Gianluigi Ferrari

Ad hoc wireless networks : a communication-theoretic perspective

Preface. List of Acronyms. 1 Related Work and Preliminary Considerations. 1.1 Introduction. 1.2 Related Work. 1.3 A New Perspective for the Design of Ad Hoc Wireless Networks. 1.4 Overview of the Underlying Assumptions in the Following Chapters. 1.5 The Main Philosophy Behind the Book. 2 A Communication-Theoretic Framework for Multi-hop Ad Hoc Wireless Networks: Ideal Scenario. 2.1 Introduction. 2.2 Preliminaries. 2.3 Communication-Theoretic Basics. 2.4 BER Performance Analysis. 2.5 Network Behaviour. 2.6 Concluding Remarks. 3 A Communication-Theoretic Framework for Multi-hop Ad Hoc Wireless Networks: Realistic Scenario. 3.1 Introduction. 3.2 Preliminaries. 3.3 Communication-Theoretic Basics. 3.4 Inter-node Interference. 3.5 RESGOMAC Protocol. 3.6 RESLIGOMAC Protocol. 3.7 Network Behavior. 3.8 Conclusions. 4 Connectivity in Ad Hoc Wireless Networks: A Physical Layer Perspective. 4.1 Introduction. 4.2 Quasi-regular Topology. 4.3 Random Topology. 4.4 Concluding Remarks and Discussion. 5 Effective Transport Capacity in Ad Hoc Wireless Networks. 5.1 Introduction. 5.2 Modeland Assumptions. 5.3 Preliminaries. 5.4 Single-Route Effective Transport Capacity. 5.5 Aggregate Effective Transport Capacity. 5.6 Comparison of the RESGO and RESLIGOMAC Protocols. 5.7 Spread-RESGO: Improved RESGOMAC Protocol with Per-route Spreading Codes. 5.8 Discussion. 5.9 Concluding Remarks. 6 Impact of Mobility on the Performance of Multi-hop Ad Hoc Wireless Networks. 6.1 Introduction. 6.2 Preliminaries. 6.3 Switching Models. 6.4 Mobility Models. 6.5 Numerical Results. 6.6 Conclusions. 7 Route Reservation in Ad Hoc Wireless Networks. 7.1 Introduction. 7.2 Related Work. 7.3 Network Models and Assumptions. 7.4 The Two Switching Schemes. 7.5 Analysis of the Two Switching Techniques. 7.6 Results and Discussion. 7.7 Concluding Remarks. 8 Optimal Common Transmit Power for Ad Hoc Wireless Networks. 8.1 Introduction. 8.2 Modeland Assumptions. 8.3 Connectivity. 8.4 BER at the End of a Multi-hop Route. 8.5 Optimal Common Transmit Power. 8.6 Performance Metrics. 8.7 Results and Discussion. 8.8 Related Work. 8.9 Conclusions. 9 Routing Problem in Ad Hoc Wireless Networks: A Cross-Layer Perspective. 9.1 Introduction. 9.2 Experimental Evidence. 9.3 Preliminaries: Analytical Models and Assumptions. 9.4 Route Selection: Simulation Study. 9.5 Network Performance Evaluation. 9.6 Discussion. 9.7 Related Work. 9.8 Conclusions. 10 Concluding Remarks. 10.1 Introduction. 10.2 Extensions of the Theoretical Framework: Open Problems. 10.3 Network Architectures. 10.4 Network Application Architectures. 10.5 Standards. 10.6 Applications. 10.7 Conclusions. Appendix A. Appendix B. Appendix C. Appendix D. Appendix E. References. Index.

Optimal Transmit Power in Wireless Sensor Networks

Power conservation is one of the most important issues in wireless ad hoc and sensor networks, where nodes are likely to rely on limited battery power. Transmitting at unnecessarily high power not only reduces the lifetime of the nodes and the network, but also introduces excessive interference. It is in the network designers best interest to have each node transmit at the lowest possible power while preserving network connectivity. In this paper, we investigate the optimal common transmit power, defined as the minimum transmit power used by all nodes necessary to guarantee network connectivity. This is desirable in sensor networks where nodes are relatively simple and it is difficult to modify the transmit power after deployment. The optimal transmit power derived in this paper is subject to the specific routing and medium access control (MAC) protocols considered; however, the approach can be extended to other routing and MAC protocols as well. In deriving the optimal transmit power, we distinguish ourselves from a conventional graph-theoretic approach by taking realistic physical layer characteristics into consideration. In fact, connectivity in this paper is defined in terms of a quality of service (QoS) constraint given by the maximum tolerable bit error rate (BER) at the end of a multihop route with an average number of hops

Noncoherent iterative (turbo) decoding

Previously, noncoherent sequence detection schemes for coded linear and continuous phase modulations have been proposed, which deliver hard decisions by means of a Viterbi algorithm. The current trend in digital transmission systems toward iterative decoding algorithms motivates an extension of these schemes. In this paper, we propose two noncoherent soft-output decoding algorithms. The first solution has a structure similar to that of the well-known algorithm by Bahl et al. (1974), whereas the second is based on noncoherent sequence detection and a reduced-state soft-output Viterbi algorithm. Applications to the combined detection and decoding of differential or convolutional codes are considered. Further applications to noncoherent iterative decoding of turbo codes and serially concatenated interleaved codes are also considered. The proposed noncoherent detection schemes exhibit moderate performance loss with respect to corresponding coherent schemes and are very robust to phase and frequency instabilities.

