On Efficiency of ARQ and HARQ Entities Interaction in WiMAX Networks

Space scienc

Utilizing IEEE 802.16 for Aeronautical Communications

Neurology & clinical neurophysiolog

Chapter Utilizing IEEE 802.16 for Aeronautical Communications

Neurology & clinical neurophysiolog

Performance Analysis of ARQ Mechanism in WiMAX Networks

WiMAX (Worldwide Interoperability for MicrowaveAccess) is the IEEE 802.16 standards-based wireless technology, provides Broadband Wireless Access (BWA) for Metropolitan Area Networks (MAN). The Automatic Repeat reQuest (ARQ) mechanism in WiMAX uses a feedback channel for the confirmation of error-free packet delivery or for packet retransmission request. This method can increase network throughput when radio channel condition is worse. In this paper attempt has been made to study the effect of implementation of ARQ on the performance of WiMAX network through simulation. Simulation study has been carried out for WiMAX network with and without enabling ARQ. The performance is been compared by considering the performance metrics like throughput, delay and jitter

Spectrum Sharing Methods in Coexisting Wireless Networks

Radio spectrum, the fundamental basis for wireless communication, is a finite resource. The development of the expanding range of radio based devices and services in recent years makes the spectrum scarce and hence more costly under the paradigm of extensive regulation for licensing. However, with mature technologies and with their continuous improvements it becomes apparent that tight licensing might no longer be required for all wireless services. This is from where the concept of utilizing the unlicensed bands for wireless communication originates. As a promising step to reduce the substantial cost for radio spectrum, different wireless technology based networks are being deployed to operate in the same spectrum bands, particularly in the unlicensed bands, resulting in coexistence. However, uncoordinated coexistence often leads to cases where collocated wireless systems experience heavy mutual interference. Hence, the development of spectrum sharing rules to mitigate the interference among wireless systems is a significant challenge considering the uncoordinated, heterogeneous systems. The requirement of spectrum sharing rules is tremendously increasing on the one hand to fulfill the current and future demand for wireless communication by the users, and on the other hand, to utilize the spectrum efficiently. In this thesis, contributions are provided towards dynamic and cognitive spectrum sharing with focus on the medium access control (MAC) layer, for uncoordinated scenarios of homogeneous and heterogeneous wireless networks, in a micro scale level, highlighting the QoS support for the applications. This thesis proposes a generic and novel spectrum sharing method based on a hypothesis: The regular channel occupation by one system can support other systems to predict the spectrum opportunities reliably. These opportunities then can be utilized efficiently, resulting in a fair spectrum sharing as well as an improving aggregated performance compared to the case without having special treatment. The developed method, denoted as Regular Channel Access (RCA), is modeled for systems specified by the wireless local resp. metropolitan area network standards IEEE 802.11 resp. 802.16. In the modeling, both systems are explored according to their respective centrally controlled channel access mechanisms and the adapted models are evaluated through simulation and results analysis. The conceptual model of spectrum sharing based on the distributed channel access mechanism of the IEEE 802.11 system is provided as well. To make the RCA method adaptive, the following enabling techniques are developed and integrated in the design: a RSS-based (Received Signal Strength based) detection method for measuring the channel occupation, a pattern recognition based algorithm for system identification, statistical knowledge based estimation for traffic demand estimation and an inference engine for reconfiguration of resource allocation as a response to traffic dynamics. The advantage of the RCA method is demonstrated, in which each competing collocated system is configured to have a resource allocation based on the estimated traffic demand of the systems. The simulation and the analysis of the results show a significant improvement in aggregated throughput, mean delay and packet loss ratio, compared to the case where legacy wireless systems coexists. The results from adaptive RCA show its resilience characteristics in case of dynamic traffic. The maximum achievable throughput between collocated IEEE 802.11 systems applying RCA is provided by means of mathematical calculation. The results of this thesis provide the basis for the development of resource allocation methods for future wireless networks particularly emphasized to operate in current unlicensed bands and in future models of the Open Spectrum Alliance

Multicast Mobility in Mobile IP Version 6 (MIPv6) : Problem Statement and Brief Survey

Publisher PD

A Real-Time Implementation of the Mobile WiMAX ARQ and Physical Layer

This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s11265-014-0890-3.[Abstract] This paper presents an innovative software-defined radio architecture for the real-time implementation of WiMAX transceivers. The architecture consists of commercially available field-programmable gate array and digital signal processor modules. We show how the architecture can be used for the real-time implementation of a full-featured standard-compliant time-division duplex WiMAX physical layer together with the ARQ functionality of the MAC layer. Both the mobile and the base station contain a transmitter and a receiver to enable real-time concurrent downlink and uplink communications. The design supports the different configurations defined by the standard and the WiMAX Forum. This work also provides the verification and validation of the proposed real-time implementation based on repeatable and reproducible performance evaluation considering the reference scenarios defined by the WiMAX Forum, including both static and mobile scenarios. Typical figures of merit such as physical-layer bit and frame error rates and MAC-layer throughput are obtained with the help of a custom-made real-time channel emulator implementing the channel models defined by the WiMAX Forum.This work has been partially supported by Indra Sistemas S.A. and the Spanish Ministry of Defence with the technical direction of PEC/ITM under grant DN8644-COINCIDENTE. The authors wish to thank J. M. Camas-Albar from Indra Sistemas S.A. for his help. This work has been additionally funded by Xunta de Galicia, Ministerio de Ciencia e Innovacin of Spain, and FEDER funds of the European Union under grants with numbers 2012/287, TEC2010-19545-C04-01, and CSD2008-00010.Xunta de Galicia; 2012/28