Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

We propose a scheduling strategy for radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS terrestrial radio access network (UTRAN) time division duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. We present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both traffic fluctuations, in the uplink and downlink direction, and variations in system interference. The goal of our scheduler is data-throughput maximization for an efficient utilization of available radio resources. The performance of our scheduling algorithm is evaluated via simulation

Incremental refinement of a multi-user-detection algorithm (II)

Multi-user detection is a technique proposed for mobile radio systems based on the CDMA principle, such as the upcoming UMTS. While offering an elegant solution to problems such as intra-cell interference, it demands very significant computational resources. In this paper, we present a high-level approach for reducing the required resources for performing multi-user detection in a 3GPP TDD multi-user system. This approach is based on a displacement representation of the parameters that describe the transmission system, and a generalized Schur algorithm that works on this representation. The Schur algorithm naturally leads to a highly parallel hardware implementation using CORDIC cells. It is shown that this hardware architecture can also be used to compute the initial displacement representation. It is very beneficial to introduce incremental refinement structures into the solution process, both at the algorithmic level and in the individual cells of the hardware architecture. We detail these approximations and present simulation results that confirm their effectiveness

A study of UMTS terrestrial radio access performance

This thesis considers the performance evaluation of third generation radio networks, in particular UMTS Terrestrial Radio Access (UTRA). First, the performance evaluation methods are presented. The typical capacity of UTRA is estimated using those methods and a few solutions are evaluated to improve the capacity and coverage. The thesis further studies the effect of base station synchronization on the performance of UTRA time division duplex mode. The performance evaluation is based on the combination of theoretical calculations, link and system level simulations, and laboratory and field measurements. It is shown that these different evaluation methods give similar results and – when combined together – they can be used for the radio network development purposes. The simulation results indicate that the typical WCDMA, i.e. UTRA frequency division duplex mode, macro cell capacity is between 600 and 1000 kbps per sector per 5 MHz. The capacity is sensitive to the environment and to the transceiver performance. The results further show that user bit rates up to 2 Mbps can be provided locally for packet data with the basic Rake receiver, but not for full coverage circuit switched connections in macro cells. The following performance enhancement techniques are evaluated in this thesis: soft combining of packet retransmissions, base station multiuser detection and 4-branch base station receiver diversity. The link level simulations show that soft combining can provide a gain up to 2.0 dB, which can be used to increase the capacity up to 60 %. The performance of base station multiuser detection is evaluated with link and system level simulations. It is shown that the studied sub-optimal multiuser detector is able to remove 60-70 % of the intra-cell interference. That gain can be utilized to improve the uplink capacity by 50-100 % or the coverage by 1-2 dB. The performance of 4-branch antenna diversity is evaluated in the simulations and in the field measurements. The results show that the average coverage gain of 4-branch diversity with two separate cross-polarized antennas is 3 dB compared to 2-branch diversity with one cross-polarized antenna. The synchronization requirements of UTRA time division duplex base stations are studied with system simulations. The results show that synchronization is a key requirement for time division duplex operation, especially for the uplink performance. The study indicates that co-location of different operators' base stations is feasible in time division duplex operation only if the two networks are synchronized and if an identical split between uplink and downlink is used.reviewe

Implementação numa FPGA de técnicas MIMO para os futuros sistemas de transmissão wireless- (sistemas de 4G/LTE)

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThis work alludes to 4G LTE technology. Techniques used for the same technology are described namely precoding and Alamouti coding and decoding. An Alamouti’s 4G system implemented to FPGA using the Xilinx System is introduced. The work also addresses the PAPR problem due to the reference pilots in the platform being generated all in phase. In this work a random pilot generator was implemented which combats the high peak power. In the receiver it was taken into account the new generation method to perform channel estimation correctly. A technique is discussed to increase the energy efficiency of the system based on PAPR reduction.O presente trabalho faz alusão à tecnologia 4G LTE. São descritas técnicas usadas na mesma tecnologia nomeadamente de precoding e codificação e descodificação Alamouti. É introduzido um sistema Alamouti 4G implementado para FPGAs usando o programa System Generator da Xilinx. O trabalho também aborda o problema do PAPR devido aos pilotos de referência na plataforma estarem sendo gerados todos em fase. Neste trabalho, um gerador aleatório de pilotos foi implementado que combate a potência de pico (PAPR). No receptor levou-se em conta o método desta nova geração para realizar a estimativa de canal corretamente

Analyse, implémentation et évaluation de performance de la future méthode d'accès HSDPA

La technologie HSDPA (High Speed Downlink Packet Access) représente la première étape d’évolution de la méthode d’accès du réseau mobile de troisième génération UMTS (Universal Mobile Telecommmunications Service). Cette technologie permet d’obtenir des débits théoriques supérieurs à 10 Mbps sur le lien descendant et de supporter des services à valeur ajoutée, tels que l’accès Internet à haute vitesse, le téléchargement de fichiers audio et vidéo, la réception de programmes télévisés et la visiophonie. Ces améliorations sont rendues possibles grâce à une combinaison de propriétés qui sont à la base du HSDPA et qui consistent à adapter le codage et la modulation en fonction des conditions du canal radio (AMC : Adaptative Modulation and Coding), à effectuer des retransmissions rapides de paquets erronés (HARQ : Hybrid Automatic Repeat ReQuest) et à utiliser des méthodes d’ordonnancement intelligentes plus rapides. Même si l’introduction de ces nouvelles techniques contribue à une augmentation de la capacité du système, elle engendre toutefois une plus grande complexité dans l’évaluation de ses performances dans des conditions réelles. Dans ce contexte, nous proposons une implémentation et une évaluation de la méthode d’accès HSDPA qui prend en considération les spécifications techniques des Node B et des terminaux mobiles d’un système UMTS. Les résultats obtenus de cette implémentation, basés sur plusieurs scénarios utilisant des données géographiques réelles, montrent que le système réussit à satisfaire aux exigences des services multimédia.High speed downlink packet access (HSDPA) is an add-on technology for W-CDMA that allows higher downlink data rates and greater base station capacity. With HSDPA, W-CDMA systems, which today are seemingly stuck at 384 kbps, will be able to shift gears and move ahead to so-called 3.5G performance with over 10 Mbps throughput on the downlink. The incorporation of HSDPA in Release 5 of the 3GPP W-CDMA specification is the most significant change on the RF side since Release 99. Advanced techniques such as adaptive modulation and coding (AMC) and hybrid automatic repeat request (HARQ) are used to modify the coding and physical layer parameters adaptively in response to the instantaneous channel quality, thus enabling gains in spectral efficiency and data rates. On the other hand, such improvements also bring a higher complexity degree in the evaluation of the radio subsystem performance. This evaluation is crucial for operators who are willing to provide value-added services with rich multimedia contents. This thesis aims at implementing and simulating a radio access network on a real geographic area using the HSDPA features. Results show that such features enable to satisfy the quality of service requirements needed to support the new data-oriented services

Design and analysis of optimal resource allocation policies in wireless networks

Ph.DDOCTOR OF PHILOSOPH