A Scalable QoS Scheduling Architecture For WiMAX Multi-Hop Relay Networks.

WiMAX Mobile Multi-hop Relay (MMR) network has been introduced to increase the capacity and extend the coverage area of a single WiMAX Base Station (BS) by the use of a Relay Station (RS)

Improving relay based cellular networks performance in highly user congested and emergency situations

PhDRelay based cellular networks (RBCNs) are the technologies that incorporate multi-hop communication into traditional cellular networks. A RBCN can potentially support higher data rates, more stable radio coverage and more dynamic services. In reality, RBCNs still suffer from performance degradation in terms of high user congestion, base station failure and overloading in emergency situations. The focus of this thesis is to explore the potential to improve IEEE802.16j supported RBCN performance in user congestion and emergency situations using adjustments to the RF layer (by antenna adjustments or extensions using multi-hop) and cooperative adjustment algorithms, e.g. based on controlling frequency allocation centrally and using distributed approaches. The first part of this thesis designs and validates network reconfiguration algorithms for RBCN, including a cooperative antenna power control algorithm and a heuristic antenna tilting algorithm. The second part of this thesis investigates centralized and distributed dynamic frequency allocation for higher RBCN frequency efficiency, network resilience, and computation simplicity. It is demonstrated that these benefits mitigate user congestion and base station failure problems significantly. Additionally, interweaving coordinated dynamic frequency allocation and antenna tilting is investigated in order to obtain the benefits of both actions. The third part of this thesis incorporates Delay Tolerate Networking (DTN) technology into RBCN to let users self-organize to connect to functional base station through multi-hops supported by other users. Through the use of DTN, RBCN coverage and performance are improved. This thesis explores the augmentation of DTN routing protocols to let more un-covered users connect to base stations and improve network load balancin

"Performance Evaluation of Wi-Fi comparison with WiMAX Networks"

Wireless networking has become an important area of research in academic and industry. The main objectives of this paper is to gain in-depth knowledge about the Wi-Fi- WiMAX technology and how it works and understand the problems about the WiFi- WiMAX technology in maintaining and deployment. The challenges in wireless networks include issues like security, seamless handover, location and emergency services, cooperation, and QoS.The performance of the WiMAX is better than the Wi-Fi and also it provide the good response in the access. It's evaluated the Quality of Service (Qos) in Wi-Fi compare with WiMAX and provides the various kinds of security Mechanisms. Authentication to verify the identity of the authorized communicating client stations. Confidentiality (Privacy) to secure that the wirelessly conveyed information will remain private and protected. Take necessary actions and configurations that are needed in order to deploy Wi-Fi -WiMAX with increased levels of security and privacyComment:

Qualitative Investigation of the Performance of Real-Time Application of IEEE 802.16e standard WiMAX Relay Networks

The ability of an application to adapt its behavior to changing network conditions depends on the available bandwidth, throughput, delay and packet loss in a network path. These are of major importance in congestion control, streaming applications, quality of service verification, relay selection and many other areas in WiMAX relay stations. Mobile WiMAX, which is based on the IEEE 802.16e standard, provides support for and enables full mobility to users. In an effort to optimize and enhance the overall network throughput, this paper will propose a mobile relay framework. WiMAX is based on the IEEE 802.16e standard, and can support various types of handovers, while allowing for full mobility from the user endpoint. Different methodologies were used to compare different aspects of WiMAX relay stations including throughput, delay, SNR and network load. OPNET modular was used to develop and measure these set of network performance metrics. To accurately measure and evaluate the aforementioned network parameters we employed techniques that were able to process large amounts of data, this aided in provision of much more informed recommendations as to the type of relay station modes that should be installed engender enhanced, improved and optimal Quality of Service (QoS) within the network perimeter. This paper measured the overall network throughput, delay, SNR and network load of relay networks comprising mainly of multimedia applications. Keywords: WiMAX, QoS, Relay Station, Simulation, Topology, Throughput, Delay, Packet Los

