| The objectives addressed in this thesis are twofold: first, the design of Quality of Service (QoS) oriented Medium Access Control (MAC) protocols for Wireless Local Area Networks (WLANs); second, the performance evaluation via analytical methods of the proposed schemes from a QoS-oriented perspective. Keywords for this thesis are: (1) Wireless, as the MAC layer lies directly on top of the physical layer, and the nature of the wireless link poses innumerable constraints on the MAC layer design. (2) Local Area Networks & Picocells, as the target is to provide collectivity to a relatively small set of users (up to a hundred), situated within a maximum range of idle hundred meters.(3) Packet transmission , as the algorithms presented in this thesis are packet oriented instead of connection (i.e. voice) oriented. (4) MultiServices & QoS, as the proposed protocols take into account that different applications with different throughput and delay requirements may be using the network at the same time. (5) Matrix-analytical Methods, as the analytical models included have infinite-state Markov chains associated which, fortunately, fit in the framework of the matrix-analytic theory developed by Marcel F. Neuts.; Chapter 2 analyzes the conditionants of the MAC layer design coming from the lower layers of the protocol stack. Therefore, it begins by describing the indoor radio propagation characteristics.; Chapter 3 starts with an overview of the different WLAN technologies. This thesis focuses on microwave WLANs, i.e. radio WLANs with modulations providing maximum bit rates.; Chapter 4 presents and evaluates FIFO by Sets CSMA (FS-CSMA), a random access MAC protocol for ad-hoc WLANs.; FIFO by Sets ALOHA (FS-ALOHA), introduced in Chapter 5, is a Collision Resolution Algorithm for the Uplink contention channel present in multimedia broadband infrastructured WLANs.; Finally, the delay and throughput characteristics of FS-ALOHA are improved in Chapter 6. This new version of the algorithm. denoted as FS-ALOHA++, is further provided with a priority mechanism (inspired by the threshold mechanism of FS-CSMA) which enables the differentiated service of two request classes, high priority and best-effort. (Abstract shortened by UMI.)... |
