radio system. The performance achieved by a wireless network employing these schemes is evaluated in terms of call blocking probability, in a multirate application scenario featuring heterogeneous traffic. Some useful design criteria to optimize the management of the scarse radio resources are also furnished: the ultimate goal is to provide radio users with high speed connections, suitable for a basic set of audio and video applications.

2000 - EVOLUZIONE DEI SISTEMI DI COMUNICAZIONE RADIOMOBILE - DALLA FONIA ALLE APPLICAZIONI MULTIMEDIALI [Relazione in Atti di Convegno]
Immovilli, Gianni
abstract

Dopo la definizione dei principali servizi radiomobili, viene presentata una breve sintesi storica della loro introduzione, certamente non esaustiva ma sufficiente a rendere manifesto il notevole successo che essi hanno riscontrato nella società e non solo in quella dell'informazione. Sono poi presentate le caratteristiche essenziali dei sistemi di prima, seconda e terza generazione. Da ultimo, un cenno sulle più importanti problematiche di ricerca ancora aperte chiude la trattazione.

1999 - Performance Analysis of Channel Allocation Schemes for Wireless Communications [Relazione in Atti di Convegno]
Casoni, Maurizio; M., Garuti; Immovilli, Gianni; Merani, Maria Luisa
abstract

This paper evaluates the performance of different networkinfrastructures for the support of multimedia services in a cellularmobile radio system. The performance of twodifferent channel allocation policies in terms of call blocking,outage probability and throughput are investigated for differentclasses of service that system users may require.A specific type of interference adaptive dynamic channel allocationscheme is here proposed and evaluated as possible solution foroptimizing the management of the scarce radio resources. The goal isto provide users with high speed connections, suitable for a basic setof audio and video applications.

1997 - A Simplified Approach to the Performance Evaluation of FDMA/CDMA Systems [Articolo su rivista]
Merani, Maria Luisa; Shahin, M. K.; Immovilli, Gianni
abstract

This work shows it is possible to apply for the performance evaluation of FDMA-CDMA cellular mobile systems a simple analytical approximated method, previously successfully proposed by two of the authors with reference to FDMA-TDMA systems. The distinctive feature of the methodology we describe is that it allows for an immediate determination of both the indexes traditionally employed to define system performance, i.e., average bit error probability and outage probability at a very low computational cost. The hypothesis required to apply the proposed approximation is that the examined spread spectrum system be characterized by a bandwidth occupancy lower than the coherence bandwidth of the transmission channel. This could be the case of a wireless DS-CDMA system envisioned to provide voice service and exploiting a processing gain of the order of a hundred. We apply our methodology to determine the performance improvements introduced increasing the protection of the transmitted information through error correcting codes and interleaving, in different operating conditions as regards the functioning of the power control loops. A comparison is also satisfyingly carried out with some other approximated analytical methods found in literature. We strongly point out that the corresponding results are achieved at a much more modest computational cost than in traditional approaches.

1996 - Design Trade-Offs in a DS-CDMA Wireless LAN with Different Priority Traffic Streams [Relazione in Atti di Convegno]
Immovilli, Gianni; Merani, Maria Luisa; M. K., Shahin
abstract

In this paper we haved faced the issue of tying the transmission design of a wireless CDMA LAN, envisioned to serve two classes of users with different priority requirements, to traffic constraints. The performance indexes we have considered to define the transmission quality experienced by network users are the average bit error probability and the outage probability.The behavior of both merit figures as a function of the coefficient of utilization of the queueing scheme modeling the system strongly evidences the trade-off between good transmission performance/high utilization of the available network resources.

1996 - La formazione degli ingegneri delle telecomunicazioni [Articolo su rivista]
Immovilli, Gianni
abstract

Il 20 Maggio 1989 e il 19 novembre 1990 sono due date importanti per le facoltà di ingegneria e per l'università tutta: dopo circa trent'anni si sono introdotte modificazioni all'ordinamento didattico universitario relativamente ai corsi di laurea della facoltà di ingegneria; immediatamente dopo si è introdotta la riforma degli ordinamenti didattici universitari. Le premesse che hanno influenzato tali disposizioni legislative, gli sviluppi successivi, la situazione attuale e le possibili evoluzioni rappresentano l'oggetto di questo articolo, con riferimento all'area culturale dell'Ingegneria delle Telecomunicazioni.

