<p>3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.</p>

<p>One goal in the development of future cellular systems is to increase performance. Channel dependent scheduling can possibly contribute to a performance enhancement. It requires channel qualityinformation and uplink channel knowledge is often incomplete. This master thesis work compares channel dependent scheduling and channel independent scheduling for a Single Carrier Frequency Division Multiple Access-based uplink in time domain and time and frequencydomain assuming continuous channel quality information updates. It also evaluates different methods for providing channel quality information by investigating how the limited channel knowledge they supply affects the performance of channel dependent scheduling.</p><p>Single-cell simulations with perfect channel knowledge indicate small gains for channel dependent scheduling. Large gains are seen when performing frequency and time domain scheduling instead of only time domain scheduling. Limited channel knowledge causes performance loss for channel dependent scheduling. The performance is only slightly decreased if a method with sufficiently frequent providing of channel quality information updates is applied.</p><p>More realistic multi-cell simulations show large gains for channel dependent scheduling. It is possible that these results are influenced by link adaptation and scheduling problems due to non predictable interference when performing dynamic scheduling. In the comparison between channel dependent and channel independent scheduling the channel dependent scheduling can benefit from the fact that the selected channel dependent scheduling algorithms result in a more static scheduling than the selected channel independent scheduling algorithms do.</p>

One goal in the development of future cellular systems is to increase performance. Channel dependent scheduling can possibly contribute to a performance enhancement. It requires channel qualityinformation and uplink channel knowledge is often incomplete. This master thesis work compares channel dependent scheduling and channel independent scheduling for a Single Carrier Frequency Division Multiple Access-based uplink in time domain and time and frequencydomain assuming continuous channel quality information updates. It also evaluates different methods for providing channel quality information by investigating how the limited channel knowledge they supply affects the performance of channel dependent scheduling. Single-cell simulations with perfect channel knowledge indicate small gains for channel dependent scheduling. Large gains are seen when performing frequency and time domain scheduling instead of only time domain scheduling. Limited channel knowledge causes performance loss for channel dependent scheduling. The performance is only slightly decreased if a method with sufficiently frequent providing of channel quality information updates is applied. More realistic multi-cell simulations show large gains for channel dependent scheduling. It is possible that these results are influenced by link adaptation and scheduling problems due to non predictable interference when performing dynamic scheduling. In the comparison between channel dependent and channel independent scheduling the channel dependent scheduling can benefit from the fact that the selected channel dependent scheduling algorithms result in a more static scheduling than the selected channel independent scheduling algorithms do.

3GPP LTE (Long Term Evolution) is a project of the Third Generation Partnership Project to improve the UMTS (Universal Mobile Telecommunications System) mobile phone standard to cope with future technology evolutions. Two duplex schemes FDD and TDD are investigated in this thesis. Several computational intensive components of the baseband processing for LTE uplink such as synchronization, channel estimation, equalization, soft demapping, turbo decoding is analyzed. Cost analysis is hardware independent so that only computational complexity is considered in this thesis. Hardware dependent discussion for LTE baseband SDR platform is given according the analysis results.

Multi-carrier systems suffer from several impairments, and communication system engineers use powerful signal processing tools to combat these impairments and keep up with the capacity/rate demands. Compressed sensing (CS) is one such tool that allows recovering any sparse signal, requiring only a few measurements in a domain that is incoherent with the domain of sparsity. Almost all signals of interest have some degree of sparsity, and in this work we utilize the sparsity of impairments in orthogonal frequency division multiplexing (OFDM) and its variants (i.e., orthogonal frequency division multiplexing access (OFDMA) and single-carrier frequency-division multiple access (SC-FDMA)) to combat them using CS. We start with the problem of peak-to-average power ratio (PAPR) reduction in OFDM. OFDM signals suffer from high PAPR and clipping is the simplest PAPR reduction scheme. However, clipping introduces inband distortions that result in compromised performance and hence needs to be mitigated at the receiver. Due to the high PAPR nature of the OFDM signal, only a few instances are clipped, these clipping distortions can be recovered at the receiver by employing CS. We then extend the proposed clipping recovery scheme to an interleaved OFDMA system. Interleaved OFDMA presents a special structure that result in only self-inflicted clipping distortions. In this work, we prove that distortions do not spread over multiple users (while utilizing interleaved carrier assignment in OFDMA) and construct a CS system that recovers the clipping distortions on each user. Finally, we address the problem of narrowband interference (NBI) in SC-FDMA. Unlike OFDM and OFDMA systems, SC-FDMA does not suffer from high PAPR, but (as the data is encoded in time domain) is seriously vulnerable to information loss owing to NBI. Utilizing the sparse nature of NBI (in frequency domain) we combat its effect on SC-FDMA system by CS recovery.

