The integration of Terrestrial Networks (TN) and Non Terrestrial Networks (NTN) has been explored within the 3GPP standardization forum, and it is now being extended toward discussions on the future 6G vision. An integrated T/NTN is highly heterogeneous and requires different communication protocols and links for each layer, resulting in increased network management and control complexity. The Software Defined Networking (SDN) paradigm can enable unified and efficient T/NTN management, allowing full resource optimization of the satellites, radio access and core network. This paper proposes an optimized SDN-based T/NTN architecture, where Low Earth Orbit (LEO) satellites are dynamically selected to act as multiple SDN controllers if the terrestrial network becomes saturated or unavailable, or to jointly operate with the terrestrial controllers under the coordination of a central terrestrial controller. From this perspective, the number of the SDN controllers and their placement are of paramount importance. A multi-controller placement strategy is evaluated for theintegratedT/NTN using the Simulated Annealing (SA) plus Tabu Search methods to search for the optimal solution in terms of average latency and SDN controllers load, while accounting for the frequent topology variations inherent to LEO satellites. In addition, the design of the SDN architecture for an integrated T/NTN system, and in particular the definition of a distributed SDN control plane (CP) across both the terrestrial and satellite segments, including the specific mechanisms required to enable LEO satellites to operate as controllers, is also addressed. Extensive simulations based on realistic T/NTN topologies, specifically, the terrestrial Agis network and the Iridium NEXT satellite constellation, show that the use of multiple controllers in optimized placements both in terrestrial and satellite segments decreases the average latency and balances the load of each controller. In addition, the proposed controller switching policy adopted for the LEO segment helps to avoid frequent reassignments and improves the reliability of the overallintegratedsystem.

Software-Defined Networking (SDN) represents a disruptive paradigm with significant potential to enhance the Internet of Things (IoT) wireless domain. However, the design and implementation guidelines for this advanced framework remain an open challenge. While adaptation of centralised protocols for low-power wireless sensor and actuator networks (WSANs) led to basic Software-Defined WSAN (SDWSAN) architectures, this approach exhibits notable limitations, particularly in large-scale and dynamic scenarios. For instance, the centralised SDN controller does not only introduce a Single Point of Failure (SPoF) for the managed network but also generates substantial overhead due to control protocols and messages (often inspired by the OpenFlow standard), which can significantly degrade Data Plane (DP) performance. This paper addresses these challenges by proposing Software-Defined Hybrid Dual Stack (SOHS), a novel hybrid architecture that integrates the distributed nature of traditional WSANs within a centralised SDN management framework. By harmonising these paradigms, SOHS optimises scalability and adaptability. Furthermore, we conduct a comprehensive comparison of the proposed hybrid dual-stack control plane architecture against existing alternatives (specifically SDN-WISE, IT-SDN, and uSDN frameworks) evaluating key metrics such as availability, overhead, and end-to-end delay. Our analysis demonstrates that SOHS achieves significant performance improvements, particularly in large-scale networks with dynamic topology changes.

The modern vision of “smarter” factory processes requires the adoption of Industrial Internet of Things (IIoT) ecosystems, where the large scale use of sensors, actuators, and connected devices enable a high amount of heterogeneous data gathering and sending to data centers for analysis and monitoring purposes. However, the foundation of the Web of Industrial Things (WoIT) faces open issues due to the constraints imposed by the involved devices, the technological heterogeneity, and the complex interactions and, hence, communications patterns. Toward this paradigm, a general framework inspired by the software defined networking (SDN) principle have been here proposed, in order to jointly optimize the application requirements by minimizing end-to-end delay and, thus, prolonging the lifetime of the IIoT ecosystem. This article derives a general SDN based architecture to handle data flows in order to support industrial applications that extend the basic publish-and-subscribe scheme. Specifically, the MQTT-SN standard have been considered, since it represents a solution suited for WoIT in the presence of resources constrained devices. The proposed integrated solution has been validated in practical scenarios, pointing out remarkable performance w.r.t. the end-to-end message delivery latency, always with a limited overhead.

Satellites and aerial platforms can be significant in the development of new telecommunications networks, allowing to deploy networks with extremely high performance even in remote areas. Recently, considering the development of quantum communication technologies, many studies are concentrated on Free Space Optic (FSO) Non-Terrestrial links, also considering that the studies performed so far on Optical Fibers (OFs) have not pointed out significant results, especially in terms of coverage. Moreover, the decrease of launch costs and the use of new satellite technologies such as CubeSats make the deployment of satellite constellations affordable. Thanks to the deployment of Non-Terrestrial Quantum Networks (NTQNs), the novel services offered by the Quantum Internet (QI) could be made easily accessible to all. In particular, Quantum Computers (QCs) can perform beyond the capabilities of any classical processor, and the interconnection of these devices on a global scale makes it possible to achieve extremely high computational capabilities, thus opening the way to new applications, such as Quantum Cloud (QCloud). Therefore, the recent studies in this area motivate this survey, which in addition to providing some base concept of quantum information, describes the current technologies needed to create quantum NT backbones. Specifically, this survey examines some studies over the period 2010–2023, which are related to the realization of quantum communications using satellites and other aerial platforms such as High Altitude Platforms (HAPS) and quantum drones. Some of the architectures that are described in this survey make use of the Software-Defined Networking (SDN) paradigm, which can be envisaged as a key enabler for the management of heterogeneous QNs in general. Furthermore, through the description of various experiments, the paper shows the applications that can be enabled by the future quantum NT backbones. In particular, in addition to improving the security of current systems through the Quantum Key Distribution (QKD), it could be possible to interconnect clusters of QCs over long distances and create extremely reliable positioning systems. Finally, the paper outlines some possible future developments.

In the recent year, quantum computing and communications (QCC) represented two revolutionary technologies that are rapidly developing and integrating to interconnect heterogeneous quantum devices within the so-called Quantum Internet (QI). Despite several investigations and developments have been performed on terrestrial quantum communications over typical optical fiber links, there are some limitations in terms of extremely high losses that can be faced by deploying several repeaters, which in turns involves impractical costs for network management, especially in terms of forwarding procedures. Quantum Satellite Networks (QSNs) is capable to overcome the constraints of terrestrial optical networks, i.e., the remarkable attenuations over long distances which makes the intercontinental communications unaffordable. The recent technological developments in terms of quantum satellite communications motivated our investigation on an ad hoc quantum satellite backbone interconnecting quantum on Earth Servers in order to achieve an unprecedented computational capacity. Our aim is to investigate existing constellations, spanning from Low Earth Orbit (LEO) up to micro-satellites, to properly derive some guidelines for designing an efficient backbone. Specifically, the focus is on evaluating the impact of forwarding approaches on the end-to-end capacity (i.e., the entanglement generation rate) to achieve a trade-off between performance and cost.

