Panagiotis Tsiakas

A Multi-Hop Relay Station Software Architecture Design, on the Basis of the WiMAX IEEE 802.16j Standard

In order to enable rapid and cost-effective deployment of WiMAX networks, relay technology which does not require backhaul line, can be considered as an essential feature for performing a successful business development. In the scope of a proposed Multi-Hop relay network architecture, (based on the recently developed IEEE 802.16j standard in order to enhance throughput, network coverage and capacity density), we provide an essential description of the Relay Station Software architecture design (PHY and MAC layers architecture), as it has been proposed by the REWIND European Research Program. The corresponding relay node is based on a highly integrated SoC device, which incorporates all baseband processing (PHY, MAC and CS), networking and control processors required for the relay station functionality. Thus, the Relay node software shall run all the PHY, MAC, scheduler and networking functionalities, required to operate a complete BS with relay functionality, and to integrate the node into the relay network.

Using New Technologies for Teaching Power Electronics and Assessing Students

In the Technological Educational Institution (T.E.I.) of Athens, new technologies are used for teaching electronic engineering modules for some time. This work presents the teaching of the module of power electronics by introducing a number of new methods. The educational portal, software simulations and electronic examinations support the teaching process and finally evaluate knowledge assimilation. Features and advantages of their implementation are presented and discussed

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A 2 × 2 Switch Matrix operating at the 3.3-3.8 GHz frequency band is presented. The design is based on PIN diode switch elements. The achieved isolation is below 80 dB, while the insertion loss is less than 2 dB for the full frequency band. The proposed 2 × 2 Switch Matrix is used as the antenna switching element in the RF Front-End of a WiMAX Relay Station, supporting both Time-domain Transmit and Receive and Simultaneous Transmit and Receive operation in Time Division Duplexing mode.

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This paper aims at describing the advantages of using relay and repeater elements in a wireless network and especially in a network based on WiMAX technology. Apart from a description of the relay and repeater entities, a comparison between them is presented based on computer simulations. All presented material is based on the findings and results of the FP7-REWIND project.

2 Switch Matrix for WiMAX Relay Station Applications

This research focuses on the architecture of a WiMAX Relay Station (RS) prototype, based on the IEEE802.16j standard. Non-Transparent (NTR) operation is implemented in Time-division Transmit and Receive (TTR) mode. The prototype is configured as a Single Unit Relay Station (SURS). MAC-based relay option is selected as well as distributed scheduling. The prototype RS frequency band of operation is 3.3–3.8 GHz.

Relay vs. Repeater Architectures in WiMAX

The IEEE 802.16j WiMAX standard outlines the method for creating a multi-hop mesh network, which can be deployed as a high speed wide-area wireless network. To realize the full potential of such high-speed mesh networks, an efficient wireless radio resource allocation extension has been developed. Load balancing is a technique to spread work between two or more elements, in order to get optimal resource utilization, maximize throughput, and minimize response time. When used in wireless terminology, it usually means a scheme of assigning a subscriber to a nearby cell based on current cell load and the added load expected by linking this subscriber. The current work describes the developed adaptation of the Ford-Fulkerson algorithm to WiMAX mesh networks.

An IEEE802.16j prototype relay station architecture

It has become apparent in the recent years that in order for the next generation of wireless technology (whether this is WiMAX, LTE or any other 4G implementation) to be able to deliver ubiquitous broadband content, the network is required to provide excellent coverage, both outdoor and indoor, and significantly higher bandwidth per subscriber [Voudouris et al., 2009]. In order to achieve that at frequencies above 2 and 3 GHz, which are targeted for future wireless technologies, network architecture must reduce significantly the cell size or the distance between the network and subscribers’ antennas. While micro, pico and femto Base Transceiver Station (BTS) technologies reduce the cost of base-station equipment, they still rely on a dedicated backhaul. One solution introduced with the WiMAX 802.16j standard is the wireless Multi-hop Relay Station (MRS), intended to overcome these challenges. On one hand, it should be small, cost-effective and easy to install for enabling mass deployment in indoor and outdoor environments and creating relatively small areas with excellent coverage and high capacity availability. On the other hand, it does not require any dedicated backhaul equipment as it receives its capacity from centralized base-stations via the same resources used for the access service. In a setting where a MRS exists, enabling MIMO transmission, the link referred to needs to be specified. This means that, when a 2x2 setting is mentioned, there can be either two transmit antennas on the base station and two receive antennas on the relay station, or two transmit antennas on the relay station and two receive antennas on the subscriber’s device [Chochliouros et al., 2009].Wireless Multi-hop Relay Stations (MRSs), when deployed in various sights, result in increased throughput or coverage. A general case, where a relay station can be used, is in situations with coverage constraints such as areas where there is presence of physical obstacles (e.g. buildings, forests), or in indoor coverage cases. Some examples are large office buildings, University campuses, and villages in unreachable areas on rockier uplands etc. Another scenario, where MRSs can be used, is for high mobility users with increased bandwidth requirements, such as trains with a great number of wireless users. Such a mobile subscriber will more likely have data rate degradations due to non-fixed position. In this case, a relay station can be considered as the most feasible solution in terms of cost and

Load balancing in limited intra-cell interference (LICI) networks based on maximum graph-flow algorithms

Relay technologies have the potential to offer extended cell coverage and improved capacity over the Next Generation Wireless Broadband Radio Access Networks. Standards development organizations are considering how to incorporate relay technologies into new standards. This article provides an overview of the relay-based technology concepts for two of the most promising next generation wireless broadband networks: WiMAX and LTE, focusing on some of the most pertinent aspects. In particular, the various potential relaying scenarios are described, while the integration and adaptation of the Multi-hop Relay in the framework of WiMAX and LTE networks is analyzed. Some consideration of the issues in designing such systems is also given, which highlights when different features within the standard are most appropriate. As these systems are very new, many open issues remain to be resolved.

A WiMAX Network Architecture Based on Multi-Hop Relays

In the scope of the REWIND European Research Program we propose a Multi-Hop Relay network architecture, based on the recently developed IEEE 802.16j standard with the aim of enhancing throughput, network coverage and capacity density. In particular, we provide an essential description of the Relay Station Software architecture design, mainly focused on the PHY and MAC layers architecture, by analyzing the essentials of the downlink and uplink data flows, on the basis of the corresponding relay node to be included in the wireless network.