Tesis doctoral de Eduardo García Villegas
Wlans, primarily the various versions of ieee 802.11 standards, and more precisely, those operating in infrastructure mode, are nowadays the most popular technologies for providing broadband radio access to ip networks, whether to extend small office/home office (soho) network lans or to provide internet access in public places. Moreover, with the advent of wi-fi certified products, different competitive brands of wlan devices are interoperable at a basic level of service. however, the increasing density of wlan access points has started to reveal the negative effects and shortcomings of the original ieee 802.11 standards. One of its key success factors, the use of unlicensed industrial scientific medical (ism) frequency bands, is at the same time one of its major drawbacks. These frequencies are freely available to the general public. On the other hand, such frequencies are defined within a small portion of the spectrum and are usually shared among several users. Besides, the medium access defined by the ieee 802.11 (csma, or listen before talk) requires a special attention to all interference issues. in this scenario, ieee wlans are unable to exploit all their potential. However, intelligent radio resource management (rrm) policies could be applied to minimize the harmful effects of interference and an uneven load distribution. Throughout this dissertation, it is shown that efficient rrm mechanisms are able to improve notably the performance of a legacy ieee wlan. this thesis explores ways of understanding the performance issues that are endemic to ieee 802.11 wlans, as well as ways of minimizing these negative effects by means of radio resource management. In fact, these problems are not new and have been studied extensively since the advent of mobile communications networks, but the particular characteristics of the 802.11 wlans require new approaches. rrm mechanisms in the field of ieee 802.11 wlans are basically intended to reduce contention and interference. This reduction is translated into an improved quality of experience (qoe), as perceived by the users. To this end, rrm should provide efficient channel allocation mechanisms, modulation selection algorithms, power control and load balancing. Given the dynamic nature of radio propagation, and due to user mobility, the parameters that define the wireless environment vary in time. Therefore, in order to maintain the required performance, we should find mechanisms that allow a dynamic and automatic reconfiguration of the network in response to the changes in the environment. To sum up, we build our scenario of interest with intelligent wi-fi devices capable of cooperating either in a centralized or a distributed manner, in order to make a better use of the shared and scarce radio resources. our contribution to rrm on wlans starts with the study and characterization of interference in the particular field of ieee 802.11 networks. Following, we develop a capacity model for large wlan deployments that takes both the effect of carried traffic and inter-cell interference into account. The model also includes the effect of rate adaptation. These capacity estimations are useful to evaluate the benefits of a rrm mechanism, for example, it was used as the metric observed by a frequency management approach. This frequency assignment mechanism makes use of all the available spectrum (overlapping and non-overlapping ism channels), since it takes the effects of both co-channel and adjacent-channel interference into account. In order to cope with the uneven load distribution usually found on hot-spots, two load balancing mechanisms are proposed after defining the concept of load: a client-driven approach, and a cell-breathing mechanism. All these mechanisms need to be integrated into a single architecture. In this regard, two radio resource management architectures are developed: a centralized architecture, as part of the uamn project, and a distributed scheme.
Datos académicos de la tesis doctoral «Self-optimzation of radio resources on ieee 802.11 networks«
- Título de la tesis: Self-optimzation of radio resources on ieee 802.11 networks
- Autor: Eduardo García Villegas
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 18/02/2010
Dirección y tribunal
- Director de la tesis
- Josep Paradells Aspas
- Tribunal
- Presidente del tribunal: jordi Casademont serra
- albert Banchs roca (vocal)
- héctor Luis Velayos muñoz (vocal)
- pedro Miguel Ruiz martínez (vocal)