The increasing diffusion of smart devices has triggered new Internet of Things (IoT) applications, where communications patterns are often in an autonomous mode. Key enabling technologies, such as relaying communications, cell size reduction and multicast communications have been identified to bring the next‐generation IoT to a complete fruition. In particular, the use of relay nodes is expected to be useful for coverage and capacity improvements, as well as to support point‐to‐multipoint services for data disseminating to subscribers communities. To this end, this study proposes a dynamic quorum links selection (DQ m ) procedure to optimise the throughput for the case of buffer‐aided relaying multicast communications. A theoretical analysis based on the Markov chain framework is provided and validated through simulation results in terms of multicast throughput and relay buffer occupancy for different sizes of the multicast group. The advantages of the proposed DQ m procedure have been highlighted by comparing the achieved performance with respect to classical conventional relay scheme. Finally, a protocol for channel state estimation is presented and the impact of the requested overhead on the performance of DQ m procedure is shown.

Spectrum sensing plays a key role in cognitive radio technology to acquire information on the occupancy status of the channel. Cyclostationary spectrum sensing is considered one of the most promising approaches. However, its performance is severely degraded by a mismatch between the actual and the nominal cyclic frequency [i.e. cyclic frequency offset (CFO)]. This is particularly true for vehicular networks, due to the high mobility and particularly to the presence of a non‐zero radial acceleration between the transmitter and the receiver that makes the signal filtered out by the Doppler channel chirped, thus introducing the CFO. Consequently, the signal to be detected has to be properly modelled as a generalised almost‐cyclostationary process. The proposed approach performs a maximum‐likelihood estimation of the CFO jointly to the detection exploiting multiple cycles, through a maximisation of the generalised likelihood ratio test. The closed‐form of false alarm probability is derived highlighting that this approach represents a constant false alarm rate detector. Numerical evaluations are provided to show the correctness of the theoretical analysis and that the performance is approximatively constant for a large range of CFO values. Moreover, comparisons with existing algorithms are provided.

Chaos theory constitutes a promising and powerful tool to address forecasting problems of nonlinear time series, since it catches the dynamical and geometrical structure of very complex systems, ensuring a superior accuracy on the predicted results in comparison to classical approaches, and lowering the complexity typical of the deep learning ones. This paper applies the nonlinear chaos theory principles to the passenger demand forecasting problem. The proposed scheme processes and analyzes the big data of passengers requests collected during one month in the city of Chengdu, China. In order to predict passenger demand behavior, the chaotic trend of the time series has been identified through the largest Lyapunov exponent research. Then, the phase space reconstruction has been pursued, through the detection of the suitable embedding dimension and time delay, to improve forecasting accuracy and avoid information redundancy. A combined local and global predictive method has been proposed, and the validity of the approach is confirmed by comparison with two state-of-art forecasting methods, the auto-regressive and the auto-regressive moving-average with exogenous input. System performance is evaluated in terms of mean squared error and mean percent forecasting error.

This paper proposes two virtual functions (VFs) placement approaches in a Fog domain. The considered solutions formulate a matching game with externalities, aiming at minimizing both the worst application completion time and the number of applications in outage, i.e., the number of applications with an overall completion time greater than a given deadline. The first proposed matching game is established between the VFs set and the fog nodes (FNs) set by taking into account the ordered sequence of services (i.e., chain) requested by each application. Conversely, the second proposed method overlooks the applications service chain structure in formulating the VF placement problem, with the aim at lowering the computation complexity without loosing the performance. Furthermore, in order to complete our analysis, the stability of the reached matchings has been theoretically proved for both the proposed solutions. Finally, performance comparisons of the proposed matching theory approaches with different alternatives are provided to highlight the superior performance of the proposed methods.

Fog Computing (FC) is an emerging paradigm that extends cloud computing toward the edge of the network. In particular, FC refers to a distributed computing infrastructure confined on a limited geographical area within which some Internet of Things applications/services run directly at the network edge on smart devices having computing, storage, and network connectivity, named fog nodes (FNs), with the goal of improving efficiency and reducing the amount of data that needs to be sent to the Cloud for massive data processing, analysis, and storage. This paper proposes an efficient strategy to offload computationally intensive tasks from end-user devices to FNs. The computation offload problem is formulated here as a matching game withexternalities, with the aim of minimizing the worst case service time by taking into account both computational and communications costs. In particular, this paper proposes a strategy based on the deferred acceptance algorithm to achieve the efficient allocation in a distributed mode and ensuring stability over the matching outcome. The performance of the proposed method is evaluated by resorting to computer simulations in terms of worst total completion time, mean waiting, and mean total completion time per task. Moreover, with the aim of highlighting the advantages of the proposed method, performance comparisons with different alternatives are also presented and critically discussed. Finally, a fairness analysis of the proposed allocation strategy is also provided on the basis of the evaluation of the Jain’s index.

This paper proposes a channel allocation scheme for Wide-Area Low-Rate Wireless Personal Area Networks (LR-WPAN) based on a cooperative centralized spectrum sensing approach. We refer here to a three-tiers LR-WPAN architecture, where we can distinguish the sensor devices level, the Child-coordinators level and, finally, the super LR-WPAN coordinator level. In the proposed scheme, channels allocation is performed by the LR-WPAN coordinator upon receiving the spectrum sensing reports from the Child-coordinators. The performance of the proposed scheme is evaluated in terms of resulting detection probability and throughput, in a scenario where Industrial, Scientific and Medical (ISM) bands are saturated and different LR-WPANs compete to the channel access. Performance comparisons with a classical scheme where the channel allocation is accomplished without performing spectrum sensing, are also presented in order to highlight the advantages of the proposed scheme.

This paper analyzes the resource allocation problem in the LTE-Unlicensed spectrum to increase performance of the unlicensed systems. The problem is modeled with a matching game approach and the proposed resource allocation algorithm consists of a heuristic based on the usage of preference lists, one for each user equipment (UE) and on unlicensed bands, to determine a many-to-many matching between UEs and component carriers (CCs), aiming at maximizing the unlicensed overall network sum rate. Hence the proposed algorithm realizes a mapping between user equipments and unlicensed channels, also considering the carrier aggregation (CA) mechanism, which is typical of LTE-U. In the simulation evaluation, we compare the proposed algorithm with the Hungarian algorithm w.r.t. the system throughput and the robustness to perturbed input data. Both algorithms have almost equivalent performances, but the Hungarian algorithm presents a higher computational complexity than the proposed one.