1996 - PRIORITY TRAFFIC IN WIRELESS PCS SYSTEMS: TRANSMISSION AND TRAFFIC PARAMETERS TRADE-OFF, [Relazione in Atti di Convegno]
Immovilli, Gianni; Merani, Maria Luisa
abstract

We have investigated a possible technique for efficiently handling the reverse link (mobile-to-base) traffic inside a cell of a wireless PCS system, assigning different priority classes to new calls and hand-offs. For the corresponding queueing scheme we have determined those traffic quantities which more directly interact with the design of the transmission system. Further, we have targeted the issue of tying the engineering of both CDMA and TDMA systems to traffic constraints. To this regard we have quantitatively demonstrated how deeply and differently the traffic parameters of the examined queueing scheme influence the capacity determination for these two systems

1995 - COMUNICAZIONI NUMERICHE NELLE RETI RADIOMOBILI [Software]
Immovilli, Gianni
abstract

Il Progetto si svolge nell’ambito dei progetti di ricerca di interesse nazionale ed è stato finanziato dal MURST nel 1989 per una durata quinquennale. Le sedi universitarie proponenti sono quelle qui indicate: Università di Bologna, Firenze, Padova, Palermo, Parma, Pisa, Politecnico di Torino. Il coordinatore centrale è il Prof. Gianni Immovilli dell’Università di Bologna.Nell’anno finanziario 1991 l’unità operativa di Firenze è stata sostituita da quella di Pavia, che ha continuato poi a collaborare fino alla fine del progetto. Nell’anno finanziario 1992 è avvenuto il rientro dell’unità operativa di Firenze e nell’ultimo anno del progetto,1993, ha partecipato alle ricerche anche l’unità operativa di L’Aquila.I temi di ricerca affrontati nel quinquennio 1989-1993 sono stati:Modello del canale, Pianificazione della rete e attribuzione delle risorse, Metodi di modulazione e codifica, Reti locali radiomobili a pacchetto, Problemi realizzativi, Problemi di localizzazione del mezzo mobile. Nel quinquennio sono state complessivamente assegnate al progetto Lit. 664.000.000 per spese di funzionamento e Lit. 256.000.000 per materiale inventariabile.A fronte di questo finanziamento, i lavori scientifici prodotti sono stati 140, considerando soltanto le pubblicazioni su riviste scientifiche internazionali e le comunicazioni a congressi internazionali. L’attività di formazione connessa ha riguardato l’assegnazione di un notevole numero di tesi di dottorato di ricerca e di tesi di laurea.Lo stato di avanzamento delle ricerche e la conclusione del programma previsto sono stati presentati durante alcune riunioni del GTTI (Gruppo Nazionale di Ricerca sulle Telecomunicazioni e la Teoria dell’Informazione) e precisamente il 25 settembre 1991 a Palermo, il 7 ottobre 1992 ad Assisi e il 20 settembre 1994 a Taormina.Le conclusioni e i risultati del Progetto di Ricerca sono stati inviati al MURST anche mediante la pubblicazione in intestazione, edita nel settembre 1995 dalle Officine Grafiche TECNOPRINT S.N.C. di BOLOGNA.

1995 - NETWORK AND SINGLE USER PERFORMANCE EVALUATION OF A MOBILE DATA SYSTEM OVER FLAT FADING TRANSMISSION CHANNELS [Articolo su rivista]
Castoldi, P.; Immovilli, Gianni; Merani, Maria Luisa
abstract

In this paper the constrasting effects of transmission impairments and capture on both the network and single user performance of a slotted Aloha system are investigated in a mobile radio environment, accounting for frequency non-selective random propagation phenomena, and employing the packet error probability in order to define packet losses and capture. With this study we demonstrate that it is possible to generalize in a real propagation context a method previously proposed in literature for evaluating the network behavior in terms of steady-state throughput, backlog and stability in conventional transmission conditions, i.e., when all the transmission channels were error free and the collisions caused the loss of all the packets involved.

1994 - OUTAGE PROBABILITY IN FDMA/TDMA MOBILE COMMUNICATION NETWORKS [Articolo su rivista]
C., Caini; Immovilli, Gianni; Merani, Maria Luisa
abstract

One of the most crucial problems to solve in the field of mobile communication networks is the evaluation for a generic link of the network of the outage probability due to the random characteristic of the transmission system, essentially determined by anomalous propagation conditions, cochannel interference and user mobility. The exact analytical solution to this problem is very burdensome, regardless to the system implementation technique considered. In this paper the effects of cochannel interference, nonselective fading and user mobility in FDMA/TDMA mobile radio networks are investigated, and an extremely simple approximated methodology is presented for the analytical evaluation of the outage probability and of the frequency reuse distance. It is worth noting that the proposed method allows to consider a general statistical description for the nonselective propagation media of the radio network. Here we successfully apply it the path loss, fading and shadowing scenario which are typical of cellular and microcellular structures.

