Méthodes avancées pour une ingénierie WLAN multi-standards

Products meeting the IEEE 802.11b and 802.11g (2.4 GHz band) and 802.11a (5 GHz band) standards are currently marketed and deployed in public places (hot spot areas) and also in private homes (ADSL WIFI terminals). If currently the systems operating in the 2.4 GHz band dominate the market, the increase in traffic could lead to the saturation of this band (only 3 separate channels) and also lead operators to move towards the 5 band. GHz. The different WLAN standards make it possible to provide raw speeds ranging from 1 to 54 Mbits/s (or even more than 100 Mbits/s with 802.11n being standardized). They therefore technically offer a large number of deployment possibilities. One of the difficulties for operators is choosing the appropriate standard based on deployment constraints for coverage and capacity. As traffic increases, densification needs also appear, which must be met with the appropriate standards. It is essential to be able to identify their limitations, in order to better guarantee the quality of service on the networks currently deployed and above all to foresee the problems which may appear during the increase in load as and when usage increases.The subject of the thesis therefore relates to a detailed analysis of the limitations of WLAN networks based on various selection criteria, including in particular the range, capacity and robustness to interference. It is then a question of concluding on recommendations and engineering rules for their deployment in areas of high traffic density. For systems operating in the 2.4 GHz band, which is a free band, interference between equipment of different standards and also between networks of competing operators are the key factors limiting the quality of service and data rates. The first step is to identify the possible sources of interference in the 2.4 GHz and 5 GHz bands, and to model the main parameters related to the jammers considered in the link budget and coverage calculations. The experimental approach was adopted to characterize the effect of jammers on the performance of 802.11 systems. A jammer model was extracted from our measurements and then we used a statistical approach to provide engineering rules to guarantee the performance of WLAN networks. At the same time, we have developed an 802.11 network simulator to realistically take into account the phenomena of WLAN propagation and interference. Thanks to this simulator, we studied the performance of these networks in a multi-user context and the effects of scaling up. The results obtained were compared to our measurements and to theoretical models