Analysis and evaluation of decentralized multiaccess Mac for ad-hoc networks

In mobile ad-hoc radio networks, terminals are mobile and heterogeneous, the architecture of the network is continuously changing, communication links are packet oriented and radio resources are scarce. Therefore, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. However, due to these network harsh conditions, decentralized Medium Access Control (MAC) protocols designed specifically for ad hoc networks are scarce. In this paper we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMATDMA in which a cross layer approach has been followed in order to maximize network throughput. A theoretical analysis of the system is presented ending up with closed expressions for the throughput and delay of the network and some simulations are presented to evaluate the performance of the system.Postprint (published version

PHY-MAC dialogue with multi-packet reception

Cross-layer design has been considered recently as a new approach when designing MAC protocols in systems with diversity such as CDMA. This paper goes one step further in the cross layer design by proposing a PHY-MAC dialogue involving the exchange of parameters such as BER and active users. By means of this PHY-MAC dialogue, system performance can be improved. A two-stage receiver is used at PHY level. The first stage tracks active users while the second stage is a data demodulator. The Modified Dynamic Queue Protocol (MDQP) is proposed as the MAC protocol of our system. When the knowledge of active users is possible, it is demonstrated by simulations that MDQP outperforms DQP.Postprint (published version

Decentralised multi-access MAC protocol for ad-hoc networks

In ad-hoc radio networks, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. Traditionally, Medium Access Control (MAC) protocols in ad hoc networks have been designed to face off the well known collision resolution problem. However, when using advanced signal processing techniques, general assumptions on collisions and packet loss are no longer valid. Besides, little has been reported about MAC algorithms dealing with multiaccess channels in ad hoc networks. In this paper, we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMA-TDMA in which a cross layer approach has been followed to dinamically adapt to the traffic load. Closed expressions for the throughput and delay of the network are presented as a function of the multipacket reception capability of the receiver, the number of codes and the packet retransmission probability.Postprint (published version

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LAMAN: Load Adaptable MAC for Ad Hoc Networks

<p/> <p>In mobile ad hoc radio networks, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency. In this paper, the load adaptable medium access control for ad hoc networks (LAMAN) protocol is described. LAMAN is a novel decentralized multipacket MAC protocol designed following a cross-layer approach. Basically, this protocol is a hybrid CDMA-TDMA-based protocol that aims at throughput maximization in multipacket communication environments by efficiently combining contention and conflict-free protocol components. Such combination of components is used to adapt the nodes' access priority to changes on the traffic load while, at the same time, accounting for the multipacket reception (MPR) capability of the receivers. A theoretical analysis of the system is developed presenting closed expressions of network throughput and packet delay. By simulations the validity of our analysis is shown and the performances of a LAMAN-based system and an Aloha-CDMA-based one are compared.</p

PHY-MAC dialogue with multi-packet reception

Cross-layer design has been considered recently as a new approach when designing MAC protocols in systems with diversity such as CDMA. This paper goes one step further in the cross layer design by proposing a PHY-MAC dialogue involving the exchange of parameters such as BER and active users. By means of this PHY-MAC dialogue, system performance can be improved. A two-stage receiver is used at PHY level. The first stage tracks active users while the second stage is a data demodulator. The Modified Dynamic Queue Protocol (MDQP) is proposed as the MAC protocol of our system. When the knowledge of active users is possible, it is demonstrated by simulations that MDQP outperforms DQP

Analysis and evaluation of decentralized multiaccess Mac for ad-hoc networks

In mobile ad-hoc radio networks, terminals are mobile and heterogeneous, the architecture of the network is continuously changing, communication links are packet oriented and radio resources are scarce. Therefore, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. However, due to these network harsh conditions, decentralized Medium Access Control (MAC) protocols designed specifically for ad hoc networks are scarce. In this paper we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMATDMA in which a cross layer approach has been followed in order to maximize network throughput. A theoretical analysis of the system is presented ending up with closed expressions for the throughput and delay of the network and some simulations are presented to evaluate the performance of the system

La configuració de les autoritats de competència. Un model per a la regulació d’organismes independents i per a la reforma de l’administració pública

La pol&iacute;tica de compet&egrave;ncia contribueix decisivament a un funcionament eficient i equitatiu de l&#39;economia. I &eacute;s que, nom&eacute;s en un marc de compet&egrave;ncia es pot garantir la millor assignaci&oacute; possible de recursos que maximitzi la generaci&oacute; de b&eacute;ns i serveis. A m&eacute;s, la pol&iacute;tica de compet&egrave;ncia t&eacute; tamb&eacute; un interessant component equitatiu en la mesura que actua com a mecanisme que vetlla per l&#39;abs&egrave;ncia de barreres injustificades a l&#39;entrada al mercat - facilitant doncs un marc igualitari en termes d&#39;oportunitats - i pel fet que contribueix a garantir que els grans operadors competeixin entre s&iacute; de tal manera que se&#39;n vegin beneficiats els consumidors i usuaris (en preus, qualitat i innovaci&oacute;). Els mecanismes a disposici&oacute; de les autoritats de compet&egrave;ncia s&oacute;n rellevants. En relaci&oacute; a les administracions p&uacute;bliques les poden sancionar quan actuen com operadors, criticar la regulaci&oacute; que emeten i fins i tot impugnar-la davant dels tribunals. Les temptacions per tal que una autoritat de compet&egrave;ncia no sigui veritablement independent s&oacute;n significatives. Davant d&rsquo;aquest risc, el document se centrar&agrave; en desenvolupar un condicionant necessari per tal que el seu funcionament sigui &ograve;ptim: la seva independ&egrave;ncia. S&#39;exposar&agrave; com es pot assegurar que les autoritats de compet&egrave;ncia gaudeixin de la independ&egrave;ncia que la seva actuaci&oacute; exigeix a trav&eacute;s de l&#39;an&agrave;lisi d&#39;elements com: la forma jur&iacute;dica que adopta la instituci&oacute;, la gesti&oacute; del seu propi personal i garanties d&#39;estabilitat del mateix, la gesti&oacute; econ&ograve;mica del pressupost que se li assigna i com determinar-lo, el nomenament i les causes de remoci&oacute; dels seus alts c&agrave;rrecs aix&iacute; com la rendici&oacute; de comptes de la instituci&oacute;. L&#39;inter&egrave;s del document va m&eacute;s enll&agrave; de les autoritats de compet&egrave;ncia. Les seves conclusions poden ser extrapolables a organismes reguladors i, tot plegat, pot constituir la llavor d&#39;una nova manera de funcionar de les administracions p&uacute;bliques

Decentralised multi-access MAC protocol for ad-hoc networks

In ad-hoc radio networks, mechanisms on how to access the radio channel are extremely important in order to improve network efficiency and, when needed, to guarantee QoS. Traditionally, Medium Access Control (MAC) protocols in ad hoc networks have been designed to face off the well known collision resolution problem. However, when using advanced signal processing techniques, general assumptions on collisions and packet loss are no longer valid. Besides, little has been reported about MAC algorithms dealing with multiaccess channels in ad hoc networks. In this paper, we present a novel decentralized multiaccess MAC protocol for Ad Hoc networks. This MAC protocol is an hybrid CDMA-TDMA in which a cross layer approach has been followed to dinamically adapt to the traffic load. Closed expressions for the throughput and delay of the network are presented as a function of the multipacket reception capability of the receiver, the number of codes and the packet retransmission probability