Performance of Fractionally Spread Multicarrier CDMA in AWGN as Well as Slow and Fast Nakagami-m Fading Channels

Abstract—In multicarrier code-division multiple-access (MCCDMA), the total system bandwidth is divided into a number of subbands, where each subband may use direct-sequence (DS) spreading and each subband signal is transmitted using a subcarrier frequency. In this paper, we divide the symbol duration into a number of fractional subsymbol durations also referred to here as fractions, in a manner analogous to subbands in MC-CDMA systems. In the proposed MC-CDMA scheme, the data streams are spread at both the symbol-fraction level and at the chip level by the transmitter, and hence the proposed scheme is referred to as the fractionally spread MC-CDMA arrangement, or FS MCCDMA. Furthermore, the FS MC-CDMA signal is additionally spread in the frequency (F)-domain using a spreading code with the aid of a number of subcarriers. In comparison to conventional MC-CDMA schemes, which are suitable for communications over frequency-selective fading channels, our study demonstrates that the proposed FS MC-CDMA is capable of efficiently exploiting both the frequency-selective and the time-selective characteristics of wireless channels. Index Terms—Broadband communications, code-division multiple access (CDMA), fractionally spreading, frequency-domain spreading, multicarrier modulation, Nakagami fading, timedomain spreading

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

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

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

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