The main purpose of this thesis is to estimate the signal arrival time in low rate wireless personal area network systems. In a dense multipath environment, the generalized maximum-likelihood (GML) algorithm can be used for the time-of-arrival (TOA) estimation. Nevertheless, the GML algorithm is very time-consuming and usually takes a long period of time, and sometimes fails to converge. Hence, a simplified scheme that would improve the algorithm is investigated. In the simplified scheme, the search is executed in a sequential form. Two threshold parameters are determined for the stop condition in the algorithm. One threshold is on the arrival time of estimated path, while the other is on the fading amplitude of estimated path. The determination of thresholds can be based on the minimum error probability, which is defined as the sum of the false alarm probability and the missing probability. Root-mean-square error statistics are used to improve the thresholds setting. In this scheme, candidate pairs of thresholds are evaluated in each appropriate range. To solve the problem that the root-mean-square error value for each pair of thresholds is calculated, the simulated annealing is adopted for searching the best threshold pair. The problem that all possible solutions in a large range must be evaluated can be solved by simulated annealing. From the simulation results, it is seen that, while the signal-to-noise ratio is larger or equal to 4dB, the proposed scheme can achieve better performance than the root-mean-square error statistics scheme.

Recently, with the fast development of wireless communications, the radio spectrum becomes a precious natural resource. Many researches and reports reveal the problems of inefficient spectrum utilization. Cognitive Radio (CR) technology is now developing for solving this critical problem. This technology will enable various kinds of wireless systems to look for and connect radio frequency spectrum that the locality leave unused by oneself, to offer the best service to user. The CR will pass in and out the idle frequency band according to the demand while receiving and dispatching the signal, avoid the frequency band that has been already used. In CR network, the objective is to maximize the throughput of secondary users while limiting the probability of colliding with primary users below a prescribed level. In this paper, we consider a distributed secondary networks model where users seek spectrum opportunities independently that overlaying the primary networks to analyze the system performance and the effect to the primary users with the existence of both primary users and secondary users under the cognitive radio networks. In the cognitive system, due to the existence of noise and fading effect, error detection cannot be avoided. Therefore, we made a comparison to the difference of the efficiency among environments of different probability of miss detection. We also propose a random hopping method for all secondary users in system will re-sensing after a random period of time. Hereby, efficiently decreases the ratio of time that influences the primary users by the secondary users, and further research the factor that influences its efficiency.

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In this thesis, we proposed a simple yet novel multicast scheduling scheme for IEEE 802.16e wireless metropolitan area networks. Specifically, we want to solve the problem that how the base station schedules data messages in a multicast superframe such that mobile stations can receive their required multicast data and the total awake time of mobile stations is minimal. We first prove that this problem is NP-complete, and then propose a greedy k-approximation algorithm, named G-EEMS, whose running time is , where n is the total number of multicast data messages and k is the size of MBS (multicast and broadcast service) zone in a frame. Simulation results show that, in terms of energy throughput, G-EEMS significantly outperforms the existing scheme, called SMBC-D.

<p>This thesis will investigate the possibilities to wireless communicate within time critical applications with the radio protocol IEEE 802.15.4.</p><p>IEEE 802.15.4 is a very quick protocol so the delays and jitter can be ignored in a small network.</p><p>The thesis handles the question: Is it possible to split a CAN-bus and send the data via radio to the other side of the CAN-bus?</p><p>The big problems with this are:</p><p>• Will it be treated like a transparent link and not disturb the original functionality?</p><p>• How does a system which is split up by radio treat new nodes on the bus?</p><p>• What will be the maximum speed and the maximum utilization factor for the split up bus?</p><p>• What new suitable protocols can be implemented on a higher level to get the split bus to work?</p><p>This is modeled and discussed, real measurement from a radio link is used in the model to see if it’s possible.</p><p>The radio communication will satisfy the demands from the company regarding their application. With an efficient error handling and a smart transmission protocol the application can be a very smart way of sending CAN-data via radio.</p> / <p>Denna rapport undersöker möjligheterna med att kommunicera trådlöst i</p><p>tidskritiska applikationer med hjälp av radioprotokollet IEEE 802.15.4.</p><p>IEEE 802.15.4 är ett väldigt snabbt protokoll så jitter och fördröjningen i sändningarna kan försummas för så små nätverk som tas upp i denna uppsats.</p><p>Går det att bryta en CAN-buss och koppla in denna radiolänk så att den</p><p>uppfattas som transparent?</p><p>Många problem kommer att dyka upp om detta görs, några av dem är dessa:</p><p>• Hur behandlar ett system nya noder som kopplas in om CAN-bussen är uppdelad?</p><p>• Vilken är den maximala hastigheten och utnyttjandefaktor som kan uppnås av den delade CAN-bussen?</p><p>• Måste ett överliggande protokoll användas för att sköta om datatrafiken mellan bussarna?</p><p>Detta modelleras och diskuteras efter det att de uppmätta mätvärdena har samlats in och analyserats.</p><p>Det som framkom var att det fungerar väldigt bra, data kommer fram i tid och felen i radiosändningarna är väldigt små. Med en väl genomtänkt felhantering och ett likaså genomtänkt omsändningsprotokoll kommer detta att fungera väldigt bra beroende på avstånd och antennval.</p>

<p><!--st1\:*{behavior:url(#ieooui) } --><!--[endif]--> <!-- /* Font Definitions */ @font-face {font-family:Garamond; panose-1:2 2 4 4 3 3 1 1 8 3; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:647 0 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-layout-grid-align:none; punctuation-wrap:simple; text-autospace:none; font-size:12.0pt; mso-bidi-font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 70.85pt 70.85pt 70.85pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --></p><p>To implement a utility wireless sensor network, investigation of different wireless protocols has been performed. The protocols are Bluetooth, Wi-Fi, IEEE 802.15.4 and Zigbee. Consecutively literature studies have made it comprehensible to understand the function of the protocols that are suitable for development of wireless sensor networks. The importance of low cost, low power, reliable and high-quality properties for long distances are significant. IEEE 802.15.4 and Zigbee protocol are proper to implement as a wireless sensor network.</p><p> </p><p>To reduce the human efforts in the configuration of the system, a comfortable method is implemented to facilitate the procedure. The applied method is based on an automatic configuration of the system. The configuration and the decision taking are implemented in the software. The system is designed to avoid interference to other wireless networks with the possibilities of reconfiguration.</p><p>A uniform hardware and software design with separate functions of the system decided by a subsequent command for configuration is preferable. This imposes an advantage that increases the flexible potential of the system when a uniform solution is implemented.</p><p> </p><p>To support the basic communication principles and control of the system, a buffer implementation has been introduced. The functionality of decision taking is distributed, configured by system commands from the host system. Detecting of system commands requires a properly operating buffer management. In consideration to the power consumption in reference to battery utilizations, the settings of RF-module and microcontroller have a powerful impact to reduce the power consumption. All possibilities of hibernates and avoidance of unnecessarily transmitting, should be deactivated to minimize the power consumption.</p><p> </p>

Thèse de doctorat : Sciences informatiques : Paris Est : 2008. / Titre provenant de l'écran-titre.

Thèse de doctorat : Informatique : Evry-Val d'Essonne : 2008. / Titre provenant de l'écran-titre.

Thèse doctorat : Télécommunications : Villeurbanne, INSA : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 180-192.

Thèse de doctorat : Automatique, Traitement du Signal et Génie Informatique : Nancy 1 : 2008. Thèse de doctorat : Automatique, Traitement du Signal et Génie Informatique : Ecole Nationale d'Ingénieurs de Sfax : 2008. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre.