The problem of wireless M2M communication is twofold: the reliability aspect and the scalability aspect. The solution to this problem demands a delay constrained random access protocol. To this end, we propose admission control based traffic-agnostic delay-constrained random access (AC/DC-RA) protocol. Our main contribution is enabling the stochastic delay constraints agnostic to the traffic, such that the stochastic delay constraint is valid with respect to a varying number of arrivals. We achieve this with an admission control decision that uses a novel collision estimation algorithm for an active number of arrivals per contention resource. We use an adaptive contention resolution algorithm to react to the varying number of arrivals. Using these tools, the admission control solves the stability problem. We show with simulations that the AC/DC-RA provide stochastic delay constrained random access in a traffic agnostic way to sustain a stable performance against Poisson and Beta arrivals without any modification to the protocol.

We study a queueing system operated with packet level coding. More specifically, we derive a closed form upper bound on the queueing delay as well as an expression for the decoding delay of a system operated with systematic network coding. Unlike previous works, the delay is considered on a per-packet basis rather than per-block, thus taking into account the low-latency property of systematic codes. Furthermore we study the tradeoff between the coding gain and the decoding delay defining the “achievable” region (packet loss vs. delay) for finite block lengths.

This paper focuses on geostationary satellite scenarios and investigates the performance of several Transmission Control Protocol (TCP) variants in a novel Performance Enhancing Proxy (PEP) architecture solution, whose added value is the use of network coding beneath the transport layer. Comparison of TCP New-Reno, Vegas, Scalable, CUBIC, Hybla, and HTCP and the cases where these transport protocols are used along with network coding is carried out by means of simulation campaigns. The obtained results show the potentials of the proposed network coding technique, resulting in the improvement of TCP connections performance in a wide range of channel conditions and the possible exploitation of future increase of the satellite link capacity.

The most widely used transport protocols (i.e, TCP and UDP) are not suitable for aeronautical services because of the reliability and strict transfer delay requirements that cannot be met by TCP and UDP in such environment. In this respect, the paper proposes a novel message-oriented transport protocol Reliable Aeronautical Services Protocol (RASP) enabling reliable aeronautical services. Simulation campaigns carried out in ns-2 show the superiority of RASP with respect to TCP in terms of end-to-end message transfer delay and number of performed retransmissions.

This work aims at introducing two novel packet retransmission techniques for reliable multicast in the framework of Instantly Decodable Network Coding (IDNC). These methods are suitable for order- and delay-sensitive applications, where some information is of high importance for an earlier gain at the receiver's side. We introduce hence an Unequal Error Protection (UEP) scheme, showing by simulations that the Quality of Experience (QoE) for the end-users is improved even without complex encoding and decoding.

The existing studies of RObust Header Compression (ROHC) have provided some understanding for memoryless channel, but the behavior of ROHC for correlated wireless channels is not well investigated in spite of its practical importance. In this paper, the dependence of ROHC against its design parameters for the Gilbert Elliot channel is studied by means of three analytical models. A first more elaborated approach accurately predicts the behavior of the protocol for the single RTP flow profile, while a simpler, analytically tractable model yields clear and insightful mathematical relationships that explain the qualitative trends of ROHC. The results are validated against a real world implementation of this protocol. Moreover, a third model studies also the less conventional yet practically relevant setting of multiple RTP flows.

The utilization of universal frequency reuse in multi-beam satellite systems introduces a non-negligible level of co-channel interference (CCI), which in turn penalizes the quality of service experienced by users. Taking this as starting point, the paper focuses on resource management performed by the gateway (hub) on the return-link, with particular emphasis on a scheduling algorithm based on bipartite graph approach. The study gives important insights into the achievable per-user rate and the role played by the number of users and spot beams considered for scheduling. More interestingly, it is shown that a free-slot assignment strategy helps to exploit the available satellite resources, thus guaranteeing a max-min rate requirement to users. Remarks about the trade-off between efficiency-loss and performance increase are finally drawn at the end of the paper.

Contention Resolution Diversity Slotted ALOHA (CRDSA) and its burst degree optimizations (CRDSA++, IRSA) make use of MAC burst repetitions and Interference Cancellation (IC) making possible to reach throughput values as high as T ≃ 0.8 in practical implementations, whereas for the traditional slotted ALOHA T ≃ 0.37. However, these new techniques introduce a frame-based access to the channel that limits the performance in terms of throughput and packet delivery delay. In this paper, a new technique named Sliding Window CRDSA (SW-CRDSA) and its counterpart for irregular repetitions (SW-IRSA) are introduced in order to exploit the advantages of MAC burst repetition and Interference Cancellation (IC) with an unframed access scheme. Numerical results are also provided in order to validate the statement of better performance.

