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Worldwide Interoperability for Microwave Access (WiMAX) is defined by the IEEE 802.16. It is an IP based, wireless broadband access technology. This technology can be implemented in 4th generation wireless technologies, for Metropolitan Area Network (MAN). The IEEE 802.16 standard includes specification for the Medium Access Control (MAC) and Physical (PHY) layers and is designed to provide broadband...
With the coexistence of various wireless technologies, next generation wireless communications will likely consist of an integrated system of networks, where the Access Points (APs) and Base Stations (BSs) work together to maximize the mobile-user Quality of Service (QoS). In such heterogeneous environment where handheld devices with different access technologies are not uncommon, it should be possible...
A femtocell is designed to use a shared broadband IP link. A bottleneck may be occurred due to the limitation of provisioned bandwidth and the existence of background traffic especially in access network. The bottleneck will certainly affect the service performance of the femtocell access point (FAP), which would influence end user experience. In order to maintain QoS requirement against backhaul...
In response to the increasing demand for asynchronous mass data exchange even by mobile users, the DTN-related technologies are considered promising for an efficient use of limited network resources and low-cost deployment at the expense of communication delays. The authors previously proposed a Virtual Segment concept aiming at a practical network infrastructure combining Internet-connected broadband...
To meet the continuously increasing demands and requirements of mobile users, next generation wireless systems are more and more relaying on the coexistence of heterogeneous wireless networks. The objective is to provide any time and anywhere connectivity to users. One of the main challenges in such a heterogeneous environment is mobility management, including network selection and Vertical Handover...
This paper presents a propagation model for prediction of path loss and performance parameters (throughput and frame loss) on OFDM-based networks. For this study, measurements on a 5.8 GHz Wimax network were carried out. The proposed model parameters have been adjusted by LS (Least Squares) optimization, using measured data as reference. The results show that the proposed model has a good agreement...
The increasing demands for multimedia applications with various QoS requirements arouse the interest of researchers in the Fourth-generation wireless networks such as WiMAX. In order to ensure that the QoS requirements of these applications are met, effective scheduling algorithms must be designed. Even though it may be trivial to ensure that the minimum QoS of all service classes is attained, this...
In this paper, we propose a general model for the broadcast polling protocol of unsaturated IEEE 802.16 networks in which each subscriber station has a finite buffer. A subscriber station can be modelled as a M/G/1/K queue with its service time determined by the broadcast polling protocol. The buffer overflow probability, network throughput and packet delay performances are analyzed. The proposed...
To meet the higher data rate requirement of emerging wireless communication technology, numerous parallel turbo decoder architectures have been developed. However, the interleaver has become a major bottleneck that limits the achievable throughput in the parallel decoders due to the massive memory conflicts. In this paper, we propose a flexible Double-Buffer based Contention-Free (DBCF) interleaver...
Real-time Internet services such as video transmission and online gaming often require privileged treatment in the Internet routers and wireless links in order to meet their real-time QoS requirements. The challenge is to know which are the services requiring higher priority and when this special treatment is needed. In this study, we introduce mechanisms to intelligently classify different traffic...
Nowadays, wireless systems allow us to have connectivity almost everywhere. Different radio access technologies are integrated in the same device and they can be used following the specific service requirements, the actual received signal levels, and the costs related to their use. Presently, technologies are always seen as alternatives, but it is envisioned that different wireless connections may...
As high speed rails become more and more popular, providing broadband internet access on high speed rails is not widespread due to the large inter-carrier interference, terrestrial obstacles and inherent carriage shielding. In this paper an integrated Worldwide Interoperability for Microwave Access-Radio over Fiber (WiMAX-RoF) system is proposed and deployed along Taiwan High Speed Rail (THSR) rail...
The main function of relay station is to enhance the network capacity and extend the coverage area. This paper analyses the performance of relay stations in IEEE 802.16j Mobile Multi-hop Relay (MMR) WiMAX for the transparent and non-transparent modes. The performance of these relays is evaluated based on the throughput for the downlink and uplink transmission using National Chiao Tung University -...
Wireless technologies have been widely deployed in the last decade making users demand for continuous connectivity. Users not only demand being attached to a network, but possibly to the one with the highest performance, or at least to a network able to fulfill their requirements. To choose the best network among different candidates, the IEEE 802.21 standard has been developed. In this paper we aim...
This paper presents a bottom up approach for implementing high throughput, scalable, layered LDPC decoding architecture for multi-standard applications. A generic implementation of fully parallel check node along with a block level Channel Memory organization scheme are two elements of novelty of this work. The proposed decoder IP core is synthesizable for all codes defined by WiMAX (WiFi) standards...
Deploying FemtoCells in WiMAX network, also called WiMAX FemtoCell architecture, gains a lot of attention due to better indoor services can be provided and WiMAX network traffic can be shared by the FemtoCell. However, since the signal of WiMAX base station (BS) is stronger than FemtoCell Base Station (fBS), the handover procedure may not be triggered even though fBS is within the BS coverage. Besides,...
The WiMAX features longer transmission distance and more accomplished support of QoS than other wireless access technologies such as 802.11. Since the standard did not specify the QoS based packet-scheduling algorithms which run on the base stations, those algorithms are open for alternative implementations. In this paper, we propose a scheduling algorithm for burst traffic in the WiMAX base station...
This paper defines an end-to-end QoS functional model for mobile WiMAX systems and investigate several technical issues. Our main contribution is to analyze the end-to-end QoS variations in mobile WiMAX systems according to the QoS functions. We discuss the strong and weak points of QoS related functions, which can be affected by the network architecture, and propose the design examples of a service...
Several radio access technologies are now likely to coexist in the same area, and form the so-called heterogeneous wireless networks. In this paper, we study the coordination between WiMAX and WiFi through radio resource management (RRM) in order to maximize the network operator??s revenue. Two solutions for the optimization problem, in which vertical handover and admission control are invoked respectively,...
The wireless network environment in the future is going to include various heterogeneous wireless networks. In a heterogeneous wireless network environment, vertical handoff processes caused by the movement of users are inevitable. However, the research related to how to achieve seamless vertical handoff and improve QoS guarantees in today's heterogeneous wireless networks is still something to work...
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