In last years, wireless networking is becoming very popular because it is able to satisfy user requests in terms of Quality of Service (QoS); when mobility is present, perhaps, hand-over issues are relevant when hosts change coverage areas during their active sessions. It is very important to mitigate mobility effects, employing an appropriate bandwidth management policy. In our work, we propose two integrated schemes: the first one is based on Markov theory and is aimed at the prediction of mobile hosts movements (in terms of future cells), while the second one is based on statistical theory and is aimed at the minimization of the wasted bandwidth used for passive reservations. So, the proposed Pattern Prediction and Passive Bandwidth Management Algorithm (3P-BMA) is the result of the integration of the Markov predictor and the statistical bandwidth management scheme. 3P-BMA is completely independent on the considered technology, mobility model and vehicular environment. We do not care if the coverage is made by UMTS or WLAN technologies, if hosts are pedestrians or mobile users, etc. Some campaigns of simulation have been led-out in order to confirm the effectiveness of the proposed idea in terms of prediction accuracy, Call Dropping/Blocking probabilities and system utilization.

Pocket Switched Networks (PSNs) are challenged wireless networks of handheld mobile devices that exploit user mobility to distribute data in an opportunistic way. In PSNs, a fundamental issue is the choice of a suitable relay node for message forwarding. In such environments, disconnections are very frequent and an end-to-end path from source to destination usually does not exist. Consequently, routing protocols are based on a hop-by-hop communication paradigm. Most of these protocols exploit social behaviour characteristics to decide whether an encountered node is a good relay. Social network information is commonly extracted from encounters detected between mobile devices. However, Internet added online social interaction techniques, which are not based on physical meetings and that reflect users' online behaviour. In this paper we present novel routing metrics for social-based routing in PSNs that exploit both offline and online users' social network information. By proposing a model of dynamic online social network that uses information extracted from offline and online user behaviour, we show that routing centrality metrics, combining node centrality extracted from dynamic online social network and centrality extracted from detected social network, improve delivery ratio and in some scenarios even reduce end-to-end delay.

The utilization of the Return Channel Satellite (RCS) in DVB systems allows a bi-directional communication via satellite. With this particular characteristic, DVB-RCS systems promoted its enormous diffusion in the commercial area and the academic research interest and, in this context, it is very important to test DVB-RCS systems using an efficient satellite channel model. Many channel models have been proposed in the literature, but most of them work at the bit level or they investigate only some aspects of channel interaction. In this paper we present a high level satellite channel model based on Markov Chains (MCs) modeling, useful in every simulation context: the proposed Markovian Satellite Channel Model (MSCM) is based on the concept of windowed observations and the idea is not to analyze a single packet, but fixing an observation window to evaluate the degradation level of the link, computing the PER associated to the specific window. The model has been verified through a deep campaign of simulations, which demonstrate how the introduced error is minimized.

Opportunistic networks are a generalization of Delay Tolerant Networks (DTNs) where communication is challenged by frequent disconnections and encounter patterns between mobile devices are unpredictable. Opportunistic routing protocols attempt to enable the forwarding of messages via encounters between devices, while dealing with the problems of large delays and lack of end-to-end connectivity. To save energy in mobile environments, such routing protocols must minimize unnecessary message replication. This paper presents FSF (Friendlist-based Social Forwarding), an opportunistic routing scheme that exploits both social network information detected through encounters between mobile devices and pre-existing online social network information. To select an effective forwarding node, FSF measures the forwarding capability of a node when compared to an encountered node in terms of node degree cen-trality measured on the temporal encounter network and online tie strength. Simulations with experimental datasets containing encounter records with corresponding Facebook friendlists of the participants show that the proposed routing scheme allows mobile users to achieve good delivery ratio, while forwarding fewer messages than other existing algorithms.

In last years, wireless networking is becoming very popular because it is able to satisfy user requests in terms of Quality of Service (QoS); when mobility is present, perhaps, hand-over issues are relevant when hosts change coverage areas during their active sessions. It is very important to mitigate mobility effects, employing an appropriate bandwidth management policy. In our work, we propose two integrated schemes: the first one is based on Markov theory and is aimed at the prediction of mobile hosts movements (in terms of future cells), while the second one is based on statistical theory and is aimed at the minimization of the wasted bandwidth used for passive reservations. So, the proposed Pattern Prediction and Passive Bandwidth Management Algorithm (3P-BMA) is the result of the integration of the Markov predictor and the statistical bandwidth management scheme. 3P-BMA is completely independent on the considered technology, mobility model and vehicular environment. We do not care if the coverage is made by UMTS or WLAN technologies, if hosts are pedestrians or mobile users, etc. Some campaigns of simulation have been led-out in order to confirm the effectiveness of the proposed idea in terms of prediction accuracy, Call Dropping/Blocking probabilities and system utilization.

DVB-RCS is an open satellite communications standard allowing a bi-directional communication via satellite. These characteristics certainly promoted its enormous diffusion in the commercial area and the academic research interest. In this context, it is very important to test DVB-RCS systems using an efficient satellite channel model. In the literature many channel models have been carried out, but most of them work at the bit level or they investigate only some aspects of channel interaction. In this work we provide a high level satellite channel model based on Discrete Time Markov Chain (DTMC) modeling, useful in every simulation context. Our model, called Quality Degree-DTMC (QD-DTMC), is based on the concept of Quality Degree (QD) of a given observation windows: the idea is not to analyze a single packet, but fixing an observation window and evaluating the QD of the link, computing the Packet Error Rate (PER) associated to the specific window. The effectiveness of the proposed idea has been evaluated through a deep campaign of simulations.

In recent years, mobile hosts desire to benefit a good level of satisfaction for the received services in wireless networks, with adequate quality of service guarantees. In this work the attention is focused on wireless services in cellular networks, where the hand-over effects need to be mitigated, through an appropriate reservation policy. Passive resources are used to ensure service continuity when mobile hosts are moving among different coverage cells. The system is modeled through a distributed set of Hidden Markov Chains and the related theory is used to design a mobility predictor (in terms of future probably visited cells), as the main component of the proposed idea, that does not depend on the considered transmission technology (GSM, UMTS, WLAN, etc.), mobility model or vehicular scenario (urban, suburban, etc.). MRSVP has been used in order to realize the active/passive bandwidth reservation in the considered network topology and a severe simulation campaign has been led-out in order to appreciate the robustness of the reservation scheme.

