Cooperative Relaying in Wireless Networks under Spatially and Temporally Correlated Interference

We analyze the performance of an interference-limited, decode-and-forward, cooperative relaying system that comprises a source, a destination, and $N$ relays, placed arbitrarily on the plane and suffering from interference by a set of interferers placed according to a spatial Poisson process. In each transmission attempt, first the transmitter sends a packet; subsequently, a single one of the relays that received the packet correctly, if such a relay exists, retransmits it. We consider both selection combining and maximal ratio combining at the destination, Rayleigh fading, and interferer mobility. We derive expressions for the probability that a single transmission attempt is successful, as well as for the distribution of the transmission attempts until a packet is transmitted successfully. Results provide design guidelines applicable to a wide range of systems. Overall, the temporal and spatial characteristics of the interference play a significant role in shaping the system performance. Maximal ratio combining is only helpful when relays are close to the destination; in harsh environments, having many relays is especially helpful, and relay placement is critical; the performance improves when interferer mobility increases; and a tradeoff exists between energy efficiency and throughput

Packet Travel Times in Wireless Relay Chains under Spatially and Temporally Dependent Interference

We investigate the statistics of the number of time slots $T$ that it takes a packet to travel through a chain of wireless relays. Derivations are performed assuming an interference model for which interference possesses spatiotemporal dependency properties. When using this model, results are harder to arrive at analytically, but they are more realistic than the ones obtained in many related works that are based on independent interference models. First, we present a method for calculating the distribution of $T$. As the required computations are extensive, we also obtain simple expressions for the expected value $\mathrm{E} [T]$ and variance $\mathrm{var} [T]$. Finally, we calculate the asymptotic limit of the average speed of the packet. Our numerical results show that spatiotemporal dependence has a significant impact on the statistics of the travel time $T$. In particular, we show that, with respect to the independent interference case, $\mathrm{E} [T]$ and $\mathrm{var} [T]$ increase, whereas the packet speed decreases

Cross-Layer design and analysis of cooperative wireless networks relying on efficient coding techniques

2011/2012This thesis work aims at analysing the performance of efficient cooperative techniques and of smart antenna aided solutions in the context of wireless networks. Particularly, original contributions include a performance analysis of distributed coding techniques for the physical layer of communication systems, the design of practical efficient coding schemes that approach the analytic limiting bound, the cross-layer design of cooperative medium access control systems that incorporate and benefit from advanced physical layer techniques, the study of the performance of such solutions under realistic network assumptions, and, finally the design of access protocols where nodes are equipped with smart antenna systems.XXV Ciclo198

On the Design of MAC Protocols for Multi-Packet Communication in IEEE 802.11 Heterogeneous Networks Using Adaptive Antenna Arrays

This paper discusses the design requirements for enabling multiple simultaneous peer-to-peer communications in IEEE 802.11 asynchronous networks in the presence of adaptive antenna arrays, and proposes two novel access schemes to realize multipacket communication (MPC). Both presented solutions, which rely on the information acquired by each node during the monitoring of the network activity, are suitable for distributed and heterogeneous scenarios, where nodes equipped with different antenna systems can coexist. The first designed scheme, called threshold access MPC (TAMPC), is based on a threshold on the load sustainable by the single-node, while the second protocol, called signal-to-interference ratio (SIR) access MPC (SAMPC), is based on an accurate estimation of the SIR and on the adoption of low density parity check codes. Both protocols, which are designed to be backward compatible with the 802.11 standard, are numerically tested in realistic scenarios. Furthermore, the performance of the two schemes is compared to the theoretical one and to that of the 802.11n extension in a mobile environment

Cross-Layer Solutions for Cooperative Medium Access Control Protocols

Abstract— Recent studies have shown that designing a Medium Access Control (MAC) protocol combined with a cooperative approach may improve the attainable network throughput, despite reducing the mean packet delay. In this paper we design a MAC scheme adopting cooperative physical layer aided cross-layer techniques. We consider a popular cooperative MAC protocol, namely the CoopMAC technique of Liu et al., which is improved by facilitating cooperative signal combining at the destination and employing two relays in the context of a successive relaying technique. The performance of the proposed scheme is evaluated by Monte-Carlo simulations. We demonstrate that a cross-layer design further improves the performance gain provided by the CoopMAC protocol over that of the legacy 802.11 Distributed Coordination Function (DCF), enhancing both the achievable network throughput and the outage probability

Relay Selection Schemes Relying on Adaptive Modulation and Imperfect Channel Knowledge for Cooperative Networks

3nonenoneF. Babich; A. Crismani; L. HanzoBabich, Fulvio; Crismani, Alessandro; L., Hanz

Design criteria and genetic algorithm aided optimization of three-stage-concatenated space-time shift keying systems

The Space-Time Shift Keying (STSK) framework subsumes diverse Multiple-Input Multiple-Output (MIMO) schemes, offering a near-capacity performance at a reduced complexity. The STSK system’s performance crucially depends on the dispersion matrix (DM) set used for encoding the transmitted symbols. We introduce a novel criterion, based on EXtrinsic Information Transfer (EXIT) chart analysis, for selecting capacity-approaching sets from candidate DMs, and a novel Genetic Algorithm (GA) for efficiently exploring the search space formed by the candidate DM sets. Our proposed GA allows obtaining DM sets that enhance the system’s performance compared to a random selection, while simultaneously reducing the search algorithm’s complexity.<br/

Interference Functionals in Poisson Networks

We propose and prove a theorem that allows the calculation of a class of functionals on Poisson point processes that have the form of expected values of sum-products of functions. In proving the theorem, we present a variant of the Campbell-Mecke theorem from stochastic geometry. We proceed to apply our result in the calculation of expected values involving interference in wireless Poisson networks. Based on this, we derive outage probabilities for transmissions in a Poisson network with Nakagami fading. Our results extend the stochastic geometry toolbox used for the mathematical analysis of interference-limited wireless networks