Au cours de cette thèse, nous nous sommes d'abord intéressés à l'optimisation des ressources et à la modulation adaptative dans les systèmes SC-FDMA (Single Carrier Frequency Division Multiple Access). Ce problème d'optimisation est combinatoire à complexité de calcul exponentielle. Afin de pallier à cette difficulté, nous avons utilisé la théorie de la dualité canonique, grâce à laquelle, la complexité du problème d'optimisation devient polynômiale et cela en constitue une amélioration remarquable. L'approche proposée est très proche de la solution optimale. Nous avons ensuite étudié la problématique complexe de l'allocation de ressources pour le "Streaming Vidéo" dans les réseaux sans fil, où il est nécessaire d'assurer une transmission vidéo de haute qualité en présence de canaux et de brouillages variables au cours du temps. Dans ce contexte, nous avons proposé une nouvelle méthode d'allocation de puissance conjointement à l'adaptation du débit vidéo. Pour ce faire, nous avons adopté une approche de la théorie de contrôle, intitulée "Risk-Sensitive Control". Nous avons dédié la troisième partie de la thèse à la conception d'une nouvelle stratégie "best-M" pour le renvoi du CQI (Channel Quality Indicator) pour les systèmes multi-utilisateurs et multi-porteuses. En générale, l'erreur d'estimation du CQI ainsi que son délai de renvoi sont gérés au niveau de la station de base. Notre nouvelle stratégie "best-M" suppose que la gestion de ces problèmes est confiée aux utilisateurs. De ce fait, la performance du système se trouve améliorée sans que son débit de signalisation ne soit augmenté en voix montante. / Adaptive resource allocation in wireless communication systems is crucial in order to support the diverse QoS needs of the services and optimize resource utilization. The design of resource allocation schemes should consider the service type for which it is intended. Moreover, due to feedback delay and channel estimation error, the Channel Quality Indicator (CQI) reported to the transmitter may not be a perfect measure of the channel quality and its use for resource allocation may severely degrade the systems performance. In this thesis, we study resource allocation and CQI reporting for wireless networks while taking the aforementioned factors into consideration. First, we consider resource allocation and adaptive modulation in uplink SC-FDMA systems. This is a combinatorial problem whose optimal solution is exponentially complex. We use canonical duality theory to derive a polynomial complexity resource allocation algorithm that provides a nearly optimal solution to the problem. Then, we focus on resource allocation for video streaming in wireless networks with time-varying interference. To this end, by using risk-sensitive control approach, we develop a cross-layer optimization framework that performs power control at the PHY/MAC layer and rate adaptation at the APPLICATION layer jointly and provides fairness among nodes. Finally, by using stochastic control and game theory, we design a robust best-M CQI reporting scheme for multi-carrier and multi-user systems which takes into account the impact of feedback delay and error in CQI computation. Performing resource allocation on the basis of the proposed CQI reporting can significantly improve the system performance.

Le SC-FDMA " Single-Carrier Frequency Division Multiple Acces ", est une technique d'accès multiple à répartition fréquentielle, permettant d'allouer efficacement aux différents mobiles, les ressources de communication. Cette technique a suscité un intérêt particulier lors des conventions de normalisation du standard 3GPP LTE " Long Term Evolution ". Le regain de considération pour cette technique, est lié au fait qu'elle engendre des signaux temporels à faible variation d'amplitude caractérisée par un faible PAPR ou " Peak to Average Power Ratio ". Cet avantage majeur, rend possible l'utilisation de l'amplificateur de puissance du système dans sa zone proche du point de compression, maximisant ainsi son rendement sans toutefois risquer l'apparition des distorsions. C'est pourquoi, ce système a été adopté dans la norme 3GPP LTE comme technique d'accès multiple pour la voix montante. Cependant, dans les spécifications du 3GPP LTE un symbole sur sept est systématiquement réservé pour l'estimation de canal sur toutes les porteuses du système engendrant ainsi une réduction importante du débit utile du signal transmis. L'objectif de cette thèse est de proposer des techniques d'estimation et d'égalisation de canal adaptées pour le SC-FDMA afin d'éviter tant que possible cette perte de débit. Nous avons pu analyser, quelques techniques d'égalisation comme celle basée sur des références fantômes, mais également quelques techniques d'estimation de canal comme celle basée sur un " Ajout de Signal "dans la bande passante du signal utile.