The present paper provides an analytical expression for the amount of theoretically transmittable data to/from a LEO or MEO satellite and a fixed ground station, during one pass, averaged over an infinite number of passes. The paper shows that this mean transmittable data amount can have a maximum as a function of the satellite orbit altitude, when the other parameters of the communications system are fixed. The paper identifies a maximization method, with which it is possible to find the altitude, at which the mean transmittable data amount is maximized. The paper also shows that, for fixed satellite orbit altitude, it is possible to find the corresponding transmission bandwidth that maximizes the mean transmittable data amount.

In this paper, the current trends and the most recent advancements in the utilization of aerospace communications for emergency rescue applications will be discussed, with a special focus on the integration of the aerospace segment with terrestrial backbones and ad hoc terrestrial networks for both data connections and assisted localization (information about position is essential in emergency relief).

The number of Coding and Modulation Schemes suggested for the two standards DVB-S2 and DVB-RCS (in its "advanced" version) is overdimensioned; a subset of schemes can be used and this only reduces the overall system performance negligibly. This paper presents the investigations performed on this rain fading mitigation technique, called Adaptive Coding and Modulation (ACM), supported by the DVB-S2 standard and shows how the sets of modulation and coding schemes, considered in the forward and in the return-links, can be changed to reduce terminal complexity and how this affects the overall system performance. It is shown that, by a careful selection of the ACM schemes, already with less than one fourth (7 or 5 out of 28) of the total number of schemes it is possible to get performance close to the optimum, but with a much lower terminal complexity.

The broadband satellite multimedia (BSM) architecture standardised by ETSI defines a satellite independent service access point (SI-SAP) interface layer that separates the satellite independent features of the upper layers from the satellite dependant features of the lower layers, and provides a mechanism to carry IP-based protocols over these satellite dependent lower layers. This enables interoperability at the IP layer between satellite systems of different physical and link layers technologies that fully comply with the SI-SAP concept. This study reviews past and current standardisation activities including the BSM quality of service (QoS) architecture, security architecture, network management that have been carried out by the ETSI Technical Committee-Satellite Earth Stations and Systems (TC-SES)/BSM working group and looking into the future to extend current SI-SAP functions that can enhance existing QoS provision and security management capabilities as well as proposing a mobility management architecture that complies with the IEEE 802.21 media independent handover framework to support BSM mobility and to allow integration of satellite networks with fixed and mobile network infrastructures. A service-based network management architecture is also proposed to allow management flexibility and integration of business and operation support functions, paving the way for satellite integration into the Internet of the future.

A multibeam satellite system can be modelled as a multiple-input multiple-output (MIMO) system with an inter-beam interference matrix that is derived from the positions of the users in the different beams. This way it is possible to apply precoding techniques, such as Tomlinson-Harashima precoding (THP), to mitigate the interference. This paper presents an analytical framework to model the interference by a simple and effective parameter, which enables to assess the uncoded bit error rate (BER) of THP in such a scenario, and to derive useful hints on the optimization of the overall system capacity.

In this paper an analytical framework is introduced for the optimization of TCP performance through joint channel coding and transmission power management in satellite communications, where both energy and bandwidth are scarce and costly resources. More specifically, the analysis takes into account the use of Low-Density Parity-Check (LDPC) codes as coding scheme for high data rate satellite communications. The analytical framework allows for the evaluation of the transmission power and coding rate that maximize the TCP throughput per unitary cost, which is a metric defined in terms of energy cost and bandwidth cost when related to throughput. Numerical examples demonstrate the usability of the proposed framework.

Satellite radio for vehicles is normally hampered by the problem of the shadowing of the line-of-sight between satellite and receiver. One possible way to overcome this challenge is to provide a new type of radio service, hereafter referred to as personalized satellite radio, in alternative to the streaming approach used for traditional radio: individual audio and multimedia files are broadcasted instead of transmitting a number of distinct continuous streams. The received files are stored in a large cache located in the receiver of each mobile terminal and are sequentially played to generate a service similar to traditional radio/entertainment programmes. The resulting file-based radio approach makes use of higher-layer coding on transport level, to ensure a sufficient file transfer reliability even when some packets are lost due to the shadowing of the line-of-sight path, and of smart techniques to build up an audible programme with no interruptions and full audio quality based upon the available files. The paper presents this novel radio concept and the results of extensive trials which were conducted with a system test-bed developed in the framework of an ESA funded project.

