A Practical Analysis of the Eects of Opportunistic Nulling in LTE-based Systems

Abstract: Due to the Internet expansion over the last decades, the pressure for the telecommunications companies to deliver a high performance broadband communication, especially wireless is imminent. Future wireless networks will need to support high data rates in order to meet the requirements of multimedia services. Furthermore, the user density will be much higher for every year and it will be an increase of amount of data communication between mobile devices. Consequently, a new generation network has been introduced, i.e. LTE also called 4G, promising better performance and speed. Nevertheless, it is not only the network that plays an important role in achieving speed and performance, but also the communication system including number of antennas used, antenna deployment, power, number of base station, and so on. Most research papers agree on one point and this is the fact that the performance and reliability may be improved when using multiple inputs and/or multiple outputs, i.e. MIMO. This Master Thesis concerns the performance acquired by studying on one hand the capacity achieved by using multiple antennas in the receiver (1 x 4 MIMO) and on the other hand studying different methods used by the base stations for scheduling the transmission to users according to their channel quality. Furthermore, the evaluation has been done numerically using measured radio channels, obtained by Ericsson. One of the methods used in this paper is opportunistic scheduling, which involves the tracking of each of the fading users’ channel fluctuation and scheduling transmission to these users when their instantaneous channel quality is close to their maximum. In order to improve the communication of those users with low channel quality, a well-known algorithm was added to the Opportunistic scheduling. This method considers previous capacity rates and it is called Proportional Fair scheduling. Another effect of using the Opportunistic scheduling is the suppression of the inter-cell interference (ICI) generated by close-by base stations, called Opportunistic nulling. In this paper, Opportunistic nulling is analysed in order to find out whether a practical suppression is achieved by this scheduling and whether factors such as delayed channel information may affect the scheduling and prevent a reliable communication with minimum interference.