Adaptive resource allocation in wireless communication systems is crucial in order to support the diverse QoS needs of the services and optimize resource utilization. The design of resource allocation schemes should consider the service type for which it is intended. Moreover, due to feedback delay and channel estimation error, the Channel Quality Indicator (CQI) reported to the transmitter may not be a perfect measure of the channel quality and its use for resource allocation may severely degrade the systems performance. In this thesis, we study resource allocation and CQI reporting for wireless networks while taking the aforementioned factors into consideration. First, we consider resource allocation and adaptive modulation in uplink SC-FDMA systems. This is a combinatorial problem whose optimal solution is exponentially complex. We use canonical duality theory to derive a polynomial complexity resource allocation algorithm that provides a nearly optimal solution to the problem. Then, we focus on resource allocation for video streaming in wireless networks with time-varying interference. To this end, by using risk-sensitive control approach, we develop a cross-layer optimization framework that performs power control at the PHY/MAC layer and rate adaptation at the APPLICATION layer jointly and provides fairness among nodes. Finally, by using stochastic control and game theory, we design a robust best-M CQI reporting scheme for multi-carrier and multi-user systems which takes into account the impact of feedback delay and error in CQI computation. Performing resource allocation on the basis of the proposed CQI reporting can significantly improve the system performance.

This thesis is dedicated to the study of the OFDM/OQAM modulation as an alternative to the OFDM modulation. We treat more especially the multi-user environment. In this respect, synchronization aspects are crucial. The different options plus the choice of the waveform are examined in this point of view. Another objective is to precisely show how the OFDM/OQAM can be adapted to a cellular transmission type, taking as reference the 3GPP/LTE system. The main contributions we have made are : 1) Analysis of the desynchronization phenomena : we analyze the effect of desynchronization, according to the time and frequency axes, on the performance of OFDM/OQAM at the receiver side. 2) Synchronization method : we analyze a method of temporal synchronization defined in a single user OFDM/OQAM transmission and we adapt it to a multi-user scenario type. 3) Proposing for a multiple access scheme : we propose a multiple access scheme based on theOFDM/OQAM modulation, alternative to the known techniques OFDMA and SC-FDMA, for the UL transmission in a 3GPP/LTE context.

Since past few decades different types of cellular networks were launched and went successful on the radio links such as WiMAX, that became very popular because of its high data rate (70Mbps) and support for providing wireless internet services over 50km distance. The UMTS Long Term Evolution (LTE) is an emerging technology in the evolution of 3G cellular services. LTE runs on an evolution of the existing UMTS infrastructure already used by over 80 percent of mobile subscribers globally. We have very limited resources in cellular technologies and it is important to utilize them with high efficiency. Single Carrier Frequency Division Multiple Access (SC-FDMA) &amp; Orthogonal Division Multiple Access (OFDMA) are major part of LTE. OFDMA was well utilized for achieving high spectral efficiency in communication system. SC-FDMA is introduced recently and it became handy candidate for uplink multiple access scheme in LTE system that is a project of Third Generation Partnership Project (3GPP). The Multiple Access Scheme in Advanced Mobile radio system has to meet the challenging requirements for example high throughput, good robustness, efficient Bit Error Rate (BER), high spectral efficiency, low delays, low computational complexity, low Peak to Average Power Ratio (PAPR), low error probability etc. Error probability is playing vital role in channel estimation and there are many ways to do channel estimation, like Wiener Channel Estimation, Bayesian Demodulation etc. In our thesis, we investigate the performance of SC-FDMA and OFDMA of LTE physical layer by considering different modulation schemes (BPSK, QPSK, 16QAM and 64QAM) on the basis of PAPR, BER, power spectral density (PSD) and error probability by simulating the model of SC-FDMA &amp; OFDMA. We use Additive White Gaussian Noise (AWGN) channel and introduce frequency selective (multipath) fading in the channel by using Rayleigh Fading model to evaluate the performance in presence of noise and fading. A set of conclusions is derived from our results describing the effect of higher order modulation schemes on BER and error probability for both OFDMA and SC-FDMA. The power spectral densities of both the multiple access techniques (OFDMA and SC-FDMA) are calculated and result shows that the OFDMA has high power spectral density. The considered modulation schemes also have a significant impact on the PAPR of both OFDMA and SC-FDMA such that the higher order modulations increase PAPR in SC-FDMA and decrease PAPR in OFDMA. However, the overall value of PAPR is minimum in SC-FDMA for all modulation schemes. The PSD calculation results also support the remarks given on PAPR. / Author 01: Abdul Samad Shaikh, Phone # 0046-760915236 Author 02 : Khatri Chandan Kumar, Phone # 0046-762649745