The co-existence of Femtocell with WiFi (in case of unlicensed spectrum splitting & sharing)

Les femtocellules et le WiFi sont souvent présentés comme étant deux technologies concurrentes. Cependant, la réalité dit totalement l'inverse; ces technologies sont supposées jouer des rôles complémentaires dans le but d'accompagner la croissance fulgurante du trafic mobile. De plus, elles sont souvent implémentées dans un même et unique équipement d'accès. Les équipements mobiles pourront ainsi choisir l'utilisation de la technologie qui représente la meilleure option. Le déploiement des femtocellules dans les hotspots WiFi permettra aux opérateurs de donner aux usagers la possibilité d'utiliser les technologies 3G. Par conséquent, grâce à ces deux technologies, la qualité de l'expérience de la communication pendant la mobilité sera sans doute meilleure. Toutefois, cette coexistence présente de nouveaux défis en vue de l'amélioration de performances en termes des débits de transmission et de qualité de service des usagers. Ainsi, nous croyons qu'un partitionnement efficace des ressources spectrales accompagné d'un réglage minutieux des paramètres de transmission permettra de maximiser les performances des deux technologies. Dans ce mémoire, nous nous intéressons à la coexistence des technologies femtocellule et WiFi : (i) Dans un premier lieu, nous proposons une technique de partage des bandes spectrales ouvertes entre le réseau WiFi et le réseau femtocellule. La technique proposée assure une qualité de service et une équité entre les transmissions concurrentes. En se basant sur plusieurs simulations, nous démontrons que la technique proposée assure un partage équitable du spectre. (ii) Dans un second lieu, nous proposons un Framework ayant pour objectif l'amélioration du débit total du réseau des femtocellules lorsque ces dernières utilisent simultanément des bandes de spectres ouvertes et d'autres sous licences. Le système étudié, comprenant le réseau WiFi et le réseau des femtocellules, a été modélisé analytiquement et ses performances ont été évaluées par plusieurs simulations. Ces dernières ont permis de quantifier l'effet de plusieurs paramètres de la technologie WiFi sur les performances du système étudié.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Femtocellule, WiFi, allocation de spectre, qualité de service, équité, capacité, spectre sans licence, modèle de back-off

Coexistence of Wi-Fi and Heterogeneous Small Cell Networks Sharing Unlicensed Spectrum

As two major players in terrestrial wireless communications, Wi-Fi systems and cellular networks have different origins and have largely evolved separately. Motivated by the exponentially increasing wireless data demand, cellular networks are evolving towards a heterogeneous and small cell network architecture, wherein small cells are expected to provide very high capacity. However, due to the limited licensed spectrum for cellular networks, any effort to achieve capacity growth through network densification will face the challenge of severe inter-cell interference. In view of this, recent standardization developments have started to consider the opportunities for cellular networks to use the unlicensed spectrum bands, including the 2.4 GHz and 5 GHz bands that are currently used by Wi-Fi, Zigbee and some other communication systems. In this article, we look into the coexistence of Wi-Fi and 4G cellular networks sharing the unlicensed spectrum. We introduce a network architecture where small cells use the same unlicensed spectrum that Wi-Fi systems operate in without affecting the performance of Wi-Fi systems. We present an almost blank subframe (ABS) scheme without priority to mitigate the co-channel interference from small cells to Wi-Fi systems, and propose an interference avoidance scheme based on small cells estimating the density of nearby Wi-Fi access points to facilitate their coexistence while sharing the same unlicensed spectrum. Simulation results show that the proposed network architecture and interference avoidance schemes can significantly increase the capacity of 4G heterogeneous cellular networks while maintaining the service quality of Wi-Fi systems

Survey of Spectrum Sharing for Inter-Technology Coexistence

Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e. (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions

A comparative investigation on the application and performance of Femtocell against Wi-Fi networks in an indoor environment

Due to the strenuous demands on the available spectrum and bandwidth, alongside the ever increasing rate at which data traffic is growing and the poor quality of experience QoE) faced with indoor communications, in order for cellular networks to remain dominant in areas pertaining to voice and data services, cellular service providers have to reform their marketing and service delivery strategies together with their overall network rchitecture. To accomplish this leap forward in performance, cellular service operators need to employ a network topology, which makes use of a mix of macrocells and small cells, effectively evolving the network, bringing it closer to the end-­‐user. This investigation explores the use of small cell technology, specifically Femtocell technology in comparison to the already employed Wi-­‐Fi technology as a viable solution to poor indoor communications.The performance evolution is done by comparing key areas in the every day use of Internet communications. These include HTTP testing, RTP testing and VoIP testing. Results are explained and the modes of operation of both technologies are compared

Fair Coexistence of Scheduled and Random Access Wireless Networks: Unlicensed LTE/WiFi

We study the fair coexistence of scheduled and random access transmitters sharing the same frequency channel. Interest in coexistence is topical due to the need for emerging unlicensed LTE technologies to coexist fairly with WiFi. However, this interest is not confined to LTE/WiFi as coexistence is likely to become increasingly commonplace in IoT networks and beyond 5G. In this article we show that mixing scheduled and random access incurs and inherent throughput/delay cost, the cost of heterogeneity. We derive the joint proportional fair rate allocation, which casts useful light on current LTE/WiFi discussions. We present experimental results on inter-technology detection and consider the impact of imperfect carrier sensing.Comment: 14 pages, 8 figures, journa

Femto Cells: Current Status and Future Directions

This is a survey paper on the recently developed and rapidly evolving field of femtocells. Quite often, it is noticed that cell-phone signals are strongly attenuated, when indoors, leading to call dropping or poor call quality. Femtocells are mini base stations that are deployed in users’ homes so that the user can directly connect to the cellular network through the femtocell instead of the outdoor macrocell, thereby increasing call quality. In the later stages of the paper, we also discuss the integration of the femtocell into the 3G architecture, as well as the various interference issues that the femtocell faces