1992 - A New Methodology for the Evaluation of Outage Probability in Cellular Systems [Relazione in Atti di Convegno]
Immovilli, Gianni; Merani, Maria Luisa
abstract

The effects od cochannel interference in cellular mobile radio networks are investigated, in order to highlight how to develop the analytical evaluation of the corresponding outage ptobability – and consequently of the frequency reuse distance – in extremely simplified manner. The methodology presented is in particolar applied when Rayleigh fading, lognormal shadowing and path losses larger than in free space are considered.It is however worth noting that this metodology can also be applied to other fading and shadowing scenarios, like microcells or satellite mobile communications, because it allows the consideration of general statistical conditions for the propagation media.

1992 - OUTAGE PROBABILITY FOR CELLULAR MOBILE RADIO SYSTEMS: SIMPLIFIED ANALYTICAL EVALUATION AND SIMULATION RESULTS [Articolo su rivista]
C., Caini; Immovilli, Gianni; Merani, Maria Luisa
abstract

A simulation program has been carried out to further check the simplified method proposed by Immovilli and Merani for the analytical evaluation of outage probability in cellular mobile radio systems, due to cochannel interference and random propagation phenomena, nonselective in type. The results of the two different procedures show an excellent agreement.

1991 - Effect of the Transmission Impairments on the Peformance of Packet Radio Network [Articolo su rivista]
Immovilli, Gianni; Merani, Maria Luisa
abstract

Packet radio has recently gained great interest in the wider context of mobile communications. In this scenario, the signal worsening due to real transmission conditions (linear and non linear distorsion, fading, interferences, noise) deeply affect the network performance. It is then necessary to verfy whether it is feasible, and if so, how to dimension the transmission system supporting the network itself, in order to respect a fixed quality condition.In this work we suggest the introduction of a quality criterion which seems particularly suitable to set up a relationship between transmission and network parameters, and therefore to solve the problem previously submitted. We determine this relationship with reference to a star topology network, where the slotted Aloha protocolo is employed in cojunction with a narrow band modulation scheme; independent, non-selective and slowly varying fading conditions on every link of the network are also assumed. The treatment developed is then applied to a significant example of packet radio network, and many numerical results are reported.

1991 - Outage probability in packet radio networks due to cochannel interferences and Rayleigh fading [Relazione in Atti di Convegno]
Immovilli, Gianni; Merani, Maria Luisa
abstract

The behavior of a packet radio network which makes use of the slotted Aloha protocol is investigated, focusing on the effects of the transmission impairments on its performance. A narrowband modulation scheme has been considered. Independent Rayleigh fading conditions and cochannel interferences on every link of the network have been accounted for. The methodology highlights the simplifications that can be introduced in evaluating the interference effects. The numerical results reported show that a good single user performance is by far a more critical target than a good network performance

1991 - Simplified Evaluation of Outage Probability for Cellular Mobile Radio Systems [Articolo su rivista]
Immovilli, Gianni; Merani, Maria Luisa
abstract

The effects of cochannel interference in a mobile radio network are investigated, to highlight a method with which to analytically evaluate the corresponding outage probability in an extremely simplified manner. The general methodology presented can in particolar be applied when Rayleigh fading, log-normal shadowing and path losses larger than those in free space are considered.

1989 - Combined Effects of Transmitter Nonlinearity and Multipath Fading on the Availability of CPFSK Systems [Articolo su rivista]
G., Corazza; Immovilli, Gianni; Merani, Maria Luisa
abstract

A study is presented whose aim is to evaluate the behaviour of CPFSK systems with modulation pulse shaping and limiter-discriminator detection in the presence of multipath fading and nonlinearity in the transmitter. This work, which completes a previous one where nonlinearities are absent, confirms the possibility to effectively control the lower bound of the system outage probability Pout (i.e. the asymptotic value of Pout when the transmitted power tends to infinity) by varying the maximum frequency deviation of the signal

1988 - Adjacent Channel and Cochannel Interferences in CPFSK Systems with Nonlinear Transmitters and Limiter-Discriminator Detection [Articolo su rivista]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

The performance of continuous-phase FSK (frequency-shift keying) systems with rectangular modulation pulse shaping and limiter-discriminator detection is analytically evaluated in the presence of transmission nonlinearities as well as adjacent channel and cochannel interference. Consideration of modulation pulses with length τ, shorter than symbol time, T, is investigated. The algorithm developed to evaluate bit-error probability shows that the choice τ/T<1 is more convenient than the conventional one, τ/T=1, and even moreso in the presence of adjacent channel interference. Moreover, for τ/T=0.5, numerical results are reported that describe system performance under different working conditions (type and bandwidth of the filters, frequency deviations of the signals, channel spacing,...) and can be used to develop design criteria