Delay tolerant networks (DTNs) are sparse wireless networks where most of the time there does not exist a complete path from the source node to the destination node. In this context, where connectivity is intermittent, but where the possibility of communication is still desirable, conventional routing protocols are unsuitable to deliver messages between nodes. The design of efficient routing protocols is a fundamental problem in DTNs. Many different routing approaches for DTNs have been proposed in the literature, each one based on different characteristics and properties. In most cases, their performance have been evaluated considering aspects like delivery ratio and delivery latency, without considering energy consumption constraint. In this work we focus on the energy consumption issues of the routing protocols. We present a performance comparison of the Epidemic, Spray and Wait, PROPHET, MaxProp and Bubble Rap routing protocols with respect to energy consumption, evaluating how the energy consumption impacts the performance of the protocols and how the different forwarding algorithms affect the energy usage in the mobile devices.

In the last years, there has been a lot of research and development in wireless networking and mobility management. We focus our attention on the management of real-time flows, in particular on the management of hand-over events, in terms of bandwidth guarantee and service continuity when the system is dealing with Mobility Independent Predictive (MIP) services, defined in Integrated Services (IS) for mobile wireless environment. The main idea of this proposal is the utilization of a pre-reservation phase in the admission control through a Markovian approach, in order to predict the amount of bandwidth needed by a mobile host during its movements among the probably visited cells. The performance evaluation of the proposed idea has been made in terms of total assigned bandwidth, system utilization and admitted/dropped MIP flows.

Vehicular communication systems represent one of the most desirable technologies when the safety, efficiency and comfort of everyday road travel need to be improved. The main advantage is the absence of an infrastructure, typical of centralized networks, that makes them very scalable and adequate for highly-variable network topologies. Vehicular Ad-hoc NETworks (VANETs) are able to provide wireless networking capability in situations where no fixed infrastructure exists and the communication among nodes can be either direct or made via relaying nodes, as in the classical ad-hoc networks. In this paper, the attention is focused mainly on the network layer of VANETs, proposing a novel approach to reduce the interference level during mobile transmission, also considering the minimization of path lengths. We propose an interference aware routing scheme for multi-radio vehicular networks and a new metric is also proposed, based both on the maximization of the average Signal to Interference level and on the minimization of the path length of the connection between source and destination. Our solution has been integrated with the AODV routing protocol to design a new MIMO Distance Vector Protocol. NS-2 has been used for implementing and testing the proposed idea, and significant performance improvements have been obtained.

An important suggestion of the standard for DVB-RCS+M is the possibility of using a continuous carrier operation mode in the return channel beyond the classical MF-TDMA mode. In order to realize it a mechanism for switching between these two modalities has to be used. In this paper, after showing the typologies of applications considered in the simulation, a proposal of a novel switching mechanism is presented and the simulation results are reported in order to provide some guidelines to the satellite operators that want to adopt in their satellite system this hybrid mode. The simulation results provide good indications and this study is the base for more depth researches.

In this work an approach to obtain an accurate high level channel model based on Discrete-Time Markov Chain, useful in some simulation context, is provided. In particular, this model is based on the concept of error trace analysis and on the degradation level of given observation windows: an observation window is fixed and the degradation level of the link, the Packet Error Rate (PER) relative to the specific window, is evaluated. This approach is useful for any wireless transmission scheme, but in our work, we apply it to the Ultra Wideband (UWB) system. Many researchers have already treated UWB channel modeling. However, to the best of our knowledge, all the proposed channel models work at the physical level investigating only some aspects of channel interaction. It has been shown through a comparative analysis, based on the occurrence of correctly and wrongly received packets, that the degradation level approach is more accurate than the classic Gilbert-Elliot model, the 3rd order Markov model and the Markov-based Trace Analysis (MTA) model.

Traditional routing protocols deployed to provide communication among mobile nodes in wireless ad hoc networks (MANET) assume a trust and collaborating environment inside the network. However, this assumption is not always true and a hostile or unprotected environment can seriously affect the protocol and network performance. In this work two kinds of approaches are applied to a well-known routing protocol called SAODV in order to improve its performance and to offer more resilience to attack from malicious nodes authenticated by the network. A preventive approach based on a cryptographic mechanism and a reactive approach to detect the anomalous and malicious behavior of nodes are considered. An extension of SAODV to offer Intrusion Detection mechanism (IDM) and trust-based mechanism (TBM) to promote the collaboration of the cooperating node and penalize the selfish nodes are proposed. Simulation results were performed in order to show the effectiveness of our proposal in comparison with AODV and SAODV.

The IEEE 802.16 protocol is one of the most promising technologies in recent years, especially in its recent version that specifies user mobility support. The purpose of this paper is to illustrate a scenario characterized by this protocol and the presence of mobile users. The goal is to create a model that can describe the time variant channel behaviour in terms of probability values, i.e. such as: what is the probability of receiving a wrong packet on the receiver side? In the literature there is a great diffusion of Markov chain based models to describe channel behaviour, but none of these is independent of scenario configurations, and also none has been tested with a realistic dynamic scenario. As a consequence we have attempted to create a new model that can be used independently of the channel configuration.

The mesh distributed mode supported by IEEE 802.16 protocol, with the capability to establish direct links between SSs (Subscriber Station) and with the wide coverage area and the promised bit rate, allows to create interesting scenarios. The protocol defines guidelines to realize request/grant process, but it does not proposes a distributed Call Admission Control (CAC) algorithm. This process is essential to guarantee QoS constraints to admitted connections. In this paper, we present GCAD-CAC (Greedy Choice with bandwidth Availabilities aware Defragmentation): a new call admission control algorithm to guarantee the respect of data flows delay constraints defined by three different traffic classes. In order to reach good results, a Greedy algorithm is used: all the new requests are accepted, but when a higher priority request is received, a lower priority admitted request is preempted. The preemption can leave in data subframe some little gaps not sufficient to new connection admission; these gaps can be collected by GCAD algorithm by activating a bandwidth availabilities defragmentation process. The algorithm quality is proved by a comparison with other two algorithms found in the literature.

