Combination of OFDM and CDMA for high data rate UWB

For Wireless Personal Area Network (WPAN) systems, resource allocation between several users within a piconet and the coexistence of several piconets are very important points to take into consideration for the optimization of high data rate Ultra Wide Band (UWB) systems. To improve the performance of the Multi-Band OFDM (Orthogonal Frequency Division Multiplex) solution proposed by the Multi-Band OFDM Alliance (MBOA), the addition of a spreading component in the frequency domain is a good solution since it makes resource allocation easier and also offers better robustness against channel frequency selectivity and narrowband interference. The Spread Spectrum - Multi-Carrier - Multiple Access (SS-MC-MA) system proposed in this article offers not only the advantages of Multi-Carrier - Coded Division Multiple Access (MC-CDMA) brought by frequency spreading, but also a more effective dynamic resource allocation in a multi-user and multi-piconet context. These improvements are obtained without increasing the complexity of the radio-frequency part compared to the classical MBOA solution

Combinaison des techniques OFDM et CDMA pour l'UWB haut débit

National audiencePour les systèmes WPAN, la gestion des ressources entre plusieurs utilisateurs d'une même picocellule ainsi que la co-existence de plusieurs picocellules sont des points importants à prendre en compte lors de l'optimisation d'un système UWB haut débit. Afin d'améliorer les performances de la solution multi band OFDM proposée par l'alliance MBOA, l'ajout d'une composante d'étalement selon l'axe fréquentiel s'avère une bonne solution pour faciliter la gestion des ressources, qui offre en outre une meilleure robustesse vis-à-vis de la sélectivité en fréquence du canal et des interférences à bande étroite. Le système SS-MC-MA que nous proposons, bénéficie non seulement des avantages du MC-CDMA apportés par l'étalement fréquentiel mais permet égalament une allocation dynamique des ressources plus efficace dans un contexte multi-utilisateurs et multi-picocellules. Ces améliorations peuvent être obtenues, sans augmenter la complexité du segment radio-fréquence par rapport à la solution MBOA

A Framework for Enhancing the Energy Efficiency of IoT Devices in 5G Network

A wide range of services, such as improved mobile broadband, extensive machine-type communication, ultra-reliability, and low latency, are anticipated to be delivered via the 5G network. The 5G network has developed as a multi-layer network that uses numerous technological advancements to provide a wide array of wireless services to fulfil such a diversified set of requirements. Several technologies, including software-defined networking, network function virtualization, edge computing, cloud computing, and tiny cells, are being integrated into the 5G networks to meet the needs of various requirements. Due to the higher power consumption that will arise from such a complicated network design, energy efficiency becomes crucial. The network machine learning technique has attracted a lot of interest from the scientific community because it has the potential to play a crucial role in helping to achieve energy efficiency. Utilization factor, access latency, arrival rate, and other metrics are used to study the proposed scheme. It is determined that our system outperforms the present scheme after comparing the suggested scheme to these parameters

Resource allocation for multicarrier CDMA systems in ultra-wideband communications

International audienceUltra-wideband (UWB) is a fast emerging technology that has attracted considerable interest in short range, high data rate wireless personal area networks (WPAN) applications. One of the main candidates for WPAN standardization is the multiband orthogonal frequency division multiplexing (MB-OFDM), supported by the Multiband OFDM Alliance (MBOA). In this paper, we propose a new low-complexity resource allocation algorithm applied to a spread spectrum multicarrier multiple-access (SS-MC-MA) waveform, which is new for high data rate UWB applications. The proposed scheme aims at maximizing the system's throughput while taking into consideration the WPAN environment and respecting the OFDM parameters of the MBOA solution. The adaptive allocation algorithm applied to OFDM and SS-MC-MA leads to roughly double the throughput compared to the MBOA solution at low attenuation levels. Furthermore, at high attenuation levels, SS-MC-MA outperforms the adaptive OFDM. Hence, we conclude that the proposed adaptive SS-MC-MA can especially be advantageously exploited for high attenuation UWB applications

Throughput maximization in linear multiuser MIMO-OFDM downlink systems

In this paper, we study the problem of maximizing the throughput of a multiuser multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system in the downlink with a total power constraint using a beamforming approach. An iterative algorithm that takes turns to optimize, jointly among users, the power allocation in the downlink, the transmit and the receive beamforming antenna vectors, and the power allocation in the virtual uplink is proposed. The algorithm is proved to converge, and the throughput increases from one iteration to the next. In addition to the total power constraint, the proposed algorithm is also capable of handling individual users' rate constraints. To reduce complexity, a geometric-programming-based power control in the high signal-to-interference-plus-noise ratio (SINR) region and an orthogonal frequency-division multiple-access scheme in the low SINR region are proposed. Numerical results illustrate that the proposed algorithm significantly outperforms the generalized zero-forcing (GZF) approach. © 2008 IEEE.published_or_final_versio

Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

Performance evaluation of fixed and variable zero padding length in ultra-wideband receiver design using MB-OFDM based on ECMA-368 standard

Advisors: Mansour Tahernezhadi.Committee members: Lichuan Liu; Donald S. Zinger.Traditional OFDM systems use Cyclic Prefix (CP) in front of an OFDM symbol to maintain orthogonality. Ultra Wide Band (UWB) systems use Multiband OFDM approach in implementing applications of Wireless Personal Area Network (WPAN). Federal Communications Commission (FCC) put some regulations on UWB to co-exist with other narrowband and spread spectrum users. MB-OFDM follows OFDM modulation scheme where CP is used but CP introduces a structure into the transmitter due to which the ripples are produced in Power Spectral Density (PSD). Because of this ripples, power back-off is required at the receiver which is as large as 1.5 dB. As an alternative to CP, Zero Padding (ZP) is used where a flat PSD is obtained which requires zero power back-off. Circular convolution in CP is a natural phenomenon but for ZP, Overlap and add method (OLA) is used to ensure circular convolution. The ZP length used for OLA method is fixed and equal to 32 samples according to ECMA-368. If timing synchronization estimation errors occur, fixed ZP length may cause Inter Symbol Interference (ISI). So, a variable ZP length is required to avoid ISI depending upon the current band. Hence, a Multi Band Timing Synchronization algorithm is proposed to achieve variable ZP length based on current band for OLA method. This method benefits large delay spread channels. Improvement in SNR is achieved at particular Bit Error Rate (BER) for large delay spread channels.M.S. (Master of Science