Classical and Bayesian Linear Data Estimators for Unique Word OFDM

Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM signaling concept, where the guard interval is built of a deterministic sequence - the so-called unique word - instead of the conventional random cyclic prefix. In contrast to previous attempts with deterministic sequences in the guard interval the addressed UW-OFDM signaling approach introduces correlations between the subcarrier symbols, which can be exploited by the receiver in order to improve the bit error ratio performance. In this paper we develop several linear data estimators specifically designed for UW-OFDM, some based on classical and some based on Bayesian estimation theory. Furthermore, we derive complexity optimized versions of these estimators, and we study their individual complex multiplication count in detail. Finally, we evaluate the estimators' performance for the additive white Gaussian noise channel as well as for selected indoor multipath channel scenarios.Comment: Preprint, 13 page

System design and validation of multi-band OFDM wireless communications with multiple antennas

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HARDWARE IMPLEMENTATION OF MISO ON ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING PLATFORM WITH THE HELP OF ALAMOUTI ALGORITHM

Many software based OFDM techniques were proposed from last half decade to improve the performance of the system. This paper tried to implement the same with Hardware implementation. We created Hardware based MISO platform with OFDM. We implemented Alamouti algorithm on this test bed. The test bed is implemented with the help of Field Programmable Gate Array (FPGA). The test bed is functionalized with the help of FPGA through Xilinx based system generator for DSP. In this paper we considered the 2×1 MISO implementation with Alamouti algorithm. The simulation results showed that BER and SNR are considerably high for MISO than SISO. The results also proved that proposed OFDM based Alamouti implementation for MISO is excellent in all performance criterionsMany software based OFDM techniques were proposed from last half decade to improve the performance of the system. This paper tried to implement the same with Hardware implementation. We created Hardware based MISO platform with OFDM. We implemented Alamouti algorithm on this test bed. The test bed is implemented with the help of Field Programmable Gate Array (FPGA). The test bed is functionalized with the help of FPGA through Xilinx based system generator for DSP. In this paper we considered the 2×1 MISO implementation with Alamouti algorithm. The simulation results showed that BER and SNR are considerably high for MISO than SISO. The results also proved that proposed OFDM based Alamouti implementation for MISO is excellent in all performance criterion

Cross-Layer Resource Allocation for MB-OFDM UWB Systems

ISBN 978-953-3076461-0International audienc

A Study of Packet Scheduling Schemes for VoIP and Best Effort Traffic in LTE Networks

The Long Term Evolution (LTE) provides all services over Internet Protocol (IP) since it is an all IP network. To use available radio resources in an effective utilization, Packet Scheduling (PS) should be considered to enhance the Quality of Service (QoS) of Real Time (RT) and Non-Real Time (NRT) traffic. In this thesis, the PS of both RT and NRT traffic is studied in LTE networks. Apriority packet scheduling algorithm is proposed. The proposed algorithm has the ability to schedule the mixed traffic, RT and NRT, simultaneously. The objective of the algorithm is to maximize the Best Effort (BE) throughput while achieves the satisfaction QoS requirements of RT throughput. According to the obtained results of the thesis, the traffic should be differentiated and the services should be prioritized, when applying delay sensitive services. A system simulation is performed to support the study for mixed services approaches with Voice over IP (VoIP) and a second BE service such as File Transfer Protocol (FTP). The performance of the proposed algorithm and the impact of the different factors on the overall system performance have been tested. The work is done at Medium Access Control (MAC) layer and Physical Layer (PHY). Finally, a good results are achieved that guarantee a good end to end performance for both voice and data services

Location-aware and Cooperative Communication in an OFDM based Ultra-wideband Radio System