Nowadays, in wireless computing, guaranteeing a certain grade of Quality of Service (QoS) during wireless sessions is an important issue, especially when non-tolerant applications are running into the system. Mobility and channel quality often affect system performance, depending on the grade of mobility of hosts. In this paper, providing QoS to mobile hosts belonging to a certain service class (Mobility Independent Predictive - MIP) is the main issue and a statistical multiplexing algorithm is proposed, in order to save an enormous amount of resources; it is based on the Cell Stay Time (CST) distribution analysis for a 2- dimensional (2D) wireless environment under the Smooth Random Mobility Model (SRMM). There are many works in literature about resource pre-reservation: they offer good QoS guarantees, but a very low system utilization, because they do not care about the fact that a passive reservation can remain unused for long time. With the help of the CST statistical multiplexing introduced in this paper, better results are obtained in terms of system utilization, while the Quality of Service and prediction error are maintained at acceptable levels. The proposed idea has been validated through many simulation campaigns, with a good performance analysis in terms of some interesting parameters, like bandwidth system utilization or prediction errors.

Ultra wide band (UWB) thanks to its physical characteristics became one of most suitable technology for indoor and outdoor personal communications. Many works have already treated problematic involving UWB transmission channel. However, at the best of our knowledge, all proposed model work at the physical level or they investigate only some aspects of channel interactions. Instead, in our work, we provide an approach to obtain an accurate high level channel model based on Discrete Time Markov Chain (DTMC) modeling useful in every simulative context. In particular, our model is based on the concept of error trace analysis and on degradation level of a given observation window: we do not analyze the single packet, but we fix an observation window and we evaluate the degradation level of the link computing the PER relative to the specific window. This new approach is more accurate than classic Gilbert-Elliot (G-E) model, 3rd order Markov model and Markov based Trace Analysis (MTA) Model as a comparative analysis, based on the occurrence of correctly and wrong received packets, showed.

The IEEE 802.16 protocol is one of the most promising technologies in recent years, especially in its recent version that specifies user mobility support. The purpose of this paper is to illustrate a scenario characterized by this protocol and the presence of mobile users. The first goal is to create a model that can describe the time variant channel behaviour in terms of probability values, i.e. such as: what is the probability of receiving a wrong packet on the receiver side. The second goal is to use the model forecast to guarantee QoS to every type of application. In literature there is a great diffusion of Markov chain based models and of other kind of model, as ARMA or filter model, to describe channel behaviour, but none of these is independent of scenario configurations, and also none has been tested with a realistic dynamic scenario. As a consequence we have attempted to create a new model that can be used independently of the channel configuration to ensure compliance with the QoS bounds.

In this paper we propose a routing algorithm based on Swarm Intelligence studies. In particular, this algorithm is based on AntNet routing with the extensions of novel metrics for the multi-objective optimization, that are minimum hop count and traffic load balancing. In order to build an optimal solution, the proposed algorithm will make use of ANT agents that consist of probe packets sent on the HAPs network. We have chosen as reference network a HAPs mesh in order to get advantages of the dynamic characteristics of these platforms. In this work we perform a comparison of a classical shortest length path and our algorithm that will try to find the minimum hop path respecting a maximum end-to-end delay bound and an equally distribution of the traffic on the HAPs network.

Deep space communications are an important research line in scientific community. The possibility of performing the communication between earth and other planets is an excitant challenge. The main issue of the communication between planet, called interplanetary (IPN) communication, is the intermittent visibility due to planet movement and the long propagation delay. In order to solve these problems a delay tolerant network (DTN) has been deployed. DTN is an architecture particularly useful in scenarios where very long transmission delays or intermittent connectivity are present, such as IPN network. The routers in DTN perform a transmission mechanism similar to the model of mail transfer protocols or the store-and-forward and it permits to determine a hop-by-hop based messages exchange. Our main contribute in this paper is the introduction of an asynchronous congestion control mechanism on the network that it is not present in the traditional DTN protocol. This control tries to resolve buffer overflow, link saturation and useless retransmission problems in order to better utilize the overall system.

Multimedia communications and, in particular, multicast communications are widely used to distribute multimedia contents. When a certain quality of service (QoS) level must be guaranteed in the multicast tree construction then a Steiner tree problem is obtained, therefore a NP-complete problem must be faced. QoS multicast has a great relevance in the research community because it can offer high performances and better resource allocation. This is relevant in the modern networks, which are composed of wireless networks, wired networks, 3G-4G networks, delay tolerant networks and so on. A better resources allocation permits to have a greater number of connected users. In order to obtain these results it is important to have a multicast tree that can satisfy some QoS requirements. In this work two meta-heurist such as genetic algorithms and simulate annealing algorithms have been considered. Moreover, new procedures and new approaches are proposed in order to obtain better algorithms performances.

This paper presents a novel Medium Access Control algorithm for the QoS support over UWB networks. Interference Mitigation techniques are combined with access control to guarantee the Packet Loss and Maximum Packet Delay satisfaction. Two QoS indexes are defined and are considered for the acceptance of a call on the network in order to maintain low the interference level of transmitting stations. Performance evaluations have been considered in terms of data throughput and maximum data packet delay.

QoS guarantee is a very important issue in wireless communications, when mobile nodes move among different coverage areas. This paper presents a novel 2D reservation scheme for WLAN environments. A general prediction technique based both on the analysis of Cell Stay Time (CST) and on the direction probabilities of hand-in and hand-out events of mobile nodes from wireless cells is outlined. In particular, a threshold-based algorithm is presented, trying to take into account the mobility behavior of mobile users, through the analysis of a directional probabilities matrix. An integrated architecture able to make active and passive reservations has been employed as a possible application of the proposed approach. Many simulations have been carried out and a performance analysis has been performed, finding a good tradeoff between bandwidth utilization and prediction error.

Recently there has been a lot of research and development in wireless networking and mobility management, with the main purpose of connection handling between mobile hosts and base stations or access points. QoS guarantee is a very important issue in wireless communications, when mobile nodes move among different coverage areas. This paper presents a general prediction technique based both on the analysis of cell stay time and on the direction probabilities of hand-in and hand-out events of mobile nodes from wireless cells. User mobility has been analyzed, in order to reduce passive resource reservations, with a high gain in system utilization. In particular, a threshold-based algorithm is presented, trying to take into account the mobility behavior of mobile users, through the analysis of a directional probabilities matrix. The performances of the 2D wireless system have been evaluated in terms of prediction error and system utilization; in addition, some comparisons with older prediction schemes have been made.

