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

Asymptotic capacity bounds for wireless networks with non-uniform traffic patterns

Abstract — We develop bounds on the capacity of wireless multihop networks when the traffic pattern is non-uniform, i.e., not all nodes are the sources and sinks of similar volumes of traffic. Our results are asymptotic, i.e., they hold with probability going to unity as the number of nodes goes to infinity. We study (i) asymmetric networks, where the numbers of sources and destinations of traffic are unequal, (ii) multicast networks, in which each created packet has multiple destinations, (iii) cluster networks, that consist of clients and a limited number of cluster heads, and each client wants to communicate with any one of the cluster heads, and (iv) hybrid networks, in which the nodes are supported by a limited infrastructure. Our findings quantify the fundamental capabilities of these wireless multihop networks to handle traffic bottlenecks, and point to correct design principles that achieve the capacity without resorting to overly complicated protocols. Index Terms — Asymmetric traffic, capacity, clustering, hybrid networks, infrastructure support, mobile ad hoc networks, multiho