Single-hop Connections Research Articles

Performance Metrics for Bluetooth Scatternet Scheduling Using Relays

Abstract: While various ad hoc mobile wireless networks are already accessible, Bluetooth is one of the most up-to-date. A single-hop connection known as piconet is a simple Bluetooth communication architecture, allowing for just eight functioning electronic equipment, seven of which are operational slaves under a single master. A common hub called a relay links a huge network named Scatternet to a number of piconets. The efficacy of Scatternet design is clearly intrinsically connected to the effectiveness of relay nodes. Because every relay has several piconet transactions to process and manage, a reduction in the number of switches might lead to poor performance instead. The major aim of this research is to examine performance characteristics which impact interplay since the role of the base station is to multiple piconet transitions. In this study, we evaluate and respond to the technical issues that must be optimally solved the Scatternet data flow based on the relay node. Keywords: Bluetooth, Piconet, Scatternet, Relay Node

A NOVEL APPROACH FOR PLACEMENT OF PHASOR MEASUREMENT UNIT & COUNTING THEIR OPTIMAL NUMBER

In India Power system monitoring is based mainly on measurements provided by Remote Terminal Unit (RTU). For power system measurement synchronized Phasor or Phasor Measurement Unit (PMU) is popular choice in abroad and its popularity is increasing day by day because of its several features. Direct measurement of voltage or current Phasor is possible because of PMU which was not possible earlier. Global positioning system (GPS) provides time synchronized data. In this paper a new approach is used for optimal placement of PMU, counting their number & time elapsed. This approach includes zero injection method along with single hop connectivity. The approach is successfully applied on IEEE-14 bus system. Here all the bus which are taken into consideration is either completely observable or at some depth of UnObservability is also taken into account.

Connectivity analysis of one-dimensional ad-hoc networks

Application and communication protocols in dynamic ad-hoc networks are exposed to physical limitations imposed by the connectivity relations that result from mobility. Motivated by vehicular freeway scenarios, this paper analyzes a number of important connectivity metrics for instantaneous snapshots of stochastic geographic movement patterns: (1) The single-hop connectivity number, corresponding to the number of single-hop neighbors of a mobile node; (2) the multi-hop connectivity number, expressing the number of nodes reachable via multi-hop paths of arbitrary hop-count; (3) the connectivity distance, expressing the geographic distance that a message can be propagated in the network on multi-hop paths; (4) the connectivity hops, which corresponds to the number of hops that are necessary to reach all nodes in the connected network. The paper develops analytic expressions for the distributions and moments of these random variables for general stationary MAP processes on a one dimensional space. The numerical results compare bursty vehicular traffic with independent movement scenarios described by a Poisson process, illustrate in examples the impact of a random communication range, and demonstrate the usefulness of MAP processes via comparison with vehicular simulation traces.

Comparing the results from various performance models of IEEE 802.11g DCF

IEEE 802.11 DCF is the most widely-used CSMA/CA access control mechanism . Recent analytic performance models for DCF have received acclaim for both their simplicity and reported accuracy. Most of these models share the assumptions of full single-hop connectivity among all stations, that DCF back-off may be modeled as a Markov process and that the network is saturated with traffic. In order to verify the accuracy of existing analytic models we developed a discrete-event simulator to record the performance of the DCF protocol and ensure that every detail of the standard is represented. Simultaneously we set up a hardware test bed to measure the same performance metrics in an environment that makes none of the simplifying assumptions of either the analytic models or the simulation. In the test bed, as in the simulator, we used the same physical parameter settings prescribed by the standard. As is the case for the analytic models we used, we subjected the simulator and the test bed to the same saturated workload for both basic and RTS/CTS access modes. Finally, we also implemented a non-saturating Markov Modulated Arrival Process (MMAP) workload model for our simulator to test the performance of DCF subject to more realistic internet traffic conditions. We describe both the simulator and the test bed in some detail in order to testify to the accuracy and detail of our results. The results show that the analytic models are mostly pessimistic for small numbers of nodes and optimistic for larger numbers of nodes. The performance measurements from the test bed, in turn, indicate that the simulation results are similarly optimistic when large numbers of nodes are concerned. Since the test bed uses an error-prone wireless channel, this latter result is, in principle, not surprising. The rate of deterioration in the actual performance is however something that is not widely known and is much more rapid than analytic models would suggest.

A Geometric Interpretation of Fading in Wireless Networks: Theory and Applications

In wireless networks with random node distribution, the underlying point process model and the channel fading process are usually considered separately. A unified framework is introduced that permits the geometric characterization of fading by incorporating the fading process into the point process model. Concretely, assuming nodes are distributed in a stationary Poisson point process in Rd , the properties of the point processes that describe the path loss with fading are analyzed. The main applications are single-hop connectivity and broadcasting.

How much wavelength conversion allows a reduction in the blocking rate?

