Small cell discovery search performance in heterogenous mobile networks

In the recent years, development of wireless communication devices lead to high demand of wireless communication system traffic and this demand is steadily rising day by day. At the same time, energy consumption problem arose in both mobile network's and mobile users' battery life time. Since the fact that development of spectral efficiency has been approaching to theoretical limits, new generation technologies are developed regarding to develop spectral efficiency. To achieve that, heterogonous network architecture is seen as best practice to solve both capacity and energy efficiency problem. To assess the effects of heterogeneous network usage to performance, scenarios such as shadowing, path loss, interference and noise power are examined and three essential setup configuration are took into consideration. Those are; non-interference setup scenario with randomly distributed small cells, interference setup scenario between formally distributed small cells, and interference setup scenario between macro cells and formally distributed small cells. In these scenarios, mobile user moves at constant speed in the area of 1 $km^2$. In this thesis, the performance effect of scanning period, cell power output, mobile user speed and small cell density parameters are examined. According to the results collected in each three scenarios, it is seen that increase of small cell density resulted with gain in power received by mobile users. However, it is also seen that excessive increase in small cell density is not much advantageous because of interference which is revealed during SINR observation. Excessive amount of small cell usage is unfavorable in terms of spectral efficiency and energy efficiency. For this reason, small cells have to be placed very carefully. In case of lack of macro cells or areas where data is highly demanded, setup of small cells could be useful. Again, in all these scenarios it is seen that increase of scanning period resulted with decrease in signal quality. However, setting scanning period very low drains mobile users' battery life quickly. For this reason, scanning period should be rebalanced according to mobile users' benefit by taking into consideration signal quality. When examining shadowing scenarios, to avoid negative effects of shadowing, small cell density can be increased or scanning period can be decreased. In case of there is no macro base station, signal quality received by mobile user is changed in micro scales. At the same time, since the fact that mobile users' transmission power changes in micro scales, increased value of small cell transmit power is resulted with redundantly increased activity cost. On the other hand, in scenarios where macro cells are present, high power output is resulted with positive effect on signal received by mobile users.