1988 - Effects of the Interferences in Cellular Digital Mobile Radio Systems Using Full Response CPM with Limiter-Discriminator Detection [Articolo su rivista]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

Spectral characteristics of signals and bit error probability of transmission systems are analytically evaluated with reference to full response CPFSK systems with rectangular modulation pulse shaping and limiter-discriminator detection, applied on a typical cellular radio network. The analysis is carried out in the case of four-level signals, in the presence of transmission nonlinearities and cochannel and adjacent channel interferences. The results obtained show that the spectral compactness cannot be assumed as a good index of a bandwidth-efficient modulation system. Moreover, in some significant cases, which differ because of vehicular locations, channel spacing and modulation parameters, they indicate the signal-to-noise ratios necessary at the receiver input to guarantee a fixed bit error probability, in both the base-to-mobile and mobile-to-base transmissions.

1986 - Nonlinear Power Amplifier Effects on the Performance of CPFSK Systems [Articolo su rivista]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

CPFSK signals with rectangular modulation pulse shaping are tested here in a transmission system including a nonlinear high-power amplifier (HPA), working at saturation. The effects of filtering followed by amplifying on power spectrum spreading of the transmitted signal and on error probability are determined. The results obtained show that, unlike other modulation systems (PSK, offset PSK, MSK), in the CPFSK case the power spectrum at HPA output can be efficiently controlled by means of filtering at the intermediate frequency (IF), if the duty-cycle τ/T of modulation pulses and the maximum angular frequency deviation ωd are suitably chosen. Moreover, by considering the transmission of a single radio frequency (RF) channel, they show that the nonlinear behavior of the transmitter has very little influence on error probability for all the ωd values of practical interest, other conditions being fixed.

1985 - On the Availability of Multilevel CPFSK Systems with Modulation Pulse Shaping During Multipath Propagation [Articolo su rivista]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

The behavior of CPFSK systems with modulation pulse shaping and limiter-discriminator detection is tested in the presence of multipath fading.With the aim of determining the eye-closure domain, a theoretical analysis is presented for a generic number of modulation levels. It is shown that, by suitably varying the maximum angular frequency deviation ωd, control of outage probabilty Pout is possible. Moreover, the choice of duty-cycle in the modulation pulse τ/T < 1 leads to a lower value of Pout with respect to the conventional case τ/T = 1, if we fix, as happens in practice, an upper bound in the transmitted power. This promising characteristic deeply differentiates the CPFSK from the PSK, DCPSK, and QAM systems: CPFSK systems, with a fixed number of modulation levels, allow us to obtain decreasing values of Pout at the cost of increasing transmission power by suitably varying the set of signal parameters, even in the absence of diversity techniques and/or adaptive equalization.

1984 - Effects of nonlinear power amplifiers on the spectrum of CPFSK signals [Relazione in Atti di Convegno]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

The nonlinear behaviour of high-power amplifiers (HPAs) constitutes a serious, conditioning performance impairment in digital radio, whenever great spectrum efficiency is required such as in modern satellite communications, terrestrial radio links or radio mobile systems. In fact, the effects of filtering followed by amplifying in transmission give rise to power spectrum spreading on account of nonlinear distortion, and consequently to an increase of adjacent channel interference. When the HPA must work at saturation in order to give out its maximum power, angle modulation systems, with constant envelope, seem to be more attractive than amplitude - and phase - modulated ones, which require linearization [1]. In this paper, the CPFSK signal with modulation pulses assumed to be rectangular, with a length ¿ less than the symbol time, T, is tested in the above-mentioned conditions. The power spectral density in the various points of the transmitter is displayed for fixed HPA characteristics (AM/AM and AM/PM conversions); its behaviour is analyzed for varying filter bandwidths and modulation parameters (duty-cycle of the modulation pulses, ¿/T, and maximum angular frequency deviation, ¿d). The results obtained, experimentally checked, show that, unlike other angle modulation systems (PSK, offset PSK, MSK), in the CPFSK case the HPA output has a power spectrum which can be efficiently controlled by means of filtering at the intermediate frequency. For this purpose, only a suitable choiche of ¿/T and ¿d is required.

1983 - A promising application of CPFSK systems with modulation pulse shaping in digital radio affected by multipath fading [Articolo su rivista]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

The behaviour of CPFSK systems, with rectangular modulation pulses shaped by a duty cycle less or equal to 1, is tested in the presence of multipath fading. It is shown that, with suitable exploitation of the intrinsic freedom degrees of the transmitted signal, it is always possible to reduce the outage probability if a sufficient transmitted power is available, even in the absence of diversity techniques.