Simple connectivity and data requirements together with high lifetime of battery are the main issues for the machine-to-machine (M2M) communications. 3GPP focuses on three main licensed standardizations based on Long Term Evolution (LTE), GSM and clean-slate technologies. The paper considers the last one and proposes a modified slotted-Aloha method to increase the capability of supporting a massive number of low-throughput devices. The proposed method increases the access rate of users belonging to each class considered in the clean-slate standard and consequently the total throughput offered by the system. To derive the mean access rate per class, we use the Markov chain approach and simulation results are provided for scenarios with different data rate and also in terms of cell average delay.

Device-to-device (D2D) communications enable the proximity communications among users with or without the use of the network infrastructure. D2D communications can increase the overall spectrum efficiency and reduce the power consumption thus a massive utilization of D2D is expected in the future 5G networks. The paper proposes a D2D resource allocation method based on the reuse of primary uplink resources. The method guarantees both a fixed quality of service (QoS) for D2D communication as well as the assigned QoS for cellular communications. It relies on the estimation of distances of all the actors related to D2D position: D2D pairs, base station and the primary devices. These distances are used to evaluate the minimum D2D transmission power which guarantees the D2D reception and jointly produces a controlled and acceptable level of interference on the primary system. The performance of primary system achieved by the proposed method is compared with the one of an unaware interference approach. The results obtained for the scenario with a D2D pair show how the method can limit the interference on primary system. For the scenario with different D2D pairs, the results highlight a better scalability with respect to the other method.

This paper proposes and compares different policies to perform the optimal link selection in the presence of buffer-aided relay for multicast communications. These policies are based on the knowledge of the instantaneous link quality indicators as well as the status of the relay buffer, and dynamically select the more suited link according to a deterministic or random criterion, whose parameters are optimized via a Markov chain theoretical framework. The performance for all the proposed methods are analytically derived and validated through intensive computer simulations for different multicast scenarios. The advantages of the proposed schemes are pointed out in terms of multicast throughput, buffer occupancy for different buffer size and multicast group size.

Power line communication technology receives today a renewed attention for a wide class of advanced applications and services, thanks to the advantage of using the existing electrical infrastructure, which requires only limited deployment costs. However, wires have been originally designed for power and not for data, and signal propagation is affected by several impairments such as impulsive noise and frequency selectivity. On the other end, new emerging application perspectives-mainly related to the smart grid or Internet of Things paradigms-need reliable unicast and/or multicast information delivery methodologies. This paper deals with an efficient multicast power line communication system based on the use of a decision direct impulsive noise mitigation scheme and of multiple transmissions of symbols in the frequency domain, allowing an efficient exploitation of the communication channel frequency diversity. The performance of the reliable multicast power line communication system is derived by resorting to the application of the absorbing Markov chain theory in terms of mean overall delivery delay and throughput, in relation to different application scenarios. Moreover, a suitable optimization procedure is also proposed here in order to achieve the best performance. The advantages of the proposed optimized reliable multicast power line communication system are finally validated by comparisons with a classical system.

Abstract The impressive increase of innovative wireless communication technologies and applications represents nowadays a key approach to enable pervasive communications environments. In particular, the emerging paradigms of the Internet of Things and capillary networks offer effective ways to make devices connected. This has triggered the development of effective methodologies and procedures to allow an unlimited number of devices to exchange information mainly in an autonomous mode. However, it is a well‐known concept that wireless networks capacity usually decreases with the number of nodes. In particular, in order to improve the throughput scalability, a promising approach is that of resorting to the use of multiple radio interfaces at each node, in order to exploit spatial reuse of frequencies. Towards this end, game theory methodologies offer efficient approaches to solve the complex radio interfaces selection and allocation problems. This paper proposes a game theory‐inspired approach to efficiently select the number of radio interfaces to be used at each node site in order to lower the energy consumption and maximise the end‐to‐end throughput of any communication on which the node is involved in. The good behaviour of the proposed approach is validated by provided theoretical framework and numerical results derived by considering different data packets wireless forwarding schemes. Copyright © 2015 John Wiley & Sons, Ltd.

Long Term Evolution-Advanced (LTE-A) and the evolved Multimedia Broadcast Multicast System (eMBMS) are the most promising technologies for the delivery of highly bandwidth demanding applications. In this paper we propose a green resource allocation strategy for the delivery of layered video streams to users with different propagation conditions. The goal of the proposed model is to minimize the user energy consumption. That goal is achieved by minimizing the time required by each user to receive the broadcast data via an efficient power transmission allocation model. A key point in our system model is that the reliability of layered video communications is ensured by means of the Random Linear Network Coding (RLNC) approach. Analytical results show that the proposed resource allocation model ensures the desired quality of service constraints, while the user energy footprint is significantly reduced.

This paper focuses on a particular application of coalitional game theory to Vehicular Ad Hoc Networks (VANET), involving only vehicular-to-vehicular communications. Moreover, networking is performed in an ad hoc basis to pursue full context awareness of vehicles. The proposed approach relies upon the setting up of cluster as soon as convoys temporarily arise in traffic dynamics. First, we define a utility function for each node under the hypothesis of being an ordinary node, cluster head or free node. We further prove that a selfish approach is suboptimal when compared to a game of coalition. Then, the communication between clusters (inter clusters communications) has been implicitly modelled according to this approach. Finally, from the simulation results, it is shown that a coalitional game outperforms a selfish approach for different nodes spatial deployment and mobility patterns.

Software-Defined Networks (SDNs) based approaches represent an opportunity for easing the deployment and the management of wide-area wireless network services. In this paper, we focus on a particular SDN management mechanism that wireless infrastructure providers need to adopt to support such services: the wireless virtual network (VN) embedding problem. We formulate the problem leveraging on optimization theory, analyzing its complexity, and proposing a general distributed auction mechanism. This mechanism leverages on the max-consensus literature to guarantee bounds on the embedding time and on the performance with respect to a Pareto optimal solution. Using extensive simulations, we confirm superior resource utilization when compared with existing distributed VN embedding solutions, proving to be an attractive and flexible resource allocation approach for wireless SDNs.

This paper deals with the performance evaluation and optimization of an efficient Hybrid Automatic Repeat Request (HARQ) scheme suitable for applications delivered over lossy multicast communication channels. In particular, differently from previously investigated strategies, this paper proposes a Modified HARQ scheme based on the Symbol Combining principle (MHARQ-SC) where multiple copies of a same packet are consecutively transmitted at each transmission opportunity. By considering as performance metrics the mean packet delivery delay and energy consumption per information packet, this paper presents suitable performance evaluation and optimization strategies tailored for multicast communications. For the sake of comparisons, it has been also analysed, under the same operational conditions, the performance of different HARQ schemes optimized for multicast communications. Numerical results have been provided in order to validate the proposed performance evaluation and optimization approaches in the case of the MHARQ-SC scheme. An important result devised here is that the reported analytical results clearly highlights the performance gain of the proposed strategy in comparison with all the other considered alternatives.