Multi-mode satellite terminals are actually the most desired devices on the market, thanks to their flexibility and suitability. A multi-mode radio communication terminal is a terminal allowing two or more transmission mode. In the last few years many research resources have been invested in the study of this new type of terminal In this work, we define a multi-mode terminal as a terminal capable of communicating both with a bent-pipe (BP) satellite and with an on-board processor (OBP) satellite and dynamically setting its transmission parameters (e.g. transmission power and code rate). In order to realize this multi- mode functionality, the most suitable technology is the software defined radio (SDR). The SDR is a set of hardware and software technologies that allow one to obtain reconfigurable architectures for network and wireless terminals. The goal of our work is to plan a satellite system based on digital video broadcast with the return channel satellite (DVB-RCS) standard in which the return channel satellite terminals (RCSTs) are able to adapt it to the channel state, configuring the transmission chain via software, respecting a certain quality of service (QoS) constraint on the packet error rate (PER).

Ultra-wideband (UWB) radio is a viable candidate for short-range multiple access communications in dense multipath environments. This paper analyzes the efficiency of direct sequence - UWB physical layer standard proposal in a indoor environment with fixed transmitters and receiver positions. The performance evaluation is carried out using the UWB channel model provided by the IEEE 802.15 channel modelling subcommittee to model the dense multipath indoor environment typical of the UWB system. DS-UWB architecture has been implemented using a Matlab Simulink tool and simulation results are evaluated in terms of bit error rate (BER) vs. transmitter-receiver distance and noise power spectral density. Moreover, a polynomial regression analysis is carried out on simulation results in order to obtain a closed formula to describe, for different scenarios, the BER as a function of data rates, noise power spectral density (PSD) and distance between the transmitter and receiver.

In last years there has been a lot of research and development in wireless communications and mobility management, with the main purpose of connections handling between mobile hosts and base stations or access points, when different coverage areas are visited. This paper presents a novel 2D reservation scheme for WLANs; a general prediction technique based both on the analysis of cell stay time (CST) and on the direction probabilities of hand-in and hand-out events of mobile nodes from wireless cells is outlined. In particular, a threshold-based algorithm is presented, trying to take into account the mobility behavior of mobile users, through the analysis of a hand-off directional probabilities (HDP) matrix. Users' mobility has been analyzed, in order to reduce passive resource reservations, with a high gain in system utilization. In particular, an integrated architecture able to make active and passive reservations has been employed as a possible application of the proposed approach. The performances of the 2D wireless system have been evaluated in terms of prediction error and system utilization; in addition, some comparisons with older prediction schemes have been made.

A multi-mode radio communication terminal is a tunable terminal for passing and/or receiving bands in at least two radio communication systems. In the last few years many research resources have been invested in the study of this new type of terminal. This study is intended for a multi-mode terminal is a terminal capable of communicating both with a bent-pipe satellite and with an on-board processor satellite. In the literature different technologies are presented and they can be used to realize the multi-mode capability of a terminal, but, the most suitable technology is the software defined radio (SDR). The SDR is a set of hardware and software technologies that allow one to obtain reconfigurable architectures for network and wireless terminals. The goal of this work is to plan a satellite system based on digital video broadcast with the return channel satellite (DVB-RCS) standard in which the return channel satellite terminals (RCSTs) are able to adapt to the channel state, configuring the transmission chain via software, respecting a certain quality of service (QoS) constraint on the packet error rate (PER).

This article presents a role dynamic management algorithm for sensor devices. The network scenario considers a wireless sensor network in which each node can assume different roles. Specifically, attention is focused on two different roles: the active and the passive role. When a sensor device assumes an active role it uses a greater amount of energy greater than the passive role. The scope of this work is to introduce a dynamic management strategy to better distribute the energy in the network varying dynamically roles of the nodes under different mobility conditions. This dynamic algorithm is applied to an energy-efficient protocol based on a cross-layered approach (ESR and EMAC) and which ensures a good node lifetime. Two different algorithms have been developed to ensure a dynamic management of the node roles with the ESR and EMAC approach. Both these approaches have been evaluated through a simulation tool OMNeT++ and their performance have been compared with the original ESR and EMAC.

This paper presents a performance evaluation of IEEE 802.16e protocol. The 802.16e PHY/MAC protocol for wireless MAN has been applied to a high altitude platform (HAP) architecture with another protocol family member: 802.16SC (single carrier). In this work an HAP serves a rural scenario with low multipath effects. Two different time-variant wireless channels have been considered: the first one for a HAP- mobile user link that is characterized by path loss and doppler effects and the second one for a mobile user - mobile user link that presents also multipath fading. Many simulation scenarios with different mobility user speeds and different modulations are reported and interesting results concerning the PER of both channel, the first under single carrier (SC), and the second under an OFDM modulation, a specific multicarrier modulation, are presented. Thus PER evaluation under different modulation and for different payload sizes are presented. Simulation results showed good channel performance if the mobility of the user is low or the mobile user is near the vertical axis of the HAP segment, but also if QPSK modulation is used. Finally Matlab elaboration to obtain PER polynomial function are presented.

The low cost of devices and the possibiliy of achieving higher data rates without increasing transmitter power make Ultra-Wideband (UWB) radio a viable candidate for short-range multiple access communications in dense multipath environments. This paper analyses the efficiency of the Direct Sequence - Spread Spectrum (DS-SS) physical layer standard proposal in an indoor environment with fixed transmitters and receiver positions. The modelling and the performance evaluation of a new channel model, where impulse response is also distance-dependent, are outlined. Packet Error Rate (PER) analysis has been carried out by using a polynomial regression technique, through the Matlab tool, on simulation results obtaining an expression for the PER as function of distance and packet length. Simulation results are evaluated in terms of PER vs transmitter-receiver distance.