1983 - On the availability of four-level CPFSK systems with modulation pulse shaping during multipath propagation [Relazione in Atti di Convegno]
O., Andrisano; G., Corazza; Immovilli, Gianni
abstract

This paper may be included in the field of research which has been developing in the last few years to analyse the availability of digital modulation systems during multipath propagation. The continuous-phase FSK systems (CPFSK) with rectangular modulation pulses shaped by a duty-cycle, τ/T, admitting of any value between 0 and 1 is considered. This system has already been studied in normal propagation conditions where a significant improvement in performance has been enphasized with respect to conventional CPFSK systems (τ/T=1 ). Now its behaviour during multipath fading is tested.We show that, with suitable exploitation of the degrees of freedom available (as an example duty-cycle of modulation pulses and maximum frequency deviation), it is always possible to obtain, as far as outage probability conditioned to multipath fading is concerned, decreasing values for increasing transmitted power, even in absence of diversity techniques.The numerical results reported with reference to a four-level CPFSK system show that, by means of suitable choice of system parameters, an improvement of more than one decade can be obtained in the outage probability, with respect to the 4-PSK system, in the range of transmitting power of practical interest. Consequently, the problem of using diversity techniques in the design of CPFSK radio links is considerably simplified.

1983 - Sistemi di modulazione per trasmissioni numeriche [Monografia/Trattato scientifico]
L., Calandrino; Immovilli, Gianni
abstract

La formazione dei presupposti teorici necessari per orientare le scelte sistemistiche e circuitali e l'introduzione di concetti e metodi di analisi adatti ad affrontare il complesso dei temi di ricerca, connessi all'affermazione delle tecniche numeriche nelle telecomunicazioni, avvenuta prevalentemente nel decennio 1965-1975, costituiscono gli obiettivi fondamentali della trattazione, consolidata dal continuo confronto con i risultati sperimentali.

1981 - Performance Analysis of Quaternary CP-FSK Systems with Modulation Pulse Shaping and Limiter-Discriminator Detection [Articolo su rivista]
G., Corazza; G., Crippa; Immovilli, Gianni
abstract

The multilevel CP-FSK transmission systems with limiter-discriminator detection in which the modulation pulses are rectangular with a length τ admitting of any value not higher than symbol time T, are here considered. First, a procedure is presented in order to determine the optimum values of the modulation levels and of the decision thresholds, which are strictly correlated with τ. Next, the optimization of four-level CP-FSK systems with reference to different types of transmission channels is carried out by determining for each the value of τ, the modulation and threshold levels and the equivalent noise bandwidth, which guarantee the error probability Pe = 10-6 with the minimum transmitting power. For comparison, the same evaluation is made for the conventional system, for which τ = T and the distribution of the modulation and threshold levels is uniform. The results obtained, experimentally verified, show that: -the optimum choice of the modulation and thresholds levels is important even if τ = T;-the optimum system performance takes place, in all the considered cases, for non-critical value τ = 0.2 T, for which the improvement compared to the conventional case is always very great.The experiments, carried out at the Telettra laboratories, have also shown that the considered modulation method allows the use of highly non linear power amplifiers in the transmitter, without any practical effect on system performance.

1979 - On the effect of a type of modulation pulse shaping in FSK transmission systems with limiter-discriminator detection [Articolo su rivista]
G., Corazza; Immovilli, Gianni
abstract

In this work we study a binary or multilevel continuous-phase FSK system with limiter-discriminator detection, in which the modulation pulses are rectangular with length τ admitting of any value not higher than the symbol time T. As an application example of the general treatment, we report numerical results in the binary case which, according to expectations, show the considerable τ influence on system performance, other conditions being fixed. In particolar, in the best operation condition of the system for Pe = 10-6 that takes place for the non-critical value τ = 0.6T, the transmission canne frequency band and the transmitting power are both smaller than those corresponding to the analogous best condition with the constraint τ = T. Besides, the transmitting power advantages which derive from the opportune choice of τ increase little by little with channel frequency band reduction. With reference to multilevel systems, we have then point out some research development lines which we think interesting.

1977 - On the Performance of the Injection-Locked Oscillator Frequency Divider [Articolo su rivista]
D., Cattabiani; Immovilli, Gianni
abstract

The performance of the injection-locked oscillator frequency divider is determined and a comparison with the phase-locked loop and Miller frequency divider is set up.The results show that it is suitable for applications to wideband FM signals.

