Fair power-controlled multiple access in mobile ad hoc networks

Previous power-controlled media access control (MAC) protocols for mobile ad hoc networks (MANET) suffer from the unfair channel access problem, i.e., it is difficult for a node to communicate with a distant node because of nearby ongoing communications. In this paper, we propose a fair power-controlled MAC protocol (FPCMA) by integrating senderinitiated busy tone with traditional power-controlled protocol. The sender-initiated busy tone is used to assist in channel access, and will be set up when a node finds it difficult to access the channel. Nearby nodes overhearing the tone will yield their transmission rights to the attempting node, thus solving the unfairness problem. Through analysis and simulation, we demonstrate that our protocol is able to balance the tradeoff between fair channel access and throughput, and is therefore more flexible than both the traditional dual busy tone and power-controlled MAC protocols.published_or_final_versio

A power-controlled MAC supporting service differentiation in mobile ad hoc networks

The original power controlled multiple access (PCMA) protocol does not support service differentiation. In this paper, we extend PCMA to form a new media access control protocol supporting service differentiation in mobile ad hoc networks. To support QoS, we first introduce the in-station access category concept in 802.1 le to PCMA. For service differentiation between access categories, our major contribution is to propose a sender-initiated busy tone based mechanism that allows a user to gain quick channel access. This quick access mechanism is only performed when the number of access failures exceeds a threshold. An access category with higher priority is assigned a lower threshold for easier channel access, and vice versa. Through analysis and simulation, we demonstrate that our protocol can provide better quality of service than 802.11e in terms of throughput, delay, loss, and fairness. © 2005 IEEE.published_or_final_versio

An Adaptive Strategy for Maximizing Throughput in MAC layer Wireless Multicast

Bandwidth efficiency of wireless multicast can be improved substantially by exploiting the fact that several receivers can be reached at the MAC layer by a single transmission. The multicast nature of the transmissions, however, introduces several design challenges, and systematic design approaches that have been used effectively in unicast and wireline multicast do not apply in wireless multicast. For example, a transmission policy that maximizes the stability region of the network need not maximize the network throughput. Therefore, the objective is to design a policy that decides when a sender should transmit in order to maximize the system throughput subject to maintaining the system stability. We present a sufficient condition that can be used to establish the throughput optimality of a stable transmission policy. We subsequently design an adaptive stable policy that allows a sender to decide when to transmit using simple computations based only on limited information about current transmissions in its neighborhood, and without using any information about the network statistics. The proposed policy attains the same throughput as the optimal offline stable policy that uses in its decision process past, present, and even future network states. We prove the throughput optimality of this policy using the suffi- cient condition and the large deviation results. We present a MAC protocol for acquiring the local information necessary for executing this policy, and implement it in ns-2. The performance evaluations demonstrate that the optimal strategy significantly outperforms the existing approaches in adhoc networks consisting of several multicast and unicast sessions

Medium Access Control Protocols for Ad-Hoc Wireless Networks: A Survey

Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work

Performance improvement of ad hoc networks using directional antennas and power control

Au cours de la dernière décennie, un intérêt remarquable a été éprouvé en matière des réseaux ad hoc sans fil capables de s'organiser sans soutien des infrastructures. L'utilisation potentielle d'un tel réseau existe dans de nombreux scénarios, qui vont du génie civil et secours en cas de catastrophes aux réseaux de capteurs et applications militaires. La Fonction de coordination distribuée (DCF) du standard IEEE 802.11 est le protocole dominant des réseaux ad hoc sans fil. Cependant, la méthode DCF n'aide pas à profiter efficacement du canal partagé et éprouve de divers problèmes tels que le problème de terminal exposé et de terminal caché. Par conséquent, au cours des dernières années, de différentes méthodes ont été développées en vue de régler ces problèmes, ce qui a entraîné la croissance de débits d'ensemble des réseaux. Ces méthodes englobent essentiellement la mise au point de seuil de détecteur de porteuse, le remplacement des antennes omnidirectionnelles par des antennes directionnelles et le contrôle de puissance pour émettre des paquets adéquatement. Comparées avec les antennes omnidirectionnelles, les antennes directionnelles ont de nombreux avantages et peuvent améliorer la performance des réseaux ad hoc. Ces antennes ne fixent leurs énergies qu'envers la direction cible et ont une portée d'émission et de réception plus large avec la même somme de puissance. Cette particularité peut être exploitée pour ajuster la puissance d'un transmetteur en cas d'utilisation d'une antenne directionnelle. Certains protocoles de contrôle de puissance directionnel MAC ont été proposés dans les documentations. La majorité de ces suggestions prennent seulement la transmission directionnelle en considération et, dans leurs résultats de simulation, ces études ont l'habitude de supposer que la portée de transmission des antennes omnidirectionnelles et directionnelles est la même. Apparemment, cette supposition n'est pas toujours vraie dans les situations réelles. De surcroît, les recherches prenant l'hétérogénéité en compte dans les réseaux ad hoc ne sont pas suffisantes. Le présent mémoire est dédié à proposer un protocole de contrôle de puissance MAC pour les réseaux ad hoc avec des antennes directionnelles en prenant tous ces problèmes en considération. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Réseaux ad hoc, Antennes directives, Contrôle de puissance

Exploiting programmable architectures for WiFi/ZigBee inter-technology cooperation

The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions. In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software-defined radio (SDR) platforms, in which every function is programmed from scratch, our programmable architectures are based on a clear decoupling between elementary commands (hard-coded into the devices) and programmable protocol logic (injected into the devices) according to which the commands execution is scheduled. Our contribution is two-fold: first, we designed and implemented a cross-technology time division multiple access (TDMA) scheme devised to provide a global synchronization signal and allocate alternating channel intervals to WiFi and ZigBee programmable nodes; second, we used the OMF control framework to define an interference detection and adaptation strategy that in principle could work in independent and autonomous networks. Experimental results prove the benefits of the envisioned solution

Location based transmission using a neighbour aware-cross layer MAC for ad hoc networks

In a typical Ad Hoc network, mobile nodes have scarce shared bandwidth and limited battery life resources, so optimizing the resource and enhancing the overall network performance is the ultimate aim in such network. This paper proposes anew cross layer MAC algorithm called Location Based Transmission using a Neighbour Aware – Cross Layer MAC (LBT-NA Cross Layer MAC) that aims to reduce the transmission power when communicating with the intended receiver by exchanging location information between nodes in one hand and on the other hand the MAC uses a new random backoff values, which is based on the number of active neighbour nodes, unlike the standard IEEE 802.11 series where a random backoff value is chosen from a fixed range of 0-31. The validation test demonstrates that the proposed algorithm increases battery life, increases spatial reuse and enhances the network performance