http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11543 Mobile swarms of autonomous underwater vehicles (AUV) have exciting potential for extending current AUV applications and adding new possibilities to the working environment of the oceans. For swarm operations to occur, fast reliable communication between all vehicles within the swarm is needed. The challenge for underwater communication is the very different and unique characteristics of the channel compared to the terrestrial environment. Acoustic communication has been the typical physical layer technology used for underwater operations and has experienced significant research and progress over the last few decades, however this focus has been predominately on longer range acoustic channels. The work presented in this paper is to determine the critical parameters of an underwater acoustic communication channel for the evaluation and development of a new MAC Protocol designed for short range communication between vehicles operating within a swarm. This paper provides a review of the essential channel characteristics and the modelling currently in use for this purpose, highlighting the difference for short range operations. It then assesses the electro-acoustic interface with investigation into the parametric relationship between digital modulation requirements and short range channel characteristics. 2013-03-12T02:51:26.950Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:11305 Research Doctorate - Doctor of Philosophy (PhD) 2012-08-21T06:59:05.600Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:8697 The opportunities and applications for a large group of coordinating autonomous underwater vehicles (AUV) is exciting and provides greater exploration opportunities than fixed sensor nodes or using a single AUV. The work presented in this paperis the development of a Medium Access Control Protocol for a cluster of small autonomous vehicles working in a centralized network topology. Acoustic communication links are typically used for underwater operations, however are substantially imited by the physics of acoustic propagation which require essentially new scheduling protocols to those being used and developed for packet radio networks. This paper provides a discussion and overview of the essential issues for developing a new MAC protocol for a cluster of closely operating underwater vehicles and presents some performance results for a proposed Adaptive Token Polling Protocol. 2012-06-05T01:32:13.974Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:9816 Bachelor Honours - Bachelor of Theology (Honours) 2012-01-30T05:30:38.552Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:9154 The ubiquitous IEEE 802.11 standard exhibits a significant amount of MAC protocol overhead inherent to contention-based random access protocols. To alleviate this overhead and improve protocol performance, a dynamic protocol timing adaptation scheme is proposed whereby the fundamental 802.11 slot time and inter-frame spacing are reduced based on techniques that exploit the actual maximum propagation distance within a wireless LAN, in addition to advances in PHY layer technologies that facilitate faster MAC processing and carrier sensing. We show through numerical analysis that the proposed scheme has the theoretical potential to increase system throughput and improve the performance of both current and emerging high-throughput 802.11 wireless LAN standards. 2011-10-12T02:10:04.637Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:6469 2010-06-11T01:00:01.923Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1459 Methionine dependence is unique to cancer cells and defined as the inability to grow in a methionine-deprived environment even if supplemented with the metabolic precursor homocysteine. Cobalamin-dependent methionine synthase (MS) catalyses the formation of methionine and tetrahydrofolate from homocysteine and methyltetrahydrofolate, thus linking the methionine and folate pathways. The apparent altered methionine metabolism in methionine-dependent cancer cells suggests a role for MS, although results to date are conflicting. We have analysed key metabolites of the MS-associated transmethylation, transsulphuration and folate pathways of the methionine-dependent MAC15A tumour model as a function of tumour progression over a 10-day period. MS activity increased 2-fold from day 1 to day 10. Cysteine, homocysteine, S-adenosylmethionine and S-adenosylhomocysteine levels in tumour cytosolic fractions decreased as a function of tumour progression. Plasma cysteine levels also decreased, whilst the distribution of folates in erythrocytes was altered, with a maximum increase in methyltetrahydrofolate observed by day 5. The increasing MS activity and decreasing cysteine levels suggest an increasing methionine requirement by the tumour, whilst the induction of enzyme activity indicates that MS is not defective in the methionine-dependent MAC15A tumour. The decrease in tumour S-adenosylmethionine and S-adenosylhomocysteine levels suggests that methionine is required for some function other than cellular methylation, e.g., incorporation into protein. Overall, the results support a theory of methionine conservation in response to tumour growth, where the methionine-dependent MAC15A tumour has a higher than normal methionine requirement. 2010-04-27T06:52:09.172Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:1731 This paper presents a simple RLC/MAC protocol architecture for a wireless IP (Internet Protocol) network. In order to support IP-based multimedia services in a wireless network, two different approaches can be used. One approach is to transmit end-to-end IP packets in a multi-hop network, such as a cellular mobile telephone network. In this case IP packets can be transmitted on high data rate air interfaces using a suitable IP header compression technique. Another possibility is to transmit non-IP packets from a UE to a BTS using standard 2G/3G air interfaces. IP packets can be generated at a BTS by encapsulating received MAC packets on an uplink. On a downlink, an IP packet received from a RAN is fragmented at a BTS for further transmission using a standard air interface. This paper first reviews the end-to-end IP packet transmission strategy based on IP header compression techniques. Next a simple RLC/MAC protocol architecturefor a wireless IP network is proposed. The proposed protocol architecture is suitable for generating IP packets at a BTS by encapsulating MAC packets. IP packet encapsulation delay at a BTS is minimized by using a reservation-based MAC protocol. The MAC protocol uses class-based reservation and priority queuing techniques to satisfy QoS needs of different classes of traffic. The RLC protocol is mapped onto the MAC protocol to minimize signaling overhead. The proposed RLC/MAC layer is simple, flexible, and generates minimum signaling load to maintain high QoS for multimedia traffic. Performance of the RLC/MAC protocol is analyzed using a simulation model. 2010-04-27T06:09:50.315Z ]]>