This paper analyzes distributed molecular communications with multiple transmitters and multiple receivers randomly placed in a 3D space. Receivers, whose positions are modeled by a homogeneous Poisson point process, are assumed to be passive and spherical. Since they are not dimensionless, their presence affects the statistics of transmitter points, resulting in a Poisson hole process, instead of the Poisson process usually adopted in previous works on multiple transmitters. Moreover, molecules emissions from different transmitters are considered asynchronous, according to a recently proposed stochastic model. Here, the intensity function of the time point processes modeling molecules emissions is given a further meaning; in particular, it is considered as the propensity function of a chemical reaction. The average amount of received molecules per time unit (receiving rate) is evaluated accordingly for each receiver. When the swarm of receivers is considered as an equivalent, single, spatially distributed receiver, the average amount of received molecules per time and volume units (receiving rate density) is introduced and analytically evaluated.

This paper is motivated by the concept that the successful, effective, and sustainable implementation of the smart city paradigm requires a close cooperation among researchers with different, complementary interests and, in most cases, a multidisciplinary approach. It first briefly discusses how such a multidisciplinary methodology, transversal to various disciplines such as architecture, computer science, civil engineering, electrical, electronic and telecommunication engineering, social science and behavioral science, etc., can be successfully employed for the development of suitable modeling tools and real solutions of such sociotechnical systems. Then, the paper presents some pilot projects accomplished by the authors within the framework of some major European Union (EU) and national research programs, also involving the Bologna municipality and some of the key players of the smart city industry. Each project, characterized by different and complementary approaches/modeling tools, is illustrated along with the relevant contextualization and the advancements with respect to the state of the art.

In this paper a hierarchical architecture for content distribution in vehicular network is proposed. A cluster-based organization of vehicles is considered based on the Named Data Networking (NDN) model where a subset of reference vehicles named barycenters plays the NDN router role. Complementary functionalities of both short-range and cellular communications are used, the former for vehicle-to-vehicle (V2V), the latter for vehicle-to-infrastructure (V2I) communications, to off-load the fixed NDN infrastructure, and increase the chance of finding a content in the VANET, while limiting the number of broadcasted information. The proposed model is described and analytical evaluations are presented to show the potential of the approach.

We introduce a class of structured (protograph-based) doubly generalized low-density parity-check (DGLDPC) codes. The proposed class leads to quasi-cyclic codes for which efficient encoder and decoder implementations are possible. In particular, we illustrate that on the additive white Gaussian noise (AWGN) channel, the introduced structured DGLDPC codes do not lose in performance with respect to unstructured DGLDPC codes. Furthermore, a sufficient condition on the code graph is derived, which allows unveiling the quasi-cyclic nature of the designed codes.

In this paper we provide the outcomes of a measurement campaign aimed at characterizing the UMTS femtocell propagation in an indoor scenario. The accuracy of a commonly adopted estimator of the signal-to-noise ratio is discussed, then the minimum measurement interval needed to derive an accurate characterization of the average received power is discussed. Finally we compare the measurement outcomes with those predicted using ray tracing tools and analytical models, showing the achievable accuracy levels.

The architecture of a digital On-Channel Repeater (OCR) for DVB-T/H signals is described in this paper. The presence of a coupling channel between the transmitting and the receiving antennas gives origin to one or more echoes, having detrimental effects on the quality of the repeated signal and critically affecting the overall system stability. A low-complexity echo canceller unit is then proposed, performing a coupling channel estimation based on the local transmission of low-power training signals. In particular, in this paper we focus on the stability issues which arise due to the non perfect echo cancellation. An upper bound on the probability of instability of the system is analytically found, providing useful guidelines for conservative OCR design, and some performance figures concerning different propagation scenarios are provided.

Intelligent transportation systems (ITS) make use of wireless communication technologies to provide traffic efficiency and road safety without altering the existing road infrastructure. To really impact on traffic management, ITS should act in real-time, requiring updated traffic information; hence, the collection of small amounts of information frequently transmitted from a high number of vehicles is needed. Cellular systems represent the most suitable technological solution to achieve this service, since they do not require any further installation of network infrastructures. However, they were designed for different applications: voice, web browsing or e-mailing. In this paper we aim at discussing the feasibility of frequent acquisition of small amount of data from vehicles through the universal mobile telecommunication system (UMTS), and at investigating its impact on the services already provided by the network. Numerical results are obtained by means of simulations, paying particular attention to realistic scenarios, both in terms of wireless systems and users mobility.

Efficient mobility management is an issue of vast economic importance for its consequences on urban and suburban mobility. In this context, telecommunications are gaining a key role, allowing to increase people safety, traffic efficiency, and travel comfort. To investigate the telecommunication systems behavior in new infomobility scenarios, advanced simulations tools are needed jointly taking into account realistic road traffic mobility and telecommunication networks protocols in all their aspects. In this paper we discuss the architecture of a complex and complete simulation platform we are developing on the behalf of the Italian project PEGASUS: the choice of traffic simulators, the network simulation and their interface will be presented and described.

