Slotted Aloha

Throughput is a key measure of the quality of a wireless data link. It is defined as the number of information bits received without error per second and we would naturally like this quantity as to be high as possible. Maximizing throughput in a direct sequence spread spectrum network by way of a link layer protocol termed the Transmission Parameter Selection Algorithm (TPSA) has also been discussed [2]. This provides real time distributed control of transmission parameters such as power level, data rate, and forward error correction rate. This thesis looks at the problem of optimizing throughput for a packet based wireless data transmission scheme from a general point of view. The purpose of this work is to show the very nature of throughput and how it can be maximized by observing its response to certain changing parameters. We have taken a more general look at throughput by considering its definition for a packet-based scheme and how it can be maximized based on the channel model being used. Unlike most of the work done on this topic, our research is focused on the transmission of data as opposed to that of voice.

This paper evaluates the effects of Rayleigh fading, shadowing, and spatial distribution of the Mobile Terminals (MTs) on the operating performance of Slotted Aloha (S-Aloha) used as a Random Access Channel (RACH). This paper also evaluates the capture probability in a channel exhibiting Rayleigh fading, shadowing, and the effect of spatial distribution of the MTs. In addition, this work presents a different version of the steady-sate probabilities of the Markov chain of S-Aloha considering capture effect. This article simulates the stabilization of S-Aloha by utilizing an algorithm that dynamically controls the retransmission probabilities. Finally, this paper presents a numerical analysis of these simulations and identifies the operating of parameters that have shown to degrade system response.

In this paper the contrasting effects of transmission impairments and capture on both the network and single user performance of a slotted Aloha system are investigated in a mobile radio environment, accounting for frequency non-selective random propagation phenomena, and employing the packet error probability in order to define packet losses and capture. With this study we demonstrate that it is possible to generalize in a real propagation context a method previously proposed in literature for evaluating the network behavior in terms of steady-state throughput, backlog and stability in conventional transmission conditions, i.e., when all the transmission channels were error-free and the collisions caused the loss of all the packets involved. Moreover, we indicate under which specific constraints on the terminal mobility we can apply this method to analytically predict the single user performance, which we show being an important design parameter. Through the numerical results repor...

A hybrid access protocol known, as contention time-division multiple access (C-TDMA), is presented and analyzed in a radio cellular multiuser system scenario. C-TDMA shows some features of contention-based (slotted-ALOHA) and reservation-based (packet reservation multiple access, PRMA) protocols. It has been recommended for use in the uplink of future European multimedia distribution systems. A simple Markov model is proposed to describe C-TDMA behavior. A complete statistical analysis of the model has ...

Abstract: Radio Frequency IDentification (RFID) technologies are intended to remotely identify devices (called tags) by means of wireless communications. A typical RFID scenario includes a reader device (called the master ) and a (potentially large) set of tags which must be ...

ABSTRACT In Ad Hoc or sensor networks, communication may be achieved between mobile nodes without a central entity (base station), in a half-duplex manner. The impact of jamming signals on those kinds of networks is studied. The contributions of this paper can be divided into two parts. In the first part, the probability of success, throughput and the maximum throughput are derived for the half-duplex Slotted ALOHA in terms of the node transmitting probability, the node receiving probability and average jamming signals rate. Results show that the probability of success, throughput and maximum throughput decrease with the increase of average jamming signals rate. In the second part, the effect of jamming signals on the maximum throughput of retransmission cut-off half-duplex Slotted ALOHA is studied. A close form equation is obtained for the transmission probability from each mobile node that maximizes the channel throughput in the presence of jamming signals. This equation provides the relationship between the new packet transmission probability from each mobile node, jamming signals rate and the number of retransmission attempts. The number of retransmission attempts plays an important role for a lower value of jamming signals rate. The results of this study may be used for system design of half-duplex contention-based multiple access schemes with and without jamming signals and retransmission cut-off.

We study in this paper some evolutionary games where competition between individuals from a large population occurs through many local interactions between randomly selected individuals. We focus on games that have the property of possessing a single interior evolutionarily stable strategy (ESS). We study in particular the effect of the time delays on the convergence of evolutionary dynamics to the

Throughput is a key measure of the quality of a wireless data link. It is defined as the number of information bits received without error per second and we would naturally like this quantity as to be high as possible. Maximizing throughput in a direct sequence spread spectrum network by way of a link layer protocol termed the Transmission Parameter Selection Algorithm (TPSA) has also been discussed [2]. This provides real time distributed control of transmission parameters such as power level, data rate, and forward error correction rate. This thesis looks at the problem of optimizing throughput for a packet based wireless data transmission scheme from a general point of view. The purpose of this work is to show the very nature of throughput and how it can be maximized by observing its response to certain changing parameters. We have taken a more general look at throughput by considering its definition for a packet-based scheme and how it can be maximized based on the channel model being used. Unlike most of the work done on this topic, our research is focused on the transmission of data as opposed to that of voice.