Performance evaluation of a WiMAX system with relay-assisted scheduling

Työssä tutkitaan IEEE 802.16j standardin määrittelemän järjestelmän suorituskykyä ja keskitytään ei-raaliaikaisiin palveluihin ja verkkoon, jossa verkon topologiaan kuuluu tukiasemien lisäksi välittimiä. Päätelaitteet ryhmitellään kahteen luokkaan sen mukaan, ovatko ne suoraan yhteydessä tukiasemaan, vai onko yhteys muodostettu välittimen avulla. Tukiasemassa toimiva skedulointialgoritmi jakaa lähetysresursseja eri käyttäjien kesken hetkellisen kanavatiedon perusteella. Työssä on rakennettu simulaattori, jonka avulla voidaan tutkia erilaisten järjestelmäparametrien, skedulointialgoritmien ja välittimien vaikutusta järjestelmän suorituskykyyn.An IEEE 802.16j based system with relay-assisted scheduling performance is evaluated in terms of the requirements set by the standard. We focus on the non-real-time (NRT) services in the downlink of a cellular network with two-hop relay transmission. Mobile stations (MSs) are grouped into the base station (BS) region and the relay station (RS) region according to their mean path losses. MSs in the BS region are connected directly to BS while MSs in the RS region receive packet from BS directly or indirectly via RS based on the CSI (Channel State Information). The RS operates in either the amplify-and-forward (AF) mode or decode-and-forward (DF) mode. We propose two relay-assisted scheduling schemes, in which the RS assists the BS in its scheduling decision and therefore we make it possible for the BS to exploit CSI on the access links without those of the relay links from all the users directly. A large amount of feedback overhead is avoided. Our objective is to explore the performance of DF and AF relays in these two different scheduling schemes. Moreover, we consider a friendly graphical user interface to realize user interaction and facilitate the investigation of the effect of different parameters to the system performance

In-band relays for next generation communication systems

Next generation mobile communication systems will operate at high system bandwidths of up to 100MHz and at carrier frequencies beyond 2GHz to provide peak data rates of up to 1Gbit/s with similar average revenues per user as todays cellular networks. High bit rates should be available to all users in a cell which is challenging due to the unfavorable propagation conditions in these bands. In-band relays are a seen as a promising technology for cellular networks to extend the high bit rate coverage and to enable cost efficient network deployments. The research in this thesis has contributed to the development of the relaying concept within the European research project WINNER. WINNER has designed a next generation radio system concept based on Orthogonal Frequency Division Multiple Access (OFDMA) with the inclusion of relays as one of the major innovations. In our work we have identified the radio resource management as the most important function to exploit the potential benefits of relay based deployments. We develop a flexible radio resource management framework that adapts to a wide range of deployments, whereas our main focus is on metropolitan area deployments. Here we propose to utilize a dynamic resource assignment based on soft frequency reuse. Further, we propose a practical way to integrate cooperative relaying in a relay network. This concept allows the cooperation of multiple radio access points within a relay enhanced cell with low overhead and small delays. In system simulations we compare the performance of relay deployments to base station only deployments in a metropolitan area network. Our results show that relay deployments are cost efficient and they increase both the network throughput as well as the high bit rate coverage of the network. Further, they show that our proposed soft frequency reuse scheme outperforms competing interference coordination schemes in the studied metropolitan area scenario. Even though the results have been obtained for WINNER system parameters, the conclusions can also be applied to OFDMA based systems such as 3GPP Long Term Evolution and WiMAX

Development of an antenna system for a relay-based wireless network. Simulation and measurement of antenna systems for relay-based wireless network, covering the backhaul and access links and applying beam forming technology.

The proliferation of modern wireless networks increases demand for high capacity and throughput in order to provide faster, more robust, efficient and broadband services to end users. Mobile WiMAX and LTE are examples of such networks in which for some cases they have exposed limited connectivity due to harsh environment. Relay stations are preferred to overcome problems of weak or no access for such network devices, that are placed in specific positions to maintain high quality of data transfer at low cost and provide the required connectivity anywhere anytime. These stations should be equipped with an antenna system capable of establishing communication between base station (backhaul link) and end users (access link). This thesis focuses on the design and development of a new antenna system that is suitable for a relay-based wireless network. Planar geometries of microstrip patch antennas are utilized. The antenna system comprises two antenna modules: a new design of a single antenna for access link and a new design of an antenna array for backhaul link realization. Both antenna specifications are compatible with the IEEE802.16j protocol standard. Hence, relay station should be capable of pointing its radiation pattern to the base station antenna, thus to achieve the desired radiation pattern of the relay station, a new beam-forming module is proposed, designed and developed to generate the proper radiation pattern. The beam-forming module incorporating digital phase shifters and attenuator chips is fabricated and tested. The optimization process using the Least Mean Square (LMS) algorithm is considered in this study to assign the proper phase and amplitude that is necessary to each radiation element excitation current, to produce the desired steered radiation pattern. A comprehensive study on the coupling effects for several relative positions between two new backhaul and access link antenna elements is performed. Two new antenna configurations for coupling reduction are tested and the simulated and measured results in terms of antenna radiation performances were compared and commented

Performance Evaluation of Wi-Fi comparison with WiMAX Networks

Abstract Wireless networking has become an important area of research in academic and industry. The main objectives of this paper is to gain in-dept