IEEE 802.16 standard family enables the convergence of fixed and mobile broadband networks through a common wide area broadband access technology. With reference to the recent IEEE802.16e-2005 amendment, aimed at supporting user mobility, in this paper we propose a scheduling strategy aimed at providing a fair service to best effort users as well as a simple link adaptation strategy to dynamically adapt the physical level behavior to the channel reliability. Numerical results, obtained via simulation, showed the effectiveness of our proposals.

This paper addresses the performance evaluation of multi-carrier code division multiple access systems both at physical and TCP levels. A partial equalization technique improving the performance at physical layer in the presence of interference is investigated and its impact on the performance at upper layer is studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user. Works of this nature enable a deep investigation of the real gain perceived by the user provided by proper signal processing techniques at the physical level.

IEEE802.16e wireless MAN-OFDMA is expected to be a significant step in the evolution of communication technologies for the provision of broadband services to mobile users. Nonetheless, its potential, in terms for instance of transport level throughput, is not clear yet, since it depends on a large number of system parameters and implementation choices. This large amount of degrees of freedom makes also an hard task the choice of the set of system parameters to be adopted in order to get the best from this technology. In order to overcome these limitations, in this paper we provide an analytical framework that can be used to get an insight on IEEE802.16e wireless MAN-OFDMA performance, and, above all, to drive the choices of network operators in terms of system configuration.

This paper addresses the performance evaluation of multi-carrier code division multiple access systems. A partial equalization technique depending on a parameter adapted to different conditions such as the number of sub-carriers, the number of active users and the mean signal-to-noise ratio is evaluated for the down-link. We analytically derive the performance of this system and the value of the equalization parameter that maximizes the performance. The partial equalization technique is shown to have the same complexity of the well known maximal ratio combining, equal gain combining and orthogonality restoring combining techniques, with significative performance improvement. Analytical results are compared with simulations showing a perfect agreement

The work deals with the impact evaluation of an intelligent transportation system (ITS) based on the GPRS (general packet radio service) technology to alert vehicles approaching an accident. The last ten years saw an unexpected increasing of wireless communication technologies, first for circuit switching services, then also for packet switching applications. This kind of technologies can now be used not only for communication issues. Here we show the application of the GPRS wireless technology to ITS in a realistic scenario to promptly alert vehicles approaching difficult and unexpected situations such as accidents and queues. The aim of this work is to show the validity of a GPRS radio system on board in order to provide warning services to vehicles near an imminent crash situation on a highway. The great advantage of the proposed solution is the adoption of the well known and spread GPRS infrastructure to improve safety on roads. Numerical results, obtained by means of a simulation tool implementing realistic traffic models, show the great improvement, in term of safety, derived by the use of an embedded alerting system

The investigation of both link and network level aspects is fundamental when a thorough analysis of mobile radio systems is required. The conventional approach, based on a complete separation between the two levels, adopted in the past for the performance evaluation of second generation systems, is not enough accurate for third generation ones, characterized by the presence of both voice and data services as well as circuit and packet switched applications. Here we describe a methodology on how to interface link and network level tools and finally show an example of application

In this paper the issue of networks interworking is faced with reference to UMTS cellular networks and IEEE 802.11 wireless local area networks. A feasible architectural solution of the integrated network is given and the possibility to serve by means of the WLAN technology also those voice calls that would be blocked by UMTS, in case of resource saturation, is investigated. The performance level provided by the integrated network in a realistic scenario is here assessed considering both IEEE 802.11a and the forthcoming IEEE 802.11e WLAN technologies for possible integration with UMTS

This work deals with the problem of cellular network reconfiguration. In particular, we focus on the development of a very complete simulation tool that allows an accurate performance analysis of realistic mobile radio systems. The results we show in the paper have been achieved by means of an integrated approach taking both the system and link level aspects into account. Since the accuracy of the simulation results depends strongly on the mobility model considered, we propose a methodology to assign a given class of mobility to the cells. Finally, to validate the simulation tool we have compared the results with those obtained in a realistic network The results show that the agreement between simulation and the measured values is very good.

In this paper, the issue of Bluetooth and IEEE802.11b coexistence in a heterogeneous environment is addressed by means of an integrated analytical approach. The methodology proposed carefully takes both physical (i.e., thermal noise, propagation, interference, modulation formats, and coding techniques) and medium access control (frequency hopping, packet structures, traffic loads) aspects into account. This model can be easily implemented when developing network simulators, thus avoiding the need of extensive bit level Monte Carlo simulations at the physical level. The mean packet error probability is evaluated as a function of the relative distance between the two systems for different conditions (e.g., propagation, packet type, traffic loading, etc). In particular, how the presence or absence of line-of-sight propagation significantly affects the coexistence distance is emphasized. Furthermore, for a fixed quality-of-service level we derive the coexistence domain of the two considered systems in terms of relative distance.