1976 - On the Effect of the Phase Comparator Delay in a Mutual Synchronization System [Articolo su rivista]
Immovilli, Gianni; L., Izzo
abstract

Referring to the mutual sincronization system proposed in [1], its performance in the presence of a delay due to the phase comparators is here esamined. It is shown that the delay may be the cause of instability in system operation and so a sufficient condition for stability is determined.

1975 - A New Mutual Synchronization System of Geographically-Separated Oscillators [Articolo su rivista]
Immovilli, Gianni
abstract

Having in mind applications to an integrated digital network, the operation of the more frequently considered mutual synchronization system of N geographically-separated oscillators is here esamined, having recourse to a schematization so general as to guarantee in practice agreement between the mathematical model and the physical system. The results obtained bring out its poor reliability thus pointing to the convenience of proposing other systems. Therefore, as a solution, a new mutual synchronization system is suggested whose greater reliability is the consequence of better use of the information available in each control center.

1974 - Some Researches on PSK Relay Systems [Articolo su rivista]
L., Calandrino; G., Crippa; Immovilli, Gianni
abstract

In the last few years the authors of this paper have focused their attention on PSK radio relay systems with the purpose of giving design criteria for them. On the results achieved has been based the design of a 13 GHz PCM system. The essentials of these investigation are here reported and, as an application example, a contribution to the optimization of PSK radio links, is given.

1973 - Analysis of the Miller Frequency Divider by two in View of Applications to wideband FM Signals [Articolo su rivista]
Immovilli, Gianni; G., Mantovani
abstract

The realization of solid state FM transmitters, which make use of microwave frequency dividers, has been recently proposed. In order to evaluate their performance, the Miller frequency divider by two is here analysed. The problem of its operation stability is studied and its response to wideband FM signals also in the presence of interferences on the useful input signal, is determined. Finally, the results of the most significant measurements, performed on a frequency diveder of the examined type, are reported. They show satisfactory agreement with the developed theory.

1971 - Alcune considerazioni sull'ottimizzazione economica di un collegamento ad onde millimetriche in guida d'onda a sezione circolare [Monografia/Trattato scientifico]
L., Calandrino; E., De Castro; Immovilli, Gianni
abstract

Viene impostato il calcolo di ottimizzazione economica di un collegamento ad onde millimetriche in guida d'onda circolare, considerando in modo del tutto generale i termini del problema, sia per quanto riguarda la scelta del sistema di modulazione e dei relativi apparati, sia per quanto attiene al tipo di guida d'onda.L'origine dello studio risale alla decisione di effettuare un collegamento sperimentale presso il Centro Onde Millimetriche (C.O.M.) di Pontecchio Marconi; il suo obiettivo è quello di dare un contributo di orientamento alla impostazione del complesso di ricerche di carattere sistemistico, circuitistico e di propagazione, necessarie per il dimensionamento del collegamento stesso.

1971 - Intersymbol, Interchannel and Cochannel Interferences in Binary and Quaternary PSK Systems [Articolo su rivista]
L., Calandrino; G., Corazza; G., Crippa; Immovilli, Gianni
abstract

In order to evaluate the performance of binary and quaternary PSK systems in the presence of intersymbol, interchannel and cochannel interferences and fadings, a procedure is illustrated and formulas are obtained.Numerical results of particular interest are given, pointing out the most suitable methods for reducing the interchannel interference effects; in quaternary systems these effects, together with those of cochannel interference, turn out to be slightly more notable than in binary systems.

1971 - The Effect of Multiple Echoes on Error Rate in Guided Millimeter-Wave PSK Systems [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

With reference to binary and quaternary, guide millimeter-wave PSK systems, the characteristics of the disturbance represented by multiple echoes, due to both mismatch reflections and mode conversions, are analysed. With regards to a link formed by many cascaded regeneration sections, realized with the same construction and installation techniques, it is shown, under rather general hypothesis, that the sum of both the thermal noise and the echoes at the output of the receiver filter, is equivalent to an additive gaussian disturbance. This allows the immediate extension to the aforesaid transmission systems of known formulae, which give the performance of the analogous echoless systems.

1970 - Error Rates in FSK Systems [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

A multilevel FSK system employing a limiter-discriminator followed by a low-pass filter as a demodulator, is considered; formulas giving, in rather general conditions, the average symbol error probability as a function of the values of the parameters characterizing the system, are obtained. The results deducible from these formulas are compared with those from different analyses of other Authors [3], [4].

