SMORT: Scalable multipath on-demand routing for mobile ad hoc networks

Increasing popularity and availability of portable wireless devices, which constitute mobile ad hoc networks, calls for scalable ad hoc routing protocols. On-demand routing protocols adapt well with dynamic topologies of ad hoc networks, because of their lower control overhead and quick response to route breaks. But, as the size of the network increases, these protocols cease to perform due to large routing overhead generated while repairing route breaks. We propose a multipath on-demand routing protocol (SMORT), which reduces the routing overhead incurred in recovering from route breaks, by using secondary paths. SMORT computes fail-safe multiple paths, which provide all the intermediate nodes on the primary path with multiple routes (if exists) to destination. Exhaustive simulations using GloMoSim with large networks (2000 nodes) confirm that SMORT is scalable, and performs better even at higher mobility and traffic loads, when compared to the disjoint multipath routing protocol (DMRP) and ad hoc on-demand distance vector (AODV) routing protocol.     

Time-critical underwater sensor diffusion with no proactive exchanges and negligible reactive floods

In this paper we study multi-hop ad hoc routing in a scalable underwater sensor network (UWSN), which is a novel network paradigm for ad hoc investigation of the world below the water surface. Unlike existing underwater acoustic networks (UAN), the new UWSN paradigm dispatches large number (in the thousands) of unmanned low-cost sensor nodes to locally monitor and report otherwise not easily accessible underwater events in a time-critical manner. Due to the large propagation latency and very low bandwidth of the acoustic channel, a new protocol stack and corresponding models are required as conventional approaches fail. In particular, we show that neither proactive routing message exchange nor reactive/on-demand flooding is adequate in the challenging new underwater environment. Unlike the terrestrial scenarios, on-demand flooding cannot be both reliable and efficient due to widespread collisions caused by the large propagation delay. On the other hand, as in terrestrial scenarios, proactive routing is more expensive and less efficient than on-demand routing in typical underwater environments. We propose a “conservative” communications architecture that minimizes the number of all packet transmissions to avoid possible acoustic collisions. This is implemented in the non-intrusive underwater diffusion (UWD), which is a multi-hop ad hoc routing and in-network processing protocol with no proactive routing message exchange and negligible amount of on-demand floods. To achieve its design goal, UWD does not rely on GPS or power hungry motors to control currents. Instead, UWD is designed in a minimalist’s framework, which assumes homogeneous GPS-free nodes and random node mobility. Our simulation study verifies the effectiveness and efficiency of our design.     

下一代移动技术UMA探讨

讨论了通过无线IP网络(未授权移动接入)传输语音、消息和多媒体信息的新技术,未授权移动接入技术是向通信技术融合迈进的第一步。介绍了未授权移动接入技术的性能和应用,对未授权移动接入技术的发展进行了预测。     

基于Kerberos身份认证的研究及改进

本文对网络安全中实现身份认证的Kerberos协议进行了详细的介绍,并分析了其局限性.在此基础上,提出了一种基于公钥密码的Kerberos改进协议.     

Highly branched radial block copolymers via dendritic initiation of aliphatic polyesters

Living ring opening polymerization of ε-caprolactone initiated from the numerous chain-end hydroxymethyl groups of the analogous dendrimeric and hyperbranched polyesters derived from 2,2-bis(hydroxymethyl) propionic acid is described. By controlling the size of the dendritic macromolecule and the molar ratio of ε-caprolactone, a variety of highly branched radial block copolymers are obtained. Comparison of the results obtained for the dendrimeric and hyperbranched initiators demonstrates that the reactivity of the chain-end hydroxymethyl groups in the dendrimer are significantly greater than in the isomeric hyperbranched case. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2793–2798, 1998     

An agent-based signaling architecture for supporting mobility in radio ATM networks

This paper presents a signaling architecture for supporting mobility in radio asynchronous transfer mode (ATM) networks. A new concept of mobile software agent, known as ‘representative’, is used for insulating fixed network entities from the effects of user mobility. It is shown that, depending on the physical locations of the mobile terminals, their representatives can be used for distributing the mobility management load within the fixed backbone network. This paper describes a location and a representative management scheme followed by a novel connection caching strategy which is used for implementing a family of low-latency and scalable ATM connection handovers. A prototype implementation of the proposed architecture and the associated experimental results are also presented to demonstrate the feasibility and performance of this agent-based signaling scheme. ©1997 by John Wiley & Sons, Ltd.     

