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排序方式: 共有103条查询结果,搜索用时 308 毫秒
1.
Mobility management for VoIP service: Mobile IP vs. SIP 总被引:4,自引:0,他引:4
Wireless Internet access has gained significant attention as wireless/mobile communications and networking become widespread. The voice over IP service is likely to play a key role in the convergence of IP-based Internet and mobile cellular networks. We explore different mobility management schemes from the perspective of VoIP services, with a focus on Mobile IP and session initiation protocol. After illustrating the signaling message flows in these two protocols for diverse cases of mobility management, we propose a shadow registration concept to reduce the interdomain handoff (macro-mobility) delay in the VoIP service in mobile environments. We also analytically compute and compare the delay and disruption time for exchanging signaling messages associated with the Mobile IP and SIP-based solutions. 相似文献
2.
Multicluster,mobile, multimedia radio network 总被引:95,自引:0,他引:95
A multi-cluster, multi-hop packet radio network architecture for wireless adaptive mobile information systems is presented. The proposed network supports multimedia traffic and relies on both time division and code division access schemes. This radio network is not supported by a wired infrastructure as conventional cellular systems are. Thus, it can be instantly deployed in areas with no infrastructure at all. By using a distributed clustering algorithm, nodes are organized into clusters. The clusterheads act as local coordinators to resolve channel scheduling, perform power measurement/control, maintain time division frame synchronization, and enhance the spatial reuse of time slots and codes. Moreover, to guarantee bandwidth for real time traffic, the architecture supports virtual circuits and allocates bandwidth to circuits at call setup time. The network is scalable to large numbers of nodes, and can handle mobility. Simulation experiments evaluate the performance of the proposed scheme in static and mobile environments.This work was supported by the U.S. Department of Justice/Federal Bureau of Investigation, ARPA/CSTO under Contract J-FBI-93-112 Computer Aided Design of High Performance Wireless Networked Systems. 相似文献
3.
Vehicular sensing where vehicles on the road continuously gather, process, and share location-relevant sensor data (e.g., road condition, traffic flow) is emerging as a new network paradigm for sensor information sharing in urban environments. Recently, smartphones have also received a lot of attention for their potential as portable vehicular urban sensing platforms, as they are equipped with a variety of environment and motion sensors (e.g., audio/video, accelerometer, and GPS) and multiple wireless interfaces (e.g., WiFi, Bluetooth and 2/3G). The ability to take a smartphone on board a vehicle and to complement the sensors of the latter with advanced smartphone capabilities is of immense interest to the industry. In this paper we survey recent vehicular sensor network developments and identify new trends. In particular we review the way sensor information is collected, stored and harvested using inter-vehicular communications (e.g., mobility-assist mobility-assisted dissemination and geographic storage), as well using the infrastructure (e.g., centralized and distributed storage in the wired Internet). The comparative performance of the various sensing schemes is important to us. Thus, we review key results by carefully examining and explaining the evaluation methodology, in the process gaining insight into vehicular sensor network design. Our comparative study confirms that system performance is impacted by a variety of factors such as wireless access methods, mobility, user location, and popularity of the information. 相似文献
4.
Cluster Size Optimization in Sensor Networks with Decentralized Cluster-Based Protocols 总被引:1,自引:0,他引:1
Network lifetime and energy-efficiency are viewed as the dominating considerations in designing cluster-based communication protocols for wireless sensor networks. This paper analytically provides the optimal cluster size that minimizes the total energy expenditure in such networks, where all sensors communicate data through their elected cluster heads to the base station in a decentralized fashion. LEACH, LEACH-Coverage, and DBS comprise three cluster-based protocols investigated in this paper that do not require any centralized support from a certain node. The analytical outcomes are given in the form of closed-form expressions for various widely-used network configurations. Extensive simulations on different networks are used to confirm the expectations based on the analytical results. To obtain a thorough understanding of the results, cluster number variability problem is identified and inspected from the energy consumption point of view. 相似文献
5.
6.
In this paper, we consider the mobility management in large, hierarchically organized multihop wireless networks. The examples of such networks range from battlefield networks, emergency disaster relief and law enforcement etc. We present a novel network addressing architecture to accommodate mobility using a Home Agent concept akin to mobile IP. We distinguish between the physical routing hierarchy (dictated by geographical relationships between nodes) and logical hierarchy of subnets in which the members move as a group (e.g., company, brigade, battalion in the battlefield). The performance of the mobility management scheme is investigated through simulation. 相似文献
7.
An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile ad hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation. 相似文献
8.
Fotini-Niovi Pavlidou Marina Ruggieri Mario Gerla Ryu Miura 《Wireless Personal Communications》2004,28(2):161-162
Wireless Personal Communications - 相似文献
9.
The deployment of underwater networks allows researchers to collect explorative and monitoring data on underwater ecosystems.The acoustic medium has been widely adopted in current research and commercial uses,while the optical medium remains experimental only.According to our survey onthe properties of acoustic and optical communicationsand preliminary simulation results have shown significant trade-offs between bandwidth,propagation delay,power consumption,and effective communication range.We propose a hybrid solution that combines the use of acoustic and optical communication in order to overcome the bandwidth limitation of the acoustic channel by enabling optical communicationwith the help of acoustic-assisted alignment between optical transmitters and receivers. 相似文献
10.
Complexity issues in basic logic 总被引:1,自引:0,他引:1
S. Aguzzoli B. Gerla Z. Haniková 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2005,9(12):919-934
We survey complexity results concerning a family of propositional many-valued logics. In particular, we shall address satisfiability
and tautologousness problems for Hájek's Basic Logic BL and for several of its schematic extensions. We shall review complexity
bounds obtained from functional representation results, as well as techniques for dealing with non-trivial ordinal sums of
continuous t-norms. 相似文献