Επικοινωνίες συσκευή-με-συσκευή για κυψελωτά δίκτυα 4ης γενιάς
Device-to-device communications for 4th generation cellular systems
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Keywords
D2D ; LTE ; Power control ; Έλεγχος ισχύος ; Παρεμβολές ; SNR ; SINR ; INR ; PLFAbstract
The purpose of this thesis is to analyze Device to Device (D2D) communications which are based on 4th Generation Networks. The study had as a goal to show the benefits as well as the problems of using D2D links inside a macrocell in terms of the increased levels of interference towards to the base station as well as to other D2D links.
In Chapter 1, we present the benefits of employing D2D technology by presenting the stages of communication and the challenges of their practical implementation. In Chapter 2, we present the architecture and design guidelines of D2D Proximity Services with an emphasis on the way this type of communications is accomplished.
In Chapters 3 and 4 we present the multiple access waveforms of OFDMA and SCFDMA that are used in the downlink and in uplink, respectively. We describe their characteristics, their advantages and disadvantages, as well as the way the radioresources are allocated in each multiple access system and the various schemes that are used for interference reduction.
Finally, in Chapter 5 we carried out a simulation in Matlab to derive the probability density function of signal to noise ratio (SNR) and the received signal to interference plus noise ratio (SINR) of the desired D2D link, which is randomly placed in a macrocell with the base station (eNodeB) placed at the center. The simulation results show the effect of power control in the D2D transmitter and the interference to noise ratio threshold at the base station on the received SNR of the desired D2D link. We also showed the impact of path loss factor in the macrocell in the SNR of the desired D2D link with and without using power control for controlling the uplink interference imposed to the base station. Finally, we examined the effect that another D2D link, which is also randomly placed in the macrocell, has on the received SINR of the desired D2D link.