Mobile ad hoc networks are characterized by multi-hop wireless links, the absence of any cellular infrastructure, and frequent host mobility. Due to the dynamic nature of the network topology and the resource constraints, routing in MANETs is a very challenging task. The advantage of multi-path routing in MANETs is not obvious because the traffic along the multiple paths will interfere with each other. The effect of the route coupling in this environment can severely limit the gain offered by multipath routing strategies. Route coupling refers to the interference between two or more multiple paths located physically close enough to interfere with each other during data communication. In this paper, a new multipath distance-vector routing protocol, the geographic multipath protocol (GMP) is proposed. This reactive algorithm computes alternate routes loop-free and zone-disjoint paths. In this way the paths are more independent of each other and the correlation-interference is very low. This permits a higher load balancing in the network and a major effectiveness of the multiple paths as far as the performance measures considered are concerned. Simulation experiments have shown that GMP outperforms unipath distance vector routing (AODV) and multipath distance vector routing

This papers presents a 2D reservation scheme in WLAN environment. A two-dimensional wireless mobility model called smooth random mobility model (SRMM) has been considered, because it makes the movement of users smoother and more realistic than well-known in literature random mobility models. A general prediction technique based both on the analysis of cell stay time and on the direction probabilities of hand-in and hand-out events of mobile nodes from wireless cells is outlined. Three different reservation policies are considered: the first scheme reserves a fixed number of cells for each hand-off; the second one permits to reserve on a greater number of cells in the first hand-off and a lower number of cells in the next hand-off events; the last policy uses an increasing adaptive reservation scheme, trying to take advantage of the lower prediction error for the first hand-off and the greater prediction error for the next hand-off. Many simulations have been carried out and a comparison between the three reservation schemes has been performed.

The low cost of devices and the possibility of achieving higher data rates without increasing transmitter power make ultra-wideband (UWB) radio a viable candidate for short-range multiple access communications in dense multipath environments. This paper analyses the efficiency of the direct sequence-spread spectrum (DS-SS) physical layer standard proposal in an indoor environment with fixed transmitters and receiver positions. The modelling and the performance evaluation of a new channel model, where impulse response is also distance- dependent, are outlined. Moreover, the performance evaluation of an ideal minimum mean square error (MMSE) receiver is exploited in terms of distance, noise and data rates dependence. packet error rate (PER) analysis has been carried out by using a polynomial regression technique, through the Matlab tool, on simulation results. Simulation results are evaluated in terms of bit error rate (BER) and PER vs. transmitter-receiver distance.

This paper presents a novel routing protocol called Geo-LANMAR. This routing scheme is able to get full advantages of group motion of mobile nodes to reduce the routing overhead and offer high network scalability. This protocol inherits same advantages of LANMAR protocol regarding the group motion support and its idea is to use the long-distance gee-forwarding for the extra-scope routing such as the terminodes routing and the optimized link-state routing (OLSR) for the intra-scope routing. Together the geo-routing forwarding scheme, a global update propagation scheme based on the hazy sighted link state routing (HSLS) between landmark nodes (cluster heads) is applied. An asymptotic analysis of Geo-LANMAR protocol is proposed and a rule that binds the intra-scope and extra-scope overhead cost is found. The novel routing scheme has been compared with the standard routing protocols such as AODV, GPSR and LANMAR.

A novel routing scheme called GeO-LANMAR routing has been proposed in this paper. This scheme combines the local link-state routing protocol until k-hop and a long-distance greedy forwarding. Geo-LANMAR supports group motion and gives high scalability for large network. It uses the concept of local group area (LGA) to define region where to forward data packets through geo-forwarding scheme. It makes usage of a virtual topology between LGAs and an optimized Hazy sighted link state (HSLS) link-state routing protocols. It combines the benefit of LANMAR protocol in terms of group motion support with the scalability of terminodes routing. A hybrid forwarding scheme (proactive and geo-routing) and a coarse topology knowledge through the HSLS protocol running between LGAs is applied. A performance evaluation of Geo-LANMAR vs. other routing protocols such as AODV, LANMAR and GPSR has been lead out.

This paper presents a novel call admission control (CAC) algorithm based on the statistical multiplexing of VBR traffic. The proposed algorithm is called statistical multiplexing based on discrete bandwidth levels of GOP rate (SMDB) because the solution is based on the discretisation of the GOP rate in a set of bandwidth levels and on the time characteristics of discrete bandwidth levels of MPEG sources. SMDB is compared with another statistical CAC based on the normal/lognormal distribution of the GOP rate (SMND). SMDB overcomes SMND in many situations such as high variance around the average video traffic GOP rate of sources and heavy traffic load. The new CAC has been tested in the new generation satellite platform called digital video broadcasting via return channel satellite (DVB-RCS). A high system utilization and multiplexing gain respecting QoS constraints is obtained

The need of new wireless communication infrastructure which can provide high-speed multimedia mobile communication service to users who are not satisfied with low-speed data and voice service provided by existing wireless network are rapidly increasing. Cellular communications using high altitude platform (HAPs) are studied for next generation broadband wireless network providing also third generation (3G) mobile services. The connection admission control issue in a HAP-UMTS communication system represents a key problem in order to increase the capacity in term of admitted users preserving the agreement quality of service. In this paper we propose a novel strategy for the admission procedure based on dynamic power sharing in order to guarantee an high fairness level to all users of the projected cellular system. Simulation results show that the proposed CAC scheme can achieve good performances managing different mixed traffic scenarios.

In the context of hierarchical mobile IPv6 integrated with a fast handover mechanism, this paper proposes two mobility anchor point (MAP) selection algorithms, both based on the classification of users depending on their mobility. Furthermore, an enhancement of one of the two algorithms is presented; it introduces the concept of bufferization at MAP level. Extensive simulations have been performed to analyse and investigate the algorithm results.

In the past few years, there has been much research in wireless adaptive networking and resource management, in order to examine how to efficiently handle wireless communications between mobile hosts and base stations. In this paper, we focus the attention on the mobile independent predictive (MIP) service class, which provides a passive reservation policy, with the goal of QoS guarantees during hand-off events. We analyzed MIP users' mobility along coverage areas, to obtain a system utilization improvement, by reducing passive resource reservations on cells that users will probably visit. A prediction technique is also proposed and calls are managed in a wireless system by a utility-based algorithm that takes into account the radio-link quality variability by a Markov channel model, based on the IEEE802.11b standard. System performances are evaluated by varying users' speed and system utilization with prediction error percentages are shown. It is observed that the proposed prediction technique causes an increase in system utilization.