In this paper we propose couple power allocation strategies for layered video services delivery over evolved Multimedia Multicast/Broadcast Service (eMBMS) networks. The proposed allocations aim at reducing the power consumption of the eNodeB (eNB) and improving the user quality of experience characterizing the delivered eMBMS flows. We consider multiple challenging scenarios which differ by: (i) the number of eNBs transmitting the same service set, and (ii) how services are delivered. In particular, we consider scenarios where services can be delivered by resorting to the Random Network Coding principle or not. We compare the proposed resource allocation models to a strategy which equally shares the transmission power budget among layers of the delivered service. Analytical results show that the proposed resource allocation strategies are characterized by a transmission power which is on average 13% smaller than the considered alternative. In addition, the optimized resource allocation can deliver each layered video service over a geographical area which is up to 25% greater than that associated to the considered alternative.

This paper deals with a clustering approach for VANETs operating in highway scenarios, where a certain degree of correlation among vehicles emerges such that a group mobility pattern is expected. The proposed protocol is inherently mobility driven as the reference metric to select a Cluster Head (CH) takes into account the node connectivity within an estimated coherence time interval. Our clustering protocol handles both cluster set up and maintaining and communications among different clusters. In particular, the inter cluster communications are accomplished by means of relay node selection. The protocol design and validation have been focused on a practical scenario adopting IEEE 802.11p communication standard, highlighting good performance in terms of connection probability, overhead and complexity.

Machine-to-Machine (M2M) communications are gaining momentum due to the rapid deployment of smart devices with self-organizing capabilities, able to interact each other without the human operator support. Ultimately, M2M paradigm allows Machine-Type Communication Devices (MTCD) to exchange data in Peer-to-Peer (P2P) mode, avoiding the need of a core network handling end-to-end communication establishment between two machines. To this end, the recent Device-to-Device (D2D) feature, introduced by the Third Generation Partnership Project (3GPP) Release 12, fosters new types of service based on the device proximity concept and helps to offload cellular networks by enabling direct-mode communications among cellular users. Furthermore, D2D is also considered a suitable technology to fully support M2M communications thanks to the reduced power consumption and the hop gain. In this paper we first review crucial aspects of M2M communications and examine major issues involving terminals operating in D2D mode in LTE-A networks. Then, a multi-hop D2D communication scheme is proposed in order to enhance end-to-end connectivity among devices in a proximity area within an LTE-A cell. We also describe a promising resource allocation approach aware of the multi-hop D2D network configuration, able to fulfil bandwidth requests of all the cooperating devices, according to the related role in the network set-up.

ABSTRACT This paper proposes a new method of data authentication and encryption for distributed networks supporting mobile software agents. Software agents are a valuable instrument in wireless distributed monitoring networks, because they can be used to concentrate monitoring efforts in certain areas where an event is taking place. In this way, events can be tracked in a dynamic and efficient way. Mobile agents have to send messages to each other in order to coordinate their actions, and those messages need to be secured by crypto credentials. However, when agents are moved over wireless networks, how can credentials be protected from sniffing by an attacker, besides layer II encryption? Moreover, if a rogue agent is injected in the network, is it possible to limit the damages it can produce? The proposed approach bridges mediated RSA with the trusted platform modules, in order to provide an efficient and secure communication between agents. The communication is secured using indeed Identity based cryptography, while maintaing the compatibility with standard RSA and eliminating the mediator introduced by mediated RSA. We will show that this approach is convenient in terms of traffic overhead, perfectly applicable to existing trusted platform modules specifications and able to limit damages that both external and internal attackers can produce to the network. Copyright © 2013 John Wiley & Sons, Ltd.

This paper deals with the issue of reliably transmission of short messages through satellite. The problem is of paramount importance for emergency and alerting scenarios. In particular, we propose a novel efficient Network Coding (NC) communication scheme aiming to improve the delivery probability of the transmitted information messages. A suitable analytical approach has been developed in order to highlight the performance of the proposed NC scheme and to allow its optimization. The accuracy of the proposed approach has been validated by resorting to computer simulations. Performance comparisons with the classical NC scheme are also presented here to highlight the advantages of the proposed NC scheme in the case of AWGN and Rician communication channels.

In this paper, we propose a novel advanced multirate design for evolved Multimedia Multicast/Broadcast Service (eMBMS) in fourth generation (4G) Long-Term Evolution (LTE)/LTE-Advanced (LTE-A) networks. The proposed design provides: i) reliability, based on random network coded (RNC) transmission, and ii) efficiency, obtained by optimized rate allocation across multi-rate RNC streams. The paper provides an in-depth description of the system realization and demonstrates the feasibility of the proposed eMBMS design using both analytical and simulation results. The system performance is compared with popular multi-rate multicast approaches in a realistic simulated LTE/LTE-A environment.

This paper deals with the application of the so called Internet of Things paradigm to the setting up of intelligent and cooperative environments. In particular, it focuses on the management of wide area Wireless Sensor Networks comprised of objects belonging to the logistic domain with the aim of transparent managing them. The IPv6 global addressing is applied allowing the dynamic tracking, information upload and retrieval and nodes management, while coping with inherent mobility. The proposed solution has been adopted in a real world case study, pointing out flexibility and responsiveness.

This paper deals with a clustering approach for VANETs operating in sparse highway scenarios. The proposed protocol is able to keep high and stable the network connectivity level to allow data exchange among nodes and, thus, achieving context awareness. The criterion adopted in forming a cluster involves the periodic distributed evaluation of connectivity indicators combining the number of neighbors and their distances, without excessive signaling overhead. In this way, data propagation leverages on vehicles physical movements instead of setting up a communications backbone, which can not properly face a high mobility level. The performance has been analyzed in a practical scenario adopting IEEE 802.11p communications standard. In particular, the election period has been optimized for different coverage ranges, pointing out the suitability of the proposed metrics.

