Lo Chee Chung,Anthony
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Publication Efficient DECT-mobile IP interworking for mobile computing(2000) Lo, Anthony; Seah, Winston; Schreuder, Edwin; CENTRE FOR WIRELESS COMMUNICATIONSDigital Enhanced Cordless Telecommunications (DECT) [1] is a general radio access technology, which supports local-area mobility only. The interconnection of DECT to Internet is inadequate to support wide-area mobility because IP [2] does not support host mobility between different subnetworks (subnets). This paper describes the interworking of DECT with Mobile IP [3] to support subnet-level mobility, while DECT is employed for user mobility within a subnet. To achieve an efficient interworking, we exploit and take advantage of the mobility features of DECT, which offers faster convergence and far fewer overheads. Hence, the Mobile IP handover latency can be reduced to improve the performance of transport protocols (e.g., TCP). We define the necessary protocol signalling for the DECT-Mobile IP interworking mobility management procedures, which require no modification to both DECT and Mobile IP.Publication On service prioritization in Mobile Ad-hoc networks(2001) Xiao, H.; Kee Chaing Chua; Seah, W.; Lo, A.; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL & COMPUTER ENGINEERINGThe aim of service prioritization is to give resource priority to certain traffic types. For example, voice service can have higher priority than data service, web surfing can have higher priority than FTP and email applications, or some users can have higher priority than others. This paper investigates the performance of service prioritization in Mobile Ad-hoc NETworks (MANETs). Two schemes, priority buffer management and priority scheduling, are applied to realize service prioritization and three service profiles are discussed as well as. Simulation results are presented to show that the priority schemes work well with TCP traffic but not with Constant Bit Rate (CBR) traffic. Besides this, the priority scheduling scheme outperforms the priority buffer management scheme in terms of average end-to-end delay of TCP packets and average throughput of TCP sessions.Publication Session Management protocol for mobile computing(1998) Lo, Anthony C.C.; Chandrasekaran, V.; Seah, Winston K.G.; Soh, C.P.; CENTRE FOR WIRELESS COMMUNICATIONSThe ACTS AC034 OnTheMove project is in the process of developing a mobile middleware architecture, called Mobile Application Support Environment (MASE), to support mobile multimedia applications over heterogeneous networks. MASE is an intermediate middleware layer between the application layer and the underlying heterogeneous networks (wireless and wireline networks). Wireless communication is unreliable, and frequent disconnections are common compared to wireline networks. Existing protocol suites such as TCP/IP have not been designed to interwork with wireless networks. Once the wireless network connection is permanently dropped, the transport may abort its connection, and any process running at the application layer would be terminated due to loss of transport connections. For applications that exchange large amounts of data, the loss of transport connections means that the applications need to start from scratch. In this paper, we describe a Session Management (SM) protocol, which enables any application to resume operation once the transport as well as the wireless network connection is restored. The SM protocol entity is part of MASE so that any mobile application could use the Session Management services for reliable data transfer. The SM protocol was designed, specified, simulated and validated using the ITU-T Specification and Description Language (SDL) and its support-tools.Publication A quantitative analysis of TCP performance over wireless multihop networks(2001) Xiao, H.; Chua, K.C.; Seah, W.; Lo, A.; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL & COMPUTER ENGINEERINGAn analytical model of a single TCP session based on a string topology in wireless multihop networks is presented. The model for the communication process considers buffering, propagation delay and access chance to the channel as well. Markov chain technique is adopted in analyzing the TCP behavior. Fully analysis is given to the case where the TCP source and destination are one hop away and the maximum TCP window size is less than the buffer size in each node. Consideration is also given to the case when the maximum TCP window size is larger than the buffer size in each node. The analytical results are validated against results using the NS simulator.Publication Flexible quality of service model for mobile Ad-hoc networks(2000) Xiao, Hannan; Seah, Winston K.G.; Lo, Anthony; Chua, Kee Chaing; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL ENGINEERINGQuality of service (QoS) support in Mobile Ad-hoc NETworks (MANETs) is a challenging task. Most of the proposals in the literature only address certain aspects of the QoS support, e.g., QoS routing, QoS medium access control (MAC) and resource reservation. However, none of them proposes a QoS model for MANETs. Meanwhile, two QoS models have been proposed for the Internet, viz., the Integrated Services (IntServ) model and the Differentiated Services (DiffServ) model, but these models are aimed for wired networks. In this paper, we propose a flexible QoS model for MANETs (FQMM) which considers the characteristics of MANETs and combines the high quality QoS of IntServ and service differentiation of DiffServ. Salient features of FQMM include: dynamics roles of nodes, hybrid provisioning and adaptive conditioning. Preliminary simulation results show that FQMM achieves better performance in terms of throughput and service differentiation than the best-effort model.Publication Automatic implementation of the ISO FTAM protocol based on an integrated specification of Estelle and ASN.1(1999-10-15) Lo, A.; Lai, R.; CENTRE FOR WIRELESS COMMUNICATIONSThere is a huge demand for methods that enable communication protocols to be speedily implemented. Application layer Protocol Data Units (PDUs) are specified in Abstract Syntax Notation One (ASN.1). Any application protocol specification is not complete until it includes the PDU type definitions and operations for manipulating, comparing and assigning ASN.1 values. Given that internationally standardized Formal Description Techniques (FDTs) do not readily support ASN.1, an automatic implementation of an application protocol cannot be easily achieved; its development can thus be a long and error-prone task. This paper describes the details of an automatic implementation of the ISO FTAM protocol using an integrated Estelle and ASN.1 specification and the software system, EASE (Estelle and ASN.1 Software Environment) which supports such a specification, demonstrating how this long and error-prone process can be addressed; an evaluation of the work done is also included. It presents a success story of the use of FDTs, in particular Estelle, for the speedy implementation of an application protocol so that developers in the communications industry have more confidence in using FDTs for their communication software developments.