In this article the issue of Bluetooth and IEEE802.11b coexistence in a heterogeneous environment is addressed by means of an analytical approach. The methodology proposed carefully takes physical (i.e., thermal noise, propagation, interference, modulation formats and coding techniques) as well as medium access control (frequency hopping, packet structures, traffic loads) aspects into account. This model can be easily implemented when developing system simulators avoiding, thus, the need of extensive bit level Monte-Carlo simulations at the physical level. Furthermore, having preliminarily fixed a quality of service level, namely the target mean PEP, we derive the coexistence domain of the two considered systems in terms of relative distance.

The performance in terms of the mean packet error probability (PEP) in a Rayleigh fading channel with thermal noise is analytically derived for a Bluetooth transmission interfered by IEEE 802.11b. The methodology proposed carefully takes PHY as well MAC aspects into account. Simulations are used to verify methodology assumptions. Moreover, we derive the coexistence domain, in terms of relative distances between the two systems, for a fixed quality of service, i.e., a target mean PEP.

Provides an abstract of articles to be presented in a forthcoming issue.

The performance of a time-division multiple-access mobile radio system adopting slow frequency hopping is analyzed by following an original procedure that allows the evaluation of thermal noise and fast fading (e.g., Rayleigh) effects on block-coded transmission with nonideal interleaving. Starting from this approach, service coverage can be analytically evaluated when the "slow" disturbances affecting the transmission are fixed. The method proposed is able to take several impairments and parameters into account, such as shadowing and discontinuous transmission. The experimental results confirmed the validity of the theoretical approach.

In this letter, a wireless local multipoint distribution system (LMDS) at millimeter waves for the last-mile broad-band distribution to users of interactive services is investigated. The system analyzed employs a coded orthogonal frequency-division multiplexing transmission scheme with frequency-division multiplexing (FDM) and/or time-division multiplexing techniques and adaptive carrier allocation to counteract the effects of the wireless communication channel. The idea of deploying the reverse channel (exploited by the user for interactivity purposes) to provide channel information to the broadcasting transmitter is introduced. System performance is evaluated for an urban microcellular radio system in an actual propagation environment and the choices of the optimum multiplexing technique and carrier allocation algorithm are discussed in the case of ideal feedback. It is found that a pure FDM technique combined with an adaptive carrier allocation algorithm giving priority to users having the largest path loss leads to the best performance.

In a shadowing-free environment, the improvement introduced by slow frequency hopping (SFH) on a TDMA-based mobile radio system can be taken into account by properly re-defining the minimum carrier-to-interference protection ratio. This protection ratio, with SFH, is dependent on the transmission system, channel model, traffic and frequency reuse parameters. The approach is used in order to analytically investigate the up-link capacity of a SFH mobile radio system, by taking into account a complete scenario, i.e. shadowing, fast fading, power control, antenna diversity, discontinuous transmission and forward error correction (FEC) with non-ideal interleaving and sectorization.

In a shadowing-free environment, the improvement introduced by slow frequency-hopping (SFH) on a time-division multiple-access based mobile radio system can be taken into account by redefining the minimum carrier-to-interference ratio. This protection ratio, with SFH, is dependent on the transmission system, channel model, traffic, and frequency reuse parameters. In this paper, the above-mentioned analysis is used in order to investigate the capacity of a SFH mobile radio system, with reference to both the uplink and downlink, by taking into account a complete scenario, i.e., shadowing, fast fading, power control, antenna diversity, discontinuous transmission, and forward error correction with nonideal interleaving and sectorization. Outage probability is evaluated by a completely analytical methodology for the uplink, whereas the downlink requires a semianalytical approach to take users' positions into account. Comparison with a pure simulative approach is used to validate the results.

In this paper a wireless local multipoint distribution system (LMDS) at 30 GHz for the last mile broadband distribution to users of interactive services is investigated. The system we propose users a coded OFDM transmission scheme with FDM and/or TDM multiplexing techniques and adaptive carrier allocation to counteract the effects of the wireless communication channel. An urban microcell in an actual propagation environment is analyzed by means of a ray-tracing tool. Coverage probability is defined and investigated and the choices of the optimum multiplexing technique and carrier allocation algorithm are discussed. It is found that a pure FDM technique with adaptive carrier allocation and priority to users having the largest path loss leads to the best performance.

A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes the propagation characteristics, the transmission techniques, and the multiple access protocols into account. The definition of service-oriented metrics is emphasized. Three different real scenarios operating at MMW are investigated with a unified perspective: intelligent transport systems, wide-band local-area networks, and local multipoint distribution systems for interactive video services. The role played by the MMW band in the development of these services is discussed. In each scenario, accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out in order to join suitable service-quality levels. The methodology considered is based on both analytical and semianalytical tools for performance evaluation.

