Protocol Architectures for wireless networks: issues, perspectives and enhancements

Abstract

In this work we have analyzed different types of wireless networks and we have investigated the behavior of different MAC and routing protocols and different protocol architectures. Specifically, we have analyzed a TDMA MAC protocol for Mobile Ad hoc NETworks called Evolutionary-TDMA (E-TDMA). Based on this protocol we have developed a cross-layer approach that uses multiple linkdisjoint paths for a pair source-destination supporting a soft QoS. For this latter point we have developed a Multipath Forward Algorithm to manage and assign the slots. We have developed two different schemes: QoS scheme 1 and QoS scheme 2 and compared these schemes in terms of throughput, delay and overhead with a well-known multipath protocol routing, the AOMDV over 802.11 MAC protocol and AOMDV over E-TDMA. We have obtained good performance exploiting advantages of a TDMA MAC protocol and a Multipath routing protocol. Simulation results have shown as a cross-layer approach permits good performance in terms of throughput, end-to-end data packets delay and overhead to be obtained. In fact, multipath routing protocols for wireless ad hoc networks have been investigated because the use of alternate paths permits a greater fault-tolerance to be obtained. As far as multipath routing protocol is concerned we have developed and analyzed a multipath routing protocol based on geographic positions of the nodes in the network, Geographic Multipath Protocol (GMP). Results, in terms of throughput and delay, show that the multiple paths with minimum interference are better. We have investigated the cross-layer approach also for Wireless Sensor Networks. Although, this kind of networks could be considered an extension of Ad hoc networks, characteristics of WSNs are so different that protocols explicitly developed for MANETs cannot be directly applied for sensors networks. After analyzed some protocols we have proposed some solutions to increase the lifetime of the sensor networks considering other important parameters as throughput and latency. Finally, our analysis of wireless networks finishes with the analysis of Wireless Mesh Networks. We have investigated multi-hop wireless networks based on the IEEE 802.16 technology. Specifically, we have analyzed the Coordinated Distributed Scheme (CDS) of the IEEE Std. 802.16 and we have developed a MAC module 6 Conlcusions 158 supporting the CDS in ns2. Moreover, we have developed two different totally distributed schemes that do not require any changes of the structure of the hardware used in the 802.16. The two schemes proposed manage the assignment of the control slots (Transmit Opportunity XmtOP), in a different fashion. We have developed the two scheme in ns2 in order to compare them with the CDS of the 802.16. Our approaches permit good performance in terms of throughput and delay to be obtained. Our approaches are independent from parameters of the network as density or topology. On the other hand, the CDS is not robust for different network conditions because the behavior of the scheme depends from the setting of particular parameters.