Using OLSR Multipoint Relays (MPRs) to estimate node positions in a Wireless Mesh Network

In this paper we address in this paper the problem of nodes localization in wireless heterogeneous networks, focussing particularly on selection methods to estimate position. The OLSR routing protocol uses special nodes called Multipoint Relay (MPR) nodes to broadcast control messages within the network. We propose a novel approach based on using these Multipoint Relay (MPR) nodes as anchor nodes to estimate nodes positions. We evaluate its performance by simulation and compare it to other selection techniques such as convex hull selection and greedy selection

Geometric Bucket Trees: Analysis of Linear Bucket Tree

International audienceWe analyse the average number of buckets in a Linear Bucket tree created by $n$ points uniformly dispatched on an interval of length $y$. A new bucket is created when a point does not fall in an existing bucket. The bucket is the interval of length 2 centered on the point. We illustrate this concept by an interesting tale of how the moon's surface took on its present form. Thanks to an explicit Laplace transform of the Poissonized sequence, and the use of dePoissonization tools, we obtain the explicit asymptotic expansions of the average number of buckets in most of the asymptotic regimes relative to $n$ and $y$

An Efficient Simulation Model for Wireless LANs Applied to the IEEE 802.11 Standard

In this research report, we propose a simple simulation model for wireless LANs. In wireless LANs, contrary to LANs different transmission results can be observed by network nodes. This phenomenon is the result of radio propagation laws where the signal decay is by far more important than on cables. This leads to new and interesting modelization and simulation problems. In this article we propose a simple but general physical model to take into account radio propagation. We then apply this model to the study of the IEEE 802.11 standard. We show how IEEE 802.11 can be efficiently modeled and simulated. This allows us to offer a detailed study of the standard. We will give performance evaluations of the IEEE 802.11 DS standard with transmisson rate 1, 2, 5.5 or 11 Mbit/s which take into account the exact protocol overhead. We also study special behaviour as broadcast transmission, performance with hidden nodes, spatial reuse

Throughput in multihop CSMA mobile adhoc network

A lot of research has been done in routing protocols for ad-hoc network especially at the IETF in the working group MANET. These studies have mostly focused on the conception of routing protocols for mobile radio networks where the radio channel capacity is generally limited. The present article does not target the study of these routing protocols but investigate how carrier sense multiple access (CSMA) protocols can be tuned to optimize the network throughput. We buid two models of interference of simultaneous transmissions and conduct simple computations to guide our optimizations. The first interference model only considers the strongest interferer as the second one takes into account all the contributions. We use simulations to test our optimizations results. The result of this paper is a guide to optimize CSMA multihop networks; the obtained results show that a good tuning of CSMA protocols in term of carrier sense threshold and transmission range allows one to gain a lot of network throughput (up to 9

Vehicular Ad-hoc Networks: Point-to-Point, Emergency and Broadcast Communications

International audienceThe aim of this paper is to analyze the Aloha medium access (MAC) scheme in one-dimensional, linear networks, which might be an appropriate assumption for Vehicular Ad-hoc NETworks (VANETs). The locations of the vehicles are assumed to follow a homegeneous Poisson point process. Assuming powerlaw mean path-loss and independent point-to-point fading we study performance metrics based on the signal-over-interference and noise ratio (SINR). In contrast to previous studies where the receivers are at a fixed distance from the transmitter, we assume here that the receivers are the nearest neighbors of the transmitters in the Poisson process and in a given direction. We derive closed formulas for the capture probability and for the density of progress of a packet sent by a given node. We compute the mean delay to send a packet transmitted at each slot until successful reception. We also evaluate an upper bound to discover the neighborhood within a given space interval. We show that we can include noise in the previous models

Stack Algorithms in Implicit Framing, Free Access and Blocked Access for CATV Networks

In this paper we present in the framework of access protocols for Cable TV (CATV) networks performant and easy implementation of stack algorithms with an implicit framing scheme. We use a stack algorithm with a single interleaved process in a free or blocked access mode. We show that the blocked access can be implemented to have a deterministic behaviour. We show that a dynamic tuning of the access persistence parameter $R$ improves the performance both in terms of throughput and delays

Active Signaling for 802.11 Networks in the ns-3 Simulator

International audienceIn wireless networks, wireless channels are often shared between multiple nodes, which may interfere when they transmit simultaneously. The media access control (MAC) scheme coordinates channel access between the different nodes. In this article, we focus one specific method of channel access, Elimination-Yield Non-Preemptive Priority Multiple Access, EY- NPMA, which is part of the European standard wireless HIPERLAN. EY-NPMA is a wireless MAC method that partly relies on "active signaling": i.e. transmitting (activity) to simply signal a node's presence (with pseudo-noise), rather than transmitting data (bits). In this article, we study the adaptation of EY-NPMA named Ey-Wifi as an extension of the 802.11-based standards. Our main focus is the implementation of a such an extension in a module of the network simulator, ns-3, with the emphasis on the software architecture

Maximizing Throughput of Linear Vehicular Ad-hoc NETworks (VANETs) -- a Stochastic Approach

International audienceIn this paper we use stochastic geometry to propose two models for Aloha-based linear VANETs. The first one uses Signal over Interference plus Noise Ratio (SINR) capture condition to qualify a successful transmission, while the second one expresses the transmission throughput as a function of SINR using Shannon's law. Assuming Poisson distribution of vehicles, power-law mean path-loss and Rayleigh fading, in these models we derive explicit formulas for the mean throughput and the probability of a successful reception at a given distance. Furthermore, we optimize two quantities directly linked to the achievable network throughput: the mean density of packet progress and the mean density of information transport. This is realized by tuning the communication range and the probability of channel access. We also present numerical examples and study the impact of external noise on an optimal tuning of network parameters

Stack Algorithms at High Loads : Analysis of Unfairness or Singular Behaviours

In this paper, we investigate the fairness of stack access algorithms in overload conditions. We show that conventional Last In First Out free-acces- s stack algorithms provide unfair channel access at high loads. A subset of end-users may starve during network overloads as the other nodes capture the whole channel capacity. We show that the First In First Out free-access stack protocol can cope with this unfairness problem. The blocked access stack algorithms are not showing unfairness problems

Performant Implementations of Tree Collision Resolution Algorithms for CATV Networks

In this paper, we analyze optimizations and adptations of the stack (tree) algorithm needed to use it as access scheme for a CATV channel access. In CATV network, we have large round trip delays, therefore it is possible have simultaneous tree collision resolution process. One approach is to handle many independant collision resolution process, another is to interleave all the collision resolution process. We give a detailed analysis of the two schemes concerning average and distribution of access delays. We show that the interleaving technique is both more simple and more efficient. This leads us to define a CATV channel access technique with interleaved collision resolution process on which we had a mechanism to offer reservation for successive slots. We a give a detailed implementation of this protocol as a thorough performance analysis. We deeply investigate the effect on throughput and delays of the end to end propagation delay and of the number of active stations