An analytical approach is proposed to evaluate the performance of a slow frequency hopping (SFH) mobile radio system. The effects of frequency diversity and interference diversity are investigated by considering the use of error correcting codes, multipath Rayleigh fading and cochannel interference; by means of an analytical procedure and proper definition of carrier-to-interference ratio the role of several parameters such as the number of hopping frequencies and system load are emphasized.

The design of high quality, high speed wireless networks to connect mobile users requires large bandwidth availability. For this reason and with the aim of implementing new wireless systems, special attention has been paid to millimetre waves networks (e.g. at 60 GHz) based on short range communications. The paper presents some results concerning indoor channel characterisation. A ray tracing method has been applied to a realistic environment, with the view to define proper analytical models for propagation parameters. More precisely, large-scale received power, Rice factor, delay spread as a function of distance and small-scale variations statistics have been investigated in the presence and in the absence of room furniture: a two-state model has been proposed and checked.

A new analytical methodology for outage probability evaluation of a vehicle-to-vehicle packet radio communication system at 60 GHz, is presented. Propagation characteristics, co-channel interference and thermal noise are taken into account, in the context of an highway traffic model. Both code division and time division multiple access schemes are analysed: results as a function of offered traffic and useful link distance are discussed. The analytical procedure is general, and can also be applied to bi-dimensional cellular structures.>

A simple procedure for designing the post-detection filter of an MSK-type receiver for continuous phase modulation with modulation index h=0.5 (generalized MSK signals) is proposed: the criterion descends from a useful, general representation of this class of signals. The frequency response of the baseband receiver filter is analytically optimized in closed form whatever the modulation pulse shaping of the transmitted signal, and signal-to-noise ratio at the receiver. The criterion is pointed out through a significant, exact representation of generalized MSK signals, whatever the modulation pulse-shaping waveform, which is assumed to be included in a time range equal to LT, T=symbol time. The main part of intersymbol interference, as appears from the representation of the CPM signal, is cancelled by applying the Nyquist criterion to the most significant function among those describing the signal structure. The numerical results obtained show a performance improvement with respect to the averaged matched filter (AMF) criterion and are very close to the results reported in the literature, deriving from more complex design criteria. The suitability of the design criterion is also tested in the presence of interferers, showing a significant advantage of the proposed filter when considering adjacent channel interference.>

A completely analytical approach is presented in order to evaluate outage probability of TDMA (time-division multiple access) local radio systems using coding and diversity to combat frequency selective fading. First, starting from a multiray model for multipath propagation, performance sensitivity is tested by suitably simplifying the channel model. An analytical expression is obtained of the probability that BER may exceed a fixed value in the presence of a simplified channel model. A suitable upper bound formulation is given to express the same probability in the presence of coding and diversity techniques. Finally, some application examples are proposed both with reference to slow frequency hopping and space diversity systems.>

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 tau , shorter than symbol time, T, is investigated. The algorithm developed to evaluate bit-error probability shows that the choice tau /T=1, and even more so in the presence of adjacent channel interference. Moreover, for tau /T=0.5, numerical results are reported that describe system performance under different working conditions and can be used to develop design criteria.>

In multilevel QAM radio systems affected by selective fading, countermeasures such as adaptive baseband equalization allow a drastic reduction of signatures. Linear and decision feedback equalization are investigated from an analytical and experimental point of view. The performance is evaluated and compared, dependence on accuracy of circuit implementation is analyzed, and simple asymptotic formulas describing the system behavior are given.

The behavior of CPFSK systems with modulation pulse shaping and limiter-discriminator detection is tested in the prsence 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 probability Poutis possible. Moreover, the choice of duty-cycle in the modulation pulse\tau/T < 1leads to a lower value of Poutwith respect to the conventional case\tau/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 Poutat 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.

A general analysis of the behavior of multilevel PSK radio links is carried out under multipath propagation conditions. A method is proposed to evaluate system unavailability due to the combined effects of noise and faded channel distortion. The "outage domain," having fixed the transmission channel, is calculated in the space of the variables which characterize any anomalous propagation condition. In particular, with reference to a "twopath model" (a "direct ray" and an "echo"), variations of carrier and symbol synchronisms due to the echo are taken into account and their importance is emphasized in realizing the numerical results. These are shown to be in very good agreement with the experimental ones which have appeared in the literature. An analytical realization of the results obtained is developed and leads to a simple asymptotic formula explaining outage probability as a function of some parameters of the echo statistics, the transmission channel adopted, and the number of modulation levels. Rapid evaluation of this formula allows us to plot outage probability as a function of spectral efficiency, measured in bits/s/Hz.