Search results for "Wireless"
showing 10 items of 879 documents
A Delay-Centric Dynamic Resource Allocation Algorithm for Wireless Communication Systems Based on HNN
2008
This paper proposes a dynamic resource-allocation (DRA) algorithm for packet data services in wireless communication systems based on Hopfleld neural networks (HNNs). The resource-allocation algorithm assumes a delay-centric approach in that it maximizes resource utilization of the overall system while minimizing the packet delay. The real-time (RT) working capability of HNN hardware implementation means that a very powerful scheduling DRA algorithm can be obtained. A generic formulation of the algorithm is presented to establish the optimal bit rate allocation. In addition, some illustrative examples of this formulation are given, considering specific wireless communication systems, such a…
Testing the H.264 error-resilience on wireless ad-hoc networks
2004
The purpose of this paper is to provide a framework to tune and evaluate the performance of the H.264 codec in 802.11b wireless ad-hoc networks. The codec's error-resilience features are measured under stress conditions typical to these networks, and the most critical parameters are presented. We present solutions concerning the random packet loss problem and show how to quickly recover from packet loss bursts.
A space-division time-division multiple access scheme for high throughput provisioning in WLANs
2005
Directional antennas may dramatically increase the capacity of a Wireless LAN by allowing several stations to simultaneously communicate. Since deployment of directive/smart antennas on the customer's terminals is awkward (for technological, cost, robustness, and convenience reasons) it is of interest to deploy advanced antenna solutions only at the Access Point. When omnidirectional transmissions are used at the Mobile Stations, the asynchronous nature of the 802.11 MAC handshake structurally limits the possibility to exploit spatial reuse. Significant throughput enhancements can be achieved only at the expense of redesigning (part of) the 802.11 MAC protocol: mainly a form of synchronizat…
Using MANET Protocols in Wireless Sensor and Actor Networks
2008
Although there are several routing protocols for wireless sensor and actor networks (WSAN), none of them have became standard. Now, there are several standard protocols for mobile ad hoc networks (MANET) that have been developed for devices with higher computing features than the sensor nodes. On the other hand, one of the main characteristics of the MANET protocols is their scalability. In this paper, we show the performance of a WSAN, when MANET protocols are used, for several topologies. We will discuss and evaluate which standard protocol is the best one depending on the number of nodes in the topology and depending on their mobility. Finally we will show their comparison. As far as we …
A MANET Autoconfiguration System based on Bluetooth Technology
2006
The availability of both Wi-Fi and Bluetooth technologies on currently available devices offers the possibility to combine both in order to make the most out of their capabilities. In this paper we propose using Bluetooth technology to solve the configuration problem of the terminals conforming an IEEE 802.11-based ad-hoc network. The main objective of mobile ad- hoc networks (MANETs) is to extend the connectivity range of nodes through packet forwarding, thereby avoiding the use of a fixed infrastructure. However, since configuration of nodes is a complex issue, we provide a fast and reliable solution to auto-configure MANET terminals. Our solution is adequate for the quick setup and deplo…
Streaming for vehicular users via elastic proxy buffer management
2004
In this article we refer to the market of vehicular networks, where groups of customers located in the same public vehicle (e.g., a train or bus) connect to a terrestrial network through a wireless/satellite backbone link. Elastic buffering is a proxy management technique devised to decouple the multimedia information retrieval rate on the network backbone from the playout streaming rate at the user terminal. It has been shown in the past that the application of elastic buffering mechanisms in terrestrial networks brings significant advantages in terms of network effectiveness. We show that elastic buffering is an extremely effective means to reduce, or even eliminate, streaming service out…
Level-Crossing Rate and Average Duration of Fades of the Envelope of Mobile-to-Mobile Fading Channels in Cooperative Networks Under Line-of-Sight Con…
2008
This paper studies the fading behavior of mobile- to-mobile (M2M) fading channels in relay-based cooperative networks under line-of-sight (LOS) conditions. Here, we assume that LOS components exist in both the direct link between the source mobile station (SMS) and the destination mobile station (DMS) as well as in the link via the mobile relay (MR). In such a propagation environment, the fading channel is referred to as the multiple-LOS second-order scattering (MLSS) channel. The fading behavior of MLSS channels is studied by analyzing the level-crossing rate (LCR) and the average duration of fades (ADF) of the received envelope. We have derived analytical expressions for the LCR, ADF, and…
Mobile radio channel models for present and future wireless communication systems
2008
From the beginnings of mobile communication, there is a high demand for realistic models for mobile fading channels. The reason for the demand is that channel models are essential for the performance evaluation, parameter optimisation, and test of mobile communication systems. Design methods for mobile fading channels are therefore of great importance for system engineers who are involved in the development of present and future mobile communication systems. In this presentation, an overview will be given about several design methodologies commonly used for the design of mobile radio channel models in present and future wireless communication systems. All presented channel models have in co…
Modeling of mobility and groups in inter-vehicular MANET-based networks
2007
This paper evaluates the behavior of mobile ad hoc networks when group mobility is involved. We concentrate on group mobility because road vehicles tend to form groups or fleets whose behavior depends on the behavior of the close-by vehicles. We propose four different group mobility models and present a mobility pattern generator, called grcmob that we designed to be used with the ns-2 simulator. We evaluate the performance of vehicular ad hoc networks under a wide number of scenarios using both TCP and UDP data traffic. We show that the number of groups is more important than the number of nodes and that the impact of area size is almost negligible. We also reveal that the mixture of inter…
Group mobility impact over TCP and CBR traffic in mobile ad hoc networks
2004
We present an analysis of the effect that mobility models have over the performance of a mobile ad hoc network. We concentrate on group mobility because there is a growing attention on the development and evaluation of MANET's approach applied to personal area networks (PANs), especially based on Bluetooth technology. We investigate the effect that the mobility model has on the performance of CBR traffic and TCP traffic. We propose four different group mobility models and describe a mobility pattern generator called grcmob to be used with the ns-2 simulator. We perform a thorough evaluation of a MANET behavior using as a reference the behavior obtained with the random waypoint mobility mode…