IoT-OAS: An OAuth-Based Authorization Service Architecture for Secure Services in IoT Scenarios

Open authorization (OAuth) is an open protocol, which allows secure authorization in a simple and standardized way from third-party applications accessing online services, based on the representational state transfer (REST) web architecture. OAuth has been designed to provide an authorization layer, typically on top of a secure transport layer such as HTTPS. The Internet of Things (IoTs) refers to the interconnection of billions of resource-constrained devices, denoted as smart objects, in an Internet-like structure. Smart objects have limited processing/memory capabilities and operate in challenging environments, such as low-power and lossy networks. IP has been foreseen as the standard communication protocol for smart object interoperability. The Internet engineering task force constrained RESTful environments working group has defined the constrained application protocol (CoAP) as a generic web protocol for RESTful-constrained environments, targeting machine-to-machine applications, which maps to HTTP for integration with the existing web. In this paper, we propose an architecture targeting HTTP/CoAP services to provide an authorization framework, which can be integrated by invoking an external oauth-based authorization service (OAS). The overall architecture is denoted as IoT-OAS. We also present an overview of significant IoT application scenarios. The IoT-OAS architecture is meant to be flexible, highly configurable, and easy to integrate with existing services. Among the advantages achieved by delegating the authorization functionality, IoT scenarios benefit by: 1) lower processing load with respect to solutions, where access control is implemented on the smart object; 2) fine-grained (remote) customization of access policies; and 3) scalability, without the need to operate directly on the device.

Extrinsic information in iterative decoding: a unified view

We address the use of the extrinsic information generated by each component decoder in an iterative decoding process. The BJCR algorithm proposed by Bahl et al. (1974) and the soft-output Viterbi algorithm (SOVA) are considered as component decoders. In both cases, we consider, in a unified view, various feedback schemes which use the extrinsic information in different fashions. Numerical results for a classical rate-1/2 turbo code and a serially concatenated code transmitted over a memoryless additive white Gaussian noise (AWGN) channel are provided. The performance of the considered schemes leads to interesting remarks about the nature of the extrinsic information.

Wireless sensor networks: performance analysis in indoor scenarios

We evaluate the performance of realistic wireless sensor networks in indoor scenarios. Most of the considered networks are formed by nodes using the Zigbee communication protocol. For comparison, we also analyze networks based on the proprietary standard Z-Wave. Two main groups of network scenarios are proposed: (i) scenarios with direct transmissions between the remote nodes and the network coordinator, and (ii) scenarios with routers, which relay the packets between the remote nodes and the coordinator. The sensor networks of interest are evaluated considering different performance metrics. In particular, we show how the received signal strength indication (RSSI) behaves in the considered scenarios. Then, the network behavior is characterized in terms of end-to-end delay and throughput. In order to confirm the experiments, analytical and simulation results are also derived.

New bounds for the Marcum Q-function

New bounds are proposed for the Marcum Q-function, which is defined by an integral expression where the 0th-order modified Bessel function appears. The proposed bounds are derived by suitable approximations of the 0th-order modified Bessel function in the integration region of the Marcum Q-function. They prove to be very tight and outperform bounds previously proposed in the literature. In particular, the proposed bounds are noticeably good for large values of the parameters of the Marcum Q-function, where previously introduced bounds fail and where exact computation of the function becomes critical due to numerical problems.

Does the Performance of LDPC Codes Depend on the Channel

In this letter, we discuss the performance of low-density parity-check (LDPC) codes on memoryless channels. Using a recently proposed analysis technique based on extrinsic information transfer (EXIT) charts, we present an interpretation of the known fact that the bit-error rate (BER) performance of an ensemble of LDPC codes shows little dependence on the specific memoryless channel. This result has been partially observed in the literature for symmetric channels and is here extended to asymmetric channels. We conjecture and demonstrate that the performance of an ensemble of LDPC codes depends primarily and solely on the mutual information (MI) between the input and the output of the channel. As a validation of this conjecture, we compare the performance of a few LDPC codes with various rates for five representative memoryless (both symmetric and asymmetric) channels, obtaining results in excellent agreement with the EXIT chart-based prediction

Decentralized binary detection with noisy communication links

This correspondence presents a Bayesian framework for distributed detection in sensor networks with noisy communication links between the sensors and the fusion center (or access point (AP)). Noisy links are modeled as binary symmetric channels (BSCs), but the proposed framework can be extended to other communication link models. To improve the system robustness against observation and communication noises, we propose schemes with 1) multiple observations and a single AP and 2) single observations and multiple APs. By using the De Moivre-Laplace approximation, we derive simple and accurate expressions for the probability of decision error in scenarios with a large number of nodes

Fundamental performance limits of communications systems impaired by impulse noise

In this paper, we investigate the ultimate performance limits, in terms of achievable information rate (IR), of communication systems impaired by impulse noise. We compare single carrier (SC) and multi-carrier (MC) transmission systems employing quadrature amplitude modulation (QAM) formats. More precisely, we consider SC schemes with coded modulations and MC systems based on orthogonal frequency division modulation (OFDM). For the MC schemes, we introduce a theoretically equivalent channel model which makes the computation of the IR feasible. This simple channel model will be referred to as interleaved MC. We show that, in the presence of impulse noise and except for systems operating at very high spectral efficiency, the IR of MC schemes is lower than that of SC schemes. More precisely, use of MC schemes may lead to an unavoidable fundamental loss with respect to SC schemes at typical coding rates, whereas MC schemes are to be preferred for very high coding rates or in uncoded systems. These results hold for additive white Gaussian noise (AWGN) and dispersive channels, either considering plain OFDM or MC schemes employing water-filling and bit-loading algorithms. In order to validate our theoretical results, we also obtain the bit error rate (BER) performance of SC and MC schemes through Monte Carlo simulations. A few trellis-coded modulation (TCM) and low-density parity-check (LDPC)-coded schemes are considered. The obtained SNR loss in the BER curves between the AWGN and impulse noise channels matches well with the corresponding IR gap.