1,721,471 research outputs found
Scheduling algorithm for packet-oriented MAC protocols in wireless multimedia systems
No full textFuture generation wireless multimedia communications will require efficient Medium Access Control (MAC) protocols able to guarantee suitable Quality of Service (QoS) levels for different traffic classes while achieving a high utilization of radio resources. This paper proposes a new scheduling technique to be adopted at the MAC level in wireless access systems, named Dynamic Scheduling-Time Division Duplexing (DS-TDD), that efficiently manages video, voice, Web and background traffics. A theoretical approach is proposed in this paper to evaluate the DS-TDD performance with voice and Web traffics. Simulation results have permitted to highlight the following promising characteristics of the DS-TDD scheme: (i) a high capacity of real-time traffics is attained with a QoS insensitive to Web and background traffic loads; (ii) a high throughput can be guaranteed while preserving the QoS levels of the different traffic classes; (iii) heavier downlink traffic loads do not modify the QoS of uplink traffics. Finally, extensive comparisons with different scheduling schemes proposed in the literature have permitted to highlight the better performance of DS-TDD
Analytical model for performance analysis of IEEE 802.11 DCF mechanism in multi-radio wireless networks
No full textWireless mesh networks suffer of scalability problems when the number of nodes grows. To solve this issue, wireless mesh networks with multi-interface nodes were introduced. In such networks it is possible to use multiple channels to implement spatial reuse of frequencies. These solutions offer a huge throughput performance improvement but they increase the complexity due to the need of implementing a selection interface policy. One of the most simple interface selection policy is random choice. In this paper we provide an analytical analysis of the Uniform Random Interface Selection strategy applied in a 802.11 DCF multi-radio network. Then we also present a set of performance results for the throughput and discard probability in function of the number of nodes and the number of interfaces
Resource Allocation Approaches for Two-Tiers Machine-to-Machine Communications in an Interference Limited Environment
No full textOne of the main challenges of supporting massive machine type communications by future mobile network, is the radio access network congestion.
A viable solution is a hierarchical architecture where cluster-grouped machines are indirectly connected to the mobile network through a cluster gateway.
This paper considers such an architecture and focuses on radio resource allocation to machine-clusters where resources can be spatially reused for concurrent transmissions.
In particular, resources can be accessed simultaneously by machines of different clusters and by different communication phases, thus resulting in an interference-limited system.
Three different resource partitioning schemes are proposed and evaluated, mainly differing on how interference is taken into account.
The aim is to minimize the packet loss probability, and thus maximizing the spectral efficiency.
Numerical results show the effectiveness of the proposed schemes in comparison to benchmark methods.
In particular, by joining resource reuse and interference-mitigation, the efficiency improves significantly
A QoS-aware policer for a fair resource sharing in wireless ATM
No full textThis paper deals with the Radio Resource Management (RRM) layer of future broadband systems capable to realize a wireless access to Asynchronous Transfer Mode networks. The interest here is in designing an efficient scheme operated by an access point to integrate demanding traffics, such as high-quality real-time video and interactive Web traffics. We adopt a time division multiple access air interface and we propose an original solution where a medium access protocol and a usage parameter control technique jointly define the radio resource management. In particular, we use a cyclic assignment scheme with a novel traffic policer based on fuzzy logic for video sources and on a token-bucket scheme for Web sources. Our technique is named Fuzzy Logic-Based Multiple Access (FLBMA) to remark the central function of the fuzzy policer. The FLBMA performance, derived through simulations, has highlighted the following interesting results: (i) very high capacity of video traffic sources in comparison with alternative RRM schemes; (ii) fair service of different traffic sources; (iii) video traffic Quality of Service independent of Web traffic load
AeroMACS: A new perspective for mobile airport communications and services
No full textBroadband wireless technologies are becoming more and more pervasive in several fields of application to supply new services and to satisfy operational constraints. Among them, this paper deals with the use of WiMAX technology in future air traffic management system. This technology is expected to increase the safety and to allow the exchange of large volume of data among heterogeneous users, including aircrafts. In particular,
Eurocontrol and ICAO identified a WiMAX based technology for communications on the airport surface, named Aeronautical Mobile Airport Communication System (AeroMACS). The scope of this paper is to provide an overview of AeroMACS, with a description of its main features, requirements, PHY and MAC profiles choices and related network architecture. Finally, the paper highlights some open issues for AeroMACS that represent critical aspects and require, up to now, additional investigations
Coordinated Scheduling and Beamforming Scheme for LTE-A HetNet Exploiting Direction of Arrival
No full textResource reuse among different cells in LTE-A networks will permit to increase the system capacity, but will require suitable interference mitigation techniques. Among these Coordinated scheduling and beamforming (CS/CB) is a promising solution. This paper proposes a new CS/CB scheme aiming to maximizing the mean system throughput taking into account the fairness among the cells. First the most suitable CB technique selection is analysed and a sub-optimum criterion based on the reciprocal angular distance between two concurrent users is proposed. Then a smart CS algorithm that allows to pair users with sufficient angular distance is introduced. The results show that the proposed scheme achieves performance close to the optimum CB scheme selection and the smart allocation permits to increase significantly the system throughput
Neural network applications to code division communication receivers
No full textIn order to enhance the bandwidth utilization, new advanced receivers for next generation mobile communications are developed. Adaptive blind multiuser detection has been widely proposed for applications in CDMA (Code Division Multiple Access) wireless communication systems for its principal advantage of eliminating training sequence to set-up recover filter coefficients. Main drawback of this technique is that it reaches the optimum behavior after a certain number of bit times, which precludes its use in typical time-varying environments. In this paper, a new neural networks approach is proposed in order to solve this drawback. In particular, this paper considers the use of a modified Kennedy-Chua neural network, based on the Hopfield model, and another neural network receiver based on Hopfield model
A Cloud to the Ground: The New Frontier of Intelligent and Autonomous Networks of Things
Full text linkThe Structure and Performance of an Optimal Continuous-Time Detector for Laplace Noise
No full textA optimal detector for a known signal in Laplace noise is determined. The analysis starts with a sampled digital receiver, leading to an asymptotic analysis when the number of samples approaches infinity. The optimum detector for Laplace Noise achieves twice the signal-to-noise ratio of the matched filter for Gaussian noise. The theoretic analysis is corroborated by computer simulations
An Optimized CoMP Transmission for a Heterogeneous Network Using eICIC Approach
No full textHeterogeneous networks deployment is one of the most promising approaches to face the expected increase of the requested communication capacity. The concept is that of increasing the cells number
while reducing their size in order to provide different layers of coverage. This paper proposes a coordinated method to face the inter and intra layer interference caused by the overlapping of heterogeneous
cells. The aim is to exploit the benefits of both the enhanced InterCell Interference Coordination (eICIC) and Coordinated MultiPoint (CoMP) approaches and to limit at the same time their drawbacks by means of their optimized joint use. The idea devised here is to build an ad-hoc CoMP system on the top of a basic eICIC mechanism. The problem is the dynamic selection of the users and the cells that are
involved in CoMP operations, with the goal of minimizing the unfulfilled data rate requests. Due to the computational complexity of the optimal solution, we propose a heuristic procedure and validate its accuracy by providing a comparison with the optimal numerical solution. In particular, our results show that the proposed method outperforms other benchmark solutions in terms of unfulfilled data rate
requests and signaling overhead
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