The main objective of this work is the proposal of a new connection admission control (CAC) algorithm guaranteeing both a high connection multiplexing level and, in particular, a good quality of service (QoS) for real-time multimedia traffic sources mapped over the service classes of the DVB-RCS standard. In this paper, we suppose a DVB-RCS system architecture using a multi-spot beam geostationary satellite with regenerative payload. We also suppose IP traffic to be carried, in return and forward directions, via DVB/MPEG-2 traffic streams instead of to the obsolete ATM encapsulation. Simulation results show that, even if the real time multimedia connections are more sensitive to the delay jitter, the agreed QoS is always guaranteed, even when the system load increases; moreover, using the proposed algorithm, a high system throughput is obtainable.

This paper focuses its attention on the rate adaptation problem in wireless network with mobile hosts. We define two new quality of service (QoS) indexes. They express the degradation degree of bandwidth and the frequency of bandwidth degradation suffered by data packet flows. These indexes are used to define and propose a new rate adaptation algorithm named degradation degree based fair algorithm (DDFA). The aim of the proposed algorithm is to fairly distribute the effects of QoS degradation among the cell visited by the mobile hosts. The DDFA algorithm has been compared with a fair adaptation algorithm proposed in the literature. The performance evaluation shows that proposed algorithm reduces the QoS degradation of flows without adding control overhead compared to the reference fair algorithm.

This work presents an enhancement of the hierarchical mobile IPv6 protocol, based on a new concept of "distribution areas" and the assignment of multiple LCoAs. It contributes to low latency and packet loss during intradomain handover events. The size and position of the distribution areas are dynamically adjusted depending on traffic load measurements and terminal/user velocity estimation. Simulation results show that it is possible to trade off packet loss and introduced overhead.

The proposal of a centralized connection admission control (CAC) procedure in the network control center of a satellite DVB-RCS system, harmonized with techniques of request scheduling, is the main objective of this work. The behavior of such DVB-RCS system architecture, that uses a multispot beam geostationary satellite with regenerative payload, is deeply analyzed and tested. Simulation results show that the proposed techniques guarantees a good QoS to all supported service classes. Particular attention is offered to RBDC traffic sources because they are more sensitive to the delay jitter and consequently they are harder to manage.

This work considers the problem of bandwidth adaptation in wireless mobile environment. In network in which the bandwidth resource changes frequently and an hard quality of service can not be guaranteed, is important to consider an adaptive approach in the bandwidth management. This work proposes new bandwidth adaptation algorithm called average degradation degree and ratio based rate adaptation. This algorithm accounts for the degradation degree and the degradation ratio of the flows as criteria to manage the bandwidth. In the literature many rate adaptation algorithms consider the fairness criteria and the protocol overhead but there is no scheme that accounts for the flow degradation degree maintaining good fairness properties. We compare the proposed algorithm with well known studied schemes: minimum adaptation, fair rate adaptation and average rate adaptation algorithm. The performances of the wireless systems have been evaluated in terms of overhead, fairness, and degradation degree and degradation ratio. Performance measurements show that the proposed algorithm is able to reduce the degradation degree and degradation ratio preserving good fairness properties without adding significative overhead.

The rapid proliferation of the Internet together with the increasing importance of broadband multimedia services has roused the research community's interest, in particular IETF, in QoS traffic. Interesting can be evaluated the QoS architecture and in particular integrated services inside the satellite platform. A multimedia satellite platform called EuroSkyWay has been considered and the IntServ controlled load services (CLS) and the behaviour of the system loaded with controlled load traffic and guaranteed (GS) traffic have been analyzed. The management of CLS is important in order to manage the category the traffic called "better than best-effort" and to guarantee a full interoperation with the terrestrial network. In particular, we have proposed a new way to manage the CLS on satellite systems. The approach is based on reduction of peak bandwidth values of CLS and the increasing of GS request delay tolerance. Different simulations have been outlined and the conformance to QoS parameters for the proposed approach has been verified. Furthermore, the admission control for different values of bandwidth levels declared in satellite admission phase and GS requests timeout have been examined.

This paper focuses on a recently proposed Diff-Serv like architecture called scalable core (SCORE). This one is used in the terrestrial network in order to offer more scalability and deterministic guaranteed services. The integration issues between a scalable terrestrial and a satellite network based on Int-Serv architecture are outlined. The Aggregated RSVP protocol on integrated scalable terrestrial and IntServ satellite network has been introduced in order to guarantee the interoperation between the SCORE architecture and the satellite segment. The system performance in terms of signalling overhead and resource utilization has been set out. The study shows that increasing aggregated bandwidth reservation can improve signalling but can under utilize the terrestrial channel. The satellite network, instead, can improve its static efficiency due to the increased number of calls accepted on the satellite link.

This paper aims at contributing to the dimensioning of the signalling bandwidth of a broadband geo-satellite system for multimedia communications. Signalling channels are used by the satellite terminals to set up connections and ask for on-demand resource assignment. A smart dimensioning of the satellite bandwidth plays a key role in the fulfillment of the service quality required by multimedia traffic and the effective exploitation of the satellite spectrum. We accomplish this task by designing a statistical centralised CAC accorded with an intelligent scheduling of the resource requests on board the satellite. The proposed traffic and resource management techniques have been tested over a simulation platform for the EuroSkyWay satellite system.

In this paper we propose and compare different techniques used by the satellite user terminals to randomly access signaling channels used for connection set-up. The reference scenario is represented by EuroSkyWay [G. Losquadro, 1996], a multimedia geostationary satellite platform conceived for providing personal communications.

This paper proposes a heuristic for re-computing the forwarding zone of route request packets for the location-aided routing (LAR) protocol in ad hoc wireless networks. We evaluate the influence of a "multi-step" resizing of the request zone on the LAR protocol performance, and make comparisons with other routing protocols (LAR scheme 1, LAR scheme 2, and promiscuous-dynamic source routing). Simulation results show that an accurate choice of the request zone size and of the number of steps for the resizing is successful in reducing the control overhead and increasing the throughput.

