autonomic communications
EURASIP Journal on Wireless Communications and Networking
The latest articles from Hindawi Publishing Corporation
- Combining OOK with PSM Modulation for Simple Transceiver of Orthogonal Pulse-Based TH-UWB Systems
This paper describes a combined modulation scheme for time-hopping ultra-wideband (TH-UWB) radio systems by using on-off keying (OOK) and pulse-shape modulation (PSM). A set of orthogonal pulses is used to represent bits in a symbol. These orthogonal pulses are transmitted simultaneously in the same pulse repetition interval resulting in a composite pulse. This scheme transmits the same number of bits by using fewer orthogonal pulses and receiver correlators than those used in PSM and biorthogonal PSM (BPSM). The proposed scheme reduces multiple-access interference and multipulse interference considerably by using crosscorrelation properties of orthogonal pulses. Since each bit is individually received by OOK, the proposed scheme requires less power. Hence, it is applicable for energy constrained and low-cost TH-UWB systems. The bit-error-rate (BER) performance is analyzed both mathematically and through computer simulations under the different channel environments. The performance of this scheme is compared with that of existing PSM and its combined modulation schemes by using two sets of orthogonal pulses. - Feedback Channel Suppression in Distributed Video Coding with Adaptive Rate Allocation and Quantization for Multiuser Applications
We present a novel rate allocation technique for distributed multiuser video coding systems without the need for a permanent feedback channel. Based on analytical calculations, the system unequally distributes the available bandwidth among the different users, taking into account the actual amount of movement in the transmitted video as well as the transmission conditions of each user. On one hand, the quantization parameters are dynamically tuned in order to optimize the decoding quality. On the other hand, a frame dropping mechanism allows the system to avoid unnecessary channel use, when the analytical estimations show that the successful decoding of a given frame is not possible because of very high motion or bad channel conditions. A significant gain in the system performance is noticed compared with the case of equal allocation of channel resources and constant quantization parameters. - Performance Evaluation of WiMAX Broadband from High Altitude Platform Cellular System and Terrestrial Coexistence Capability
The performance obtained from providing worldwide interoperability for microwave access (WiMAX) from high altitude platforms (HAPs) with multiple antenna payloads is investigated, and the coexistence capability with multiple-operator terrestrial WiMAX deployments is examined. A scenario composed of a single HAP and coexisting multiple terrestrial WiMAX base stations deployed inside the HAP coverage area (with radius of 30 km) to provide services to fixed users with the antenna mounted on the roof with a directive antenna to receive signals from HAPs is proposed. A HAP cellular configuration with different possible reuse patterns is established. The coexistence performance is assessed in terms of HAP downlink and uplink performance, interfered by terrestrial WiMAX deployment. Simulation results show that it is effective to deliver WiMAX via HAPs and share the spectrum with terrestrial systems. - A QoS-Aware Mesh Protocol for Future Home Networks Using Autonomic Architecture
Autonomic networking is an emerging approach for the research community to engineer systems and architectures that will increase the quality of service (QoS) and robustness of future network architectures. In this article, we investigate the key concept of adding a knowledge plane to enable the automated control and management of home resources taking into account wireless mesh topology basis. This new supplementary plane helps to make an intelligent decision to select network paths that have sufficient resources to satisfy the QoS requirements of the admitted connections. - Discrete-Time Second-Order Distributed Consensus Time Synchronization Algorithm for Wireless Sensor Networks
This paper proposes a novel discrete-time second-order distributed consensus time synchronization (SO-DCTS) algorithm for wireless sensor networks. The consensus properties and convergence rates of the SO-DCTS algorithm are analyzed for both directed and undirected networks. Additionally, the convergence region and optimal convergence rate of the SO-DCTS algorithm are determined for undirected networks and this convergence rate is shown to be superior to that of the first-order DCTS (FO-DCTS) algorithm under careful algorithm design. Furthermore, the asymptotic expectation and mean square synchronization error are investigated for the SO-DCTS algorithm when there is Gaussian delay between network nodes. Finally, simulation results are provided to verify these analytical results. - Downlink Coexistence Performance Assessment and Techniques for WiMAX Services from High Altitude Platform and Terrestrial Deployments
We investigate the performance and coexistence techniques for worldwide interoperability for microwave access (WiMAX) delivered from high altitude platforms (HAPs) and terrestrial systems in shared 3.5 GHz frequency bands. The paper shows that it is possible to provide WiMAX services from individual HAP systems. The coexistence performance is evaluated by appropriate choice of parameters, which include the HAP deployment spacing radius, directive antenna beamwidths based on adopted antenna models for HAPs and receivers. Illustrations and comparisons of coexistence techniques, for example, varying the antenna pointing offset, transmitting and receiving antenna beamwidth, demonstrate efficient ways to enhance the HAP system performance while effectively coexisting with terrestrial WiMAX systems. - An Intelligent Handover Management System for Future Generation Wireless Networks
Future generation wireless networks should provide to mobile users the best connectivity to services anywhere at anytime. The most challenging problem is the seamless intersystem/vertical mobility across heterogeneous wireless networks. In order to answer it, a vertical handover management system is needed. In our paper, we propose an intelligent solution answering user requirements and ensuring service continuity. We focus on a vertical handover decision strategy based on the context-awareness concept. The given strategy chooses the appropriate time and the most suitable access network among those available to perform a handover. It uses advanced decision algorithms (for more efficiency and intelligence) and it is governed by handover policies as decision rules (for more flexibility and optimization). To maintain a seamless service continuity, handover execution is based on mobile IP functionalities. We study our decision system in a case of a 3G/UMTS-WLAN scenario and we discuss all the handover decision issues in our solution. - Bandwidth Impacts of Localizing Peer-to-Peer IP Video Traffic in Access and Aggregation Networks
This paper examines the burgeoning impact of peer-to-peer (P2P) traffic IP video traffic. High-quality IPTV or Internet TV has high-bandwidth requirements, and P2P IP video could severely strain broadband networks. A model for the popularity of video titles is given, showing that some titles are very popular and will often be available locally; making localized P2P attractive for video titles. The bandwidth impacts of localizing P2P video to try and keep traffic within a broadband access network area or within a broadband access aggregation network area are examined. Results indicate that such highly localized P2P video can greatly lower core bandwidth usage. - Statistical Analysis of Multipath Fading Channels Using Generalizations of Shot Noise
This paper provides a connection between the shot-noise analysis of Rice and the statistical analysis of multipath fading wireless channels when the received signals are a low-pass signal and a bandpass signal. Under certain conditions, explicit expressions are obtained for autocorrelation functions, power spectral densities, and moment-generating functions. In addition, a central limit theorem is derived identifying the mean and covariance of the received signals, which is a generalization of Campbell_s theorem. The results are easily applicable to transmitted signals which are random and to CDMA signals. - Wireless Telemedicine and Applications
- Models for Call Acceptance Based on Handoff Guarantees
Call admission control (CAC) is important for cellular wireless networks to provide quality-of-service (QoS) requirements to users. Static and adaptive CAC schemes, respectively, make unrealistic assumptions about the distributions of the handof