This work focuses on providing effective end-to-end (E2E) communications for critical monitoring applications through Wireless Sensor Networks. In particular, the case of frequent disconnection and reconnection has been analyzed, deriving effective routing strategies to cope with this problem. Basing on a recent IETF draft scheme, namely RPL, capable of accommodating several practical situations, a novel approach, called eN Route (NR), has been proposed. In particular, it relies on a two tier network architecture with a hybrid tree-mesh topology, which can be locally rearranged depending on link failures, mainly due to mobility. This is done in a completely distributed way by maintaining a specific neighbor table built only by sniffing data messages to not increase the signaling overhead. The proposed solutions functionalities have been described and compared in terms of connectivity efficiency, E2E path length distribution and E2E latency statistic, giving also some figures on overhead. The analyses have shown NR to achieve better results in in terms of network connectivity latency and overhead, despite some drawbacks, even though RPL is able to achieve comparable performance at the expenses of higher signaling overhead. As a consequence, it has been pointed out the way RPL future releases can profit from NR approach to improve performance.

This paper proposes an energy efficient antennas allocation method for network-coded MIMO multicast communications. By means of the definition of a suitable objective function it is shown that it is possible to select the optimal number of antennas in transmission/reception and the most convenient modulation scheme in order to minimize both the overall mean energy consumption and delivery delay. Simulation results are provided in the paper in order to validate the proposed optimization method and to highlight its advantages in comparison with similar rate-based approaches already proposed in literature, where symbol error rate is evaluated as a comparing metric for MIMO performance.

In this paper we propose an end-to-end solution for urban infrastructure-to-vehicle traffic data delivery based on a class of unequal error protection (UEP) rateless codes called expanding window fountain (EWF) codes. The proposed solution relies on attractive features that rateless codes introduce to networks with unpredictable dynamics: the universal capacity approaching property which is well-matched to time-varying behavior of wireless links, and the innovative nature of each encoded packet which makes both time-consuming retransmission and content-reconciliation mechanisms unnecessary. Furthermore, usage of EWF codes allows separation of delivered data in importance classes with different error protection and recovery time guarantees, enabling mobile users to retrieve more important information more reliably and in shorter time span, thus making the proposed solution suitable for time-critical services. The addressed urban communication scenario consists of large number of sensors that sample and relay traffic flow information to network of Access Points (APs). APs use the existing underlying communication infrastructure, such as metropolitan area networks (MANs), to exchange traffic flow data, encode it using EWF coding principles, and finally disseminate it to roaming vehicles that join the network service in an ad-hoc manner in order to retrieve information regarding the surrounding environment. The proposed approach is suitable for real-time applications, such as frequent periodic reporting of urban traffic conditions, that could be used by on-board computers to provide improved navigation for end-users.

In this paper, an enhanced access protocol minimizing message delivering latency is proposed. It is basically based on modified version of Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol in which one sensor at a time is allowed to deviate from standard rules behaving like a cheater and keeping the Contention Window (CW) fixed and equal to the minimum value. The proposed scheme efficiency is proved resorting to game theoretic framework, while its performance is analytically derived through a Markov model for a worst case conditions. Focusing on Wireless Body Area Networks (WBANs) application scenario, main system figures, in terms of delivering delay and dropping probability, are further pointed out by means of numerical simulations, highlighting optimal agreement with theoretical results as well as the protocol suitability for critical situation management.

In this paper, an approach minimizing delivery latency, while keeping transmitted power below a certain threshold, is proposed to provide reliable real time wireless communications when applying network coding principle in order to point out additional advantage in terms of capacity. An analytical tool is proposed to derive the performance of optimal power adaptation scheme NC scheme aiming at minimizing the number of coded packets transmitted on a link-by-link basis, thereby lowering the end-to-end delay and overall power consumption.

Location awareness in wireless sensor network (WSNs) application is often too expensive to be achieved by endowing each node with use a GPS receiver. Approach based on range-free methods, where nodes can estimate their location basing on neighbors and nodes that known their position (anchors), can be envisaged. This paper deals with the optimization of APIT algorithm in wide area WSN scenario for critical scenarios applications.

This paper presents a data gathering scheme designed for an emergency monitoring Wireless Sensor Network (WSN), which employs distributed rateless encoding and dispersion of the encoded data toward the perimeter of the monitored area, where it is collected by a mobile collector (MC). Rate-less codes are low encoding/decoding complexity codes, suitable for resource constrained devices, such as sensor nodes, while the proposed distributed encoding and dispersion, performed using only local knowledge, are adapted to WSNs where the frequent changes in underlying topology and connectivity are expected. The proposed scheme allows for data persistence and efficient data gathering in the scenarios where decentralized WSNs are deployed in inaccessible locations with no infrastructure support, where nodes are prone to failures due to harsh operating conditions and where the access of the MC to the monitoring area is severely limited.

In this paper, we propose a novel approach for data gathering in wireless sensor networks (WSN) based on distributed rateless codes. Rateless codes are an efficient, lowcomplexity solution for coded data transmission over channels with packet erasures, which motivates their application in distributed network scenarios such as WSN. Recently proposed distributed rateless coding techniques for WSN are node-centric, i.e., collecting sufficient number of different sensor data packets and performing rateless encoding is the task of sensor nodes. In the proposed packet-centric approach, this task is assigned to encoded packets called rateless packets. While randomly moving through the network, rateless packets collect and encode into their content required number of uniformly sampled sensor data packets, completing their paths in randomly selected network nodes. Using this approach, any degree distribution of rateless codes can be exactly obtained. The problem of uniform combining of sensor data into rateless packets, and uniform dispersion throughout the network is addressed. The efficiency of the proposed scheme and comparison with the performance of centralized rateless codes are demonstrated by simulation results.

This paper deals with the evaluation of the end-to-end packet delay for a lossy network where network coding is adopted to achieve better performance. Differently from previous published papers on this subject, connection oriented services are assumed, this means that packets have to be in-order received and wait at the receiver buffer till all the previous ones have been correctly delivered. The focus is on a network model where two source nodes broadcast packets to a group of two sink nodes over lossy wireless channels. Three different alternatives have been considered in order to assure a reliable data multicasting, namely: a classical random linear network coding scheme, a linear network coding combined with a basic ARQ or, alternatively, with a soft combined ARQ scheme. Performance comparisons provided by means of analytical and numerical results clearly highlight that the better solution is to adopt the latter alternative.

This paper deals with the application of Kalman filtering (KF) techniques to the localization of a swarm of mobile agents in a wireless sensor network (WSN). In particular, both extended (EKF) and unscented (UKF) Kalman filters have been investigated referring to a typical urban scenario with energetic and resource constraints. A cooperation strategy among sensor nodes, based on a virtual diversity scheme, has been introduced allowing the swarm tracking under severe propagation conditions. The effectiveness of the proposed solution has been assessed by means of simulations concerning a squad of robots moving in realistic scenarios. It has been shown that UKF achieves a higher accuracy and reliability than EKF in localizing the barycenter of the robot squad. Further, the proposed solution provides advantages in terms of measurement update frequency and, hence, of energy saving.