Many recent researches have been conducted on the topic of multimedia applications management in integrated terrestrial-satellite systems with W-CDMA air interfaces. Among the many research issues, the design of suitable radio resource management techniques for soft-QoS guarantees to the user applications surely deserves a particular attention. This paper tries to contribute to this issue by reporting the lessons learned during a performance assessment study on a multi-tier UMTS system simulation platform. It shows that the achievement of good performance is strongly related to the right choice of call management algorithms, which take into account both the nature of the delivered traffic at each coverage level and the effects of the presence of the soft-handoff.

This paper proposes and analyses an architecture providing IP quality of service in integrated terrestrial-satellite networks. The IP Integrated Services framework is used to reserve resources on the satellite path and is combined with Differentiated Services in the terrestrial core network. A seamless integration is achieved by means of a gateway station that acts as interworking unit between terrestrial and satellite segments. The main focus is on the best mapping of integrated service traffic classes over satellite bearer connections.

This paper analyses the performances of two types of CAC algorithms proposed for deciding the admission of new connections in a geostationary satellite system. Both algorithms are specifically designed for high latency networks as they are characterized by low processing time on board, simple parameters, and real-time decisions. Tests are performed on the multimedia satellite platform of EuroSkyWay and aim at assessing the robustness of the CAC algorithms in guaranteeing the target quality to heterogeneous applications and in exploiting effectively the satellite bandwidth.

A new scheme for the management of real-time traffic over high-latency broadband satellite networks is described. Early studies on this topic have been reported by Iera, Molinaro and Marano (see IEEE J. Select Areas Commun.,, vol.18, p.2393-2403, 2000), with reference to an integrated terrestrial-satellite platform. In this paper, further enhancement is introduced into the traffic management scheme with a view to both the reduction of intrinsic impairments caused by the adverse operational environment and the achievement of better performance levels and QoS guarantees. A real-time traffic handling strategy, including distributed connection admission control (CAC) and traffic resource management (TRM) schemes, is harmonized with an in-band signaling technique for burst-based bandwidth request and with an effective policy for the allocation of radio resources. Furthermore, the impact of traffic reshaping at the satellite terminal on the CAC-TRM technique is tested. Added features reduce the adverse effects of the long propagation delay across the satellite link and show outstanding effectiveness in improving CAC-TRM performance and network resource efficiency, while matching service quality requirements. The main reason for the improved performance of the overall management scheme is the adaptability to different traffic profiles conveyed over satellite links.

An attractive challenge in the global communications scenario is the effective transmission of real-time bursty traffic over integrated terrestrial-satellite links. In this paper, the study focuses on the cited issue. In early studies we proposed a solution based on a connection admission control (CAC) scheme, coupled with a traffic resource management (TRM) functionality onboard. In the present work, the traffic handling strategy is complemented with a re-shaping module in the satellite terminal. The additional functionality shows outstanding effectiveness in improving CAC-TRM performance, especially when the long propagation delay across the satellite link prevents the CAC itself to guarantee the target QoS to certain types of traffic. By adopting an "intelligent" shaping at the satellite terminal the full effectiveness in managing system resources and in guaranteeing QoS is recovered, under a wide range of loading conditions and offered traffic profiles. The resulting policy is adaptable, in the sense that it can be dynamically adapted to the traffic profile.

This paper focuses on the analysis of two classes of TDMA-based MAC algorithms for wireless-ATM networks: the urgency-based class, scheduling the bandwidth requests on the basis of their urgency, and the buffer-based class, relying on the estimation of the queue length in the mobile terminals. The main features of the proposed urgency-based algorithms are: contention-based DAMA access, dynamic adaptation of reservation bandwidth, use of piggybacking and control mini-slots to handle real-time VBR traffic, and a scheduling mechanism based on the expiry time of the buffered cells. These aspects contribute to the better performance of urgency-based algorithms in handling heterogeneous traffic when compared to the buffer-based ones.

This paper describes a multiple access protocol, which answers the need for an efficient handling of the traffic coming from a wide range of broadband applications over geo-synchronous satellite air-interfaces. We propose a hybrid medium access control scheme, which combines both random access and demand assignment multiple access policies. It is coupled with a connection admission control algorithm, exploiting the advantages of statistical multiplexing. Dynamic management of the frame header allows minimizing the signaling overhead and maximizing the effectiveness of the reservation procedure.

In this paper we propose the use of an in-band signalling technique coupled with a distributed connection admission control and traffic resource management scheme, to combat the effects of high-latency in geostationary satellite systems. In-band request signalling is introduced to manage burst-based bandwidth demand from satellite terminals transmitting real-time variable bit rate traffic. Performance evaluation has shown the effectiveness of this technique in guaranteeing the service quality negotiated at connection set-up between the user and the network.

In this paper, a novel strategy for handling ATM connections of different natures, traffic profile, and QoS requirements in enhanced satellite systems is proposed. The conducted research starts from early studies on resource management in integrated terrestrial-satellite environments and focuses on a combined connection admission control/traffic resource management strategy for QoS provisioning to both real-time and non-real-time constant and variable bit rate sources. The resulting connection handling policy is dynamic, and effectively exploits the system bandwidth through the statistical multiplexing of traffic sources and a preemptive policy over the satellite air interface. The proposed strategy is suited for a generic integrated ATM-satellite system, although its effectiveness has been assessed on a multimedia satellite platform, based on the Ka-band payload and on-board processing.

Multi-tier cellular systems can answer the rising need for high transmission capacity and provide solutions for supporting heterogeneous (narrow-band and broad-band) traffic. The system analysed in this paper consists of a GEO satellite spot covering micro and macro-cellular layers to provide global user reachability and additional bandwidth. Enhanced traffic and resource management algorithms are proposed to effectively exploit the potential advantages of the multi-tier solution. The basic feature is the allocation of each connection to the most convenient hierarchical layer, according to the user mobility profile (fast/slow) and traffic nature. The system is loaded by heterogeneous traffic sources with different requirements in terms of bandwidth on the two radio link directions (symmetric and asymmetric data), delivery requirements and integrity needs. Algorithms are compared under different external conditions and their performance is assessed in terms of new call blocking and handoff dropping probabilities.