1969 - Indagine preliminare sulla modulazione FSK [Monografia/Trattato scientifico]
L., Calandrino; Immovilli, Gianni
abstract

Il presente lavoro si inserisce nell'ambito di una indagine generale sui diversi sistemi di modulazione digitale di una portante radio, avente lo scopo di individuare quello più idoneo per un collegamento in guida d'onda circolare, operante nel campo delle onde millimetriche, che si vuole realizzare presso il C.O.M. (Centro Onde Millimetriche) di Pontecchio Marconi. In questa prima nota viene considrato il sistema FSK a due livelli e di esso vengono determinate le caratteristiche che deve avere il sistema stesso perchè risulti uguale a un valore fissato la probabilità di errore, conseguente al rumore termico che inevitabilmente si somma all'oscillazione modulata, in presenza, anche, di distorsioni lineari introdotte dal canale di trasmissione. I valori dei diversi parametri in gioco (potenza in trasmissione, larghezza di banda, ecc. ), che così si ottengono, costituiscono elementi fondamentali di confronto del sistema di modulazione in esame con altri, soprattutto con quelli di fase, coerenti e differenziali, binari e quaternari, e con quelli FSK a più di due livelli. Un ulteriore elemento da considerare è dato dalla complessità e sicurezza di funzionamento dei circuiti necessari per effettuare le operazioni di mo-demodulazione; tali circuiti, dato il notevole sviluppo che ha avuto la tecnica della modulazione di frequenza, sono generalmente, oltre che semplici, di sicuro affidamento nel caso dei sistemi FSK.

1969 - Indagine preliminare sulle modulazioni PSK e DCPSK [Monografia/Trattato scientifico]
L., Calandrino; Immovilli, Gianni
abstract

Lo studio del sistema di modulazione di fase (PM) per la trasmissione di segnali digitali si inserisce nell'ambito di una ricerca, il cui scopo è quello di pervenire alla scelta del procedimento di modulazione più opportuno per un collegamento in guida d'onda circolare, operante nel campo delle onde millimetriche, da realizzare presso il C.O.M. (Centro Onde Millimetriche) di Pontecchio Marconi. In questo lavoro abbiamo considerato i sistemi di modulazione digitale di fase coerente (PSK) e differenziale (DCPSK) sia a due, sia a quattro livelli. Per ciascuno di tali sistemi, dopo avere analizzato le proprietà spettrali, ci siamo interessati dei problemi riguardanti la loro generazione e demodulazione. Successivamente abbiamo proceduto alla determinazione della probabilità di errore nel riconoscimento dei dati trasmessi, che nasce per effetto di un rumore termico che si somma all'oscillazione modulata, mettendo anche in conto l'interferenza intersimbolo, conseguente ad una distorsione lineare introdotta dal canale di trasmissione, e talune imperfezioni del ricevitore. Abbiamo inoltre esaminato il caso in cui al segnale utile si sommino segnali interferenti, il che si verifica sia per effetto di canali radio adiacenti, sia per effetto di echi dovuti a successive conversioni e riconversioni di modo nonchè a riflessioni per disadattamento nella trasmissione in guida d'onda circolare.I risultati via via esposti nel presente lavoro, unitamente alla considerazione dei problemi riguardanti la complessità del modem, forniscono utili criteri di valutazione sia per il confronto fra i sistemi PSK e DCPSK binari e quaternari, sia per il confronto con altri sistemi di modulazione, ad esempio quelli FSK binari e a più livelli.

1969 - Intersymbol Interference in Binary and Quaternary PSK and DCPSK Systems - Part I [Articolo su rivista]
L., Calandrino; G., Crippa; Immovilli, Gianni
abstract

The expressions of error probability are determined for binary and quaternary, coherent and differentally coherent phase-shift-keyed systems in presence of intersymbol interference due to the linear distortion produced by a real transmission channel. Such a distortion gives rise to amplitude and phase deviations, which must be determined, with fixed channel characteristics, for each distinct pulse pattern. This determination and the consequent numerical computation of the average error rate in some cases of practical interest will be reported in Part II.

1969 - Intersymbol Interference in Binary and Quaternary PSK and DCPSK Systems - Part II [Articolo su rivista]
L., Calandrino; G., Crippa; Immovilli, Gianni
abstract

The expressions obtained in Part I, giving in general conditions the error rate in binary and quaternary, coherent and differentially coherent phase-shift-keyed systems due to thermal noise in presence of intersymbol interference, are applied to the case of a real channel with a gaussian amplitude characteristic. The effects of a bandwidth limitation and of a nonconstant group delay in the four modulation systems above are evaluated and the results are reported in diagrams.