GMNF-DVMRP: an enhanced version of distance vector multicast routing protocol

In this paper we propose an enhancement to the Distance Vector Multicast Routing Protocol (DVMRP), called ‘Group Membership Near First DVMRP’ (GMNF-DVMRP), to decrease the network cost (NC) of the multicast tree formed by DVMRP. A simulation is implemented to compare our enhanced version and the original DVMRP. We find that our method saves about 5%–7% of NC of the multicast tree formed by DVMRP. © 1998 John Wiley & Sons, Ltd.     

面向IPTV应用的DSLAM设备特性分析与对策

IPTV的传输网对多播和服务质量的支持将很大程度上决定用户使用IPTV的感受,在分析现有DSLAM设备的特性基础上,提出了还应注意的问题和解决方法,使传输网对服务质量的支持能有较大改善.     

Vinyl monomers bearing chromophore moieties and their polymers. II. Fluorescence and initiation behavior of N-(4-N′, N′-dimethylaminophenyl)maleimide and its polymer

A maleimide bearing electron-donating chromophore, N-(4-N′,N′-dimethylaminophenyl)-maleimide (DMAPMI) was synthesized from N, N-dimethylaminoaniline and maleic anhydride in the presence of acetic anhydride and sodium acetate. DMAPMI can be easily copolymerized with vinyl acetate (VAc). In addition, it can be easily homopolymerized by UV light irradiation or by using AIBN or BPO as an initiator. The fluorescence spectra of DMAPMI and its polymer or copolymer were recorded and compared at the same chromophore concentrations. It was observed that the fluorescence emission intensity of DMAPMI was much lower than those of its polymers. This may be due to the occurrence of intermolecular charge transfer interaction between the electron-donating dimethylaminophenyl moiety and acrylic electron-accepting carbon-carbon double bond in the monomer. The model compound, N-(4-N′, N′-dimethylaminophenyl)succinimide (DMAPSI), which has no carbon-carbon double bond, displayed the same fluorescence behavior as DMAPMI polymers. The fluorescence of DMAPMI polymers and DMAPSI can be quenched by electron-deficient compounds such as AN, TCNE, MMA, etc. All these results supported the above conclusion. This is another example of the “fluorescence structural self-quenching effect” termed by us previously and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. Study of the initiation behavior of DMAPMI and its polymer showed that they could initiate the photopolymerization of AN, by combination with BPO, they could also initiate the thermopolymerization of vinyl monomers such as MMA. © 1996 John Wiley & Sons, Inc.     

用于爆轰驱动的射流起爆实验研究

爆轰驱动激波风洞的自由来流模拟范围与驱动气体的爆轰极限密切相关,爆轰极限越宽则模拟范围越大。驱动气体一般是通过点火管进行起爆的,提高点火管的起爆能力可以拓宽爆轰极限。为了提高点火管起爆能力,就点火管口径、点火气体爆轰敏感性和单/双点火管3种因素的影响进行了实验研究。在不同的点火管初始条件下,对驱动段波速进行了测量。结论如下:(1)提高点火管口径可以显著提升起爆能力;(2)点火气体爆轰敏感性对起爆能力有影响,点火管为缩径内型面时,低敏感性气体起爆能力更强,点火管为等径内型面时则低敏感性气体和高敏感性气体的起爆能力大体持平;(3)在保证射流同步的前提下,双点火管能够提高起爆能力,为保证射流同步性需使用化学恰当比的氢氧混气等爆轰敏感性强的点火气体。