Toward All-IP networks : IP and wireless networks convergence

Abstract

In this thesis the state of the art for IP networks and the two most predominant wireless access networks, UMTS and Wireless LANs, has been reviewed with respect to the enhancements required toward the objective of supporting services across different network technologies in a seamless manner. Three main areas of research were identified as key in the path toward All-IP networks: i) IP-based mobility management, ii) IP-based UMTS Radio Access Networks and iii) QoS for Wireless LANs.<br/><br/>Future All-IP networks require of an IP-based mobility management protocol to support mobility across heterogeneous networks. Several protocols are being proposed in the IETF for this purpose with Mobile IPv6, Hierarchical Mobile IPv6 and Fast Handovers for Mobile IPv6 being the ones with a higher acceptance. Our contribution in this area has been the thorough study of the performance enhancements provided by each protocol and their associated costs in realistic scenarios to support the design process of Mobile IPv6-based networks where the suitability of the different options has to be evaluated. In addition, we proposed a combination of Hierarchical Mobile IPv6 and Fast Handovers for Mobile IPv6, based on the description provided in the Hierarchical Mobile IPv6 draft, that aims to outperform both proposals by adding the advantages of each of them.<br/><br/>During the evaluation of the IP-based mobility management protocols, the mobility model influence over the performance results led to an additional line of study where the main characteristics of the Random Waypoint mobility model were analyzed. The random waypoint model is a commonly used mobility model for simulations of wireless communication networks. We gave a formal description of this model in terms of a discrete- time stochastic process which provides a deep understanding on the characteristics of the mobility created by its usage. The results of our work are of practical value for performance analysis of communication networks to avoid misinterpretation of simulation results.<br/><br/>UMTS networks being deployed today based on the Release'99 specifications use ATM transport in the Radio Access Network (RAN). The specifications for future releases include options to support IP transport in the RAN, however, several challenges are introduced with regard to a significant increase in the transport protocol overhead and the provision of QoS guarantees. These challenges have to be addressed to ensure an efficient usage of the scarce RAN resources. Our work focused first in reducing the resources needed in the air interface for the expected most relevant application in future 3G networks, Voice over IP (VoIP). We designed a radio access bearer for VoIP when Robust Header Compression (RoHC) is used that reduces in about 50% the resources required in the air interface. Then, a multiplexing scheme for the reduction of the overhead in the wired part of the RAN that allows QoS differentiated scheduling was described and evaluated. The results showed an increase in the efficiency of the RAN resources usage between 100% and 260%, in our scenarios, when combined with RoHC. Finally, we proposed and evaluated a QoS differentiated scheduling mechanism based on Earliest-Deadline-First that fulfills the RAN specific synchronization requirements while providing the QoS differentiation required by the applications. <br/><br/>The IEEE 802.11 standard presents relevant defficiencies in order to support applications with QoS requirements. The integration of the Wireless LAN technology in future All-IP networks heavily depends on the success of the upcoming 802.11e standard which extends the 802.11MAC layer to provide QoS guarantees. With our work in this area we contributed to the 802.11e research standardization effort and designed three extensions of the 802.11 MAC layer to provide delay guarantees (DIME-EF) and bandwidth guarantees, absolute (ARME) or relative (DWFQ). <br/>Moreover, we analyzed the implications of introducing Wireless LAN capabilities in battery limited mobile devices as for example cellular phones. Based on the significant impact observed of the 802.11 power save mode over the 802.11e QoS mechanisms we designed and evaluated a solution that provides a soft upper bound of the data frames downlink delay according to the downlink frame interarrival time while minimizing the battery consumption. Part of this work has been used for the design and configuration of the NEC 3G/WLAN mobile terminal N900iL.