Die auf dem orthogonalen Frequenzmultiplex (OFDM, Orthogonal Frequency Division Multiplexing) basierende Ultra-Breitband-(UWB, Ultra-wideband) Technologie stellt eine verheißungsvolle Technologie dar, um hohe Datenübertragungsraten und Lokalisierungs- und deren Tracking-Anwendungen zu realisieren. Im Gegensatz zu anderen Systemen ist die Reichweite von OFDM UWB Systemen durch eine strenge Regulierung sehr stark begrenzt. Darüber hinaus ist die Lokalisierung nicht zufriedenstellend. Damit sind bereits die beiden größten Nachteile im Bezug auf bestehende OFDM UWB System benannt. Die Motivation und Hauptaufgabe dieser Arbeit ist damit die Lösung der eben genannten Nachteile. Es wird ein OFDM UWB System vorgestellt, das Space Frequency Block Coding (SFBC) und FFH OFDM miteinander verbindet. Dieses vereinte System wertet die räumliche und frequentielle Diversität eines OFDM-Symbols aus und zeigt dabei eine hohe Güte in der Punkt-zu-Punkt Kommunikation. Beim Design von kooperativen UWB-Systemen wird ein AF-(Amplify-and-Forward) basiertes echtzeitfähriges SFBC-TFC (Time Frequency Code) Protokoll vorgestellt. In Kombination mit den oben genannten Strategien, kann eine Erhöhung in den Reichweite von OFDM UWB Systemen erreicht werden. In den Ausführungen zur Ortung anhand von OFDM UWB Signalen wird ein Algorithmus entwickelt, der aufgrund einer Kanalschätzung eine Minimierung des Phasenversatzes zwischen geschätztem und realem Kanal im Frequenzbereich durchführt. Diese Minimierung erwirkt eine Unterdrückung der Energie am Ende der Kanalimpulsantwort (CIR, Channel Impulse Response) im Zeitbereich. Zum Zweck der einfachen Implementierbarkeit wird das RTT (Round-Trip-Time) Messprotokoll in WiMedia UWB Systemen dahingehend verändert, dass das mobile Gerät keine Minimierung vornimmt. Es leitet seine Informationen an das mit ihm Kommunizierende, stationäre Gerät weiter, das direkt den gesamten Zeitversatz innerhalb des RTT berechnet. Der vorgeschlagene Algorithmus und das vorgeschlagene Protokoll haben ein besseres Ortungsvermögen als bekannte UWB Lokalisierungsprozeduren und bedürfen nur etwas zusätzlicher Berechnungsleistung. Diese Arbeit zeigt, dass Systeme mit hohen Datenraten wie OFDM UWB auch eine gute Lokalisierungsgenauigkeit erreichen können. Zusätzlich ist die Schwachstelle einer limitierten Reichweite ebenso kompensiert worden. Diese Erweiterungen dienen der Entwicklung von nützlichen UWB-Applikationen und sichern den Anteil der OFDM UWB Technik im Markt der drahtlosen Kommunikationssysteme der Zukunft.The Orthogonal Frequency Division Multiplexing (OFDM) based Ultra-wideband (UWB) is one of the most promising technologies for high data rate transmission and localization and tracking applications. However, the restricted transmit power causes a shorter communication range compared to other indoor radio systems. In addition, the ranging functionality is still not well supported by the current OFDM based UWB technology. These two drawbacks are the main disadvantages existing in the current OFDM UWB systems. To get rid of the two drawbacks, is the motivation and main task of this thesis. Within the scope of this thesis, a joint design of Space Frequency Block Coding (SFBC) with Fast Frequency Hopping (FFH) OFDM scheme is investigated in a multiple antenna OFDM UWB system. The joint scheme is able to exploit spatial and frequency domain diversity within one OFDM symbol, and can improve the data transmission quality in point-to-point communication. To the cooperative communication in UWB systems, an Amplify-and-Forward (AF) based distributed SFBC-TFC (Time Frequency Code) protocol is designed. In combination with the aforementioned strategies an increase in the communication range is achieved. Within the scope of this thesis, accurate ranging schemes for the OFDM UWB systems are designed. Fine ToA detection method based on the estimated channel is developed. The fine ToA is estimated by minimizing the accumulated energy of the tail taps of the estimated Channel Impulse Response (CIR). For the purpose of a feasible implementation, the Round-Trip-Time (RTT) measurement protocol in [WiM09] is modified in a way that the complicated computational tasks are burden onto the powerful device. The proposed fine ToA detection method and modified RTT protocol provides an accurate ranging capability and ensures feasible implementation to the MB-OFDM UWB systems. In carrying out this scheme, only some computational tasks are needed, no extra hardware support is required. It is shown in this thesis, OFDM UWB systems with very high data rate transmission and good ranging capability could be achieved, and the weakness of limited communication range is also compensated. These improvements will cause the rise of more valuable UWB applications for customers and ensures a bright future for the OFDM UWB technique