This paper deals with a communication infrastructure needed to allow a swarm of robots performing dust cleaning and garbage collection task in an urban area. It outlines the required communication links, analyses them regarding security, describes in details the implementation and figure out some performance test results.

In this paper, we propose a novel approach for data gathering in wireless sensor networks (WSN) based on distributed rateless codes. Rateless codes are an efficient, low-complexity solution for coded data transmission over erasure channels, which motivates their application in distributed network scenarios such as WSN. Recently proposed distributed rateless coding techniques for WSN are node-centric, i.e., the task of collecting sufficient number of different sensor data packets and performing rateless encoding is responsibility of sensor nodes. In the proposed packet- centric approach, this task is assigned to encoded data packets called rateless packets. While randomly moving through the network, rateless packets collect required number of uniformly sampled sensor data packets, finishing their paths in randomly selected network nodes. Using this approach, any degree distribution of rateless codes can be exactly obtained. The problem of uniform combining of sensor data into rateless packets, and uniform dispersion throughout the network is addressed. The efficiency of the proposed scheme and its comparison with the performance of centralized rateless codes are demonstrated by simulation results.

This paper deals with a wireless pervasive communication system to support advanced healthcare applications. The proposed system is based on an ad hoc interaction of mobile body sensor networks with independent wireless sensor networks already deployed within the environments in order to allow a continuous and context aware health monitoring for patients along their daily life scenarios with an unprecedented precision and flexibility of sensing. After an accurate protocol characterization, simulation results are provided, underlining remarkable performance with respect to existing solutions, for different mobility models and node density values.

Wireless sensor networking (WSNing) is drawing the attention of both scientific and industrial communities as it represents a low cost and effective approach to develop intelligent environments. As a result, a remarkable effort is nowadays spent to standardize a reference communication platform, as far as the PHY and MAC layers are concerned. Recently, indicated as IEEE 802.15.4a standard, IR-UWB technology is an efficient candidate for PHY layer, due to its high transmission rate and the additional benefit of localization capability. This paper deals with a localization scheme that makes use of an innovative time of arrival protocol based on dirty templates correlation, with the aim of improving their performance in noisy channels. Achieved results point out the suitability of the proposed approach for several realistic scenarios, despite the fact that the ranging accuracy is reduced by the influence of long term fading effects.

Abstract In this paper, we present the comparison between a distributed and a centralized authentication protocol for wireless sensor networks (WSN). We outline the difference between authentication and key‐agreement schemes and we propose a novel approach based on the use of polynomial functions to produce a distributed bi‐directional authentication. The advantages of this approach are: speed of operation that can allow multiple subsequent authentications, thus support to mobility; balanced energy consumption if compared with the imbalanced centralized approach and the prevention of partition attacks. Copyright © 2008 John Wiley & Sons, Ltd.

This paper deals with a class of localization protocols conceived for applications to wireless sensor networks (WSN), in the presence of typical energetic and resource constraints. It has been supposed that only one mobile anchor node is always localized by resorting to global navigation satellite system (GNSS) support system. The first scheme proposed (GNSS Alone, GA) assumes that sensor nodes may interact only with this anchor node to evaluate their own positions. In addition to this, a smart cooperation strategy among sensor nodes, i.e., GNSS in ranging (GIR) scheme, has been introduced to face possible anchor node outage, due to hostile operation scenario. The proposed solutions have been in-depth characterized and evaluated within a practical scenario. The obtained results point out the protocol localization accuracy, latency and overhead, with respect to the nodes density. According to this, the most suited applications for both GA and GIR approaches are indicated.

This paper deals with the problem of supporting sink mobility in a wireless sensor network. It focuses on a specific scenario, where mobile nodes act themselves as both end-users, when querying the WSN for specific information, and as sinks, when gathering the queried data. Due to the mobility of users and to the topology of the network, sinks experience frequent disconnections from the WSN. A system architecture, and the related protocols, capable of supporting the envisioned application domain has been proposed. The performance of the proposed system architecture has been evaluated by means of simulative studies, together with addressing the impact of mobility, deployment geometry and routing parameters.

This paper deals with a system level design solution to support information gathering in the presence of a mobile querying node that experiences frequent disconnections from a Wireless Sensor Network (WSN), an application scenario that embraces the area of Intelligent Transportation Systems (ITS). The proposed scheme basically relies on the network capability of autonomously adapting to sink mobility in order to properly deliver the requested data. The system is defined as far as its functional elements and related communications protocols, together with validating its effectiveness by means of a simulative study. In particular, the performance in terms of delivering latency and packet delivery ratio has been investigated for several network topologies, architecture and mobility pattern, always highlighting a remarkable quality of provided services together with robustness with regard to operative conditions.

The adoption of wireless sensor networks (WSN) for wide area environmental monitoring is currently considered one of the most challenging application scenario for this emerging technology. The promise of an unmanaged, self-configuring and self-powered wireless infrastructure, with a continuously decreasing cost per unit, attracts the attention of both final users and system integrators, replacing previously deployed wired solutions and opening new business opportunities. This challenge might be afforded by resorting to a complete system level design to jointly address and optimize all the involved aspects. Besides, the design guide lines need to be inspired by the application requirements rather than technology driven. Following this approach, this paper presents an overall solution focusing both on node, network and remote user interface issues. The proposed platform in finally applied to a realistic user defined scenario oriented to agro-food production phase monitoring within GoodFood Integrated Project. The results of the validation phase presented highlight remarkable advantages both in terms of cost and complexity reduction and experienced QoS enhancement as well and, consequently, validating the WSN technology adoption.

This paper deals with the performance evaluation of an efficient medium access control (MAC) technique based on the use of an adaptive modulation and coding (AMC) scheme that significantly improves the downstream data rate and guarantees specific quality of service (QoS) requirements in wireless communication systems. Basically, the access scheme considered in this paper relies on physical channel monitoring and state mapping into a variable rate packet format. In particular, a suitable analytical model is proposed herein in order to predict the system performance, i.e., the average packet queuing delay in the case of a non-stationary transmission channel. Comparisons between analytical predictions and simulation results are provided to validate our model and highlight the improvement of the AMC technique with respect to a static rate allocation scheme, especially in the case of heavy tailed traffic conditions.

