Dimitris Skyrianoglou

Seamless continuity of real-time video across UMTS and WLAN networks: challenges and performance evaluation

This article addresses several challenges related to the evolution toward seamless interworking of wireless LAN and 3G cellular networks. The main objective is to evaluate the conditions and restrictions under which seamless continuity of video sessions across the two networks is feasible. For this purpose, we formulate a number of practical interworking scenarios, where UMTS subscribers with ongoing real-time video sessions hand over to WLAN, and we study the feasibility of seamless continuity by means of simulation. We particularly quantify the maximum number of UMTS subscribers that can be admitted to the WLAN, subject to maintaining the same level of UMTS QoS and respecting the WLAN policies. Our results indicate that the WLAN can support seamless continuity of video sessions for only a limited number of UMTS subscribers, which depends on the applied WLAN policy, access parameters, and QoS requirements. In addition to this study, we do address several other issues that are equally important to seamless session continuity, such as the QoS discrepancies across UMTS and WLAN, the vertical handover details, and various means of access control and differentiation between regular WLAN data users and UMTS subscribers. The framework for discussing these issues is created by considering a practical UMTS/WLAN interworking architecture.

MAC protocol and traffic scheduling for wireless ATM networks

The Medium Access Control (MAC) protocol defined in the Wireless ATM Network Demonstrator (WAND) system being developed within the project Magic WAND is presented. Magic WAND is investigating extensions of ATM technology to cover wireless customer premises networks, in the framework of the Advanced Communications Technologies and Services (ACTS) programme, funded by the European Union. The MAC protocol, known as MASCARA, uses a dynamic TDMA scheme, which combines reservation‐ and contention‐based access methods to provide multiple access efficiency and quality of service guarantees to wireless ATM terminal connections sharing a common radio channel. The paper focuses on the description of PRADOS, a delay‐oriented traffic scheduling algorithm, which aims at satisfying the requirements of the various traffic classes defined by the ATM architecture. Simulation results are presented to assess the performance of the proposed algorithm in scheduling transmission of variable bit rate connections.

Traffic scheduling in wireless ATM networks

Wireless ATM is enjoying enormous research interest in the last few years, because of its ability to combine multimedia applications support, together with the freedom of mobility. One of the key design issues is the medium access control (MAC) protocol for the radio interface. This paper presents the traffic scheduling algorithm used in the MAC protocol of the Wireless ATM Network Demonstrator (WAND) system being developed within project Magic WAND. Magic WAND is investigating wireless ATM technology for customer premises networks in the framework of the Advanced Communications Technologies and Services (ACTS) programme, funded by the European Union. The proposed algorithm is delay oriented to meet the requirements of the various traffic classes defined by the ATM architecture. Simulation results are presented to assess the performance of the algorithm.

A centralized approach to dynamic channel assignment in wireless ATM LANs

A centralized approach for dynamic channel assignment (DCA) in wireless ATM system is presented. The proposed approach applies to structured wireless ATM LANs, where base stations act as hubs to offer wireless access to mobile units. An intradomain DCA entity (IADCA) is introduced for the dynamic assignment of resources to the requesting base stations, taking into account mutual interference constraints and current resource usage. The IADCA entity is based on two different reservation disciplines and multiple assignment policies when candidate carriers are available. Simulation results for a number of scenarios are presented to assess the performance of the proposed approach.

Seamless multimedia QoS across UMTS and WLANs

The main objective of this paper is to evaluate the conditions and restrictions under which seamless multimedia QoS provision across UMTS and IEEE 802.11e WLANs is feasible. For this purpose, we consider a practical interworking scenario, where UMTS subscribers with ongoing real-time video sessions handover to WLAN, and we study the feasibility of seamless continuity by means of simulation. We particularly quantify the maximum number of UMTS subscribers that can be admitted to the WLAN, subject to maintaining the same level of UMTS QoS and respecting the WLAN policies. Our results indicate that the WLAN can support seamless continuity of video sessions for a relatively small number of UMTS subscribers, which depends on the applied WLAN policy, access parameters and QoS requirements. In addition to this study, we do address several other issues that are equally important to seamless session continuity such as the QoS discrepancies across UMTS and WLAN. The framework for discussing these issues is created by considering a practical UMTS/WLAN interworking architecture.

Supporting UMTS QoS in Wireless LANs

This paper focuses on how the UMTS Quality of Service (QoS) architecture can be supported in Wireless LANs (WLANs), deployed as alternative access networks to the UMTS core. More specifically, the paper addresses the provision of UMTS QoS over WLANs and proposes a solution based on the introduction of the Wireless Adaptation Layer (WAL). The WAL provides means for extending the UMTS QoS in WLAN environments, independently of the underlying WLAN technology. Moreover, the WAL configuration to support the provisioning of UMTS QoS is discussed. In this context, a mapping between UMTS QoS attributes and WAL modules is proposed and justified.

A framework for mobility and QoS provisioning in IPv6 DECT networks

The Internet Protocol suite is emerging as the ubiquitous communication platform for almost every conceivable information exchange. Hence, a worldwide effort to support IP functionality over any existing link technology has started, including the booming wireless industry. DECT is a well-standardized wireless access network technology, supporting high bitrate digital communications. Moreover, IPv6, the emerging Internet Protocol version, extends support for mobility, QoS, wireless nodes and addressing issues. We propose a framework for mobility and QoS provisioning in IPv6 DECT networks. Mobile IPv6 is deployed, in conjunction with standard DECT mobility procedures to provide a suitable environment for Internet users on the move. Furthermore, RSVP is utilized to handle QoS signaling.

Investigation of Alternative ARQ Schemes for a Wireless ATM Network

The application of two alternative ARQ schemes on the WAND (Wireless ATM Network Demonstrator, ACTS project AC085) system is examined. These schemes are the Selective Repeat Protocol (SRP) and the Partial selective Repeat superIMposEd on gbn (PRIME) ARQ protocol. This work discusses the advantages and disadvantages of each alternative, and focuses on the performance evaluation and performance comparison of the two protocols, as we on the comparison of these protocols with Go-Back-N ARQ, the protocol used in WAND.