We study the problem of routing and wavelength assignment (RWA) in a WDM optical network under different hop assumptions, i.e., with and without wavelength converters, considering the objective of minimizing the blocking rate. We design a heuristic with two interactive phases, one for the routing and one for the wavelength assignment, which generalizes a previous algorithm by Noronha and Ribeiro [Eur. J. Oper. Res. 171, 797 (2006)] based on a Tabu Search scheme using a partition coloring reformulation for uniform traffic and single-hop connections. Considering nonuniform traffic, we explore a reformulation of the RWA problem as a generalized partition coloring problem and develop a Tabu Search algorithm to solve it. We also explore how to integrate multihop connections, with the addition of conversion features at some or at all optical nodes. Experiments are done on several traffic and network instances. Most heuristic solutions are excellent as illustrated by the very small gap between the values provided by the heuristic and the optimal values of the linear relaxation. We next show that conversion features, although often considered an added value, are of little help in improving on the blocking rate except for some very particular traffic instances, even on realistic network topologies.

Satellite communication system integrated into terrestrial ISDN

This paper presents an advanced satellite communication system named DYANET II. This system uses satellite channels as subscriber lines for ISDN customers as well as trunk circuits for overflow traffic. The system can offer the same ISDN services to satellite customers as those available to terrestrial subscribers in terms of numbering, signaling, and charging systems as well as user-network interfaces. It can also set up satellite channels on a demand assignment basis to achieve efficient satellite channel utilization, and to connect customers by single-hop satellite connections. A compact, lightweight Earth station has been developed for remote customers and temporary demands such as exhibitions.

Coupled reservation protocols for hierarchical single-hop photonic networks

Future photonic LANs and MANs may be based upon single-hop architectures using wavelength division multiplexing (WDM) and passive star coupling. Recently, however, single-hop designs have been introduced which use a hierarchical structure employing simple wavelength routing functions. A salient feature of this type of network is that a set of wavelengths can be reused locally, while maintaining full single-hop connectivity through a different set of globally shared wavelengths. In such a network, wavelength routing divides the system into separate local and remote subnetworks, which may be accessed from each station by a single tunable transmitter. As a result, media access protocol operation can be implemented independently for each subnetwork, or it may be coupled between levels. These two options are investigated, focusing on remote subnetwork performance. Since global connectivity is achieved using a single set of remote wavelengths, it is important that they are efficiently used. The proposed protocols implement different forms of dynamic movable boundary TDMA, using various request/allocation mechanisms motivated by the channel controller approach. It is shown that, in such networks, remote channel efficiency can be improved significantly through a strong coupling of local and remote system operation.

Impact of transmission delay in audiovisual communications

AbstractIn this paper, the design and results are presented of an experimental study which was conducted in order to assess subjectively the impact of transmission delay in audiovisual communications. This study was undertaken using two 64 kb/s videotelephones which were connected over links incorporating simulated one‐way circuit propagation delays of 0 ms, 250 ms and 500 ms. From the results obtained it was concluded that audiovisual communication is weakly affected by propagation delay. In general, performance degradation between terrestrial and single‐hop satellite connections was minimal and in most cases statistically insignificant. A subsidiary conclusion is that the presence of the visual cues appears to mitigate the impact of transmission delay in audiovisual communication.

A new satellite communication system integrated into public switched networks-DYANET

A system concept of a common alternative routing system is proposed for reducing total network costs by integrating satellite communications into public-switched networks, where satellite systems carry overflow traffic from terrestrial systems through common satellite channels. This concept has been realized by a satellite communication system called DYANET (dynamic channel assigning and routing satellite aided digital networks), which provides trunk circuits in combination with terrestrial systems. The key technologies developed for DYANET are a centralized network control system and a transponder hopping demand assignment TDMA (time-division multiple-access) system, to assure single-hop connection and to use satellite channel efficiently. The authors describe the system concept and configuration, the network control system, and the results of its commercial use.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Interworking IEEE 802/FDDI LANs via the ISDN frame relay bearer service

The author presents a generic architecture for interconnecting LANs (local area networks) through the ISDN (integrated services digital network) bearer services, particularly the frame relay bearer service. The architecture is derived from the IEEE 802.1 MAC (medium access control) bridge and ISDN frame relay standards. An algorithm for MAC/ISDN address resolution that makes minimal use of the WAN (wide area network) bandwidth (which is potentially the most expensive resource) is presented. The algorithm uses a MAC/ISDN address resolution server to resolve addresses for new stations, the resolution in all other cases (e.g. stations moving from the ISDN address to another) being fully distributed. To prevent a server failure from inhibiting communication to new stations, a backup server may be provided. A practical implementation of the architecture has been found capable of supporting full throughput at ISDN hyperchannel rates (384-1920 kb/s) for all IEEE 802.3 frame lengths. Frame relay is seen as having a number of important advantages for LAN interconnection, including the following: a large number of virtual circuits available, giving the potential for a rich interconnection architecture with single-hop connections across the ISDN; and low processing overhead enabling efficient use of ISDN channels, including ISDN hyperchannels (384-1920 kb/s). >