The adoption of wireless sensor networks (WSNs) in several key applications has recently became affordable thanks to technological advancements, leading to the definition of IEEE 802.15.4 standard. However to realize reliable end-to-end application by means of unreliable elements (since nodes usually cope with several limitations in terms of power supply, maintenance, hardware and software resources), a great deal of work needs to be done to design and optimize proper communications protocols. In particular, the medium access control (MAC) layer issues seems to be the most challenging in realizing such a system. In this paper, a novel class of MAC layer protocols, optimizing IEEE 802.15.4 basic scheme, is proposed. In particular, to enhance the overall performance, we resort to an adaptive approach able to dynamically vary the duty cycle at each node basing on the traffic load estimation. To this purpose, we first analyze an ideal algorithm, according to which, the traffic load is exactly known at the coordinator side. Moreover, we propose a real version of the MAC protocol in which the traffic amount is estimated by means of the channel occupation. Simulations performed on a realistic scenario point out remarkable gain both in term of communications efficiency, link throughput, node lifetime and adaptability in comparison with the static scheme.

The adoption of Wireless Sensor Networks (WSN) for wide area environmental monitoring is currently considered one of the most challenging application scenario for this emerging technology. The promise of an unmanaged, self-configuring and self-powered wireless infrastructure attracts the attention of both final users and system integrators, replacing previously deployed wired solutions and opening new business opportunities. Even if many habitat monitoring applications usually do not provide for strictly real-time performances, however, smart power saving procedures have to be adopted, especially to increase the network lifetime. A common approach is to introduce a low power sleep mode, in which the node's radio section is switched off. In adhoc networking scenarios, this definitely requires the adoption of synchronization procedures, properly scheduling the packet transmission time and avoiding both overhearing effects and collisions. In this paper, a novel class of MAC layer protocols, named STAR MAC, that aims at efficiently managing the node's low power mode, is presented, and properly integrated within a routing scheme, according to the cross-layer design for minimizing the signaling overhead. The proposed solution is applied to a realistic user defined scenario oriented to agro-food production phase monitoring, highlighting remarkable advantages both in terms of cost and complexity reduction and QoS enhancement as well and, consequently, validating the WSN technology adoption.

In this paper, an analytical framework aiming at evaluating the performance, in terms of both buffer occupation and packet delay, for an ARQ-SR protocol application in wireless communications has been proposed. The present analysis involves a general communication channel model including both shadowing and fading effects. In particular, following a hierarchical approach, it has been modeled as a time discrete nested Markov chain. Moreover the traffic source model has been assumed as Markovian. The accurateness of the proposed solution has been validated by means of numerical simulation under several practical scenarios, as far as the physical channel and the traffic model are concerned. In particular, three different traffic models have been taken into account, always highlighting a remarkable accordance between the analytical predictions and numerical results.

In this paper, a middleware architecture that enables transparent inter-operability between two different wireless networks is presented. In particular, access to the communication channel is maintained by adaptively switching between GPRS (General Packet Radio Service) and Bluetooth interfaces, both established automatically with the assistance of an RFID tag. The access channels are continuously monitored, allowing the device to switch to the Bluetooth interface, whenever this lower-cost alternative is available. A preliminary field trial has been set up, which has demonstrated the effectiveness of the approach in supporting seamless handover procedures within a heterogeneous network as envisioned for future wireless communications systems.

In this paper we evaluate the energy, event delivery, and delay performance of a number of medium access control protocols suitable for ultra-wideband (UWB) physical layer. While ultra-wideband is a promising technology, it creates unique challenges in MAC protocol design. Firstly, we analytically inspect the energy consumption of three UWB suitable MAC protocols and secondly concentrate on simulation of the IEEE 802.15.4 MAC and its UWB version. Comparison between UWB and direct sequence radios with the 802.15.4 MAC protocol clearly show the superior performance of UWB technology

Ultra-wideband (UWB) systems have been envisaged as optimal candidates to provide high data rate communications within short range. In this paper, a novel cross-layer approach suitable for TH-UWB systems is proposed, named punctured hopping (PH). PH scheme permits to limit the throughput reduction of the basic full rate turbo coding scheme, while maintaining the same code free distance. The proposed coding scheme performs parity bits puncturing. However, different from the rate compatible punctured turbo codes (RCPTC) scheme, it works on the idea that the less significant bits in a coded frame are not completely discarded as only half of their impulses are punctured. Thus preserving the error correcting capabilities jointly with a better spectral efficiency. The performance of the proposed PH coding scheme has been examined using theoretical analysis in additive white Gaussian noise channel and simulations in a realistic multipath fading channel. It has been compared with the uncoded, the basic full rate, and the RCPTC systems in order to underline its effectiveness. The results show a significant performance gain in comparison with the RCPTC and, hence, a significant reduction of the performance loss in comparison with the basic full rate turbo coding scheme, while maintaining the same throughput of the RCPTC.

In this paper, an efficient adaptive link control (ALC) technique is presented with the aim of improving the throughput, and preserving quality of service (QoS) requirements in wireless data communication systems. Basically, the proposed access scheme relies on selecting different modulation and coding schemes (MCS) in relation to the channel propagation conditions estimated by means of acknowledgment messages. Further, two different strategies for selecting the most suitable MCS are proposed and optimized. Comparisons with the static rate allocation scheme highlight a remarkable gain even in the presence of heavy tailed traffic conditions and significant user mobility

This paper deals with a novel cross-layer approach, involving both physical and data link layers, suitable for TH-UWB systems, named punctured hopping (PH). PH scheme permits to limit the throughput reduction of the basic full rate turbo coding scheme, while maintaining the same code free distance. The proposed coding scheme performs a puncturing of the parity bits, but, differently from the rate compatible punctured turbo codes (RCPTC) scheme, the less significant bits within a coded frame are not completely discarded as only half of their impulses are punctured, thus preserving the error correcting capabilities jointly with achieving a better spectral efficiency. The performance of the proposed PH coding scheme has been derived in an indoor multipath fading channel and compared with the uncoded, the basic full rate and the RCPTC systems. The results show a significant performance gain in comparison with the RCPTC and, hence, a significant reduction of the performance loss in comparison with the basic full rate turbo coding scheme, while maintaining the same throughput of the RCPTC

Precision agriculture (PA) represents a novel paradigm for managing agro-food production, by monitoring the physical parameters of different farming zones. This might be pursued by means of different communication infrastructures, but the most promising technology seems to be the wireless sensor network (WSN). However, merely applying this approach to the PA context, while resulting in a more flexible communication platform, still exhibits a rigid information management architecture. This limitation can be overcome by applying the ambient intelligent (AmI) paradigm to create an environment highly interactive with all the users involved in the process. Our proposal deals with the porting of the AmI concepts on a highly-integrated WSN platform with a special focus on the routing strategies. In particular, we investigate a class of dynamic flooding algorithm which is aware of the status of neighbor nodes in terms of geographical position and residual battery charge. By comparing this approach with the gossiping and the static flooding schemes, we are able to highlight a remarkable improvement in the network life-time with a particular regard to the most solicited nodes, without increasing complexity.