The work presented in this paper aims at contributing to the design of traffic and resource management techniques suited for integrated ATM-satellite systems with composite traffic load. The proposed techniques exploit sources statistical multiplexing and pre-emption based dynamic resource assignment. The features making the techniques suitable for ATM-satellite environments are: very low on-board processing, easy algorithm tuneability, statistical multiplexing of VBR sources, good exploitation of satellite bandwidth, and QoS provisioning to real-time and non-real-time traffic sources. The effectiveness of the proposed strategies is assessed on the Euro-SkyWay multimedia satellite platform.

User speed estimation can be exploited to improve the teletraffic performance in a mobile radio environment with multi-tier coverage. Many algorithms exploit the dwell time estimation to classify the users' speed and assign them to the right hierarchical layer. Most of them assume a constant user speed for the entire call. Thus, they loose their effectiveness in environments in which the mobile speed changes during the call. A new effective scheme for channel allocation and handoff management, based on the concept of bonus time, is proposed in this paper. Sophisticated simulative tools showed that the new scheme performs better, compared to the traditional ones, under a wide range of load distributions and vehicle traffic conditions both in urban and sub-urban environments.

In this paper, a new way to manage users having different mobility in a two-tier cellular system, through the use of the techniques of overlapping coverage and channel rearrangement, is provided. Overlapping coverage areas of nearby base stations arise in cellular communications systems, especially in small cell high-capacity microcellular configurations. With overlap, some users may have access to channels at more that one base station. This enhanced access can be used to improve teletraffic performance characteristics. Channel rearrangements are used to benefit users who are in range of only one base station. An analytical model is developed to determine performance measures.

This paper illustrates the development of an approximate analytical model for a communication network providing integrated services to a population of mobile users, and presents performance results to both validate the analytical approach, and assess the quality of the services offered to the end users. The analytical model is based on continuous-time multidimensional birth-death processes, and it is focused on just one of the cells in the network. The cellular system is assumed to provide three classes of service: the basic voice service, a data service with bit rate higher than the voice service and a multimedia service with one voice and one data component. In order to improve the overall network performance, some channels can be reserved to handovers, and multimedia calls that cannot complete a handover are decoupled, by transferring to the target cell only the voice component and suspending the data connection until a sufficient number of channels becomes free. Numerical results demonstrate the accuracy of the approximate model, as well as the effectiveness of the newly proposed multimedia call decoupling approach.

To accomplish the task of providing a wireless access to the fixed network in a UMTS scenario, DECT is also expected to support multimedia traffic requiring multi-slot allocation. To this aim, a modified channel access algorithm, based on a slot-segmentation technique is adopted and combined with a priority-based management of the access requests. This paper illustrates the interesting effects of these enhancements in traditional DECT. The results of a performance evaluation activity in a multi-cell environment with wide-band and narrow-band traffic is reported. Achieved improvements are manifest in terms of both throughput and guaranteed QoS to each type of traffic.

In microcellular systems, cell overlapping can be effectively adopted to improve the teletraffic performance of the mobile terminal population. Anyway, the greatest advantages are mainly achievable by those users, located within an overlapping region, which can exploit the opportunity of receiving acceptable radio signals from more base stations. Effective resource assignment policies are thus necessary to make users located far from overlapping regions benefit from this feature as well. To this aim, a dynamic channel allocation scheme, based on the concepts of reserve channels and protection threshold, is proposed in this paper. A detailed description is given and, by means of analytical tools, it is shown that better performance compared to traditional schemes are attainable under a wide range of load distribution.

Future cellular systems are expected to use differently sized and shaped cells, depending on the area to be covered (urban or rural) and the user density. This paper proposes a cellular system that uses a two-tier cellular scheme, with macrocells and microcells. Mobile users are grouped into two classes, "slow" and "fast" users: to estimate user speed, a procedure is implemented, based on the evaluation of the amount of time a mobile station resides in a microcell. A channel assignment strategy, which tries to allocate "slow" users to the low tier (microcells) and "fast" users to the high tier (macrocells), is proposed: in this way, low mobility users undergo handovers at microcell boundaries, and high mobility users undergo handovers at macrocell boundaries. A simulation study is carried out to show that the handover rate, as well as the system signaling load, are kept at an acceptable level.

Future cellular systems are expected to use multilayered, multisized cells to cover non-homogeneous populated areas. An example in literature is given by a 2 level hierarchical architecture in which an overlaying macrocell provides a group of overflow channels utilized when a microcell, which covers a densely populated area, is not able to accommodate a new call, or a handover from another microcell. The macrocell has the higher hierarchical position, meaning that it can receive handover requests from microcells, lower in the hierarchy, as well as from other macrocells. On the contrary, a call served by the macrocell cannot handover to a microcell. This paper proposes a reversible hierarchical scheme characterized by the presence of handover attempts from macrocells to microcells. The scheme is conceived so that the microcells are given the majority of the traffic load as they are able to operate with very high capacity, while the macrocells, having lower channel utilization, can better carry out their support task. An analytical study is carried out showing that the system performance can be improved, at the expense of relatively little increase of network control overhead, when compared with the classical, i.e. nonreversible hierarchical scheme.

It is not an easy task in the UMTS environment to effectively design the transport and the management of traffic belonging to multimedia teleservices, due to the difficult communication requirements of such applications. It is proposed to contemporary use at the "transport" layer of the system several bearers, one for each traffic component of the multimedia service. Furthermore, a two-level (static and dynamic) priority mechanism is to be adopted by the higher protocol levels of the UMTS for the adaptation of call set-up, channel access, and admission control procedures to the nature of the multimedia services and to optimise the sharing of radio channel resources and the management of the reservation buffer. The results achieved demonstrate that the proposed mechanism shows a good performance especially during periods in which the system traffic load is high and reacts well to the worsening of the multimedia service quality, both in terms of information loss and synchronisation of its traffic components.

Wireless-PCS systems, through the introduction of new conception control functions, aim to respond to the user expectation of high performing services and the need for flexibility in the management of disparate categories of multimedia and multi-requirement applications supported by the networks. This paper contributes to the ongoing research work in this scenario by describing some proposals for the handling of multimedia teleservices both at the transport and control level, across the wired and wireless sides of an ATM-based wireless PCS system. Admission control on both sides, mobility management in the fixed side and resource allocation renegotiation are topics on which the study focuses.