1969 - Realizzazione e collaudo di un demodulatore di frequenza a correlazione ampiezza-fase [Monografia/Trattato scientifico]
L., Calandrino; E., De Castro; Immovilli, Gianni
abstract

Si riferisce sul progetto e sulla realizzazione di un demodulatore di frequenza a correlazione ampiezza-fase operante alla frequenza intermedia di 70MHz, con banda del filtro IF di 12 MHz e con un carico di 60 canali telefonici. Si riportano poi alcuni risultati sperimentali che confermano la validità della teoria svolta in precedenti lavori e mettono in evidenza la necessità di dedicare particolare cura alla realizzazione del limitatore che precede il discriminatore.

1968 - Criteri di progetto di un demodulatore di frequenza a correlazione ampiezza-fase [Monografia/Trattato scientifico]
L., Calandrino; E., De Castro; Immovilli, Gianni
abstract

Viene proposta una soluzione circuitale per il demodulatore di frequenza a correlazione ampiezza-fase e ne vengono determinate le condizioni di funzionamento ottimale. I risultati di questa ottimizzazione sono particolarmente favorevoli, poichè mostrano, con riferimento ad un caso tipico, che il circuito proposto è in grado di dare un miglioramento della soglia di ricezione di circa 4 dB rispetto al demodulatore FM convenzionale.Vengono inoltre riportati i risultati delle misure effettuate sul circuito che realizza uno dei principali blocchi funzionali del demodulatore stesso

1968 - On the Performance of Amplitude-Phase Correlation FM Demodulators [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

The optimum performance is determined for amplitude-phase correlation FM demodulators which exploit a particular aspect of the statistical dependence between the frequency and amplitude deviations produced by a white noise perturbing an FM wave. Besides, a report is given on the numerical results obtained with reference to typical working conditions.

1967 - Coincidence of Pulses in Amplitude and Frequency Deviations Produced by a Random Noise Perturbing an FM wave. An Amplitude-Phase Correlation FM Demodulator [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

One of the ways in which statistical dependence is manifested between frequency and amplitude deviations produced by a white noise perturbing an FM wave, is examined: it is shown that the noise pulses present on instantaneous frequency have a correspondence, probability near 1, with analogous negative pulses on the amplitude deviation. A detailed study on this fact is reported.An amplitude-phase correlation FM demodulator is proposed which, exploiting the above phenomenon, largely eliminates the effect of noise pulses on output, though giving rise to some non-linear distortion of the demodulated signal. This distortion can be kept within modest values as soon as the modulation index is sufficiently above 1.

1967 - Cross-Correlation and Statistical Dependence between Envelope and Frequency Deviation of a Sine Wave plus Random Noise [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

Cross-correlation and statistical dependence between the envelope V(t) and angular frequency deviation Φ’(t) of a sine wave plus random noise are discussed with a view to possible application to frequency demodulation. In particular it is shown that the cross-correlation function RΦ’V(τ) vanishes because the joint probability density p2(Φ1’, V2; τ) turns out to be an even function of Φ1’. Besides, a short discussion on some features of the phase deviation allows not only to show that V(t) and Φ’(t), while uncorrelated, are not independent, but also, by a different method, to prove once more the vanishing of RΦ’V(τ).

1967 - Recenti ricerche su una categoria di demodulatori di frequenza a correlazione ampiezza fase [Relazione in Atti di Convegno]
L., Calandrino; S., Graffi; Immovilli, Gianni
abstract

Al demodulatore classico ideale di frequenza si può imputare una perdita di informazione in quanto non tiene alcun conto dell'ampiezza istantanea, la quale è statisticamente dipendente dalla deviazione di fase prodotta dal rumore. Di qui l'idea di studiare una categoria di demodulatori FM, costituiti da due demodulatori di tipo classico, uno di frequenza ed uno di ampiezza, e da un ulteriore circuito capace di effettuare un opportuno "confronto" fra le deviazioni di frequenza e di ampiezza prodotte dal rumore, allo scopo di pervenire ad un miglior rapporto segnale/rumore in uscita.La ricerca ha dato origine a risultati di qualche interesse, che talora si inquadrano in un contesto più generale e che, in parte, sono già stati oggetto di pubblicazioni [6,7]. La presente comunicazione riassume i risultati fino ad oggi ottenuti ed accenna ad alcune prospettive di ulteriori sviluppi.

1966 - Noise power reduction through comparison with another statistically dependent noise [Articolo su rivista]
L., Calandrino; Immovilli, Gianni
abstract

Consider a signal s(t) in presence of an additive noise n(t) and suppose that another noise v(t), statistically dependent on n(t), is available. This paper discusses the problem of the above mentioned statistical dependence in order to reduce the power of the noise n(t). No hypotheses on the signal nature are being made. The use of linear networks is examined in detail and we show how the noise power can be reduced to a lower limit which depends on the cross-correlation function of n(t) and v(t).