This paper deals with an efficient dynamic bandwidth allocation technique is presented based on traffic prediction. In particular, the self-similar traffic modeling is herein considered and the accuracy of several prediction techniques is taken into account. With the aim of improving the overall system performance a corrective factor is introduced applying it to predicted traffic level. This approach is then applied to a satellite IP network based on the DVB-RCS standard highlighting the noticeable advantages of the proposed allocation policy in terms of link delay both in the case of a single traffic class and in a multiclass environment based on the DiffServ model.

This paper presents the design, the analysis and the optimization of some efficient channel coding schemes for the enhanced data services provisioning within next generation wireless systems, specifically the TETRA Release 2 system. Three different turbo codes schemes are compared: the parallel and serial concatenation of convolutional codes, respectively, PCCC and SCCC, and block turbo coding (BTC). Basing on the specific-services, some practical rules are drawn to lead to an efficient codes design, while respecting the physical and MAC layers features. By means of numerical simulations, SCCC are proved to outperform not only BTC but also PCCC, though the latter is the scheme widely accepted within the majority of communications standards. Besides, the advantages obtained both in terms of performance and complexity, afford the high-speed, interactive and QoS-oriented multimedia services supply.

In this paper, a middleware architecture allowing the transparent mobility among two different wireless networks is presented. The proposed scheme is basically based on adaptively maintaining the access to the communication channel for a mobile client enabled with GPRS (General Packet Radio Service) and Bluetooth interfaces. In particular, both the GPRS and the Bluetooth connections are automatically established by means of an RFID tag. To validate this architecture, a preliminary field trial have been set up pointing out the effectiveness of the proposed approach in supporting seamless handover procedures within a heterogeneous network.

Wireless local area networks represent one of the most interesting technological improvements in the last period. Many people are using WLAN commonly just to connect to the Internet or for e-mail downloading. WLAN do not offer at the moment a satisfactory QoS support for multimedia traffic. The aims of the IEEE 802.11e standard is to develop some schemes for supporting multimedia traffic in an in-home environment. On the other hand, in the last few years link adaptation has gained a lot of attention due to its improvement to the channel occupancy and capacity optimization. In this paper a link adaptation algorithm suitable for using in a WLAN, based on the IEEE 802.11e draft, with QoS support is proposed.

In this paper, a medium access control (MAC) technique for wireless systems that efficiently manages adaptive modulation and coding (AMC) schemes is presented with the aim of improving the downstream data rate, together with preserving quality of service (QoS) requirements. Basically, the proposed access scheme relies on physical channel monitoring and state mapping into a variable rate packet format. A suitable analytical model is proposed herein in order to predict the system performance, i.e., the average packet queuing delay or, equivalently, the average queue length. In particular, the non-stationary transmission channel is modeled as a Markov chain and each state is associated with a particular modulation and coding scheme (MCS) for a specified data rate. Comparisons between analytical predictions and simulation results are provided to validate our model and to highlight the improvement of the proposed technique with respect to a static rate allocation scheme, especially in the presence of heavy tailed traffic conditions, like those arising in remote file transfer typical of a Web connection.

Next generation wireless systems, as Universal Mobile Telecommunications System (UMTS), aim at revolutionizing the actual wireless communication paradigm offering real time multimedia services now available on fixed terminals whose quality of service (QoS) requirements could be satisfied by network resources adaptation to traffic conditions. Since radio interface is based on CDMA technology, this system suffers form mutual interference among active connections. Approximately, the communication quality decreases at the increasing of active users number. As a consequence, there exists an active user threshold below which an intolerable QoS degradation is produces, especially for those applications named in 3GPP standard as interactive or background. Therefore, proper admission control (AC) algorithm that mitigates mutual interference by keeping active users under a dynamic threshold, is a crucial topic in UMTS system optimization. This paper deals with an advanced AC scheme proposal that estimates the requesting connections signal to noise plus interference ratio (SINR) by means of accurate multiple access interference (MAI) analysis results. Basically, this algorithm verifies the possibility of a new call admission by valuating if an overall power configuration there exists, whose predicted SINR values satisfy each QoS constraints. Whenever a new connection is accepted, a further optimization is performed in order to allow a QoS higher than the requested value under a maximum radiated power constraint. This value is delivered to power control (PC) algorithm jointly with the associated SINR value. Numerical simulations, closely related to an UMTS system, underline a remarkable number of active users increase up to four times traditional AC policies, together with the maximization of QoS requirements.

This paper deals with the application of hybrid automatic repeat request (H-ARQ) techniques to reliable data communications in wireless 3G networks, whose typical applications have to match accurate quality of service (QoS) requirements. A common approach to guarantee such services enhances the H-ARQ features by exploiting turbo codes error correction capabilities. This paper, following the previous approach, investigates the further benefits achievable by developing a strategy that establishes a connection between packet retransmissions and decoding results. Two kinds of these techniques, belonging to soft recombining schemes, are proposed and applied, respectively, to consecutive received packet replicas, or to decoding algorithm outputs, in both cases, without remarkable hardware complexity increase. By means of analytical derivations and simulations, focused on a typical universal mobile telecommunication system (UMTS) environment, a noticeable bit error rate (BER) and, then, frame error rate (FER) improvements have been shown. For the proposed schemes, whenever communications suffer from low signal to noise ratio (SNR) values, significant link throughput increase is also pointed out. As a consequence, these techniques can assure a lower packet delivery delay, besides avoiding transmitted power wasting, if compared with protocols commonly used in wired networks.

This paper deals with an advanced admission control (AC) scheme that estimates the requesting connections signal-to-noise plus interference ratio (SINR) by means of accurate multiple access interference (MAI) analysis results. This algorithm verifies the possibility of a new call admission by valuating if a power configuration exists, whose predicted SINR values satisfy each QoS constraints. Numerical simulations, closely related to the UMTS system, underline a remarkable number of active users increase up to four times traditional AC policies, together with the maximisation of QoS requirements.

This paper deals with the application of hybrid automatic repeat request (H-ARQ) techniques to reliable data communications in wireless 3G networks. Basically, retransmission of coded data is endowed with soft combining schemes applied, respectively, to packet replicas, or to decoding algorithm outputs. By means of analytical derivations and simulations on UMTS environment, a noticeable bit error rate (BER) and, then, frame error rate (FER) improvements have been shown. A significant link throughput increase is also pointed out with a consequent reduced packet delivery delay and power wasting.