This paper presents the development of a compact, ruggedized satellite terminal, to be used for communications in emergency situation. The terminal provides GSM coverage in disaster area, where existing communication infrastructure is destroyed or overloaded. It uses GSM backhauling over satellite to transport GSM signalling and data traffic to the core GSM network infrastructure in the disaster-safe area. Additionally, basic data services such as HTTP Web browsing and email are also provided via WiFi access. Issues related to the terminal design and the tests that have been undertaken are presented in the paper.

Combining some of the best terrestrial and satellite systems' characteristics, high altitude platforms (HAPs) have recently emerged as an alternative solution for the provision of broadband services. Characterised by challenging propagation conditions in the allocated frequency bands, they require efficient utilisation of radio interface in order to make best use of the available spectrum. This paper analyses possible utilisation of DVB-S2 standard on HAPs, focusing on the performance of its adaptive coding and modulation (ACM) procedures as a mean of maximizing the link reliability and throughput. Two distinct operating scenarios are addressed, one assuming static channel conditions with the applied rain fading and the other representing mobile channel conditions along a representative railway track We show that by considering only a subset of transmission modes (MODCODs) defined by the DVB-S2 standard, the system could be optimized in terms of achievable spectral efficiency as well as in terms of implementation complexity. A procedure for optimal MODCOD subset selection is proposed, taking into account the predefined switching thresholds and round-trip time delay.

We compare some block equalizers for single-carrier satellite systems subject to hard propagation conditions such as high Doppler spread, non-line-of-sight (NLOS), and non-negligible multipath fading. These impairments are relevant when the very high speed of a mobile receiver forces to use a non-directional antenna. First, we compare low-complexity time-domain and frequency-domain block equalizers. Then, we propose a novel frequency-domain equalizer based on a fast Fourier transform (FFT) with size higher than the length of the processed block. Thanks to the increased frequency resolution, the proposed equalizer yields improved performance with respect to the conventional frequency-domain equalizer. Simulation results validate the effectiveness of the proposed technique.

Terrestrial and satellite networks have dominated the telecommunications arena for years. In parallel with these two well-established technologies, a new alternative based on platforms located in the stratosphere, termed high altitude platforms (HAP's), has gained considerable interest in the past few years. In this paper, we consider an integrated HAP-satellite architecture and propose a reliable multicast protocol that capitalizes upon the HAP-layer to perform local retransmissions. Our protocol relies on a progressive packet-level forward error correction (FEC) scheme. The performance of this multicast protocol has been supported thorough the comparison with a theoretical bound in the literature.

This paper shows a novel approach for routing datagrams in ad-hoc networks, called distributed ant routing (DAR). This approach belongs to the class of routing algorithms inspired by the behavior of the ant colonies in locating food and storing food. The algorithm aims at minimizing complexity in the nodes and this is achieved at the expenses of the optimality of the derived solution. The work also describes an analytical approach to the problem: The validity of the heuristic approach, ant routing, is supported by mathematical proofs and the same methods helps in the selection of the algorithm parameters. Simulation results are presented at the end to confirm the mathematical calculations.

Nongeostationary satellite constellations with intersatellite links are a challenge for networking due to their continuously changing topology. In order to make maximal use of the network's capacities, special attention has to be paid to routing and traffic engineering. Multiprotocol label switching (MPLS) as underlying protocol is an interesting candidate for this task since it offers many possibilities to exert influence on traffic flows and supports today's dominating Internet protocol traffic very well. This paper describes a general MPLS-based networking concept for satellite networks and discusses different scenarios considering the particularities and constraints of the dynamic topology. Functional elements of MPLS like ingress, egress, or core routers have to be mapped onto the physical entities of the network and prerequisites for traffic engineering are discussed. Routing and rerouting of paths is of key interest since this affects route computation effort and routing performance. Thus, an analytical estimation of routing effort is deduced and numerical and simulation results are presented.

Seamless mobility and security are two of the main issues interesting those users, who need to keep working while travelling. Making a careful use of existing standard layer 3 protocols IPsec and mobile IP (MoIP), this paper provides a solution to integrate mobility at IP layer and virtual private network (VPN) services. The solution applies to a wide range of possible situations. We give an overview of all facing problems and we mention both advices and architectural requirements, needed to deploy the proposed solution in a real scenario. In the end we demonstrate the validity of the proposed solution by presenting an implementation on a Linux-based testbed. The deployment of the testbed allows also to show some performances of the combination of MoIP and IPsec, in terms of average added overhead.