Juan J. Alcaraz

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This paper is focused on data transmission scheduling in V2I communications, where a central station, the roadside beacon, decides how to allocate system resources among the vehicles under coverage. We consider non-safety applications, whose commercial appeal is expected to accelerate the deployment of VANETs. In this case, the main objective is to deliver(More)
Cooperative inter-vehicular applications rely on the periodic exchange of broadcast single-hop status messages among vehicles, called beacons. The aggregated load on the wireless channel due to beacons can prevent the transmission of other types of messages, what is called channel congestion due to beaconing activity. In this paper we propose a novel(More)
Automatic identification based on radio frequency identification (RFID) is progressively being introduced into industrial environments, enabling new applications and processes. In the context of communications, RFID rely mostly on Frame Slotted Aloha (FSA) anticollision protocols. Their goal is to reduce the time required to detect all the tags within range(More)
In Cooperative Automatic Repeat reQuest (C-ARQ) protocols, the retransmission process between a pair of nodes can be assisted by a relay node. We investigate the performance of C-ARQ algorithms in cellular access networks, where the use of relays is a promising strategy for future evolutions. By means of Markov analysis and simulation we show that the(More)
In many practical RFID applications tags are attached to items that pass through the reader’s field moving at a constant speed, following a fixed path. The time-constrained presence of the tags in the identification region introduce the possibility that tags exit the system without being identified (lost tags). Reliability is a practical requirement in most(More)
In Radio Frequency Identification facilities the identification delay of a set of tags is mainly caused by the random access nature of the reading protocol, yielding a random identification time of the set of tags. In this paper, the cumulative distribution function of the identification time is evaluated using a discrete time Markov chain for single-set(More)
In Cooperative Automatic Repeat reQuest (C-ARQ) protocols, one or more nodes can act as relays, collaborating in the frame retransmission process between a sender and a destination node. In the framework of a broadband mobile access network, we consider a relay enhanced cell where the sender represents the base station, and an undefined number of relays can(More)
TCP, the dominant transport protocol for Internet applications, suffers severe performance degradation due to packet losses when a wireless link is present in the end-to-end path. For this reason, the 3G specification entity, 3GPP, has defined a reliable link layer protocol, RLC, to support packet switched services over UMTS. RLC provides error recovery in(More)